Post‐Resistance Exercise Ingestion of Amino Acids Attenuates the Initial Increase in Plasma TNFα and TNFr1 Expression on Monocyte Subpopulations

TNFα is associated with inhibited muscle protein synthesis and increased protein loss during the acute phase reaction to muscle damage. Ingestion of amino acids (AA's) post‐resistance exercise have been shown to augment the anabolic response to exercise, switching net protein balance from negative to positive. However, whether post‐exercise AA's are able to regulate TNFα or expression of TNFr1 on monocytes remains unclear. OBJECTIVE To examine the effect of post‐resistance exercise amino acid ingestion on plasma tumor necrosis factor alpha (TNFα) and tumor necrosis factor receptor 1 (TNFr1) expression on monocyte subpopulations. METHODS Ten resistance‐trained men (24.7±3.4y; 90.1±11.3kg; 176.0±4.9cm) ingested supplement (SUPP) or placebo (PL) immediately post‐exercise in a randomized, counter‐balanced cross‐over design. Blood samples were obtained at baseline (BL), immediately (IP), 30‐minutes (30P), 1‐hour (1H), 2‐hours (2H), and 5‐hours (5H) post‐exercise to assess plasma concentrations of lactate, myoglobin, TNFα; and expression of TNFr1 on classical, intermediate, and non‐classical monocytes. Magnitude based inferences calculated from 90% confidence intervals were used to provide inferences on the true effects of SUPP compared to PL. Differences between BL and all subsequent time points were calculated for each treatment group. This approach uses the smallest worthwhile changes to establish the likelihood (in percentage terms) of the experimental condition having a positive, trivial or negative effect. Qualitative inferences, based on quantitative chances, were assessed as: <1%, almost certainly not; 1–4.99%, very unlikely; 5–24.99%, unlikely; 25–74.99%, possibly; 75–94.99%, likely; 95–99%, very likely; and >99%, almost certainly. If there was a greater than 5% chance that the true value was both greater and smaller, the effect was considered mechanistically unclear. Comparisons between treatments were further analyzed using Cohen's d.RESULTS Exercise volume, and changes in plasma concentrations of lactate and myoglobin were similar between treatments. Differences between treatments for changes in plasma TNFα and TNFr1 expression on all monocyte subpopulations from BL to IP were interpreted as either “unclear” or “likely trivial”, suggesting that the response to exercise was similar across treatments. Plasma TNFα concentrations were “likely attenuated” (91.6% likelihood effect) from BL to 30P in the SUPP group compared with PL ( d = 0.87; mean effect: 2.3 ± 2.4 pg·mL −1 ). TNFr1 expressions on classical (75.9% likelihood effect) and intermediate (93.0% likelihood effect) monocytes were “likely attenuated” from BL to 2H in the SUPP group compared with PL (d = 0.67; mean effect: 510 ± 670 RFU, and d = 1.05; mean effect: 2500 ± 2300 RFU, respectively). TNFr1 expression on non‐classical monocytes was “likely attenuated” (77.6% likelihood effect) from BL to 1H in the SUPP group compared with PL ( d = 0.69; mean effect: 330 ± 430 RFU). DISCUSSION Ingestion of an amino acid supplement immediately post‐exercise appears to attenuate both plasma TNFα concentrations and TNFr1 expression on monocyte subpopulations in resistance trained men. Support or Funding Information There is no support or funding to disclose 1 Amino acid composition of SUPPEssential amino acids (g/serving)Leucine 1.86 Isoleucine 0.98 Valine 1.2 Histidine 0.53 Methionine 0.53 Phenylalanine 0.96 Threonine 0.84 Tryptophan 0.29 Lysine 1.59Total 8.78Nonessential amino acids (g/serving)Serine 1.08 Glutamic acid 4.07 Proline 1.85 Glycine 0.36 Alanine 0.67 Aspartic acid 1.51 Tyrosine 0.95 Arginine 0.72 Cystine 0.13Total 11.34SUPP = supplement; g = grains