RPS6KB1 and obesity due to melanocortin 4 receptor deficiency: The basal phosphorylation levels of PKB, p70s6K, p42/p44 MAPKs and p90RSK1 were significantly lower in the cells from patients with OB/T2D compared to those from normal subjects, as previously observed in patients with obesity, apart from p90RSK-1, where no modification was reported (18,26).