TCF7L2 and type 2 diabetes mellitus: Transcription factor 7-like 2 (TCF7L2), a Wingless and Int (Wnt) signaling-associated transcription factor located on chromosome 10q25, has emerged as a consistently replicated susceptibility gene for type 2 diabetes [6-8], possibly through the impairment of glucagon-like peptide-1-induced insulin secretion [9].