Interaction of GLP-1 with NPY, VIP and galanin

Many central neurotransmitters are involved in the control of feeding behaviour and disturbed metabolism of these neuropeptides contribute to hyperphagia and feeding related disorders of diabetes. GLP-1 had been found to decrease food intake when administered intracerebro ventricular (ICV). It is not known whether this effect is direct or through modulation of other feeding regulatory peptides like NPY and galanin. The present study was conducted to know the interaction of GLP-1 with NPY, VIP and galanin by measuring changes in contents of these peptides in hypothalamus, brain stem, intestine and pancreas in normal and diabetic rats which were infused with 32 nmol/kg body wt/day GLP-1 or saline (controls) for one week. GLP-1 infusion significantly decreased NPY, VIP and galanin contents in normal and diabetic rats in intestine and hypothalamus while no significant changes in brain stem were observed. A significant decrease in pancreatic NPY and VIP was also observed in diabetic rats. It is concluded that GLP-1 acts centrally and peripherally directly and via humoral and nervous factors. NPY, VIP and galanin have autocrine and paracrine role in CNS, pancreas and intestine. GLP-1 act by modulation of these peptides in these tissues.