艾塞那肽对糖尿病大鼠肝脏组织胰岛素抵抗的影响

Effects of exenatide therapy on hepatic insulin resistance in high-fat diet and low-dose streptozotocin-induced diabetic rats

目的 研究胰高糖素样肽1受体激动剂艾塞那肽对高脂喂养联合小剂量链脲佐菌素诱导的糖尿病大鼠肝脏组织胰岛素抵抗的影响及其机制.方法 健康雄性6周龄SD大鼠采用随机数字法分为正常对照组（C组,n=6）、正常对照＋艾塞那肽处理组（C＋E组,n=6）、糖尿病组（D组,n=5）以及糖尿病＋艾塞那肽处理组（D＋E组,n=5）,由高脂饮食加小剂量STZ诱导成2型糖尿病后,D＋E组以及C＋E组大鼠予艾塞那肽,5μg腹部皮下注射,每天1次干预;8周后,分别测定空腹葡萄糖出现率、肝糖输出率、甘油出现率、甘油糖异生相关参数;测定外源性胰岛素持续输注状态下的肝糖输出和葡萄糖输注率.同时行透射电子显微镜观察大鼠肝脏组织超微结构改变.多组间数据比较采用单因素方差分析.结果 D＋E组大鼠空腹血糖、血浆甘油三酯、总胆固醇、低密度脂蛋白、稳态模型胰岛素抵抗指数（HOMA-IR）水平均显著低于D组,但显著高于C组及C＋E组,差异均有统计学意义（F=82.827、81.648、27.613、26.300、105.234,均P＜0.05）,ISI则显著高于D组大鼠,但仍显著低于C组及C＋E组（F=17.566,P＜0.05）.空腹状态下,D＋E组大鼠的葡萄糖出现率、甘油出现率、肝糖输出率、甘油糖异生相关参数（甘油转化为葡萄糖的百分率、来源于甘油的葡萄糖百分比、甘油糖异生速率）均显著低于D组大鼠,但仍显著高于C组及C＋E组（F=68.424、41.543、68.424、40.223、17.491、86.465,均P＜0.05）.胰岛素钳夹稳态时,D＋E组大鼠内源性肝糖输出较D组大鼠显著抑制,但仍显著高于C组及C＋E组（F=85.403,P＜0.05）;其外源性葡萄糖输注率则显著高于D组大鼠,仍显著低于C组及C＋E组（F=49.954,P＜0.05）.超微结构研究显示D＋E组大鼠的肝细胞超微结构损伤显著减轻.结论 胰高糖素样肽1受体激动剂艾塞那肽显著改善糖尿病大鼠肝脏组织超微结构损伤,进而改善其肝胰岛素抵抗.

Objective To investigate the effects and mechanism of glucagon-like peptide-1 agonist exenatide on hepatic insulin resistance in high-fat diet and low-dose streptozotocin-induced diabetic rats.Methods Twenty-two 6-week-old male SD rats were randomly divided into non-diabetic control group （C,n=6）,non-diabetic＋exenatide group （C＋E,n=6）,diabetic group （D,n=5） and diabetic＋exenatide group （D＋ E,n=5）.Among them,the diabetic rats were induced by high-fat diet and low-dose streptozotocin.After eight weeks,isotope tracer technology was used to check the rate of appearance of glucose（GRa）,glycerol （GRa＇） and gluconeogenesis following infusion of 3-^3H-glucose and U-^13C-glycerol.Hepatic glucose production （HGP） and the rate of glucose infusion （GIR） were assessed using a hyperinsulinemic-euglycemic clamp with infusion of 3-^3H-glucose.Meanwhile,the ultrastructure changes of the rats＇ liver were further studied.The one-way ANOVAs followed by a Student-Newman-Keuls post hoc test for multiple comparisons were used for statistics.Results In the D＋E group,fasting blood glucose,triglyceride,total cholesterol,lower density lipoprotein,and homeostasis model assessment for insulin resistance （HOMA-IR） were significantly decreased compared with those in the D group,but still significantly higher than those in the C and C ＋ E group （F=82.827,81.648,27.613,26.300,105.234,all P〈0.05）.In the D＋E group,the GRa,GRa＇ HGP and GNG parameters （glycerol converted to glucose %,glucose derived from glycerol,gluconeogenesis from glycerol） were also decreased compared with the D group,but still significantly higher than that in the C and C＋E group （F=68.424,41.543,68.424,40.223,17.491,86.465,all P〈0.05）,while the exogenous glucose infusion rate were markedly increased compared with the D group,but still significantly lower than those in the C and C ＋ E group （F=49.954,P〈0.05）.At the same time,ultrastructure observation revealed that exenatide attenuated the swollen mitochondrial and endoplasmic reticulum inside the cells of liver of the diabetic rats.Conclusion The glucagon-like peptide-1 agonist,exenatide,can significantly improve hepatic insulin resistance through alleviating the ultrastructure damage of the hepatic cells in the diabetic rats.