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.

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.

Alpha-solanine inhibits endothelial inflammation via nuclear factor kappa B signaling pathway.

BACKGROUND: Alpha-solanine (α-solanine) is the main glycoalkaloid in potato plants. It possesses anticarcinogenic properties and exerts toxic effects. Alpha-solanine can regulate the nuclear factor kappa B (NF-κB) signaling pathway in cancer cells and macrophages. However, little is known about the anti-inflammatory effects and the related molecular mechanisms of α-solanine on endothelial cells. OBJECTIVES: This study aims to examine the effects of α-solanine on endothelial inflammation in vitro, and to evaluate its influence on regulating the NF-κB signaling pathway. MATERIAL AND METHODS: Tumor necrosis factor alpha (TNF-α)-pcDNA3.1(+) plasmid vector was constructed and transfected into human umbilical vein endothelial cells (HUVECs). The expression of TNF-α was examined with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot. Following treatment with α-solanine or the specific NF-κB inhibitor SN50 for 24 h, cell viability was detected using Cell Counting Kit-8 (CCK-8) assay. Interleukin 6 (IL-6) and TNF-α levels in cell supernatant were detected using enzyme-linked immunosorbent assay (ELISA). The relative protein levels of phospho-P65 (p-P65), phospho-inhibitor of NF-κBα (p-IκBα) and IκB kinase (IKK) α/ß were examined with western blot. RESULTS: The α-solanine inhibits TNF-α-induced inflammatory injury in HUVECs. Compared with control cells, the cell viability was significantly decreased, the levels of TNF-α and IL-6 were significantly increased, and the relative protein levels of p-P65, p-IκBα and IKKα/ß were significantly upregulated in TNF-α-overexpressed cells. The treatment with α-solanine or SN50 decreased the levels of TNF-α and IL-6, and downregulated the relative protein levels of p-P65, p-IκBα and IKKα/ß in TNF-α-overexpressed HUVECs. CONCLUSIONS: This study demonstrated for the first time that α-solanine inhibits endothelial inflammation through the NF-κB signaling pathway. The α-solanine was suggested to be an inhibitor of the NF-κB signaling pathway in endothelial cells. The anti-inflammatory effect of α-solanine may provide a new perspective for the prevention and treatment of phlebitis.