Effects of starvation on phospholipid metabolism of pancreatic islets

It was the aim of the present study to examine the extent to which starvation-induced impairment of glucose-stimulated insulin secretion is linked to changes of islet phospholipid metabolism. For this purpose both islets isolated from mice starved for 60 hr and islets maintained in culture for 1 week in a low (3.3 mM) glucose medium were studied together with relevant control islets. When challenged with a high glucose concentration the insulin response of both groups of islets was totally blunted. The effect of food restriction on 14C-glucose incorporation into different phospholipid classes was less prominent. On a percentage basis phosphatidylserine biosynthesis of islets isolated from starved mice was most affected, whereas the biosynthesis of phosphatidylcholine was only marginally impaired. Culture of islets for 1 week at the low glucose concentration affected the phospholipid biosynthesis even less and there was only a small decrease of 14C-glucose incorporation into phosphatidylcholine. In general, cultured islets synthesized more phospholipids than the freshly isolated ones. No dose-response relationship was found between various degrees of glucose-stimulated insulin secretion and 14C-glucose incorporation into different phospholipid classes of islets isolated from fed mice. The present data thus provided no evidence that an impairment of the islet phospholipid turnover contributes to the starvation-induced impairment of insulin secretion. There was also no close correlation between phospholipid biosynthesis in terms of 14C-glucose incorporation and glucose-stimulated insulin secretion.