Baoping Jiang

Dihydromyricetin ameliorates the oxidative stress response induced by methylglyoxal via the AMPK/GLUT4 signaling pathway in PC12 cells

Dihydromyricetin (DMY), the major bioactive flavonoid ingredient extracted from the leaves of Ampelopsis grossedentata (Hand.-Mazz) W.T. Wang, displays multiple pharmacological activities, including oxidation resistance, antitumor properties and free radical scavenging capacities. However, the role of DMY in methylglyoxal (MG)-induced diabetes-associated cognitive decline and its underlying molecular mechanisms are unclear. The aim of the present study was to evaluate the effects of DMY on oxidative stress and glucose transport activity in a MG-induced PC12 cell line and to explore the related mechanisms. The effects of DMY on cell survival and apoptosis were examined, and the dysregulation of intracellular Ca(2+) was determined. Oxidative stress was evaluated by monitoring ROS production and the glutathione to glutathione disulfide ratio. The effects of DMY on glucose metabolism were investigated using a fluorescently labeled deoxyglucose analog and by measuring ATP and lactate production. Western blot analysis was performed to examine the protein levels of glyoxalase I (Glo-1), glucose transporter 4 (GLUT4), AMP-activated protein kinase (AMPKα) and phosphorylated AMPKα (p-AMPKα). The results revealed that DMY suppressed cellular oxidative stress in PC12 cells and balanced glucose metabolism. Additionally, DMY reduced GLUT4 translocation dysfunction and increased Glo-1 and p-AMPKα expression. We found that DMY protected PC12 cells against MG-induced apoptosis and glycometabolic disorders, at least in part by restraining the hyperactivation of p-AMPK activity and normalizing the translocation of GLUT4 from the intracellular compartment, resulting in a balance in glucose uptake. This result indicates that DMY may serve as a novel and effective candidate agent to treat diabetic encephalopathy by reducing the toxicity of MG.

Metabolomics reveals the protective of Dihydromyricetin on glucose homeostasis by enhancing insulin sensitivity

Dihydromyricetin (DMY), an important flavanone found in Ampelopsis grossedentata, possesses antioxidative properties that ameliorate skeletal muscle insulin sensitivity and exert a hepatoprotective effect. However, little is known about the effects of DMY in the context of high-fat diet (HFD)-induced hepatic insulin resistance. Male Sprague-Dawley(SD) rats were fed a HFD(60% fat) supplemented with DMY for 8 weeks. The administration of DMY to the rats with HFD-induced insulin resistance reduces hyperglycemia, plasma levels of insulin, and steatosis in the liver. Furthermore, DMY treatment modulated 24 metabolic pathways, including glucose metabolism, the TCA cycle. DMY significantly enhanced glucose uptake and improved the translocation of glucose transporter 1. The specificity of DMY promoted the phosphorylation of AMP-activated protein kinase (AMPK). In addition, the exposure of HepG2 cells to high glucose concentrations impaired the insulin-stimulated phosphorylation of Akt2 Ser474 and insulin receptor substrate-1 (IRS-1) Ser612, increased GSK-3β phosphorylation, and upregulated G6Pase and PEPCK expression. Collectively, DMY improved glucose-related metabolism while reducing lipid levels in the HFD-fed rats. These data suggest that DMY might be a useful drug for use in type 2 diabetes insulin resistance therapy and for the treatment of hepatic steatosis.

The Flower Tea Coreopsis tinctoria Increases Insulin Sensitivity and Regulates Hepatic Metabolism in Rats Fed a High-Fat Diet

An infusion of Coreopsis tinctoria (CT) flowering tops is traditionally used in Portugal to control hyperglycemia; however, the effects of CT protection against high-fat diet (HFD)-induced hepatic insulin resistance have not been systematically studied and the precise mechanism of action is not clear. The metabolomic profiles of insulin-resistant rats fed a HFD and a CT-supplemented diet (HFD supplemented with CT drinking) for 8 weeks were investigated. Serum samples for clinical biochemistry and liver samples for histopathology and liquid chromatography-mass spectrometry-based metabolomic research were collected. Western blot and quantitative real-time PCR analyses were further used to measure the expression of several relevant enzymes together with perturbed metabolic pathways. Using analysis software, the CT treatment was found to significantly ameliorate the disturbance in 10 metabolic pathways. Combined metabolomic, Western blot, and quantitative real-time PCR analyses revealed that CT treatment significantly improved the glucose homeostasis by, on the one hand, through inhibiting the expression of gluconeogenic pathway key proteins glucose-6-phosphatase and phosphoenolpyruvate carboxykinase and, on the other hand, via regulating the mRNA or protein levels of the Krebs cycle critical enzymes (citrate synthase, succinate dehydrogenase complex, subunit A, flavoprotein, and dihydrolipoamide S-succinyltransferase). These results provide metabolic evidence of the complex pathogenic mechanism involved in hepatic insulin resistance and that the supplementation with CT improves insulin resistance at a global scale. Liquid chromatography-mass spectrometry-based metabolomics approaches are helpful to further understand diabetes-related mechanisms.

Minocycline inhibits ICAD degradation and the NF-κB activation induced by 6-OHDA in PC12 cells.

6-Hydroxydopamine (6-OHDA) is a neurotoxin that is commonly employed to induce lesions of the dopaminergic pathways to generating experimental models of Parkinsons disease (PD) in rodents. Antioxidant and anti-inflammatory therapy approaches have been the focus of attention in the treatment of neurodegenerative. PD and Alzheimers diseases, and oxidative stress have been implicated in these diseases. In this study, we investigated the neuroprotective effects of minocycline and the signalling pathway that is possibly involved in a PC12 cell model of PD. The results indicated that 6-OHDA cytotoxicity was accompanied by an increment in lactate dehydrogenase (LDH) release, an increase in caspase-3 protein activity, an increase in ROS generation, MDA content and decrease in the SOD, CAT activities and cell viability. Moreover, treatment with 6-OHDA alone for 24h resulted in ICAD degradation, increased nuclear translocation of NF-κB, and increased p53 expression. However, pretreatment with minocycline (5, 10, 20 µM) for 24h significantly reduced LDH release, reduced caspase-3 protein production, reduced ROS production, MDA content and attenuated the decrease in SOD, CAT activities and cell viability. Additionally, minocycline (20 µM) markedly decreased the levels of cleaved ICAD protein, down-regulated p53 activity and inhibited the nuclear translocation of NF-κB. The neuroprotective effects of minocycline were attributable to its potent antioxidant activities, which prevented the nuclear translocation of NF-κB and the subsequent promotion of cell death. Therefore, the present study supports the notion that minocycline may be a promising neuroprotective agent for the treatment of Parkinsons disease.

Protective effects of marein on high glucose-induced glucose metabolic disorder in HepG2 cells

BACKGROUND Our previous study has shown that Coreopsis tinctoria increases insulin sensitivity and regulates hepatic metabolism in high-fat diet (HFD)-induced insulin resistance rats. However, it is unclear whether or not marein, a major compound of C. tinctoria, could improve insulin resistance. Here we investigate the effect and mechanism of action of marein on improving insulin resistance in HepG2 cells. METHODS We investigated the protective effects of marein in high glucose-induced human liver carcinoma cell HepG2. In kinase inhibitor studies, genistein, LY294002, STO-609 and compound C were added to HepG2 cells 1h before the addition of marein. Transfection with siRNA was used to knock down LKB1, and 2-(N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl) amino)-2-deoxyglucose (2-NBDG), an effective tracer, was used to detect glucose uptake. RESULTS The results showed for the first time that marein significantly stimulates the phosphorylation of AMP-activated protein kinase (AMPK) and the Akt substrate of 160kDa (AS160) and enhanced the translocation of glucose transporter 1 (GLUT1) to the plasma membrane. Further study indicated that genistein (an insulin receptor tyrosine kinase inhibitor) altered the effect of marein on glucose uptake, and both LY294002 (a phosphatidylinositol 3-kinase inhibitor) and compound C (an AMP-activated protein kinase inhibitor) significantly decreased marein-stimulated 2-NBDG uptake. Additionally, marein-stimulated glucose uptake was blocked in the presence of STO-609, a CaMKK inhibitor; however, marein-stimulated AMPK phosphorylation was not blocked by LKB1 siRNA in HepG2 cells. Marein also inhibited the phosphorylation of insulin receptor substrate (IRS-1) at Ser 612, but inhibited GSK-3β phosphorylation and increased glycogen synthesis. Moreover, marein significantly decreased the expression levels of FoxO1, G6Pase and PEPCK. CONCLUSIONS Consequently, marein improved insulin resistance induced by high glucose in HepG2 cells through CaMKK/AMPK/GLUT1 to promote glucose uptake, through IRS/Akt/GSK-3β to increase glycogen synthesis, and through Akt/FoxO1 to decrease gluconeogenesis. Marein could be a promising leading compound for the development of hypoglycemic agent or developed as an adjuvant drug for diabetes mellitus.

Metabolomics reveals that vine tea (Ampelopsis grossedentata) prevents high-fat-diet-induced metabolism disorder by improving glucose homeostasis in rats

Background Vine tea (VT), derived from Ampelopsis grossedentata (Hand.-Mazz.) W.T. Wang, is an alternative tea that has been consumed widely in south China for hundreds of years. It has been shown that drinking VT on a daily basis improves hyperlipidemia and hyperglycemia. However, little is known about the preventive functions of VT for metabolic dysregulation and the potential pathological mechanisms involved. This paper elucidates the preventive effects of VT on the dysregulation of lipid and glucose metabolism using rats maintained on a high-fat-diet (HFD) in an attempt to explain the potential mechanisms involved. Methods Sprague Dawley (SD) rats were divided into five groups: a group given normal rat chow and water (control group); a group given an HFD and water (HFD group); a group given an HFD and Pioglitazone (PIO group), 5 mg /kg; and groups given an HFD and one of two doses of VT: 500 mg/L or 2000 mg/L. After 8 weeks, changes in food intake, tea consumption, body weight, serum and hepatic biochemical parameters were determined. Moreover, liver samples were isolated for pathology histology and liquid chromatography-mass spectrometry (LC-MS)-based metabolomic research. Results VT reduced the serum levels of glucose and total cholesterol, decreased glucose area under the curve in the insulin tolerance test and visibly impaired hepatic lipid accumulation. Metabolomics showed that VT treatment modulated the contents of metabolic intermediates linked to glucose metabolism (including gluconeogenesis and glycolysis), the TCA cycle, purine metabolism and amino acid metabolism. Conclusion The current results demonstrate that VT may prevent metabolic impairments induced by the consumption of an HFD. These effects may be caused by improved energy-related metabolism (including gluconeogenesis, glycolysis and TCA cycle), purine metabolism and amino acid metabolism, and reduced lipid levels in the HFD-fed rats.

Marein protects against methylglyoxal-induced apoptosis by activating the AMPK pathway in PC12 cells

Abstract Diabetic encephalopathy, which is characterized by cognitive decline and dementia, commonly occurs in patients with long-standing diabetes. Previous studies have suggested that methylglyoxal (MG), an endogenous toxic compound, plays an important role in diabetic complications such as cognitive impairment. MG induces neuronal apoptosis. To clarify whether marein, a major compound from the hypoglycemic plant Coreopsis tinctoria, prevents PC12 cell damage induced by MG, we cultured PC12 cells in the presence of MG and marein. Marein attenuated MG-induced changes in the mitochondrial membrane potential (ΔΨm), mitochondrial permeability transition pores (mPTPs), intracellular Ca2+ levels, the production of reactive oxygen species (ROS), glutathione (GSH)/glutathione disulfide (GSSG) and adenosine triphosphate (ATP), and the increase in the percentage of apoptotic cells. Marein also increased glyoxalase I (Glo1) activity, phospho-AMPKα (Thr172) and Bcl-2 expression and diminished the activation of Bax, caspase-3 and inhibitor of caspase-activated deoxyribonuclease (ICAD). Importantly, pretreatment of cells with marein diminished the compound C-induced inactivation of p-AMPK. Molecular docking simulation showed that marein interacted with the γ subunit of AMPK. In conclusion, we found for the first time that the neuroprotective effect of marein is due to a reduction of damage to mitochondria function and activation of the AMPK signal pathway. These results indicate that marein may be a potent compound for preventing/counteracting diabetic encephalopathy.

The protective effects of the native flavanone flavanomarein on neuronal cells damaged by 6-OHDA

BACKGROUND Flavanomarein is the main component of Coreopsis tinctoria Nutt. (C. tinctoria), which is a globally well-known flower tea that has a distinct flavor and many beneficial health effects, such as antioxidant activities. We aimed to explore the effect of flavanomarein on a 6-hydroxydopamine (6-OHDA)-lesioned cell model of oxidative stress. METHODS In this study, we used 6-OHDA-lesioned PC12 cells and primary cortical neurons to investigate the protective effects of flavanomarein and its potential mechanism. RESULTS The results indicated that pretreatment with flavanomarein (25, 50, or 100 µM for 24 h) significantly increased the cell viability, reduced the lactate dehydrogenase (LDH) release and improved the mitochondrial membrane potential (∆Ψm) and mitochondrial impairment. Additionally, flavanomarein markedly reduced the gene expression of tumor necrosis factor (TNF)-α and protein kinase C ζ (PKC-ζ), the nuclear translocation of p65, and the levels of p-AMPK-α and acetyl-p53. Flavanomarein also elevated the gene expression of P85α, PKC-β1, and Bcl-2, the protein expression of Sirt1 and ICAD, and the phosphorylation level of AKT. CONCLUSIONS Together, these results suggest that flavanomarein protects PC12 cells and primary cortical neurons from 6-OHDA-induced neurotoxicity by upregulating the PI3K/AKT signaling pathway and attenuating the nuclear factor kappa B (NF-κB) signaling pathway. Therefore, our study provides evidence that may aid in the development of a potential compound against 6-OHDA toxicity.

Aqueous Extract of Black Maca Prevents Metabolism Disorder via Regulating the Glycolysis/Gluconeogenesis-TCA Cycle and PPARα Signaling Activation in Golden Hamsters Fed a High-Fat, High-Fructose Diet

Maca (Lepidium meyenii Walpers) has been used as a dietary supplement and ethnomedicine for centuries. Recently, maca has become a high profile functional food worldwide because of its multiple biological activities. This study is the first explorative research to investigate the prevention and amelioration capacity of the aqueous extract of black maca (AEM) on high-fat, high-fructose diet (HFD)-induced metabolism disorder in golden hamsters and to identify the potential mechanisms involved in these effects. For 20 weeks, 6-week-old male golden hamsters were fed the following respective diets: (1) a standard diet, (2) HFD, (3) HFD supplemented with metformin, or (4) HFD supplemented with three doses of AEM (300, 600, or 1,200 mg/kg). After 20 weeks, the golden hamsters that received daily AEM supplementation presented with the beneficial effects of improved hyperlipidemia, hyperinsulinemia, insulin resistance, and hepatic steatosis in vivo. Based on the hepatic metabolomic analysis results, alterations in metabolites associated with pathological changes were examined. A total of 194 identified metabolites were mapped to 46 relative metabolic pathways, including those of energy metabolism. In addition, via in silico profiling for secondary maca metabolites by a joint pharmacophore- and structure-based approach, a compound-target-disease network was established. The results revealed that 32 bioactive compounds in maca targeted 16 proteins involved in metabolism disorder. Considering the combined metabolomics and virtual screening results, we employed quantitative real-time PCR assays to verify the gene expression of key enzymes in the relevant pathways. AEM promoted glycolysis and inhibited gluconeogenesis via regulating the expression of key genes such as Gck and Pfkm. Moreover, AEM upregulated tricarboxylic acid (TCA) cycle flux by changing the concentrations of intermediates and increasing the mRNA levels of Aco2, Fh, and Mdh2. In addition, the lipid-lowering effects of AEM in boththe serum and liver may be partly related to PPARα signaling activation, including enhanced fatty acid β-oxidation and lipogenesis pathway inhibition. Together, our data demonstrated that AEM intervention significantly improved lipid and glucose metabolism disorder by regulating the glycolysis/gluconeogenesis-TCA cycle and by modulating gene expression levels involved in the PPARα signaling pathway.