Scientists discovered an amazing hormone that was produced by adipose tissue cells in the late fifties of the last century. This hormone was called leptin, from Greek «leptos». In the translation, the word means graceful, thin, and beautiful. The leptin hormone turned out to be unique, because it activated the sense of satiation. This function of a biologically active substance was considered the only one for a long time. But scientists found some new facts and qualities of the hormone. This is the theme of our article.
- What is leptin.
- Hormone functions.
- What affects leptin.
- Normal range in the blood.
- Drugs of the future.
What is leptin
Leptin is a hormone that is synthesized by adipocytes: fat cells or lipocytes. It is encoded by the obesity gene, and its receptors are affiliated with a lot of brain areas. For example:
- the arcuate nucleus of the hypothalamus or the accumulation of neuroendocrine cells near the third ventricle of the cerebrum;
- the part of the brain responsible for the sense of smell;
- the largest group of serotonergic cells with dopamine;
- hippocampus as the central formation of the limbic system;
- cortex and nucleus of the central nervous tract that are responsible for smell and taste.
Leptin is the satiety hormone. In other words, it is produced when the body already has enough energy and does not need additional food intake. Unfortunately, obese patients are often not receptive to such signals. They are resistant to leptin. High blood triglyceride concentrations have been shown to play a large role in this resistance. It blocks the penetration of leptin across the blood-brain barrier.
Leptin improves memory, concentration, it also affects the synaptic plasticity of the hippocampus, and has a neuroprotective effect. The hormone minimizes the risk of developing Parkinson’s and Alzheimer’s diseases. It can simulate the level of neurotransmitters, neurotrophic factors, and to control depression.
Today, almost everything is known about the hormone:
- the size of its molecule is 160 kD;
- amino acids as part of the substance;
- the fragment of the polypeptide chain that blocks food intake.
It is clear that leptin regulates the formation and accumulation of fat in the body. One more feature of the hormone is the sexual characteristics of the distribution of fatty tissue. It is considered to be that obesity occurs in case of disturbance of its secretion. It was found that leptin synthesis is associated with the Ob gene that was known as the main participant in the obesity development at the end of the 20th century. Later, leptin receptors were found on the cell membranes of the neurocytes of the hypothalamus and thalamus. The fact confirmed the hypothesis that the hormone was an antagonist of neuropeptide Y (NP Y), which stimulated a hunger.
Leptin and NP Y are in effect according to the “±” system in the bodies of people with normal weight. Leptin freely passes through the blood-brain barrier, while the ventromedial part of the hypothalamus and the area located nearby become a target. In lay terms, such a cooperation between leptin and the central nervous system provides a dependence of appetite of the mood.
Leptin performs its functions through contact with ObRs receptors, which are located in the brain and a few tissues on the periphery. There are several clones of Ob receptors with different areal organization. They transport hormone molecules across the border between blood and cerebrospinal fluid, and provide major control capabilities in the hypothalamus. In fact, leptin is a coordinator of neuroendocrine processes in the human body, that is associated with energy potential. In the normal state of affairs, leptin level rises after eating, so appetite tends to zero.
Leptin hormone in the human body:
- controls the saturation center: inhibits the synthesis of neuropeptide Y;
- stimulates the production of anoretics, appetite suppressants;
- affects the production of sex hormones;
- increases the thermal formation processes in the body;
- blocks food hankering;
- prevents lipotoxicosis (fat deposition in tissues not intended for fat deposition);
- controls overeating.
In addition, leptin helps as an antidepressant when injected into the hippocampal system. But there is no positive effect when the hormone acts on the hypothalamus. The leptin has a close connection with the human reproductive system and the hormonal background. For example, it is believed that only women with normal level of leptin can have normal periods and fertility possible. And the fatty tissue of the omentum in obese patients has an increased ability to break down insulin, which partially reduces the effects of hyperinsulinemia. Leptin secretion is impacted by bad habits, especially smoking.
If patients have leptin resistance, this is considered to be a sign of metabolic disorders. Leptin provokes neurotrophic and neuroprotective effects in patients with Alzheimer’s disease. Also, the hormone stimulates the synthesis of sex hormones, the thyroid body, and STH (somatotropic hormone).
What affects leptin
The level of leptin in the body can be increased and decreased as any other biologically active substance. These factors can increase the concentration of the hormone in the bloodstream: dexamethasone, insulin, stress, excess body weight, testosterone. Insomnia, estrogen, exercise lead to the reduction of leptin
Normal range in the blood
The level of leptin in the bloodstream varies depending on the daytime: at night it is 30% lower than during the day. If a feeling of hunger appears at night, it means that the norm of the hormone in the blood is violated. The concentration of leptin drops by more than 50% with a decrease in body weight by 10%. At the same time, a 10% weight gain increases the level of leptin in many times over. A day of significant overeating raises the rate by 40%.
Drugs of the future
Pharmacologists have created modern drugs and drugs of the future based on the functions of leptin in the body and its ability to correlate to metabolic processes. These preparations can normalize metabolism. For example, recombinant leptin. This injectable drug can be used for the treatment of hereditary obesity. This pathology leads to a mutation of the leptin gene. As a result, people meat with a minimization of the leptin hormone in the blood.
A lack of a hormone and extra pounds are combined with a violation of normal growth, a decrease of libido, erectile dysfunction, and a secondary decrease in thyroid function. On this basis, scientists concluded that the peptide is closely related to all these endocrine glands. Subcutaneous injections of recombinant human leptin sharply suppress appetite and stimulate metabolism in three days after injection. The concentration of thyroid hormones in the blood returns to normal in a month after injection. The most effective among the means that restore the perception of insulin and leptin are «Metformin», «Siofor “Byetta”».
The European Commission recently approved Aegerion Pharmaceuticals’ drug Myalepta. It is intended to correct the rare disease lipodystrophy as an adjuvant for leptin deficiency. Today, it is the only remedy for combating leptin deficiency that affects the root cause of the pathology. This is a significant point, because lipodystrophy leads to serious organ damage without treatment.
In addition, drugs that correct fat metabolism are also important. The course of diabetes mellitus, the severity of hypertension, kidney disease, coronary artery disease, and human reproductive ability are depended on obesity.