Vitamin D 1,25-Dihydroxyvitamin D3 reduces lipid accumulation in hepatocytes by inhibiting M1 macrophage polarization

Figure 4 Effect of vitamin D receptor-peroxisome proliferator activated receptor γ pathway modulating 1,25-dihydroxy-vitamin D administration on high-fat diet/fatty acid-induced hepatic macrophage polarization. Wild-type C57BL/6 mice were fed either normal control (NC) diet or high-fat (HF) diet for 16 week, or HF diet plus 1,25-dihydroxy-vitamin D [1,25(OH)2D3] (20 µg/kg) by oral gavage every alternate day for 16 weeks. Phosphate-buffered saline by oral gavage served as a control (n = 10/group). Hepatic macrophages were isolated from mice administered NC diet, HF diet alone or plus 1,25(OH)2D3. RAW264.7 macrophages were incubated with palmitic acid (0.5 mmol/L) for 24 hours or Dulbecco's modified Eagle’s medium as a normal control. Lipopolysaccharide (100 ng/mL) or interleukin-4 (5 ng/mL) treatment served as positive controls for macrophage M1 or M2 polarization. For administration of 1,25(OH)2D3, RAW264.7 macrophages were incubated with 1,25(OH)2D3 (20 ng/mL) for a further 24 hours. A: MRNA expression of vitamin D receptor (VDR)-peroxisome proliferator activated receptor γ on hepatic macrophages; B: Protein expression of VDR and PPARγ on hepatic macrophages; C: MRNA expression of VDR and PPARγ on RAW264.7 macrophages; D: Protein expression of VDR and PPARγ on RAW264.7 macrophages. Values are mean ± SEM, ^aP < 0.05, ^bP < 0.01, n = 10 animals per group, n = 3 experiments; VDR: Vitamin D receptor; PPARγ: Peroxisome proliferator activated receptor γ; NC: Normal control; HF: High-fat; VD3: 1,25-dihydroxy-vitamin D; PA: Palmitic acid; LPS: Lipopolysaccharide; IL: Interleukin.