The Influence of Sex, Training Status, and Fatty Acid Supplementation on T-lymphocyte Populations at Rest and in Response to Acute Exercise.

Abstract

This series of studies began with an examination of the effects of training status (Tr vs UTr) and sex on the resting levels and redistribution of senescent (CD28-CD57+) and naïve (CD28+CD57-) T-lymphocytes (CD4+, CD8+) following a treadmill test to volitional exhaustion. In this first study exercise elicited a redistribution of senescent CD4+, CD8+ and naïve CD4+,CD8+ T-lymphocytes. UTr had a higher proportion of senescent and a lower proportion of naïve CD8+ T-lymphocytes than Tr. Males had a higher proportion of senescent and lower proportion of naïve T-lymphocytes than females with the highest percentage of senescent and lowest percentage of naïve T-lymphocytes observed in UTr males. CMV was a covariate in the senescent and naïve CD8+ T-lymphocytes. This study highlighted important sex and training status differences in the senescent and naïve T-lymphocyte redistribution in response to exercise. These findings led on to an investigation of the T-lymphocyte (CD4+, CD8+, γδ+) response to a period of 2 weeks increased volume training (39% increase in volume) in trained females (Tr, n=13) compared to a period of 2 weeks habitual activity in female controls (UTr, n=13). This second study observed no difference in the resting T-lymphocyte profile from the pre to post increased volume training period. The resting number of CD3+ and proportion of γδ+ T-lymphocytes was greater in the Tr compared to the UTr. The resting proportion of CD4+T-lymphocytes and the CD4+:CD8+ ratio was greater in the UTr compared to the Tr. CMV was a covariate in the analysis of CD8+, CD28+ CD8+, and naïve CD8+ T-lymphocyte cell numbers but not in the analysis of T-lymphocyte proportions. The increased volume training period had no effect on resting T-lymphocyte populations in Tr females, and T-lymphocyte populations also did not change with 2 weeks of habitual exercise in UTr. The total energy, carbohydrate and protein intake was greater in Tr compared to the UTr during the increased volume training period and was greater than normal in the Tr group. These dietary influences may partly explain the absence of any change in T-lymphocyte proportions pre to post training period in Tr. Differences in the proportions of γδ+, CD4+ and the ratio of CD4+:CD8+ T-lymphocytes at rest between the Tr and UTr warrants further investigation. The final study of this series is presented in two parts. The first part focused on the influence of 4 weeks supplementation at 0.1g/kg body mass/day with n-3 polyunsaturated fatty acids (PUFA) as fish oil (FO, n=10), or short-chain saturated fatty acids (SFA) as coconut oil (CO, n=10) on T-lymphocyte (CD4+,CD8+, γδ+) differentiated populations at rest and in response to exercise in trained males. Changes were examined by Day (Baseline to pre supplementation, Pre Sup (4 week control period), and pre supplementation to post supplementation, Post Sup (4 week supplementation period)). During a 4 week baseline control period no changes were observed in the blood lipid profile in both FO and CO groups. During the control period a main effect of exercise was observed in all the CD3+ and γδ+ T-lymphocytes subsets. During the control period an interaction of group-by-day was observed in the senescent CD8+ T-lymphocytes from BL to Pre Sup the proportion and number decreased in the FO group and increased in the CO group. Inclusion of CMV as a covariate introduced a main effect of group on the CD4+ naïve proportions and cell counts and the group-by-day interaction observed on the CD8+ senescent T-lymphocyte proportions and cell counts disappeared. During the 4 week supplementation period this study observed an increase in the n-3 PUFAs, EPA (20:5n-3), DHA (22:6n-3) and DPA (22:5n-3) in the FO group but not in the CO group (with no changes in blood lipid profile on CO). During the supplementation period a main effect of exercise was observed in all the CD3+ and γδ+ T-lymphocyte subsets except for the proportion of CD8+ naïve T-lymphocytes. The proportion of CD8+ naïve T-lymphocytes was lower at rest and in response to exercise in FO and CO groups after supplementation. CMV was a significant covariate in senescent CD4+ T-lymphocyte cell counts. At the post exercise time point the γδ+ T-lymphocyte count increased in the FO group but decreased in the CO group, following the supplementation period. However, this observation did not quite reach statistical significance. Although a difference between the groups was evident for γδ+ T-lymphocyte count and proportion there was insufficient evidence to conclude whether the difference was supplement related. It would appear that dose, duration and type of fatty acids ingested could all be important in the overall response but these require further study. The second part of this final study investigated the influence of 4 week supplementation at 0.1g/kg body mass/day with n-3 polyunsaturated fatty acids (PUFA) as fish oil (FO, n=10) or short-chain saturated fatty acids (SFA) as coconut oil (CO, n=10) on plasma Th1 cytokine: IL-2, TNF- α and IFN-γ, and Th2 cytokine IL-4, IL-6 and IL-10 concentrations, and expression of the T-lymphocyte activation marker CD69 at rest and in response to exercise in trained males. Changes were examined by Day (Baseline to pre supplementation (4 week control period), and pre supplementation to post supplementation (4 week supplementation period)). This study observed an increase in n-3 PUFAs, EPA (20:5n-3), DHA (22:6n-3) and DPA (22:5n-3) in the FO group but not in the CO group. There was a significant mobilisation of activated CD4+ CD69+ and CD8+ CD69+ (P<0.05) T-lymphocyte numbers in response to exercise in both FO and CO groups. CMV infection was a significant covariate on the number and proportion of CD4+CD69+ T-lymphocytes (P<0.05) but not on the number or proportion of CD8+CD69+ T-lymphocytes. During the supplementation period there was a significant effect of Day on TNF-α, IL-6, IL-4 and IL-2 with IFN-γ and IL-10 trending towards a difference. The plasma cytokine concentration was greater at post supplementation compared to pre supplementation for both FO and CO groups. Latent CMV infection was a significant covariate for TNF-α, IL-6, IL-4, IL-2, IFN-γ and IL-10. In the current study we observed no evidence of a difference between the CO and FO groups for early T-lymphocyte activation marker or plasma cytokine concentrations despite the membrane lipid composition change over the 4 week supplementation period. It would appear that the plasma Th1 and Th2 cytokine concentration increased from pre supplementation to post supplementation on both PUFA and SFA, highlighting a potential link between fatty acid incorporation and cytokine expression that needs closer examination. The results of this series of studies highlight that sex and training status impact upon the T-lymphocyte pool at rest and in response to exercise. Increasing the volume of training for 2 weeks without dietary restriction does not alter the resting T-lymphocyte pool in trained females. Alterations to the T-lymphocyte pool at rest and in response to exercise are not related to FO or CO supplementation. Furthermore, the response of Th1, Th2 plasma cytokines, and the early activation marker CD69 at rest and in response to exercise does not differ between a group supplemented with FO compared to a group supplemented with CO it would appear that Th1 and Th2 plasma cytokines increase post supplementation in both groups. Particular avenues of interest for future research would be, to explore the sex differences in T-lymphocyte subsets at rest and in response to exercise, to determine whether these sex differences are key in susceptibility to disease/infection and to determine the tissue targets of lymphocytes mobilised during exercise.