Author(s): SAWADA, S., LIU, Z., NAITO, H., MACHIDA, S., Institution: JUNTENDO UNIVERSITY, Country: JAPAN, Abstract-ID: 1249

INTRODUCTION:
Phase angle (PhA) assessed via bioelectrical impedance analysis is an indicator of cellular integrity and reportedly improves with resistance training [1-2]. However, the molecular responses underlying the inter-individual differences in exercise-induced PhA changes remain poorly understood. This study aimed to explore serum miRNA alterations as potential molecular biomarkers associated with changes in PhA after a bodyweight-based resistance training intervention.
METHODS:
Twenty-four community-dwelling older adults (68.6 ± 6.1 years; 9 men and 15 women) completed whole-body PhA assessments using the InBody 770 before and after a 12-week, twice-weekly bodyweight-based resistance training program. The program consisted of progressive bodyweight-based resistance exercises targeting major muscle groups based on our previously published training protocols [3-5]. Participants were classified into PhA improvement and non-improvement groups according to changes in PhA, and fourteen participants (7 per group; 3 men and 4 women each) were selected and matched for age and sex. Blood samples were also collected before and after the intervention, and serum miRNA expression profiles were analyzed using the GeneChip miRNA 4.0 Array. Differentially expressed miRNAs were selected using fold-change and p-value criteria for exploratory analysis.
RESULTS:
After the program, PhA showed heterogeneous responses. The participants were categorized into improvement (n = 7) and non-improvement (n = 7) groups. In the improvement group, serum miRNA profiling showed marked alterations in multiple miRNAs following the intervention, with nine miRNAs exhibiting fold changes greater than 3 in absolute value (p<0.05). Among these, four miRNAs (hsa-miR-4423-3p, hsa-miR-335-5p, hsa-miR-191-5p, and hsa-let-7b-5p) exhibited particularly large alterations, with fold changes exceeding 5 in absolute value. In contrast, the non-improvement group had fewer serum miRNAs meeting the inclusion criteria. These results indicate that pronounced serum miRNA alterations are predominantly observed in participants with improved PhA.
CONCLUSION:
These findings suggest that marked alterations in serum miRNAs occur predominantly in participants with improved PhA following bodyweight-based resistance training. This exploratory analysis highlights the potential link between qualitative cellular adaptations assessed by bioelectrical impedance analysis and exercise-induced molecular responses, which warrants further investigation.
References:
1. Campa F, et al. Rev Endocr Metab Disord, 2023. 24(3):439-449.
2. Liu S, et al. Arch Gerontol Geriatr, 2024. 119:105318.
3. Ozaki H, et al. J Sports Sci Med, 2020. 19(4):721-726.
4. Sawada S, et al. BMC Geriatr, 2021. 21(1):464.
5. Liu Z, et al. Sports (Basel), 2025. 13(1):8.