# Effects of Dietary Highland Barley at Different Inclusion Levels on Normobaric Hypoxia Tolerance, Oxidative Stress, Energy Metabolism, and Gut Microbiota in Mice

## TL;DR

Feeding mice a moderate amount of highland barley improves their ability to survive in low-oxygen conditions by boosting blood cells, antioxidants, and gut bacteria diversity.

## Contribution

This study identifies a moderate 20% highland barley inclusion as optimal for enhancing hypoxia tolerance and gut microbiota in mice.

## Key findings

- Mice fed 20% highland barley had significantly longer hypoxia survival times and increased red blood cell and hemoglobin levels.
- The 20% group showed higher ATP and superoxide dismutase activity in brain and heart tissues, indicating better energy and antioxidant capacity.
- Gut microbiota diversity increased in the 20% group, with distinct microbial community structures observed across different supplementation levels.

## Abstract

Background: Normobaric acute hypoxia models are widely applied to assess tolerance to acute hypoxic stress. Highland barley is a cereal crop originating from and traditionally cultivated in high-altitude regions; however, the dose–response relationship underlying its effects on hypoxia tolerance remains unclear. Methods: Male ICR mice were randomly allocated to five groups (n = 8 per group) and fed an AIN-93M basal diet or experimental diets supplemented with 20%, 40%, 60%, or 80% highland barley for 13 weeks. Hypoxia survival time was evaluated using a normobaric asphyxial hypoxia model, in which oxygen is progressively depleted in a sealed chamber by continuous respiration with carbon dioxide absorbed by soda lime. Hematological parameters, indices of oxidative stress and energy metabolism, and gut microbiota composition were also assessed. Results: Compared with the control group, dietary supplementation with 20% highland barley was associated with a longer hypoxia survival time (mean difference: 9.49 min; 95% CI: −2.05 to 21.02), whereas the 80% group exhibited the shortest survival time (approximately 40.6 min). In the 20% group, red blood cell count and hemoglobin concentration increased by 41.6% and 42.1%, respectively. ATP content and superoxide dismutase activity in brain tissue increased by 33.2% and 28.4%, respectively, with similar trends observed in heart tissue. In addition, gut microbiota α-diversity was increased in the 20% highland barley group, and distinct separation of microbial community structures was observed among groups receiving different supplementation levels. Conclusions: Overall, the data suggest that moderate dietary supplementation with highland barley (20%) is associated with a favorable physiological and microbiota profile under normobaric asphyxial hypoxic challenge, suggesting the presence of a potentially effective intake range for highland barley-based nutritional intervention.