Dietary conjugated linoleic acid increases PPARγ gene expression in adipose tissue of obese rat, and improves insulin resistance

Conjugated linoleic acid (CLA) is a class of positional, geometric, conjugated dienoic isomers of linoleic acid. Dietary CLA supplementation has resulted in a dramatic decrease in body fat mass in mice. However, some but not all studies in mice and humans have found that CLA promoted insulin resistance, and there were conflicting reports on the effects of CLA on peroxisomal proliferator-activated receptor-gamma (PPAR gamma) activation and expression. The objective of present study was to investigate the effect of CLA on insulin resistance and its molecular mechanisms. Fifty male Wistar rats were randomly designed to the control, high-fat and high-fat with CLA (0.75. 1.50. and 3.00 g in per 100 g diet) groups. The effect of CLA on insulin sensitivity and the mechanism of resisting diabetes by CLA were investigated by RT-PCR assay. The results showed that supplementation with CLA significantly reduced body weight gain and white fat pad weight in the rats, the levels of plasma free fatty acids (FFA), triglycerides (TGs), cholesterin (TC), leptin, insulin and blood glucose concentration in the obese rats of CLA group were also decreased compared to the rats in the high-fat group. Dietary CLA increased the mRNA expression of PPAR gamma, fatty acid binding proteins (aP2), fatty acid transporter protein (FATP), acyl-CoA synthetase (ACS) and adiponectin in the adipose tissues of obese rats. The results suggest that CLA may ameliorate insulin resistance by activating PPAR gamma, and increasing the expression of PPAR gamma target genes such as apt, FATP, FAT, and adiponectin in the white adipose tissue. (C) 2008 Elsevier Ltd. All rights reserved.