A Comparison Of Tnfr1 And Tnfr2 Expression On Monocyte Subsets Following Continuous And Interval Exercise

Abstract

PURPOSE: To examine the tumor necrosis factor receptor (TNFR) 1 and 2 response on monocyte subsets to interval and continuous aerobic exercise. METHODS: Six men (22.5±3.9 yrs; 180.8±5.0 cm; 80.5±6.6 kg; 11.8±4.3 %BF; 44.2±2.4 ml·kg-1·min-1) completed three cycling protocols: moderate continuous (MCT), sprint-interval (SIT), and high-intensity-interval (HIIT), in a randomized order. Visit 1 consisted of a maximal graded exercise test (VO2max) on a cycle ergometer. HIIT consisted of 15 90-sec bouts at 85% VO2max and 90-sec active recovery periods. SIT consisted of 15 20-sec bouts at 130% max wattage and 160-sec active recovery periods. MCT was a continuous bout at 65% VO2max. Each trial duration was 53 min, including a 5-min warm-up and a 3-min recovery. Blood was collected before (PRE), immediately (IP), 30 minutes (30M), 2 hours (2H), 6 hours (6H) and 24 hours (24H) post-exercise. Changes in surface expression, as measured by median fluorescent intensity (MFI) of TNFR 1 and 2 on monocyte subsets (classical: CD14++CD16−; intermediate: CD14++CD16+; and non-classical: CD14+CD16++) were analyzed via flow cytometry. Changes in TNFR1 and 2 expression were determined using a mixed model regression with fixed effects on time and condition. RESULTS: Analysis indicated a time effect for TNFR1 expression on classical (F=4.450, p=0.001) and intermediate (F=3.517, p=0.006) monocytes. TNFR1 expression on classical monocytes decreased (p < 0.05) from PRE (6637 ± 704 MFI), IP (6538 ± 522 MFI), 30M (6836 ± 661 MFI), and 2H (6600 ± 564 MFI) at 6H (5934 ± 814 MFI) and 24H (6156 ± 516 MFI). TNFR1 expression on intermediate monocytes decreased (p <0.05) from PRE (6391 ± 649 MFI), 30M (6618 ± 655 MFI) and 2H (6418 ± 569 MFI) at 6H (5912 ± 814 MFI) and 24H (5936 ± 443 MFI). A time effect (F= 4.079, p=0.002) was observed for TNFR2 expression on intermediate monocytes, with a decrease (p< 0.05) from PRE (25528 ± 3188 MFI) at 30M (22327 ± 4067 MFI), 2H (21008 ± 5113 MFI), and 6H (20515 ± 5918 MFI). TNFR2 expression on intermediate monocytes recovered by 24H (25483 ± 3189 MFI). CONCLUSION: Changes in TNFR1 and TNFR2 expression were observed across time, with no differences observed between conditions. Therefore, TNFR1 and TNFR2 expression on monocytes may not be dependent on intensity, but more investigation in necessary. Partially supported by the NSCA Foundation