The effects of dietary vitamin D supplementation and in vitro 1,25 dihydroxyvitamin D 3 treatment on autophagy in bone marrow-derived dendritic cells from high-fat diet-induced obese mice.

Obesity is associated with the dysregulation of vitamin D metabolism and altered immune responses in bone marrow-derived dendritic cells (BMDCs). Vitamin D can affect the differentiation, maturation, and activation of dendritic cells (DCs) and regulate autophagy via vitamin D receptor signaling. Autophagy was shown to be involved in the functions of DCs. We investigated the effects of dietary vitamin D supplementation and in vitro 1,25-dihydroxyvitamin D ₃ (1,25(OH) ₂ D ₃ ) treatment on autophagy in BMDCs from control diet (CON)-fed lean and high-fat diet (HFD)-induced obese mice. C57BL/6 male mice were fed CON or HFD with 10% or 45% kcal fat, respectively, supplemented with 1,000 or 10,000 IU vitamin D/kg diet (vDC or vDS) for 12 weeks. BMDCs were generated by culturing bone marrow cells from the mice with 20 ng/mL rmGM-CSF and treated with 1 nM 1,25(OH) ₂ D ₃ . Maturation of BMDCs was induced by lipopolysaccharide (50 ng/mL) stimulation. Treatment with 1,25(OH) ₂ D ₃ inhibited the expression of phenotypes related to DC function (MHC class Ⅱ, CD86, CD80) and production of IL-12p70 by BMDCs from control and obese mice, regardless of dietary vitamin D supplementation. LC3Ⅱ/Ⅰ and VPS34 protein levels increased, and p62 expression decreased, after 1,25(OH) ₂ D ₃ treatment of the BMDCs in CON-vDC only. Vdr mRNA levels decreased following 1,25(OH) ₂ D ₃ treatment of BMDCs in the HFD-vDC. In conclusion, autophagy flux was increased by 1,25(OH) ₂ D ₃ treatment of the BMDCs in CON-vDC but not in the HFD-vDC group. This suggests that the decreased expression of Vdr following 1,25(OH) ₂ D ₃ treatment might have affected autophagy flux in BMDCs from obese mice.
Competing Interests: Declaration of competing interest The authors declare no conflict of interest.
(Copyright © 2021. Published by Elsevier Inc.)