Quercetin reduces obesity-associated ATM infiltration and inflammation in mice: a mechanism including AMPKα1/SIRT1

The Role of Sirtuins in Antioxidant and Redox Signaling

SIGNIFICANCE

Antioxidant and redox signaling (ARS) events are regulated by critical molecules that modulate antioxidants, reactive oxygen species (ROS) or reactive nitrogen species (RNS), and/or oxidative stress within the cell. Imbalances in these molecules can disturb cellular functions to become pathogenic. Sirtuins serve as important regulators of ARS in cells. Recent Advances: Sirtuins (SIRTs 1-7) are a family of nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases with the ability to deacetylate histone and nonhistone targets. Recent studies show that sirtuins modulate the regulation of a variety of cellular processes associated with ARS. SIRT1, SIRT3, and SIRT5 protect the cell from ROS, and SIRT2, SIRT6, and SIRT7 modulate key oxidative stress genes and mechanisms. Interestingly, SIRT4 has been shown to induce ROS production and has antioxidative roles as well.

CRITICAL ISSUES

A complete understanding of the roles of sirtuins in redox homeostasis of the cell is very important to understand the normal functioning as well as pathological manifestations. In this review, we have provided a critical discussion on the role of sirtuins in the regulation of ARS. We have also discussed mechanistic interactions among different sirtuins. Indeed, a complete understanding of sirtuin biology could be critical at multiple fronts.

FUTURE DIRECTIONS

Sirtuins are emerging to be important in normal mammalian physiology and in a variety of oxidative stress-mediated pathological situations. Studies are needed to dissect the mechanisms of sirtuins in maintaining redox homeostasis. Efforts are also required to assess the targetability of sirtuins in the management of redox-regulated diseases. Antioxid. Redox Signal. 28, 643-661.

Grape pomace extract induced beige cells in white adipose tissue from rats and in 3T3-L1 adipocytes

This study investigated the effects of a grape pomace extract (GPE) rich in phenolic compounds on brown-like adipocyte induction and adiposity in spontaneously hypertensive (SHR) and control normotensive Wistar-Kyoto (WKY) rats fed a high-fat diet (HFD). HFD consumption for 10 weeks significantly increased epididymal white adipose tissue (eWAT) in WKY but not in SHR rats. Supplementation with GPE (300 mg/kg body weight/day) reduced adipocyte diameter and increased levels of proteins that participate in adipogenesis and angiogenesis, i.e., peroxisome-proliferator activated receptor gamma (PPARγ), vascular endothelial grow factor-A (VEGF-A) and its receptor 2 (VEGF-R2), and partially increased the uncoupling protein 1 (UCP-1) in WKY. In both strains, GPE attenuated adipose inflammation. In eWAT from SHR, GPE increased the expression of proteins involved in adipose tissue "browning," i.e., PPARγ-coactivator-1α (PGC-1α), PPARγ, PR domain containing 16 (PRDM16) and UCP-1. In primary cultures of SHR adipocytes, GPE-induced UCP-1 up-regulation was dependent on p38 and ERK activation. Accordingly, in 3T3-L1 adipocytes treated with palmitate, the addition of GPE (30 μM) activated the β-adrenergic signaling cascade (PKA, AMPK, p38, ERK). This led to the associated up-regulation of proteins involved in mitochondrial biogenesis (PGC-1α, PPARγ, PRDM16 and UCP-1) and fatty acid oxidation (ATGL). These effects were similar to those exerted by (-)-epicatechin and quercetin, major phenolic compounds in GPE. Overall, in HFD-fed rats, supplementation with GPE promoted brown-like cell formation in eWAT and diminished adipose dysfunction. Thus, winemaking residues, rich in bioactive compounds, could be useful to mitigate the adverse effects of HFD-induced adipose dysfunction.

The Flavonoid Quercetin Ameliorates Liver Inflammation and Fibrosis by Regulating Hepatic Macrophages Activation and Polarization in Mice

At present, there are no effective antifibrotic drugs for patients with chronic liver disease; hence, the development of antifibrotic therapies is urgently needed. Here, we performed an experimental and translational study to investigate the potential and underlying mechanism of quercetin treatment in liver fibrosis, mainly focusing on the impact of quercetin on macrophages activation and polarization. BALB/c mice were induced liver fibrosis by carbon tetrachloride (CCl₄) for 8 weeks and concomitantly treated with quercetin (50 mg/kg) or vehicle by daily gavage. Liver inflammation, fibrosis, and hepatic stellate cells (HSCs) activation were examined. Moreover, massive macrophages accumulation, M1 macrophages and their related markers, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and monocyte chemotactic protein-1 (MCP-1) in livers were analyzed. In vitro, we used Raw 264.7 cells to examine the effect of quercetin on M1-polarized macrophages activation. Our results showed that quercetin dramatically ameliorated liver inflammation, fibrosis, and inhibited HSCs activation. These results were attributed to the reductive recruitment of macrophages (F4/80⁺ and CD68⁺) into the liver in quercetin-treated fibrotic mice confirmed by immunostaining and expression levels of marker molecules. Importantly, quercetin strongly inhibited M1 polarization and M1-related inflammatory cytokines in fibrotic livers when compared with vehicle-treated mice. In vitro, studies further revealed that quercetin efficiently inhibited macrophages activation and M1 polarization, as well as decreased the mRNA expression of M1 macrophage markers such as TNF-α, IL-1β, IL-6, and nitric oxide synthase 2. Mechanistically, the inhibition of M1 macrophages by quercetin was associated with the decreased levels of Notch1 expression on macrophages both in vivo and in vitro. Taken together, our data indicated that quercetin attenuated CCl₄-induced liver inflammation and fibrosis in mice through inhibiting macrophages infiltration and modulating M1 macrophages polarization via targeting Notch1 pathway. Hence, quercetin holds promise as potential therapeutic agent for human fibrotic liver disease.

Food Bioactives and Their Effects on Obesity-Accelerated Inflammatory Bowel Disease

Current views support the concept that obesity is linked to a worsening of the course of inflammatory bowel diseases (IBDs). Gut microbiota and adipose tissue macrophage (ATM) are considered key mediators or contributors in obesity-associated intestinal inflammation. Dietary components can have direct or indirect effects on "normal" or "healthy" microbial composition and participate in adiposity and metabolic status with gut inflammation. In this perspective, we highlight food-derived bioactives that have a potential application in the prevention of obesity-exacerbated IBD, targeting energy metabolism, M1 (classical activated)-M2 (alternatively activated) macrophage polarization, and gut microbiota.

Flavonoids, Dairy Foods, and Cardiovascular and Metabolic Health: A Review of Emerging Biologic Pathways

A growing body of nutritional science highlights the complex mechanisms and pleiotropic pathways of cardiometabolic effects of different foods. Among these, some of the most exciting advances are occurring in the area of flavonoids, bioactive phytochemicals found in plant foods; and in the area of dairy, including milk, yogurt, and cheese. Many of the relevant ingredients and mechanistic pathways are now being clarified, shedding new light on both the ingredients and the pathways for how diet influences health and well-being. Flavonoids, for example, have effects on skeletal muscle, adipocytes, liver, and pancreas, and myocardial, renal, and immune cells, for instance, related to 5'-monophosphate-activated protein kinase phosphorylation, endothelial NO synthase activation, and suppression of NF-κB (nuclear factor-κB) and TLR4 (toll-like receptor 4). Effects of dairy are similarly complex and may be mediated by specific amino acids, medium-chain and odd-chain saturated fats, unsaturated fats, branched-chain fats, natural trans fats, probiotics, vitamin K1/K2, and calcium, as well as by processing such as fermentation and homogenization. These characteristics of dairy foods influence diverse pathways including related to mammalian target of rapamycin, silent information regulator transcript-1, angiotensin-converting enzyme, peroxisome proliferator-activated receptors, osteocalcin, matrix glutamate protein, hepatic de novo lipogenesis, hepatic and adipose fatty acid oxidation and inflammation, and gut microbiome interactions such as intestinal integrity and endotoxemia. The complexity of these emerging pathways and corresponding biological responses highlights the rapid advances in nutritional science and the continued need to generate robust empirical evidence on the mechanistic and clinical effects of specific foods.

Natural products, an important resource for discovery of multitarget drugs and functional food for regulation of hepatic glucose metabolism

Imbalanced hepatic glucose homeostasis is one of the critical pathologic events in the development of metabolic syndromes (MSs). Therefore, regulation of imbalanced hepatic glucose homeostasis is important in drug development for MS treatment. In this review, we discuss the major targets that regulate hepatic glucose homeostasis in human physiologic and pathophysiologic processes, involving hepatic glucose uptake, glycolysis and glycogen synthesis, and summarize their changes in MSs. Recent literature suggests the necessity of multitarget drugs in the management of MS disorder for regulation of imbalanced glucose homeostasis in both experimental models and MS patients. Here, we highlight the potential bioactive compounds from natural products with medicinal or health care values, and focus on polypharmacologic and multitarget natural products with effects on various signaling pathways in hepatic glucose metabolism. This review shows the advantage and feasibility of discovering multicompound-multitarget drugs from natural products, and providing a new perspective of ways on drug and functional food development for MSs.

Molecular mechanisms of the anti-obesity effect of bioactive ingredients in common spices: a review

The mechanisms of the anti-obesity effects of bioactive compounds in common spices in adipocytes, animal models and human participants have been reviewed.

Regulation of macrophage migration in ischemic mouse hearts via an AKT2/NBA1/SPK1 pathway

The role of the AKT2/NBA1/SPK1 signaling cascade in macrophage migration regulation and post-ischemic cardiac remodeling was investigated. We determined that the AKT2/NBA1/SPK1 signaling cascade regulated macrophage migration. A novel role for NBA1 in macrophage migration was discovered. Elevated AKT2 phosphorylation, NBA1, SPK1 (along with phosphorylated SPK1) levels, macrophage recruitment, apoptosis, and fibrosis were found within the infarct area. Atorvastatin had a beneficial effect on cardiac remodeling following myocardial infarction by inhibiting AKT2/NBA1/SPK1-mediated macrophage recruitment, apoptosis, and collagen deposition while increasing angiogenesis in the infarct area. Atorvastatin-related protection of cardiac remodeling following myocardial infarction was abolished in SPK1-KO mice. The AKT2/NAB1/SPK1 pathway is a novel regulating factor of macrophage migration and cardiac remodeling after myocardial infarction.

Carnosic acid prevents COL1A2 transcription through the reduction of Smad3 acetylation via the AMPKα1/SIRT1 pathway

Carnosic acid (CA), a major bioactive component in rosemary extract, has many biological and pharmaceutical activities. Smad3 acetylation can regulate the transcription of type I α2 collagen (COL1A2), which is the major component of the extracellular matrix (ECM). The aim of the current study was to evaluate whether CA inhibits COL1A2 transcription via the reduction of Smad3 acetylation against liver fibrosis. The results showed that CA treatment significantly suppressed COL1A2 transcription and markedly decreased the deposition of ECM induced by dimethylamine (DMN) in rats. Importantly, the suppression of COL1A2 transcription following CA treatment depended on the reduction of Smad3 acetylation via the activation of Sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide⁺ (NAD⁺)-dependent deacetylase. SIRT1 siRNA increased the acetylation of Smad3 and blocked CA-down-regulated Smad3 deacetylation. Notably, CA-mediated AMP-activated protein kinase-α1 (AMPKα1) activation not only increased AMPKα1 phosphorylation but also increased SIRT1 expression, thus leading to a significant reduction in Smad3 acetylation. Furthermore, CA-mediated SIRT1 activation was inhibited by AMPKα1 siRNA. Collectively, CA can inhibit the transcription of COL1A2 through SIRT1-mediated Smad3 deacetylation, and the activation of SIRT1 by CA involves the AMPKα1/SIRT1 pathway in liver fibrosis.

Combination treatment with quercetin and resveratrol attenuates high fat diet-induced obesity and associated inflammation in rats via the AMPKα1/SIRT1 signaling pathway

Diet-induced obesity is associated with systemic inflammation, which is considered to originate predominantly from the adipose tissue. Quercetin and resveratrol are two dietary polyphenols that exhibit anti-inflammatory properties and anti-insulin resistance when administered in isolation or combination (CQR). It remains unknown whether CQR reduces high fat diet (HFD)-induced obesity and inflammation in rats. In the current study, 46 male Wistar rats were divided into two groups, one of which was fed a normal diet (ND, 5.4% fat, w/w) and one of which was fed a HFD (45% fat, w/w) for 3 weeks. Following removal of the 12 most obesity-resistant rats from the HFD group, the remaining rats were divided into two sub-groups: A HFD group and a HFD+CQR group (administered 120 mg/kg/day resveratrol and 240 mg/kg/day quercetin). The results revealed that the HFD+CQR group had significantly lower body weights at 11 weeks compared with the HFD group and had significantly reduced visceral adipose tissue weights and adipocyte sizes. Serum lipid profiles were also significantly ameliorated in the HFD+CQR group. CQR attenuated the expression of systemic proinflammatory adipokines, including leptin, tumor necrosis factor-α, monocyte chemoattractant protein-1 and interleukin-6. It also reduced the recruitment of mast cells to the epididyotic adipose tissue (EAT). Furthermore, CQR reversed the HFD-induced suppression of 5'-adenosine monophosphate-activated protein kinase α1 (AMPKα1) phosphorylation and sirtuin 1 (SIRT1) expression in EAT. In conclusion, CQR may suppress obesity and associated inflammation via the AMPKα1/SIRT1 signaling pathway in rats fed a HFD.

Protective effect of quercetin and rutin encapsulated liposomes on induced oxidative stress

Natural antioxidants show many pharmacological properties, but poor solubility and inability to cross cell membrane. Liposomes are biocompatible and phospholipid vesicles able to carry hydrophilic, hydrophobic, and amphiphilic molecules. This paper focus on the synthesis of anionic, cationic and zwitterionic liposomes, loaded with quercetin or rutin, and on the evaluation of their cytotoxicity and protective effects against oxidative stress. Chemical characterization was obtained by dynamic light scattering and z-potential experiments. In vitro cell behavior was evaluated by Neutral Red Uptake test. All liposomes, empty and loaded with antioxidants, are stable. The cytotoxicity of both quercetin and rutin encapsulated in zwitterionic and anionic liposomes is higher than that of their solutions. Quercetin and rutin loaded in cationic liposomes are able to inhibit the toxic effect of empty liposomes. The encapsulation of rutin at 5.0×10^-5 and 5.0×10^-4M, in zwitterionic and anionic liposomes, protects fibroblasts by H₂O₂ treatment, while the loading with quercetin does not have effect on improving cell viability. All data suggest that the tested liposomes are stable and able to include quercetin and rutin. The liposomes encapsulation of antioxidants makes easier their internalization by cells. Moreover, zwitterionic and anionic liposomes loaded with rutin protect cells by oxidative stress. Liposomes stability together with their good in vitro cytocompatibility, both empty and loaded with antioxidant molecules, makes these systems suitable candidates as drug delivery systems. Moreover, the encapsulation of rutin, is able to protect cells by oxidative stress.

Quercetin-Induced AMP-Activated Protein Kinase Activation Attenuates Vasoconstriction Through LKB1-AMPK Signaling Pathway

The vascular tone plays an important role in blood pressure and flow. It is influenced by the contraction of vascular smooth muscle cells (VSMCs), which in turn is regulated by the balance between the myosin light chain kinase (MLCK) and the phosphorylated myosin light chain (p-MLC). Quercetin is a common flavonoid which is found in many fruits and red wine. Although quercetin has been widely reported to be involved in cell proliferation, migration, and apoptosis in VSMCs, it has not yet been demonstrated whether quercetin is related to vasocontraction, a function regulated by the AMP-activated protein kinase (AMPK) signaling pathway. Accordingly, the aim of this study is to investigate the molecular mechanism through which the quercetin-activated LKB1-AMPK signaling pathway regulates the contraction of VSMCs. In cultured VSMCs, quercetin activated AMPK in a dose- and time-dependent manner. Quercetin inhibited the phenylephrine (PE)-induced expression of MLCK and p-MLC through the LKB1-AMPK signaling pathway and decreased the mRNA level of MLCK. Adenovirus-AMPK DN α1 and AMPK DN α2-transduced VSMCs displayed higher p-MLC expression. Moreover, quercetin inhibited the PE-mediated contraction in rat aorta. These data suggest that the quercetin-activated LKB1-AMPK signaling pathway regulates VSMC contraction by inhibiting MLCK and p-MLC; hence, it may be a therapeutic intervention for the treatment of cardiovascular disorders such as atherosclerosis and hypertension.

The Beneficial Effects of Quercetin, Curcumin, and Resveratrol in Obesity

Over the past two decades, obesity has been one of the major public health concerns in most countries. In the search for new molecules that could be used for the treatment of obesity, good perspectives have been opened up for polyphenols, a class of natural bioactive phytochemicals. Experimental and limited clinical trial evidence supports that some polyphenols such as quercetin, curcumin, and resveratrol have potential benefit functions on obesity treatment. This brief review focuses on the main functions of the above-named polyphenols on adipose tissue. These polyphenols may play beneficial effects on adipose tissue under obese condition by alleviating intracellular oxidative stress, reducing chronic low-grade inflammation, inhibiting adipogenesis and lipogenesis, and suppressing the differentiation of preadipocytes to mature adipocytes.

Sarpogrelate hydrochloride ameliorates diabetic nephropathy associated with inhibition of macrophage activity and inflammatory reaction in db/db mice

The aim of this study was to evaluate the effects of sarpogrelate hydrochloride (SH), a selective serotonin 2A receptor antagonist, on diabetic nephropathy in a type 2 diabetes mouse model. We treated db/m and db/db mice with SH (30 mg/kg/day) for 12 weeks. Rat renal proximal tubule cells (NRK-52E) and mouse macrophages (Raw 264.7) were stimulated by high glucose (30 mM glucose) or LPS (100 ng/ml) with or without SH (20 μM). We found that SH treatment increased serum adiponectin level and decreased urinary albumin, macrophage infiltration to glomeruli, and renal inflammatory and fibrosis signals, which were highly expressed in diabetic mice. Proximal tubule cells treated with high glucose (30 mM) also showed increased inflammatory and fibrosis signals. However, SH (20 μM) treatment reduced these changes. Moreover, SH treatment inhibited LPS-stimulated macrophage migration and activation. These findings suggest that SH ameliorates diabetic nephropathy not only by suppressing macrophage infiltration, but also by anti-inflammatory and anti-fibrotic effects.

Ampelopsin attenuates the atrophy of skeletal muscle from d-gal-induced aging rats through activating AMPK/SIRT1/PGC-1α signaling cascade

The atrophy of skeletal muscle is highly correlated with oxidative damage, excessive apoptosis and dysfunctional autophagy. Ampelopsin, a natural flavonoid, has multiple biological functions including anti-inflammatory, anti-oxidative, and hepatoprotective functions. Sprague-Dawley (SD) rats subjected to intraperitoneal injection of d-galactose (d-gal) at the dose of 150mg/kg·d revealed an obvious atrophy of skeletal muscle with significantly reduced muscle mass/body mass ratio, cross-sectional area and fiber diameter of skeletal muscle in d-gal-induced aging rats when compared to normal control rats without d-gal administration for 6 consecutive weeks. In contrast, the combinatorial administration of d-gal at the identical dose and DHM at the dose of 100 or 200mg/kg·d could alleviate the reduction of these hallmarks associated with the atrophy of skeletal muscle. In addition, d-gal administration could result in obvious apoptosis and impaired autophagy in skeletal muscle, which could be mitigated upon DHM treatment due to its role in decreasing ubiquitin and Atrogin-1/MAFbx and up-regulating AMPK and SIRT1 signal pathways. Therefore, DHM may be a potential candidate for the prevention and treatment of skeletal muscle atrophy associated aging process.

Recent Advances in Nanoparticle-Mediated Delivery of Anti-Inflammatory Phytocompounds

Phytocompounds have been used in medicine for decades owing to their potential in anti-inflammatory applications. However, major difficulties in achieving sustained delivery of phyto-based drugs are related to their low solubility and cell penetration, and high instability. To overcome these disadvantages, nanosized delivery technologies are currently in use for sustained and enhanced delivery of phyto-derived bioactive compounds in the pharmaceutical sector. This review focuses on the recent advances in nanocarrier-mediated drug delivery of bioactive molecules of plant origin in the field of anti-inflammatory research. In particular, special attention is paid to the relationship between structure and properties of the nanocarrier and phytodrug release behavior.

Phloretin Prevents High-Fat Diet-Induced Obesity and Improves Metabolic Homeostasis

Reactive oxygen species generated as a by-product in metabolism play a central role in the development of obesity and obesity-related metabolic complications. The objective of the current study is to explore the possibility to block obesity and improve metabolic homeostasis via phloretin, a natural antioxidant product from apple tree leaves and Manchurian apricot. Both preventive and therapeutic activities of phloretin were assessed using a high-fat diet-induced obesity mouse model. Phloretin was injected intraperitoneally twice weekly into regular and obese mice fed a high-fat diet. The effects of phloretin treatment on body weight and composition, fat content in the liver, glucose and lipid metabolism, and insulin resistance were monitored and compared to the control animals. Phloretin treatment significantly blocks high-fat diet-induced weight gain but did not induce weight loss in obese animals. Phloretin improved glucose homeostasis and insulin sensitivity and alleviated hepatic lipid accumulation. RT-PCR analysis showed that phloretin treatment suppresses expression of macrophage markers (F4/80 and Cd68) and pro-inflammatory genes (Mcp-1 and Ccr2) and enhances adiponectin gene expression in white adipose tissue. In addition, phloretin treatment elevated the expression of fatty acid oxidation genes such as carnitine palmitoyltransferase 1a and 1b (Cpt1a and Cpt1b) and reduced expression of monocyte chemoattractant protein-1 (Mcp-1), de novo lipogenesis transcriptional factor peroxisome proliferator-activated receptor-γ 2 (Pparγ2), and its target monoacylglycerol O-acyltransferase (Mgat-1) genes. These results provide direct evidence to support a possible use of phloretin for mitigation of obesity and maintenance of metabolic homeostasis.

Impacts of Dietary Phytochemicals in the Presence and Absence of Pesticides on Longevity of Honey Bees (Apis mellifera)

Because certain flavonols and phenolic acids are found in pollen and nectar of most angiosperms, they are routinely ingested by Apis mellifera, the western honey bee. The flavonol quercetin and the phenolic acid p-coumaric acid are known to upregulate detoxification enzymes in adult bees; their presence or absence in the diet may thus affect the toxicity of ingested pesticides. We conducted a series of longevity assays with one-day-old adult workers to test if dietary phytochemicals enhance longevity and pesticide tolerance. One-day-old bees were maintained on sugar syrup with or without casein (a phytochemical-free protein source) in the presence or absence of quercetin and p-coumaric acid as well as in the presence or absence of two pyrethroid insecticides, bifenthrin and β-cyfluthrin. Dietary quercetin (hazard ratio, HR = 0.82), p-coumaric acid (HR = 0.91) and casein (HR = 0.74) were associated with extended lifespan and the two pyrethroid insecticides, 4 ppm bifenthrin (HR = 9.17) and 0.5 ppm β-cyfluthrin (HR = 1.34), reduced lifespan. Dietary quercetin enhanced tolerance of both pyrethroids; p-coumaric acid had a similar effect trend, although of reduced magnitude. Casein in the diet appears to eliminate the life-prolonging effect of p-coumaric acid in the absence of quercetin. Collectively, these assays demonstrate that dietary phytochemicals influence honey bee longevity and pesticide stress; substituting sugar syrups for honey or yeast/soy flour patties may thus have hitherto unrecognized impacts on adult bee health.

Adipose Tissue-Specialized Immunologic Features Might Be the Potential Therapeutic Target of Prospective Medicines for Obesity

Excessive lipid accumulation in adipose tissue is either the source of obesity or the cause and result of chronic local inflammation, and recent studies indicate that the accumulation may induce many other specialized immunologic features with macrophages and epidemic diseases. We analyze the effective stages of immune cells in adipose tissue, including macrophage recruitment, macrophage polarization, and macrophage-like phenotype preadipocyte possession to find optimal sites as drug targets. Subsequently, some main signaling pathways are summarized in this review, including the AMP-activated protein kinase (AMPK) pathway, the JNK signaling pathway, and a novel one, the Notch signaling pathway. We illustrate all these points in order to determine the general pathogenesis of chronic low-grade local inflammation in adipose tissue and the related signaling pathways. In addition, signal-associated prospective compounds, such as berberine, are summarized and discussed with potential targets in pathogenesis. This might provide some possible thoughts and novel therapies for studying chronic inflammatory diseases, such as insulin resistance and type 2 diabetes mellitus.

Protective effect of quercetin on high-fat diet-induced non-alcoholic fatty liver disease in mice is mediated by modulating intestinal microbiota imbalance and related gut-liver axis activation

Gut microbiota is involved in obesity, metabolic syndrome and the progression of nonalcoholic fatty liver disease (NAFLD). It has been recently suggested that the flavonoid quercetin may have the ability to modulate the intestinal microbiota composition, suggesting a prebiotic capacity which highlights a great therapeutic potential in NAFLD. The present study aims to investigate benefits of experimental treatment with quercetin on gut microbial balance and related gut-liver axis activation in a nutritional animal model of NAFLD associated to obesity. C57BL/6J mice were challenged with high fat diet (HFD) supplemented or not with quercetin for 16 weeks. HFD induced obesity, metabolic syndrome and the development of hepatic steatosis as main hepatic histological finding. Increased accumulation of intrahepatic lipids was associated with altered gene expression related to lipid metabolism, as a result of deregulation of their major modulators. Quercetin supplementation decreased insulin resistance and NAFLD activity score, by reducing the intrahepatic lipid accumulation through its ability to modulate lipid metabolism gene expression, cytochrome P450 2E1 (CYP2E1)-dependent lipoperoxidation and related lipotoxicity. Microbiota composition was determined via 16S ribosomal RNA Illumina next-generation sequencing. Metagenomic studies revealed HFD-dependent differences at phylum, class and genus levels leading to dysbiosis, characterized by an increase in Firmicutes/Bacteroidetes ratio and in Gram-negative bacteria, and a dramatically increased detection of Helicobacter genus. Dysbiosis was accompanied by endotoxemia, intestinal barrier dysfunction and gut-liver axis alteration and subsequent inflammatory gene overexpression. Dysbiosis-mediated toll-like receptor 4 (TLR-4)-NF-κB signaling pathway activation was associated with inflammasome initiation response and reticulum stress pathway induction. Quercetin reverted gut microbiota imbalance and related endotoxemia-mediated TLR-4 pathway induction, with subsequent inhibition of inflammasome response and reticulum stress pathway activation, leading to the blockage of lipid metabolism gene expression deregulation. Our results support the suitability of quercetin as a therapeutic approach for obesity-associated NAFLD via its anti-inflammatory, antioxidant and prebiotic integrative response.

Quercetin intake, MATE1 polymorphism, and metabolic syndrome in Korean population: Hallym aging study

Multidrug and toxic compound extrusion transporter-1 (MATE1) is a quercetin transporter. We examined the associations of quercetin intake and polymorphism of MATE1 in relation to metabolic syndrome (MetS) in Hallym Aging Study. Quercetin intake and the measurements for MetS were assessed in 2004. Six tagging single nucleotide polymorphisms (SNPs) at MATE1 gene were genotyped in 428 Korean adults in 2012. We found a lower prevalence of MetS with quercetin intake; compared to the lowest quartile, odds ratios (ORs, 95% confidence intervals; CIs) were 0.44 (0.24-0.84) for the 3^rd quartile. Individuals with the minor allele of MATE1, rs2453589, tended to have a lower prevalence of MetS compared to those with the major allele (OR=0.69; CI=0.36-1.34). However, interactions between quercetin intake and six MATE1 polymorphisms in relation to MetS were not significant (p for interaction ≥0.37). In conclusion, intake of quercetin was associated with MetS in Korean populations.

Quercetin and derivatives: useful tools in inflammation and pain management

Inflammation represents a very frequent condition in humans; it is often underestimated, making the problem an increasingly alarming phenomenon. For these reasons, conventional therapies are losing their effectiveness, leaving room for innovative therapies. In this field, natural products showed their efficacy in various diseases; and flavonoids, in particular quercetin, is known for its broad range of activities. In this review, we have highlighted its efficacy in various models of inflammation, focusing also on the activity of its semisynthetic derivatives, and those naturally present in plant extracts. Finally, the analgesic property of quercetin, intrinsically linked to its anti-inflammatory action, has been also evaluated, to investigate about an innovative approach to this interesting natural compound, such as analgesic remedial.

Long-Term Quercetin Dietary Enrichment Partially Protects Dystrophic Skeletal Muscle

Duchenne muscular dystrophy (DMD) results from a genetic lesion in the dystrophin gene and leads to progressive muscle damage. PGC-1α pathway activation improves muscle function and decreases histopathological injury. We hypothesized that mild disease found in the limb muscles of mdx mice may be responsive to quercetin-mediated protection of dystrophic muscle via PGC-1α pathway activation. To test this hypothesis muscle function was measured in the soleus and EDL from 14 month old C57, mdx, and mdx mice treated with quercetin (mdxQ; 0.2% dietary enrichment) for 12 months. Quercetin reversed 50% of disease-related losses in specific tension and partially preserved fatigue resistance in the soleus. Specific tension and resistance to contraction-induced injury in the EDL were not protected by quercetin. Given some functional gain in the soleus it was probed with histological and biochemical approaches, however, in dystrophic muscle histopathological outcomes were not improved by quercetin and suppressed PGC-1α pathway activation was not increased. Similar to results in the diaphragm from these mice, these data suggest that the benefits conferred to dystrophic muscle following 12 months of quercetin enrichment were underwhelming. Spontaneous activity at the end of the treatment period was greater in mdxQ compared to mdx indicating that quercetin fed mice were more active in addition to engaging in more vigorous activity. Hence, modest preservation of muscle function (specific tension) and elevated spontaneous physical activity largely in the absence of tissue damage in mdxQ suggests dietary quercetin may mediate protection.

A Low Dose of Dietary Quercetin Fails to Protect against the Development of an Obese Phenotype in Mice

The purpose of this study was to examine the effect of a 40% high-fat diet (HFD) supplemented with a dietary attainable level of quercetin (0.02%) on body composition, adipose tissue (AT) inflammation, Non-Alcoholic Fatty-Liver Disease (NAFLD), and metabolic outcomes. Diets were administered for 16 weeks to C57BL/6J mice (n = 10/group) beginning at 4 weeks of age. Body composition and fasting blood glucose, insulin, and total cholesterol concentrations were examined intermittently. AT and liver mRNA expression (RT-PCR) of inflammatory mediators (F4/80, CD206 (AT only), CD11c (AT only) TLR-2 (AT only), TLR-4 (AT only), MCP-1, TNF-α, IL-6 (AT only), and IL-10 (AT only)) were measured along with activation of NFκB-p65, and JNK (western blot). Hepatic lipid accumulation, gene expression (RT-PCR) of hepatic metabolic markers (ACAC1, SREBP-1, PPAR-γ), protein content of Endoplasmic Reticulum (ER) Stress markers (BiP, phosphorylated and total EIF2α, phosphorylated and total IRE1α, CHOP), and hepatic oxidative capacity were assessed (western blot). Quercetin administration had no effect at mitigating increases in visceral AT, AT inflammation, hepatic steatosis, ER Stress, decrements in hepatic oxidative capacity, or the development of insulin resistance and hypercholesterolemia. In conclusion, 0.02% quercetin supplementation is not an effective therapy for attenuating HFD-induced obesity development. It is likely that a higher dose of quercetin supplementation is needed to elicit favorable outcomes in obesity.

Antiobesity Effects of Hydroethanolic Extract of Jacaranda decurrens Leaves

Obesity is a worldwide epidemic that reduces life expectancy; therefore, the search for new alternative and effective treatments is ongoing. The aim of the present investigation was to identify the chemical compounds in the hydroethanolic extract of leaves of Jacaranda decurrens subsp. symmetrifoliolata and to evaluate their toxicity and antiobesity effects. High-performance liquid chromatography was used to identify the chemical constituents, and acute toxicity was evaluated in rats treated with doses of 2 and 5 g·kg-1 body mass. The antiobesity effect was determined in rats with hypercaloric diet-induced obesity. Our results revealed the presence of compounds, such as jacaric, ursolic, and oleic acids, as well as luteolin, quercetin, and kaempferol, in the extract. The acute toxicity tests revealed that rats treated with elevated doses of the extract showed no signs of toxicity. The extract induced reduction in total body mass and the white adipose tissue depots. The obese rats treated with the extract showed an increased fluid intake and feces excretion while their serum total cholesterol and triglyceride levels decreased compared to those in the controls, without any hematological changes. Taken together, the results showed that the constituents of J. decurrens extracts included phenolic compounds and exhibited antiobesity effects with no toxicity.

Green tea extract intake during lactation modified cardiac macrophage infiltration and AMP-activated protein kinase phosphorylation in weanling rats from undernourished mother during gestation and lactation

Maternal dietary restriction is often associated with cardiovascular disease in offspring. The aim of this study was to investigate the effect of green tea extract (GTE) intake during lactation on macrophage infiltration, and activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and serine-threonine kinase Akt (Akt) in the hearts of weanlings exposed to maternal dietary protein restriction. Pregnant Wistar rats were fed control (C) or low-protein diets (LP) throughout gestation. Following delivery, the dams received a control or a GTE-containing control diet during lactation: control diet during gestation and lactation (CC), low-protein diet during gestation and lactation (LPC), low-protein diet during gestation and 0.12% GTE-containing low-protein diet during lactation (LPL), and low-protein diet during gestation and 0.24% GTE-containing low-protein diet during lactation (LPH). The female offspring were sacrificed at day 22. Biochemical parameters in the plasma, macrophage infiltration, degree of fibrosis and expression levels of AMPK and Akt were examined. The plasma insulin level increased in LPH compared with LPC. Percentage of the fibrotic areas and the number of macrophages in LPC were higher than those in CC. Conversely, the fibrotic areas and the macrophage number in LPH were smaller (21 and 56%, respectively) than those in LPC. The levels of phosphorylated AMPK in LPL and LPH, and Akt in LPH were greater than those in LPC. In conclusion, maternal protein restriction may induce macrophage infiltration and the decrease of insulin levels. However, GTE intake during lactation may suppress macrophage infiltration and restore insulin secretion function via upregulation of AMPK and insulin signaling in weanlings.

Phytochemicals as novel agents for the induction of browning in white adipose tissue

Obesity and its associated metabolic syndrome continue to be a health epidemic in westernized societies and is catching up in the developing world. Despite such increases, little headway has been made to reverse adverse weight gain in the global population. Few medical options exist for the treatment of obesity which points to the necessity for exploration of anti-obesity therapies including pharmaceutical and nutraceutical compounds. Defects in brown adipose tissue, a major energy dissipating organ, has been identified in the obese and is hypothesized to contribute to the overall metabolic deficit observed in obesity. Not surprisingly, considerable attention has been placed on the discovery of methods to activate brown adipose tissue. A variety of plant-derived, natural compounds have shown promise to regulate brown adipose tissue activity and enhance the lipolytic and catabolic potential of white adipose tissue. Through activation of the sympathetic nervous system, thyroid hormone signaling, and transcriptional regulation of metabolism, natural compounds such as capsaicin and resveratrol may provide a relatively safe and effective option to upregulate energy expenditure. Through utilizing the energy dissipating potential of such nutraceutical compounds, the possibility exists to provide a therapeutic solution to correct the energy imbalance that underlines obesity.

Role of nutraceutical SIRT1 modulators in AMPK and mTOR pathway: Evidence of a synergistic effect

OBJECTIVE

The aim of this study was to evaluate the effect of different natural substances on SIRT1 expression and on AMPK and mTOR phosphorylation. Moreover, we investigated the presence of a synergistic effect between the substances.

METHODS

Human cervical carcinoma cells were seeded in 12-well plates, then incubated with the nine tested substances (resveratrol, quercetin, berberine, catechin, tyrosol, ferulic acid, niclosamide, curcumin, and malvidin) at different concentrations and left in incubation for 3, 6, and 24 h. The targeting proteins' expression and phosphorylation were evaluated by immunoblotting, and cytotoxicity tests were performed by CellTiter-Blue Cell Viability Assay.

RESULTS

No statistically significant decrease (P > 0.05) in the number of viable cells was found. The expression of SIRT1 was significantly increased in all experimental groups compared with the control group (P < 0.001). Instead, the simultaneous administration involved a significant and synergistic increase in the expression of SIRT1 for some but not all of the tested compounds. Finally, the individual administration of berberine, quercetin, ferulic acid, and tyrosol resulted in a statistically significant increase in AMPK activation and mTOR inhibition, whereas their associated administration did not reveal a synergistic effect.

CONCLUSIONS

Our results provide evidence that all compounds have the potential to stimulate SIRT1 and sustain the stimulating action of resveratrol on SIRT1, already widely reported in the literature. In this regard, we confirm the interaction of these substances also with the pathway of AMPK and mTOR, in support of the studies that highlight the importance of SIRT1/AMPK and mTOR pathway in many diseases.

Luteolin reduces obesity-associated insulin resistance in mice by activating AMPKα1 signalling in adipose tissue macrophages

AIMS/HYPOTHESIS

Inflammatory polarisation of adipose tissue macrophages (ATMs) plays a critical role in the development of obesity-associated metabolic diseases such as insulin resistance and diabetes. Our previous study indicated that dietary luteolin (LU) could prevent the establishment of insulin resistance in mice fed a high-fat diet (HFD). Here, we further investigated the effects of LU, which is a natural flavonoid, on pre-established insulin resistance and obesity-associated ATM polarisation in mice.

METHODS

Five-week-old C57/BL6 mice were fed on a low-fat diet or HFD for 20 weeks, with some mice receiving supplementation with 0.01% LU from weeks 1 or 10 of the HFD to assess the actions of LU on insulin resistance and ATM polarisation. Furthermore, the role of LU in metabolic-dysfunction-associated macrophage phenotypes was investigated in vitro.

RESULTS

Dietary LU supplementation, either for 20 weeks or from weeks 10 to 20 of an HFD, significantly improved insulin resistance in HFD-fed mice. In addition, inflammatory macrophage infiltration and polarisation were suppressed in mouse epididymal adipose tissues. Furthermore, LU treatment directly reversed lipopolysaccharide-stimulated and metabolism-regulated molecules, and induced inflammatory polarisation in mouse RAW264.7 cells and peritoneal cavity resident macrophages. Finally, using the selective AMP-activated protein kinase (AMPK) inhibitor compound C and Ampkα1 (also known as Prkaa1) silencing with siRNA, we found that LU activated AMPKα1 in macrophages to inhibit their inflammatory polarisation and enhanced insulin signals in adipocytes that were stimulated with macrophage-conditioned media.

CONCLUSIONS/INTERPRETATION

Dietary LU ameliorated insulin resistance in diet-induced obese mice by promoting AMPKα1 signalling in ATMs.

Induction of heme oxygenase-1 with dietary quercetin reduces obesity-induced hepatic inflammation through macrophage phenotype switching

BACKGROUND/OBJECTIVES

Obesity-induced steatohepatitis accompanied by activated hepatic macrophages/Kupffer cells facilitates the progression of hepatic fibrinogenesis and exacerbates metabolic derangements such as insulin resistance. Heme oxyganase-1 (HO-1) modulates tissue macrophage phenotypes and thus is implicated in protection against inflammatory diseases. Here, we show that the flavonoid quercetin reduces obesity-induced hepatic inflammation by inducing HO-1, which promotes hepatic macrophage polarization in favor of the M2 phenotype.

MATERIALS/METHODS

Male C57BL/6 mice were fed a regular diet (RD), high-fat diet (HFD), or HFD supplemented with quercetin (HF+Que, 0.5g/kg diet) for nine weeks. Inflammatory cytokines and macrophage markers were measured by ELISA and RT-PCR, respectively. HO-1 protein was measured by Western blotting.

RESULTS

Quercetin supplementation decreased levels of inflammatory cytokines (TNFα, IL-6) and increased that of the anti-inflammatory cytokine (IL-10) in the livers of HFD-fed mice. This was accompanied by upregulation of M2 macrophage marker genes (Arg-1, Mrc1) and downregulation of M1 macrophage marker genes (TNFα, NOS2). In co-cultures of lipid-laden hepatocytes and macrophages, treatment with quercetin induced HO-1 in the macrophages, markedly suppressed expression of M1 macrophage marker genes, and reduced release of MCP-1. Moreover, these effects of quercetin were blunted by an HO-1 inhibitor and deficiency of nuclear factor E2-related factor 2 (Nrf2) in macrophages.

CONCLUSIONS

Quercetin reduces obesity-induced hepatic inflammation by promoting macrophage phenotype switching. The beneficial effect of quercetin is associated with Nrf2-mediated HO-1 induction. Quercetin may be a useful dietary factor for protecting against obesity-induced steatohepatitis.

Oral quercetin administration transiently protects respiratory function in dystrophin-deficient mice

KEY POINT

PGC-1α pathway activation has been shown to decrease disease severity and can be driven by quercetin. Oral quercetin supplementation protected respiratory function for 4-6 months during a 12 month dosing regimen. This transient protection was probably due to a failure to sustain elevated SIRT1 activity and downstream PGC-1α signalling. Quercetin supplementation may be a beneficial treatment as part of a cocktail provided continued SIRT1 activity elevation is achieved.

ABSTRACT

Duchenne muscular dystrophy (DMD) impacts 1 : 3500 boys and leads to muscle dysfunction culminating in death due to respiratory or cardiac failure. There is an urgent need for effective therapies with the potential for immediate application for this patient population. Quercetin, a flavonoid with an outstanding safety profile, may provide therapeutic relief to DMD patients as the wait for additional therapies continues. This study evaluated the capacity of orally administered quercetin (0.2%) in 2 month old mdx mice to improve respiratory function and end-point functional and histological outcomes in the diaphragm following 12 months of treatment. Respiratory function was protected for the first 4-6 months of treatment but appeared to become insensitive to quercetin thereafter. Consistent with this, end-point functional measures were decreased and histopathological measures were more severe in dystrophic muscle compared to C57 and similar between control-fed and quercetin-fed mdx mice. To better understand the transient nature of improved respiratory function, we measured PGC-1α pathway activity, which is suggested to be up-regulated by quercetin supplementation. This pathway was largely suppressed in dystrophic muscle compared to healthy muscle, and at the 14 month time point dietary quercetin enrichment did not increase expression of downstream effectors. These data support the efficacy of quercetin as an intervention for DMD in skeletal muscle, and also indicate the development of age-dependent quercetin insensitivity when continued supplementation fails to drive the PGC-1α pathway. Continued study is needed to determine if this is related to disease severity, age or other factors.

At the interface of antioxidant signalling and cellular function: Key polyphenol effects

The hypothesis that dietary (poly)phenols promote well‐being by improving chronic disease‐risk biomarkers, such as endothelial dysfunction, chronic inflammation and plasma uric acid, is the subject of intense current research, involving human interventions studies, animal models and in vitro mechanistic work. The original claim that benefits were due to the direct antioxidant properties of (poly)phenols has been mostly superseded by detailed mechanistic studies on specific molecular targets. Nevertheless, many proposed mechanisms in vivo and in vitro are due to modulation of oxidative processes, often involving binding to specific proteins and effects on cell signalling. We review the molecular mechanisms for 3 actions of (poly)phenols on oxidative processes where there is evidence in vivo from human intervention or animal studies. (1) Effects of (poly) phenols on pathways of chronic inflammation leading to prevention of some of the damaging effects associated with the metabolic syndrome. (2) Interaction of (poly)phenols with endothelial cells and smooth muscle cells, leading to effects on blood pressure and endothelial dysfunction, and consequent reduction in cardiovascular disease risk. (3) The inhibition of xanthine oxidoreductase leading to modulation of intracellular superoxide and plasma uric acid, a risk factor for developing type 2 diabetes.

Corosolic acid inhibits adipose tissue inflammation and ameliorates insulin resistance via AMPK activation in high-fat fed mice

BACKGROUND

Adipose tissue inflammation is tightly associated with the development of insulin resistance. Corosolic acid (CRA), a natural triterpenoid, is well known as "phyto-insulin" due to its insulin-like activities. However, its underlying mechanism remains unknown.

PURPOSE

In this study, we investigated the mechanisms of CRA on improving insulin resistance both in vivo and in vitro.

METHODS

C57BL/6 mice were fed with normal diet, high-fat diet (HFD) or HFD with CRA, respectively. General biochemical parameters in blood and glucose intolerance in mice were assayed. Meanwhile, proinflammatory cytokines and macrophage infiltrations in adipose tissues were analyzed by real-time PCR and immunohistochemical staining. The effects of CRA on insulin signaling transduction and AMPK activity in adipose tissues were investigated by western blot. Furthermore, the effects of CRA on AMPK were confirmed on 3T3-L1 cells by using both AMPK inhibitor and AMPKα1/2-specific siRNA RESULTS: CRA attenuated hyperlipidemia, improved insulin sensitivity and glucose intolerance in mice. Meanwhile, it alleviated inflammation in adipose tissues, demonstrated by the suppression of IKKβ phosphorylation and down-regulation of gene expressions of proinflammatory cytokines. Histological analysis revealed that CRA attenuated macrophage infiltrations into adipose tissue. It also improved insulin signaling transduction by modification of Ser/Thr phosphorylation of IRS-1 and downstream Akt, thereby improved insulin sensitivity in HFD-fed mice. Furthermore, CRA regulated AMPK activation in a LKB1-dependent manner. AMPKα knockdown in adipocytes abolished the inhibitory effects of CRA on IKKβ and IRS-1 serine phosphorylation, indicating that CRA inhibited inflammation and ameliorated insulin resistance via AMPK activation.

CONCLUSIONS

CRA inhibited inflammation with improvement in adipose tissue dysfunction and ameliorated insulin resistance in an AMPK-dependent manner.

Non-alcoholic steatohepatitis: emerging molecular targets and therapeutic strategies

Non-alcoholic fatty liver disease - the most common chronic liver disease - encompasses a histological spectrum ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). Over the next decade, NASH is projected to be the most common indication for liver transplantation. The absence of an effective pharmacological therapy for NASH is a major incentive for research into novel therapeutic approaches for this condition. The current focus areas for research include the modulation of nuclear transcription factors; agents that target lipotoxicity and oxidative stress; and the modulation of cellular energy homeostasis, metabolism and the inflammatory response. Strategies to enhance resolution of inflammation and fibrosis also show promise to reverse the advanced stages of liver disease.

Bergamot Reduces Plasma Lipids, Atherogenic Small Dense LDL, and Subclinical Atherosclerosis in Subjects with Moderate Hypercholesterolemia: A 6 Months Prospective Study

Background: Some patients experience statin-induced side effects or prefer nutraceutical approaches for the treatment of dyslipidemia. This has led to a search for alternative therapeutic approaches for dyslipidemia management. In recent studies Citrus bergamia (known as Bergamot) juice was able to reduce serum levels of lipids. Such benefit may be attributed to high amounts of flavonoids contained in Bergamot fruit juice (neoeriocitrin, neohesperidin, naringin). The aim of the present study was to fully investigate the effects of a Bergamot extract on cardio-metabolic parameters, including plasma lipids, atherogenic lipoproteins and subclinical atherosclerosis.

Methods: Eighty subjects (42 men and 38 women, mean age: 55 ± 13 years) with moderate hypercholesterolemia [e.g., with plasma LDL-cholesterol concentrations between 160 and 190 mg/dl (between 4.1 and 4.9 mmol/l)] were included. A Bergamot-derived extract (Bergavit R^®) was given at a fixed dose daily (150 mg of flavonoids, with 16% of neoeriocitrin, 47% of neohesperidin and 37% of naringin) for 6 months. Lipoprotein subfractions were assessed by gel electrophoresis. With this methodology low density lipoprotein (LDL) subclasses are distributed as seven bands (LDL-1 and -2 as large LDL, and LDL-3 to -7 as atherogenic small, dense LDL). Subclinical atherosclerosis was assessed by carotid intima-media thickness (cIMT) using B-mode ultrasound.

Results: After 6 months, Bergavit R^® reduced total cholesterol (from 6.6 ± 0.4 to 5.8 ± 1.1 mmol/l, p < 0.0001), triglycerides (from 1.8 ± 0.6 to 1.5 ± 0.9 mmol/l, p = 0.0020), and LDL-cholesterol (from 4.6 ± 0.2 to 3.7 ± 1.0 mmol/l, p < 0.0001), while HDL- cholesterol increased (from 1.3 ± 0.2 to 1.4 ± 0.4 mmol/l, p < 0.0007). In addition, a significant increase in LDL-1 (from 41.2 ± 0.2 to 49.6 ± 0.2%, p < 0.0001) was accompanied by decreased small, dense LDL-3, -4, and 5 particles (from 14.5 ± 0.1 to 9.0 ± 0.1% p < 0.0001; 3.2 ± 0.1 to 1.5 ± 0.1% p = 0.0053; 0.3 ± 0.0% to 0.1 ± 0.0% p = 0.0133, respectively). cIMT also decreased from 1.2 ± 0.4 to 0.9 ± 0.1 mm (p < 0.0001).

Conclusion: This is the first study investigating the effects of Bergamot flavonoids supplementation on cardio-metabolic risk in dyslipidemic subjects. Bergavit R^® (Bergamot juice extract) supplementation significantly reduced plasma lipids and improved the lipoprotein profile. cIMT was also reduced significantly over a relatively short time frame of 6 months.

Quercetin oppositely regulates insulin-mediated glucose disposal in skeletal muscle under normal and inflammatory conditions: The dual roles of AMPK activation

SCOPE

Quercetin is a dietary flavonoid whose role in the regulation of the activity of insulin remains controversial. Our study aimed to investigate how quercetin and its major metabolite quercetin-3-glucuronide (Q-3-G) regulate insulin-mediated glucose disposal in skeletal muscle under normal and inflammatory conditions.

METHODS AND RESULTS

Under normal conditions, quercetin impaired glucose and insulin tolerance and attenuated insulin-mediated phosphorylation of Akt substrate of 160 kDa (AS160) and TBC1D1 without affecting Akt activity in male Institute of Cancer Research (ICR) mice. However, under inflammatory conditions, quercetin exhibited an opposite effect in these animals. In C2C12 cells, quercetin also decreased insulin-stimulated AS160 and TBC1D1 phosphorylation and glucose uptake in the absence of an inflammatory insult, whereas it improved the action of insulin under inflammatory conditions. Knockdown of adenosine 5'-monophosphate-activated protein kinase α (AMPKα) blocked the differential effects of quercetin under both conditions. Unlike quercetin, Q-3-G had no influence on insulin-induced phosphorylation of AS160 and TBC1D1 and glucose uptake in C2C12 myotubes under normal conditions. Q-3-G displayed a similar regulation with quercetin in glucose disposal under inflammatory conditions.

CONCLUSION

Quercetin suppressed insulin-mediated glucose disposal in skeletal muscle tissue/cells under normal conditions while it ameliorated impaired glucose uptake under inflammatory conditions with activation of AMPK. In contrast, Q-3-G ameliorated insulin resistance in skeletal cells under inflammatory conditions without affecting glucose disposal under normal conditions.

The sirtuins: Markers of metabolic health

The sirtuins represent a class of proteins first discovered orthologus to the yeast silent information regulator 2 protein that have been retained in mammalian species. Currently, seven sirtuins have been identified in humans, and their functions currently surpass their originally identified role as histone deacetylase and chromatin silencers to encompass nutrient sensing and metabolic function. All seven sirtuins require NAD(+) in order to carry out their enzymatic activity, and thus become activated in conditions of nutrient depletion, starvation, and cellular stress. Caloric restriction and increased physical activity have been postulated, though perhaps controversially, to mediate sirtuin function. Here, we review the current literature surrounding the functions of the seven human sirtuins, mediators of their function, and the roles they play in metabolic health related to dietary and physical activity interventions. Despite the controversy surrounding sirtuin function with regard to longevity, we have aimed to show that regardless of its effects on aging, sirtuin function is pivotal to pathways involving metabolic health, and should therefore be investigated with regard to improving metabolic diseases such as obesity and type 2 diabetes.

Salicornia herbacea prevents weight gain and hepatic lipid accumulation in obese ICR mice fed a high-fat diet

BACKGROUND

Foods that are rich in fat and or sodium chloride promote obesity and associated diseases, whereas intake of dietary fiber averts obesity development. Salicornia herbacea (SH) is a rich source of dietary fiber and high in sodium chloride; therefore, we investigated whether replacing common salt with SH in a high-fat diet could prevent obesity development.

RESULTS

Mice were divided into five groups: group ND was fed a normal diet, group HD was fed a high-fat diet, group HD-NaCl was fed a high fat diet with sodium chloride 10 g kg(-1) , group HD-CL was fed a high-fat diet with cellulose 30 g kg(-1) and group HD-SH was fed a high-fat diet with SH powder 50 g kg(-1) . The amount of sodium chloride and cellulose added in the respective diet was equivalent to their amount in SH. Data from our study showed that, SH supplementation significantly decreased body weight gain, liver weight, hepatic triglyceride, serum leptin and insulin, along with the mRNA level of key lipid anabolic genes such as SREBP-1c, PPARγ and FAS compared to the HD group.

CONCLUSION

The results of this study demonstrated that SH is a potential natural anti-obesity agent that can be used in place of sodium chloride.

Antioxidant Phytochemicals for the Prevention and Treatment of Chronic Diseases

Overproduction of oxidants (reactive oxygen species and reactive nitrogen species) in the human body is responsible for the pathogenesis of some diseases. The scavenging of these oxidants is thought to be an effective measure to depress the level of oxidative stress of organisms. It has been reported that intake of vegetables and fruits is inversely associated with the risk of many chronic diseases, and antioxidant phytochemicals in vegetables and fruits are considered to be responsible for these health benefits. Antioxidant phytochemicals can be found in many foods and medicinal plants, and play an important role in the prevention and treatment of chronic diseases caused by oxidative stress. They often possess strong antioxidant and free radical scavenging abilities, as well as anti-inflammatory action, which are also the basis of other bioactivities and health benefits, such as anticancer, anti-aging, and protective action for cardiovascular diseases, diabetes mellitus, obesity and neurodegenerative diseases. This review summarizes recent progress on the health benefits of antioxidant phytochemicals, and discusses their potential mechanisms in the prevention and treatment of chronic diseases.

Quercetin suppresses immune cell accumulation and improves mitochondrial gene expression in adipose tissue of diet-induced obese mice

SCOPE

To examine the effect of dietary quercetin on the function of epididymal adipose tissue (EAT) in Western diet-induced obese mice.

METHODS AND RESULTS

C57BL/6J mice were fed a control diet; a Western diet high in fat, cholesterol, and sucrose; or the same Western diet containing 0.05% quercetin for 18 weeks. Supplementation with quercetin suppressed the increase in the number of macrophages, the decrease in the ratio of CD4(+) to CD8(+) T cells in EAT, and the elevation of plasma leptin and tumor necrosis factor α levels in mice fed the Western diet. Comprehensive gene expression analysis revealed that quercetin suppressed gene expression associated with the accumulation and activation of immune cells, including macrophages and lymphocytes in EAT. It also improved the expression of the oxidative stress-sensitive transcription factor NFκB, NADPH oxidases, and antioxidant enzymes. Quercetin markedly increased gene expression associated with mitochondrial oxidative phosphorylation and mitochondrial DNA content.

CONCLUSION

Quercetin most likely universally suppresses the accumulation and activation of immune cells, including antiinflammatory cells, whereas it specifically increased gene expression associated with mitochondrial oxidative phosphorylation. Suppression of oxidative stress and NFκB activity likely contributed to the prevention of the accumulation and activation of immune cells and resulting chronic inflammation.

Inhibition of HMGB1 release via salvianolic acid B-mediated SIRT1 up-regulation protects rats against non-alcoholic fatty liver disease

The inflammatory mediator high-mobility group box 1 (HMGB1) plays a critical role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). However, the regulation of HMGB1 in NAFLD, particularly through sirtuin 1 (SIRT1), remains unclear. In this study, we investigated the role of SIRT1-mediated inhibition of HMGB1 release in NAFLD and the effect of salvianolic acid B (SalB), which is a water-soluble phenolic acid extracted from Radix Salvia miltiorrhiza, on NAFLD through SIRT1/HMGB1 signaling. In vivo, SalB treatment significantly attenuated high-fat diet (HFD)-induced liver damage, hepatic steatosis, and inflammation. Importantly, SalB significantly inhibited HMGB1 nuclear translocation and release, accompanied by SIRT1 elevation. In HepG2 cells, palmitic acid (PA)-induced pro-inflammatory cytokines release were blocked by HMGB1 small interfering RNA (siRNA) transfection. Moreover, pharmacological SIRT1 inhibition by Ex527 induced HMGB1 translocation and release, whereas SIRT1 activation by resveratrol or SalB reversed this trend. SIRT1 siRNA abrogated the SalB-mediated inhibition of HMGB1 acetylation and release, suggesting that SalB-mediated protection occurs by SIRT1 targeting HMGB1 for deacetylation. We are the first to demonstrate that the SIRT1/HMGB1 pathway is a key therapeutic target for controlling NAFLD inflammation and that SalB confers protection against HFD- and PA-induced hepatic steatosis and inflammation through SIRT1-mediated HMGB1 deacetylation.