Increased Energy Expenditure, Ucp1 Expression, and Resistance to Diet-induced Obesity in Mice Lacking Nuclear Factor-Erythroid-2-related Transcription Factor-2 (Nrf2).

The NRF2 (also known as NFE2L2) transcription factor is a critical regulator of genes involved in defense against oxidative stress. Previous studies suggest thatNrf2plays a role in adipogenesisin vitro, and deletion of theNrf2gene protects against diet-induced obesity in mice. Here, we demonstrate that resistance to diet-induced obesity inNrf2(-/-)mice is associated with a 20-30% increase in energy expenditure. Analysis of bioenergetics revealed thatNrf2(-/-)white adipose tissues exhibit greater oxygen consumption. White adipose tissue showed a >2-fold increase inUcp1gene expression. Oxygen consumption is also increased nearly 2.5-fold inNrf2-deficient fibroblasts. Oxidative stress induced by glucose oxidase resulted in increasedUcp1expression. Conversely, antioxidant chemicals (such asN-acetylcysteine and Mn(III)tetrakis(4-benzoic acid)porphyrin chloride) and SB203580 (a known suppressor ofUcp1expression) decreasedUcp1and oxygen consumption inNrf2-deficient fibroblasts. These findings suggest that increasing oxidative stress by limitingNrf2function in white adipocytes may be a novel means to modulate energy balance as a treatment of obesity and related clinical disorders.

Telmisartan but not valsartan increases caloric expenditure and protects against weight gain and hepatic steatosis.

The potential effects of angiotensin II receptor blockers (ARBs) on adipose tissue biology and body weight are of considerable interest, because these agents are frequently used to treat hypertension in patients who are prone to visceral obesity, the metabolic syndrome, and diabetes. In rats fed a high-fat, high-carbohydrate diet, we compared the effects of 2 ARBs, telmisartan and valsartan, on body weight, food intake, energy expenditure, fat accumulation, fat cell size, and hepatic triglyceride levels. Telmisartan, but not valsartan, promoted increases in caloric expenditure and protected against dietary-induced weight gain. In the telmisartan-treated rats, absolute food intake, but not food intake adjusted for body weight, was lower than in valsartan-treated rats or controls. Telmisartan reduced the accumulation of visceral fat and decreased adipocyte size to a much greater extent than valsartan and was also associated with a significant reduction in hepatic triglyceride levels. Moreover, telmisartan, but not valsartan, increased the expression of both nuclear-encoded and mitochondrial-encoded genes in skeletal muscle known to play important roles in mitochondrial energy metabolism. Thus, in addition to a class effect of ARBs in modulating adipocyte size, these findings raise the possibility that certain molecules, like telmisartan, may have a particularly strong impact on fat cell volume and fat accumulation, as well as distinctive effects on energy metabolism, that may help protect against dietary-induced visceral obesity and weight gain.