LEP and metabolic syndrome: Previous studies have suggested some candidate genes for MetS, including the insulin-induced gene 2 (INSIG2) [6,7], ghrelin gene (GHRL) [8,9,10,11,12,13,14], leptin (LEP) [7,11,15,16,17,18,19], and leptin receptor genes (LEPR) [11,16,17,19,20].