Assessment of Endothelial and Microvascular Function in CKD: Older and Newer Techniques, Associated Risk Factors, and Relations with Outcomes

BACKGROUND

Endothelium is the inner cellular lining of the vessels that modulates multiple biological processes including vasomotor tone, permeability, inflammatory responses, hemostasis, and angiogenesis. Endothelial dysfunction, the basis of atherosclerosis, is characterized by an imbalance between endothelium-derived relaxing factors and endothelium-derived contracting factors.

SUMMARY

Starting from the semi-invasive venous occlusion plethysmography, several functional techniques have been developed to evaluate microvascular function and subsequently used in patients with CKD. Flow-mediated dilatation of the forearm is considered to be the "gold standard," while in the last years, novel, noninvasive methods such as laser speckle contrast imaging and near-infrared spectroscopy are scarcely used. Moreover, several circulating biomarkers of endothelial function have been used in studies in CKD patients. This review summarizes available functional methods and biochemical markers for the assessment of endothelial and microvascular function in CKD and discusses existing evidence on their associations with comorbid conditions and outcomes in this population. Key Messages: Accumulated evidence suggests that endothelial dysfunction occurs early in CKD and is associated with target organ damage, progression of renal injury, cardiovascular events, and mortality. Novel methods evaluating microvascular function can offer a detailed, real-time assessment of underlying phenomena and should be increasingly used to shed more light on the role of endothelial dysfunction on cardiovascular and renal disease progression in CKD.

Comparison of ambulatory central hemodynamics and arterial stiffness in patients with diabetic and non-diabetic CKD

Increased arterial stiffness is independently associated with renal function decline in patients with diabetes mellitus (DM). Whether DM has additional deleterious effects on central hemodynamics and arterial stiffness in chronic kidney disease (CKD) patients is yet unknown. This study aimed to compare ambulatory central BP, arterial stiffness parameters, and trajectories between patients with diabetic and non‐diabetic CKD. This study examined 48 diabetic and 48 non‐diabetic adult patients (>18 years) with CKD (eGFR: <90 and ≥15 ml/min/1.73 m²), matched in a 1:1 ratio for age, sex, and eGFR within CKD stages (2, 3a, 3b and 4). All patients underwent 24‐h ABPM with the Mobil‐O‐Graph device. Parameters of central hemodynamics [central systolic (cSBP) and diastolic blood pressure (cDBP), pulse pressure (PP)], wave reflection [augmentation index (AIx), and pressure (AP)] and pulse wave velocity (PWV) were estimated from the 24‐h recordings. Diabetic CKD patients had higher 24‐h cSBP (118.57 ± 10.05 vs. 111.59 ± 9.46, P = .001) and 24‐h cPP (41.48 ± 6.80 vs. 35.25 ± 6.98, P < .001) but similar 24‐h cDBP (77.09 ± 8.14 vs. 76.34 ± 6.75 mmHg, P = .625) levels compared to patients with non‐diabetic CKD. During day‐ and nighttime periods, cSBP and cPP levels were higher in diabetics compared to non‐diabetics. 24‐h PWV (10.10 ± 1.62 vs. 9.61 ± 1.80 m/s, P = .165) was numerically higher in patients with DM, but no between‐group differences were noted in augmentation pressure and index. In multivariate analysis, DM, female gender, and peripheral SBP were independently associated with higher cPP levels. Patients with diabetic CKD have higher ambulatory cSBP and increased arterial stiffness, as indicated by higher ambulatory cPP. These finding suggest that DM is a factor independently contributing to the adverse macrocirculatory profile of CKD patients.

The presence of diabetes mellitus further impairs structural and functional capillary density in patients with chronic kidney disease

OBJECTIVE

Endothelial dysfunction has been associated with increased cardiovascular events and overall mortality. Microvascular damage is prevalent both in diabetes mellitus (DM) and chronic kidney disease (CKD). Our aim was to compare microcirculatory function parameters in diabetic and non-diabetic CKD patients via nailfold video-capillaroscopy.

METHODS

We included 48 diabetic and 48 non-diabetic adult CKD patients. 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

Diabetic patients presented significantly lower capillary density during reactive hyperemia (36.3 ± 3.8 vs 38.3 ± 4.3 capillaries/mm² , P = .022) and at venous congestion (37.8 ± 4.0 vs 39.8 ± 4.2 capillaries/mm² , P = .015). When stratified according to CKD stages, only in stage 3b capillary density was significantly lower in diabetic compared to non-diabetic subjects at baseline, during postocclusive hyperemia (36.8 ± 2.7 vs 40.0 ± 4.3 capillaries/mm² , P = .037) and venous congestion (38.3 ± 2.8 vs 41.5 ± 3.5 capillaries/mm² , P = .022).

CONCLUSIONS

Capillary density during postocclusive 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 structural and functional impairment in CKD. These differences are more prominent in CKD stage 3b.

P1294AMBULATORY BLOOD PRESSURE PROFILE IN PERITONEAL DIALYSIS COMPARED TO HEMODIALYSIS AND CHRONIC KIDNEY DISEASE PATIENTS

Background and Aims

Hypertension is highly prevalent in dialysis patients and is often poorly controlled. Data on the ambulatory blood pressure (BP) profile of patients undergoing peritoneal dialysis (PD) are scarce. The aim of this study is to compare the ambulatory BP profile of PD patients with that of hemodialysis (HD) and to pre-dialysis CKD patients.

Method

38 patients undergoing PD were matched in a 1:2 ratio for age, gender and dialysis vintage with 76 HD patients and in a 1:1 ratio for age and gender with 38 CKD stages 2-4 patients. Patients under PD and HD underwent 48-hour and CKD patients 24-hour ambulatory BP monitoring. BP levels were compared for the 48hour, 1st and 2nd 24hour, daytime and nighttime periods. Two-way mixed ANOVA analysis for repeated measurements was used to evaluate the effect of dialysis modality and time on ambulatory BP in PD and HD.

Results

During all periods studied, SBP and DBP were numerically higher but not statistically different in PD than in HD patients. SBP was significantly higher in PD or HD compared with predialysis CKD (PD:138.38±20.97; HD:133.75±15.5; CKD:125.52±13.4 mmHg, p=0.003; PD vs CKD: p=0.003; HD vs CKD: p=0.041 accordingly); significant differences were also evident during the daytime and nighttime periods. DBP displayed a similar trend in the total period studied (PD:82.34±15.22; HD:80.47±11.13; CKD:76.81±7.82 mmHg, p=0.108), but the difference significant only during the second nighttime period. Repeated-measurements analysis showed no effect of dialysis modality and no interaction between modality and time on ambulatory BP during all periods studied.

Conclusion

Average BP levels are similar between PD and HD patients, but higher for both groups compared to CKD counterparts. The dialysis modality had no significant effect on ambulatory BP profile.

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 (&gt;18 years) with CKD (eGFR: &lt;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.

P0763A COMPARATIVE STUDY OF ARTERIAL STIFFNESS AND WAVE REFLECTIONS IN DIABETIC AND NON-DIABETIC PATIENTS WITH CKD

Background and Aims

Arterial stiffness is associated with increased risk for target-organ damage, cardiovascular events and overall mortality in the general population, patients with diabetes mellitus and patients with chronic kidney disease (CKD) of all stages. This is the first study to evaluate in comparison arterial stiffness and arterial wave reflections in diabetic and non-diabetic patients with CKD.

Method

This study included 48 diabetic and 48 non-diabetic adult patients (&gt;18 years) with CKD (eGFR: &lt;90 και ≥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 patients underwent carotid-femoral pulse wave velocity (PWV), central blood pressure (BP), and wave reflections measurement with applanation tonometry (Sphygmocor, Atcor Medical, Australia).

Results

Office systolic and diastolic blood pressure was similar between diabetic and non-diabetic subjects with CKD in total and across CKD stages. Office brachial pulse pressure (PP) was significantly lower in non-diabetics (49.00±8.0 vs 52.67±8.7 mmHg, p= 0.034). Office PWV was marginally higher in diabetics compared with non-diabetics (10.89±2.0 vs 10.06±2.2 m/sec, p=0.056). In CKD stages 2 and 4, no significant difference in PWV between the two groups was noted, but PWV was higher for diabetics in CKD stages 3a (11.28±1.4 vs 9.83±1.5 m/sec, p=0.023) and 3b (11.13±1.9 vs 9.46±1.2 m/sec, p=0.016). Heart-rate-adjusted augmentation index [AIx(HR75)] was higher in diabetic compared with non-diabetic subjects only in CKD stage 4 (32.08±4.2 vs 25.92±6.6%, p=0.013).

Conclusion

Diabetic CKD patients present higher arterial stiffness than non-diabetic counterparts. The additional contribution of diabetes towards increased arterial stiffness is more prominent in patients with moderately impaired renal function (CKD stage 3a and 3b), whereas at stage 4, PWV was increased independent of diabetes presence.

P0156SHORT-TERM BLOOD PRESSURE VARIABILITY IN DIABETIC AND NON-DIABETIC PATIENTS WITH CKD STAGE 2, 3A, 3B AND 4

Background and Aims

Blood pressure variability (BPV) is an important risk factor for cardiovascular events and mortality in patients with chronic kidney disease (CKD). Previous evidence suggests that BPV is gradually increasing across CKD stages. Whether type 2 diabetes mellitus (DM) is an additional risk factor for increased BPV has never been studied. The aim of this study is to examine in comparison BPV in diabetic and non-diabetic patients with CKD.

Method

We included 48 diabetic and 48 non-diabetic adult patients (&gt;18 years) with CKD (eGFR: &lt;90 και ≥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 patients underwent 24-hour ambulatory blood pressure (BP) measurement with the Mobil-O-Graph device. Brachial BP variability was calculated with validated formulas. We calculated standard deviation (SD), weighted SD (wSD), coefficient of variation (CV), and average real variability (ARV) of BP during the 24-hour, day- and night-time periods with validated formulas.

Results

In total population, ambulatory systolic BP (SBP) levels were significantly higher in diabetics compared to non-diabetic counterparts in all studied periods. No significant differences were evidence for ambulatory diastolic BP (DBP) in total or across CKD stages. In total, 24-hour SBP SD (15.43±4.34 vs 13.38±3.35, p=0.011), wSD (14.41±4.11 vs 12.53±3.19, p=0.014) and ARV (10.94±2.75 vs 9.46±2.10, p=0.004) were higher in patients with DM compared to those without DM. In addition, 24hour DBP SD (11.04±2.39 vs 9.80±2.28, p=0.010), wSD (10.30±2.52vs 9.05±1.99, p=0.008), CV (14.77±3.05 vs 13.14±2.96, p=0.009) and ARV (8.23±2.10 vs 7.10±1.33, p=0.002) were again different between groups. Across CKD stages 2 and 3a, BPV indices were insignificantly higher in patients with DM. In CKD Stage 3b, 24-hour SBP-SD (16.30±4.52 vs 11.35±2.62, p=0.003), wSD (15.42±4.54 vs 10.77±2.30, p=0.004), ARV (12.46±3.19 vs 8.34±2.07, p=0.001) and 24-hour DBP-CV (14.84±3.63 vs 12.18±1.91, p=0.035) were higher in diabetic compared to non-diabetic patients. In contrast, no difference between groups existed in CKD Stage 4.

Conclusion

Patients with DM present increased BPV in CKD Stages 2, 3a and 3b (moderately impaired renal function). This difference is not apparent in patients with advanced CKD at Stage 4.

P1287A COMPARATIVE STUDY OF BLOOD PRESSURE VARIABILITY INDICES BETWEEN PATIENTS UNDERGOING PERITONEAL DIALYSIS AND THOSE UNDER HEMODIALYSIS OR WITH CHRONIC KIDNEY DISEASE

Background and Aims

Blood pressure variability (BPV) indices have been independently associated with cardiovascular events and mortality in hemodialysis (HD) patients. Data on short-term BPV in patients on peritoneal dialysis (PD) are totally absent. This study examined short-term BPV parameters of patients undergoing PD in comparison to HD and pre-dialysis chronic kidney disease (CKD) patients.

Method

38 PD patients were matched for age, gender and dialysis vintage with 76 HD in 1:2 ratio patients and for age and gender with 38 patients with CKD stage 2-4 in 1:1 ration. BPV parameters [standard deviation (SD), weighted SD (wSD), coefficient-of-variation (CV) and average-real-variability (ARV)] were calculated from data from 48hour (PD, HD) and 24hour (CKD) ambulatory BP monitoring according to validated formulas.

Results

There were no significant differences in BPV indexes studied between PD and HD patients but all BPV indexes in these patients were numerically higher than those in CKD patients. Systolic ARV was significantly higher in PD or HD compared with predialysis CKD during the first and the second interdialytic 24hour periods, both daytime period and nighttime 2 (1st 24hour period: PD:11.86±3.19; HD:11.23±3.45; CKD:9.81±2.49, p=0.016, 2nd 24hour period: PD: 12.18±4.11; HD: 12.96±4.57; CKD: 9.81±2.49, p&lt;0.001). Analysis of diastolic ARV and systolic and diastolic wSD showed similar results. Τhere were no differences with regards to dipping pattern and systolic and diastolic CV during all periods studied.

Conclusion

BPV indices are similar between PD and HD patients and higher compared to CKD counterparts. Despite what was theoretically expected, PD patients demonstrate high fluctuations in BP in the absence of abrupt shifts in volume.

Ambulatory Blood Pressure Trajectories and Blood Pressure Variability in Diabetic and Non-Diabetic Chronic Kidney Disease

BACKGROUND

Diabetic kidney disease is the leading cause of end-stage renal disease worldwide. Whether diabetes mellitus (DM) is an additional factor leading to elevated blood pressure (BP) levels and BP variability (BPV) in patients with chronic kidney disease (CKD) is unknown. This study aimed to compare ambulatory BP levels, BP trends and BPV in diabetic and non-diabetic patients with CKD.

METHODS

This study included 48 diabetic and 48 non-diabetic adult patients (>18 years) with CKD (estimated glomerular filtration rate [eGFR] <90 and ≥15 mL/min/1.73 m2), matched in a 1:1 ratio for age, sex and eGFR within each CKD stage (2, 3a, 3b and 4). All patients underwent 24-h ambulatory BP measurement with the Mobil-O-graph device. To evaluate the effect of DM and time on the trajectories of 24-h BP levels, we performed two-way mixed ANOVA analysis for repeated measurements using hourly means. BPV was calculated with validated formulas.

RESULTS

In total, patients with DM had significantly higher 24-h systolic BP (SBP; 132.13 ± 10.71 vs. 124.16 ± 11.45; p = 0.001) and pulse pressure (PP; 57.1 ± 9.6 vs. 49.5 ± 10.9; p < 0.001), but similar 24-h diastolic BP (DBP; 75.00 ± 8.43 vs. 74.62 ± 6.86 mm Hg; p = 0.809) compared to patients without DM. A similar trend was evident across all CKD stages. The effect of DM on BP trajectories during the recording period was significant for SBP (F = 18.766, p < 0.001, partial η2 = 0.261) and marginally significant for DBP (F = 3.782, p = 0.057, partial η2 = 0.067). Twenty-four hour SBP SD, weighted SD (wSD) and average real variability (ARV; 10.94 ± 2.75 vs. 9.46 ± 2.10; p = 0.004), as well as 24 h DBP SD, wSD, coefficient of variation (CV) and ARV (8.23 ± 2.10 vs. 7.10 ± 1.33; p = 0.002) were significantly higher in diabetic compared to non-diabetic CKD patients.

CONCLUSIONS

Ambulatory SBP and PP levels are higher and SBP-profile is different in patients with diabetic compared to those with non-diabetic CKD. Systolic and diastolic BPV are also higher in diabetics. These findings may signify a higher cardiovascular risk for patients with both DM and CKD compared to patients with CKD alone, through higher BP levels and BPV.

Human Leukocyte Antigen Compatibility and De Novo Donor-Specific Antibodies in Long-term Renal Transplant Patients With Stable Graft Function

PURPOSE

De novo donor-specific antibodies (DSA) are associated with antibody-mediated rejection leading to late renal transplant failure. The aim of this study was to evaluate whether HLA compatibility is associated with sensitization along with other risk factors.

METHODS

Eighty-nine stable renal transplant recipients (47 men) were studied. Patients were classified into 2 groups according to HLA compatibility between donor and recipient, group A (1-4/8 matches) and group B (5-8/8 matches). Cold ischemia time (CIT) and delayed graft function (DGF) were recorded along with time with a functional graft. Anti-HLA antibodies were detected using a Luminex single-antigen bead assay and were further classified into DSA and non-DSA.

RESULTS

HLA group A consisted of 49 (56%) transplant recipients while 38 (44%) were classified to group B, with functional grafts for 10.9 ± 6.7 and 14.8 ± 8.5 years, respectively (P = .019). Group A patients had more anti-HLA antibodies than group Β (P = .001) and this correlation was retained for DSA patients. De novo anti-HLA were detected in 40 patients; DSA were detected in 19 (21.8%). DSA (+) patients had recorded with functional renal grafts for 11 ± 5 years, compared to 14.4 ± 8.6 years (P = .048) for anti-HLA negative patients. Increased CIT and DGF were associated with anti-HLA antibodies detection but no with DSA.

CONCLUSION

HLA compatibility is probably correlated with DSA in a context of a more general anti-HLA sensitization, and both have a negative effect on long-term renal graft outcome.

Interrelations among the adipocytokines leptin and adiponectin, oxidative stress and aseptic inflammation markers in pre- and early-pubertal normal-weight and obese boys

PURPOSE

Presumed interrelationships among deleterious aspects of adipose tissue metabolism, inflammation, and cellular oxidative stress could be influenced by pubertal hormonal changes. They were investigated in pre- and early pubertal normal-weight and obese boys before and after an exercise bout employed as an energy demanding stimulator.

METHODS

Cross-sectional study. Seventy-six healthy pre- (mean ± SD, 10.6 ± 0.2 years old, 28 normal-weight, and 11 obese) and early-(11.4 ± 0.2 years old, 25 normal-weight, and 12 obese) pubertal boys, were blood-sampled before and after a bout of exercise at 70% VO₂ max. Leptin, adiponectin, markers of inflammation (high-sensitivity C-reactive protein, high sensitivity IL-6), pro- (thiobarbitouric acid reactive substances, protein carbonyls) and anti- (glutathione, oxidized glutathione, glutathione peroxidase, catalase, total antioxidant capacity) oxidation were measured.

RESULTS

Baseline and post-exercise adiponectin was greater and leptin and high-sensitivity C-reactive protein were lower in normal-weight than in obese pre- and early pubertal boys, while high sensitivity IL-6 was greater in obese than in normal-weight pre-pubertal boys. In pre-pubertal obese boys: at baseline, high-sensitivity C-reactive protein correlated negatively with catalase; high sensitivity IL-6 correlated positively with protein carbonyls; Δ (difference during exercise) adiponectin correlated positively with Δcatalase. In all boys: at baseline, high sensitivity IL-6 correlated positively with leptin and was the best negative and the second best positive predictor for post-exercise glutathione/oxidized glutathione and protein carbonyls, respectively; leptin was the best negative predictor for post-exercise glutathione; waist to height ratio was the best positive predictor for post-exercise thiobarbitouric acid reactive substances; body mass index z-score and adiponectin were, respectively, the best positive predictor for post-exercise protein carbonyls and catalase.

CONCLUSIONS

In all subjects, leptin and adiponectin predict negatively and positively anti-oxidation, respectively, while high sensitivity IL-6 predicts positively and negatively pro- and anti-oxidation, respectively. High-sensitivity C-reactive protein is increased and negatively associated with anti-oxidation in pre-pubertal obese boys, suggesting that childhood obesity is associated with aseptic inflammation and oxidative stress.

Antioxidation improves in puberty in normal weight and obese boys, in positive association with exercise-stimulated growth hormone secretion

BACKGROUND

Oxidative stress is associated with obesity while the evidence for the role of GH in pro- and antioxidation is inconclusive. This study investigates the relationships between growth hormone (GH), pro- and antioxidation in relation to obesity and puberty before and after an acute bout of exercise.

METHODS

In this case-control study, 76 healthy normal-weight and obese, prepubertal and pubertal boys underwent a blood sampling before and immediately after an aerobic exercise bout until exhaustion at 70% maximal oxygen consumption. Markers of prooxidation (thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PCs)) and antioxidation (glutathione (GSH), oxidized glutathione disulfide (GSSG), GSH/GSSG ratio, glutathione peroxidase (GPX), catalase, and total antioxidant capacity (TAC)) and hormones (GH, insulin-like growth factor (IGF)-1, IGF-BP-3, luteinizing hormone, follicle-stimulating hormone, and testosterone) were measured.

RESULTS

Baseline and postexercise TBARS and PCs were greater, while baseline GSH, GSH/GSSG ratio, GPX, and TAC were lower in obese than that in normal-weight participants. In all participants, waist was the best negative and positive predictor for postexercise GPX and TBARS, respectively. Baseline TAC was greater in pubertal than that in pre-pubertal participants. In all participants, baseline GH was the best negative predictor for postexercise PCs. Significant positive linear correlation exists between the exercise-associated GH, and GSSG increases in pubertal normal-weight boys.

CONCLUSIONS

Higher prooxidation and lower antioxidation were observed in obese boys, while antioxidation improves with puberty and postexercise, paralleling GH accentuated secretion.