The Mechanism Of Palmitic Acid Causing Islet Cells Apoptosis In Pancreatic Islet Cells

Objective: To investigate the effect of chronic exposure to highlevel palmitic acid on islet cells apoptosis and the release of insulin .thereby to understand the role of palmitic acid in the pathogenesis of type 2 diabetes mellitus.Methods: The islet cells of SD adult rats which had been prepared bycollagenase digestion and purified by Ficoll-400 were cultured in RPMI-1640 for 7days, As the islets cells flatten to monolayer, they were cultured with or without palmitic acid (0, 0.125, 0.25, 0.5mmol/L)for 48 hours and then incubated in KRBB containing glucose of 2. 8mmol/L and 28mmol/L. insulin concentrations in KRBB were determined by radio immunological methods. The percentage of apoptotic cells was assessed by Tunel and FCM . Morphological observation by a fluorescence microscope was conducted after double staining of the cells with AO/EB .Results: No obvious effects was observed after a 48-h incubation ofpalmitic acid of different concentrations at low glucose level (2. 8mmol/L) (P>0. 05) , while with the stimulation of high-level glucose(28mmol/L),the insulin secretion was significantly inhibited by palmitic acid (p<0.05) . Palmitic acid of different concentrations all have theapoptosis-inducing effects on islet cells.Conclusion: Palmitic acid have no effect on basic insulin secretion butcan inhabit the insulin secretion with the stimulation of high-level glucose and induce islet cells apoptosis.part two: The mechanism of palmitic acid causing islet cells apoptosis in pancreatic islet cellsObjective: To investigate the effect of triglycerides accumulation ofislet cells that be treated with palmitic acid in vitro and to measure NO content of medium , the expression of Bax and Bcl-2.Methods: The islet cells of SD adult rats which had been prepared bycollagenase digestion and purified by Ficoll-400 were natured in RPMI-1640 for 7days, As the islets cells flatten to monolayer, they were cultured with or without palmitic acid (0> 0.125, 0.25 > 0. 5mmol/L) for 48 hours, the deposition of fat droplets in the islet cells were observed by oil red O-staining . we used the nitrate reduction Test to measure NO content of the medium On the 0 hour, 24 hour, 48 hour respectively . we tested the expressions Bax and Bcl-2 by means of immunoblotting and through flow cytometry.Results: (1) palmitic acid can cause triglycerides accumulation of isletcells in vitro, (2) compared with control, the production of NO was markly induced by palmitic acid on the 24 hour, 48 hour respectively (K0. 05) . (3) The expression of Bax was positive in B^ C ^ D groups and negative in control group, the expression of Bcl-2 was positive in B and control groups and negative in C and D groups by means of immunoblotting. With the increasing concentrations of palmitic acid, the expression of Bax increased ,the expression of Bcl-2 decreased.Conclusion: palmitic acid can cause triglycerides accumulation of islet cells and induce islet cells apoptosis . and the apoptosis may be the...