The immune system and serum glutamine during a triathlon

Amino acids analysis reveals serum methionine contributes to diagnosis of the Kawasaki disease in mice and children

BACKGROUND

Kawasaki disease (KD) patients often lack early and definitive diagnosis due to insufficient clinical criteria, whereas biomarkers might accelerate the diagnostic process and treatment.

METHODS

The KD mouse models were established and thirteen amino acids were determined. A total of 551 serum samples were collected including KD patients (n = 134), HCs (n = 223) and KD patients after intravascular immunoglobulin therapy (IVIG, n = 194). A paired analysis of pre- and post-IVIG was employed in 10 KD patients.

RESULTS

The pathological alterations of the aorta, myocardial interstitium and coronary artery vessel were observed in KD mice; the serum levels of methionine in KD mice (n = 40) were markedly altered and negatively correlated with the C-reactive protein levels. Consistent with the mouse model, serum methionine were significantly decreased in KD children, with the relative variation ratio of KD with HCs above 30% and AUROC value of 0.845. Serum methionine were correlated with Z-Score and significantly restored to the normal ranges after KD patient IVIG treatment. Another case-control study with 10 KD patients with IVIG sensitivity and 20 healthy controls validated serum methionine as a biomarker for KD patients with AUROC of 0.86. Elevation of serum DNMT1 activities, but no differences of DNMT3a and DNMT3b, were observed in KD patients when comparing with those in the HCs.

CONCLUSIONS

Our study validated that serum methionine was a potential biomarker for KD, the alteration of which is associated with the activation of DNMT1 in KD patients.

Glutamine supplementation accelerates functional recovery of EDL muscles after injury by modulating the expression of S100 calcium-binding proteins

The aim of the current study was to investigate the effect of glutamine supplementation on the expression of HSP70 and the calcium-binding proteins from the S100 superfamily in the recovering extensor digitorum longus (EDL) muscle after injury. Two-month-old Wistar rats were subjected to cryolesion of the EDL muscle and then randomly divided into two groups (with or without glutamine supplementation). Starting immediately after the injury, the supplemented group received daily doses of glutamine (1 g/kg/day, via gavage) for 3 and 10 days orally. Then, muscles were subjected to histological, molecular, and functional analysis. Glutamine supplementation induced an increase in myofiber size of regenerating EDL muscles and prevented the decline in maximum tetanic strength of these muscles evaluated 10 days after injury. An accelerated upregulation of myogenin mRNA levels was detected in glutamine-supplemented injured muscles on day 3 post-cryolesion. The HSP70 expression increased only in the injured group supplemented with glutamine for 3 days. The increase in mRNA levels of NF-κB, the pro-inflammatory cytokines IL-1β and TNF-α, and the calcium-binding proteins S100A8 and S100A9 on day 3 post-cryolesion in EDL muscles was attenuated by glutamine supplementation. In contrast, the decrease in S100A1 mRNA levels in the 3-day-injured EDL muscles was minimized by glutamine supplementation. Overall, our results suggest that glutamine supplementation accelerates the recovery of myofiber size and contractile function after injury by modulating the expression of myogenin, HSP70, NF-κB, pro-inflammatory cytokines, and S100 calcium-binding proteins.

The Prophylactic Effects of Glutamine on Muscle Protein Synthesis and Degradation in Rats with Ethanol-Induced Liver Damage

The purpose of this research was to investigate the prophylactic effects of glutamine on muscle protein synthesis and degradation in rats with ethanol-induced liver injury. For the first 2 weeks, Wistar rats were divided into two groups and fed a control (n = 16) or glutamine-containing diet (n = 24). For the following 6 weeks, rats fed the control diet were further divided into two groups (n = 8 per group) according to whether their diet contained no ethanol (CC) or did contain ethanol (CE). Rats fed the glutamine-containing diet were also further divided into three groups (n = 8 per group), including a GG group (glutamine-containing diet without ethanol), GE group (control diet with ethanol), and GEG group (glutamine-containing diet with ethanol). After 6 weeks, results showed that hepatic fatty change, inflammation, altered liver function, and hyperammonemia had occurred in the CE group, but these were attenuated in the GE and GEG groups. Elevated intestinal permeability and a higher plasma endotoxin level were observed in the CE group, but both were lower in the GE and GEG groups. The level of a protein synthesis marker (p70S6K) was reduced in the CE group but was higher in both the GE and GEG groups. In conclusion, glutamine supplementation might elevate muscle protein synthesis by improving intestinal health and ameliorating liver damage in rats with chronic ethanol intake.

Physical Exercise and Immune System: Perspectives on the COVID-19 pandemic

Physical exercise training (PET) has been considered an excellent non-pharmacological strategy to prevent and treat several diseases. There are various benefits offered by PET, especially on the immune system, promoting changes in the morphology and function of cells, inducing changes in the expression pattern of pro and anti-inflammatory cytokines. However, these changes depend on the type, volume and intensity of PET and whether it is being evaluated acutely or chronically. In this context, PET can be a tool to improve the immune system and fight various infections. However, the current COVID-19 pandemic, caused by SARS-CoV-2, which produces cytokine storm, inducing inflammation in several organs, with high infection rates in both sedentary and physically active individuals, the role of PET on immune cells has not yet been elucidated. Thus, this review focused on the role of PET on immune system cells and the possible effects of PET-induced adaptive responses on SARS-CoV-2 infection and COVID-19.

Effects of inducing exercise on growing mice by means of three-dimensional structure in rearing environment

We reared ICR mice during a growth period (3 to 10 weeks of age) and examined the effect of exercise induction, by enriching the rearing environment with obstacles such as ladders, compared to the standard environment. Environmental enrichment significantly increased the amount of exercise in both sexes (P<0.01). Enriched exercise mice had higher body weight than control mice at 6 to 9 weeks of age in males and 8 weeks of age in females (P<0.05). The sexual maturation of female enriched exercise mice was significantly advanced compared to the control (P<0.001). Enriched exercise mice showed decreased anxiety-like behavior in the open field test and lower plasma corticosterone levels in both sexes compared to the control, and differences were statistically significant in males (P<0.05). In both sexes, enriched exercise appeared to increase natural killer cells in blood compared to the control, but no statistical differences was detected. In conclusion, we confirmed that daily low-stress exercise could be induced using a three-dimensional rearing environment in growing mice. In addition, we suggest that exercise has beneficial effects on physical growth, sexual maturation and anxiety-like behavior. Furthermore, environmental enrichment might be more effective in male than female in group-housed mice.

The impact of triathlon training and racing on athletes' general health

Although the sport of triathlon provides an opportunity to research the effect of multi-disciplinary exercise on health across the lifespan, much remains to be done. The literature has failed to consistently or adequately report subject age group, sex, ability level, and/or event-distance specialization. The demands of training and racing are relatively unquantified. Multiple definitions and reporting methods for injury and illness have been implemented. In general, risk factors for maladaptation have not been well-described. The data thus far collected indicate that the sport of triathlon is relatively safe for the well-prepared, well-supplied athlete. Most injuries 'causing cessation or reduction of training or seeking of medical aid' are not serious. However, as the extent to which they recur may be high and is undocumented, injury outcome is unclear. The sudden death rate for competition is 1.5 (0.9-2.5) [mostly swim-related] occurrences for every 100,000 participations. The sudden death rate is unknown for training, although stroke risk may be increased, in the long-term, in genetically susceptible athletes. During heavy training and up to 5 days post-competition, host protection against pathogens may also be compromised. The incidence of illness seems low, but its outcome is unclear. More prospective investigation of the immunological, oxidative stress-related and cardiovascular effects of triathlon training and competition is warranted. Training diaries may prove to be a promising method of monitoring negative adaptation and its potential risk factors. More longitudinal, medical-tent-based studies of the aetiology and treatment demands of race-related injury and illness are needed.

Leukocytosis, muscle damage and increased lymphocyte proliferative response after an adventure sprint race

The effect of an adventure sprint race (ASR) on T-cell proliferation, leukocyte count and muscle damage was evaluated. Seven young male runners completed an ASR in the region of Serra do Espinhaço, Brazil. The race induced a strong leukocytosis (6.22±2.04×10³ cells/mm³ before vs 14.81±3.53×10³ cells/mm³ after the race), marked by a significant increase of neutrophils and monocytes (P<0.05), but not total lymphocytes, CD3⁺CD4⁺ or CD3⁺CD8⁺ cells. However, the T-cell proliferative response to mitogenic stimulation was increased (P=0.025) after the race, which contradicted our hypothesis that ASR, as a high-demand competition, would inhibit T-cell proliferation. A positive correlation (P=0.03, r=0.79) was observed between the proliferative response of lymphocytes after the race and the time to complete the race, suggesting that the proliferative response was dependent on exercise intensity. Muscle damage was evident after the race by increased serum levels of aspartate amino transferase (24.99±8.30 vs 50.61±15.76 U/L, P=0.003). The results suggest that humoral factors and substances released by damaged muscle may be responsible for lymphocyte activation, which may be involved in muscle recovery and repair.

Extensive inflammatory cell infiltration in human skeletal muscle in response to an ultraendurance exercise bout in experienced athletes

The impact of a 24-h ultraendurance exercise bout on systemic and local muscle inflammatory reactions was investigated in nine experienced athletes. Blood and muscle biopsies were collected before (Pre), immediately after the exercise bout (Post), and after 28 h of recovery (Post28). Circulating blood levels of leukocytes, creatine kinase (CK), C-reactive protein (CRP), and selected inflammatory cytokines were assessed together with the evaluation of the occurrence of inflammatory cells (CD3(+), CD8(+), CD68(+)) and the expression of major histocompatibility complex class I (MHC class I) in skeletal muscle. An extensive inflammatory cell infiltration occurred in all athletes, and the number of CD3(+), CD8(+), and CD68(+) cells were two- to threefold higher at Post28 compared with Pre (P < 0.05). The inflammatory cell infiltration was associated with a significant increase in the expression of MHC class I in muscle fibers. There was a significant increase in blood leukocyte count, IL-6, IL-8, CRP, and CK at Post. At Post28, total leukocytes, IL-6, and CK had declined, whereas IL-8 and CRP continued to increase. Increases in IL-1β and TNF-α were not significant. There were no significant associations between the magnitude of the systemic and local muscle inflammatory reactions. Signs of muscle degenerative and regenerative events were observed in all athletes with various degrees of severity and were not affected by the 24-h ultraendurance exercise bout. In conclusion, a low-intensity but very prolonged single-endurance exercise bout can generate a strong inflammatory cell infiltration in skeletal muscle of well-trained experienced ultraendurance athletes, and the amplitude of the local reaction is not proportional to the systemic inflammatory response.

Resposta da frequência cardíaca e da concentração de lactato após cada segmento do triathlon olímpico

INTRODUÇÃO: As respostas fisiológicas de cada uma das modalidades envolvidas no triathlon são diferentes. Cargas de treino poderiam ser melhores prescritas se consideradas as individualidades fisiológicas de cada segmento para cada atleta. OBJETIVO: Observar o comportamento das variáveis fisiológicas, frequência cardíaca (FC) e concentração de lactato sanguíneo, antes e depois de cada segmento do triathlon: natação, ciclismo e corrida. MÉTODOS: Doze atletas do sexo masculino cumpriram uma prova de triathlon com distância olímpica. Coletas de sangue da polpa digital foram feitas antes do início da prova, após a natação, após o ciclismo, após a corrida e, ainda, uma hora após a prova. Cada atleta foi monitorizado com frequencímetro (Polar® S610) durante toda a prova. Análises estatísticas foram realizadas através da correlação de Spearman e teste de Wilcoxon para amostras não paramétricas (p<0,05). RESULTADOS: Nesta pesquisa, a maior intensidade foi registrada, em ambos os parâmetros fisiológicos, durante o ciclismo (86,3% da frequencia cardíaca máxima (FCmáx); 6,98mmol), seguida pela natação (85,2% FCmáx; 5,75mmol) e corrida (83,6% FCmáx; 4,47mmol), respectivamente. CONCLUSÃO: Conclui-se que a prescrição da carga de treino para o triathlon será mais eficiente se baseada nas respostas fisiológicas (FC e o lactato sanguíneo) individuais de cada modalidade.

Outbreak of leptospirosis among triathlon participants in Langau, Austria, 2010

We report on the first documented outbreak of leptospirosis in Austria. In July 2010, four cases of serologically confirmed leptospirosis occurred in athletes after a triathlon held in Langau. Heavy rains preceded the triathlon (rainfall: 22 mm). The index case (Patient A) was a 41-year-old previously healthy male, who was admitted to hospital A on July 8 with a four-day history of fever up to 40°C that began 14 days after attending the triathlon event. On July 7, patient B, a 42-year-old male, was admitted to the same hospital, with signs and symptoms of kidney failure. Hemodialysis was performed every other day for 3 weeks. While the serum drawn on the day of admission was negative for antibodies against Leptospira, a specimen from July 28 tested positive with Leptospira interrogans. On July 11, patient C, a 40-year-old male, was admitted to hospital B for nephritis. On July 14, patient D, a 44-year-old male, was admitted to hospital C with a ten days history of intermittent fever, mild dry cough and headache. Our report underlines that in Austria recreational users of bodies of freshwater must be aware of an existing risk of contracting leptospirosis, particularly after heavy rains. The suppressive influence of a triathlon on the immune system is well documented and therefore an outbreak in this population group can be seen as a sensitive indicator concerning possible risk for the general population.

Glutamine deprivation causes enhanced plating efficiency of a herpes simplex virus type 1 ICP0-null mutant

Isoleucine deprivation of cellular monolayers prior to infection has been reported to result in partial complementation of a herpes simplex virus type 1 (HSV-1) ICP0 null (ICP0(-)) mutant. We now report that glutamine deprivation alone is able to enhance the plating efficiency of an ICP0(-) virus and that isoleucine deprivation has little or no effect. Because a low glutamine level is associated with stress and because stress is known to induce reactivation, low levels of glutamine may be relevant to the reactivation of HSV-1 from latency. Additionally, we demonstrate that arginine and methionine deprivation result in partial complementation of the ICP0(-) virus.

Glutamine: the nonessential amino acid for performance enhancement

Glutamine is a popular dietary supplement consumed for purported ergogenic benefits of increased strength, quicker recovery, decreased frequency of respiratory infections, and prevention of overtraining. From a biochemical standpoint, glutamine does play a physiologic role in each of these areas, but it remains only one of a host of factors involved. This review examines the effects of glutamine on exercise and demonstrates a lack of evidence for definitive positive ergogenic benefits as a result of glutamine supplementation.

Plasma Glutamine Changes After High-Intensity Exercise in Elite Male Swimmers

The aim of this study was to establish the pattern and time course of plasma glutamine recovery after acute, high-intensity exercise in well-trained swimmers. In Study 1, elite male swimmers (n=8) performed 15 x 100 m swimming intervals (ITS) at 70% and 95% of maximal 100m freestyle time. Resting plasma glutaminle levels were determined on a nonexercise control day (0% ITS). Venous blood samples were obtained prior to, immediately afte;, and 30, 60, 120, and 150 mini postexercise. In Study 2, the 95% ITS was repeated in elite male swuimmers (n=8), while control subjects (n=8) did not exercise, to test for any diurnal variation in plasma glutamine levels. Venous blood samples were obtained prior to and 2, 4, 6, and 8 h postexercise. In Study 1, no change was observed in plasma glutamine following the 0% (control) and 70% ITS, but following the 95% ITS glutamine decreased significantly (p < 0.01) over the recovery period. In Study 2, plasma glutamine again decreased over the recovery period in the swimmers, but no changes were observed in the controls. It was concluded that intensive swim traininlg results in postexercise decreases in plasma glutamine levels. Because glutamine has been suggested as a marker of overtraining, a need to measure glutaminle at standard times within training programs is indicated.

Plasma glutamine concentration in spinal cord injured patients

Glutamine, a non-essential amino acid, is the most important source of energy for macrophages and lymphocytes. Reduction in its plasma concentration is related with loss of immune function, as leukocyte proliferation and cytokine production. It is well known that glutamine is largely produced by the skeletal muscle which is severely compromised as a consequence of the paralysis due to the damage of the spinal cord. In spinal cord injury (SCI) patients, infections, such as pneumonia and sepsis in general, are a major cause of morbidity and mortality. In comparison with the control group, a 54% decrease in plasma glutamine concentration was observed as well as a decrease in the production of TNF and IL-1 by peripheral blood mononuclear cells cultivated for 48 h in SCI patients. Therefore, we propose that a decrease in plasma glutamine concentration is an important contributor to the immunosuppression seen in SCI patients.

Medical considerations in triathlon competition: recommendations for triathlon organisers, competitors and coaches

Competitors in triathlons experience a range of environmental conditions and physiological demands in excess of that found in individual sport events of comparable duration. Consequently, there is a broad range of possible medical problems and complications that must be taken into account when preparing for such races. For most competitors, an Olympic-distance triathlon typically takes between 2-4 hours to complete. This race begins with a swimming segment of 1500 m. Given the wide variety of race venues found around the world, these swims occur in an assortment of water temperatures (from warm to cold) and conditions (from ocean surf to lake calm). Swimmers often exit the water in a state of moderate dehydration and hypothermia and then immediately start the 40 km cycling leg. Many do so in their swimming attire. A wide variety of road surfaces, technically challenging topography, variable environmental conditions and dramatically changing velocities can be encountered on the cycle course. The race concludes with a 10 km running leg. Since it is the final leg, it is often completed in higher ambient temperatures than those encountered at the start, with the athlete possibly running in a significant state of dehydration and fatigue. Other medical problems commonly encountered in triathlon include: muscle cramping, heat illness, postural hypotension, excessive exposure to ultraviolet radiation, musculoskeletal injuries and trauma, gastrointestinal problems as well as post-race bacterial infection, immunosuppression, sympathetic nervous system and psychological exhaustion, and haemolysis. The rate of occurrence of such events and the severity of their potentially negative outcomes is a function of the methods used by both the race organisers and the competitors to prevent or respond to the conditions imposed by the race. Triathletes also commonly compete in both shorter 'sprint distance' events (in the range of a 0.75 km swim, 20 km cycle and 5 km run) and longer events including both one-half and full Ironman distances (2.5 and 3.8 km swim, 80 and 180 km cycle, 20 and 42 km run, respectively), as well as ultra-distance events that exceed the Ironman distance. In the longer events, the previously mentioned medical considerations are further magnified and additional considerations such as hyponatraemia can also occur. Reducing risk associated with these concerns is accomplished by: taking into account weather and water temperature/conditions data prior to event scheduling; effective swim, cycle and run course organisation and management; environmental monitoring prior to and during the event; the implementation of a water safety plan; provision of appropriate fluid replacement throughout the course; implementation of helmet use and non-drafting regulations in the cycling leg; and competitor knowledge regarding fluid replacement, biomechanical technique, physical preparation, safe equipment and course familiarity. Despite these concerns, triathlon participation appears to relatively safe for persons of all ages, assuming that high-risk adults undertake health screening.

Validation of a new highly standardised, lab-independent whole-blood leukocyte function assay for clinical trials (ILCS)

Physical stress induced in healthy volunteers by the Loughborough intermittent shuttle test (LIST) was used to validate a newly developed whole-blood cell culture system (Instant leukocyte culture system (ILCS). Exercise induced immune modulation was investigated through measurement of cytokine levels after activating leukocytes in peripheral blood ex vivo using the physiologic stimulant lipopolysaccharide (LPS). LPS induced production of three different cytokines, interferon gamma (IFNgamma), interleukin-6 (IL-6), and interleukin-10 (IL-10). IFNgamma levels were significantly decreased (P = 0.02 and P = 0.001 ) and IL-10 levels significantly increased (P= 0.04 and 0.03) after exercise. LPS induced IL-6 production was only marginally further increased by exercise. In conclusion, the ILCS system provided a reliable ex vivo method, showing common as well as subject specific features in the time course of the immune modulation caused by the LIST protocol. This system will be useful for studies of the elderly, where cytokine standardisation is notoriously difficult.

Glutamine supplementation in vitro and in vivo, in exercise and in immunodepression

In situations of stress, such as clinical trauma, starvation or prolonged, strenuous exercise, the concentration of glutamine in the blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Glutamine is used as a fuel by some cells of the immune system. Provision of glutamine or a glutamine precursor, such as branched chain amino acids, has been seen to have a beneficial effect on gut function, on morbidity and mortality, and on some aspects of immune cell function in clinical studies. It has also been seen to decrease the self-reported incidence of illness in endurance athletes. So far, there is no firm evidence as to precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated. Other aspects of glutamine and glutamine supplementation are also addressed.

Glutamine supplementation further enhances exercise-induced plasma IL-6

Exercise stimulates the production and release of interleukin-6 (IL-6) from skeletal muscle. Glutamine is also synthesized in skeletal muscle and is involved in protein synthesis within this tissue. During exercise, plasma levels of glutamine decline, and this may affect the concentration of plasma IL-6 via a decrease in IL-6 synthesis and release from muscle. We hypothesized that glutamine supplementation would attenuate the exercise-induced decrease in plasma glutamine concentration and, thus, further enhance levels of plasma IL-6. Eight healthy men participated in a randomized, double-blind, crossover study in which they performed 2 h of cycle ergometry at 75% of peak O2 uptake. They received glutamine, glutamine-rich protein, or placebo supplementation at intervals during and 2 h after exercise. Exercise induced an 11-fold increase in plasma IL-6, which was further enhanced by glutamine (18-fold) and glutamine-rich protein (14-fold) supplementation, administered at doses that attenuated the exercise-induced decrease in plasma glutamine concentration.

Prolonged suppression of the innate immune system in the horse following an 80 km endurance race

REASONS FOR PERFORMING STUDY

An increased susceptibility to bacterial and viral infections of the respiratory tract, which results in a loss of performance, has been reported in racehorses. Much research has focused on the influence of high-intensity exercise of a short duration on immune system function in horses, but scant attention has been given to prolonged endurance exercise as an immune modulator.

OBJECTIVES

The objective of this study was to evaluate the effect of an 80 km endurance race on the monocyte and neutrophil oxidative burst, serum cortisol, glutamine and plasma glucose concentrations in 8 endurance-trained horses (mean +/- s.d. age 9.4 +/- 2.2 years).

METHODS

Blood samples were drawn from the horses prior to and following an 80 km ride.

RESULTS

Mean time for completion of the 80 km race was 306 +/- 40 mins. Immediately post race mean serum cortisol concentration, blood monocyte and neutrophil counts were higher and blood lymphocyte counts and plasma glucose concentration were lower compared with prerace values (P < 0.05). Neutrophil and monocyte oxidative burst activity decreased following the race and had not regained prerace values after 3 days of rest (P < 0.05).

CONCLUSIONS

The present study indicates that long duration exercise in horses has a negative impact on the function of the innate immune system that lasts several days post race. Precise mechanisms instigating the fall in innate immune system function are unclear and multifactorial, but may be attributed, at least in part, to a high serum cortisol response during very prolonged exercise.

POTENTIAL CLINICAL RELEVANCE

A prolonged bout of exercise results in a long-term suppression of the innate immune system function in horses which may, in part, account for the observed increase of infectious episodes in horses during training.

U0126 and PD98059, specific inhibitors of MEK, accelerate differentiation of RAW264.7 cells into osteoclast-like cells

Osteoclasts are multinucleated cells that differentiate from hematopoietic cells and possess characteristics responsible for bone resorption. To study the involvement of mitogen-activated protein kinases (MAPKs) in osteoclastogenesis of the murine monocytic cell line RAW264.7, which can differentiate into osteoclast-like cells in the presence of the receptor activator of nuclear factor kappa B ligand (RANKL), we treated the cells with specific inhibitors of p38 MAPK, PD169316 and SB203580, and specific inhibitors of MAPK extracellular signaling-regulated kinase (ERK) kinase (MEK), U0126 and PD98059. Each inhibitor blocked differentiation into osteoclast-like cells when the cells were plated at the standard cell density (2000-4000 cells per well (96-well)). However, the effect of MEK inhibitors on osteoclastogenesis varied according to the initial cell density during culture, because cell growth was clearly inhibited by them. When the cells were plated at more than 8000 cells per well, marked enhancement and acceleration of the differentiation were observed. In addition, immunoblot analysis revealed that phosphorylation of ERK was increased by treatment with the p38 inhibitors, whereas the MEK inhibitors increased phosphorylation of p38, which implies a seesaw-like balance between ERK and p38 phosphorylation. We suggest that osteoclastogenesis is regulated under a balance between ERK and p38 pathways and that the MEK/ERK pathway negatively regulates osteoclastogenesis while the p38 pathway does so positively. This is the first report that an inhibitor of signal transduction enhanced osteoclastogenesis.

Exercise and hypoxia: effects on leukocytes and interleukin-6-shared mechanisms?

Stress-induced immunological reactions to exercise have stimulated much research into stress immunology and neuroimmunology. It has been suggested that exercise can be employed as a model of temporary immunosuppression, which occurs during physical stress, such as hypoxia. Acute exercise and acute hypoxia mediate in principle identical effects on circulating lymphocyte and neutrophil numbers. Thus, during exercise and hypoxia, lymphocytes are recruited to the blood. After the stress, the number of lymphocytes declines after the stress, whereas the neutrophil number continues to increase. When exercise is performed during hypoxia, the exercise-induced immune changes are pronounced. There is some evidence that the exercise- and hypoxia-induced changes in leukocyte subpopulations are mediated by neuroendocrinological factors such as catecholamines, growth hormone, and cortisol. In contrast, although exercise, as well as hypoxia, is associated with increased plasma levels of IL-6, the mechanisms are not likely to be the same. Thus, during exercise, contracting skeletal muscles are the main source of IL-6 production, whereas the source of IL-6 during hypoxia has not been demonstrated. The increased level of adrenaline contributes to the enormous increase in plasma IL-6 only to a minor degree during strenuous exercise. However, the only modest increase in IL-6 during hypoxia may be linked to hormonal changes, whereas the prolonged increase in IL-6 during chronic hypoxia is likely to be multifactorial.

Effect of an endurance race on muscle amino acids, pro- and macroglycogen and triglycerides

Glycogenolysis and lipolysis are essential for energy production in muscle during prolonged exercise but less is known about the role of amino acid metabolism. The aim was to study the effect of an endurance race on pro- and macroglycogen, triglycerides and amino acid concentrations in muscle and on selected blood parameters, especially the amino acid response in the blood during the recovery phase. Seven endurance-trained horses completed a race covering 100-120 km. Blood samples were collected one day before the race, after the finish and 1 and 8 days after the race. Needle biopsy specimens from the gluteus medius muscle were taken on completion of the race and 8 days postrace. The pro- and macroglycogen concentrations were lower and most amino acid concentrations were higher in the muscle after the finish of the race, than 8 days postrace, whereas the triglyceride concentrations did not differ. The concentrations of several amino acids in serum were higher during the recovery phase than before the race. The observed changes suggest that an endurance race influences amino acid metabolism and a net protein degradation may occur that persists during the recovery phase. Furthermore, the results suggest that macroglycogen is utilised to a greater extent than proglycogen during an endurance race. Further research is needed concerning amino acid metabolism during an endurance race as it seems to play an important role both for performance and recovery after exercise.

Exercise-induced immunodepression- plasma glutamine is not the link

The amino acid glutamine is known to be important for the function of some immune cells in vitro. It has been proposed that the decrease in plasma glutamine concentration in relation to catabolic conditions, including prolonged, exhaustive exercise, results in a lack of glutamine for these cells and may be responsible for the transient immunodepression commonly observed after acute, exhaustive exercise. It has been unclear, however, whether the magnitude of the observed decrease in plasma glutamine concentration would be great enough to compromise the function of immune cells. In fact, intracellular glutamine concentration may not be compromised when plasma levels are decreased postexercise. In addition, a number of recent intervention studies with glutamine feeding demonstrate that, although the plasma concentration of glutamine is kept constant during and after acute, strenuous exercise, glutamine supplementation does not abolish the postexercise decrease in in vitro cellular immunity, including low lymphocyte number, impaired lymphocyte proliferation, impaired natural killer and lymphokine-activated killer cell activity, as well as low production rate and concentration of salivary IgA. It is concluded that, although the glutamine hypothesis may explain immunodepression related to other stressful conditions such as trauma and burn, plasma glutamine concentration is not likely to play a mechanistic role in exercise-induced immunodepression.

Branched-chain amino acid supplementation and the immune response of long-distance athletes

OBJECTIVE

Intense long-duration exercise has been associated with immunosuppression, which affects natural killer cells, lymphokine-activated killer cells, and lymphocytes. The mechanisms involved, however, are not fully determined and seem to be multifactorial, including endocrine changes and alteration of plasma glutamine concentration. Therefore, we evaluated the effect of branched-chain amino acid supplementation on the immune response of triathletes and long-distance runners.

METHODS

Peripheral blood was collected prior to and immediately after an Olympic Triathlon or a 30k run. Lymphocyte proliferation, cytokine production by cultured cells, and plasma glutamine were measured.

RESULTS

After the exercise bout, athletes from the placebo group presented a decreased plasma glutamine concentration that was abolished by branched-chain amino acid supplementation and an increased proliferative response in their peripheral blood mononuclear cells. Those cells also produced, after exercise, less tumor necrosis factor, interleukins-1 and -4, and interferon and 48% more interleukin-2. Supplementation stimulated the production of interleukin-2 and interferon after exercise and a more pronounced decrease in the production of interleukin-4, indicating a diversion toward a Th1 type immune response.

CONCLUSIONS

Our results indicate that branched-chain amino acid (BCAA) supplementation recovers the ability of peripheral blood mononuclear cells proliferate in response to mitogens after a long distance intense exercise, as well as plasma glutamine concentration. The amino acids also modify the pattern of cytokine production leading to a diversion of the immune response toward a Th1 type of immune response.

Effect of glutamine and protein supplementation on exercise-induced decreases in salivary IgA

Postexercise immune impairment has been linked to exercise-induced decrease in plasma glutamine concentration. This study examined the possibility of abolishing the exercise-induced decrease in salivary IgA through glutamine supplementation during and after intense exercise. Eleven athletes performed cycle ergometer exercise for 2 h at 75% of maximal oxygen uptake on 3 separate days. Glutamine (a total of 17.5 g), protein (a total of 68.5 g/6.2 g protein-bound glutamine), and placebo supplements were given during and up to 2 h after exercise. Unstimulated, timed saliva samples were obtained before exercise and 20 min, 140 min, 4 h, and 22 h postexercise. The exercise protocol induced a decrease in salivary IgA (IgA concentration, IgA output, and IgA relative to total protein). The plasma concentration of glutamine was decreased by 15% 2 h postexercise in the placebo group, whereas this decline was abolished by both glutamine and protein supplements. None of the supplements, however, was able to abolish the decline in salivary IgA. This study does not support that postexercise decrease in salivary IgA is related to plasma glutamine concentrations.

Exercise and the immune system: regulation, integration, and adaptation

Stress-induced immunological reactions to exercise have stimulated much research into stress immunology and neuroimmunology. It is suggested that exercise can be employed as a model of temporary immunosuppression that occurs after severe physical stress. The exercise-stress model can be easily manipulated experimentally and allows for the study of interactions between the nervous, the endocrine, and the immune systems. This review focuses on mechanisms underlying exercise-induced immune changes such as neuroendocrinological factors including catecholamines, growth hormone, cortisol, beta-endorphin, and sex steroids. The contribution of a metabolic link between skeletal muscles and the lymphoid system is also reviewed. The mechanisms of exercise-associated muscle damage and the initiation of the inflammatory cytokine cascade are discussed. Given that exercise modulates the immune system in healthy individuals, considerations of the clinical ramifications of exercise in the prevention of diseases for which the immune system has a role is of importance. Accordingly, drawing on the experimental, clinical, and epidemiological literature, we address the interactions between exercise and infectious diseases as well as exercise and neoplasia within the context of both aging and nutrition.

Conseqüências do exercício para o metabolismo da glutamina e função imune

Para o atleta, o objetivo do treinamento é aperfeiçoar sua capacidade física para obtenção do melhor desempenho em competições. Isso o leva a procurar os mais novos e eficientes métodos de treinamento. Um aspecto importante do programa de treinamento é o período de recuperação entre as sessões de exercícios, imprescindível para que ocorram as adaptações fisiológicas, como as alterações morfológicas e a supercompensação das reservas energéticas. A liberação de glutamina pelos músculos esqueléticos é aumentada durante o exercício. Como conseqüência, o conteúdo muscular de glutamina diminui após um exercício extenuante. Este aminoácido, entretanto, é muito importante para a funcionalidade dos leucócitos (linfócitos, macrófagos e neutrófilos). Portanto, após um exercício intenso, a concentração plasmática de glutamina diminui, suprimindo a função imune e tornando o indivíduo mais suscetível a infecções respiratórias. Nesta revisão são discutidas as implicações do exercício sobre o metabolismo dos músculos esqueléticos e leucócitos.

Change in perforin-positive peripheral blood lymphocyte (PBL) subpopulations following exercise

Perforin, one of the cytotoxic proteins of the immune system, plays a prominent role in protection against viral and bacterial infections. We investigated its expression in PBL and their CD3+, CD4+, CD8+ and CD16+ and/or CD56+ subpopulations in endurance athletes before and after a triathlon. Lymphocyte subpopulations were analysed by flow cytometry following separation of peripheral blood mononuclear cells and staining with antibodies against specific membrane antigens and intracellular perforin. The number of total lymphocytes decreased from 2.1 x 10(3)/microl before the triathlon to 1.0 x 10(3)/microl 1 h after the triathlon (P < 0.01). Interestingly, there was already a significant spontaneous decline in the percentage of CD3+/perforin+, and in CD8+/perforin+ cells, in the week proceeding the triathlon, when subjects were instructed to refrain from strenuous exercise training. The percentage of CD3+/perforin+, CD8+/perforin+ and CD16+ and/or CD56+/perforin+ cells in each lymphocyte subpopulation decreased 1 h after exercise even further from 14.3% to 5.8% (P < 0.05), 18.5% to 6.5% (P < 0.05) and 77.3% to 67.3%, respectively. However, at 18 h and 48 h after exercise the percentage of perforin-expressing CD3+, CD8+ and CD16+/56+ cells increased again towards baseline levels. Compared with normal controls, baseline perforin co-expression in CD3+ and CD8+ lymphocytes was significantly higher in trained athletes. From our data we conclude that trained athletes have an increased percentage of perforin+ PBL and that following exercise the percentage of perforin+ and therefore potentially cytotoxic lymphocytes transiently decreases in peripheral blood.

Glutamine and the immune system

Glutamine is utilised at a high rate by cells of the immune system in culture and is required to support optimal lymphocyte proliferation and production of cytokines by lymphocytes and macrophages. Macrophage-mediated phagocytosis is influenced by glutamine availability. Hydrolysable glutamine dipeptides can substitute for glutamine to support in vitro lymphocyte and macrophage functions. In man plasma and skeletal muscle glutamine levels are lowered by sepsis, injury, burns, surgery and endurance exercise and in the overtrained athlete. The lowered plasma glutamine concentrations are most likely the result of demand for glutamine (by the liver, kidney, gut and immune system) exceeding the supply (from the diet and from muscle). It has been suggested that the lowered plasma glutamine concentration contributes, at least in part, to the immunosuppression which accompanies such situations. Animal studies have shown that inclusion of glutamine in the diet increases survival to a bacterial challenge. Glutamine or its precursors has been provided, usually by the parenteral route, to patients following surgery, radiation treatment or bone marrow transplantation or suffering from injury. In most cases the intention was not to stimulate the immune system but rather to maintain nitrogen balance, muscle mass and/or gut integrity. Nevertheless, the maintenance of plasma glutamine concentrations in such a group of patients very much at risk of immunosuppression has the added benefit of maintaining immune function. Indeed, the provision of glutamine to patients following bone marrow transplantation resulted in a lower level of infection and a shorter stay in hospital than for patients receiving glutamine-free parenteral nutrition.

Dietary glutamine enhances cytokine production by murine macrophages

To examine the effects of dietary glutamine on cytokine production by macrophages, mice were fed for 2 wk on a control diet that included 200.0 g casein/kg providing 19.6 g glutamine/kg or a glutamine-enriched diet that provided 54.8 g glutamine/kg partly at the expense of casein. There were no differences in weight gain between animals fed the two diets. The plasma concentrations of a number of amino acids differed according to the diet fed; this variation largely reflected the variation in the levels of the different amino acids in the diets. Plasma glutamine concentration was not significantly affected by dietary glutamine level. The production of three cytokines, tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6, was greater for lipopolysaccharide-stimulated macrophages from mice fed the glutamine-enriched diet. Thus, increasing the amount of glutamine in the murine diet enhances the ability of macrophages to respond to stimulation, at least in terms of cytokine production. These observations suggest that increasing the availability of glutamine orally could promote immune responses involving macrophage-derived cytokines.

Exercise and the immune system--influence of nutrition and ageing

In essence, the immune system is enhanced during moderate and severe exercise, and only intense long-duration exercise is followed by impairment of the immune system. The latter includes suppressed concentration of lymphocytes, suppressed natural killer cell activity, lymphocyte proliferation and secretory IgA in saliva. During the time of immune impairment, referred to as "the open window", microbial agents, especially viruses may invade the host and infections may be established. One reason for the "overtraining effect" seen in elite athletes could be that this window of opportunism for pathogens is longer and the degree of immunosuppression more pronounced. Alterations in metabolism and metabolic factors may contribute to exercise-associated changes in immune function. Reductions in plasma-glutamine concentrations, altered plasma-glucose level, free oxygen radicals and prostaglandins (PG) released by the elevated number of neutrophils and monocytes may influence the function of lymphocytes and contribute to the impaired function of the later cells. Thus, nutritional supplementation with glutamine, carbohydrate, anti-oxidants or PG-inhibitors may, in principle, influence exercise-associated immune function. Although several intervention studies have been performed, it is premature to make recommendations regarding nutritional supplementation to avoid post-exercise impairment of the immune system.

Dietary glutamine enhances murine T-lymphocyte responsiveness

To examine the effects of dietary glutamine on lymphocyte function, male mice aged 6 wk were fed for 2 wk one of three isonitrogenous, isocaloric diets, which varied in glutamine concentration. The control diet included 200 g casein/kg, providing 19.6 g glutamine/kg; the glutamine-enriched diet provided 54.8 g glutamine/kg partly at the expense of casein; and the alanine + glycine-enriched diet provided 13.3 g glutamine/kg. The plasma concentrations of a number of amino acids varied because of the diet fed. The plasma glycine concentration was greater in mice fed the alanine + glycine-enriched diet (380 +/- 22 micromol/L) than in mice fed the control (177 +/- 17 micromol/L) or the glutamine-enriched (115 +/- 18 micromol/L) diets. The plasma glutamine concentration was greater in mice fed the glutamine-enriched diet (945 +/- 117 micromol/L) than in those fed the diet enriched with alanine + glycine (561 +/- 127 micromol/L), but was not different from that in mice fed the control diet (791 +/- 35 micromol/L). There was a significant linear relationship between the amount of glutamine in the diet and plasma glutamine concentration (r = 0.655, P = 0.015). Plasma alanine concentration was unaffected by diet. The reason for the lack of effect of increasing the amount of alanine in the diet upon its concentration in the circulation may relate to its use by the liver. Thymidine incorporation (56 +/- 18 kBq/well versus <10 kBq/well), expression of the alpha-subunit of the interleukin-2 receptor (62 versus 30% receptor positive cells) and interleukin-2 production [189 +/- 28 versus 106 +/- 5 (control) or 61 +/- 13 (alanine + glycine enriched) ng/L] were greater for concanavalin A-stimulated spleen lymphocytes from mice fed the glutamine-enriched diet compared to those from mice fed the other two diets. Thus, increasing the amount of glutamine in the murine diet enhances the ability of T lymphocytes to respond to mitogenic stimulation. Taken together, these observations suggest that increasing the oral availability of glutamine could promote the T-cell driven, cell-mediated immune response.

Exercise and immune function. Recent developments

Comparison of immune function in athletes and nonathletes reveals that the adaptive immune system is largely unaffected by athletic endeavour. The innate immune system appears to respond differentially to the chronic stress of intensive exercise, with natural killer cell activity tending to be enhanced while neutrophil function is suppressed. However, even when significant changes in the level and functional activity of immune parameters have been observed in athletes, investigators have had little success in linking these to a higher incidence of infection and illness. Many components of the immune system exhibit change after prolonged heavy exertion. During this 'open window' of altered immunity (which may last between 3 and 72 hours, depending on the parameter measured), viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection. However, no serious attempt has been made by investigators to demonstrate that athletes showing the most extreme post-exercise immunosuppression are those that contract an infection during the ensuing 1 to 2 weeks. This link must be established before the 'open window' theory can be wholly accepted. The influence of nutritional supplements, primarily zinc, vitamin C, glutamin and carbohydrate, on the acute immune response to prolonged exercise has been measured in endurance athletes. Vitamin C and glutamine have received much attention, but the data thus far are inconclusive. The most impressive results have been reported in the carbohydrate supplementation studies. Carbohydrate beverage ingestion has been associated with higher plasma glucose levels, an attenuated cortisol and growth hormone response, fewer perturbations in blood immune cell counts, lower granulocyte and monocyte phagocytosis and oxidative burst activity, and a diminished pro- and anti-inflammatory cytokine response. It remains to be shown whether carbohydrate supplementation diminishes the frequency of infections in the recovery period after strenuous exercise. Studies on the influence of moderate exercise training on host protection and immune function have shown that near-daily brisk walking compared with inactivity reduced the number of sickness days by half over a 12- to 15-week period without change in resting immune function. Positive effects on immunosurveillance and host protection that come with moderate exercise training are probably related to a summation effect from acute positive changes that occur during each exercise bout. No convincing data exist that moderate exercise training is linked with improved T helper cell counts in patients with HIV, or enhanced immunity in elderly participants.

Glutamine, exercise and immune function. Links and possible mechanisms

Glutamine is the most abundant free amino acid in human muscle and plasma and is utilised at high rates by rapidly dividing cells, including leucocytes, to provide energy and optimal conditions for nucleotide biosynthesis. As such, it is considered to be essential for proper immune function. During various catabolic states including surgical trauma, infection, starvation and prolonged exercise, glutamine homeostasis is placed under stress. Falls in the plasma glutamine level (normal range 500 to 750 mumol/L after an overnight fast) have been reported following endurance events and prolonged exercise. These levels remain unchanged or temporarily elevated after short term, high intensity exercise. Plasma glutamine has also been reported to fall in patients with untreated diabetes mellitus, in diet-induced metabolic acidosis and in the recovery period following high intensity intermittent exercise. Common factors among all these stress states are rises in the plasma concentrations of cortisol and glucagon and an increased tissue requirement for glutamine for gluconeogenesis. It is suggested that increased gluconeogenesis and associated increases in hepatic, gut and renal glutamine uptake account for the depletion of plasma glutamine in catabolic stress states, including prolonged exercise. The short term effects of exercise on the plasma glutamine level may be cumulative, since heavy training has been shown to result in low plasma glutamine levels (< 500 mumol/L) requiring long periods of recovery. Furthermore, athletes experiencing discomfort from the overtraining syndrome exhibit lower resting levels of plasma glutamine than active healthy controls. Therefore, physical activity directly affects the availability of glutamine to the leucocytes and thus may influence immune function. The utility of plasma glutamine level as a marker of overtraining has recently been highlighted, but a consensus has not yet been reached concerning the best method of determining the level. Since injury, infection, nutritional status and acute exercise can all influence plasma glutamine level, these factors must be controlled and/or taken into consideration if plasma glutamine is to prove a useful marker of impending overtraining.

Effect of glutamine supplementation on changes in the immune system induced by repeated exercise

The ability of lymphocytes to proliferate and generate lymphokine activated killer (LAK) cell activity in vitro is dependent on glutamine. In relation to intense exercise the lymphocyte concentration, the proliferative response, the natural killer and LAK cell activity, and the plasma glutamine concentration decline. It has been hypothesized that in relation to physical activity a lack of glutamine may temporarily affect the function of the immune system.

PURPOSE

The purpose of this study was to examine the influence of glutamine supplementation on exercise-induced immune changes.

METHODS

In a randomized cross-over placebo-controlled study, eight healthy male subjects performed three bouts of ergometer bicycle exercise lasting 60, 45, and 30 min at 75% of their VO2max separated by 2 h of rest.

RESULTS

The arterial plasma glutamine concentration declined from 508 +/- 35 (pre-exercise) to 402 +/- 38 microM (2 h after the last exercise bout) in the placebo trial and was maintained above pre-exercise levels in the glutamine supplementation trial. The numbers of circulating lymphocytes and the phytohemagglutinin-stimulated lymphocyte proliferative response declined 2 h after, respectively, during each bout of exercise, whereas the LAK cell activity declined 2 h after the third bout. Glutamine supplementation in vivo, given in the described doses at the specific times, did not influence these changes.

CONCLUSION

The present study does not appear to support the hypothesis that those aspects of postexercise immune changes studied are caused by decreased plasma glutamine concentrations.

Contrasting plasma free amino acid patterns in elite athletes: association with fatigue and infection

AIM

There is little information on the plasma free amino acid patterns of elite athletes against which fatigue and nutrition can be considered. Therefore the aim was to include analysis of this pattern in the medical screening of elite athletes during both especially intense and light training periods.

METHODS

Plasma amino acid analysis was undertaken in three situations. (1) A medical screening service was offered to elite athletes during an intense training period before the 1992 Olympics. Screening included a blood haematological/biochemical profile and a microbial screen in athletes who presented with infection. The athletes were divided into three groups who differed in training fatigue and were considered separately. Group A (21 track and field athletes) had no lasting fatigue; group B (12 judo competitors) reported heavy fatigue at night but recovered overnight to continue training; group C (18 track and field athletes, one rower) had chronic fatigue and had been unable to train normally for at least several weeks. (2) Athletes from each group were further screened during a post-Olympic light training period. (3) Athletes who still had low amino acid levels during the light training period were reanalysed after three weeks of additional protein intake.

RESULTS

(1) The pre-Olympics amino acid patterns were as follows. Group A had a normal amino acid pattern (glutamine 554 (25.2) micromol/l, histidine 79 (6.1) micromol/l, total amino acids 2839 (92.1) micromol/l); all results are means (SEM). By comparison, both groups B and C had decreased plasma glutamine (average 33%; p<0.001) with, especially in group B, decreased histidine, glucogenic, ketogenic, and branched chain amino acids (p<0.05 to p<0.001). None in group A, one in group B, but ten athletes in group C presented with infection: all 11 athletes had plasma glutamine levels of less than 450 micromol/l. No intergroup differences in haematological or other blood biochemical parameters, apart from a lower plasma creatine kinase activity in group C than in group B (p<0.05) and a low neutrophil to lymphocyte ratio in the athletes with viral infections (1.2 (0.17)), were found. (2) During post-Olympic light training, group A showed no significant amino acid changes. In contrast, group B recovered normal amino acid levels (glutamine 528 (41.4) micromol/l, histidine 76 (5.3) micromol/l, and total amino acids 2772 (165) micromol/l) (p<0.05 to p<0.001) to give a pattern comparable with that of group A, whereas, in group C, valine and threonine had increased (p<0.05), but glutamine (441 (24.5) micromol/l) and histidine (58 (5.3) micromol/l) remained low. Thus none in group A, two in group B, but ten (53%) in group C still had plasma glutamine levels below 450 micromol/l, including eight of the 11 athletes who had presented with infection. (3) With the additional protein intake, virtually all persisting low glutamine levels increased to above 500 micromol/l. Plasma glutamine rose to 592 (35.1) micromol/l and histidine to 86 (6.0) micromol/l. Total amino acids increased to 2761 (128) micromol/l (p<0.05 to p<0.001) and the amino acid pattern normalised. Six of the ten athletes on this protein intake returned to increased training within the three weeks.

CONCLUSION

Analysis of these results provided contrasting plasma amino acid patterns: (a) a normal pattern in those without lasting fatigue; (b) marked but temporary changes in those with acute fatigue; (c) a persistent decrease in plasma amino acids, mainly glutamine, in those with chronic fatigue and infection, for which an inadequate protein intake appeared to be a factor.

Recovery of the immune system after exercise

In the recovery phase after intense exercise is found suppressed blood concentration of lymphocytes, suppressed natural immunity of blood lymphocytes, decreased concentration of secretory IgA in mucosa, but increased blood concentration of neutrophils and increased levels in the blood of inflammatory cytokines. Thus, after intense long-term exercise, the immune system is characterized by concomitant inflammation and temporary suppression of the cellular immune system, the most pronounced findings being 2-4 h after the exercise. The underlying mechanisms are multifactorial and include neuroendocrinological and metabolic factors. High levels of cytokines, especially interleukin-6, are found in the recovery period after eccentric exercise, and it has been demonstrated that a close association exists between muscle damage and increased levels of interleukin-6.