Fat tissue is a source of bioactive substances, one of which is leptin, a peptide-type hormone. From this article you will learn about its pharmacodynamic action.
- Protein hormone leptin.
- Indicator of energy metabolism.
- Relationship to insulin and other hormones.
- Leptin in Men and Women.
- Laennek and leptin.
The protein hormone leptin
The biologically active compound leptin is synthesized in the subcutaneous fatty tissue and is endowed by nature with numerous abilities. It was it that made scientists look at the usual fat cells as an endocrine gland. Today it is absolutely clear that leptin plays a leading role in the regulation of the body’s energy metabolism and is a pleiotropic mediator in a complex system of neuroendocrine functions.
The hormone, by its nature, is a protein with a molecular weight of 16 kD. It circulates freely in the bloodstream, but can be partially bound to its adipose tissue neighbors. Leptin correlates with the circadian rhythm, increasing its level at night. Its secretion is pulsed and controlled by the ob gene, whose mutation is affiliated with obesity, overeating, hypodynamia, and low energy metabolism with the development of diabetes mellitus 2. Fat cell size is the key to hormone synthesis. The bigger the adipocytes, the more powerful they are at synthesizing leptin, and vice versa.
Indicator of energy exchange
The hormone is an indicator of energy reserves in the body and a mediator of energy balance. Leptin performs its functions through CNS: in hypothalamic nuclei it causes a decrease in the feeling of hunger. In addition to fat metabolism, leptin controls puberty, growth, and secretion of tropic hormones. It is also necessary to guarantee the action of insulin, and is able to influence reproduction, bypassing the pituitary gland, because its receptors are localized in the ovaries.
Melanocortins, the conductors of hormone bioinfluence, perform their task by contacting leptin receptors both in the hypothalamus and outside the CNS. Until recently, there were 5 isoforms of the hormone receptors, today there are 6. All of them belong to the cytokine family, i.e. they are affiliated with interleukins and can control inflammation. Serum leptin levels rise after several days of heavy eating and fall within a few hours of starvation.
Relationship to insulin and other hormones
The amount of leptin increases at the peak of insulin synthesis during food intake and is correlated with insulin concentration. Leptin production is activated by infectious agents, cytokines, and internal toxins. The hormone controls body weight through its ability to stimulate the sympathetic nervous system, i.e. to activate heat production and energy expenditure.
Leptin is synthesized in small doses by the placenta, skeletal musculature, mammary gland epithelium and mucosa of the digestive system. Gastrin and cholecystokinin are also produced in the stomach and biliary system, which minimize leptin synthesis in the stomach, but cause its increase in plasma. This can be used to correct appetite temporarily. Leptin production by adipose tissue is controlled by sex steroids, mainly testosterone. Leptin reaches the brain by crossing the blood-brain barrier via the satiety transport mechanism.
Once the serum leptin level reaches 30 ng/mL, a further increase in the hormone does not cause a parallel increase in its concentration in cerebral tissues and cerebrospinal fluid. This may play a role in the development of leptin resistance and obesity.
Leptin in Men and Women
There is a correlation between blood and urine leptin concentrations, which makes it possible to use this to indirectly assess serum leptin levels. Leptin in women is higher than in men and decreases with age. This is independent of BMI (body mass index) and age-related hormonal shifts. Insulin resistance is affiliated with leptin in both sexes, especially in old age. Serum concentrations of the hormone are high in breastfed infants compared to formula-fed infants. This suggests that artificial feeding increases the risk of obesity in older children.
Leptin can be called a physiological aging hormone. In men and women, it activates fatty acid oxidation in mitochondria, which provokes the minimization of triglyceride levels in tissues. And the increase of these very triglycerides in cells is considered to be a metabolic trigger for accelerating apoptosis – programmed cell death. Leptin also affects sexual function by modulating the synthesis of luteinizing and follicle stimulating hormones under hypothalamic control. The hormone controls reproduction in both women and men.
There is a direct correlation between leptin levels in men with dehydroepiandrosterone sulfate and an inverse relationship with testosterone concentrations. Leptin is affiliated with T- and B-lymphocyte function and bone density. Low levels of the hormone are more frequently recorded in women with spinal fractures.
Leptin directly affects bones, causing their fragility, and this effect is stronger than the effect of the same leptin mediated-central pathway. Daily fluctuations of the hormone in plasma in men after 20 years of age range from 0.5 to 13.8 ng/ml, and in women of the same age, the range is 1.1 to 27.6 ng/ml. Determination of leptin levels is important for differential diagnosis of obesity, risk assessment of diabetes mellitus 2, CHD, and secondary amenorrhea.
Laennek and leptin
Not so long ago an innovative drug Laennek – hydrolysate of human placenta – appeared on the pharmacological market of the country. Leptin is a part of it. Clinical trials reliably confirmed hepatoprotective and immunomodulatory function of the hormone. Scientific data on leptin pharmacodynamics suggest its significant contribution to the therapeutic effect of Laennek preparte. Taking into account the localization of leptin receptors in male and female reproductive organs, the indications for the use of the drug can be significantly expanded, and Laennek with leptin as a component is able to normalize reproductive function. And this has a direct correlation with life expectancy.
It turns out that leptin in its pharmacodynamics is a low-molecular-weight protein hormone that supports normal metabolism and significantly slows the aging of the human body.