INS and obesity due to melanocortin 4 receptor deficiency: As mentioned in section Lipid influence on the O-GlcNAc regulatory system, hyperphysiological levels of insulin appeared to be required for lipid infusion to potentiate HBP product synthesis in skeletal muscle (52, 53) and obesity was associated with higher skeletal muscle UDP-GlcNAc in two hyperinsulinemic mouse models (49, 50) but not in insulin deficient Zucker Diabetic Fatty rats (54).