A Cell Specific Effect of MBOAT7 MAFLD-risk Variant on Immune Cells

BACKGROUND

Disease risk variants are likely to affect gene expression in a context- and cell-type specific manner. The membrane bound O-acyltransferase domain containing 7 (MBOAT7) rs8736 metabolic-dysfunction-associated fatty liver disease (MAFLD)-risk variant was recently reported to be a negative regulator of toll-like receptors (TLRs) signalling in macrophages. Whether this effect is generic or cell-type specific in immune cells is unknown.

METHODS

We investigated the impact of modulating TLR signaling on MBOAT7 expression in peripheral blood mononuclear cells (PBMCs). We also examined whether the rs8736 polymorphism in MBOAT7 regulates this effect. Furthermore, we measured the allele-specific expression of MBOAT7 in various immune cell populations under both unstimulated and stimulated conditions.

RESULTS

We show that MBOAT7 is down-regulated by TLRs in PBMCs. This effect is modulated by the MBOAT7 rs8736 polymorphism. Additionally, we provide evidence that MBOAT7 acts primarily as a modulator of TLR signalling in mononuclear phagocytes.

CONCLUSION

Our results highlight the importance of studying Genome-Wide Association Studies (GWAS) signals in the specific cell types in which alterations of gene expression are found.

Cyclin Dependent Kinase Inhibitor 2A Genetic and Epigenetic Alterations Interfere with Several Immune Components and Predict Poor Clinical Outcome

Cyclin dependent kinase inhibitor 2A (CDKN2A) is a well-known tumor suppressor gene as it functions as a cell cycle regulator. While several reports correlate the malfunction of CDKN2A with the initiation and progression of several types of human tumors, there is a lack of a comprehensive study that analyzes the potential effect of CDKN2A genetic alterations on the human immune components and the consequences of that effect on tumor progression and patient survival in a pan-cancer model. The first stage of the current study was the analysis of CDKN2A differential expression in tumor tissues and the corresponding normal ones and correlating that with tumor stage, grade, metastasis, and clinical outcome. Next, a detailed profile of CDKN2A genetic alteration under tumor conditions was described and assessed for its effect on the status of different human immune components. CDKN2A was found to be upregulated in cancerous tissues versus normal ones and that predicted the progression of tumor stage, grade, and metastasis in addition to poor prognosis under different forms of tumors. Additionally, CDKN2A experienced different forms of genetic alteration under tumor conditions, a characteristic that influenced the infiltration and the status of CD8, the chemokine CCL4, and the chemokine receptor CCR6. Collectively, the current study demonstrates the potential employment of CDKN2A genetic alteration as a prognostic and immunological biomarker under several types of human cancers.

Loss of metabolic adaptation in lean MAFLD is driven by endotoxemia leading to epigenetic reprogramming

Lean patients with MAFLD have an initial adaptive metabolic response characterised by increased serum bile acids and Farnesoid X Receptor (FXR) activity. How this adaptive response wanes resulting in an equal or perhaps worse long-term adverse outcome compared to patients with obese MAFLD is not known. We show that patients with lean MAFLD have endotoxemia while their macrophages demonstrate excess production of inflammatory cytokines in response to activation by Toll-like receptor (TLR) ligands when compared to healthy subjects. Alterations of the lean MAFLD macrophage epigenome drives this response and suppresses bile acids signalling to drive inflammation. Our data suggests that selectively restoring bile acids signalling might restore adaptive metabolic responses in patients with MAFLD who are lean.

Metabolic dysfunction-associated fatty liver disease: a year in review

PURPOSE OF REVIEW

In 2020, a novel comprehensive redefinition of fatty liver disease was proposed by an international panel of experts. This review aims to explore current evidence regarding the impact of this new definition on the current understanding of the epidemiology, pathogenesis, diagnosis, and clinical trials for fatty liver disease.

RECENT FINDINGS

The effectiveness of metabolic dysfunction-associated fatty liver disease (MAFLD) was compared to the existing criteria for nonalcoholic fatty liver disease (NAFLD). Recent data robustly suggest the superior utility of MAFLD in identifying patients at high risk for metabolic dysfunction, the hepatic and extra-hepatic complications, as well as those who would benefit from genetic testing, including patients with concomitant liver diseases. This change in name and criteria also appears to have improved disease awareness among patients and physicians.

SUMMARY

The transformation in name and definition from NAFLD to MAFLD represents an important milestone, which indicates significant tangible progress towards a more inclusive, equitable, and patient-centred approach to addressing the profound challenges of this disease. Growing evidence has illustrated the broader and specific contexts that have tremendous potential for positively influencing the diagnosis and treatment. In addition, the momentum accompanying this name change has included widespread public attention to the unique burden of this previously underappreciated disease.

Biomarkers of Metabolic (Dysfunction)-associated Fatty Liver Disease: An Update

The prevalence of metabolic (dysfunction)-associated fatty liver disease (MAFLD) is rapidly increasing and affects up to two billion individuals globally, and this has also resulted in increased risks for cirrhosis, hepatocellular carcinoma, and liver transplants. In addition, it has also been linked to extrahepatic consequences, such as cardiovascular disease, diabetes, and various types of cancers. However, only a small proportion of patients with MAFLD develop these complications. Therefore, the identification of high-risk patients is paramount. Liver fibrosis is the major determinant in developing these complications. Although, liver biopsy is still considered the gold standard for the assessment of patients with MAFLD. Because of its invasive nature, among many other limitations, the search for noninvasive biomarkers for MAFLD remains an area of intensive research. In this review, we provide an update on the current and future biomarkers of MAFLD, including a discussion of the associated genetics, epigenetics, microbiota, and metabolomics. We also touch on the next wave of multiomic-based biomarkers.

Macrophages in metabolic associated fatty liver disease

Metabolic associated fatty liver disease (MAFLD), formerly named non-alcoholic fatty liver disease is the most common liver disorder in many countries. The inflammatory subtype termed steatohepatitis is a driver of disease progression to cirrhosis, hepatocellular carcinoma, liver transplantation, and death, but also to extrahepatic complications including cardiovascular disease, diabetes and chronic kidney disease. The plasticity of macrophages in response to various environmental cues and the fact that they can orchestrate cross talk between different cellular players during disease development and progression render them an ideal target for drug development. This report reviews recent advances in our understanding of macrophage biology during the entire spectrum of MAFLD including steatosis, inflammation, fibrosis, and hepatocellular carcinoma, as well as for the extra-hepatic manifestations of MAFLD. We discuss the underlying molecular mechanisms of macrophage activation and polarization as well as cross talk with other cell types such as hepatocytes, hepatic stellate cells, and adipose tissue. We conclude with a discussion on the potential translational implications and challenges for macrophage based therapeutics for MAFLD.