The PubMed search using “Hepatocyte Nuclear Factor 1”, “Leucine”, and “Diabetes Mellitus, Type 2” resulted in five articles about amino acid substitution, such as the effect of Ile/Leu27 polymorphism variants of the hepatocyte nuclear factor-1alpha gene on pancreatic beta-cell function in type 2 diabetes [20]. Here, HNF1A is linked to type 2 diabetes mellitus.