HOMA-IR: Homeostatic Model Assessment for Insulin Resistance; T2DM: type 2 diabetes mellitus; NAFLD: nonalcoholic fatty liver disease; HTN: hypertension; OSA: obstructive sleep apnea; GERD: gastroesophageal reflux disease; GLP-1: glucagon-like peptide-1. This evidence concerns the gene GCG and diabetes mellitus.