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

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

Methods: 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).

Results: 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.

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