Abstract-Endothelial dysfunction is a crucial feature in the evolution of atherosclerosis. Adiponectin is an adipocytespecific plasma protein with antiatherogenic and antidiabetic properties. In the present study, we investigated the relation between adiponectin and endothelium-dependent vasodilation. We analyzed endothelial function in 202 hypertensive patients, including those who were not taking any medication. Forearm blood flow was measured by strain-gauge plethysmography. Plasma adiponectin level was highly correlated with the vasodilator response to reactive hyperemia in the total (rϭ0.257, PϽ0.001) and no-medication (rϭ0.296, Pϭ0.026) groups but not with nitroglycerin-induced hyperemia, indicating that adiponectin affected endothelium-dependent vasodilation. Multiple regression analysis of data from all hypertensive patients revealed that plasma adiponectin level was independently correlated with the vasodilator response to reactive hyperemia. Vascular reactivity was also analyzed in aortic rings from adiponectinknockout (KO) and wild-type (WT) mice. Adiponectin-KO mice showed obesity, hyperglycemia, and hypertension compared with WT mice after 4 weeks on an atherogenic diet. Endothelium-dependent vasodilation in response to acetylcholine was significantly reduced in adiponectin-KO mice compared with WT mice, although no significant difference was observed in endothelium-independent vasodilation in response to sodium nitroprusside. Our observations suggest that hypoadiponectinemia is associated with impaired endothelium-dependent vasorelaxation and that the measurement of plasma adiponectin level might be helpful as a marker of endothelial dysfunction.

Increased production of reactive oxygen species (ROS) in diabetes may be a common pathway linking diverse pathogenic mechanisms of diabetic vascular complications, including nephropathy. Assessment of the oxidative stress production pathway is therefore important for the prediction and prevention of diabetic complications. However, ROS production mechanisms remain unclear in diabetic glomeruli. To identify the source and determine the mechanisms of ROS production in the diabetic kidney, diabetes was induced with streptozotocin in rats. After 6 wk, glomerular ROS production had increased in the streptozotocin rat kidney, as assessed by dihydroethidium-derived chemiluminescence. ROS production was increased by the addition of NADH or L-arginine and was partially reduced by the addition of diphenylene iodonium or N(G)-nitro-L-arginine methyl ester, identifying NAD(P)H oxidase and nitric oxide (NO) synthase (NOS) as ROS sources. The mRNA and protein expression of endothelial NOS (eNOS), as measured by real-time RT-PCR and Western blotting, increased significantly (mRNA level, 1.3-fold; protein level, 1.8-fold). However, the dimeric form of eNOS was decreased in diabetic glomeruli, as measured by low-temperature SDS-PAGE. Production of renal ROS and NO by uncoupled NOS was imaged by confocal laser microscopy after renal perfusion of 2',7'-dichlorofluorescein diacetate (a ROS marker) and diaminorhodamine-4M AM (a NO marker) with L-arginine. Accelerated ROS production and diminished bioavailable NO caused by NOS uncoupling were noted in the diabetic kidney. Administration of tetrahydrobiopterin (BH4), a cofactor for eNOS, reversed the decreased dimeric form of eNOS and glomerular NO production. Our results indicate that NAD(P)H oxidase and uncoupling of eNOS contribute to glomerular ROS production, mediated by the loss of BH4 availability. These mechanisms are potential key targets for therapeutic interventions.

Objective. To investigate endothelial function and levels of vascular oxidative stress in rat adjuvantinduced arthritis (AIA), in view of mounting evidence for an association between rheumatoid arthritis (RA) and accelerated vascular disease.Methods. Thoracic aortic rings were prepared from AIA and control rats. After preconstriction by norepinephrine, the vasodilatory response to acetylcholine was determined. The amounts of 4-hydroxy-2-nonenal (HNE) and nitrotyrosine in AIA rat aortas were measured by Western blotting. Homogenates of the aortas were incubated with various substrates for superoxide-producing enzymes, and superoxide production was assessed by fluorogenic oxidation of dihydroethidium to ethidium. Expression of endothelial nitric oxide synthase (eNOS) in aortas was examined by real-time reverse transcriptase-polymerase chain reaction and Western blotting. Serum levels of tetrahydrobiopterin (BH 4 ), a critical eNOS cofactor, were determined by high-performance liquid chromatography.Results. Endothelium-dependent relaxation of the aortic ring was significantly depressed in AIA rats compared with control rats. The amounts of HNE and nitrotyrosine were increased in AIA rat aortas, indicating overproduction of reactive oxygen species. Incubation of AIA rat aorta homogenates with NADH or L-arginine, a substrate of eNOS, resulted in a significant increase in superoxide production. Endothelial NOS was highly expressed in AIA rat aortas. Serum levels of BH 4 were significantly lower in AIA. Treatment of AIA with BH 4 reversed the endothelial dysfunction, suggesting that its deficiency may contribute to the uncoupling of eNOS.Conclusion. Vascular dysfunction in RA can be partially modeled in animals. NAD(P)H oxidase and uncoupled eNOS are responsible for the increase in vascular oxidative stress, which is likely to be involved in the endothelial dysfunction in AIA.

Our previous study revealed the antihypertensive effects of green coffee bean extract (GCE) ingestion in spontaneously hypertensive rats. We suggested that this antihypertensive action was due to the fact that