Leptin has many different effects, but obesity scientists seem to be most interested in it. Leptin is responsible for the feeling of satiety, in obese people it often does not work properly - the phenomenon of leptin resistance may be to blame for this. They can lead to the fact that large amounts of leptin - instead of suppressing the appetite - will actually stimulate it.
The nameleptinderives from the Greek word leptos, which can be translated as "thin". Leptin is a protein with 146 amino acids in its molecule. The gene responsible for the synthesis of leptin is called Ob - "ob" from obese, meaning obesity, and it is found in humans on chromosome 7. The best known relationships between leptin, appetite regulation and adipose tissue content. However, protein also affects a number of other body systems, including on the reproductive system, immune system or bone and joint systems. As in the case of other hormones, the best situation in the case of leptin is when in the body there are concentrations adequate to its needs - both excess and deficiency of leptin can be a source of various he alth problems.
Leptin: hormone production
Leptin production takes place primarily in white (subcutaneous) adipose tissue. The amount of the released hormone directly depends on how much fat a given person has in their body. In a patient with significantly extensive deposits of adipose tissue, high leptin levels can be found in the body, while in a slim person with little adipose tissue, the opposite situation may be encountered, i.e. with a small amount of circulating leptin. Due to the fact that women naturally have greater deposits of adipose tissue, it is in this sex that higher blood leptin levels are observed. Adipose tissue is indeed the primary source of leptin, but it is not the only tissue in the human body that can produce leptin. Although in much smaller amounts, leptin can also be produced in:
- bearing
- ovaries
- stomach
- brown adipose tissue
- bone marrow
- skeletal muscle
Leptin: leptin resistance and its relationship withobesity
Leptin, as already mentioned, is sometimes called the satiety hormone. It was also mentioned that the more body fat a person has, the greater the amount of leptin in their body. Theoretically, it would seem that obese people should not feel hungry - but in reality it is definitely the opposite. Leptin resistance is a state in which the brain "does not respond" to leptin. The exact cause of leptin resistance is not clear. It is suspected that in the case of the circulation of extremely large amounts of leptin in the body (as it happens in obese people), the number of leptin receptors may decrease or their sensitivity to this hormone may decrease. When the body does not perceive the signals related to the feeling of satiety, then the patient's appetite may be abnormally high. The problem is quite significant, because it leads to a vicious circle mechanism - the patient consumes too much food, which means that he accumulates more and more fatty tissue. More fat also means more leptin, which should normally suppress the appetite. However, when a patient has leptin resistance, increasing amounts of the satiety hormone only support the pathology. Leptin resistance may be secondary to the development of overweight or obesity in the patient - this is the most common situation. Leptin disorders, however, can also be a primary pathology. Leptin gene mutations are a rare but possible cause of obesity. Such patients experience extremely severe appetite control disorders, which causes them to develop extremely excess body weight quite quickly, which may be accompanied by fertility disorders and insulin resistance. Interestingly, leptin can be an enemy of weight loss. Thanks to the diet, patients can lose excessive amounts of body fat. When this happens, there is also - according to the mechanisms already described - a decrease in the amount of leptin in the body. On the other hand, the feeling of hunger is associated with the lack of leptin. Certainly, the increase in appetite does not make it easier for patients to maintain a slim figure, it is also possible that it is the changes in the amount of leptin that appear as a result of weight loss that may be one of the mechanisms related to the occurrence of the so-called yo-yo effect.
Leptin: use in medicine
Leptin as a drug is used primarily in patients with impaired synthesis of this substance. Giving leptin to such patients can lead to a significant reduction in their body weight. Additionally, a leptin deficiency can lead to a delay in sexual maturation - in this situationadministration of exogenous preparations of this protein can also eliminate the disorders existing in patients. Another condition in which leptin analogues are used is lipodystrophy.
Leptin: effects in the body
Leptin is mainly known as a hormone associated with the phenomena of appetite regulation. Protein is considered to be the so-called satiety hormone (it is said to have an anorexic effect). Appetite suppression is due to the effect of leptin on the hypothalamus. Thanks to it, the production of neuropeptide Y is inhibited in the hypothalamus - this neurotransmitter, on the other hand, is one of the substances that stimulate the appetite. Leptin also works by stimulating the production of alpha-MSH in the hypothalamus, i.e. a substance that is associated with inhibiting the feeling of hunger. Leptin acts antagonistically to the appetite-stimulating hormone ghrelin. Fluctuations in the concentration of leptin in the body are observed throughout the day. High amounts of it occur, among others at night and in the morning, which is explained by the fact that during the night rest there is a need to suppress the feeling of hunger. Leptine leads to changes in a number of metabolic processes, the protein leads, among others, to to:
- intensification of lipolysis (fat breakdown) and gluconeogenesis (carbohydrate production) processes,
- inhibition of lipogenesis (the process of accumulation of fatty compounds deposits), but also to reduce insulin production or the transport of sugars to adipose tissue deposits.
The actions of leptin, however, focus not only on the phenomena related to the amount of food consumed. Protein also has a certain relationship with sex hormones - together with kisspeptin, leptin regulates the onset of sexual maturation. It has already been noticed that in obese girls with large amounts of leptin, menstruation may begin earlier. Leptin also affects the release of sex hormones itself, because the protein stimulates the secretion of the hypothalamic gonadoliberin GnRH (GnRH in turn stimulates the pituitary gland to release LH and FSH, and these compounds lead to an increase in the release of sex hormones from the ovaries or testicles). the ability to regulate the course of the immune response (e.g. by activating macrophages, stimulating certain types of lymphocytes to divide, and by influencing the production of cytokines). Protein also plays some functions during pregnancy, because pregnant women have increased amounts of leptin - one of the hormone's actions is to prevent uterine contractions. Leptin is also associated with bone growth processes - it can accelerate terminationskeletal growth.