Experimental protocol
After 2 weeks of acclimatization, fasting blood glucose (FBG) levels of KKAy mice were estimated by using a glucometer (Kyoto, Japan). The mice with FBG (after 5 h fasting) values >11.1 mmol/L were considered as diabetic and randomly divided into 2 groups according to their body weight and blood glucose levels: control group, KKAy mice were administered by daily oral gavage with 0.5% sodium carboxy methyl cellulose (CMC-Na) alone (n = 10); and metformin group, KKAy mice were administered by oral gavage with metformin (200 mg/kg/day) dissolved in 0.5% CMC-Na (n = 10). The dosage we used was according to previous report [4] and the result of pre-experiment. These agents were administered to each mouse for 5 weeks at about 8:30 a.m everyday. FBG of each animal was recorded every week.