Inhibitory effect of esculetin on free-fatty-acid-induced lipid accumulation in human HepG2 cells through activation of AMP-activated protein kinase

The Coumarin-Derivative Esculetin Protects against Lipotoxicity in Primary Rat Hepatocytes via Attenuating JNK-Mediated Oxidative Stress and Attenuates Free Fatty Acid-Induced Lipid Accumulation

Coumarin derivates have been proposed as a potential treatment for metabolic-dysfunction-associated fatty liver disease (MAFLD). However, the mechanisms underlying their beneficial effects remain unclear. In the present study, we explored the potential of the coumarin derivate esculetin in MAFLD, focusing on hepatocyte lipotoxicity and lipid accumulation. Primary cultures of rat hepatocytes were exposed to palmitic acid (PA) and palmitic acid plus oleic acid (OA/PA) as models of lipotoxicity and lipid accumulation, respectively. Esculetin significantly reduced oxidative stress in PA-treated hepatocytes, as shown by decreased total reactive oxygen species (ROS) and mitochondrial superoxide production and elevated expression of antioxidant genes, including Nrf2 and Gpx1. In addition, esculetin protects against PA-induced necrosis. Esculetin also improved lipid metabolism in primary hepatocytes exposed to nonlipotoxic OA/PA by decreasing the expression of the lipogenesis-related gene Srebp1c and increasing the expression of the fatty acid β-oxidation-related gene Ppar-α. Moreover, esculetin attenuated lipid accumulation in OA/PA-treated hepatocytes. The protective effects of esculetin against lipotoxicity and lipid accumulation were shown to be dependent on the inhibition of JNK and the activation of AMPK, respectively. We conclude that esculetin is a promising compound to target lipotoxicity and lipid accumulation in the treatment of MAFLD.

Natural Compounds with Aldose Reductase (AR) Inhibition: A Class of Medicative Agents for Fatty Liver Disease

Fatty liver disease (FLD), which includes both non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (ALD), is a worldwide health concern. The etiology of ALD is long-term alcohol consumption, while NAFLD is defined as an abnormal amount of lipid present in liver cells, which is not caused by alcohol intake and has recently been identified as a hepatic manifestation of metabolic syndrome (such as type 2 diabetes, obesity, hypertension, and obesity). Inflammation, oxidative stress, and lipid metabolic dysregulation are all known to play a role in FLD progression. Alternative and natural therapies are desperately needed to treat this disease since existing pharmaceuticals are mostly ineffective. The aldose reductase (AR)/polyol pathway has recently been shown to play a role in developing FLD by contributing to inflammation, oxidative stress, apoptosis, and fat accumulation. Herein, we review the effects of plantderived compounds capable of inhibiting AR in FLD models. Natural AR inhibitors have been found to improve FLD in part by suppressing inflammation, oxidative stress, and steatosis via the regulation of several critical pathways, including the peroxisome proliferator-activated receptor (PPAR) pathway, cytochrome P450 2E1 (CYP2E1) pathway, AMP-activated protein kinase (AMPK) pathway, etc. This review revealed that natural compounds with AR inhibitory effects are a promising class of therapeutic agents for FLD.

Metabolic Syndrome Ameliorated by 4-Methylesculetin by Reducing Hepatic Lipid Accumulation

Obesity is a chronic metabolic disease caused by an imbalance between energy intake and expenditure during a long period and is characterized by adipose tissue disfunction and hepatic steatosis. The aim of this study was to investigate the effect of 4-methylesculetin (4-ME), a coumarin derivative, upon adipose microenvironment and hepatic steatosis in mice induced by a high-fat diet (HFD), and to explore potential mechanisms of its beneficial effect on metabolic disorders. HFD-fed mice displayed visceral obesity, insulin resistance, and hepatic lipid accumulation, which was remarkably ameliorated by 4-ME treatment. Meanwhile, 4-ME ameliorated adipocyte hypertrophy, macrophage infiltration, hypoxia, and fibrosis in epididymal adipose tissue, thus improving the adipose tissue microenvironment. Furthermore, 4-ME reversed the increase in CD36, PPAR-γ, SREBP-1, and FASN, and the decrease in CPT-1A, PPAR-α, and Nrf2 translocation into the nucleus in livers of HFD mice and in FFA-incubated hepatocytes. Moreover, the beneficial effects of 4-ME upon lipid deposition and the expression of proteins related to lipid metabolism in FFA-induced LO2 cells were abolished by ML385, a specific Nrf2 inhibitor, indicating that Nrf2 is necessary for 4-ME to reduce hepatic lipid deposition. These findings suggested that 4-ME might be a potential lead compound candidate for preventing obesity and MAFLD.

CGX, a standardized herbal syrup, inhibits colon-liver metastasis by regulating the hepatic microenvironments in a splenic injection mouse model

Background: Colon-liver metastasis is observed in approximately 50% of patients with colorectal cancer and is a critical risk factor for a low survival rate. Several clinical studies have reported that colon-liver metastasis is accelerated by pathological hepatic microenvironments such as hepatic steatosis or fibrosis. Chunggan syrup (CGX), a standardized 13-herbal mixture, has been prescribed to patients with chronic liver diseases, including fatty liver, inflammation and fibrotic change, based on preclinical and clinical evidence.

Aim of the study: In the present study, we investigated anti-liver metastatic the effects of CGX in a murine colon carcinoma (MC38)-splenic injection mouse model.

Materials and methods: C57BL/6N mice were administered with CGX (100, 200 or 400 mg/kg) for 14 days before or after MC38-splenic injection under normal and high-fat diet (HFD) fed conditions. Also, above experiment was repeated without MC38-splenic injection to explore underlying mechanism.

Results: The number of tumor nodules and liver weight with tumors were sup-pressed by preadministration of CGX in both normal and HFD fed mice. Regarding its mechanisms, we found that CGX administration significantly activated epithelial-cadherin (E-cadherin), but decreased vascular endothelial-cadherin (VE-cadherin) in hepatic tissues under MC38-free conditions. In addition, CGX administration significantly reduced hepatic steatosis, via modulation of lipolytic and lipogenic molecules, including activated adenosine monophosphate activated protein kinase (AMPK) and peroxisome proliferator activated receptor-alpha (PPARα).

Conclusion: The present data indicate that CGX exerts an anti-colon-liver metastatic property via modulation of hepatic lipid related microenvironments.

Adipose and non-adipose perspectives of plant derived natural compounds for mitigation of obesity

ETHNOPHARMACOLOGICAL RELEVANCE

Phyto-preparations and phyto-compounds, by their natural origin, easy availability, cost-effectiveness, and fruitful traditional uses based on accumulated experiences, have been extensively explored to mitigate the global burden of obesity.

AIM OF THIS REVIEW

The review aimed to analyse and critically summarize the prospect of future anti-obesity drug leads from the extant array of phytochemicals for mitigation of obesity, using adipose related targets (adipocyte formation, lipid metabolism, and thermogenesis) and non-adipose targets (hepatic lipid metabolism, appetite, satiety, and pancreatic lipase activity). Phytochemicals as inhibitors of adipocyte differentiation, modulators of lipid metabolism, and thermogenic activators of adipocytes are specifically discussed with their non-adipose anti-obesogenic targets.

MATERIALS AND METHODS

PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets. The taxonomically accepted name of each plant in this review has been vetted from "The Plant List" (www.theplantlist.org) or MPNS (http://mpns.kew.org).

RESULTS

Available knowledge of a large number of phytochemicals, across a range of adipose and non-adipose targets, has been critically analysed and delineated by graphical and tabular depictions, towards mitigation of obesity. Neuro-endocrinal modulation in non-adipose targets brought into sharp dual focus, both non-adipose and adipose targets as the future of anti-obesity research. Numerous phytochemicals (Berberine, Xanthohumol, Ursolic acid, Guggulsterone, Tannic acid, etc.) have been found to be effectively reducing weight through lowered adipocyte formation, increased lipolysis, decreased lipogenesis, and enhanced thermogenesis. They have been affirmed as potential anti-obesity drugs of future because of their effectiveness yet having no threat to adipose or systemic insulin sensitivity.

CONCLUSION

Due to high molecular diversity and a greater ratio of benefit to risk, plant derived compounds hold high therapeutic potential to tackle obesity and associated risks. This review has been able to generate fresh perspectives on the anti-diabetic/anti-hyperglycemic/anti-obesity effect of phytochemicals. It has also brought into the focus that many phytochemicals demonstrating in vitro anti-obesogenic effects are yet to undergo in vivo investigation which could lead to potential phyto-molecules for dedicated anti-obesity action.

Anti-diabetic effect of hydroxybenzoic acid derivatives in free fatty acid-induced HepG2 cells via miR-1271/IRS1/PI3K/AKT/FOXO1 pathway

Type 2 diabetes is characterized by insulin resistance (IR) and increased hepatic glucose production. MicroRNAs (miRs) are considered regulators of glucose metabolism. This study evaluated anti-diabetic activity of hydroxybenzoic acid derivatives and determined the involvement of miR-1271. Among the hydroxybenzoic acid derivatives, gallic acid (GA) showed the best anti-diabetic activity. GA improved free fatty acid (FFA)-induced hepatic IR, increased glucose consumption, and decreased reactive oxygen species. GA inhibited the upregulation of miR-1271 induced by FFA and upregulated its targets such as p-IRS, p-PI3K, p-AKT, and p-FOXO1, accompanied by the regulation of glucose metabolism genes. The involvement of miR-1271 in the protective effect of GA against IR was further confirmed in the presence of miR-1271 mimic or miR-1271 inhibitor. Our results suggest that GA attenuates IR via the miR-1271/IRS/PI3K/AKT/FOXO1 pathway and thus might be considered for the management of IR. PRACTICAL APPLICATIONS: MicroRNAs can regulate insulin resistance by affecting protein expressions involved in insulin signaling. Experimental data suggest that some phytochemicals regulate the expression of various microRNAs. However, it is not clear whether phenolic acids play any role in the hepatic insulin signaling pathway through the regulation of microRNA expression. This study assessed the anti-diabetic activity of hydroxybenzoic acid derivatives through down-regulation of microRNA-1271 and its association with the IRS1/PI3K/AKT/FOXO1 pathways. This research will be able to offer basic information regarding a potential therapeutic strategy to control hepatic insulin resistance.

Taxifolin and Sorghum Ethanol Extract Protect against Hepatic Insulin Resistance via the miR-195/IRS1/PI3K/AKT and AMPK Signalling Pathways

This study aimed to evaluate the effects of taxifolin and sorghum ethanol extract on free fatty acid (FFA)-induced hepatic insulin resistance. FFA treatment decreased glucose uptake by 16.2% compared with that in the control, whereas taxifolin and sorghum ethanol extract increased the glucose uptake. Additionally, taxifolin and sorghum ethanol extract increased the expression of p-PI3K, p-IRS1, p-AKT, p-AMPK, and p-ACC in FFA-induced hepatocytes. Furthermore, FFA treatment increased the expression of miR-195. However, compared with the FFA treatment, treatment with taxifolin and sorghum ethanol extract decreased miR-195 expression in a dose-dependent manner. Taxifolin and sorghum ethanol extract enhanced p-IRS1, p-PI3K, p-AMPK, p-AKT, and p-ACC expression by suppressing miR-195 levels in miR-195 mimic- or inhibitor-transfected cells. These results indicate that taxifolin and sorghum ethanol extract attenuate insulin resistance by regulating miR-195 expression, which suggests that taxifolin and sorghum ethanol extract may be useful antidiabetic agents.

Pentacyclic triterpenoids from Cyclocarya paliurus and their antioxidant activities in FFA-induced HepG2 steatosis cells

Six undescribed pentacyclic triterpenoids including four triterpenoid aglycones, 1β,2a,3β,23-tetrahydroxyurs-12-en-28-ursolic acid, 2a,3a,6β,19α,23-pentahydroxyurs-12-en-28-ursolic acid, 2α,3α,20β,23-tetrahydroxyurs-12-en-28-ursolic acid and 1β,2a,3β,23-tetrahydroxyurs-12,20(30)-dien-28-ursolic acid, and two triterpenoid glucosides, 2a,3a,23-trihydroxy-12,20(30)-dien-28-ursolic acid 28-O-β-d-glucopyranoside and 1-oxo-3β,23-dihydroxyolean-12-en-28-oic acid 28-O-β-d-xylopyranoside, along with 5 known triterpenoids were isolated from a CH₃Cl-soluble extract of the leaves of Cyclocarya paliurus. Their structures were established on the basis of chemical and spectroscopic approaches. These compounds were assessed for their antioxidant effects on FFA-induced hepatic steatosis in HepG2 cells. The results revealed that three saponins and two aglycones markedly increased SOD activity and reduced MDA level.