Consequences of a diet-induced obesity on the plasticity of the Pancreatic Intrinsic Nervous System and the nervous control of pancreatic endocrine secretion in young mice

Objective Pancreatic Intrinsic Nervous System (PINS) is involved in the control of pulsatility and amplitude of insulin secretion (IS) both altered in obese and type 2 diabetic patients. However, little is known about the role of the PINS during obesity and in the genesis of pancreatic endocrine dysfunctions. The aim of our study was to determine the impact of obesity upon the PINS and its functional consequences upon IS in young mice. Methods C57BL/6J mice aged 4 weeks received either a normal diet (ND; n=20) or a western (hyperlipidic hyperenergetic) diet (WD; n=20) for 12 weeks. 4 weeks old mice (n=16) were also used as initial controls (iC). After sacrifice, pancreases were removed and placed in short term organ culture for 1 hour. The impact of PINS upon endocrine function was studied by adding to the culture the nicotinic receptors agonist dymethylphenylPiperazinium (DMPP) in presence or absence of hexamethonium (nicotinic antagonist) or Nω-nitro-L-arginine methyl ester (L-NAME, inhibitor of NO synthase NOS) or sodium nitroprusside, (SNP, NO donor). Supernatant of culture was collected and frozen for further analysis of insulin by ELISA. Immunohistological analyses were performed to determine nerve fibers density and to phenotype neurons with choline acetyltransferase (Chat) and NOS antibodies. Results PINS stimulation by DMPP induced a time dependent increase in IS which was significantly larger in ND as compared to WD mice (P=0.01). Interestingly, the IS profile was identical in ND and iC mice (P=0.39). This secretion was fully blocked in presence of hexamethonium. Addition of L-Name significantly inhibited insulin release in ND mice (P<0.01) while SNP reduced IS at an intermediate level (p=0.06). Neither L-Name nor SNP altered IS in WD mice. PINS density was less in ND compared to iC mice (P<0.05), whereas there was no difference between WD and iC mice. Cholinergic innervation increased significantly with age in both WD and ND mice. Unlike ND mice in whom there was an increase of NOS-neurons with age (P<0.05), WD mice had a significant decrease (P<0.05). Conclusion Altogether, our study suggests that WD could induce neuroplastic changes in the PINS that could be involved in pancreatic dysfunctions observed during obesity.