Does biological sex impact intestinal epithelial injury, small intestine permeability, gastrointestinal symptoms and systemic cytokine profile in response to exertional-heat stress?

ABSTRACT

This study aimed to determine the influence of biological sex on intestinal injury, permeability, gastrointestinal symptoms, and systemic cytokine profile in response to exertional-heat stress. Male (n= 13) and eumenorrheic female (n= 11) endurance runners completed 2 h running at 60% V̇O_2max in 35°C. Blood samples were collected pre- and post-exercise and during recovery to determine plasma intestinal fatty-acid binding protein (I-FABP) and systemic cytokine profile. Urinary lactulose:L-rhamnose ratio was used to determine small intestine permeability. I-FABP increased 479% pre- to post-exercise (p< 0.001), with no difference between sexes (p= 0.432). No differences between sexes were observed for small intestine permeability (p= 0.808), gut discomfort, total, upper- and lower-gastrointestinal symptoms. However, males reported significantly higher flatulence (p= 0.049) and abdominal stitch (p= 0.025) compared to females. IL-6, IL-8, IL-10 and IL-1ra increased pre- to post-exercise (p< 0.05), with no difference between sexes. However, IL-1β increased post-exercise in males only, and was higher in males compared to females (p= 0.044). Findings suggest that when females are in the follicular phase of the menstrual cycle, biological sex has no effect on intestinal epithelial injury and permeability, and minimal effect on gastrointestinal symptoms and systemic cytokine profile in response to exertional-heat stress.

KEYWORDS:

• Gender
• running
• I-FABP
• gastrointestinal distress

Acknowledgments

Firstly, the authors would like to thank all the participants that volunteered to take part in this study. The authors gratefully acknowledge the contributions of Prof. Peter Gibson and Dr. Cecilia Kitic for their assistance with experimental design and sample analysis, respectively. The study and manuscript writing were supported by a ‘Monash University, Faculty of Medicine Nursing & Health Sciences Strategic Grant Scheme’ and a ‘Monash University Postgraduate Publication Award’.

Authors’ contributions

Ricardo Costa was the chief investigator of this research. Ricardo Costa and Rhiannon Snipe contributed towards the original research idea, development of the experimental design, data and sample collection and analysis, preparation and review of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a Monash University, Faculty of Medicine Nursing & Health Sciences Strategic Grant Scheme [grant number SGS15-0128] and a Monash University Postgraduate Publication Award.