LEP and obesity due to melanocortin 4 receptor deficiency: In addition, leptin down-regulated CYP24A1 and up-regulated CYP27B1, CYP27A1, and VDR, all of which play key roles in vitamin D metabolism In summary, this study confirmed the relationship between obesity, vitamin D metabolism and osteoblastic development, and the direct effect of leptin on vitamin D metabolism and osteoblastic differentiation of BMSCs may protect bone under the effect of low serum 25(OH)D in obese people (Lim et al., 2019; Li J. et al., 2020).