Free vitamin D is independently associated with systolic blood pressure in diabetic patients with impaired kidney function.

Vitamin D contributes to blood pressure (BP) regulation. We compared the association of BP in diabetic patients with either total vitamin D - the standard way of analyzing the vitamin D status - or free vitamin D, because only free vitamin D passes the cell membrane and interacts with the nuclear vitamin D receptor (VDR). An analytical cross-sectional study was conducted with 178 diabetic patients with impaired kidney function. Free and total vitamin D concentrations were measured in all patients. Multiple linear regression analysis considering patient age, sex, body mass index, height, smoking and drinking situation, the use of antihypertensive drugs, cholecalciferol treatment, C-reactive protein and estimated glomerular filtration rate as confounding factors were conducted to compare the association of free and total vitamin D with systolic and diastolic blood pressure (SBP and DBP). Multiple linear regression analysis revealed that neither SBP nor DBP was correlated with total vitamin D (SBP, 95% CI -0.405 ~ 0.159, p = 0.390; DBP, 95% CI -0.131 ~ 0.142, p = 0.933) (Table 2). However, the concentration of free vitamin D was independently associated with SBP (95% CI -2.691 ~ -0.210; p = 0.022) (Table 3), but not with DBP (95% CI -0.934 ~ 0.285; p = 0.293). In conclusion, free - but not total - vitamin D serum concentrations in patients with diabetes and impaired kidney function are inversely correlated with SBP. This study suggests that free vitamin D measurements might be more clinically relevant - as compared to measurements of total vitamin D - to adjust vitamin D therapy in diabetic patients with impaired kidney function.

Association of factor V Leiden mutation with delayed graft function, acute rejection episodes and long-term graft dysfunction in kidney transplant recipients.

We analysed whether the factor V Leiden mutation--the most common hereditary predisposing factor for venous thrombosis--is associated with early and long-term graft dysfunction after kidney transplantation in 394 Caucasian kidney transplant recipients. The presence of factor V Leiden mutation was identified by allele specific PCR. The prevalence of the factor V Leiden mutation was compared to 32216 unselected neonates. The prevalence of the factor V Leiden mutation (GA genotype) was similar in 394 kidney transplant recipients and 32216 neonates. The frequency of known factors predicting long-term graft function were similar in patients with the GA genotype and with the normal factor V gene (GG genotype). The GA genotype was associated with the occurrence of no primary graft function (risk: 2.87: 95% confidence interval: 1.01-8.26; p < 0.05), the number of dialysis after transplantation in patients with no primary graft function until graft function (7.5 +/- 2.06 dialysis in GA patients; 4.2 +/- 0.36 dialyses in GG patients; p < 0.05), and the risk for at least one acute rejection episode (risk: 3.83; 95% confidence interval: 1.38-10.59; p < 0.02). The slope of l/creatinine per year was significantly lower in patients with the GA genotype (GA patients: -0.0204 +/- 0.008 dl/mg per year; GG patients: 0.0104 +/- 0.004 dl/mg per year; p < 0.02). The annual enhancement of the daily protein excretion rate was elevated in patients with the GA genotype (GA patients: 38.5 +/- 16.6 mg/24 h per year; GG patients: 4.9 +/- 4.4 mg/24 h per year; p < 0.02). Our study showed that the factor V Leiden mutation is associated with the occurrence of delayed graft function, acute rejection episodes and chronic graft dysfunction after kidney transplantation.

Activity of the endothelin system in kidney allograft recipients is not associated with progression of chronic graft dysfunction.

Endothelin (ET) A receptor antagonists have been shown to be beneficial in rat models of chronic kidney allograft dysfunction. We investigated urinary and plasma ET-1 (uET-1, pET-1) and BigET-1 (uBigET-1, pBigET-1) concentrations, and plasma soluble ET-converting enzyme (ECE) concentration in 310 adult Caucasian kidney allograft recipients with graft survival of more than 2 years from the outpatients department of our clinic. All patients were on cyclosporine A- or FK506-based immunosuppression protocols. From all available measurements since transplantation, we calculated the slope of serum creatinine(-1)/year (slopeCrea) as a parameter for progression of chronic graft dysfunction, as well as the mean of serum creatinine (meanCrea) from most recent year before measurements as a parameter for actual graft function. The slope of urinary protein excretion/year (slopeProt) and mean of urinary protein concentration (meanProt) from most recent year was calculated analogue. uET-1 and uBigET-1 were adjusted for protein excretion by calculating uET-1/meanProt and uBigET-1/meanProt. Blood and urine probes for measurements were always drawn immediately before morning dosage of immunosuppressants. There was no significant correlation of any measured component of the ET system with slopeCrea or slopeProt. MeanCrea (mg/dl) was significantly correlated with pBigET-1 (fmol/ml) and pET-1 (fmol/ml) (pBigET-1: r=0.179, P=0.001; pET-1: r=0.161, P=0.009). The other measured components of the ET systems were not significant correlated with meanCrea. In conclusion, the actual graft function is associated with elevated pET-1 and BigET-1 concentrations as it is well known from other forms of impaired kidney function. However, the actual concentration of ET-1, soluble ECE, and BigET-1 in urine and plasma in our study is not associated with parameters for progression of chronic graft dysfunction.

Interaction of the endothelin system and calcineurin inhibitors after kidney transplantation.

Plasma endothelin (ET)-1 concentrations have been shown to be elevated in patients receiving calcineurin-inhibitors (CI). We investigated urinary and plasma ET-1 (uET-1, pET-1), BigET-1 (uBigET-1, pBigET-1) concentrations, and plasma soluble endothelin-converting enzyme (ECE) concentrations in 381 adult caucasian kidney allograft recipients with graft survival of more than 2 years from the outpatients department of our clinic. Blood and urine probes were always drawn immediately before morning dosage of immunosuppressants. Mean of urinary protein excretion (meanProt) and mean of serum creatinine (meanCrea) were calculated from all available measurements in the most recent year. uET-1 and uBigET-1 were adjusted for urinary protein excretion by calculating uET-1/meanProt and uBigET-1/meanProt. Patients (n=310) were on a cyclosporine A or FK506 (CI-group) based immunosuppression protocol, and 71 patients were immunosuppressed without use of CI (nonCI group). Time since transplantation was similar in both groups (mean+/-S.D.; CI-group: 7.55+/-2.50; nonCI-group: 7.74+/-3.06 years, P=0.240) as well as meanCrea (mean+/-S.D.; CI-group: 1.97+/-1.34; nonCI-group: 1.77+/-1.29 mg/dl, P=0.326). pET-1 was significantly higher in the CI-group, compared with nonCI (mean+/-S.D.; 0.87+/-1.4 versus 0.56+/-0.76 fmol/ml, P=0.011). pBigET-1 was similar (mean+/-S.D.; 0.85+/-1.41 versus 0.70+/-1.21 fmol/ml, P=0.33). ECE concentrations were higher in the CI group (mean+/-S.D.; 14.30+/-18.02 versus 9.23+/-7.42 ng/ml, P=0.001). uET-1/meanProt and uBigET-1/meanProt concentration were similar in the CI-group compared with the nonCI-group (mean+/-S.D.; uET-1/meanProt: 15+/-24 versus 21+/-40 pmol/g, P=0.139; uBigET-1/meanProt: 34+/-55 versus 19+/-23pmol/g, P=0.248). pET-1 elevation in patients receiving CI might be more likely to be due to elevated conversion of pBig-ET-1 by more ECE, and not to higher concentrations of pBigET-1.