Carbohydrate intake during endurance exercise increases natural killer cell responsiveness to IL-2

Comparison of the lymphocyte response to interval exercise versus continuous exercise in recreationally trained men

The purpose of this investigation was to compare changes in circulating lymphocyte subset cell counts between high-intensity interval exercise (HIIE), sprint interval exercise (SIE), and moderate-intensity continuous exercise (MICE). Recreationally active men (n ​= ​11; age: 23 ​± ​4 ​yr; height: 179.9 ​± ​4.5 ​cm; body mass: 79.8 ​± ​8.7 ​kg; body fat %:12.6 ​± ​3.8%; V̇O2max: 46.6 ​± ​3.9 ​ml⋅kg-1⋅min-1) completed a maximal graded exercise test to determine maximal oxygen uptake (V̇O2max) and three duration-matched cycling trials (HIIE, SIE, and MICE) in a randomized, counterbalanced fashion. HIIE consisted of fifteen 90-s bouts at 85% V̇O2max interspersed with 90-s active recovery periods. SIE consisted of fifteen 20-s bouts at 130% maximal power and 160-s active recovery periods. MICE was a continuous bout at 65% V̇O2max. Total exercise duration was 53 ​min in all three trials, including warm-up and cool-down. Blood was collected before, immediately post, 30 ​min, 2 ​h, 6 ​h, and 24 ​h post-exercise. Changes in lymphocyte subset counts, and surface expression of various markers were analyzed via flow cytometry. Changes were assessed using mixed model regression analysis with an autoregressive first order repeated measures correction. Significant decreases were observed in absolute counts of CD56dim NK cells, CD19+ B cells, CD4+ T cells, and CD8+ T cells 30 ​min and 24-h post-exercise in all three trials. Despite resulting in greater total work and oxygen consumption, MICE elicited similar changes in lymphocyte subset counts and receptor expression compared to both SIE and HIIE. Similarly, while the two interval trials resulted in differing oxygen consumption and total work, no differences in the lymphocyte response were observed. Though both forms of exercise resulted in declines in circulating lymphocyte cell counts, neither exercise type provides an immune-related advantage when matched for duration.

Dietary Polyphenol and Methylsulfonylmethane Supplementation Improves Immune, DAMP Signaling, and Inflammatory Responses During Recovery From All-Out Running Efforts

Nutritional ingredients with defined mechanisms of action can be useful in the recovery of the body from the physical demands of a habitual training plan. The purpose of this study was to determine the effect of dietary supplementation with optimized curcumin, pomegranate ellagitannins, and MSM (R + MSM) on immune-associated mRNA during early recovery (i.e., up to 8 h post-exercise) following all-out running efforts (5-km, 10-km, and 21.1-km). Subjects (N = 14) were randomized to either a supplement (R + MSM) or a control group using an open label design. The study was completed over a period of 31-day prior to a scheduled half-marathon race. Venous blood samples were collected into PAXgene tubes at baseline, subsequent samples were collected at 2, 4, and 8 h after each running effort. A 574-plex mRNA Immunology Array (NanoString) was measured for each sample and ROSALIND^® Advanced Analysis Software was used to examined changes in 31 annotated immune response pathways and specific mRNA changes. The greatest change in immune pathways occurred at 2 h (GSS > 3) followed by 4 h (GSS 2–3) and 8 h (GSS 1–2). R + MSM was associated with an increase in innate immunity (CAMP, LTF, TIRAP, CR1, IL1R1, CXCR1, PDCDILG2, and GNLY) and a blunted/smaller increase in damage-associated molecular pattern (DAMP) signaling/inflammation (TLR4, TLR5, S100A8, S100A9, and IFP35). We also found changes in immune-associated mRNA that have not been previously linked to exercise recovery (SOCS1, SOCS2, MME, CECAM6, MX1, IL-1R2, KLRD1, KLRK1, and LAMP3). Collectively these results demonstrate that supplementation with a combination of optimized curcumin, pomegranate ellagitannins, and methylsulfonylmethane resulted in changes that may improve biological recovery from all-out running efforts.

Metabolomics reveals sex-specific metabolic shifts and predicts the duration from positive to negative in non-severe COVID-19 patients during recovery process

Metabolic profiling in COVID-19 patients has been associated with disease severity, but there is no report on sex-specific metabolic changes in discharged survivors. Herein we used an integrated approach of LC-MS-and GC-MS-based untargeted metabolomics to analyze plasma metabolic characteristics in men and women with non-severe COVID-19 at both acute period and 30 days after discharge. The results demonstrate that metabolic alterations in plasma of COVID-19 patients during the recovery and rehabilitation process were presented in a sex specific manner. Overall, the levels of most metabolites were increased in COVID-19 patients after the cure relative to acute period. The major plasma metabolic changes were identified including fatty acids in men and glycerophosphocholines and carbohydrates in women. In addition, we found that women had shorter length of hospitalization than men and metabolic characteristics may contribute to predict the duration from positive to negative in non-severe COVID-19 patients. Collectively, this study shed light on sex-specific metabolic shifts in non-severe COVID-19 patients during the recovery process, suggesting a sex bias in prognostic and therapeutic evaluations based on metabolic profiling.

Exercise, Immunity, and Illness

It is generally accepted that moderate amounts of exercise improve immune system functions and hence reduce the risk of infection whereas athletes engaged in regular prolonged and/or intensive training have a higher than “normal” incidence of minor infections, especially of the upper respiratory tract (URT, e.g., common cold and influenza). This is likely related to regular acute (and possibly chronic) periods of exercise-induced changes in immune function. URT infections can compromise performance directly if suffered shortly before or during competition or indirectly if suffered at other times via effects on training and/or physiological adaptations. This chapter covers the effects of exercise (acute and chronic), both positive and negative, on immune function and consequent infection risk, and considers the current state-of-the-art for monitoring and assessing this in athletes.

Carbohydrate Intake Does Not Counter the Post-Exercise Decrease in Natural Killer Cell Cytotoxicity

In a study using a randomized crossover approach, cyclists (n = 20, overnight fasted) engaged in three 75 km time trials while ingesting water (WAT) or carbohydrate (0.2 g/kg every 15 min) from bananas (BAN) or a 6% sugar beverage (SUG). Blood samples were collected pre-exercise and 0 h, 1.5 h, and 21 h post-exercise and analyzed for natural killer (NK) cytotoxicity activity (NKCA) using pure NK cell populations. The two carbohydrate trials (BAN, SUG) compared to WAT were associated with higher post-exercise glucose and lower cortisol, total blood leukocyte, neutrophil, and NK cell counts (interaction effects, p < 0.001). The immediate post-exercise increase in NK cell counts was higher in WAT (78%) compared to BAN (32%) and SUG (15%) trials (p ≤ 0.017). The 1.5 h post-exercise decrease in NK cell counts did not differ after WAT (-46%), BAN (-46%), and SUG (-51%) trials. The pattern of change in post-exercise NKCA differed between trials (p < 0.001). The 1.5 h post-exercise decreases in NKCA were 23%, 29%, and 33% in the WAT, BAN, and SUG trials, respectively, but trial contrasts did not differ significantly. Carbohydrate ingestion from BAN or SUG attenuated immediate post-exercise increases in leukocyte, neutrophil, and NK cell counts, but did not counter the 1.5 h decreases in NK cell counts and NKCA.

The Anti-Inflammatory Actions of Exercise Training

The list of diseases with a known inflammatory etiology is growing. Cardiovascular disease, osteoporosis, diabetes, geriatric cachexia, and Alzheimer's disease have all been shown to be linked to or exacerbated by aberrantly regulated inflammatory processes. Nevertheless, there is mounting evidence that those who are physically active, or who become physically active, have a reduction in biomarkers associated with chronic inflammation. There was strong early consensus that exercise-induced reductions in inflammation were explained by body mass index or body fatness, but recent studies provide support for the contention that exercise has body fat-independent anti-inflammatory effects. With few exceptions, the anti-inflammatory effects of exercise appear to occur regardless of age or the presence of chronic diseases. What remains unclear are the mechanisms by which exercise training induces these anti-inflammatory effects, but there are several intriguing possibilities, including release of endogenous products, such as heat shock proteins; selective reduction of visceral adipose tissue mass or reducing infiltration of adipocytes by macrophages; shift in immune cell phenotype; cross-tolerizing effects; or exercise-induced shifts in accessory proteins of toll-like receptor signaling. However, future research endeavors are likely to uncover additional potential mechanisms, and it could be some time before functional mechanisms are made clear. In summary, the potential anti-inflammatory influences of exercise training may provide a low-cost, readily available, and effective treatment for low-grade systemic inflammation and could contribute significantly to the positive effects of exercise training on chronic disease.

Immune cell changes in response to a swimming training session during a 24-h recovery period

Understanding the impact of training sessions on the immune response is crucial for the adequate periodization of training, to prevent both a negative influence on health and a performance impairment of the athlete. This study evaluated acute systemic immune cell changes in response to an actual swimming session, during a 24-h recovery period, controlling for sex, menstrual cycle phases, maturity, and age group. Competitive swimmers (30 females, 15 ± 1.3 years old; and 35 males, 16.5 ± 2.1 years old) performed a high-intensity training session. Blood samples were collected before, immediately after, 2 h after, and 24 h after exercise. Standard procedures for the assessment of leukogram by automated counting (Coulter LH 750, Beckman) and lymphocytes subsets by flow cytometry (FACS Calibur BD, Biosciences) were used. Subjects were grouped according to competitive age groups and pubertal Tanner stages. Menstrual cycle phase was monitored. The training session induced neutrophilia, lymphopenia, and a low eosinophil count, lasting for at least 2 h, independent of sex and maturity. At 24 h postexercise, the acquired immunity of juniors (15-17 years old), expressed by total lymphocytes and total T lymphocytes (CD3(+)), was not fully recovered. This should be accounted for when planning a weekly training program. The observed lymphopenia suggests a lower immune surveillance at the end of the session that may depress the immunity of athletes, highlighting the need for extra care when athletes are exposed to aggressive environmental agents such as swimming pools.

Effect of a high and low dose of caffeine on human lymphocyte activation in response to antigen stimulation

This study investigated the effect of caffeine on antigen-stimulated lymphocyte activation. Six males rested for 3.5 h after ingesting 0 (PLA), 2, or 6 (6CAF) mg·kg(-1) body mass of caffeine. The number of antigen-stimulated NK CD69(+) cells increased in 6CAF at 1 h compared with PLA (P = 0.021). Caffeine did not influence the number of antigen-stimulated CD69(+) T cells or the geometric mean fluorescence intensity expression of CD69 on antigen-stimulated lymphocytes, suggesting caffeine has little effect on antigen-stimulated lymphocyte activation.

Baker's yeast beta glucan supplementation increases salivary IgA and decreases cold/flu symptomatic days after intense exercise

Strenuous exercise, such as running a marathon, is known to suppress mucosal immunity for up to 24 hr, which can increase the risk of developing an upper respiratory tract infection (URTI) and reduced performance capacity (Allgrove JE, Geneen L, Latif S, Gleeson M. Influence of a fed or fasted state on the s-IgA response to prolonged cycling in active men and women. Int J Sport Nutr Exerc Metab. 2009;19(3):209–221; Barrett B, Locken K, Maberry R, Schwamman J, Brown R, Bobula J, Stauffacher EA. The Wisconsin Upper Respiratory Symptom Survey (WURSS): a new research instrument for assessing the common cold. J Fam Pract. 2002;51(3):265; Carpenter KC, Breslin WL, Davidson T, Adams A, McFarlin BK. Baker's yeast beta glucan supplementation increases monocytes and cytokines post-exercise: implications for infection risk? Br J Nutr. 2012;1–9). While many dietary interventions have been used to combat postexercise immune suppression, most have been ineffective. The key purpose of this study was to determine if baker's yeast β-glucan (BG) could positively affect the immune system of individuals undergoing intense exercise stress using two experiments. In the first (E1; N = 182 men and women), BG was compared to placebo supplementation for the incidence of URTI symptoms for 28 days postmarathon. In the second (E2; N = 60 men and women) changes in salivary immunoglobulin A (IgA) were evaluated after 50-min of strenuous cycling when participants had been supplemented for 10 days with either BG (250 mg/day) or placebo (rice flour). For E1, subjects reported URTI symptoms using a daily health log. For E2, saliva was collected prior to, immediately, and 2-hr postexercise using a salivette. Data for E1 and E2 were analyzed using separate analyses of variance (ANOVAs) with repeated measures (p < .05). In E1, BG was associated with a 37% reduction in the number of cold/flu symptom days postmarathon compared to placebo (p = .026). In E2, BG was associated with a 32% increase in salivary IgA (p = .048) at 2 hr after exercise compared to placebo. In summary, the present study demonstrates that BG may reduce URTI symptomatic days and improve mucosal immunity (salivary IgA) postexercise.

Fish oil supplementation augments post-exercise immune function in young males

PURPOSE

Fish oils and related fatty acid components have anti-inflammatory properties, with beneficial effects against various disorders such as cardiovascular disease. A single bout of exercise can alter immune function. However, the effects of fish oil on immune function after a single bout of exercise are currently unknown. This study investigated the effect of supplementation with fish oil on the immune response to an acute bout of endurance exercise.

METHODS

Sixteen male subjects underwent a six week double blind randomised placebo controlled supplementation trial involving two groups (fish oil or placebo oil, 3g/day). They attended for two visits, the first involving a maximal exercise test and the second involving a 1-h bout of endurance exercise on a cycle ergometer at 70% (V)O(2peak). Blood samples were taken pre-supplementation, pre-exercise (post-supplementation), immediately, 1 and 3h post-exercise. Samples were analysed for plasma IL-6, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and cortisol; peripheral blood mononuclear cell (PBMC) IL-2, IL-4 and IFN-γ production; neutrophil phagocytosis/oxidative burst; and natural killer (NK) cell cytotoxic activity.

RESULTS

Post-supplementation EPA concentration was increased (P=0.0127) in the fish oil group. At 3h post-exercise PBMC IL-2 (P=0.0067) and NK cell activity (P=0.0163) was greater in the fish oil compared with the control group. However, PBMC IL-4 and IFN-γ productions, plasma IL-6 and cortisol concentrations, as well as neutrophil activity were unaffected by fish oil supplementation.

CONCLUSION

The current study demonstrates that fish oil supplementation reduces increases PBMC IL-2 production and NK cell cytotoxic activity in the recovery period after exercise.

Exercise-induced immunodepression in endurance athletes and nutritional intervention with carbohydrate, protein and fat-what is possible, what is not?

Heavily exercising endurance athletes experience extreme physiologic stress, which is associated with temporary immunodepression and higher risk of infection, particularly upper respiratory tract infections (URTI). The aim of this review is to provide a critical up-to-date review of existing evidence on the immunomodulatory potential of selected macronutrients and to evaluate their efficacy. The results of 66 placebo-controlled and/or crossover trials were compared and analysed. Among macronutrients, the most effective approach to maintain immune function in athletes is to consume ≥6% carbohydrate during prolonged exercise. Because inadequate nutrition affects almost all aspects of the immune system, a well-balanced diet is also important. Evidence of beneficial effects from other macronutrients is scarce and results are often inconsistent. Using a single nutrient may not be as effective as a mixture of several nutritional supplements. Due to limited research evidence, with the exception of carbohydrate, no explicit recommendations to reduce post-exercise URTI symptoms with single macronutrients can be derived.

Baker's yeast β-glucan supplementation increases monocytes and cytokines post-exercise: implications for infection risk?

Strenuous aerobic exercise is known to weaken the immune system, and while many nutritional supplements have been proposed to boost post-exercise immunity, few are known to be effective. The purpose of the present study was to evaluate whether 10 d of supplementation with a defined source of baker's yeast β-glucan (BG, Wellmune WGP®) could minimise post-exercise immunosuppression. Recreationally active men and women (n 60) completed two 10 d trial conditions using a cross-over design with a 7 d washout period: placebo (rice flour) and baker's yeast BG (250 mg/d of β-1,3/1,6-glucans derived from Saccharomyces cerevisiae) before a bout of cycling (49 ± 6 min) in a hot (38 ± 2°C), humid (45 ± 2 % relative humidity) environment. Blood was collected at baseline (before supplement), pre- (PRE), post- (POST) and 2 h (2H) post-exercise. Total and subset monocyte concentration was measured by four-colour flow cytometry. Plasma cytokine levels and lipopolysaccharide (LPS)-stimulated cytokine production were measured using separate multiplex assays. Total (CD14+) and pro-inflammatory monocyte concentrations (CD14+/CD16+) were significantly greater at POST and 2H (P< 0·05) with BG supplementation. BG supplementation boosted LPS-stimulated production of IL-2, IL-4, IL-5 and interferon-γ (IFN-γ) at PRE and POST (P< 0·05). Plasma IL-4, IL-5 and IFN-γ concentrations were greater at 2H following BG supplementation. It appears that 10 d of supplementation with BG increased the potential of blood leucocytes for the production of IL-2, IL-4, IL-5 and IFN-γ. The key findings of the present study demonstrate that BG may have potential to alter immunity following a strenuous exercise session.

Effect of Pleuran (β-glucan from Pleurotus ostreatus) supplementation on cellular immune response after intensive exercise in elite athletes

Excessive and exhausting physical loads depress the immune system. Carbohydrate consumption may minimize the postexercise suppression of the innate immune system. β-Glucan is a well-known immunomodulator, with positive effects on the functioning of immunocompetent cells. The goal of this study was to determine whether β-glucan dietary supplementation from the mushroom Pleurotus ostreatus decreases the suppressed immune system responses induced by short-term high-intensity exercise in humans. In this double-blind pilot study, 20 elite athletes were randomized to β-glucan (n = 9) or placebo (n = 11) groups; these groups consumed 100 mg of β-glucan (Imunoglukan) or placebo supplements, respectively, once a day for 2 months. Venous whole blood was collected before and after 2 months of supplementation (baseline), both immediately and 1 h after (recovery period) a 20-min intensive exercise bout at the end of the supplementation period. The blood samples were used to measure the cell counts of leukocytes, erythrocyte, and lymphocytes; subpopulations of lymphocytes, granulocytes, and monocytes; and natural killer (NK) cell activity (NKCA). A 28% reduction in NKCA (p < 0.01) below the baseline value was observed in the placebo group during the recovery period, whereas no significant reduction in NKCA was found in the β-glucan group. In addition, no significant decrease in NK cell count was measured in the β-glucan group during the recovery period. Immune cell counts did not differ significantly between the groups. These results indicate that insoluble β-glucan supplementation from P. ostreatus may play a role in modulating exercise-induced changes in NKCA in intensively training athletes.

Effect of a single and repeated dose of caffeine on antigen-stimulated human natural killer cell CD69 expression after high-intensity intermittent exercise

Several studies investigating the effect of caffeine on immune function following exercise have used one large bolus dose of caffeine. However, this does not model typical caffeine consumption. Therefore, the purpose of this study was to investigate whether small repeated doses of caffeine ingested throughout the day would elicit a similar response as one large bolus dose ingested 1 h prior to exercise on antigen-stimulated NK cell CD69 expression following strenuous intermittent exercise. In a randomized cross-over design, 15 healthy males completed six 15 min blocks of intermittent running consisting of maximal sprinting interspersed with less intense running and walking. Participants had ingested either 0 (PLA), 2 mg kg(-1) body mass (BM) caffeine on three separate occasions during the day (3 × CAF) or one dose of 6 (1 × CAF) mg kg(-1) BM caffeine, 1 h before exercise. At 1-h post-exercise, the number of antigen-stimulated CD3(-)CD56(+) cells expressing CD69 was lower on 1 × CAF compared with PLA [P < 0.05; PLA: 42.0 (34.0) × 10(6) cells L(-1), 1 × CAF: 26.2 (25.0) × 10(6) cells L(-1)], with values on 1 × CAF at this time point remaining close to pre-supplement. 1 × CAF tended to attenuate the exercise-induced increase in geometric mean fluorescence intensity of CD69 expression on antigen-stimulated CD3(-)CD56(+) cells 1-h post-exercise [P = 0.055; PLA: 141 (28)%, 1 × CAF: 119 (20)%]. These findings suggest that although one large bolus dose of caffeine attenuated the exercise-induced increase in antigen-stimulated NK cell CD69 expression 1 h following strenuous intermittent exercise, this attenuation at no point fell below pre-supplement values and caffeine does not appear to depress NK cell CD69 expression.

Knowledge of carbohydrate consumption does not alter natural killer cell activity following an acute bout of high-intensity aerobic exercise

Carbohydrate consumption during strenuous aerobic exercise reportedly minimizes post-exercise suppression of the innate immune system. One of the most common measurements of innate immunity is natural killer cell activity (NKCA). It is not known whether actual carbohydrate consumption or merely the knowledge of carbohydrate consumption mediates alteration in NKCA. The purpose of the present investigation was to determine if knowledge of carbohydrate beverage could result in alteration of RPE and NKCA, independent of actual carbohydrate intake. We recruited 11 male and female endurance athletes and randomly assigned them to either a correct or false knowledge of carbohydrate intake, such that in the false group, subjects were informed that they were receiving the carbohydrate beverage (CHO), but actually received a placebo (PLA) beverage. CHO and PLA beverages were matched to be similar in taste and appearance. Subjects completed 60 min of cycle ergometry (74% of VO2 peak). Venous blood samples were collected before (PRE), immediately after (POST), and 2 h after (2H) exercise and used to determine plasma glucose concentration, leukocyte total and differential counts, and NKCA. Data were statistically analyzed using a 3-factor analysis of variance (ANOVA) (p < 0.05). We did not find a significant effect of knowledge of drink type on leukocyte count, leukocyte differential, or NKCA. Drink type did not significantly alter leukocyte total, differential counts, or NKCA. There was a significant effect of exercise on NKCA. Knowledge of drink type does not alter innate immunity following exercise as assessed by leukocyte counts and NKCA.

Total lymphocyte CD8 expression is not a reliable marker of cytotoxic T-cell populations in human peripheral blood following an acute bout of high-intensity exercise

Cytotoxic T-lymphocytes co-express the T-cell receptor, CD3 and the MHC I restricted antigen CD8. Although total CD8 expression is often used to identify CD8(+) T-cells in blood, errors are associated with this method as some CD3 negative natural killer (NK)-cells are known to express CD8. As greater relative proportions of NK-cells are found in the blood compartment after exercise, these errors are likely to be amplified in post exercise blood samples. To test this, isolated blood lymphocytes obtained from aerobically trained male subjects before, immediately after and 1h after an exhaustive treadmill-running protocol were surface stained for CD3, CD4, CD8, CD16, and CD56 and analysed by multi-colour flow cytometry. It was found that 25.4+/-16.9% of all CD8(+) cells at rest were CD3 negative, CD8(dim+) and expressed the NK-cell markers CD16 and CD56. The magnitude of this error increased to 40.8+/-20.7% immediately after exercise due to an influx of CD8(dim+) NK-cells. Although all CD8(bright+) cells expressed CD3, gating around the CD8(bright+) cells only identified 79.2+/-8.7% of the total CD3(+)/CD8(+) T-cell population; however, the magnitude of this error did not change after exercise despite the altered proportions of CD8(bright+) and CD8(dim+) cells. In conclusion, total lymphocyte expression of CD8 should not be used as a single antigenic marker to identify CD8(+) T-cells after an acute bout of exercise. Although there are errors associated with using CD8(bright+) as a single antigenic marker to identify CD3(+) T-cells, these are not amplified in response to exercise.

Carbohydrate consumption during cycling increases in vitro NK cell responses to IL-2 and IFN-gamma

INTRODUCTION

Exercise has been shown to lower blood natural killer cell concentration and activity for up to 24-h after exercise; however, the mechanism underlying this effect is not clearly defined. We have speculated that an exercise-induced change in T-cell control of NK cells is at least partly responsible for the post-exercise suppression. As a follow-up to our previous research, the purpose of this study was to examine the T and NK cells responses during and following moderate/high-intensity endurance exercise.

METHODS

Eight male subjects (20+/-1 y; VO(2peak)=67.22+/-2.79 mL.kg(-1).mL(-1)) were recruited to complete two 1-h (75-80% VO(2peak)) cycling trials in a random counterbalanced order: carbohydrate (CHO) and placebo (PLA). Venous blood samples were collected before (PRE), immediately (POST), 2-h (2H), and 4-h (4H) after exercise. NK (CD3(-)/56(+)) and activated NK (CD3(-)/56(+)/69(+)) number were measured using flow cytometry. NK cell activity (NKCA) was determined using both a (51)Cr release assay (NKCA-51) and activated NK cell number (NKCA-69). Whole blood samples were stimulated with IL-2, IFN-gamma, IL-4, IL-12, and no stimulation for 12-h and then analyzed for NK cell activity using a (51)Cr release assay (NKCA-51).

RESULTS

Leukocyte counts and unstimulated NKCA were not different between CHO and PLA; however, exercise significantly increased NKCA (P<.05). Fold change in IL-2, IFN-gamma, and IL-2+IFN-gamma-stimulated NKCA were significantly greater in CHO compared to PLA (P<.05). No effect of drink was found for IL-4, IL-12, and IL-4+IL-12-stimulated NKCA.

DISCUSSION

The fold change in IL-2-stimulated NKCA is consistant with our previous published work. The drink effect for Th1 (but not Th2) cytokines suggests they may play a more significant role in modulating NKCA following a strenuous bout of aerobic exercise when CHO is consumed.

Influence of carbohydrate on immune function following 2 h cycling

The influence of carbohydrate compared with placebo ingestion on changes in immune cell counts and functions following 2 h intensive cycling was studied in 12 trained cyclists who functioned as their own controls. The subjects performed two tests 2 weeks apart where they cycled for 2 h at approximately 64% Watts(max) while receiving 4 mL x kg(-1) x 15 min(-1) carbohydrate (6%) (Cho) or placebo (Pla) beverages. Blood samples were collected 30 min preexercise, and immediately and 1 h postexercise. The samples were assayed for plasma cortisol and epinephrine, blood leukocyte subset counts, PHA-induced lymphocyte proliferation, and natural killer cell activity (NKCA). Compared with Pla ingestion, Cho attenuated exercise-induced changes in plasma cortisol, blood neutrophil, and monocyte counts, but not in total blood lymphocyte, T cell, and NK cell counts, PHA-induced lymphocyte proliferation, and NKCA. Thus despite a strong attenuating influence of carbohydrate ingestion on exercise-induced changes in plasma cortisol and blood neutrophil and monocyte counts, other immune measures related to lymphocyte subset counts, and function were unaffected.

Puberty effects on NK cell responses to exercise and carbohydrate intake in boys

Previous research has demonstrated that younger versus older animals and humans experience smaller perturbations in natural killer (NK) cells in response to physiological stress.

PURPOSE

To determine whether the smaller perturbations in NK cells induced by strenuous exercise and carbohydrate (CHO) intake, previously reported in children, are influenced by puberty.

METHODS

Twenty 12-yr-old boys, distinguished as prepubertal (Tanner (T) 1, N = 7), early pubertal (T2, N = 7), or pubertal (T3-5, N = 6), cycled for 60 min at 70% VO(2max) while drinking 6% CHO (CT) or flavored water (WT). Blood was collected at rest and during (30 and 60 min) and following (30 and 60 min) exercise to identify NK cells as CD3(-)CD56(dim) or CD3(-)CD56(dim). CD69 expression on CD3(-)CD56(+) cells was also determined.

RESULTS

A puberty x CHO x exercise interaction was found for the proportion, but not number, of CD56(dim) cells (P = 0.06). CD56(dim) cell counts were lower in CT versus WT (P < 0.001). Responses of CD56(bright) proportions (P = 0.007) and counts (P = 0.03) depended on pubertal status, but not CHO. The CD56(bright):CD56(dim) ratio remained stable during exercise, but during recovery was higher in T1 and T3-5 versus T2 (P = 0.08) and in CT versus WT (P = 0.04). During recovery, CD3(-)CD56(+) cells expressed higher levels of CD69 (P = 0.01), with no change in the proportion of CD69(+) cells.

CONCLUSION

These results confirm the influence of puberty on the distribution of NK cell subsets in response to exercise and CHO intake. Increased CD69 expression suggests that NK cells increase activation status during recovery from physiological stress.

The effect of dietary control and carbohydrate supplementation on the immune and hormonal responses to rowing exercise

To determine the effect of carbohydrate supplementation on the immune and stress hormone responses to 1 h of strenuous rowing exercise, 22 male subjects were randomly assigned to a placebo (PLA, n = 11) or carbohydrate (CHO, n = 11) group. Subjects completed 3 d of modified dietary intake, a standardized pre-exercise meal, and consumed either a carbohydrate beverage (1 g·kg body mass–1) or a non-caloric placebo drink before, during, and after a 1 h rowing trial. Increases were observed in adrenocorticotrophic hormone, cortisol, blood leukocytes, neutrophils, and natural killer cell concentrations and activity, whereas the ability of peripheral blood monouclear cells (PBMCs) to respond (interleukin-2 (IL-2) production) to stimulation was reduced 5 min after exercise in both groups (p < 0.05). Lymphocytes were also elevated, but in the PLA group only (p < 0.05). One hour after exercise, blood leukocytes remained elevated owing to increased neutrophil concentrations, whereas a number of lymphocyte subsets (CD3+, CD3+/4+, CD3+/8+, CD20+, CD25+, CD4+/25+, CD8+/25+) and the ability of PBMCs to respond to stimulation (IL-2, interferon-γ (IFN-γ) production) were lower than resting values in both groups (p < 0.05). Carbohydrate supplementation to athletes in the post-prandial state undergoing a 1 h rowing trial resulted in attenuation of the post-exercise increase in peripheral blood lymphocyte concentration, but had little effect on the ability of PBMCs to produce cytokines following stimulation, natural killer cell activity, stress hormone concentrations, exercise performance, or self-reported incidence of illness during the 14 d period following the experimental trial.

Energy restriction with different protein quantities and source: implications for innate immunity

OBJECTIVE

Physical age, energy restriction (ER), and weight loss have been reported to suppress indices of innate immunity, which may increase the risk of illness. To evaluate these interactions, we recruited older, postmenopausal women (50 to 80 years) to fill one of the following 9-week ER (1250 kcal/d) groups: beef [n = 14; reported intakes 46% carbohydrate (CHO):24% protein (PRO):30% fat], chicken (n = 15; 51% CHO:25% PRO:24% fat), or CHO (n = 14; 59% CHO:17% PRO:24% fat), or a non-intervention control (n = 11).

RESEARCH METHODS AND PROCEDURES

Fasting blood was collected before and after ER to determine leukocyte phenotype, neutrophil oxidative burst capacity, natural killer cell activity, stimulated interleukin-2 and interferon-gamma production, and blood zinc and iron concentrations.

RESULTS

No significant effects of ER (8.6% weight loss) or PRO quantity and source were found for the majority of indices of innate immunity. Small but significant (p < 0.05) declines in interleukin-2 production were found in the chicken and CHO groups only; however, the clinical significance of this finding is not known.

DISCUSSION

In the present study, 9 weeks of moderate ER did not suppress immunity in postmenopausal women. Also, contrary to our hypothesis, differential zinc and iron intakes did not significantly alter immunity.

Effects of graded carbohydrate supplementation on the immune response in cycling

PURPOSE

This study examined the acute immune response after three standardized cycling sessions of 4-h duration in the field with varying carbohydrate (CHO) supplementation in a randomized, double-blind, placebo-controlled fashion. We hypothesized that the ingestion of carbohydrate (6 or 12% CHO beverages; placebo (P) without CHO) during exercise attenuates the exercise-induced immune response in a dose-dependent manner.

METHODS

A total of 14 male competitive cyclists and triathletes (age: 25 +/- 5 yr; height: 180 +/- 7 cm; weight: 72 +/- 9 kg; VO2max: 67 +/- 6 mL.min(-1).kg(-1)) cycled for 4 h on a 400-m track at a given workload of 70% of the individual anaerobic threshold (198 +/- 21 W). Leukocyte and lymphocyte subpopulations were measured by flow cytometry before, immediately, and 1 and 19 h after exercise. In addition, C-reactive protein (CRP) interleukin 6 (IL-6), and cortisol were determined.

RESULTS

The exercise-induced increase in leukocytes, neutrophils, and monocytes was significantly attenuated to the same extent by 6 and 12% CHO (P < 0.001). No differences could be demonstrated for lymphocytes and natural killer cells. The increase in CRP was attenuated significantly by 12% CHO only (P < 0.05), whereas the increase in cortisol and IL-6 was significantly reduced by 6 and 12% CHO (P < 0.001). The postexercise neutrophilia, which dominated the exercise-induced leukocytosis, was strongly related to the postexercise concentration of cortisol (r = 0.72; P < 0.001).

CONCLUSIONS

Because of the lacking dose-dependent difference, the ingestion of at least 6% CHO beverages can sufficiently attenuate the exercise-induced immune response and stress, especially in phagocytizing cells (neutrophils and monocytes) by the reduced release of cortisol.

Sex-based effects on the distribution of NK cell subsets in response to exercise and carbohydrate intake in adolescents

Carbohydrate (CHO) supplementation and female sex independently influence the natural killer (NK) cell response to acute exercise. Consequently, this study sought to elucidate sex-based differences in the distribution of NK cell subsets (i.e., CD56dimand CD56bright) in response to exercise and CHO intake. Twenty-two healthy 14-yr-old girls ( n = 11) and boys ( n = 11) cycled for 60 min at 70% maximal oxygen consumption while drinking 6% CHO (CT) or flavored water (WT). Blood was collected at rest, during exercise (30 and 60 min), and during recovery (30 and 60 min) to identify CD3−CD56dimand CD3−CD56brightNK cells. The activation marker CD69 was also determined on CD3−CD56+cells. CD56dimresponses, expressed as proportions or cell counts, were greater ( P ≤ 0.01) in girls by 67 and 105%, respectively. CD56brightcell counts ( P = 0.006), but not CD56brightproportions ( P = 0.89), were greater in girls by 82%. Both CD56dimand CD56brightsubset responses, expressed as proportions or cell counts, were lower ( P ≤ 0.01) in CT vs. WT by 33–36%. The CD56bright-to-CD56dimratio decreased at 30 min of exercise but increased during recovery ( P < 0.001), with no effect of sex or CHO. Regardless of trial, CD3−CD56+cells expressed ∼18% higher levels of CD69 during recovery in girls but not boys ( P = 0.03), despite similar proportions and counts of CD69+cells. These results demonstrate sex-based differences in the distribution of NK cell subsets and activation status in response to exercise, but not CHO intake, and further support the need to control for sex in exercise immunology studies.

Physical Activity Status, But Not Age, Influences Inflammatory Biomarkers and Toll-Like Receptor 4

BACKGROUND

Chronic inflammation has been implicated in the development of cardiovascular disease, diabetes mellitus, cachexia, and osteoporosis. Regular physical activity has been purported to possess "anti-inflammatory" properties which may limit chronic inflammation. Recently, we hypothesized that toll-like receptor 4 (TLR4) may play a role in activity-induced modulation of inflammation. Therefore, the purpose of this study was to determine the association between age, physical activity status, biomarkers of inflammation, and TLR4.

METHODS

Male and female participants (n = 84) were recruited to fill one of the following groups: young (18-30 years), active; young, inactive; old (60-80 years), active; or old, inactive. To assess physical activity status, participants completed a Paffenbarger Physical Activity Questionnaire and a modified Balke submaximal treadmill test. After grouping and screening, participants were given a standard mixed diet to consume 24 hours prior to arriving at the laboratory. Participants were instructed to consume all food by 10 pm the night prior to blood sampling (8-hour fast). Following 30 minutes of seated rest in a quiet room, venous blood samples were collected. Lipopolysaccharide-stimulated inflammatory cytokine production and plasma high-sensitivity C-reactive protein (hsCRP) were determined by enzyme-linked immunosorbent assay, and TLR4 expression was determined by flow cytometry.

RESULTS

Lipopolysaccharide-stimulated interleukin-6, interleukin-1beta, and tumor necrosis factor-alpha production, TLR4 expression, and hsCRP were significantly lower in active compared to inactive participants (p <.05). Also, older participants had significantly higher hsCRP than young participants had (p <.05).

CONCLUSIONS

The findings of the present study support previous reports which infer that acute exercise or a physically active lifestyle may possess anti-inflammatory properties. Also this study, along with previous work from our laboratory, suggests that TLR4 may play a role in regulating the link between inflammatory cytokine production and a physically active lifestyle.

Chronic Resistance Exercise Training Improves Natural Killer Cell Activity in Older Women

BACKGROUND

Regular exercise has been reported to slow the age-associated declines in natural killer cell activity (NKCA). To evaluate this response, we recruited older, postmenopausal women (65-85 years old) to fill one of two groups: training (10 weeks of resistance exercise; TR) or control.

METHODS

Blood samples were collected from an arm vein in the TR group at rest (PRE), immediately following (POST), and 2 hours (2H) following an acute bout of resistance exercise both before (BEFORE) and after (AFTER) training. Leukocytes and NKCA were determined by flow cytometry and a whole blood (51)Cr release assay, respectively.

RESULTS

Acute exercise increased total leukocyte (p < .05), CD8 (p < .05), CD4 (p < .05), and CD56 counts (p < .05), but there was no effect of training. NKCA was greater TR-AFTER-PRE (136%), -POST (80%), and -2H (127%) compared to similar values from TR-BEFORE (p < .05).

CONCLUSION

Increased resting NKCA after chronic resistance training suggests that immunity has been improved.

Influence of carbohydrate delivery on the immune response during exercise and recovery from exercise

Acute, sustained, moderate- to high-intensity exercise has been shown to induce significant alterations in the distribution and function of leukocytes during recovery. In many instances, these changes have been found to reflect a transient impairment of immune function in vitro during recovery from such exercise. Carbohydrate supplementation during exercise has been associated with an attenuation of cortisol production. Because cortisol has been linked to immunosuppression, a growing body of research has examined the influence of carbohydrate supplementation on immune function in response to exercise. New areas along this line of inquiry involve examination of the cytokine response to exercise and the role that carbohydrate may play in regulating the production of proinflammatory cytokines. Inter-relations among the immune response, production of specific cytokines, and cortisol are also examined. The clinical significance of an attenuated immune response when exercising as a result of the administration of supplemental carbohydrate is yet to be determined.

TLR4 is lower in resistance-trained older women and related to inflammatory cytokines

INTRODUCTION/PURPOSE

Regular exercise may offset age-associated increases in inflammatory cytokines and reduce the risk of developing diseases with an inflammatory etiology by exerting "anti-inflammatory" effects. Toll-like receptor 4 (TLR4) signaling stimulates inflammatory cytokine production, and may explain the "anti-inflammatory" effect attributed to regular exercise. Therefore, the purpose of the present study was to compare the effect of acute (3 sets, 9 exercises, 10 repetitions at 80% of the 1-repetition maximum) and chronic resistance exercise on TLR4 and inflammatory cytokines.

METHODS

Venous blood samples were collected from trained (TR, N = 10) and untrained (UT, N = 10) older (65-80 yr) postmenopausal women: before (PRE), immediately post (POST), and 2 h (2H), 6 h (6H), and 24 h (24H) after completion of exercise. Cell-surface expression of TLR4 (two-color immunofluorescent cytometry), LPS (25 microg x mL(-1))-stimulated cytokine production (ELISA), plasma cytokines (ELISA), and mRNA expression of TLR4 and cytokines (RT-PCR) were determined for each sample.

RESULTS

TR had 124% less cell-surface TLR4 expression than UT (P < 0.05). A significant time effect was found for LPS-stimulated IL-6, IL-1beta, and TNF-alpha, where 6H was significantly greater than all other samples. No significant effects were found for plasma (IL-6 and TNF-alpha) or mRNA expression (IL-6, TNF-alpha, and IL-1beta) of inflammatory cytokines. When subjects were grouped according to cell-surface TLR4 expression (HI and LO), LPS-stimulated TNF-alpha (302%), IL-1beta (209%), and IL-6 (167%) production was greater for HI than LO (P < 0.05).

CONCLUSION

Regularly exercising older women expressed less cell-surface TLR4 but did not have lower plasma levels or produce less LPS-stimulated inflammatory cytokines at rest or in response to a single bout of resistance exercise. TLR4 changes may explain the "anti-inflammatory" effect that has recently been attributed to chronic (2x wk for previous 24 months) resistance exercise training.