Insulin resistance can be considered as synonymous with metabolic syndrome. One of the main causes of this condition is obesity. Thus, there is a clear connection between leptin and the development of the metabolic syndrome. Adipose tissue is the main source of energy in the human body and a powerful endocrine organ that synthesizes bioactive substances such as leptin, which control all biochemical processes in the human body.
Leptin belongs to the class of adipocytokines. It is a non-glycosylated peptide from the interleukin family. Leptin is both a cytokine and a hormone at the same time, which is able to regulate appetite and body weight, as well as energy balance. It is controlled by the hypothalamus on the principle of feedback. You will learn from the article wow leptin is involved in cardiometabolic syndrome.
- Insulin resistance.
- Adipose tissue and adipokine.
- The special role of leptin.
Cardiometabolic syndrome is a combination of risk factors that contribute to the development of pathology of the heart and blood vessels in patients with insulin resistance.
In total, the group of such pathologies-provocateurs includes three main diseases:
- hypertonic disease;
Leptin resistance and insulin resistance are related to aging. The mechanisms of dependence of resistant states on age are not yet fully understood. The leading role belongs to the hypothalamic-pituitary system and hyperactivity of the sympathetic nervous system. Certainly, neurotransmitters and an abnormal concentration of leptin play a role in potentiating the central mechanisms of insulin resistance.
Adipose tissue and adipokines
Adipose tissue is not only a powerful source of energy, but also an organ that secretes many hormones known as adipokines. There are more than 50 of them, and everyday researchers find new ones. These hormones influence the constancy of glucose levels in the bloodstream by correlating tissue sensitivity to insulin. They also control fat metabolism, inflammation, blood clotting, and the formation of new capillaries.
Adiponectin and leptin are especially important for insulin resistance. The first is produced only by mature fat cells. Its synthesis stimulates insulin, and this secretion is inactivated by interleukins, glucocorticosteroids. Adiponectin increases lipid oxidation in the periphery, lowers the concentration of free fatty acids in the bloodstream, minimizing the amount of intracellular triglycerides in the liver and muscles.
In addition, the biosubstance also reduces the level of glucose in the blood without activating the synthesis of insulin. The concentration of adiponectin itself is correlated with tissue sensitivity to insulin. In other words, hormone hyposynthesis can provoke insulin resistance and diabetes mellitus. The connection between adiponectin and insulin indirectly confirms the fact that an increase of the hormone in the blood reduces insulin resistance.
It has been proven that the hormone stimulates the phosphorylation of the tyrosine residue of the insulin receptor and increases the action of insulin in skeletal muscle and liver. It automatically reduces insulin resistance.
There is another mechanism: the supply of fatty acids to the liver and their oxidation decreases by activating protein kinase, which leads to a decrease in glucose synthesis by the liver and a decrease in insulin resistance. In addition, adiponectin has anti-inflammatory and anti-atherogenic properties.
The hormone minimizes the proliferation and migration of myocytes, the capture of low-density lipids by atherosclerotic plaque, and blocks the transformation of macrophages into foam cells in the capillary endothelium. Adiponectin minimizes the destruction of the vascular wall and activates the production of nitric oxide. It dilates blood vessels, inhibits the proliferation of smooth muscles, adhesion of blood cells, and demonstrates antiplatelet properties.
The correlation of plasma adiponectin concentration with the atherogenic coefficient and triglyceride level is negative, and positive with the level of high-density lipoproteins. Adiponectin blocks the activation of endothelial adhesive molecules and the formation of cytokines by macrophages. This leads to minimization of inflammation and makes it possible to classify the hormone as an antiatherogenic endocompound. It is involved in protecting atherosclerotic plaque from rupture.
Another adipose tissue hormone is resistin, which is considered a trigger for metabolic disorders associated with obesity and diabetes. The hormone blocks the uptake of glucose by target tissues, in fact, being an insulin antagonist. The level of resistin is supposed to be a predictive marker of obesity. Recently, the participation of resistin in the inflammatory response has been proved, fixing a direct correlation between the concentration of the hormone in plasma and the severity of the inflammatory response.
The special role of leptin
Leptin is a hunger hormone, which was the first of the adipokines discovered and is synthesized by cells of white adipose tissue, skeletal muscles, stomach, and placenta. Leptin receptors are located in the brain, in the hypothalamus. The centers of hunger, thermoregulation and saturation are located close to each other. It can explain the feeling of cold when fasting and hot when overeating.
The main role of the hormone is to suppress appetite and stimulate energy expenditure. Such mechanisms are implemented through minimizing the synthesis of neuropeptides in the hypothalamus. The effect of leptin on taste buds has been alco proven. The hormone regulates human eating behavior.
It is believed that with obesity there is a compensatory resistance of the hypothalamus to the central signal of leptin with regard to insulin resistance or metabolic syndrome. This moment by type of feedback causes hyperleptinemia. This condition, with prolonged existence, blocks the synthesis of insulin RNA and there is a direct relationship between the concentration of the hormone and the severity of insulin resistance.
Leptin levels are related not only to body mass index (BMI), but also to blood pressure, i.e. hypertension. In addition, the hormone correlates with the concentration of atherogenic lipoproteins and is able to activate the cellular immune response by influencing the synthesis of pro-inflammatory cytokines.
Adipose tissue is an active endocrine-metabolic organ that plays a major role in the development of obesity, insulin resistance (cardiometabolic syndrome) and type 2 diabetes mellitus.