Abstract
BackgroundPreviously, we reported that vitamin A-enriched diet (129 mg/kg diet) intake reduces the adiposity development in obese rats of WNIN/Ob strain. Here, we hypothesize that dose lesser than 129 mg of vitamin A/kg diet would also be effective in ameliorating the development of obesity in these rats.MethodsFive-month-old male lean and obese rats designated as A & B were divided into four subgroups (I, II, III and IV) consisting of 8 rats from each phenotype and received diets containing 2.6 mg (control group), 26 mg, 52 mg and 129 mg vitamin A/kg diet as retinyl palmitate for 20 weeks. Body composition and morphological analysis of brown adipose tissue (BAT) was analyzed. Expression of uncoupling protein 1 (UCP1), retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) in BAT and levels of Bcl2 and Bax in epididymal white adipose tissue (eWAT) were determined by immunoblotting.ResultsVitamin A supplementation to obese rats at doses of 52 and 129 mg/kg diet showed reduced body weight gain and adiposity compared to control diet-fed obese rats receiving 2.6 mg of vitamin A/kg diet. In BAT of obese rats, vitamin A supplementation at doses of 26 and 52 mg of vitamin A/kg diet resulted in increased UCP1 expression with concomitant decrease in RARα and RXRα levels compared to control diet-fed obese rats. Further, transmission electron microscopy study revealed an increase in number of BAT mitochondria of obese rats supplemented with 26 and 52 mg of vitamin A/kg diet. Also, obese rats fed on 52 mg/kg diet resulted in increased apoptosis by altering the ratio of Bcl2 to Bax protein levels in eWAT. Notably, most of these changes were not observed in lean rats fed vitamin A-enriched diets.ConclusionIn conclusion, chronic consumption of 52 mg of vitamin A/kg diet seems to be an effective dose in ameliorating obesity possibly through mitochondriogenesis, UCP1-mediated thermogenesis in BAT and apoptosis in eWAT of obese rats. Therefore, the role of dietary vitamin A in correcting human obesity would be of unquestionable relevance and can only be addressed by future studies.
Highlights
We reported that vitamin A-enriched diet (129 mg/kg diet) intake reduces the adiposity development in obese rats of WNIN/Ob strain
The dose used in previous study was substantially high, here we hypothesized that chronic feeding of vitamin A-enriched diets less than 129 mg/kg diet would be effective in ameliorating the development of obesity in these rats
There was a reduction in the body weight gain, total body fat and fat% without affecting food intake in vitamin A fed-obese rats (BIII & BIV respectively) receiving 52 and 129 mg/kg diet, while no such changes were observed in obese rats fed on 26 mg of vitamin A/kg diet (BII) as against the control diet-fed obese rats (BI)
Summary
We reported that vitamin A-enriched diet (129 mg/kg diet) intake reduces the adiposity development in obese rats of WNIN/Ob strain. We reported that chronic feeding of diet rich in vitamin A (129 mg/kg diet) for a period of 2 months decreased body weight gain and adiposity in adult male obese rats of WNIN/Ob strain [4,5]. This was majorly attributed to the activation of thermogenic pathway through up-regulation of the uncoupling protein 1 (UCP1) gene [4]. The dose used in previous study (though within the safe upper limit) was substantially high, here we hypothesized that chronic feeding of vitamin A-enriched diets less than 129 mg/kg diet would be effective in ameliorating the development of obesity in these rats
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