Peptide YY antagonizes beta-adrenergic-stimulated release of insulin in dogs

Safety and efficacy of a side-to-side duodeno-ileal anastomosis for weight loss and type-2 diabetes: duodenal bipartition, a novel metabolic surgery procedure

Background

Partial bypass of the GI tract may promote weight loss by decreased absorption of nutrients and changes in incretins. The aim of the study was to evaluate the safety and efficacy of performing a side-to-side duodeno-ileal anastomosis.

Methods

Seven 40–50 kg female Yorkshire pigs were allocated to a duodeno-ileal anastomosis (DIA), and were compared to a control group (SHAM). Swine’s weights were followed for 56 days. Gastroscopies were also performed at 28 days. Blood samples were also taken at regular intervals (CBC and Basic biochemistry profiles). At autopsy, gross changes and histological changes of the liver, duodenum and ileum samples were performed.

Results

While the SHAM group gained 33.2 % more weight at 56 days, the DIA group had shown a weight loss of −6.8 %, for a difference of 40.0 % between the 2 groups (p < 0.05). One pig developed an incisional hernia. Gastroscopies demonstrated normal healing without ulceration or inflammation at 28 days. Histological examination of the anastomosis at 56 days showed normal and smooth healing, with absence of liver toxicity.

Conclusion

In this porcine model with short follow-up, a side-to-side duodeno-ileal anastomosis provided excellent weight loss without apparent nutritional or grossly aberrant histological changes.

Combination of peptide YY3-36 with GLP-1(7-36) amide causes an increase in first-phase insulin secretion after IV glucose

CONTEXT

The combination of peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) has been proposed as a potential treatment for diabetes and obesity. However, the combined effects of these hormones, PYY(3-36) and GLP-1(7-36 amide), on glucose homeostasis are unknown.

OBJECTIVE

This study sought to investigate the acute effects of PYY(3-36) and GLP-1(7-36) amide, individually and in combination, on insulin secretion and sensitivity.

SETTING AND DESIGN

Using a frequently sampled iv glucose tolerance test (FSIVGTT) and minimal modeling, this study measured the effects of PYY(3-36) alone, GLP-1(7-36) amide alone, and a combination of PYY(3-36) and GLP-1(7-36) amide on acute insulin response to glucose (AIRg) and insulin sensitivity index (SI) in 14 overweight human volunteers, studied in a clinical research facility.

RESULTS

PYY(3-36) alone caused a small but nonsignificant increase in AIRg. GLP-1(7-36) amide alone and the combination of PYY(3-36) and GLP-1(7-36) amide did increase AIRg significantly. No significant differences in SI were observed with any intervention.

CONCLUSIONS

PYY(3-36) lacks any significant acute effects on first-phase insulin secretion or SI when tested using an FSIVGTT. Both GLP-1(7-36) amide alone and the combination of PYY3-36 and GLP-1(7-36) amide increase first-phase insulin secretion. There does not seem to be any additive or synergistic effect between PYY(3-36) and GLP-1(7-36) amide on first-phase insulin secretion. Neither hormone alone nor the combination had any significant effects on SI.

Mechanisms underlying the insulinostatic effect of peptide YY in mouse pancreatic islets

Peptide YY is an insulinostatic peptide which is released into the circulation from the intestinal mucosa upon food intake. Peptide YY is also co-stored with glucagon in the secretory granules of the pancreatic alpha cells. We examined the mechanisms underlying the insulinostatic effect of peptide YY in isolated mouse pancreatic islets. We found that peptide YY (0.1 nmol/l-1 mumol/l) inhibited glucose (11.1 mmol/l)-stimulated insulin secretion from incubated isolated islets, with a maximal inhibition of approximately 70% observed at a dose of 1 nmol/l (p < 0.001). Also in perifused islets the peptide (1 nmol/l) inhibited insulin secretion in response to 11.1 mmol/l glucose (p < 0.001). Furthermore, peptide YY inhibited glucose-stimulated cyclic AMP formation (by 67%, p < 0.05), and insulin secretion stimulated by dibutyryl cyclic AMP (p < 0.01). In contrast, the peptide was without effect both on the cytoplasmic Ca2+ concentration in dispersed mouse islet-cell suspensions as measured by the FURA 2-AM technique, and on insulin release in isolated islets, when stimulated by the protein kinase C-activator 12-O-tetradecanoyl phorbol 13-acetate. Finally, in pre-labelled perifused islets, peptide YY caused a small and transient increase in the 86Rb+ efflux (p < 0.001), but only in the absence of extracellular Ca2+. We conclude that peptide YY inhibits glucose-stimulated insulin secretion from isolated mouse islets by inhibiting two different steps in the cyclic AMP cascade, that is, both the accumulation and the action of the cyclic nucleotide.(ABSTRACT TRUNCATED AT 250 WORDS)