PCSK9 and APOA4: the dynamic duo in TMAO-induced cholesterol metabolism and cholelithiasis

Background and Aims

Cholesterol synthesis and gallstone formation are promoted by trimethylamine-N-oxide (TMAO), a derivative of trimethylamine, which is a metabolite of gut microbiota. However, the underlying mechanisms of TMAO-induced lithogenesis remain incompletely understood. This study aimed to explore the specific molecular mechanisms through which TMAO promotes gallstone formation.

Methods

Enzyme-linked immunosorbent assays were used to compare serum concentrations of TMAO, apolipoprotein A4 (APOA4), and proprotein convertase subtilisin/kexin type 9 (PCSK9) between patients with cholelithiasis and normal controls. A murine model of TMAO-induced cholelithiasis was employed, incorporating assays of gallstone weight and bile cholesterol content, along with RNA sequencing of murine hepatic tissue. A TMAO-induced AML12 hepatocyte line was constructed and transfected with targeted small interfering RNAs and overexpression plasmids. In vivo and in vitro experiments were performed to determine the expression and regulation of genes related to cholesterol metabolism.

Results

Serum TMAO and PCSK9 levels were elevated, whereas APOA4 levels were reduced in patients with cholelithiasis. Furthermore, our murine model demonstrated that TMAO upregulated hepatic expression of PCSK9, 3-hydroxy-3-methylglutaryl-CoA reductase, and ATP-binding cassette sub-family G member 5/8, while reducing APOA4 expression, thereby modulating cholesterol metabolism and promoting lithogenesis. PCSK9 and APOA4 were identified as key regulatory genes in the cholesterol metabolic pathway. PCSK9 knockdown increased APOA4 expression, while APOA4 overexpression led to reduced PCSK9 expression.

Conclusions

We have discovered that TMAO dysregulates cholesterol metabolism by initiating a feedback loop, upregulating PCSK9 expression, and downregulating APOA4 expression in murine hepatic tissue, thereby promoting gallstone formation. In clinical practice, hyperlipidemia, a risk factor for cardiovascular diseases, also promotes gallstone formation, which should warrant attention. Regulation of blood lipid levels is necessary for patients with cholelithiasis. Targeting PCSK9 and APOA4 may represent a promising approach for the prevention and treatment of cholelithiasis.

Full text

https://www.xiahepublishing.com/2310-8819/JCTH-2024-00403

The study was recently published in the Journal of Clinical and Translational Hepatology.

The Journal of Clinical and Translational Hepatology (JCTH) is owned by the Second Affiliated Hospital of Chongqing Medical University and published by XIA & HE Publishing Inc. JCTH publishes high quality, peer reviewed studies in the translational and clinical human health sciences of liver diseases. JCTH has established high standards for publication of original research, which are characterized by a study’s novelty, quality, and ethical conduct in the scientific process as well as in the communication of the research findings. Each issue includes articles by leading authorities on topics in hepatology that are germane to the most current challenges in the field. Special features include reports on the latest advances in drug development and technology that are relevant to liver diseases. Regular features of JCTH also include editorials, correspondences and invited commentaries on rapidly progressing areas in hepatology. All articles published by JCTH, both solicited and unsolicited, must pass our rigorous peer review process.

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