慢性间歇低氧对大鼠肝细胞IRS-2、 FoxO1表达的影响

Effects of chronic intermittent hypoxia on IRS-2 and FoxO1 expression in rat heptocytes

目的 观察慢性间歇低氧条件下,大鼠肝细胞形态学变化及胰岛素受体底物-2 （IRS-2）、叉头框蛋白O1（FoxO1）的蛋白表达,并探讨IRS-2、FoxO1与胰岛素抵抗的相关性.方法 取24只6周龄健康雄性Sprauge-Dawley大鼠,采用随机数字表法分为正常对照组（NC组）、慢性间歇低氧4周组（CIH4组）、慢性间歇低氧8周组（CIH8组）,每组8只.CIH4组和CIH8组暴露于间歇低氧舱内：最低氧浓度6％ ～ 8％,持续时间8 h/d.NC组无间歇低氧暴露正常饲养,CIH4组、CIH8组和NC组分别于第4周、第8周及第8周禁食12 h后测定空腹血糖、空腹胰岛素水平,并采用稳态模型评估-胰岛素抵抗指数（HOMA-IR）和胰岛素敏感性指数（ISI）评价胰岛素抵抗,对肝组织行HE染色观察形态学变化,采用免疫组织化学方法测定肝细胞IRS-2、FoxO1蛋白表达,以平均灰度值表示其蛋白表达量,二者成反比关系.结果 与NC组相比,CIH4组、CIH8组空腹血糖、胰岛素、HOMA-IR升高,ISI降低,且CIH8组更为显著,差异有统计学意义（F=50.23 ～90.26,P均＜0.05）.与NC组相比,CIH4组与CIH8组IRS-2蛋白表达降低,FoxO1蛋白表达增高且在核内重新分布,CIH8组更为显著,差异有统计学意义（F=69.46,618.94,P均＜0.05）.Pearson相关分析显示：HMOA-IR与IRS-2平均灰度值呈正相关（r=0.857,P＜0.05）,与FoxO1平均灰度值呈负相关（r=-0.926,P＜0.05）,ISI与IRS-2平均灰度值呈负相关（r=-0.823,P＜0.05）,与FoxO1平均灰度值呈正相关（r=0.848,P＜0.05）.结论 慢性间歇低氧条件下,大鼠肝细胞受损并发生胰岛素抵抗,同时IRS-2和FoxO1蛋白表达异常,且随暴露时间延长肝细胞损伤程度及胰岛素抵抗程度均逐渐加重.

Objective To observe the histomorphologic alteration and expression of insulin receptor substrate （IRS）-2 and FoxO1 in rat heptocytes,and investigate the association of IRS-2 and FoxO1 with insulin resistance induced by chronic intermitted hypoxia.Methods Twenty-four healthy male Sprauge-Dawley rats at 6-week age were divided into normal control group （NC group）,chronic intermittent hypoxia for 4 weeks group （CIH4 group） and chronic intermittent hypoxia for 8 weeks group （CIH8 group） according to random number table,with 8 rats in each group.CIH4 group and CIH8 group were placed in intermittent low oxygen cabin for 8 hours per day,the minimum oxygen concentration was 6%-8%.NC group was placed in normal air cabin.Fasting blood glucose and fasting insulin level were measured on 4th week,8th week and after an overnight fast of 12 hours on 8th week in CIH4,CIH8 and NC group,respectively.Homeostatic model assessment of insulin resistance index （HOMA-IR） and insulin sensitive index （ISI） were used to evaluate insulin resistance.HE staining was used for morphologic study of liver.IRS-2 and FoxO1 expression in heptocytes were analyzed by immunohistochemistry.Average gray value was used to represent the protein expression,and which was inversely proportional to average gray value.Results Compared with NC group,CIH4 and CIH8 group had elevated fasting blood glucose,fasting insulin,HOMA-IR,and reduced ISI,especially in CIH8 group （F =50.23-90.26,all P 〈 0.05）.Compared with NC group,the expression of IRS-2 decreased in CIH4 and CIH8 group;the expression of FoxO1 increased in CIH4 and CIH8 group with the re-distribution in the nucleus,especially in CIH8 group （F =69.46,618.94,all P 〈 0.05）.Pearson correlation analysis showed that HOMA-IR was positively correlated with the average gray value of IRS-2 （r =0.857,P 〈 0.05）,but was negatively correlated with the average gray value of FoxO1 （r =-0.926,P 〈 0.05）.ISI was negatively correlated with the average gray value of IRS-2 （r =-0.823,P 〈 0.05） and was positively correlated with the average gray value of FoxO1 （r=0.848,P〈0.05）.Conclusions In intermittent hypoxia,the liver is damaged along with the occurrence of insulin resistance and the abnormal expression of IRS-2 and FoxO1,which are aggravated with the exposure time of hypoxia.