Peptide YY3–36-induced inhibition of food intake in female monkeys

PYY (3-36) protects against high fat feeding induced changes of pancreatic islet and intestinal hormone content and morphometry

BACKGROUND

Prolonged high fat feeding negatively impacts pancreatic and intestinal morphology. In this regard, direct effects of PYY(3-36) on intestinal cell and pancreatic islet morphometry are yet to be fully explored in the setting of obesity.

METHODS

We examined the influence of 21-days twice daily treatment with PYY(3-36) on these parameters in mice fed a high fat diet (HFD).

RESULTS

PYY(3-36) treatment decreased food intake, body weight and circulating glucose in HFD mice. In terms of intestinal morphology, crypt depth was restored to control levels by PYY(3-36), with an additional enlargement of villi length. PYY(3-36) also reversed HFD-induced decreases of ileal PYY, and especially GLP-1, content. HFD increased numbers of PYY and GIP positive ileal cells, with PYY(3-36) fully reversing the effect on PYY cell detection. There were no obvious differences in the overall number of GLP-1 positive ileal cells in all mice, barring PYY(3-36) marginally decreasing GLP-1 villi cell immunoreactivity. Within pancreatic islets, PYY(3-36) significantly decreased alpha-cell area, whilst islet, beta-, PYY- and delta-cell areas remained unchanged. However, PYY(3-36) increased the percentage of beta-cells while also reducing percentage alpha-cell area. This was related to PYY(3-36)-induced reductions of beta-cell proliferation and apoptosis frequencies. Co-localisation of islet PYY with glucagon or somatostatin was elevated by PYY(3-36), with GLP-1/glucagon co-visualisation increased when compared to lean controls.

CONCLUSION

PYY(3-36) exerts protective effects on pancreatic and intestinal morphology in HFD mice linked to elevated ileal GLP-1 content.

GENERAL SIGNIFICANCE

These observations highlight mechanisms linked to the metabolic and weight reducing benefits of PYY(3-36).

Effect of sterilization and of dietary fat and carbohydrate content on food intake, activity level, and blood satiety-related hormones in female dogs

Animal sterilization is suggested to promote food overconsumption, although it is unknown whether this effect is mediated by variations in satiety-related hormones, which are released in response to food intake. The aim of this study was to evaluate the effect of sterilization and of the main energy-delivery nutrients, fat and nonstructural carbohydrates, on food intake, blood concentration of satiety-related hormones, and activity level in dogs. In a 2-phase experiment (phase I [Ph.I], 74 d, and Ph.II, 84 d), 12 female Beagle dogs were assigned to a control group (intact in both phases) and a sterilization group (spayed 20 d before Ph.II). In each phase, dogs received a high-carbohydrate (HC) diet (313 and 105 g/kg DM starch and fat, respectively) and a high-fat (HF) diet (191 and 213 g/kg DM starch and fat, respectively), both high in total dietary fiber (>200 g/kg DM) and providing 27% ME as protein, in 2 consecutive periods following a crossover arrangement. During each period, dogs' voluntary DMI and activity level were recorded during 5 d. Then, energy allowance was restricted to 0.7 maintenance and the level of intake of a common challenge food offered 4 h after feeding the experimental diets (challenge food intake [ChFI]) was used as an index of the satiety state of dogs. Blood concentration of active ghrelin, cholecystokinin (CCK), total peptide YY (PYY), and insulin were determined before and 15, 60, 120, 240, and 360 min after feeding. Voluntary DMI was greater ( < 0.05) in HF-fed dogs, but ChFI did not differ between diets ( > 0.10). Dogs fed the HF diet showed a lower increase of CCK at 120 ( < 0.01) and 240 min ( < 0.05), resulting in a lower ( < 0.001) total area under the curve from 0 to 240 min (tAUC). A lower PYY elevation ( < 0.05) was also found in HF-fed dogs at 120 min. Only active ghrelin concentration at 240 min and insulin tAUC correlated ( < 0.05) with ChFI (r = 0.357 and r = -0.364, respectively), suggesting a role of these hormones in appetite. Dog sterilization did not affect voluntary DMI, ChFI, or blood hormones ( > 0.10) but led to a reduced activity level compared with control dogs ( < 0.05). In summary, dog sterilization was not associated with an impaired appetite control. Feeding dogs the HF diet led to energy overconsumption and to a lower blood elevation of CCK and PYY but was not associated with a weaker satiating effect 4 h later compared with the HC diet.

Regulation of energy balance by a gut-brain axis and involvement of the gut microbiota

Despite significant progress in understanding the homeostatic regulation of energy balance, successful therapeutic options for curbing obesity remain elusive. One potential target for the treatment of obesity is via manipulation of the gut-brain axis, a complex bidirectional communication system that is crucial in maintaining energy homeostasis. Indeed, ingested nutrients induce secretion of gut peptides that act either via paracrine signaling through vagal and non-vagal neuronal relays, or in an endocrine fashion via entry into circulation, to ultimately signal to the central nervous system where appropriate responses are generated. We review here the current hypotheses of nutrient sensing mechanisms of enteroendocrine cells, including the release of gut peptides, mainly cholecystokinin, glucagon-like peptide-1, and peptide YY, and subsequent gut-to-brain signaling pathways promoting a reduction of food intake and an increase in energy expenditure. Furthermore, this review highlights recent research suggesting this energy regulating gut-brain axis can be influenced by gut microbiota, potentially contributing to the development of obesity.

Effect of glycemic load on peptide-YY levels in a biracial sample of obese and normal weight women

Black women suffer a disproportionately higher rate of obesity than their white counterparts. Reasons for this racial disparity may reflect underlying differences in the appetite suppressing peptide-YY (PYY). The PYY response to food is differentially influenced by macronutrient content but the effect of glycemic load on PYY response is unknown. This study examined whether glycemic load influences fasting and postprandial PYY levels and whether fasting and postprandial PYY levels are lower in obese black women compared to normal weight black women and to white women. Data were collected from 40 women (20 black, 20 white; 10 each normal weight vs. obese) at the University of North Carolina Clinical and Translational Research Center (CTRC). Participants completed in counterbalanced order two 4(1/2)-day weight-maintenance, mixed macronutrient high vs. low glycemic load diets followed by a test meal of identical composition. Total PYY levels were assessed before and after each test meal. Results show no differences in fasting PYY levels but significantly less postprandial PYY area under the curve (PYY(AUC)) in the group of obese black women compared to each other group (race x obesity interaction, P < 0.04). PYY(AUC) was positively related to insulin sensitivity (P < 0.004) but was not affected by glycemic load (main and interactive effects, P > 0.27). These findings indicate that postprandial PYY secretion is not affected by glycemic load but is blunted in obese black women compared with normal weight black women and with white women; additionally, they begin to address whether blunted PYY secretion contributes uniquely to the pathogenesis of obesity in black women.