publications
Complete collection of works that I am an author on.
2024
- Preclinical Multi-Omic Assessment of Pioglitazone in Skeletal Muscles of Mice Implanted with Human HER2/neu Overexpressing Breast Cancer XenograftsStuart A. Clayton , Alan D. Mizener , Marcella Whetsell , Lauren E. Rentz , Ethan M. Meadows , Werner J. Geldenhuys , and Emidio E. PistilliBioRxiv, Apr 2024
Breast cancer (BC) is the most prevalent cancer worldwide and is accompanied by fatigue during both active disease and remission in the majority of cases. Our lab has measured fatigue in isolated muscles from treatment-naive BC patient-derived orthotopic xenograft (BC-PDOX) mice. Here, we conducted a preclinical trial of pioglitazone in BC-PDOX mice to determine its efficacy in ameliorating BC-induced muscle fatigue, as well as its effects on transcriptomic, metabolomic, and lipidomic profiles in skeletal muscle. Methods: The pioglitazone and vehicle groups were treated orally for 4 weeks upon reaching a tumor volume of 600 mm3. Whole-animal indirect calorimetry was used to evaluate systemic metabolic states. The transcriptome was profiled using short-read bulk RNA sequencing (RNA-seq). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to profile the metabolome and lipidome. Fast and slow skeletal muscle function were evaluated using isolated ex vivo testing. Results: Pioglitazone was associated with a significant overall decrease in metabolic rate, with no changes in substrate utilization. RNA-seq supported the downstream effects of pioglitazone on target genes and displayed considerable upregulation of mitochondrial bioenergetic pathways. Skeletal muscle metabolomic and lipidomic profiles exhibited dysregulation in response to BC, which was partially restored in pioglitazone-treated mice compared to vehicle-treated BC-PDOX mice. Despite molecular support for pioglitazones efficacy, isolated muscle function was not affected by pioglitazone treatment. Conclusions: BC induces multi-omic dysregulation in skeletal muscle, which pioglitazone partially ameliorates. Future research should focus on profiling systemic metabolic dysfunction, identifying molecular biomarkers of fatigue, and testing alternative pioglitazone treatment regimens.
- Effects of Pioglitazone on Metabolomic and Lipidomic Profiles in Skeletal Muscles of Mice Implanted with Her2/neu+ Breast Cancer PDXsStuart A. Clayton , Alan D. Mizener , Marcella Whetsell , Lauren E. Rentz , Werner Geldenhuys , and Emidio E. PistilliTranslational Research Cancer Centers Consortium, Feb 2024
- New Perspectives for Estimating Body Composition From Computed Tomography: Clothing Associated ArtifactsLauren E. Rentz , Briauna M. Malone , Beth Vettiyil , Erik A. Sillaste , Alan D. Mizener , Stuart A. Clayton , and Emidio E. PistilliAcademic Radiology, Feb 2024
Retrospective analysis of computed tomography (CT) imaging has been widely utilized in clinical populations as the “gold standard” method for quantifying body composition and tissue volumes. Thousands of published studies across the last 30 years suggest a concerningly high heterogeneity for statistical associations involving skeletal muscle and adiposity across patient populations that represent all types of cancer, COPD, and recently COVID-19. Like most clinical datasets, the extensive presence of confounds, inconsistencies, and missing data tend to complicate post hoc imaging analyses. In addition to obvious data artifact, ample threats to study validity can be well concealed by lengthy patient charts, co-occurring factors, and methodological limitations. In the absence of a highly controlled environment, we neglect to consider the multiplicity of factors that can influence naturally occurring data, and thus, real-world utility of findings. Most importantly, we often fail to rehumanize collections of datapoints to understand patterns, compound clinical effects, and limitations experienced by both the clinical team and patient that maximize the value of post hoc conclusions.
2023
- Systemic Effects Of Breast Cancer Chemotherapy On Skeletal Muscle Physiology: Insights From Clinical And Molecular InvestigationsAlan D. Mizener , Lauren E. Rentz , Stuart A. Clayton , Erik A. Silaste , Ben D. Hatcher , Marcella A. Whetsell , and Emidio E. PistilliGreat Lakes Breast Cancer Research Symposium, Sep 2023
- Sexual Dimorphism of Skeletal Muscle in a Mouse Model of Breast Cancer: A Functional and Molecular AnalysisLauren E. Rentz , Marcella A. Whetsell , Stuart A. Clayton , Alan D. Mizener , Ida Holásková , Matthew G. Chapa , Emily H. Hoblitzell , Timothy D. Eubank , and Emidio E. PistilliInternational Journal of Molecular Sciences, Jul 2023
Breast cancer incidence in men is statistically rare; however, given the lack of screening in males, more advanced stages at initial diagnosis result in lower 5-year survival rates for men with breast cancer compared to women. A sexual dimorphism, with respect to the effect of tumor growth on cachexia incidence and severity, has also been reported across cancer types. The purpose of this study was to examine the sexual dimorphism of breast cancer as it pertains to skeletal muscle function and molecular composition. Using female and male transgenic PyMT mice, we tested the hypothesis that the isometric contractile properties and molecular composition of skeletal muscle would be differentially affected by breast tumors. PyMT tumor-bearing mice of each sex, corresponding to maximal tumor burden, were compared to their respective controls. RNA sequencing of skeletal muscle revealed different pathway alterations that were exclusive to each sex. Further, differentially expressed genes and pathways were substantially more abundant in female tumor mice, with only minimal dysregulation in male tumor mice, each compared to their respective controls. These differences in the transcriptome were mirrored in isometric contractile properties, with greater tumor-induced dysfunction in females than male mice, as well as muscle wasting. Collectively, these data support the concept of sexually dimorphic responses to cancer in skeletal muscle and suggest that these responses may be associated with the clinical differences in breast cancer between the sexes. The identified sex-dependent pathways within the muscle of male and female mice provide a framework to evaluate therapeutic strategies targeting tumor-associated skeletal muscle alterations.
2018
- Chronic exposure to electronic cigarettes results in impaired cardiovascular function in miceI. Mark Olfert , Evan DeVallance , Hannah Hoskinson , Kayla W. Branyan , Stuart Clayton , Christopher R. Pitzer , D. Patrick Sullivan , Matthew J. Breit , Zhongxin Wu , Powsiri Klinkhachorn , and 6 more authorsJournal of Applied Physiology, Mar 2018
Proponents for electronic cigarettes (Ecigs) claim that they are a safe alternative to tobacco-based cigarettes; however, little is known about the long-term effects of exposure to E-cig vapor on vascular function. The purpose of this study was to determine the cardiovascular consequences of chronic E-cig exposure. Female mice (C57BL/6 background strain) were randomly assigned to chronic daily exposure to E-cig vapor, standard (3R4F reference) cigarette smoke, or filtered air (n = 15/group). Respective whole body exposures consisted of four 1-h-exposure time blocks, separated by 30-min intervals of fresh air breaks, resulting in intermittent daily exposure for a total of 4 h/day, 5 days/wk for 8 mo. Noninvasive ultrasonography was used to assess cardiac function and aortic arterial stiffness (AS), measured as pulse wave velocity, at three times points (before, during, and after chronic exposure). Upon completion of the 8-mo exposure, ex vivo wire tension myography and force transduction were used to measure changes in thoracic aortic tension in response to vasoactive-inducing compounds. AS increased 2.5- and 2.8-fold in E-cig- and 3R4F-exposed mice, respectively, compared with air-exposed control mice (P < 0.05). The maximal aortic relaxation to methacholine was 24% and 33% lower in E-cig- and 3R4F-exposed mice, respectively, than in controls (P < 0.05). No differences were noted in sodium nitroprusside dilation between the groups. 3R4F exposure altered cardiac function by reducing fractional shortening and ejection fraction after 8 mo (P < 0.05). A similar, although not statistically significant, tendency was also observed with E-cig exposure (P < 0.10). Histological and respiratory function data support emphysema-associated changes in 3R4F-exposed, but not E-cig-exposed, mice. Chronic exposure to E-cig vapor accelerates AS, significantly impairs aortic endothelial function, and may lead to impaired cardiac function. The clinical implication from this study is that chronic use of E-cigs, even at relatively low exposure levels, induces cardiovascular dysfunction.
2017
- Vaping to Vascular Damage: The Role of E-Cigarettes on Vascular FunctionStuart Clayton , Evan DeVallance , Kayla Branyan , Christopher Pitzer , Matthew Breit , Hannah Hoskinson , Powsiri Klinkhachorn , Brett Erdreich , Paul Chantler , and Mark OlfertFASEB, Apr 2017
Electronic cigarettes (E-cigs) have exponentially increased in popularity and usage due to the perception that e-cigs are safe, their usefulness as a cigarette-smoking cessation tool, and the appeal of heavily marketed flavors. There is little known about the long-term effects of E-cig vapor exposure, particularly in the context of vascular dysfunction. We hypothesize that the long-term use of E-cig vapor decreased aortic function, and increase aortic stiffness. Data were obtained from C57BL/6 female mice exposed to 3R4F reference cigarette (N=5–7), cappuccino flavored E-vapor (18 mg/ml nicotine, N=7), or filtered air (N=7–8) for 4 h/day, 5 d/wk for 8 months. Food and water were administered ad libitum. Before and after the exposure, in-vivo aortic stiffness (pulse wave velocity) was measured using B-mode and Doppler ultrasound by obtain blood flow signals at the aortic arch and before the carotid bifurcation from a single image, which were gated to the EKG. At the end of the exposure the thoracic aorta was dissected, sectioned into rings and mounted onto an ex-vivo wire tension myograph system. Force transduction was used to measure the changes in aortic tension in response to methacholine, or sodium nitroprusside. Aortic stiffness increased (0.45±0.20 m/s) in the air-exposed group, reflecting the normal aging process. However, an accelerated age-associated aortic stiffness was noted in the cigarette (1.28±0.27 m/s) and E-cig (1.14±0.24 m/s) groups (ANOVA, p<0.05). In animals exposed to filtered air, the maximal aortic relaxation achieved to methacholine was 90%, compared to 60% and 70% in the cigarette and E-cig groups, respectively (p<0.05). No differences were noted in sodium nitroprusside dilation between groups. Our data suggests that 8 months of E-cig significantly accelerated the age-associated increase in aortic stiffness, and significantly impaired aortic endothelial-dependent but not endothelial-independent dilation. These data show the E-cigs induce similar vascular dysfunction to cigarette smoke exposure suggesting that E-cig have similar risk to develop accelerated cardiovascular aging and disease.
- Exercise Reverses Metabolic Syndrome Perivascular Adipose Tissue Impairment of Aortic RelaxationEvan DeVallance , Kayla Branyan , Kent Lemaster , Stuart Clayton , Carly Killmer , Jefferson Frisbee , and Paul ChantlerFASEB, Apr 2017
Thoracic aorta perivascular adipose tissue (PVAT) mediates aortic function through paracrine signaling. In health these factors are predominately anti-inflammatory and aide in proper vascular function. Our previous data shows PVAT is “brown-like” expressing high levels of Uncoupling Protein-1 (UCP-1), however in the metabolic syndrome (MetS) the PVAT loses the expression of UCP-1 shifting to a white-like phenotype. This shift is accompanied with increased oxidative stress and expression of pro-inflammatory cytokines, which can impair aortic endothelial nitric oxide (NO) production and alter extracellular matrix composition. The objective of the study was to determine the therapeutic efficacy of aerobic exercise in an animal model of MetS (obese zucker rats: OZR) specifically on PVAT mediated NO production, aortic relaxation, and aortic stiffness. OZR PVAT expression of UCP-1 decreased 100-fold accompanied by a greater than 70 fold increase in both TNFα and IL-6. This inflammatory secretion profile further diminished endothelial dependent relaxation of the aorta by 15%. Using the DHE assay, we found a >100% increased superoxide production in the PVAT (p<0.01). Exercise is known to have anti-oxidant and anti-inflammatory benefits but little is know of this impact on PVAT. We previously found improved UCP-1, SOD-1, TNFα and IL-6 gene expression in OZRs following 8 weeks of treadmill training. Exercise improved aortic endothelial relaxation 10% (p<0.01), additionally PVAT augmented relaxation 10% (p<0.01) instead of impairing. This may be the result of diminished superoxide production (DHE fluorescence p<0.05) in the PVAT restoring a healthy pro/anti inflammatory balance. Exercise also reduced constricting responses to phenylephrine with and without PVAT. Similarly in the lean rats (LZR) exercise training increased UCP-1 expression along with SOD-1 with marginal increase in aortic relaxation and PVAT mediated aortic relaxation. Exercise also augmented the anti-contractile effects of PVAT. Structurally MetS causes increase deposition of collagen with fragmentation of elastin increasing the aorta’s resistance to deformation. OZR have increase elastin modulus compared to LZR (561 vs. 304 N, p<0.01) showing increased stiffness, which is completely reversed by exercise training (561 vs. 337 N, p<0.01) in OZR. Previous PVAT gene expression showed increase in MMP9 a marker that correlate strongly with aortic stiffness and similar to the elastin modulus exercise training completely returns expression level to that of LZRs. This establishes a correlative relationship between PVAT expression of MMPs and mechanical aortic stiffness. In summary MetS PVAT mediates increases in both functional (endothelial function) and structural stiffness (matrix remodeling). 8 weeks of treadmill training in OZRs promotes beneficial gene expression in the PVAT leading to reduced superoxide production, decreased pro-inflammatory cytokines, and retention of aortic elastic properties.
- Can exercise protect against chronic stress induced cerebral microvessel changes in Lean and Obese Zucker rats?Whitney Jordan Sheets , Shinichi Asano , Mariah Dawson , Melissa Ashman , Stuart Clayton , Steven Brooks , Jefferson Frisbee , and Paul ChantlerFASEB, Apr 2017
Chronic stress-induced depression is a major cardiovascular risk factor, and metabolic Syndrome (MetS) is linked with depression. The relationship among chronic stress/depression (UCMS), MetS, CVD, and cerebrovascular dysfunction is poorly understood. We determined how UCMS and Exercise training affected cerebral microvessels density (MVD), and the pro (nitric oxide, VEGF, STAT3) and anti (TSP-1) angiogenic factors. We hypothesize that UCMS will decrease MVD in Obese Zucker Rats (OZR = MetS), and exercise training will prevent this rarefaction by increasing pro-angiogenic mediators, while reducing anti-angiogenic factors including oxidative stress. Nine-week old lean rats (LZR) and OZR were randomly assigned (n=6/group) to: Control(C), Exercise (EX), subjected daily to an UCMS, and EX+UCMS for 8 weeks. At 17 weeks, brains were removed and snap frozen in Tissue Tek medium. Cortex MVD were measured by fluorescence IHC (rat anti-CD31 antibody). Oxidative stress was assessed in cerebral tissue by ELISA technique (anti 3-Nitrotyrosine antibody) and by DHE. Cerebral inflammatory and angiogenic markers for STAT3, VEGF and TSP-1 were measured by western blot or ELISA. MVD was decreased (−31%, p<0.05) in the cortex from OZR-UCMS vs. OZR control. Exercise training attenuated UCMS induced decreased MVD in OZR by 41%. In contrast, there were no significant differences (8% decrease to 4% increase) in MVD among LZR groups. In both LZR and OZR UCMS increased oxidative stress, and decreased nitric oxide in the cerebral vessels. Although VEGF results were not yet significant, a slight decrease was seen in OZR UCMS that was recovered with exercise training in UCMS. Initial data also suggests that TSP-1, which is higher in OZR vs. LZR control, is also influenced by UCMS, and Ex. Compared to LZR-C, LZR-UCMS had an 74% increase in STAT3. Although both OZR-C and OZR UCMS exhibited significantly increased STAT3 phosphorylation compared to LZR-C, there was no difference between OZR-C and OZR UCMS. Both LZR-Ex and OZR-Ex attenuated UCMS induced elevated STAT3 activity. Taken together, UCMS drives the development of decreased brain MVD in OZR. Chronic stress and obesity both independently increased STAT3 signaling in the brain, which was then abrogated by exercise in both lean and obese animals. Exercise also prevented the onset of cortical rarefaction seen in OZR-UCMS. We are further exploring TSP1 and VGEF pathways.