In Vitro Mechanisms of β-Glucan, Taurine, and L-Arginine in CoCl2-Treated H9c2 Cardiomyoblasts and a Pre–Post β-Glucan-Rich Mushroom Extract Study in Athletes

The effects of nutraceuticals β-glucan, taurine, and L-arginine under hypoxia, and their significance for athletes, remain unknown. We evaluated these compounds in vitro and tested β-glucan supplementation in athletes. H9c2 cardiomyoblasts were subjected to CoCl2-induced chemical hypoxia to assess metabolic activity, morphology, transcript profiles, and mitochondrial/glycolytic function. In an uncontrolled, single-arm pre–post trial, 50 male athletes received β-glucan-rich mushroom extract (320 mg/day) for 40 days. Body composition, complete blood count, and cardiopulmonary exercise testing were assessed pre- and post-supplementation. CoCl2 decreased MTT metabolic activity to 67.29 ± 0.87% of control. The three compounds significantly increased MTT metabolic activity (83.65–97.40%; p < 0.001 vs. positive control). Taurine, β-glucan, and L-arginine all reduced Hif1a transcript (FC = 0.44, 0.58, and 0.47, respectively; all p < 0.001 vs. positive control). Seahorse examination revealed partial preservation of mitochondrial parameters and improved glycolytic reserve, with L-arginine (120.4%) and taurine (105.1%) numerically higher than the negative control (86.0 ± 20.2%), but neither difference was statistically significant. The transcriptional alterations were compound-specific and exploratory. Athletes who supplemented with multi-mushroom extract for 40 days had higher relative VO2/kg (46.26 ± 2.33 to 53.12 ± 3.75 mL/min/kg; +14.8%; p < 0.001), absolute VO2 (3138.46 ± 313.38 to 3503.82 ± 371.73 mL/min; +11.6%; p < 0.001), and peak RQ (1.096 ± 0.048 to 1.308 ± 0.082; p < 0.001). HCT dropped (44.53 ± 2.81% to 42.10 ± 2.64%; p < 0.001), MCV increased (86.37 ± 2.20 to 89.67 ± 2.32 fL; p < 0.001), and MCHC fell (35.10 ± 0.80 to 33.78 ± 0.53 g/dL; p < 0.001). WBC levels reduced (7.53 ± 1.31 to 6.80 ± 1.02 × 103/µL; p = 0.004), neutrophils fell (61.00 ± 8.34% to 52.02 ± 5.66%; p < 0.001), lymphocytes rose (27.80 ± 3.67% to 35.17 ± 1.65%; p < 0.001), and monocytes increased (2.75 ± 0.44% to 4.35 ± 0.64%; p < 0.001). The human component was an uncontrolled, single-arm, pre–post study with no placebo, randomization, or blinding; hence, the results are hypothesis-generating. In CoCl2-treated H9c2 cells, the compounds improved metabolic activity and partially preserved bioenergetics. The uncontrolled human trial suggests β-glucan supplementation improves aerobic performance and alters hematological indices, though randomized controlled trials are needed to confirm these preliminary findings.