Muscle NAD+ depletion and Serpina3n as molecular determinants of murine cancer cachexia—the effects of blocking myostatin and activins

Abstract

Objective Cancer cachexia and muscle loss are associated with increased morbidity and mortality. In preclinical animal models, blocking activin receptor (ACVR) ligands has improved survival and prevented muscle wasting in cancer cachexia without an effect on tumour growth. However, the underlying mechanisms are poorly understood. This study aimed to identify cancer cachexia and soluble ACVR (sACVR) administration-evoked changes in muscle proteome. Methods Healthy and C26 tumour-bearing (TB) mice were treated with recombinant sACVR. The sACVR or PBS control were administered either prior to the tumour formation or by continued administration before and after tumour formation. Muscles were analysed by quantitative proteomics with further examination of mitochondria and nicotinamide adenine dinucleotide (NAD + ) metabolism. To complement the first prophylactic experiment, sACVR (or PBS) was injected as a treatment after tumour cell inoculation. Results Muscle proteomics in TB cachectic mice revealed downregulated signatures for mitochondrial oxidative phosphorylation (OXPHOS) and increased acute phase response (APR). These were accompanied by muscle NAD + deficiency, alterations in NAD + biosynthesis including downregulation of nicotinamide riboside kinase 2 ( Nrk2 ), and decreased muscle protein synthesis. The disturbances in NAD + metabolism and protein synthesis were rescued by treatment with sACVR. Across the whole proteome and APR, in particular, Serpina3n represented the most upregulated protein and the strongest predictor of cachexia. However, the increase in Serpina3n expression was associated with increased inflammation rather than decreased muscle mass and/or protein synthesis. Conclusions We present evidence implicating disturbed muscle mitochondrial OXPHOS proteome and NAD + homeostasis in experimental cancer cachexia. Treatment of TB mice with a blocker of activin receptor ligands restores depleted muscle NAD + and Nrk2 , as well as decreased muscle protein synthesis. These results indicate putative new treatment therapies for cachexia and that although acute phase protein Serpina3n may serve as a predictor of cachexia, it more likely reflects a condition of elevated inflammation.

Targeting Mitochondria by SS-31 Ameliorates the Whole Body Energy Status in Cancer- and Chemotherapy-Induced Cachexia

“…Consistent with the marked changes in muscle mitochondrial function, several metabolites were severely affected ( Figure 5 a). A decrease in muscle NADH was observed in C26 OXFU mice ( p -value = 0.051), supporting the emerging concept of cancer-induced perturbations to redox metabolism [ 19 ], also consistent with the reduced succinate levels. Increases in the amino acids glutamine, isoleucine, leucine, valine and phenylalanine were observed in C26 OXFU mice, suggesting increased protein degradation.…”

ACVR2B antagonism as a countermeasure to multi‐organ perturbations in metastatic colorectal cancer cachexia

“…This is not the first evidence that targeting ACVR2B signalling may benefit oxidative metabolism. Recent investigations have shown that citrate, citrate synthase enzyme activity, and SDH are mildly improved in mice‐exposed chemotherapy and C26 tumours 24,65,66 . Interestingly, this work also demonstrated unchanged protein expression of several mitochondrial proteins indicating that targeting ACVR2B signalling may have context‐specific effects on skeletal muscle metabolism 24,65 …”

“…Recent investigations have shown that citrate, citrate synthase enzyme activity, and SDH are mildly improved in mice-exposed chemotherapy and C26 tumours. 24,65,66 Interestingly, this work also demonstrated unchanged protein expression of several mitochondrial proteins indicating that targeting ACVR2B signalling may have context-specific effects on skeletal muscle metabolism. 24,65 Recent discussion over the multi-organ perturbations occurring with progression of cachexia has highlighted how just as skeletal muscle wasting occurs in numerous models of cancer, other organs including fat, bone, and cardiac tissue also deteriorate.…”

“…24,65,66 Interestingly, this work also demonstrated unchanged protein expression of several mitochondrial proteins indicating that targeting ACVR2B signalling may have context-specific effects on skeletal muscle metabolism. 24,65 Recent discussion over the multi-organ perturbations occurring with progression of cachexia has highlighted how just as skeletal muscle wasting occurs in numerous models of cancer, other organs including fat, bone, and cardiac tissue also deteriorate. [9][10][11]51 Interestingly, in the present study, fat wasting was ameliorated in ACVR2B/Fc-treated tumour mice, suggesting that targeting ACVR2B is sufficient to preserve fat mass along with muscle mass, independent of food consumption.…”

Blocking myostatin: muscle mass equals muscle strength?

“…Muscle wasting is frequently observed in the elderly population and patients with chronic diseases, in up to 50% of patients 5,6 . In several disease models of muscle wasting, an upregulation of myostatin has been shown including cancer cachexia, 7–10 chemotherapy, 11 kidney failure, 12–15 heart failure, 6 spinal muscular atrophy, 16 vitamin D deficiency in infantile nephropathic cystinosis, 17 glucocorticoids, 14,18 and oculopharyngeal muscular dystrophy (OPMD) 19 . This shows that myostatin signalling in humans is indeed a valid target for therapeutic interventions in various muscle wasting conditions.…”