Effects of konjac extract on insulin sensitivity in high fat diet rats

To evaluate the effects of konjac extract (KE) on insulin sensitivity in insulin resistance (IR) rats induced by high fat diet (HFD).

Wistar rats were fed on HFD for 4 weeks, then treated with KE 1.5, 3.0 g/kg/d and metformin (Met) 0.1 g/kg/d for 4 weeks, respectively. The effects of KE on intake of food and drink, body weight, and excretion were investigated. Serum insulin was measured by double-radioimmunoassay. Blood glucose, total cholesterol (TC), triglycerides (TG), and high-density lipoprotein-cholesterol (HDL-C) were measured by enzyme methods, respectively. Low-density lipoprotein-cholesterol (LDL-C) was calculated. Tissue glycogen was determined by modified anthracene ketone method and tissue TG by glycerin phosphor sour oxidation enzyme method. Insulin sensitivity was measured by modified glucose-insulin tolerance test (K value).

HFD caused IR after 4 weeks (K value: 5.2+/-0.9 vs 8.3+/-0.7, P<0.01), the levels of blood insulin, TG, and LDL-C increased, while HDL-C, glycogen in liver and skeletal muscle decreased. The storage of TG in liver and skeletal muscle increased. After HFD rats were treated with KE 1.5 and 3.0 g/kg/d for 4 weeks, respectively, the fasting blood glucose (FBG) was decreased from 6.4+/-0.4 to 6.05+/-0.26, 6.0+/-0.3 (P<0.01). Serum TC, TG, LDL-C were decreased, while HDL-C/TC was increased as compared with HFD rats. There was no significant effect on insulin level. KE 1.5, 3.0 g/kg/d, and Met 0.1 g/kg/d could improve insulin sensitivity (K values were 6.1+/-0.5, 5.9+/-0.6, and 6.5+/-0.8 vs 5.2+/-0.9, P<0.05), elevate glycogen, and decrease TG in liver and skeletal muscle.

KE could promote glycogen syntheses and adjust blood lipid metabolism so as to improve IR in HFD rats.