FNDC5 and obesity due to melanocortin 4 receptor deficiency: In mice with diet-induced obesity, subcutaneous irisin infusion produced an AMPK-dependent reduction in hepatic mRNA expression and nuclear translocation of the transcription factor Srebf2, and a subsequent decrease in expression of its downstream targets Hmgcr, Hmgcs (encoding enzymes for cholesterol biosynthesis) and Ldlr2 (supporting hepatocyte LDL-C uptake).