Gly-Ala-Gly-Val-Gly-Tyr, a novel synthetic peptide, improves glucose transport and exerts beneficial lipid metabolic effects in 3T3-L1 adipoctyes

Recently, it has been demonstrated that fibroin and fibroin-derived peptides enhances insulin sensitivity and glucose metabolism in adipocytes. Here, we show that a synthetic hexapeptide Gly-Ala-Gly-Val-Gly-Tyr (GAGVGY) derived from repetitive amino acid sequence of fibroin improves glucose transport and exerts beneficial lipid metabolic effects in 3T3-L1 adipocytes. GAGVGY increases both basal and insulin-stimulated glucose uptake through enhancement of GLUT1 expression and PI 3-K-dependent GLUT4 translocation, respectively. GAGVGY treatment also led to a significant reduction in the expression of lipogenic genes including sterol regulatory element binding protein-1c (SREBP1c), peroxisome proliferator-activated receptor-γ (PPARγ), and fatty acid synthase (FAS) in mature 3T3-L1 adipocytes, which was corroborated with decreased lipid accumulation by GAGVGY treatment. Additionally, in cells undergoing differentiation, mRNA levels of adipogenic genes including PPARγ and CCAAT/enhancer binding protein α (C/EBPα), stearoyl-CoA desaturase 1 (SCD1), and FAS were suppressed by GAGVGY. Furthermore, GAGVGY increased AMP-activated protein kinase (AMPK) phosphorylation and adiponectin secretion in 3T3-L1 adipocytes. The latter effect was supported with evidence showing increased AMPK activation in C2C12 myocytes treated with 3T3-L1-adipocyte-conditioned medium. Together, our data suggest that GAGVGY has multiple beneficial effects on glucose and lipid metabolism, and would control hyperglycemia without the adverse effect of weight gain.     

人参皂苷Compound K通过AMPK及SREBP1途径改善非酒精性脂肪肝的机制研究

目的：研究人参皂苷Compound K（CK）对非酒精性脂肪肝的改善作用及其与腺苷酸激活蛋白激酶（AMPK）及固醇调节元件结合蛋白（SREBP1）信号转导通路的关系。方法：采用高脂饲料喂养C57BL/6J雄性小鼠9周,建立非酒精性脂肪肝动物模型;9周后随机分为5组,正常饲料组（RD）,高脂饲料组（HFD）,给药组（HFD+CK 3,9,27 mg·kg^-1）,每天灌胃给药1次,每周测2次体质量,连续11周。实验结束后,分别称量小鼠体质量和肝质量;检测三酰甘油（TG）、胆固醇（cholesterol）、非游离脂肪酸（NEFA）、谷草转氨酶（AST）和谷丙转氨酶（ALT）水平。苏木素-伊红（HE）染色观察肝脏病理变化,Western blot法检测AMPK和乙酰辅酶A羧化酶（ACC）的磷酸化表达,PCR法检测脂肪合成转录因子SREBP1及其靶基因（FAS、SCD1）的基因表达。结果：治疗11周后,与RD组比较, HFD组小鼠肝质量及肝质量与体质量的比值显著增加（P<0.001,P<0.05）,HE染色显示HFD组较RD组肝细胞明显增大且伴有大泡性脂肪变,说明高脂饲料诱导非酒精性脂肪肝模型的建立。与HFD组比较,给药组小鼠体质量、肝质量显著降低（P<0.05）,血脂（TG、CHO、NEFA）和肝功（sAST和sALT）指标也显著降低（P<0.05,P<0.01,P<0.001）;HE染色也说明给药组能够明显改善肝脏病理状态,从而改善肝细胞脂肪变性;Western blot结果显示HFD组较RD组,AMPK和ACC磷酸化均被抑制,给药组较HFD组,AMPK和ACC均被磷酸化,且随药物浓度的增加,磷酸化越明显;PCR法结果显示HFD较RD组,脂肪合成转录因子SREBP1及其靶基因表达显著增强,而在给药组上述基因表达均显著被抑制。结论：CK对非酒精性脂肪肝具有改善作用,其机制之一可能是通过激活AMPK和ACC的磷酸化、抑制脂肪合成转录因子SREBP1及其靶基因的表达来实现的。     

Effect and mechanism of waterborne prolonged Zn exposure influencing hepatic lipid metabolism in javelin goby Synechogobius hasta

The present study was conducted to determine the effect and mechanism of waterborne Zn exposure influencing hepatic lipid deposition and metabolism in javelin goby Synechogobius hasta. S. hasta were exposed to four waterborne Zn concentrations (Zn 0.005 [control], 0.18, 0.36 and 0.55 mg l^?1, respectively) for 60 days. Sampling occurred at days 20, 40 and 60, respectively. Zn exposure increased Zn content, declined hepatic lipid content and reduced viscerosomatic and hepatosomatic indices and lipogenic enzyme activities, including 6‐phosphogluconate dehydrogenase (6PGD), glucose‐6‐phosphate dehydrogenase (G6PD), malic enzyme (ME) and fatty acid synthase (FAS). At days 20 and 60, Zn exposure decreased hepatic mRNA levels of 6PGD, G6PD, ME, FAS, acetyl‐CoA carboxylase (ACC)α, ACCβ, hormone‐sensitive lipase (HSL)a, HSLb, sterol‐regulator element‐binding protein (SREBP)‐1, peroxisome proliferators‐activated receptor (PPAR)α and PPARγ. However, the mRNA levels of CPT 1 and adipose triglyceride lipase increased following Zn exposure. On day 40, Zn exposure reduced hepatic mRNA expression of 6PGD, G6PD, ME, FAS, ACCα, ACCβ, HSLa, HSLb, SREBP‐1 and PPARγ but increased mRNA expression of CPT 1, adipose triglyceride lipase and PPARα. General speaking, Zn exposure reduced hepatic lipid content by inhibiting lipogenesis and stimulating lipolysis. For the first time, the present study provided evidence that chronic Zn exposure differentially influenced mRNA expression and activities of genes and enzymes involved in lipogenic and lipolytic metabolism in a duration‐dependent manner, and provided new insight into the relationship between metal elements and lipid metabolism. Copyright © 2015 John Wiley & Sons, Ltd.     

Mono-2-ethylhexyl phthalate induces the expression of genes involved in fatty acid synthesis in HepG2 cells

Mono-2-ethylhexyl phthalate (MEHP) is a major bioactive metabolite in the widely used industrial plasticizer diethylhexyl phthalate (DEHP) that has been found to be toxic to the liver. The aim of this study is to determine whether MEHP exposure can change the expression of fatty acid metabolism-related genes in HepG2 cells, which might be related to non-alcoholic fatty liver disease (NAFLD). The results revealed that exposure to MEHP promoted lipid accumulation in HepG2 cells. The levels of intracellular triglycerides in the hepatocytes increased after exposure to 0.8–100 μM MEHP for 24 h and 48 h. The genetic expressions of SREBP-1c, ChREBP, ACC1, FASN, and SCD significantly increased at 6 h after exposure to MEHP. At 24 h, the expression of the SREBP-1c and ChREBP genes remained increased, while the expression of the FASN and SCD genes decreased. At 48 h, the expression of SREBP-1c, ChREBP, ACC1, FASN, and SCD decreased. Furthermore, the levels of proteins including ACC1, FASN, SCD, and ChREBP (except SREBP-1c) increased at 24 h. These findings suggest that MEHP exposure can promote fatty acid synthesis in hepatocytes by regulating the expression of relevant genes and proteins, contributing to NAFLD.     

Mechanisms underlying the metabolic actions of galegine that contribute to weight loss in mice

BACKGROUND AND PURPOSE: Galegine and guanidine, originally isolated from Galega officinalis, led to the development of the biguanides. The weight-reducing effects of galegine have not previously been studied and the present investigation was undertaken to determine its mechanism(s) of action. EXPERIMENTAL APPROACH: Body weight and food intake were examined in mice. Glucose uptake and acetyl-CoA carboxylase activity were studied in 3T3-L1 adipocytes and L6 myotubes and AMP activated protein kinase (AMPK) activity was examined in cell lines. The gene expression of some enzymes involved in fat metabolism was examined in 3T3-L1 adipocytes. KEY RESULTS: Galegine administered in the diet reduced body weight in mice. Pair-feeding indicated that at least part of this effect was independent of reduced food intake. In 3T3-L1 adipocytes and L6 myotubes, galegine (50 microM-3 mM) stimulated glucose uptake. Galegine (1-300 microM) also reduced isoprenaline-mediated lipolysis in 3T3-L1 adipocytes and inhibited acetyl-CoA carboxylase activity in 3T3-L1 adipocytes and L6 myotubes. Galegine (500 microM) down-regulated genes concerned with fatty acid synthesis, including fatty acid synthase and its upstream regulator SREBP. Galegine (10 microM and above) produced a concentration-dependent activation of AMP activated protein kinase (AMPK) in H4IIE rat hepatoma, HEK293 human kidney cells, 3T3-L1 adipocytes and L6 myotubes. CONCLUSIONS AND IMPLICATIONS: Activation of AMPK can explain many of the effects of galegine, including enhanced glucose uptake and inhibition of acetyl-CoA carboxylase. Inhibition of acetyl-CoA carboxylase both inhibits fatty acid synthesis and stimulates fatty acid oxidation, and this may to contribute to the in vivo effect of galegine on body weight.     

氢杨梅素改善高脂饮食诱导的肥胖小鼠肝脏脂肪沉积及机制（英文）

有文献报道, SIRT1-AMPK信号通路可能在DHM改善肝脏细胞甘油三酯蓄积、胰岛素抵抗等作用中发挥作用。为此,本课题拟进一步观察DHM对高脂饮食诱导的肥胖小鼠肝脏脂肪沉积的影响,并探讨其可能机制。C57BL/6J小鼠采用普通饲料和高脂饲料喂养,同时分别用或不用低剂量(125 mg/kg)或高剂量(250 mg/kg)的DHM处理16周。实验期间,每两周检测体重一次。16周后,眼眶静脉取血并处死动物,同时取肩胛下、附睾与腹股沟的脂肪并用电子秤进行称重,并记录脂肪重量。全自动生化分析仪检测:血清甘油三酯(triglyceride,TG)、血清总胆固醇(totalcholesterol,TC)、血清高密度脂蛋白(high-densitylipoprotein,HDL)、血清低密度脂蛋白(low-densitylipoprotein,LDL)。取肝脏甲醛固定、HE和油红O染色检测肝脏脂肪沉积情况;比色法检测肝脏MDA和SOD含量; Realtime PCR检测相关指标的基因表达:IL-6、IL-8、TNF-α、乙酰辅酶A羧化酶(acetyl-Co A carboxylase, ACC)、固...     

五味子-甘草配伍的含药血清对肝细胞脂质堆积的影响及机制研究

目的研究大剂量五味子配伍甘草后对肝细胞脂质堆积的干预作用,并探讨相关机制。方法 SD大鼠给予五味子(SF,五味子生药量为3.9 g·kg-1的醇提物)、五味子-甘草(SG,1∶1,1∶1.5,3.9 g·kg-1),1次/d,连续给药7 d后制备含药血清。基于L02细胞,分对照组(C)、SF、SG(1∶1)和(1∶1.5)组,作用48 h后,检测LDH释放量、细胞内TG、TC含量;RT-PCR法检测PPAR-α、PPAR-γ、Fabp1/2、SREBP1c、ACCα、FAS的mRNA表达。结果与C组比,SF升高TG、TC含量,降低PPAR-α、PPAR-γ的mRNA表达,升高SREBP1c、ACCα的mRNA表达;与SF比,SG(1∶1)降低TG、TC含量,降低Fabp1/2、FAS的mRNA表达,升高SREBP1c的mRNA表达;SG(1∶1.5)仅降低TC含量,升高PPAR-γ、SREBP1c的mRNA表达,降低Fabp1/2、FAS的mRNA表达。结论五味子含药血清可显著升高肝细胞中TG、TC含量,配伍甘草可降低其升高的TG、TC含量,降低脂质堆积,其机制可能与调控PPAR-α、PPAR-γ、Fabp1/2、SREBP1c、ACCα、FAS基因mRNA的表达有关。     

蛇床子素通过激活过氧化物酶体增殖物激活受体α调节肝细胞内脂肪酸代谢

目的探讨蛇床子素是否通过激活过氧化物酶体增殖物激活受体(PPAR)α调节肝细胞内的脂肪酸代谢。方法 大鼠肝细胞在用蛇床子素12.5～100μmol.L-1作用24 h后,用比色法测定细胞内甘油三酯(TG)和游离脂肪酸(FFA)含量,用逆转录聚合酶链反应法测定PPARαmRNA表达的变化。PPARα抑制剂MK886 1μmo.lL-1预处理肝细胞2 h后,观察蛇床子素100μmo.lL-1作用24 h后对细胞内TG和FFA含量以及PPARα调控的靶基因包括固醇调节元件结合蛋白(SREBP)-1/2、脂肪酸合酶(FAS)、二脂酰甘油酰基转移酶(DGAT)、肉碱软脂酰转移酶(CPT)-1a、脂肪酸转运蛋白(FATP)4和肝脂肪酸结合蛋白(L-FABP)mRNA表达的影响。结果 蛇床子素12.5～100μmol.L-1可明显降低肝细胞内TG和FFA的含量(P<0.01),同时也能明显增加肝细胞内PPARαmRNA的表达(P<0.01)。在用PPARα抑制剂MK886预处理后,蛇床子素降低肝细胞内TG和FFA的作用则明显被减弱(P<0.01),同时抑制SREBP-1/2,FAS和DGAT mRNA表达的作用明显减弱或完全消失(P<0.01),增加CPT-1a,FATP4和L-FABPmRNA表达的作用也明显减弱或完全消失(P<0.01)。结论 蛇床子素通过激活肝细胞中PPARα后可降低细胞中的TG和FFA含量,其机制与激活PPARα后随后抑制SREBP-1/2,FAS和DGAT的基因表达以及增加CPT-1a,FATP4和L-FABP的基因表达有关。     

Taurine prevents high‐fat diet‐induced‐hepatic steatosis in rats by direct inhibition of hepatic sterol regulatory element‐binding proteins and activation of AMPK

This study investigated if the protective effect of taurine against high fat diet‐induced hepatic steatosis involves modulating the hepatic activity of 5' AMP‐activated protein kinase (AMPK) and levels/activity of the sterol regulatory element‐binding proteins‐1/2 (SREBP1/2). Rats were divided into four groups (n = 12/group) as (a) STD, fed standard diet (3.85 kcal/g); (b) STD + taurine (500 mg/kg); (c) HFD, fed HFD (4.73 kcal/g); and (d) HFD + taurine. All treatments were conducted for 12 weeks. Independent of food intake or modulating glucose or insulin levels, taurine administration to STD and HFD‐fed rats significantly lowered weekly weight gain and the accumulation of the retroperitoneal, visceral and subcutaneous fats. In both groups, taurine also reduced serum and hepatic levels of triglycerides and cholesterol and reduced hepatic mRNA and protein levels of fatty acid synthase (FAS), acetyl CoA carboxylase‐1 (ACC‐1), HMG‐CoA‐reductase and HMG‐CoA synthetase. In control rats only, taurine reduced hepatic levels of mature forms of sterol regulatory element‐binding proteins (SREBP)‐1/2. In HFD‐fed rats, taurine reduced SREBP‐1/2 precursor and mature forms in the livers of HFD‐fed rats. Besides, taurine significantly increased levels of glutathione (GSH), the activity of superoxide dismutase (SOD), and the activity of AMPK and its downstream β‐oxidation genes including peroxisome proliferator‐activated receptor‐α (PPAR‐α) and carnitine palmitoyltransferase (CPT‐1) in the livers of both the control and HFD‐fed rats. In conclusion, taurine protects against HFD‐induced hepatic steatosis stimulating antioxidant levels, and concomitant stimulating hepatic β‐oxidation and suppressing lipid synthesis, mediated by activation of AMPK and suppression of SREBP‐1.     

Enhancing effects of anagliptin on myoblast differentiation and the expression of mitochondrial biogenetic factors in C2C12 mouse skeletal muscle cells

To investigate the regulatory effects of anagliptin, a DPP-IV inhibitor used to treat type 2 diabetes mellitus (T2DM), on myoblast differentiation and mitochondrial biogenesis in C2C12 mouse skeletal muscle cells. C2C12 myoblasts were differentiated into myotubes and then treated with anagliptin (10, 25, and 50 μmol/L) for 24 hours. In C2C12 myotubes, anagliptin treatment was significantly increased the expression of MHC, PGC1α, Sirt-1, NRF-1, and TFAM and the phosphorylation of AMPK and ACC in a concentration-dependent manner. Anagliptin also significantly increased the total ATP levels in the myotubes. These results suggest that anagliptin can help prevent skeletal muscle dysfunction in T2DM by promotion of myoblast differentiation and enhancement of energy production via upregulation of mitochondrial biogenetic factors and activation of the AMPK/ACC signalling pathway.     

Similar changes in muscle lipid metabolism are induced by chronic high‐fructose feeding and high‐fat feeding in C57BL/J6 mice

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脂肪生成影响恶性肿瘤发展与转移机制的研究进展

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Ginkgolide C reduced oleic acid-induced lipid accumulation in HepG2 cells

Ginkgolide C, isolated from Ginkgo biloba, is a diterpene lactone that has multiple biological functions and can improve Alzheimer disease and platelet aggregation. Ginkgolide C also inhibits adipogenesis in 3T3-L1 adipocytes. The present study evaluated whether ginkgolide C reduced lipid accumulation and regulated the molecular mechanism of lipogenesis in oleic acid-induced HepG2 hepatocytes. HepG2 cells were treated with 0.5?mM oleic acid for 48?h to induce a fatty liver cell model. Then, the cells were exposed to various concentrations of ginkgolide C for 24?h. Staining with Oil Red O and the fluorescent dye BODIPY 493/503 revealed that ginkgolide C significantly reduced excessive lipid accumulation in HepG2 cells. Ginkgolide C decreased peroxisome proliferator-activated receptor γ and sterol regulatory element-binding protein 1c to block the expression of fatty acid synthase. Ginkgolide C treatment also promoted the expression of adipose triglyceride lipase and the phosphorylation level of hormone-sensitive lipase to enhance the decomposition of triglycerides. In addition, ginkgolide C stimulated CPT-1 to activate fatty acid β-oxidation, significantly increased sirt1 and phosphorylation of AMP-activated protein kinase (AMPK), and decreased expression of acetyl-CoA carboxylase for suppressed fatty acid synthesis in hepatocytes. Taken together, our results suggest that ginkgolide C reduced lipid accumulation and increased lipolysis through the sirt1/AMPK pathway in oleic acid-induced fatty liver cells.     

丹皮酚对小鼠酒精性脂肪肝中Adip/CaMKKβ/AMPK通路的影响

目的研究Adip/CaMKKβ/AMPK通路是否参与丹皮酚(paeonol,Pae)治疗小鼠酒精性脂肪肝的过程。方法在小鼠酒精性脂肪肝模型的基础上给予丹皮酚治疗后,通过ELISA法检测小鼠血清中各炎症因子和TG、TC,同时用ELISA法检测小鼠血清中Adip和ACC表达水平,用qPCR法及Westren blot法检测小鼠肝组织Adip、CaMKKβ、AMPKα和SREBP1c核酸和蛋白水平。 结果 Adip表达水平在各处理组无显著变化;酒精诱导增加炎症因子和TG、TC表达,降低了CaMKKβ和AMPKα在核酸和蛋白磷酸化水平上的表达,水飞蓟宾与丹皮酚降低了炎症因子和TG、TC表达,提高了CaMKKβ和AMPKα在核酸和蛋白磷酸化水平上的表达;酒精诱导增加了SREBP1c在核酸和蛋白水平上的表达,水飞蓟宾与丹皮酚降低了SREBP1c的表达。 结论 从Adip/CaMKKβ/AMPK信号传导的变化验证了丹皮酚可通过此信号转导来减轻酒精性脂肪肝的脂肪变性损伤和炎症水平。     

牛蒡子苷对L6骨骼肌细胞中腺苷酸活化蛋白激酶信号通路的影响

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A novel berberine‐metformin hybrid compound exerts therapeutic effects on obese type 2 diabetic rats

In this study, we investigated the biological activities of a novel berberine‐metformin hybrid compound (BMH473) as an anti‐diabetic agent. BMH473 exhibited significant anti‐hyperglycaemic and anti‐hyperlipidaemic effects on T2DM rats. In white adipose tissue, BMH473 reduced the perirenal and epididymal adipose tissue mass and modulated the lesions in perirenal adipose tissue, by inhibiting the protein expressions of PPAR‐?, C/EBP‐α and SREBP‐1c as well as the mRNA expressions of lipogenic genes. Moreover, BMH473 downregulated the levels of pro‐inflammatory cytokines in perirenal adipose tissue through the suppression of p‐NF‐κB. In liver, BMH473 reduced liver ectopic fat accumulation, by regulating the protein expression levels of SREBP‐1c and PPAR‐α as well as the mRNA expression levels of lipogenic genes. In addition, BMH473 inhibited hepatic gluconeogenesis by promoting the phosphorylation levels of AMPK α and ACC, and down‐regulating the mRNA expression levels of FBPase, G6Pase and PEPCK. Furthermore, BMH473 exhibited significant inhibitory effects on lipogenesis and lipid accumulation in 3T3‐L1 adipocytes by modulating the protein expression levels of PPAR‐?, C/EBP‐α and SREBP‐1 c as well as the mRNA expression levels of lipogenic genes. In conclusion, our results suggest that the newly synthesized BMH473 is beneficial for maintaining glucose and lipid homeostasis in type 2 diabetic rats, and exhibits better anti‐hyperlipidaemic effects compared to metformin and berberine.