Microarray datasets have been interrogated to determine whether the expression of vitamin D-related genes is modulated in adipocytes during inflammation. The datasets were from human adipocytes and preadipocytes incubated with macrophage-conditioned medium (U937 cells). In adipocytes, exposure to the conditioned medium for 24 h resulted in a major increase (82.2-fold) in mRNA level of CYP27B1, the gene encoding the enzyme that converts 25-hydroxycholecalciferol to the active form of vitamin D3, 1,25-dihydroxycholecalciferol; exposure for 4 h also raised CYP27B1 mRNA level (10.9-fold). The level of the mRNA encoding the vitamin D receptor (VDR) was increased after 24 h (7.7-fold), but there was no change at 4 h. In contrast, incubation with conditioned medium for either 4 or 24 h had no effect on the expression of the CYP24 and CYP2R1 genes, which encode enzymes that catalyze a 24-hydroxylation and the conversion of vitamin D3 to 25-hydroxycholecalciferol, respectively. In preadipocytes, the only effect of the macrophage-conditioned medium was to stimulate CYP27B1 expression (5.7-fold) after 24 h. It is concluded that the capacity of adipocytes to produce active vitamin D3 hormone and its nuclear receptor is strongly upregulated by secretory products from macrophages; this is consistent with a counter-regulatory effect of the vitamin D system to ameliorate inflammation.
Adipobiology 2011; 3: 31-36.
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