Abstract 294: Heavy Alcohol Use Worsens Peripheral Artery Disease-Associated Myopathy

Heavy alcohol use can induce skeletal muscle dysfunction referred to as alcoholic myopathy. Likewise, peripheral artery disease (PAD) is characterized by an acquired skeletal muscle metabolic myopathy in ischemic muscles of the lower extremity. Although epidemiological studies have shown that heavy alcohol consumption is associated with a greater risk of PAD, data are lacking on the contribution of alcohol-related myopathy on PAD-associated skeletal muscle pathology. We compared myofiber morphometrics, mitochondrial respiration, and oxidative stress measures in gastrocnemius biopsies from PAD patients with heavy alcohol use (>7 or >14 drinks per week, for females and males, respectively) (n=13) to PAD patients (n=13) and non-PAD controls (n=17) consuming moderate to low/no alcohol. Myofiber area and diameter were lower in heavy-drinking PAD patients compared to low/moderate drinkers (p=0.03 and p=0.04, respectively) and non-PAD controls (p=0.02 and p<0.001, respectively). Myofiber roundness was significantly higher in heavy-drinking PAD patients compared to low/moderate drinkers (p=0.04) and non-PAD controls (p<0.001). Although there were no significant differences between PAD groups in mitochondrial respiration, PAD patients with heavy alcohol consumption tended to have lower respiration for Complex I (p=0.14), Complex II (p=0.10), and Complex IV (p=0.16) compared to PAD patients without heavy alcohol use. Both PAD groups had significantly reduced respiration of all Complexes compared to non-PAD controls (p<0.05). These data suggest that alcohol abuse may accentuate skeletal muscle pathology in PAD patients.

Aging alters gastrocnemius muscle hemoglobin oxygen saturation (StO2) characteristics in healthy individuals

PURPOSE

Functional limitations during exercise from alterations in the balance of oxygen supply and demand-as reported by lower tissue oxygen saturation and longer recovery time-are well documented in clinical populations. We aimed to assess changes in skeletal muscle hemoglobin oxygen saturation (StO₂) characteristics during exercise as a result of aging in otherwise healthy individuals.

METHODS

We recruited healthy male and female participants (n = 101) from three age ranges-young (18-39 years), middle age (40-65 years), and older (> 65 years)-to complete exercise tests commonly used in clinical populations. Using near-infrared spectroscopy (NIRS) we assessed StO₂ in the medial gastrocnemius during the Gardner Treadmill Protocol and 6 min walk test (6MWT).

RESULTS

Minimum StO₂ (%) during the treadmill test was significantly lower for both middle-age (36.1 ± 20.6) and older (27.3 ± 19.4) participants compared to young (46.8 ± 14.8) (p < 0.05 and p < 0.01 respectively), and recovery time (minutes) was significantly prolonged (young = 0.22 ± 0.34; middle age = 0.66 ± 0.52; older = 1.04 ± 1.00) (p < 0.001 for both middle age and older compared to young). Similar results were shown during the 6MWT, as minimum StO₂ (%) was lower in middle-age (41.7 ± 17.2) and older (40.0 ± 25.9) participants compared to young (53.6 ± 14.5) (p < 0.05), and recovery times (minutes) were prolonged (young: 0.11 ± 0.17; middle age: 0.46 ± 0.42; older: 0.93 ± 0.43) (p < 0.001 for both middle age and older compared to young). Simple linear regression analyses demonstrated that age predicted treadmill recovery and 6MWT recovery.

CONCLUSION

Our study provides evidence that aging, even in otherwise healthy individuals, negatively impacts muscle StO₂ characteristics. In older individuals, working muscle tissue may reach lower oxygen saturation during exercise and take longer to return to baseline oxygen saturation post-exercise.

Effect of Age and Acute-Moderate Intensity Exercise on Biomarkers of Renal Health and Filtration

Aerobic exercise elicits a multitude of physiological improvements in both healthy and diseased populations. However, acute changes in renal health and filtration with aerobic exercise remain difficult to quantify by traditional biomarkers to estimate glomerular filtration rate (eGFR). This study aimed to determine if an acute bout of moderate-intensity aerobic exercise transiently improves non-traditional biomarkers when compared to traditional biomarkers of renal health and filtration in individuals without cardiometabolic diseases. Thirty-nine participants (n = 18 men; n = 21 women; age 32.5 + 12.6 yr; height 171.1 + 11.4 cm; weight 78.7 + 15.6 kg; BMI 27.1 + 5.8) completed a single bout of moderate-intensity (50-60% HRR) aerobic exercise. Blood and urine samples were collected and compared before and post-exercise. Serum creatinine, urine epidermal growth factor (uEGF), uEGF/urine creatinine ratio (uEGFR), and cystatin C (CyC) were measured. In addition, eGFR-MDRD and the CKD-epidemiology equations were used to analyze renal clearance. Relative to pre-exercise measures: serum creatinine (p = 0.26), uEGF (p = 0.35), and uEGFR (p = 0.09) remained unchanged, whereas cystatin C (p = 0.00) significantly increased post-exercise. CyC eGFR was the only estimator of renal filtration to significantly change (p = 0.04). In conclusion, CyC is the only biomarker of renal health and filtration to significantly increase after aerobic exercise. Further investigation focused on sampling time and exercise-intensity is needed to solidify the current understanding of renal health and filtration.

High-Fat Diet Augments the Effect of Alcohol on Skeletal Muscle Mitochondrial Dysfunction in Mice

Previous studies have shown that chronic heavy alcohol consumption and consumption of a high-fat (HF) diet can independently contribute to skeletal muscle oxidative stress and mitochondrial dysfunction, yet the concurrent effect of these risk factors remains unclear. We aimed to assess the effect of alcohol and different dietary compositions on mitochondrial activity and oxidative stress markers. Male and female mice were randomized to an alcohol (EtOH)-free HF diet, a HF + EtOH diet, or a low-Fat (LF) + EtOH diet for 6 weeks. At the end of the study, electron transport chain complex activity and expression as well as antioxidant activity and expression, were measured in skeletal muscles. Complex I and III activity were diminished in muscles of mice fed a HF + EtOH diet relative to the EtOH-free HF diet. Lipid peroxidation was elevated, and antioxidant activity was diminished, in muscles of mice fed a HF + EtOH diet as well. Consumption of a HF diet may exacerbate the negative effects of alcohol on skeletal muscle mitochondrial health and oxidative stress.

Metabolomics of peripheral artery disease

The science of metabolomics has emerged as a novel tool for studying changes in metabolism that accompany different disease states. Several studies have applied this evolving field to the study of various cardiovascular disease states, which has led to improved understanding of metabolic changes that underlie heart failure and ischemic heart disease. A significant amount of progress has also been made in the identification of novel biomarkers of cardiovascular disease. Another common atherosclerotic disease, peripheral artery disease (PAD) affects arteries of the lower extremities. Although certain aspects of the disease pathophysiology overlap with other cardiovascular diseases in general, PAD patients suffer unique manifestations that lead to significant morbidity and mortality as well as severe functional limitations. Furthermore, because over half of PAD patients are asymptomatic, there is a need for improved diagnostic and screening methods. Identification of metabolites associated with the disease may thus be a promising approach for PAD. However, PAD remains highly understudied. In this chapter, we discuss the application of metabolomics to the study of PAD.

Endothelial cell-derived pro-fibrotic factors increase TGF-β1 expression by smooth muscle cells in response to cycles of hypoxia-hyperoxia

BACKGROUND

The vascular pathology of peripheral artery disease (PAD) encompasses abnormal microvascular architecture and fibrosis in response to ischemia-reperfusion (I/R) cycles. We aimed to investigate the mechanisms by which pathological changes in the microvasculature direct fibrosis in the context of I/R.

METHODS

Primary human aortic endothelial cells (ECs) were cultured under cycles of normoxia-hypoxia (NH) or normoxia-hypoxia-hyperoxia (NHH) to mimic I/R. Primary human aortic smooth muscle cells (SMCs) were cultured and treated with media from the ECs.

FINDINGS

The mRNA and protein expression of the pro-fibrotic factors platelet derived growth factor (PDGF)-BB and connective tissue growth factor (CTGF) were significantly upregulated in ECs undergoing NH or NHH cycles. Treatment of SMCs with media from ECs undergoing NH or NHH cycles led to significant increases in TGF-β1, TGF-β pathway signaling intermediates, and collagen expression. Addition of neutralizing antibodies against PDGF-BB and CTGF to the media blunted the increases in TGF-β1 and collagen expression. Treatment of SMCs with PAD patient-derived serum also led to increased TGF-β1 levels.

INTERPRETATION

In an in-vitro model of I/R, which recapitulates the pathophysiology of PAD, increased secretion of PDGF-BB and CTGF by ECs was shown to be predominantly driving TGF-β1-mediated expression by SMCs. These cell culture experiments help elucidate the mechanism and interaction between ECs and SMCs in microvascular fibrosis associated with I/R. Thus, targeting these pro-fibrotic factors may be an effective strategy to combat fibrosis in response to cycles of I/R.

FUNDING

National Institute on Aging at the National Institutes of Health grant number R01AG064420.

RESEARCH IN CONTEXT

Evidence before this study: Previous studies in gastrocnemius biopsies from peripheral artery disease (PAD) patients showed that transforming growth factor beta 1 (TGF-β1), the most potent inducer of pathological fibrosis, is increased in the vasculature of PAD patients and correlated with collagen deposition. However, the exact cellular source of TGF-β1 remained unclear. Added value of this study: Exposing cells to cycles of normoxia-hypoxia-hyperoxia (NHH) resulted in pathological changes that are consistent with human PAD. This supports the idea that the use of NHH may be a reliable, novel in vitro model of PAD useful for studying associated pathophysiological mechanisms. Furthermore, pro-fibrotic factors (PDGF-BB and CTGF) released from endothelial cells were shown to induce a fibrotic phenotype in smooth muscle cells. This suggests a potential interaction between these cell types in the microvasculature that drives increased TGF-β1 expression and collagen deposition. Thus, targeting these pro-fibrotic factors may be an effective strategy to combat fibrosis in response to cycles of ischemia-reperfusion.

MicroRNAs in peripheral artery disease: potential biomarkers and pathophysiological mechanisms

Peripheral artery disease (PAD) is a disease of atherosclerosis in the lower extremities. PAD carries a massive burden worldwide, while diagnosis and treatment options are often lacking. One of the key points of research in recent years is the involvement of microRNAs (miRNAs), which are short 20-25 nucleotide single-stranded RNAs that can act as negative regulators of post-transcriptional gene expression. Many of these miRNAs have been discovered to be misregulated in PAD patients, suggesting a potential utility as biomarkers for PAD diagnosis. miRNAs have also been shown to play an important role in many different pathophysiological aspects involved in the initiation and progression of the disease including angiogenesis, hypoxia, inflammation, as well as other cellular functions like cell proliferation and migration. The research on miRNAs in PAD has the potential to lead to a whole new class of diagnostic tools and treatments.

Transcriptomic Regulations Underlying Pair-bond Formation and Maintenance in the Socially Monogamous Male and Female Prairie Vole

BACKGROUND

The ability to form enduring social bonds is characteristic of human nature, and impairments in social affiliation are central features of severe neuropsychiatric disorders including autism spectrum disorder and schizophrenia. Owing to its ability to form long-term pair-bonds, the socially monogamous prairie vole has emerged as an excellent model to study the neurobiology of social attachment. Despite the enduring nature of the bond, however, surprisingly few genes have been implicated in the pair-bonding process in either sex.

METHODS

Male and female prairie voles (Microtus ochrogaster) were cohabitated with an opposite-sex partner for 24 hours or 3 weeks, and transcriptomic regulations in the nucleus accumbens were measured by RNA sequencing.

RESULTS

We found sex-specific response patterns despite similar behavioral indicators of pair-bond establishment. Indeed, 24 hours of cohabitation with an opposite-sex partner induced widespread transcriptomic changes that remained sustained to some extent in females after 3 weeks but returned to baseline before a second set of regulations in males. This led to a highly sexually biased nucleus accumbens transcriptome at 3 weeks related to processes such as neurotransmission, protein turnover, and DNA transcription. In particular, we found sex-specific alterations of mitochondrial dynamics following cohabitation, with a shift toward fission in males.

CONCLUSIONS

In addition to identifying the genes, networks, and pathways involved in the pair-bonding process in the nucleus accumbens, our work illustrates the vast extent of sex differences in the molecular mechanisms underlying pair-bonding in prairie voles and paves the way to further our understanding of the complex social bonding process.

Effects of Acute Partial Sleep Deprivation and High-Intensity Interval Exercise on Postprandial Network Interactions

Introduction: High-intensity interval exercise (HIIE) is deemed effective for cardiovascular and autonomic nervous system (ANS) health-related benefits, while ANS disturbance increases the risk for cardiovascular disease (CVD). Postprandial lipemia and acute-partial sleep deprivation (APSD) are considered as CVD risk factors due to their respective changes in ANS. Exercising in the morning hours after APSD and have a high-fat breakfast afterwards may alter the interactions of the cardiovascular, autonomic regulation, and postprandial lipemic systems threatening individuals' health. This study examined postprandial network interactions between autonomic regulation through heart rate variability (HRV) and lipemia via low-density lipoprotein (LDL) cholesterol in response to APSD and HIIE. Methods: Fifteen apparently healthy and habitually good sleepers (age 31 ± 5.2 SD yrs) completed an acute bout of an isocaloric HIIE (in form of 3:2 work-to-rest ratio at 90 and 40% of VO₂ reserve) after both a reference sleep (RSX) and 3-3.5 h of acute-partial sleep deprivation (SSX) conditions. HRV time and frequency domains and LDL were evaluated in six and seven time points surrounding sleep and exercise, respectively. To identify postprandial network interactions, we constructed one correlation analysis and one physiological network for each experimental condition. To quantify the interactions within the physiological networks, we also computed the number of links (i.e., number of significant correlations). Results: We observed an irruption of negative links (i.e., negative correlations) between HRV and LDL in the SSX physiological network compared to RSX. Discussion: We recognize that a correlation analysis does not constitute a true network analysis due to the absence of analysis of a time series of the original examined physiological variables. Nonetheless, the presence of negative links in SSX reflected the impact of sleep deprivation on the autonomic regulation and lipemia and, thus, revealed the inability of HIIE to remain cardioprotective under APSD. These findings underlie the need to further investigate the effects of APSD and HIIE on the interactions among physiological systems.

Expanding the Reactive Sulfur Metabolome: Intracellular and Efflux Measurements of Small Oxoacids of Sulfur (SOS) and H2S in Human Primary Vascular Cell Culture

Hydrogen sulfide (H2S) is an endogenous signaling molecule which is important for cardiovascular health, but its mechanism of action remains poorly understood. Here, we report measurements of H2S as well as its oxidized metabolites, termed small oxoacids of sulfur (SOS = HSOH and HOSOH), in four human primary vascular cell lines: smooth muscle and endothelial cells derived from both human arterial and coronary tissues. We use a methodology that targets small molecular weight sulfur species; mass spectrometric analysis allows for species quantification to report cellular concentrations based on an H2S calibration curve. The production of H2S and SOS is orders of magnitude higher in smooth muscle (nanomolar) as compared to endothelial cell lines (picomolar). In all the primary lines measured, the distributions of these three species were HOSOH >H2S > HSOH, with much higher SOS than seen previously in non-vascular cell lines. H2S and SOS were effluxed from smooth muscle cells in higher concentrations than endothelial cells. Aortic smooth muscle cells were used to examine changes under hypoxic growth conditions. Hypoxia caused notable increases in HSOH and ROS, which we attribute to enhanced sulfide quinone oxidase activity that results in reverse electron transport.

Shared and distinct mechanisms of skeletal muscle atrophy: A narrative review

Maintenance of skeletal muscle mass and function is an incredibly nuanced balance of anabolism and catabolism that can become distorted within different pathological conditions. In this paper we intend to discuss the distinct intracellular signaling events that regulate muscle protein atrophy for a given clinical occurrence. Aside from the common outcome of muscle deterioration, several conditions have at least one or more distinct mechanisms that creates unique intracellular environments that facilitate muscle loss. The subtle individuality to each of these given pathologies can provide both researchers and clinicians with specific targets of interest to further identify and increase the efficacy of medical treatments and interventions.

In the absence of cardiometabolic diseases, is age an independent factor in assessing renal health and filtration? A pilot study

Introduction: Serum creatinine (sCr) is conventionally used to characterize the progressive decline in renal filtration (RF). Assessment of RF and renal health (RH) is traditionally believed to be agedependent. However, in the absence of cardiometabolic disease (CMD), this may not be the case. Objectives: The purpose of this study was to determine the magnitude of age as an influencing factor independent of CMD with novel markers of RH/RF in a single health assessment. Patients and Methods: Fifty-four participants (n = 27 men; n = 27 women; age 33.4 ± 12.5 years; BMI 26.5 ± 5.5; SBP 120 ± 10.4; DBP 77.7 ± 6.7; CHOL 174 ± 30) free of CMD were recruited to assess sCr, urine creatinine (uCr), cystatin C (CyC), and urine epidermal growth factor (uEGF) to calculate estimates of RH/F via uEGF/uCr ratio (uEGFR), eGFR - modification of diet in renal disease (MDRD), CKD-EPI, and sCr/CyC eGFR. Results: There were no significant differences between age groups (20s, 30s, 40s, 50s) in biomarkers and estimates of RH/RF, sCr (P=0.91), uEGF (P=0.46), CyC (P=0.13), CyC eGFR (P= 0.10), MDRD (P=0.12), CKD-EPI (P=0.80), and sCr/CyC eGFR (P=0.12). Post-hoc analysis revealed uEGFR was the only significantly different variable between 40s and 50s age groups (P= 0.02). Conclusion: Changes in RH/RF appear to be independent of age in the absence of CMD. Indicating RH/RF could potentially be maintained in adulthood and throughout the older adult years with the continued absence of CMD.

Phytochemicals as Therapeutic Interventions in Peripheral Artery Disease

Peripheral artery disease (PAD) affects over 200 million people worldwide, resulting in significant morbidity and mortality, yet treatment options remain limited. Among the manifestations of PAD is a severe functional disability and decline, which is thought to be the result of different pathophysiological mechanisms including oxidative stress, skeletal muscle pathology, and reduced nitric oxide bioavailability. Thus, compounds that target these mechanisms may have a therapeutic effect on walking performance in PAD patients. Phytochemicals produced by plants have been widely studied for their potential health effects and role in various diseases including cardiovascular disease and cancer. In this review, we focus on PAD and discuss the evidence related to the clinical utility of different phytochemicals. We discuss phytochemical research in preclinical models of PAD, and we highlight the results of the available clinical trials that have assessed the effects of these compounds on PAD patient functional outcomes.

Can athletes be tough yet compassionate to themselves? Practical implications for NCAA mental health best practice no. 4

Recent tragic events and data from official NCAA reports suggest student-athletes' well-being is compromised by symptoms of mental health (MH) disorders. Self-compassion (SC) and mental toughness (MT) are two psychological constructs that have been shown effective against stressors associated with sports. The purpose of this study was to investigate SC, MT, and MH in a NCAA environment for the first time and provide practical suggestions for MH best practice No.4. In total, 542 student-athletes participated across Divisions (M_age = 19.84, SD = 1.7). Data were collected through Mental Toughness Index, Self-Compassion Scale, and Mental Health Continuum–Short Form. MT, SC (including mindfulness), and MH were positively correlated. Males scored higher than females on all three scales. No differences were found between divisions. SC partially mediated the MT-MH relationship, but moderation was not significant. Working towards NCAA MH best practice should include training athletes in both MT and SC skills (via mindfulness).

Developing and training mental toughness in sport: a systematic review and meta-analysis of observational studies and pre-test and post-test experiments

Objective

To investigate the efficacy of interventions designed to train and develop mental toughness (MT) in sport.

Design

Systematic review and meta-analysis.

Data sources

Journal articles, conference papers and doctoral theses indexed in Embase, Scopus, PubMed and SPORTDiscus from inception to 22 November 2019.

Eligibility criteria for selecting studies

Observational and pre–post experimental designs on the efficacy of physical and/or psychological interventions designed to promote MT in athletes.

Results

A total of 12 studies, published between 2005 and 2019, were included in the review. A majority of the studies included a sample comprised exclusively of male athletes (54.55%), MT interventions were primarily psychological (83.33%) and most studies measured MT via self-report (75%). The Psychological Performance Inventory (25%), the Mental Toughness Questionnaire-48 (16.67%), and the Mental, Emotional and Bodily Toughness Inventory (16.67%) were the most popular inventories used to measure MT. Methodological quality assessments for controlled intervention studies (k=7), single group pre-test–post-test designs (k=4) and single-subject designs (k=1) indicated that the risk of bias was high in most (75%) of the studies. The meta-analysis involving k=10 studies revealed a large effect (d=0.80, 95% CI 0.30 to 1.28), with variability across studies estimated at 0.56.

Conclusion

Although the findings of this review suggest there are effective, empirically based interventions designed to train MT in sport, practitioners should be aware of the level of validity of intervention research before adopting any of the MT training programmes reported in the applied sport psychology literature.