Relationship Between High Fat Feeding, Insulin Resistance and TNF-? Gene Expression In Growing Rats

Abstract

The purposes of this study were to examine the effects of high-fat diet on various anthropometric and biochemical parameters, and to elucidate the roles of TNF-α in the development of diet-induced insulin resistance. Thirty weanling female Sprague-Dawley rats were randomly assigned to a moderately high-fat soy oil, high-fat soy oil or high-fat tallow diet, and were provided equivalent calories per day, in excess of their requirements for growth and maintenance. After 9 weeks of diet treatment, oral glucose tolerance tests (2 g/ kg BW) were performed following an overnight fast. After 10 weeks of diet treatment, body composition analysis was performed by Dual X-Ray Absorptiometry. Liver, muscle, and fat tissues were collected for RNA analysis. Quantitative RT-PCR was used to assess TNF-α gene expression in the tissues. Statistical analysis was performed using the general linear model procedure and correlation procedure of SAS. Rats fed the high-fat diets had significantly greater body mass, percent body fat, and fasting insulin concentrations than the moderately high- fat fed rats. Fasting blood glucose and leptin concentrations were not significantly different between any of the 3 treatment groups. The high-fat diets significantly increased insulin resistance compared to the moderately high-fat diet. Rats fed high-fat tallow diets had significantly greater TNF-α mRNA abundance in liver tissue and significantly less TNF-α mRNA abundance in adipose tissue compared to the rats fed diets containing soybean oil. Results of this study demonstrate differential effects of varying fatty acid composition of high energy diets on TNF-α gene expression in adipose tissue and the liver which were associated with the development of insulin resistance in growing rats.