The Effects Of High Free Fatty Acid On Islet Function And Islet Apoptosis

Objective To investigate the effects of high free fatty acid on rat islet secretion and islet cells apoptosis in vitro.Metheods SD rat islets were isolated and identified through DTZ staining, then according to the concentration of free fatty acid(FFA) in medium and the culture days, islets were divided into six groups: normal control group 1(glucose 5.6 mmol/L, incubated 1 day), FFA group 1(FFA 0.25 mmol/L, incubated 1 day), FFA group 2(FFA 0.5 mmol/L, incubated 1 day); normal control group 2(glucose 5.6mmol/L,incubated 3 days), FFA group 3(FFA 0.25 mmol/L, incubated 3 days), FFA group 4(FFA 0.5 mmol/L, incubated 3 days). After the treatment, the insulin concentrations in culture medium were detectded by radio-immunity after glucose-stimulated insulin secretion test; Apoptotic cells in islets were indentified by TUNEL method; the expression of insulin mRNA, PDX-1 mRNA ,Caspase-3 mRNA and Bax mRNA were quantitated by semi quantitative reverse transcription-polymerase chain reaction(SQ RT-PCR).Results (1) Compare with normal control group1, insulin secretion decreased when islets were incubated in FFA group 1 and FFA group 2 under 5.6 mmol/L glucose stimulation(P<0.05); compare with FFA group 1,insulin secretion decreased when islets were incubated in FFA group 2 under 5.6 mmol/L glucose stimulation (P<0.05); compare with normal control group1, insulin secretion decreased when islets were incubated in FFA group 1 and FFA group 2 under 15.6 mmol/L glucose stimulation (P<0.05); compare with FFA group 1,insulin secretion decreased when islets were incubated in FFA group 2 under 15.6 mmol/L glucose stimulation (P<0.05); compare with normal control group 2, insulin secretion decreased when islets were incubated in FFA group 3 and FFA group 4 under 5.6 mmol/L glucose stimulation(P<0.05); compare with FFA group 3, insulin secretion decreased when islets were incubated in FFA group 4 under 5.6 mmol/L glucose stimulation (P<0.05); compare with normal control group 2, insulin secretion decreased when islets were incubated in FFA group 3 and FFA group 4 under 15.6 mmol/L glucose stimulation (P<0.05); compare with FFA group 3, insulin secretion decreased when islets were incubated in FFA group 4 under 15.6 mmol/L glucose stimulation (P<0.05). (2) Compare with normal control group 1, insulin and PDX-1 gene expression were lower in FFA group 1 and FFA group 2(P<0.05) ; compare with FFA group 1, insulin and PDX-1 gene expression were lower in FFA group 2(P<0.05); compare with normal control group 2, insulin and PDX-1 gene expression were lower in FFA group 3 and FFA group 4(P<0.05) ; compare with FFA group 3, insulin gene and PDX-1 gene expression were lower in FFA group 4(P<0.05); (3) The apoptotic ratios of islet cells in FFA group 1 and FFA group 2 were respectively higher than in normal control group 1(P<0.05); the apoptotic ratios of islet cells in FFA group 2 were higher than in FFA group 1(P<0.05); the apoptotic ratios of islet cells in FFA group 3 and FFA group 4 were respectively higher than in normal control group 2(P<0.05); the apoptotic ratios of islet cells in FFA group 4 were higher than in FFA group 3(P<0.05). (4) Compare with normal control group 1, Caspase-3 and Bax gene expression were higher in FFA group 1 and FFA group 2(P<0.05) ; compare with FFA group 1, Caspase-3 and Bax gene expression were higher in FFA group 2(P<0.05); compare with normal control group 2, Caspase-3 and Bax gene expression were higher in FFA group 3 and FFA group 4(P<0.05) ; compare with FFA group 3, Caspase-3 and Bax gene expression were higher in FFA group 4(P<0.05).Conclusion (1) The glucose-simulated insulin secretion decreased markedly in high free fatty acid circumstance, there was correlated with incubation concentration.(2) Exposure of islated rat islets to high concentration of free fatty acid decreased insulin and PDX-1 gene expression.(3) The apoptotic ratios and the gene expression of Caspase-3 and Bax increased when islets were in high concentration of free fatty acid, and there was correlated with incubation concentration, suggesting that high free fatty acid induced islet cells apoptosis possiblely by increasing the apoptotic genes.