Piperine Improves Lipid Dysregulation by Modulating Circadian Genes Bmal1 and Clock in HepG2 Cells

Metabolic disorders are closely associated with the dysregulation of circadian rhythms. Many bioactive components with lipid metabolism-regulating effects have been reported to function through circadian clock-related mechanisms. As the main pungent principle of black pepper, piperine (PIP) has been demonstrated to possess anti-obesity bioactivity by affecting hepatic lipid metabolism-related factors. However, whether the circadian clock genes Bmal1 and Clock are involved in the protective effect of PIP against lipid metabolism disorders remains unknown. In this work, oleic acid (OA) induced lipid accumulation in HepG2 cells. The effect of PIP on redox status, mitochondrial functions, and circadian rhythms of core clock genes were evaluated. Results revealed that PIP alleviated circadian desynchrony, ROS overproduction, and mitochondrial dysfunction. A mechanism study showed that PIP could activate the SREBP-1c/PPARγ and AMPK/AKT-mTOR signaling pathways in a Bmal1/Clock-dependent manner in HepG2 cells. These results indicated that Bmal1 and Clock played important roles in the regulating effect of PIP on hepatic lipid homeostasis.     

Boesenbergia pandurata Attenuates Diet-Induced Obesity by Activating AMP-Activated Protein Kinase and Regulating Lipid Metabolism

Obesity, a chronic metabolic disorder, is characterized by enlarged fat mass and dysregulation of lipid metabolism. The medicinal plant, Boesenbergia pandurata (Roxb.) Schltr., has been reported to possess anti-oxidative and anti-inflammatory properties; however, its anti-obesity activity is unexplored. The present study was conducted to determine whether B. pandurata extract (BPE), prepared from its rhizome parts, attenuated high-fat diet (HFD)-induced obesity in C57BL/6J mice. The molecular mechanism was investigated in 3T3-L1 adipocytes and HepG2 human hepatoma cells. BPE treatment decreased triglyceride accumulation in both 3T3-L1 adipocytes and HepG2 hepatocytes by activating AMP-activated protein kinase (AMPK) signaling and regulating the expression of lipid metabolism-related proteins. In the animal model, oral administration of BPE (200 mg/kg/day for 8 weeks) significantly reduced HFD-induced body weight gain without altering the amount of food intake. In addition, elevated serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides were suppressed by BPE administration. Fat pad masses were reduced in BPE-treated mice, as evidenced by reduced adipocyte size. Furthermore, BPE protected against the development of nonalcoholic fatty liver by decreasing hepatic triglyceride accumulation. BPE also activated AMPK signaling and altered the expression of lipid metabolism-related proteins in white adipose tissue and liver. Taken together, these findings indicate that BPE attenuates HFD-induced obesity by activating AMPK and regulating lipid metabolism, suggesting a potent anti-obesity agent.     

Beneficial effects of vaccenic acid on postprandial lipid metabolism and dyslipidemia: Impact of natural trans‐fats to improve CVD risk

Abnormal non‐fasting (postprandial) lipid metabolism has been recognized as a significant contributor to dyslipidemia and cardiovascular disease (CVD) risk. Clinically, impaired metabolism of lipoproteins following a meal (e.g. chylomicrons) has been demonstrated in a number of chronic diseases, including obesity, insulin resistance, as well as type 1 and 2 diabetes. Given the proposed effects of dietary trans fat to contribute to a lipid profile that increases CVD risk, there has been a public health campaign in many countries to eliminate these fatty acids from the food supply. In contrast, our group has recently reported novel lipid‐lowering benefits of a major naturally‐occurring trans fatty acid vaccenic acid (VA, shorthand lipid name 18:1 trans‐11), in an animal model of dyslipidemia and the metabolic syndrome. Studies to date have shown that dietary supplementation of VA effectively reduces not only fasting lipids, but also postprandial triacylglycerol and chylomicron concentrations in obese JCR:LA‐cp rats. Evidence from animal studies to date suggest that VA may down‐regulate hepatic fatty acid synthesis and directly influence lipogenesis in the intestine. The discovery of new bioactive properties of VA is supported by clinical studies which have provided increased momentum for industry applications. In this review we summarize the emerging beneficial view of natural trans fats that have distinct and differential properties compared to those synthetically produced in partially hydrogenated vegetable oils (PHVO), with a particular focus on fasting and postprandial lipid metabolism in CVD risk.     

Neochlorogenic Acid Attenuates Hepatic Lipid Accumulation and Inflammation via Regulating miR-34a In Vitro

Neochlorogenic acid (5-Caffeoylquinic acid; 5-CQA), a major phenolic compound isolated from mulberry leaves, possesses anti-oxidative and anti-inflammatory effects. Although it modulates lipid metabolism, the molecular mechanism is unknown. Using an in-vitro model of nonalcoholic fatty liver disease (NAFLD) in which oleic acid (OA) induced lipid accumulation in HepG2 cells, we evaluated the alleviation effect of 5-CQA. We observed that 5-CQA improved OA-induced intracellular lipid accumulation by downregulating sterol regulatory element-binding protein 1 (SREBP1) and fatty acid synthase (FASN) expression, which regulates the fatty acid synthesis, as well as SREBP2 and HMG-CoA reductases (HMG-CoR) expressions, which regulate cholesterol synthesis. Treatment with 5-CQA also increased the expression of fatty acid β-oxidation enzymes. Remarkably, 5-CQA attenuated OA-induced miR-34a expression. A transfection assay with an miR-34a mimic or miR-34a inhibitor revealed that miR-34a suppressed Moreover, Sirtuin 1 (SIRT1) expression and inactivated 5’ adenosine monophosphate-activated protein kinase (AMPK). Our results suggest that 5-CQA alleviates lipid accumulation by downregulating miR-34a, leading to activation of the SIRT1/AMPK pathway.     

Anti-Inflammatory Effect of Ginsenoside Rg5 in Lipopolysaccharide-Stimulated BV2 Microglial Cells

Microglia are resident immune cells in the central nervous system. They play a role in normal brain development and neuronal recovery. However, overactivation of microglia causes neuronal death, which is associated with neurodegenerative diseases, such as Parkinson’s disease and Alzheimer’s disease. Therefore, controlling microglial activation has been suggested as an important target for treatment of neurodegenerative diseases. In the present study, we investigated the anti-inflammatory effect of ginsenoside Rg5 in lipopolysaccharide (LPS)-stimulated BV2 microglial cells and rat primary microglia. The data showed that Rg5 suppressed LPS-induced nitric oxide (NO) production and proinflammatory TNF-α secretion. In addition, Rg5 inhibited the mRNA expressions of iNOS, TNF-α, IL-1β, COX-2 and MMP-9 induced by LPS. Further mechanistic studies revealed that Rg5 inhibited the phophorylations of PI3K/Akt and MAPKs and the DNA binding activities of NF-κB and AP-1, which are upstream molecules controlling inflammatory reactions. Moreover, Rg5 suppressed ROS production with upregulation of hemeoxygenase-1 (HO-1) expression in LPS-stimulated BV2 cells. Overall, microglial inactivation by ginsenoside Rg5 may provide a therapeutic potential for various neuroinflammatory disorders.     

Soyasapogenol C from Fermented Soybean (Glycine Max) Acting as a Novel AMPK/PPARα Dual Activator Ameliorates Hepatic Steatosis: A Novel SANDA Methodology

(1) Background: Soyasapogenol C (SSC), a derivative of soyasapogenol B (SSB), is specifically found high in many fermented soybean (Glycine max) products, including Cheonggukjang (in Korean). However, the biological activities for preventing and treating hepatic steatosis, and the precise underlying mechanisms of SSC, remain to be explored. (2) Methods: A novel SANDA (structural screening, ADMET prediction, network pharmacology, docking validation, and activity evaluation) methodology was used to examine whether SSC exerts hepatoprotective effects in silico and in vitro. (3) Results: SSC had better ADMET characteristics and a higher binding affinity with predicted targets chosen from network pathway analysis than SSB. SSC induced the phosphorylation of AMP-activated protein kinase (AMPK) and stimulated the nuclear translocation of peroxisome proliferator-activated receptor alpha (PPARα), further enhancing PPAR response element (PPRE) binding activity in HepG2 cells. Concurrently, SSC significantly inhibited triglyceride accumulation, which was associated with the suppression of lipogenesis genes and the enhancement of fatty acid oxidation gene expression in HepG2 cells. (4) Conclusions: Soyasapogenol C, discovered using a novel SANDA methodology from fermented soybean, is a novel AMPK/PPARα dual activator that is effective against hepatic steatosis. Dietary supplementation with soyasapogenol C may prevent the development of hepatic steatosis and other diseases associated with fat accumulation in the liver.     

Inhibitory Activities of Rare Ginsenoside Rg4 on Cecal Ligation and Puncture-Induced Sepsis

Sepsis is an uncontrolled response to inflammatory infection and is associated with high levels of mortality and morbidity. Rg4 is a rare ginsenoside mainly found in the leaves of Panax ginseng C. A. Meyer and the major protopanaxatriol-type ginsenoside of black ginseng. In this study, we determined whether Rg4 affects cecal ligation and puncture (CLP)-induced sepsis. Animals were separated into the following six groups: control group, CLP-operated group, CLP plus maslinic acid (MA), and CLP plus Rg4 (5, 10, or 15 mg/kg). Survival rate, body weight changes, inflammatory cytokines, and histological analyses were assessed. Human endothelial cells were activated with the high-mobility group box 1 (HMGB1) protein and Rg4. Cell viability was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Enzyme-linked immunosorbent assay (ELISA) and Western blot analysis were used to assess inflammation and gene expression, respectively. After CLP surgery, the Rg4-administered group exhibited a higher survival rate and body weight compared with the untreated control group. Rg4 treatment reduced cytokine levels, including tumor necrosis factor (TNF)-α and interleukin (IL)-1β, as well as nitric oxide (NO) levels and renal inflammation. After Rg4 treatment of HMGB1-activated cells, the expressions of toll-like receptor (TLR) 4 and TNF-α were decreased, and the activation of phosphoinositide 3-kinase (PI3K)/AKT signaling increased cell viability. In summary, Rg4 inhibited inflammation and exhibited a protective effect against CLP-induced sepsis, thereby reinforcing cell survival against septic responses.     

P2Y2R Deficiency Ameliorates Hepatic Steatosis by Reducing Lipogenesis and Enhancing Fatty Acid β-Oxidation through AMPK and PGC-1α Induction in High-Fat Diet-Fed Mice

Non-alcoholic fatty liver disease (NAFLD) is a chronic metabolic liver disease associated with obesity and insulin resistance. Activation of the purinergic receptor P2Y2R has been reported to promote adipogenesis, inflammation and dyslipidemia in adipose tissues in obese mice. However, the role of P2Y2R and its mechanisms in NAFLD remain unknown. We hypothesized that P2Y2R deficiency may play a protective role in NAFLD by modulating lipid metabolism in the liver. In this study, we fed wild type and P2Y2R knockout mice with a high-fat diet (HFD) for 12 weeks and analyzed metabolic phenotypes. First, P2Y2R deficiency effectively improved insulin resistance with a reduction in body weight and plasma insulin. Second, P2Y2R deficiency attenuated hepatic lipid accumulation and injury with reduced alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Third, P2Y2R deficiency decreased the expression of fatty acid synthesis mediators (cluster of differentiation (CD36), fatty acid synthase (FAS), and stearoyl-CoA desaturase 1 (SCD1)); and increased the expression of adipose triglyceride lipase (ATGL), a lipolytic enzyme. Mechanistically, P2Y2R deficiency increased the AMP-activated protein kinase (AMPK) activity to improve mitochondrial fatty acid β-oxidation (FAO) by regulating acetyl-CoA carboxylase (ACC) and carnitine palmitoyltransferase 1A (CPT1A)-mediated FAO pathway. In addition, P2Y2R deficiency increased peroxisome proliferator-activated gamma co-activator-1α (PGC-1α)-mediated mitochondrial biogenesis. Conclusively, P2Y2R deficiency ameliorated HFD-induced hepatic steatosis by enhancing FAO through AMPK signaling and PGC-1α pathway, suggesting P2Y2R as a promising therapeutic target for NAFLD.     

Role of n-3 Fatty Acids on Bile Acid Metabolism and Transport in Dyslipidemia: A Review

Dietary n-3 fatty acids, especially of marine origin, eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3), have always been lauded for their profound effects on regulating the risk factors for major metabolic disorders. Yet, their consumption rate is poor compared to n-6 fatty acids [linoleic acid (18:2n-6)], which are predominantly consumed. Hence, the skewed n-6 to n-3 fatty acid ratio may have a bearing on the risk factors of various diseases, including dyslipidemia. Dyslipidemia and other lifestyle diseases associated with it, such as diabetes, obesity, hypertension, are a growing concern in both developed and developing countries. A common strategy for addressing dyslipidemia involves bile acid (BA) sequestration, to interrupt the enterohepatic circulation of BA, resulting in the modulation of lipid absorption in the intestine, thereby normalizing the levels of circulating lipids. The BA homeostasis is under the tight control of hepatic and enteric BA transporters. Many investigations have reported the effects of dietary constituents, including certain fatty acids on the reabsorption and transport of BA. However, a critical review of the effects of n-3 fatty acids on BA metabolism and transport is not available. The present review attempts to explore certain unmapped facets of the n-3 fatty acids on BA metabolism and transport in dyslipidemia, and their interplay with biological processes involving lipid rafts and gut microbiome.     

Therapies for the Treatment of Cardiovascular Disease Associated with Type 2 Diabetes and Dyslipidemia

Cardiovascular disease (CVD) is the leading cause of death worldwide and is the clinical manifestation of the atherosclerosis. Elevated LDL-cholesterol levels are the first line of therapy but the increasing prevalence in type 2 diabetes mellitus (T2DM) has positioned the cardiometabolic risk as the most relevant parameter for treatment. Therefore, the control of this risk, characterized by dyslipidemia, hypertension, obesity, and insulin resistance, has become a major goal in many experimental and clinical studies in the context of CVD. In the present review, we summarized experimental studies and clinical trials of recent anti-diabetic and lipid-lowering therapies targeted to reduce CVD. Specifically, incretin-based therapies, sodium-glucose co-transporter 2 inhibitors, and proprotein convertase subtilisin kexin 9 inactivating therapies are described. Moreover, the novel molecular mechanisms explaining the CVD protection of the drugs reviewed here indicate major effects on vascular cells, inflammatory cells, and cardiomyocytes, beyond their expected anti-diabetic and lipid-lowering control. The revealed key mechanism is a prevention of acute cardiovascular events by restraining atherosclerosis at early stages, with decreased leukocyte adhesion, recruitment, and foam cell formation, and increased plaque stability and diminished necrotic core in advanced plaques. These emergent cardiometabolic therapies have a promising future to reduce CVD burden.     

Regulation of Hepatocyte Lipid Metabolism and Inflammatory Response by 25-Hydroxycholesterol and 25-Hydroxycholesterol-3-sulfate

Dysregulation of lipid metabolism is frequently associated with inflammatory conditions. The mechanism of this association is still not clearly defined. Recently, we identified a nuclear oxysterol, 25-hydroxycholesterol-3-sulfate (25HC3S), as an important regulatory molecule involved in lipid metabolism in hepatocytes. The present study shows that 25HC3S and its precursor, 25-hydroxycholesterol (25HC), diametrically regulate lipid metabolism and inflammatory response via LXR/SREBP-1 and IκBα/NFκB signaling in hepatocytes. Addition of 25HC3S to primary rat hepatocytes decreased nuclear LXR and SREBP-1 protein levels, down-regulated their target genes, acetyl CoA carboxylase 1 (ACC1), fatty acid synthase (FAS), and SREBP-2 target gene HMG reductase, key enzymes involved in fatty acid and cholesterol biosynthesis. 25HC3S reduced TNFα-induced inflammatory response by increasing cytoplasmic IκBα levels, decreasing NFκB nuclear translocation, and consequently repressing expression of NFκB-dependent genes, IL-1β, TNFα, and TRAF1. NFκB-dependent promoter reporter gene assay showed that 25HC3S suppressed luciferase activity in the hepatocytes. In contrast, 25HC elicited opposite effects by increasing nuclear LXR and SREBP-1 protein levels, and by increasing ACC1 and FAS mRNA levels. 25HC also decreased cytoplasmic IκBα levels and further increased TNFα-induced NFκB activation. The current findings suggest that 25HC and 25HC3S serve as potent regulators in cross-talk of lipid metabolism and inflammatory response in the hepatocytes.     

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.