Transcriptional activation of the human insulin receptor gene by 1,25‐dihydroxyvitamin D 3

Treatment with 10 −8 m 1,25‐dihydroxyvitamin D 3 for 24 h causes transcriptional activation of the human insulin receptor gene in U‐937 human promonocytic cells. The activation seems to potentiate the response to insulin in terms of glucose oxidation. Wortmannin, a phosphatidylinositol 3‐kinase inhibitor, causes a greater inhibition of insulin‐stimulated glucose oxidation in 1,25‐dihydroxyvitamin D 3 ‐treated cells than in untreated cells. This suggests a stimulation of phosphatidylinositol 3‐kinase activity by 1,25‐dihydroxyvitamin D 3 , which could mediate, at least in part, the potentiation of the insulin response. Copyright © 2002 John Wiley & Sons, Ltd.