Post-occlusive reactive hyperemia and skeletal muscle capillary hemodynamics.

Post-occlusive reactive hyperemia (PORH) is an accepted diagnostic tool for assessing peripheral macrovascular function. While conduit artery hemodynamics have been well defined, the impact of PORH on capillary hemodynamics remains unknown, despite the microvasculature being the dominant site of vascular control. Therefore, the purpose of this investigation was to determine the effects of 5 min of feed artery occlusion on capillary hemodynamics in skeletal muscle. We tested the hypothesis that, upon release of arterial occlusion, there would be: 1) an increased red blood cell flux (fRBC) and red blood cell velocity (VRBC), and 2) a decreased proportion of capillaries supporting RBC flow compared to the pre-occlusion condition. METHODS: In female Sprague-Dawley rats (n = 6), the spinotrapezius muscle was exteriorized for evaluation of capillary hemodynamics pre-occlusion, 5 min of feed artery occlusion (Occ), and 5 min of reperfusion (Post-Occ). RESULTS: There were no differences in mean arterial pressure (MAP) or capillary diameter (Dc) between pre-occlusion and post-occlusion (P > 0.05). During 30 s of PORH, capillary fRBC was increased (pre: 59 ± 4 vs. 30 s-post: 77 ± 2 cells/s; P < 0.05) and VRBC was not changed (pre: 300 ± 24 vs. 30 s post: 322 ± 25 µm/s; P > 0.05). Capillary hematocrit (Hctcap) was unchanged across the pre- to post-occlusion conditions (P > 0.05). Following occlusion, there was a 20-30% decrease in the number of capillaries supporting RBC flow at 30 s and 300 s-post occlusion (pre: 92 ± 2%; 30 s-post: 66 ± 3%; 300 s-post: 72 ± 6%; both P < 0.05). CONCLUSION: Short-term feed artery occlusion (i.e. 5 min) resulted in a more heterogeneous capillary flow profile with the presence of capillary no-reflow, decreasing the percentage of capillaries supporting RBC flow. A complex interaction between myogenic and metabolic mechanisms at the arteriolar level may play a role in the capillary no-reflow with PORH. Measurements at the level of the conduit artery mask significant alterations in blood flow distribution in the microcirculation.

Low Vitamin D Levels are Associated with Vascular Endothelial Dysfunction in Patients with Poorly Controlled Type 2 Diabetes: A Retrospective Study.

AIM: This study aimed to determine the association between serum 25-hydroxyvitamin D (25(OH)D) levels and vascular endothelial function in patients with type 2 diabetes (T2D). METHODS: This retrospective study included 113 patients with poorly controlled T2D who were admitted for in-hospital diabetes educational program and underwent measurements of serum 25(OH)D levels and reactive hyperemia index (RHI). RESULTS: Serum 25(OH)D levels significantly correlated with RHI in T2D patients. Receiver operating characteristic (ROC) curve analysis showed that serum 25(OH)D level of 16.5 ng/mL is the optimal cutoff level for predicting vascular endothelial dysfunction (RHI＜1.67), with a sensitivity of 68.5%, specificity of 67.9%, and area under the ROC curve of 0.668 (95% confidence interval [CI]: 0.566-0.770, p=0.002). The mean RHI was significantly lower (1.70±0.54) in patients with low 25(OH)D levels (n=56, 25(OH)D levels ＜16.5 ng/mL) than that (1.99±0.58; p＜0.001) in patients with high 25(OH)D levels (n=57, 25(OH)D level ≥ 16.5 ng/mL). The proportion of patients with RHI＜1.67 was higher in the low 25(OH)D group than in the high 25(OH)D group (38% vs. 18%; p＜0.001). Multivariate logistic regression analysis identified that serum 25(OH)D level ＜16.5 ng/mL was associated with increased odds of RHI ＜1.67 (odds ratio 4.598, 95% CI 1.961-10.783, p＜0.001). CONCLUSION: The results demonstrated the association of serum 25(OH)D levels with endothelial function in poorly controlled T2D patients and identified serum 25(OH)D level of ＜16.5 ng/mL as a predictor of RHI ＜1.67. Serum 25(OH)D level is a potentially useful marker of vascular endothelial dysfunction in poorly controlled T2D patients.

Hyponatremia and Renal Venous Congestion in Heart Failure Patients.

OBJECTIVE: The interrelationship between the heart and kidneys has a great importance in the homeostasis of the cardiovascular system. Heart failure patients present intrarenal arterial hypoperfusion and intrarenal venous congestion due to reduced left ventricle ejection fraction, which triggers numerous neurohormonal factors. The aim of this study was to investigate intrarenal vascularization (arterial and venous), as well as the links between it and systemic congestion and, on the other side, with the mortality in patients with heart failure. Material and Methods. This cross-sectional study was performed on a group of 44 patients with heart failure in different stages of evolution and 44 healthy subjects, matched for age and gender, as controls. Serum natremia, NT-proBNP, and creatinine analyses were performed in all patients and controls. Renal and cardiac ultrasonography was done in all patients and controls, recording intrarenal arterial resistive index (RRI), intrarenal venous flow (IRVF) pattern, renal venous stasis index (RVSI), and left ventricular ejection fraction (LVEF). Data are recorded and presented as mean ± standard deviation. Statistical analyses were performed using the Student t-test, ANOVA test, and the Pearson correlation. Differences were considered statistically significant at the value of p < 0.05. RESULTS: Hyponatremia was identified in 47.72% of the HF patients. This study revealed correlations between serum natremia and LVEF, NT-proBNP, serum creatinine, interlobar venous RVSI (p < 0.00001), and interlobar artery RRI (p ≤ 0.002). Hyponatremia and renal venous congestion represent negative prognostic factors in HF patients. CONCLUSION: In HF patients, hyponatremia was correlated with cardiac dysfunction and intrarenal venous congestion. Hyponatremia and renal venous congestion represented negative prognostic factors in HF patients.

Platelet and Erythrocyte Extravasation across Inflamed Corneal Venules Depend on CD18, Neutrophils, and Mast Cell Degranulation.

Platelet extravasation during inflammation is under-appreciated. In wild-type (WT) mice, a central corneal epithelial abrasion initiates neutrophil (PMN) and platelet extravasation from peripheral limbal venules. The same injury in mice expressing low levels of the ß2-integrin, CD18 (CD18hypo mice) shows reduced platelet extravasation with PMN extravasation apparently unaffected. To better define the role of CD18 on platelet extravasation, we focused on two relevant cell types expressing CD18: PMNs and mast cells. Following corneal abrasion in WT mice, we observed not only extravasated PMNs and platelets but also extravasated erythrocytes (RBCs). Ultrastructural observations of engorged limbal venules showed platelets and RBCs passing through endothelial pores. In contrast, injured CD18hypo mice showed significantly less venule engorgement and markedly reduced platelet and RBC extravasation; mast cell degranulation was also reduced compared to WT mice. Corneal abrasion in mast cell-deficient (KitW-sh/W-sh) mice showed less venule engorgement, delayed PMN extravasation, reduced platelet and RBC extravasation and delayed wound healing compared to WT mice. Finally, antibody-induced depletion of circulating PMNs prior to corneal abrasion reduced mast cell degranulation, venule engorgement, and extravasation of PMNs, platelets, and RBCs. In summary, in the injured cornea, platelet and RBC extravasation depends on CD18, PMNs, and mast cell degranulation.

Endothelial Function in Patients With Von Willebrand Disease.

In patients with von Willebrand disease (vWD) the interest in age-related comorbidities has grown, because the life expectancy of these patients has increased. The research question of this study was whether patients with vWD show a different endothelial function compared to the general population. A total of 37 patients with type 1 (n = 23), type 2 (n = 10) and type 3 (n = 4) vWD, 14 controls and 38 patients with coronary artery disease (CAD) were included in this study. Five markers of endothelial dysfunction (MOED) were determined. Moreover, the endothelial function was examined using the Itamar Endo-PAT. The reactive hyperemia index (RHI) was calculated from the results. The markers soluble intercellular adhesion molecule-1 (p = 0.171), P-Selectin (p = 0.512), interleukin-6 (p = 0.734) and monocyte chemoattractant protein-1 (p = 0.761) showed higher levels in patients with vWD, but were not significantly different compared to the control group. RHI was impaired in CAD-patients (1.855), whereas vWD patients had mean results of 1.870 and controls 2.112 (p = 0.367). In this study, the endothelial function measurements of patients with von Willebrand disease were not significantly different compared to healthy controls.

Pannexin 1 channels control the hemodynamic response to hypoxia by regulating O2-sensitive extracellular ATP in blood.

Pannexin 1 (Panx1) channels export ATP and may contribute to increased concentration of the vasodilator ATP in plasma during hypoxia in vivo. We hypothesized that Panx1 channels and associated ATP export contribute to hypoxic vasodilation, a mechanism that facilitates the matching of oxygen delivery to metabolic demand of tissue. Male and female mice devoid of Panx1 (Panx1-/-) and wild-type controls (WT) were anesthetized, mechanically ventilated, and instrumented with a carotid artery catheter or femoral artery flow transducer for hemodynamic and plasma ATP monitoring during inhalation of 21% (normoxia) or 10% oxygen (hypoxia). ATP export from WT vs. Panx1-/-erythrocytes (RBC) was determined ex vivo via tonometer experimentation across progressive deoxygenation. Mean arterial pressure (MAP) was similar in Panx1-/- (n = 6) and WT (n = 6) mice in normoxia, but the decrease in MAP in hypoxia seen in WT was attenuated in Panx1-/- mice (-16 ± 9% vs. -2 ± 8%; P < 0.05). Hindlimb blood flow (HBF) was significantly lower in Panx1-/- (n = 6) vs. WT (n = 6) basally, and increased in WT but not Panx1-/- mice during hypoxia (8 ± 6% vs. -10 ± 13%; P < 0.05). Estimation of hindlimb vascular conductance using data from the MAP and HBF experiments showed an average response of 28% for WT vs. -9% for Panx1-/- mice. Mean venous plasma ATP during hypoxia was 57% lower in Panx1-/- (n = 6) vs. WT mice (n = 6; P < 0.05). Mean hypoxia-induced ATP export from RBCs from Panx1-/- mice (n = 8) was 82% lower than that from WT (n = 8; P < 0.05). Panx1 channels participate in hemodynamic responses consistent with hypoxic vasodilation by regulating hypoxia-sensitive extracellular ATP levels in blood.NEW & NOTEWORTHY Export of vasodilator ATP from red blood cells requires pannexin 1. Blood plasma ATP elevations in response to hypoxia in mice require pannexin 1. Hemodynamic responses to hypoxia are accompanied by increased plasma ATP in mice in vivo and require pannexin 1.

Cortisol level after dexamethasone suppression test in patients with non-functioning adrenal incidentaloma is positively associated with the duration of reactive hyperemia response on microvascular bed.

PURPOSE: Data on endothelial derangements in patients with non-functioning adrenal incidentaloma (NFAI) are scarce. METHODS: We investigated if NFAI patients present clinical, biochemical and endothelial alterations compared to individuals without an adrenal lesion and also the associations among these variables. Forty-two NFAI and 40 controls were evaluated. NFAI diagnosis and controls were defined according to the current guidelines and based on a normal adrenal imaging exam, respectively. Body composition was evaluated by dual emission X-ray absorptiometry. Endothelial reactivity was assessed by two methods: tonometry (Endo-PAT®) and laser speckle contrast imaging (LSCI). RESULTS: There were no differences between groups regarding age, gender, ethnicity, smoking status, and statin use. The frequency of metabolic syndrome according to the International Diabetes Federation criteria was 69% and 57.9%, respectively in NFAI and controls (p = 0.36), whereas the atherosclerotic cardiovascular disease (ASCVD) risk was 63.4% and 66.7% (p = 0.81). The clinical, laboratory, and anthropometric characteristics, as well as body composition, were similar between the groups. Additionally, any differences between groups were observed on endothelial reactivity tests. Nevertheless, we noted an association between cortisol levels after 1 mg-dexamethosone suppression test (1 mg-DST) and the duration of post-occlusive reactive hyperemia tested on microcirculation (r = 0.30; p = 0.03). NFAI patients require more antihypertensive drugs to achieve blood pressure control (p = 0.04). The number of antihypertensive drugs used to control blood pressure correlated with cortisol levels after 1 mg-DST (r = 0.29; p = 0.03). CONCLUSIONS: Since both groups herein investigated had a high frequency of metabolic syndrome and ASCVD risk, it might explain similarities observed on endothelial reactivity. Nevertheless, prolonged reactive hyperemia response on microcirculation was correlated with cortisol levels under suppression.

Prostaglandin contribution to postexercise hyperemia is dependent on tissue oxygenation during rhythmic and isometric contractions.

The role of prostaglandins (PGs) in exercise hyperemia is controversial. We tested their contributions in moderate intensity forearm exercise, whether their release is oxygen (O2 )-dependent or affected by aging. A total of 12 young (21 ± 1 years) and 11 older (66 ± 2 years) recreationally active men performed rhythmic and isometric handgrip contractions at 60% maximum voluntary contraction for 3 min during air breathing after placebo, after cyclooxygenase (COX) inhibition with aspirin, while breathing 40% O2 and during their combination (aspirin + 40% O2 ). Forearm blood flow (FBF) was recorded with venous occlusion plethysmography (forearm vascular conductance (FVC): FBF/mean arterial pressure). Venous efflux of PGI2 and PGE2 were assessed by immunoassay. Postcontraction increases in FVC were similar for rhythmic and isometric contractions in young and older men, and accompanied by similar increases in efflux of PGI2 and PGE2 . Aspirin attenuated the efflux of PGI2 by 75%-85%, PGE2 by 50%-70%, (p < .05 within group; p > .05 young versus. older), and postcontraction increases in FVC by 22%-27% and 17%-21% in young and older men, respectively (p < .05 within group and young versus. older). In both age groups, 40% O2 and aspirin + 40% O2 caused similar inhibition of the increases in FVC and efflux of PGs as aspirin alone (p < .05 within group). These results indicate that PGs make substantial contributions to the postcontraction hyperemia of rhythmic and isometric contractions at moderate intensities in recreationally active young and older men. Given PGI2 is mainly released by endothelium and PGE2 by muscle fibers, we propose PG generation is dependent on the contraction-induced falls in O2 at these sites.

Ocular Manifestations of COVID-19 (SARS-CoV-2): A Critical Review of Current Literature.

The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in China in the city of Wuhan in December of 2019 and since then more than 5,000,000 people have been infected, with approximately 338,000 deaths worldwide. The virus causes the coronavirus disease 2019 (COVID-19), which is characterized by fever, myalgia and cough, with severe acute respiratory syndrome being the most fearsome complication. Nevertheless, the vast majority of cases present mild symptoms or none. Central nervous system and cardiovascular manifestations have been reported. The range of ocular manifestations, either as a result of the infection or as a result of the treatment, has not yet been discussed. In this study, a systematic review of current literature relevant to COVID-19 was performed with focus on modes of transmission, ocular manifestations related to infection and medications, as well as the control of infection in ophthalmic practice.

Sirt1 during childhood is associated with microvascular function later in life.

Microvascular dysfunction often precedes other age-related macrovascular conditions and predicts future cardiovascular risk. Sirtuin 1 (Sirt1) has recently emerged as a protein that protects the vasculature and reduces the risk of cardiovascular diseases. We tested the hypothesis that lower Sirt1 during childhood is associated with a reduced microvascular function during adulthood. Thirty-four adults (34 ± 3 yr) from the Augusta Heart Study returned to participate in the present clinical observational study. Sirt1 was assessed in samples collected during both adulthood and participants' childhood (16 ± 3 yr), and data were divided based on childhood Sirt1 concentrations: <3 ng/dL (LowCS; n = 16) and ≥3 ng/dL (HighCS; n = 18). MVF was evaluated in all of the adults using laser-Doppler flowmetry coupled with three vascular reactivity tests: 1) local thermal hyperemia (LTH), 2) post-occlusive reactive hyperemia (PORH), and 3) iontophoresis of acetylcholine (ACh). The hyperemic response to LTH was significantly (P ≤ 0.044) lower in the LowCS than in the HighCS group. Similarly, the LowCS also exhibited an ameliorated (P ≤ 0.045) response to the PORH test and lower (P ≤ 0.008) vasodilation in response to iontophoresis of ACh when compared with the HighCS. Positive relationships were identified between childhood Sirt1 and all MVF reactivity tests (r≥0.367, P ≤ 0.004). Novel observations suggest that lower Sirt1 during childhood is associated with premature microvascular dysfunction in adulthood. These findings provide evidence that Sirt1 may play a critical role in microvascular function and have therapeutic potential for the prevention of age-associated vascular dysfunction in humans.NEW & NOTEWORTHY With a longitudinal cohort, novel observations from the present study demonstrate that individuals who had lower Sirt1 early in life exhibit premature microvascular dysfunction during adulthood and may be at higher risk to develop CVD. These results provide experimental evidence that Sirt1 may play an important role in microvascular function with age and represent a potential therapeutic target to prevent premature vascular dysfunction.

Shear-thinning behaviour of blood in response to active hyperaemia: Implications for the assessment of arterial shear stress-mediated dilatation.

NEW FINDINGS: What is the central question of this study? Quantitative values of shear rate-specific blood viscosity and shear stress in the human macrovasculature in response to exercise hyperaemia are unknown. What is the main finding and its importance? Using the handgrip exercise model, we showed that an increase in brachial artery shear rate led to a decrease in blood viscosity, despite concomitant haemoconcentration. This shear-thinning behaviour of blood, secondary to increased erythrocyte deformability, blunted the expected increase in brachial artery shear stress based on shear rate prediction. Our data yield new insights into the magnitude and regulation of macrovascular blood viscosity and shear stress in physiological conditions of elevated metabolic demand and blood flow in humans. ABSTRACT: Blood viscosity is a well-known determinant of shear stress and vascular resistance; however, accurate quantitative assessments of shear rate-specific blood viscosity in the macrovasculature in conditions of elevated blood flow are inherently difficult, owing to the shear-thinning behaviour of blood. Herein, 12 men performed graded rhythmic handgrip exercise at 20, 40, 60 and 80% of their maximal workload. Brachial artery shear rate and diameter were measured via high-resolution Duplex ultrasound. Blood was sampled serially from an i.v. cannula in the exercising arm for the assessment of blood viscosity (cone-plates viscometer). We measured ex vivo blood viscosity at 10 discrete shear rates within the physiological range documented for the brachial artery in basal and exercise conditions. Subsequently, the blood viscosity data were fitted with a two-phase exponential decay, facilitating interpolation of blood viscosity values corresponding to the ultrasound-derived shear rate. Brachial artery shear rate and shear stress increased in a stepwise manner with increasing exercise intensity, reaching peak values of 940 ± 245 s-1 and 3.68 ± 0.92 Pa, respectively. Conversely, brachial artery shear rate-specific blood viscosity decreased with respect to baseline values throughout all exercise intensities by ∼6-11%, reaching a minimal value of 3.92 ± 0.35 mPa s, despite concomitant haemoconcentration. This shear-thinning behaviour of blood, secondary to increased erythrocyte deformability, blunted the expected increase in shear stress based on shear rate prediction. Consequently, the use of shear stress yielded a higher slope for the brachial artery stimulus versus dilatation relationship than shear rate. Collectively, our data refute the use of shear rate to infer arterial shear stress-mediated processes.

The effects of the analysis strategy on the correlation between the NIRS reperfusion measures and the FMD response.

This study aimed to investigate the correlation between near-infrared spectroscopy (NIRS)-derived measures of microvascular responses using a range of different analysis and flow-mediated dilation (FMD). Additionally, we aimed to investigate whether assessing NIRS and FMD simultaneously or non-simultaneously would affect this association. Thirty-five healthy young individuals (26 ±â€¯13 years old) participated in the study. Twenty were submitted to a simultaneous NIRS/FMD test (NIRS probe placed below the cuff during FMD test) and fifteen to a non-simultaneous FMD and NIRS intervention (NIRS test performed 20 min after FMD). NIRS-derived oxygen saturation signal (StO2) during reperfusion was analyzed as follow: upslope of a 10 s (slope 10 s) and 30 s (slope 30 s) reperfusion window immediately following cuff deflation, time for the StO2 to reach the pre-occlusion (baseline) values after cuff release (time to baseline) and to reach the peak after cuff release (time to max), difference between the minimum and maximum StO2 value reached after cuff deflation (Magnitude) and; the total area under the reperfusion curve above the baseline value until the end of the 2 min post cuff release (AUC 2 min). There was a significant positive correlation between slope 10 s and FMD in the simultaneous (r = 0.60; p < 0.05) and non-simultaneous (r = 0.62; p < 0.05) assessments. There was no significant correlation between NIRS-derived slope 30 s, time to baseline, time to max, magnitude, and AUC 2 min and the FMD in both methods. The association between NIRS and FMD is analysis strategy dependent, regardless if assessed simultaneously or non-simultaneously.

Potential interaction of inflammatory hyperemia and hyperphosphatemia in tumorigenesis.

The present article proposes that the association of inflammation with cancer is potentially mediated by the interaction of inflammatory hyperemia and hyperphosphatemia. Hyperemia increases blood flow rate and blood volume, and hyperphosphatemia is caused by elevated serum levels of dysregulated inorganic phosphate. It is hypothesized that the interaction of inflammatory hyperemia and hyperphosphatemia circulates increased amounts of inorganic phosphate to the tumor microenvironment, where increased uptake of inorganic phosphate through sodium-phosphate cotransporters is sequestered in cells. Elevated levels of intracellular phosphorus increase biosynthesis of ribosomal RNA, leading to increased protein synthesis that supports tumor growth. The present article also proposes that the interaction of inflammatory hyperemia and hyperphosphatemia may help explain a chemopreventive mechanism associated with NSAIDs.

Oxygen tension-mediated erythrocyte membrane interactions regulate cerebral capillary hyperemia.

The tight coupling between cerebral blood flow and neural activity is a key feature of normal brain function and forms the basis of functional hyperemia. The mechanisms coupling neural activity to vascular responses, however, remain elusive despite decades of research. Recent studies have shown that cerebral functional hyperemia begins in capillaries, and red blood cells (RBCs) act as autonomous regulators of brain capillary perfusion. RBCs then respond to local changes of oxygen tension (PO2) and regulate their capillary velocity. Using ex vivo microfluidics and in vivo two-photon microscopy, we examined RBC capillary velocity as a function of PO2 and showed that deoxygenated hemoglobin and band 3 interactions on RBC membrane are the molecular switch that responds to local PO2 changes and controls RBC capillary velocity. Capillary hyperemia can be controlled by manipulating RBC properties independent of the neurovascular unit, providing an effective strategy to treat or prevent impaired functional hyperemia.

Free Vitamin D: Relationship to Insulin Sensitivity and Vascular Health in Youth.

OBJECTIVE: To evaluate the relationship of free 25 hydroxy vitamin D [free 25(OH)D] or bioavailable vitamin D (BioD) concentrations to insulin sensitivity and cardiovascular disease risk markers in normal weight and overweight youth. STUDY DESIGN: Cross-sectional study of 79 adolescents 15.4 ± 0.2 years, 18 normal weight, 30 overweight, and 31 overweight with prediabetes who underwent peripheral arterial tonometry, dual-energy x-ray absorptiometry, and hyperinsulinemic-euglycemic clamp in subset (n = 71) for determination of reactive hyperemia index (RHI), body composition, and insulin sensitivity. 25(OH)D and vitamin D binding protein were measured; free 25(OH)D and BioD were calculated. RESULTS: Across tertiles of free 25(OH)D concentrations (4.0 ± 0.2, 7.5 ± 0.3, and 17.0 ± 2.1 pg/mL, P < .001), the group in the lowest tertile had significantly higher percent body fat (37.8 ± 1.1, 35.2 ± 1.5 and 25.3 ± 2.1%, P < .001), lower insulin sensitivity (4.4 ± 0.4, 6.7 ± 1.2, and 8.2 ± 0.9 mg/kg fat-free mass/minute per µu/mL, P = .03), lower RHI (1.42 ± 0.06, 1.54 ± 0.06, and 1.77 ± 0.09, P = .002), higher high-sensitivity C-reactive protein (3.4 ± 0.6, 1.7 ± 0.3, and 1.6 ± 0.4 mg/L, P = .015) compared with the second and third tertiles, respectively. Free 25(OH)D levels were inversely related to percent body fat and high-sensitivity C-reactive protein, and positively related to RHI and insulin sensitivity. The relationships of free 25(OH)D to RHI and to insulin sensitivity were no longer significant after adjusting for %body fat. Similar relationships were observed for BioD. CONCLUSIONS: Youth with low free 25(OH)D or BioD concentrations have lower insulin sensitivity and worse endothelial function and inflammatory biomarkers compared with those with more sufficient 25(OH)D. However, the effects of vitamin D on these biomarkers may not be independent of the effect of adiposity.

Reduced insulin sensitivity in young, normoglycaemic subjects alters microvascular tissue oxygenation during postocclusive reactive hyperaemia.

NEW FINDINGS: What is the central question of the study? Are measures of reduced insulin sensitivity in young, normoglycaemic subjects correlated with near-infrared spectroscopy-derived microvascular responsiveness [tissue oxygen saturation reperfusion rate (STO2 upslope)] during postocclusive reactive hyperaemia? What is the main finding and its importance? A sevenfold range of hepatic insulin sensitivity is significantly correlated (r = 0.44, P = 0.02) with STO2 upslope after transient tissue ischaemia. Near-infrared spectroscopy may be an important tool for determining altered microvascular function before onset of hyperglycaemia. Identification of pre-type 2 diabetes much earlier than with the present clinical criteria is important for pre-emptive measures against microvascular deterioration. ABSTRACT: Near-infrared spectroscopy (NIRS) measurement of postocclusive reactive hyperaemia (PORH) tissue oxygen saturation reperfusion rate [STO2 upslope (as a percentage per minute)] has recently been correlated with the percentage of flow-mediated dilatation (%FMD). Cardiovascular disease is associated with impairments in %FMD. Reduced insulin sensitivity may negatively affect the vascular system for many years before prediabetes/type 2 diabetes states. The aim of this study was to determine whether static and dynamic STO2 parameters during PORH are correlated with reduced insulin sensitivity in young, normoglycaemic subjects. Glucose and insulin were measured during an oral glucose tolerance test in 18- to 26-year-old, healthy subjects (11 men and 11 women), and STO2 was measured during PORH of antebrachial muscle. Hepatic (ISIHOMA ) and whole-body (ISICOMP ) insulin sensitivities were calculated. The STO2 upslope was negatively correlated with minimal STO2 (r = -0.5, P = 0.01). The change of STO2 from minimum to baseline (ΔSTO2 ) was significantly negatively correlated with fasting insulin (r = -0.5, P = 0.01) and a positively correlated with ISIHOMA (r = 0.65, P = 0.001). The minimum STO2 was significantly negatively correlated with ISIHOMA , and STO2 upslope was significantly positively correlated with ISIHOMA (r = 0.44, P = 0.02). The minimum STO2 (a measure of O2 extraction while the cuff was inflated), ΔSTO2 (a measure of the amount of reperfusion) and STO2 upslope (a measure of responsiveness of the microcirculation to ischaemia) were all positively correlated with ISIHOMA , one of the longest-used measures of insulin sensitivity. The NIRS-derived STO2 might be a useful tool for assessing how levels of reduced insulin sensitivity in young, normoglycaemic adults affect the microvasculature.

Peri-operative endothelial dysfunction in patients undergoing minor abdominal surgery: An observational study.

BACKGROUND: Myocardial injury after noncardiac surgery is common and associated with major adverse cardiac events. Surgery induces acute endothelial dysfunction, which might be central in the pathophysiology of myocardial injury; however, the relationship between surgical stress and endothelial function remains incompletely understood. OBJECTIVES: This study aimed to assess the acute peri-operative changes in endothelial function after minor elective abdominal surgery. DESIGN: A prospective, observational, single-centre study. SETTING: A university hospital from February 2016 to January 2017. PATIENTS: Sixty patients undergoing elective minor abdominal surgery. MAIN OUTCOME MEASURES: The change in endothelial function, expressed as the reactive hyperaemia index (RHI), was assessed by non-invasive digital pulse tonometry. RHI, biomarkers of nitric oxide bioavailability and oxidative stress were assessed prior to and 4 h after surgery. RESULTS: RHI decreased significantly from 1.93 [95% confidence interval (95% CI 1.78 to 2.09)] before surgery to 1.76 (95% CI 1.64 to 1.90), P = 0.03, after surgery. The nitric oxide production, L-arginine/asymmetric dimethylarginine, decreased significantly from a ratio of 213.39 (95% CI 188.76 to 241.2) to a ratio of 193.3 (95% CI 171.82 to 217.54), P = 0.03. Plasma biopterins increased significantly after surgery, while the ratio between tetrahydrobiopterin and dihydrobiopterin was unchanged. Total ascorbic acid decreased significantly after surgery (P < 0.001), while its oxidation ratio was unchanged. CONCLUSION: Elective minor abdominal surgery impaired systemic endothelial function early after surgery. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT02690233.

Relation of Elevated Serum Uric Acid Level to Endothelial Dysfunction in Patients with Acute Coronary Syndrome.

AIM: Serum uric acid (SUA) level is known to have a prognostic value in patients with acute coronary syndrome (ACS). Endothelial function plays an important role in the development of cardiovascular disease. Although relation between SUA level and endothelial function has been previously studied in various populations, it is partially understood in patients with ACS. METHODS: A total of 55 patients with ACS with measurements of SUA level and reactive hyperemia index (RHI) to evaluate endothelial function were included. They were classified into three groups according to the tertiles of SUA level. The tertiles of SUA level were as follows: low tertile, ≤ 5.2 mg/dl; intermediate tertile, 5.3 to 6.5 mg/dl; and high tertile, ≥ 6.6 mg/dl. RESULTS: Mean SUA level and RHI were 5.8±1.5 mg/dl and 1.88±0.58. There was a significant negative correlation between SUA level and RHI (r=-0.41, p=0.002). RHI was stepwisely observed in favor of the higher tertile groups (2.14±0.74 vs. 1.84±0.45 vs. 1.67±0.38, p=0.04). Multivariate analysis showed elevated SUA level as an independent predictor of reduced RHI. CONCLUSION: Elevated SUA level was significantly associated with endothelial dysfunction in patients with ACS, possibly leading to subsequent poor outcomes following ACS.

Serum Uric Acid Levels are Associated with Cardiometabolic Risk Factors in Healthy Young and Middle-Aged Adults / Os Níveis Séricos de Ácido Úrico estão Associados a Fatores de Risco Cardiometabólico em Adultos Jovens e de Meia-Idade Saudáveis

Abstract Background: Observational studies have highlighted an association between serum uric acid (SUA) levels and cardiovascular risk factors. Despite the growing body of evidences, several studies were conducted in older individuals or in carriers of diseases susceptible to affect SUA levels and cardiometabolic risk markers. Objective: To evaluate the relationship of SUA with body adiposity, metabolic profile, oxidative stress, inflammatory biomarkers, blood pressure and endothelial function in healthy young and middle-aged adults. Methods: 149 Brazilian adults aged 20-55 years, both sexes, underwent evaluation of body adiposity, SUA, fasting glucose and insulin, lipid profile, malondialdehyde (MDA), high sensitivity C-reactive protein (hs-CRP), adiponectin, blood pressure and endothelial function. Endothelial function was assessed by the reactive hyperemia index (RHI) derived from peripheral arterial tonometry method. Participants were allocated in two groups according to SUA levels: control group (CG; n = 130; men ≤ 7 mg/dL, women ≤ 6 mg/dL) and hyperuricemia group (HG; n = 19; men > 7 mg/dL, women > 6 mg/dL). A P-value < 0.05 was considered statistically significant. Results: After adjustment for confounders, participants in HG compared with those in CG displayed higher body mass index (BMI): 34.15(33.36-37.19) vs.31.80 (26.26-34.42) kg/m2,p = 0.008, higher MDA: 4.67(4.03-5.30) vs. 3.53(3.10-4.07) ng/mL, p < 0.0001 and lower RHI: 1.68 ± 0.30 vs. 2.05 ± 0.46, p = 0.03). In correlation analysis adjusted for confounders, SUA was positively associated (p < 0.05) with BMI, waist circumference, LDL-cholesterol, triglycerides and MDA, and negatively associated (p < 0.05) with HDL-cholesterol, adiponectin and RHI. Conclusions: This study suggests that in healthy young and middle-aged adults higher SUA levels are associated with higher body adiposity, unfavorable lipid and inflammatory phenotype, higher oxidative stress and impaired endothelial function.

Resumo Fundamento: Estudos observacionais têm destacado uma associação entre níveis de ácido úrico sérico (AUS) e fatores de risco cardiovascular. Apesar do crescente conjunto de evidências, vários estudos foram realizados em indivíduos mais velhos ou em portadores de doenças passíveis de influenciar os níveis de AUS e marcadores de risco cardiometabólico. Objetivo: Avaliar a relação do AUS com adiposidade corporal, perfil metabólico, estresse oxidativo, biomarcadores de inflamação, pressão arterial e função endotelial em adultos jovens e de meia-idade saudáveis. Métodos: 149 adultos, brasileiros, com idades entre 20 e 55 anos, de ambos os sexos, foram submetidos a avaliação de adiposidade corporal, AUS, glicose e insulina de jejum, perfil lipídico, malondialdeído (MDA), proteína C-reativa ultra-sensível (PCR-us), adiponectina, pressão arterial e função endotelial. A função endotelial foi avaliada pelo índice de hiperemia reativa (RHI) derivado do método de tonometria arterial periférica. Os participantes foram divididos em dois grupos de acordo com os níveis de AUS: grupo de controle (GC; n = 130; homens ≤ 7 mg/dL, mulheres ≤ 6mg/dL) e grupo de hiperuricemia (GH; n = 19; homens > 7mg/dL, mulheres > 6mg/dL). Valor de p < 0,05 foi considerado estatisticamente significativo. Resultados: Após ajuste para fatores de confundimento, os participantes do GH comparados aos do GC apresentaram índice de massa corporal (IMC) mais alto: 34,15 (33,36-37,19) vs. 31,80 (26,26-34,42) kg/m2, p = 0,008, MDA mais alto: 4,67(4,03-5,30) vs. 3,53(3,10-4,07) ng/mL, p < 0,0001 e RHI mais baixo: 1,68 ± 0,30 vs. 2,05 ± 0,46, p = 0,03. Na análise de correlação ajustada para fatores de confundimento, o AUS se associou positivamente (p < 0,05) com IMC, circunferência da cintura, LDL colesterol, triglicérides e MDA, e se associou negativamente (p < 0,05) com HDL colesterol, adiponectina e RHI. Conclusões: Este estudo sugere que, em adultos jovens e de meia-idade saudáveis, níveis mais altos de AUS estão associados a maior adiposidade corporal, fenótipo inflamatório e de lipídios desfavorável, maior estresse oxidativo e função endotelial comprometida.