Quercetin reduces obesity-induced hepatosteatosis by enhancing mitochondrial oxidative metabolism via heme oxygenase-1

Therapeutic potential of traditional Chinese medicine in the prevention and treatment of digestive inflammatory cancer transformation: Portulaca oleracea L. as a promising drug

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) has been used for centuries to treat various types of inflammation and tumors of the digestive system. Portulaca oleracea L. (POL), has been used in TCM for thousands of years. The chemical composition of POL is variable and includes flavonoids, alkaloids, terpenoids and organic acids and other classes of natural compounds. Many of these compounds exhibit powerful anti-inflammatory and anti-cancer-transforming effects in the digestive system.

AIM OF STUDY

In this review, we focus on the potential therapeutic role of POL in NASH, gastritis and colitis and their associated cancers, with a focus on the pharmacological properties and potential mechanisms of action of the main natural active compounds in POL.

METHODS

The information and data on Portulaca oleracea L. and its main active ingredients were collated from various resources like ethnobotanical textbooks and literature databases such as CNKI, VIP (Chinese literature), PubMed, Science Direct, Elsevier and Google Scholar (English literatures), Wiley, Springer, Tailor and Francis, Scopus, Inflibnet.

RESULTS

Kaempferol, luteolin, myricetin, quercetin, genistein, EPA, DHA, and melatonin were found to improve NASH and NASH-HCC, while kaempferol, apigenin, luteolin, and quercetin played a therapeutic role in gastritis and gastric cancer. Apigenin, luteolin, myricetin, quercetin, genistein, lupeol, vitamin C and melatonin were found to have therapeutic effects in the treatment of colitis and its associated cancers. The discovery of the beneficial effects of these natural active compounds in POL supports the idea that POL could be a promising novel candidate for the treatment and prevention of inflammation-related cancers of the digestive system.

CONCLUSION

The discovery of the beneficial effects of these natural active compounds in POL supports the idea that POL could be a promising novel candidate for the treatment and prevention of inflammation-related cancers of the digestive system. However, clinical data describing the mode of action of the naturally active compounds of POL are still lacking. In addition, pharmacokinetic data for POL compounds, such as changes in drug dose and absorption rates, cannot be extrapolated from animal models and need to be measured in patients in clinical trials. On the one hand, a systematic meta-analysis of the existing publications on TCM containing POL still needs to be carried out. On the other hand, studies on the hepatic and renal toxicity of POL are also needed. Additionally, well-designed preclinical and clinical studies to validate the therapeutic effects of TCM need to be performed, thus hopefully providing a basis for the validation of the clinical benefits of POL.

Chinese herbal medicines: The modulator of nonalcoholic fatty liver disease targeting oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

Plants are a natural treasure trove; their secondary metabolites participate in several pharmacological processes, making them a crucial component in the synthesis of novel pharmaceuticals and serving as a reserve resource foundation in this process. Nonalcoholic fatty liver disease (NAFLD) is associated with the risk of progression to hepatitis and liver cancer. The "Treatise on Febrile Diseases," "Compendium of Materia Medica," and "Thousand Golden Prescriptions" have listed herbal remedies to treat liver diseases.

AIM OF THE REVIEW

Chinese herbal medicines have been widely used for the prevention and treatment of NAFLD owing to their efficacy and low side effects. The production of reactive oxygen species (ROS) during NAFLD, and the impact and potential mechanism of ROS on the pathogenesis of NAFLD are discussed in this review. Furthermore, common foods and herbs that can be used to prevent NAFLD, as well as the structure-activity relationships and potential mechanisms, are discussed.

METHODS

Web of Science, PubMed, CNKI database, Google Scholar, and WanFang database were searched for natural products that have been used to treat or prevent NAFLD in the past five years. The primary search was performed using the following keywords in different combinations in full articles: NAFLD, herb, natural products, medicine, and ROS. More than 400 research papers and review articles were found and analyzed in this review.

RESULTS

By classifying and discussing the literature, we obtained 86 herbaceous plants, 28 of which were derived from food and 58 from Chinese herbal medicines. The mechanism of NAFLD was proposed through experimental studies on thirteen natural compounds (quercetin, hesperidin, rutin, curcumin, resveratrol, epigallocatechin-3-gallate, salvianolic acid B, paeoniflorin, ginsenoside Rg1, ursolic acid, berberine, honokiol, emodin). The occurrence and progression of NAFLD could be prevented by natural antioxidants through several pathways to prevent ROS accumulation and reduce hepatic cell injuries caused by excessive ROS.

CONCLUSION

This review summarizes the natural products and routinely used herbs (prescription) in the prevention and treatment of NAFLD. Firstly, the mechanisms by which natural products improve NAFLD through antioxidant pathways are elucidated. Secondly, the potential of traditional Chinese medicine theory in improving NAFLD is discussed, highlighting the safety of food-medicine homology and the broader clinical potential of multi-component formulations in improving NAFLD. Aiming to provide theoretical basis for the prevention and treatment of NAFLD.

DNA Mutagenicity of Hydroxyhydroquinone in Roasted Coffee Products and Its Suppression by Chlorogenic Acid, a Coffee Polyphenol, in Oxidative-Damage-Sensitive SAMP8 Mice

Hydroxyhydroquinone (HHQ) is an oxidative component produced by roasting coffee beans and has been reported to generate relatively large amounts of reactive oxygen species (ROS). In this study, we used senescence-accelerated mouse prone 8 (SAMP8) mice to determine whether HHQ consumption increases oxidative-stress-induced injury, because in SAMP8 mice, the activity of 8-oxoguanine DNA glycosylase 1, which repairs oxidative modifications in DNA, is decreased. The results showed that two out of twelve (16.7%) HHQ-treated mice presented polyuria and glucosuria around 2 months after the start of treatment, indicating that HHQ may act as a mutagen against SAMP8 mice, which is sensitive to oxidative damage. No abnormalities were observed in the chlorogenic acid (coffee polyphenol, CPP)-treated group. The concentration of hydrogen peroxide in the serum of SAMP8 mice was significantly higher than that in SAMR1 (senescence-resistant) control mice, and the concentration was further increased in the HHQ-treated group. CPP, when coexisting with HHQ at the rate contained in roasted coffee, decreased the amount of hydrogen peroxide in the serum of SAMP8 mice. Although CPP can act both oxidatively and antioxidatively as a polyphenol, CPP acts more antioxidatively when coexisting with HHQ. Thus, the oxidative effect of HHQ was shown to be counteracted by CPP.

Icariin alleviates high-fat diet-induced nonalcoholic fatty liver disease via up-regulating miR-206 to mediate NF-κB and MAPK pathways

Nonalcoholic fatty liver disease (NAFLD) is an abnormal lipid accumulation disease in hepatocytes. The existing drugs for NAFLD have some side effects, so new therapeutic agents are required to be explored. In this study, the effect and mechanism of icariin (ICA) on high-fat diet-induced NAFLD were investigated. Firstly, a high-fat diet was used to construct a NAFLD rat model and HepG2 cells were treated with 1 mM free fatty acid (FFA). After ICA treatment, the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBil), triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured; liver injury and lipid deposition were observed by H&E and Oil Red O staining; interleukin-1β (IL-1β), IL-12, and IL-6 were measured by enzyme-linked immunosorbent assay. Additionally, qRT-PCR and western blot were performed to detect miR-206 expression and NF-κB/MAPK pathway-related protein expression in liver tissues and cells. After a variety of trials, we discovered that compared with the NAFLD group, ICA significantly reduced ALT, AST, TBil, TG, TC, and LDL-C levels and increased HDL-C levels, and improved liver tissue injury and lipid deposition. Moreover, ICA reduced IL-1β, IL-12, and IL-6 levels in liver tissues and cells as well as inhibited MAPK and NF-κB-related protein expression in the liver tissues. Notably, ICA could significantly increase miR-206 expression in liver tissues and cells. Further experiments confirmed that inhibition of miR-206 was able to reverse the effect of ICA on NAFLD. In conclusion, ICA can alleviate NAFLD by upregulating miR-206 to mediate NF-κB and MAPK pathways.

Hepatokines: the missing link in the development of insulin resistance and hyperandrogenism in PCOS?

The liver plays a critical role in several metabolic pathways, including the regulation of glucose and lipid metabolism. Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease worldwide, is closely associated with insulin resistance (IR) and metabolic syndrome (MetS). Hepatokines, newly discovered proteins secreted by hepatocytes, have been linked to the induction of these metabolic dysregulations. Polycystic ovary syndrome (PCOS), the most common endocrine disorder in women of reproductive age, has been associated with NAFLD and IR, while hyperandrogenism additionally appears to be implicated in the pathogenesis of the latter. However, the potential role of hepatokines in the development of metabolic disorders in PCOS has not been fully investigated. Therefore, the aim of this review is to critically appraise the current evidence regarding the interplay of hepatokines with NAFLD, hyperandrogenism, and IR in PCOS.

The regulatory role and mechanism of exosomes in hepatic fibrosis

Globally, the prevalence and fatality rates of liver disorders are on the rise. Among chronic liver conditions, hepatic fibrosis stands out as a central pathological process. Despite this, approved treatments for hepatic fibrosis are currently lacking. Exosomes, small extracellular vesicles secreted by various cell types, play a significant role in intercellular communication and have emerged as essential mediators in liver fibrosis. In this regard, this review compiles the mechanisms through which exosomes regulate hepatic fibrosis, encompassing diverse targets and signaling pathways. Furthermore, it delves into the regulatory impact of exosomes modulated by natural plant-derived, endogenous, and synthetic compounds as potential therapeutic strategies for addressing hepatic fibrosis.

Molecular Mechanism Pathways of Natural Compounds for the Treatment of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world, and its incidence continues to increase each year. Yet, there is still no definitive drug that can stop its development. This review focuses mainly on lipotoxicity, oxidative stress, inflammation, and intestinal flora dysbiosis to understand NAFLD's pathogenesis. In this review, we used NCBI's PubMed database for retrieval, integrating in vivo and in vitro experiments to reveal the therapeutic effects of natural compounds on NAFLD. We also reviewed the mechanisms by which the results of these experiments suggest that these compounds can protect the liver from damage by modulating inflammation, reducing oxidative stress, decreasing insulin resistance and lipid accumulation in the liver, and interacting with the intestinal microflora. The natural compounds discussed in these papers target a variety of pathways, such as the AMPK pathway and the TGF-β pathway, and have significant therapeutic effects. This review aims to provide new possible therapeutic lead compounds and references for the development of novel medications and the clinical treatment of NAFLD. It offers fresh perspectives on the development of natural compounds in preventing and treating NAFLD.

Dose Dependent Effects of Aqueous Extract of Garcinia cambogia Desr. Against Letrozole Induced Polycystic Ovarian Syndrome in Female Adult Rats With Possible Mechanisms Exploration

Background

Polycystic ovarian syndrome (PCOS) is an endocrine metabolic disorder of women.

Purpose

This study aimed to explore the potential of aqueous extract of Garcinia cambogia Desr. (AEGC) in PCOS.

Methodology

The HPLC was used to determine the phytoconstituents present in Garcinia cambogia. Thirty adult female albino rats were divided into 6 groups: Normal control (NC) disease Control (PCOS; letrozole 1 mg/kg), plant extract (AEGC 100, 300, 500 mg/kg) and standard (metformin; 20 mg/kg). Disease was confirmed by vaginal smear cytology. After 10 weeks, animals were euthanized, ovaries dissected for histopathology, blood collected for hormonal and biochemical analysis.

Results

HPLC analysis showed the presence of phenolic contents; chlorogenic acid, gallic acid, coumaric acid while flavonoid contents were quercetin, kaempferol, and rutin. After treatment, there was dose dependent reduction of weight, ovarian cysts, improvement of follicle growth. DPPH radical scavenging percentage was 67.89%. Hormonal analysis showed a significant improvement (P < .05) in follicle stimulating hormone (FSH), estrogen, and progesterone while a reduction in testosterone, luteinizing hormone (LH) and insulin level. Antioxidant enzymatic markers were significantly (P < .05) increased. Lipid profile and LFTs were also improved.

Conclusions

The study validated the potential of Garcinia cambogia in the management of PCOS.

Iron-frataxin involved in the protective effect of quercetin against alcohol-induced liver mitochondrial dysfunction

Emerging evidence supports the beneficial effect of quercetin on liver mitochondrial disorders. However, the molecular mechanism by which quercetin protects mitochondria is limited, especially in alcoholic liver disease. In this study, C57BL/6N mice were fed with Lieber De Carli liquid diet (28% ethanol-derived calories) for 12 weeks plus a single binge ethanol and intervened with quercetin (100 mg/kg.bw). Moreover, HepG2^CYP2E1+/+ were stimulated with ethanol (100 mM) and quercetin (50 µM) to investigate the effects of mitochondrial protein frataxin. The results indicated that quercetin alleviated alcohol-induced histopathological changes and mitochondrial functional disorders in mice livers. Consistent with increased PINK1, Parkin, Bnip3 and LC3II as well as decreased p62, TOM20 and VDAC1 expression, the inhibition of mitophagy by ethanol was blocked by quercetin. Additionally, quercetin improved the imbalance of iron metabolism-related proteins expression in alcohol-fed mice livers. Compared with ethanol-treated Lv-empty HepG2^CYP2E1+/+ cells, frataxin deficiency further exacerbated the inhibition of mitochondrial function. Conversely, restoration of frataxin expression ameliorated the effect of ethanol. Furthermore, frataxin deficiency reduced the protective effects of quercetin on mitochondria disordered by ethanol. Attentively, ferric ammonium citrate (FAC) and deferiprone decreased or increased frataxin expression in HepG2^CYP2E1+/+, respectively. Notably, we further found FAC reversed the increasing effect of quercetin on frataxin expression. Ultimately, silencing NCOA4 attenuated the inhibition of quercetin on LDH release and mitochondrial membrane potential increase, and similar results were observed by adding FAC. Collectively, these findings demonstrated quercetin increased frataxin expression through regulating iron level, thereby mitigating ethanol-induced mitochondrial dysfunction.

Quercetin alleviates cyclophosphamide-induced premature ovarian insufficiency in mice by reducing mitochondrial oxidative stress and pyroptosis in granulosa cells

BACKGROUND

Exposure to cyclophosphamide (CTX) induces premature ovarian insufficiency (POI). Quercetin is a natural flavonoid that exhibits anti-inflammatory and antioxidant properties, and its antioxidant activity is correlated with POI. However, the mechanism underlying its protective role in CTX-induced ovarian dysfunction is unclear. This study aimed to explore whether quercetin can protect ovarian reserves by activating mitochondrial biogenesis and inhibiting pyroptosis.

METHODS

Thirty-six female C57BL/6 mice were randomly subdivided into six groups. Except for the control group, all groups were injected with 90 mg/kg CTX to establish a POI model and further treated with coenzyme 10 or various doses of quercetin. The mice were sacrificed 48 h after 10 IU pregnant mare serum gonadotropin was injected four weeks after treatments. We used enzyme-linked immunosorbent assays to detect serum hormone expression and light and transmission electron microscopy to assess ovarian tissue morphology and mitochondria. Additionally, we tested oxidant and antioxidant levels in ovarian tissues and mitochondrial function in granulosa cells (GCs). The expression of mitochondrial biogenesis and pyroptosis-related proteins and mRNA was analyzed using western blotting and RT-qPCR.

RESULTS

Quercetin elevated serum anti-Müllerian hormone, estradiol, and progesterone levels, decreased serum follicle-stimulating hormone and luteinizing hormone levels, and alleviated ovarian pathology. It reduced the mitochondrial DNA content and mitochondrial membrane potential. Furthermore, it upregulated ATP levels and the mRNA and protein expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), mitochondrial transcription factor A, and superoxide dismutase 2. In addition, it suppressed NOD-like receptor pyrin domain containing 3, caspase-1, interleukin-1β, and gasdermin D levels in the GCs of POI mice.

CONCLUSIONS

Quercetin protected the ovarian reserve from CTX-induced ovarian damage by reversing mitochondrial dysfunction and activating mitochondrial biogenesis via the PGC1-α pathway. Moreover, quercetin may improve ovarian functions by downregulating pyroptosis in the CTX-induced POI model. Thus, quercetin can be considered a potential agent for treating POI.

Nonalcoholic steatohepatitis and mechanisms by which it is ameliorated by activation of the CNC-bZIP transcription factor Nrf2

Non-alcoholic steatohepatitis (NASH) represents a global health concern. It is characterised by fatty liver, hepatocyte cell death and inflammation, which are associated with lipotoxicity, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, iron overload and oxidative stress. NF-E2 p45-related factor 2 (Nrf2) is a transcription factor that combats oxidative stress. Remarkably, Nrf2 is downregulated during the development of NASH, which probably accelerates disease, whereas in pre-clinical studies the upregulation of Nrf2 inhibits NASH. We now review the scientific literature that proposes Nrf2 downregulation during NASH involves its increased ubiquitylation and proteasomal degradation, mediated by Kelch-like ECH-associated protein 1 (Keap1) and/or β-transducin repeat-containing protein (β-TrCP) and/or HMG-CoA reductase degradation protein 1 (Hrd1, also called synoviolin (SYVN1)). Additionally, downregulation of Nrf2-mediated transcription during NASH may involve diminished recruitment of coactivators by Nrf2, due to increased levels of activating transcription factor 3 (ATF3) and nuclear factor-kappaB (NF-κB) p65, or competition for promoter binding due to upregulation of BTB and CNC homology 1 (Bach1). Many processes that downregulate Nrf2 are triggered by transforming growth factor-beta (TGF-β), with oxidative stress amplifying its signalling. Oxidative stress may also increase suppression of Nrf2 by β-TrCP through facilitating formation of the DSGIS-containing phosphodegron in Nrf2 by glycogen synthase kinase-3. In animal models, knockout of Nrf2 increases susceptibility to NASH, while pharmacological activation of Nrf2 by inducing agents that target Keap1 inhibits development of NASH. These inducing agents probably counter Nrf2 downregulation affected by β-TrCP, Hrd1/SYVN1, ATF3, NF-κB p65 and Bach1, by suppressing oxidative stress. Activation of Nrf2 is also likely to inhibit NASH by ameliorating lipotoxicity, inflammation, ER stress and iron overload. Crucially, pharmacological activation of Nrf2 in mice in which NASH has already been established supresses liver steatosis and inflammation. There is therefore compelling evidence that pharmacological activation of Nrf2 provides a comprehensive multipronged strategy to treat NASH.

Effects of Fagonia indica on Letrozole-Induced Polycystic Ovarian Syndrome (PCOS) in Young Adult Female Rats

Polycystic ovarian syndrome is a multidisciplinary endocrinopathy of reproductive-aged women that provokes insulin resistance, hyperandrogenism, cardiovascular problems, obesity, and menstrual complications. The present study was designed to investigate the effectiveness of ethanolic extract of Fagonia indica in letrozole-induced PCOS young adult female rats. HPLC was carried out to find the phenolic and flavonoid content of the ethanolic extract of Fagonia indica. Twenty-five female rats were taken and initially divided into two groups: group I (control group) and group II (PCOS group). PCOS was induced by letrozole given orally by gavage. Body weight was recorded weekly and vaginal cytology was analyzed daily. After induction of disease, the PCOS group is further divided into four groups (n = 5): group II (positive control with PCOS), group III (metformin 20 mg/kg treated group), group IV (ethanolic extract of Fagonia indica 500 mg/kg treated group), and group V (metformin plus Fagonia extract). At the end of experimental period, the blood sample of each rat was collected and serum was separated by centrifugation. Afterwards hormonal analysis, lipid profile and liver functioning tests were performed. Ovaries were removed and preserved for histopathological findings while the liver of each rat was stored for the determination of antioxidant potential assessment. Fagonia indica was found to possess quercetin as one of the major flavonoid phytoconstituents. The plant extract exhibited its beneficial effects by restoring hormonal balance, lipid profile, and liver functioning markers. Treatment with F. indica reduced body weight, resolved ovarian cysts, and showed positive effects on follicular growth. Treatment with plant also increased the levels of antioxidant enzymes. This study validates the potential of Fagonia indica for the amelioration of metabolic, as well as, hormonal disturbances that occurred in PCOS.

S-Acetyl-Glutathione Attenuates Carbon Tetrachloride-Induced Liver Injury by Modulating Oxidative Imbalance and Inflammation

Liver fibrosis, depending on the stage of the disease, could lead to organ dysfunction and cirrhosis, and no effective treatment is actually available. Emergent proof supports a link between oxidative stress, liver fibrogenesis and mitochondrial dysfunction as molecular bases of the pathology. A valid approach to protect against the disease would be to replenish the endogenous antioxidants; thus, we investigated the protective mechanisms of the S-acetyl-glutathione (SAG), a glutathione (GSH) prodrug. Preliminary in vitro analyses were conducted on primary hepatic cells. SAG pre-treatment significantly protected against cytotoxicity induced by CCl4. Additionally, CCl4 induced a marked increase in AST and ALT levels, whereas SAG significantly reduced these levels, reaching values found in the control group. For the in vivo analyses, mice were administered twice a week with eight consecutive intraperitoneal injections of 1 mL/kg CCl4 (diluted at 1:10 in olive oil) to induce oxidative imbalance and liver inflammation. SAG (30 mg/kg) was administered orally for 8 weeks. SAG significantly restored SOD activity, GSH levels and GPx activity, while it strongly reduced GSSG levels, lipid peroxidation and H₂O₂ and ROS levels in the liver. Additionally, CCl4 induced a decrease in anti-oxidants, including Nrf2, HO-1 and NQO-1, which were restored by treatment with SAG. The increased oxidative stress characteristic on liver disfunction causes the impairment of mitophagy and accumulation of dysfunctional and damaged mitochondria. Our results showed the protective effect of SAG administration in restoring mitophagy, as shown by the increased PINK1 and Parkin expressions in livers exposed to CCl4 intoxication. Thus, the SAG administration showed anti-inflammatory effects decreasing pro-inflammatory cytokines TNF-α, IL-6, MCP-1 and IL-1β in both serum and liver, and suppressing the TLR4/NFkB pathway. SAG attenuated reduced fibrosis, collagen deposition, hepatocellular damage and organ dysfunction. In conclusion, our results suggest that SAG administration protects the liver from CCl4 intoxication by restoring the oxidative balance, ameliorating the impairment of mitophagy and leading to reduced inflammation.

Targeting Mitochondrial ROS-Mediated Ferroptosis by Quercetin Alleviates High-Fat Diet-Induced Hepatic Lipotoxicity

Background: The protective effect of quercetin on nonalcoholic fatty liver disease (NAFLD) has been reported, but its mechanism remains poorly understood. Recently, quercetin was reported to be capable of inhibiting ferroptosis, which is a recognized type of regulated cell death. Moreover, hepatic ferroptosis plays an important role in the progression of NAFLD, but experimental evidence is limited. Hence, our study aimed to investigate the effect of quercetin on hepatic ferroptosis in high-fat diet (HFD)-induced NAFLD and further elucidate the underlying molecular mechanism.

Methods: C57BL/6J mice were fed either a normal diet (ND), an HFD, or an HFD supplemented with quercetin for 12 weeks. Hepatic lipid peroxidation, steatosis, ferroptosis and iron overload were examined. In vitro, steatotic L-02 cells was used to study the potential mechanism.

Results: We found that the HFD caused lipid peroxidation, lipid accumulation and ferroptosis in the liver, which were rescued by quercetin supplementation. Consistent with the in vivo results, quercetin alleviated lipid droplet accumulation and reduced the levels of lipid reactive oxygen species (ROS) and ferroptosis in steatotic L-02 cells. Using a mitochondrial ROS (MtROS) scavenger (Mito-TEMPO) and ferroptosis specific inhibitor (Fer-1), we found that quercetin remarkably alleviated lipid droplet accumulation and lipid peroxidation by reducing MtROS-mediated ferroptosis in steatotic L-02 cells.

Conclusion: Our data showed that HFD consumption induced lipid accumulation and triggered ferroptosis in liver, ultimately leading to hepatic lipotoxicity, which can be alleviated by quercetin. Findings from this study provide new insight into the mechanism by which quercetin can be used for the prevention and treatment of NAFLD.

A comprehensive review on phytochemicals for fatty liver: are they potential adjuvants?

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome and, as such, is associated with obesity. With the current and growing epidemic of obesity, NAFLD is already considered the most common liver disease in the world. Currently, there is no official treatment for the disease besides weight loss. Although there are a few synthetic drugs currently being studied, there is also an abundance of herbal products that could also be used for treatment. With the World Health Organization (WHO) traditional medicine strategy (2014-2023) in mind, this review aims to analyze the mechanisms of action of some of these herbal products, as well as evaluate toxicity and herb-drug interactions available in literature.

Quercetin extracted from Sophora japonica flower improves growth performance, nutrient digestibility, cecal microbiota, organ indexes, and breast quality in broiler chicks

Objective

The objective of this study was to evaluate the effects of supplementing quercetin extracted from Sophora japonica flower (QS) to the diet of broiler chicks on their growth performance, apparent nutrient digestibility, cecal microbiota, serum lipid profiles, relative organ weight, and breast muscle quality.

Method

A total of 1088 1-day-old broiler chicks (mixed sex) were randomly assigned to four groups based on the initial body weight (43.00 ± 0.29 g). The experimental period was 35 days (starter, days 0-7; grower, days 7-21; finisher, days 21-35). There were 17 replicate cages per treatment and 16 birds per cage. Dietary treatments consisted of birds receiving basal diet without quercetin as the control group and treatment groups consisted of birds fed basal diet supplemented with 0.2, 0.4, or 0.6 g/kg QS.

Results

With the increase of the QS dosage, body weight gain during days 0-7 (P = 0.021), 7-21 (P = 0.010), and 1-35 (P = 0.045), feed intake during days 0-7 (P = 0.037) and 1-35 (P = 0.025), apparent dry matter digestibility (P = 0.008), apparent energy retention (P = 0.004), cecal lactic acid bacteria counts (P = 0.023), the relative weight of breast muscle (P = 0.014), pH value from breast muscle (P < 0.001), and the water holding capacity of breast muscle (P = 0.012) increased linearly, whereas the drip loss from breast muscle (P = 0.001) decreased linearly.

Conclusion

The addition of QS in the diet of broiler chicks had positive effects on the breast muscle yield and breast muscle quality, and improved the dry matter digestibility and energy retention by increasing cecal beneficial bacteria counts, thus improving growth performance.

O-Glycoside quercetin derivatives: Biological activities, mechanisms of action, and structure-activity relationship for drug design, a review

Quercetin as a valuable natural flavonoid has shown extensive biological activities, including anticancer, antioxidant, antibacterial, antiinflammatory, anti-Alzheimer, antifungal, antiviral, antithalassemia, iron chelation, antiobesity, antidiabetic, antihypertension, and antiphospholipase A2 (PLA2) activities, by the modulation of various targets and signaling pathways that have attracted much attention. However, the low solubility and poor bioavailability of quercetin have limited its applications; therefore, the researchers have tried to design and synthesize many new derivatives of quercetin through different strategies to modify quercetin restrictions and improve its biological activities. This review categorized the O-glycoside derivatives of Quercetin into two main classes, 3-O-glycoside and other O-glycoside derivatives. Also, it studied biological activities, structure-activity relationship (SAR), and the action mechanism of O-glycoside quercetin derivatives. Overall, we summarized past and present research for discovering new potent lead compounds.

Quercetin derivatives: Drug design, development, and biological activities, a review

More studies are needed to develop new drugs for problems associated with drug resistance and unfavorable side effects. The natural flavonoid of quercetin revealed a wide range of biological activities by the modulation of various targets and signaling pathways. However, quercetin's low solubility and poor bioavailability have restricted its applicability; as a result, researchers have attempted to design and synthesize numerous novel quercetin derivatives using various methodologies in order to modify quercetin's constraints; the physico-chemical properties of quercetin's molecular scaffold make it appealing for drug development; low molecular mass and chemical groups are two of these characteristics. Therefore, the biological activities of quercetin derivatives, as well as the relationship between activity and chemical structure and their mechanism of action, were investigated. These quercetin-based molecules could be valuable in the creation and discovery of medications for a number of diseases.

Hepatocyte-derived exosomal miR-27a activates hepatic stellate cells through the inhibition of PINK1-mediated mitophagy in MAFLD

The role of exosome-mediated mitophagy in the crosstalk between hepatocytes (HCs) and hepatic stellate cells (HSCs) in metabolic-associated fatty liver disease (MAFLD) remains unknown. Serum exosomal miR-27a levels were markedly increased and positively correlated with liver fibrosis in MAFLD patients and mice. Exosomal miR-27a was released from lipotoxic HCs and specifically transmitted to recipient-activated HSCs. PINK1, the key target of miR-27a, primarily mediates mitophagy. Overexpression of miR-27a or knockdown of PINK1 or lipotoxic HC-exosomal miR-27a impaired mitochondria (inhibiting mitophagy, respiration, membrane potential, and transcription while promoting reactive oxygen species production) in activated HSCs and stimulated HSC-derived fibroblasts (promoting activation and proliferation while inhibiting autophagy). High exosomal miR-27a serum levels and a lack of hepatic PINK1-mediated mitophagy were directly related to liver fibrosis in MAFLD mice. Lipotoxic HC exosome transplantation aggravated the degree of PINK1-mediated mitophagy suppression, steatohepatitis, lipidosis, and fibrosis in the livers of MAFLD mice with cirrhosis. Both in vitro and in vivo, exosomes derived from miR-27a-knockdown HCs could not facilitate the abovementioned deteriorating effects. In conclusion, lipotoxic HC-exosomal miR-27a plays a pivotal role in inhibiting mitophagy and in promoting MAFLD-related liver fibrosis by negatively regulating PINK1 expression.

Microglia Regulate Neuronal Circuits in Homeostatic and High-Fat Diet-Induced Inflammatory Conditions

Microglia are brain resident macrophages, which actively survey the surrounding microenvironment and promote tissue homeostasis under physiological conditions. During this process, microglia participate in synaptic remodeling, neurogenesis, elimination of unwanted neurons and cellular debris. The complex interplay between microglia and neurons drives the formation of functional neuronal connections and maintains an optimal neural network. However, activation of microglia induced by chronic inflammation increases synaptic phagocytosis and leads to neuronal impairment or death. Microglial dysfunction is implicated in almost all brain diseases and leads to long-lasting functional deficiency, such as hippocampus-related cognitive decline and hypothalamus-associated energy imbalance (i.e., obesity). High-fat diet (HFD) consumption triggers mediobasal hypothalamic microglial activation and inflammation. Moreover, HFD-induced inflammation results in cognitive deficits by triggering hippocampal microglial activation. Here, we have summarized the current knowledge of microglial characteristics and biological functions and also reviewed the molecular mechanism of microglia in shaping neural circuitries mainly related to cognition and energy balance in homeostatic and diet-induced inflammatory conditions.

Nonalcoholic fatty liver disease: The role of quercetin and its therapeutic implications

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease, affecting almost one-third of the general population and 75% of obese patients with type 2 diabetes. The aim of this article is to review the current evidence concerning the role of quercetin, a natural compound and flavonoid, and its possible therapeutic effects on this modern-day disease. Despite the fact that the exact pathophysiological mechanisms through which quercetin has a hepatoprotective effect on NAFLD are still not fully elucidated, this review clearly demonstrates that this flavonoid has potent antioxidative stress action and inhibitory effects on hepatocyte apoptosis, inflammation, and generation of reactive oxygen species, factors which are linked to the development of the disease. NAFLD is closely associated with increased dietary fat consumption, especially in Western countries. The hepatoprotective effect of quercetin against NAFLD merits serious consideration and further validation by future studies.

The Protective Role of the Heme Catabolic Pathway in Hepatic Disorders

Significance: As the central metabolic organ, the liver is exposed to a variety of potentially cytotoxic, proinflammatory, profibrotic, and carcinogenic stimuli. To protect the organism from these deleterious effects, the liver has evolved a number of defense systems, which include antioxidant substrates and enzymes, anti-inflammatory tools, enzymatic biotransformation systems, and metabolic pathways. Recent Advances: One of the pivotal systems that evolved during phylogenesis was the heme catabolic pathway. Comprising the important enzymes heme oxygenase and biliverdin reductase, this complex pathway has a number of key functions including enzymatic activities, but also cell signaling, and DNA transcription. It further generates two important bile pigments, biliverdin and bilirubin, as well as the gaseous molecule carbon monoxide. These heme degradation products have potent antioxidant, immunosuppressive, and cytoprotective effects. Recent data suggest that the pathway participates in the regulation of metabolic and hormonal processes implicated in the pathogenesis of hepatic and other diseases. Critical Issues: This review discusses the impact of the heme catabolic pathway on major liver diseases, with particular focus on the involvement of cellular targeting and signaling in the pathogenesis of these conditions. Future Directions: To utilize the biological consequences of the heme catabolic pathway, several unique therapeutic strategies have been developed. Research indicates that pharmaceutical, nutraceutical, and lifestyle modifications positively affect the pathway, delivering potentially long-term clinical benefits. However, further well-designed studies are needed to confirm the clinical benefits of these approaches. Antioxid. Redox Signal. 35, 734-752.

Targeting Mitochondrial Biogenesis with Polyphenol Compounds

Appropriate mitochondrial physiology is an essential for health and survival. Cells have developed unique mechanisms to adapt to stress circumstances and changes in metabolic demands, by meditating mitochondrial function and number. In this context, sufficient mitochondrial biogenesis is necessary for efficient cell function and haemostasis, which is dependent on the regulation of ATP generation and maintenance of mitochondrial DNA (mtDNA). These procedures play a primary role in the processes of inflammation, aging, cancer, metabolic diseases, and neurodegeneration. Polyphenols have been considered as the main components of plants, fruits, and natural extracts with proven therapeutic effects during the time. These components regulate the intracellular pathways of mitochondrial biogenesis. Therefore, the current review is aimed at representing an updated review which determines the effects of different natural polyphenol compounds from various plant kingdoms on modulating signaling pathways of mitochondrial biogenesis that could be a promising alternative for the treatment of several disorders.

Quercetin as a protective agent for liver diseases: A comprehensive descriptive review of the molecular mechanism

Quercetin is the major representative of the flavonoid subgroup of flavones, with good pharmacological activities for the treatment of liver diseases, including liver steatosis, fatty hepatitis, liver fibrosis, and liver cancer. It can significantly influence the development of liver diseases via multiple targets and multiple pathways via antifat accumulation, anti-inflammatory, and antioxidant activity, as well as the inhibition of cellular apoptosis and proliferation. Despite extensive research on understanding the mechanism of quercetin in the treatment of liver diseases, there are still no targeted therapies available. Thus, we have comprehensively searched and summarized the different targets of quercetin in different stages of liver diseases and concluded that quercetin inhibited inflammation of the liver mainly through NF-κB/TLR/NLRP3, reduced PI3K/Nrf2-mediated oxidative stress, mTOR activation in autophagy, and inhibited the expression of apoptotic factors associated with the development of liver diseases. In addition, quercetin showed different mechanisms of action at different stages of liver diseases, including the regulation of PPAR, UCP, and PLIN2-related factors via brown fat activation in liver steatosis. The compound inhibited stromal ECM deposition at the liver fibrosis stage, affecting TGF1β, endoplasmic reticulum stress (ERs), and apoptosis. While at the final liver cancer stage, inhibiting cancer cell proliferation and spread via the hTERT, MEK1/ERK1/2, Notch, and Wnt/β-catenin-related signaling pathways. In conclusion, quercetin is an effective liver protectant. We hope to explore the pathogenesis of quercetin in different stages of liver diseases through the review, so as to provide more accurate targets and theoretical basis for further research of quercetin in the treatment of liver diseases.

Quercetin and non-alcoholic fatty liver disease: A review based on experimental data and bioinformatic analysis

Quercetin, a polyphenol widely present in the plant kingdom, has received great interest due to pleiotropic effects. As evidenced by animal and cellular studies, quercetin exerts hepatoprotection against non-alcoholic fatty liver disease (NAFLD), particularly in hepatic steatosis and hepatitis. Mechanically, various hypotheses of such protective effects have been actively proposed, including improving fatty acid metabolism, anti-inflammation, anti-oxidant, modulating gut microbiota and bile acid, etc. Here, the role of quercetin in NAFLD was summarized. With a particular focus on molecular mechanism, we comprehensively discussed the pathways of quercetin on NAFLD based on the analysis from Gene Expression Omnibus (GEO) database and experimental evidence.

The Roles of Dietary, Nutritional and Lifestyle Interventions in Adipose Tissue Adaptation and Obesity

The obesity and the associated non-communicable diseases (NCDs) are globally increasing in their prevalence. While the modern-day lifestyle required less ventilation of metabolic energy through muscular activities, this lifestyle transition also provided the unlimited accession to foods around the clock, which prolong the daily eating period of foods that contained high calorie and high glycemic load. These situations promote the high continuous flux of carbon substrate availability in mitochondria and induce the indecisive bioenergetic switches. The disrupted bioenergetic milieu increases the uncoupling respiration due to the excess flow of the substrate-derived reducing equivalents and reduces ubiquinones into the respiratory chain. The diversion of the uncoupling proton gradient through adipocyte thermogenesis will then alleviate the damaging effects of free radicals to mitochondria and other organelles. The adaptive induction of white adipose tissues (WAT) to beige adipose tissues (beAT) has shown beneficial effects on glucose oxidation, ROS protection and mitochondrial function preservation through the uncoupling protein 1 (UCP1)-independent thermogenesis of beAT. However, the maladaptive stage can eventually initiate with the persistent unhealthy lifestyles. Under this metabolic gridlock, the low oxygen and pro-inflammatory environments promote the adipose breakdown with sequential metabolic dysregulation, including insulin resistance, systemic inflammation and clinical NCDs progression. It is unlikely that a single intervention can reverse all these complex interactions. A comprehensive protocol that includes dietary, nutritional and all modifiable lifestyle interventions, can be the preferable choice to decelerate, stop, or reverse the NCDs pathophysiologic processes.

Antioxidant Activity of Sprouts Extracts Is Correlated with Their Anti-Obesity and Anti-Inflammatory Effects in High-Fat Diet-Fed Mice

Obesity is closely associated with oxidative stress and chronic inflammation leading to related metabolic diseases. Some natural extracts or polyphenols reportedly possess anti-obesity and anti-inflammatory effects as well as antioxidant activity. In this study, we assessed the correlations between the antioxidant, anti-obesity, and anti-inflammatory activities of plant extracts with potent antioxidant activity in diet-induced obese mice. Sprouts of Cedrela sinensis (CS) and Oenothera biennis L. (OB) were selected as the most potent antioxidant plant based on analysis of in vitro antioxidant activity of the extracts of ten different edible plants. C57BL/6 mice were fed with a high-fat diet (HFD) and orally treated with 50% ethanol extract of CS or OB at 50 or 100 mg/kg body weight 5 days a week for 14 weeks. Body weight gain, weight of adipose tissue, adipocyte size, and levels of lipid metabolism, inflammation, and oxidative stress markers were investigated. The CS or OB extract reduced body weight gain, visceral adipose tissue weight, adipocyte size, and plasma leptin levels, and expressions of adipogenic genes (PPARγ and fatty acid synthase) in the adipose tissue and liver of HFD-fed mice. Both extracts also reduced mRNA levels of pro-inflammatory cytokines (IL-6 and TNF-α) and oxidative stress-related genes (heme oxygenase- (HO-) 1 and p40^phox). Body weight gain of mice was significantly correlated with visceral adipose tissue weight and adipocyte size. Body weight gain and adipocyte size were significantly correlated with plasma total cholesterol and 8-epi PGF2α levels, mRNA levels of leptin, HO-1, p40^phox, and CD-11 in the adipose tissue, and mRNA levels of TNF-α in the adipose tissue and liver. These results suggest that the CS and OB extracts with potent antioxidant activity may inhibit fat deposition in adipose tissue and subsequent inflammation.

Research progress in use of traditional Chinese medicine monomer for treatment of non-alcoholic fatty liver disease

With the improvement of people's living standards and the change of eating habits, non-alcoholic fatty liver disease (NAFLD) has gradually become one of the most common chronic liver diseases in the world. However, there are no effective drugs for the treatment of NAFLD. Therefore, it is urgent to find safe, efficient, and economical anti-NAFLD drugs. Compared with western medicines that possess fast lipid-lowering effect, traditional Chinese medicines (TCM) have attracted increasing attention for the treatment of NAFLD due to their unique advantages such as multi-targets and multi-channel mechanisms of action. TCM monomers have been proved to treat NAFLD through regulating various pathways, including inflammation, lipid production, insulin sensitivity, mitochondrial dysfunction, autophagy, and intestinal microbiota. In particular, peroxisome proliferator-activated receptor α (PPAR-α), sterol regulatory element-binding protein 1c (SREBP-1c), nuclear transcription factor kappa (NF-κB), phosphoinositide 3-kinase (PI3K), sirtuin1 (SIRT1), AMP-activated protein kinase (AMPK), p53 and nuclear factor erythroid 2-related factor 2 (Nrf2) are considered as important molecular targets for ameliorating NAFLD by TCM monomers. Therefore, by searching PubMed, Web of Science and SciFinder databases, this paper updates and summarizes the experimental and clinical evidence of TCM monomers for the treatment of NAFLD in the past six years (2015-2020), thus providing thoughts and prospects for further exploring the pathogenesis of NAFLD and TCM monomer therapies.

Effects of quercetin on exercise performance, physical activity and blood supply in a novel model of sustained hind-limb ischaemia

BACKGROUND

There are currently few effective drugs to treat the leg symptoms of peripheral arterial disease (PAD). Previous studies have suggested that the nutraceutical, quercetin, can improve exercise performance and reduce pain sensitivity in healthy mice and improve blood supply in a rodent model of acute hind-limb ischaemia. These models may not be relevant to people with PAD. The aim of this study was to examine the effect of quercetin on exercise performance, physical activity and blood supply in a novel mouse model of sustained hind-limb ischaemia.

METHODS

Hind-limb ischaemia was induced in 6-month-old male apolipoprotein E-deficient mice using a novel two-stage surgical procedure. Five days after induction of ischaemia, mice were allocated to commence dietary quercetin or a control diet for 4 weeks. The primary outcome was exercise performance evaluated using a treadmill test. Other outcomes included physical activity, estimated by an open field test, and hind-limb blood supply, assessed by laser Doppler monitoring.

RESULTS

A sustained reduction in relative limb blood supply (P < 0.001) was achieved consistently in all 48 mice before allocation to a control (n = 24) or quercetin (n = 24) diet. Quercetin did not improve exercise performance (P = 0.785), physical activity (P = 0.151) or relative limb blood supply (P = 0.954) over the 4-week assessment period.

CONCLUSION

These data suggest that quercetin does not improve exercise performance, physical activity or limb blood supply in mice with sustained hind-limb ischaemia, and therefore is unlikely be an effective treatment for PAD.

Samnamul (Shoots of Aruncus dioicus) Inhibit Adipogenesis by Downregulating Adipocyte-Specific Transcription Factors in 3T3-L1 Adipocytes

Adipocyte-specific transcription factors and antioxidants are considered the best target of obesity. Aruncus dioicus var. kamtschaticus (A. dioicus, Samnamul) is easily available owing to edible and inexpensive. However, the anti-adipogenic effects of the underlying mechanism of A. dioicus extract (ADE) have not yet been reported. In the present study, we evaluate anti-adipogenic pathway in 3T3-L1 adipocytes, antioxidant activities and quantified phenolics using high-performance liquid chromatography of ADE. The results revealed ADE had reduced adipocyte differentiation (0.72-fold vs. MDI (media of differentiation) control), triglyceride (TG; 0.50-fold vs. MDI control, p < 0.001), and total cholesterol contents (0.77-fold vs. MDI control) by regulating adipocyte-specific transcription factors (C/EBPα, PPARγ, and SREBP1) and their downstream mRNA (AdipoQ, Ap2, SREBP1-c, and FAS) levels. Furthermore, ADE has higher total phenol and flavonoid contents and scavenging assay in the DPPH and ABTS+. In particularly, ADE contains chlorogenic acid (7.04 mg/kg), caffeic acid (20.14 mg/kg), ferulic acid (1.74 mg/kg), veratric acid (29.31 mg/kg), cinnamic acid (4.70 mg/kg), and quercetin (4.18 mg/kg). In conclusion, since these phenols, especially quercetin, in the ADE appear to reduce differentiation, TG and cholesterol content by regulating adipocyte-specific transcription factors in adipocytes, ADE has the potential to be developed into a new antioxidant and anti-obesity therapeutics.

Network Pharmacology-Based Strategy for the Investigation of the Anti-Obesity Effects of an Ethanolic Extract of Zanthoxylum bungeanum Maxim

Network pharmacology is considered as the next paradigm in drug discovery. In an era when obesity has become global epidemic, network pharmacology becomes an ideal tool to discover novel herbal-based therapeutics with effective anti-obesity effects. Zanthoxylum bungeanum Maxim (ZBM) is a medicinal herb. The mature pericarp of ZBM is used for disease treatments and as spice for cooking. Here, we used the network pharmacology approach to investigate whether ZBM possesses anti-obesity effects and reveal the underlying mechanism of action. We first built up drug–ingredient–gene symbol–disease network and protein–protein interaction network of the ZBM-related obesity targets, followed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. The results highlight apoptosis as a promising signaling pathway that mediates the anti-obesity effects of ZBM. Molecular docking also reveals quercetin, a compound in ZBM has the highest degree of connections in the compound-target network and has direct bindings with the apoptotic markers. Furthermore, the apoptotic effects of ZBM are further validated in 3T3-L1 adipocytes and in the high-fat diet–induced obesity mouse model. These findings not only suggest ZBM can be developed as potential anti-obesity therapeutics but also demonstrate the application of network pharmacology for the discovery of herbal-based therapeutics for disease treatments.

Lactobacillus fermentum promotes adipose tissue oxidative phosphorylation to protect against diet-induced obesity

The gut microbiota has pivotal roles in metabolic homeostasis and modulation of the intestinal environment. Notably, the administration of Lactobacillus spp. ameliorates diet-induced obesity in humans and mice. However, the mechanisms through which Lactobacillus spp. control host metabolic homeostasis remain unclear. Accordingly, in this study, we evaluated the physiological roles of Lactobacillus fermentum in controlling metabolic homeostasis in diet-induced obesity. Our results demonstrated that L. fermentum-potentiated oxidative phosphorylation in adipose tissue, resulting in increased energy expenditure to protect against diet-induced obesity. Indeed, oral administration of L. fermentum LM1016 markedly ameliorated glucose clearance and fatty liver in high-fat diet-fed mice. Moreover, administration of L. fermentum LM1016 markedly decreased inflammation and increased oxidative phosphorylation in gonadal white adipose tissue, as demonstrated by transcriptome analysis. Finally, metabolome analysis showed that metabolites derived from L. fermentum LM1016-attenuated adipocyte differentiation and inflammation in 3T3-L1 preadipocytes. These pronounced metabolic improvements suggested that the application of L. fermentum LM1016 could have clinical applications for the treatment of metabolic syndromes, such as diet-induced obesity.

Heme Oxygenase-1 Suppresses Wnt Signaling Pathway in Nonalcoholic Steatohepatitis-Related Liver Fibrosis

Methods

Mice were fed with a methionine-choline-deficient (MCD) diet for 8 weeks to induce steatohepatitis-related liver fibrosis and were treated with HO-1 inducer Hemin and inhibitor ZnPP. Mouse sera were collected for the biochemical analysis, and livers were obtained for further histological observation and gene expression analysis. HSC-T6 cells were cultured for the in vitro study and were administrated with Hemin and si-HO-1 to induce or inhibit the expression of HO-1. qPCR and Western blot were used to assess the mRNA and protein levels of genes.

Results

MCD-fed mice developed marked macrovesicular steatosis, focal necrosis, and inflammatory infiltration and pericellular fibrosis in liver sections. Administration of Hemin could significantly ameliorate the severity of steatosis, inflammation, and fibrosis and also could decrease the serum ALT and AST. We demonstrated that HO-1 induction was able to downregulate the key regulator of the canonical Wnt pathway Wnt1 and the noncanonical Wnt pathway Wnt5a. The downstream factors of the Wnt pathway β-catenin and NFAT5 were inhibited by Hemin, but GSK-3β was upregulated compared to the MCD group, which were consistent with the in vitro study. Hemin markedly inhibited the TGF-β1/Smad signaling pathway in both in vivo and in vitro studies.

Conclusion

Our study demonstrated that HO-1 inhibited the activation of canonical and noncanonical Wnt signaling pathways in NASH-related liver fibrosis. Thus, these results may suggest a new therapeutic strategy for NASH-related liver fibrosis.

Tricarboxylic acid cycle dehydrogenases inhibition by naringenin: experimental and molecular modelling evidence

The study of polyphenols’ effects on health has been gaining attention lately. In addition to reacting with important enzymes, altering the cell metabolism, these substances can present either positive or negative metabolic alterations depending on their consumption levels. Naringenin, a citrus flavonoid, already presents diverse metabolic effects. The objective of this work was to evaluate the effect of maternal naringenin supplementation during pregnancy on the tricarboxylic acid cycle activity in offspring’s cerebellum. Adult female Wistar rats were divided into two groups: (1) vehicle (1 ml/kg by oral administration (p.o.)) or (2) naringenin (50 mg/kg p.o.). The offspring were euthanised at 7th day of life, and the cerebellum was dissected to analyse citrate synthase, isocitrate dehydrogenase (IDH), α-ketoglutarate dehydrogenase (α-KGDH) and malate dehydrogenase (MDH) activities. Molecular docking used SwissDock web server and FORECASTER Suite, and the proposed binding pose image was created on UCSF Chimera. Data were analysed by Student’s t test. Naringenin supplementation during pregnancy significantly inhibited IDH, α-KGDH and MDH activities in offspring’s cerebellum. A similar reduction was observed in vitro, using purified α-KGDH and MDH, subjected to pre-incubation with naringenin. Docking simulations demonstrated that naringenin possibly interacts with dehydrogenases in the substrate and cofactor binding sites, inhibiting their function. Naringenin administration during pregnancy may affect cerebellar development and must be evaluated with caution by pregnant women and their physicians.

Systematic investigation on the chemical basis of anti-NAFLD Qushi Huayu Fang. Part 1: A study of metabolic profiles in vivo and in vitro by high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry

Qushi Huayu Fang (QHF) is a clinic-empirical prescription for treating non-alcoholic fatty liver disease (NAFLD) in China, which is composed of five herbs. However, the bioactive constituents responsible for the efficacy of QHF remain unclear. Thus, a high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry method was established and adopted to identify the constituents of QHF, and profile its metabolism in vivo and in vitro. Among the 66 constituents in QHF, only 14 compounds of six structural types were absorbed, and 34 metabolites were generated through eight metabolic pathways. A total of 20 metabolites were first reported, including four organic acids, one iridoid, two flavones, five naphthols, three anthraquinones, and five stilbenes. Glucuronidation and sulfation were the main metabolic pathways, and the intestinal metabolism played an important role in the biotransformation of QHF. Many compounds, especially those detected in the liver, the target organ of QHF, were reported to display the anti-NAFLD activity. This is the first study to explore the constituents of QHF and its metabolism in vivo and in vitro, thus realizing the first step to clarify the chemical basis of QHF qualitatively, and laying the foundation for further research on the anti-NAFLD mechanism of QHF.

Plant Sterol Ester of α-Linolenic Acid Attenuates Nonalcoholic Fatty Liver Disease by Rescuing the Adaption to Endoplasmic Reticulum Stress and Enhancing Mitochondrial Biogenesis

Nonalcoholic fatty liver disease (NAFLD) is becoming more common in the world and is presenting a great challenge concerning prevention and treatment. Plant sterol ester of α-linolenic acid (PS-ALA) has a potential benefit to NAFLD. To examine the effect of PS-ALA on NAFLD, C57BL/6J mice were given a control diet, high fat and high cholesterol diet (HFD), and HFD plus 2% PS, 1.3% ALA, or 3.3% PS-ALA for 16 weeks. Our results showed that PS-ALA treatment suppressed hepatic steatosis, ameliorated lipid disorder, attenuated inflammatory response, and inhibited oxidative stress. In the molecular level, PS-ALA downregulated high transcriptional and translational levels of endoplasmic reticulum (ER) stress markers (Grp78 and Chop) leading to decreased protein expression of transcription factor and key enzymes involved in de novo lipogenesis (Srebp-1c and Fas) and cholesterol synthesis (Srebp-2 and Hmgcr). In parallel, PS-ALA blocked Nlrp3 activation and reduced release of IL-1β and IL-18 via inhibiting ER stress-induced sensitization of unfolded protein response sensors (Ire1α and Xbp1s). Finally, PS-ALA improved HFD-induced mitochondrial damage and fatty acid accumulation as exhibited by higher protein and mRNA expression of key genes administering mitochondrial biogenesis (Pgc-1α, Nrf1, and Tfam) and fatty acid β-oxidation (Pparα and Cpt1a). In conclusion, our study originally demonstrated that PS-ALA rescued ER stress, enhanced mitochondrial biogenesis, and thus ameliorated NAFLD.

Crosstalk between mitochondrial metabolism and oxidoreductive homeostasis: a new perspective for understanding the effects of bioactive dietary compounds

Mitochondria play an important role in a number of fundamental cellular processes, including energy production, biosynthetic pathways and cellular oxidoreductive homeostasis (redox status), and their dysfunction can lead to numerous pathophysiological consequences. As the biochemical mechanisms orchestrating mitochondrial metabolism and redox homeostasis are functionally linked, mitochondria have been identified as a potential therapeutic target. Consequently, considerable effort has been made to evaluate the efficacy of natural compounds that modulate mitochondrial function. Molecules produced by plants (for example, polyphenols and isothiocyanates) have been shown to modulate mitochondrial metabolism/biogenesis and redox status; however, despite the existence of a functional link, few studies have considered the combined efficacy of these mitochondrial functions. The present review provides a complete overview of the molecular pathways involved in modulating mitochondrial metabolism/biogenesis and redox status. Crosstalk between these critical mechanisms is also discussed, whilst major data from the literature regarding their antioxidant abilities are described and critically analysed. We also provide a summary of recent evidence regarding the ability of several plant-derived compounds to target these mitochondrial functions. An in-depth understanding of the functional link between mitochondrial metabolism/biogenesis and redox status could facilitate the analysis of the biological effects of natural compounds as well as the development of new therapeutic approaches.

Mitophagy in Hepatic Insulin Resistance: Therapeutic Potential and Concerns

Metabolic syndrome, characterized by central obesity, hypertension, and hyperlipidemia, increases the morbidity and mortality of cardiovascular disease, type 2 diabetes, nonalcoholic fatty liver disease, and other metabolic diseases. It is well known that insulin resistance, especially hepatic insulin resistance, is a risk factor for metabolic syndrome. Current research has shown that hepatic fatty acid accumulation can cause hepatic insulin resistance through increased gluconeogenesis, lipogenesis, chronic inflammation, oxidative stress and endoplasmic reticulum stress, and impaired insulin signal pathway. Mitochondria are the major sites of fatty acid β-oxidation, which is the major degradation mechanism of fatty acids. Mitochondrial dysfunction has been shown to be involved in the development of hepatic fatty acid–induced hepatic insulin resistance. Mitochondrial autophagy (mitophagy), a catabolic process, selectively degrades damaged mitochondria to reverse mitochondrial dysfunction and preserve mitochondrial dynamics and function. Therefore, mitophagy can promote mitochondrial fatty acid oxidation to inhibit hepatic fatty acid accumulation and improve hepatic insulin resistance. Here, we review advances in our understanding of the relationship between mitophagy and hepatic insulin resistance. Additionally, we also highlight the potential value of mitophagy in the treatment of hepatic insulin resistance and metabolic syndrome.

Quercetin reduces atherosclerotic lesions by altering the gut microbiota and reducing atherogenic lipid metabolites

AIMS

Epidemiological studies have correlated cardiovascular disease and atherosclerosis with lifestyle factors such as sedentary behaviour and a high-calorie diet. Recent studies of pathogenesis have highlighted the significance of the intestinal microbiota and chronic inflammation with respect to both the onset and development of atherosclerosis. This study examined the hypothesis that the oral administration of quercetin to low-density lipoprotein receptor-null (Ldlr^-/- ) mice would improve gut health by altering the gut microbiota and controlling the levels of atherogenic lipid metabolites and proinflammatory mediators in the intestine and serum.

METHODS AND RESULTS

Mice were maintained on a high-fat diet with or without oral quercetin administration for 12 weeks. Quercetin treatment suppressed body weight gains and reduced the extent of atherosclerotic lesions in the aortic sinus. Reduced malondialdehyde and increased interleukin 6 levels further indicated the protective effect of quercetin against immune/inflammatory responses and oxidative stress. Furthermore, quercetin led to decreased intestinal levels of cholesterol, lysophosphatidic acids and atherogenic lysophosphatidylcholine (LPC 18:1) and an increased level of coprostanol. A phylum-level microbial analysis revealed that quercetin treatment reduced the abundance of Verrocomicrobia and increased microbiome diversity and the abundances of Actinobacteria, Cyanobacteria and Firmicutes. A Spearman analysis revealed negative correlations of Actinobacteria with intestinal and plasma LPC 18:1 and caecal cholesterol levels and of Firmicutes and Cyanobacteria with the plasma LPC 18:1 level.

CONCLUSIONS

This study demonstrated the ability of quercetin treatment to reduce lipid levels, as well as the areas of atherosclerotic lesions and sizes of plaques. This treatment also altered the composition of the gut microbiota and decreased the levels of atherogenic lipid metabolites.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oral quercetin treatment may represent a new approach to mitigating the onset and development of atherosclerosis.

Prunus Mahaleb Fruit Extract Prevents Chemically Induced Colitis and Enhances Mitochondrial Oxidative Metabolism via the Activation of the Nrf2 Pathway

SCOPE

Polyphenols exhibit their antioxidant activity downstream the activation of the nuclear factor erythroid 2-related factor 2 pathway (Nrf2), but the connection between lipid metabolism and the Nrf2 pathway is still unknown. Flavonoid-rich concentrated extract from Prunus mahaleb (mahaleb concentrated fruit extract; MCFE) may act on oxido-reductive homeostasis and hepatic lipid metabolism via Nrf2.

METHODS & RESULTS

MCFE ability to enhance the activity of Nrf2-mediated antioxidant/detoxifying enzymes is investigated in liver and colon of BALB/c mice. After a 4-week supplementation, macroscopic, histological, and biochemical signs of colitis are examined in mouse colon pulsed with 5% (w/v) dextran sodium sulfate (DSS). Untreated or DSS-supplemented mice are used as negative or positive control. MCFE effect on liver lipid metabolism and its possible link with the Nrf2 pathway is investigated. MCFE intake increases antioxidant defenses in mice colon and its pretreatment blunts pathological signs of colitis, as compared to positive control. In the liver, the increase in antioxidant defenses is associated with enhanced oxidative metabolism and with higher levels of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and of hemeoxygenase-1 (HO-1), in comparison with negative controls.

CONCLUSION

Cytoprotective and hypolipidemic effect produced by MCFE intake results, at least in part, by the activation of the Nrf2 pathway.

HO-1 overexpression and underexpression: Clinical implications

In this review we examine the effects of both over- and under-production of heme oxygenase-1 (HO-1) and HO activity on a broad spectrum of biological systems and on vascular disease. In a few instances e.g., neonatal jaundice, overproduction of HO-1 and increased HO activity results in elevated levels of bilirubin requiring clinical intervention with inhibitors of HO activity. In contrast HO-1 levels and HO activity are low in obesity and the HO system responds to mitigate the deleterious effects of oxidative stress through increased levels of bilirubin (anti-inflammatory) and CO (anti-apoptotic) and decreased levels of heme (pro-oxidant). Site specific HO-1 overexpression diminishes adipocyte terminal differentiation and lipid accumulation of obesity mediated release of inflammatory molecules. A series of diverse strategies have been implemented that focus on increasing HO-1 and HO activity that are central to reversing the clinical complications associated with diseases including, obesity, metabolic syndrome and vascular disease.

Looking beyond PGC-1α: emerging regulators of exercise-induced skeletal muscle mitochondrial biogenesis and their activation by dietary compounds

Despite its widespread acceptance as the "master regulator" of mitochondrial biogenesis (i.e., the expansion of the mitochondrial reticulum), peroxisome proliferator-activated receptor (PPAR) gamma coactivator-1 alpha (PGC-1α) appears to be dispensable for the training-induced augmentation of skeletal muscle mitochondrial content and respiratory function. In fact, a number of regulatory proteins have emerged as important players in skeletal muscle mitochondrial biogenesis and many of these proteins share key attributes with PGC-1α. In an effort to move past the simplistic notion of a "master regulator" of mitochondrial biogenesis, we highlight the regulatory mechanisms by which nuclear factor erythroid 2-related factor 2 (Nrf2), estrogen-related receptor gamma (ERRγ), PPARβ, and leucine-rich pentatricopeptide repeat-containing protein (LRP130) may contribute to the control of skeletal muscle mitochondrial biogenesis. We also present evidence supporting/refuting the ability of sulforaphane, quercetin, and epicatechin to promote skeletal muscle mitochondrial biogenesis and their potential to augment mitochondrial training adaptations. Targeted activation of specific pathways by these compounds may allow for greater mechanistic insight into the molecular pathways controlling mitochondrial biogenesis in human skeletal muscle. Dietary activation of mitochondrial biogenesis may also be useful in clinical populations with basal reductions in mitochondrial protein content, enzyme activities, and/or respiratory function as well as individuals who exhibit a blunted skeletal muscle responsiveness to contractile activity. Novelty The existence of redundant pathways leading to mitochondrial biogenesis refutes the simplistic notion of a "master regulator" of mitochondrial biogenesis. Dietary activation of specific pathways may provide greater mechanistic insight into the exercise-induced mitochondrial biogenesis in human skeletal muscle.

Dietary Polyphenols Protect Against Oleic Acid-Induced Steatosis in an in Vitro Model of NAFLD by Modulating Lipid Metabolism and Improving Mitochondrial Function

In this study, we aimed to determine the relative effectiveness of common dietary polyphenols or the isoquinoline alkaloid berberine in protecting against molecular mechanisms underlying non-alcoholic fatty liver disease (NAFLD) involving changes to cellular lipid metabolism and bioenergetics. In a model of steatosis using HepG2 hepatocytes, exposure of the cells to 1.5 mM oleic acid (OA) for 24 h caused steatosis and distorted cell morphology, induced the expression of mRNA for enzymes that are involved in lipogenesis and fatty acid oxidation (FAS and CPT1A), and impaired indices of aerobic energy metabolism (PPARγ mRNA expression, mitochondrial membrane potential (MMP), and galactose-supported ATP production). Co-treatment with 10 µM of selected polyphenols all strongly protected against the steatosis and changes in cell morphology. All polyphenols, except cyanidin, inhibited the effects on FAS and PPARγ and further increased CPT1A1 expression, suggesting a shift toward increased β-oxidation. Resveratrol, quercetin, catechin, and cyanidin, however not kuromanin or berberine, ameliorated the decreases in MMP and galactose-derived ATP. Berberine was unique in worsening the decrease in galactose-derived ATP. In further investigations of the mechanisms involved, resveratrol, catechin, and berberine increased SIRT1 enzyme activity and p-AMPKα^Thr172 protein, which are involved in mitochondrial biogenesis. In conclusion, selected polyphenols all protected against steatosis with similar effectiveness, however through different mechanisms that increased aerobic lipid metabolism and mitochondrial function.

Quercetin preserves redox status and stimulates mitochondrial function in metabolically-stressed HepG2 cells

Hyperglycemia augments formation of intracellular reactive oxygen species (ROS) with associated mitochondrial damage and increased risk of insulin resistance in type 2 diabetes. We examined whether quercetin could reverse chronic high glucose-induced oxidative stress and mitochondrial dysfunction. Following long-term high glucose treatment, complex I activity was significantly decreased in isolated mitochondria from HepG2 cells. Quercetin dose-dependently recovered complex I activity and lowered cellular ROS generation under both high and normal glucose conditions. Respirometry studies showed that quercetin could counteract the detrimental increase in inner mitochondrial membrane proton leakage resulting from high glucose while it increased oxidative respiration, despite a decrease in electron transfer system (ETS) capacity, and lower non-ETS oxygen consumption. A quercetin-stimulated increase in cellular NAD⁺/NADH was evident within 2 h and a two-fold increase in PGC-1α mRNA within 6 h, in both normal and high glucose conditions. A similar pattern was also found for the mRNA expression of the repulsive guidance molecule b (RGMB) and its long non-coding RNA (lncRNA) RGMB-AS1 with quercetin, indicating a potential change of the glycolytic phenotype and suppression of aberrant cellular growth which is characteristic of the HepG2 cells. Direct effects of quercetin on PGC-1α activity were minimal, as quercetin only weakly enhanced PGC-1α binding to PPARα in vitro at higher concentrations. Our results suggest that quercetin may protect mitochondrial function from high glucose-induced stress by increasing cellular NAD⁺/NADH and activation of PGC-1α-mediated pathways. Lower ROS in combination with improved complex I activity and ETS coupling efficiency under conditions of amplified oxidative stress could reinforce mitochondrial integrity and improve redox status, beneficial in certain metabolic diseases.

Health promoting properties of blueberries: a review

With the strengthening of the link between diet and health, several foodstuffs have emerged as possessing potential health benefits such as phenolic rich fruits and vegetables. Blueberries, along with other berries, given their flavonoid and antioxidant content have long since been considered as a particularly interesting health promoting fruit. Therefore, the present work aimed to compile the existing evidences regarding the various potential benefits of blueberry and blueberry based products consumption, giving particular relevance to in vivo works and epidemiological studies whenever available. Overall, the results demonstrate that, while the evidences that support a beneficial role of blueberry and blueberry extracts consumption, further human based studies are still needed.

Frataxin-Mediated PINK1-Parkin-Dependent Mitophagy in Hepatic Steatosis: The Protective Effects of Quercetin

SCOPE

Naturally occurring quercetin has been found to induce mitophagy and prevent nonalcoholic fatty liver disease (NAFLD). However, it still remains elusive whether frataxin upregulation by quercetin contributes to the beneficial effect through mitophagy or not.

METHODS AND RESULTS

Adult male C57BL/J mice were fed a high-fat diet (HFD, 60% of energy from fat) with quercetin (100 mg kg-1 body weight) or not for 10 weeks. Quercetin alleviated HFD-induced histopathological changes, disorders of lipid metabolism, and mitochondrial damage. Moreover, quercetin blocked mitophagy suppression by HFD based on the increased LC3II, PTEN-induced putative kinase 1 (PINK1) and Beclin1 expressions, as well as decreased p62 levels. Quercetin also improved the Parkin translocation to mitochondria confirmed by immunofluorescence. Specifically, frataxin was lowered in the liver of HFD-fed mice or HepG2 cell incubated with oleate/palmitate but restored by quercetin, and quercetin's regulation of frataxin may depend on p53. Furthermore, lentivirus-mediated stable knockdown of frataxin in HepG2 inhibited PINK1-Parkin-associated mitophagy and resulted in lipid accumulation. Frataxin was further decreased by free fatty acids in knockdown cells concomitantly with depressed PINK1-Parkin-associated mitophagy, which was partially normalized by quercetin.

CONCLUSION

Quercetin alleviated hepatic steatosis by enhancing frataxin-mediated PINK1/Parkin-dependent mitophagy, highlighting a promising preventive strategy and mechanism for NAFLD by quercetin.