IRS1 and obesity due to melanocortin 4 receptor deficiency: Fernandez-Twinn et al. (103) hypothesized that male offspring exposed to maternal diet-induced obesity may drive IR (eventually T2D) in later life, which was associated with the reduction in IRS-1 targeted by miR-126, because at 8 weeks old, male offspring did not exhibit an obese phenotype but exhibited decreased levels of IRS-1 protein.