Andrea Irazoki

Weight loss is a potentially deadly hallmark of many cancers, including lung cancer. In particular, the loss of skeletal muscle mass and function impairs survival and lowers quality of life. Despite being a major determinant of prognosis, the molecular drivers of muscle wasting remain ill-defined. Therefore, there is a critical need for human molecular data to support the development of effective therapies for this currently untreatable condition. Here, we utilize cutting-edge proteomics technology to longitudinally map the proteome and phosphoproteome of skeletal muscle from patients with newly diagnosed, advanced-stage non-small cell lung cancer during their treatment. Leveraging deep in vivo clinical phenotyping of activity, body composition, muscle quality, and nutritional risk, we identified 118/174 muscle proteins/phospho-sites associated with cachexia at diagnosis with indications of sexual dimorphism. Treatment altered 278 proteins and 1,155 phospho-sites, of which 137/91 proteins/phospho-sites were associated with muscle wasting. Our findings highlight disrupted calcium, anabolic, and stress signalling, alongside extracellular matrix and mitochondrial alterations, as key molecular features of cachexia in non-small cell lung cancer. These clinically anchored proteomic and phosphoproteomic signatures provide potential targets for future research.

Cancer-associated cachexia is characterized by weight loss, muscle wasting, systemic inflammation, and functional decline. This multifactorial syndrome is highly prevalent and detrimental in patients with advanced-stage non–small cell lung cancer (NSCLC). To investigate the cellular and molecular underpinnings of muscle wasting, we analyzed skeletal muscle biopsies from NSCLC patients and healthy matched controls using quantitative proteomics, histology, fluorescence-activated cell sorting, gene expression profiling, and high-resolution respirometry. Skeletal muscle from patients was characterized by type II muscle fiber atrophy, greater collagen deposition, and redistribution of lipids to the extracellular matrix. This coincided with a shift in fibro-adipogenic progenitors (FAPs), favouring the CD90⁻ subtype, and experiments using conditioned media indicated a catabolic secretory phenotype from patient-derived FAPs. Proteomic and functional analyses revealed dysregulated calcium handling, downregulation of key mitochondrial proteins, and altered respiratory capacity in muscle samples from patients with NSCLC. These alterations, along with fiber-type specific mitochondrial remodelling, were accompanied by STAT3 activation and immune cell infiltration, suggesting a link between mitochondrial dysfunction and local inflammation. These results provide the first human evidence that altered FAP composition, mitochondrial homeostasis, calcium handling, and immune cell landscape coincide with muscle wasting in NSCLC, highlighting potential therapeutic targets to treat patients with cancer-associated cachexia.

Short Purpose: Blocking the Activin receptor type IIA and B (ActRIIA/IIB) has clinical potential to increase muscle mass and improve glycemic control in obesity, cancer, and aging. However, the impact of blocking ActRIIA/IIB on strength, metabolic regulation and insulin action remains unclear. Methods: Here, we investigated the effect of short- (10 mg/kg once, 40h) or long-term (10 mg/kg twice weekly, 21 days) antibody targeting ActRIIA/IIB (αActRIIA/IIBab) in lean and diet-induced obese mice and engineered human muscle tissue. Results: Short-term α ActRIIA/IIB administration in lean mice increased insulin-stimulated glucose uptake in skeletal muscle by 76-105%. Despite this, α ActRIIA/IIB-treated mice exhibited 33% elevated fasting blood glucose and glucose intolerance. Moreover, long-term α ActRIIA/IIB treatment increased average muscle mass (20%) and reduced fat mass (-8%) in obese mice but did not change insulin-stimulated glucose uptake in skeletal muscle or adipose tissue, yet induced marked glucose intolerance, and increased hepatic glucose output in response to pyruvate. Concomitantly, long-term α ActRIIA/IIBab treatment increased strength (30%) in mouse soleus muscle and prevented activin A-induced loss of tissue strength in engineered human muscle tissue. Surprisingly, long-term α ActRIIA/IIBab treatment lowered volitional running (-250%). Conclusion: Our findings demonstrate that, in accordance with human studies, ActRIIA/IIB blockade holds promise for increasing muscle mass, strength, and insulin sensitivity. However, contrary to the improved glycemic control in humans, ActRIIA/IIB blockade in mice causes severe glucose intolerance and lowers voluntary physical activity. Our study underscores the complex metabolic and functional consequences of ActRIIA/IIB blockade, and highlight species differences on glycemic control, which warrant further investigation.

Butyrate, a gut microbiota‐derived metabolite, supports cellular health. In pancreatic beta cells, inflammation and oxidative stress disrupt mitochondrial function, contributing to dysfunction. This study explores how butyrate influences mitochondrial function and redox balance to protect beta cells from interleukin‐1beta (IL‐1β)‐induced stress. Pancreatic mouse islets were treated with IL‐1β and/or butyrate for 10 days to model chronic inflammation in type 2 diabetes, and their effects on mitochondrial health and oxidative stress were studied. Butyrate protected against IL‐1β‐induced impairment of insulin secretion by enhancing mitochondrial function, as evidenced by an increased glucose‐stimulated oxygen consumption rate and a higher mitochondrial membrane potential compared to IL‐1β treatment alone. IL‐1β increased mitochondrial mass, but the mitochondria appeared smaller and rounded, indicating fragmentation. In contrast, butyrate co‐treatment promoted mitochondrial hyperfusion, as evidenced by elongated mitochondria, higher levels of fusion proteins Opa1 and Mfn2, and lower levels of fission protein Fis1 compared to IL‐1β alone. Furthermore, butyrate reduced IL‐1β‐induced reactive oxygen species (ROS) production, antioxidant enzyme gene expression, and protein oxidation, indicating protection against oxidative stress. Butyrate co‐treatment further enhanced redox balance by increasing reduced glutathione (GSH) levels and the ratio of GSH to oxidized glutathione (GSSG). These findings suggest that butyrate acts as a potent modulator of mitochondrial function and redox balance, counteracting IL‐1β‐induced dysfunction and providing a potential therapeutic strategy for improving insulin secretion in inflammatory conditions.

Background: Cancer cachexia, affecting up to 80% of patients with cancer, is characterized by muscle and fat loss with functional decline. Preclinical research seeks to uncover the molecular mechanisms underlying cachexia to identify potential targets. Housing laboratory mice at ambient temperature induces cold stress, triggering thermogenic activity and metabolic adaptations. Yet, the impact of housing temperature on preclinical cachexia remains unknown. Methods: Colon 26 carcinoma (C26)‐bearing and PBS‐inoculated (Ctrl) mice were housed at standard (ST; 20°C–22°C) or thermoneutral temperature (TN; 28°C–32°C). They were monitored for body weight, composition, food intake and systemic factors. Upon necropsy, tissues were weighed and used for evaluation of ex vivo force and respiration, or snap frozen for biochemical assays. Results: C26 mice lost 7.5% body weight ( p = 0.0001 vs. Ctrls), accounted by decreased fat mass (−35%, p < 0.0001 vs. Ctrls), showing mild cachexia irrespective of housing temperature. All C26 mice exhibited reduced force (−40%, p < 0.0001 vs. Ctrls) and increased atrogene expression (3‐fold, p < 0.003 vs. Ctrls). Cancer altered white adipose tissue (WAT)'s functional gene signature (49%, p < 0.05 vs. Ctrls), whereas housing temperature reduced brown adipose tissue (BAT)'s (−78%, p < 0.05 vs. ST Ctrl). Thermogenic capacity measured by Ucp1 expression decreased upon cancer in both WAT and BAT (−93% and −63%, p < 0.0044 vs. Ctrls). Cancer‐driven glucose intolerance was noted at ST (26%, p = 0.0192 vs. ST Ctrl), but restored at TN (−23%, p = 0.005 vs. ST C26). Circulating FGF21, GDF‐15 and IL‐6 increased in all C26 mice (4‐fold, p < 0.009 vs. Ctrls), with a greater effect on IL‐6 at TN (76%, p = 0.0018 vs. ST C26). Tumour and WAT Il6 mRNA levels remained unchanged, while cancer induced skeletal muscle (SkM) Il6 (2‐fold, p = 0.0016 vs. Ctrls) at both temperatures. BAT Il6 was only induced in C26 mice at TN (116%, p = 0.0087 vs. ST C26). At the bioenergetics level, cancer increased SkM SERCA ATPase activity at ST (4‐fold, p = 0.0108 vs. ST Ctrl) but not at TN. In BAT, O ₂ consumption enhanced in C26 mice at ST (119%, p < 0.03 vs. ST Ctrl) but was blunted at TN (−44%, p < 0.0001 vs. ST C26). Cancer increased BAT ATP levels regardless of temperature (2‐fold, p = 0.0046 vs. Ctrls), while SERCA ATPase activity remained unchanged at ST and decreased at TN (−59%, p = 0.0213 vs. TN Ctrl). Conclusions: In mild cachexia, BAT and SkM bioenergetics are susceptible to different housing temperatures, which influences cancer‐induced alterations in glucose metabolism and systemic responses.

Decline in mitochondrial function is linked to decreased muscle mass and strength in conditions like sarcopenia and type 2 diabetes. Despite therapeutic opportunities, there is limited and equivocal data regarding molecular cues controlling muscle mitochondrial plasticity. Here we uncovered that the mitochondrial mRNA-stabilizing protein SLIRP, in complex with LRPPRC, is a PGC-1α target that regulates mitochondrial structure, respiration, and mtDNA-encoded-mRNA pools in skeletal muscle. Exercise training effectively counteracts mitochondrial defects caused by genetically-induced LRPPRC/SLIRP loss, despite sustained low mtDNA-encoded-mRNA pools, by increasing mitoribosome translation capacity and mitochondrial quality control. In humans, exercise training robustly increases muscle SLIRP and LRPPRC protein across exercise modalities and sexes, yet less prominently in individuals with type 2 diabetes. SLIRP muscle loss reduces Drosophila lifespan. Our data points to a mechanism of post-transcriptional mitochondrial regulation in muscle via mitochondrial mRNA stabilization, offering insights into how exercise enhances mitoribosome capacity and mitochondrial quality control to alleviate defects.

Summary: Cancer cachexia is a metabolic condition affecting up to 80% of patients with cancer. Cachexia is mediated by reduced muscle and fat mass and impaired function, and it lowers survival for patients. With no approved drugs to treat cachexia, preclinical efforts focus on understanding the molecular mechanisms underlying this condition to reveal treatment targets. Housing laboratory mice at ambient temperature imposes cold stress, leading to induced thermogenic activity and consequent whole-body metabolic adaptations. Yet, the impact of housing temperature in in vivo preclinical cachexia remains unknown. We found that thermoneutral (TN) housing in C26 carcinoma-bearing (C26) mice affected lean and fat mass, but not muscle weight or force. TN housing improved glucose tolerance in C26 mice, while enhancing circulating abundance of FGF21 and IL-6. Thermogenic tissues, especially brown adipose tissue, exhibited housing temperature-dependent molecular responses to cancer in oxygen consumption, ATP levels and SERCA ATPase activity, which are all crucial for cancer-induced whole-body metabolic adaptations. We conclude that molecular and systemic adaptations to cancer in mice critically depend on housing temperature, which should be considered in the design and interpretation of preclinical cancer studies.

Some forms of mitochondrial dysfunction induce sterile inflammation through mitochondrial DNA recognition by intracellular DNA sensors. However, the involvement of mitochondrial dynamics in mitigating such processes and their impact on muscle fitness remain unaddressed. Here we report that opposite mitochondrial morphologies induce distinct inflammatory signatures, caused by differential activation of DNA sensors TLR9 or cGAS. In the context of mitochondrial fragmentation, we demonstrate that mitochondria-endosome contacts mediated by the endosomal protein Rab5C are required in TLR9 activation in cells. Skeletal muscle mitochondrial fragmentation promotes TLR9-dependent inflammation, muscle atrophy, reduced physical performance and enhanced IL6 response to exercise, which improved upon chronic anti-inflammatory treatment. Taken together, our data demonstrate that mitochondrial dynamics is key in preventing sterile inflammatory responses, which precede the development of muscle atrophy and impaired physical performance. Thus, we propose the targeting of mitochondrial dynamics as an approach to treating disorders characterized by chronic inflammation and mitochondrial dysfunction.

During aging, skeletal muscle undergoes a loss of mass, strength and function, encompassed in the biological process termed sarcopenia. Given demographic aging, it is essential to comprehend the molecular determinants resulting in age-related sarcopenia. Here we studied the role of the mitophagy adaptor BNIP3 in mitochondrial homeostasis and muscle during aging. Our findings reveal that BNIP3 orchestrates mitochondrial and lysosomal function to mitigate muscle inflammation and atrophy during aging.

Sarcopenia is one of the main factors contributing to the disability of aged people. Among the possible molecular determinants of sarcopenia, increasing evidences suggest that chronic inflammation contributes to its development. However, a key unresolved question is the nature of the factors that drive inflammation during aging and that participate in the development of sarcopenia. In this regard, mitochondrial dysfunction and alterations in mitophagy induce inflammatory responses in a wide range of cells and tissues. However, whether accumulation of damaged mitochondria (MIT) in muscle could trigger inflammation in the context of aging is still unknown. Here, we demonstrate that BCL2 interacting protein 3 (BNIP3) plays a key role in the control of mitochondrial and lysosomal homeostasis, and mitigates muscle inflammation and atrophy during aging. We show that muscle BNIP3 expression increases during aging in mice and in some humans. BNIP3 deficiency alters mitochondrial function, decreases mitophagic flux and, surprisingly, induces lysosomal dysfunction, leading to an upregulation of Toll‐like receptor 9 (TLR9)‐dependent inflammation and activation of the NLRP3 (nucleotide‐binding oligomerization domain (NOD)‐, leucine‐rich repeat (LRR)‐, and pyrin domain‐containing protein 3) inflammasome in muscle cells and mouse muscle. Importantly, downregulation of muscle BNIP3 in aged mice exacerbates inflammation and muscle atrophy, and high BNIP3 expression in aged human subjects associates with a low inflammatory profile, suggesting a protective role for BNIP3 against age‐induced muscle inflammation in mice and humans. Taken together, our data allow us to propose a new adaptive mechanism involving the mitophagy protein BNIP3, which links mitochondrial and lysosomal homeostasis with inflammation and is key to maintaining muscle health during aging.