Doles, Jason D.

Abstract GNE myopathy (GNEM) is a neuromuscular disorder caused by biallelic mutations in the gene GNE , which encodes a bifunctional enzyme essential for the biosynthesis of sialic acid. Despite extensive characterization, no effective therapies or validated biomarkers exist, and the molecular mechanisms driving disease pathology remain poorly understood. This study identifies the proteoglycan serglycin as a preliminary candidate biomarker in GNEM and investigates the mechanisms underlying its dysregulation. Proteomic analysis of serum samples from GNEM patients revealed reduced circulating serglycin levels. In contrast, increased intracellular serglycin was observed in GNE knockout and GNEM patient iPSC-derived myoblasts, suggesting impaired secretion and/or degradation. To investigate the basis of this accumulation, intracellular trafficking and autophagic pathways were examined. Proteomic profiling from HEK GNE knockout cells revealed alterations in pathways involved in membrane trafficking, Golgi function, and glycoprotein processing, consistent with broader disruptions in the secretory system that may impair serglycin export and contribute to its intracellular retention. In GNEM iPSC-derived myoblasts, serglycin overlapped with LAMP1-positive lysosomal compartments and the ER-phagy receptor FAM134B, suggesting association with lysosomal and ER-phagy related pathways. Functional assays further indicated impaired autophagic flux in mutant cells. Together, these findings support a model in which combined defects in secretion and autophagic clearance contribute to intracellular serglycin accumulation and reduced circulating levels. This study identifies serglycin as a potential circulating biomarker for GNEM and highlights dysregulation of secretory and degradative pathways as converging features of disease pathology.

Cognitive impairment in sepsis survivors is a growing clinical challenge as the number of sepsis cases rise and acute mortality rates fall. It is estimated that up to 70% of sepsis patients experience cognitive dysfunction and many report persistent dysfunction post‐sepsis. Cognitive impairment is a broad term that refers to sepsis‐associated brain dysfunction or encephalopathy (SABD or SAE, respectively). While many contributors, such as inflammation, blood–brain barrier dysfunction, and extended microglial activation are implicated in SABD/SAE development, much is still unknown regarding the underlying mechanistic causes of persistent cognitive defects in sepsis survivors. Here, we employed cecal ligation and puncture (CLP) to model surgical sepsis in mice, after which mice were subjected to multiple memory function assays for up to 2 months post‐sepsis. Furthermore, single‐cell RNA sequencing and validation studies were performed with murine hippocampi to query alterations in the brain microenvironment. Our study shows that CLP mice exhibited decreased spontaneous alternation at 4 weeks and decreases in both short‐ and long‐term recognition (at 6 weeks and 2 weeks, respectively) accompanied by substantially altered cell type makeup of the hippocampus, including hippocampal neuron and pericyte loss. Finally, transcriptional alterations in the macrophage populations implicate aberrant activation in CLP survivors. In conclusion, post‐sepsis mice exhibit reduced memory capacity and altered hippocampal cell composition and transcriptional profiles. This study and associated data set will be valuable for further investigation of the underlying pathophysiology of SABD/SAE and elucidation of potential therapeutic candidates.

Cancer cachexia is a multifactorial syndrome involving muscle and fat wasting, inflammation, and metabolic dysfunction. Across cancer subtypes, pancreatic cancer has one of the highest cachexia incidence rates at ∼80%. Given the advanced age of most pancreatic cancer patients, we sought to query cancer-associated muscle wasting using an age-matched murine model. We found that histamine and histamine decarboxylase (HDC) activity were specifically elevated in the muscles of aged tumor-bearing mice. We further found that (1) wasting stimuli induced histamine production and enhanced HDC activity; (2) exogenous histamine was sufficient to induce atrophy-associated gene expression; (3) inhibition of HDC activity by α-fluoromethylhistidine (FMH) protected against atrophy; (4) treatment of tumor-bearing mice with FMH rescued muscle wasting; and (5) a calcineurin inhibitor was able to rescue histamine-associated increases in calcium/atrogene signaling. In summary, we present a novel metabolic pathway that has significant implications for the treatment of cachectic cancer patients.

Reduced skeletal muscle mass and oxidative capacity coexist in patients with pulmonary emphysema and are independently associated with higher mortality. If reduced cellular respiration contributes to muscle atrophy in that setting remains unknown. Using a mouse with genetically induced pulmonary emphysema that recapitulates muscle dysfunction, we found that reduced activity of succinate dehydrogenase (SDH) is a hallmark of its myopathic changes. We generated an inducible, muscle-specific SDH knockout mouse that demonstrates lower mitochondrial oxygen consumption, myofiber contractility, and exercise endurance. Respirometry analyses show that in vitro complex I respiration is unaffected by loss of SDH subunit C in muscle mitochondria, which is consistent with the pulmonary emphysema animal data. SDH knockout initially causes succinate accumulation associated with a down-regulated transcriptome but modest proteome effects. Muscle mass, myofiber type composition, and overall body mass constituents remain unaltered in the transgenic mice. Thus, while SDH regulates myofiber respiration in experimental pulmonary emphysema, it does not control muscle mass or other body constituents.

Cancer cachexia, and its associated complications, represent a large and currently untreatable roadblock to effective cancer management. Many potential therapies have been proposed and tested—including appetite stimulants, targeted cytokine blockers, and nutritional supplementation—yet highly effective therapies are lacking. Innovative approaches to treating cancer cachexia are needed. Members of the Kruppel-like factor (KLF) family play wide-ranging and important roles in the development, maintenance, and metabolism of skeletal muscle. Within the KLF family, we identified KLF10 upregulation in a multitude of wasting contexts—including in pancreatic, lung, and colon cancer mouse models as well as in human patients. We subsequently interrogated loss-of-function of KLF10 as a potential strategy to mitigate cancer associated muscle wasting. In vivo studies leveraging orthotopic implantation of pancreas cancer cells into wild-type and KLF10 KO mice revealed significant preservation of lean mass and robust suppression of pro-atrophy muscle-specific ubiquitin ligases Trim63 and Fbxo32, as well as other factors implicated in atrophy, calcium signaling, and autophagy. Bioinformatics analyses identified Transforming growth factor beta (TGF-β), a known inducer of KLF10 and cachexia promoting factor, as a key upstream regulator of KLF10. We provide direct in vivo evidence that KLF10 KO mice are resistant to the atrophic effects of TGF-β. ChIP-based binding studies demonstrated direct binding to Trim63 , a known wasting-associated atrogene. Taken together, we report a critical role for the TGF-β/KLF10 axis in the etiology of pancreatic cancer–associated muscle wasting and highlight the utility of targeting KLF10 as a strategy to prevent muscle wasting and limit cancer-associated cachexia.

Abstract Cancer cachexia is a multifactorial syndrome entailing muscle and fat wasting, inflammation, and metabolic dysfunction. Pancreatic cancer has the highest incidence of cachexia at around 80%. However, there are no FDA approved therapy for cachexia in the clinic yet. This is mostly because of the failure of preclinical therapies to demonstrate success in the clinic. Most preclinical studies utilize 6-8 week old mice which roughly corresponds to a human age of ~ 20 years. However, the median age of diagnosis of pancreatic cancer is ~70 years. Given widespread physiology, microenvironment, and metabolism differences in young and aged skeletal muscle, we sought to study cancer cachexia in mice aged to >78 weeks, which corresponds to a human age of greater than 60 years. Our previously published study reported little difference in tumor growth or survival between the two cohorts, yet significant alterations in the muscle transcriptome. Building on this work, we show significant differences in the muscle metabolome of young/aged control and tumor bearing mice. Notably, histamine was higher in aged versus young control mice and even higher in the aged tumor-bearing cohort. We show higher activity of histamine decarboxylase (HDC), the enzyme that converts histidine to histamine in the muscles of aged tumor-bearing mice. Addition of cancer conditioned-media (CM) to C2C12 myotubes was able to induce histamine production and HDC activity in vitro, which demonstrates the ability of muscle cells to induce histamine independent of mast cells. We further show that addition of histamine to myotubes is sufficient to increase atrophy-associated markers. Inhibition of HDC activity by α-fluoromethylhistidine (FMH) in the in vitro model of cachexia protected against myotube thinning. Finally, we treated tumor-bearing aged mice with FMH and observed a) decreased histamine in the muscles 2) decreased HDC activity in the muscles 3) decreased muscle wasting, 4) decreased atrophy markers. Together, we present a novel wasting-associated metabolic pathway and corresponding therapeutic avenue for cancer cachexia that may have been overlooked if not for the use of a more-age-appropriate model of pancreatic cancer. Citation Format: Aneesha Dasgupta, Rebecca E. Schmitt, Jessica Z. Schneider, Tatsuyoshi Kono, Chih-Chun Lee, Carmella Evans-Molina, Jason D. Doles. Targeting differential metabolism in an aged model of cancer cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 356.