The Effect Of Chronic Intermittent Hypoxia And High-fat-feeding On The Islet Cell Apoptosis Of Rabbits

Objective:To investigate the effects of chronic intermittent hypoxia (CIH)and high-fat-feeding on the apoptosis of islet cells and related mechanism,and analyse the synergistic effect between CIH and high-fat-feeding.To present a new view for the pathophysiologic relationship of OSAHS and T2DM.Methods:Using prospective animal experiment,randomized controlled study and factorial experiment,24 New-Zealand white rabbits(4 months old) were divided into the following 4 groups:control group(C),chronic intermittent hypoxia group(H),high-fat-feeding group(F)and hypoxia & high-fat-feeding group(H+F).Each group had 6 rabbits.Rabbits in group H and H+F were placed in a cabin into which nitrogen and air were periodically infused every 8 minutes for 5h/day.The lowest level of oxygen concentration was at 8%.Group F and H+F were fed with fat-rich-stoyer..The intervention experiment lasted for 8 weeks.Blood samples for measurements of total cholesterol(TC),low density lipoprotein cholesterol(LDL-CH)and free fatty acids(FFA)were collected and body weight was measured at 0,4W and 8W.After intervention of eight weeks, each rabbit was put to death by injecting air into ear-lip vein.Then the rabbits were dissected and the pancreata were picked quickly.One part was fixed in formaldehyde for the detection of the apoptosis of islet cells by TUNEL method;the other was preserved in liquid nitrogen immediately for Caspase-3 detection using RT-PCR and Western blot.All results of Caspase-3 expression were used for semi-quantitative analysis. Comparisons among groups were analysed by LSD-test.The effects analysis of two factors of CIH and high-fat-feeding on the apoptosis of islet cells, expression changes of Caspase-3 at mRNA and protein level were carried out using factor analysis.Results:1.Multiple comparisons of lipids.FFA level in group H+F at 8W was (0.75±0.35)mmol/L,which was the highest among the three time points (P＜0.05),vs(0.20±0.14)mmol/L(0W)and(0.27±0.13)mmol/L(4W).2.The 2×2 factorial analysis showed no significant diffrence in the apoptosis of islet cells and Caspase-3 expression by CIH,as the P value of the apoptosis rate of islet cells,the expression level of Caspase-3 mRNA and the level of Caspase-3 protein were 0.22,0.90,and 0.27.The main effect of high-fat-feeding had statistic significance,as the P value of the apoptosis rate of islet cells,the expression level of Caspase-3 mRNA,the level of Caspase-3 protein were 0.01,0.03 and 0.03.The two factores had no significant synergistic effects on the apoptosis of islet cells,as the P value were 0.84,0.97 and 0.80.Conclusion:1.This study confirms that high-fat-feeding can induce the apoptosis of islet cells.It seems that the apoptosis may be by Caspase-3 pathway.2.The combination effect of CIH and high-fat-feeding doesn't induce the apoptosis of islet cells.