MAP4K4 and obesity due to melanocortin 4 receptor deficiency: Though no significant changes were observed in Slc2a2 mRNA expression, Gck expression was significantly reduced in iKO mouse islets compared with those derived from Flox/Flox animals (Fig. 5B), suggesting that islets lacking Map4k4 expression may not properly sense the slow rise in glucose that occurs during HFD-induced obesity.