IU Indianapolis ScholarWorks :: Browsing by Author "O'Connell, Thomas M."

Browsing by Author "O'Connell, Thomas M."

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Cachexia induced by cancer and chemotherapy yield distinct perturbations to energy metabolism
(Wiley, 2019-01-24) Pin, Fabrizio; Barreto, Rafael; Couch, Marion E.; Bonetto, Andrea; O'Connell, Thomas M.; Otolaryngology -- Head and Neck Surgery, School of Medicine
Background Cancer cachexia is a metabolic disorder involving perturbed energy balance and altered mitochondrial function. Chemotherapy is a primary treatment option for many types of cancer, but there is substantial evidence that some chemotherapeutic agents can also lead to the development and progression of cachexia. In this study, we apply a comprehensive and systems level metabolomics approach to characterize the metabolic perturbations in murine models of cancer-induced and chemotherapy-induced cachexia. Knowledge of the unique pathways through which cancer and chemotherapy drive cachexia is necessary in order to develop effective treatments. Methods The murine Colon26 (C26) adenocarcinoma xenograft model was used to study the metabolic derangements associated with cancer-induced cachexia. In vivo administration of Folfiri (5-fluorouracil, irinotecan, and leucovorin) was used to model chemotherapy-induced cachexia. Comprehensive metabolic profiling was carried out using both nuclear magnetic resonance-based and mass spectrometry-based platforms. Analyses included plasma, muscle, and liver tissue to provide a systems level profiling. Results The study involved four groups of CD2F1 male mice (n = 4–5), including vehicle treated (V), C26 tumour hosts (CC), Folfiri treated (F), and C26 tumour hosts treated with Folfiri (CCF). Significant weight loss including skeletal muscle was observed for each of the experimental groups with the tumour hosts showing the most dramatic change (−3.74 g vs. initial body weight in the CC group). Skeletal muscle loss was evident in all experimental groups compared with V, with the CCF combination resulting in the most severe depletion of quadriceps mass (−38% vs. V; P < 0.001). All experimental groups were characterized by an increased systemic glucose demand as evidenced by decreased levels of circulating glucose (−47% in CC vs. V; P < 0.001) and depletion of liver glucose (−51% in CC vs. V; P < 0.001) and glycogen (−74% in CC vs. V; P < 0.001). The cancer-induced and chemotherapy-induced cachexia models displayed unique alterations in flux through the tricarboxylic acid cycle and β-oxidation pathways. Cancer-induced cachexia was uniquely characterized by a dramatic elevation in low-density lipoprotein particles (+6.9-fold vs. V; P < 0.001) and a significant increase in the inflammatory marker, GlycA (+33% vs. V; P < 0.001). Conclusions The results of this study demonstrated for the first time that cancer-induced and chemotherapy-induced cachexia is characterized by a number of distinct metabolic derangements. Effective therapeutic interventions for cancer-induced and chemotherapy-induced cachexia must take into account the specific metabolic defects imposed by the pathological or pharmacological drivers of cachexia.
The critical role of dietary foliage in maintaining the gut microbiome and metabolome of folivorous sifakas
(Springer Nature, 2018-09-27) Greene, Lydia K.; McKenney, Erin A.; O'Connell, Thomas M.; Drea, Christine M.; Otolaryngology -- Head and Neck Surgery, School of Medicine
The gut microbiome (GMB) of folivores metabolizes dietary fiber into nutrients, including short-chain fatty acids (SCFAs); however, experiments probing the consequences of foliage quality on host GMBs are lacking. We therefore examined GMB structure and function via amplicon sequencing and Nuclear Magnetic Resonance spectroscopy in 31 captive sifakas (Propithecus coquereli) during dietary manipulations associated with husbandry. Supplementing standard diets with diverse foliage blends, versus with a single plant species, promoted more diverse GMBs, enriched for taxa implicated in plant-fiber metabolism, but depleted in taxa implicated in starch metabolism and bile tolerance. The consumption of diverse blends was associated with greater concentrations of colonic SCFAs. Abundant foliage, via forest access, promoted compositionally distinct and more stable GMBs, but reduced concentrations of SCFAs, possibly reflecting selection of high-quality leaves. In 11 subjects denied forest access, we examined the temporal pace of microbial shifts when supplemental foliage was abruptly switched between diverse blends and single species. The sifaka GMB responded within days, with community diversity and composition closely tracking foliage diversity. By providing experimental evidence that the folivore GMB is sensitive to minor changes in dietary foliage, we reveal the fragility of specialist GMBs, with implications for managing the wellbeing of endangered wildlife.
Higher glucose availability augments the metabolic responses of the C2C12 myotubes to exercise-like electrical pulse stimulation
(American Physiological Society, 2021) Lautaoja, Juulia H.; O'Connell, Thomas M.; Mäntyselkä, Sakari; Peräkylä, Juuli; Kainulainen, Heikki; Pekkala, Satu; Permi, Perttu; Hulmi, Juha J.; Otolaryngology -- Head and Neck Surgery, School of Medicine
The application of exercise-like electrical pulse simulation (EL-EPS) has become a widely used exercise mimetic in vitro. EL-EPS produces similar physiological responses as in vivo exercise, while less is known about the detailed metabolic effects. Routinely, the C2C12 myotubes are cultured in high-glucose medium (4.5 g/L), which may alter EL-EPS responses. In this study, we evaluate the metabolic effects of EL-EPS under the high- and low-glucose (1.0 g/L) conditions to understand how substrate availability affects the myotube response to EL-EPS. The C2C12 myotube, media, and cell-free media metabolites were analyzed using untargeted nuclear magnetic resonance (NMR)-based metabolomics. Furthermore, translational and metabolic changes and possible exerkine effects were analyzed. EL-EPS enhanced substrate utilization as well as production and secretion of lactate, acetate, 3-hydroxybutyrate, and branched-chain fatty acids (BCFAs). The increase in BCFAs correlated with branched-chain amino acids (BCAAs) and BCFAs were strongly decreased when myotubes were cultured without BCAAs suggesting the action of acyl-CoA thioesterases on BCAA catabolites. Notably, not all EL-EPS responses were augmented by high glucose because EL-EPS increased phosphorylated c-Jun N-terminal kinase and interleukin-6 secretion independent of glucose availability. Administration of acetate and EL-EPS conditioned media on HepG2 hepatocytes had no adverse effects on lipolysis or triacylglycerol content. Our results demonstrate that unlike in cell-free media, the C2C12 myotube and media metabolites were affected by EL-EPS, particularly under high-glucose condition suggesting that media composition should be considered in future EL-EPS studies. Furthermore, acetate and BCFAs were identified as putative exerkines warranting more research. NEW & NOTEWORTHY: The present study examined for the first time the metabolome of 1) C2C12 myotubes, 2) their growth media, and 3) cell-free media after exercise-like electrical pulse stimulation under distinct nutritional loads. We report that myotubes grown under high-glucose conditions had greater responsiveness to EL-EPS when compared with lower glucose availability conditions and increased media content of acetate and branched-chain fatty acids suggests they might act as putative exerkines warranting further research.
Metabolomics analysis reveals dysregulation in one carbon metabolism in Friedreich Ataxia
(Elsevier, 2022) O'Connell, Thomas M.; Logsdon, David L.; Payne, R. Mark; Otolaryngology -- Head and Neck Surgery, School of Medicine
Friedreich Ataxia (FA) is a rare and often fatal autosomal recessive disease in which a mitochondrial protein, frataxin (FXN), is severely reduced in all tissues. With loss of FXN, mitochondrial metabolism is severely disrupted. Multiple therapeutic approaches are in development, but a key limitation is the lack of biomarkers reflecting the activity of FXN in a timely fashion. We predicted this dysregulated metabolism would present a unique metabolite profile in blood of FA patients versus Controls (Con). Plasma from 10 FA and 11 age and sex matched Con subjects was analyzed by targeted mass spectrometry and untargeted NMR. This combined approach yielded quantitative measurements for 540 metabolites and found 59 unique metabolites (55 from MS and 4 from NMR) that were significantly different between cohorts. Correlation-based network analysis revealed several clusters of pathway related metabolites including a cluster associated with one‑carbon (1C) metabolism composed of formate, sarcosine, hypoxanthine, and homocysteine. Receiver operator characteristics analyses demonstrated an excellent ability to discriminate between Con and FA with AUC values >0.95. These results are the first reported metabolomic analyses of human patients with FA. The metabolic perturbations, especially those related to 1C metabolism, may serve as a valuable biomarker panel of disease progression and response to therapy. The identification of dysregulated 1C metabolism may also inform the search for new therapeutic targets related to this pathway.
Microbial nitrogen limitation in the mammalian large intestine
(Springer Nature, 2018-12) Reese, Aspen T.; Pereira, Fátima C.; Schintlmeister, Arno; Berry, David; Wagner, Michael; Hale, Laura P.; Wu, Anchi; Jiang, Sharon; Durand, Heather K.; Zhou, Xiyou; Premont, Richard T.; Diehl, Anna Mae; O'Connell, Thomas M.; Alberts, Susan C.; Kartzinel, Tyler R.; Pringle, Robert M.; Dunn, Robert R.; Wright, Justin P.; David, Lawrence A.; Otolaryngology -- Head and Neck Surgery, School of Medicine
Resource limitation is a fundamental factor governing the composition and function of ecological communities. However, the role of resource supply in structuring the intestinal microbiome has not been established and represents a challenge for mammals that rely on microbial symbionts for digestion: too little supply might starve the microbiome while too much might starve the host. We present evidence that microbiota occupy a habitat that is limited in total nitrogen supply within the large intestines of 30 mammal species. Lowering dietary protein levels in mice reduced their faecal concentrations of bacteria. A gradient of stoichiometry along the length of the gut was consistent with the hypothesis that intestinal nitrogen limitation results from host absorption of dietary nutrients. Nitrogen availability is also likely to be shaped by host-microbe interactions: levels of host-secreted nitrogen were altered in germ-free mice and when bacterial loads were reduced via experimental antibiotic treatment. Single-cell spectrometry revealed that members of the phylum Bacteroidetes consumed nitrogen in the large intestine more readily than other commensal taxa did. Our findings support a model where nitrogen limitation arises from preferential host use of dietary nutrients. We speculate that this resource limitation could enable hosts to regulate microbial communities in the large intestine. Commensal microbiota may have adapted to nitrogen-limited settings, suggesting one reason why excess dietary protein has been associated with degraded gut-microbial ecosystems.
PDK4 drives metabolic alterations and muscle atrophy in cancer cachexia
(Wiley, 2019-06) Pin, Fabrizio; Novinger, Leah J.; Huot, Joshua R.; Harris, Robert A.; Couch, Marion E.; O'Connell, Thomas M.; Bonetto, Andrea; Anatomy and Cell Biology, School of Medicine
Cachexia is frequently accompanied by severe metabolic derangements, although the mechanisms responsible for this debilitating condition remain unclear. Pyruvate dehydrogenase kinase (PDK)4, a critical regulator of cellular energetic metabolism, was found elevated in experimental models of cancer, starvation, diabetes, and sepsis. Here we aimed to investigate the link between PDK4 and the changes in muscle size in cancer cachexia. High PDK4 and abnormal energetic metabolism were found in the skeletal muscle of colon-26 tumor hosts, as well as in mice fed a diet enriched in Pirinixic acid, previously shown to increase PDK4 levels. Viral-mediated PDK4 overexpression in myotube cultures was sufficient to promote myofiber shrinkage, consistent with enhanced protein catabolism and mitochondrial abnormalities. On the contrary, blockade of PDK4 was sufficient to restore myotube size in C2C12 cultures exposed to tumor media. Our data support, for the first time, a direct role for PDK4 in promoting cancer-associated muscle metabolic alterations and skeletal muscle atrophy.
Sperm function, protein phosphorylation, and metabolism differ in mice lacking successive sperm-specific glycolytic enzymes†
(Oxford, 2017-10) Huang, Zaohua; Danshina, Polina V.; Mohr, Kathleen; Qu, Weidong; Goodson, Summer G.; O'Connell, Thomas M.; O'Brien, Deborah A.; Otolaryngology -- Head and Neck Surgery, School of Medicine
Glyceraldehyde 3-phosphate dehydrogenase-S (GAPDHS) and phosphoglycerate kinase 2 (PGK2), two isozymes restricted to the male germline, catalyze successive steps in the glycolytic pathway in mammalian sperm. Although gene targeting of each isozyme demonstrated that glycolysis is required for normal sperm motility and male fertility, the phenotype of mice lacking GAPDHS is more severe than that of mice lacking PGK2. This study examined sperm function, signaling pathways, and metabolism to investigate factors that contribute to the phenotypic differences between these knockout models. Sperm from the two knockouts exhibited comparable deficits in zona binding, in vitro fertilization with or without zona drilling, and capacitation-dependent tyrosine phosphorylation. In contrast, signaling and metabolic differences were apparent prior to capacitation. Phosphorylation of sperm protein phosphatase 1, which has been associated with the acquisition of motile capacity during epididymal maturation, was deficient only in GAPDHS-null sperm. Carnitine, choline, phosphocholine, and taurine were elevated in sperm from both knockouts immediately after collection from the epididymis. However, only carnitine levels in PGK2-null sperm were significantly different from wild-type sperm, while all four metabolites were significantly higher in GAPDHS-null sperm. We confirmed that glycolysis is required for robust hyperactivation, but found that the motility of PGK2-null sperm improved to levels comparable to wild-type sperm with pyruvate as the sole metabolic substrate. This nonglycolysable substrate did not improve progressive motility in GAPDHS-null sperm. These results identify multiple signaling and metabolic defects that are likely contributors to male infertility and the absence of progressive sperm motility seen in mice lacking GAPDHS.
Tumor, Fat and Skeletal Muscle Crosstalk via IL-6R Trans-Signaling Mediates Pancreatic Cancer Cachexia
(2020-10) Rupert, Joseph Emil; Zimmers, Teresa A.; Broxmeyer, Hal E.; Goebl, Mark G.; O'Connell, Thomas M.; Quilliam, Lawrence A.
Cachexia, the involuntary loss of fat and muscle is associated with pancreatic ductal adenocarcinoma (PDAC), contributing to its 90% 5-year mortality rate. Elevated Interleukin-6 (IL-6) expression is associated with cachexia severity and reduced survival in patients. IL-6 in cancer is well documented, but IL-6 signaling crosstalk among tissues is not. IL-6 signals by binding membrane-bound IL-6 receptor (IL-6R) (classical signaling) or soluble IL- 6R (sIL6R; trans-signaling) produced by shedding of the membrane receptor primarily from muscle, liver and leukocytes. Herein I investigate the role of tumorderived IL-6 on muscle and fat crosstalk in PDAC. Loss of IL-6 expression in murine KPC PDAC cells was accomplished by CRISPR/Cas9 mutagenesis of the Il6 gene. Orthotopic KPC IL-6 knockout (KPC-IL-6KO) tumor-bearing mice had reduced cachexia, with attenuated fat loss and no significant muscle loss, and longer survival versus KPC controls. Only KPC tumor-bearing mice had significant myosteatosis, aberrant branched chain amino acid and fatty acid metabolism, and reduced pyruvate entry into the TCA-cycle, determined by increased pyruvate dehydrogenase kinase 4 (PDK4) expression in muscle. Muscle was a main source of sIL6R, and fat a primary contributor of IL-6 in KPC tumor-bearing mice. Myosteatosis leads to activation of lipid-sensitive kinases like protein kinase C theta (PKCθ, gene name Prkcq) in muscle. KPC tumorbearing mice had increased muscle PKCθ activation, and PKCθ is known to regulate metabolism and inflammation. Prkcq-/- KPC tumor-bearing mice had reduced cachexia and maintained muscle mass and force production versus wild type tumor-bearing mice. Together these data implicate progressive signaling mechanisms whereby tumor-derived IL-6 is associated with increased muscle IL6R expression and fat lipolysis, promoting myosteatosis and muscle PKCθ activation, ultimately increasing cachexia severity in PDAC.

Browsing by Author "O'Connell, Thomas M."

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