Impact of obesity on the molecular response to a single bout of exercise in a preliminary human cohort.

OBJECTIVE: The health benefits of exercise are well documented, but several exercise-response parameters are attenuated in individuals with obesity. The goal of this pilot study was to identify molecular mechanisms that may influence exercise response with obesity. METHODS: A multi-omics comparison of the transcriptome, proteome, and phosphoproteome in muscle from a preliminary cohort of lean individuals (n = 4) and individuals with obesity (n = 4) was performed, before and after a single bout of 30 minutes of unilateral cycling at 70% maximal oxygen uptake (VO2 peak). Mass spectrometry and RNA sequencing were used to interrogate the proteome, phosphoproteome, and transcriptome from muscle biopsy tissue. RESULTS: The main findings are that individuals with obesity exhibited transcriptional and proteomic signatures consistent with reduced mitochondrial function, protein synthesis, and glycogen synthesis. Furthermore, individuals with obesity demonstrated markedly different transcriptional, proteomic, and phosphoproteomic responses to exercise, particularly biosynthetic pathways of glycogen synthesis and protein synthesis. Casein kinase II subunit alpha and glycogen synthase kinase-3ß signaling was identified as exercise-response pathways that were notably altered by obesity. CONCLUSIONS: Opportunities to enhance exercise responsiveness by targeting specific molecular pathways that are disrupted in skeletal muscle from individuals with obesity await a better understanding of the precise molecular mechanisms that may limit exercise-response pathways in obesity.

Skeletal muscle mitochondrial dysfunction and muscle and whole body functional deficits in cancer patients with weight loss.

Reductions in skeletal muscle mass and function are often reported in patients with cancer-associated weight loss and are associated with reduced quality of life, impaired treatment tolerance, and increased mortality. Although cellular changes, including altered mitochondrial function, have been reported in animals, such changes have been incompletely characterized in humans with cancer. Whole body and skeletal muscle physical function, skeletal muscle mitochondrial function, and whole body protein turnover were assessed in eight patients with cancer-associated weight loss (10.1 ± 4.2% body weight over 6-12 mo) and 19 age-, sex-, and body mass index (BMI)-matched healthy controls to characterize skeletal muscle changes at the whole body, muscle, and cellular level. Potential pathways involved in cancer-induced alterations in metabolism and mitochondrial function were explored by interrogating skeletal muscle and plasma metabolomes. Despite similar lean mass compared with control participants, patients with cancer exhibited reduced habitual physical activity (57% fewer daily steps), cardiorespiratory fitness [22% lower V̇o2peak (mL/kg/min)] and leg strength (35% lower isokinetic knee extensor strength), and greater leg neuromuscular fatigue (36% greater decline in knee extensor torque). Concomitant with these functional declines, patients with cancer had lower mitochondrial oxidative capacity [25% lower State 3 O2 flux (pmol/s/mg tissue)] and ATP production [23% lower State 3 ATP production (pmol/s/mg tissue)] and alterations in phospholipid metabolite profiles indicative of mitochondrial abnormalities. Whole body protein turnover was unchanged. These findings demonstrate mitochondrial abnormalities concomitant with whole body and skeletal muscle functional derangements associated with human cancer, supporting future work studying the role of mitochondria in the muscle deficits associated with cancer.NEW & NOTEWORTHY To our knowledge, this is the first study to suggest that skeletal muscle mitochondrial deficits are associated with cancer-associated weight loss in humans. Mitochondrial deficits were concurrent with reductions in whole body and skeletal muscle functional capacity. Whether mitochondrial deficits are causal or secondary to cancer-associated weight loss and functional deficits remains to be determined, but this study supports further exploration of mitochondria as a driver of cancer-associated losses in muscle mass and function.

Adipose tissue macrophage populations and inflammation are associated with systemic inflammation and insulin resistance in obesity.

Obesity is accompanied by numerous systemic and tissue-specific derangements, including systemic inflammation, insulin resistance, and mitochondrial abnormalities in skeletal muscle. Despite growing recognition that adipose tissue dysfunction plays a role in obesity-related disorders, the relationship between adipose tissue inflammation and other pathological features of obesity is not well-understood. We assessed macrophage populations and measured the expression of inflammatory cytokines in abdominal adipose tissue biopsies in 39 nondiabetic adults across a range of body mass indexes (BMI 20.5-45.8 kg/m2). Skeletal muscle biopsies were used to evaluate mitochondrial respiratory capacity, ATP production capacity, coupling, and reactive oxygen species production. Insulin sensitivity (SI) and ß cell responsivity were determined from test meal postprandial glucose, insulin, c-peptide, and triglyceride kinetics. We examined the relationships between adipose tissue inflammatory markers, systemic inflammatory markers, SI, and skeletal muscle mitochondrial physiology. BMI was associated with increased adipose tissue and systemic inflammation, reduced SI, and reduced skeletal muscle mitochondrial oxidative capacity. Adipose-resident macrophage numbers were positively associated with circulating inflammatory markers, including tumor necrosis factor-α (TNFα) and C-reactive protein (CRP). Local adipose tissue inflammation and circulating concentrations of TNFα and CRP were negatively associated with SI, and circulating concentrations of TNFα and CRP were also negatively associated with skeletal muscle oxidative capacity. These results demonstrate that obese humans exhibit increased adipose tissue inflammation concurrently with increased systemic inflammation, reduced insulin sensitivity, and reduced muscle oxidative capacity and suggest that adipose tissue and systemic inflammation may drive obesity-associated metabolic derangements.NEW AND NOTEWORTHY Adipose inflammation is proposed to be at the nexus of the systemic inflammation and metabolic derangements associated with obesity. The present study provides evidence to support adipose inflammation as a central feature of the pathophysiology of obesity. Adipose inflammation is associated with systemic and peripheral metabolic derangements, including increased systemic inflammation, reduced insulin sensitivity, and reduced skeletal muscle mitochondrial respiration.

The effects of ß1 and ß1+2 adrenergic receptor blockade on the exercise-induced mobilization and ex vivo expansion of virus-specific T cells: implications for cellular therapy and the anti-viral immune effects of exercise.

The adoptive transfer of donor-derived virus-specific T cells (VSTs) is an effective treatment for infections following allogeneic hematopoietic cell transplantation. Acute exercise mobilizes effector lymphocytes and VSTs to the circulation and augments the ex vivo manufacture of VSTs. This study determined if ß2 adrenergic receptor (AR) signaling precipitated the VST response to acute exercise. Healthy participants (n = 12) completed 30 min of steady-state cycling exercise after ingesting a placebo, a ß1 + 2 AR antagonist (nadolol) or a ß1 AR antagonist (bisoprolol). Circulating VSTs to cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus (AdV) antigens were enumerated before and after exercise, and peripheral blood mononuclear cells were cultured with viral peptides for 8 days to expand multi-VSTs. Compared with placebo, nadolol blunted the exercise-induced mobilization of CMV-VSTs (Δ VSTs/100,000 CD3+ T cells = 93 ± 104 vs. 22 ± 91 for placebo and nadolol, respectively; p = 0.036), while bisoprolol did not, despite both drugs evoking similar reductions in exercising heart rate and blood pressure. Circulating AdV and EBV VSTs (VSTs/mL blood) only increased after exercise with placebo. Although not significant, nadolol partially mitigated exercise-induced increases in multi-VST expansion, particularly in participants that demonstrated an exercise-induced increase in VST expansion. We conclude that exercise-induced enhancements in VST mobilization and expansion are at least partially ß2 AR mediated, thus highlighting a role for the ß2 AR in targeted therapy for the augmentation of VST immune cell therapeutics in the allogeneic adoptive transfer setting. Moreover, long-term regular exercise may provide additional viral protection in the host through frequent ß2 AR-dependent mobilization and redistribution of VSTs cumulated with each bout of exercise.

Methylarginine metabolites are associated with attenuated muscle protein synthesis in cancer-associated muscle wasting.

Cancer cachexia is characterized by reductions in peripheral lean muscle mass. Prior studies have primarily focused on increased protein breakdown as the driver of cancer-associated muscle wasting. Therapeutic interventions targeting catabolic pathways have, however, largely failed to preserve muscle mass in cachexia, suggesting that other mechanisms might be involved. In pursuit of novel pathways, we used untargeted metabolomics to search for metabolite signatures that may be linked with muscle atrophy. We injected 7-week-old C57/BL6 mice with LLC1 tumor cells or vehicle. After 21 days, tumor-bearing mice exhibited reduced body and muscle mass and impaired grip strength compared with controls, which was accompanied by lower synthesis rates of mixed muscle protein and the myofibrillar and sarcoplasmic muscle fractions. Reductions in protein synthesis were accompanied by mitochondrial enlargement and reduced coupling efficiency in tumor-bearing mice. To generate mechanistic insights into impaired protein synthesis, we performed untargeted metabolomic analyses of plasma and muscle and found increased concentrations of two methylarginines, asymmetric dimethylarginine (ADMA) and NG-monomethyl-l-arginine, in tumor-bearing mice compared with control mice. Compared with healthy controls, human cancer patients were also found to have higher levels of ADMA in the skeletal muscle. Treatment of C2C12 myotubes with ADMA impaired protein synthesis and reduced mitochondrial protein quality. These results suggest that increased levels of ADMA and mitochondrial changes may contribute to impaired muscle protein synthesis in cancer cachexia and could point to novel therapeutic targets by which to mitigate cancer cachexia.

NK cell function is impaired during long-duration spaceflight.

Maintaining astronaut health during space travel is paramount for further human exploration of the solar system beyond Earth's orbit. Of concern are potential dysregulations in immunity, which could increase the likelihood of cancer and latent viral reactivation. Natural killer (NK) cells are critical effectors of the innate immune system, and their function and phenotype are important to immunosurveillance of nascent tumors and latent viral infections. We compared changes in NK cell phenotype and function in eight crew members who completed an ~6-mo mission to the International Space Station (ISS) with healthy controls who remained on Earth. Assessments were made before (180 and 60 days before launch), during [flight day + 90 days (FD+90) and 1 day before return (R-1)], and after the mission (at R+0, R+18, R+33, and R+66). These samples, plus an additional in-flight sample (FD+180), were collected from a crew member who spent 340 days (~1 yr) on the ISS. NK cell cytotoxic activity (NKCA) against K562 leukemia targets in vitro was reduced by ~50% at FD+90 in ISS crew but not controls. This decrease was more pronounced in "rookie" compared with "veteran" crew members. The ~1-yr mission crew member did not show declines in NKCA against K562 until late in the mission (R-1 and R+0). NK cell numbers, expression of activating and inhibitory receptors, target cell binding, and expression and degranulation of perforin and granzyme B were unaltered with spaceflight. Similarly, when we exposed an immortalized NK cell line (NK-92) to sera collected at different mission time points (before, during, and after flight), there was no effect on NKCA. This is the first study to report impaired NK cell function during long-duration space travel. Countermeasures may be needed to mitigate immune system impairment in exploration class mission crew during long-duration spaceflight missions. NEW & NOTEWORTHY Immune system impairment may inhibit future human space exploration missions to Mars. Natural killer (NK) cells are key components of immunity and vital for tumor surveillance and the prevention of latent virus reactivation. We report that NK cell function is impaired in astronauts during an ~6-mo orbital space mission compared with preflight levels and ground-based controls. Declines in NK cell function were more marked in first-time "rookie" fliers. Countermeasures are needed to preserve NK cell-mediated immunity during spaceflight.

A single exercise bout augments adenovirus-specific T-cell mobilization and function.

Adoptive transfer of virus-specific T-cells (VSTs) effectively treats viral infections following allogeneic hematopoietic stem cell transplantation (alloHSCT), but logistical difficulties have limited widespread availability of VSTs as a post-transplant therapeutic. A single exercise bout mobilizes VSTs specific for latent herpesviruses (i.e. CMV and EBV) to peripheral blood and augments their ex vivo expansion. We investigated whether exercise exerts similar effects on T-cells specific for a NON-latent virus such as adenovirus, which is a major contributor to infection-related morbidity and mortality after alloHSCT. Thirty minutes of cycling exercise increased circulating adenovirus-specific T-cells 2.0-fold and augmented their ex vivo expansion by ~33% compared to rest without altering antigen and MHC-specific autologous target cell killing capabilities. We conclude that exercise is a simple and economical adjuvant to boost the isolation and manufacture of therapeutic VSTs specific to latent and non-latent viruses from healthy donors.

Vigorous exercise mobilizes CD34+ hematopoietic stem cells to peripheral blood via the ß2-adrenergic receptor.

Acute dynamic exercise mobilizes CD34+ hematopoietic stem cells (HSCs) to the bloodstream, potentially serving as an economical adjuvant to boost the collection of HSCs from stem cell transplant donors. The mechanisms responsible for HSC mobilization with exercise are unknown but are likely due to hemodynamic perturbations, endogenous granulocyte-colony stimulating factor (G-CSF), and/or ß2-adrenergic receptor (ß2-AR) signaling. We characterized the temporal response of HSC mobilization and plasma G-CSF following exercise, and determined the impact of in vivo ß-AR blockade on the exercise-induced mobilization of HSCs. Healthy runners (n = 15) completed, in balanced order, two single bouts of steady state treadmill running exercise at moderate (lasting 90-min) or vigorous (lasting 30-min) intensity. A separate cohort of healthy cyclists (n = 12) completed three 30-min cycling ergometer trials at vigorous intensity after ingesting: (i) 10 mg bisoprolol (ß1-AR antagonist); (ii) 80 mg nadolol (ß1 + ß2-AR antagonist); or (iii) placebo, in balanced order with a double-blind design. Blood samples collected before, during (runners only), immediately after, and at several points during exercise recovery were used to determine circulating G-CSF levels (runners only) and enumerate CD34+ HSCs by flow cytometry (runners and cyclists). Steady state vigorous but not moderate intensity exercise mobilized HSCs, increasing the total blood CD34+ count by ∼4.15 ±â€¯1.62 Δcells/µl (+202 ±â€¯92%) compared to resting conditions. Plasma G-CSF increased in response to moderate but not vigorous exercise. Relative to placebo, nadolol and bisoprolol lowered exercising heart rate and blood pressure to comparable levels. The number of CD34+ HSCs increased with exercise after the placebo and bisoprolol trials, but not the nadolol trial, suggesting ß2-AR signaling mediated the mobilization of CD34+ cells [Placebo: 2.10 ±â€¯1.16 (207 ±â€¯69.2%), Bisoprolol 1.66 ±â€¯0.79 (+163 ±â€¯29%), Nadolol: 0.68 ±â€¯0.54 (+143 ±â€¯36%) Δcells/µL]. We conclude that the mobilization of CD34+ HSCs with exercise is not dependent on circulating G-CSF and is likely due to the combined actions of ß2-AR signaling and hemodynamic shear stress.