High-dose taurine aggravates alcohol-induced liver injury, study shows

High-dose taurine worsens alcohol-induced liver injury

The researchers first tested whether taurine could compensate for reduced intestinal taurine availability and protect against alcohol-induced liver damage. Contrary to this hypothesis, high-dose taurine aggravated hepatic injury in alcohol-fed mice. Compared with alcohol feeding alone, the high-dose taurine group showed increased liver-to-body weight ratio, higher hepatic triglyceride accumulation, more severe steatosis on histology and elevated serum alanine aminotransferase and aspartate aminotransferase levels. Markers of hepatocyte death and inflammation were also increased. TUNEL staining revealed more apoptotic hepatocytes, while hepatic macrophage activation and inflammatory gene expression, including Tnfα and Cxcl2, were enhanced. These findings suggest that high-dose taurine did not simply increase liver fat, but also intensified hepatocellular injury and inflammatory responses.

Disrupted lipid metabolism: less oxidation, more lipogenesis

To explore the underlying mechanisms, the authors performed hepatic RNA sequencing and molecular validation. High-dose taurine supplementation altered the hepatic transcriptome in alcohol-fed mice. Although pathways related to energy metabolism, including the tricarboxylic acid cycle, were upregulated, key genes involved in fatty acid β-oxidation were downregulated. Particularly important was the reduction of Cpt1a, a key enzyme that facilitates mitochondrial fatty acid entry and oxidation. Cpt1a expression was decreased at both mRNA and protein levels. At the same time, fatty acid synthase, encoded by Fasn, was increased, indicating enhanced lipogenesis. This combination-reduced fatty acid oxidation and increased lipid synthesis-provides a plausible explanation for the aggravated hepatic steatosis observed after high-dose taurine supplementation.

Gut dysbiosis and impaired intestinal barrier function

The study also highlights the gut-liver axis as a major contributor to taurine-associated liver injury. High-dose taurine supplementation shifted gut microbial composition in alcohol-fed mice, reducing microbial diversity and changing the abundance of major bacterial groups. Notably, bacteria associated with detrimental effects increased, while beneficial bacteria decreased. A key microbial signal was the enrichment of hydrogen sulfide-producing bacteria, including Prevotella. Functional assays showed increased hydrogen sulfide production in caecal contents. Because excessive hydrogen sulfide has been linked to oxidative stress and intestinal barrier dysfunction, this microbial shift may help explain the worsening of intestinal and hepatic injury.

Consistent with this interpretation, high-dose taurine was associated with intestinal epithelial damage, reduced expression of the tight junction gene Cldn1 and altered claudin-1 localisation. The researchers also found increased bacterial translocation to the liver, shown by higher hepatic 16S rRNA levels and increased Escherichia coli staining. These changes paralleled stronger hepatic inflammatory responses, supporting a model in which high-dose taurine aggravates ALD by disrupting intestinal homeostasis and increasing microbial leakage to the liver.

Bile acid dysregulation adds another layer

Taurine is essential for bile acid conjugation, but excessive taurine intake under alcohol exposure disturbed bile acid-related pathways. High-dose taurine reduced hepatic Baat expression, a key enzyme involved in bile acid conjugation, and altered taurine-conjugated bile acid profiles. In faeces, taurine supplementation increased taurine-conjugated bile acids in alcohol-fed mice and further suppressed ileal Shp expression, suggesting selective disruption of intestinal FXR-associated signalling.

These bile acid changes are important because bile acids are not only digestive molecules, but also metabolic and immunological signalling mediators. Disturbing their composition and intestinal signalling may amplify alcohol-induced metabolic injury and gut-liver crosstalk.

Low-dose taurine shows a protective profile

A particularly important aspect of the study is the comparison with low-dose taurine. At 0.2 g/kg body weight/day, taurine did not show the toxicity observed at high dose. Instead, it reduced hepatic fat accumulation, lowered liver injury markers and decreased Fasn protein expression. Low-dose taurine also increased the ratio of taurine-conjugated bile acids to total bile acids, suggesting improved bile acid conjugation without suppressing hepatic taurine synthesis. This finding supports a nuanced conclusion: taurine biology in ALD is not simply good or bad. Its effects appear dose-dependent, context-dependent and closely linked to the gut-liver axis.

Implications for supplementation and public health

This study has timely relevance because taurine is commonly consumed through supplements and energy drinks, and these products may be used alongside alcohol. The findings do not prove that taurine is harmful in humans at typical dietary levels, but they raise an important caution: excessive taurine intake may carry risks in individuals with alcohol misuse or existing liver disease. From a research perspective, the study provides a mechanistic framework linking high-dose taurine to hepatic lipid dysregulation, gut dysbiosis, hydrogen sulfide production, intestinal barrier impairment, bacterial translocation and bile acid disruption. From a clinical perspective, it reinforces the need to evaluate supplement dose, disease context and host-microbiome interactions before recommending taurine in ALD.

Overall, Pei and colleagues reveal a dose-dependent paradox in taurine supplementation. Low-dose taurine may support hepatic metabolism, whereas high-dose taurine may worsen alcohol-induced liver injury. This work calls for more careful dose-response studies and for greater caution when translating nutritional supplements into liver disease prevention or treatment.