Peroxisome proliferator-activated receptor alpha (PPARalpha) activation in rodents is thought to improve insulin sensitivity by decreasing ectopic lipids in non-adipose tissues. Fenofibrate, a lipid-modifying agent that acts as a PPARalpha agonist, may prevent adipocyte hypertrophy and insulin resistance by increasing intracellular lipolysis from adipose tissue. Consistent with this hypothesis, fenofibrate decreased visceral fat mass and adipocyte size in high fat diet-fed obese mice, and concomitantly increased the expression of PPARalpha target genes involved in fatty acid beta-oxidation in both epididymal adipose tissue and differentiated 3T3-L1 adipocytes. However, mRNA levels of adipose marker genes, such as leptin and TNFalpha, were decreased in epididymal adipose tissue by fenofibrate treatment. Fenofibrate not only reduced circulating levels of free fatty acids and triglycerides, but also normalized hyperinsulinemia and hyperglycemia in obese mice. Blood glucose levels of fenofibrate-treated mice were significantly reduced during intraperitoneal glucose tolerance test compared with obese controls. These results suggest that fenofibrate-induced fatty acid beta-oxidation in visceral adipose tissue may be one of the major factors leading to decreased adipocyte size and improved insulin sensitivity.
3T3 Cells ; Adipocytes/cytology/*drug effects ; Animals ; Antilipemic Agents/*pharmacology ; Blood Glucose ; Body Weight ; Cell Enlargement/*drug effects ; Dietary Fats ; Gene Expression Regulation/drug effects ; Glucose Tolerance Test ; Insulin/blood ; *Insulin Resistance ; Leptin/genetics ; Lipids/blood ; Mice ; Mice, Inbred C57BL ; Mice, Obese ; PPAR alpha/*metabolism ; Procetofen/*pharmacology ; Tumor Necrosis Factor-alpha/genetics

Leptin receptor deficiency causes morbid obesity and hyperlipidemia in mice. Since physical exercise enhances energy expenditure, it is an important part of successful weight-control regimens. We investigated the mechanism by which swim training regulates leptin receptor deficiency-induced obesity and lipid disorder in a mouse model of obesity (obese db/db mouse). Swim training for 6 weeks significantly decreased body weight gain and adipose tissue mass in both sexes of obese and lean mice, compared to their respective sedentary controls. These effects were particularly evident in obese mice. Swim training also caused significant decreases in serum levels of triglycerides, free fatty acids and total cholesterol in both obese and lean mice. In obese mice, swim training increased the levels of mRNAs and proteins encoding uncoupling protein 1 (UCP1), UCP2 and UCP3 in brown adipose tissue, white adipose tissue and skeletal muscle, respectively. In conclusion, these findings suggest that, in mice, swim training can effectively prevent body weight gain, adiposity and lipid disorders caused by leptin receptor deficiency, in part through activation of UCPs in adipose tissue and skeletal muscle, which may contribute to alleviating metabolic syndromes, such as obesity, hyperlipidemia and type 2 diabetes.
Adipose Tissue/metabolism ; Animals ; Body Weight ; Female ; Ion Channels/genetics/*metabolism ; Lipid Metabolism ; Male ; Mice ; Mitochondrial Proteins/genetics/*metabolism ; Muscle, Skeletal/metabolism ; Obesity/genetics/*metabolism/prevention & control ; *Physical Conditioning, Animal ; RNA, Messenger/metabolism ; Receptors, Cell Surface/*deficiency/genetics/*metabolism ; Receptors, Leptin ; Swimming