FNDC5 and obesity due to melanocortin 4 receptor deficiency: The downregulation of dyslipidaemia-promoting genes by irisin was more consistent in the lean-derived adipocytes, perhaps reflecting the multifactorial nature of lipid regulation under dietary stress; this raises questions about irisin's potential to reverse, as well as prevent, a postmenopausal dyslipidaemic state that often arises with the obesity component of MetS.