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Review
. 2023 Sep;12(3):191-206.
doi: 10.1007/s13679-023-00519-y. Epub 2023 Jul 5.

The Role of Tumor Necrosis Factor-Alpha in the Pathogenesis and Treatment of Nonalcoholic Fatty Liver Disease

Affiliations
Review

The Role of Tumor Necrosis Factor-Alpha in the Pathogenesis and Treatment of Nonalcoholic Fatty Liver Disease

Ilias D Vachliotis et al. Curr Obes Rep. 2023 Sep.

Abstract

Purpose of review: To summarize experimental and clinical evidence on the association between tumor necrosis factor-α (TNF-α) and nonalcoholic fatty liver disease (NAFLD) and discuss potential treatment considerations.

Recent findings: Experimental evidence suggests that TNF-α is a cytokine with a critical role in the pathogenesis of NAFLD. Although, the production of TNF-α may be an early event during the course of nonalcoholic fatty liver (NAFL), TNF-α may play a more substantial role in the pathogenesis of nonalcoholic steatohepatitis (NASH) and NAFLD-associated fibrosis. Moreover, TNF-α may potentiate hepatic insulin resistance, thus interconnecting inflammatory with metabolic signals and possibly contributing to the development of NAFLD-related comorbidities, including cardiovascular disease, hepatocellular carcinoma, and extra-hepatic malignancies. In clinical terms, TNF-α is probably associated with the severity of NAFLD; circulating TNF-α gradually increases from controls to patients with NAFL, and then, to patients with NASH. Given this potential association, various therapeutic interventions (obeticholic acid, peroxisome proliferator-activated receptors, sodium-glucose co-transporter 2 inhibitors, glucagon-like peptide-1 receptor agonists, probiotics, synbiotics, rifaximin, vitamin E, pentoxifylline, ursodeoxycholic acid, fibroblast growth factor-21, n-3 polyunsaturated fatty acids, statins, angiotensin receptor blockers) have been evaluated for their effect on TNF-α and NAFLD. Interestingly, anti-TNF biologics have shown favorable metabolic and hepatic effects, which may open a possible therapeutic window for the management of advanced NAFLD. The potential key pathogenic role of TNF-α in NAFLD warrants further investigation and may have important diagnostic and therapeutic implications.

Keywords: Inflammation; Nonalcoholic fatty liver disease; Nonalcoholic steatohepatitis; Treatment; Tumor necrosis factor-α.

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Conflict of interest statement

The authors have no competing interests to declare that are relevant to the content of this article.

Figures

Fig. 1
Fig. 1
The role of TNF-α in the pathogenesis of NAFLD. In the liver, TNF-α is primarily produced by the KCs, which respond to two types of stimuli: the DAMPs, which are released by lipid-infiltrated and damaged hepatocytes, and the gut-derived PAMPs, which translocate from the intestine to the liver, due to an impaired intestinal epithelial barrier. Both DAMPs and PAMPs bind TLRs on the surface of the KCs and activate the NF-κB, which is the key signaling pathway for the transcription of TNF-α. Furthermore, fat-stressed hepatocytes also contribute to TNF-α production via the interaction between DAMPs/PAMPs and TLRs, albeit to a lesser extent. Once released, TNF-α binds TNFR and stimulates the assembly of complex I, which initiates two important downstream signaling pathways, i.e., the JNK and NF-κB pathways, through which TNF-α induces the transcription of target genes involved in inflammation, cell proliferation, and survival. Besides these cellular responses, TNF-α also induces cell death by enabling the assembly of the death-inducing protein complex II, leading to either apoptosis or necroptosis. Besides, inflammation, survival, and apoptosis, TNF-α also contributes to IR and NAFL development; TNF-α perpetuates IR in hepatocytes as it blocks insulin signaling at the post-receptor level; TNF-α triggers the expression of SOCS, which prevent tyrosine phosphorylation of IRS-1 and IRS-2 and promote their early degradation. Likewise, TNF-α-mediated activation of JNK contributes to the phosphorylation of serine of IRS-1 and IRS-2, which inhibits their signaling. In addition, TNF-α is proposed as a potential positive regulator of the mTORC1 pathway in the hepatocytes, inducing the expression of the SREBP-1c, the main transcription factor of de novo lipogenesis. TNF-α-induced SREBP-1c, in addition to promoting de novo lipogenesis, also suppresses the IRS-1/2 synthesis, thus contributing to IR. Notably, TNF-α also antagonizes adiponectin and suppresses its insulin-sensitizing effect on the hepatocytes. Finally, TNF-α is involved in hepatic fibrogenesis; TNF-α induces the production of TGF-β by the hepatocytes and KCs, upregulates the expression of periostin in the hepatocytes and TIMP-1 in HSCs, which facilitate collagen deposition and EM stabilization

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