Heavy load exercise induced dysfunction of immunity and neuroendocrine responses in rats

To determine whether immunity and neuroendocrine system is altered by different loads of exercise training in rats, eight-week-old male Sprague-Dawley rats were randomly assigned to one of the three groups: 1) cage control group (CCG); 2) moderate load training (MLT) (swimming at the intensity of 1.4 m/sec water flowing for 60 min per day); 3) heavy load training (HLT) (swimming at the intensity of 1.8 m/sec water flowing for 120 min per day). MLT and HLT rats were assigned to swim for 6 days per week for total of 6 weeks. All rats were sacrificed 36 h after their last training session. Splenocytes were pooled for assay of cell proliferation and neuropeptide contents in the hypothalamus, hypophysis and plasma were determined by radioimmunoassay while glucocorticoid specific binding in intact thymus was measured by radioligand binding assay. All rats were weighed weekly. The results showed that after 6-week training, rat splenocyte proliferation in response to Con A and LPS decreased in HLT rats compared with MLT and CCG rats. In addition, the contents of beta-endorphin, dynorphin A, arginine vasopressin and oxytocin in the hypothalamus, hypophysis and plasma were altered by HLT, as shown by increased plasma concentration of glucocorticoids and decreased glucocorticoids specific binding in intact thymus compared with MLT and CCG. Furthermore, a decreased body mass in HLT rats has been observed. The body mass of HLT rats was significantly lower than that in CCG and MLT rats at the end of the swimming training period. These data suggest that 6-week heavy load training induces the dysfunction of immunity and neuroendocrine responses, which might be one of the underlying mechanisms of immune dysfunction in overtraining.

Effects of chronic and acute training on glucocorticoid receptors concentrations in rats

The effects of chronic endurance training and acute exercise on glucocorticoid receptors were investigated in rats. For chronic endurance training, rats were exposed to progressive running training on a motor-driven treadmill for 3, 5 and 7 weeks, twice a day and 6 days a week. The samples were taken, 34-36 hours after the last exercise bout. Some of the 7-week training rats were killed by decapitation 7 days following the last exercise bout. The glucocorticoid receptors in hepatic cytosol in 5-week and 7-week rats decreased as compared to the sedentary control. There was no significant difference between the glucocorticoid receptors in hepatic cytosol in some of the 7-week rats those who had stopped training for 7 days and those in the controls. The chronic endurance training did not lead to change of the apparent dissociation constant (Kd). The changes of glucocorticoid receptors after acute exercise have also been investigated and it showed profound decreases of glucocorticoid receptors in renal and myocardial cytosol in low intensity (swimming without an extra weight for 60 minutes) and high intensity (swimming with a weight equal to 6% of body mass for 60 minutes) training groups. The decreases in glucocorticoid receptors in renal and myocardial cytosol were less prominent after low intensity training. These results demonstrated that both acute exercise training and chronic endurance training could lead to a decrease in glucocorticoid receptors, which was in a training intensity- and training load volume-dependent manner, and the changes in glucocorticoid receptors during exercise training were reversible.

Modulation of NKT cells and Th1/Th2 imbalance after alpha-GalCer treatment in progressive load-trained rats

Purpose: The purpose of this study was to determine whether α-galactosylceramide (α-GalCer), a synthetic glycolipid agonist of natural killer T (NKT) cells, can ameliorate exercise-induced immune imbalance. Methods: Eight-week-old female Sprague-Dawley rats were trained with a progressively increasing load for 9 weeks. At 36 h and at 7 d after training, groups of rats were euthanized. The whole blood was used to detect hemoglobin(Hb), plasma was analyzed for hormones testosterone(T) and corticosterone(C), and spleen was harvested for detecting NKT cells and interferon-γ (IFN-γ) and interleukin (IL)-4 producing cells. Results: Two-way analysis of variance (ANOVA) showed significant differences between training and time in Series 1. The results showed, at 36h after training, that the decrease in Hb, T and C concentration reflected overtraining or excessive exercise. At 7 d after training, NKT cell populations decreased, and a T helper 1/T helper 2 (Th1/Th2) lymphocyte imbalance occurred. In Series 2, α-galactosylceramide (α-GalCer), an NKT cell activator was found to enhance NKT cell numbers by 69% and shift the Th1/Th2 lymphocyte imbalance by observably decreasing the frequency of IL-4 secreting cells. Conclusion: These data showed that, in addition to Th1/Th2 self-regulation, α-GalCer played an important modulatory role in the exercise-induced Th1/Th2 lymphocyte imbalance, which may be correlative with NKT immunoregulatory cells.

The Influence of Family Sports Attitude on Children's Sports Participation, Screen Time, and Body Mass Index

Background: Children’s physical health is an important resource for a country’s future construction. However, researchers found that the physical fitness of young children around the world has declined during the two decades, from 1992 to 2012. The decline in the physique of young children has caused widespread concern around the world. Children’s main living places are families and kindergartens, so this research explores the impact of family factors on children’s body mass index (BMI) from the perspective of family attitudes, children’s sports participation, and screen time.

Methods: A cross-sectional study was used to conduct a questionnaire survey of children in China. A total of 600 children were investigated, and 589 valid questionnaires were obtained. SPSS21.0 statistical analysis software was used for descriptive analysis, mean comparison, and correlation analysis of the data. AMOS 21.0 was used to construct a structural equation model and carry out path analysis.

Results: (1) There are significant differences in children’s family sports attitude, sports participation, screen time, and BMI with different family structures, and parents’ education levels. (2) Family sports attitude is significantly positively correlated with parents’ education levels and children’s sports participation, and negatively correlated with children’s screen time and BMI. (3) Children’s sports participation and screen time play a chain-mediating role between family sports attitude and children’s BMI, and the role is a complete mediating role. Therefore, family sports attitudes can affect children’s physical health by affecting children’s sports participation and screen time. To promote children’s physical health, we should pay attention to the intervention of family sports attitude. (4) The mediating effects of exercise participation and screen time are similar in different family structures, so the structure of this study can be applied to different family structures.

Conclusions: Children’s family sports attitude, sports participation, and screen time can affect children’s BMI. Children’s screen time and sports participation play a chain-mediating role in the influence of family sports attitudes on the path of children’s BMI. The results of this study will provide a useful reference for teachers and parents to control children’s physical health.

Long-term endurance training induced changes in glucocorticoid receptors concentrations in rat and in man

AIM

The responsiveness of target cells to glucocorticoids is directly related to the number and the functional state of intracellular glucocorticoid receptors (GR), which mediated the role of glucocorticoids. Although the effects of acute training on GR have been well characterized, less is known about the effects of chronic training on GR. The purpose of the present study was to describe the effects of long-term endurance training on GR.

METHODS

Male Sprague-Dawley rats were divided into 2 groups at random, 7 as controls and exercisers (swimming 40-50 min/day for 80 days), respectively. All rats were sacrificed 24 hours after their last training session for measurements of the GR in liver and brain cytosol and thymus cells by radioligand binding assay with 3H-dexamethasone. This study was also carried out on 8 trained adult, 8 aged as well as 6 retired athletes, whose GR in peripheral leukocytes were analyzed.

RESULTS

GR in hepatic cytosol and intact thymus cells of rats were significantly lower in exercise group than those in the controls. But the apparent dissociation constant (kd) was not changed. The GR in brain cytosol of rats indicated no significant reduction after training. The GR in peripheral leukocytes of the adult and aged athletes were also significantly lower than that in the controls. However, there was no significant difference between the GR in the retired athletes and that in the controls.

CONCLUSIONS

This study demonstrated that long-term endurance training could lead to a decrease in GR and that the changes in GR were reversible during training. The possible mechanisms and the physiological significance of these changes need to be determined.