LEP and obesity due to melanocortin 4 receptor deficiency: GM3 expression in visceral adipose tissue, and gene expression of GM3 synthase (GM3S; St3gal5), were significantly elevated in ob/ob mice (which display obesity and metabolic syndrome because of deficiency of the appetite suppressor hormone leptin) and in mouse models of obesity induced by high-fat diet (Tagami et al., 2002; Nagafuku et al., 2015).