The effects of 1,25(OH) 2 D 3 treatment on metabolic reprogramming and maturation in bone marrow-derived dendritic cells from control and diabetic mice.

Activated dendritic cells (DCs) undergo significant metabolic reprogramming, which is characterized by an increase in aerobic glycolysis and a concurrent progressive loss of oxidative phosphorylation. The modulation of metabolic reprogramming is believed to be closely related to the function of DCs. Vitamin D has been reported to inhibit the maturation of DCs. DC dysfunction has been reported in diabetic patients, and hyperglycemia is associated with impaired glycolytic metabolism in immune cells. Therefore, vitamin D and diabetes may affect intracellular metabolism, thereby regulating the activity of DCs. We investigated the effect of in vitro treatment of 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) on metabolic reprogramming and maturation of bone marrow-derived dendritic cells (BMDCs) from diabetic mouse. Six-week-old male C57BLKS/J-m + /m + mice (CON) and C57BLKS/J-db/db mice (db/db) were fed with a 10% kcal fat diet for seven weeks. BMDCs were generated by culturing bone marrow cells from the mice with rmGM-CSF (20 ng/mL) in the absence or presence of 10 nM 1,25(OH) 2 D 3 . The maturation of BMDCs was induced via lipopolysaccharide (LPS, 50 ng/mL) stimulation for 24 h. LPS stimulation induced iNOS protein expression and decreased the mitochondrial respiration, while increased lactate production and the expression of glycolytic pathway-related genes (Glut1 and Pfkfb3) in BMDCs from both CON and db/db groups. In LPS-stimulated mature BMDCs, 1,25(OH) 2 D 3 treatment decreased the expression of surface markers related to immunostimulatory functions (MHC class II, CD80, CD86, and CD40) and production of IL-12p70 in both CON and db/db groups. While the mRNA level of the gene related to glucose uptake (Glut1) was increased in both groups, lactate production was decreased by 1,25(OH) 2 D 3 treatment. mTORC1 activity was suppressed following 1,25(OH) 2 D 3 treatment. Collectively, our findings confirmed that metabolic reprogramming occurred in BMDCs following LPS stimulation. In vitro 1,25(OH) 2 D 3 treatment induced tolerogenic phenotypes by reducing the expression of surface markers, as well as cytokine production. However, no significant difference was observed regarding the effects of 1,25(OH) 2 D 3 treatment on metabolic conversion and maturation of BMDCs between the control and diabetic mice. Additionally, the decreased aerobic glycolysis induced by the 1,25(OH) 2 D 3 treatment appeared to be associated with the diminished maturation of BMDCs, and mTORC1 appears to play a key role in the 1,25(OH) 2 D 3 -mediated regulation of glycolysis.
Competing Interests: Conflict of interests The authors declare no conflict of interests.
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