LEP and obesity due to melanocortin 4 receptor deficiency: Compared to male SDT rats, SDT fatty (fa/fa) rats showed overt obesity, and hyperglycemia and hyperlipidemia at younger ages (5~6 weeks), which is associated with hyperphagia by an induced disorder of leptin action, and plasma triglyceride (TG) and total cholesterol (TC) levels in SDT fatty (fa/fa) rats were significantly higher than those in original SDT rats.