The effects of 1,25(OH) 2 D 3 treatment on immune responses and intracellular metabolic pathways of bone marrow-derived dendritic cells from lean and obese mice.

Vitamin D affects differentiation, maturation, and activation of dendritic cells (DCs). Obesity-related immune dysfunction is associated with metabolic changes in immune cells. Objectives of the study are to investigate the effects of vitamin D and obesity on immune responses and markers related to immunometabolism of bone marrow-derived dendritic cells (BMDCs). Bone marrow cells (BMCs) were isolated from lean and obese mice, and BMDCs were generated by culturing BMCs with rmGM-CSF. BMDCs were treated with 1 or 10 nM of 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ), and maturation was induced by LPS (50 ng/ml) stimulation for 24 hr. Cell phenotypes, cytokine productions, and expression of proteins and genes involved in Akt/mTOR signaling pathway and glycolytic pathway were determined. 1,25(OH) 2 D 3 treatment inhibited differentiation of BMDCs (CD11c + %), expression of phenotypes related with DC function (MHC class II and CD86) and production of IL-12p70 in both lean and obese mice. The expression of PD-L1 and the ratio of IL-10/IL-12p70 were increased by 1,25(OH) 2 D 3 . With 1,25(OH) 2 D 3 treatment, Akt/mTOR signaling pathway was suppressed, and expression of genes related to glycolysis (Glut1, Pfkfb4, and Hif1A) was increased. The upregulation of glycolysis-related genes observed with 1,25(OH) 2 D 3 treatment seems to be associated with the induction of tolerogenic features of BMDCs from lean and obese mice, and Hif1A seems to have a potential role in conveying the effect of 1,25(OH) 2 D 3 on glycolysis.