Journal of Cachexia, Sarcopenia and Muscle

Background and AimsOver 80% of patients with pancreatic cancer experience cachexia, characterized by severe muscle and fat loss. While all the mechanistic understanding comes from preclinical models, the translatable nature of these findings to humans remains a critical gap due to the limited knowledge of human cachexia biology. MethodsWe generated matched gene and microRNA profiles from rectus abdominis muscle of 55 pancreatic ductal adenocarcinoma and 18 control subjects. Differentially expressed genes and microRNAs were identified at 1.5-fold change and p<0.05. ResultsGene expression results revealed a striking sex-specific difference at the expression and pathway levels. In both sexes, co-expression gene network analysis identified more significant modules and hub genes at 1-month of weight loss than the traditionally used six months, suggesting that gene alterations may be more dynamic in the early stages of the disease progression. When comparing hub genes from humans to experimental models of cachexia, genes such as RELA, DDX21, WDR75, PTPN1, and CRIP3 exhibited similar patterns of expression, suggesting their potential role in cachexia. microRNAs also exhibited sex-specific expression. Although several common miRNAs were identified between sexes, their gene targets differed, indicating that microRNAs may regulate gene targets in a sex-specific manner. ConclusionsThe dataset can serve as a resource for validating preclinical findings and exploring previously unexplored molecules in cachexia. Future studies will functionally characterize the role of the hub genes and microRNAs in cachexia. This is the first study to identify sex-specific genes and microRNAs from a single cancer type.

Cancer cachexia is a highly prevalent wasting syndrome in cancer patients. Inflammation is hallmarks of symptomatic cachexia, however early stages of cachexia are not well understood, including differences between biological sexes. In a mouse model of early cachexia, muscle from males showed strong mitochondrial defects, whereas females were characterized by inflammatory and stress response. We demonstrate a novel link between the increase in purinergic receptor P26Y, and dysregulated Ca2+ homeostasis, mitochondrial dysfunction and damage, and inflammation during early stages of cancer cachexia. Low levels of miR-379-3p were associated with poor survival of patients with lung cancer. Restoring miR-379-3p levels in mice prevented loss of muscle mass and function. miR-379-3p targeted P2r6y and restored mitochondrial content and function, inhibited type II interferon response, and regulated the expression of Ca2+-related and apoptotic markers. This supports miR-379-3p as a hub regulating multiple processes underlying cachexia and represent a therapeutic target for cancer patients.

RationaleMechanical ventilation plays an important role in critical illness-associated diaphragm weakness. Weakness contributes to difficult weaning and is associated with increased morbidity and mortality. Diaphragm weakness is caused by a combination of atrophy and dysfunction of myofibers, which are large syncytial cells maintained by a population of myonuclei. Each myonucleus provides gene transcripts to a finite fiber volume, termed the myonuclear domain. Changes in myonuclear number in myofibers undergoing atrophy has not been investigated in mechanically ventilated ICU patients. Myonuclear number is a determinant of transcriptional capacity, and therefore critical for muscle regeneration after atrophy. ObjectivesOur objective was to investigate if and how myonuclear number changes in the diaphragm of mechanically ventilated ICU patients and whether changes are associated with myofiber atrophy. MethodsWe used a combination of transcriptomics, immunohistochemistry, and confocal microscopy to study myonuclear alterations in diaphragm and quadriceps biopsies from mechanically ventilated ICU patients. ResultsMyonuclear number and myonuclear domain were reduced in patients with diaphragm myofiber atrophy. Intrinsic apoptotic pathway activation was identified as a mechanism underlying myonuclear removal in the diaphragm of mechanically ventilated ICU patients. Total transcriptional activity in myofibers decreased with myonuclear loss. Furthermore, muscle stem cell number was reduced in the patients with diaphragm atrophy. ConclusionWe identified myonuclear loss due to intrinsic apoptotic pathway activation as a potential mechanism underlying diaphragm atrophy in mechanically ventilated patients. This provides novel insights in diaphragm weakness of ICU patients. Targeted therapies may limit development of diaphragm weakness and improve weaning outcome.

Background: Skeletal muscle atrophy and low physical performance are associated with disease progression and higher mortality rates in multiple pathological conditions. Here, we determined whether body composition and physical performance would predict mortality in metastatic non-small cell lung cancer (NSCLC) patients. In addition, we defined whether plasma samples from NSCLC patients would directly affect the homeostasis of skeletal muscle cells. Methods: The prospective cohort included 55 metastatic NSCLC patients and seven age-matched control subjects. We assessed clinical characteristics, body composition, cancer cachexia, and quality of life (QoL). We determined physical performance with a series of functional tests. We analyzed skeletal muscle and adipose tissue areas. Finally, we evaluated the overall survival rate, and additional blood samples were collected from a subcohort of eighteen patients for further studies in cell culture and metabolomic analysis. Results: We found that physical performance, not body composition, was associated with overall survival in this cohort. Moreover, incubation with plasma derived from NSCLC patients with low physical performance impaired the metabolism and proliferation of primary human myotubes. Unbiased metabolomics revealed several metabolites differentially expressed in the plasma of NSCLC patients with low physical performance compared to healthy control subjects, with serine and N2,N2-dimethylguanosine (M22G) being the most reduced and increased metabolites, respectively. Conclusion: These novel findings confirm physical performance as a significant predictor of overall survival in metastatic NSCLC patients and provide insights into cancer-induced circulating factors that can directly affect skeletal muscle homeostasis and prognosis.

BackgroundThe age-related progressive decline in skeletal muscle function is characterised by declining mitochondrial quality control and perturbed fatty acid metabolism, contributing to frailty and increased mortality. The actin cytoskeleton, a key structural component of skeletal muscle, has recently been implicated in mitochondrial anchoring and dynamics. However, the role of actin-regulating proteins, including the Rho GTPase Rac1, in mitochondrial function and age-associated metabolic and functional muscle deterioration remains undefined. MethodsSkeletal muscle from mice with inducible muscle-specific deletion of Rac1 (Rac1 imKO) underwent unbiased mass spectrometry-based proteomic profiling. Mitochondrial morphology was assessed by transmission electron microscopy, and physiological parameters, including muscle mass and contraction-stimulated palmitate oxidation in isolated soleus muscle, were evaluated. Mitochondrial respiratory function was determined by high-resolution respirometry in permeabilised gastrocnemius skeletal muscle fibre bundles. Biochemically, muscular triacylglycerol (TG) content, mRNA (qPCR) and protein (immunoblotting) content were determined. In vastus lateralis muscle biopsies from healthy, untrained young (20-30 years) and old, sarcopenic (83-94 years) men, Rac1 and mitochondrial respiratory protein abundances were measured. A complementary human genetic association analysis was performed using the FinnGen dataset. ResultsRac1 deficiency triggered muscle wasting in middle-aged mice (Gastrocnemius: -10%; Quadriceps: -7%). Preceding muscle wasting, gene set enrichment analysis identified enrichment in fatty acid metabolism and oxidative phosphorylation pathways, consistent with increased mitochondrial volume density in Rac1 imKO muscle (subsarcolemmal: +467%; intermyofibrillar: +166%). Despite mitochondrial expansion at this stage, Rac1 deficiency attenuated the increase in palmitate oxidation in response to muscle contraction (-62%). At the muscle-wasting stage, Rac1 imKO muscle exhibited reduced mitochondrial respiratory capacity (-25-32%). Additionally, the mitochondrial dysfunction was associated with an accumulation of muscle TG (+78%, p = 0.096) and upregulation of fatty acid transporter, CD36 protein content (+25%), indicative of altered fatty acid handling. In humans, Rac1 muscle protein content was increased in old, sarcopenic subjects compared to young (+41%), and negatively correlated with quadriceps cross-sectional area (CSA) (r = -0.475) and type II fibre CSA (r = -0.466). In old, sarcopenic muscle, Rac1 protein content correlated negatively with protein content of multiple mitochondrial respiratory complexes (CI: r = -0.690, CIV: r = -0.938, CV: r = -0.704). GWAS further identified associations between Rac1 SNP variants and lipid metabolic and muscle-wasting diseases. ConclusionsMuscle Rac1 deficiency reduces mitochondrial respiratory capacity and metabolic flexibility through impaired fatty acid metabolism, leading to muscle wasting and highlighting a potential therapeutic target in age-related functional decline.

Cancer cachexia affects up to 80% of cancer patients and results in reduced quality of life and survival. We previously demonstrated that the transcriptional repressor Forkhead box P1 (FoxP1) is upregulated in skeletal muscle of cachectic mice and people with cancer, and when overexpressed in skeletal muscle is sufficient to induce pathological features characteristic of cachexia. However, the role of myofiber-derived FoxP1 in both normal muscle physiology and cancer-induced muscle wasting remains largely unexplored. To address this gap, we generated a conditional mouse line with myofiber-specific ablation of FoxP1 (FoxP1SkmKO) and found that in cancer-free mice, deletion of FoxP1 in skeletal myofibers resulted in increased myofiber size in both males and females, with a significant increase in muscle mass in males. In response to murine KPC pancreatic tumor burden, we found that myofiber-derived FoxP1 is required for cancer-induced muscle wasting and diaphragm muscle weakness in male mice. In summary, our findings identify myofiber-specific FoxP1 as a negative regulator of skeletal muscle with sex-specific differences in the context of cancer. NEW & NOTEWORTHYHere we identify myofiber-derived FoxP1 as a negative regulator of skeletal muscle with sex-specific effects in cancer. Under cancer-free conditions, FoxP1 knockout increased myofiber size in male and female mice. However, in response to pancreatic cancer, FoxP1 was required for muscle wasting and weakness in males but not females. This highlights the need to consider sexual dimorphism in cancer-induced muscle pathologies and provides evidence suggesting that targeting FoxP1 could help mitigate these effects in males.

ObjectiveDuchenne Muscular Dystrophy (DMD) is characterized by progressive muscle wasting leading to early loss of motor function. Functional tests monitor disease progression and serve as clinical trial endpoints, but are influenced by maturation in younger patients, variability, and patient motivation. Blood biomarkers, that can predict disease progression and objectively evaluate treatment responses, offer a valuable alternative. In this study, we investigated whether longitudinal observations of biomarkers myostatin and the creatine/creatinine ratio (Cr/Crn) are associated with functional tests, such as 6-minute walk test, North Star Ambulatory Assessment (NSAA), 10-meter walk-run test velocity, Performance of Upper Limb (PUL2.0), and disease milestones like loss of ambulation (LoA), overhead reach. and hand-to-mouth function. MethodsWe used real-world longitudinal data from 74 DMD patients followed for up to 11 years with annual visits to the LUMC outpatient clinic, linked to 408 serum samples. Associations between biomarkers, functional tests, and clinical milestones were assessed using linear mixed models and time-dependent Cox models, respectively. ResultsLower Cr/Crn levels and higher myostatin levels were associated with better functional performance and a less rapid decline in ambulation, given fixed treatment and BMI. Children with one-unit higher log2-myostatin levels had, on average, 4.73 points higher NSAA and 3.40 points higher PUL2.0 (both p < 0.001), and were 42% less likely to lose ambulation over the following year. Conversely, children with one-unit lower log2-ratio levels had, on average, 7.18 points higher NSAA and 11.40 points higher PUL2.0 (both p < 0.001), and were 3.67 times more likely to remain ambulant. We also proved that incorporating log2-myostatin and log2-Cr/Crn as endpoints could reduce the required sample size for clinical trials by more than half without compromising statistical power. For instance, to detect a yearly drop of 3 points in the NSAA with 80% power, recruitment requires almost 80 participants in a 1:1 randomized trial, in contrast to a little more than 50 patients for the respective value of log2-myostatin or log2-Cr/Crn. InterpretationThese findings support the potential of myostatin and Cr/Crn as prognostic biomarkers to enhance trial design and endpoint in clinical and interventional trials for DMD.

BackgroundCancer-associated cachexia is characterized by progressive loss of skeletal muscle and adipose tissue driven by systemic inflammation and metabolic dysregulation. AMP-activated protein kinase (AMPK) is a central regulator of energy homeostasis, but its role in cachexia and its therapeutic potential remains incompletely defined. We investigated AMPK signaling during cachexia and whether pharmacological AMPK activation alone or combined with ghrelin could ameliorate disease manifestations. MethodsCachexia was induced in male C57BL/6 mice by Lewis lung carcinoma (LLC) implantation. Additional models included fibrosarcoma (CHX and MN/MCA1) and chronic lymphocytic choriomeningitis virus (LCMV) infection. AMPK was activated using AICAR and BC1618 (AB), alone or combined with ghrelin (AB+G). Metabolic, inflammatory, and functional outcomes were assessed in hypothalamus, skeletal muscle, adipose tissue, and serum. ResultsLLC-bearing mice developed cachexia characterized by reduced body weight, lean and fat mass, hypophagia, and elevated circulating IL-6 and corticosterone. Cachectic LLC mice displayed increased Il6 and Il1{beta} expression in hypothalamus, skeletal muscle, and white adipose tissue (WAT). Furthermore, AMPK activation failed to increase in hypothalamus or peripheral tissues despite profound energy deficit. A similar defect in AMPK responsiveness was observed in CHX and LCMV models, indicating a conserved feature of cachexia. AB treatment in LLC mice reduced circulating IL-6 and corticosterone levels and decreased skeletal muscle atrogene expression and IL-6/STAT3 signaling, partially preserving muscle mass, fiber size, and grip strength. However, food intake remained low, and WAT was largely unresponsive, maintaining elevated Il6 expression and tissue loss. Ghrelin alone increased food intake in LLC mice but did not ameliorate the cachectic phenotype. In contrast, AB+G restored food intake and prevented loss of lean and fat mass. LLC AB+G mice exhibited reduced hypothalamic Il6 and serotonin transporter (Slc6a4) expression, normalized adipocyte morphology and serum leptin levels, decreased adipose Il6 and Atgl expression and reduced WAT sympathetic innervation. AB+G further lowered circulating corticosterone levels, and provided greater protection against muscle wasting, with increased Pgc1 expression and improved muscle function. Neither intervention affected tumor growth or tumor inflammatory gene expression. ConclusionsCancer cachexia is associated with a central and peripheral failure to appropriately activate AMPK signaling in response to the energetic stress imposed by cachexia. Combined AMPK activation and ghrelin administration exerted complementary effects on energy homeostasis, inflammation, and tissue wasting, resulting in greater protection against cachexia than either intervention alone. These findings support combined AMPK-ghrelin targeting as a promising therapeutic strategy for cancer cachexia.

The cellular and molecular consequences of lack of dystrophin in humans are only partially known, which is crucial for the development of new therapies aiming to slow or stop the progression Duchenne and Becker muscular dystrophies. We analyzed muscle biopsies of DMD patients and controls using single nuclei RNA sequencing (snRNAseq) and correlated the results with clinical data. DMD samples displayed an increase in regenerative fibers, satellite cells and fibro-adipogenic progenitor cells (FAPs) and a decrease in slow fibers and smooth muscle cells. Samples from patients with stable mild weakness were characterized by an increase in regenerative fibers, while those from patients with progressive weakness had fewer muscle fibers and increased FAPs. DMD muscle fibers displayed a strong regenerative signature, while DMD FAPs upregulated genes producing extracellular matrix and molecules involved in several signaling pathways. An analysis of intercellular communication profile identified FAPs as a key regulator of cell signaling in DMD samples. We show significant differences in the gene expression profiled of the different cell populations present in DMD muscle samples compared to controls.

BackgroundAberrant NAD+ metabolism has been implicated in the pathogenesis of cancer cachexia, highlighting this pathway as a potential therapeutic target to mitigate skeletal muscle wasting. However, it remains unclear whether chemotherapeutic agents contribute to the onset of cachexia by disrupting NAD+ metabolism. Here, we investigated the effects of commonly used chemotherapy regimens on NAD+ metabolism in skeletal muscle and liver of healthy mice. MethodsHealthy mice were treated with either 2-week regimens of folfiri or cisplatin, or 5-week regimens of folfiri or folfox, with vehicle-treated mice serving as controls. Cachexia-related outcomes were assessed, while skeletal muscle and liver tissues were analyzed for NAD metabolites and markers of NAD+ metabolism. Given the consistent downregulation of the NAD+ biosynthetic enzyme Nrk2 in cachectic chemotherapy-treated mice, we examined skeletal muscle Nrk2/NRK2 expression across published murine and human cachexia datasets, and in additional models of muscle wasting and hypertrophy. ResultsNAD+ loss was observed in atrophic muscle following administration of cisplatin (2-week treatment; -14% vs controls, p=0.047) and folfiri (5-week treatment; -18%, p=0.069). In contrast, muscle NAD+ levels were preserved in non-atrophic groups (2-week folfiri and 5-week folfox). Muscle Nrk2 was the most responsive NAD+ biosynthetic enzyme, showing consistent downregulation across chemotherapy models with ongoing or developing muscle loss: cisplatin (-93%, p<0.001), folfiri (-84%, p<0.001) and folfox (-92%, p<0.001). In the liver, NAD+ levels declined after prolonged 5-week folfiri (-20%, p=0.013) and folfox (-15%, p=0.043) treatments. These changes were accompanied by distinct alterations in NAD+ biosynthesis pathways, indicating treatment-specific reorganization of hepatic NAD+ metabolism. Cross-study analyses revealed early and consistent skeletal muscle Nrk2 downregulation across multiple murine cachexia models and human inactivity studies, whereas cachexia-targeted interventions in rodents and resistance training in humans increased its expression. ConclusionsThese findings demonstrate that chemotherapy distrupts tissue NAD+ metabolism, with skeletal muscle NAD+ loss accompanying muscle atrophy and hepatic NAD+ levels declining after prolonged treatment. The early and robust responsiveness of muscle Nrk2 expression to changes in muscle mass underscores its potential as a dynamic indicator for predicting treatment-induced changes in muscle mass. Together, these results provide new molecular insight into the metabolic basis of chemotherapy-induced muscle wasting and support further investigation of NAD+-targeted strategies in this context.

Skeletal muscle regeneration is a cardinal feature of muscle pathologies and is crucial for post-exercise recovery and traumatic sports injuries. Regeneration of damaged muscle in humans is a prolonged process and is accompanied by pain and physical dysfunction, highlighting the unmet need for effective interventions to accelerate the regenerative process. Through cellular and preclinical models, we have previously identified nicotinamide (NAM) and pyridoxine (PN) as potent stimulators of Muscle Stem Cells (MuSCs). Herein we investigated if a combination of NAM and PN could enhance MuSC activity and improve muscle regeneration in healthy volunteers during recovery from eccentric contractions. MethodsThis randomized, double-blind, placebo-controlled trial enrolled male participants aged 18-50 years supplemented daily with 714mg NAM and 19mg PN (NAM/PN) or placebo for 8 days following unilateral eccentric muscle contractions using Neuromuscular Electrical Stimulation (NMES). MuSC was quantified by immunohistofluorescence on vastus lateralis muscle biopsies. Results39 out of 43 enrolled participants completed the study. Supplementation of NAM/PN was well tolerated and increased blood concentrations of NAM and PN vitamers. The NMES protocol caused myofiber necrosis and triggered a strong MuSC response. After 8 days, the number of Pax7, MyoD, and myogenin positive cells per damaged fiber was significantly higher in NAM/PN vs placebo groups (+29-67%). NAM/PN also increased the proportion of regenerating fibers re-expressing embryonic myosin (+37%). ConclusionDaily oral NAM/PN supplementation following eccentric muscle damaging contractions enhances MuSC activity and accelerates muscle regeneration. These findings provide new possibilities for targeted therapeutic interventions in muscle repair. Trial registrationNCT04874662 One Sentence SummaryMuscle regeneration is enhanced by nicotinamide and pyridoxine supplementation, accelerating recovery and offering therapeutic potential.

Skeletal muscle wasting results from numerous conditions, such as sarcopenia, glucocorticoid therapy or intensive care. It prevents independent living in the elderly, predisposes to secondary diseases, and ultimately reduces lifespan. There is no approved drug therapy and the major causative mechanisms are not fully understood. Dual specificity phosphatase 22 (DUSP22) is a pleiotropic signaling molecule that plays important roles in immunity and cancer. However, the role of DUSP22 in skeletal muscle wasting is unknown. In this study, DUSP22 was found to be upregulated in sarcopenia patients and models of skeletal muscle wasting. DUSP22 knockdown or pharmacological inhibition prevented multiple forms of muscle wasting. Mechanistically, targeting DUSP22 suppressed FOXO3a, a master regulator of skeletal muscle wasting, via downregulation of the stress-activated kinase JNK, which occurred independently of aberrant Akt activation. DUSP22 targeting was also effective in human skeletal muscle cells undergoing atrophy. In conclusion, phosphatase DUSP22 is a novel target for preventing skeletal muscle wasting. The DUSP22-JNK-FOXO3a axis could be exploited to treat sarcopenia or related aging disorders.

BackgroundCancer-associated cachexia, a frequent complication of solid tumours, is not recorded in cancer registries. Cachexia affects patients diagnosed with non-small cell lung cancer (NSCLC); however, a detailed characterization of nutritional and body composition parameters matched with blood-based, non-invasive markers is lacking. We hypothesized that a systematic characterization of cachectic patients may facilitate the development of interventions aimed to improve clinical outcomes. MethodsWe conducted a prospective study of 51 patients diagnosed with locally advanced unresectable NSCLC who underwent concurrent chemoradiotherapy followed by immunotherapy at the HUB-ICO Comprehensive Cancer Centre from 2022 to 2024. The primary objectives were (1) to determine the prevalence of cachexia according to Fearons criteria and (2) to comprehensively characterize patients before and after completing chemoradiotherapy in terms of nutritional status, metabolic parameters, body composition and circulating cytokine levels. Here, we report the baseline assessment results. ResultsMost patients were male (80%), ever smokers (98%) with a median age of 68 years. All patients completed the planned concurrent chemoradiotherapy regimen, while only 43% initiated durvalumab consolidation therapy. At baseline, 53% of patients met the diagnostic criteria for cachexia. Women were more likely to have cachexia at baseline compared to men, although these differences were not statistically significant. Cachexia was significantly associated with tumor stage (p < 0.001), performance status (p = 0.027), lower skeletal muscle index (p = 9e-4) and total adipose tissue index (p = 0.004), elevated C-Reactive Protein blood levels (p = 0.004), moderate to severe malnutrition (p < 0.001), reduced caloric intake (p = 0.007) and diminished physical strength (p=0.001). Proteomic profiling using the O-link platform revealed significant differences in circulating cytokine levels between cachectic and non-cachectic patients. Cachexia was significantly associated with elevated levels of CCL23, IL-6, IL-11, Oncostatin M (OSM), pentraxin-related protein 3 (PTX3), and agouti-related protein (AGRP), among others, demonstrating varying degrees of correlation with caloric intake. GDF15 was associated with weight loss (p = 0.00014), but not with calorie intake or body composition. ConclusionsThis prospective study reveals that cancer cachexia is highly prevalent in patients with unresectable locally advanced NSCLC. In addition to previously known cytokines, we identified several understudied cytokines, which may contribute to a more comprehensive characterization of the cachexia phenotype and help uncover potential targets for therapeutic interventions.

Patients with chronic obstructive pulmonary disease (COPD)-pulmonary emphysema often develop locomotor muscle dysfunction, which is independently associated with disability and higher mortality in that population. Muscle dysfunction entails reduced muscle mass and force-generation capacity, which are influenced by fibers integrity. Myogenesis, which is muscle turnover driven by progenitor cells such as satellite cells, contributes to the maintenance of muscle integrity in the context of organ development and injury-repair cycles. Injurious events crucially occur in COPD patients skeletal muscles in the setting of exacerbations and infections which lead to acute decompensations for limited periods of time after which, patients typically fail to recover the baseline status they had before the acute event. Autophagy, which is dysregulated in muscles from COPD patients, is a key regulator of satellite cells activation and myogenesis, yet very little research has so far investigated the mechanistic role of autophagy dysregulation in COPD muscles. Using a genetically inducible murine model of COPD-driven muscle dysfunction and confirmed with a second genetic animal model, we found a significant myogenic dysfunction associated with a reduced proliferative capacity of freshly isolated satellite cells. Transplantation experiments followed by lineage tracing suggest that an intrinsic defect in satellite cells, and not in the COPD environment, plays a dominant role in the observed myogenic dysfunction. RNA sequencing analysis of freshly isolated satellite cells suggests dysregulation of transcripts associated with control of cell cycle and autophagy, which is confirmed by a direct observation of COPD mice satellite cells fluorescent-tracked autophagosome formation. Moreover, spermidine-induced autophagy stimulation leads to improved satellite cells autophagosome turnover, replication rate and myogenesis. Our data suggests that pulmonary emphysema causes a disrupted myogenesis, which could be improved with stimulation of autophagy and satellite cells activation, leading to an attenuated muscle dysfunction in this context.

BackgroundCancer cachexia is a complex metabolic syndrome that severely impacts patient mobility, treatment strategies, and quality of life. However, no treatments are available to mitigate the debilitating consequences of cancer cachexia. Unacylated ghrelin (UnAG), the main circulating form of ghrelin, enhances muscle growth and mitochondrial function in various diseases, but its effects in cancer cachexia remain to be tested. MethodsMale C57Bl6/N mice were assigned to one of three treatment groups: non-tumor-bearing (NTB), tumor-bearing (TB), or tumor-bearing treated with unacylated ghrelin (TB+UnAG). Over four weeks, we monitored body weight, food intake, and tumor size. We assessed muscle mass, contractility, mitochondrial oxygen consumption rate (OCR), and reactive oxygen species (ROS) production. Proteomic analysis was performed to elucidate the downstream effects of UnAG. Cell culture assays were performed to measure the in vitro effects of cancer cell-secreted factors and UnAG on myoblasts. ResultsGastrocnemius and quadriceps muscle masses were reduced by 20-30% in TB mice compared to NTB controls; however, UnAG treatment prevented approximately 50% of this loss. Beyond muscle mass, UnAG enhanced the isometric maximum specific force of the extensor digitorum longus by 70% in TB mice. This improvement in muscle quality was associated with preferential upregulation of myosin heavy chain expression in TB+UnAG mice. UnAG also increased mitochondrial OCR while reducing ROS production. Mitochondrial DNA (mtDNA) copy number, which was reduced in TB mice, was restored by UnAG, while the reduced mtDNA mutation frequency in TB mice was maintained with treatment, indicating improved mtDNA integrity. Consistent with enhanced mitochondrial function, treadmill running time was significantly increased in TB+UnAG mice. Proteomic analysis revealed that UnAG downregulated proteins associated with proteolysis, while normalizing antioxidant enzyme thioredoxin and proteins involved in calcium handling. Cancer cell-conditioned medium reduced myotube width in vitro, but UnAG treatment preserved myotube structure.. ConclusionUnAG protects against cancer cachexia by targeting multiple risk factors, including myosin heavy chain expression, mitochondrial bioenergetics, and modulation of protein degradation pathways.

BackgroundMYORG (myogenesis-regulating glycosidase) and STRADB (STE20-related kinase adapter protein beta) were previously identified as activity-mediated skeletal muscle genes with potential roles in frailty and sarcopenia. We hypothesized that, if these genes are sustained by neuromuscular contractile activity, their expression should be consistently downregulated in muscular dystrophies, conditions defined by progressive muscle degeneration and secondary functional disuse. MethodsWe performed a systematic cross-dataset transcriptomic analysis of five publicly available GEO microarray datasets of human skeletal muscle. Discovery analysis was conducted in GSE3307 (Affymetrix HG-U133A/B; samples spanning DMD, LGMD2A/B/I, BMD, FSHD, JDM, ALS, AQM versus healthy controls). Independent external validation was performed in GSE38417 (HG-U133 Plus 2.0, DMD; n=16/6), GSE11681 (HG-U133A/B, LGMD2A; n=8-10/9-10), GSE465 (HG-U95Av2/B/C, multi-disease), and GSE1007 (HG-U95B/C/E, DMD; n=10-11/11). Raw CEL files underwent array-level quality assessment using NUSE and RLE diagnostics prior to normalization. Seven poor-quality arrays were excluded (none from Control, DMD, or LGMD groups). Remaining arrays were processed by robust multi-array average (RMA) normalization, and differential expression was assessed by limma with Benjamini-Hochberg FDR correction. ResultsMYORG was significantly downregulated in DMD (log2 fold-change [logFC] = -0.93, adj.P<0.001), LGMD2A (logFC = -0.82, adj.P<0.01), LGMD2B (logFC = -1.01, adj.P<0.01), and LGMD2I (logFC = -1.03, adj.P<0.01) in GSE3307. STRADB was significantly reduced in DMD (logFC = -0.33, adj.P<0.05) and showed a near-significant trend in LGMD2I (logFC = - 0.42, adj.P = 0.061). MYORG downregulation in DMD was independently replicated in GSE38417 (logFC = -1.40, adj.P<0.001) and GSE1007 (logFC = -0.80, adj.P<0.001). STRADB was also significantly downregulated in GSE38417 DMD (logFC = -0.45, adj.P<0.001). Deoxygalactonojirimycin, an iminosugar and an FDA/EMA-approved pharmacological chaperone (migalastat/Galafold) for Fabry disease, has been reported to be a specific molecular interactor that stabilizes MYORG protein in skeletal muscle. ConclusionsThis multi-dataset study further supports the role of MYORG and STRADB as activity-sensitive muscle genes that are robustly downregulated in DMD and LGMD. The pharmacological interaction between migalastat and MYORG provides a mechanistically grounded rationale for investigating this approved agent as an adjunct therapy in muscular dystrophies, in combination with the existing standard of care. This also supports active investigation of iminosugar analogs to target MYORG as potential therapeutics for improving skeletal muscle function in dystrophies, frailty, and sarcopenia.

BackgroundSkeletal muscle atrophy is prevalent worldwide and is a major detractor from length and quality of life. It is often diagnosed and treated as a single disorder, but the causal stimuli and progression of atrophy vary widely. Malnutrition and disuse are two common causes of muscle atrophy, and despite their prevalence and extensive characterization, there have been no direct comparisons of how these two types of atrophy progress and whether they differentially affect skeletal muscle fiber types. The purpose of this study is to directly compare atrophy from fasting and disuse and provide a transcriptomic resource for future research on both conditions. MethodsWe fasted or hindlimb suspended (HS) two cohorts of 12-week-old female C57/bl6 mice. Mice were fasted for up to 72 hours to induce malnutrition atrophy or were hindlimb suspended for 0, 3, 7, 14, or 28 days to induce disuse atrophy. At each timepoint, mice were euthanized and three muscles (tibialis anterior (TA), extensor digitorum longus (EDL), and soleus) were weighed and collected for RNA sequencing. Atrophy progression and gene expression changes were compared across muscle fiber types and atrophy stimuli. ResultsWe found differences in atrophy progression between muscle fiber types based on fiber twitch speed and atrophy stimulus. Fasted mice lost 25% of their body weight and 23% of fast-twitch TA mass with little change in soleus. In contrast, HS mice lost 40% of the slower-twitch soleus but the effect on the TA was negligible. Gene expression varied in response to both atrophy stimuli, but a greater number of genes changed with fasting compared to HS in the EDL and soleus. By muscle type, a greater transcriptional shift occurred in the EDL with fasting while the soleus showed more gene changes during HS. Enrichment analysis of transcriptional changes showed similarities (downregulation in muscle growth pathways) and differences (increased fatty acid metabolism in fasting and increased neuronal activity in HS) between atrophy stimuli. ConclusionsAtrophy progression varies based on stimuli and muscle fiber type. This study provides a large, matched data set where the effects of different atrophic stimuli can be easily and directly compared in multiple fiber types. To our knowledge, this is the first study to closely compare these two atrophy stimuli in a muscle type-specific context. This work demonstrates that atrophy is not a single disorder and that the development of therapies may need to be tailored to the atrophic stimulus.

More than 85% of patients with pancreatic ductal adenocarcinoma (PDAC) suffer from cachexia, a debilitating syndrome characterized by the loss of muscle and fat and remains an unmet medical need. While chemotherapy remains an effective treatment option, it can also induce weight and muscle loss in patients with cancer. Gemcitabine combined with nab paclitaxel (GnP) is a first line treatment option for patients with PDAC but GnPs effect on cachexia has not been comprehensively investigated. We interrogated the effects of GnP in a murine model of pancreatic cancer cachexia. Mice were orthotopically implanted with the cachexia inducing pancreatic cell line (KPC) and were administered GnP or vehicle. The controls underwent sham surgery. We defined GnP effects on cachexia and tumor burden by evaluating muscle and cardiac mass and function, fat mass, bone morphometry, and hematology measurements. We completed RNA sequencing and deep proteome profiling in skeletal and cardiac muscle. KPC+GnP reduced tumor burden over 50% and increased survival compared to KPC. KPC vehicle group had more than 15% muscle mass loss and decreased left ventricular mass, this was not present in KPC+GnP when compared to controls. RNA Seq and deep proteomics analyses suggested that muscle and cardiac dysfunction pathways activated in KPC group were either reversed or decreased in KPC+GnP. In all, our data suggests that GnP protects against muscle and cardiac wasting in an experimental model of PDAC cachexia. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/536434v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@1d394f7org.highwire.dtl.DTLVardef@1d8fdaforg.highwire.dtl.DTLVardef@f709d4org.highwire.dtl.DTLVardef@a668e0_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG

BackgroundAgeing is accompanied by progressive declines in skeletal muscle mass and strength, culminating in sarcopenia, a condition that contributes to frailty, multimorbidity, and mortality. Age-related changes to mitochondria lead to oxidative damage and dysfunction and are proposed to occur early in the trajectory of sarcopenia, supporting the candidacy of mitochondrial-protective therapies. Here, we test the efficacy of mitochondrial uncoupler BAM15 in age-dependent sarcopenic mouse models. MethodsMale and female MitoQC mice aged 24 months received either standard chow or chow supplemented with BAM15 (0.033% mg/g) ad libitum for eight weeks (n=13-14/group). Young (3-month-old) mice served as reference controls (n=8/group). Muscle mitochondrial respiration was assessed in permeabilized fib res, and contractile function was measured in isolated extensor digitorum longus and soleus muscles. Mitophagy was quantified by immunofluorescence confocal microscopy. Data were analyzed using one-or two-way ANOVA followed by Dunnetts or Bonferronis multiple comparison tests. ResultsAged male and female mice exhibited reduced gastrocnemius muscle mass relative to body mass compared with young controls (p<0.05; [~]18% and [~]32% loss, respectively). BAM15 did not alter muscle size but reversed the age-related loss of contractile function in EDL muscles, to that of the young reference controls in both sexes (p<0.05; [~]33% in males, [~]16% in females). In male mice, BAM15 improved mitochondrial efficiency, evidenced by restoration of Complex I-linked respiration and decreased proton leak ([~]52% improvement; p<0.05), and normalized protein levels of oxidative stress marker 4 -HNE, without changes in mitophagy or mitochondrial content. In females, BAM15 did not improve mitochondrial parameters, which may be, in part, due to aged female muscle exhibiting unchanged Complex I leak and 4-HNE protein abundance, alongside lower complex I subunit (NDUFB8) protein abundance. ConclusionsBAM15 improved skeletal muscle mitochondrial efficiency and contractile function in aged male mice, supporting the potential of mitochondrial uncoupling as a therapeutic strategy for sarcopenia.

Allogeneic hematopoietic stem cell transplantation (HSCT) is a life-saving treatment for hematologic malignancies, but long-term survivors present with lower muscle mass and functional capacity. In adult HSCT survivors 10-20 years after treatment, single nucleus RNA sequencing uncovered elevated XRRA1 expression levels in all muscle nuclei populations, which was retained in primary muscle stem cell cultures. HSCT survivors were characterized in vivo by impaired neuromuscular innervation that associated with muscle weakness, and lower muscle stem cell neurotrophic action. Despite these impairments, the molecular and physiological responses to heavy resistance training (HReT) were preserved in HSCT survivors, as demonstrated in a pre-registered clinical trial (ClinicalTrials.gov: NCT04922970). After 12 weeks of HReT, gains in muscle mass and strength were similar in HSCT survivors and healthy controls. In addition, we observed that [~]9% of muscle-resident immune cells persist into adulthood and that bone marrow derived cells do not adopt alternative cell fates in muscle tissue, resolving long-standing questions in human muscle biology. Together, these findings uncover molecular mechanisms of HSCT sequelae in muscle nuclei and muscle stem cells, which, importantly, can at least partly be overcome by mechanical loading. Given the growing population of HSCT survivors and the multitude of benefits of HReT for all organ systems, our findings support the importance of HReT in this population to promote healthspan. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/26351644v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@14322d1org.highwire.dtl.DTLVardef@a30589org.highwire.dtl.DTLVardef@c07930org.highwire.dtl.DTLVardef@544b02_HPS_FORMAT_FIGEXP M_FIG C_FIG