Author(s): ITO, R., UCHINO, T.1, UCHIDA, M.1, FUJIE, S.1, IEMITSU, K.1, KOJIMA, C.1, NAKAMURA, M.2, SHIMIZU, K.2, TANIMURA, Y.2, SHINOHARA, Y.1, HASHIMOTO, T.1, ISAKA, T.1, IEMITSU, M.1, Institution: RITSUMEIKAN UNIV, Country: JAPAN, Abstract-ID: 1018

INTRODUCTION:
Antimicrobial peptides LL-37, present in the saliva, has an important role in oral immune function. LL-37 exerts antimicrobial activity by disrupting the membranes of bacterial and viral cells. A few studies indicated an increase in salivary LL-37 secretion after high-intensity and long-duration acute exercise [1, 2]. However, it remains unclear whether the acute effects of different exercise intensities or durations on salivary LL-37 secretion. This study aimed to clarify the acute effects of different exercise intensities and durations on the secretion of LL-37 in saliva.
METHODS:
Fourteen healthy young men (age: 21.6 ± 1.6 years, height: 173.8 ± 3.8 cm, weight: 63.8 ± 6.0 kg, VO2max: 42.0 ± 4.7 ml/kg/min) with no exercise habits participated in this study. Maximal oxygen uptake (VO2max) was measured approximately 1 week before the main trials. All participants randomly performed [Intensity study] cycling exercise for 30 minutes at 35% (Low), 55% (Moderate), and 75%VO2max (High) and [Duration study] cycling exercise for 30 (Short), 60 (Middle), and 90-minutes (Long) at 55%VO2max. Saliva samples were collected before (baseline), immediately after (post), and 60 minutes after exercise (post-60 min) each trial. The salivary LL-37 concentrations were measured by enzyme-linked immunoassay. The effects of different exercise intensities (Low, Moderate, High) or durations (Short, Middle, Long) were determined using three trials × three time points (baseline, post, and post-60 min each exercise) of two-way repeated-measures ANOVA. A p<0.05 was considered statistically significant.
RESULTS:
In the intensity study, no significant differences in the percentage change from baseline were observed in salivary LL-37 concentration at post as well as post-60 min among the Low, Moderate, and High trials.
In the duration study, the percentage change from baseline in salivary LL-37 concentration at post significantly increased by 40.7% in the Middle trial and 58.6% in the Long trial compared to the Short trial (each p<0.05). However, no significant differences were observed in the percentage change in salivary LL-37 concentration at post-60 min compared to baseline among the three different exercise durations trials.
CONCLUSION:
These results suggest that salivary LL-37 secretion may be independent of exercise intensity and may be stimulated depending on exercise duration.