Ginsenoside Rk1 improves endothelial function in diabetes through activating peroxisome proliferator-activated receptors.

Ginsenoside Rk1, one kind of ginsenoside, is a minor ginsenoside found in Panax ginseng and used as traditional Chinese medicine for centuries. It exhibits anti-tumor and anti-aggregation effects. However, little research has been done on its effect on endothelial function. This study investigated whether ginsenoside Rk1 improved endothelial dysfunction in diabetes and the underlying mechanisms in vivo and in vitro. Male C57BL/6 mice were fed with a 12 week high-fat diet (60% kcal % fat), whereas treatment groups were orally administered with ginsenoside Rk1 (10 and 20 mg per kg per day) in the last 4 weeks. Aortas isolated from C57BL/6 mice were induced by high glucose (HG; 30 mM) and co-treated with or without ginsenoside Rk1 (1 and 10 µM) for 48 h ex vivo. Moreover, primary rat aortic endothelial cells (RAECs) were cultured and stimulated by HG (44 mM) to mimic hyperglycemia, with or without the co-treatment of ginsenoside Rk1 (10 µM) for 48 h. Endothelium-dependent relaxations of mouse aortas were damaged with elevated oxidative stress and downregulation of three isoforms of peroxisome proliferator-activated receptors (PPARs), PPAR-α, PPAR-ß/δ, and PPAR-γ, as well as endothelial nitric oxide synthase (eNOS) phosphorylation due to HG or high-fat diet stimulation, which also existed in RAECs. However, after the treatment with ginsenoside Rk1, these impairments were all ameliorated significantly. Moreover, the vaso-protective and anti-oxidative effects of ginsenoside Rk1 were abolished by PPAR antagonists (GSK0660, GW9662 or GW6471). In conclusion, this study reveals that ginsenoside Rk1 ameliorates endothelial dysfunction and suppresses oxidative stress in diabetic vasculature through activating the PPAR/eNOS pathway.

3,4',5-Trimethoxy-trans-stilbene ameliorates hepatic insulin resistance and oxidative stress in diabetic obese mice through insulin and Nrf2 signaling pathways.

Resveratrol has profound benefits against diabetes. However, whether its methylated derivative 3,4',5-trimethoxy-trans-stilbene (3,4',5-TMS) also plays a protective role in glucose metabolism is not characterized. We aimed to study the anti-diabetic effects of 3,4',5-TMS in vitro and in vivo. Insulin-resistant HepG2 cells (IR-HepG2) were induced by high glucose plus dexamethasone whilst six-week-old male C57BL/6J mice received a 60 kcal% fat diet for 14 weeks to establish an obese diabetic model. 3,4',5-TMS did not reduce the cell viability of IR-HepG2 cells at concentrations of 0.5 and 1 µM, which enhanced the capability of glycogen synthesis and glucose consumption in IR-HepG2 cells. Four-week oral administration of 3,4',5-TMS at 10 mg kg-1 day-1 ameliorated insulin sensitivity and glucose tolerance of diet-induced obese (DIO) mice. 3,4',5-TMS activated the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway by inhibiting phosphorylation of insulin receptor substrate (IRS)-1 at Ser307 and increasing the protein levels of IRS-1 and IRS-2 to restore the insulin signaling pathway in diabetes. 3,4',5-TMS also upregulated the phosphorylation of glycogen synthase kinase 3 beta (GSK3ß) at Ser9. 3,4',5-TMS suppressed oxidative stress by increasing the protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H : quinone oxidoreductase 1 (NQO1) and antioxidant enzyme activity. In summary, 3,4',5-TMS alleviated hepatic insulin resistance in vitro and in vivo, by the activation of the insulin signaling pathway, accomplished by the suppression of oxidative stress.

Baicalin ameliorates insulin resistance and regulates hepatic glucose metabolism via activating insulin signaling pathway in obese pre-diabetic mice.

BACKGROUND: Diabetes belongs to the most prevalent metabolic diseases worldwide, which is featured with insulin resistance, closely associated with obesity and urgently needs to be treated. Baicalin, belonging to natural flavonoids, has been reported to inhibit oxidative stress or inflammatoin. PURPOSE: This study investigated the properties of baicalin on modulating abnormal glucolipid metabolism, as well as the underlying in-vitro and in-vivo mechanisms. METHODS: Insulin-resistant (IR)-HepG2 cells were stimulated by dexamethasone (20 µM) and high glucose (50 mM) for 48 h and incubated with or without baicalin or metformin for another 16 h. Male C57BL/6 J mice were fed with a high-fat diet (HFD, 60 % kcal% fat) during the total 14 weeks. Obese mice were then administered with baicalin (50 and 100 mg/kg) or vehicle solution everyday through oral gavage during the last 4-week period. Moreover, baicalin metabolisms in vitro and in vivo were determined using UPLC/MS/MS to study its metabolism situation. RESULTS: Exposure to dexamethasone and high glucose damaged the abilities of glycogen synthesis and glucose uptake with elevated oxidative stress and increased generation levels of advanced glycation end-products (AGEs) in HepG2 cells. These impairments were basically reversed by baicalin treatment. Four-week oral administration with baicalin ameliorated hyperglycemia and dyslipidemia in HFD-induced obese and pre-diabetic mice. Downregulation of IRS/PI3K/Akt signaling pathway accomplished with reduced GLUT4 expression and enhanced GSK-3ß activity was observed in insulin resistant HepG2 cells as well as liver tissues from pre-diabetic mice; and such effect was prevented by baicalin. Moreover, baicalin and its matabolites were detected in IR-HepG2 cells and mouse plasma. CONCLUSION: The study illustrated that baicalin alleviated insulin resistance by activating insulin signaling pathways and inhibiting oxidative stress and AGEs production, revealing the potential of baicalin to be a therapeutic natural flavonoid against hepatic insulin and glucose-lipid metabolic disturbance in pre-diabetes accompanied with obesity.

Portulaca Oleracea L. (Purslane) Extract Protects Endothelial Function by Reducing Endoplasmic Reticulum Stress and Oxidative Stress through AMPK Activation in Diabetic Obese Mice.

Portulaca oleracea L. (purslane) is a food and a traditional drug worldwide. It exhibits anti-inflammatory, anti-oxidative, anti-tumor, and anti-diabetic bioactivities; but its activity on diabetic-associated endothelial dysfunction is unknown. This study aimed to investigate the effect of purslane on endothelial function and the underlying mechanisms. Male C57BL/6 mice had 14-week ad libitum access to a high-fat rodent diet containing 60% kcal% fat to induce obesity and diabetes whereas purslane extract (200 mg/kg/day) was administered during the last 4 weeks via intragastric gavage. Primary rat aortic endothelial cells and isolated mouse aortas were cultured with a risk factor, high glucose or tunicamycin, together with purslane extract. By ESI-QTOF-MS/MS, flavonoids and their glycoside products were identified in the purslane extract. Exposure to high glucose or tunicamycin impaired acetylcholine-induced endothelium-dependent relaxations in aortas and induced endoplasmic reticulum (ER) stress and oxidative stress with the downregulation of 5' AMP-activated protein kinase (AMPK)/ endothelial nitric oxide synthase (eNOS) signaling. Co-incubation with purslane significantly ameliorated these impairments. The effects of purslane were abolished by Compound C (AMPK inhibitor). Four-week purslane treatment ameliorated aortic relaxations, ER stress, and oxidative stress in diabetic obese mice. This study supported that purslane protected endothelial function, and inhibited ER stress and oxidative stress in vasculature through AMPK/eNOS activation, revealing its therapeutic potential against vascular complications in diabetes.

Anti-inflammatory activity of flavonols via inhibiting MAPK and NF-κB signaling pathways in RAW264.7 macrophages.

Fisetin (Fis), quercetin (Que), and myricetin (Myr) are flavonols with similar structure but different number of hydroxyl groups. The present research focused on the anti-inflammatory effect of these three flavonols in lipopolysaccharide-stimulated RAW264.7 cells. The number and site of hydroxyl group in flavonols obviously affected their anti-inflammation activity. These flavonols suppressed the overproduction of nitric oxide. Fis showed the best activity with an inhibition rate of 52% at 20 µM. Moreover, the flavonols reduced the levels of ROS, TNF-α, and IL-6. The mechanistic study showed that they inhibited the activation of NF-κB and MAPK pathways by suppressing the phosphorylation of IκBα, p65, JNK, ERK, p38, MEK, and reducing the nuclear translocation of NF-κB p65. In addition, the metabolism of the flavonols was examined. The results indicated that Fis was both methylated and glucuronidated. Que and Myr were mainly transformed into methylated products. This study highlights the anti-inflammatory activity of flavonols, particularly Fis, which has the potential for the prevention or treatment of inflammation as an adjuvant medicine or food additive.

Exploration of natural flavones' bioactivity and bioavailability in chronic inflammation induced-type-2 diabetes mellitus.

Diabetes, being the most widespread illness, poses a serious threat to global public health. It seems that inflammation plays a critical role in the pathophysiology of diabetes. This review aims to demonstrate a probable link between type 2 diabetes mellitus (T2DM) and chronic inflammation during its development. Additionally, the current review examined the bioactivity of natural flavones and the possible molecular mechanisms by which they influence diabetes and inflammation. While natural flavones possess remarkable anti-diabetic and anti-inflammatory bioactivities, their therapeutic use is limited by the low oral bioavailability. Several factors contribute to the low bioavailability, including poor water solubility, food interaction, and unsatisfied metabolic behaviors, while the diseases (diabetes, inflammation, etc.) causing even less bioavailability. Throughout the years, different strategies have been developed to boost flavones' bioavailability, including structural alteration, biological transformation, and innovative drug delivery system design. This review addresses current advancements in improving the bioavailability of flavonoids in general, and flavones in particular. Clinical trials were also analyzed to provide insight into the potential application of flavonoids in diabetes and inflammatory therapies.

3,3',4,5'-Tetramethoxy-trans-stilbene Improves Insulin Resistance by Activating the IRS/PI3K/Akt Pathway and Inhibiting Oxidative Stress.

The potential anti-diabetic effect of resveratrol derivative, 3,3',4,5'-tetramethoxy-trans-stilbene (3,3',4,5'-TMS) and its underlying mechanism in high glucose (HG) and dexamethasone (DXMS)-stimulated insulin-resistant HepG2 cells (IR-HepG2) were investigated. 3,3',4,5'-TMS did not reduce the cell viability of IR-HepG2 cells at the concentrations of 0.5-10 µM. 3,3',4,5'-TMS increased the potential of glucose consumption and glycogen synthesis in a concentration-dependent manner in IR-HepG2 cells. 3,3',4,5'-TMS ameliorated insulin resistance by enhancing the phosphorylation of glycogen synthase kinase 3 beta (GSK3ß), inhibiting phosphorylation of insulin receptor substrate-1 (IRS-1), and activating phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway in IR-HepG2 cells. Furthermore, 3,3',4,5'-TMS significantly suppressed levels of reactive oxygen species (ROS) with up-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) expression. To conclude, the beneficial effect of 3,3',4,5'-TMS against insulin resistance to increase glucose consumption and glycogen synthesis was mediated through activation of IRS/PI3K/Akt signaling pathways in the IR-HepG2 cells, accomplished with anti-oxidative activity through up-regulation of Nrf2.

Panax notoginseng extract and total saponin suppress diet-induced obesity and endoplasmic reticulum stress in epididymal white adipose tissue in mice.

BACKGROUND: Investigation on protective effects of Panax notoginseng against obesity and its related mechanisms is incomplete. Present study aimed to investigate the potential anti-obesity effect of the total saponins (PNS) and ethanolic extract of P. notoginseng (PNE). METHODS: Six-week-old male C57BL/6J mice received 45% kcal fat diet for 12 weeks to induce obesity. Oral administration of PNS and PNE at 20 mg/kg/day was applied for the last 4 weeks in the obese mice. Lipid profile was determined by ELISA. Histological examination was performed in liver and fat tissues. Protein levels were measured by Western blot. RESULTS: PNS and PNE did not cause weight loss. PNE but not PNS decreased the mass of epididymal and retroperitoneal white adipose tissue, accompanied by a reduction in adipocyte hypertrophy. PNS and PNE improved lipid profile by reducing the concentrations of triglyceride, total cholesterol and low-density lipoprotein cholesterol in plasma or liver samples. PNS and PNE also relieved fatty liver in obese mice. PNS and PNE inhibited expression and phosphorylation of endoplasmic reticulum (ER) stress-responsive proteins in hypertrophic adipose tissue. CONCLUSIONS: PNS and PNE can regulate ER stress-mediated apoptosis and inflammation to alleviate obesity.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies.

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, and EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low/moderate levels may favor tumorigenesis, while higher levels would exert antitumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "doubleedged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

Panax Notoginseng Protects against Diabetes-Associated Endothelial Dysfunction: Comparison between Ethanolic Extract and Total Saponin.

Previous studies revealed a cardioprotective potential of Panax notoginseng to relieve acute myocardial infarction and focal cerebral ischemia-reperfusion. However, whether P. notoginseng protects endothelial function in diabetes and the underlying mechanisms remain to be explored. P. notoginseng contains several chemical components including saponins, which are commonly believed as the major bioactive ingredients. The present study was aimed to examine and compare the vaso-protective effects of the ethanolic extract of P. notoginseng (PNE) and total saponin (PNS). Both aortas and carotid arteries were isolated from male C57BL/6J mice for ex vivo treatment with risk factors (high glucose or tunicamycin) with and without the presence of PNS and PNE. Diabetic model was established by feeding the mice with a high-fat diet (45% kcal% fat) for 12 weeks, while PNS and PNE were administrated by oral gavage at 20 mg/kg/day for another 4 weeks. Ex vivo exposure to high glucose impaired acetylcholine-induced endothelium-dependent relaxations in mouse aortas, decreased phosphorylation of AMPK and eNOS, and induced endoplasmic reticulum (ER) stress and oxidative stress. These effects were reversed by cotreatment of PNS and PNE with PNS being more potent. Furthermore, the vaso-protective effects were abolished by Compound C (AMPK inhibitor). Chronic treatment with PNS and PNE improved endothelium-dependent relaxations and alleviated ER stress and oxidative stress in aortas from high-fat diet-induced obese mice. PNE was more effective to improve glucose sensitivity and normalize blood pressure in diabetic mice. The present results showed that PNS and PNE reduced ER stress and oxidative stress and, subsequently, improved endothelial function in diabetes through AMPK activation. This study provides new inspiration on the therapeutic potential of P. notoginseng extract against vascular diseases associated with metabolic disorders.

The anti-inflammatory potential of Portulaca oleracea L. (purslane) extract by partial suppression on NF-κB and MAPK activation.

Portulaca oleracea L. (Purslane) has great potential as food and traditional drugs in several countries. The purpose of this study was to evaluate the anti-inflammatory effects of purslane extract on lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Purslane extracts significantly reduced LPS-induced synthesis of NO in a dose-dependent manner, as well as the expression levels of iNOS and COX-2. The productions of TNF-α and IL-6 were also significantly reduced at the higher dose of 400 µg/ml. Meanwhile, the expression levels of P65, p-P65, p-MEK and p-IκB-α were inhibited dose-dependently. The nuclear translocation of P65 was partially prevented by the extract, which explained the inhibition of NF-κB pathway. In addition, three reported flavonoids, named luteolin, kaempferol and quercitrin, were identified in the extract, which might be responsible for its anti-inflammatory effects. Above all, our research has partially proved that purslane could be considered as a natural anti-inflammatory agent in further applications.