Regulation of PPAR-γ activity in lipid-laden hepatocytes affects macrophage polarization and inflammation in nonalcoholic fatty liver disease

Systematic pharmacology and experimental validation to elucidate the inflammation-associated mechanism of Huanglian Wendan (HLWD) decoction in the treatment of MAFLD associated with atherosclerosis

ETHNOPHARMACOLOGICAL RELEVANCE

Metabolic-associated fatty liver disease (MAFLD) and atherosclerosis are very common disorders that frequently coexist. The therapeutic efficacy of Huanglian Wendan (HLWD) decoction, a traditional Chinese medicine (TCM) prescription, is satisfactory in treating MAFLD associated with atherosclerosis. However, the underlying mechanisms through which HLWD exerts its effects need to be elucidated. Given the complex composition of HLWD and its multiple therapeutic targets, pharmacological investigation is challenging.

AIM OF THIS STUDY

This study aimed to identify the effective compounds in HLWD and elucidate the mechanisms involved in its therapeutic effect on MAFLD associated with atherosclerosis.

MATERIALS AND METHODS

We used a systematic pharmacology method to identify effective compounds present in HLWD and determine the mechanism by which it affects MAFLD associated with atherosclerosis. The effective components of HLWD were identified through ultrahigh-performance liquid chromatography-q exactive-orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS). Next, a comprehensive in silico method was used to predict potential related targets and disease targets for these compounds to establish corresponding pathways. The accuracy of our assumed systemic pharmacology results was determined by conducting follow-up experiments.

RESULTS

By conducting UHPLC-Q-Orbitrap HRMS combined with network analysis, we identified 18 potentially active components of HLWD and assessed the inflammatory regulatory mechanism by which it affects MAFLD associated with atherosclerosis on the basis of 52 key targets. We used a high-fat, high-cholesterol (HFHC)-induced mice model of MAFLD associated with atherosclerosis to confirm our results. We found that administering HLWD significantly improved the appearance of their liver and reduced their body weight, liver weight, blood lipids, hepatic damage, and hepatic pathology. HLWD also decreased atherosclerotic lesion areas, foam cells, and inflammatory cells in the aorta. HLWD showed anti-inflammatory effects, suppressed M1 polarization, and promoted M2 polarization in the liver and aorta. HLWD might also regulate peroxisome proliferator-activated receptor-γ (PPARγ)/nuclear factor kappa-B (NF-κB) signaling to influence macrophage polarization and inflammation.

CONCLUSIONS

Our results showed that HLWD protected against HFHC diet-induced MAFLD associated with atherosclerosis by regulating PPARγ/NF-κB signaling, thus adjusting macrophage polarization and inflammation. Additionally, pharmacochemistry research, network pharmacology analysis, and experimental verification can be combined to form a comprehensive model used in studies on TCM.

Targeting hepatic macrophages for non-alcoholic fatty liver disease therapy

Non-alcoholic fatty liver disease (NAFLD) and its more advanced form, non-alcoholic steatohepatitis (NASH), have become global health challenges with significant morbidity and mortality rates. NAFLD encompasses several liver diseases, ranging from simple steatosis to more severe inflammatory and fibrotic forms. Ultimately, this can lead to liver cirrhosis and hepatocellular carcinoma. The intricate role of hepatic macrophages, particularly Kupffer cells (KCs) and monocyte-derived macrophages (MoMFs), in the pathogenesis of NAFLD and NASH, has received increasing attention. Hepatic macrophages can interact with hepatocytes, hepatic stellate cells, and endothelial cells, playing a crucial role in maintaining homeostasis. Paradoxically, they also participate in the pathogenesis of some liver diseases. This review highlights the fundamental role of hepatic macrophages in the pathogenesis of NAFLD and NASH, emphasizing their plasticity and contribution to inflammation and fibrosis, and hopes to provide ideas for subsequent experimental research and clinical treatment.

Application of PPAR Ligands and Nanoparticle Technology in Metabolic Steatohepatitis Treatment

Metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH) is a major disease worldwide whose effective treatment is challenging. Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor superfamily and function as ligand-activated transcription factors. To date, three distinct subtypes of PPARs have been characterized: PPARα, PPARβ/δ, and PPARγ. PPARα and PPARγ are crucial regulators of lipid metabolism that modulate the transcription of genes involved in fatty acid (FA), bile acid, and cholesterol metabolism. Many PPAR agonists, including natural (FAs, eicosanoids, and phospholipids) and synthetic (fibrate, thiazolidinedione, glitazar, and elafibranor) agonists, have been developed. Furthermore, recent advancements in nanoparticles (NPs) have led to the development of new strategies for MASLD/MASH therapy. This review discusses the applications of specific cell-targeted NPs and highlights the potential of PPARα- and PPARγ-targeted NP drug delivery systems for MASLD/MASH treatment.

Effect of triggering receptor expressed on myeloid cells 2-associated alterations on lipid metabolism in macrophages in the development of non-alcoholic fatty liver disease

BACKGROUND AND AIM

Triggering receptor expressed on myeloid cells 2 (TREM2) plays crucial roles in metabolic homeostasis and inflammatory response. Altered metabolic function in macrophages could modulate their activation and immune phenotype. The present study aimed to investigate the expression of TREM2 in non-alcoholic fatty liver disease (NAFLD) and to clarify the underlying mechanism of TREM2 on macrophages lipid metabolism and oxidative stress.

METHODS

Hepatic TREM2 expression and its relationship with NAFLD progression were analyzed in patients with NAFLD and mice fed a high-fat diet. Lipid metabolism and oxidative stress were investigated in macrophages from NAFLD mice or stimulated with saturated fatty acids. Knockdown and overexpression of TREM2 were further explored.

RESULTS

Triggering receptor expressed on myeloid cells 2+ macrophages were increased along with NAFLD development, characterized by aggravated steatosis and liver damage in humans and mice. TREM2 expression was upregulated and lipid metabolism was changed in macrophages from NAFLD mice or metabolically activated by saturated fatty acid in vitro, as demonstrated by increased lipid uptake and catabolism, but reduced de novo synthesis of fatty acids (FAs). Regulation of TREM2 expression in lipid-laden macrophages reprogrammed lipid metabolism, especially the fatty acid oxidation capacity of mitochondria. TREM2 knockdown promoted oxidative stress by aggravating FAs deposition in mitochondria. Intervention of mitochondrial FAs transport in lipid-laden macrophages alleviated FA deposition and reactive oxygen species production induced by TREM2 knockdown.

CONCLUSIONS

Triggering receptor expressed on myeloid cells 2 expression was associated with the lipid metabolic profile and reactive oxygen species production in macrophages. High expression of TREM2 in macrophages may protect the liver from oxidative stress in NAFLD.

Lipidomics in pathogenesis, progression and treatment of nonalcoholic steatohepatitis (NASH): Recent advances

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting up to 30% of the general adult population. NAFLD encompasses a histological spectrum ranging from pure steatosis to non-alcoholic steatohepatitis (NASH). NASH can progress to cirrhosis and is becoming the most common indication for liver transplantation, as a result of increasing disease prevalence and of the absence of approved treatments. Lipidomic readouts of liver blood and urine samples from experimental models and from NASH patients disclosed an abnormal lipid composition and metabolism. Collectively, these changes impair organelle function and promote cell damage, necro-inflammation and fibrosis, a condition termed lipotoxicity. We will discuss the lipid species and metabolic pathways leading to NASH development and progression to cirrhosis, as well as and those species that can contribute to inflammation resolution and fibrosis regression. We will also focus on emerging lipid-based therapeutic opportunities, including specialized proresolving lipid molecules and macrovesicles contributing to cell-to-cell communication and NASH pathophysiology.