Regarding genetic studies in humans, several single-nucleotide polymorphisms of RBP4 were reported to be associated with metabolic diseases and related risk factors, including the risk of hypertriglyceridemia in Chinese Hans [136], increased serum high density lipoprotein levels [137], risk of gestational diabetes [138], higher body mass index [139], elevated insulin resistance [140], and type 2 diabetes mellitus [141,142,143]. This evidence concerns the gene RBP4 and type 2 diabetes mellitus.