Green Tea Extract Rich in Epigallocatechin-3-Gallate Prevents Fatty Liver by AMPK Activation via LKB1 in Mice Fed a High-Fat Diet

A combination of Pueraria lobata and Silybum marianum protects against alcoholic liver disease in mice

BACKGROUND

Excess alcohol exposure leads to alcoholic liver disease (ALD). Pueraria lobata (PUE) and Silybum marianum (SIL) are two well-known hepatoprotective herbal remedies with various activities. The possible effect of combination of PUE and SIL on ALD has not been elucidated yet.

PURPOSE

We aimed to demonstrate that the combination of PUE and SIL prevents against alcoholic liver injury in mice using a model of chronic-plus-single-binge ethanol feeding.

STUDY DESIGN

Male C57BL/6 mice were randomly divided into five groups (n = 8-10), namely the control group (CON), ethanol-induced liver injury group (ETH), 150 mg/kg PUE treated group (PUE), 60 mg/kg SIL treated group (SIL), 210 mg/kg PUE+SIL treatment group (PUE+SIL). Except control group, all animals were fed a modified Lieber-DeCarli ethanol liquid diet for 10 days. While, control group received Lieber-DeCarli control diet containing isocaloric maltose dextrin substituted for ethanol. On day 11, the mice orally received a single dose of 31.5% (v/v) ethanol (5 g/kg BW) or an isocaloric maltose solution.

RESULTS

Ethanol exposure caused liver injury, as demonstrated by remarkably increased plasma parameters, histopathological changes, the increased lipid accumulation, oxidative stress and inflammation in liver. These alterations were ameliorated by the treatments of PUE, SIL and PUE+SIL. While, the PUE+SIL treatment showed the most effective protection, which was associated with reducing alcohol-induced hepatic steatosis via upregulating LKB1/AMPK/ACC signaling, and inhibiting hepatic inflammation via LPS-triggered TLR4-mediated NF-κB signaling pathway. Our results also indicated that the hepatoprotective effects of SIL+PUE might mainly attribute to the protection of SIL and PUE alone in alcohol-induced hepatic steatosis and hepatic inflammation, respectively.

CONCLUSION

These findings also suggest that the combination of PUE and SIL has a potential to be developed as a functional food for the management of ALD.

Green Tea Extracts Attenuate Brain Dysfunction in High-Fat-Diet-Fed SAMP8 Mice

Unhealthy diet promotes progression of metabolic disorders and brain dysfunction with aging. Green tea extracts (GTEs) have various beneficial effects and alleviate metabolic disorders. GTEs have neuroprotective effects in rodent models, but their effects against brain dysfunction in models of aging fed unhealthy diets are still unclear. Here, we showed that GTEs attenuate high-fat (HF) diet-induced brain dysfunction in senescence-accelerated mouse prone-8 (SAMP8), a murine model of senescence. SAMP8 mice were fed a control diet, HF diet, or HF diet with 0.5% GTEs (HFGT) for four months. The HF diet reduced memory retention and induced amyloid β_1–42 accumulation, whereas GTEs attenuated these changes. In HF diet-fed mice, lipid oxidative stress, assessed by malondialdehyde levels, was increased. The levels of proteins that promote synaptic plasticity, such as brain-derived neurotrophic factor (BDNF) and postsynaptic density protein 95 (PSD95), were reduced. These alterations related to brain dysfunction were not observed in HFGT diet-fed mice. Overall, our data suggest that GTEs intake might attenuate brain dysfunction in HF diet-fed SAMP8 mice by protecting synaptic plasticity as well as via anti-oxidative effects. In conclusion, GTEs might ameliorate unhealthy diet-induced brain dysfunction that develops with aging.

A Polyphenol-Enriched Supplement Exerts Potent Epigenetic-Protective Activity in a Cell-Based Model of Brain Ischemia

Bioactive components, due in part to their epigenetic properties, are beneficial for preventing several human diseases including cerebrovascular pathologies. However, no clear demonstration supports the idea that these molecules still conserve their epigenetic effects when acting at very low concentrations reproducing the brain levels achieved after oral administration of a micronutrient supplement. In the present study, we used a cellular model of brain ischemia to investigate the neuroprotective and epigenetic activities of a commercially available micronutrient mixture (polyphenol-enriched micronutrient mixture, PMM) enriched in polyphenols ((-)-epigallocatechin-3-gallate, quercetin, resveratrol), α-lipoic acid, vitamins, amino acids and other micronutrients. Mimicking the suggested dietary supplementation, primary cultures of mouse cortical neurons were pre-treated with PMM and then subjected to oxygen glucose deprivation (OGD). Pre-treatment with PMM amounts to provide bioactive components in the medium in the nanomolar range potently prevented neuronal cell death. The protection was associated with the deacetylation of the lysin 310 (K310) on NF-κB/RelA as well as the deacetylation of H3 histones at the promoter of Bim, a pro-apoptotic target of ac-RelA(K310) in brain ischemia. Epigenetic regulators known to shape the acetylation state of ac-RelA(K310) moiety are the histone acetyl transferase CBP/p300 and the class III histone deacetylase sirtuin-1. In view of that evidence, the protection we here report unveils the efficacy of bioactive components endowed with either inhibitory activity on CBP/p300 or stimulating activity on the AMP-activated protein kinase–sirtuin 1 pathway. Our results support a potential synergistic effect of micronutrients in the PMM, suggesting that the intake of a polyphenol-based micronutrient mixture can reduce neuronal vulnerability to stressful conditions at concentrations compatible with the predicted brain levels reached by a single constituent after an oral dose of PMM.

Epigallocatechin Gallate Modulates Muscle Homeostasis in Type 2 Diabetes and Obesity by Targeting Energetic and Redox Pathways: A Narrative Review

Obesity is associated with the hypertrophy and hyperplasia of adipose tissue, affecting the healthy secretion profile of pro- and anti-inflammatory adipokines. Increased influx of fatty acids and inflammatory adipokines from adipose tissue can induce muscle oxidative stress and inflammation and negatively regulate myocyte metabolism. Muscle has emerged as an important mediator of homeostatic control through the consumption of energy substrates, as well as governing systemic signaling networks. In muscle, obesity is related to decreased glucose uptake, deregulation of lipid metabolism, and mitochondrial dysfunction. This review focuses on the effect of epigallocatechin-gallate (EGCG) on oxidative stress and inflammation, linked to the metabolic dysfunction of skeletal muscle in obesity and their underlying mechanisms. EGCG works by increasing the expression of antioxidant enzymes, by reversing the increase of reactive oxygen species (ROS) production in skeletal muscle and regulating mitochondria-involved autophagy. Moreover, EGCG increases muscle lipid oxidation and stimulates glucose uptake in insulin-resistant skeletal muscle. EGCG acts by modulating cell signaling including the NF-κB, AMP-activated protein kinase (AMPK), and mitogen-activated protein kinase (MAPK) signaling pathways, and through epigenetic mechanisms such as DNA methylation and histone acetylation.

When to Initiate Weight Loss Medications in the NAFLD Population

Nonalcoholic fatty liver disease (NAFLD) is characterized by histological evidence of hepatic steatosis, lobular inflammation, ballooning degeneration and hepatic fibrosis in the absence of significant alcohol use and other known causes of chronic liver diseases. NAFLD is subdivided into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). NAFL is generally benign but can progress to NASH, which carries a higher risk of adverse outcomes including cirrhosis, end-stage liver disease, hepatocellular carcinoma and death if liver transplantation is not pursued in a timely fashion. Currently, lifestyle modifications including healthy diet and increased physical activity/exercise culminating in weight loss of 5% to >10% is the cornerstone of treatment intervention for patients with NAFLD. Patients with NAFLD who fail to obtain this goal despite the help of dietitians and regimented exercise programs are left in a purgatory state and remain at risk of developing NASH-related advance fibrosis. For such patients with NAFLD who are overweight and obese, healthcare providers should consider a trial of FDA-approved anti-obesity medications as adjunct therapy to provide further preventative and therapeutic options as an effort to reduce the risk of NAFLD-related disease progression.

Potential Therapeutic Benefits of Herbs and Supplements in Patients with NAFLD

Our aim is to review the efficacy of various herbs and supplements as a possible therapeutic option in the treatment and/or prevention of nonalcoholic fatty liver disease (NAFLD). We performed a systematic review of medical literature using the PubMed Database by searching the chemical names of many common herbs and supplements with “AND (NAFLD or NASH)”. Studies and medical literature that discussed the roles and usage of herbs and supplements in NAFLD and nonalcoholic steatohepatitis (NASH) from inception until 20 June 2018 were reviewed. Many studies have claimed that the use of various herbs and supplements may improve disease endpoints and outcomes related to NAFLD and/or NASH. Improvement in liver function tests were noted. Amelioration or reduction of lobular inflammation, hepatic steatosis, and fibrosis were also noted. However, well-designed studies demonstrating improved clinical outcomes are lacking. Furthermore, experts remain concerned about the lack of regulation of herbs/supplements and the need for further research on potential adverse effects and herb–drug interactions. In conclusion, preliminary data on several herbs have demonstrated promising antioxidant, anti-inflammatory, anti-apoptotic, and anti-adipogenic properties that may help curtail the progression of NAFLD/NASH. Clinical trials testing the safety and efficacy must be completed before widespread use can be recommended.

Green tea extracts reduce leukocyte cell-Derived chemotaxin 2 and selenoprotein P levels in the livers of C57BL/6J mice fed a high-fat diet

Epidemiological studies suggest that green tea extracts (GTEs), including catechins such as epigallocatechin gallate and epicatechin gallate, have a beneficial effect on obesity, hyperglycemia, insulin resistance, endothelial dysfunction, and inflammation. Although several studies have shown that catechins directly modulate the cellular and molecular alterations in the liver tissue, the contributions of indirect mechanisms underlying these systemic effects of catechins remain unclear. In this study, we report that, in the C57BL/6J mouse liver, GTEs reduce high-fat diet-induced increases in the levels of hepatokines, liver-derived secretary proteins such as leukocyte cell-derived chemotaxin 2 and selenoprotein P production, which have been shown to induce systemic adverse effects, including several metabolic diseases. These findings suggest that the systemic effects of GTEs involve the regulation of hepatokine production as an indirect mechanism.

Green tea extracts ameliorate high-fat diet-induced muscle atrophy in senescence-accelerated mouse prone-8 mice

Muscle atrophy (loss of skeletal muscle mass) causes progressive deterioration of skeletal function. Recently, excessive intake of fats was suggested to induce insulin resistance, followed by muscle atrophy. Green tea extracts (GTEs), which contain polyphenols such as epigallocatechin gallate, have beneficial effects on obesity, hyperglycemia, and insulin resistance, but their effects against muscle atrophy are still unclear. Here, we found that GTEs prevented high-fat (HF) diet–induced muscle weight loss in senescence-accelerated mouse prone-8 (SAMP8), a murine model of senescence. SAMP8 mice were fed a control diet, an HF diet, or HF with 0.5% GTEs (HFGT) diet for 4 months. The HF diet induced muscle weight loss with aging (measured as quadriceps muscle weight), whereas GTEs prevented this loss. In HF diet–fed mice, blood glucose and plasma insulin concentrations increased in comparison with the control group, and these mice had insulin resistance as determined by homeostasis model assessment of insulin resistance (HOMA-IR). In these mice, serum concentrations of leukocyte cell–derived chemotaxin 2 (LECT2), which is known to induce insulin resistance in skeletal muscle, were elevated, and insulin signaling in muscle, as determined by the phosphorylation levels of Akt and p70 S6 kinases, tended to be decreased. In HFGT diet–fed mice, these signs of insulin resistance and elevation of serum LECT2 were not observed. Although our study did not directly show the effect of serum LECT2 on muscle weight, insulin resistance examined using HOMA-IR indicated an intervention effect of serum LECT2 on muscle weight, as revealed by partial correlation analysis. Accordingly, GTEs might have beneficial effects on age-related and HF diet–induced muscle weight loss, which correlates with insulin resistance and is accompanied by a change in serum LECT2.

Moutan Cortex Protects Hepatocytes against Oxidative Injury through AMP-Activated Protein Kinase Pathway

Moutan Cortex, the root bark of Paeonia suffruticosa ANDREWS in Ranunculaceae, has widely demonstrated analgesic, anti-spasmodic, and anti-inflammatory effects in various cancer and immune cell lines. Oxidative stress is associated with development of several diseases, including liver disease. We prepared the water extract of Moutan Cortex (MCE) to investigate the cytoprotective activities and its mechanism. MCE protected hepatocytes from arachidonic acid (AA)+iron induced oxidative stress, as indicated by reactive oxygen species (ROS) production and cell viability analysis. MCE also suppressed mitochondrial dysfunction in AA+iron-treated human hepatocyte-derived hepatocellular carcinoma cell line, HepG2 cells. In addition, MCE treatment induces AMP-activated protein kinase (AMPK) and liver kinase B1 phosphorylation, which play a role in inhibition of oxidative stress induced cell death. Moreover, one of the MCE compounds, chlorogenic acid, exerted protective effects against oxidative stress and apoptosis. Taken together, MCE protected hepatocytes against AA+iron-induced oxidative stress through AMPK activation, and may be a candidate for the treatment of liver disease.

Effect of the consumption of green tea extract during pregnancy and lactation on metabolism of mothers and 28d-old offspring

The objective was to investigate the effects of the maternal consumption of the green tea extract during pregnancy and lactation on mothers and offspring metabolism. The female Wistar rats, on the first day of pregnancy until the end of lactation, was divided into groups: MC– received water and ME– received green tea extract (400 mg/kg body weight/day), both ingested control diet. After lactation, at day 28^th post-partum, the mothers and pups from each mother were euthanized and composed the groups: FC– pup from mother received water and FE– pup from mother received green tea extract. The ME group increased IL-10/TNF-α ratio and IL-1β content in the mesenteric and IL-1β content in retroperitoneal adipose tissues, and decreased catalase activity. The FE group decreased the retroperitoneal adipose tissue relative weight and SOD activity, but increased adiponectin, LPS, IL-10 and IL-6 content and IL-10/TNF-α ratio in retroperitoneal, IL-10 and TNF-α content in gonadal, and IL-6 content in mesenteric adipose tissues. In summary, the maternal consumption of green tea extract associated with control diet ingestion during pregnancy and lactation altered the inflammatory status of mothers and 28d-old offspring. These data elucidate the effects of green tea during pregnancy and lactation on maternal and offspring metabolism.

Potential Biological Effects of (-)-Epigallocatechin-3-gallate on the Treatment of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a major health issue throughout the world. However, no validated treatments for NAFLD are currently available. In-depth studies have demonstrated the efficacy of (-)-epigallocatechin-3-gallate (EGCG), a main bioactive chemical extracted from green tea, in treating NAFLD. EGCG exhibits multi-pronged preventive and therapeutic activities, including promoting lipid and glucose metabolism, anti-lipid peroxidation and anti-inflammation activities, anti-fibrosis, and anti-NAFLD related tumor, thus contributing to the mitigation of NAFLD occurrence and progression. The objectives of this paper are to review and discuss the currently known targets, signaling pathways and roles of EGCG that interfere with NAFLD pathogenesis, then providing additional experimental evidence and the foundation for the further studies and clinical applications of EGCG in the prevention and treatment of NAFLD.

Diosgenin prevents high-fat diet-induced rat non-alcoholic fatty liver disease through the AMPK and LXR signaling pathways

Non-alcoholic fatty liver disease (NAFLD) is a major public health concern worldwide. The aim of the present study was to observe the effect of diosgenin on NAFLD and investigate the underlying mechanisms. Diosgenin treatment increased the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in HepG2 cells. Diosgenin significantly inhibited high glucose (HG)-induced triglyceride (TG) accumulation and sterol regulatory element‑binding protein-1c (SREBP-1c) mRNA increase in HepG2 cells, which were partially abolished by the AMPK inhibitor compound C. Diosgenin also significantly inhibited the increase of liver X receptor (LXR) α mRNA induced by HG or T0901317. However, T0901317‑induced upregulation of LXRα and SREBP-1c mRNA was not blocked by compound C. Following a high-fat diet for 16 weeks, the body and liver weights of the experimental rats were significantly increased, but this effect was significantly suppressed by diosgenin. Diosgenin and fenofibrate ameliorated lipid deposition in the liver and reduced the increase of hepatic TG content. Diosgenin significantly decreased the alanine aminotransferase (ALT) level, whereas fenofibrate significantly increased the ALT and aspartate aminotransferase levels. Diosgenin also increased AMPK and ACC phosphorylation and suppressed LXRα in the liver. In conclusion, the results of the present study suggested that diosgenin is a potential agent for preventing the development of NAFLD through the AMPK and LXR signaling pathways.

Green tea (Camellia sinensis) and l-theanine: Medicinal values and beneficial applications in humans-A comprehensive review

Green tea (Camellia sinensis) is a famous herb, and its extract has been extensively used in traditional Chinese medicinal system. In this context, several studies have revealed its health benefits and medicinal potentialities for several ailments. With ever increasing scientific knowledge, search for safer, potential and novel type of health-related supplements quest, scientists are re-directing their research interests to explore natural resources i.e. medicinal herbs/plant derived compounds. Green tea consumption has gained a special attention and popularity in the modern era of changing lifestyle. The present review is aimed to extend the current knowledge by highlighting the importance and beneficial applications of green tea in humans for safeguarding various health issues. Herein, we have extensively reviewed, analyzed, and compiled salient information on green tea from the authentic published literature available in PubMed and other scientific databases. Scientific literature evidenced that owing to the bioactive constituents including caffeine, l-theanine, polyphenols/flavonoids and other potent molecules, green tea has many pharmacological and physiological functions. It possesses multi-beneficial applications in treating various disorders of humans. This review also provides in-depth insights on the medicinal values of green tea which will be useful for researchers, medical professionals, veterinarians, nutritionists, pharmacists and pharmaceutical industry. Future research emphasis and promotional avenues are needed to explore its potential therapeutic applications for designing appropriate pharmaceuticals, complementary medicines, and effective drugs as well as popularize and propagate its multidimensional health benefits.

Potential Biological Effects of (-)-Epigallocatechin-3-gallate on the Treatment of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a major health issue throughout the world. However, no validated treatments for NAFLD are currently available. In‐depth studies have demonstrated the efficacy of (‐)‐epigallocatechin‐3‐gallate (EGCG), a main bioactive chemical extracted from green tea, in treating NAFLD. EGCG exhibits multi‐pronged preventive and therapeutic activities, including promoting lipid and glucose metabolism, anti‐lipid peroxidation and anti‐inflammation activities, anti‐fibrosis, and anti‐NAFLD related tumor, thus contributing to the mitigation of NAFLD occurrence and progression. The objectives of this paper are to review and discuss the currently known targets, signaling pathways and roles of EGCG that interfere with NAFLD pathogenesis, then providing additional experimental evidence and the foundation for the further studies and clinical applications of EGCG in the prevention and treatment of NAFLD.

Decaffeinated green and black tea polyphenols decrease weight gain and alter microbiome populations and function in diet-induced obese mice

PURPOSE

Decaffeinated green tea (GT) and black tea (BT) polyphenols inhibit weight gain in mice fed an obesogenic diet. Since the intestinal microflora is an important contributor to obesity, it was the objective of this study to determine whether the intestinal microflora plays a role in the anti-obesogenic effect of GT and BT.

METHODS

C57BL/6J mice were fed a high-fat/high-sucrose diet (HF/HS, 32% energy from fat; 25% energy from sucrose) or the same diet supplemented with 0.25% GTP or BTP or a low-fat/high-sucrose (LF/HS, 10.6% energy from fat, 25% energy from sucrose) diet for 4 weeks. Bacterial composition was assessed by MiSeq sequencing of the 16S rRNA gene.

RESULTS

GTP and BTP diets resulted in a decrease of cecum Firmicutes and increase in Bacteroidetes. The relative proportions of Blautia, Bryantella, Collinsella, Lactobacillus, Marvinbryantia, Turicibacter, Barnesiella, and Parabacteroides were significantly correlated with weight loss induced by tea extracts. BTP increased the relative proportion of Pseudobutyrivibrio and intestinal formation of short-chain fatty acids (SCFA) analyzed by gas chromatography. Cecum propionic acid content was significantly correlated with the relative proportion of Pseudobutyrivibrio. GTP and BTP induced a significant increase in hepatic 5'adenosylmonophosphate-activated protein kinase (AMPK) phosphorylation by 70 and 289%, respectively (P < 0.05) determined by Western blot.

CONCLUSION

In summary, both BTP and GTP induced weight loss in association with alteration of the microbiota and increased hepatic AMPK phosphorylation. We hypothesize that BTP increased pAMPK through increased intestinal SCFA production, while GTPs increased hepatic AMPK through GTP present in the liver.

Green tea polyphenol treatment attenuates atherosclerosis in high-fat diet-fed apolipoprotein E-knockout mice via alleviating dyslipidemia and up-regulating autophagy

Background: Green tea polyphenol (GTP) is a polyphenol source from green tea that has drawn wide attention owing to epidemiological evidence of its beneficial effects in the prevention of cardiovascular disease; the underlying molecular mechanisms of these effects are not well understood. This study aimed to investigate the effects of GTP treatment on autophagy regulation in the vessel wall and lipid metabolism of HFD-fed male ApoE-knockout mice. Methods: Adult male ApoE-knockout mice (n = 30) fed with a high-fat diet (HFD) were treated with either vehicle or GTP (3.2 or 6.4 g/L) administered via drinking water for 15 weeks, and C57BL/6J mice fed with standard chow diet (STD) were used as the control group. Metabolic parameters, expression of key mRNAs and proteins of hepatic lipid metabolism and autophagy in the vessel wall of mice were determined after the 15-week treatment. Results: A HFD induced atherosclerosis formation and lipid metabolism disorders as well as reduced autophagy expression in the vessel wall of ApoE-knockout mice, but GTP treatment alleviated the lipid metabolism disorders, decreased the oxLDL levels in serum, and increased the mRNA and protein expressions of hepatic PPARα and autophagy markers (LC3, Beclin1 and p62) in the vessel wall of ApoE-knockout mice. Conclusions: Our findings suggest that GTP supplementation showed marked suppression of atherogenesis through improved lipid metabolism as well as through a direct impact on oxLDL and autophagy flux in the vessel wall.

Emerging roles of SIRT1 in fatty liver diseases

Fatty liver diseases, which are commonly associated with high-fat/calorie diet, heavy alcohol consumption and/or other metabolic disorder causes, lead to serious medical concerns worldwide in recent years. It has been demonstrated that metabolic homeostasis disruption is most likely to be responsible for this global epidemic. Sirtuins are a group of conserved nicotinamide adenine dinucleotide (NAD⁺) dependent histone and/or protein deacetylases belonging to the silent information regulator 2 (Sir2) family. Among seven mammalian sirtuins, sirtuin 1 (SIRT 1) is the most extensively studied one and is involved in both alcoholic and nonalcoholic fatty liver diseases. SIRT1 plays beneficial roles in regulating hepatic lipid metabolism, controlling hepatic oxidative stress and mediating hepatic inflammation through deacetylating some transcriptional regulators against the progression of fatty liver diseases. Here we summarize the latest advances of the biological roles of SIRT1 in regulating lipid metabolism, oxidative stress and inflammation in the liver, and discuss the potential of SIRT1 as a therapeutic target for treating alcoholic and nonalcoholic fatty liver diseases.

Nutritional approaches for managing obesity-associated metabolic diseases

Obesity is an ongoing pandemic and serves as a causal factor of a wide spectrum of metabolic diseases including diabetes, fatty liver disease, and cardiovascular disease. Much evidence has demonstrated that nutrient overload/overnutrition initiates or exacerbates inflammatory responses in tissues/organs involved in the regulation of systemic metabolic homeostasis. This obesity-associated inflammation is usually at a low-grade and viewed as metabolic inflammation. When it exists continuously, inflammation inappropriately alters metabolic pathways and impairs insulin signaling cascades in peripheral tissues/organs such as adipose tissue, the liver and skeletal muscles, resulting in local fat deposition and insulin resistance and systemic metabolic dysregulation. In addition, inflammatory mediators, e.g., proinflammatory cytokines, and excessive nutrients, e.g., glucose and fatty acids, act together to aggravate local insulin resistance and form a vicious cycle to further disturb the local metabolic pathways and exacerbate systemic metabolic dysregulation. Owing to the critical role of nutrient metabolism in controlling the initiation and progression of inflammation and insulin resistance, nutritional approaches have been implicated as effective tools for managing obesity and obesity-associated metabolic diseases. Based on the mounting evidence generated from both basic and clinical research, nutritional approaches are commonly used for suppressing inflammation, improving insulin sensitivity, and/or decreasing fat deposition. Consequently, the combined effects are responsible for improvement of systemic insulin sensitivity and metabolic homeostasis.

Puerarin promotes ABCA1-mediated cholesterol efflux and decreases cellular lipid accumulation in THP-1 macrophages

It was reported that puerarin decreases the total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglyceride (TG) and increases high-density lipoprotein cholesterol (HDL-C) level, but the underlying mechanism is unclear. This study was designed to determine whether puerarin decreased lipid accumulation via up-regulation of ABCA1-mediated cholesterol efflux in THP-1 macrophage-derived foam cells. Our results showed that puerarin significantly promoted the expression of ATP-binding cassette transporter A1 (ABCA1) mRNA and protein via the AMP-activated protein kinase (AMPK)-peroxisome proliferator-activated receptor gamma (PPARγ)-liver X receptor-alpha (LXR-α) pathway and decreased cellular lipid accumulation in human THP-1 macrophage-derived foam cells. The miR-7 directly targeted 3' untranslated region of STK11 (Serine/Threonine Kinase 11), which activated the AMPK pathway. Transfection with miR-7 mimic significantly reduced STK11 expression in puerarin-treated macrophages, decreased the phosphorylation of AMPK, down-regulated the expression of the PPARγ-LXR-α-ABCA1 expression. Additionally, treatment with miR-7 decreased cholesterol efflux and increased cholesterol levels in THP-1 macrophage-derived foam cells. Our study demonstrates that puerarin promotes ABCA1-mediated cholesterol efflux and decreases intracellular cholesterol levels through the pathway involving miR-7, STK11, and the AMPK-PPARγ-LXR-α-ABCA1 cascade.

Supplementation with Vitis vinifera L. skin extract improves insulin resistance and prevents hepatic lipid accumulation and steatosis in high-fat diet-fed mice

Nonalcoholic fatty liver disease is one of the most common complications of obesity. The Vitis vinifera L. grape skin extract (ACH09) is an important source of polyphenols, which are related to its antioxidant and antihyperglycemic activities. We hypothesized that ACH09 could also exert beneficial effects on metabolic disorders associated with obesity and evaluated ACH09's influence on high-fat (HF) diet-induced hepatic steatosis and insulin resistance in C57BL/6 mice. The animals were fed a standard diet (10% fat, control) or an HF diet (60% fat, HF) with or without ACH09 (200mg/[kg d]) for 12weeks. Our results showed that ACH09 reduced HF diet-induced body weight gain, prevented hepatic lipid accumulation and steatosis, and improved hyperglycemia and insulin resistance. The underlying mechanisms of these beneficial effects of ACH09 may involve the activation of hepatic insulin-signaling pathway because the expression of phosphorylated insulin receptor substrate-1, phosphatidylinositol 3-kinase, phosphorylated Akt serine/threonine kinase 1, and glucose transporter 2 was increased by ACH09 and correlated with improvement of hyperglycemia, hyperinsulinemia, and insulin resistance. ACH09 reduced the expression of the lipogenic factor sterol regulatory-element binding protein-1c in the liver and upregulated the lipolytic pathway (phosphorylated liver kinase B1/phosphorylated adenosine-monophosphate-activated protein kinase), which was associated with normal hepatic levels of triglyceride and cholesterol and prevention of steatosis. ACH09 prevented the hepatic oxidative damage in HF diet-fed mice probably by restoration of antioxidant activity. In conclusion, ACH09 protected mice from HF diet-induced obesity, insulin resistance, and hepatic steatosis. The regulation of hepatic insulin signaling pathway, lipogenesis, and oxidative stress may contribute to ACH09's protective effect.

Effect of Green Tea Extract on Systemic Metabolic Homeostasis in Diet-Induced Obese Mice Determined via RNA-Seq Transcriptome Profiles

Green tea (GT) has various health effects, including anti-obesity properties. However, the multiple molecular mechanisms of the effects have not been fully determined. The aim of this study was to elucidate the anti-obesity effects of GT via the analysis of its metabolic and transcriptional responses based on RNA-seq profiles. C57BL/6J mice were fed a normal, high-fat (60% energy as fat), or high-fat + 0.25% (w/w) GT diet for 12 weeks. The GT extract ameliorated obesity, hepatic steatosis, dyslipidemia, and insulin resistance in diet-induced obesity (DIO) mice. GT supplementation resulted in body weight gain reduction than mice fed high-fat through enhanced energy expenditure, and reduced adiposity. The transcriptome profiles of epididymal white adipose tissue (eWAT) suggested that GT augments transcriptional responses to the degradation of branched chain amino acids (BCAAs), as well as AMP-activated protein kinase (AMPK) signaling, which suggests enhanced energy homeostasis. Our findings provide some significant insights into the effects of GT for the prevention of obesity and its comorbidities. We demonstrated that the GT extract contributed to the regulation of systemic metabolic homeostasis via transcriptional responses to not only lipid and glucose metabolism, but also amino acid metabolism via BCAA degradation in the adipose tissue of DIO mice.

Beneficial Effects of Tea and the Green Tea Catechin Epigallocatechin-3-gallate on Obesity

Green tea has been shown to have beneficial effects against cancer, obesity, atherosclerosis, diabetes, bacterial and viral infections, and dental caries. The catechin (−)-epigallocatechin-3-gallate (EGCG) has shown the highest biological activity among green tea catechins (GTCs) in most of the studies. While several epidemiological studies have shown the beneficial effects of tea and GTCs on obesity, some studies have failed to do this. In addition, a large number of interventional clinical studies have shown these favorable effects, and cellular and animal experiments have supported those findings, and revealed the underlying anti-obesity mechanisms. One of the mechanisms is enhanced cellular production of reactive oxygen species, which is mediated through the pro-oxidant action of EGCG, leading to the activation of adenosine monophosphate-activated protein kinase, which suppresses gene and protein expression of enzymes and transcription factors involved in adipogenesis and lipogenesis, and stimulates those involved in lipolysis. Recently, scientific evidence supporting the beneficial anti-obesity effects of green tea and GTCs has been increasing. However, future investigations are still required to clarify the reasons for the inconsistent results reported in the human studies; to achieve this, careful adjustment of confounding factors will be required.

Herbal medicines and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), which is characterized by excessive fat accumulation in the liver of patients who consume little or no alcohol, becomes increasingly common with rapid economic development. Long-term excess fat accumulation leads to NAFLD and represents a global health problem with no effective therapeutic approach. NAFLD is considered to be a series of complex, multifaceted pathological processes involving oxidative stress, inflammation, apoptosis, and metabolism. Over the past decades, herbal medicines have garnered growing attention as potential therapeutic agents to prevent and treat NAFLD, due to their high efficacy and low risk of side effects. In this review, we evaluate the use of herbal medicines (including traditional Chinese herbal formulas, crude extracts from medicinal plants, and pure natural products) to treat NAFLD. These herbal medicines are natural resources that can inform innovative drug research and the development of treatments for NAFLD in the future.