Daniela Leonardis

Phosphate May Promote CKD Progression and Attenuate Renoprotective Effect of ACE Inhibition

Phosphate may promote the onset and progression of chronic nephropathies. Here we evaluated the relationships between baseline serum phosphate levels, disease progression, and response to ACE inhibition in 331 patients with proteinuric nephropathies in the prospective Ramipril Efficacy In Nephropathy (REIN) trial. Independent of treatment, patients with phosphate levels in the highest two quartiles progressed significantly faster either to ESRD or to a composite endpoint of doubling of serum creatinine or ESRD compared with patients with phosphate levels below the median (P < 0.001). Results were similar when we analyzed phosphate as a continuous variable (P ≤ 0.004). The renoprotective effect of ramipril decreased as serum phosphate increased (P ≤ 0.008 for interaction); this modification of the treatment effect by phosphate persisted despite adjusting for potential confounders such as GFR and urinary protein. In summary, these data suggest that phosphate is an independent risk factor for progression of renal disease among patients with proteinuric CKD, and high levels of phosphate may even attenuate the renoprotective effect of ACE inhibitors. Future trials should test whether reducing serum phosphate improves renal outcomes and optimizes the renoprotective effect of ACE inhibition.

ACE Inhibition Is Renoprotective among Obese Patients with Proteinuria

Obesity may increase the risk for progression of CKD, but the effect of established renoprotective treatments in overweight and obese patients with CKD is unknown. In this post hoc analysis of the Ramipril Efficacy In Nephropathy (REIN) trial, we evaluated whether being overweight or obese influences the incidence rate of renal events and affects the response to ramipril. Of the 337 trial participants with known body mass index (BMI), 105 (31.1%) were overweight and 49 (14.5%) were obese. Among placebo-treated patients, the incidence rate of ESRD was substantially higher in obese patients than overweight patients (24 versus 11 events/100 person-years) or than those with normal BMI (10 events/100 person-years); we observed a similar pattern for the combined endpoint of ESRD or doubling of serum creatinine. Ramipril reduced the rate of renal events in all BMI strata, but the effect was higher among the obese (incidence rate reduction of 86% for ESRD and 79% for the combined endpoint) than the overweight (incidence rate reduction of 45 and 48%, respectively) or those with normal BMI (incidence rate reduction of 42 and 45%, respectively). We confirmed this interaction between BMI and the efficacy of ramipril in analyses that adjusted for potential confounders, and we observed a similar effect modification for 24-hour protein excretion. In summary, obesity predicts a higher incidence of renal events, but treatment with ramipril can essentially abolish this risk excess. Furthermore, the reduction in risk conferred by ramipril is larger among obese than nonobese patients.

Circulating soluble receptor of advanced glycation end product inversely correlates with atherosclerosis in patients with chronic kidney disease

The soluble receptor of advanced glycation end product (sRAGE) prevents vascular damage in experimental animal models, and observational studies in the general population support the hypothesis that sRAGE may exert a protective role on the vasculature. To test this in patients with chronic kidney disease, we determined the relationship between plasma sRAGE and carotid atherosclerosis in 142 patients with an average estimated glomerular filtration rate (eGFR) of 32 ml/min per 1.73 m(2) and 49 healthy control individuals matched for age and gender. Plasma sRAGE was significantly higher in patients with chronic kidney disease than in the control cohort. In an aggregate analysis of the patients and controls, there was a significant inverse relationship between eGFR and sRAGE, with a breakpoint in the regression line at 64 ml/min per 1.73 m(2). Significant inverse relationships were found for sRAGE to intima-media thickness and plaque number in the patients with chronic kidney disease, but no such associations were found in the controls. On covariance analysis, the slopes of intima-media thickness and plaque number to sRAGE were significantly steeper in patients with chronic kidney disease than in the controls. Furthermore, a significant interaction was found between sRAGE and smoking for predicting atherosclerotic plaques in patients with chronic kidney disease. The pathophysiological significance of this correlation will have to await more mechanistic studies.

Reproducibility of the response to short-term low salt intake in essential hypertension

Background The reproducibility of the arterial pressure response to changes in salt intake in essential hypertensives has been little investigated. Objective To study the reproducibility of the response to salt in 14 untreated patients with mild essential hypertension. Methods After a run-in phase (1 month), each patient ingested, in random order and with cross-over, 1 week of high salt intake (170 mmol/day) and 1 week of low salt intake (40 mmol/day). The identical experimental protocol was then repeated after an average interval of 3.4 months. Arterial pressure was measured (clinic arterial pressure and 24 h ambulatory monitoring) on the seventh day of each diet period. The reproducibility of the arterial pressure response was assessed in terms the intraclass correlation coefficient and the K statistics. Results There was a good compliance with the dietary prescription because the urinary Na excretion was on average very close to the prescribed intake both during the first and during the second salt intake period. Both clinic and 24 h arterial pressure fell significantly (P<0.01) and to the same extent in the low-salt phases of the study. Clinic arterial pressure was consistently higher than 24 h ambulatory arterial pressure but the average changes induced by salt depletion were similar. The variability of 24 h ambulatory arterial pressure at constant salt intake was lower than that of clinic arterial pressure. However, the arterial pressure response to salt showed the same variability with the two methods. The reproducibility of the dichotomous classification of patients into salt-sensitive and -resistant was low both in terms of 24 h ambulatory and in terms of clinic blood pressure. Conclusion Although on rechallenging the average arterial pressure response to salt remains unchanged in essential hypertensives, the individual responses are variable and the reproducibility of the dichotomous classification is unsatisfactory. The problem of dichotomizing patients into salt-sensitive and -resistant ones is only in very little part resolved by more precise arterial pressure estimates.

Long-term visit-to-visit office blood pressure variability increases the risk of adverse cardiovascular outcomes in patients with chronic kidney disease

Long-term visit-to-visit blood pressure (BP) variability predicts a high risk for cardiovascular events in patients with essential hypertension. Whether long-term visit-to-visit BP variability holds the same predictive power in predialysis patients with chronic kidney disease (CKD) is unknown. Here we tested the relationship between long-term visit-to-visit office BP variability and a composite end point (death and incident cardiovascular events) in a cohort of 1618 patients with stage 2-5 CKD. Visit-to-visit systolic BP variability was significantly and independently related to baseline office, maximal, and average systolic BPs, age, glucose, estimated glomerular filtration rate, and albumin, and to the number of visits during the follow-up. Both the standard deviation of systolic BP (hazard ratio: 1.11, 95% confidence interval: 1.01-1.20) and the coefficient of variation of systolic BP (hazard ratio: 1.15, 95% confidence interval: 1.02-1.29) were significant predictors of the combined end point independent of peak and average systolic BP, cardiovascular comorbidities, Framingham risk factors, and CKD-related risk factors. Antihypertensive treatment (β-blockers and sympatholytic drugs) significantly abrogated the excess risk associated with high systolic BP variability. Thus, large visit-to-visit systolic BP variability in patients with CKD predicts a higher risk of death and nonfatal cardiovascular events independent of underlying BP levels.

Association of a Polymorphism in a Gene Encoding a Urate Transporter with CKD Progression

BACKGROUND AND OBJECTIVES Hyperuricemia predicts a high risk for CKD progression but there is no large clinical trial in humans indicating that this relationship is causal in nature. The rs734553 single-nucleotide polymorphism (SNP) of the GLUT9 urate transporter gene was strongly associated with uric acid (UA) levels in a large meta-analysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This prospective study adopted the Mendelian randomization approach. The rs734553 SNP was used as an instrumental variable to investigate the relationship between UA and renal outcomes in a cohort of 755 patients with CKD who were enrolled between October 18, 2005, and October 2, 2008. The association between the polymorphism and UA was preliminary confirmed in a series of 211 healthy volunteers enrolled between January 1, 2001, and July 12, 2011, from the same geographic area as the patients with CKD. The study end point was a composite renal-end point (i.e., >30% decrease in the GFR, dialysis, or transplantation). Patients were followed up for a median of 36 months. RESULTS In healthy individuals, serum UA levels were highest in homozygotes for the T allele (risk allele), intermediate in heterozygotes for the same allele, and lowest in those without the risk allele (P<0.001), but no such relationship was found in patients with CKD. In the CKD cohort, homozygotes (TT) and heterozygotes (GT) for the risk allele had a 2.35 times higher risk (hazard ratio, 2.35; 95% confidence interval, 1.25 to 4.42; P=0.008) of CKD progression. The risk for CKD progression by rs734553 remained unmodified in analyses adjusting for proteinuria, GFR, and other classical and CKD-peculiar risk factors. CONCLUSIONS A GLUT9 polymorphism, which is strongly associated with serum UA levels in healthy individuals of the general population with normal renal function, holds a strong predictive power for CKD progression. These findings are compatible with the hypothesis that the link between UA and CKD progression is causal in nature.

Association of IL-6 and a Functional Polymorphism in the IL-6 Gene with Cardiovascular Events in Patients with CKD

BACKGROUND AND OBJECTIVES High serum IL-6 is a major risk factor for cardiovascular disease (CVD) in the general population. This cytokine is substantially increased in patients with CKD, but it is still unknown whether the link between IL-6 and CVD in CKD is causal in nature. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In a cohort of 755 patients with stages 2-5 CKD, consecutively recruited from 22 nephrology units in southern Italy, this study assessed the relationship of serum IL-6 with history of CVD, as well as with incident cardiovascular (CV) events (mean follow up±SD, 31±10 months) and used the functional polymorphism (-174 G/C) in the promoter of the IL-6 gene to investigate whether the link between IL-6 and CV events is causal. RESULTS In adjusted analyses, serum IL-6 above the median value was associated with history of CVD (P<0.001) and predicted the incidence rate of CV events (hazard ratio, 1.66; 95% confidence interval [95% CI], 1.11 to 2.49; P=0.01). Patients homozygous for the risk allele (C) of the -174 G/C polymorphism had higher levels of IL-6 than did those with other genotypes (P=0.04). Homozygous CC patients more frequently had a history of CVD (odds ratio, 2.15; 95% CI, 1.15 to 4.00; P=0.02) as well as a 87% higher rate of incident CV events (hazard ratio, 1.87; 95% CI, 1.02 to 3.44; P=0.04) compared with other genotypes. CONCLUSIONS In patients with stages 2-5 CKD, high serum IL-6 is associated with history of CVD and predicts incident CV events. The parallel relationship with history of CVD and incident CV events of the -174 G/C polymorphism in the IL-6 gene suggests that IL-6 may be causally involved in the high CV risk in this population.

Sleep Disordered Breathing in Renal Transplant Patients

Sleep disordered breathing (SDB) is a prevalent, important nontraditional cardiovascular (CV) risk factor in end‐stage renal disease patients. The prevalence of SDB in renal transplant patients is unknown. We compared polysomnographic studies in 163 transplant patients with matched samples in the general population and explored longitudinally the effect of return to dialysis after graft failure on SDB in three consecutive cases. Episodes of nocturnal hypoxemia, average and minimal O2 saturation overnight in transplant patients did not differ from those in individuals in the general population matched for age, gender and body mass index (BMI). The prevalence of moderate‐to‐severe SBD in these patients did not exceed the estimated prevalence of the same disturbance in the general population. The respiratory disturbance index in transplant patients was directly associated with BMI (p < 0.001). In the longitudinal study all indicators of SDB coherently increased after transplant failure. The prevalence of SDB in transplant patients does not differ from that in well‐matched individuals in the general population. The favorable effect of renal transplantation on CV risk may be at least partially explained by the lack of risk excess for SDB in this population. Longitudinal observations after transplant failure are compatible with the hypothesis that renal transplantation reverses SDB.

A polymorphism in the major gene regulating serum uric acid associates with clinic SBP and the white-coat effect in a family-based study.

Objectives: Hyperuricemia associates with hypertension, but it is uncertain whether this relationship is causal in nature. Glucose transporter 9 (GLUT9) gene is a major genetic determinant of plasma uric acid levels in humans. Since polymorphisms are randomly distributed at mating (Mendelian randomization), studies based on GLUT9 polymorphisms may provide unconfounded assessment of the nature of the link between uric acid and hypertension. Methods: We tested the association between uric acid, the rs734555 polymorphism of the GLUT9 gene and arterial pressure in a family-based study including 449 individuals in a genetically homogenous population in Southern Italy. Results: Serum uric acid levels were strongly associated (P < 0.001) with all components of clinic and 24-h ambulatory blood pressures (BPs). However, only clinic SBP and the white-coat effect (the difference in clinic systolic and daytime systolic ambulatory blood pressure monitoring) associations remained significant after adjustment for classical risk factor and the estimated glomerular filtration rate. Serum uric acid was strongly associated with the risk allele (T) of the rs734555 polymorphism (P < 0.001). Furthermore, TT individuals showed higher clinic SBP (129 + SEM 1 mmHg) than GT (125 + 1 mmHg) and GG individuals (122 + 3 mmHg), as well as a higher white-coat effect (P = 0.02), confirming that the association between uric acid and these BP components is unconfounded by environmental risk factors. Conclusion: Results in this family-based study are compatible with the hypothesis that uric acid is a causal risk factor for hypertension. Trials testing uric acid-lowering interventions are needed to definitively establish the causal implication of hyperuricemia in human hypertension.

High estimated pulmonary artery systolic pressure predicts adverse cardiovascular outcomes in stage 2-4 chronic kidney disease

High estimated pulmonary artery systolic pressure (ePASP) is an established risk factor for mortality and cardiovascular (CV) events in the general population. High ePASP predicts mortality in dialysis patients but such a relationship has not been tested in patients with early CKD. Here we estimated the prevalence and the risk factors of high ePASP in 468 patients with CKD stage 2-4 and determined its prognostic power for a combined end point including cardiovascular death, acute heart failure, coronary artery disease, and cerebrovascular and peripheral artery events. High ePASP (35 mm Hg and above) was present in 108 CKD patients. In a multivariate logistic regression model adjusted for age, diabetes, hemoglobin, left atrial volume (LAV/BSA), left ventricular mass (LVM/BSA), and history of CV disease, age (OR, 1.06; 95% CI, 12 1.04-1.09) and LAV/BSA (OR, 1.05; 95% CI, 1.03-1.07) were the sole significant independent predictors of high ePASP. Elevated ePASP predicted a significantly high risk for the combined cardiovascular end point both in unadjusted analyses (HR, 2.70; 95% CI, 1.68-4.32) and in analyses adjusting for age, eGFR, hemoglobin, LAV/BSA, LVM/BSA, and the presence of diabetes and CV disease (HR, 1.75; 95% CI, 1.05-2.91). High ePASP is relatively common in patients with stage 2-4 CKD and predicts adverse CV outcomes independent of established classical and CKD-specific risk factors. Whether high ePASP is a modifiable risk factor in patients with CKD remains to be determined in randomized clinical trials.