SARS-CoV-2 receptor ACE2 is upregulated by fatty acids in human MASH

The global prevalence and impact of steatotic liver disease and viral infections: A systematic review and meta-analysis

BACKGROUND

Steatotic liver disease (SLD) affects ~30% of adults worldwide. The global population is continuously threatened by epidemic and endemic viral diseases. This study aims to thoroughly examine the interaction between SLD and major viral diseases.

METHODS

We systematically searched databases from inception to April 2, 2024, for observational studies recording viral-infected adult patients with eligible data on the presence of hepatic steatosis.

RESULTS

Six hundred thirty-six eligible studies were included in the analysis of SLD prevalence. Among patients with monoinfections, the highest SLD prevalence was observed in those infected with HCV at 49% (95% CI: 47%-51%), followed by SARS-CoV-2 (39%, 95% CI [34%-44%]), HIV (39%, 95% CI [33%-44%]), and HBV (36%, 95% CI [32%-40%]). Additionally, co-infections, such as HCV-HIV and HBV-HCV, exhibit even higher SLD prevalence. The prevalence of steatohepatitis is particularly high in HIV-infected (24%, 95% CI: 17%-30%) and HCV-infected (18%, 95% CI: 13%-24%) populations. The co-existence of SLD with viral infections was associated not only with the progression of liver disease but also with more severe outcomes of the infections and poorer responses to antiviral treatment. The combination of cardiometabolic risk factors and viral-associated and host factors contributes to the higher risk of SLD in viral-infected populations.

CONCLUSIONS

SLD is highly prevalent in viral-infected populations, and the reciprocal interactions between SLD and viral diseases exacerbate both conditions, leading to poorer patient outcomes in general.

Post-COVID-19 Pandemic Sequelae in Liver Diseases

During the coronavirus disease 2019 (COVID-19) pandemic, several studies highlighted a worse prognosis for patients with alterations in liver function tests, especially those with pre-existing liver diseases. However, further studies are needed to define the long-term impact of the COVID-19 pandemic on liver diseases. Long COVID-19 encompasses a wide range of signs and symptoms, including exacerbations of pre-existing chronic conditions or new onset conditions developed after the COVID-19 acute phase. Therefore, the long-term effects of COVID-19 extensively include hepatic manifestations. The co-expression of angiotensin-converting receptor 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) has been demonstrated also in enterocytes, cholangiocytes, and hepatocytes. Studies on the post-COVID-19 sequelae have shown the presence of steatosis and necroinflammation in the liver, concomitantly with an alteration of inflammation, cytolysis and cholestasis indices. Some studies also demonstrated an increased risk for hepatobiliary pathologies, including secondary biliary cholangitis and worsening of the severity of metabolic-associated fatty liver disease (MASLD). Based on these premises, this review aims to provide an overview of the pathophysiological mechanisms contributing to COVID-19-related liver and hepatobiliary damage; explore its implications for liver inflammation and fibrosis, with a particular focus on MASLD and metabolic dysfunction-associated steatohepatitis (MASH); and analyze the short- and long-term COVID-19 sequelae. A literature search was conducted using the PubMed database for relevant studies published in English.

Angiotensin-converting enzyme 2 and hepatic SARS-CoV-2 infection: Regulation, association, and therapeutic implications

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters host cells via the angiotensin-converting enzyme 2 (ACE2) receptor. Mounting evidence has indicated the presence of hepatic SARS-CoV-2 infection and liver injury in patients with coronavirus disease 2019 (COVID-19). Understanding the mechanisms of hepatic SARS-CoV-2 infection is crucial for addressing COVID-19-related liver pathology and developing targeted therapies. This editorial discusses the significance of ACE2 in hepatic SARS-CoV-2 infection, drawing on the research by Jacobs et al. Their findings indicate that hepatic ACE2 expression, frequency of hepatic SARS-CoV-2 infection, and severity of liver injury are elevated in patients with pre-existing chronic liver diseases. These data suggest that hepatic ACE2 could be a promising therapeutic target for COVID-19.

The lack of PPARα exacerbated the progression of non-alcoholic steatohepatitis in mice with spleen deficiency syndrome by triggering an inflammatory response

Background

In addition to abnormal liver inflammation, the main symptoms of non-alcoholic steatohepatitis (NASH) are often accompanied by gastrointestinal digestive dysfunction, consistent with the concept of spleen deficiency (SD) in traditional Chinese medicine. As an important metabolic sensor, whether peroxisome proliferator-activated receptor alpha (PPARα) participates in regulating the occurrence and development of NASH with SD (NASH-SD) remains to be explored.

Methods

Clinical liver samples were collected for RNA-seq analysis. C57BL/6J mice induced by folium sennae (SE) were used as an SD model. qPCR analysis was conducted to evaluate the inflammation and metabolic levels of mice. PPARα knockout mice (PPARαko) were subjected to SE and methionine-choline-deficient (MCD) diet to establish the NASH-SD model. The phenotype of NASH and the inflammatory indicators were measured using histopathologic analysis and qPCR as well.

Results

The abnormal expression of PPARα signaling, coupled with metabolism and inflammation, was found in the results of RNA-seq analysis from clinical samples. SD mice showed a more severe inflammatory response in the liver evidenced by the increases in macrophage biomarkers, inflammatory factors, and fibrotic indicators in the liver. qPCR results also showed differences in PPARα between SD mice and control mice. In PPARαko mice, further evidence was found that the lack of PPARα exacerbated the inflammatory response phenotype as well as the lipid metabolism disorder in NASH-SD mice.

Conclusion

The abnormal NR signaling accelerated the vicious cycle between lipotoxicity and inflammatory response in NAFLD with SD. Our results provide new evidence for nuclear receptors as potential therapeutic targets for NAFLD with spleen deficiency.