Which of the Following Is True of Leptin

Which of the following is true of leptin?

A) Leptin is a product of protein metabolism.
B) Leptin levels are decreased during overeating and obesity.
C) Mutations of the leptin gene are the most common cause of obesity.
D) Plasma leptin levels are related to body fat content only in obese persons.
E) Few cases of human obesity are related to a mutation of the gene for leptin and leptin receptors.