Although conflicting results have been reported, raising doubt about the postulated relationship of RBP4 with insulin sensitivity in humans, our results in Hmga1-deficient mice confirm that an inverse correlation indeed exists between RBP4 and insulin sensitivity in vivo, in this animal model of diabetes, lending support to previous hypotheses that lowering RBP4 levels would be helpful in ameliorating insulin resistance, at least in mice. The gene discussed is RBP4; the disease is diabetes mellitus.