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% V̇O2max 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−CD56dim or CD3−CD56bright. CD69 expression on CD3−CD56+ cells was also determined.
Results: A puberty × CHO × exercise interaction was found for the proportion, but not number, of CD56dim cells (P = 0.06). CD56dim cell counts were lower in CT versus WT (P < 0.001). Responses of CD56bright proportions (P = 0.007) and counts (P = 0.03) depended on pubertal status, but not CHO. The CD56bright:CD56dim 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.
1Children's Exercise and Nutrition Centre; 2Departments of Pediatrics and Medicine; and 3Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, CANADA
Address for correspondence: Mark A. Tarnopolsky, M.D., Ph.D., FRCP(C), 4U4 Department of Neurology, McMaster University Medical Centre, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5; E-mail: email@example.com
Submitted for publication July 2005.
Accepted for publication November 2005.