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The growth hormone acts to counteract weight loss: study (image of representation) & nbsp | & nbspPhoto: & nbspGetty Images
Washington DC: In a recent study, scientists discovered that growth hormone (GH) plays an important role in weight loss and maintaining one's weight. According to research published in the journal Nature Communications, GH stimulates skeletal maturation and linear bone growth, also helps maintain tissues and organs throughout life, also acts directly on the brain to retain the brain. energy when the body loses weight.
"The growth hormone has been known for decades, but our discovery shows that it does so much more than previously thought," said Jose Donato Junior, one of the authors of the study.
"GH receptors are found in large amounts in muscles and tissues, in the liver and in organs directly involved in growth metabolism, but we found that the brain was also filled with GH receptors. This is entirely new, "Donato said.
"We have also found that GH in the brain is not only involved in the metabolism of growth, but that it also influences the metabolic responses that conserve energy when we are hungry or when a diet is new. This discovery, also new in science, has important implications in terms of understanding why weight loss is so difficult, "added Donato.
"For decades, scientists have been trying to understand why it is so difficult to maintain the weight gained after the sacrifices of a successful diet and why it is so easy to regain weight lost. now considered the main hormone that helps conserve energy when we are hungry, "Donato said.
Levels of leptin in the blood are known to drop in response to weight loss, he explained, but this knowledge has never resulted in the creation of a diet or drug. a successful leptin therapy that allows people to lose weight without taking it back quickly.
"The process of weight loss obviously involves several metabolic processes and several hormones in addition to leptin, that's where GH comes in. We found that in response to weight loss, GH acts on the body. brain in the same way as leptin.Low weight triggers an increase in the level of GH in the blood, "Donato said.
"In the recently published article, we show that signaling by the central growth hormone also promotes neuroendocrine adaptations during food deprivation," added Donato.
GH receptors in the brain are located in the hypothalamus, the highest center of the autonomic nervous system. The pulses of the hypothalamus influence the cells of the neuro-vegetative system and regulate the smooth muscle tissue in the intestine and blood vessels, the heart muscle, all the glands and the kidneys, among other organs.
The researchers found that GH receptors in the hypothalamus specifically activated a small population of neurons called AgRP, which is an abbreviation for agouti-related protein. AgRP neurons, in turn, increase the production of AgRP, which increases appetite and decreases metabolism and energy expenditure.
"AgRP is one of the most powerful stimulants of appetite." It's curious how a small number of AgRP neurons, only a few thousand trillion neurons in the hypothalamus, can play a role as important, "said Donato.
To conduct a detailed study of the influence of GH signaling on AgRP neurons, scientists elevated genetically engineered mice with AgRP-specific GH receptor ablation (called AgRP knockout mice GHR). Their experiments also used a control group comprising non-genetically modified wild-type mice.
In various experiments, the researchers measured the energy expenditure of the whole body in the two groups of mice on a 60% diet restriction diet. Their objective was to determine whether a lack of adaptive response to the resulting energy gap would have a significant impact on the energy balance.
They found that control mice decreased their energy expenditure during dietary restriction, which is consistent with the adaptive responses that conserve energy in this situation.
The energy expenditure of AgRP GHR KO mice during food restriction decreased significantly less, suggesting that they did not save energy as efficiently as the control mice.
As a result, AgRP GHR KO mice showed a higher rate of weight loss, mainly due to a decrease in fat mbad (energy reserves), but also a loss of mbad lean (vital organs, bones, muscle, ligaments, tendons and body fluids). .
"In other words, we discovered that weight loss resulted in an increased rate of growth hormone of the hypothalamus, which activated the AgRP neurons, making weight loss more difficult and intensifying the feeling of hunger.It is exactly the same function as leptin, "Donato said.
Conservation of energy is so important to the body, he added, that evolution has endowed man with two energy conservation mechanisms, one activated by leptin and the other by GH.
"One works as an alternative for the other.This is why weight loss treatments based solely on leptin do not work.The mechanism of GH should be treated at the same time, "Donato said.
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