N-Acetyl-Cysteine Supplementation does not Alter the Erythropoietin Response in Trained Endurance Athletes in Acute Hypoxia

Abstract

To assess the potential effect of N-Acteyl-Cysteine (NAC) supplementation on the magnitude of EPO response with acute exposure to hypoxia in trained endurance athletes, 10 trained male endurance athletes engaged in a placebo-controlled crossover design, featuring two conditions: a placebo (PLA) condition and an NAC condition. Each condition featured a day of baseline testing followed by an 1800 mg/day supplementation period lasting eight days and, finally, a six hour acute hypoxic exposure (FIO2 = 15.8%, ~2500m). Subject serum EPO (EPO), total hemoglobin mass (Hbmass), and hematocrit (Hct) measurements were recorded during the baseline visit of each condition in addition to immediately prior to hypoxic exposure in order to evaluate changes in subject hematological metrics in response to each supplementation condition. Additionally, EPO was measured every two hours during hypoxic exposure to evaluate the EPO response in each condition. Eight days of NAC supplementation prior to acute hypoxic exposure did not significantly alter the EPO (IU/L) response between baseline and pre hypoxic exposure (10.4±2.9 vs. 9.9±1.5; p=0.52) when compared with the PLA condition(10.9±2.5 vs. 10.2±2.0; p=0.23). Additionally, no significant changes were seen in Hbmass (g/kg) in the NAC condition (15.75±0.97 vs 16.01±0.68; p=0.58) when compared to the PLA condition (15.58±0.72 vs 15.84±0.97; p=0.24). Finally, no significant changes were seen in hematocrit (%) in the NAC condition (46.2±1.6 vs 46.6±1.9; p= 0.57) when compared to the PLA condition (45.8±2.7 vs 46.4±2.2; p=0.23). EPO increased at each time point after tent entry in both conditions but the magnitude of increase (NACΔ 32.3±23.6% vs PLAΔ 31.4±20.9%) was not significantly different between conditions. NAC supplementation prior to acute hypoxic exposure has no significant impact on EPO concentration in trained endurance athletes. The large variation in intra-subject EPO response to hypoxia between conditions may have concealed any impact that NAC supplementation had on EPO response.