Bidirectional effect of vitamin D on brown adipogenesis of C3H10T1/2 fibroblast-like cells

Brown adipose tissue (BAT) dissipates caloric energy as heat and plays a role in glucose and lipid metabolism. Therefore, augmentation and activation of BAT are the focus of new treatment strategies against obesity, a primary risk factor of metabolic syndrome. The vitamin D system plays a crucial role in mineral homeostasis, bone metabolism, and cell proliferation and differentiation. In this study, we investigated the effects of vitamin D3 [1,25(OH)2D3] on brown adipocyte differentiation.

These data indicate the potential of vitamin D and its analogs as therapeutics for the treatment of obesity and related metabolic diseases.

The mouse fibroblast-like cell line C3H10T1/2 was differentiated into brown adipocytes in the presence of 1,25(OH)2D3. The effect of 1,25(OH)2D3 on brown adipocyte differentiation was assessed by measuring lipid accumulation, the expression of related genes, and cytotoxicity. The viability of C3H10T1/2 cells was measured using the Cell Counting Kit-8 assay. Gene expression was investigated using quantitative reverse transcription-polymerase chain reaction. Protein expression was estimated using western blotting.

1,25(OH)2D3 inhibited adipocyte differentiation and exerted a cytotoxic effect at 1 nM. However, in the physiological concentration range (50-250 pM), 1,25(OH)2D3 promoted uncoupling protein 1 (UCP1) expression in C3H10T1/2 cells. This effect was not observed when 1,25(OH)2D3 was added 48 h after the initiation of differentiation, suggesting that the vitamin D system acts in the early phase of the differentiation program. We showed that 1,25(OH)2D3 increased the expression of two key regulators of brown adipogenesis, PR domain containing 16 (Prdm16) and peroxisome proliferator-activated receptor γ coactivator-1α (Pgc1α ). Furthermore, 1,25(OH)2D3 increased Ucp1 expression in 3T3-L1 beige adipogenesis in a dose-dependent manner.