Leptin: a hormone linked to obesity.
What is Leptin?
Leptin is a hormone involved in the regulation of body weight. Leptin name derives from the Greek word meaning leptos intestine, which is due to its obvious role in body weight control through regulation of appetite and thermogenesis (the process by which fat burning).
Structure of leptin
Who produces it?
It originated in various tissues, mainly in adipose tissue (body fat) and is secreted into the blood, where it travels to the brain and other tissues, causing fat loss, decreased appetite or other functions, depending on where ACT .
The complex systems that regulate fisiopatogénesis of obesity have been subject of intense research in recent years. This is because obesity is a highly prevalent condition worldwide, especially in industrialized countries and is considered one of the major health problems.
Normally when an increase in body fat, leptin acts on the hypothalamus (a gland in the brain) to decrease appetite and increase metabolism.
In obese leptin secretion increases reaching values ??achieved four times higher than in non-obese, reflecting a state of leptin resistance (ie this hormone but can not act).
This hormone is secreted into the bloodstream mainly by adipose tissue, stomach and some liver cells. It is also synthesized by the placenta during pregnancy and is secreted into the maternal circulation, so that its concentration is elevated during normal pregnancy, especially in the second and third quarter.
The presence of leptin gastric (stomach), and response to food, suggesting the involvement of this hormone in controlling acute intake.
Leptin does most of its metabolic effects by interacting with specific receptors in the central nervous system and peripheral tissues.
Besides the presence of leptin receptor in the brain are found in peripheral organs, which extends its scope
With regard to peripheral tissues found in lung, kidney, liver, pancreas, adrenal cortex, ovary, testis, skeletal muscle, hematopoietic cells, adipose tissue and the gastrointestinal tract.
What people are increased leptin values?
Obese subjects have high leptin levels, after weight loss, leptin levels, which fell below the estimated value based on fat mass, the brain may indicate the adequacy of fatty deposits
How does leptin?
At the level of the brain, leptin inhibits food intake (loss of appetite), active energy expenditure (fat loss) and affects many metabolic processes.
Leptin is involved in controlling the medium term energy balance. Genetic defects involving the absence of leptin in mice and humans, determines early onset morbid obesity.
Leptin travels through the blood and plasma levels are correlated with total fat mass.
What functions does besides being linked to obesity?
Participates in the inflammatory response while modifying the immune function. (Ie is related to the immune system)
Involved in the regulation onset of puberty and reproduction function. It has been shown that extremely thin adolescents start so late puberty, so it has been suggested that leptin informs the brain, on the existing amount of fat mass to the onset of puberty and female reproduction.
Stimulating effect of gonadal function (sexual glands), creating a link between adipose tissue and the reproductive function. This union may be accounting for the reduced fertility found in very thin women, such as athletes or ballet dancers and leptin secretion could signal the gonads when there is enough stored energy to sustain a pregnancy
Modifies the glucose metabolism. Stimulates lipolysis in adipocytes, causing a change in the distribution of lipids in muscle tissue
Constitutes an essential metabolic signal modulates the secretion of growth hormone.
Is leptin resistance causes obesity?
It has been suggested that obesity occurs because after a certain amount of leptin transport system from the brain to the blood develops because saturated or an alteration in its level of brain receptors.
Due to this resistance state is that the majority of obese individuals are exaggerated appetite (hyperphagia) although leptin having excess, ie hormone sends this information is not recorded by the brain causing a decrease in the reply
Leptin resistance in man (b).
Leptin resistance observed in obese individuals with persistently high circulating levels of leptin. Low leptin levels are permanently associated with inadequate mass and adipose tissue may be associated with neuroendocrine disturbances, such as reproductive system abnormalities.
How is leptin?
The leptin determination is performed in the laboratory with a simple blood
Its determination is performed with a method called radioimmunoassay.
What are your values?
Serum leptin levels in people with normal weight range in the range of 1 to 15 ng / ml, however in subjects with body mass index (BMI) greater than 30 can be found values ??of 30 ng / ml or higher .
Plasma leptin correlates positively with body mass index (BMI) and the percentage of total fat in humans
In the general population there is great variation in the concentration of leptin which suggests a multifactorial modulation secretion.
Another factor that determines the values ??of leptin is sex, women have higher levels than men, even after adjusting the values ??according to BMI, body fat percentage, the thickness of skin folds and age.
Furthermore, after fasting or caloric restriction, leptin levels fall in greater proportion than expected based on the reduction of fatty deposits. This reduction in leptin levels cause increased appetite and decreased energy expenditure.
What are the prospects for future applications of leptin?
Identifying genes regulated by leptin has improved knowledge about how leptin causes its effects on weight and appetite, and can also provide new targets for designing drugs that stimulate weight loss.
The growing awareness of this hormone opens new perspectives in the difficult field of obesity therapeutic. Once this is achieved unlock mechanism "leptin resistance" will surely have more effective therapeutic tools for the treatment of obese patients
In addition to its application in the treatment of obesity this hormone has application prospects in other areas such as the prevention of diabetic retinopathy and the risk of vascular thrombosis and abnormalities in the reproductive system, among others.