LEP and diabetes mellitus: Leptin-deficient (ob/ob) mice and leptin receptor-deficient (db/db) mice have been established as obese and diabetic animal models, showing severe obesity and diabetes with abnormal pituitary/adrenal hormone secretion, insulin resistance, insulinemia, hyperglycemia, hyperlipidemia, immune function impairment, and high risk of liver disease, in particular NAFLD [91,95,96].