Effects of Vitamin D supplementation or deficiency on metabolic phenotypes in mice of different sexes

Vitamin D is a steroid hormone precursor that was initially recognized for its important roles in calcium-phosphate homeostasis and bone health. However, the resent prevalence of vitamin D deficiency has high-lighted its non-skeletal function, such as its important role in regulating endogenous metabolism. The aim of the present study was to examine the roles of vitamin D supplementation or deficiency on metabolic phenotypes in both male and female mice by using targeted metabolomics analysis. Six weeks old C57BL/6 mice of different sexes were fed with standard chow diet (1000 IU/kg vitamin D3 contained), vitamin D deficient diet (0 IU/kg vitamin D3 contained), or vitamin D enriched diet (10,000 IU/kg vitamin D3 contained) for a total of 14 weeks. Liver pathological analysis showed that vitamin D deficiency caused significant fat deposition in both male and female mice. While vitamin D supplementation was found to improve the accumulation of fat in the liver tissue. Metabolomics analysis indicated that metabolic perturbation related to vitamin D regulation in male mice mainly involved in tricarboxylic acid cycle, fatty acylcarnitine and fatty acid metabolism, sugar metabolism, glutathione metabolism, steroid hormone and pyrimidine metabolism. Based on the criteria of VIP> 1 in OPLS-DA analysis and P < 0.05 in hypothesis test, a total of 62 metabolites and 78 metabolites were found to be significantly changed in VD-deficiency group and VD-supplement group compared with the control group, respectively. While for female mice, the metabolites disturbance mainly involved in fatty acylcarnitine and fatty acid metabolism, TCA, sugar metabolism, folate cycle, methionine cycle, and purine metabolism. A total of 38 and 57 metabolites were found to be significantly changed (VIP>1 and P < 0.05) in VD-deficiency group and VD-supplement group compared with the control group, respectively. Energy metabolism was the most relevant metabolic pathway for vitamin D regulation in both male and female mice. Sex-specific changes of fatty acyl carnitines and dehydro-epiandrosterone were observed in the vitamin D supplementation groups. However, most of the energy meta-bolism related compounds exhibited the same trend in vitamin D supplementation groups of different sexes. Pearson's correlation analysis indicated that vitamin D was significantly correlated (P < 0.05) with the levels of D-fructose 6-phosphate, D-glucose 1-phosphate, D-glucose 6-phosphate, DL-pyroglutamic acid, 2-oxoglutarate, L-glutamic acid, and fumarate, which were all involved in the sugar metabolism pathway. The results achieved in this study demonstrated that vitamin D significantly regulated the metabolism of lipid and sugar, and the regulation showed a certain sex specificity.

Automated summary

Vitamin D plays important roles in calcium-phosphate homeostasis and bone health. Recent studies have shown its non-skeletal functions in regulating endogenous metabolism. This study examined the effects of vitamin D supplementation or deficiency on metabolic phenotypes in mice using targeted metabolomics analysis. The results showed that vitamin D deficiency caused fat deposition in the liver, while supplementation improved fat accumulation. Metabolic perturbations related to vitamin D regulation were observed in various metabolic pathways.