Abstract:

Objective     To investigate the effects of long-term high-protein diet on expressions of IRS2 and GLUT2 in the liver of diet-induced obese rats. Methods      Diet-induced obese rat models were established by feeding Wistar rats(n=34) a high-calorie and high-fat diet. The obese male rats were randomly divided into three groups: the high-protein diet group ( HP group, n=12, protein: 36.7% ) , the high-fat diet group (HF group, n=11, fat: 38.3%), and the normal food group ( NC group, n=11 ).The total calorie ingestion of each rat per day was similar and consistent for 24 weeks. After 24 weeks, fasting blood glucose ( FBG ) and fasting blood insulin(FINS ) were assayed and  QUICKI was calculated to evaluate the insulin sensitivity. mRNA and protein expressions of IRS2 and GLUT2 were determined by RT-PCR and the Western blot method. Results     The insulin sensitivity index (QUICKI) of the HP group was 11.31% higher(P<0.05)than that of the NC group. Also, among the HP group, the IRS2 mRNA and protein were 16% (P<0.05) and 24%(P<0.05)higher, while the GLUT2 mRNA and protein were 24%(P<0.05) and 25%(P<0.05)higher. However, the corresponding indicators of the HF group, compared with those of the NC group, were remarkably low. Conclusion      A long-term high-protein diet can raise expressions of IRS2 and GLUT2 in the liver of diet-induced obese rats. This may be one of the mechanisms of how a long-term high-protein diet can improve the insulin sensitivity of diet-induced obese rats.

Key words: High- protein diet; Diet-induced obesity; Insulin sensitivity; IRS2; GLUT2; Rat, Wistar