SLC5A2 and obesity due to melanocortin 4 receptor deficiency: the metabolic effects of sodium-glucose cotransporter-2 inhibitors (SGLT2i), such as lipolysis and ectopic fat reduction, seem related to the synthesis of fibroblast growth factor-21 (FGF-21), and FGF-21 analogs are now under investigation for the treatment of obesity complications such as metabolic dysfunction-associated steatotic liver disease.