Leptin is a peptide hormone produced in the adipocytes of adipose tissue. It is also known to be produced in the stomach, placenta and some fetal tissues [3]. The polypeptide is encoded by the ob gene and the resulting protein has four alpha helical domains which makes it similar to the class-1 family of cytokines [1].
The main function of leptin is to regulate adipose tissue or fat mass by suppression of the appetite and increase of energy metabolism. Leptin also plays a part in reproduction and the immune system. The actions of leptin are acheived by communication with neurons in the hypothalamus where leptin receptors (LepR) are located. The amount of leptin in cirulation is proportional
to the amount of fat stores in the body [2]. By interacion with neurons associated with other hormones, leptin works with the hypothalamus to govern the balance of energy intake and energy metabolism according to how much energy stores are already present.
to the amount of fat stores in the body [2]. By interacion with neurons associated with other hormones, leptin works with the hypothalamus to govern the balance of energy intake and energy metabolism according to how much energy stores are already present.The Leptin Feedback Loop
Leptin hormone was first observed and its DNA encoding sequence determined in 1944 by Dr. J Friedman(Rockefeller University) and others. They cloned a mutant form of the ob gene from an obese mouse. The mice with mutations in both ob genes became very fat and inactive. They administered what is now called leptin and the result was weight loss and decreased food consumption in the mice [3]. This experiment provided evidence that body weight must be under hormonal control and raised the question of whether or not leptin plays a role in other regulatory mechanisms.
References
1. Robertson, S., Myers, M., Leinninger, G. (2008). Molecular and neural mediators of leptin action. Physiology & Behavior. 94: 637-642.
2. Robinson, C., Kordon, D., & Hanoune, J. (2002). Brain Somatic Cross-Talk and the Central Control of Metabolism. Germany. Springer-Verlag, Berlin, Heidelberg. pp.15-17
3. Trayhurn, P., Mercer, J.,& Rayner, D. (1999, February). Leptin: Fundamental aspects. International Journal of Obesity & Related Metabolic Disorders, 23, s22.
