In a recent study, scientists have discovered that growth hormone (GH) plays an important role when it comes to losing and maintaining weight. According to the research published in the journal Nature Communications, GH stimulates skeletal maturation and linear bone growth, as well as helps maintain tissue and organs throughout life, also acts directly on the brain to conserve energy when the body loses weight.
“Growth hormone has been known for decades, but our discovery shows it does a lot more than was thought,” said Jose Donato Junior, one of the authors of the study. “GH receptors are found in large quantities in muscle and tissue, in the liver, and in organs directly involved in growth metabolism, but we found that the brain is also full of GH receptors. This is entirely new,” said Donato.
“We also found that brain GH is not only involved in growth metabolism but, above all, influences the metabolic responses that conserve energy when we’re hungry or on a diet. This discovery, which is also new to science, has important implications in terms of understanding why it’s so hard to lose weight,” added Donato.
Bloodstream leptin levels are known to fall in response to weight loss, he explained. But, this knowledge has never resulted in the creation of a successful diet or therapy with leptin that could enable subjects to lose weight and not regain it soon afterwards.
To conduct a detailed study of the influence of GH signalling on AgRP neurons, the scientists bred genetically modified mice with AgRP-specific GH receptor ablation (called AgRP GHR knockout mice). Their experiments also used a control group comprising wild-type mice that were not genetically modified.
In various experiments, the researchers measured whole-body energy expenditure in the two groups of mice when subjected to a diet with 60 per cent food restriction. Their aim was to determine whether a lack of adaptive response to the resulting energy deficit would have a significant impact on energy balance.
They found that the control mice decreased energy expenditure during food restriction, which is consistent with the adaptive responses that conserve energy in this situation.