NUS Breakthrough in Engineering Gut Bacteria for Liver and Brain Health
In a groundbreaking development from Singapore's National University of Singapore (NUS), researchers have engineered beneficial gut bacteria to combat hepatic encephalopathy (HE), a devastating complication of liver failure. This innovation addresses a critical gap in current treatments by targeting the gut-liver-brain axis, where toxins from a failing liver, primarily ammonia, leak into the bloodstream and impair brain function.
The study, published in the prestigious journal Cell on April 24, 2026, demonstrates how these 'living medicines' not only neutralize toxins but also restore essential nutrients, offering hope for millions affected by liver disease worldwide, including in Singapore where chronic hepatitis B prevalence stands at 3.6 percent, contributing significantly to cirrhosis cases.
Led by Professor Matthew Wook Chang from NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI) and the Yong Loo Lin School of Medicine, the team transformed the safe probiotic Lactobacillus plantarum WCFS1 into a multi-functional therapeutic agent. This work highlights NUS's leadership in synthetic biology, positioning Singapore as a hub for microbiome-based therapies in higher education research.
Understanding Hepatic Encephalopathy: The Silent Threat of Liver Failure
Hepatic encephalopathy arises when the liver can no longer detoxify blood, allowing ammonia and other metabolites to cross the blood-brain barrier. Symptoms range from mild confusion and anxiety to severe cognitive impairment, tremors, and coma. Globally, HE affects 30 to 45 percent of cirrhosis patients, with recurrence in up to 40 percent, making it the leading cause of hospital readmissions for those with advanced liver disease.
In Singapore, liver cirrhosis accounts for 0.9 percent of years of life lost (YLL), driven by viral hepatitis, alcohol, and rising non-alcoholic fatty liver disease (NAFLD). With NAFLD prevalence climbing amid metabolic syndrome, HE poses an escalating challenge for the nation's healthcare system, underscoring the urgency of innovative solutions from institutions like NUS.
The condition disrupts the gut-liver-brain axis—a bidirectional communication pathway where gut microbiota influence liver function and brain health via metabolites, immune signals, and the vagus nerve. Dysbiosis in liver disease exacerbates toxin production and nutrient deficiencies, perpetuating a vicious cycle.
The Gut-Liver-Brain Axis: How Microbes Shape Organ Health
The gut microbiome, comprising trillions of microbes, produces short-chain fatty acids, vitamins, and amino acids essential for host physiology. In liver cirrhosis, dysbiosis leads to increased ammonia from glutamine deamination and reduced branched-chain amino acids (BCAAs)—valine, leucine, isoleucine—which are crucial for brain neurotransmitter synthesis.
Ammonia, a byproduct of protein metabolism, normally enters the urea cycle in the liver for excretion. Liver failure shunts it to the brain, where it causes astrocyte swelling, oxidative stress, and neuroinflammation, impairing cognition. NUS researchers targeted this axis by reprogramming bacteria to intervene at the gut level, preventing systemic toxin spread.
This approach leverages synthetic biology principles: genetic circuits sense environmental cues (high ammonia) and trigger responses like metabolite consumption or production, mimicking natural microbial dynamics but with precision engineering.
NUS SynCTI's Engineering Marvel: Designing Living Therapeutics
Professor Chang's team at SynCTI selected L. plantarum WCFS1 for its GRAS (Generally Recognized as Safe) status and colonization ability in the gut. Using CRISPR and synthetic genetic circuits, they created two complementary strains:
- Ammonia Scavenger Strain: Expresses transporters and enzymes to uptake ammonia and convert it to BCAAs via transamination pathways, replenishing depleted nutrients.
- Glutamine Deaminase Strain: Degrades L-glutamine, a major ammonia precursor, reducing its availability for bacterial fermentation into ammonia.
A cocktail of both strains was administered orally to mice. The modular design allows future customization for other metabolites.
For more on the study, see the full paper in Cell.
Experimental Breakthroughs: Results from Mouse Models
In thioacetamide (TAA)-induced liver fibrosis models mimicking human cirrhosis and HE, the bacterial cocktail slashed blood ammonia by up to 10-fold and normalized brain levels. Metabolomics confirmed BCAA restoration and glutamine reduction.
Cognitive tests—Y-maze for spatial memory, elevated plus maze for anxiety—showed significant improvements, outperforming rifaximin. Survival rates rose, neuroinflammation markers (IL-6, TNF-α) dropped, and neuronal signaling recovered.
Histology revealed less liver fibrosis, highlighting dual gut-liver benefits. These outcomes validate the multi-target strategy.
Superior to Standard Care: Why This Outshines Rifaximin
Rifaximin reduces gut bacteria non-specifically, risking dysbiosis, while lactulose causes diarrhea. NUS bacteria preserved microbiome alpha-diversity, avoided resistance, and cleared naturally within 72 hours—no long-term colonization risks.
One-month safety studies confirmed no toxicity, positioning them as superior for chronic HE management. Dr. Nikhil Aggarwal noted HE's 40% recurrence rate, emphasizing the need for comprehensive therapies.
Details in NUS press release and Straits Times coverage.
Safety Profile and Microbiome Harmony
Safety is paramount in live biotherapeutics. The strains showed no virulence, genotoxicity, or immune overactivation. Post-treatment, they were undetectable after 72 hours, minimizing ecological disruption.
Unlike antibiotics, they enhanced microbiome resilience, crucial for preventing secondary infections in vulnerable patients.
Path to Clinic: Patents, Trials, and Singapore's Biotech Future
NUS SynCTI filed a patent, paving way for human trials. Prof. Chang envisions capsule-form delivery, scalable for Asia's rising NAFLD burden. Singapore's A*STAR and funding ecosystem support translation.
This elevates NUS's role in precision medicine, fostering collaborations and jobs in synthetic biology.
Broader Implications for Higher Education and Research in Singapore
NUS SynCTI exemplifies interdisciplinary higher ed: biology, engineering, medicine converge. It attracts talent, secures grants, and boosts Singapore's rank in QS biotech subjects.
Impacts research careers, with demand for microbiome experts surging.
Future Horizons: Modular Therapies Beyond HE
The platform targets urea cycle disorders, hyperammonemia. Long-term studies planned; clinical partnerships eyed. Prof. Chang: "From bench to bedside."
Revolutionizes treatment for 1.3 million annual cirrhosis deaths globally.
Conclusion: A Microbial Shield for the Future
NUS's engineered gut bacteria herald a new era in treating liver-brain disorders, blending innovation with safety. As research advances, it promises better lives for liver patients, underscoring Singapore's higher ed prowess.
