Vitamin A supplementation induces adipose tissue loss through apoptosis in lean but not in obese rats of the WNIN/Ob strain

Vitamin A is a known regulator of adipose tissue growth. In this paper, we report the possible role of dietary vitamin A supplementation in the regulation of adipose tissue mass, using a novel obese rat model of the WNIN/Ob strain developed at the National Centre for Laboratory Animal Sciences of the National Institute of Nutrition, India. Twenty-four male lean and obese rats of the WNIN/Cb strain were broadly divided into two groups at 7 months of age; each group was subdivided into two subgroups consisting of six lean and six obese rats and they were given diets containing either 2(.)6 mg or 129 mg vitamin A/kg diet for 2 months. Feeding a high but non-toxic dose of vitamin A (129 mg/kg diet) resulted in a significant reduction in the adiposity index and retroperitoneal white adipose tissue (RPWAT) weight in obese rats while a marginal reduction was observed in lean rats. Further, this treatment resulted in a significantly increased RPWAT apoptotic index and Bax protein expression and a decreased expression of Bcl2 in the lean rats. However, no such changes were observed in the RPWAT of the obese rats subjected to identical treatment. Thus, our data suggests that chronic dietary vitamin A supplementation at a high dose effectively regulates adipose tissue mass both in the lean and obese phenotypes of the WNIN/Ob rat strain, perhaps through different mechanisms.