101. Acylated and unacylated ghrelin impair skeletal muscle atrophy in mice.
- Author
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Porporato PE, Filigheddu N, Reano S, Ferrara M, Angelino E, Gnocchi VF, Prodam F, Ronchi G, Fagoonee S, Fornaro M, Chianale F, Baldanzi G, Surico N, Sinigaglia F, Perroteau I, Smith RG, Sun Y, Geuna S, and Graziani A
- Subjects
- Acylation, Animals, Cachexia metabolism, Cachexia prevention & control, Cell Line, Ghrelin metabolism, MAP Kinase Signaling System, Male, Mechanistic Target of Rapamycin Complex 2, Mice, Mice, Inbred C57BL, Mice, Knockout, Mice, Transgenic, Multiprotein Complexes metabolism, Muscle Denervation, Muscle, Skeletal drug effects, Muscle, Skeletal metabolism, Muscle, Skeletal pathology, Muscular Atrophy metabolism, Muscular Atrophy pathology, Protein Binding, Proto-Oncogene Proteins c-akt metabolism, Receptors, Ghrelin metabolism, Signal Transduction, TOR Serine-Threonine Kinases metabolism, Ghrelin chemistry, Ghrelin pharmacology, Muscular Atrophy prevention & control
- Abstract
Cachexia is a wasting syndrome associated with cancer, AIDS, multiple sclerosis, and several other disease states. It is characterized by weight loss, fatigue, loss of appetite, and skeletal muscle atrophy and is associated with poor patient prognosis, making it an important treatment target. Ghrelin is a peptide hormone that stimulates growth hormone (GH) release and positive energy balance through binding to the receptor GHSR-1a. Only acylated ghrelin (AG), but not the unacylated form (UnAG), can bind GHSR-1a; however, UnAG and AG share several GHSR-1a-independent biological activities. Here we investigated whether UnAG and AG could protect against skeletal muscle atrophy in a GHSR-1a-independent manner. We found that both AG and UnAG inhibited dexamethasone-induced skeletal muscle atrophy and atrogene expression through PI3Kβ-, mTORC2-, and p38-mediated pathways in myotubes. Upregulation of circulating UnAG in mice impaired skeletal muscle atrophy induced by either fasting or denervation without stimulating muscle hypertrophy and GHSR-1a-mediated activation of the GH/IGF-1 axis. In Ghsr-deficient mice, both AG and UnAG induced phosphorylation of Akt in skeletal muscle and impaired fasting-induced atrophy. These results demonstrate that AG and UnAG act on a common, unidentified receptor to block skeletal muscle atrophy in a GH-independent manner.
- Published
- 2013
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