Leptin | Laboratory research

Leptin The main mediator between adipose tissue and the hypothalamic-pituitary system. It is a protein that causes obesity.

Genetic defect of leptin (the synthesis of which is related to the Ob gene - the obesity gene) causes pathological obesity, which can be treated with exogenous hormone therapy.

Leptin is involved in the regulation of body weight and increases during weight gain. A 10% reduction in body weight results in a 53% reduction in leptin concentration. In contrast, a 10% weight gain increases blood serum leptin levels by 300%. Elevated leptin levels in such patients are explained by "leptin resistance", which is associated with a shift in hormone transport proteins or dysfunction of soluble leptin receptors.

Excess leptin leads to inhibition of insulin secretion, to the development of insulin resistance of skeletal muscle and adipose tissue, to a decrease in the action of insulin on liver cells, which leads to an increase in glycemia.

Leptin levels are related to endocrine status. Its concentration is higher in women. This may be due to the peculiarity of the distribution of adipose tissue, as women have a more developed layer of subcutaneous fat, and this leads to a different rate of leptin synthesis.

High levels of leptin explain why blood vessel thrombosis develops more often in overweight people than in people of normal weight. A clot has been shown to develop as a result of a special interaction between leptin and platelet receptors. In general, leptin levels in the blood are associated with insulin and proinsulin levels.

Leptin levels reflect not only the amount of fat accumulated, but also changes in energy metabolism: it decreases during hunger, and even increases when food is consumed in excess. In practice, this is a signal of the body's adaptation to changing conditions of existence, the main aspect of which is the ability to switch from carbohydrates to fat metabolism during fasting (starvation).

There is a close relationship between hyperleptinemia and insulin resistance. Considering the inhibitory effect of leptin on the development of obesity, it is believed that the production of leptin in the norm increases in response to the increase in the concentration of insulin, which prevents further production and release of insulin by the principle of negative feedback. The level of leptin is closely related not only to the body mass index (BMI), but also to the level of blood pressure, the concentration of atherogenic lipoproteins and the index of insulin resistance.

A decrease in serum leptin levels can be caused by stress, intense physical exercises, and long-term sedentary lifestyle. Metabolism slows down, kilograms accumulate quickly, and at this time, menstrual cycle disorders are often observed in women, which can eventually become the cause of infertility and osteoporosis.

Clinical studies have shown that leptin levels vary by race, it is lower in African-American women, which predisposes them to excess weight.

When to take a leptin test?

Leptin is a marker of the secretory activity of adipose tissue, an additional marker of insulin resistance (together with the HOMA index):

• Suspicion of genetic leptin deficiency (obesity developed in early ASC);
• In the research complex of weight gain or weight problems;
• Impaired reproductive function in the face of reduced nutrition and excessive physical activity;
• In a set of studies to determine the risk factors for cardiovascular disease;
• Differential diagnostics of type 2 diabetes and obesity;
• Recurrent thrombosis.

How to prepare for the test?

The test is required on an empty stomach.

Research material

Venous blood

Possible interpretation of the results

Plasma leptin concentration is modulated by various physiological (restriction of food intake, exposure to cold) and hormonal factors (insulin, catecholamines, glucocorticoids, thyroid hormones, etc.).

Serum leptin levels decline rapidly in response to starvation and reflect profound changes in energy balance. Also, low levels of leptin lead to overeating, decreased secretion of the thyroid gland and reproductive hormones, and immunity.

Leptin levels are elevated:

• during obesity
• Type 2 diabetes
• During excessive caloric feeding

Leptin levels are impaired:

• when hungry
• During weight loss
•  In obesity associated with genetic deficiency of leptin