Effect of high fat diet on skeletal muscle uncoupling protein 3 and hypothalamic neuropeptide Y expression in rats

Abstract

Obesity results when energy intake is greater than energy expenditure. Skeletal muscles (SK.M) UCP3 and central NPY play an important role in energy balance. The aim is to study the effects of high-fat diet for 16 weeks on (SK.M) UCP3 expression [mRNA and protein], and hypothalamic NPYmRNA expression in rats. Obese-prone Sprague Dawley rats were fed beef tallow (46%) of energy as fat "HFD" and control group fed libitum diets containing 4.5% of energy as fat (control), for 16 weeks. Body weight and food intake were measured every 3 days throughout the experimental period. After the feeding period is completed, hindlimb skeletal muscle was isolated for subsequent determinations of triglyceride. Skeletal UCP3 mRNA& protein expression and hypothalamic NPY and long isoform of leptin receptor (Ob-Rb) mRNA were assessed by (RT-PCR) and Immunoblotting respectively. Plasma glucose, triglyceride, insulin, leptin, and free fatty acids levels were significantly higher in rats fed the HFD compared to control group, while circulating adiponectin level was significantly reduced in HFD rats. HFD resulted in a significant increase in (SK.M) triglyceride, and mRNA levels of skeletal UCP3 mRNA and protein by (3.84 folds) and (2.1 folds) respectively, but without significant change in hypothalamic NPY mRNA and Ob-Rb mRNA expressions compared to control group. The results show that high fat diet induces obesity with marked induction of UCP3 expression. The development of obesity in spite of the upregulation of UCP3 may indicate that obesity may be caused by mechanisms independent of thermogensis and the central mechanisms could be involved.