DRD2 and obesity due to melanocortin 4 receptor deficiency: Since protein levels of DRD1 and DRD2 generally did not follow mRNA expression patterns, we performed correlation analyses between DRD1 and DRD2 protein expression and obesity and hyperglycemia in subjects without T2D and with NGT or IFG, and T2D (cohort 1), respectively (Fig. 4).