INS and obesity due to melanocortin 4 receptor deficiency: Additionally, HDAC5 can interact with the GLUT4 enhancer factor (GEF) in adipocytes for the repression of Glut4 promoter activity (Sparling et al., 2008; Weems and Olson, 2011), suggesting a plausible mechanism by which Glut4 expression and insulin-mediated glucose uptake are dysregulated in obesity and T2D.