Cardiovascular effects of cholecalciferol treatment in dialysis patients--a randomized controlled trial.

BACKGROUND: Patients on chronic dialysis are at increased risk of vitamin D deficiency. In observational studies plasma 25-hydroxyvitamin D (p-25(OH) D) levels are inversely correlated with plasma BNP and adverse cardiovascular outcomes. Whether a causal relation exists has yet to be established. The aim of this study was to test the hypothesis that cholecalciferol supplementation improves cardiac function and reduces blood pressure (BP) and pulse wave velocity (PWV) in patients on chronic dialysis. METHODS: In a randomized, placebo-controlled, double-blind study, we investigated the effect of 75 µg (3000 IU) cholecalciferol daily for 6 months, in patients on chronic dialysis. We performed two-dimensional echocardiography, with doppler and tissue-doppler imaging, 24-h ambulatory BP (24-h BP), PWV, augmentation index (AIx), central BP (cBP) and brain natriuretic peptide (BNP) measurements at baseline and after 6 months. RESULTS: Sixty-four patients were allocated to the study. Fifty dialysis patients with a mean age of 68 years (range: 46-88) and baseline p-25(OH) D of 28 (20;53) nmol/l completed the trial. Cholecalciferol increased left ventricular (LV) volume, but had no impact on other parameters regarding LV structure or left atrial structure. LV systolic function, LV diastolic function, PWV, cBP, AIx and BNP were not changed in placebo or cholecalciferol group at follow-up. 24-h BP decreased significantly in placebo group and tended to decrease in cholecalciferol group without any difference between treatments. CONCLUSION: Six months of cholecalciferol treatment in patients on chronic dialysis did not improve 24-h BP, arterial stiffness or cardiac function. TRIAL REGISTRATION: NCT01312714, Registration Date: March 9, 2011.

Abnormal function of the vasopressin-cyclic-AMP-aquaporin2 axis during urine concentrating and diluting in patients with reduced renal function. A case control study.

BACKGROUND: The kidneys ability to concentrate and dilute urine is deteriorated during progressive renal insufficiency. We wanted to test the hypothesis that these phenomena could be attributed to an abnormal function of the principal cells in the distal part of the nephron. METHODS: Healthy control subjects and patients with chronic kidney diseases were studied. Group 1 comprised healthy subjects, n = 10. Groups 2-4 comprised patients with chronic kidney disease (Group 2, n = 14, e-GFR ≤ 90 m1/min; Group 3, n = 11, 60 m1/min ≤ e-GFR < 90 ml/min; and Group 4, n = 16, 15 ml/min ≤ e-GFR < 60 ml/min). The subjects collected urine during 24 hours. A urine concentrating test was done by thirsting during the following 12 hours. Thereafter, a urine diluting test was performed with a water load of 20 ml/kg body weight. The effect variables were urinary excretions of aquaporin2 (u-AQP2), cyclic-AMP (u-c-AMP), urine volume (UV), free water clearance (CH2O), urine osmolarity (u-Osm), and plasma arginine vasopressin (p-AVP). RESULTS: After fluid deprivation, u-Osm increased. In all groups, UV and CH2O decreased and u-AQP2 and u-c-AMP increased in Groups 1 and 2, but were unchanged in Group 3 and 4. P-AVP was significantly higher in Group 4 than in the other groups. During urine diluting, UV and CH2O reached significantly higher levels in Groups 1-3 than Group 4. Both before and after water loading, u-AQP2 and p-AVP were significantly higher and u-c-AMP was significantly lower in Group 4 than the other groups. Estimated-GFR was correlated negatively to p-AVP and positively to u-c-AMP. CONCLUSIONS: Patients with moderately severe chronic kidney disease have a reduced renal concentrating and diluting capacity compared to both patients with milder chronic kidney disease and healthy control subjects. These phenomena can be attributed, at least partly, to an abnormally decreased response in the AVP-c-AMP-AQP2 axis.ClinicalTrials.Gov Identifier: NCT00313430.

Effect of BQ-123, an endothelin antagonist, on renal hemodynamics, tubular function, vasoactive hormones, and blood pressure in healthy humans: a dose response study.

BACKGROUND: Endothelin contributes to the maintenance of vascular tonus in both the systemic circulation and in regional vascular beds. The purpose of the study was to measure the effect of the endothelin A antagonist BQ-123 on renal hemodynamics, tubular function, vasoactive hormones, and blood pressure (BP) in healthy men. METHODS: In a randomized, placebo-controlled, double-blind dose-response study of 11 healthy men we measured the effect of BQ-123 on glomerular filtrations rate (GFR), renal plasma flow (RPF), fractional excretion of sodium (FENa), lithium clearance (CLi), BP, and plasma concentrations of renin (PRC), angiotensin II (Ang II), atrial and brain natriuretic peptides (ANP, BNP), and vasopressin (AVP). BQ-123 was infused intravenously at the rate of 0.1, 0.2, and 0.3 mg/kg for 1 h, and the effects were measured before, during, and after infusion. RESULTS: The GFR and RPF were not significantly changed by BQ-123. The FENa was increased (20%, medium dose), and CLi was unchanged. Systolic BP remained constant, whereas diastolic BP decreased (-6.3%, medium dose), and pulse rate increased (7.1%, medium dose). BQ-123 increased both PRC (62%, medium dose) and Ang II (70%, medium dose). The changes in FENa, diastolic BP, pulse rate, and Ang II gradually increased up to medium dose, and in PRC up to high dose. The ANP, BNP, and AVP were practically unchanged by BQ-123. CONCLUSIONS: Infusion of an endothelin A antagonist resulted in an increase in renal sodium excretion despite a stimulation of the renin-angiotensin system and a decrease in diastolic BP.