Establishment and Assessment of Mice Models of Type 2 Diabetes Mellitus

Objective To establish type 2 diabetes mellitus(T2DM)KM mouse models via the combined use of high-calorie diet and multiple administration of low-dose streptozotocin(STZ). Methods Based on the randomized number table,30 KM mice were equally and randomly divided into 2 groups:modeling group and control group. Mice in the modeling group were given foods with high calories for one month and injected with 30 mg/kg STZ via the left lower abdominal cavity for 2-4 consecutive days,while mice in the control group were fed with standard maintenance foods and the same dose of citrate buffer solution. The general conditions including food and water intake and mice weight were recorded. Blood glucose level was measured 1,2,4,5,12,and 21 weeks after STZ injection. When the glucose level became stabilized,the serum insulin and blood lipids [including total cholesterol(TC),triacylglycerol(TG),high-density lipoprotein(HDL) and low-density lipoprotein(LDL)],and hemoglobin a1c (HbA1c)were measured,and oral glucose tolerance test were performed. Results The modeling group had a 100% survival rate. After STZ injection,the body weight of mice in the modeling group reached the peak in the forth week,and later the growth rate decreased,still significantly lower than that of control group mice till the 21^st week(t=3.160,P=0.006). Their blood glucose level was significantly higher than that of mice before STZ injection and in the control group(all P<0.05);as time went on,it was also rising,and it remained high till the 21^st week [(26.38±1.34)mmol/L]. In the 4^th week,the fasting blood glucose of mice in the modeling group was(11.86±3.33)mmol/L,which was significantly higher than that of mice in the control group [(6.37±1.27)mmol/L](t=-3.830,P=0.002). Fasting serum insulin of mice in the modeling group showed no significant difference compared with control group [(5.73±0.24)mU/L vs.(5.48±0.32)mU/L;t=-0.863,P=0.416]. Insulin sensitivity index was 0.0145±0.0039,which was significantly lower than that(0.0267±0.0039)in control group(t=4.414,P=0.003). In the 6^th week,the blood glucose levels of mice in the modeling group were(15.35±1.82),(26.45±1.07),(25.58±1.46),and(26.15±1.00)mmol/L 0,30,60,and 120 min after oral gavage of D-glucose,which were all significantly higher than those in the control group [(6.88±1.75)(t=-8.203,P=0.000),(17.65±2.94)(t=-6.884,P=0.000),(13.18±2.04)(t=-12.110,P=0.000),and(7.37±3.40)mmol/L(t=-12.969,P=0.000)]. In the 8^th week,serum TC and TG levels of mice in the modeling group were(3.83±0.06)and(2.20±0.20)mmol/L,which were significantly higher than those in the control group [(3.10±0.10)(t=11.000,P=0.000)and(0.90±0.10)mmol/L(t=10.070,P=0.000)]. HDL level of mice in the modeling group was(2.03±0.06)mmol/L,which was significantly lower than that in the control group [(2.48±0.02)mmol/L;t=11.662,P=0.000]. LDL level was increased but showed no significant difference [(0.34±0.08)mmol/L vs.(0.26±0.02)mmol/L](t=1.680,P=0.168). HbA1c content of mice in the modeling group was(7.30±0.31)%,which was significantly higher than that(4.40±0.32)% in the control group(t=-11.587,P=0.000). Conclusion KM mice models of T2DM were successfully established after high-calorie diet and multiple administration of low-dose STZ.