Effect of exercise on glutamine metabolism in macrophages of trained rats

Exercising immune cells: The immunomodulatory role of exercise on atrial fibrillation

Exercise training is generally beneficial for cardiovascular health, improving stroke volume, cardiac output, and aerobic capacity. Despite these benefits, some evidence indicates that endurance training may increase the risk of atrial fibrillation (AF), particularly in highly trained individuals. Among multiple mechanisms, autonomic tone changes and atrial remodeling have been proposed as main contributors for exercise-induced AF. However, the contribution of local and systemic immunity is poorly understood in the development of atrial arrhythmogenic substrates. Here we aim to update the field of immunomodulation in the context of exercise and AF by compiling and reconciling the most recent evidence from preclinical and human studies and rationalize the applicability of "lone" AF terminology in athletes.

Effect of moderate exercise under hypoxia on Th1/Th2 cytokine balance

INTRODUCTION AND OBJECTIVE

Moderate exercise performed in normoxia can be immunostimulatory, while strenuous exercise can be immunosuppressive. However, less is known about the effects of exercise under hypoxia on cytokines. The aim of this study was to evaluate the effects of an acute exercise session performed under hypoxia similar to an altitude of 4200 m on cytokine balance. Our hypothesis was that exercise, even of moderate intensity, associated with hypoxia may induce different changes in relation to the normoxic condition.

METHODS

Eight healthy male volunteers were exercised on a treadmill for 1 hour at an intensity of 50% VO_2peak under normoxic or hypoxic condition (4200 m). Blood samples were collected at rest and immediately 1 hour after the exercise, respectively to determine cytokines, hormones and metabolites. The two-way ANOVA and the Bonferroni post hoc test were used and the significance adopted was P < .05.

RESULTS

While IL-2, the IL-2/IL-4 ratio and glutamine decreased under hypoxia, IL-6 and IL-1ra increased. There were increases in the IL-2/IL-4 ratio, IL-6, IL-1ra and IL-10/TNF-α in normoxia. There were no differences in cortisol or glucose.

CONCLUSION

Moderate exercise under hypoxia condition changes the Th1/Th2 balance including IL-2, IL-4 and TNF-α cytokines, suggesting a Th2 response after 1 hour rest.

Glutamine as an Anti-Fatigue Amino Acid in Sports Nutrition

Glutamine is a conditionally essential amino acid widely used in sports nutrition, especially because of its immunomodulatory role. Notwithstanding, glutamine plays several other biological functions, such as cell proliferation, energy production, glycogenesis, ammonia buffering, maintenance of the acid-base balance, among others. Thus, this amino acid began to be investigated in sports nutrition beyond its effect on the immune system, attributing to glutamine various properties, such as an anti-fatigue role. Considering that the ergogenic potential of this amino acid is still not completely known, this review aimed to address the main properties by which glutamine could delay fatigue, as well as the effects of glutamine supplementation, alone or associated with other nutrients, on fatigue markers and performance in the context of physical exercise. PubMed database was selected to examine the literature, using the keywords combination “glutamine” and “fatigue”. Fifty-five studies met the inclusion criteria and were evaluated in this integrative literature review. Most of the studies evaluated observed that glutamine supplementation improved some fatigue markers, such as increased glycogen synthesis and reduced ammonia accumulation, but this intervention did not increase physical performance. Thus, despite improving some fatigue parameters, glutamine supplementation seems to have limited effects on performance.

Performance and altitude: Ways that nutrition can help

High altitudes are a challenge for human physiology and for sports enthusiasts. Several reasons lead to deterioration in performance at high altitudes. Hypoxia owing to high altitude causes a breakdown of homeostasis with imbalance in several physiological systems, including the immune system. The reduction in mucosal immunity and inflammation and the predominance of the humoral immune response causes a condition of immunosuppression and an increased likelihood of infection. In addition, it is known that worsening of the immune response is associated with reduced performance. On the other hand, immunonutrition plays an important role in modulating the effects of physical exercise on the immune system. However, to our knowledge, few studies have evaluated the effect of nutrition on the immune system after exercise in hypoxia. Although the association between exercise and hypoxia has been shown to be more severe for the body owing to the sum of stressful agents, supplementation with carbohydrates and glutamine seems to play a relevant role in mitigating immunosuppressive effects. These findings, although limited by the fact that they are the result of very few studies, shed light on a relevant theme for sports physiology and nutrition and suggest that both supplements may be useful for athletes, visitors, and workers in high-altitude regions. The aim of this review was to discuss the effects of high-altitude hypoxia on the human body from the point of view of exercise immunology because it is known that transient immunosuppression after strenuous exercise and competition should be followed by reduction in training overload and worse performance.

Importance of exercise immunology in health promotion

Chronic physical exercise with adequate intensity and volume associated with sufficient recovery promotes adaptations in several physiological systems. While intense and exhaustive exercise is considered an important immunosuppressor agent and increases the incidence of upper respiratory tract infections (URTI), moderate regular exercise has been associated with significant disease protection and is a complementary treatment of many chronic diseases. The effects of chronic exercise occur because physical training can induce several physiological, biochemical and psychological adaptations. More recently, the effect of acute exercise and training on the immunological system has been discussed, and many studies suggest the importance of the immune system in prevention and partial recovery in pathophysiological situations. Currently, there are two important hypotheses that may explain the effects of exercise and training on the immune system. These hypotheses including (1) the effect of exercise upon hormones and cytokines (2) because exercise can modulate glutamine concentration. In this review, we discuss the hypothesis that exercise may modulate immune functions and the importance of exercise immunology in respect to chronic illnesses, chronic heart failure, malnutrition and inflammation.

Phagocytic responses of peritoneal macrophages and neutrophils are different in rats following prolonged exercise

OBJECTIVE

To analyze the effects of exhausting long-duration physical exercise (swimming) sessions of different durations and intensities on the number and phagocytic capacity of macrophages and neutrophils in sedentary rats.

INTRODUCTION

Exercise intensity, duration and frequency are important factors in determining immune response to physical effort. Thus, the effects of exhausting long-duration exercise are unclear.

METHODS

Wistar rats were divided into two groups: an untreated group (macrophage study) and oyster glycogen-treated rats (neutrophil study). In each group, the animals were subdivided into five groups (10 rats per group): unexercised controls, an unadapted low-intensity exercise group, an unadapted moderate-intensity exercise group, a preadapted low-intensity exercise group and a preadapted moderate-intensity exercise group. All exercises were performed to exhaustion, and preadaptation consisted of 5, 15, 30 and 45 min sessions.

RESULTS

Macrophage study: the number of peritoneal macrophages significantly decreased (9.22 ± 1.78 x 10(6)) after unadapted exercise but increased (21.50 ± 0.63 x 10(6)) after preadapted low-intensity exercise, with no changes in the moderate-intensity exercise group. Phagocytic capacity, however, increased by more than 80% in all exercise groups (low/moderate, unadapted/preadapted). Neutrophil study: the number of peritoneal neutrophils significantly decreased after unadapted (29.20 ± 3.34 x 10(6)) and preadapted (50.00 ± 3.53 x 10(6)) low-intensity exercise but increased after unadapted (127.60 ± 5.14 x 10(6)) and preadapted (221.80 ± 14.85 x 10(6)) moderate exercise. Neutrophil phagocytic capacity decreased by 63% after unadapted moderate exercise but increased by 90% after corresponding preadapted sessions, with no changes in the low-intensity exercise groups.

CONCLUSION

Neutrophils and macrophages of sedentary rats respond differently to exercise-induced stress. Adaptation sessions reduce exercise-induced stress on the immune system.