Vitamin D Does Not Play a Functional Role in Adipose Tissue Development in Rodent Models

Scope Several studies have proposed a role of vitamin D in adipogenesis. Here, we sought to study the impact of the vitamin D receptor (Vdr) on adipocyte size in young and old mice and the effect of maternal vitamin D deficiency on fetal adipogenesis. Methods and results Histological analysis of adipose tissues shows that Vdr knockout (KO) mice have smaller adipocytes than wild‐type (WT) mice. Next, we compare young and old Vdr‐KO and WT mice and find no differences in adipocyte sizes between weaned Vdr‐KO and WT mice. However, 1‐year‐old Vdr‐KO mice, suffering from alopecia, have smaller‐sized adipocytes than WT mice, although they consume more food. To elucidate whether vitamin D can directly impact adipocyte development at a critical stage of adipogenesis, we feed rat dams a vitamin D deficient (0 IU kg−1) or vitamin D adequate (1000 IU kg−1) diet. Neither DNA microarray analysis of the adipose tissues of the newborn rats nor the adipocyte sizes of 21‐day‐old offspring show significant differences between the two groups. Conclusion Data indicate that vitamin D does not play a fundamental role in adipogenesis because vitamin D does not affect fetal adipogenesis. Moreover, the smaller adipocytes observed in adult Vdr‐KO mice are presumably caused by an increased energy expenditure due to alopecia. Vitamin D is involved in a plethora of functions and has repeatedly been shown to influence cell proliferation, differentiation, and morphology. The role of vitamin D in adipocytes and adipogenesis is elucidated. In two experiments using vitamin D receptor knockout mice, it is found that vitamin D affects adipose tissue morphology, but has no effects on biomarkers of nutrient oxidation.