二甲双胍对2型糖尿病大鼠血清和胰腺骨钙素水平的影响

目的探讨骨钙素对2型糖尿病大鼠胰岛B细胞功能的影响，分析二甲双胍干预下骨钙素与糖、脂及胰岛素代谢的关系。方法将36只8周龄健康雄性SD大鼠（体重180～230g）按随机数字表法分为正常对照组、非二甲双胍干预组和二甲双胍干预组，每组各12只。正常对照组予普通饲料喂养，其他2组予高脂饲料喂养。第8周末，非二甲双胍干预组和二甲双胍干预组腹腔注射25μg/g链脲佐菌素，正常对照组注射25μg／g无菌柠檬酸一柠檬酸钠溶液。第10周末行口服葡萄糖耐量试验，二甲双胍干预组予100mg·kg-1·d-1二甲双胍灌胃4周，其他2组予同体积蒸馏水灌胃。第4、8、10、14周末取血，检测空腹血糖、空腹胰岛素、胰岛素敏感指数、甘油三酯、总胆固醇、高密度脂蛋白胆固醇及骨钙素水平。14周末处死大鼠，光镜下观察胰腺组织病理改变，采用免疫组化SP法检测胰腺组织骨钙素变化。采用单因素方差分析、LSD法和Pearson直线相关分析进行数据统计。结果第10周末，非二甲双胍干预组大鼠成模10只，二甲双胍干预组大鼠成模9只。第8周末，非二甲双胍干预组和二甲双胍干预组体重、甘油三酯、总胆固醇和空腹胰岛素水平明显高于正常对照组（F值分别为86．04、74．25、13．12、157．65，均P〈0．01），高密度脂蛋白胆固醇和胰岛素抵抗指数低于正常对照组（F值分别为12．13、24．01，均P〈0．01）。第14周末，非二甲双胍干预组和二甲双胍干预组胰腺组织骨钙素含量较正常对照组显著减少（分别为0．84±0．09、2．55±0．24、3．17±0．08，F=12．14，P〈0．05）。Pearson相关分析示，胰腺骨钙素含量与空腹血糖、甘油三酯、总胆固醇呈负相关（r值分别为-0．811、-0．699、-0．733，均P〈0．05），与空腹胰岛素、胰岛素抵抗指数、高密度脂蛋白胆固醇呈正相关（r值分别为0．826、0．414、0．706，均P〈0．05）。结论骨钙素能促进2型糖尿病大鼠胰岛B细胞分泌胰岛素。二甲双胍干预后血清和胰腺骨钙素含量增加，提示其可能具有促进骨钙素分泌的功能。

Effects of metformin on serum and pancreas osteocalcin in type 2 diabetic rats

Objective To investigate the effect of osteocalcin on function of β-cell in type 2 diabetic rats, and to analyze the relationship of metformin with osteocalcin, glucose, lipid and insulin metabolism. Methods Thirty-six healthy Sprague-Dawlay （SD） rats aged 8 weeks were randomly assigned to group A （ n = 12）, B （ n = 12 ） , and C （ n = 12 ）. Those of group A were fed normally, while those of group B and C were fed with high-fat diet. At 8 weeks, 25 μg/g streptozotocin （STZ） was injected into abdominal cavity of rats in group B and C, and 25 μg/g sodium citrate solution was injected into rats in group A. At 10 weeks, oral glucose tolerance test （OGTF） was conducted, and the rats of group C were treated with 25 mg·kg-1 · d-1 metformin for 4 weeks. At 4, 8, 10 and 14 weeks, serum levels of osteocalcin, fasting plasma glucose （FPG）, fasting insulin （FINS）, insulin sensitivity index （ISI）, triglyceride （TG）, total cholesterol （TC）, and high-density lipoprotein cholesterol （HDL-C） were tested. At 14 week, all the rats were killed, and the pancreatic tissue was observed under microscope. The expression of osteocalcin was detected by immunohistochemical method. One-way of variance, LSD t test and Pearson linear correlation were used for data analysis. Results At 10 weeks, 19 diabetic rats were successfully established in group B and C. At 8 weeks, body weight, TG, TC, and FINS in group B and C were significantly higher than those in group A （F values were 86. 04, 74. 25, 13.12 and 157.65, respectively; all P 〈 0. 01 ）, while HDL-C and ISI were lower （ F values were 12. 13 and 24. 01, respectively; all P 〈 0. 01 ）. At 14 weeks, in group B and C, osteocalcin in pancreas were significantly decreased （0. 84 ＋ 0.09, 2. 55 ＋ 0. 24 and 3. 17 -＋ 0. 08, respectively; F value was 12. 14, P 〈 0. 05 ）. Pearson linear correlation analysis showed that pancreas osteocalcin was negatively correlated with FPG, TG and TC （ r values were - 0. 811, - 0. 699 and - 0. 733, respectively; all P 〈 0. 05 ） , and positively correlated with serum FINS, ISI, and HDL-C （r values were 0. 826, 0. 414 and 0. 706, respectively; all P 〈 0.05）. Conclusions Osteocalcin could promote islet β-cells insulin secretion in type 2 diabetes rats. Serum and pancreas osteocalcin in group C was higher than that in group B after intervention with metformin, which suggests that metformin may promote the secretion of osteocalcin.