MAP2K6 and obesity due to melanocortin 4 receptor deficiency: However, it is significant that an in vivo study was conducted based on the findings of previous studies on MEK6 that used human and 3T3-L1 cells [15,24] and reported a regulatory role of MEK6 in p38 activity and M1/M2 inflammatory factors to suppress lipolysis and thermogenesis but induce lipid accumulation and inflammation thereby exacerbating the state of obesity.