sincalide and Insulin-Resistance

We studied the effect of CCK-8 on BP and blood content of CGRP in rats with hypertension caused by fructose or inhibition of NO synthase with L-NAME. The decrease in the CGRP content was found during the development of fructose-induced hypertension, but not L-NAME-caused hypertension. Administration of CCK-8 to fructose-fed animals reduced BP and increased the content of CGRP. In rats with hypertension caused by NO deficit, CCK-8 lowered BP, but did not affect the content of CGRP. These findings suggest that CGRP mediates the hypotensive effect of CCK-8 in fructose-induced hypertension, but not in NO-deficient hypertension.

Topics: Animals; Blood Pressure; Calcitonin Gene-Related Peptide; Cholecystokinin; Fructose; Hypertension; Insulin Resistance; Male; Nitric Oxide; Nitric Oxide Synthase; Peptide Fragments; Rats; Rats, Wistar; Signal Transduction

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

Cholecystokinin (CCK) is a hormone that has important physiological effects on energy balance. This study has used a stable CCK(1) receptor agonist, (pGlu-Gln)-CCK-8, to evaluate the metabolic effects of prolonged administration in normal mice. Twice-daily injection of (pGlu-Gln)-CCK-8 for 28 days resulted in significantly lowered body weights (P<0.05) on days 24 and 28, which was associated with decreased accumulated calorie intake (P<0.01) from day 12 onward. Nonfasting plasma glucose was significantly reduced (P<0.05) on day 28, while plasma insulin concentrations were increased (P<0.05). After 28 days, glucose tolerance and glucose-mediated insulin secretion were not significantly different in (pGlu-Gln)-CCK-8-treated mice. However, following a 15-min refeeding period in 18-h fasted mice, glucose levels were significantly (P<0.05) decreased by (pGlu-Gln)-CCK-8 despite similar food intake and nutrient-induced insulin levels. Insulin sensitivity in (pGlu-Gln)-CCK-8-treated mice was significantly (P<0.01) improved compared with controls. Accumulation of triacylglycerol in liver was reduced (P<0.01) but there were no differences in circulating cholesterol and triacylglycerol concentrations, as well as triacylglycerol content of pancreatic, muscle, and adipose tissue in (pGlu-Gln)-CCK-8 mice. These data highlight the beneficial metabolic effects of prolonged (pGlu-Gln)-CCK-8 administration and confirm a lack of detrimental effects.

Topics: Animals; Anti-Obesity Agents; Blood Glucose; Energy Intake; Hyperglycemia; Hypoglycemic Agents; Insulin; Insulin Resistance; Insulin-Secreting Cells; Liver; Male; Mice; Postprandial Period; Receptor, Cholecystokinin A; Signal Transduction; Sincalide; Time Factors; Triglycerides; Weight Gain

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

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

Hemodynamic nitrate tolerance has been shown to result in an insulin-resistant state. We studied whether nitrate tolerance induced by a 7-day continuous exposure to transdermal nitroglycerin influenced the meal-induced insulin sensitization phenomenon in rabbits.. Changes in insulin sensitivity in response to feeding in conscious rabbits were determined by rapid insulin sensitivity test, in both nitrate-tolerant and nitrate-intolerant animals. In a separate series of experiments with anesthetized rabbits with or without nitrate tolerance, the hyperinsulinemic euglycemic glucose clamping methods was used to study the effect of intraportal infusion of cholecystokinin (CCK) on whole-body insulin sensitivity.. Rabbits with normal feeding exhibited a 46 ± 6% increase in insulin sensitivity as compared with their matching fasting controls. A 7-day period of treatment with patches releasing 0.07 mg of nitroglycerin per hour yielded nitrate tolerance and a state of insulin resistance and no increase in insulin sensitivity in response to food. Intraportal infusion of CCK8 (0.3-3.0 μg/kg over 20 minutes) resulted in a dose-dependent increase in insulin sensitivity in normal but not in nitrate-tolerant, fasted anesthetized animals.. Nitrate tolerance blocks both the meal-induced insulin sensitization phenomenon and the insulin-sensitizing effect of intraportal CCK.

Topics: Animals; Blood Glucose; Blood Pressure; Cyclic GMP; Drug Tolerance; Eating; Fasting; Glucose Clamp Technique; Heart Rate; Insulin Resistance; Liver; Male; Nitroglycerin; Rabbits; Sincalide

In mice, eNOS (endothelial nitric oxide synthase) maintains in vivo pancreatic secretory responses to carbachol or cholecystokinin octapeptide (CCK-8), maintains insulin sensitivity, and modulates pancreatic microvascular blood flow (PMBF). eNOS(-/-) mice are insulin resistant, and their exocrine pancreatic secretion is impaired. We hypothesized that the reduced exocrine pancreatic secretion in eNOS(-/-) mice is due to insulin resistance or impaired PMBF. To test this hypothesis, we gave eNOS(-/-) and wild-type (WT) mice pioglitazone (20 or 50 mg.kg(-1).day(-1)), an insulin-sensitizing peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activator, and measured pancreatic protein secretion evoked by CCK-8 (160 pmol.kg(-1).h(-1), a maximal stimulus). We also measured insulin resistance, serum glucose, C-peptide, insulin, pancreatic RNA digestive enzyme expression, and PMBF (microsphere technique). In WT mice, pioglitazone did not increase CCK-8-stimulated protein output over baseline. In eNOS(-/-) mice, however, pioglitazone substantially increased the low CCK-8-stimulated protein output that is characteristic of these mutant mice (P < 0.005). Pioglitazone abolished the CCK-8-evoked hyperinsulinemia (P < 0.005) and increased insulin sensitivity of eNOS(-/-) mice (P < 0.05), the latter based on hyperinsulinemic-euglycemic clamp studies. Pioglitazone had no effect on PMBF or pancreas mRNA expression of insulin or digestive enzymes. We conclude that in hyperinsulinemic eNOS(-/-) mice, a nonobese model of insulin resistance relevant to diabetes mellitus and possibly chronic pancreatitis, reduced pancreatic secretion is caused, at least in part, by insulin resistance. Insulin-sensitizing PPAR-gamma agonists such as pioglitazone may thus simultaneously correct endocrine and exocrine pancreatic disorders.

Topics: Animals; Gene Expression; Hyperinsulinism; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Liver; Mice; Nitric Oxide Synthase Type III; Pancreas; Pancreatic Juice; Phosphoproteins; Pioglitazone; Regional Blood Flow; RNA, Messenger; Signal Transduction; Sincalide; Somatostatin; Thiazolidinediones

Insulin resistance is followed by an islet adaptation resulting in a compensating increase in insulin secretion and hyperinsulinemia. The mechanism underlying this increased insulin secretion is not established. We studied whether islet phospholipase A(2) (PLA(2)) contributes by using C57BL/6J mice fed a high-fat diet, since we previously showed that the insulin responses to the two PLA(2)-activating insulin secretagogues carbachol and cholecystokinin (CCK) are enhanced in this model. CCK (100 nM) and carbachol (100 microM) stimulated [(3)H]AA efflux, reflecting PLA(2) activation, both in islets from mice after 12 weeks on high-fat diet and in controls. The efflux increase was more pronounced in islets from high-fat diet-fed mice during both CCK (by 93 +/- 46%; P = 0. 034) and carbachol (by 64 +/- 22%; P = 0.009) stimulation. Also a direct PLA(2) activation by mellitin (2 microg/ml) elicited a potentiated efflux in islets from the insulin-resistant mice (by 361 +/- 107%; P = 0.002). The results suggest that exaggerated non-glucose-induced PLA(2) activation contributes to the islet compensation in insulin resistance.

Topics: Animals; Arachidonic Acid; Blood Glucose; Body Weight; Carbachol; Diabetes Mellitus, Type 2; Dietary Fats; Enzyme Activation; Fatty Acids, Nonesterified; Female; Glucose; Hyperinsulinism; Insulin; Insulin Resistance; Insulin Secretion; Islets of Langerhans; Melitten; Mice; Mice, Inbred C57BL; Phospholipases A; Sincalide; Time Factors

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

Insulin secretion in response to acetylcholine receptor activation by carbachol in insulin resistance induced by 12 weeks of high-fat diet in C57BL/6J mice is exaggerated. To study whether this persists after a longer period of time and also involves other non-glucose stimuli, we fed C57BL/6J mice a high-fat diet for 24 weeks. Both hyperinsulinemia (341 +/- 33 vs. 148 +/- 15 pmol/l) and slight hyperglycemia (7.8 +/- 0.2 vs. 6.1 +/- 0.1 mmol/l) were evident at this time point. The insulinotropic response to high dose carbachol (0.53 micromol/kg; 3403 +/- 377 vs. 1595 +/- 429 pmol/l), to the glucose analogue, 2-deoxyglucose (6 mmol/kg; 2014 +/- 315 vs. 1167 +/- 200 pmol/l), to cholecystokinin-8 (15.9 nmol/kg; 499 +/- 93 vs. 119 +/- 40 pmol/l) and to glucagon-like peptide-1 (32 nmol/kg; 307 +/- 86 vs. 71 +/- 9 pmol/l), were all exaggerated in mice given high-fat diet. In contrast, the insulin response to glucose was impaired. This shows that insulin resistance is accompanied by a general islet supersensitivity to non-glucose stimuli, which persists over a long period of time.

Topics: Animals; Antimetabolites; Blood Glucose; Body Weight; Carbachol; Deoxyglucose; Diet; Female; Glucagon; Glucagon-Like Peptide 1; Glucose; Insulin; Insulin Resistance; Insulin Secretion; Islets of Langerhans; Mice; Mice, Inbred C57BL; Muscarinic Agonists; Peptide Fragments; Protein Precursors; Sincalide; Stimulation, Chemical

Pancreatic exocrine and endocrine function in postpancreatitic rats treated with cholecystokinin (CCK) receptor antagonist loxiglumide was compared with that treated with saline and CCK octapeptide (CCK-8) or with that in normal control rats. Treatment with loxiglumide (50 mg/kg body weight), CCK-8 (2.5 micrograms/kg body weight), or saline (2.5 ml/kg body weight) was given three times a day for 6 days starting 1 day after the induction of acute pancreatitis by a 4-h subcutaneous infusion of 20 micrograms/kg body weight/h of caerulein. On day 8, pancreatic exocrine and endocrine function was simultaneously determined following an intravenous injection of a mixed solution of 0.2 g/kg body weight glucose plus 100 ng/kg body weight caerulein. Basal pancreatic juice flow was significantly increased in all of the postpancreatitic rats irrespective of the treatment, whereas the maximal juice flow in the loxiglumide- and saline-treated rats was significantly low compared with the CCK-8-treated and the control rats. Basal and the peak protein outputs in the loxiglumide-treated rats were comparable to those in saline-treated rats, but were lower than those in the control or the CCK-8-treated rats. Although serum glucose concentrations in all of the postpancreatitic rats were similar to those in the control rats, stimulated as well as basal insulin release tended to be high compared with the control rats. In particular, loxiglumide-treated rats showed the exaggerated insulin response compared with other groups of rats. These present observations indicate that administration of high dose of loxiglumide for a long period decreases pancreatic enzyme output and causes insulin resistance.

Topics: Acute Disease; Animals; Ceruletide; Glucose; Injections, Intravenous; Injections, Subcutaneous; Insulin; Insulin Resistance; Insulin Secretion; Islets of Langerhans; Male; Pancreatitis; Proglumide; Rats; Rats, Wistar; Receptors, Cholecystokinin; Sincalide