Dehydration decreases saliva antimicrobial proteins important for mucosal immunity.
The aim of the study was to investigate the effect of exercise-induced dehydration and subsequent overnight fluid restriction on saliva antimicrobial proteins important for host defence (secretory IgA (SIgA), α-amylase, and lysozyme). On two randomized occasions, 13 participants exercised in the heat, either without fluid intake to evoke progressive body mass losses (BML) of 1%, 2%, and 3% with subsequent overnight fluid restriction until 0800 h in the following morning (DEH) or with fluids to offset losses (CON). Participants in the DEH trial rehydrated from 0800 h until 1100 h on day 2. BML, plasma osmolality (Posm), and urine specific gravity (USG) were assessed as hydration indices. Unstimulated saliva samples were assessed for flow rate (SFR), SIgA, α-amylase, and lysozyme concentrations. Posm and USG increased during dehydration and remained elevated after overnight fluid restriction (BML = 3.5% ± 0.3%, Posm = 297 ± 6 mosmol·kg⁻¹, and USG = 1.026 ± 0.002; P < 0.001). Dehydration decreased SFR (67% at 3% BML, 70% at 0800 h; P < 0.01) and increased SIgA concentration, with no effect on SIgA secretion rate. SFR and SIgA responses remained unchanged in the CON trial. Dehydration did not affect α-amylase or lysozyme concentration but decreased secretion rates of α-amylase (44% at 3% BML, 78% at 0800 h; P < 0.01) and lysozyme (46% at 3% BML, 61% at 0800 h; P < 0.01), which were lower than in CON at these time points (P < 0.05). Rehydration returned all saliva variables to baseline. In conclusion, modest dehydration (~3% BML) decreased SFR, α-amylase, and lysozyme secretion rates. Whether the observed magnitude of decrease in saliva AMPs during dehydration compromises host defence remains to be shown.
Extremes Research Group, Bangor University, Bangor, Gwynedd, UK.
Matthew B
MB
Fortes
Bethany C
BC
Diment
Umberto
U
Di Felice
Neil P
NP
Walsh
D000328:Adult; D003681:Dehydration / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D015536:Down-Regulation; D005080:Exercise Test; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D018928:Immunity, Mucosal; D007071:Immunoglobulin A, Secretory / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009043:Motor Activity; D009061:Mouth Mucosa / Q000276:immunology*; D009113:Muramidase / Q000378:metabolism; D012463:Saliva / Q000276:immunology* / Q000378:metabolism; D012471:Salivary Proteins and Peptides / Q000378:metabolism*; D055291:Salivary alpha-Amylases / Q000378:metabolism; D012472:Salivation; D012720:Severity of Illness Index; D055815:Young Adult
D007071:Immunoglobulin A, Secretory; D012471:Salivary Proteins and Peptides; D055291:Salivary alpha-Amylases; D009113:Muramidase