Leptin was first described in 1994 by the scientist Jeffrey Friedman. The word leptin, which comes from the Greek, literally means “thin”. Leptin, which is assigned to the proteohormones, is responsible for regulating appetite.
What is Leptin?
Proteohormones are those hormones that are structured like proteins and yet take on typical tasks of hormones - such as messenger functions and regulatory mechanisms.
Leptin is a typical such protein compound with hormonal function. Leptin is mainly formed and released in fat cells (adipocytes).
Leptin is also produced in much smaller quantities in the bone marrow, placenta and gastric mucosa. Leptin has an appetite suppressant effect in the human body and is therefore actively involved in regulating the amount of food consumed.
Production, manufacturing & education
Leptin is a fat-insoluble protein compound that is produced in the fat cells of the human body. The placenta, the spinal cord and the skeletal muscles also produce leptin in very small quantities.
The neuropeptides released via the hypothalamus, which stimulate the appetite and encourage people to eat, are inhibited by the leptin. The most important task of leptin is therefore to act as a receptor for neuropeptides. Leptin also serves as a receptor for POMC (Proopiomelanocortin) and KART (cocaine and amphetamine-regulated transcript).
Here, however, leptin works in almost the opposite way: POMC and CART have an appetite suppressant effect, but they must first be activated by leptin.
As soon as the fat deposits in the adipocytes are reduced, the leptin level in the blood decreases. The low concentration in turn ensures that the appetite is stimulated. U.a. therefore the person experiences a feeling of hunger.
Function, effect & properties
Leptin is an endogenous hormone that is mainly produced in the fat cells. By inhibiting appetite-stimulating neuropeptides on the one hand and by activating appetite-suppressing transmitters such as POMC and KART, leptin has a direct effect on the amount of food that a person consumes.
The amount of leptin in the blood is directly dependent on the amount of fat deposits. When the body's own adipocytes are full, the fat cells produce leptin, which curbs the appetite. If the proportion of fat in the adipocytes falls, they stop producing leptin; Appetite arises.
The described fluctuation in the fat percentage is not externally perceptible to humans, i.e. corpulent people are not always hungry any more than thin people are constantly hungry. It has not yet been sufficiently proven whether leptin takes on other tasks.
Illnesses, ailments & disorders
Leptin can cause high blood pressure and an increase in heart rate by stimulating the nervous system. However, this is rather unusual and as such is not a clinical picture worth treating. The symptoms also usually subside quickly.
Soon after the discovery of leptin, the scientists were able to identify the function of the hormone, namely a regulation of appetite. For years the diet industry and also medical research have tried to take advantage of the appetite suppressing effects of leptin.
It has been assumed that obese people suffer from a leptin deficiency and therefore have constant appetite, which ultimately leads to massive obesity. From then on, attempts were made to artificially supply this assumed deficiency in the form of a leptin-containing tablet. Extensive tests showed, however, that obese people did not suffer from a leptin deficiency; rather, many obese people even had a very high leptin level (leptin paradox).
It was subsequently demonstrated that obese people in many cases do not suffer from a leptin deficiency, but from leptin resistance. The body's own leptin cannot inhibit the appetite-stimulating neuropeptides and at the same time cannot activate the appetite-suppressing transmitters POMC and CART. Patients suffering from leptin resistance are therefore very often obese and can only achieve and maintain a healthy body weight with enormous willpower and discipline.
However, the latest research gives cause for hope. A research group from Boston was able to show which regions in the brain or in the hypothalamus are responsible for leptin resistance. They were able - at least in animal experiments - to stimulate the hypothalamus to form chaperones. Chaperones are proteins that support hormones in their work. A leptin resistance could thus be lifted at least in part, so that perhaps in the near future a remedy for obesity, which has its origin in leptin resistance, could be found.
One interesting line of research is trying to establish a connection between eating disorders and leptin. It seems like some people can control their appetite more disciplined than others. Patients suffering from anorexia seem to be able to turn off their appetite altogether. Whether there is a connection between such diseases and a disturbed leptin balance has not yet been answered satisfactorily.
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