The Effects of Vitamin D on Insulin Release From Isolated Islets of Rats

Background: vitamin d (vit d) affects glucose metabolism. receptors of vitamin d have been identified in β cells and studies show that vitamin d deficiency reduces glucose-stimulated insulin secretion (gsis). objectives: the aim of this study was to examine the effect of vitamin d on insulin release from isolated islets of rats. materials and methods: islets were isolated from male wistar rats, weighing 200-250 grams, using the collagenase digestion method. insulin release was assessed following 24 and 48 hours coincubation of islets with vitamin d (0.1, 1 and 10 nm) and glucose (5.6, 11.1 and 16.7 mm). in addition, islets were preincubated with vitamin d for 24 and 48 hours and gsis was assessed for one hour in the presence of 5.6 and 16.7 mm glucose. results: coincubation of islets with vitamin d (10 nm) and 11.1 mm glucose increased islet insulin release (37.27 ± 3.75 vs. 24.64 ± 2.83 ng/ islet/24 hours; p < 0.05), while vitamin d (1 and 10 nm) decreased insulin release in the presence of 16.7 mm glucose (21.14 ± 3.58 and 18.65 ± 3.84 vs. 37.71 ± 4.63 ng/ islet/24 hours; p < 0.05). islets preincubation with vitamin d (1 and 10 nm) increased gsis in the presence of 16.7 mm glucose (4.39 ± 0.73 and 4.39 ± 0.63 vs. 2.07 ± 0.43 ng/islet/1 hour; p < 0.05). conclusions: preincubation of islets with vitamin d increased gsis but decreased insulin release in coincubation with high levels of glucose. insulin secretion from β cells in the presence of glucose seems to be related to the dosage of vitamin d and duration of preincubation.