Quercetin Upregulates Uncoupling Protein 1 in White/Brown Adipose Tissues through Sympathetic Stimulation

The bioavailability, absorption, metabolism, and regulation of glucolipid metabolism disorders by quercetin and its important glycosides: A review

Quercetin and its glycosides (QG), vitally natural flavonoid, have been popular for health benefits. However, the absorption and metabolism affect their bioavailability, and the metabolic transformation alters their biological activities. This review systematically summarizes the bioavailability and pathways for the absorption and metabolism of quercetin/QG in vivo and in vitro, the biological activities and mechanism of quercetin/QG and their metabolites in treating glucolipid metabolism are discussed. After oral administration, quercetin/QG are mainly absorbed by the intestine, undergo phase II metabolism in the small intestine and liver to form conjugates and are metabolized into small phenolic acids by intestinal microbiota. Quercetin/QG and their metabolites exert beneficial effects on regulating glucolipid metabolism disorders, including improving insulin resistance, inhibiting lipogenesis, enhancing thermogenesis, modulating intestinal microbiota, relieving oxidative stress, and attenuating inflammation. This review enhances understanding of the mechanism of quercetin/QG regulate glucolipid metabolism and provides scientific support for the development of functional foods.

Roles of citrus fruits on energy expenditure, body weight management, and metabolic biomarkers: a comprehensive review

Citrus fruits are widely consumed for their nutritional and health benefits. They belong to the Rutaceae and have many varieties, such as sweet orange (Citrus sinensis), which is the most popular. Citrus fruits are rich in water (>80%), dietary fiber, and vitamins. They also contain bioactive components, which may modulate energy metabolism and lipid oxidation through various mechanisms. These mechanisms include stimulating β3-adrenergic receptors, increasing mitochondrial biogenesis and thermogenesis, activating AMP kinase and peroxisome proliferator-activated receptor-gamma coactivator-1α pathways, inhibiting lipogenesis and lipid accumulation, and inducing browning of white adipose tissue. This review summarizes the mechanisms and outcomes of citrus fruits and their metabolites on energy metabolism and body weight in different experimental models. The literature was searched for in vitro and in vivo animal and human studies that investigated the effects of citrus consumption on energy expenditure, thermogenesis, adipogenesis, and lipid accumulation. Citrus fruits and their metabolites have shown promising effects on energy metabolism and lipid oxidation in in vitro and in vivo animal studies. However, the evidence from human studies is limited and inconsistent. Possible reasons for the discrepancy are briefly discussed, and knowledge gaps and research needs are identified for future studies. Citrus fruits may have beneficial effects on energy metabolism and body weight, but more rigorous and well-designed human trials are needed to confirm their efficacy and safety.

Cymbopogon schoenanthus (L) extract ameliorates high fat diet-induced obesity and dyslipidemia via reducing expression of lipogenic and thermogenic proteins

Globally, obesity has become one of the major health problems. This study was conducted to evaluate the anti-obesity potential of Cymbopogon schoenanthus methanolic extract (CS) in rats. Fifty male Wistar rats of six to eight weeks old, 100-120 g body weight (BW) were randomly assigned into 5 groups (n = 10): The control group was fed a basal diet. CS-group was supplied with basal diet and orally given CS (200 mg/kg BW) for 12 weeks. HFD-group was fed a high-fat diet (HFD) for 18 weeks. HFD + CS-group was fed on HFD and CS HFD then CS-group was fed HFD for 12 weeks then shifted to basal diet and CS for another 6 weeks. Phytochemical analysis of CS indicated the presence of various terpenes and flavonoid compounds. Among the compounds characterized are quercetin, apigenin, luteolin, orientin, eudesmene, cymbopogonol, caffeic acid, coumaric acid, and linolenic acid. Supplementation of HFD significantly increased the body weight, levels of serum triacylglycerol, total cholesterol, very low-density lipoprotein, low-density lipo-protein (HDL), glucose, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. In addition, HFD up-regulated the protein expression of uncoupling protein (UCP)-1 in both brown and white adipose tissue; and the expression of hepatic mRNA of sterol regulatory element-binding protein (SREBP)-1c and SREBP-2. However, it decreased the serum level of HDL, and protein expression level of UCP-1 in both brown and white adipose tissue. Treatment of HFD-fed animals with CS extract either concurrently (HFD + CS-group), or after obesity induction (HFD then CS-group) significantly reversed all HFD-induced alterations in body weight; food intake; serum biochemical profile (including hyperglycemia, dyslipidemia); and tissue gene expressions. These results indicate that CS methanolic extract ameliorated HFD-induced obesity, serum biochemical, hepatic, and adipose tissue gene expression alterations. CS extract accomplished these effects mostly through its various identified bioactive compounds which have been proven to have anti-obesity and anti-diabetic activities.

Healthy Aging in Times of Extreme Temperatures: Biomedical Approaches

Climate extremes and rising energy prices present interconnected global health risks. Technical solutions can be supplemented with biomedical approaches to promote healthy longevity in hot and cold conditions. In summer, reducing basal metabolic rate through mild caloric restriction or CR mimetics, such as resveratrol, can potentially be used to lower body temperature. In winter, activating brown adipose tissue (BAT) for non-shivering thermogenesis and improved metabolic health can help adaptation to colder environments. Catechins found in green tea and in other food could be alternatives to drugs for these purposes. This review examines and discusses the biomedical evidence supporting the use of CR mimetics and BAT activators for health benefits amid increasingly extreme temperatures.

Mulberry leaf flavonoids activate BAT and induce browning of WAT to improve type 2 diabetes via regulating the AMPK/SIRT1/PGC-1α signaling pathway

Mulberry (Morus alba L.) leaf is a well-established traditional Chinese botanical and culinary resource. It has found widespread application in the management of diabetes. The bioactive constituents of mulberry leaf, specifically mulberry leaf flavonoids (MLFs), exhibit pronounced potential in the amelioration of type 2 diabetes (T2D). This potential is attributed to their ability to safeguard pancreatic β cells, enhance insulin resistance, and inhibit α-glucosidase activity. Our antecedent research findings underscore the substantial therapeutic efficacy of MLFs in treating T2D. However, the precise mechanistic underpinnings of MLF's anti-T2D effects remain the subject of inquiry. Activation of brown/beige adipocytes is a novel and promising strategy for T2D treatment. In the present study, our primary objective was to elucidate the impact of MLFs on adipose tissue browning in db/db mice and 3T3-L1 cells and elucidate its underlying mechanism. The results manifested that MLFs reduced body weight and food intake, alleviated hepatic steatosis, improved insulin sensitivity, and increased lipolysis and thermogenesis in db/db mice. Moreover, MLFs activated brown adipose tissue (BAT) and induced the browning of inguinal white adipose tissue (IWAT) and 3T3-L1 adipocytes by increasing the expressions of brown adipocyte marker genes and proteins such as uncoupling protein 1 (UCP1) and beige adipocyte marker genes such as transmembrane protein 26 (Tmem26), thereby promoting mitochondrial biogenesis. Mechanistically, MLFs facilitated the activation of BAT and the induction of WAT browning to ameliorate T2D primarily through the activation of AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) signaling pathway. These findings highlight the unique capacity of MLF to counteract T2D by enhancing BAT activation and inducing browning of IWAT, thereby ameliorating glucose and lipid metabolism disorders. As such, MLFs emerge as a prospective and innovative browning agent for the treatment of T2D.

Recent Advances in Potential Health Benefits of Quercetin

Quercetin, a flavonoid found in fruits and vegetables, has been a part of human diets for centuries. Its numerous health benefits, including antioxidant, antimicrobial, anti-inflammatory, antiviral, and anticancer properties, have been extensively studied. Its strong antioxidant properties enable it to scavenge free radicals, reduce oxidative stress, and protect against cellular damage. Quercetin's anti-inflammatory properties involve inhibiting the production of inflammatory cytokines and enzymes, making it a potential therapeutic agent for various inflammatory conditions. It also exhibits anticancer effects by inhibiting cancer cell proliferation and inducing apoptosis. Finally, quercetin has cardiovascular benefits such as lowering blood pressure, reducing cholesterol levels, and improving endothelial function, making it a promising candidate for preventing and treating cardiovascular diseases. This review provides an overview of the chemical structure, biological activities, and bioavailability of quercetin, as well as the different delivery systems available for quercetin. Incorporating quercetin-rich foods into the diet or taking quercetin supplements may be beneficial for maintaining good health and preventing chronic diseases. As research progresses, the future perspectives of quercetin appear promising, with potential applications in nutraceuticals, pharmaceuticals, and functional foods to promote overall well-being and disease prevention. However, further studies are needed to elucidate its mechanisms of action, optimize its bioavailability, and assess its long-term safety for widespread utilization.

Influence of Polyphenols on Adipose Tissue: Sirtuins as Pivotal Players in the Browning Process

Adipose tissue (AT) can be classified into two different types: (i) white adipose tissue (WAT), which represents the largest amount of total AT, and has the main function of storing fatty acids for energy needs and (ii) brown adipose tissue (BAT), rich in mitochondria and specialized in thermogenesis. Many exogenous stimuli, e.g., cold, exercise or pharmacological/nutraceutical tools, promote the phenotypic change of WAT to a beige phenotype (BeAT), with intermediate characteristics between BAT and WAT; this process is called "browning". The modulation of AT differentiation towards WAT or BAT, and the phenotypic switch to BeAT, seem to be crucial steps to limit weight gain. Polyphenols are emerging as compounds able to induce browning and thermogenesis processes, potentially via activation of sirtuins. SIRT1 (the most investigated sirtuin) activates a factor involved in mitochondrial biogenesis, peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), which, through peroxisome proliferator-activated receptor γ (PPAR-γ) modulation, induces typical genes of BAT and inhibits genes of WAT during the transdifferentiation process in white adipocytes. This review article aims to summarize the current evidence, from pre-clinical studies to clinical trials, on the ability of polyphenols to promote the browning process, with a specific focus on the potential role of sirtuins in the pharmacological/nutraceutical effects of natural compounds.

Quercetin 3-O-glucuronide-rich lotus leaf extract promotes a Brown-fat-phenotype in C3H10T1/2 mesenchymal stem cells

Lotus (Nelumbo nucifera Gaertn.) is an aquatic perennial crop planted worldwide and its leaf (also called "He-Ye") has therapeutic effects on obesity. However, whether the underlying mechanism leads to increased energy expenditure by activation of brown adipocytes has not been clarified. Here, murine C₃H₁₀T_1/2 mesenchymal stem cells (MSCs) were employed to investigate the effects of ethanol extracts from lotus leaf (LLE) on brown adipocytes formation and the underlying molecular mechanisms. The results showed LLE was rich in polyphenols (383.7 mg/g) and flavonoids (178.3 mg/g), with quercetin 3-O-glucuronide (Q3G) the most abundant (128.2 μg/mg). In LLE-treated C₃H₁₀T_1/2 MSCs, the expressions of lipolytic factors (e.g., ATGL, HSL, and ABHD5) and brown regulators (e.g., Sirt1, PGC-1α, Cidea, and UCP1) were significantly upregulated compared to that in the untreated MSCs. Furthermore, LLE promoted mitochondrial biogenesis and fatty acid β-oxidation, as evidenced by increases in the expression of Tfam, Cox7A, CoxIV, Cox2, Pparα, and Adrb3. Likewise, enhanced browning and mitochondrial biogenesis were also observed in Q3G-stimulated cells. Importantly, LLE and Q3G induced phosphorylation of AMPK accompanied by a remarkable increase in the brown fat marker UCP1, while pretreatment with Compound C (an AMPK inhibitor) reversed these changes. Moreover, stimulating LLE or Q3G-treated cells with CL316243 (a beta3-AR agonist) increased p-AMPKα/AMPKα ratio and UCP1 protein expression, indicating β3-AR/AMPK signaling may involve in this process. Collectively, these observations suggested that LLE, especially the component Q3G, stimulates thermogenesis by activating brown adipocytes, which may involve the β3-AR/AMPK signaling pathway.

Nutraceuticals in Brown Adipose Tissue Activation

Obesity and its associated comorbidities have become pandemic, and challenge the global healthcare system. Lifestyle changes, nutritional interventions and phamaceuticals should be differently combined in a personalized strategy to tackle such a public health burden. Altered brown adipose tissue (BAT) function contributes to the pathophysiology of obesity and glucose metabolism dysfunctions. BAT thermogenic activity burns glucose and fatty acids to produce heat through uncoupled respiration, and can dissipate the excessive calorie intake, reduce glycemia and circulate fatty acids released from white adipose tissue. Thus, BAT activity is expected to contribute to whole body energy homeostasis and protect against obesity, diabetes and alterations in lipid profile. To date, pharmacological therapies aimed at activating brown fat have failed in clinical trials, due to cardiovascular side effects or scarce efficacy. On the other hand, several studies have identified plant-derived chemical compounds capable of stimulating BAT thermogenesis in animal models, suggesting the translational applications of dietary supplements to fight adipose tissue dysfunctions. This review describes several nutraceuticals with thermogenic properties and provides indications, at a molecular level, of the regulation of the adipocyte thermogenesis by the mentioned phytochemicals.

Reduction of Obesity and Insulin Resistance through Dual Targeting of VAT and BAT by a Novel Combination of Metabolic Cofactors

Obesity is an epidemic disease worldwide, characterized by excessive fat accumulation associated with several metabolic perturbations, such as metabolic syndrome, insulin resistance, hypertension, and dyslipidemia. To improve this situation, a specific combination of metabolic cofactors (MC) (betaine, N-acetylcysteine, L-carnitine, and nicotinamide riboside) was assessed as a promising treatment in a high-fat diet (HFD) mouse model. Obese animals were distributed into two groups, orally treated with the vehicle (obese + vehicle) or with the combination of metabolic cofactors (obese + MC) for 4 weeks. Body and adipose depots weights; insulin and glucose tolerance tests; indirect calorimetry; and thermography assays were performed at the end of the intervention. Histological analysis of epidydimal white adipose tissue (EWAT) and brown adipose tissue (BAT) was carried out, and the expression of key genes involved in both fat depots was characterized by qPCR. We demonstrated that MC supplementation conferred a moderate reduction of obesity and adiposity, an improvement in serum glucose and lipid metabolic parameters, an important improvement in lipid oxidation, and a decrease in adipocyte hypertrophy. Moreover, MC-treated animals presented increased adipose gene expression in EWAT related to lipolysis and fatty acid oxidation. Furthermore, MC supplementation reduced glucose intolerance and insulin resistance, with an increased expression of the glucose transporter Glut4; and decreased fat accumulation in BAT, raising non-shivering thermogenesis. This treatment based on a specific combination of metabolic cofactors mitigates important pathophysiological characteristics of obesity, representing a promising clinical approach to this metabolic disease.

The metabolic and molecular mechanisms of α‑mangostin in cardiometabolic disorders (Review)

α-mangostin is a xanthone predominantly encountered in Garcinia mangostana. Extensive research has been carried out concerning the effects of this compound on various diseases, including obesity, cancer and metabolic disorders. The present review suggests that α-mangostin exerts promising anti-obesity, hepatoprotective, antidiabetic, cardioprotective, antioxidant and anti-inflammatory effects on various pathways in cardiometabolic diseases. The anti-obesity effects of α-mangostin include the reduction of body weight and adipose tissue size, the increase in fatty acid oxidation, the activation of hepatic AMP-activated protein kinase and Sirtuin-1, and the reduction of peroxisome proliferator-activated receptor γ expression. Hepatoprotective effects have been revealed, due to reduced fibrosis through transforming growth factor-β 1 pathways, reduced apoptosis and steatosis through reduced sterol regulatory-element binding proteins expression. The antidiabetic effects include decreased fasting blood glucose levels, improved insulin sensitivity and the increased expression of GLUT transporters in various tissues. Cardioprotection is exhibited through the restoration of cardiac functions and structure, improved mitochondrial functions, the promotion of M2 macrophage populations, reduced endothelial and cardiomyocyte apoptosis and fibrosis, and reduced acid sphingomyelinase activity and ceramide depositions. The antioxidant effects of α-mangostin are mainly related to the modulation of antioxidant enzymes, the reduction of oxidative stress markers, the reduction of oxidative damage through a reduction in Sirtuin 3 expression mediated by phosphoinositide 3-kinase/protein kinase B/peroxisome proliferator-activated receptor-γ coactivator-1α signaling pathways, and to the increase in Nuclear factor-erythroid factor 2-related factor 2 and heme oxygenase-1 expression levels. The anti-inflammatory effects of α-mangostin include its modulation of nuclear factor-κB related pathways, the suppression of mitogen-activated protein kinase activation, increased macrophage polarization to M2, reduced inflammasome occurrence, increased Sirtuin 1 and 3 expression, the reduced expression of inducible nitric oxide synthase, the production of nitric oxide and prostaglandin E2, the reduced expression of Toll-like receptors and reduced proinflammatory cytokine levels. These effects demonstrate that α-mangostin may possess the properties required for a suitable candidate compound for the management of cardiometabolic diseases.

Impact of Phytochemicals on PPAR Receptors: Implications for Disease Treatments

Peroxisome proliferator-activated receptors (PPARs) are members of the ligand-dependent nuclear receptor family. PPARs have attracted wide attention as pharmacologic mediators to manage multiple diseases and their underlying signaling targets. They mediate a broad range of specific biological activities and multiple organ toxicity, including cellular differentiation, metabolic syndrome, cancer, atherosclerosis, neurodegeneration, cardiovascular diseases, and inflammation related to their up/downstream signaling pathways. Consequently, several types of selective PPAR ligands, such as fibrates and thiazolidinediones (TZDs), have been approved as their pharmacological agonists. Despite these advances, the use of PPAR agonists is known to cause adverse effects in various systems. Conversely, some naturally occurring PPAR agonists, including polyunsaturated fatty acids and natural endogenous PPAR agonists curcumin and resveratrol, have been introduced as safe agonists as a result of their clinical evidence or preclinical experiments. This review focuses on research on plant-derived active ingredients (natural phytochemicals) as potential safe and promising PPAR agonists. Moreover, it provides a comprehensive review and critique of the role of phytochemicals in PPARs-related diseases and provides an understanding of phytochemical-mediated PPAR-dependent and -independent cascades. The findings of this research will help to define the functions of phytochemicals as potent PPAR pharmacological agonists in underlying disease mechanisms and their related complications.

Potential Role of Quercetin in Polycystic Ovary Syndrome and Its Complications: A Review

Polycystic ovary syndrome (PCOS) is a common multisystem disease with reproductive, metabolic and psychological abnormalities. It is characterized by a high prevalence rate in women of childbearing age and highly heterogeneous clinical manifestations, which seriously harm women’s physical and mental health. Quercetin (QUR) is a natural compound of flavonoids found in a variety of foods and medicinal plants. It can intervene with the pathologic process of PCOS from multiple targets and channels and has few adverse reactions. It is mentioned in this review that QUR can improve ovulation disorder, relieve Insulin resistance (IR), reduce androgen, regulate lipid metabolism, regulate gut microbiota and improve vascular endothelial function, which is of great significance in the treatment of PCOS.

Factors Associated with White Fat Browning: New Regulators of Lipid Metabolism

Mammalian adipose tissue can be divided into white and brown adipose tissue based on its colour, location, and cellular structure. Certain conditions, such as sympathetic nerve excitement, can induce the white adipose adipocytes into a new type of adipocytes, known as beige adipocytes. The process, leading to the conversion of white adipocytes into beige adipocytes, is called white fat browning. The dynamic balance between white and beige adipocytes is closely related to the body’s metabolic homeostasis. Studying the signal transduction pathways of the white fat browning might provide novel ideas for the treatment of obesity and alleviation of obesity-related glucose and lipid metabolism disorders. This article aimed to provide an overview of recent advances in understanding white fat browning and the role of BAT in lipid metabolism.

Rutaecarpine Promotes Adipose Thermogenesis and Protects against HFD-Induced Obesity via AMPK/PGC-1α Pathway

Pharmacological activation of adaptive thermogenesis to increase energy expenditure is considered to be a novel strategy for obesity. Peroxisome-proliferator-activated receptor γ co-activator-1α (PGC-1α), which serves as an inducible co-activator in energy expenditure, is highly expressed in brown adipose tissues (BAT). In this study, we found a PGC-1α transcriptional activator, natural compound rutaecarpine (Rut), which promoted brown adipocytes mitochondrial biogenesis and thermogenesis in vitro. Chronic Rut treatment reduced the body weight gain and mitigated insulin sensitivity through brown and beige adipocyte thermogenesis. Mechanistic study showed that Rut activated the energy metabolic pathway AMP-activated protein kinase (AMPK)/PGC-1α axis, and deficiency of AMPK abolished the beneficial metabolic phenotype of the Rut treatment in vitro and in vivo. In summary, a PGC-1α transcriptional activator Rut was found to activate brown and beige adipose thermogenesis to resist diet-induced obesity through AMPK pathway. Our findings serve as a further understanding of the natural compound in adipose tissue and provides a possible strategy to combat obesity and related metabolic disorders.

A critical evaluation of risk to reward ratio of quercetin supplementation for COVID-19 and associated comorbid conditions

The interim results of the large, multinational trials on coronavirus disease 2019 (COVID‐19) using a combination of antiviral drugs appear to have little to no effect on the 28‐day mortality or the in‐hospital course. Therefore, there is a still vivid interest in finding alternate re‐purposed drugs and nutrition supplements, which can halt or slow the disease severity. We review here the multiple preclinical studies, partially supported by clinical evidence showing the quercetin's possible therapeutic/prophylaxis efficacy against severe acute respiratory syndrome coronavirus (SARS‐CoV) as well as comorbidities like chronic obstructive pulmonary disease (COPD), diabetes mellitus, obesity, coagulopathy, and hypertension. Currently, 14 interventional clinical trials are underway assessing the efficacy of quercetin along with other antiviral drugs/nutritional supplements as prophylaxis/treatment option against COVID‐19. The present review is tempting to suggest that, based on circumstantial scientific evidence and preliminary clinical data, the flavonoid quercetin can ameliorate COVID‐19 infection and symptoms acting in concert on two parallel and independent paths: inhibiting key factors responsible for SARS‐CoV‐2 infections and mitigating the clinical manifestations of the disease in patients with comorbid conditions. Despite the broad therapeutic properties of quercetin, further high power randomized clinical trials are needed to firmly establish its clinical efficacy against COVID‐19.

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

ETHNOPHARMACOLOGICAL RELEVANCE

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

AIM OF THIS REVIEW

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Metabolic functions of flavonoids: From human epidemiology to molecular mechanism

Dietary flavonoid intake is associated with the regulation of nutrient metabolism in the living body. Observational and cohort studies have reported a negative association between flavonoid intake and the risk of metabolic and cardiovascular diseases. Several intervention trials in humans have also supported the benefits of dietary flavonoids. In experimental studies using animal models, a daily diet rich in typical flavonoids such as catechins, anthocyanin, isoflavone, and quercetin was shown to improve whole-body energy expenditure, mitochondrial activity, and glucose tolerance. For some flavonoids, molecular targets for the metabolic modulations have been suggested. Although the effect of flavonoids on neurons has been unclear, several flavonoids have been shown to regulate thermogenesis and feeding behavior through modulating autonomic and central nervous systems. Based on epidemiological and experimental studies, this review summarizes the evidence on the metabolic benefits of flavonoids and their potential mechanism of action in metabolic regulation.

Activation of Brown Adipose Tissue and Promotion of White Adipose Tissue Browning by Plant-based Dietary Components in Rodents: A Systematic Review

Activation of brown adipose tissue (BAT) and promotion of white adipose tissue (WAT) browning is considered a potential tool to combat obesity and cardiometabolic disorders. The use of plant-based dietary components has become one of the most used strategies for activating BAT and promoting WAT browning in rodents. The main reason is because plant-based dietary components are usually recognized as safe when the dose is properly adjusted, and they can easily be administrated by being added to the diet or dissolved in water. The present systematic review aimed to study the effects of plant-based dietary components on activation of BAT and promotion of WAT browning in rodents. A systematic search of PubMed and Scopus (from 1978 to 2019) identified eligible studies. Studies assessing the effects of plant-based dietary components added to diet and/or water on uncoupling protein 1 (UCP1) expression in BAT and/or WAT were included. Studies that used dietary components of animal origin, did not specify the effects on UCP1, or were conducted in other species different from mice or rats were excluded. Of 3919 studies identified in the initial screening, 146 studies were finally included in the review. We found that tea extract catechins, resveratrol, capsaicin and capsinoids, cacao extract flavanols, and quercetin were the most studied components. Scientific evidence suggests that some of these dietary components activate BAT and promote WAT browning via activation of the AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) pathways. These findings reveal that there is strong scientific evidence supporting the use of plant-based dietary components to activate BAT and promote WAT browning in rodents and thus to potentially combat obesity and cardiometabolic 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.

Combination of α-Glycosyl-Isoquercitrin and Soybean Fiber Promotes Quercetin Bioavailability and Glucagon-like Peptide-1 Secretion and Improves Glucose Homeostasis in Rats Fed a High-Fat High-Sucrose Diet

This study examined the effects of a combination of soybean fiber and α-glycosyl-isoquercitrin (AGIQ) on improving quercetin bioavailability and glucose metabolism in rats fed an obesogenic diet. For 9 weeks, rats were individually fed a control diet, a high-fat high-sucrose (H) diet, H with soybean fiber (HS), or with AGIQ (HQ), or with both (HSQ). Quercetin derivatives in plasma, feces, urine, and cecal content were quantified by high-performance liquid chromatography to assess the bioavailability of quercetin, and meal tolerance tests were performed to assess postprandial glycemia and glucagon-like peptide-1 (GLP-1) responses. The HSQ group had higher plasma quercetin levels than HQ. The postprandial glycemia was attenuated in the HSQ group when compared to the H group. The basal plasma GLP-1 concentrations positively correlated with plasma quercetin derivative concentrations. Hence, the combination of soybean fiber and AGIQ could be beneficial for reducing the risk of glucose intolerance, possibly involving enhanced quercetin bioavailability and GLP-1 secretion.

Pharmacogenetic-based management of depression: Role of traditional Persian medicine

Depression is one of the most common mental disorders worldwide. The genetic factors are linked to depression and anti-depressant outcomes. Traditional Persian medicine (TPM) manuscripts have provided various anti-depressant remedies, which may be useful in depression management. This review has studied the bioactive compounds, underlying mechanisms, and treatment outcomes of the medicinal plants traditionally mentioned effective for depression from "The storehouse of medicament" (a famous pharmacopeia of TPM) to merge those with the novel genetics science and serve new scope in depression prevention and management. This review paper has been conducted in two sections: (1) Collecting medicinal plants and their bioactive components from "The storehouse of medicament," "Physician's Desk Reference (PDR) for Herbal Medicines," and "Google scholar" database. (2) The critical key factors and genes in depression pathophysiology, prevention, and treatment were clarified. Subsequently, the association between bioactive components' underlying mechanism and depression treatment outcomes via considering polymorphisms in related genes was derived. Taken together, α-Mangostin, β-carotene, β-pinene, apigenin, caffeic acid, catechin, chlorogenic acid, citral, ellagic acid, esculetin, ferulic acid, gallic acid, gentiopicroside, hyperoside, kaempferol, limonene, linalool, lycopene, naringin, protocatechuic acid, quercetin, resveratrol, rosmarinic acid, and umbelliferone are suitable for future pharmacogenetics-based studies in the management of depression.

Ethanol extract from Moringa oleifera leaves modulates brown adipose tissue and bone morphogenetic protein 7 in high-fat diet mice

BACKGROUND AND AIM

Brown adipose tissue's (BAT) ability to increase energy expenditure has become a new focus in obesity research. The amount and activity of BAT are inversely correlated with body-mass index and body fat percentage. Bone morphogenetic protein 7 (BMP7) plays a role in the differentiation and development of BAT, which can be increased by bioactive compounds from several medicinal plants. Moringa oleifera (MO) leaves are rich with vitamin, minerals, and bioactive compounds and have been used for treating obesity-related diseases in the past. The aim of this study was to explore the potency of MO leaf extract (MOLE) to modulate BAT differentiation in mice fed a high-fat diet (HFD).

MATERIALS AND METHODS

Twenty-four, 5-week-old male Deutsche Denken Yoken mice (Mus musculus) were randomly divided into four groups: The normal chow diet group was fed a normal diet, the HFD group was fed a HFD, the HFD+MOLE1, and the HFD+MOLE2 groups were fed HFD and MOLE in a dose of 280 and 560 mg/kg body weight (BW)/day, respectively. The experiment was performed for 7 weeks. At the end of the experiment, histological analysis was performed on the interscapular BAT, and blood was drawn for BMP7 protein levels.

RESULTS

After 7 weeks, BAT weight in the HFD group was nearly twice in the weight of the HFD+MOLE1 group (125±13.78 mg vs. 75±13.78 mg; p<0.001). There was also a significant increase in BAT cell density in the HFD+MOLE1 group. BMP7 serum protein levels were significantly higher in the HFD+MOLE1 group compared to the HFD group.

CONCLUSIONS

The administration of MOLE in a dose of 280 mg/kg BW/day in HFD-mice induces BAT differentiation and proliferation by upregulating BMP7 protein levels.

Role of Dietary Polyphenols in Adipose Tissue Browning: A Narrative Review

Lifestyle modifications such as energy restriction and increased physical activity are highly effective in the management of obesity. However, adherence to these therapeutic approaches is poor. On the other hand, synthetic drugs used for obesity control are plagued by adverse effects. Despite these failures, adipose tissue is still an attractive therapeutic target for novel molecules, and thus, the characterisation of new and safer anti-obesity drugs is of significant interest. For this reason, in recent years, phenolic constituents of diverse plants have drawn much attention due to their health-promoting properties, opening new research lines related to brown adipose tissue activation and white adipose tissue (WAT) browning. The goal is to increase energy expenditure levels through thermogenic activity activation by multiple factors, like polyphenols. The suggested mechanisms by which polyphenols can modulate thermogenesis include Nor-epinephrine/Catechol-O-Methyl-Transferase (NE/COMT) inhibition, PPARγ co-activator alpha (PGC-1α)-dependent pathways activation, and mitochondrial biogenesis, among others. Although polyphenols such as quercetin, catechins, chrysin, luteolin, curcumin, resveratrol, gallic acid, and lignans have shown a positive effect on Non-Shivering Thermogenesis and WAT browning, most of them have only been active in murine models or in vitro systems, and their reproducibility in humans has to be proved. Probably in the future, an approach that includes these compounds as part of the nutritional regimen in conjunction with physical exercise, pharmacological and surgical therapy, would allow modulating a pathophysiological mechanism that is still elusive.

Recent developments in natural products for white adipose tissue browning

Excess accumulation of white adipose tissue (WAT) causes obesity which is an imbalance between energy intake and energy expenditure. Obesity is a serious concern because it has been the leading causes of death worldwide, including diabetes, stroke, heart disease and cancer. Therefore, uncovering the mechanism of obesity and discovering anti-obesity drugs are crucial to prevent obesity and its complications. Browning, inducing white adipose tissue to brown or beige (brite) fat which is brown-like fat emerging in WAT, becomes an appealing therapeutic strategy for obesity and metabolic disorders. Due to lack of efficacy or intolerable side-effects, the clinical trials that promote brown adipose tissue (BAT) thermogenesis and browning of WAT have not been successful in humans. Obviously, more specific means still need to be developed to activate browning of white adipose tissue. In this review, we summarized seven kinds of natural products (alkaloids, flavonoids, terpenoids, long chain fatty acids, phenolic acids, else and extract) promoting white adipose tissue browning which can ameliorate the metabolic disorders, including obesity, dislipidemia, insulin resistance and diabetes. Since natural products are important drug sources and the browning property plays a significant role in not only obesity treatment but also in type 2 diabetes (T2DM) improvement, natural products of inducing browning may be an irreplaceable drug discovery orientation for obesity, diabetes and even other metabolic disorders.

Anti-Obesity Effects of Sargassum thunbergii via Downregulation of Adipogenesis Gene and Upregulation of Thermogenic Genes in High-Fat Diet-Induced Obese Mice

Obesity is a metabolic disease characterized by an increased risk of type 2 diabetes, hypertension, and cardiovascular disease. We have previously reported that compounds isolated from brown alga, Sargassum thunbergii (ST; Sargassum thunbergii (Mertens ex Roth) Kuntze), inhibit adipogenesis in 3T3-L1 cells. However, the in vivo anti-obesity effects of these compounds have not been previously reported. Therefore, the objective of this study was to determine the effects of ST on weight loss, fat accumulation, as well as risk factors for type 2 diabetes and cardiovascular disease in high-fat diet (HFD)-induced obese mice. ST treatment significantly decreased body weight and fat accumulation in HFD-induced obese mice, while reducing insulin and factors related to cardiovascular diseases (triglyceride and total cholesterol) in serum. ST-induced downregulation of PPARγ in white adipose tissue, and upregulation of the thermogenic genes, UCP-1 and UCP-3, in brown adipose tissue was also observed. In addition, oral administration of ST reduced the occurrence of fatty liver, as well as the amount of white adipose tissue in HFD mice. Cumulatively, these results suggest that ST exerts anti-obesity effects and may serve as a potential anti-obesity therapeutic agent.

Effect of quercetin on nonshivering thermogenesis of brown adipose tissue in high-fat diet-induced obese mice

Activating nonshivering thermogenesis in brown adipose tissue (BAT) is a promising strategy to prevent obesity. This study investigated whether quercetin supplementation improves obesity in mice by increasing nonshivering thermogenesis in BAT and white adipose tissue (WAT) browning. Compared to high-fat diet (HFD)-fed mice, mice fed a HFD supplemented with 1% quercetin (HFDQ) had reduced body weight and total plasma cholesterol. In HFDQ-fed mice, retroperitoneal WAT (RWAT) weight was decreased, and browning effect and lipolysis were increased. HFDQ-fed mice had increased expression of nonshivering thermogenesis genes in BAT, including uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC1α), cell death-inducing DFFA-like effector A (CIDEA), and mitochondrial transcriptional factor A (mtTFA). Quercetin supplementation increased genes and proteins in β₃-adrenergic receptor (ADRB3), p38 mitogen-activated protein kinase (MAPK), and AMP-activated protein kinase (AMPK) pathways in HFD-fed mice, which were suppressed by an AMPK inhibitor or an ADRB3 antagonist. Energy expenditure and core body temperature were not changed by quercetin, but physical activity was increased in HFDQ mice during dark periods at room and cold temperatures. Quercetin also decreased the Firmicutes to Bacteroidetes ratio and increased short-chain fatty acid production in the feces of HFD-fed mice. In summary, quercetin supplementation in HFD-fed mice may attenuate obesity. Although the study did not show consistency in data at molecular and pathophysiological levels between BAT function and obesity, it also shows promising health effects of quercetin, accompanied by improved physical activity and gut microbiota dysbiosis.

Strawberry (Fragaria × ananassa cv. Romina) methanolic extract promotes browning in 3T3-L1 cells

In recent years, the conversion of white adipocytes to brown-like adipocytes by pharmacological and dietary compounds has gained attention as an effective strategy to fight obesity. Strawberry bioactive compounds present several biological activities including antioxidant, anti-inflammatory, anti-cancer, anti-atherosclerotic and antiadipogenic properties. However, to the best of our knowledge, the possible role of strawberry bioactive compounds in white adipose tissue (WAT) browning has never been explored. Our results demonstrated that a strawberry methanolic extract (SE) significantly reduced 3T3-L1 pre-adipocytes differentiation, and down-regulated the mRNA expression of the adipogenic transcription factors CCAAT/enhancer-binding protein (C/REB- α) and peroxisome proliferation-activated receptor (PPAR-γ). It also down-regulated the mRNA expression of resistin and angiotensinogen, two genes considered as markers of white adipocytes, while increased the mRNA expression of pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4) and uncoupling protein 1 (UCP1) which, conversely, are brown adipocyte-specific markers. Likewise, SE stimulated AMP-activated protein kinase (AMPKα), sirtuin 1 (Sirt1) and the peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC-1α), suggesting a possible increase in mitochondrial biogenesis. It also stimulated oxygen consumption rate and uncoupled respiration. Taken together, all these results suggest that SE induces brown fat-like phenotype in 3T3-L1 cells and may have potential therapeutic implications for treatment and/or prevention of obesity.

Crosstalk between obesity, diabetes, and alzheimer's disease: Introducing quercetin as an effective triple herbal medicine

Obesity and diabetes are the most common metabolic disorders, which are strongly related to Alzheimer's disease (AD) in aging. Diabetes and obesity can lead to the accumulation of amyloid plaques, neurofibrillary tangles (NFTs), and other symptoms of AD through several pathways, including insulin resistance, hyperglycemia, hyperinsulinemia, chronic inflammation, oxidative stress, adipokines dysregulation, and vascular impairment. Currently, the use of polyphenols has been expanded in animal models and in-vitro studies because of their comparatively negligible adverse effects. Among them, quercetin (QT) is one of the most abundant polyphenolic flavonoids, which is present in fruits and vegetables and displays many biological, health-promoting effects in a wide range of diseases. The low bioavailability and poor solubility of QT have also led researchers to make various QT-involved nanoparticles (NPs) to overcome these limitations. In this paper, we review significant molecular mechanisms induced by diabetes and obesity that increase AD pathogenesis. Then, we summarize in vitro, in vivo, and clinical evidence regarding the anti-Alzheimer, anti-diabetic and anti-obesity effects of QT. Finally, QT in pure and combination form using NPs has been suggested as a promising therapeutic agent for future studies.

Metabolic Impact of Flavonoids Consumption in Obesity: From Central to Peripheral

The prevention and treatment of obesity is primary based on the follow-up of a healthy lifestyle, which includes a healthy diet with an important presence of bioactive compounds such as polyphenols. For many years, the health benefits of polyphenols have been attributed to their anti-oxidant capacity as free radical scavengers. More recently it has been described that polyphenols activate other cell-signaling pathways that are not related to ROS production but rather involved in metabolic regulation. In this review, we have summarized the current knowledge in this field by focusing on the metabolic effects of flavonoids. Flavonoids are widely distributed in the plant kingdom where they are used for growing and defensing. They are structurally characterized by two benzene rings and a heterocyclic pyrone ring and based on the oxidation and saturation status of the heterocyclic ring flavonoids are grouped in seven different subclasses. The present work is focused on describing the molecular mechanisms underlying the metabolic impact of flavonoids in obesity and obesity-related diseases. We described the effects of each group of flavonoids in liver, white and brown adipose tissue and central nervous system and the metabolic and signaling pathways involved on them.

Modulation of Chronic Inflammation by Quercetin: The Beneficial Effects on Obesity

Obesity has become a major risk factor for the development of chronic diseases such as insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. Moreover, obesity induces chronic inflammation in adipose tissue, liver, skeletal muscle, and the vascular system. Quercetin is the major representative of the flavonoid subclass of flavonols, which is ubiquitously contained within natural plants such as green tea, and vegetables, including onions and apples. Researchers have focused greater attention to the beneficial physiological roles of quercetin, which has anti-oxidative, anti-inflammatory, and anti-fibrotic effects on insulin resistance and atherosclerosis in obesity-related diseases. Also, the anti-inflammatory effects of quercetin on intestinal microbiota have been demonstrated in obesity. In addition, there is increasing evidence that quercetin is associated with epigenetic activities in cancer, and in maternal undernutrition during gestation and lactation. In this review, we focus on the chemical properties of quercetin, its dietary sources in obesity, and its anti-inflammatory effects on insulin resistance, atherosclerosis, intestinal microbiota, and maternal under-nutrition with epigenetic activity.

Stimulation of brown adipose tissue by polyphenols in extra virgin olive oil

Obesity is one of the main public health problems of the 21^st century resulting from an imbalance between calorie intake and energy expenditure. Currently, the search for new treatments against this pathology has become a priority. One of the therapeutic strategies against obesity could be the activation of brown adipose tissue through different molecules such as the phenolic compounds of extra virgin olive oil (EVOO). The objective of this review was to provide an update of scientific knowledge on the relationship between EVOO phenolic compounds and brown adipose tissue.According to this review, it has been demonstrated that extra virgin olive oil phenolic compounds can have beneficial effects on obesity by activating brown adipose tissue and enhance thermogenesis through different signaling pathways mediated by molecules such as AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) or sirtuin 1 (Sirt1).

Low molecular weight blue mussel hydrolysates inhibit adipogenesis in mouse mesenchymal stem cells through upregulating HO-1/Nrf2 pathway

Blue mussel proteins are a good source of bioactive peptides. In this study, blue mussel hydrolysate (BMH) with anti-adipogenic effect in mouse mesenchymal stem cells (mMSC) was produced by peptic hydrolysis at 1:500 of pepsin/substrate ratio for 120 min. Additionally, BMH with below 1 kDa (BMH < 1 kDa) showed the highest anti-adipogenic effect in mMSC. BMH < 1 kDa increased lipolysis and down-regulated adipogenic transcription factors including peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP1). Generation of intracellular reactive oxygen species during adipogenesis was markedly decreased by BMH < 1 kDa treatment, which is attributed to the up-regulation of heme oxygenase-1 (HO-1) through Nrf2 translocation into the nucleus. Moreover, ZnPP, HO-1 inhibitor, treatment abolished BMH < 1 kDa-mediated HO-1 expression and anti-adipogenic effect in mMSCs through down-regulating adipogenic transcription factors. Taken together, BMH < 1 kDa may be a potential ingredient of nutraceuticals and/or functional foods in ameliorating obesity.

Fruit of Hovenia dulcis Thunb. Induces Nonshivering Thermogenesis through Mitochondrial Biogenesis and Activation by SIRT1 in High-Fat Diet-Fed Obese Mice and Primary Cultured Brown Adipocytes

Brown adipocytes, which contain abundant mitochondria, use stored energy as fuel during a process named nonshivering thermogenesis. Thus, the pharmacological activation of thermogenesis in brown adipose tissue (BAT) has become a promising target for treating obesity. We investigated the effect of fruit of Hovenial dulcis Thunb. (FHD), a frequently used herbal treatment for liver diseases, on thermogenesis and its mechanism using primary cultured brown adipocytes and BAT of high-fat-diet (HFD)-induced obese mice. Thermogenesis-related factors including UCP1 and PGC1α increased with FHD treatment. FHD also increased mitochondrial biogenesis and activation factors such as nuclear respiratory factor (NRF)1 and oxidative phosphorylation (OXPHOS) complex. Furthermore, FHD increased the intercellular nicotinamide adenine dinucleotide (NAD⁺) level and sirtuin 1 (SIRT1) activity, which may be responsible for the activation of the thermogenic reaction. Overall, our results suggest that FHD can be a novel option for obesity treatment due to its thermogenic action through mitochondrial biogenesis and activation.

Prevention effect of quercetin and its glycosides on obesity and hyperglycemia through activating AMPKα in high-fat diet-fed ICR mice

Quercetin and its glycosides possess various health beneficial functions, but comparative study of them on energy metabolism in different tissues are not well studied. In this study, we investigated AMP-activated protein kinase regulated glucose metabolism in the skeletal muscle and lipid metabolism in the white adipose tissue and liver to compare the effectiveness of quercetin and its glycosides, namely isoquercitrin, rutin, and enzymatically modified isoquercitrin, in male ICR mice. The mice were fed a standard or high-fat diet supplemented with 0.1% quercetin and its glycosides for 13 weeks. Quercetin glycosides, but not quercetin, decreased body weight gain and fat accumulation in the mesenteric adipose tissue in high-fat groups. All compounds decreased high-fat diet-increased plasma glucose and insulin levels. Moreover, all compounds significantly increased AMP-activated protein kinase phosphorylation in either standard or high-fat diet-fed mice in all tissues tested. As its downstream events, all compounds induced glucose transporter 4 translocation in the muscle. In the white adipose tissue and liver, all compounds increased lipogenesis while decreased lipolysis. Moreover, all compounds increased browning markers and decreased differentiation markers in adipose tissue. Therefore, quercetin and its glycosides are promising food components for prevention of adiposity and hyperglycemia through modulating AMP-activated protein kinase-driven pathways.

Mangiferin induces the expression of a thermogenic signature via AMPK signaling during brown-adipocyte differentiation

Mangiferin (MF) from Mangifera indica has been serendipitously found to ameliorate obesity and is used as an antioxidant, anti-inflammatory, antimicrobial, and anticancer agent. Nonetheless, the mechanism of MF-induced brown-adipose-tissue activation has not been studied. Therefore, we investigated the effect of MF on thermogenic features during brown-adipocyte differentiation. Treatment with MF improved the expression of a brown-fat signature and of mitochondrial-mass-related genes, thus resulting in UCP1 induction. MF also raised the expression of other thermogenic regulators, including peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α), PR domain-containing protein 16 (PRDM16), and peroxisome proliferator-activated receptors alpha and gamma (PPAR-α and -γ). MF promoted mitochondrial biogenesis, judging by increased expression of cell death-inducing DNA fragmentation factor α-like effector A (CIDEA), mitochondrial transcription factor A (TFAM), iodothyronine deiodinase 2 (DIO2), cytochrome c oxidase subunit 7A (COX7A), cyclooxygenase 2 (COX2), sirtuin 1 (SIRT1), and nuclear respiratory factor 1 (NRF1). MF treatment increased the mitochondrial DNA amount and improved mitochondrial respiratory function by increasing the oxygen consumption rate during brown-adipocyte differentiation. A gene knockdown assay involving small interfering RNA and competitive inhibition with dorsomorphin revealed that MF may promote thermogenesis in brown preadipocytes via activation of AMPK signaling. Collectively, our findings suggest that MF may be a novel pharmaceutical agent that can ameliorate obesity via activation of brown adipose tissue.

Feeding brown fat: dietary phytochemicals targeting non-shivering thermogenesis to control body weight

Excessive adipose accumulation, which is the main driver for the development of secondary metabolic complications, has reached epidemic proportions and combined pharmaceutical, educational and nutritional approaches are required to reverse the current rise in global obesity prevalence rates. Brown adipose tissue (BAT) is a unique organ able to dissipate energy and thus a promising target to enhance BMR to counteract a positive energy balance. In addition, active BAT might support body weight maintenance after weight loss to prevent/reduce relapse. Natural products deliver valuable bioactive compounds that have historically helped to alleviate disease symptoms. Interest in recent years has focused on identifying nutritional constituents that are able to induce BAT activity and thereby enhance energy expenditure. This review provides a summary of selected dietary phytochemicals, including isoflavones, catechins, stilbenes, the flavonoids quercetin, luteolin and resveratrol as well as the alkaloids berberine and capsaicin. Most of the discussed phytochemicals act through distinct molecular pathways e.g. sympathetic nerve activation, AMP-kinase signalling, SIRT1 activity or stimulation of oestrogen receptors. Thus, it might be possible to utilise this multitude of pathways to co-activate BAT using a fine-tuned combination of foods or combined nutritional supplements.

Quercetin attenuates adipose hypertrophy, in part through activation of adipogenesis in rats fed a high-fat diet

An impaired capacity of adipose tissue expansion leads to adipocyte hypertrophy, inflammation and insulin resistance (IR) under positive energy balance. We previously showed that a grape pomace extract, rich in flavonoids including quercetin (Q), attenuates adipose hypertrophy. This study investigated whether dietary Q supplementation promotes adipogenesis in the epididymal white adipose tissue (eWAT) of rats consuming a high-fat diet, characterizing key adipogenic regulators in 3T3-L1 pre-adipocytes. Consumption of a high-fat diet for 6 weeks caused IR, increased plasma TNFα concentrations, eWAT weight, adipocyte size and the eWAT/brown adipose tissue (BAT) ratio. These changes were accompanied by decreased levels of proteins involved in angiogenesis, VEGF-A and its receptor 2 (VEGF-R2), and of two central adipogenic regulators, i.e. PPARγ and C/EBPα, and proteins involved in mature adipocyte formation, i.e. fatty acid synthase (FAS) and adiponectin. Q significantly reduced adipocyte size and enhanced angiogenesis and adipogenesis without changes in eWAT weight and attenuated systemic IR and inflammation. In addition, high-fat diet consumption increased eWAT hypoxia inducible factor-1 alpha (HIF-1α) levels and those of proteins involved in adipose inflammation (TLR-4, CD68, MCP-1, JNK) and activation of endoplasmic reticulum (ER) stress, i.e. ATF-6 and XBP-1. Q mitigated all these events. Q and quercetin 3-glucoronide prevented TNFα-mediated downregulation of adipogenesis during 3T3-L1 pre-adipocytes early differentiation. Together, Q capacity to promote a healthy adipose expansion enhancing angiogenesis and adipogenesis may contribute to reduced adipose hypertrophy, inflammation and IR. Consumption of diets rich in Q could be useful to counteract the adverse effects of high-fat diet-induced adipose dysfunction.

Impact of Adaptive Thermogenesis in Mice on the Treatment of Obesity

Obesity and associated metabolic diseases have become a priority area of study due to the exponential increase in their prevalence and the corresponding health and economic impact. In the last decade, brown adipose tissue has become an attractive target to treat obesity. However, environmental variables such as temperature and the dynamics of energy expenditure could influence brown adipose tissue activity. Currently, most metabolic studies are carried out at a room temperature of 21 °C, which is considered a thermoneutral zone for adult humans. However, in mice this chronic cold temperature triggers an increase in their adaptive thermogenesis. In this review, we aim to cover important aspects related to the adaptation of animals to room temperature, the influence of housing and temperature on the development of metabolic phenotypes in experimental mice and their translation to human physiology. Mice studies performed in chronic cold or thermoneutral conditions allow us to better understand underlying physiological mechanisms for successful, reproducible translation into humans in the fight against obesity and metabolic diseases.

A minireview of quercetin: from its metabolism to possible mechanisms of its biological activities

Quercetin, one of the most taken flavonoid with diet, belongs to the family of flavonols in which kaempferol and myricetin are also found. Quercetin occurs as a glycoside (with linked sugars) or as an aglycone (without linked sugars). Although quercetin has many different forms in nature, the form found in plants is quercetin-3-O-glucoside, which generally functions as a pigment that gives color to a multitude of fruits and vegetables. The recent literature has been reviewed using PubMed, Science Direct, and Embase databases. In this article, we reviewed quercetin with respect to chemical properties, absorption mechanism, metabolism, bioavailability, food sources, bioactivities, and possible health-promoting mechanisms. Quercetin is known as an antioxidant, anti-inflammatory, cardioprotective, and anti-obesity compound. It is thought to be beneficial against cardiovascular diseases, cancer, diabetes, neurological diseases, obesity, allergy asthma, and atopic diseases. Further clinical studies with large sample sizes are needed to determine the appropriate dose and form of quercetin for preventing diseases.

Dietary Sea Buckthorn Pomace Induces Beige Adipocyte Formation in Inguinal White Adipose Tissue in Lambs

The sea buckthorn contains substantial amounts of bioactive compounds. The objective of this study was to investigate the effects of dietary sea buckthorn pomace (SBP) on sheep beige adipocyte formation. A total of thirty lambs were equally divided into three groups and fed with diets containing different levels of SBP: 0% SBP (Control), 7.8% SBP (7.8SBP), and 16.0% SBP (16SBP). The results showed that dietary SBP affected inguinal adipocytes' size distribution, and increased both UCP1 protein content (p < 0.05) and mitochondrial numbers (p < 0.05). mRNA expression of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), nuclear respiratory factor 1, and mitochondrial transcription factor A were increased when animals were subjected to 16% SBP (p < 0.05). Supplementation with 16% SBP increased CCAAT/enhancer-binding protein β content (p < 0.05) and PR domain containing 16 mRNA abundance (p < 0.05). Consistently, inguinal white adipose tissue (iWAT) from the 16SBP group exhibited increased insulin sensitivity, which was associated with elevated glucose transporter 4 abundance (p < 0.05). Importantly, AMP-activated protein kinase (AMPK) was activated in the 16SBP group (p < 0.05). Collectively, these results suggest that dietary SBP promotes iWAT browning in lambs, which might be through the activation of the AMPK-PGC-1α-UCP1 signaling pathway.