Comparative Analysis of Circulating Metabolomic Profiles Identifies Shared Metabolic Alterations Across Distinct Multi-Stressor Military Training Operations.

Military training provides insight into metabolic responses under unique physiological demands that can be comprehensively characterized by global metabolomic profiling to identify potential strategies for improving performance. This study identified shared changes in metabolomic profiles across three distinct military training exercises varying in magnitude and types of stress. Blood samples collected before and after three real or simulated military training exercises were analyzed using the same untargeted metabolomic profiling platform. Exercises included a three-week survival school course (ST, n=36), a four-day arctic cross country ski march (AT, n=24), and a 28-day controlled diet- and exercise-induced energy deficit (CED, n=26). Log2-fold changes of >±1 in 191, 121 and 64 metabolites were identified in the ST, AT and CED datasets, respectively. Most metabolite changes were within lipid (57-63%) and amino acid metabolism (18-19%) pathways, and changes in 87 were shared across studies. The largest and most consistent increases in shared metabolites were found in acylcarnitine, fatty acid, ketone, and glutathione metabolism pathways, whereas the largest decreases were in diacylglycerol and urea cycle metabolism pathways. Multiple shared metabolites were consistently correlated with biomarkers of inflammation, tissue damage, and anabolic hormones across studies. These three studies of real and simulated military training revealed overlapping alterations in metabolomic profiles despite differences in environment and the stressors involved. Consistent changes in metabolites related to lipid metabolism, ketogenesis and oxidative stress suggest a potential common metabolomic signature associated with inflammation, tissue damage and suppression of anabolic signaling that may characterize unique physiological demands of military training.

In Vitro Fermentation Shows Polyphenol and Fiber Blends Have an Additive Beneficial Effect on Gut Microbiota States.

Polyphenols and fermentable fibers have shown favorable effects on gut microbiota composition and metabolic function. However, few studies have investigated whether combining multiple fermentable fibers or polyphenols may have additive beneficial effects on gut microbial states. Here, an in vitro fermentation model, seeded with human stool combined from 30 healthy volunteers, was supplemented with blends of polyphenols (PP), dietary fibers (FB), or their combination (PPFB) to determine influence on gut bacteria growth dynamics and select metabolite changes. PP and FB blends independently led to significant increases in the absolute abundance of select beneficial taxa, namely Ruminococcus bromii, Bifidobacterium spp., Lactobacillus spp., and Dorea spp. Total short-chain fatty acid concentrations, relative to non-supplemented control (F), increased significantly with PPFB and FB supplementation but not PP. Indole and ammonia concentrations decreased with FB and PPFB supplementation but not PP alone while increased antioxidant capacity was only evident with both PP and PPFB supplementation. These findings demonstrated that, while the independent blends displayed selective positive impacts on gut states, the combination of both blends provided an additive effect. The work outlines the potential of mixed substrate blends to elicit a broader positive influence on gut microbial composition and function to build resiliency toward dysbiosis.

Effects of testosterone enanthate on aggression, risk-taking, competition, mood, and other cognitive domains during 28 days of severe energy deprivation.

RATIONALE: Behavioral effects of testosterone depend on dose, acute versus sustained formulation, duration of administration, personality, genetics, and endogenous levels of testosterone. There are also considerable differences between effects of endogenous and exogenous testosterone. OBJECTIVES: This study was the secondary behavioral arm of a registered clinical trial designed to determine if testosterone protects against loss of lean body mass and lower-body muscle function induced by a severe energy deficit typical of sustained military operations. METHODS: Behavioral effects of repeated doses of testosterone on healthy young men whose testosterone was reduced by severe energy deficit were examined. This was a double-blind, placebo-controlled, between-group study. Effects of four weekly intramuscular injections of testosterone enanthate (200 mg/week, N = 24) or matching placebo (N = 26) were evaluated. Determination of sample size was based on changes in lean body mass. Tasks assessing aggression, risk-taking, competition, social cognition, vigilance, memory, executive function, and mood were repeatedly administered. RESULTS: During a period of artificially induced, low testosterone levels, consistent behavioral effects of administration of exogenous testosterone were not observed. CONCLUSIONS: Exogeneous testosterone enanthate (200 mg/week) during severe energy restriction did not reliably alter the measures of cognition. Study limitations include the relatively small sample size compared to many studies of acute testosterone administration. The findings are specific to healthy males experiencing severe energy deficit and should not be generalized to effects of other doses, formulations, or acute administration of endogenous testosterone or studies conducted with larger samples using tests of cognitive function designed to detect specific effects of testosterone.

Meeting report of the sixth annual tri-service microbiome consortium symposium.

The Tri-Service Microbiome Consortium (TSMC) was founded to enhance collaboration, coordination, and communication of microbiome research among DoD organizations and to facilitate resource, material and information sharing amongst consortium members, which includes collaborators in academia and industry. The 6th Annual TSMC Symposium was a hybrid meeting held in Fairlee, Vermont on 27-28 September 2022 with presentations and discussions centered on microbiome-related topics within seven broad thematic areas: (1) Human Microbiomes: Stress Response; (2) Microbiome Analysis & Surveillance; (3) Human Microbiomes Enablers & Engineering; (4) Human Microbiomes: Countermeasures; (5) Human Microbiomes Discovery - Earth & Space; (6) Environmental Micro & Myco-biome; and (7) Environmental Microbiome Analysis & Engineering. Collectively, the symposium provided an update on the scope of current DoD microbiome research efforts, highlighted innovative research being done in academia and industry that can be leveraged by the DoD, and fostered collaborative opportunities. This report summarizes the activities and outcomes from the 6th annual TSMC symposium.

Active ascent accelerates the time course but not the overall incidence and severity of acute mountain sickness at 3,600 m.

Acute mountain sickness (AMS) typically peaks following the first night at high altitude (HA) and resolves over the next 2-3 days, but the impact of active ascent on AMS is debated. To determine the impact of ascent conditions on AMS, 78 healthy Soldiers (means ± SD; age = 26 ± 5 yr) were tested at baseline residence, transported to Taos, NM (2,845 m), hiked (n = 39) or were driven (n = 39) to HA (3,600 m), and stayed for 4 days. AMS-cerebral (AMS-C) factor score was assessed at HA twice on day 1 (HA1), five times on days 2 and 3 (HA2 and HA3), and once on day 4 (HA4). If AMS-C was ≥0.7 at any assessment, individuals were AMS susceptible (AMS+; n = 33); others were nonsusceptible (AMS-; n = 45). Daily peak AMS-C scores were analyzed. Ascent conditions (active vs. passive) did not impact the overall incidence and severity of AMS at HA1-HA4. The AMS+ group, however, demonstrated a higher (P < 0.05) AMS incidence in the active vs. passive ascent cohort on HA1 (93% vs. 56%), similar incidence on HA2 (60% vs. 78%), lower incidence (P < 0.05) on HA3 (33% vs. 67%), and similar incidence on HA4 (13% vs. 28%). The AMS+ group also demonstrated a higher (P < 0.05) AMS severity in the active vs. passive ascent cohort on HA1 (1.35 ± 0.97 vs. 0.90 ± 0.70), similar score on HA2 (1.00 ± 0.97 vs. 1.34 ± 0.70), and lower (P < 0.05) score on HA3 (0.56 ± 0.55 vs. 1.02 ± 0.75) and HA4 (0.32 ± 0.41 vs. 0.60 ± 0.72). Active compared with passive ascent accelerated the time course of AMS with more individuals sick on HA1 and less individuals sick on HA3 and HA4.NEW & NOTEWORTHY This research demonstrated that active ascent accelerated the time course but not overall incidence and severity of acute mountain sickness (AMS) following rapid ascent to 3,600 m in unacclimatized lowlanders. Active ascenders became sicker faster and recovered quicker than passive ascenders, which may be due to differences in body fluid regulation. Findings from this well-controlled large sample-size study suggest that previously reported discrepancies in the literature regarding the impact of exercise on AMS may be related to differences in the timing of AMS measurements between studies.

Biomarkers of oxidative stress, diet and exercise distinguish soldiers selected and non-selected for special forces training.

INTRODUCTION: The metabolomic profiles of Soldiers entering the U.S. Special Forces Assessment and Selection course (SFAS) have not been evaluated. OBJECTIVES: To compare pre-SFAS blood metabolomes of Soldiers selected during SFAS versus those not selected, and explore the relationships between the metabolome, physical performance, and diet quality. METHODS: Fasted blood samples and food frequency questionnaires were collected from 761 Soldiers prior to entering SFAS to assess metabolomic profiles and diet quality, respectively. Physical performance was assessed throughout SFAS. RESULTS: Between-group differences (False Discovery Rate < 0.05) in 108 metabolites were detected. Selected candidates had higher levels of compounds within xenobiotic, pentose phosphate, and corticosteroid metabolic pathways, while non-selected candidates had higher levels of compounds potentially indicative of oxidative stress (i.e., sphingomyelins, acylcarnitines, glutathione, amino acids). Multiple compounds higher in non-selected versus selected candidates included: 1-carboxyethylphenylalanine; 4-hydroxy-nonenal-glutathione; α-hydroxyisocaproate; hexanoylcarnitine; sphingomyelin and were associated with lower diet quality and worse physical performance.  CONCLUSION: Candidates selected during SFAS had higher pre-SFAS levels of circulating metabolites that were associated with resistance to oxidative stress, higher physical performance and higher diet quality. In contrast, non-selected candidates had higher levels of metabolites potentially indicating elevated oxidative stress. These findings indicate that Soldiers who were selected for continued Special Forces training enter the SFAS course with metabolites associated with healthier diets and better physical performance. Additionally, the non-selected candidates had higher levels of metabolites that may indicate elevated oxidative stress, which could result from poor nutrition, non-functional overreaching/overtraining, or incomplete recovery from previous physical activity.

Sex differences in body composition and serum metabolome responses to sustained, physical training suggest enhanced fat oxidation in women compared with men.

Sex differences in energy metabolism during acute, submaximal exercise are well documented. Whether these sex differences influence metabolic and physiological responses to sustained, physically demanding activities is not well characterized. This study aimed to identify sex differences within changes in the serum metabolome in relation to changes in body composition, physical performance, and circulating markers of endocrine and metabolic status during a 17-day military training exercise. Blood was collected, and body composition and lower body power were measured before and after the training on 72 cadets (18 women). Total daily energy expenditure (TDEE) was assessed using doubly labeled water in a subset throughout. TDEE was greater in men (4,085 ± 482 kcal/d) than in women (2,982 ± 472 kcal/d, P < 0.001), but not after adjustment for dry lean mass (DLM). Men tended to lose more DLM than women (mean change [95% CI]: -0.2[-0.3, -0.1] vs. -0.0[-0.0, 0.0] kg, P = 0.063, Cohen's d = 0.50) and have greater reductions in lower body power (-244[-314, -174] vs. -130[-209, -51] W, P = 0.085, d = 0.49). Reductions in DLM and lower body power were correlated (r = 0.325, P = 0.006). Women demonstrated greater fat oxidation than men (Δfat mass/DLM: -0.20[-0.24, -0.17] vs. -0.15[-0.17, -0.13] kg, P = 0.012, d = 0.64). Metabolites within pathways of fatty acid, endocannabinoid, lysophospholipid, phosphatidylcholine, phosphatidylethanolamine, and plasmalogen metabolism increased in women relative to men. Independent of sex, changes in metabolites related to lipid metabolism were inversely associated with changes in body mass and positively associated with changes in endocrine and metabolic status. These data suggest that during sustained military training, women preferentially mobilize fat stores compared with men, which may be beneficial for mitigating loss of lean mass and lower body power.NEW & NOTEWORTHY Women preferentially mobilize fat stores compared with men in response to sustained, physically demanding military training, as evidenced by increased lipid metabolites and enhanced fat oxidation, which may be beneficial for mitigating loss of lean mass and lower body power.

Ketone Monoester Plus Carbohydrate Supplementation Does Not Alter Exogenous and Plasma Glucose Oxidation or Metabolic Clearance Rate During Exercise in Men Compared with Carbohydrate Alone.

BACKGROUND: Increasing ß-hydroxybutyrate (ßHB) availability through ketone monoester (KE) plus carbohydrate supplementation is suggested to enhance physical performance by sparing glucose use during exercise. However, no studies have examined the effect of ketone supplementation on glucose kinetics during exercise. OBJECTIVES: This exploratory study primarily aimed to determine the effect of KE plus carbohydrate supplementation on glucose oxidation during steady-state exercise and physical performance compared with carbohydrate alone. METHODS: Using a randomly assigned, crossover design, 12 men consumed 573 mg KE/kg body mass plus 110 g glucose (KE+CHO) or 110 g glucose (CHO) before and during 90 min of steady-state treadmill exercise [54 ± 3% peak oxygen uptake (V˙O2peak)] wearing a weighted vest (30% body mass; 25 ± 3 kg). Glucose oxidation and turnover were determined using indirect calorimetry and stable isotopes. Participants performed an unweighted time to exhaustion (TTE; 85% V˙O2peak) after steady-state exercise and a weighted (25 ± 3 kg) 6.4 km time trial (TT) the next day after consuming a bolus of KE+CHO or CHO. Data were analyzed by paired t-tests and mixed model ANOVA. RESULTS: ßHB concentrations were higher (P < 0.05) after exercise [2.1 mM (95% CI: 1.6, .6)] and the TT [2.6 mM (2.1, 3.1)] in KE+CHO compared with CHO. TTE was lower [-104 s (-201, -8)], and TT performance was slower [141 s (19,262)] in KE+CHO than in CHO (P < 0.05). Exogenous [-0.01 g/min (-0.07, 0.04)] and plasma [-0.02 g/min (-0.08, 0.04)] glucose oxidation and metabolic clearance rate {MCR [0.38 mg·kg-1·min-1 (-0.79, 1.54)]} were not different, and glucose rate of appearance [-0.51 mg·kg-1·min-1 (-0.97, -0.04)], and disappearance [-0.50 mg·kg-1·min-1 (-0.96, -0.04)] were lower (P < 0.05) in KE+CHO compared with CHO during steady-state exercise. CONCLUSIONS: In the current study, rates of exogenous and plasma glucose oxidation and MCR were not different between treatments during steady-state exercise, suggesting blood glucose utilization is similar between KE+CHO and CHO. KE+CHO supplementation also results in lower physical performance compared with CHO alone. This trial was registered at www. CLINICALTRIALS: gov as NCT04737694.

Orally Ingested Probiotic, Prebiotic, and Synbiotic Interventions as Countermeasures for Gastrointestinal Tract Infections in Nonelderly Adults: A Systematic Review and Meta-Analysis.

Meta-analyses have not examined the prophylactic use of orally ingested probiotics, prebiotics, and synbiotics for preventing gastrointestinal tract infections (GTIs) of various etiologies in adult populations, despite evidence that these gut microbiota-targeted interventions can be effective in treating certain GTIs. This systematic review and meta-analysis aimed to estimate the effects of prophylactic use of orally ingested probiotics, prebiotics, and synbiotics on GTI incidence, duration, and severity in nonelderly, nonhospitalized adults. CENTRAL, PubMed, Scopus, and Web of Science were searched through January 2022. English-language, peer-reviewed publications of randomized, placebo-controlled studies testing an orally ingested probiotic, prebiotic, or synbiotic intervention of any dose for ≥1 wk in adults who were not hospitalized, immunosuppressed, or taking antibiotics were included. Results were analyzed using random-effects meta-analyses of intention-to-treat (ITT) and complete case (CC) cohorts. Heterogeneity was explored by subgroup meta-analysis and meta-regression. The risk of bias was assessed using the Cochrane risk-of-bias 2 tool. Seventeen publications reporting 20 studies of probiotics (n = 16), prebiotics (n = 3), and synbiotics (n = 1) were identified (n > 6994 subjects). In CC and ITT analyses, risk of experiencing ≥1 GTI was reduced with probiotics (CC analysis-risk ratio: 0.86; 95% CI: 0.73, 1.01) and prebiotics (risk ratio: 0.80; 95% CI: 0.66, 0.98). No effects on GTI duration or severity were observed. Sources of heterogeneity included the study population and number of probiotic strains administered but were often unexplained, and a high risk of bias was observed for most studies. The specific effects of individual probiotic strains and prebiotic types could not be assessed owing to a lack of confirmatory studies. Findings indicated that both orally ingested probiotics and prebiotics, relative to placebo, demonstrated modest benefit for reducing GTI risk in nonelderly adults. However, results should be interpreted cautiously owing to the low number of studies, high risk of bias, and unexplained heterogeneity that may include probiotic strain-specific or prebiotic-specific effects. This review was registered at PROSPERO as CRD42020200670.

Characterizing Relationships Among the Cognitive, Physical, Social-emotional, and Health-related Traits of Military Personnel.

INTRODUCTION: Personnel engaged in high-stakes occupations, such as military personnel, law enforcement, and emergency first responders, must sustain performance through a range of environmental stressors. To maximize the effectiveness of military personnel, an a priori understanding of traits can help predict their physical and cognitive performance under stress and adversity. This work developed and assessed a suite of measures that have the potential to predict performance during operational scenarios. These measures were designed to characterize four specific trait-based domains: cognitive, health, physical, and social-emotional. MATERIALS AND METHODS: One hundred and ninety-one active duty U.S. Army soldiers completed interleaved questionnaire-based, seated task-based, and physical task-based measures over a period of 3-5 days. Redundancy analysis, dimensionality reduction, and network analyses revealed several patterns of interest. RESULTS: First, unique variable analysis revealed a minimally redundant battery of instruments. Second, principal component analysis showed that metrics tended to cluster together in three to five components within each domain. Finally, analyses of cross-domain associations using network analysis illustrated that cognitive, health, physical, and social-emotional domains showed strong construct solidarity. CONCLUSIONS: The present battery of metrics presents a fieldable toolkit that may be used to predict operational performance that can be clustered into separate components or used independently. It will aid predictive algorithm development aimed to identify critical predictors of individual military personnel and small-unit performance outcomes.

Severe, short-term sleep restriction reduces gut microbiota community richness but does not alter intestinal permeability in healthy young men.

Sleep restriction alters gut microbiota composition and intestinal barrier function in rodents, but whether similar effects occur in humans is unclear. This study aimed to determine the effects of severe, short-term sleep restriction on gut microbiota composition and intestinal permeability in healthy adults. Fecal microbiota composition, measured by 16S rRNA sequencing, and intestinal permeability were measured in 19 healthy men (mean ± SD; BMI 24.4 ± 2.3 kg/m2, 20 ± 2 years) undergoing three consecutive nights of adequate sleep (AS; 7-9 h sleep/night) and restricted sleep (SR; 2 h sleep/night) in random order with controlled diet and physical activity. α-diversity measured by amplicon sequencing variant (ASV) richness was 21% lower during SR compared to AS (P = 0.03), but α-diversity measured by Shannon and Simpson indexes did not differ between conditions. Relative abundance of a single ASV within the family Ruminococcaceae was the only differentially abundant taxon (q = 0.20). No between-condition differences in intestinal permeability or ß-diversity were observed. Findings indicated that severe, short-term sleep restriction reduced richness of the gut microbiota but otherwise minimally impacted community composition and did not affect intestinal permeability in healthy young men.

In vitro gut microbiome response to carbohydrate supplementation is acutely affected by a sudden change in diet.

BACKGROUND: Interactions between diet, stress and the gut microbiome are of interest as a means to modulate health and performance. Here, in vitro fermentation was used to explore the effects of a sudden change in diet, 21 days sole sustenance on the Meal, Ready-to-Eat (MRE) U.S. military combat ration, on inter-species competition and functional potential of the human gut microbiota. Human fecal samples collected before and after MRE intervention or consuming a habitual diet (HAB) were introduced to nutrient-rich media supplemented with starch for in vitro fermentation under ascending colon conditions. 16S rRNA amplicon and Whole-metagenome sequencing (WMS) were used to measure community composition and functional potential. Specific statistical analyses were implemented to detect changes in relative abundance from taxa, genes and pathways. RESULTS: Differential changes in relative abundance of 11 taxa, Dorea, Lachnospira, Bacteroides fragilis, Akkermansia muciniphila, Bifidobacterium adolescentis, Betaproteobacteria, Enterobacteriaceae, Bacteroides egerthii, Ruminococcus bromii, Prevotella, and Slackia, and nine Carbohydrate-Active Enzymes, specifically GH13_14, over the 24 h fermentation were observed as a function of the diet intervention and correlated to specific taxa of interest. CONCLUSIONS: These findings suggest that consuming MRE for 21 days acutely effects changes in gut microbiota structure in response to carbohydrate but may induce alterations in metabolic capacity. Additionally, these findings demonstrate the potential of starch as a candidate supplemental strategy to functionally modulate specific gut commensals during stress-induced states.

Changes in Immune Function during Initial Military Training.

PURPOSE: Initial military training (IMT) is a transitionary period wherein immune function may be suppressed and infection risk heightened due to physical and psychological stress, communal living, and sleep deprivation. This study characterized changes in biomarkers of innate and adaptive immune function, and potential modulators of those changes, in military recruits during IMT. METHODS: Peripheral leukocyte distribution and mitogen-stimulated cytokine profiles were measured in fasted blood samples, Epstein-Barr (EBV), varicella zoster (VZV), and herpes simplex 1 (HSV1) DNA was measured in saliva by quantitative polymerase chain reaction as an indicator of latent herpesvirus reactivation, and diet quality was determined using the healthy eating index measured by food frequency questionnaire in 61 US Army recruits (97% male) at the beginning (PRE) and end (POST) of 22-wk IMT. RESULTS: Lymphocytes and terminally differentiated cluster of differentiation (CD)4+ and CD8+ T cells increased PRE to POST, whereas granulocytes, monocytes, effector memory CD4+ and CD8+ T cells, and central memory CD8+ T cells decreased ( P ≤ 0.02). Cytokine responses to anti-CD3/CD28 stimulation were higher POST compared with PRE, whereas cytokine responses to lipopolysaccharide stimulation were generally blunted ( P < 0.05). Prevalence of EBV reactivation was higher at POST ( P = 0.04), but neither VZV nor HSV1 reactivation was observed. Diet quality improvements were correlated with CD8+ cell maturation and blunted proinflammatory cytokine responses to anti-CD3/CD28 stimulation. CONCLUSIONS: Lymphocytosis, maturation of T-cell subsets, and increased T-cell reactivity were evident POST compared with PRE IMT. Although EBV reactivation was more prevalent at POST, no evidence of VZV or HSV1 reactivation, which are more common during severe stress, was observed. Findings suggest increases in the incidence of EBV reactivation were likely appropriately controlled by recruits and immune-competence was not compromised at the end of IMT.

Effects of energy balance on cognitive performance, risk-taking, ambulatory vigilance and mood during simulated military sustained operations (SUSOPS).

Sustained operations (SUSOPS) require military personnel to conduct combat and training operations while experiencing physical and cognitive stress and limited sleep. These operations are often conducted in a state of negative energy balance and are associated with degraded cognitive performance and mood. Whether maintaining energy balance can mitigate these declines is unclear. This randomized crossover study assessed the effects of energy balance on cognitive performance, risk-taking propensity, ambulatory vigilance, and mood during a simulated 72-h SUSOPS. METHODS: Ten male Soldiers (mean ± SE; 22.4 ± 1.7 y; body weight 87.3 ± 1.1 kg) completed two, 72-h simulated SUSOPS in random order, separated by 7 days of recovery. Each SUSOPS elicited ∼4500 kcal/d total energy expenditure and restricted sleep to 4 h/night. During SUSOPS, participants consumed either an energy-balanced or restricted diet that induced a 43 ± 3% energy deficit. A cognitive test battery was administered each morning and evening to assess: vigilance, working memory, grammatical reasoning, risk-taking propensity, and mood. Real-time ambulatory vigilance was assessed each morning, evening, and night via a wrist-worn monitoring device. RESULTS: Participants exhibited heightened risk-taking propensity (p = 0.047) with lower self-reported self-control (p = 0.021) and fatigue (p = 0.013) during energy deficit compared to during energy balance. Vigilance accuracy (p < 0.001) and working memory (p = 0.040) performance decreased, and vigilance lapses increased (p < 0.001) during SUSOPS, but did not differ by diet. Percentage of correct responses to ambulatory vigilance stimuli varied during SUSOPS (p = 0.019) independent of diet, with generally poorer performance during the morning and night. Total mood disturbance (p = 0.001), fatigue (p < 0.001), tension (p = 0.003), and confusion (p = 0.036) increased whereas vigor decreased (p < 0.001) during SUSOPS, independent of diet. CONCLUSION: Prolonged physical activity combined with sleep restriction is associated with impaired vigilance, memory, and mood state. Under such conditions, maintaining energy balance prevents increased risk-taking and improves self-control, but does not improve other aspects of cognitive function or mood. Given the small sample in the present study, replication in a larger cohort is warranted.

Effect of exogenous testosterone in the context of energy deficit on risky choice: Behavioural and neural evidence from males.

Previous research has shown greater risk aversion when people make choices about lives than cash. We tested the hypothesis that compared to placebo, exogenous testosterone administration would lead to riskier choices about cash than lives, given testosterone's association with financial risk-taking and reward sensitivity. A double-blind, placebo-controlled, randomized trial was conducted to test this hypothesis (Clinical Trials Registry: NCT02734238, www.clinicaltrials.gov). We collected functional magnetic resonance imaging (fMRI) data from 50 non-obese males before and shortly after 28 days of severe exercise-and-diet-induced energy deficit, during which testosterone (200 mg testosterone enanthate per week in sesame oil) or placebo (sesame seed oil only) was administered. Because we expected circulating testosterone levels to be reduced due to severe energy deficit, testosterone administration served a restorative function to mitigate the impact of energy deficit on testosterone levels. The fMRI task involved making choices under uncertainty for lives and cash. We also manipulated whether the outcomes were presented as gains or losses. Consistent with prospect theory, we observed the reflection effect such that participants were more risk averse when outcomes were presented as gains than losses. Brain activation in the thalamus covaried with individual differences in exhibiting the reflection effect. Testosterone did not impact choice, but it increased sensitivity to negative feedback following risky choices. These results suggest that exogenous testosterone administration in the context of energy deficit can impact some aspects of risky choice, and that individual differences in the reflection effect engage a brain structure involved in processing emotion, reward and risk.

Effects of short-chain fatty acids on intestinal function in an enteroid model of hypoxia.

The healthy GI tract is physiologically hypoxic, but this may be perturbed by certain acute and chronic stressors that reduce oxygen availability systemically. Short-chain fatty acids have been shown to have beneficial effects on intestinal barrier function and inflammation. Therefore, our objective was to see whether short-chain fatty acids (SCFA) would improve GI barrier function, reduce production of pro-inflammatory cytokines, and increase the expression of genes regulating GI barrier function in enteroids exposed to hypoxia. Human duodenal enteroid monolayers were placed under hypoxia (1.0% O2) for 72 h with either 24, or 48 h pre-treatment with a high acetate ratio of SCFA's or high butyrate ratio or placed under hypoxia concurrently. Transepithelial electrical resistance (TEER) increased with SCFA pre-treatment, especially 48 h of pre-treatment and this was maintained through the first 48 h of hypoxia while cells saw barrier function dramatically decrease by 72 h of hypoxia exposure. Inflammatory protein secretion largely decreased with exposure to hypoxia, regardless of SCFA pre-treatment. Gene expression of several genes related to barrier function were decreased with exposure to hypoxia, and with concurrent and 24 h SCFA pre-treatment. However, 48 h SCFA pre-treatment with a high butyrate ratio increased expression of several metabolic and differentiation related genes. Overall, pre-treatment or concurrent treatment with SCFA mixtures were not able to overcome the negative impacts of hypoxia on intestinal function and cells ultimately still cannot be sustained under hypoxia for 72 h. However, 48 h pre-treatment maintains TEER for up to 48 h of hypoxia while upregulating several metabolic genes.

Metabolomics of testosterone enanthate administration during severe-energy deficit.

INTRODUCTION: Testosterone administration attenuates reductions in total body mass and lean mass during severe energy deficit (SED). OBJECTIVES: This study examined the effects of testosterone administration on the serum metabolome during SED. METHODS: In a double-blind, placebo-controlled clinical trial, non-obese men were randomized to receive 200-mg testosterone enanthate/wk (TEST) (n = 24) or placebo (PLA) (n = 26) during a 28-d inpatient, severe exercise- and diet-induced energy deficit. This study consisted of three consecutive phases. Participants were free-living and provided a eucaloric diet for 14-d during Phase 1. During Phase 2, participants were admitted to an inpatient unit, randomized to receive testosterone or placebo, and underwent SED for 28-d. During Phase 3, participants returned to their pre-study diet and physical activity habits. Untargeted metabolite profiling was conducted on serum samples collected during each phase. Body composition was measured using dual-energy X-ray absorptiometry after 11-d of Phase 1 and after 25-d of Phase 2 to determine changes in fat and lean mass. RESULTS: TEST had higher (Benjamini-Hochberg adjusted, q < 0.05) androgenic steroid and acylcarnitine, and lower (q < 0.05) amino acid metabolites after SED compared to PLA. Metabolomic differences were reversed by Phase 3. Changes in lean mass were associated (Bonferroni-adjusted, p < 0.05) with changes in androgenic steroid metabolites (r = 0.42-0.70), acylcarnitines (r = 0.37-0.44), and amino acid metabolites (r = - 0.36-- 0.37). Changes in fat mass were associated (p < 0.05) with changes in acylcarnitines (r = - 0.46-- 0.49) and changes in urea cycle metabolites (r = 0.60-0.62). CONCLUSION: Testosterone administration altered androgenic steroid, acylcarnitine, and amino acid metabolites, which were associated with changes in body composition during SED.

Orally Ingested Probiotics, Prebiotics, and Synbiotics as Countermeasures for Respiratory Tract Infections in Nonelderly Adults: A Systematic Review and Meta-Analysis.

The impact of gut microbiota-targeted interventions on the incidence, duration, and severity of respiratory tract infections (RTIs) in nonelderly adults, and factors moderating any such effects, are unclear. This systematic review and meta-analysis aimed to determine the effects of orally ingested probiotics, prebiotics, and synbiotics compared with placebo on RTI incidence, duration, and severity in nonelderly adults, and to identify potential sources of heterogeneity. Studies were identified by searching CENTRAL, PubMed, Scopus, and Web of Science up to December 2021. English-language, peer-reviewed publications of randomized, placebo-controlled studies that tested an orally ingested probiotic, prebiotic, or synbiotic intervention of any dose for ≥1 wk in adults aged 18-65 y were included. Results were synthesized using intention-to-treat and per-protocol random-effects meta-analysis. Heterogeneity was explored by subgroup meta-analysis and meta-regression. Risk of bias was assessed using the Cochrane risk-of-bias assessment tool for randomized trials version 2 (RoB2). Forty-two manuscripts reporting effects of probiotics (n = 38), prebiotics (n = 2), synbiotics (n = 1) or multiple -biotic types (n = 1) were identified (n = 9179 subjects). Probiotics reduced the risk of experiencing ≥1 RTI (relative risk = 0.91; 95% CI: 0.84, 0.98; P = 0.01), and total days (rate ratio = 0.77; 95% CI: 0.71, 0.83; P < 0.001), duration (Hedges' g = -0.23; 95% CI: -0.39, -0.08; P = 0.004), and severity (Hedges' g = -0.16; 95% CI: -0.29, -0.03; P = 0.02) of RTIs. Effects were relatively consistent across different strain combinations, doses, and durations, although reductions in RTI duration were larger with fermented dairy as the delivery matrix, and beneficial effects of probiotics were not observed in physically active populations. Overall risk of bias was rated as "some  concerns" for most studies. In conclusion, orally ingested probiotics, relative to placebo, modestly reduce the incidence, duration, and severity of RTIs in nonelderly adults. Physical activity and delivery matrix may moderate some of these effects. Whether prebiotic and synbiotic interventions confer similar protection remains unclear due to few relevant studies. This trial was registered at https://www.crd.york.ac.uk/prospero/ as CRD42020220213.

Initial military training modulates serum fatty acid and amino acid metabolites.

Initial military training (IMT) results in increased fat-free mass (FFM) and decreased fat mass (FM). The underlying metabolic adaptations facilitating changes in body composition during IMT are unknown. The objective of this study was to assess changes in body composition and the serum metabolome during 22-week US Army IMT. Fifty-four volunteers (mean ± SD; 22 ± 3 year; 24.6 ± 3.7 kg/m2 ) completed this longitudinal study. Body composition measurements (InBody 770) and blood samples were collected under fasting, rested conditions PRE and POST IMT. Global metabolite profiling was performed to identify metabolites involved in energy, carbohydrate, lipid, and protein metabolism (Metabolon, Inc.). There was no change in body mass (POST-PRE; 0.4 ± 5.1 kg, p = 0.59), while FM decreased (-1.7 ± 3.5 kg, p < 0.01), and FFM increased (2.1 ± 2.8 kg, p < 0.01) POST compared to PRE IMT. Of 677 identified metabolites, 340 differed at POST compared to PRE (p < 0.05, Q < 0.10). The majority of these metabolites were related to fatty acid (73%) and amino acid (26%) metabolism. Increases were detected in 41% of branched-chain amino acid metabolites, 53% of histidine metabolites, and 35% of urea cycle metabolites. Decreases were detected in 93% of long-chain fatty acid metabolites, while 58% of primary bile acid metabolites increased. Increases in amino acid metabolites suggest higher rates of protein turnover, while changes in fatty acid metabolites indicate increased fat oxidation, which likely contribute changes in body composition during IMT. Overall, changes in metabolomics profiles provide insight into metabolic adaptions underlying changes in body composition during IMT.

Circulating and skeletal muscle microRNA profiles are more sensitive to sustained aerobic exercise than energy balance in males.

MicroRNAs (miRNAs) regulate molecular processes governing muscle metabolism. Physical activity and energy balance influence both muscle anabolism and substrate metabolism, but whether circulating and skeletal muscle miRNAs mediate those effects remains unknown. This study assessed the impact of sustained physical activity with participants in energy balance (BAL) or deficit (DEF) on circulating and skeletal muscle miRNAs. Using a randomized cross-over design, 10 recreational active healthy males (mean ± SD, 22 ± 5 years, 87 ± 11 kg) completed 72 h of high aerobic exercise-induced energy expenditures in BAL (689 ± 852 kcal/day) or DEF (-2047 ± 920 kcal/day). Blood and muscle samples were collected under rested/fasted conditions before (PRE) and immediately after 120 min load carriage exercise bout at the end (POST) of the 72 h. Trials were separated by 7 days. Circulating and skeletal muscle miRNAs were measured using microarray RT-qPCR. Independent of energy status, 36 circulating miRNAs decreased (P < 0.05), while 10 miRNAs increased and three miRNAs decreased in skeletal muscle (P < 0.05) at POST compared to PRE. Of these, miR-122-5p, miR-221-3p, miR-222-3p and miR-24-3p decreased in circulation and increased in skeletal muscle. Two circulating (miR-145-5p and miR-193a-5p) and four skeletal muscle (miR-21-5p, miR-372-3p, miR-34a-5p and miR-9-5p) miRNAs had time-by-treatment effects (P < 0.05). These data suggest that changes in miRNA profiles are more sensitive to increased physical activity compared to energy status, and that changes in circulating miRNAs in response to high levels of daily aerobic exercise are not reflective of changes in skeletal muscle miRNAs. KEY POINTS: Circulating and skeletal muscle miRNA profiles are more sensitive to high levels of aerobic exercise-induced energy expenditure compared to energy status. Changes in circulating miRNA in response to high levels of daily sustained aerobic exercise are not reflective of changes in skeletal muscle miRNA.