Unfavorable blood rheology is closely associated with arterial stiffness in obese patients

Red blood cell dysfunction: a new player in cardiovascular disease

The primary role of red blood cells (RBCs) is to transport oxygen to the tissues and carbon dioxide to the lungs. However, emerging evidence suggests an important role of the RBC beyond being just a passive carrier of the respiratory gases. The RBCs are of importance for redox balance and are actively involved in the regulation of vascular tone, especially during hypoxic and ischaemic conditions by the release of nitric oxide (NO) bioactivity and adenosine triphosphate. The role of the RBC has gained further interest after recent discoveries demonstrating a markedly altered function of the cell in several pathological conditions. Such alterations include increased adhesion capability, increased formation of reactive oxygen species as well as altered protein content and enzymatic activities. Beyond signalling increased oxidative stress, the altered function of RBCs is characterized by reduced export of NO bioactivity regulated by increased arginase activity. Of further importance, the altered function of RBCs has important implications for several cardiovascular disease conditions. RBCs have been shown to induce endothelial dysfunction and to increase cardiac injury during ischaemia-reperfusion in diabetes mellitus. Finally, this new knowledge has led to novel therapeutic possibilities to intervene against cardiovascular disease by targeting signalling in the RBC. These novel data open up an entirely new view on the underlying pathophysiological mechanisms behind the cardiovascular disease processes in diabetes mellitus mediated by the RBC. This review highlights the current knowledge regarding the role of RBCs in cardiovascular regulation with focus on their importance for cardiovascular dysfunction in pathological conditions and therapeutic possibilities for targeting RBCs in cardiovascular disease.

The role of arginase in the microcirculation in cardiovascular disease

In the microcirculation, the exchange of nutrients, water, gas, hormones, and waste takes place, and it is divided into the three main sections arterioles, capillaries, and venules. Disturbances in the microcirculation can be measured using surrogate parameters or be visualized either indirectly or directly.Arginase is a manganese metalloenzyme hydrolyzing L-arginine to urea and L-ornithine. It is located in different cell types, including vascular cells, but also in circulating cells such as red blood cells. A variety of pro-inflammatory factors, as well as interleukins, stimulate increased arginase expression. An increase in arginase activity consequently leads to a consumption of L-arginine needed for nitric oxide (NO) production by endothelial NO synthase. A vast body of evidence convincingly showed that increased arginase activity is associated with endothelial dysfunction in larger vessels of the vascular tree. Of note, arginase also influences the microcirculation. Arginase inhibition leads to an increase in the bioavailability of NO and reduces superoxide levels, resulting in improved endothelial function. Arginase inhibition might, therefore, be a potent treatment strategy in cardiovascular medicine. Recently, red blood cells emerged as an influential player in the development from increased arginase activity to endothelial dysfunction. As red blood cells directly interact with the microcirculation in gas exchange, this could constitute a potential link between arginase activity, endothelial dysfunction and microcirculatory disturbances.The aim of this review is to summarize recent findings revealing the role of arginase in regulating vascular function with particular emphasis on the microcirculation.

Clinical Impact of Hemorheology on Subclinical Myocardial Injury in Patients with Hypertension

Background

The blood concentration of high-sensitivity cardiac troponin T (hs-cTnT) is a useful biomarker for myocardial injury or the pathogenesis of hypertension. Little is known about the relationship between hemorheology and myocardial injury in patients with hypertension. This cross-sectional study aimed to clarify the clinical impact of hemorheology on subclinical myocardial injury assessed with a microchannel array flow analyzer (MC-FAN) and its impact on hs-cTnT in patients with hypertension.

Methods

A total of 447 outpatients (men: 181; women: 266; mean age: 65 ± 13 years), with no history of cardiovascular disease, including admission for heart failure, who were undergoing treatment for hypertension, were enrolled. Whole blood passage time (WBPT) as a marker of hemorheology was measured with a MC-FAN, and the relationship between hs-cTnT levels and various clinical parameters, including WBPT, was examined.

Results

hs-cTnT levels were detected in 400 patients (89.5%). WBPT was significantly higher in patients with detectable hs-cTnT levels than in those with undetectable hs-cTnT levels (60.5 ± 16.8 s versus 50.2 ± 14.2 s, P < 0.001). In patients with detectable hs-cTnT levels, there was a significant positive correlation between WBPT and hs-cTnT level (r = 0.33; P < 0.001). Multiple regression analysis revealed that WBPT was an independent variable when hs-cTnT was a subordinate factor (β = 0.15; P < 0.01). Receiver-operating characteristic curve analysis indicated that a cutoff value for WBPT of 55.6 s yielded the largest area under the curve (0.744; P < 0.001) for discriminating high hs-cTnT levels as ≥ 0.014 ng/mL.

Conclusion

The results indicate that WBPT is independently associated with hs-cTnT in hypertensive patients with no history of cardiovascular events, suggesting that impairment of hemorheology in small cardiac vessels causes subclinical myocardial injury. In addition, the study suggests that progression of myocardial injury can be prevented by maintaining WBPT at approximately ≤ 55 s.

Usefulness of the Whole Blood Passage Time as a Predictor of Primary Cardiovascular Events in Patients With Traditional Cardiovascular Risk Factors

BACKGROUND

Recent clinical studies have reported that impaired hemorheology is a significant cardiovascular risk factor, but there has been no prospective study of its relationship with cardiovascular events. The aim of this prospective study was to assess the efficacy of whole blood passage time (WBPT), measured by a microchannel array flow analyzer (MC-FAN), as a predictor of primary cardiovascular events in patients with traditional cardiovascular risk factors.

METHODS

The study enrolled 1,134 outpatients with traditional cardiovascular risk factors but no history of cardiovascular events (438 men and 696 women; mean ± standard deviation age, 67 ± 11 years). Based on the value of WBPT, the patients were assigned to one of three groups: L (low, WBPT < 50 s; n = 499), M (medium, WBPT 50 - 70 s; n = 295), or H (high, WBPT > 70 s; n = 340). The utility of the WBPT as a predictor of primary cardiovascular events was evaluated.

RESULTS

During the follow-up period (median 81.9 months), major adverse cardiovascular events (MACE) occurred in 95 cases (L, 21 cases (4.2%); M, 24 cases (8.1%); H, 50 cases (14.7%); P < 0.001, log-rank test). In multivariate Cox regression analyses, the risk for MACE was significantly higher in group H than in group L (hazard ratio, 2.32; 95% confidence interval, 1.31 - 3.20; P < 0.01). A WBPT cut-off of 72.4 s yielded the largest area under the curve of 0.705 (95% confidence interval: 0.678 - 0.732), with a sensitivity of 51.7% and specificity of 85.4% for discriminating between those who did and did not experience MACE during the follow-up period.

CONCLUSION

This study showed that WBPT evaluated by a MC-FAN was a predictor of primary cardiovascular events in patients with traditional cardiovascular risk factors.

Association of Hemorheology With High-Sensitivity Cardiac Troponin T Levels in Patients With Type 2 Diabetes Mellitus Assessed by Microchannel Array Flow Analyzer

Background

Recent studies on high-sensitivity cardiac troponin T (hs-cTnT) and whole blood passage time (WBPT), estimated by hemorheology assessed with the microchannel array flow analyzer (MC-FAN), have revealed the significance of cardiovascular risk factors. However, there are no known reports on the relationship between these two clinical parameters. This cross-sectional study aimed to clarify the associations between WBPT and hs-cTnT levels in patients with type 2 diabetes mellitus from the perspective of subclinical myocardial injury or the primary prevention of cardiovascular events.

Methods

A total of 301 outpatients (men, 116; women, 185; mean age, 65 ± 11 years), with no history of cardiovascular diseases, undergoing treatment for diabetes mellitus were enrolled. Hs-cTnT levels and WBPT were measured using a commercial device, and the relationship between hs-cTnT levels and various clinical parameters, including WBPT, was examined.

Results

Hs-cTnT levels were detected in 261 (86.7%) patients. WBPT was significantly higher in patients with detectable hs-cTnT levels than in those with undetectable hs-cTnT levels (64 ± 18 s vs. 51 ± 13 s, P < 0.001). In patients with detectable hs-cTnT levels, there was a significantly positive correlation between WBPT and hs-cTnT levels (r = 0.40; P < 0.001). Furthermore, multiple regression analysis revealed that WBPT (β = 0.24; P < 0.001) was an independent variable when hs-cTnT was a subordinate factor. Conversely, patients with high (≥ 70 s; odds ratio, 5.3 (95% CI, 1.6 - 16.1); P < 0.01) and median (50.2 - 69.8 s; odds ratio, 3.8 (95% CI, 1.2 - 12.4); P < 0.05) WBPT had a significantly higher risk for high hs-cTnT levels (≥ 0.014 ng/mL) than those with low WBPT (≤ 50.0 s).

Conclusions

The results of this study indicated independent associations of hemorheology with hs-cTnT in patients with type 2 diabetes mellitus assessed by MC-FAN. We suggest that an increase in hs-cTnT levels can be prevented by maintaining WBPT at ≤ 50.0 s.

Relationship Between Hemorheology Assessed Using Microchannel Array Flow Analyzer and Kidney Function in Hypertensive Patients

Background

Kidney function is known to be closely associated with the pathogenesis of hypertension. In contrast, hemorheology assessed using microchannel array flow analyzer (MC-FAN) has demonstrated the significance of cardiovascular risk factors in recent clinical studies. The present cross-sectional study aimed to clarify the relationship between hemorheology assessed by MC-FAN and kidney function in hypertensive patients from the perspective of primary prevention of cardiovascular events.

Methods

In total, 453 outpatients undergoing treatment for hypertension (176 men and 277 women; mean age ± standard deviation: 65 ± 13 years) with no history of cardiovascular disease were enrolled. Whole blood passage time (WBPT) was measured using MC-FAN as a marker of hemorheology, and the relationships with various clinical parameters including kidney function were examined.

Results

A significant correlation was observed between WBPT and the parameters of kidney function such as estimated glomerular filtration rate (r = -0.14, P < 0.01), urinary albumin excretion (r = 0.40, P < 0.001), and renal resistive index (r = 0.44, P < 0.001). Furthermore, multivariate analysis demonstrated urinary albumin excretion, renal resistive index, skin autofluorescence, derivatives of reactive oxygen metabolites, and hematocrit as independent variables for WBPT as a subordinate factor.

Conclusions

The results of the present study indicate that hemorheology assessed by the MC-FAN is significantly associated with markers of kidney function, such as albuminuria and increased renovascular resistance, in hypertensive patients.

Impact of Hemorheology Assessed by the Microchannel Method on Pulsatility Index of the Common Carotid Artery in Patients With Type 2 Diabetes Mellitus

Background

Type 2 diabetes mellitus is known to be closely associated with the risk of ischemic stroke. Recent clinical studies have reported that a high pulsatility index (PI) of the cerebral or carotid artery, which is estimated by ultrasonography, also reflects a risk of ischemic stroke. This cross-sectional study aimed to clarify the impact of hemorheology assessed by the microchannel method on the PI of the common carotid artery (CCA) in patients with type 2 diabetes mellitus in terms of the primary prevention of ischemic stroke.

Methods

In total, 349 outpatients on treatment for type 2 diabetes mellitus (131 men and 218 women; mean age ± standard deviation: 65 ± 11 years) with no history of cardiovascular events, including ischemic stroke, were enrolled. The whole blood passage time (WBPT) as a marker of hemorheology and the PI of CCA were measured using commercial devices, and their relationships to various clinical parameters were examined.

Results

A significant positive correlation was observed between WBPT and the PI of CCA (r = 0.49, P < 0.001). Furthermore, multivariate analysis revealed that patients with high WBPT (≥70 s) had significantly higher risk (odds ratio: 5.2; 95% confidence interval: 2.4 - 9.2; P < 0.001) of being detected with a high PI of CCA (≥ 2) than those with low WBPT (≤ 52.0 s).

Conclusion

The results of this study indicated that WBPT was an important determination factor for the PI of CCA, suggesting that an increase in WBPT can potentially predict the incidence of ischemic stroke in patients with type 2 diabetes mellitus.

Impaired blood rheology is associated with endothelial dysfunction in patients with coronary risk factors

To investigate the relationship between blood rheology and endothelial function in patients with coronary risk factors, brachial arterial flow-mediated vasodilatation (FMD), an index of endothelial function and blood passage time (BPT), an index of blood rheology, and fasting blood cell count, glucose metabolism, and plasma fibrinogen, lipid, C-reactive protein, and whole blood viscosity levels were measured in 95 patients with coronary risk factors and 37 healthy controls. Brachial arterial FMD after reactive hyperemia was assessed by ultrasonography. BPT was assessed using the microchannel method. In healthy controls, BPT significantly correlated with FMD (r = - 0.325, p <  0.05), HDL cholesterol (r = - 0.393, p <  0.05), body mass index (BMI; r = 0.530, p <  0.01), and plasma fibrinogen concentration (r = 0.335, p <  0.05). In a multivariate regression analysis adjusted for all clinical variables, BPT remained significantly associated with BMI and fibrinogen, but not with FMD, in healthy controls. In patients with coronary risk factors, BPT significantly correlated with FMD (r = - 0.331, p <  0.01), HDL cholesterol (r = - 0.241, p <  0.05), BMI (r = 0.290, p <  0.01), hematocrit (r = 0.422, p <  0.001), white blood cell count (r = 0.295, p <  0.01), platelet count (r = 0.204, p <  0.05), and insulin (r = 0.210, p <  0.05). In a multivariate regression analysis adjusted for all clinical variables, BPT remained strongly associated with FMD and hematocrit in patients with coronary risk factors. These data indicate that BPT is closely associated with FMD in patients with coronary risk factors and suggest that the measurement of blood rheology using the microchannel method may be useful in evaluating brachial arterial endothelial function as a marker of atherosclerosis in these patients.

Rivaroxaban attenuates leukocyte adhesion in the microvasculature and thrombus formation in an experimental mouse model of type 2 diabetes mellitus

INTRODUCTION

Thrombosis is a major complication in diabetes mellitus. Since Factor Xa inhibitors are not only inhibit the coagulation system but also attenuate the leukocyte-endothelial interaction in acute inflammation models, the purpose of this study is to confirm the similar effects of rivaroxaban in a mouse model of type 2 diabetes mellitus.

MATERIALS AND METHODS

In the treatment groups, either 5 or 10mg/kg of rivaroxaban dissolved in DMSO was orally given to KK-A(y) mice for 7 weeks (n=6 in each group). KK-A(y) mice fed by chow containing DMSO without rivaroxaban for 7 weeks were served for the control group (n=6). Following clamping of the mesenteric vein for 20 minutes, intravital microscopic observation of the intestinal microcirculation and the measurement of bleeding time after the needle puncture were carried-out. In another series, the calculation for blood cell counts and the measurement of blood fluidity using micro channel array flow analyzer (MC-FAN) were performed.

RESULTS

The initial event in the microvasculature is the leukocyte adhesion on endothelium. Then, the leukocytes make clusters and the platelets are involved in. These leukocyte-platelet conjugates aggregate and form thrombus. The leukocyte adherence and the microthrombus formation was significantly suppressed with the treatment of 10 mg/kg of rivaroxaban compared to the control group (P<0.05). While, the bleeding time was significantly extended with the treatment with 10mg/kg of rivaroxaban (P<0.01). The blood fluidity was maintained best with the treatment of 10 mg/kg rivaroxaban.

CONCLUSIONS

Rivaroxaban attenuates the leukocyte-platelet-endothelial interaction, which leads to the attenuation of microthrombus formation in a mouse model of diabetes mellitus.

Blood viscosity as a forgotten factor and its effect on pulmonary flow

Background

The effect of smoking on blood viscosity is widely known. There are, however, few studies on the effect of blood viscosity on pulmonary circulation.

Methods

We aimed to observe the relationship between blood viscosity and pulmonary circulation among smokers and non-smokers. The study comprised 114 subjects in three groups: group 1, ex-smokers; group 2, smoked at least 10 packs/year and still smoking; group 3, never smoked. Blood viscosity (BV), pulmonary blood flow (PBF), and right ventricular systolic pressure (RVSP) were measured in all subjects.

Results

PBF was significantly lower in group 1 compared with group 3 (p < 0.05). BV in group 1 was significantly higher than group 3 (p < 0.05) while BV in group 2 was significantly higher than group 3 (p < 0.05). PBF in group 2 was significantly lower than group 3 (p = 0.01).

Conclusions

We believe that BV is a significant and forgotten factor that plays an important role in pulmonary and cardiovascular diseases. BV may affect PF even during the course of smoking, and before the clinical onset of chronic obstructive pulmonary disease (COPD). Therefore, individuals at risk of pulmonary hypertension could be detected earlier with a simple blood test.

Regulation of adipose tissue energy availability through blood flow control in the metabolic syndrome

Maintenance of blood flow rate is a critical factor for tissue oxygen and substrate supply. The potentially large mass of adipose tissue deeply influences the body distribution of blood flow. This is due to increased peripheral resistance in obesity and the role of this tissue as the ultimate destination of unused excess of dietary energy. However, adipose tissue cannot grow indefinitely, and the tissue must defend itself against the avalanche of nutrients provoking inordinate growth and inflammation. In the obese, large adipose tissue masses show lower blood flow, limiting the access of excess circulating substrates. Blood flow restriction is achieved by vasoconstriction, despite increased production of nitric oxide, the vasodilatation effects of which are overridden by catecholamines (and probably also by angiotensin II and endothelin). Decreased blood flow reduces the availability of oxygen, provoking massive glycolysis (hyperglycemic conditions), which results in the production of lactate, exported to the liver for processing. However, this produces local acidosis, which elicits the rapid dissociation of oxyhemoglobin, freeing bursts of oxygen in localized zones of the tissue. The excess of oxygen (and of nitric oxide) induces the production of reactive oxygen species, which deeply affect the endothelial, blood, and adipose cells, inducing oxidative and nitrosative damage and eliciting an increased immune response, which translates into inflammation. The result of the defense mechanism for adipose tissue, localized vasoconstriction, may thus help develop a more generalized pathologic response within the metabolic syndrome parameters, extending its effects to the whole body.

The influence of metabolic syndrome and chronic kidney disease on hemorheology assessed by the microchannel method

Metabolic syndrome (MetS) and chronic kidney disease (CKD) are individual risk factors for cardiovascular disease (CVD). Abnormal hemorheology may be associated with CVD in both disorders. The present study investigated the impact of MetS and CKD on hemorheology. We studied 138 adults (women/men=63/75, mean age=52.2 years), who included 87 participants with MetS and 33 with CKD. The hemorheology was assessed by the index of 'whole blood passage time (WBPT)' using the Micro Channel array Flow ANalyzer (MC-FAN). The WBPT values of MetS participants were significantly higher than those of non-MetS participants (52.5±13.1 vs. 46.3±7.7 sec, p=0.03). The WBPT values of CKD participants were significantly higher than those of non- CKD (55.5±12.7 vs. 48.6±11.0 sec, p=0.003). The significant influence of MetS and CKD on WBPT was qualified by their effect modification to WBPT (p=0.04). There was a significantly greater influence of the combination of MetS and CKD on WBPT (59.9±13.4 sec) in comparison to the influence of non-MetS and CKD (46.6±3.5) or non-CKD and MetS (50.0±12.2). The influence of the combination of MetS and CKD was clearer in men, relative to women. Abnormal hemorheology as assessed using MC-FAN may be enhanced by the combination of MetS and CKD.

High blood viscosity is closely associated with cigarette smoking and markedly reduced by smoking cessation

BACKGROUND

Cigarette smoking is an independent risk factor for cardiovascular events such as myocardial infarction and stroke. To date, a useful and convenient method of predicting such events in smokers has not been established. The rheological properties of blood assessed by the microchannel method reflect the blood's viscosity and the state of microthrombus formation, which may predict cardiovascular thrombotic events.

METHODS AND RESULTS

Blood fluidity was assessed in 74 smoking patients (54 men, 20 women, mean age 57.9 years) by measuring the blood passage time (BPT) in an aliquot (100 µl) of blood using the Micro Channel Array Flow Analyzer. BPT was significantly related with smoking variables such as daily consumption of tobacco (r = 0.236, P = 0.044), Brinkman's index (r = 0.252, P = 0.033), the Fagerstrom Test for Nicotine Dependence (r = 0.257, P = 0.029), and the score of a self-rating depression scale (r = 0.236, P < 0.05). Multivariate regression analysis revealed that an independent BPT determinant was daily consumption of tobacco (r = 0.326, P = 0.045). Furthermore, smoking cessation markedly decreased BPT from 63.0 s to 49.7 s (P = 0.002) at 3 months after the start of therapy.

CONCLUSIONS

Unfavorable blood rheology is closely associated with cigarette smoking and may reflect increased cardiovascular risk in smokers. The study results also suggest that such risk can be reduced after only 3 months of smoking cessation.