HIF1A and obesity due to melanocortin 4 receptor deficiency: Adipocyte-specific knockout of Hif1β – the obligate partner of hypoxia-inducible factors (Hif1a, Hif2a, and Hif3a) - reduced weight gain relative to wild-type controls and showed decreased high-fat diet (HFD)-induced obesity and glucose intolerance (10), indicating that the adipocyte-response to hypoxia is negative.