杨梅素对膳食诱导的C57BL/6小鼠肥胖及氧化应激的干预作用

Myricetin protects against diet-induced obesity and ameliorates oxidative stress in C57BL/6 mice 杨梅素对膳食诱导的C57BL/6小鼠肥胖及氧化应激的干预作用 1 first-author 2 1 1 corresp ‡Corresponding Author ‡Corresponding Author †E-mail:zjuchenwei@zju.edu.cn †E-mail:zjuchenwei@zju.edu.cn zjuchenwei@zju.edu.cn Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou 310058, China Department of Food Science and Nutrition, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang University, Hangzhou 310058, China College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310035, China College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310035, China Background: 2 Myricetin is a naturally occurring antioxidant commonly found in various plants. However, little information is available with respect to its direct anti-obesity effects. Objective: 2 This study was undertaken to investigate the effect of myricetin on high-fat diet (HFD)-induced obesity in C57BL/6 mice. Results: 2 Administration of myricetin dramatically reduced the body weight of diet-induced obese mice compared with solely HFD-induced mice. Several parameters related to obesity including serum glucose, triglyceride, and cholesterol were significantly decreased in myricetin-treated mice. Moreover, obesity-associated oxidative stress (glutathione peroxidase (GPX) activity, total antioxidant capacity (T-AOC), and malondialdehyde (MDA)) and inflammation (tumor necrosis factor-α (TNF-α)) were ameliorated in myricetin-treated mice. Further investigation revealed that the protective effect of myricetin against HFD-induced obesity in mice appeared to be partially mediated through the down-regulation of mRNA expression of adipogenic transcription factors peroxisome proliferator-activated receptor γ ( PPARγ ) and CCAAT/enhancer-binding protein α ( C/EBPα ), and lipogenic transcription factor sterol regulatory element-binding protein 1c ( SREBP-1c ). Conclusions: 2 Consumption of myricetin may help to prevent obesity and obesity-related metabolic complications. 目的 2 研究杨梅素（myricetin）对高脂膳食（HFD）诱导的C57BL/6小鼠肥胖的干预作用，并探讨其作用机理。 创新点 2 首次在高脂膳食诱导的C57BL/6肥胖小鼠模型中证明杨梅素可明显减轻肥胖小鼠的体重，同时改善伴随肥胖的氧化应激和炎症。分子机理研究表明杨梅素通过下调脂代谢相关的转录因子（ PPARγ 、 C/EBPα 和 SREBP-1c ）mRNA的表达，从而发挥减肥功效。 方法 2 将C57BL/6小鼠分为正常膳食组（ND，n=12）和高脂膳食组（HFD， n =24），分别给予正常膳食和高脂膳食喂食2周。之后，高脂膳食组分为高脂膳食组（ n =12）和杨梅素保护组（HFD+M，灌胃150 mg/(kg·d)的杨梅素， n =12），继续处理10周。分析小鼠常规生理指标（体重和脏器重量）、生化指标（血糖浓度、甘油三酯和总胆固醇含量）、氧化应激指标（谷胱甘肽过氧化物酶（GPX）、超氧化物歧化酶（SOD）和总抗氧化能力（T-AOC））和炎症指标（肿瘤坏死因子α（TNF-α））等。苏木精-伊红染色法（H & E）和油红染色法分别观察脂肪组织和肝脏组织形态。实时逆转录聚合酶链反应（RT-PCR）分析小鼠脂肪组织 PPARγ 、 C/EBPα 和 SREBP-1c 等基因的mRNA表达水平。 结论 2 与高脂膳食对照组相比，杨梅素处理可以显著减轻肥胖小鼠的体重。同时能显著降低肥胖小鼠血糖、甘油三酯和总胆固醇的含量。此外，杨梅素处理能缓解伴随肥胖的氧化应激（GPX活性、T-AOC和丙二醛（MDA））和炎症（TNF-α）。分子机理研究发现杨梅素通过下调脂肪细胞生成（ PPARγ 和 C/EBPα ）和脂质合成（ SREBP-1c ）密切相关的转录因子的mRNA表达。本研究结果将为杨梅素减肥产品的开发提供一定的理论依据。 Myricetin Obesity Adipogenesis Oxidative stress 杨梅素 肥胖 脂肪生成 氧化应激 Introduction 1 The World Health Organization (WHO) has estimated that globally more than 1.4 billion individuals are overweight or obese (Ng et al., 2014 2014 ). A growing body of evidence confirms that obesity is closely associated with a series of chronic diseases, such as type 2 diabetes mellitus, cardiovascular diseases, non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and certain cancers (Grundy, 1998 1998 ; Tilg and Moschen, 2006 2006 ). The high prevalence of obesity has made it a serious public health concern. Several factors including genetic, environmental, and psychological factors greatly influence the occurrence and development of obesity. Recently, increasing attention has been paid to exploiting natural components extracted from a normal diet as a viable strategy to inhibit the onset of obesity (Yun, 2010 2010 ; Jeong et al., 2014 2014 ). Some blended phytochemicals from fruits and vegetables reportedly have the potential to suppress diet-induced obesity (Song et al., 2013 2013 ; Zhao et al., 2015 2015 ). Oxidative stress has been implicated in the development of obesity-related metabolic disorders, such as cardiovascular diseases, atherosclerosis, and hypertension (Furukawa et al., 2004 2004 ; Galinier et al., 2006 2006 ). Antioxidant defense systems may be impaired as a consequence of excessive oxidative stress in obesity (Furukawa et al., 2004 2004 ). In addition, obesity is associated with a chronic, low-grade inflammatory state. Obesity-related inflammatory responses can be partially mediated by oxidative stress (Wood et al., 2009 2009 ). Targeted intervention of inflammatory pathways may help to prevent obesity-associated metabolic disorders (Gregor and Hotamisligil, 2011 2011 ). Naturally occurring antioxidant compounds including flavonoids, anthocyanidins, and catechins have been reported to affect the regulation of lipid metabolism through modulating oxidative stress conditions (Hogan et al., 2010 2010 ; Yen et al., 2011 2011 ). Myricetin is a major flavonoid found in various foods, including onions, bayberries, grapes, and tea (Harnly et al., 2006 2006 ; Chen W. et al., 2011 2011 ; Li et al., 2012 2012 ). Accumulating evidence shows that myricetin has antioxidant, anti-inflammatory, and anticancer activities (Lu et al., 2006 2006 ; Chen et al., 2013a 2013a ; 2013b 2013b ; 2015 2015 ). In addition, it can lower plasma-glucose levels, improve the insulin-signaling pathway, and reduce hyperglycemia (Ong and Khoo, 2000 2000 ; Liu et al., 2005 2005 ; 2007 2007 ). Myricetin is also confirmed to have therapeutic benefits in relation to cardiovascular diseases associated with obesity (Ong and Khoo, 1997 1997 ). However, little information is available with respect to the direct anti-obesity effects of myricetin on high-fat diet (HFD)-induced C57BL/6 mice through modulating the oxidative stress pathway. In this study, we aimed to investigate the effects of myricetin on the development of obesity in HFD-induced C57BL/6 mice by examining serum glucose, triglyceride (TG), and cholesterol profiles as well as oxidative stress indicators. We then evaluated the gene expression of adipogenesis-and lipogenesis-related transcription factors in epididymal white adipocytes. Our results provide a foundation for future studies on the application of myricetin for the preclinical prevention and treatment of obesity. Materials and methods 1 Reagents 2 Myricetin (purity >96%) was obtained from the National Institutes for Food and Drug Control (Beijing, China). Oil Red O was purchased from Sigma-Aldrich Co. (CA, USA), TRIzol from Invitrogen (Carlsbad, CA, USA), and SYBR Green PCR Master Mix from Roche (Basel, Switzerland). All other reagents used were of analytical grade. Animal experiments 2 All the animal experimental procedures in this study were conducted in the Animal Experiment Center of Zhejiang University (Hangzhou, China). The animal protocol was approved by the Institutional Animal Care and Use Committee of Zhejiang University. Animal diets were obtained from Medicience Ltd. (Yangzhou, China). Myricetin was dissolved in normal saline (NS)/Tween-80 (25:1, v/v) by grinding with a mortar and pestle. Male C57BL/6 mice at 4 weeks of age were purchased from the Silaike Experimental Animal Co., Ltd. (Shanghai, China). The mice were housed in a pathogen-free facility under a 12-h light/12-h dark cycle ((22±2) °C, 40%–70% relative humidity), and had ad libitum access to water and diet. After 5-d adaptation, the mice were randomly divided into two groups: a normal diet group (ND) fed a diet containing 10% fat, and an HFD group fed a diet containing 45% fat. Both diets were maintained for 2 weeks. For the obesity challenge study: (1) 12 mice in the ND group were fed an ND administered with vehicle (NS/Tween-80 (25:1, v/v)) by oral gavage; (2) 12 mice in the HFD group were fed an HFD administered with vehicle (NS/Tween-80 (25:1, v/v)) by oral gavage; (3) another 12 mice in the HFD group were fed an HFD with myricetin at 150 mg/(kg·d) (M150), in accordance with Choi et al. ( 2014 2014 ). All mice were permitted ad libitum consumption of water. After 10 weeks, all mice were sacrificed following 12-h fasting. Blood samples were collected, and liver and adipose tissue samples were collected, weighed, and stored at −80 °C for further assessment. Biochemical analyses 2 The blood samples were centrifuged at 3000 r/min for 15 min and then were collected for biochemical analyses. Serum glucose, TG, total cholesterol (TC), and malondialdehyde (MDA) levels were measured using commercial enzyme kits (Elabscience, China) according to the manufacturer’s protocols. Glutathione peroxidase (GPX), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) were determined by enzymatic methods using ELISA kits (Sigma, CA, USA) according to the manufacturer’s instructions (Wu et al., 2013c 2013c ; Yu et al., 2016 2016 ). Hematoxylin and eosin staining 2 Morphological analysis of adipocytes was performed on hematoxylin and eosin (H & E)-stained sections as described (Wu et al., 2013a 2013a ). Epididymal white adipose tissue samples were dissected and fixed in 10% formalin for 24 h, then dehydrated by ethanol solutions. The samples were then embedded in paraffin wax and sliced. The fixed tissue slices were stained with H & E, mounted by neutral sizing, and dried. Images were obtained using a Nikon microscope (Tokyo, Japan). Oil Red O staining 2 Oil Red O staining was performed as described by Wu et al. ( 2013b 2013b ). Sections, approximately 4–5 μm thick, were cut from liver tissue using a freeze microtome. The sections were fixed in 4% formaldehyde for 20 min and then stained with Oil Red O for 30 min. The slices were washed with 60% isopropanol three times to remove unbound dye and were then photographed. Images were obtained using a Nikon microscope. Real-time reverse transcription-PCR 2 Real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed as described by Wu et al. ( 2014 2014 ) and Lei et al. ( 2015 2015 ). Total RNA was isolated from the epididymal adipose tissue of each mouse using TRIzol (Invitrogen) and then pooled for the RT-PCR analysis. Single-stranded complementary DNA (cDNA) was synthesized using the PrimeScript RT reagent kit (TaKaRa, Japan) according to the manufacturer’s instruction. Quantitative real-time PCR was carried out using an ABI Prism 7900HT Sequence Detection System (Applied Biosystems, Foster City, CA, USA). The 20-μl reaction mixture consisted of 1×SYBR Green PCR Master Mix, 0.25 μmol/L of cDNA, and 0.2 μmol/L of each primer. The PCR conditions were as follows: denaturation for 10 min at 95 °C, followed by 40 cycles at 95 °C for 10 s, and then at 60 °C for 60 s. The following primers were used: PPARγ, 5'-CGC TGA TGC ACT GCC TAT GA-3' (forward) and 5'-AGA GGT CCA CAG AGC TGA TTC-3' (reverse); C/EBP-α, 5'-AGC AAC GAG TAC CGG GTA CG-3' (forward) and 5'-TGT TTG GCT TTA TCT CGG CTC-3' (reverse); SREBP-1c, 5'-TTG TGG AGC TCA AAG ACC TG-3' (forward) and 5'-TGC AAG AAG CGG ATG TAG TC-3' (reverse); β-ACTIN, 5'-ATG TGG ATC AGC AAG CAG GA-3' (forward) and 5'-AAG GGT GTA AAA CGC AGC TCA-3' (reverse). A relative gene-expression quantification method was used to calculate the fold change in mRNA expression according to the comparative C T method using β-ACTIN for normalization. Results were obtained from at least three independent experiments. Statistical analysis 2 All experimental data were analyzed using SPSS (Version 20.0) and expressed as the mean±standard deviation (SD). One-way analysis of variance (ANOVA) was used to evaluate the statistical differences among different groups. A P -value of < 0.05 was considered statistically significant. Results 1 Myricetin ameliorates obesity in HFD-induced mice 2 In the current study, C57BL/6 mice were fed an ND, HFD, or HFD+M (150 mg/(kg·d)) by oral gavage for 10 weeks. HFD-fed mice had a significantly higher body weight than ND-fed mice (Fig. 1a 1a ). Administration of myricetin significantly reduced the body weight of mice fed an HFD. At the end of the experiments, a 19.8% reduction in body weight was observed in the myricetin-treated group relative to the HFD-fed control group. There were no significant differences in the food or calorie intake between the HFD and HFD+M groups (Figs. 1b and 1c 1b and 1c ), suggesting that food intake did not have a significant role in the manipulation of the body weight of the mice. Changes in body weight (a), food intake (b), calorie intake (c), epididymal fat (d), subcutaneous fat (e), perirenal fat (f), and total fat (g) by the treatment of myricetin (150 mg/(kg·d)) or vehicle for male C57BL/6 mice. Data represent mean±SD ( n =12). # P< 0.05 versus ND group; * P < 0.05 versus HFD group. 1 kcal=4.1868 kJ Myricetin reduces visceral fat in HFD-induced mice 2 To determine the effect of myricetin on visceral fat, mice adipose tissues were excised and weighed. The HFD led to significant increases in epididymal (148.2%, Fig. 1d 1d ), subcutaneous (208.7%, Fig. 1e 1e ), perirenal (205.6%, Fig. 1f 1f ), and total (170.4%, Fig. 1g 1g ) fat relative to the ND-fed group. Consistent with our expectation, administration of myricetin significantly reduced these increases, to 43.2% (epididymal), 46.5% (subcutaneous), 49.1% (perirenal), and 45.3% (total fat). In conclusion, myricetin provides protection against obesity in HFD-induced mice by decreasing visceral fat accumulation. Myricetin reduces serum biochemical parameters in HFD-induced mice 2 Obesity is accepted as a chronic disease which is associated with alteration of serum parameters. Therefore, we investigated serum glucose (Fig. 2a 2a ), total TG (Fig. 2b 2b ), and cholesterol (Fig. 2c 2c ) concentrations with or without myricetin treatment. The glucose and total TG levels were significantly elevated in the HFD treatment group. However, there were no significant differences in the levels of glucose and TG between the ND group and the myricetin-treated group. Myricetin-treated mice also showed a slight reduction in serum cholesterol compared with those in the HFD-induced group. Serum glucose (a), triglyceride (b), and cholesterol (c) levels were decreased by the treatment with myricetin. Data represent mean±SD ( n =12). # P< 0.05 versus ND group; * P < 0.05 versus HFD group Effects of myricetin on adiponectin, leptin, TNF-α, and insulin 2 We determined adiponectin, leptin, tumor necrosis factor-α (TNF-α), and insulin levels. The HFD group showed a 28.17% reduction in serum adiponectin compared with the ND group (Fig. 3a 3a ). Administration of myricetin resulted in a 15.77% increase in adiponectin compared with the HFD-treated group. The leptin level was significantly increased by 100% in HFD-fed mice relative to ND-fed mice. However, in mice receiving myricetin the increase in leptin level was reduced to 55.34% (Fig. 3b 3b ). Next, we investigated the effect of myricetin administration on the inflammation marker TNF-α in HFD-induced mice. A marked increase in the production of TNF-α was observed in HFD-fed mice compared with ND-fed mice (Fig. 3c 3c ). The myricetin treatment group showed a much smaller increase in TNF-α content. To identify the effect of myricetin on obesity-associated insulin resistance, we determined the insulin level. The HFD significantly increased the insulin level by 28.63%, whereas myricetin-treated mice had slightly less insulin than those in the ND group (Fig. 3d 3d ). Changes in adiponectin (a), leptin (b), TNF-α (c), and insulin (d) levels of male C57BL/6 mice by treatment of myricetin or vehicle. Data represent mean±SD ( n =12). # P< 0.05 versus ND group; * P< 0.05 versus HFD group Effects of myricetin on serum antioxidant capacity 2 A growing amount of evidence indicates that obesity is linked to excessive oxidative stress. Therefore, we investigated the antioxidant capacity of myricetin in HFD-fed mice. GPX is an important endogenous antioxidant enzyme that is responsible for reactive oxygen species (ROS) scavenging. The serum GPX content was 24.6% lower in the HFD group than in the ND group (Fig. 4a 4a ). Administration of myricetin significantly elevated the amount of GPX by 49.6% compared with the amount in the HFD group. Our results showed a significant elevation of MDA level by 51.7% in the HFD group compared with that in the ND-treated group (Fig. 4b 4b ). However, the MDA level in the myricetin-treated group showed no significant increase, suggesting that myricetin could correct the lipid peroxidation condition. Further investigation showed that there were no significant differences in serum SOD activity among ND, HFD, and myricetin-treated groups (Fig. 4c 4c ). In addition, myricetin showed the ability to overcome the reduction in T-AOC induced by the HFD (Fig. 4d 4d ). Effects of myricetin on serum GPX (a), MDA (b), SOD (c), and T-AOC (d) levels of male C57BL/6 mice. Data represent mean±SD ( n =12). # P< 0.05 versus ND group; * P < 0.05 versus HFD group Effects of myricetin on morphology of white adipose and liver tissues 2 To characterize the morphological change in adipocytes at the end of myricetin treatment, we analyzed the epididymal white adipose tissue samples. The adipocytes in the ND group were small with clear morphology and complete structure (Fig. 5a 5a ). Adipocytes of the HFD group showed an uneven size and irregular arrangement. Strikingly, a decrease in the diameter of adipocytes of epididymal fats was noticed in mice treated with myricetin compared with those in the HFD group. Based on these observations, we conclude that myricetin can suppress fat accumulation in white adipose tissue. Next, we performed a histological analysis of liver sections from mice receiving diets with or without myricetin (Fig. 5b 5b ). The liver sections were stained by Oil Red O and then examined by microscopic imaging. The liver sections from HFD-fed mice exhibited a red color indicative of lipid accumulation. Conversely, administration of myricetin attenuated HFD-induced fat accumulation in the liver tissue. (a) Effects of myricetin on morphological changes in epididymal adipose tissue. H&E stained epididymal adipose tissue. (b) Effects of myricetin on lipid accumulation in liver section. Oil-Red O stained mice liver section. The samples were examined using Nikon (Tokyo, Japan) microscope imaging Effects of myricetin on obesity-related transcription factors in epididymal white adipose tissue 2 The reduction in body weight of HFD-induced mice receiving myricetin suggested that myricetin was capable of regulating transcription factors involved in adipogenesis (including adipogenic genes: peroxisome proliferator-activated receptor γ ( PPARγ ), CCAAT/enhancer-binding protein α ( C/EBPα )) and lipogenesis (sterol regulatory element-binding protein 1c ( SREBP-1c )). The fold change in gene expression in epididymal white adipocytes was measured by RT-PCR. Marked increase in PPARγ and C/EBPα gene expressions was observed in HFD-fed mice compared with ND-fed mice (Figs. 6a and 6b 6a and 6b ). Administration of myricetin significantly reduced HFD-induced upregulation of PPARγ and C/EBPα . SREBP-1c was also markedly higher in HFD-fed mice than in ND-fed mice (Fig. 6c 6c ). Mice receiving myricetin showed reduced SREBP-1c gene expression compared with HFD-fed mice. In conclusion, our results suggest that myricetin appeared to inhibit obesity partly by down-regulation of adipogenesis-and lipogenesis-related gene expressions. Expression of PPARγ (a), C/EBPα (b), and SREBP-1c (c). Data represent mean±SD ( n =12). ### P< 0.001 versus ND group; *** P< 0.001 versus HFD group Discussion 1 The prevalence and severity of obesity are growing worldwide (Ng et al., 2014 2014 ). Several Food and Drug Administration (FDA)-approved anti-obesity drugs are commercially available for use in weight control and weight reduction, but undesirable side-effects have made it difficult for obese patients to achieve long-term maintenance of weight loss (Colon-Gonzalez et al., 2012 2012 ; Wong et al., 2012 2012 ). Therefore, safer and efficacious agents are needed urgently to inhibit the occurrence and development of obesity on a long-term basis. Recently, several natural phytochemicals derived from fruits and vegetables have been demonstrated to suppress obesity and obesity-related metabolic syndrome (Keophiphath et al., 2009 2009 ; Chen Y.K. et al., 2011 2011 ; Ueda and Ashida, 2012 2012 ). In the present study, we found that myricetin, a naturally occurring small molecule, could provide protection against HFD-induced obesity in C57BL/6 mice. HFD leads to a progressive gain in body weight both in humans and animals. In this study, HFD caused elevated body weight in C57BL/6 mice, but administration of myricetin attenuated the HFD-induced weight gain. Given that there were no significant differences in food and calorie intake between the HFD and HFD+M groups, we conclude that the appetites of the mice were unaffected by myricetin treatment. Myricetin administration also attenuated increases in glucose, total TG, and TC levels in the serum caused by HFD. Leptin is an adipocyte-derived hormone that contributes to maintenance of food intake and improvement of energy homeostasis in peripheral tissues, such as the liver and muscle (Kim and Park, 2011 2011 ). After HFD treatment, leptin levels increased notably in our experiment, in accordance with a previous report (Frederich et al., 1995 1995 ). Adiponectin, produced by adipose tissue, has been shown to stimulate food intake and decrease energy expenditure (Kubota et al., 2007 2007 ). We found that administration of myricetin increased the levels of leptin and decreased the levels of adiponectin in obese mice, suggesting that adiponectin and leptin are involved in the anti-obesity action of myricetin. Excessive oxidative stress has been characterized in obesity and obesity-related metabolic complications. Accumulating evidence suggests that antioxidant defense systems are impaired in diet-induced obesity (Hogan et al., 2010 2010 ; Yen et al., 2011 2011 ). GPXs play a pivotal role in the maintenance of physiologically produced ROS. MDA, as an important lipid peroxidation product, has been used as a marker for evaluation of oxidative stress. In the present study, we found myricetin significantly promoted GPX activity and decreased MDA levels in HFD-fed mice, suggesting that myricetin could improve antioxidant capacity in vivo. Oxidative stress is closely linked to inflammation in obesity (Wood et al., 2009 2009 ) and elevated pro-inflammatory cytokines have been reported to augment the development of the metabolic syndrome associated with obesity (Hotamisligil et al., 1996 1996 ). TNF-α is a pro-inflammatory cytokine that has a critical role in multiple inflammatory diseases, including obesity, diabetes, osteoporosis, and rheumatoid arthritis (Feldmann and Maini, 2001 2001 ; Xu et al., 2002 2002 ; Tweedie et al., 2007 2007 ). We found that administration of myricetin reduced TNF-α levels in HFD-induced mice. Collectively, these results suggest that the development of obesity and obesity-related metabolic syndrome could be prevented by myricetin through modulating oxidative stress conditions. Adipose tissue grows by hypertrophy (cell size increase) and hyperplasia (cell number increase) in obese mice. Lipid is stored in adipose tissues when energy intake exceeds energy expenditure, resulting in hypertrophy and body weight gain (Kim and Park, 2011 2011 ). Myricetin treatment effectively reduced the size and number of epididymal adipocytes and hepatocytes, and lessened fat mass compared with the HFD-induced mice without myricetin. This observation suggests that myricetin might inhibit the process of adipogenesis and lipid accumulation during cell differentiation. To gain more mechanistic insight into the anti-obesity effect of myricetin, we examined the expression of lipogenic-and adipogenic-related genes. PPARγ and C/EBPα are regulators of many genes involved in the adipose phenotype and lipid metabolism (Hou et al., 2012 2012 ). Administration of myricetin resulted in a down-regulation of PPARγ and C/EBPα . SREBP-1c regulates the expression of target genes involved in fatty acid synthesis (Joseph et al., 2002 2002 ). The pronounced decrease in serum and hepatic TG found in the myricetin-treated group suggests that altered gene expression of SREBP-1c in adipocytes might be an underlying mechanism. This hypothesis was confirmed by the observation that the expression of lipogenic transcription factor SREBP-1c was suppressed by myricetin treatment. Taken together, these observations suggest that myricetin may suppress the expression of adipogenic and lipogenic genes, thereby regulating the onset of obesity. Conclusions 1 In summary, the present study showed that myricetin decreased serum glucose levels, regulated lipid metabolism, and provided protection against HFD-induced oxidative stress in obese mice. A further mechanistic study revealed that administration of myricetin down-regulated the expression of adipogenic ( PPARγ and C/EBPα ) and lipogenic ( SREBP-1c ) genes in HFD-induced mice. No deaths or abnormalities resulted from this experiment. 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All institutional and national guidelines for the care and use of laboratory animals were followed. 10.1631/jzus.B1600074 Project supported by the Scientific Research Foundation of the Education Department of Zhejiang Province (No. Y201328143), the Food Science and Engineering the Most Important Discipline of Zhejiang Province (No. JYTSP20142012), the National Key Technology R & D Program of China (No. 2012BAD33B08), and the Foundation of Fuli Institute of Food Science, Zhejiang University (2013), China 2016-02-19 2016-05-12 2016-04-28 2022-01-05 Copyright © Zhejiang University and Springer-Verlag Berlin Heidelberg 2016 2016 Journal of Zhejiang University-SCIENCE B (Biomedicine and Biotechnology) 06 17