Ghrelin is best known for its role in the mechanisms of hunger, but it has two different forms, only one of which induces hunger. Both forms are known to affect muscle tissue metabolism, and this may be one of the ways in which calorie restriction slows the onset of muscle loss with age, a condition known as sarcopenia. Researchers here increase levels of the non-hunger-inducing ghrelin in mice and show that this does indeed slow the onset and progression of sarcopenia, and thus might be a basis for therapy.
Sarcopenia, the decline in muscle mass and functionality during aging, might arise from age-associated endocrine dysfunction. Indeed, muscle wasting follows the general decline in trophic hormones and the establishment of a chronic mild inflammatory status characteristic of aging. Ghrelin is a gastric hormone peptide circulating in both acylated (AG) and unacylated (UnAG) forms that have anti-atrophic activity on skeletal muscle. AG is the endogenous ligand of the growth hormone secretagogue receptor (GHSR-1a), and it is involved in metabolic regulation and energetic balance through induction of appetite, food intake, and adiposity. UnAG does not induce GH release and has no
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