β-patchoulene protects against non-alcoholic steatohepatitis via interrupting the vicious circle among oxidative stress, histanoxia and lipid accumulation in rats

Patchoulene epoxide mitigates colitis and hepatic damage induced by dextran sulfate sodium by regulating the colonic microbiota and purine metabolism

Introduction

Ulcerative colitis (UC) is often characterized by dysbiosis of the colonic microbiota and metabolic disturbances, which can lead to liver damage. Patchoulene epoxide (PAO), a tricyclic sesquiterpene derived from the aged essential oil of Pogostemonis Herba, is known for its anti-inflammatory and ulcer-healing properties. However, its dual protective role against UC and liver injury remains largely unexplored. This study aims to elucidate the protective effect and underlying mechanism of PAO against dextran sulfate sodium (DSS)-induced UC and liver injury in mice.

Methods

Colitis and liver injury in mice were induced by adding 3% DSS to their drinking water continuously for 7 days, and PAO at the doses of 20 and 40 mg/kg was administered orally to mice daily from the first day until the experimental endpoint. Stool consistency scores, blood stool scores, and body weights were recorded weekly. Disease activity index (DAI) was determined before necropsy, where colon and liver tissues were collected for biochemical analyses. Additionally, the fecal microbiome and its metabolites of treated mice were characterized using 16S rRNA amplicon sequencing and metabolomics.

Results

PAO significantly reduced the disease activity index and mitigated colonic atrophy in UC mice. It also improved colonic and hepatic pathological changes by safeguarding tight and adherens junctions, and suppressing the generation of pro-inflammatory cytokines and lipopolysaccharide. These beneficial effects were attributed to PAO's capability to regulate the colonic microbiota and metabolic processes. PAO was found to enhance the diversity of the colonic microbiota and to shift the microbial balance in UC mice. Specifically, it restored the microbiota from an Akkermansia-dominated state, characteristic of UC, to a healthier Muribaculaceae-dominated composition. Furthermore, PAO corrected the colon metabolic disturbance in UC mice by modulating the purine metabolism, notably increasing the abundance of deoxyadenosine, adenosine and guanine in UC mice.

Conclusions

The therapeutic effect of PAO on UC and liver injury was mainly attributed to its regulation of colonic microbiota and purine metabolism. These insights emphasize the overall therapeutic benefits of PAO in treating UC and liver injury.

CD36 in liver diseases

Cluster of differentiation 36 (CD36) is a transmembrane glycoprotein with the ability to bind to multiple ligands and perform diverse functions. Through the recognition of long-chain fatty acids, proteins containing thrombospondin structural homology repeat domains such as thrombospondin-1, and molecules with molecular structures consistent with danger- or pathogen-associated molecular patterns, CD36 participates in various physiological and pathological processes of the body. CD36 is widely expressed in various cell types, including hepatocytes and KCs in the liver, where it plays a pivotal role in lipid metabolism, inflammation, and oxidative stress. Accumulating evidence suggests that CD36 plays a complex role in the development of nonalcoholic simple fatty liver disease and NASH and contributes to the pathogenesis of inflammatory liver injury, hepatitis B/hepatitis C, liver fibrosis, and liver cancer. This review summarizes the current understanding of the structural properties, expression patterns, and functional mechanisms of CD36 in the context of liver pathophysiology. Furthermore, the potential of CD36 as a therapeutic target for the prevention and treatment of liver diseases is highlighted.

Terpenoids: Natural Compounds for Non-Alcoholic Fatty Liver Disease (NAFLD) Therapy

Natural products have been the most productive source for the development of drugs. Terpenoids are a class of natural active products with a wide range of pharmacological activities and therapeutic effects, which can be used to treat a variety of diseases. Non-alcoholic fatty liver disease (NAFLD), a common metabolic disorder worldwide, results in a health burden and economic problems. A literature search was conducted to obtain information relevant to the treatment of NAFLD with terpenoids using electronic databases, namely PubMed, Web of Science, Science Direct, and Springer, for the period 2011-2021. In total, we found 43 terpenoids used in the treatment of NAFLD. Over a dozen terpenoid compounds of natural origin were classified into five categories according to their structure: monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, and tetraterpenoids. We found that terpenoids play a therapeutic role in NAFLD, mainly by regulating lipid metabolism disorder, insulin resistance, oxidative stress, and inflammation. The AMPK, PPARs, Nrf-2, and SIRT 1 pathways are the main targets for terpenoid treatment. Terpenoids are promising drugs and will potentially create more opportunities for the treatment of NAFLD. However, current studies are restricted to animal and cell experiments, with a lack of clinical research and systematic structure-activity relationship (SAR) studies. In the future, we should further enrich the research on the mechanism of terpenoids, and carry out SAR studies and clinical research, which will increase the likelihood of breakthrough insights in the field.

Biological Mechanisms and Related Natural Inhibitors of CD36 in Nonalcoholic Fatty Liver

Non-alcoholic fatty liver disease (NAFLD), a spectrum of liver disorders from non-alcoholic fatty liver (NAFL) to the more severe non-alcoholic steatohepatitis (NASH), is the leading etiology of chronic liver disease and its global prevalence is increasing. Hepatic steatosis, a condition marked by an abnormal buildup of triglycerides in the liver, is the precursor to NAFLD. Differentiated cluster 36 (CD36), a scavenger receptor class B protein, is a membrane receptor that recognizes multiple lipid and non-lipid ligands. It is generally agreed that CD36 contributes significantly to hepatic steatosis by taking part in fatty acid uptake as well as triglyceride storage and secretion. While there has not been any conclusive research on how CD36 inhibitors prevent NAFLD from progressing and no clinically approved CD36 inhibitors are currently available for use in NAFLD, CD36 remains a target worthy of further investigation in NAFLD. In recent years, the potential role of natural products acting through CD36 in treating non-alcoholic fatty liver disease has attracted much attention. This paper offers an overview of the pathogenesis of CD36 in NAFLD and summarizes some of the natural compounds or extracts that are currently being investigated for modulating NAFLD via CD36 or the CD36 pathway, providing an alternative approach to the development of CD36-related drugs in NAFLD.

Plant-derived bioactive compounds regulate the NLRP3 inflammasome to treat NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a liver disorder characterized by abnormal accumulation of hepatic fat and inflammatory response with complex pathogenesis. Over activation of the pyrin domain-containing protein 3 (NLRP3) inflammasome triggers the secretion of interleukin (IL)-1β and IL-18, induces pyroptosis, and promotes the release of a large number of pro-inflammatory proteins. All of which contribute to the development of NAFLD. There is a great deal of evidence indicating that plant-derived active ingredients are effective and safe for NAFLD management. This review aims to summarize the research progress of 31 active plant-derived components (terpenoids, flavonoids, alkaloids, and phenols) that alleviate lipid deposition, inflammation, and pyroptosis by acting on the NLRP3 inflammasome studied in both in vitro and in vivo NAFLD models. These studies confirmed that the NLRP3 inflammasome and its related genes play a key role in NAFLD amelioration, providing a starting point for further study on the correlation of plant-derived compounds treatment with the NLRP3 inflammasome and NAFLD.