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

The active metabolite of vitamin D 3 , 1α,25‐dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ), inhibited morphologic and enzymatic expression during differentiation of preadipocyte to adipocyte. In the presence of ∼6.4–20 × 10 −10 M 1,25(OH) 2 D 3 , the triacylglycerol accumulation was only 50% of that of fully differentiated control cells. High‐affinity binding sites for 1,25(OH) 2 D 3 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) 2 D 3 . 1,25(OH) 2 D 3 , 1(OH)D 3 , 24,25(OH) 2 D 3 , and 24(OH)D 3 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) 2 D 3 receptor. It is suggested that the action of vitamin D 3 on preadipocyte differentiation may result from a receptor‐mediated event.