Microbiota-derived isovalerate ameliorates sex-specific gut barrier dysfunction in malnutrition.

Summary

Using specific pathogen-free and germ-free mice, targeted metabolomics, and human-derived colonoid monolayers, the study identified branched-chain fatty acids, particularly isovalerate, as microbiota-derived regulators of intestinal barrier integrity. Isovalerate enemas and leucine gavage restored claudin-8 localization and reduced permeability in malnourished male mice, providing a mechanistic link between malnutrition, dysbiosis, gut leak, and sepsis risk.

Key Findings

• Malnutrition increased colonic permeability and bacterial translocation in male specific pathogen-free mice but not in female mice.
• Branched-chain fatty acids were depleted in malnourished mice, and isovalerate improved epithelial barrier function in human-derived colonoid monolayers.
• Isovalerate enemas or leucine gavage restored claudin-8 localization and reduced colonic permeability in malnourished male mice.

Clinical Implications

The findings support future testing of microbiota-directed nutritional strategies, such as leucine supplementation or targeted delivery of branched-chain fatty acids, in malnourished patients at risk of bacterial translocation and sepsis. Clinical translation requires dose, safety, sex-specific effects, and microbiome-dependent responses to be established.

Limitations

• The principal efficacy experiments were conducted in mice, limiting direct extrapolation to human malnutrition and sepsis.
• The observed effects were sex-specific in vivo, and the determinants of this sex difference require further investigation.

Future Directions

Future studies should evaluate leucine or isovalerate-based interventions in clinically relevant malnutrition models, define optimal delivery and dosing, assess antimicrobial and metabolic safety, and determine whether baseline microbiome composition predicts response. Early-phase human studies should include gut permeability, bacterial translocation, and infection outcomes.