We all know leptin regulates appetite. It is a hormone, released by fat cells, that there is plenty of fat around -- essentially a 'stop eating' signal produced by fat cells and received in the brain. When leptin was first identified, people thought maybe those with PWS had abnormal leptin levels -- but that is not the case. - most obese individuals with PWS secrete plenty of leptin.
Nevertheless, there may be other aspects of leptin metabolism that are irregular in PWS (beyond the point of leptin being released by the fat cells). Leptin also regulates puberty -- you need to have enough leptin before your body will enter puberty (interesting evolutionary sidenote: it is believed to be the physiological signal that lets the body know there is enough food around to support pregnancy/new babies). Anyway, there are only a very few individuals in the world who have an actual genetic defect in their leptin production. They are very obese and hypogonadic (ie, not sexually mature, etc). Here they gave 3 of those individuals leptin for 18 months with striking results -- all drastically reduced body weight, became more active, sexually matured, and had personality changes moving from more passive and 'infantile' to more assertive and adult-like. To me, this article is a nice demonstration that by fixing one problem, you can affect many aspects of a person's life.
Licinio J, Caglayan S, Ozata M, Yildiz BO, de Miranda PB, O'Kirwan F, Whitby R, Liang L, Cohen P, Bhasin S, Krauss RM, Veldhuis JD, Wagner AJ, DePaoli AM, McCann SM, Wong ML.
Phenotypic effects of leptin replacement on morbid obesity, diabetes mellitus, hypogonadism, and behavior in leptin-deficient adults . PNAS 101 4531-4536, 2004.
