目的:阐明在营养过度刺激条件下二甲双胍对胰岛素原合成和胰岛素的影响。
方法:将来自7名供体的人胰岛在5.5mmol/L葡萄糖和0.5mmol/L棕榈酸盐下培养12、24或72小时。最初12小时后,将二甲双胍(25μmol/L)与棕榈酸盐一起引入。测量胰岛素原和胰岛素。激素原转化酶1/3(PC1/3)和羧肽酶E(CPE)的表达,通过蛋白质印迹测定。青少年肥胖,用二甲双胍和正常葡萄糖耐量治疗(n=5),糖尿病前期(n=14),包括或2型糖尿病(T2DM;n=7)。空腹胰岛素原,胰岛素,葡萄糖,测量2小时葡萄糖和糖化血红蛋白。计算胰岛素原/胰岛素比率(PI/I)。
结果:在人类胰岛中,棕榈酸盐治疗12和24小时会按比例增加胰岛素原和胰岛素。72小时后,胰岛素原而不是胰岛素继续增加,这与PC1/3和CPE的表达降低有关。PC1/3和CPE的二甲双胍归一化表达,胰岛素原和胰岛素分泌。在肥胖的青少年中,治疗前,2型糖尿病患者的空腹胰岛素原和胰岛素浓度高于正常糖耐量患者。2型糖尿病患者和糖尿病前期患者接受二甲双胍治疗后PI/I降低,再加上减少2小时葡萄糖和糖化血红蛋白。
结论:长期营养过度刺激后,二甲双胍使胰岛素原和胰岛素分泌正常,再加上转化酶的标准化,在孤立的胰岛中。在肥胖的青少年中,二甲双胍治疗与改善PI/I相关,与改善血糖控制相结合。
To elucidate how proinsulin synthesis and insulin was affected by metformin under conditions of nutrient overstimulation.
Isolated human pancreatic islets from seven donors were cultured at 5.5 mmol/L glucose and 0.5 mmol/L palmitate for 12, 24 or 72 h. Metformin (25 μmol/L) was introduced after initial 12 h with palmitate. Proinsulin and insulin were measured. Expression of prohormone convertase 1/3 (PC1/3) and carboxypeptidase E (CPE), was determined by western blot. Adolescents with obesity, treated with metformin and with normal glucose tolerance (n = 5), prediabetes (n = 14), or type 2 diabetes (T2DM; n = 7) were included. Fasting proinsulin, insulin, glucose, 2-h glucose and glycated haemoglobin were measured. Proinsulin/insulin ratio (PI/I) was calculated.
In human islets, palmitate treatment for 12 and 24 h increased proinsulin and insulin proportionally. After 72 h, proinsulin but not insulin continued to increase which was coupled with reduced expression of PC1/3 and CPE. Metformin normalized expression of PC1/3 and CPE, and proinsulin and insulin secretion. In adolescents with obesity, before treatment, fasting proinsulin and insulin concentrations were higher in subjects with T2DM than with normal glucose tolerance. PI/I was reduced after metformin treatment in subjects with T2DM as well as in subjects with prediabetes, coupled with reduced 2-h glucose and glycated haemoglobin.
Metformin normalized proinsulin and insulin secretion after prolonged nutrient-overstimulation, coupled with normalization of the converting enzymes, in isolated islets. In adolescents with obesity, metformin treatment was associated with improved PI/I, which was coupled with improved glycaemic control.