Aging significantly alters physiological states, leading to poor prognosis in critical conditions like sepsis. Recent research highlights that aging gut microbiota sepsis susceptibility is largely driven by shifts in microbial composition. Specifically, aged hosts show a marked increase in the abundance of Klebsiella aerogenes. This particular bacterium plays a pivotal role in compromising the intestinal barrier.

Furthermore, scientists identified that specific strains of Klebsiella aerogenes carry a variant of the histidine decarboxylase gene. This genetic variation allows the bacteria to produce excessive levels of histamine within the gut. Consequently, these high histamine levels directly contribute to intestinal injury. Importantly, the study found that this metabolic byproduct is a primary driver of barrier dysfunction.

Mechanistically, the excess histamine interferes with the HA-Nlrp6-LC3 axis. It inhibits the expression of Nlrp6, a key protein that usually binds to LC3 to facilitate autophagy. When histamine prevents this binding, autophagy becomes impaired. Thus, the intestinal cells cannot maintain their integrity, allowing pathogens to translocate into the bloodstream more easily.

Additionally, targeting this pathway offers hope for new treatments. Modulating histamine levels or overexpressing Nlrp6 significantly reduced inflammation in experimental sepsis models. These findings suggest that managing the gut's chemical environment could save lives. Therefore, clinical focus should shift toward the metabolic outputs of the aging microbiome.

How does the gut microbiome change with age to increase sepsis risk?

As individuals age, the gut microbiome often loses diversity and sees an increase in pathobionts like Klebsiella aerogenes. These bacteria produce metabolites such as histamine that weaken the intestinal lining, making it easier for infections to become systemic and lead to sepsis.

What is the HA-Nlrp6-LC3 axis?

This is a biological pathway where histamine (HA) regulates the protein Nlrp6. Nlrp6 normally binds to LC3 to promote autophagy, a process that keeps intestinal cells healthy. In aged hosts, high histamine levels block this pathway, leading to gut barrier failure during sepsis.

Can targeting histamine improve outcomes for elderly sepsis patients?

Experimental studies suggest that modulating histamine levels or restoring Nlrp6 function can significantly reduce intestinal damage and inflammation. This indicates that therapies targeting microbial metabolites could be a novel approach for treating sepsis in older populations.

Disclaimer: This content is for informational and educational purposes only and is not intended as medical advice or a substitute for professional healthcare guidance. Always seek the advice of a qualified health provider regarding any medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Liang H et al. Aging-caused the changes of the gut microbiota drive intestinal barrier dysfunction and increase sepsis susceptibility. Gut Microbes. 2026 Dec 31. doi: 10.1080/19490976.2026.2630475. PMID: 41723572.

Colbert JF et al. Aging-associated augmentation of gut microbiome virulence capability drives sepsis severity. mBio. 2023;14(3):e0005223. doi:10.1128/mbio.00052-23.

Wang X et al. Gut Microbiota Metabolites Targeting the Immune Response in Sepsis. International Journal of General Medicine. 2025;18:3845-3860.