高脂喂养联合链脲佐菌素注射的糖尿病大鼠模型特征

A Rat Model of Type 2 Diabetes Mellitus Induced by High Fat Chow and Low Dose Streptozotocin Injection

目的观察高脂喂养联合低剂量STZ注射的Sprague Dawley(SD)大鼠2型糖尿病模型的代谢特征、病理学以及胰岛分子生物学变化.方法4周龄雄性SD大鼠36只随机分为三组:(1)正常对照组(Control)9只,普通饲料喂养.(2)高脂组(High Fat chow,HE)9只,高脂饲料喂养,为普通饲料中添加20%脂肪(猪油和蛋黄粉各50%)和20%蔗糖.(3)糖尿病组(DM)18只.喂养4周后腹腔注射STZ(40 mg/kg).所有大鼠做灌胃葡萄糖耐量(OGTY)试验.放免法测定血清胰岛素,免疫组化染色观察胰岛β细胞的形态学特点,彩色图像分析系统测定胰岛素表达量,RT-PCR测定胰腺β细胞胰岛素mRNA表达水平.结果糖尿病大鼠空腹血糖(FBG)、胰岛素水平(FINS)显著高于Control组和HE组大鼠(P＜0.01),空腹血清甘油三酯(TG)和游离脂肪酸(FFA)水平显著高于Control组(P＜0.05);胰岛β细胞吸光度(A)显著低于高脂组大鼠(P＜0.05),降低11.6%.胰岛素免疫反应阳性区占胰岛百分比显著低于Control组和HE组,分别下降31.9%(P＜0.05)和43.1%(P＜0.01).胰岛素mRNA表达水平显著低于HE组(P＜0.05).STZ注射后48 h(基线值)大鼠FBG水平的分布情况为:A组(FBG＜10.0 mmol/L)占7/18;B组(FBG 10～19.9 mmol/L)占5/18;C组(FBG≥20mmol/L)占6/18.STZ注射后9 d的0GTT结果与基线值相比,B组OGTT值总体变化最小,A组FBG的变异最大,达到25%.结论高脂喂养联合低剂量STZ注射的糖尿病大鼠模型模拟2型糖尿病发生的主要病理生理过程,具有高血糖、高胰岛素血症以及血脂异常等基本特征.

Objective To investigate the metabolic features, morphological changes of pancreatic islets and insulin mRNA expression in Sprague Dawley （SD） rat model of type 2 diabetes mellitus （T2DM）, induced by high fat chow and low dose of streptozotocin （STZ） injection. Methods Thirty six 4 week-old male SD rats initially weighing 83.3 ± 5.1 g, got from the Peking University Health Science Center, were randomly divided into three groups： （ 1 ） Control group （Control, n = 9）, fed with a standard chow. （2） High fat chow group （HF, n = 9）, fed with extra high-fat chow containing 20% fat （50% lard and 50% yolk powder） and 20% sugar. （3） Diabetes mellitus group （DM, n = 18）, induced by intraperitoneal injection （i. p） of STZ （40mg/kg） after 4 weeks of high-fat chow feeding. Oral glucose tolerance test （OGTY） was peformed. Serum insulin levels, morphologic changes of pancreatic islet β cells and insulin mRNA expression of β cells were detected by radioimmunoassay, immunohistochemistry and reverse transcriptase-polymerase chain reaction （RT-PCR）, respectively. The insulin content of islet cells was quantified with a color image analyzer. Results In diabetic rats, fasting blood glucose level （FBG） and serum insulin level （FINS） were prominently increased （P 〈 0.01）, as compared with those of control and HF groups. However, serum triglyceride （TG） and free fat acid level （FFA） were only higher than those in control group （P 〈 0.05）. Optical density （OD） values of islet （cells were remarkably decreased in comparison with those in HF group（ P 〈 0.05）. There were 31.9% and 43.1% less immunohistochemically-stained insulin areas per islet in the diabetic group in comparison with that in control （ P 〈 0.05） and HF groups （ P 〈 0.01）. Insulin mRNA expression was notably reduced than that of HF group（ P 〈 0.05）. On the basis of FBG levels measured at 48 h after STZ administration （baseline values）, the diabetic rats distribution was as following： group A （FBG〈 10.0 mmol/L） accounting for 7/18, group B （FBG 10 - 19.9 mmol/L） 5/18 and group C（FBG≥20 mmol/L） 6/18. Among the three groups, in comparison with the baseline values, the OGTT values measured at 9 days after STZ injection showed a least total change in the group B and a most considerable FBG variation in the group A, up to 25 % . Conclusion A rat model developed by high fat chow and low dose STZ injection presented major pathophysiological manifestations of type 2 diabetes mellitus such as hyperglycemia, hyperinsulinemia and dyslipidemia.