Project description:A limited mechanistic understanding of skeletal muscle wasting after acute spinal cord injury (SCI) precludes targeted molecular interventions. Here, we demonstrate marked systemic wasting also affecting neurologically intact non-paralyzed (supralesional) muscle early after SCI. Systemic muscle mass loss propagates muscle weakness, affects fast type 2 myofibers preferentially, and becomes exacerbated after high (T3) compared to low (T9) thoracic paraplegia indicating lesion-level dependent (“neurogenic”) mechanisms. The wasting of non-paralyzed muscle, its rapid onset and severity beyond what can be explained by disuse implies additional systemic drivers. Muscle transcriptome and biochemical analysis revealed a glucocorticoid-mediated catabolic signature of SCI-induced systemic muscle wasting that was mitigated i) by endogenous glucocorticoid ablation (adrenalectomy), ii) by pharmacological glucocorticoid receptor (GR) blockade, and was iii) completely prevented, relative to T9 SCI, by genetic muscle-specific GR deletion. We provide evidence of neurogenic hypercortisolism underlying a rapid systemic and functionally relevant muscle wasting syndrome after acute SCI.
Project description:Cancer-induced muscle wasting reduces quality of life, complicates or precludes cancer treatments, and predicts early mortality. Herein, we investigated the requirement of the muscle-specific E3 ubiquitin ligase, MuRF1, for muscle wasting induced by pancreatic cancer. Murine pancreatic cancer (KPC) cells, or saline, were injected into the pancreas of WT and MuRF1-/- mice, and tissues analyzed throughout tumor progression. KPC tumors induced progressive wasting of skeletal muscle and systemic metabolic reprogramming in WT mice, but not MuRF1-/- mice. KPC tumors from MuRF1-/- mice also grew slower, and showed an accumulation of metabolites normally depleted by rapidly growing tumors. Mechanistically, MuRF1 was necessary for the KPC-induced increases in cytoskeletal and muscle contractile protein ubiquitination, and the depression of proteins that support protein synthesis. Together, these data demonstrate that MuRF1 is required for KPC-induced skeletal muscle wasting, whose deletion reprograms the systemic and tumor metabolome and delays tumor growth.
Project description:Cancer-induced muscle wasting reduces quality of life, complicates or precludes cancer treatments, and predicts early mortality. Herein, we investigated the requirement of the muscle-specific E3 ubiquitin ligase, MuRF1, for muscle wasting induced by pancreatic cancer. Murine pancreatic cancer (KPC) cells, or saline, were injected into the pancreas of WT and MuRF1-/- mice, and tissues analyzed throughout tumor progression. KPC tumors induced progressive wasting of skeletal muscle and systemic metabolic reprogramming in WT mice, but not MuRF1-/- mice. KPC tumors from MuRF1-/- mice also grew slower, and showed an accumulation of metabolites normally depleted by rapidly growing tumors. Mechanistically, MuRF1 was necessary for the KPC-induced increases in cytoskeletal and muscle contractile protein ubiquitination, and the depression of proteins that support protein synthesis. Together, these data demonstrate that MuRF1 is required for KPC-induced skeletal muscle wasting, whose deletion reprograms the systemic and tumor metabolome and delays tumor growth.
Project description:Investigating muscle wasting in a murine model of cancer cachexia, we identified Oncostatin M (OSM) as a potential mediator of inflammatory responses in skeletal muscle. OSM is a member of the IL-6 family of cytokines and has crucial functions in cell growth, differentiation, and inflammation. Our results demonstrate that OSM induces muscle atrophy. To understand if its effect is specific or it is a general effect of IL6 family cytokines, primary myotubes were treated with OSM, IL6 and LIF for 48hrs. Our findings showed that OSM potently induces muscle wasting in differentiated myotubes.
Project description:Skeletal muscle wasting is commonly associated with chronic kidney disease (CKD), resulting in increased morbidity and mortality. However, the link between kidney and muscle function remains poorly understood. Here, we took a complementary interorgan approach to investigate skeletal muscle wasting in CKD. We identified an increased production and elevated blood levels of soluble pro-cachectic factor Activin A, directly linking experimental and human CKD to skeletal muscle wasting programs. Systemic pharmacological blockade of Activin A using soluble activin receptor type IIB ligand trap prevented muscle wasting in a mouse model of experimental CKD.
Project description:Reduced PABPN1 levels cause aging-associated muscle wasting. PABPN1 is a multi-functional regulator of mRNA processing. To elucidate the molecular mechanisms causing PABPN1-mediated muscle wasting, we compared the transcriptome to the proteome in mouse muscles expressing shRNA to PABPN1 (shPab). We found greater variations in the proteome as compared to mRNA expression profiles. Protein accumulation in the shPab proteome was concomitant with reduced proteasomal activity. Notably, protein acetylation appeared to be enriched in shPab versus control proteomes (63%). An acetylome study in shPab muscles revealed prominent peptide deacetylation associated with elevated sirtuin-1 (SIRT1) deacetylase. We show that SIRT1 mRNA levels are controlled by PABPN1 via an alternative polyadenylation site utilization. SIRT1 inhibition reversed PABPN1 activity and muscle cell function. Moreover, deacetylation inhibition increased PABPN1 levels and reversed muscle wasting. We suggest that perturbation of a multifactorial regulatory loop involving PABPN1 and SIRT1 plays an imperative role in aging-associated muscle wasting.
Project description:The purpose of this study is to assess if Gtx-024 is effective in increasing lean body mass in subjects with muscle wasting related to cancer.
Project description:Purpose: Muscle wasting (or atrophy) occurs in primary neuromuscular diseases and during aging, with sarcopenia affecting 35.4% and 75.5% of women and man over 60 years of age. Mitochondrial dysfunction is proposed to contribute to muscle wasting. Here, we show that chronic adaptation to mitochondrial Precursor Over-accumulation Stress (mPOS) causes muscle wasting. mPOS is a newly discovered cell stress mechanism caused by the saturation or damage of the mitochondrial protein import machinery, which consequently leads to the toxic accumulation of precursor proteins in the cytosol. Methods: We generated transgenic mice with a two-fold increase of Ant1, an adenine nucleotide translocase involved in ATP/ADP exchange on the inner mitochondrial membrane (IMM). We found that these animals progressively lose muscle mass. At two years of age, the skeletal muscle becomes barely quantifiable, without affecting the overall lifespan. We then performed whole-transcriptome RNA-sequencing on skeletal muscle samples of male and female mice at 6 months of age. Results: After alignment and quantification, we show that the ANT1-transgenic muscles have a drastically remodeled transcriptome that represses protein synthesis, and stimulates proteasomal function, autophagy, lysosomal amplification and Gadd45a-signaling. These four processes are all known to promote muscle wasting. Conclusions: These results suggest that chronic proteostatic adaptation to mPOS is a robust mechanism of muscle wasting, and it leads to or depends in part on a robust set of transcriptional adaptations. This finding may help the understanding of how mitochondria contribute to muscle wasting during aging. It may also have implications for diseases that are associated with ANT1 overexpression.