incretins and trichlorosucrose

The consumption of non-nutritive, low, or no-calorie sweeteners (LCS) is increasing globally. Previously thought to be physiologically inert, there is a growing body of evidence that LCS not only provide a sweet taste but may also elicit metabolic effects in the gastrointestinal tract. This review provides a brief overview of the chemical and receptor-binding properties and effects on chemosensation of different LCS but focuses on the extent to which LCS stimulates glucose transport, incretin and insulin secretion, and effects on glucose tolerance. Aspartame and sucralose both bind to a similar region of the sweet receptor. For sucralose, the data are contradictory regarding effects on glucose tolerance in humans and may depend on the food or beverage matrix and the duration of administration, as suggested by longer term rodent studies. For aspartame, there are fewer data. On the other hand, acesulfame-potassium (Ace-K) and saccharin have similar binding characteristics to each other but, while Ace-K may increase incretin secretion and glucose responses in humans, there are no data on saccharin except in rats, which show impaired glucose tolerance after chronic administration. Additional research, particularly of the effects of chronic consumption, is needed to provide concrete evidence for beneficial or detrimental effects of LCS on blood glucose regulation in humans.

Topics: Animals; Aspartame; Blood Glucose; Carbohydrate Metabolism; Gastrointestinal Tract; Glucose Intolerance; Humans; Incretins; Insulin; Insulin Secretion; Meta-Analysis as Topic; Models, Animal; Non-Nutritive Sweeteners; Randomized Controlled Trials as Topic; Saccharin; Sucrose; Thiazines

Macronutrient "preloads" can stimulate glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), slow gastric emptying, and reduce postprandial glycemic excursions. After sweet preloads, these effects may be signaled by sodium-glucose cotransporter-1 (SGLT1), sweet taste receptors, or both.. We determined the effects of 4 sweet preloads on GIP and GLP-1 release, gastric emptying, and postprandial glycemia.. Ten healthy subjects were studied on 4 separate occasions each. A preload drink containing 40 g glucose, 40 g tagatose/isomalt mixture (TIM), 40 g 3-O-methylglucose (3OMG; a nonmetabolized substrate of SGLT1), or 60 mg sucralose was consumed 15 min before a (13)C-octanoic acid-labeled mashed potato meal. Blood glucose, plasma total GLP-1 and GIP, serum insulin, and gastric emptying were determined.. Both glucose and 3OMG stimulated GLP-1 and GIP release in advance of the meal (each P < 0.05), whereas TIM and sucralose did not. The overall postprandial GLP-1 response was greater after glucose, 3OMG, and TIM than after sucralose (P < 0.05), albeit later after TIM than the other preloads. The blood glucose and insulin responses in the first 30 min after the meal were greatest after glucose (each P < 0.05). Gastric emptying was slower after both 3OMG and TIM than after sucralose (each P < 0.05).. In healthy humans, SGLT1 substrates stimulate GLP-1 and GIP and slow gastric emptying, regardless of whether they are metabolized, whereas the artificial sweetener sucralose does not. Poorly absorbed sweet tastants (TIM), which probably expose a greater length of gut to nutrients, result in delayed GLP-1 secretion but not in delayed GIP release. These observations have the potential to optimize the use of preloads for glycemic control. This trial was registered at www.actr.org.au as ACTRN12611000775910.

Topics: Adult; Blood Glucose; Dietary Sucrose; Disaccharides; Female; Gastric Emptying; Gastric Inhibitory Polypeptide; Glucagon-Like Peptide 1; Glucose; Hexoses; Humans; Incretins; Insulin; Male; Postprandial Period; Signal Transduction; Sodium-Glucose Transporter 1; Sucrose; Sugar Alcohols; Sweetening Agents; Young Adult

The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), play an important role in glucose homeostasis in both health and diabetes. In mice, sucralose, an artificial sweetener, stimulates GLP-1 release via sweet taste receptors on enteroendocrine cells. We studied blood glucose, plasma levels of insulin, GLP-1, and GIP, and gastric emptying (by a breath test) in 7 healthy humans after intragastric infusions of 1) 50 g sucrose in water to a total volume of 500 ml (approximately 290 mosmol/l), 2) 80 mg sucralose in 500 ml normal saline (approximately 300 mosmol/l, 0.4 mM sucralose), 3) 800 mg sucralose in 500 ml normal saline (approximately 300 mosmol/l, 4 mM sucralose), and 4) 500 ml normal saline (approximately 300 mosmol/l), all labeled with 150 mg 13C-acetate. Blood glucose increased only in response to sucrose (P<0.05). GLP-1, GIP, and insulin also increased after sucrose (P=0.0001) but not after either load of sucralose or saline. Gastric emptying of sucrose was slower than that of saline (t50: 87.4+/-4.1 min vs. 74.7+/-3.2 min, P<0.005), whereas there were no differences in t50 between sucralose 0.4 mM (73.7+/-3.1 min) or 4 mM (76.7+/-3.1 min) and saline. We conclude that sucralose, delivered by intragastric infusion, does not stimulate insulin, GLP-1, or GIP release or slow gastric emptying in healthy humans.

Topics: Adult; Blood Glucose; Dose-Response Relationship, Drug; Female; Gastric Emptying; Gastric Inhibitory Polypeptide; Glucagon-Like Peptide 1; Humans; Incretins; Insulin; Male; Single-Blind Method; Stomach; Sucrose; Sweetening Agents; Time Factors; Young Adult

It is difficult to know if the cause for obesity is the type of sweetener, high fat (HF) content, or the combination of sweetener and fat. The purpose of the present work was to study different types of sweeteners; in particular, steviol glycosides (SG), glucose, fructose, sucrose, brown sugar, honey, SG + sucrose (SV), and sucralose on the functionality of the adipocyte. Male Wistar rats were fed for four months with different sweeteners or sweetener with HF added. Taste receptors T1R2 and T1R3 were differentially expressed in the tongue and intestine by sweeteners and HF. The combination of fat and sweetener showed an additive effect on circulating levels of GIP and GLP-1 except for honey, SG, and brown sugar. In adipose tissue, sucrose and sucralose stimulated TLR4, and c-Jun N-terminal (JNK). The combination of HF with sweeteners increased NFκB, with the exception of SG and honey. Honey kept the insulin signaling pathway active and the smallest adipocytes in white (WAT) and brown (BAT) adipose tissue and the highest expression of adiponectin, PPARγ, and UCP-1 in BAT. The addition of HF reduced mitochondrial branched-chain amino transferase (BCAT2) branched-chain keto acid dehydrogenase E1 (BCKDH) and increased branched chain amino acids (BCAA) levels by sucrose and sucralose. Our data suggests that the consumption of particular honey maintained functional adipocytes despite the consumption of a HF diet.

Topics: 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); Adiponectin; Adipose Tissue; Animals; Diet, High-Fat; Dietary Fats; Dietary Sugars; Honey; Incretins; Inflammation; Insulin; Male; Membrane Transport Proteins; Mitochondrial Proteins; Monocarboxylic Acid Transporters; NF-kappa B; Obesity; PPAR gamma; Rats, Wistar; Solute Carrier Proteins; Stevia; Sucrose; Sweetening Agents; Taste; Taste Buds; Toll-Like Receptor 4; Transaminases; Uncoupling Protein 1

Intestinal enteroendocrine cells (IECs) secrete gut peptides in response to both nutrients and non-nutrients. Glucose and amino acids both stimulate gut peptide secretion. Our hypothesis was that the facilitative glucose transporter, GLUT2, could act as a glucose sensor and the calcium-sensing receptor, CasR, could detect amino acids in the intestine to modify gut peptide secretion. We used isolated loops of rat small intestine to study the secretion of gluco-insulinotropic peptide (GIP), glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) secretion stimulated by luminal perfusion of nutrients or bile acid. Inhibition of the sodium-dependent glucose cotransporter 1 (SGLT1) with phloridzin partially inhibited GIP, GLP-1 and PYY secretion by 45%, suggesting another glucose sensor might be involved in modulating peptide secretion. The response was completely abolished in the presence of the GLUT2 inhibitors phloretin or cytochalasin B. Given that GLUT2 modified gut peptide secretion stimulated by glucose, we investigated whether it was involved in the secretion of gut peptide by other gut peptide secretagogues. Phloretin completely abolished gut peptide secretion stimulated by artificial sweetener (sucralose), dipeptide (glycylsarcosine), lipid (oleoylethanolamine), short chain fatty acid (propionate) and major rat bile acid (taurocholate) indicating a fundamental position for GLUT2 in the gut peptide secretory mechanism. We investigated how GLUT2 was able to influence gut peptide secretion mediated by a diverse range of stimulators and discovered that GLUT2 affected membrane depolarisation through the closure of K+(ATP)-sensitive channels. In the absence of SGLT1 activity (or presence of phloridzin), the secretion of GIP, GLP-1 and PYY was sensitive to K+(ATP)-sensitive channel modulators tolbutamide and diazoxide. L-amino acids phenylalanine (Phe), tryptophan (Trp), asparagine (Asn), arginine (Arg) and glutamine (Gln) also stimulated GIP, GLP-1 and PYY secretion, which was completely abolished when extracellular Ca2+ was absent. The gut peptide response stimulated by the amino acids was also blocked by the CasR inhibitor Calhex 231 and augmented by the CasR agonist NPS-R568. GLUT2 and CasR regulate K- and L-cell activity in response to nutrient and non-nutrient stimuli.

Topics: Amino Acids; Aniline Compounds; Animals; Benzamides; Calcium; Cyclohexylamines; Cytochalasin B; Enteroendocrine Cells; Glucose Transporter Type 2; In Vitro Techniques; Incretins; Intestine, Small; KATP Channels; Male; Phenethylamines; Phloretin; Phlorhizin; Propylamines; Rats; Rats, Sprague-Dawley; Receptors, Calcium-Sensing; Sodium-Glucose Transporter 1; Sucrose; Sweetening Agents

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are released during meals from endocrine cells located in the gut mucosa and stimulate insulin secretion from pancreatic beta-cells in a glucose-dependent manner. Although the gut epithelium senses luminal sugars, the mechanism of sugar sensing and its downstream events coupled to the release of the incretin hormones are not clearly elucidated. Recently, it was reported that sucralose, a sweetener that activates the sweet receptors of taste buds, triggers incretin release from a murine enteroendocrine cell line in vitro. We confirmed that immunoreactivity of alpha-gustducin, a key G-coupled protein involved in taste sensing, is sometimes colocalized with GIP in rat duodenum. We investigated whether secretion of incretins in response to carbohydrates is mediated via taste receptors by feeding rats the sweet-tasting compounds saccharin, acesulfame potassium, d-tryptophan, sucralose, or stevia. Oral gavage of these sweeteners did not reduce the blood glucose excursion to a subsequent intraperitoneal glucose tolerance test. Neither oral sucralose nor oral stevia reduced blood glucose levels in Zucker diabetic fatty rats. Finally, whereas oral glucose increased plasma GIP levels approximately 4-fold and GLP-1 levels approximately 2.5-fold postadministration, none of the sweeteners tested significantly increased levels of these incretins. Collectively, our findings do not support the concept that release of incretins from enteroendocrine cells is triggered by carbohydrates via a pathway identical to the sensation of "sweet taste" in the tongue.

Topics: Administration, Oral; Animals; Dietary Sucrose; Duodenum; Gastric Inhibitory Polypeptide; Glucagon-Like Peptide 1; Heterotrimeric GTP-Binding Proteins; Incretins; Male; Mice; Mice, Inbred C57BL; Rats; Rats, Wistar; Rats, Zucker; Saccharin; Stevia; Sucrose; Sweetening Agents; Thiazines; Transducin; Tryptophan