Interrelationship between brachial artery function and renal small artery sclerosis in chronic kidney disease

Endothelial Function Assessment by Flow-Mediated Dilation Method: A Valuable Tool in the Evaluation of the Cardiovascular System

Cardiovascular diseases (CVDs) in the course of atherosclerosis are one of the most critical public health problems in the world. Endothelial cells synthesize numerous biologically active substances involved in regulating the functions of the cardiovascular system. Endothelial dysfunction is an essential element in the pathogenesis of atherosclerosis. Thus, the assessment of endothelial function in people without overt CVD allows for a more accurate estimate of the risk of developing CVD and cardiovascular events. The assessment of endothelial function is primarily used in scientific research, and to a lesser extent in clinical practice. Among the tools for assessing endothelial function, we can distinguish biochemical and physical methods, while physical methods can be divided into invasive and non-invasive methods. Flow-mediated dilation (FMD) is based on the ultrasound assessment of changes in the diameter of the brachial artery as a result of increased blood flow. FMD is a non-invasive, safe, and repeatable test, but it must be performed by qualified and experienced medical staff. The purpose of this paper is to present the literature review results on the assessment of endothelial function using the FMD method, including its methodology, applications in clinical practice and research, limitations, and future perspectives.

Structural changes in renal arterioles are closely associated with central hemodynamic parameters in patients with renal disease

Although central hemodynamics are known to be closely associated with microvascular damage, their association with lesions in the small renal arteries has not yet been fully clarified. We focused on arterioles in renal biopsy specimens and analyzed whether their structural changes were associated with noninvasive vascular function parameters, including central blood pressure (BP) and brachial-ankle pulse wave velocity (baPWV). Forty-four nondiabetic patients (18-50 years of age) with preserved renal function underwent renal biopsy. Wall thickening of arterioles was analyzed based on the media/diameter ratio, and hyalinosis was analyzed by semiquantitative grading. Associations of these indexes (arteriolar wall remodeling grade index (RG index) and arteriolar hyalinosis index (Hyl index)) with clinical variables were analyzed. Multiple regression analyses demonstrated that the RG index was significantly associated with central systolic BP (β = 0.97, p = 0.009), serum cystatin C-based estimated glomerular filtration rate (β = -0.36, p = 0.04), and high-density lipoprotein cholesterol levels (β = -0.37, p = 0.02). The Hyl index was significantly associated with baPWV (β = 0.75, p = 0.01). Our results indicate that aortic stiffness and abnormal central hemodynamics are closely associated with renal microvascular damage in young to middle-aged, nondiabetic kidney disease patients with preserved renal function.

Albuminuria rather than glomerular filtration rate is associated with vascular endothelial function in patients with type 2 diabetes

AIMS

Albuminuria and reduced glomerular filtration rate (GFR) are manifestations of diabetic kidney disease and are both shown to be associated with cardiovascular outcomes. However, the differential association of albuminuria and reduced GFR with endothelial dysfunction, an early feature of atherosclerotic vascular damage, remains unclear. In this study, we investigated the association between albuminuria or estimated GFR (eGFR) and flow-mediated dilatation (FMD), a marker of endothelial function, in patients with type 2 diabetes.

METHODS

This study included 633 patients with type 2 diabetes. The FMD of the brachial artery was measured by ultrasonography. Albuminuria was evaluated by urinary albumin-to-creatinine ratio (ACR).

RESULTS

The mean FMD and eGFR, and the median value of ACR were 6.7%, 66.5 mL/min/1.73m² and 12.5 mg/g creatinine, respectively. Impaired FMD was found in patients with advanced stages of chronic kidney disease based on both GFR and albuminuria categories. Multivariate analysis after adjusting for potential confounders revealed that ACR, but not eGFR, was significantly and inversely associated with FMD.

CONCLUSIONS

Albuminuria is associated with FMD, independently of traditional cardiovascular risk factors in patients with type 2 diabetes. This study suggests a close relationship between albuminuria, rather than reduced GFR, and endothelial dysfunction in type 2 diabetes.

A high normal ankle-brachial index is associated with biopsy-proven severe renal small artery intimal thickening and impaired renal function in chronic kidney disease

A significant relationship has been established between central hemodynamics and renal microvascular damage. We hypothesized that the increase in the ankle-brachial index (ABI) with age is due to increased arterial stiffness and wave reflection and is thus associated with the pathogenesis of the renal small artery in patients with chronic kidney disease (CKD). We recruited 122 patients with CKD (stages 1-5) who underwent renal biopsy and ABI measurements between 2010 and 2013. Renal small artery intimal thickening (SA-IT) severity was assessed by semiquantitative grading. The median age was 47 years, with a range of 15-86 years (47% women). The median estimated glomerular filtration rate (eGFR) was 62 mL/min/1.73 m². Compared with patients with the lowest 1-3 SA-IT index quartile, those with the highest quartile of the SA-IT index were older in age had higher mean arterial pressure, ABI, brachial-ankle pulse wave velocity, and lower eGFR. ABI was positively associated with SA-IT severity and inversely associated with eGFR. Multivariate logistic regression analyses showed that ABI was significantly associated with the highest quartile of the SA-IT index (odds ratio per SD increase in ABI, 1.83; 95% confidence interval, 1.08-3.26) and low eGFR (<60 mL/min/1.73 m²) (odds ratio per SD increase in ABI, 1.74; 95% confidence interval, 1.03-3.03). In conclusion, a high normal ABI was associated with severe renal small artery intimal thickening and low eGFR in patients with CKD.

Association of renal arteriosclerosis and hypertension with renal and cardiovascular outcomes in Japanese type 2 diabetes patients with diabetic nephropathy

AIMS/INTRODUCTION

The present retrospective study investigated the impact of renal arteriosclerosis (AS) and hypertension (HT) on long-term renal and cardiovascular outcomes in Japanese type 2 diabetes patients with biopsy-proven diabetic nephropathy.

MATERIALS AND METHODS

A total of 185 patients were enrolled. Patients were divided into four groups stratified by renal AS status and the presence of HT. The outcomes for this study were the first occurrence of renal events (a need for dialysis or a 30% decline in estimated glomerular filtration rate from baseline) and cardiovascular events (cardiovascular death, non-fatal myocardial infarction, coronary intervention or non-fatal stroke).

RESULTS

The proportion of renal AS scores ≥1 was 88.3% among patients with normal-range blood pressure (BP) and 95.4% among patients with HT. During a mean follow-up period of 7.6 years, 129 episodes of renal composite events and 55 episodes of cardiovascular events were observed. Compared with patients with no renal AS and normal-range BP, a renal AS score ≥1 increased the risk of renal composite events with a multivariable-adjusted hazard ratio of 3.21 (95% confidence interval [95% CI] 1.27-8.14) in patients with normal-range BP and 4.99 (95% CI 1.98-12.54) in patients with HT, whereas renal AS score ≥1 increased the risk of cardiovascular events with a multivariable-adjusted hazard ratio of 6.06 (95% CI 1.24-29.61) in patients with normal-range BP and 10.02 (95% CI 1.92-52.39) in patients with HT.

CONCLUSIONS

Renal AS was associated with increasing risks for renal composite events and cardiovascular events in both normal-range BP and HT. The risks of renal composite events and cardiovascular events were the highest in both renal AS and HT.

The Relationship between Carotid and Femoral Artery Intima-Media Thickness and Histopathologic Grade of Atherosclerosis in Patients with Chronic Kidney Disease

BACKGROUND/AIMS

Variability in the grade of atherosclerosis among patients with chronic kidney disease (CKD) could affect the ultrasound measurements of intima media thickness (IMT). We sought to investigate IMTs of carotid (cIMT) and femoral (fIMT) arteries in CKD patients and assess the degree of their correlation with histopathological atherosclerosis.

METHODS

Eighty-nine out of 99 enrolled subjects completed this study. The subjects were divided into 3 groups: 34 patients with CKD (Case group), 31 with coronary artery disease undergoing coronary artery bypass graft (CABG, positive control group), and 24 healthy kidney donors (negative control group). For histopathological assessment of atherosclerosis, arterial tissue samples were obtained from the patients in each study group. The cIMT and fIMTs were measured by ultrasonography.

RESULTS

Histopathological atherosclerosis was present in 82.3, 100, and 20.8% of CKD, CABG, and donor groups respectively (p < 0.001). CKD patients had higher values of cIMT and fIMT than the donor group (p = 0.01 and 0.004, respectively). cIMT was positively correlated with the grade of atherosclerosis in the CKD group only (p < 0.001), while fIMT was correlated with the grade of atherosclerosis in both CKD and donor groups (p < 0.001 and p = 0.009 respectively). In CKD patients, cIMT >0.65 mm and femoral values >0.57 mm predicted the presence of histopathological atherosclerosis with sensitivities of 96 and 92% respectively.

CONCLUSION

Higher values of cIMT and fIMT in CKD patients are associated with higher rates and degrees of histopathological atherosclerosis. Additionally, when compared to fIMT, cIMT has a higher sensitivity for detecting atherosclerosis in CKD patients.

Dietary intake of inorganic phosphorus has a stronger influence on vascular-endothelium function than organic phosphorus

Phosphorus management through dietetic therapy is vital for the prevention of cardiovascular disease in chronic kidney disease patients. There are two main sources of phosphorus in the diet, organic phosphorus from protein and inorganic phosphorus from food additives. The adverse effects of high phosphorus intake on vascular-endothelium function have been reported; however, the differences in the effects of organic phosphorus versus inorganic phosphorus are not clear. In this study, we examined an acute effect of these high phosphorus meals intake on vascular-endothelium function. This was a randomized, double-blind, cross-over test study design targeting healthy young men. We conducted a food intake test using two test meals, one high in organic phosphorus from organic food sources, and one high in inorganic phosphorus from food additives. Endothelium-dependent vasodilation, phosphorus and calcium in the urine and blood, and phosphorus-related hormones were measured preprandial to 120 min postprandial. The results showed higher serum and urine phosphorus values after the high inorganic phosphorus meal, and a significant reduction in endothelium-dependent vasodilation at 30 min postprandial. These findings are evidence that inorganic phosphorus has a stronger influence on vascular-endothelium function than organic phosphorus.

Exercise training with dietary restriction enhances circulating irisin level associated with increasing endothelial progenitor cell number in obese adults: an intervention study

Objective

Circulating endothelial progenitor cells (EPCs) correlate negatively with obesity. Previous studies have shown that exercise significantly restores circulating EPC levels in obese people; however, the underlying mechanisms have not been elucidated. Recently, irisin has been reported to have a critical role in the regulation of EPCs. This exercise-induced myokine has been demonstrated to play a therapeutic role in obesity. In this study, we hypothesized that the increase in circulating irisin may form a link with increasing EPC levels in obese people after exercise.

Methods

Seventeen obese adults completed an 8-week program of combined exercise and dietary intervention. Clinical characteristics, blood biochemistry, and circulating irisin levels of subjects were measured before and after eight weeks of training. EPC levels were evaluated via flow cytometry, and EPC migratory and adhesive functions were also determined.

Results

Circulating irisin levels significantly increased following the 8-week training program (P < 0.05). We furthermore observed an improvement in EPC numbers (P < 0.05), and EPC migratory and adhesive functions (P < 0.001 and P < 0.05, respectively) after the intervention. Additionally, we detected a positive correlation between changes in irisin and changes in EPC number (r = 0.52, P < 0.05).

Discussion

For the first time, a positive correlation between increasing irisin levels and increasing EPC levels has been reported after an 8-week program, consisting of exercise and dietary intervention. This result suggests a novel effect of irisin on the regulation of EPC mobilization, which might contribute to improvement of endothelial function in obese people.

Endothelial Function Is Impaired in Patients Receiving Antihypertensive Drug Treatment Regardless of Blood Pressure Level: FMD-J Study (Flow-Mediated Dilation Japan)

Hypertension is associated with endothelial dysfunction. Blood pressure significantly correlates with endothelial function in antihypertensive drug-naive subjects. The purpose of this study was to determine whether treatment status affects the relationship between blood pressure and endothelial function. We measured flow-mediated vasodilation (FMD) in 2297 subjects, including 1822 antihypertensive drug-naive subjects and 475 treated hypertensive patients. FMD significantly decreased in relation to increase in systolic blood pressure (8.2±3.1% in subjects with systolic blood pressure of <120 mm Hg, 7.5±2.8% for 120-129 mm Hg, 7.1±2.8% for 130-139 mm Hg, and 6.7±2.6% for ≥140 mm Hg; P<0.001). Systolic blood pressure was independently associated with FMD in untreated subjects. In contrast, there was no significant relationship between systolic blood pressure and FMD in treated hypertensive patients (4.6±3.1% in treated hypertensives with systolic blood pressure of <120 mm Hg, 4.8±2.7% for 120-129 mm Hg, 4.9±2.8% for 130-139 mm Hg, and 4.5±2.3% for ≥140 mm Hg; P=0.77). Propensity score matching analysis revealed that the prevalence of endothelial dysfunction defined as FMD of less than the division point for the lowest tertile, and the middle tertile of FMD was significantly higher in treated hypertensive patients than in untreated subjects in all systolic blood pressure categories. Endothelial function assessed by FMD was impaired regardless of the level of blood pressure achieved by antihypertensive drug treatment in hypertensive patients.

An exaggerated blood pressure response to exercise is associated with nitric oxide bioavailability and inflammatory markers in normotensive females

This study was designed to examine the associations of an exaggerated systolic blood pressure (SBP) response to exercise with the indices of nitric oxide (NO) bioavailability, oxidative stress, inflammation and arterial stiffness in normotensive females. The subjects included 84 normotensive females without a history of cardiovascular disease or stroke who were not taking any medications. Each subject performed a multistage graded submaximal exercise stress test using an electric bicycle ergometer, and their blood pressure was measured at rest and during the last minute of each stage. The brachial-ankle pulse wave velocity, plasma nitrate/nitrite (NO_x), plasma thiobarbituric acid-reactive substances, high-sensitivity C-reactive protein (hs-CRP) and fibrinogen levels and the white blood cell count were measured. An exaggerated SBP response to exercise was defined according to the criteria of the Framingham Study (peak SBP: ⩾190 mm Hg). An exaggerated SBP response to exercise was observed in 27 subjects. A multiple logistic regression analysis revealed that the hs-CRP (odds ratio (OR): 1.05, 95% confidence interval (CI): 1.03-1.07, P=0.015) and plasma NO_x levels (OR: 0.92, 95% CI: 0.87-0.98, P=0.014) were significantly associated with an exaggerated SBP response to exercise. Furthermore, the percent change in SBP was found to be significantly associated with an increase in the hs-CRP (P for trend=0.006) and a decrease in the plasma NO_x levels (P for trend=0.001). These results suggest that an exaggerated SBP response to exercise was associated with the NO bioavailability and inflammatory status in normotensive females.

The relationships between visit-to-visit blood pressure variability and renal and endothelial function in chronic kidney disease

Visit-to-visit blood pressure variability has been shown to be an independent risk factor for cardiovascular diseases. High visit-to-visit blood pressure variability and endothelial dysfunction are observed in patients with chronic kidney disease. It is therefore assumed that high variability in visit-to-visit blood pressure measurements may be associated with endothelial dysfunction in these patients. The present study investigated the associations between visit-to-visit blood pressure variability and renal and endothelial function in patients with chronic kidney disease. We analyzed 150 consecutive patients with predialysis chronic kidney disease who visited our outpatient clinic from January 2006 to December 2010. The study examined the relationships between variability in visit-to-visit systolic blood pressure levels or mean systolic blood pressure (M SBP) and estimated glomerular filtration rate (eGFR) and flow-mediated dilation, an index of endothelial function. Variability in visit-to-visit systolic blood pressure showed a significant negative association with eGFR, independent of age, hemoglobin A1c, low-density lipoprotein (LDL) cholesterol and uric acid, whereas M SBP did not. Similarly, variability in SBP showed a significant negative association with flow-mediated dilation, independent of age, eGFR, HbA1c, LDL cholesterol and M SBP. These data indicate that variability in visit-to-visit blood pressure measurements is associated with impaired renal and endothelial function in patients with chronic kidney disease. This finding suggests that reducing blood pressure fluctuations might have beneficial effects in patients with chronic kidney disease, although this point needs to be addressed by future studies.