Aging-caused the changes of the gut microbiota drive intestinal barrier dysfunction and increase sepsis susceptibilityOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This study investigated how aging-related gut microbiota changes increase susceptibility to sepsis through intestinal barrier dysfunction. Researchers combined fecal microbiota transplantation, 16S sequencing, metabolomics, and genetically engineered bacteria. They tested whether microbiota from aged hosts transfer sepsis vulnerability and which bacterial metabolite is responsible. Mechanistic work examined histamine, the histidine decarboxylase gene, and the Nlrp6-LC3 autophagy axis. Barrier function was assessed with permeability assays, histology, and cytokine measurements.
Who was studied?
The work used both humans and mice. Fecal samples came from aged and young septic patients, and experiments used aged (22 to 24 months) and young (8 to 10 weeks) C57BL/6 mice. Sepsis was induced by cecal ligation and puncture. Patient and mouse feces were transplanted into young pseudo-germ-free mice. Caco2 intestinal cells were used for cellular validation. Genetically engineered Klebsiella aerogenes strains, including a histidine decarboxylase deletion mutant, tested causal roles in mice.
What were the most important findings?
Aged mice showed higher sepsis mortality, with all aged mice dying after cecal ligation and puncture while about half of young mice survived. Microbiota from aged donors transferred worse intestinal injury and inflammation to young recipient mice. 16S sequencing showed increased Klebsiella aerogenes in aged hosts, driving elevated histamine, which enrichment analysis tied to histidine metabolism. Strains carrying a histidine decarboxylase gene variant were the main histamine producers, and deleting the gene reduced histamine and barrier damage. Histamine impaired the barrier by inhibiting Nlrp6, reducing Nlrp6-LC3 binding and autophagy. Overexpressing Nlrp6 or lowering histamine eased inflammation.
What are the greatest implications of this study?
The findings suggest that targeting the histamine-Nlrp6-LC3 axis could offer a therapeutic approach for sepsis, particularly in older patients. Restoring microbiota balance or blocking histamine may protect the intestinal barrier. Histamine-producing Klebsiella aerogenes emerges as a candidate driver of age-related sepsis vulnerability. Most mechanistic evidence is from mice and cells, so human treatment effects remain unproven. The authors note the study lacked stratified age analysis and did not clarify why this bacterium expands with aging.