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

Figure 5 Administration of 1,25-dihydroxy-vitamin D inhibiting fatty-acid-induced proinflammatory M1 polarization of macrophages directly relieves lipid accumulation and metabolism in hepatocytes. 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-dihydroxy-vitamin D [1,25(OH)2D3], RAW264.7 macrophages were incubated with 1,25(OH)2D3 (20 ng/mL) for a further 24 hours. The cell culture supernatants were collected and prepared for conditioned media (CMs). AML12 hepatocytes were treated with different CMs from RAW264.7 macrophages for 24 hours. A: Lipid accumulation in AML12 hepatocytes determined by Oil Red O staining (200 ×); B: Proinflammatory cytokines mRNA expression on AML12 hepatocytes; C: Lipid metabolism genes mRNA expression on AML12 hepatocytes; D: Lipid metabolism enzymes protein expression on AML12 hepatocytes. Values are mean ± SEM, ^aP < 0.05, ^bP < 0.01, n = 3 experiments; CM: Conditioned media; NC: Normal control; LPS: Lipopolysaccharide; IL: Interleukin; PA: Palmitic acid; VD3: 1,25-dihydroxy-vitamin D; TNFα: Tumor necrosis factor α; SREBP1C: Sterol-regulatory element binding protein 1C; FASN: Fatty acid synthetase; ACOX1: Acyl-CoA oxidase 1; CPT1A: Carnitine palmitoyltransferase 1A.