Leptin is a protein hormone involved in the regulation of energy intake and expenditure by the body. Leptin is an important cytokine that plays a key role in the regulation of appetite, food intake and metabolism.
Structure and function
Leptin is a 16 kDa adipose-derived protein comprising 167 amino acids. The hormone is coded for by the ob gene which is located on chromosome 7 in humans.
The majority of the leptin hormone is produced in white fat deposits in the body. Levels of leptin are directly associated with total amounts of fat in the body. Leptin may also be produced in the brown adipose tissue and by other body parts such as the ovaries, skeletal muscle, fundic glands in the stomach, placenta, bone marrow, pituitary gland and liver.
At the Jackson Laboratory in the 1950s, a certain genetic strain of mice homozygous for the ob (obese) mutation were found to eat excessive amounts and to be massively obese. Studies of mice with a similar phenotype in the 1960's allowed researchers to characterize the defective gene.
During the 1990's, the ob gene was mapped and eventually identified as responsible for the production of a hormone that could regulate food intake and body weight.
One of the main researchers, Jeffrey Friedman announced the discovery of the ob gene in 1994 and called the hormone leptin, which originates from the Greek word "lepto" meaning "thin," referring to the fact that the normal allele of the ob gene keeps you thin.