Recently, it has been shown that mild mitochondrial uncoupling can be protective in several disease models, including insulin resistance [37], hypertriglyceridemia and fatty liver disease [9], and can have a regulatory role in endocrine cross-talk via the induction of fibroblast growth factor 21 and the growth hormone/insulin-like growth factor I axis [10]. The gene discussed is FGF21; the disease is fatty liver disease.