New Zealand blackcurrant extract modulates the heat shock response in men during exercise in hot ambient conditions.

PURPOSE: To determine if 7d of New Zealand blackcurrant (NZBC) extract alters the heat shock, inflammatory and apoptotic response during prolonged exertional-heat stress. METHODS: Ten men (Age: 29 ± 2 years, Stature: 1.82 ± 0.02 m, Mass: 80.3 ± 2.7 kg, V̇O2max: 56 ± 2 mL·kg-1·min-1) ingested two capsules of CurraNZ™ (NZBC extract: 210 mg anthocyanins·day-1) or PLACEBO for 7d prior to 1 h treadmill run (65% V̇O2max) in hot ambient conditions (34 °C/40% RH). Blood samples were collected before (Pre), immediately after (Post), 1 h after (1-Post), and 4 h after (4-Post) exercise. Heat shock proteins (HSP90, HSP70, HSP32) were measured in plasma. HSP and protein markers of inflammatory capacity (TLR4, NF-κB) and apoptosis (BAX/BCL-2, Caspase 9) were measured in peripheral blood mononuclear cells (PBMC). RESULTS: eHSP32 was elevated at baseline in NZBC(+ 31%; p < 0.001). In PLACEBO HSP32 content in PBMC was elevated at 4-Post(+ 98%; p = 0.002), whereas in NZBC it fell at Post(- 45%; p = 0.030) and 1-Post(- 48%; p = 0.026). eHSP70 was increased at Post in PLACEBO(+ 55.6%, p = 0.001) and NZBC (+ 50.7%, p = 0.010). eHSP90 was increased at Post(+ 77.9%, p < 0.001) and 1-Post(+ 73.2%, p < 0.001) in PLACEBO, with similar increases being shown in NZBC (+ 49.0%, p = 0.006 and + 66.2%, p = 0.001; respectively). TLR4 and NF-κB were both elevated in NZBC at PRE(+ 54%, p = 0.003 and + 57%, p = 0.004; respectively). Main effects of study condition were also shown for BAX/BCL-2(p = 0.025) and Caspase 9 (p = 0.043); both were higher in NZBC. CONCLUSION: 7d of NZBC extract supplementation increased eHSP32 and PBMC HSP32 content. It also increased inflammatory and apoptotic markers in PBMC, suggesting that NZBC supports the putative inflammatory response that accompanies exertional-heat stress.

Repeated short cold-water immersions are sufficient to habituate to the cold, but do not lead to adaptations during exercise in normobaric hypoxia.

We sought to assess the effects of repeated cold-water immersions (CWI) on respiratory, metabolic, and sympathoadrenal responses to graded exercise in hypoxia. Sixteen (2 female) participants (age: 21.2 ± 1.3 years; body fat: 12.3 ± 7.7%; body surface area 1.87 ± 0.16 m2, VO2peak: 48.7 ± 7.9 mL/kg/min) underwent 6 CWI in 12.0 ± 1.2 °C. Each CWI was 5 min, twice daily, separated by ≥4 h, for three consecutive days, during which metabolic data were collected. The day before and after the repeated CWI intervention, participants ran in normobaric hypoxia (FIO2 = 0.135) for 4 min at 25%, 40%, 60%, and 75% of their sea level peak oxygen consumption (VO2peak). CWI had no effect on VO2 (p > 0.05), but reduced the VE (CWI #1: 27.1 ± 17.8 versus CWI #6: 19.9 ± 12.1 L/min) (p < 0.01), VT (CWI #1: 1.3 ± 0.4 vs CWI #6: 1.1 ± 0.4 L) (p < 0.01), and VE:VO2 (CWI #1: 53.5 ± 24.1 vs CWI #6: 41.6 ± 20.5) (p < 0.01) during subsequent CWI. Further, post exercise plasma epinephrine was lower after CWI compared to before (103.3 ± 43.1; 73.4 ± 34.6 pg/mL) (p = 0.03), with no change in pre-exercising values (75.4 ± 30.7; 72.5 ± 25.9 pg/mL). While these changes were noteworthy, it is important to acknowledge there were no changes in pulmonary (VE, VT, and VE:VO2) or metabolic (VO2, SmO2, and SpO2) variables across multiple hypoxic exercise workloads following repeated CWI. CWI habituated participants to cold water, but this did not lead to adaptations during exercise in normobaric hypoxia.

Exercise induced plasma volume expansion lowers cardiovascular strain during 15-km cycling time-trial in acute normobaric hypoxia.

The purpose of our study was to assess the influence of a single high-intensity interval exercise (HIIE) bout in normoxia on plasma volume (PV) and consequent cycling performance in normobaric hypoxia (0.15 FiO2, simulating ~2,500 m). Eight males (VO2peak: 48.8 ± 3.4 mL/kg/min, 24.0 ± 1.6 years) completed a hypoxic 15 km cycling time trial (TT), followed by a crossover intervention of either HIIE (8x4 min cycling bouts at 85% of VO2peak) or CON (matched kJ production from HIIE at 50% of VO2peak). 48 hours post intervention, an identical TT was performed. Cardiovascular parameters were measured via impedance cardiography during each TT. Changes in PV was measured 24 and 48 hours post HIIE and CON. HIIE increased PV at 24 (4.1 ± 3.9%, P = 0.031) and 48 (6.7 ± 1.7, P = 0.006) hours post, while no difference was observed following the CON (1.3 ± 1.1% and 0.3 ± 2.8%). The higher PV led to an increased stroke volume (P = 0.03) and cardiac output (P = 0.02) during the hypoxic TT, while heart rate was not changed (P = 0.49). We observed no changes in time to completion (-0.63 ± 0.57 min, P = 0.054) and power output (7.37 ± 7.98 W, P = 0.078) between TTs. In the absence of environmental stress, a single bout of HIIE was an effective strategy to increase PV and reduce the cardiovascular strain during a cycling TT at moderate simulated altitude but did not impact hypoxic exercise performance. Trial registration: Clinical Trials ID: NCT05800808.

The effect of sex, menstrual cycle phase and oral contraceptive use on intestinal permeability and ex-vivo monocyte TNFα release following treatment with lipopolysaccharide and hyperthermia.

PURPOSE: Investigate the impact of sex, menstrual cycle phase and oral contraceptive use on intestinal permeability and ex-vivo tumour necrosis factor alpha (TNFα) release following treatment with lipopolysaccharide (LPS) and hyperthermia. METHODS: Twenty-seven participants (9 men, 9 eumenorrheic women (MC) and 9 women taking an oral contraceptive pill (OC)) completed three trials. Men were tested on 3 occasions over 6 weeks; MC during early-follicular, ovulation, and mid-luteal phases; OC during the pill and pill-free phase. Intestinal permeability was assessed following a 4-hour dual sugar absorption test (lactulose: rhamnose). Venous blood was collected each trial and stimulated with 100 µg·mL-1 LPS before incubation at 37 °C and 40 °C and analysed for TNFα via ELISA. RESULTS: L:R ratio was higher in OC than MC (+0.003, p = 0.061) and men (+0.005, p = 0.007). Men had higher TNFα responses than both MC (+53 %, p = 0.004) and OC (+61 %, p = 0.003). TNFα release was greater at 40 °C than 37 °C (+23 %, p < 0.001). CONCLUSIONS: Men present with lower resting intestinal barrier permeability relative to women regardless of OC use and displayed greater monocyte TNFα release following whole blood treatment with LPS and hyperthermia. Oral contraceptive users had highest intestinal permeability however, neither permeability or TNFα release were impacted by the pill cycle. Although no statistical effect was seen in the menstrual cycle, intestinal permeability and TNFα release were more variable across the phases.

Anthocyanin-Rich Blackcurrant Extract Preserves Gastrointestinal Barrier Permeability and Reduces Enterocyte Damage but Has No Effect on Microbial Translocation and Inflammation After Exertional Heat Stress.

This study investigated the effects of 7 days of 600 mg/day anthocyanin-rich blackcurrant extract intake on small intestinal permeability, enterocyte damage, microbial translocation, and inflammation following exertional heat stress. Twelve recreationally active men (maximal aerobic capacity = 55.6 ± 6.0 ml·kg-1·min-1) ran (70% VO2max) for 60 min in an environmental chamber (34 °C, 40% relative humidity) on two occasions (placebo/blackcurrant, randomized double-blind crossover). Permeability was assessed from a 4-hr urinary excretion of lactulose and rhamnose and expressed as a ratio of lactulose/rhamnose. Venous blood samples were taken at rest and 20, 60, and 240 min after exercise to measure enterocyte damage (intestinal fatty acid-binding protein); microbial translocation (soluble CD14, lipopolysaccharide-binding protein); and interleukins 6, interleukins 10, and interleukins 1 receptor antagonist. Exercise increased rectal temperature (by ∼2.8 °C) and heart rate (by ∼123 beats/min) in each condition. Blackcurrant supplementation led to a ∼12% reduction in lactulose/rhamnose ratio (p < .0034) and enterocyte damage (∼40% reduction in intestinal fatty acid-binding protein area under the curve; p < .0001) relative to placebo. No between-condition differences were observed immediately after exercise for lipopolysaccharide-binding protein (mean, 95% confidence interval [CI]; +80%, 95% CI [+61%, +99%]); soluble CD14 (+37%, 95% CI [+22%, +51%]); interleukins 6 (+494%, 95% CI [+394%, +690%]); interleukins 10 (+288%, 95% CI [+105%, +470%]); or interleukins 1 receptor antagonist (+47%, 95% CI [+13%, +80%]; all time main effects). No between-condition differences for these markers were observed after 60 or 240 min of recovery. Blackcurrant extract preserves the GI barrier; however, at subclinical levels, this had no effect on microbial translocation and downstream inflammatory processes.

The combined effects of exercise-induced muscle damage and heat stress on acute kidney stress and heat strain during subsequent endurance exercise.

PURPOSE: The purpose of the study was to investigate the combined effect of downhill running and heat stress on muscle damage, as well as on heat strain and kidney stress during subsequent running in the heat. METHODS: In a randomized cross-over study, ten non-heat-acclimated, physically active males completed downhill running in temperate (EIMD in Temp) and hot (EIMD in Hot) conditions followed by an exercise-heat stress (HS) test after 3-h seated rest. Blood and urine samples were collected immediately pre- and post-EIMD and HS, and 24 h post-EIMD (post-24 h). Core temperature and thermal sensation were measured to evaluate heat strain. Serum creatine kinase (CK), maximal voluntary isometric contraction of the quadriceps (MVC) and perceived muscle soreness were measured to evaluate muscle damage. Urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) levels were measured to indicate acute kidney stress. RESULTS: CK, MVC and perceived soreness were not different between conditions at any timepoints. In the EIMD in Hot condition, urinary NGAL was significantly elevated from pre- to post-HS (pre-HS: 6.56 {1.53-12.24} ng/min, post-HS: 13.72 {7.67-21.46} ng/min, p = 0.034). Such elevation of NGAL or KIM-1 was not found in the EIMD in Temp condition. CONCLUSIONS: As compared with downhill running in a temperate environment, downhill running in a hot environment does not appear to aggravate muscle damage. However, elevated NGAL levels following EIMD in a hot environment suggest such exercise may increase risk of mild acute kidney injury during subsequent endurance exercise in the heat.

Short-term hot water immersion results in substantial thermal strain and partial heat acclimation; comparisons with heat-exercise exposures.

OBJECTIVE: To examine the effectiveness of hot water immersion (HWI) as a heat acclimation strategy in comparison to time and temperature matched, exercise-heat acclimation (EHA). METHODS: 8 males performed heat stress tests (HST) (45 min of cycling at 50% of VO2max in 40 °C, 40% RH) before and after heat acclimation sessions. Acclimation sessions were either three consecutive bouts of HWI (40 min of submersion at 40 °C) or EHA (40 min of cycling at 50% VO2max in 40 °C, 40% RH). RESULTS: Average change in tympanic temperature (TTympanic) was significantly higher following HWI (2.1 °C ± 0.4) compared to EHA (1.5 °C ± 0.4) (P < 0.05). Decreases in peak heart rate (HR) (HWI: -10 bpm ± 8; EHA: -6 ± 7), average HR (-7 bpm ± 6; -3 ± 4), and average core temperature (-0.4 °C ± 0.3; -0.2 ± 0.4) were evident following acclimation (P < 0.05), but not different between interventions (P > 0.05). Peak rate of perceived exertion (RPEPeak) decreased for HWI and EHA (P < 0.05). Peak thermal sensation (TSPeak) decreased following HWI (P < 0.05) but was not different between interventions (P > 0.05). Plasma volume increased in both intervention groups (HWI: 5.9% ± 5.1; EHA: 5.4% ± 3.7) but was not statistically different (P > 0.05). CONCLUSION: HWI induced significantly greater thermal strain compared to EHA at equivalent temperatures during time-matched exposures. However, the greater degree of thermal strain did not result in between intervention differences for cardiovascular, thermoregulatory, or perceptual variables. Findings suggest three HWI sessions may be a potential means to lower HR, TCore, and perceptual strain during exercise in the heat.

The Potential Role of Exercise-Induced Muscle Damage in Exertional Heat Stroke.

Exertional heat stroke (EHS) is a life-threatening condition that affects mainly athletes, military personnel, firefighters, and occupational workers. EHS is frequently observed in non-compensable conditions (where the body is unable to maintain a steady thermal balance) as a result of heavy heat stress and muscle contraction associated with prolonged and strenuous physical and occupational activities, resulting in central nervous system dysfunction followed by multi-organ damage and failure. Since the pathophysiology of EHS is complex and involves multiple organs and systems, any condition that changes the interrelated systems may increase the risk for EHS. It has been suggested that exercise-induced muscle damage (EIMD) can lead to thermoregulatory impairment and systemic inflammation, which could be a potential predisposing factor for EHS. In this review article, we aim to (1) address the evidence of EIMD as a predisposing factor for EHS and (2) propose a possible mechanism of how performing muscle-damaging exercise in the heat may aggravate muscle damage and subsequent risk of EHS and acute kidney injury (AKI). Such an understanding could be meaningful to minimize the risks of EHS and AKI for individuals with muscle damage due to engaging in physical work in hot environments.

Accuracy and Reliability of Commercial Wrist-Worn Pulse Oximeter During Normobaric Hypoxia Exposure Under Resting Conditions.

Purpose: The present study analyzed peripheral blood oxygen saturation (SpO2) and heart rate (HR) measurements taken on the Garmin fenix® 5X Plus watch, comparing them to measurements taken on a standard medical-grade pulse oximeter during normobaric hypoxia exposure under resting conditions. Methods: Thirteen women (mean ± SD: Age 20 ± 1 years, height 165 ± 5 cm, mass, 67 ± 9 kg) and ten men (mean ± SD: Age 21 ± 3 years, height 177 ± 6 cm, mass 78 ± 11 kg) sat inside a customized environmental chamber while the fraction of inspired oxygen (FIO2) was adjusted to simulate altitudes of 12,000; 10,000; 8,000; 6,000; and 900 ft. The novel commercial device (Garmin fenix®) and a medical-grade pulse oximeter (Nonin® 7500) were used to measure SpO2 and HR in triplicate at each simulated altitude. Bland-Altman analyses were used to assess differences between methods. Results: Bland-Altman analysis indicated 3.3% bias for SpO2 measurements taken on the Garmin fenix® at 12,000 ft of simulated altitude (limits of agreement: -1.9-8.6%). Mean differences in SpO2 measurements were smaller at the remaining simulated altitudes, where bias measurements ranged from 0.7% to 0.8%. The Garmin fenix® also underestimated heart rate, but those discrepancies were minimal (bias measurements at all simulated altitude exposures were < 1.0 bpm). Conclusions: With the exception of readings taken at 12,000 ft of simulated altitude, the Garmin fenix® exhibits minimal overestimation of SpO2 and minimal underestimation of HR during simulated altitude exposure. These data suggest the Garmin fenix® watch may be a viable method to monitor SpO2 and HR under most ambient environmental conditions.

Effects of exercise in hot and humid conditions and bovine colostrum on salivary immune markers.

The purpose of this study was to examine the effects of exercise in a hot and humid environment on salivary lactoferrin and lysozyme. A secondary aim was to quantify the effects of 14-day bovine colostrum (BC) supplementation on salivary lactoferrin and lysozyme at rest and following exercise in hot and humid conditions. Using a randomized, double-blind, and counterbalanced design, ten males (20 ± 2 years, VO2max 55.8 ± 3.7 mL kg-1 min-1, 11.8 ± 2.7% body fat) ran for 46 ± 7.7 min at 95% of ventilatory threshold in a 40 °C and 50% RH environment after 14-days of supplementation with either BC or placebo. Saliva was collected pre, post, 1-h, and 4-h post exercise, and was analyzed for lactoferrin and lysozyme using ELISA. There was an immediate increase in the concentration and secretion rate of lactoferrin and lysozyme (p < 0.05) with exercise, but BC had no effect (p > 0.05). Saliva flow rate was not different between conditions [(PLA: pre: 0.54 ± 0.3, post: 0.44 ± 0.3, 1-h: 0.67 ± 0.3, 4-h: 1.0 ± 0.4 mL min-1); (BC: pre: 0.58 ± 0.2, post: 0.37 ± 0.1, 1-h: 0.63 ± 0.2, 4-h: 0.83 ± 0.4 mL min-1)]. There were no differences in thermoregulatory markers (core temperature or physiological strain index) between BC and placebo trials. Interestingly, exercise-induced heat stress did not impair mucosal immune parameters, instead participants showed a transient increase in salivary lactoferrin and lysozyme. Further, 14-day BC supplementation had no effect on mucosal immunity at any time point.

Addition of pectin-alginate to a carbohydrate beverage does not maintain gastrointestinal barrier function during exercise in hot-humid conditions better than carbohydrate ingestion alone.

The objective of this study was to compare the effects of consuming a 16% maltodextrin+fructose+pectin-alginate (MAL+FRU+PEC+ALG) drink against a nutrient-matched maltodextrin+fructose (MAL+FRU) drink on enterocyte damage and gastrointestinal permeability after cycling in hot and humid conditions. Fourteen recreational cyclists (7 men) completed 3 experimental trials in a randomized placebo-controlled design. Participants cycled for 90 min (45% maximal aerobic capacity) and completed a 15-min time-trial in hot (32 °C) humid (70% relative humidity) conditions. Every 15 min, cyclists consumed 143 mL of either (i) water; (ii) MAL+FRU+PEC+ALG (90 g·h-1 CHO/16% w/v); or (iii) a ratio-matched MAL+FRU drink (90 g·h-1 CHO/16% w/v). Blood was sampled before and after exercise and gastrointestinal (GI) permeability, which was determined by serum measurements of intestinal fatty acid binding protein (I-FABP) and the percent ratio of lactulose (5 g) to rhamnose (2 g) recovered in postexercise urine. Compared with water, I-FABP decreased by 349 ± 67pg·mL-1 with MAL+FRU+PEC+ALG (p = 0.007) and by 427 ± 56 pg·mL-1 with MAL+FRU (p = 0.02). GI permeability was reduced in both the MAL+FRU+PEC+ALG (by 0.019 ± 0.01, p = 0.0003) and MAL+FRU (by 0.014 ± 0.01, p = 0.002) conditions relative to water. In conclusion, both CHO beverages attenuated GI barrier damage to a similar extent relative to water. No metabolic, cardiovascular, thermoregulatory, or performance differences were observed between the CHO beverages. Novelty Consumption of multiple-transportable CHO, with or without hydrogel properties, preserves GI barrier integrity and reduces enterocyte damage during prolonged cycling in hot-humid conditions.

Dietary supplementation with New Zealand blackcurrant extract enhances fat oxidation during submaximal exercise in the heat.

OBJECTIVES: This study investigated the effect of 7 days' supplementation with New Zealand blackcurrant extract on thermoregulation and substrate metabolism during running in the heat. DESIGN: Randomized, double-blind, cross-over study. METHODS: Twelve men and six women (mean±SD: Age 27±6 years, height 1.76±0.10m, mass 74±12kg, V̇O2max 53.4±7.0mLkg-1min-1) completed one assessment of maximal aerobic capacity and one familiarisation trial (18°C, 40% relative humidity, RH), before ingesting 2×300mgday-1 capsules of CurraNZ™ (each containing 105mg anthocyanin) or a visually matched placebo (2×300mg microcrystalline cellulose M102) for 7 days (washout 14 days). On day 7 of each supplementation period, participants completed 60min of fasted running at 65% V̇O2max in hot ambient conditions (34°C and 40% relative humidity). RESULTS: Carbohydrate oxidation was decreased in the NZBC trial [by 0.24gmin-1 (95% CI: 0.21-0.27gmin-1)] compared to placebo (p= 0.014, d=0.46), and fat oxidation was increased in the NZBC trial [by 0.12gmin-1 (95% CI: 0.10 to 0.15gmin-1)], compared to placebo (p=0.008, d=0.57). NZBC did not influence heart rate (p=0.963), rectal temperature (p=0.380), skin temperature (p=0.955), body temperature (p=0.214) or physiological strain index (p=0.705) during exercise. CONCLUSIONS: Seven-days intake of 600mg NZBC extract increased fat oxidation without influencing cardiorespiratory or thermoregulatory variables during prolonged moderate intensity running in hot conditions.

Prolonged treadmill running in normobaric hypoxia causes gastrointestinal barrier permeability and elevates circulating levels of pro- and anti-inflammatory cytokines.

This study examined the impact of treadmill running in normobaric hypoxia on gastrointestinal barrier permeability and the systemic inflammatory response. Ten recreationally active participants completed two 1-h bouts of matched-workload treadmill exercise (65% normoxic maximal oxygen consumption) in counterbalanced order. One bout was performed in normoxia (NORM: fraction of inspired oxygen (FIO2) = 20.9%) and the other in normobaric hypoxia (HYP: FIO2 = 13.5%). Minute ventilation, respiratory rate (RR), tidal volume (VT), oxygen consumption, carbon dioxide production, respiratory exchange ratio (RER), and heart rate (HR) were measured with a metabolic cart. Peripheral oxygen saturation (SpO2) was measured with pulse oximetry. Absolute tissue saturation (StO2) was measured with near-infrared spectroscopy. Fatty acid-binding protein (I-FABP) and circulating cytokine concentrations (interleukin (IL)-1Ra, IL-6, IL-10) were assayed from plasma samples that were collected pre-exercise, postexercise, 1 h-postexercise, and 4 h-postexercise. Data were analyzed with 2-way (condition × time) repeated-measures ANOVAs. Newman-Keuls post hoc tests were run where appropriate (p < 0.05). As compared with NORM, 1 h of treadmill exercise in HYP caused greater (p < 0.05) changes in minute ventilation (+30%), RR (+16%), VT (+10%), carbon dioxide production (+18%), RER (+16%), HR (+4%), SpO2 (-16%), and StO2 (-10%). Gut barrier permeability and circulating cytokine concentrations were also greater (p < 0.05) following HYP exercise, where I-FABP was shown increased at postexercise (+68%) and IL-1Ra at 1 h-postexercise (+266%). I-FABP and IL-1Ra did not change (p > 0.05) following NORM exercise. IL-6 and IL-10 increased with exercise in both study conditions but were increased more (p < 0.05) following HYP at postexercise (+705% and +127%, respectively) and 1 h-postexercise (+400% and +128%, respectively). Novelty Normobaric hypoxia caused significant desaturation and increased most cardiopulmonary responses by 10%-30%. Significant gut barrier permeability and increased pro- and anti-inflammatory cytokine concentrations could promote an "open window" in the hours following HYP exercise.

Reduced inflammatory and phagocytotic responses following normobaric hypoxia exercise despite evidence supporting greater immune challenge.

This study examined changes in immune markers following sustained treadmill exercise in normobaric hypoxia. Ten subjects performed 1 h of treadmill exercise (65% maximal oxygen uptake) under normoxic (NORM: fraction of inspired oxygen (FIO2) = 20.9%) and normobaric hypoxic (HYP: FIO2 = 13.5%) conditions. Blood samples, collected before, after (Post), 1 h after (1-Post), and 4 h after (4-Post) exercise, were assayed for plasma cytokines (interleukin (IL)-1RA/IL-1ß/IL-8/tumor necrosis factor alpha (TNF-α)) and markers of leukocyte activation (macrophage inflammatory protein-1ß (MIP-1ß)/myeloperoxidase (MPO)/soluble intercellular adhesion molecule-1 (sICAM-1)) using ELISA. Pro- to anti-inflammatory cytokine ratios (TNF-α/IL-1RA; IL-1ß/IL-1RA) were calculated. Peripheral blood mononuclear cells (PBMC) were analyzed for changes in inflammatory status (phosphorylated nuclear factor kappa B/nuclear factor kappa B) using Western Blot. Data were analyzed with 2-way (condition × time) repeated-measure ANOVAs with Newman-Keuls post hoc tests. MIP-1ß was elevated at 1-Post HYP exercise (+11%; p < 0.01) but did not increase following exercise in NORM. TNF-α/IL-1RA and IL-1ß/IL-1RA ratios were both reduced (p < 0.05) following HYP exercise (-16% and -52%, respectively, at 1-Post and -7% and -32%, respectively, at 4-Post). IL-8 increased (p < 0.05) at Post and 1-Post NORM (+33% and +57%, respectively) and HYP (+60% and +83%, respectively) exercise, but was not different between conditions (p > 0.05). Interestingly, plasma sICAM-1 did not increase (p > 0.05) following NORM exercise but was increased (p < 0.05) at Post (+17%), 1-Post (+16%), and 4-Post (+14%) HYP exercise. There was also a delayed peak in plasma MPO concentrations following HYP exercise and PBMC exhibited a reduced (p < 0.05) inflammatory capacity at Post (-38%) and 1-Post (-49%). Novelty Following HYP exercise, participants exhibited (i) circulatory bias towards anti-inflammation; (ii) elevated sICAM; (iii) delayed peak in plasma MPO; and (iv) diminished inflammatory response in PBMC. Collectively, these data suggest immunosuppression. This is undesirable, given that elevated MIP-1ß (reported here) and elevated intestinal fatty acid binding protein (reported previously) both suggest higher lipopolysaccharide concentrations following HYP exercise.

Dietary curcumin supplementation does not alter peripheral blood mononuclear cell responses to exertional heat stress.

INTRODUCTION: Curcumin reduces gut barrier damage and plasma cytokine responses to exertional heat stress. However, the role of peripheral blood mononuclear cell (PBMC) in this response remains unclear. PURPOSE: This work investigated the effect of 3 days of 500 mg/day dietary curcumin supplementation on PBMC responses to exertional heat stress in non-heat acclimated humans. METHODS: Eight participants ran (65% VO2max) for 60 min in an environmental chamber (37 °C/25% RH) two times (curcumin/placebo). Blood samples were collected pre, post, 1 h post, and 4 h post-exercise. PBMC were isolated from blood samples and the protein content of markers along the TLR4 signaling pathway (TLR4, MyD88, pNF-κB, NF-κB), indicators of cellular energy status (SIRT1 and p-AMPK), and mediators of cellular heat shock response (pHSF-1 and HSP70) were examined with Western blot. Data were analyzed with two-way (condition × time) RM-ANOVAs with Newman-Keuls post hocs. RESULTS: As compared to placebo, curcumin did not alter protein expression in PBMC (p > 0.05). However, in both study conditions at 1 h post-reductions were noted in TLR 4 (- 21.5%; p = 0.03), HSP70 (- 11.0%; p = 0.04), pAMPK (- 48.5%; p < 0.01), and SIRT1 (- 47.8%; p < 0.01). Remarkably, the ratio of pNF-κB to NF-κB was elevated in both conditions at this same timepoint (+ 75.4%; p = 0.02). CONCLUSIONS: Inflammatory protein expression in PBMC did not differ between curcumin and placebo conditions. Downregulation of pAMPK/SIRT1 and release of HSP70 to the bloodstream may compensate for reduced TLR4, allowing PBMC to maintain inflammatory capacity and preventing an "open window" during the hours following hyperthermic exercise.

Heat acclimation increases inflammatory and apoptotic responses to subsequent LPS challenge in C2C12 myotubes.

This work investigated the ability of a 6-day heat acclimation protocol to impart heat acclimation-mediated cross-tolerance (HACT) in C2C12 myotubes, as indicated by changes in inflammatory and apoptotic responses to subsequent lipopolysaccharide (LPS) challenge. Myotubes were incubated at 40 °C for 2 h/day over 6 days (HA) or maintained for 6 days at 37 °C (C). Following 24 h recovery, myotubes from each group received either no stimulation or 500 ng/ml LPS for 2 h (HA + LPS and C + LPS, respectively). Cell lysates were collected and analyzed for protein markers of the heat shock response, inflammation, and apoptosis. As compared to C, HA exhibited an elevated heat shock response [HSP70 (+ 99%); HSP60 (+ 216%); HSP32 (+ 40%); all p < 0.01] and reduced inflammatory and apoptotic signaling [p-NF-ĸB:NF-ĸB (- 99%%); p-JNK (- 49%); all p < 0.01]. When compared to C + LPS, HA + LPS also exhibited an elevated heat shock response [HSP70 (+ 68%); HSP60 (+ 32%); HSP32 (+ 38%); all p < 0.01]. However, inflammatory and apoptotic responses in HA + LPS were increased [p-IKBa:IKBa (+ 432%); p-NF-ĸB:NF-ĸB (+ 283%); caspase-8p18 (+ 53%); p-JNK (+ 41%); all p < 0.05]. This unanticipated finding may be due to increased TLR4-mediated signaling capacity in HA + LPS, as indicated by upregulation of TLR4 [(+ 24%); MyD88 (+ 308%); p-NIK (+ 199%); and p-IKKα/b (+ 81%); all p < 0.05]. Data suggest HA reduces inflammatory and apoptotic signaling in skeletal muscle cells that are maintained under basal conditions. However, HACT is selective and does not apply to TLR4 signaling in the present model.

Heat acclimation increases mitochondrial respiration capacity of C2C12 myotubes and protects against LPS-mediated energy deficit.

This work investigated the effect of a 6-day heat acclimation (HA) protocol on myotube metabolic responses at baseline and in response to a subsequent lipopolysaccharide (LPS) challenge. C2C12 myotubes were incubated for 2 h/day at 40 °C for 6 days (HA) or maintained at 37 °C (C). Following 24-h recovery, myotubes were challenged with 500 ng/ml LPS for 2 h, then collected for analysis of protein markers of mitochondrial biogenesis and macronutrient storage. Functional significance of these changes was confirmed with mitochondrial respiration and glycolytic measurements on a Seahorse XF-96 analyzer. HA stimulated mitochondrial biogenesis and increased indicators of mitochondrial content [SIRT1 (+ 62%); PGC-1α (+ 57%); NRF-1 (+ 40%); TFAM (+ 141%); CS (+ 25%); CytC (+ 38%); all p < 0.05]. Altered lipid biosynthesis enzymes [p-ACCa:ACC (+ 59%; p = 0.04) and FAS (- 86%; p < 0.01)] suggest fatty acid generation may have been downregulated, whereas increased GLUT4 (+ 69%; p < 0.01) and LDH-B (+ 366%; p < 0.01) suggest aerobic glycolytic capacity may have been improved. Mitochondrial biogenesis signaling in HA myotubes was suppressed by 500 ng/ml LPS (PGC-1α, NRF-1, TFAM; all p > 0.05) but increased LDH-B (+ 30%; p = 0.02) and CPT-1 (+ 55%; p < 0.01) suggesting improved catabolic function. Basal respiration was increased in HA myotubes (+ 8%; p < 0.01) and HA myotubes maintained elevated basal respiration during LPS challenge (+ 8%; p < 0.01). LPS reduced peak respiration in C myotubes (- 6%; p < 0.01) but did not impair peak respiration in HA myotubes (p > 0.05). Oxidative reliance was elevated in HA over that in control (+ 25%; p < 0.01) and in HA + LPS over C + LPS (+ 30%; p < 0.01). In summary, HA stimulated mitochondrial biogenesis in C2C12 myotubes. HA myotubes exhibited (1) elevated basal/peak mitochondrial respiration capacities; (2) greater oxidative reliance; and (3) protection against LPS-mediated respiration impairment. Collectively, these data suggest HA may improve aerobic metabolism in skeletal muscle and protect against LPS-mediated energy deficit.

Short-term dietary curcumin supplementation reduces gastrointestinal barrier damage and physiological strain responses during exertional heat stress.

Szymanski MC, Gillum TL, Gould LM, Morin DS, Kuennen MR. Short-term dietary curcumin supplementation reduces gastrointestinal barrier damage and physiological strain responses during exertional heat stress. J Appl Physiol 124: 330-340, 2018. First published September 21, 2017; doi: 10.1152/japplphysiol.00515.2017 .-This work investigated the effect of 3 days of 500 mg/day dietary curcumin supplementation on gastrointestinal barrier damage and systems-physiology responses to exertional heat stress in non-heat-acclimated humans. Eight participants ran (65% V̇o2max) for 60 min in a Darwin chamber (37°C/25% relative humidity) two times (Curcumin/Placebo). Intestinal fatty acid-binding protein (I-FABP) and associated proinflammatory [monocyte chemoattractant protein-1, tumor necrosis factor-α (TNF-α), interleukin-6] and anti-inflammatory [interleukin-1 receptor antagonist (IL-1RA), interleukin-10 (IL-10)] cytokines were assayed from plasma collected before (Pre), after (Post) and 1 (1-Post) and 4 (4-Post) h after exercise. Core temperature and HR were measured throughout exercise; the physiological strain index (PSI) was calculated from these variables. Condition differences were determined with 2-way (condition × time) repeated-measures ANOVAs. The interaction of condition × time was significant ( P = 0.05) for I-FABP and IL-1RA. Post hoc analysis indicated I-FABP increased more from Pre to Post (87%) and 1-Post (33%) in Placebo than in Curcumin (58 and 18%, respectively). IL-1RA increased more from Pre to 1-Post in Placebo (153%) than in Curcumin (77%). TNF-α increased ( P = 0.01) from Pre to Post (19%) and 1-Post (24%) in Placebo but not in Curcumin ( P > 0.05). IL-10 increased ( P < 0.01) from Pre to Post (61%) and 1-Post (42%) in Placebo not in Curcumin ( P > 0.05). The PSI, which indicates exertional heatstroke risk, was also lower ( P < 0.01) in Curcumin than Placebo from 40 to 60 min of exercise. These data suggest 3 days curcumin supplementation may improve gastrointestinal function, associated cytokines, and systems-level physiology responses during exertional heat stress. This could help reduce exertional heatstroke risk in non-heat-acclimated individuals. NEW & NOTEWORTHY Exercise-heat stress increases gastrointestinal barrier damage and risk of exertional heatstroke. Over the past decade at least eight different dietary supplements have been tested for potential improvements in gastrointestinal barrier function and systems-level physiology responses during exercise-heat stress. None have been shown to protect against both insults simultaneously. In this report 3 days of 500 mg/day dietary curcumin supplementation are shown to improve gastrointestinal barrier function, associated cytokine responses, and systems-level physiology parameters. Further research is warranted.

Exercise increases lactoferrin, but decreases lysozyme in salivary granulocytes.

INTRODUCTION: Intracellular lactoferrin (Lac) and lysozyme (Lys) content play an important role in regulating inflammation and promoting host protection. While exercise has demonstrated an increase in Lac and Lys concentration in exocrine solutions, little is known regarding intracellular concentration changes in response to exercise. PURPOSE: To quantify intracellular Lac and Lys concentration before and after exercise in salivary CD45+CD15+ cells. METHODS: 11 males (20.3 ± 0.8 years, 57.2 ± 7.6 mL/kg/min V̇O2pk, 11.1 ± 3.9% body fat) ran for 45 min at 75% of VO2pk. 12 mL of stimulated saliva were collected pre and immediately post exercise. Saliva was filtered through a 30-µm filter before analysis of leukocytes (CD45+) and granulocytes (CD45+CD15+) using flow cytometry. RESULTS: Median fluorescent intensity (MFI) of Lac increased from pre (64,268 ± 46,036 MFI) to post (117,134 ± 88,115 MFI) exercise (p <0.05). Lys MFI decreased with exercise (pre: 16,933 ± 8249; post: 11,616 ± 6875) (p <0.05). CONCLUSION: Acute running resulted in an increased Lac concentration which could lead to a decrease in inflammation, adding further evidence of the anti-inflammatory effects of exercise. Conversely, the exercise-associated decrease of intracellular Lys content could be the cause of increased Lys in exocrine solutions.