Effect of fatty acids on insulin release: role of chain length and degree of unsaturation

The purpose of the present study was to examine the role played by structural differences among fatty acids in their effect on insulin secretion by isolated perifused murine islets. Insulin secretion measured by radioimmunoassay was assessed either as total insulin output (ng.6 islets-1.20 min-1) or as percent of basal insulin secretion. Raising the glucose concentration from a basal 5.5 to 27.7 mM caused an increase of insulin output from 6.69 +/- 1.59 to 19.92 +/- 4.99 ng.6 islets-1.20 min-1 (P < 0.05) in control (untreated) islets. However, after 20-min exposure of islets to 5 mM 16:0 or 18:2, the effect of 27.7 mM glucose was enhanced or diminished, respectively. Basal insulin output (100% basal) changed to 44 +/- 10% basal (P < 0.005) with the addition of 5 mM 4:0 but was not altered when 4:0 was replaced by 6:0. Insulin output increased modestly with 5 mM 8:0 but significantly (P < 0.05) with 10:0 until a maximal of 280 +/- 24% basal with 12:0 (P < 0.01), then fell to 110 +/- 18 and 93 +/- 15% basal (P < 0.05) with 14:0 and 16:0, respectively. The addition of 5 mM 18:0 inhibited insulin secretion to 30 +/- 10% of basal (P < 0.003), and this effect was not caused by fatty acid interference with insulin assay.(ABSTRACT TRUNCATED AT 250 WORDS)