Burlet Elodie, Jain Sushil K
Departments of Pediatrics and Biochemistry & Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA, 71130, USA.
Mol Cell Biochem. 2017 May;429(1-2):1-10. doi: 10.1007/s11010-016-2931-7. Epub 2017 Jan 13.
Blood and tissue levels of manganese (Mn) are lower in type 2 diabetic and atherosclerosis patients compared with healthy subjects. Adiponectin has anti-diabetic and anti-atherogenic properties. Impairment in Disulfide bond A-like protein (DsbA-L) is associated with low adiponectin levels and diabetes. This study investigates the hypothesis that the beneficial effects of Mn supplementation are mediated by adiponectin and DsbA-L. At 6 weeks of age, Male Zucker diabetic fatty rats (ZDF) were randomly divided into two groups: diabetic controls and Mn-supplemented diabetic rats. Each rat was supplemented with Mn (D+Mn, 16 mg/kg BW) or water (placebo, D+P) daily for 7 weeks by oral gavage. For cell culture studies, Human Umbilical Vein Endothelial Cells (HUVEC) or 3T3L1 adipocytes were pretreated with Mn (0-10 µM MnCl) for 24 h, followed by high glucose (HG, 25 mM) or normal glucose (5 mM) exposure for another 24 h. Mn supplementation resulted in higher adiponectin (p = 0.01), and lower ICAM-1 (p = 0.04) and lower creatinine (p = 0.04) blood levels compared to those in control ZDF rats. Mn-supplemented rats also caused reduced oxidative stress (ROS) and NADPH oxidase, and higher DsbA-L expression in the liver (p = 0.03) of ZDF rats compared to those in livers of control rats; however, Fe levels in liver were lower but not significant (p = 0.08). Similarly, treatment with high glucose (25 mM) caused a decrease in DsbA-L, which was prevented by Mn supplementation in HUVEC and adipocytes. Mechanistic studies with DsbA-L siRNA showed that the beneficial effects of Mn supplementation on ROS, NOX4, and ICAM-1 expression were abolished in DsbA-L knock-down HUVEC. These studies demonstrate that DsbA-L-linked adiponectin mediates the beneficial effects observed with Mn supplementation and provides evidence for a novel mechanism by which Mn supplementation can increase adiponectin and reduce the biomarkers of endothelial dysfunction in diabetes.
与健康受试者相比，2型糖尿病患者和动脉粥样硬化患者血液和组织中的锰（Mn）水平较低。脂联素具有抗糖尿病和抗动脉粥样硬化特性。二硫键A样蛋白（DsbA-L）功能受损与脂联素水平低及糖尿病有关。本研究探讨了锰补充剂的有益作用是由脂联素和DsbA-L介导的这一假说。6周龄时，将雄性Zucker糖尿病脂肪大鼠（ZDF）随机分为两组：糖尿病对照组和锰补充糖尿病大鼠。通过口服灌胃，每天给每只大鼠补充锰（D+Mn，16mg/kg体重）或水（安慰剂，D+P），持续7周。对于细胞培养研究，人脐静脉内皮细胞（HUVEC）或3T3L1脂肪细胞先用锰（0-10µM MnCl）预处理24小时，然后再暴露于高糖（HG，25mM）或正常葡萄糖（5mM）环境中24小时。与对照ZDF大鼠相比，补充锰导致脂联素水平升高（p=0.01），细胞间黏附分子-1（ICAM-1）水平降低（p=0.04），肌酐水平降低（p=0.04）。与对照大鼠肝脏相比，补充锰的大鼠还导致ZDF大鼠肝脏中的氧化应激（ROS）和NADPH氧化酶降低，DsbA-L表达升高（p=0.03）；然而，肝脏中的铁水平较低但无统计学意义（p=0.08）。同样，高糖（25mM）处理导致HUVEC和脂肪细胞中DsbA-L降低，而锰补充可预防这种降低。用DsbA-L siRNA进行的机制研究表明，在DsbA-L敲低的HUVEC中，补充锰对ROS、NOX4和ICAM-1表达的有益作用被消除。这些研究表明，与DsbA-L相关的脂联素介导了补充锰所观察到的有益作用，并为补充锰可增加脂联素并降低糖尿病患者内皮功能障碍生物标志物的新机制提供了证据。
