Dietary vitamin A supplementation in rats: suppression of leptin and induction of UCP1 mRNA

All-trans-retinoic acid (RA), an active metabolite of vitamin A, induces th e gene expression of uncoupling protein 1 (UCP1) in brown adipose tissue (B AT) and suppresses leptin gene expression in white adipose tissue (WAT) whe n given as an acute dose, These contrasting effects of RA leave in doubt th e overall effect of chronic RA or vitamin A supplementation on energy homeo stasis, To investigate the effects of dietary vitamin A supplementation on leptin and UCP1 gene expression, rats were fed either a normal diet (2.6 re tinol/kg diet) or a vitamin A-supplemented diet (129 mg retinol/kg diet) fo r 8 weeks, and adiposity, serum leptin levels, leptin mRNA levels in perire nal WAT, UCP1 and UCP2 mRNA levels in BAT, and beta(3)-adrenergic receptor mRNA levels in BAT and WAT were examined, Rats on both diets gained a simil ar amount of weight, but there was a small 9% decrease in the adiposity ind ex in the vitamin A-supplemented rats. Dietary vitamin A supplementation in creased UCP1 gene expression in BAT by 31%, but suppressed leptin gene expr ession by 44% and serum leptin levels by 65%, UCP2 and beta(3)-adrenergic r eceptor gene expression in BAT and perirenal WAT were unchanged by the vita min A diet. These data suggest that dietary vitamin A has a role in regulat ing energy homeostasis by enhancing UCP1 gene expression and decreasing ser um leptin levels.