目的:观察二甲双胍对慢性暴露于高糖和高游离脂肪酸的大鼠离体胰岛细胞胰岛素分泌功能的影响。方法:将大鼠离体胰岛细胞培养于5.5~16.7 mmol/L葡萄糖或5.5 mmol/L软脂酸中48 h,再加入不同浓度二甲双胍(0~5 mg/L)培养24 h。收集各组胰岛细胞,加入5.5~16.7 mmol/L葡萄糖刺激培养1 h。收集培养液,用放免法测定其基础及葡萄糖刺激的胰岛素分泌(GSIS)水平。结果:低糖组(5.5 mmol/L葡萄糖)用不同浓度二甲双胍(0~5 mg/L)处理后的β细胞基础及葡萄糖刺激的胰岛素分泌无显著性差异(Pgt;0.05);高糖(16.7 mmol/L葡萄糖)及高脂(0.5 mmol/L棕榈酸)组β细胞基础胰岛素分泌较对照组明显增高(Plt;0.01),GSIS较对照组明显降低(Plt;0.01);用2.5~5 mg/L二甲双胍干预后,高糖及高脂组β细胞基础胰岛素分泌较未治疗组明显降低(Plt;0.01),GSIS较未治疗组明显增高(Plt;0.01)。结论:低糖环境下,二甲双胍对β细胞胰岛素分泌功能无明显影响;慢性高糖及高脂可致β细胞胰岛素分泌功能受损;而2.5~5 mg/L二甲双胍能改善糖脂毒性所致β细胞胰岛素分泌功能异常。提示二甲双胍降糖效果除了其外周作用外,可能对糖脂中毒的β细胞具有直接保护作用。
Objective To analyze the glucolipotoxicity effects of glucose combined with free fatty acid (FFA) on ketone production and ultrastructure of skeletal muscle, by exogenous elevating circulating glucose and FFA concentration. Methods Fifty Wistar rats were divided into high-fat-feed induced obesity group (OB group, n=40) and ordinary feed as normal control group (NC group, n=10). Circulating glucose and FFA levels were increased by infusion in high-fat-fed obese rats. The levels of serum lipid, plasma FFA and beta-hydroxybutyric acid were detected by the horizontal colorimetry, and the microstructure of skeletal muscle was observed by transmission electron microscopy, especially the changes of the mitochondrial structure. Euglycemic-hyperinsulinemic clamp with tracer infusion was performed to assess peripheral insulin sensitivity. Results The average weight and body fat ratio in the OB group was higher than that in the NC group (P<0.05). Insulin clamp test to assess peripheral insulin sensitivity showed that the steady-state glucose Infusion rate in the OB group during clamp test was significantly lower than that in the NC group [OB: (19.26±1.84) mg/(kg·min)vs. NC: (28.82±1.69) mg/(kg·min), P<0.05]. The mitochondrial denaturation of skeletal muscle in the OB group of rats was observed, and the swelling and crest permutation, the accumulation of lipid droplets and cavitation were formed, and hypertrophy of mitochondria were also seen after intralipid and glucose infusion, which was obvious in the combined infusion group. Conclusions By exogenous elevating circulating glucose and FFA concentration, the products of ketone body increases. The mitochondrial damage of skeletal muscle suggests that mitochondrial may be the potential target of glucoxicity and lipotocicity.