Peptide-YY3-36/glucagon-like peptide-1 combination treatment of obese diabetic mice improves insulin sensitivity associated with recovered pancreatic ß-cell function and synergistic activation of discrete hypothalamic and brainstem neuronal circuitries.

OBJECTIVE: Obesity-linked type 2 diabetes (T2D) is a worldwide health concern and many novel approaches are being considered for its treatment and subsequent prevention of serious comorbidities. Co-administration of glucagon like peptide 1 (GLP-1) and peptide YY3-36 (PYY3-36) renders a synergistic decrease in energy intake in obese men. However, mechanistic details of the synergy between these peptide agonists and their effects on metabolic homeostasis remain relatively scarce. METHODS: In this study, we utilized long-acting analogues of GLP-1 and PYY3-36 (via Fc-peptide conjugation) to better characterize the synergistic pharmacological benefits of their co-administration on body weight and glycaemic regulation in obese and diabetic mouse models. Hyperinsulinemic-euglycemic clamps were used to measure weight-independent effects of Fc-PYY3-36 + Fc-GLP-1 on insulin action. Fluorescent light sheet microscopy analysis of whole brain was performed to assess activation of brain regions. RESULTS: Co-administration of long-acting Fc-IgG/peptide conjugates of Fc-GLP-1 and Fc-PYY3-36 (specific for PYY receptor-2 (Y2R)) resulted in profound weight loss, restored glucose homeostasis, and recovered endogenous ß-cell function in two mouse models of obese T2D. Hyperinsulinemic-euglycemic clamps in C57BLKS/J db/db and diet-induced obese Y2R-deficient (Y2RKO) mice indicated Y2R is required for a weight-independent improvement in peripheral insulin sensitivity and enhanced hepatic glycogenesis. Brain cFos staining demonstrated distinct temporal activation of regions of the hypothalamus and hindbrain following Fc-PYY3-36 + Fc-GLP-1R agonist administration. CONCLUSIONS: These results reveal a therapeutic approach for obesity/T2D that improved insulin sensitivity and restored endogenous ß-cell function. These data also highlight the potential association between the gut-brain axis in control of metabolic homeostasis.

Proteomic Analysis of Restored Insulin Production and Trafficking in Obese Diabetic Mouse Pancreatic Islets Following Euglycemia.

For the treatment of patients with prediabetes or diabetes, clinical evidence has emerged that ß-cell function can be restored by glucose-lowering therapeutic strategies. However, little is known about the molecular mechanisms underlying this functional adaptive behavior of the pancreatic ß-cell. This study examines the dynamic changes in protein expression and phosphorylation state associated with (pro)insulin production and secretory pathway function mediated by euglycemia to induce ß-cell rest in obese/diabetic db/db islet ß-cells. Unbiased quantitative profiling of the protein expression and phosphorylation events that occur upon ß-cell adaption during the transition from hyperglycemia to euglycemia was assessed in isolated pancreatic islets from obese diabetic db/db and wild-type (WT) mice using quantitative proteomics and phosphoproteomics together with bioinformatics analysis. Dynamic changes in the expression and phosphorylation of proteins associated with pancreatic ß-cell (pro)insulin production and complementary regulated-secretory pathway regulation were observed in obese diabetic db/db islets in a hyperglycemic environment, relative to WT mouse islets in a normal euglycemic environment, that resolved when isolated db/db islets were exposed to euglycemia for 12 h in vitro. By similarly treating WT islets in parallel, the effects of tissue culture could be mostly eliminated and only those changes associated with resolution by euglycemia were assessed. Among such regulated protein phosphorylation-dependent signaling events were those associated with COPII-coated vesicle-dependent ER exit, ER-to-Golgi trafficking, clathrin-coat disassembly, and a particular association for the luminal Golgi protein kinase, FAM20C, in control of distal secretory pathway trafficking, sorting, and granule biogenesis. Protein expression and especially phosphorylation play key roles in the regulation of (pro)insulin production, correlative secretory pathway trafficking, and the restoration of ß-cell secretory capacity in the adaptive functional ß-cell response to metabolic demand, especially that mediated by glucose.