P1012NAIL CAPILLARY DENSITY DURING POSTOCCLUSIVE REACTIVE HYPEREMIA AND VENOUS CONGESTION IS MORE IMPAIRED IN DIABETIC COMPARED TO NON-DIABETIC CKD PATIENTS

Background and Aims Αlterations in endothelial function and capillary circulation have been associated with increased cardiovascular events and overall mortality. Both diabetes mellitus (DM) and chronic kidney disease (CKD) have been associated with microcirculatory damage. Nailfold video-capillaroscory can provide a thorough assessment of capillary density and microcirculation changes. This is the first study examining in comparison microcirculatory function parameters in diabetic and non-diabetic patients with CKD. Method We included 48 diabetic and 48 non-diabetic adult patients (>18 years) with CKD (eGFR: <90 and ≥15mL/min/1.73m2), matched in a 1:1 ratio for age, sex and eGFR within each CKD stage (2, 3a, 3b and 4). All participants underwent nailfold video-capillaroscopy, during which capillary density was measured at normal conditions (baseline), after a 4-minute arterial occlusion (postocclusive reactive hyperemia) and at the end of a 2-minute venous occlusion (congestion phase). Results Baseline demographic, anthropometric and laboratory characteristics were similar between patients with and without diabetes in total and in CKD stages. Overall, no significant differences at baseline capillary density were observed between groups; however diabetic patients presented significantly lower capillary density during reactive hyperemia (36.3±3.8 vs 38.3±4.3 capillaries/mm2, p=0.022) and at venous congestion (37.8±4.0 vs 39.8±4.2 capillaries/mm2, p=0.015). When stratified according to CKD stages, the between-group differences in parameters of interest were not significant in stages 2, 3a and 4. In stage 3b, capillary density was significantly lower in diabetic compared to non-diabetic subjects at baseline (31.1±2.8 vs 33.4±3.4 capillaries/mm2, p=0.044), during postocclusive hyperemia (36.8±2.7 vs 40.0±4.3 capillaries/mm2, p=0.037) and venous congestion (38.3±2.8 vs 41.5±3.5 capillaries/mm2, p=0.022). Conclusion Capillary density during postocclusive reactive hyperemia and after venous congestion is lower in diabetic compared to non-diabetic CKD patients, a finding indicative that diabetes is an additional factor contributing to microcirculatory functional impairment in CKD. These differences are more prominent in CKD stage 3b, and less prominent in earlier and later stages.

Sympathoexcitation constrains vasodilation in the human skeletal muscle microvasculature during postocclusive reactive hyperemia

We used diffuse correlation spectroscopy to investigate sympathetic vasoconstriction, local vasodilation, and integration of these two responses in the skeletal muscle microvasculature of 20 healthy volunteers. Diffuse correlation spectroscopy probes were placed on the flexor carpi radialis muscle or vastus lateralis muscle, and a blood flow index was derived continuously. We measured hemodynamic responses during sympathoexcitation induced by forehead cooling, after which the effects of the increased sympathetic tone on vasodilatory responses during postocclusive reactive hyperemia (PORH) were examined. PORH was induced by releasing arterial occlusion (3 min) in an arm or leg. To increase sympathetic tone during PORH, forehead cooling was begun 60 s before the occlusion release and ended 60 s after the release. During forehead cooling, mean arterial pressure rose significantly and was sustained at an elevated level. Significant vasoconstriction and decreases in blood flow index followed by gradual blunting of the vasoconstriction also occurred. The time course of these responses is in good agreement with previous observations in animals. The acute sympathoexcitation diminished the peak vasodilation during PORH only in the vastus lateralis muscle, but it hastened the decline in vasodilation after the peak in both the flexor carpi radialis muscle and vastus lateralis muscle. Consequently, the total vasodilatory response assessed as the area of the vascular conductance during the first minute of PORH was significantly diminished in both regions. We conclude that, in humans, the integrated effects of sympathetic vasoconstriction and local vasodilation have an important role in vascular regulation and control of perfusion in the skeletal muscle microcirculation. NEW & NOTEWORTHY We used diffuse correlation spectroscopy to demonstrate that acute sympathoexcitation constrains local vasodilation in the human skeletal muscle microvasculature during postocclusive reactive hyperemia. This finding indicates that integration of sympathetic vasoconstriction and local vasodilation is importantly involved in vascular regulation and the control of perfusion of the skeletal muscle microcirculation in humans.

Effects of oral N-acetylcysteine on walking capacity, leg reactive hyperemia, and inflammatory and angiogenic mediators in patients with intermittent claudication

Increased oxidative stress and inflammation contribute to impaired walking capacity and endothelial dysfunction in patients with intermittent claudication (IC). The goal of the study was to determine the effects of oral treatment with the antioxidant N-acetylcysteine (NAC) on walking capacity, leg postocclusive reactive hyperemia, circulating levels of inflammatory mediators, and whole blood expression of angiogenic mediators in patients with IC. Following a double-blinded randomized crossover design, 10 patients with IC received NAC (1,800 mg/day for 4 days plus 2,700 mg before the experimental session) and placebo (PLA) before undergoing a graded treadmill exercise test. Leg postocclusive reactive hyperemia was assessed before and after the test. Blood samples were taken before and after NAC or PLA ingestions and 5 and 30 min after the exercise test for the analysis of circulating inflammatory and angiogenic markers. Although NAC increased the plasma ratio of reduced to oxidized glutathione, there were no differences between experimental sessions for walking tolerance and postocclusive reactive hyperemia. Plasma concentrations of soluble vascular cell adhesion protein-1, monocyte chemotactic protein-1, and endothelin-1 increased similarly following maximal exercise after PLA and NAC ( P < 0.001). Whole blood expression of pro-angiogenic microRNA-126 increased after maximal exercise in the PLA session, but treatment with NAC prevented this response. Similarly, exercise-induced changes in whole blood expression of VEGF, endothelial nitric oxide synthase and phosphatidylinositol 3-kinase R2 were blunted after NAC. In conclusion, oral NAC does not increase walking tolerance or leg blood flow in patients with IC. In addition, oral NAC prevents maximal exercise-induced increase in the expression of circulating microRNA-126 and other angiogenic mediators in patients with IC.