GPT and metabolic syndrome: Vit D: Vitamin D; MetS: Metabolic syndrome; U.S.: United States; UK: United Kingdom; NHANES: National Health and Nutrition Examination Survey; TG: Triglycerides; HbA1C: Hemoglobin A1C; BP: Blood pressure; WC: Waist circumference; FBS: Fasting blood sugar; BMI: Body mass index; HDL-C: High-density lipoprotein-C; HDL: High-density lipoprotein; LAP: Lipid accumulation product; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; IR: Insulin resistance