Dry blood spot samples to monitor immune-associated mRNA expression in intervention studies: Impact of Baker's yeast beta glucan

Monitoring immunological response to physical stressors in a field setting is challenging because existing methods require a laboratory visit and traditional blood collection via venipuncture. The purpose of this study was to determine if our optimized dry blood spot (DBS) methodology yields sufficient total RNA to quantify the effect of Baker's Yeast Beta Glucan supplementation (BYBG; Wellmune; 250 mg/d) on post-exercise mRNA expression. Participants had venous DBS samples collected prior to (PRE), and immediately (POST), 2 (2H), and 4 (4H) hrs after completion of a 90 min run/walk trial in a hot, humid environment. Total RNA extracted from DBS was analyzed using a 574-plex Human Immunology mRNA panel (Nanostring). BYBG supplementation was associated with the increased expression of 12 mRNAs (LTB4R, PML, PRFM1, TNFRSF14, LCK, MYD88, STAT3, CCR1, TNFSF10, LILRB3, MME, and STAT6) and decreased expression of 4 mRNAs (MAP4K1, IKBKG, CD5, and IL4R) across all post-exercise time points. In addition to individually changed mRNA targets, we found eleven immune-response pathways that were significantly enriched by BYBG following exercise (TNF Family signaling, immunometabolism, oxidative stress, toll-like receptor (TLR) signaling, Treg differentiation, autophagy, chemokine signaling, complement system, Th2 differentiation, cytokine signaling, and innate immune). The present approach showed that DBS samples can be used to yield useful information about mRNA biomarkers in an intervention study. We have found that BYBG supplementation induces changes at the mRNA level that support the immune system and reduce susceptibility to opportunistic infection (i.e., upper respiratory tract infection) and facilitate improved physical recovery from exercise. Future studies may look to use DBS sampling for testing other nutritional, health, or medical interventions.