sincalide and Obesity

This review describes the premises for accurate measurement of the gut hormone and satiety factor cholecystokinin (CCK) in circulation. Such a description is useful for nutrition and obesity research in which CCK in its satiety role has evoked considerable interest during the last decades. The background for the review is two sorts of considerations or concerns. First, CCK is a complex peptide system that in several ways challenges plasma measurements because the concentrations in plasma are very low (in the femtomolar to low picomolar range), and the bioactive CCK circulates in different molecular forms (CCK-58, -33, -22, and -8). Furthermore, there are major specificity problems because the structurally similar gastrin hormone circulates in 10- to 20-fold higher concentrations, and in addition, plasma proteins may, due to their high concentration, interfere in an unspecific way with immunoassay measurements. The second concern is that several obesity studies in recent decades have been based on commercial CCK kits with often inadequate documentation of the reliability in plasma measurement. Consequently, many plasma CCK results in today's obesity studies are difficult to compare. Moreover, the use of even fairly reliable commercial CCK kits has recently suffered from sudden discontinuation of the kit production, which has endangered several projects in nutrition and obesity research.

Topics: Animals; Appetite Regulation; Bias; Biomedical Research; Blood Chemical Analysis; Blood Proteins; Cholecystokinin; Gastrins; Humans; Nutritional Sciences; Nutritional Status; Obesity; Peptide Fragments; Plasma; Satiety Response

Of the many factors that influence food intake, there is strong evidence that opioid and CCK peptides, which stimulate feeding and elicit satiety, respectively, are important components that may act in concert to regulate energy balance. Cholecystokinin peptides have been isolated in both the brain and gastrointestinal tract, and changes in concentration in the brain and in plasma have been shown to vary with feeding. Peripherally injected CCK has been shown to elicit satiety in many species, including humans, an effect that may be mediated in the CNS via the vagus. In several species, most notably the sheep, direct injection into the CSF potently decreases food intake. Questions remaining regarding the role of CCK peptides in eliciting satiety include the sites and mechanisms of action. It is unknown whether CCK acts directly on receptors, indirectly on some other parameter, or as a neurotransmitter. Although opioid peptides have also been localized in portions of both the periphery and brain, a specific physiological role for their presence has not yet been determined. Opioid peptides from three families--endorphins, enkephalins, and dynorphins--have been shown to stimulate feeding in various species. They have been active at several opioid receptor types in the CNS, but there is limited evidence to suggest they affect food intake when administered peripherally. In contrast, peripheral injection of opiate antagonists has effectively decreased food intake, an observation that led to the original hypothesis that opioids were involved in the hunger component in the control of food intake and that excess concentrations might be involved in the development of obesity. An increasing body of evidence supports the concept that opioid and CCK peptides may interact to control food intake, but the evidence is more suggestive than conclusive.

Topics: Amino Acid Sequence; Animals; Behavior, Animal; beta-Endorphin; beta-Lipotropin; Brain; Ceruletide; Cholecystokinin; Digestive System Physiological Phenomena; Dynorphins; Eating; Endorphins; Enkephalins; Fasting; Food; Humans; Immunologic Techniques; Kinetics; Morphine; Nervous System; Neurons; Obesity; Peptide Fragments; Protein Precursors; Receptors, Cell Surface; Receptors, Cholecystokinin; Satiation; Sincalide; Species Specificity; Structure-Activity Relationship; Tissue Distribution

Since the mid-1970s, evidence has accumulated that cholecystokinin (CCK) has a role as a neuromodulator or neurotransmitter in the central nervous system as well as in the periphery. CCK has been shown to have a variety of effects on gastrointestinal functions and is one of the main candidates for a role as a peripheral negative feedback signal to stop feeding behavior. CCK produces satiety not only in animals but also in man: it reduces appetite and activation arising from the preparation of a meal and inhibits intake of liquid and solid food in both lean and obese subjects. The closely related peptide caerulein has similar effects. The site of action of peripherally administered CCK seems to be on an abdominal organ innervated by gastric vagal branches and relayed to the brain by afferent vagal fibres, since selective gastric vagotomy blocks the satiety effect, but pharmacological antagonism of vagal motor effects or lesions of the ventromedial hypothalamus do not. CCK also may have a role in the regulation of pain perception. In mice, CCK and caerulein were shown to produce a decrement in response to noxious stimulation after peripheral and central administration. In man, caerulein was demonstrated to relieve pain originating from biliary and renal colic as well as from cancer and ischemia. A series of studies in healthy man revealed that caerulein also alleviates experimentally induced cutaneous pain. Data from animal studies suggest that CCK-like peptides not only are able to produce analgesic effects on their own, but also are involved in the modulation of opioid systems mediating analgesia. Further study of these effects of CCK should elucidate the regulatory connections between the life-sustaining functions of feeding and pain sensation.

Topics: Analgesics; Animals; Appetite Depressants; Central Nervous System; Ceruletide; Cholecystokinin; Digestive System; Dogs; Endorphins; Feeding Behavior; Female; Gastrointestinal Motility; Haplorhini; Humans; Hunger; Male; Mice; Neural Pathways; Obesity; Pain; Rats; Satiety Response; Sincalide; Vagus Nerve

A review of the satiating effect of cholecystokinin in humans reveals that the synthetic C-terminal octapeptide of cholecystokinin (CCK-8) inhibits liquid and solid food intake in non-obese men and women, and in obese men. Side effects, such as nausea, slight stomach sickness or abdominal cramps are infrequent and transient, and they are neither necessary nor sufficient for the inhibition of intake. These results demonstrate the efficacy of the satiating effect of CCK-8 in humans. The therapeutic potential of CCK-8 cannot be estimated until further studies are performed that demonstrate the efficacy of CCK-8 for decreasing body weight and that the safety of CCK-8 when it is administered repetitively for prolonged periods is established.

Topics: Cholecystokinin; Eating; Humans; Obesity; Satiety Response; Sincalide

The satiety effect of cholecystokinin (CCK) that was first observed in rats has now been extended to chickens, rabbits, pigs, sheep, rhesus monkeys, lean mice, genetically obese mice and rats, neurologically obese rats, lean men and women, and obese men. The effect is specific and can be obtained in animals and humans without reports or signs of sickness. The mechanism of the effect is unknown, but the gastric vagal fibers are necessary for the effect. This has led to the hypothesis that the satiety effect is due to activation of vagal afferent fibers that inhibit the central control system of feeding by CCK acting directly on recently described vagal CCK receptors and/or indirectly through a gastric smooth muscle effect that vagal receptors are sensitive to.

Topics: Animals; Brain; Cholecystokinin; Eating; Feeding Behavior; Humans; Muscle, Smooth; Obesity; Peptide Fragments; Satiation; Sincalide; Stomach; Vagotomy; Vagus Nerve

CCK is understood to play a major role in appetite regulation. Difficulties in measuring CCK have limited the potential to assess its profile in relation to food-induced satiety. Improvements in methodology and progress in theoretical understanding of satiety/satiation make it timely for this to be revisited.. First, examine how physiologically relevant postprandial CCK8/33(s) profiles are influenced by fat (HF) or carbohydrate (HCHO) meals. Second, to examine relationships between postprandial CCK and profiles of satiety (hunger/fullness) and satiation (meal size).. Sixteen overweight/obese adults (11 females/5 males) participated in a randomised-crossover study (46 years, 29.8 kg/m(2)) in a university research centre. Plasma was collected preprandially and for 180 min postprandially. Simultaneously, ratings of hunger/fullness were tracked for 180 min before an ad libitum lunch was provided.. CCK8/33(s) levels increased more rapidly and reached a higher peak following HF compared to HCHO breakfast (F(1,15)=14.737, p<0.01). Profiles of hunger/fullness did not differ between conditions (F(1,15)=0.505, p=0.488; F(1,15)=2.277, p=0.152). There was no difference in energy intake from the ad libitum meal (HF-3958 versus HCHO-3925 kJ; t(14)=0.201, p=0.844). CCK8/33(s) profiles were not associated with subjective appetite during early and late phases of satiety; nor was there an association between CCK8/33(s) and meal size.. These results demonstrate CCK levels were higher after HF meal compared to HCHO isocaloric meal. There was no association between CCK levels and intensity of satiety, or with meal size. Under these circumstances, CCK does not appear to play a unique independent role in satiety/satiation. CCK probably acts in conjunction with other peptides and the action of the stomach.

Topics: Adult; Appetite Regulation; Blood Glucose; Cross-Over Studies; Diet, High-Fat; Dietary Carbohydrates; Female; Humans; Insulin; Male; Middle Aged; Obesity; Postprandial Period; Satiation; Sincalide

To investigate appetite responses over 4 h to fructose beverages in obese men, relative to glucose and whey protein. Second, to investigate the effect of combining whey and fructose on postprandial appetite hormones.. Randomized, double-blind crossover study of four beverages (1.1 MJ) containing 50 g of whey, fructose, glucose or 25 g whey+25 g fructose. Blood samples and appetite ratings were collected for 4 h then a buffet meal was offered.. Twenty-eight obese men (age: 57.0+/-1.6 years, body mass index: 32.5+/-0.6 kg/m(2)).. Plasma ghrelin (total), glucagon-like peptide-1 (GLP-1 7-36), cholecystokinin-8, glucose, insulin and appetite ratings were assessed at baseline and 30, 45, 60, 90, 120, 180, 240 min after beverages, followed by measurement of ad libitum energy intake.. Fructose produced lower glycaemia and insulinaemia compared to the glucose treatment (P<0.0001); whereas postprandial ghrelin, GLP-1 and cholecystokinin responses were similar after both treatments. Whey protein produced a prolonged (2-4 h) suppression of ghrelin (P=0.001) and elevation of GLP-1 (P=0.002) and cholecystokinin (P=0.003) that were reduced when combined with fructose, while glucose and insulin responses were similar. Energy intake after 4 h was independent of beverage type (glucose 4.7+/-0.2 MJ; fructose 4.9+/-0.3 MJ; whey 4.6+/-0.3 MJ; whey/fructose 4.8+/-0.3 MJ; P>0.05).. In obese men, fructose- and glucose-based beverages had similar effects on appetite and associated regulatory hormones, independent of the differing glycaemic and insulinaemic responses. The contrasting profile of plasma ghrelin, GLP-1 and cholecystokinin after whey protein consumption did not impact on ad libitum intake 4 h later and was attenuated when 50% of whey was replaced with fructose.

Topics: Appetite; Beverages; Blood Glucose; Cholecystokinin; Cross-Over Studies; Dietary Carbohydrates; Double-Blind Method; Energy Intake; Fructose; Ghrelin; Glucagon-Like Peptide 1; Glucose; Humans; Insulin; Male; Middle Aged; Milk Proteins; Obesity; Peptide Fragments; Peptide Hormones; Whey Proteins

The aim of this study was to test the hypothesis that gastric distension can enhance the effect of cholecystokinin (CCK) on reduction of food intake in men and women. Eight normal-weight subjects of each gender were tested four times each with either CCK or saline infusion crossed with gastric distension or no distension. Intravenous infusion of a low dose of CCK octapeptide (CCK-8; 112 ng/min for 23 min) combined with a subthreshold gastric distension induced by a water-filled balloon (300 ml) resulted in a significant (means +/- SED: 191 +/- 61 g in men, 209 +/- 61 g in women, and 200 +/- 43 g combined) reduction in intake of a liquid meal compared with saline infusion and unfilled gastric balloon. This combined effect was the result of a large and significant CCK effect when the stomach was distended (CCK vs. saline with distension: 169 +/- 43 g) and a small and insignificant distension effect (distension vs. no distension without CCK: 31 +/- 43 g). The CCK effect alone on intake (CCK vs. saline) without distension was not significant in men (72 +/- 61 g) but was significant in women (121 +/- 61 g). These results are consistent with the hypothesis that CCK's suppression of food intake is enhanced when the stomach is distended.

Topics: Adult; Appetite Depressants; Catheterization; Eating; Female; Gastric Dilatation; Gastric Emptying; Humans; Male; Obesity; Sex Factors; Sincalide; Stomach

Six of eight obese men ate significantly less food during an intravenous infusion of the C-terminal octapeptide of cholecystokinin (CCK-8, 4 ng . kg-1 . min-1) than during a saline infusion in a double blind experimental paradigm. Subjects stopped eating sooner during CCK-8. CCK-8 did not change the rate of eating. No overt side effects were reported or observed. This is the first report of the satiety effect of CCK-8 in obese humans and it suggests that the therapeutic potential of CCK-8 for the treatment of obesity deserves investigation.

Topics: Body Weight; Cholecystokinin; Eating; Energy Intake; Humans; Male; Obesity; Peptide Fragments; Sincalide

Intestinal nutrient sensing regulates food intake and energy metabolism by acting locally and relaying nutritional status to the brain. It is unclear whether these mechanisms are altered in obese humans.. We aimed to investigate differences in duodenal nutrient sensing in humans with or without obesity and the effects of transiently blocking vagal transmission on nutrient sensing, hunger, and appetite.. In a single-blinded, randomized, cross-over design, subjects with or without obesity (n = 14 and n = 11, respectively) were infused intraduodenally with saline or a combination of glucose and oleic acid for 90 min (glucose load: 22.5 g, 1 kcal/min; oleic acid load: 10 g, 1 kcal/min) in the presence or absence of local anesthetic (benzocaine). Blood was sampled at 10-min intervals (120-240 min) and 15-min intervals until termination of the study for measurements of gut hormones, insulin, leptin, and C-peptide. Hunger and satiety sensations were scored using the visual analog scale, and hepatic glucose production and glucose oxidation rates were measured.. Duodenal nutrient infusion in lean subjects led to a 65% drop in acyl ghrelin release and robustly increased cholecystokinin 8 (CCK-8) release (65%; P = 0.023); benzocaine infusion delayed this response (2-factor repeated-measures analysis of variance, P = 0.0065). In contrast, subjects with obesity had significantly blunted response to nutrient infusion, and no further effects were observed with benzocaine. Additionally, significant delays were observed in peptide YY (3-36), pancreatic polypeptide, glucose inhibitory peptide, and glucagon-like peptide 1 (7-36) response. No significant interactions were found between body mass index (BMI) or baseline hormone levels and areas under the curve for hormones except CCK-8 (BMI, P = 0.018; baseline CCK, P = 0.013). Nutrient-induced hunger and satiety sensations were impeded by benzocaine only in the lean cohort. Hunger and satiety sensations in subjects with obesity were not responsive to nutrient entry into the duodenum, and no additional effects were observed by blocking neural signaling.. Nutrient-induced gut hormone release and response to transient vagal blockade are significantly blunted in subjects with obesity. This trial was registered at clinicaltrials.org as NCT02537314.

Topics: Appetite; Benzocaine; Gastrointestinal Hormones; Humans; Nutrients; Obesity; Oleic Acid; Satiety Response; Sincalide

A group of peptide-based, long-acting, stable, highly selective cholecystokinin 1 receptor (CCK-1R) agonists with the potential to treat obesity has been identified and characterized, based on systematic investigation of synthetic CCK-8 analogues with N-terminal linkage to fatty acids. Sulfated Tyr in such compounds was stable in neutral buffer. CCK-1R selectivity was achieved mostly by introducing d- N-methyl-Asp instead of Asp at the penultimate position of CCK-8. Our compound 9 (NN9056) showed similar in vitro CCK-1R potency and CCK-1R affinity as CCK-8, very high selectivity for CCK-1R over the cholecystokinin 2 receptor (CCK-2R), strong reduction of food intake in lean pigs for up to 48 h after one subcutaneous injection without adverse effects, a plasma half-life of 113 h in minipigs after intravenous injection, and acceptable chemical stability in a neutral liquid formulation. In addition, we found a highly selective CCK-2R agonist by replacing Gly in a CCK-8 derivative with Glu.

Topics: Animals; Anti-Obesity Agents; Female; Humans; Molecular Structure; Obesity; Receptors, Cholecystokinin; Sincalide; Structure-Activity Relationship; Swine

Research shows that rats and humans on a high-fat diet (HFD) are less sensitive to satiety signals known to act via vagal afferent pathways. We hypothesize that HFD causes an upregulation of 2-pore domain potassium channels, resulting in hyperpolarization of nodose ganglia (NG) and decreased vagal response to satiety signals, which contribute to hyperphagia. We show that a 2-week HFD caused an upregulation of 2-pore domain TWIK-related spinal cord K+ (TRESK) and TWIK-related acid-sensitive K+ 1 (TASK1) channels by 330% ± 50% and 60% ± 20%, respectively, in NG. Patch-clamp studies of isolated NG neurons demonstrated a decrease in excitability. In vivo single-unit NG recordings showed that a 2-week HFD led to a 55% reduction in firing frequency in response to CCK-8 or leptin stimulation. NG electroporation with TRESK siRNA restored NG responsiveness to CCK-8 and leptin. Rats fed a 2-week HFD consumed ~40% more calories compared with controls. Silencing NG TRESK but not TASK1 channel expression in HFD-fed rats restored normal calorie consumption. In conclusion, HFD caused upregulation of TRESK channels, resulting in NG hyperpolarization and decreased vagal responsiveness to satiety signals. This finding provides a pharmacological target to prevent or treat HFD-induced hyperphagia.

Topics: Animals; Diet, High-Fat; Energy Intake; Gene Silencing; Homeostasis; Humans; Leptin; Male; Nerve Tissue Proteins; Neurons; Obesity; Potassium; Potassium Channels; Potassium Channels, Tandem Pore Domain; Rats; Rats, Sprague-Dawley; RNA, Small Interfering; Sincalide; Spinal Cord; Transcriptome; Up-Regulation; Vagus Nerve

The sites of action regulating meal size (MS) and intermeal interval (IMI) length by glucagon like peptide-1 (7-36) (GLP-1 (7-36)) and cholecystokinin-8 (CCK-8) reside in the areas supplied by the two major branches of the abdominal aorta, celiac and cranial mesenteric arteries. We hypothesized that infusing GLP-1 near those sites reduces body weight (BW) and adding CCK-8 to this infusion enhances the reduction. Here, we measured BW in diet-induced obese (DIO) male rats maintained and tested on normal rat chow and infused with saline, GLP-1 (0.5nmol/kg) and GLP-1+CCK-8 (0.5nmol/kg each) in the aorta once daily for 21days. We found that GLP-1 and GLP-1+CCK-8 decrease BW relative to saline vehicle and GLP-1+CCK-8 reduced it more than GLP-1 alone. Reduction of BW by GLP-1 alone was accompanied by decreased 24-h food intake, first MS, duration of first meal and number of meals, and an increase in latency to first meal. Reduction of BW by the combination of the peptides was accompanied by decrease 24-h food intake, first MS, duration of first meal and number of meals, and increase in the IMI length, satiety ratio and latency to first meal. In conclusion, GLP-1 reduces BW and CCK-8 enhances this reduction if the peptides are given near their sites of action.

Topics: Animals; Anti-Obesity Agents; Aorta; Cholecystokinin; Diet, High-Fat; Disease Models, Animal; Drug Therapy, Combination; Eating; Feeding Behavior; Glucagon-Like Peptide 1; Male; Obesity; Peptide Fragments; Rats, Sprague-Dawley; Satiation; Time Factors; Weight Loss

We hypothesized that exogenous gastrin releasing peptide-29 (GRP-29), cholecystokinin-8 (CCK-8) and their combination reduce body weight (BW). To test this hypothesis, BW was measured in four groups of diet-induced obese (DIO) male rats infused in the aorta (close to the junctions of the celiac and cranial mesenteric arteries) with saline, CCK-8 (0.5 nmol/kg), GRP-29 (0.5 nmol/kg) and CCK-8+GRP-29 (0.5 nmol/kg each) once daily for a total of 23 days. We found that CCK-8, GRP-29 and CCK-8+GRP-29 reduce BW relative to saline control. In conclusion, CCK-8, GRP-29 and their combination reduce BW in the DIO rat model. If infused near their gastrointestinal sites of action CCK-8, GRP-29 and their combination may have a role in regulating BW.

Topics: Animals; Body Weight; Cholecystokinin; Diet; Drug Therapy, Combination; Gastrin-Releasing Peptide; Gastrointestinal Agents; Infusions, Parenteral; Male; Obesity; Peptide Fragments; Rats; Weight Loss

In an effort to mimic in part the redundancy of satiety peptides involved in energy homeostasis, the combined benefits of the well-established satiety peptide CCK8 and an apparently anorectic peptide obestatin were studied in Swiss albino mice. The optimal dose of obestatin that was required to give the most pronounced effect with CCK8 was worked out by varying the concentration of obestatin while keeping CCK8 concentration constant at 200 nmol/KgBW. Mice administered 160 nmol obestatin and 200 nmol CCK8 per kilogram body weight showed the most drastic reduction in food intake. Gain in body weight was arrested after day four during the eight day experiment. These studies reemphasize the beneficial effects imparted by co-administration of obestatin and CCK8 and their potential use towards countering obesity.

Topics: Animals; Body Weight; Eating; Lipid Metabolism; Male; Mice; Obesity; Peptide Hormones; Sincalide

Glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK) exert important complementary beneficial metabolic effects. This study assessed the biological actions and therapeutic utility of a novel (pGlu-Gln)-CCK-8/exendin-4 hybrid peptide compared with the stable GLP-1 and CCK mimetics exendin-4 and (pGlu-Gln)-CCK-8, respectively. All peptides significantly enhanced in vitro insulin secretion. Administration of the peptides, except (pGlu-Gln)-CCK-8 alone, in combination with glucose significantly lowered plasma glucose and increased plasma insulin in mice. All treatments elicited appetite-suppressive effects. Twice-daily administration of the novel (pGlu-Gln)-CCK-8/exendin-4 hybrid, (pGlu-Gln)-CCK-8 alone, or (pGlu-Gln)-CCK-8 in combination with exendin-4 for 21 days to high-fat-fed mice significantly decreased energy intake, body weight, and circulating plasma glucose. HbA1c was reduced in the (pGlu-Gln)-CCK-8/exendin-4 hybrid and combined parent peptide treatment groups. Glucose tolerance and insulin sensitivity also were improved by all treatment modalities. Interestingly, locomotor activity was decreased in the hybrid peptide group, and these mice also exhibited reductions in circulating triglyceride and cholesterol levels. Pancreatic islet number and area, as well β-cell area and insulinotropic responsiveness, were dramatically improved by all treatments. These studies highlight the clear potential of dual activation of GLP-1 and CCK1 receptors for the treatment of type 2 diabetes.

Topics: Animals; Blood Glucose; Diabetes Mellitus, Type 2; Diet, High-Fat; Exenatide; Glucagon; Insulin; Mice; Obesity; Peptides; Satiation; Sincalide; Venoms

Apolipoprotein AIV (Apo AIV) and cholecystokinin (CCK) are secreted in response to fat consumption, and both cause satiation via CCK 1 receptor (CCK-1R)-containing vagal afferent nerves to the nucleus of the solitary tract (NTS), where Apo AIV is also synthesized. Fasted male Long-Evans rats received ip CCK-8 or fourth-ventricular (i4vt) Apo AIV alone or in combination. Food intake and c-Fos proteins (a product of the c-Fos immediate-early gene) were assessed. i4vt Apo AIV and/or ip CCK at effective doses reduced food intake and activated c-Fos proteins in the NTS and hypothalamic arcuate nucleus and paraventricular nucleus. Blockade of the CCK-1R by i4vt lorglumide adjacent to the NTS attenuated the satiating and c-Fos-stimulating effects of CCK and Apo AIV, alone or in combination. Maintenance on a high-fat diet (HFD) for 10 weeks resulted in weight gain and attenuation of both the behavioral and c-Fos responses to a greater extent than occurred in low-fat diet-fed and pair-fed HFD animals. These observations suggest that NTS Apo AIV or/and peripheral CCK requires vagal CCK-1R signaling to elicit satiation and that maintenance on a HFD reduces the satiating capacity of these 2 signals.

Topics: Animals; Apolipoproteins A; Appetite Depressants; Appetite Regulation; Appetite Stimulants; Appetitive Behavior; Behavior, Animal; Cholecystokinin; Diet, High-Fat; Hormone Antagonists; Infusions, Intraventricular; Injections, Intraperitoneal; Male; Nerve Tissue Proteins; Neurons, Afferent; Obesity; Rats; Rats, Long-Evans; Receptor, Cholecystokinin A; Recombinant Proteins; Sincalide; Solitary Nucleus

Cholecystokinin (CCK) is a gastrointestinal hormone that has been proposed as a potential therapeutic option for obesity-diabetes. As such, (pGlu-Gln)-CCK-8 is an N-terminally modified CCK-8 analogue with improved biological effectiveness over the native peptide.. The current study has examined the in vitro stability, biological activity and in vivo therapeutic applicability of a novel second generation mini-PEGylated form of (pGlu-Gln)-CCK-8, (pGlu-Gln)-CCK-8[mPEG].. (pGlu-Gln)-CCK-8[mPEG] was completely resistant to enzymatic degradation and in addition displayed similar insulinotropic (p<0.05 to p<0.001) and satiating effects (p<0.01 to p<0.001) as (pGlu-Gln)-CCK-8. This confirmed the capability of (pGlu-Gln)-CCK-8[mPEG] to bind to and activate the CCK receptor. Sub-chronic twice daily injection of (pGlu-Gln)-CCK-8[mPEG] in high fat fed mice for 35days significantly decreased body weight gain (p<0.05), food intake (p<0.01 to p<0.001) and triacylglycerol deposition in liver (p<0.001) and muscle (p<0.001). Furthermore, (pGlu-Gln)-CCK-8[mPEG] markedly improved intraperitoneal glucose tolerance (p<0.05) and insulin sensitivity (p<0.001). Despite this therapeutic profile, once daily injection of (pGlu-Gln)-CCK-8[mPEG] in high fat fed mice for 33days, at the same dose, was not associated with alterations in food intake and body weight. In addition, metabolic responses to exogenous glucose and insulin injection were similar to saline treated controls.. These studies emphasise the therapeutic potential of (pGlu-Gln)-CCK-8[mPEG] and similar molecules.. A more detailed analysis of the dose and administration schedule employed for (pGlu-Gln)-CCK-8[mPEG] could provide a novel and effective compound to treat obesity-diabetes.

Topics: Animals; Cells, Cultured; Diabetes Mellitus; Eating; Insulin; Insulin Resistance; Insulin Secretion; Male; Mice; Obesity; Polyethylene Glycols; Sincalide

Deficits in satiation signaling during obesogenic feeding have been proposed to play a role in hyperphagia and weight gain in animals prone to become obese. However, whether this impaired signaling is due to high fat (HF) feeding or to their obese phenotype is still unknown. Therefore, in the current study, we examined the effects of CCK-8 (0.5, 1.0, 2.0, and 4.0 μg/kg) on suppression of food intake of HF-fed obese prone (OP) and resistant (OR) rats. Additionally, we determined the role of endogenous CCK in lipid-induced satiation by measuring plasma CCK levels following a lipid gavage, and tested the effect of pretreatment with devazepide, a CCK-1R antagonist on intragastric lipid-induced satiation. Finally, we examined CCK-1R mRNA levels in the nodose ganglia. We show that OP rats have reduced feeding responses to the low doses of exogenous CCK-8 compared to OR rats. Furthermore, OP rats exhibit deficits in endogenous CCK signaling, as pretreatment with devazepide failed to abolish the reduction in food intake following lipid gavage. These effects were associated with reduced plasma CCK after intragastric lipid in OP but not OR rats. Furthermore, HF feeding resulted in downregulation of CCK-1Rs in the nodose ganglia of OP rats. Collectively, these results demonstrate that HF feeding leads to impairments in lipid-induced CCK satiation signaling in obese-prone rats, potentially contributing to hyperphagia and weight gain.

Topics: Animals; Cholecystokinin; Devazepide; Diet, High-Fat; Dietary Fats; Down-Regulation; Eating; Feeding Behavior; Hormone Antagonists; Male; Obesity; Rats; Signal Transduction; Sincalide

The current study has determined the ability of (pGlu-Gln)-CCK-8 to counter the development of diet-induced obesity-diabetes and examined persistence of beneficial metabolic effects in high fat and ob/ob mice, respectively. Twice daily injection of (pGlu-Gln)-CCK-8 in normal mice transferred to a high fat diet reduced energy intake (p < 0.001), body weight (p < 0.01), circulating insulin and LDL-cholesterol (p < 0.001) and improved insulin sensitivity (p < 0.001) as well as oral and intraperitoneal (p < 0.001) glucose tolerance. Energy intake, body weight, circulating insulin and glucose tolerance of (pGlu-Gln)-CCK-8 mice were similar to lean controls. In addition, (pGlu-Gln)-CCK-8 prevented the effect of high fat feeding on triacylglycerol accumulation in liver and muscle. Interestingly, (pGlu-Gln)-CCK-8 significantly (p < 0.001) elevated pancreatic glucagon content. Histological examination of the pancreata of (pGlu-Gln)-CCK-8 mice revealed no changes in islet number or size, but there was increased turnover of beta-cells with significantly (p < 0.001) increased numbers of peripherally located alpha-cells, co-expressing both glucagon and GLP-1. Beneficial metabolic effects were observed similarly in ob/ob mice treated twice daily with (pGlu-Gln)-CCK-8 for 18 days, including significantly reduced energy intake (p < 0.05), body weight (p < 0.05 to p < 0.01), circulating glucose (p < 0.05 to p < 0.01) and insulin (p < 0.05 to p < 0.001) and improved glucose tolerance (p < 0.05) and insulin sensitivity (p < 0.001). Notably, these beneficial effects were still evident 18 days following cessation of treatment. These studies emphasize the potential of (pGlu-Gln)-CCK-8 for the treatment of obesity-diabetes.

Topics: Animals; Blood Glucose; Body Weight; Diabetes Mellitus, Experimental; Dietary Fats; Eating; Glucagon; Glucose Tolerance Test; Insulin; Insulin Resistance; Lipids; Mice; Mice, Obese; Obesity; Pancreas; Receptors, Cholecystokinin; Sincalide

Compromise of gastric inhibitory polypeptide (GIP) receptor action and activation of cholecystokinin (CCK) receptors represent mechanistically different approaches to the possible treatment of obesity-related diabetes. In the present study, we have compared the individual and combined effects of (Pro(3))GIP[mPEG] and (pGlu-Gln)-CCK-8 as an enzymatically stable GIP receptor antagonist and CCK receptor agonist molecule, respectively.. Twice-daily injections of (pGlu-Gln)-CCK-8 alone and in combination with (Pro(3))GIP[mPEG] in high-fat-fed mice for 34 days significantly decreased the energy intake throughout the entire study (P<0.05 to P<0.01). Body weights were significantly depressed (P<0.05 to P<0.01) in all treatment groups from day 18 onwards. Administration of (pGlu-Gln)-CCK-8, (Pro(3))GIP[mPEG] or a combination of both peptides significantly (P<0.01 to P<0.001) decreased the overall glycaemic excursion in response to both oral and intraperitoneal glucose challenge when compared with the controls. Furthermore, oral glucose tolerance returned to lean control levels in all treatment groups. The beneficial effects on glucose homeostasis were not associated with altered insulin levels in any of the treatment groups. In keeping with this, the estimated insulin sensitivity was restored to control levels by twice-daily treatment with (pGlu-Gln)-CCK-8, (Pro(3))GIP[mPEG] or a combination of both peptides. The blood lipid profile on day 34 was not significantly different between the high-fat controls and all treated mice.. These studies highlight the potential of (pGlu-Gln)-CCK-8 and (Pro(3))GIP[mPEG] in the treatment of obesity-related diabetes, but there was no evidence of a synergistic effect of the combined treatment.

Topics: Animals; Anti-Obesity Agents; Blood Glucose; Body Weight; Diabetes Mellitus, Type 2; Diet, High-Fat; Drug Therapy, Combination; Energy Intake; Insulin Resistance; Male; Mice; Obesity; Receptors, Cholecystokinin; Receptors, Gastrointestinal Hormone; Sincalide; Time Factors

Cholecystokinin (CCK) is a gastrointestinal hormone with potential therapeutic promise for obesity-diabetes. The present study examined the effects of twice daily administration of the N-terminally modified stable CCK-8 analogue, (pGlu-Gln)-CCK-8, on metabolic control and hypothalamic gene expression in high fat fed mice. Sub-chronic twice daily injection of (pGlu-Gln)-CCK-8 for 16 days significantly decreased body weight (p<0.05), energy intake (p<0.01), circulating blood glucose (p<0.001), and plasma insulin (p<0.001) compared to high fat controls. Furthermore, (pGlu-Gln)-CCK-8 markedly improved glucose tolerance (p<0.05) and insulin sensitivity (p<0.05). Assessment of hypothalamic gene expression on day 16 revealed significantly elevated NPY (p<0.05) and reduced POMC (p<0.05) and MC4R (p<0.05) mRNA expression in (pGlu-Gln)-CCK-8 treated mice. High fat feeding or (pGlu-Gln)-CCK-8 treatment had no significant effects on hypothalamic gene expression of receptors for leptin, CCK₁ and GLP-1. These studies underscore the potential of (pGlu-Gln)-CCK-8 for the treatment of obesity-diabetes and suggest modulation of NPY and melanocortin related pathways may be involved in the observed beneficial effects.

Topics: Animals; Blood Glucose; Cholecystokinin; Diet, High-Fat; Energy Intake; Gene Expression Regulation; Glucagon-Like Peptide 1; Humans; Hypothalamus; Insulin; Leptin; Male; Mice; Obesity; Peptide Fragments; Peptides; Pro-Opiomelanocortin; Receptor, Melanocortin, Type 4

The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK) are gastrointestinal peptides with important physiological effects. However, rapid enzymatic degradation results in short-lived biological actions.. This study has examined metabolic actions of exendin-4, GIP[mPEG] and a novel CCK-8 analogue, (pGlu-Gln)-CCK-8 as enzymatically stable forms of GLP-1, GIP and CCK, respectively.. All peptides significantly (p < 0.01-p < 0.001) stimulated insulin secretion from BRIN BD11 cells, and acute in vivo experiments confirmed prominent antihyperglycaemic and insulinotropic responses to GLP-1 or GIP receptor activation in normal mice. Twice daily injection of (pGlu-Gln)-CCK-8 alone and in combination with exendin-4 or GIP[mPEG] in high fat-fed mice significantly decreased accumulated food intake (p < 0.05-p < 0.01), body weight gain (p < 0.05-p < 0.01) and improved (p < 0.05) insulin sensitivity in high fat-fed mice. However, there was no evidence for superior effects compared to (pGlu-Gln)-CCK-8 alone. Combined treatment of (pGlu-Gln)-CCK-8 and exendin-4 resulted in significantly (p < 0.05) lowered circulating glucose levels and improved (p < 0.05) intraperitoneal glucose tolerance. These effects were superior to either treatment regime alone but not associated with altered insulin concentrations. A single injection of (pGlu-Gln)-CCK-8, or combined with exendin-4, significantly (p < 0.05) lowered blood glucose levels 24 h post injection in untreated high fat-fed mice.. This study highlights the potential of (pGlu-Gln)-CCK-8 alone and in combination with incretin hormones for the treatment of type 2 diabetes.

Topics: Animals; Anti-Obesity Agents; Appetite Regulation; Cell Line; Diabetes Mellitus, Type 2; Diet, High-Fat; Drug Therapy, Combination; Exenatide; Gastric Inhibitory Polypeptide; Hyperglycemia; Hypoglycemic Agents; Incretins; Insulin; Insulin Resistance; Insulin Secretion; Insulin-Secreting Cells; Male; Mice; Mice, Inbred Strains; Obesity; Peptides; Rats; Sincalide; Time Factors; Venoms

Cholecystokinin (CCK) is a rapidly degraded gastrointestinal peptide that stimulates satiety and insulin secretion. We aimed to investigate the beneficial weight-lowering and metabolic effects of the novel N-terminally modified CCK analogue, (pGlu-Gln)-CCK-8.. The biological actions of (pGlu-Gln)-CCK-8 were comprehensively evaluated in pancreatic clonal BRIN BD11 cells and in vivo in high-fat-fed and ob/ob mice.. (pGlu-Gln)-CCK-8 was completely resistant to enzymatic degradation and its satiating effects were significantly (p < 0.05 to p < 0.001) more potent than CCK-8. In BRIN-BD11 cells, (pGlu-Gln)-CCK-8 exhibited enhanced (p < 0.01 to p < 0.001) insulinotropic actions compared with CCK-8. When administered acutely to high-fat-fed or ob/ob mice, (pGlu-Gln)-CCK-8 improved glucose homeostasis. Sub-chronic twice daily injections of (pGlu-Gln)-CCK-8 in high-fat-fed mice for 28 days significantly decreased body weight (p < 0.05 to p < 0.001), accumulated food intake (p < 0.05 to p < 0.001), non-fasting glucose (p < 0.05) and triacylglycerol deposition in pancreatic (p < 0.01), adipose (p < 0.05) and liver (p < 0.001) tissue, and improved oral (p < 0.05) and i.p. (p < 0.05) glucose tolerance and insulin sensitivity (p < 0.001). Similar observations were noted in ob/ob mice given twice daily injections of (pGlu-Gln)-CCK-8. In addition, these beneficial effects were not reproduced by simple dietary restriction and were not associated with changes in energy expenditure. There was no evidence for development of tolerance to (pGlu-Gln)-CCK-8, and analysis of histology or blood-borne markers for pancreatic, liver and renal function in mice treated with (pGlu-Gln)-CCK-8 suggested little abnormal pathology.. These studies emphasise the potential of (pGlu-Gln)-CCK-8 for the alleviation of obesity and insulin resistance.

Topics: Animals; Cholecystokinin; Comorbidity; Diabetes Mellitus; Disease Models, Animal; Glucose; Homeostasis; Insulin Resistance; Male; Mice; Mice, Obese; Obesity; Sincalide

Obesity of middle-aged mammals is followed at old age by anorexia and cachexia leading to sarcopenia. Complex age- and body composition-related alterations in the regulation of energy homeostasis may be assumed in the background. We aimed to test the possible contribution of age- and body composition-related changes of satiety responses to catabolic brain-gut-axis peptide cholecystokinin (CCK) to these alterations in energy balance during aging. Male Wistar rats (6-8 animals/group) aged 2 months (juvenile), 3 months (young adult), 6 or 12 months (early or late middle-aged), and 24 months (old) were injected intraperitoneally with 5 μg CCK-8 prior to re-feeding after 48-h food-deprivation. CCK suppressed re-feeding in young adult (26.8%), early middle-aged (35.5%), and old (31.4%) animals, but not in juvenile or late middle-aged rats (one-way ANOVA). CCK-resistance of 12 months old rats was prevented by life-long calorie-restriction: CCK suppressed their re-feeding by 46.8%. Conversely, in highfat diet-induced obese 6 months old rats CCK failed to suppress re-feeding. In conclusion, age-related changes in satiety responsiveness to CCK may contribute to the age-related obesity of middle-aged as well as to the anorexia of old animals. CCK-responsiveness is also influenced by body composition: calorie-restriction prevents the resistance to CCK, pre-existing obesity enhances it.

Topics: Adiposity; Age Factors; Aging; Animals; Anorexia; Body Composition; Caloric Restriction; Diet, High-Fat; Energy Metabolism; Feeding Behavior; Homeostasis; Injections, Intraperitoneal; Male; Obesity; Rats; Rats, Wistar; Satiety Response; Sincalide

Interactions between gastrointestinal signals are a part of integrated systems regulating food intake (FI). We investigated whether cholecystokinin (CCK)-8 and urocortin systems potentiate each other to inhibit FI and gastric emptying (GE) in fasted mice. Urocortin 1 and urocortin 2 (1 microg/kg) were injected ip alone or with CCK (3 microg/kg) in lean, diet-induced obese (DIO) or corticotropin-releasing factor receptor-2 (CRF(2))-deficient mice. Gastric vagal afferent activity was recorded from a rat stomach-vagus in vitro preparation. When injected separately, urocortin 1, urocortin 2, or CCK did not modify the 4-h cumulative FI in lean mice. However, CCK plus urocortin 1 or CCK plus urocortin 2 decreased significantly the 4-h FI by 39 and 27%, respectively, compared with the vehicle + vehicle group in lean mice but not in DIO mice. Likewise, CCK-urocortin-1 delayed GE in lean but not DIO mice, whereas either peptide injected alone at the same dose had no effect. CCK-urocortin 2 suppression of FI was observed in wild-type but not CRF(2)-deficient mice. Gastric vagal afferent activity was increased by intragastric artery injection of urocortin 2 after CCK at a subthreshold dose, and the response was reversed by devazepide. These data establish a peripheral synergistic interaction between CCK and urocortin 1 or urocortin 2 to suppress FI and GE through CRF(2) receptor in lean mice that may involve CCK modulation of gastric vagal afferent responsiveness to urocortin 2. Such synergy is lost in DIO mice, suggesting a resistance to the satiety signaling that may contribute to maintain obesity.

Topics: Animals; Cholecystokinin; Drug Synergism; Eating; Gastric Emptying; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Obese; Models, Biological; Obesity; Peptide Fragments; Rats; Receptors, Corticotropin-Releasing Hormone; Satiation; Signal Transduction; Stomach; Urocortins; Vagus Nerve

Little is known regarding satiety effects of systemically administered cholecystokinin (CCK-8) in propensity or resistance to dietary-induced obesity (DIO), and of its effect under conditions of melanocortin-3/4R blockade. We found that CCK-8 exerted greater satiety effects in DIO-prone but not DIO-resistant rats, and this occurred only when the rats were placed on a high-fat (HF) diet, when DIO-prone rats failed to compensate for the greater energy density of the diet. CCK-8 also suppressed intake stimulated by melanocortin-3/4R antagonist, SHU9119, but only after 24h of increased feeding. This suggests that under both of these conditions, responsiveness to CCK's satiety effect is not so much affected by a HF diet or significant increases in body weight per se, but by a failure to rapidly limit food intake to that needed only for metabolic need. Identification of an early feeding mediator that is most strongly activated by a HF diet or by an acute challenge to energy homeostasis should provide an ideal anti-obesity target adjunct to CCK-8.

Topics: Animals; Diet; Male; Melanocyte-Stimulating Hormones; Obesity; Rats; Rats, Sprague-Dawley; Receptor, Melanocortin, Type 3; Receptor, Melanocortin, Type 4; Satiety Response; Sincalide

Leptin, the product of the obese gene, reduces food intake and body weight in rats and mice, whereas administration of the gut-peptide CCK reduces meal size but not body weight. In the current experiments, we report that repeated daily combination of intracerebroventricular leptin and intraperitoneal CCK results in significantly greater loss of body weight than does leptin alone. However, leptin plus CCK treatment does not synergistically reduce the size of individual 30-min sucrose meals during this period, and the effect of leptin-CCK combination on daily chow intake, while significant, is small compared with the robust effects on body weight loss. This synergistic effect on body weight loss depends on a peripheral action of CCK and a central action of leptin. These data suggest a previously unsuspected role for CCK in body weight regulation that may not depend entirely on reduction of feeding behavior and suggest a strategy for enhancing the effects of leptin in leptin-resistant obese individuals.

Topics: Adipose Tissue; Animals; Body Weight; Brain Chemistry; Carrier Proteins; Dietary Sucrose; Dose-Response Relationship, Drug; Drug Synergism; Eating; Injections, Intraperitoneal; Injections, Intraventricular; Leptin; Male; Obesity; Rats; Rats, Sprague-Dawley; Receptors, Cell Surface; Receptors, Leptin; Satiation; Sincalide

The Koletsky ("corpulent) obese rat is homozygous for an autosomal recessive mutation of the leptin receptor (Lepr) that results in hyperphagia, obesity, and hyperlipidemia. Unlike the Lepr mutation that characterizes the fatty Zucker rat (Lepr(fa)), the Koletsky mutation (Lepr(fak)) is null. Because the Lepr(fak) mutation is null, exogenous leptin should have no effect on body weight or food intake in fa(k)/fa(k) rats. We confirmed that prediction: murine leptin, administered into the third ventricle for 5 consecutive days, did not affect daily food intake or body weight in fa(k)/fa(k) rats but produced dose-related inhibitions of food intake and body weight in +/+ and +/fa(k) rats. Although fa(k)/fa(k) rats did not respond to leptin, their response to CCK-8 (4 microg/kg ip) injected before 30-min test meals of 10% sucrose was not different from that of +/+ or +/fa(k) rats. These results demonstrate that the fa(k)/fa(k) rat is a good model in which to analyze the controls of food intake, energy expenditure, and energy storage in the absence of leptin effects.

Topics: Animals; Carrier Proteins; Dietary Sucrose; Disease Models, Animal; Eating; Injections, Intraventricular; Leptin; Obesity; Rats; Rats, Mutant Strains; Receptors, Cell Surface; Receptors, Leptin; Satiation; Sincalide; Weight Gain; Weight Loss

Gastric emptying plays an important role in regulating food intake. This study was designed to investigate whether intraperitoneally injected urocortin reduces gastric emptying, feeding, and body weight in lean and ob/ob obese mice.. Food intake and body weight were measured after intraperitoneal injections of one of the following: urocortin, deamidated form of urocortin (urocortin OH), corticotropin-releasing factor (CRF), CRF6-33, cholecystokinin octapeptide (CCK-8), and leptin in 16-hour food-deprived animals. Gastric emptying was assessed 2, 4, or 8 hours after intraperitoneal injection. Repeated injections of urocortin were continued for 5 days in ob/ob mice.. Urocortin (0.003-3 nmol) dose-dependently and potently decreased food intake and body weight gain in lean mice. The ranking order of potency was urocortin > urocortin OH >/= CRF > CCK-8 > CRF6-33 > leptin. Gastric emptying was also potently reduced by urocortin with a similar ranking order of potency of urocortin > CRF > urocortin OH > CCK-8. Simultaneous administration of urocortin and CRF receptor antagonist, alpha-helical CRF9-41, blocked the effects of urocortin. Urocortin reduced food intake and body weight gain, as well as the rate of gastric emptying, in ob/ob mice, which was significantly faster than that of lean mice. Five daily injections of urocortin significantly lowered body weight and improved glycemic control in ob/ob mice.. The urocortin-induced decrease in food intake and body weight in lean and ob/ob mice is closely related to gastric emptying and opens new possibilities for the treatment of obesity.

Topics: Animals; Blood Glucose; Body Weight; Corticotropin-Releasing Hormone; Dose-Response Relationship, Drug; Eating; Gastric Emptying; Injections, Intraperitoneal; Leptin; Male; Mice; Obesity; Proteins; Reference Values; Sincalide; Urocortins

Rats postnatally overnourished due to a reduced litter size become persistently overweight. A presumed pathophysiological mechanism consists of a change in the activity and responsiveness to neuropeptides of the neuronal system regulating feeding behavior. This study aimed to find differences in the action of neuropeptide Y, orexin-A and cholecystokinin on single unit activity of the ventromedial hypothalamic nucleus in brain slices of normal and postnatally overfed juvenile rats. NPY inhibited significantly more neurons (15 of 23) of obese than of normal rats (6 of 27; p < 0.01, chi2). Orexin-A and CCK-8S mainly activated the neurons without significant differences between the groups. In conclusion, the stronger inhibition by NPY of VMN neurons which signal satiety might contribute to increased feeding behavior in postnatally overfed rats.

Topics: Action Potentials; Age Factors; Animals; Carrier Proteins; Eating; Electrophysiology; Female; Intracellular Signaling Peptides and Proteins; Male; Neurons; Neuropeptide Y; Neuropeptides; Nootropic Agents; Obesity; Orexins; Organ Culture Techniques; Pregnancy; Rats; Rats, Wistar; Sincalide; Ventromedial Hypothalamic Nucleus

Perinatal malnutrition and growth retardation at birth are suggested to be important risk factors for the development of overweight and syndrome X in later life. Underlying mechanisms are unknown. Body weight and food intake are regulated, e.g. by hypothalamic neuropeptidergic systems which are thought to be highly vulnerable to persisting malorganization due to perinatal malnutrition. To investigate possible consequences for hypothalamic cholecystokinin-8S (CCK-8S) in the offspring, pregnant Wistar rats were fed an 8% protein diet during pregnancy and lactation (low-protein group; LP) while control mothers (CO) received a 17% protein isocaloric standard diet. LP offspring displayed underweight at birth (P < 0.05) and during suckling (P < 0.001), while leptin levels were not altered. At weaning, under basal conditions CCK-8S was decreased in LP offspring in the paraventricular hypothalamic nucleus and arcuate hypothalamic nucleus (P < 0.05), as well as in the dorsomedial hypothalamic nucleus, lateral hypothalamic area and ventromedial hypothalamic nucleus (P < 0.01). In summary, these data indicate (1) an inhibition of the satiety peptide CCK-8S in main regulators of body weight and food intake in low-protein malnourished newborn rats; (2) no direct relationship of hypothalamic CCK-8S to circulating leptin at this age; and (3) no neurochemical signs of hypothalamic CCKergic dysregulation in this animal model at the age of weaning.

Topics: Animals; Animals, Newborn; Birth Weight; Body Weight; Dietary Proteins; Disease Models, Animal; Eating; Female; Hypothalamus; Insulin Resistance; Male; Maternal-Fetal Exchange; Nutrition Disorders; Obesity; Pregnancy; Pregnancy Complications; Rats; Rats, Wistar; Sincalide

Recent studies in genetically obese and diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats suggest defects of cholecystokinin (CCK)-A receptor gene expression and CCK-A receptor-mediated biological functions such as pancreatic juice, protein, and gastric acid secretion. The present studies were undertaken to further examine CCK-A receptor gene expression and CCK-A receptor-mediated biological functions in the pancreas, stomach, and brain of OLETF rats. Expression of the CCK-A receptor gene could not be detected in the stomach, pancreas and brain by the reverse-transcription polymerase chain reaction (RT-PCR) method and Southern blotting of the PCR products. Southern blot analysis of genomic DNA from OLETF and control Long-Evans Tokushima Otsuka (LETO) rats with CCK-A receptor fragment as a probe revealed different restriction bands. Expression of the CCK-B receptor gene was observed in the stomach, pancreas, and brain in both OLETF and LETO rats by the RT-PCR method, with expression of the CCK-B receptor gene markedly enhanced in OLETF rats compared with that in LETO rats. Consistent with the defect of CCK-A receptor gene expression, CCK-A receptor-mediated biological functions were not observed in these organs. Perfused exocrine and endocrine pancreas of OLETF rats were insensitive to CCK stimulation but not to carbamylcholine stimulation. Basal gastric acid and pepsinogen secretions in OLETF rats were higher than in LETO rats. OLETF rats showed a significantly higher average daily food intake, gained body weight faster, and were heavier than LETO rats. The present study confirmed that OLETF rats have CCK-A receptor gene anomalies and demonstrated deficient CCK-A receptor-mediated biological function in the pancreas, stomach, and brain.

Topics: Animals; Arginine; Blood Glucose; Blotting, Northern; Blotting, Southern; Brain; Carbachol; DNA Primers; Gastric Acid; Gastric Mucosa; Gene Expression; Insulin; Male; Obesity; Pancreatin; Pepsinogen A; Rats; Rats, Long-Evans; Rats, Wistar; Receptor, Cholecystokinin A; Receptors, Cholecystokinin; Reverse Transcriptase Polymerase Chain Reaction; Sincalide

Cholecystokinin (CCK) is a 33-amino acid peptide with multiple functions in both the central nervous system (via CCK-B receptors) and the periphery (via CCK-A receptors). CCK mediation of satiety via the A-receptor subtype suggest a role for CCK in the management of obesity. The carboxy terminal octapeptide (CCK-8) is fully active in this regard, but is lacking in receptor selectivity, metabolic stability, and oral bioavailability. Inversion of the chirality of Asp7 in conjunction with N-methylation of Phe8 produces compound 5 which exhibits high affinity and 2100-fold selectivity for CCK-A receptors. Compound 6 (Hpa(SO3H)-Nle-Gly-Trp-Nle-MeAsp-Phe-NH2), derived from moving the N-methyl group from Phe to Asp, decreased CCK-B affinity substantially without affecting CCK-A affinity, giving a compound with 6600-fold selectivity for CCK-A receptors. These compounds inhibit food intake with nanomolar potency following intraperitoneal administration in fasted rats. In addition to greater potency, compound 6 produces weight loss in rats when administered over nine consecutive days. Intranasal administration of 6 potently inhibits feeding in beagle dogs. Compound 6 produces potent anorectic activity via the CCK-A receptor system.

Topics: Administration, Intranasal; Amino Acids; Animals; Appetite Depressants; Binding, Competitive; Body Weight; Dogs; Eating; Molecular Structure; Obesity; Oligopeptides; Peptides; Protein Binding; Rats; Receptor, Cholecystokinin A; Receptors, Cholecystokinin

Clinical as well as experimental studies in insulinopenic diabetes mellitus have demonstrated abnormal pancreatic exocrine responses to cholecystokinin (CCK). In the present study, we examined pancreatic exocrine and endocrine function in the recently developed genetically diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats and compared them with those in the control Long-Evans Tokushima Otsuka (LETO) rats of the same age. Stepwise increasing doses of CCK octapeptide (CCK-8; 0.027-7.0 nmol.kg-1.h-1) evoked a characteristic biphasic dose-response curve for pancreatic juice and protein output in the LETO rats, whereas the OLETF rats were totally insensitive to CCK-8 stimulation. However, the responsiveness and the sensitivity to both carbamylcholine and secretin were similar in the two groups. Intraduodenal infusion of casein (500 mg/h) failed to stimulate pancreatic exocrine secretion in the OLETF rats despite a greater CCK response than in the LETO rats (peak response: 8.43 +/- 0.97 vs 5.12 +/- 0.30 pmol/l in LETO, P < 0.01). Intravenous infusion of CCK-8 (4.4 nmol.kg-1.20 min-1) caused a significant increase in serum insulin concentrations and a concomitant decrease in glucose levels in the LETO rats but not in the OLETF rats. On the other hand, an intravenous bolus injection of 1.1 mmol/kg glucose caused a greater insulin release in the OLETF rats than in the LETO rats. In contrast, gastric acid secretion in the OLETF rats was significantly high in basal and in response to intravenous infusion of CCK-8 compared with that in the LETO rats. Four subcutaneous injections of 20 micrograms/kg caerulein at hourly intervals over 3 h induced acute pancreatitis in the LETO rats but did not elicit any significant increase in serum amylase or lipase activities and pancreatic wet weight or histological evidence of acute pancreatitis in the OLETF rats. These results indicate that the exocrine and endocrine pancreas of the recently developed genetically diabetic OLETF rats are totally and specifically insensitive to exogenous and endogenous CCK stimulation, whereas parietal cells in these rats are sensitive to CCK stimulation.

Topics: Acute Disease; Animals; Carbachol; Caseins; Ceruletide; Cholecystokinin; Duodenum; Gastric Acid; Glucose; Injections; Insulin; Islets of Langerhans; Male; Obesity; Pancreas; Pancreatitis; Rats; Rats, Inbred Strains; Secretin; Sincalide

This work expands recent observations that Otsuka Long-Evans Tokushima Fatty (OLETF) rats show little or no pancreatic expression of the cholecystokinin (CCK)-A receptor gene. We examined whether the CCK-A and -B receptor genes were expressed in the brain (hypothalamus) of OLETF rats in comparison with control (Long-Evans Tokushima Otsuka = LETO) rats. CCK-A receptor mRNA was detected in the hypothalamus of LETO rats but not OLETF rats. The CCK-B receptor gene was expressed in the hypothalamus in both strains. Cerebroventricular administration of CCK-8 sulfate inhibited daily food intake in LETO rats, but not in OLETF rats. These results show that in OLETF rats the absence of CCK-A receptor gene expression in the hypothalamus results in hyperphagia because of lack of satiety.

Topics: Animals; Base Sequence; Cholecystokinin; Diabetes Insipidus; Hyperphagia; Hypothalamus; Male; Molecular Sequence Data; Obesity; Polymerase Chain Reaction; Rats; Rats, Mutant Strains; Receptor, Cholecystokinin A; Receptors, Cholecystokinin; Satiation; Sincalide

Amylin has been demonstrated to produce anorexia in rodents. Its mechanism of action is unknown. We have studied the effect of amylin on food intake in mice in a variety of paradigms to determine whether it inhibits food intake by a peripheral mechanism of action. In addition, we determined its effect in genetically obese mice models and whether its effects differed in aged mice. Cholecystokinin is the prototypic satiety agent. The effects of amylin on reducing food intake were not attenuated by the cholecystokinin antagonist L-364718, suggesting that it does not produce its effect through the release of cholecystokinin. A number of gastrointestinal peptides produce anorexia by stimulating ascending vagal fibers. For this reason, we studied the effect of truncal vagotomy on the suppression of feeding induced by amylin. Vagotomy did not prevent amylin from inhibiting food intake. Amylin was equally effective at reducing food intake in genetically obese (ob/ob) and lean (ob/c) mice and in diabetic (db/db) and lean (db/c) mice. Amylin effectively suppressed food intake in mice over the age of 4-22 mo. These studies further support the role of the pancreatic hormone amylin as a peripherally acting satiety agent.

Topics: Amyloid; Analysis of Variance; Animals; Benzodiazepinones; Devazepide; Diabetes Mellitus; Eating; Injections, Intraperitoneal; Islet Amyloid Polypeptide; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Obesity; Sincalide; Vagotomy

Cholecystokinin octapeptide sulfate (CCK 8 S) appears to act via a serotonergic mechanism on several behavioral paradigms, including satiety. In the present study, CCK 8 S was found to induce slight nonsignificant serotonergic changes in hypothalamic nuclei of the normal rat. In the "cafeteria" rat, however, it increased both 5-HT and 5-HIAA levels in the ventromedial hypothalamus (VMH), 5-HT levels in the paraventricular nucleus (PVN) and decreased 5-HIAA levels in the dorsomedial hypothalamus (DMH). These data suggest that the primary site of action of CCK 8 S is in the median hypothalamus, contrasting with an absence of effect in the lateral hypothalamus (LH). The involvement of 5-HT in the effect of CCK 8 S is further suggested. However, the relationship between these neurochemical changes and CCK 8 S-induced satiety is not clear. Nonetheless, a special sensitivity to CCK 8 S of the obese "cafeteria" rat is evidenced, which contrasts with a reduced response of genetic obesity models.

Topics: Animals; Female; Hydroxyindoleacetic Acid; Hypothalamus; Obesity; Rats; Rats, Inbred Strains; Satiation; Serotonin; Sincalide

Pancreatic membrane receptors for cholecystokinin (CCK) in obese and nonobese Zucker rats were compared with the use of a biologically active [125I]iodo-CCK-8 radioprobe. Membrane homogenates from obese rats bound half the amount of radioligand in 2 h as did membranes from lean rats (specifically bound, 7.0% vs. 14.0%; P less than 0.001). The reduced binding in membranes from obese rats did not result from kinetic effects or radioligand degradation; similar rates of association and dissociation of [125I]iodo-CCK-8 were obtained in membrane preparations from both, and no differences were found in the extent of radioligand degradation in the two membrane preparations. These differences also did not reflect an effect of cell size, as pancreatic acinar cells from obese and nonobese rats had about the same perimeters (24.6 and 26.3 micron, respectively) and areas (30.1 and 34.2 micron 2, respectively). Scatchard-type plots of competitive displacement data for CCK-binding sites on pancreatic membranes from both genotypes were curvilinear and were analyzed by a two-site binding model. The Kd values for both the high (0.56 vs. 0.45 nM) and low (9.0 vs. 14 nM) affinity sites on membranes from nonobese and obese rats, respectively, were the same (P greater than 0.1), whereas the capacities for CCK in the high (365 vs. 165 fmol/mg protein) and low (1020 vs. 360 fmol/mg protein) affinity regions were significantly different (P less than 0.025). This difference in CCK receptor capacity was reflected by a reduced pancreatic protein secretory response in the obese rat. After injections of 40, 80, 160, and 320 ng CCK/kg BW, total pancreatic protein secretion in nonobese rats increased 5, 12, 19, and 21 times above basal levels, whereas the same doses caused 2-, 6-, 12-, and 13-fold increases in obese rats. Whereas the reduced secretion in the obese rat may reflect a difference in the intracellular machinery leading to protein secretion between the two genotypes, these data are more consistent with a direct mechanism, whereby reduced numbers of pancreatic receptors for CCK are responsible for reduced protein secretion.

Topics: Animals; Binding, Competitive; Cell Membrane; Iodine Radioisotopes; Kinetics; Male; Obesity; Pancreas; Proteins; Rats; Rats, Zucker; Receptors, Cell Surface; Receptors, Cholecystokinin; Sincalide

Obese Zucker rats are less responsive than their lean littermates to the effects of cholecystokinin-octapeptide on satiety and pancreatic growth and exocrine function. We hypothesized that the hyperphagia observed in obese Zucker rats may be caused by a decreased pyloric contractile response to cholecystokinin, resulting in an increased rate of gastric emptying, decreased postprandial gastric distention, and thus decreased satiety. Pyloric muscle strips from six obese Zucker rats and six lean littermates were mounted in separate tissue baths and isometric contraction was measured in response to acetylcholine and cholecystokinin-octapeptide. The dose-response curves for acetylcholine- and cholecystokinin-octapeptide-stimulated pyloric muscle contraction were similar for both the obese and the lean rats. (For cholecystokinin, D50 obese = 4.0 +/- 0.6 nM, D50 lean = 3.4 +/- 0.2 nM; P = 0.16). We conclude that the decreased satiety response to cholecystokinin-octapeptide observed in obese Zucker rats is not secondary to a decreased pyloric responsiveness to cholecystokinin.

Topics: Acetylcholine; Animals; Dose-Response Relationship, Drug; Male; Muscle Contraction; Obesity; Pylorus; Rats; Rats, Zucker; Satiation; Satiety Response; Sincalide

Gallbladder emptying and filling was studied in eight diabetic and six normal control patients. None of the patients had gallstones. Cholescintigraphy was performed using [99mTc]disofenin, and gallbladder emptying was studied using a 45-min i.v. infusion of the octapeptide of cholecystokinin (OP-CCK) 20 ng/kg X hr. The peak filling rate was greater in diabetic than in normal subjects; however, emptying of the gallbladder in response to OP-CCK was significantly less in the diabetic subjects (51.6 +/- 10.4% compared with 77.2 +/- 4.9%). When the diabetic group was subdivided into obese and nonobese diabetics, the obese diabetics had a much lower percentage of emptying than the nonobese diabetics (30.0 +/- 10.4% compared with 73.1 +/- 9.3%). These findings suggest that obese diabetics may have impaired emptying of the gallbladder even in the absence of gallstones. The more rapid rate of gallbladder filling in obesity may indicate hypotonicity of the gallbladder. The combination of these abnormalities may predispose the obese diabetic to the development of gallstones.

Topics: Adult; Aged; Diabetes Mellitus; Gallbladder; Humans; Imino Acids; Male; Middle Aged; Obesity; Radionuclide Imaging; Risk; Sincalide; Technetium; Technetium Tc 99m Disofenin; Time Factors

There is increasing evidence that peptides in the brain are important in the control of food intake. Administration of opioid and CCK peptides have elicited hunger and satiety, respectively. To evaluate the interaction of these peptides and their role in the central nervous system, concentrations of met-enkephalin were measured in the hypothalamus of rats following peripheral administration of CCK; in addition, effects of feeding and fasting and obesity were studied. In CCK- vs. saline-injected rats met-enkephalin concentrations were decreased in the paraventricular nucleus (PVN), suprachiasmatic nucleus (SC), supraoptic nucleus (SON), dorsomedial hypothalamus (DMH) and ventromedial hypothalamus (VMH). In fed compared with fasted rats met-enkephalin concentrations were higher in the anterior hypothalamus (AH) and lower in the SC; in obese compared with lean rats, concentrations were higher in the AH, PVN, SC, SON, DMH, lateral hypothalamus and VMH. These results show that peripheral injections of CCK can decrease concentrations of met-enkephalin in the brain and suggest a mechanism by which these peptides may interact to influence behavior. In addition, the findings support the hypothesis that the hyperphagia which is typical of obese rats may be due to increased concentrations of met-enkephalin.

Topics: Animals; Brain; Enkephalin, Methionine; Fasting; Feeding Behavior; Female; Hypothalamus; Obesity; Olfactory Bulb; Phenotype; Pituitary Gland; Rats; Rats, Zucker; Sincalide; Tissue Distribution

The ob/ob mouse has a defect in short-term satiety mechanisms because ob/ob mice eat larger meals than leans and have abnormal postprandial behaviors. We suggested that this defect involved a failure to release CCK normally in response to ingested nutrients and/or decreased receptor sensitivity to CCK. McLaughlin and Baile reported that female obese mice were less sensitive to the satiating effect of CCK-8, a result consistent with the hypothesis of decreased receptor sensitivity. To investigate this possibility further, we determined the sensitivity to exogenous CCK-8 of obese and lean male mice. Adult male C57Bl/6J ob/ob and male +/+ controls were injected with CCK-8 (1, 2, 4, and 8 micrograms/kg, IP) 15 min prior to the presentation of solid food (Noyes pellets) after 4.5 hr food deprivation in the dark. Food intake (FI) was measured at 30 min and 150 min. CCK-8 decreased FI during the first 30 min in both obese and lean mice (p less than 0.01). The threshold dose for inhibition of FI was 2 micrograms/kg in obese and 4 micrograms/kg in lean. Since obese mice weighed approximately twice as much as lean mice, their total dose of CCK-8 was equal to that of lean mice. Thus, obese male mice were at least as sensitive to the satiating effect of CCK-8 as lean male mice. These results do not confirm McLaughlin and Baile's result in female mice eating in the light and they suggest that the defect in satiety in obese male mice is not the result of decreased sensitivity of CCK receptors.

Topics: Animals; Feeding Behavior; Injections, Intraperitoneal; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Obesity; Satiation; Sincalide

Opiates, morphine and [D-Ala2-D-Leu5]-enkephalin (DADLE), inhibited the K+-stimulated release of cholecystokinin (CCK) from the hypothalamus of both Zucker obese (fa/fa) and lean (Fa/-) rats, in vitro. Morphine and DADLE did not inhibit the K+-stimulated release of CCK from frontal cortex from either strain. The opiates did not affect basal efflux of CCK and their effects were all blocked by equimolar concentrations of naloxone. These studies indicate a regional specificity for the effect of opiates on CCK release, and may provide evidence for a cellular mechanism by which endogenous opiates modulate feeding behavior.

Topics: Animals; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Frontal Lobe; Hypothalamus; Morphine; Naloxone; Obesity; Potassium; Rats; Rats, Zucker; Sincalide

Topics: Animals; Cholecystokinin; Drinking Behavior; Feeding Behavior; Female; Obesity; Rats; Rats, Zucker; Satiation; Sincalide

Topics: Animals; Cholecystokinin; Circadian Rhythm; Feeding Behavior; Female; Obesity; Rats; Rats, Zucker; Satiation; Sincalide