Low protein diet confers resistance to the inhibitory effects of interleukin 1β on insulin secretion in pancreatic islets☆

High protein content in the diet during childhood and adolescence has been associated to the onset insulin-dependent diabetes mellitus. We investigated the effect of interleukin-1β (IL-1β) on insulin secretion, glucose metabolism, and nitrite formation by islets isolated from rats fed with normal protein (NP, 17%) or low protein (LP, 6%) after weaning. Pretreatment of islets with IL-1β for 1 h or 24 h inhibited the insulin secretion induced by glucose in both groups, but it was less marked in LP than in NP group. Islets from LP rats exhibited a decreased IL-1β-induced nitric oxide (NO) production, lower inhibition of D-[U14C]-glucose oxidation to 14CO2 and less pronounced effect of IL-1β on α-ketoisocaproic acid-induced insulin secretion than NP islets. However, when the islets were stimulated by high concentrations of K+ the inhibitory effect of IL-1β on insulin secretion was not different between groups. In conclusion, protein restriction protects β-cells of the deleterious effect of IL-1β, apparently, by decreasing NO production. The lower NO generation in islets from protein deprived rats may be due to increased free fatty acids oxidation and consequent alteration in Ca2+ homeostasis.