Demonstration of 1α,25‐dihydroxyvitamin D3 receptor‐like molecule in ST 13 and 3T3 L1 preadipocytes and its inhibitory effects on preadipocyte differentiation

Abstract

The active metabolite of vitamin D₃, 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), inhibited morphologic and enzymatic expression during differentiation of preadipocyte to adipocyte. In the presence of ∼6.4–20 × 10⁻¹⁰ M 1,25(OH)₂D₃, the triacylglycerol accumulation was only 50% of that of fully differentiated control cells. High-affinity binding sites for 1,25(OH)₂D₃ binding component sediments at 3.3 S in 4–24% (w/v) sucrose gradients prepared in hypertonic buffer. Binding assay revealed that N_max was 70 fmol/mg protein and 90 fmol/mg protein, and K_d value was 170 pM and 37 pM in cell lines ST 13 and 3T3 L1, respectively. We also found that differentiated adipocytes did not contain specific receptors for 1,25(OH)₂D₃. 1,25(OH)₂D₃, 1(OH)D₃, 24,25(OH)₂D₃, and 24(OH)D₃ all suppressed differentiation of preadipocytes to adipocytes, and the dose required closely reflected the affinities of the various metabolites and the synthetic derivative for 1,25(OH)₂D₃ receptor. It is suggested that the action of vitamin D₃ on preadipocyte differentiation may result from a receptor-mediated event.