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The Effect of Long-Term Cholecalciferol Supplementation on Vascular Calcification in Chronic Kidney Disease Patients With Hypovitaminosis D
ORIGINAL RESEARCH
The Effect of Long-Term Cholecalciferol Supplementation on Vascular Calcification in Chronic Kidney Disease Patients With Hypovitaminosis D Farid Samaan, MD, PhD,* Aluızio B. Carvalho, MD, PhD,* Roberta Pillar, MD,* Lillian A. Rocha, MD, PhD,* Jose L. Cassiolato, MD,† Lilian Cuppari, PhD,* and Maria Eug^enia F. Canziani, MD, PhD* Objective: The role of vitamin D supplementation on vascular calcification (VC) in patients with chronic kidney disease (CKD) is controversial. The objective of this study was to evaluate the effects of long-term cholecalciferol supplementation on VC in nondialysis patients with CKD stages 3–4 with hypovitaminosis D. Design and Methods: Eighty patients aged 18–85 years with creatinine clearance between 15 and 60 mL/min/1.73 m2 and serum 25(OH)D level , 30 ng/mL were enrolled in a 18-month prospective study. Individuals with vitamin D insufficiency (25-hydroxyvitamin D [25(OH)D] level between 16 and 29 ng/mL) were included in a randomized, double-blind, two-arm study to receive cholecalciferol or placebo. Patients with vitamin D deficiency [25(OH)D , 15 ng/mL] were included in an observational study and mandatorily received cholecalciferol. The coronary artery calcium score was obtained by multislice computed tomography at baseline and the 18th month. Results: During the study, VC did not change in the treated insufficient group (418 [81–611] to 364 [232–817] AU, P 5 0.25) but increased in the placebo group (118 [37–421] to 199 [49–490] AU, P 5 0.01). The calcium score change was inversely correlated with 25(OH)D change (r 5 20.45; P 5 0.037) in the treated insufficient group but not in the placebo group. Renal function did not change in the insufficient, treated, and placebo groups. In multivariate analysis, there was no difference in VC progression between the treated and placebo insufficient groups (interaction P 5 0.92). In the deficient group, VC progressed (265 [84–733] to 333 [157–745] AU; P 5 0.006) and renal function declined (33 [26–43] to 23 [17–49] mL/min/1.73 m2; P 5 0.04). The calcium score change was inversely correlated with cholecalciferol cumulative doses (r 5 20.41; P 5 0.048) and kidney function change (r 5 20.43; P 5 0.033) but not with 25(OH)D change (r 5 20.08; P 5 0.69). Conclusion: Vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D. Conclusion: Vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D. Ó 2018 by the National Kidney Foundation, Inc. All rights reserved.
Introduction
H
YPOVITAMINOSIS D HAS been associated with higher cardiovascular morbidity and mortality in the general population and in patients with chronic kidney disease (CKD).1-6 Among the cardiovascular abnormalities in patients with CKD, vascular calcification (VC) is of major interest. Cross-sectional studies have demonstrated a positive correlation between low levels of 25-hydroxyvitamin D (25(OH)D) and VC in both dialysis and nondialysis CKD *
Nephrology Division, Federal University of S~ao Paulo, S~ao Paulo, Brazil. Cardios Research Institute, S~ao Paulo, Brazil. Support: Foundation for Research Support of the State of S~ao Paulo (FAPESP) and Coordination of Improvement of Higher Level Personnel (CAPES). Financial Disclosure: The authors declare that they have no conflict of interest. Address correspondence to Maria Eug^enia F. Canziani, MD, PhD, Rua Pedro de Toledo 282, CEP 04039-000, S~ao Paulo, SP Brazil. E-mail: dialisefor@ †
uol.com.br Ó
2018 by the National Kidney Foundation, Inc. All rights reserved. 1051-2276/$36.00 https://doi.org/10.1053/j.jrn.2018.12.002
Journal of Renal Nutrition, Vol -, No - (-), 2019: pp 1-9
patients.7,8 Furthermore, in a prospective study, de Boer et al.9 showed a strong association between low 25(OH)D levels and development of VC in patients with CKD. This relationship may arise from vitamin D actions on cells of the blood vessels, which are relevant to cardiovascular physiology and pathology.10 Supporting this, studies have shown that hypovitaminosis D is related to endothelial dysfunction and osteochondrogenic transformation of vascular smooth muscle cells, both of which are key processes for VC.11 As hypovitaminosis D is a frequent finding in patients with CKD, Kidney Disease Outcomes Quality Initiative (KDOQI) and Kidney Disease: Improving Global Outcomes (KDIGO) recommend to assess and restore 25(OH)D concentrations by vitamin D supplementation in this population.12,13 Restoration of 25(OH)D levels remains a challenge in these patients as most of the previous randomized controlled trials of vitamin D supplementation have shown conflicting results due to short-term protocols (,6 months) and variable doses and types of vitamin D.14-16 Cholecalciferol, also known as vitamin D3, is a type of vitamin D frequently used in 1
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clinical practice. It has high affinity to hepatic 25-hydroxylase, vitamin D–binding protein, and vitamin D receptor.16 Data on the impact of vitamin D supplementation on VC in patients with CKD are scarce and controversial. Thus, this study aimed to evaluate the effects of long-term cholecalciferol supplementation on VC in stage 3-4 CKD patients with hypovitaminosis D.
Methods Patients Eighty patients with creatinine clearance between 15 and 60 mL/min/1.73 m2 and serum 25(OH)D , 30 ng/mL were selected from the CKD outpatient clinic of the Federal University of S~ao Paulo, Brazil. The exclusion criteria were age ,18 and .85 years; nephrotic syndrome; immobilization in the last 3 months; liver, autoimmune, infectious, or neoplastic diseases; positive serology for HIV; previous use of cholecalciferol or multivitamin containing vitamin D; previous or current use of active vitamin D analogs or bisphosphonates; use of corticosteroids and immunosuppressive drugs in the last 3 months; hypercalcemia (ionized calcium .1.40 mmol/L); and serum intact parathormone (iPTH) level .500 pg/mL. The study was reviewed and approved by the Ethics Advisory Committee of the Federal University of S~ao Paulo, and each patient signed the informed consent form. This study was
registered at the Brazilian Clinical Trials Registry (ReBec—www.ensaiosclinicos.gov.br) under the number RBR-95j5pm.
Study Design and Supplementation Protocol In this 18-month prospective study, 80 CKD patients with hypovitaminosis D were included. During the follow-up, 12 patients did not complete the study due to withdrawal (5 patients), dialysis onset (2), prolonged hospitalization (2), and death (3). These patients had similar 25(OH)D levels, creatinine clearance, bone mineral profile, blood pressure, and coronary calcium score at baseline to those who finished the study. Therefore, 68 patients were considered in the final analysis (Fig. 1). Forty-four individuals with vitamin D insufficiency (25(OH)D level between 16 and 29 ng/mL) were included in the randomized, double-blind, two-arm study to receive 1:1 cholecalciferol or placebo. An independent researcher generated a computerized random list, and the allocation sequence of 20 patients was concealed in a closed box. The twenty-four patients with vitamin D deficiency (25(OH)D level # 15 ng/mL) were separately analyzed and mandatorily received cholecalciferol. Cholecalciferol was supplemented orally with a concentration of 1,000 IU/drop (Magister Handling Pharmacy Ltd., S~ao Paulo, Brazil). The placebo solution was identical in appearance, smell, and flavor to cholecalciferol. The duration of vitamin D supplementation was
Figure 1. Study design and patient distribution.
VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION
18 months in all study groups. The treated insufficient group received a fixed dose of 50,000 IU/month of cholecalciferol for 18 months without adjustment. The placebo insufficient group received 50,000 IU/month in the same manner. The deficient group was initially treated with 50,000 IU of cholecalciferol weekly for 12 weeks. After this period, the maintenance dose was adjusted according to serum 25(OH)D levels. Patients with vitamin D deficiency who had achieved 25(OH)D levels $ 30 ng/mL received a monthly dose of 50,000 IU, whereas in those with 25(OH)D levels , 30 ng/ mL, the weekly regime was maintained until the next serum 25(OH)D measurement. Vitamin D discontinuation criteria were serum ionized calcium level .1.40 mmol/L or 25(OH)D level .150 ng/mL. Responsiveness to cholecalciferol was evaluated by the percentage of patients that achieved 25(OH)D level $ 30 ng/mL at the 18th month and by the standardized change in 25(OH)D level (25(OH)D level at 18 months – baseline/100,000 IU of cholecalciferol administered over time) as described previously.17 For patients under the monthly cholecalciferol regime, compliance with the treatment was ensured by drug administration at the research center. For patients under weekly regime, adherence was ensured by returning of empty bottles at the visits. Patients were given sunscreen protector (SPF 30) and instructed to use it 20 min before and every 3 h of sun exposure during the study period to minimize the effects of skin production of vitamin D. No control of types of clothes or dietary intake of vitamin D–rich foods was performed. A noncalcium phosphate binder was prescribed if serum phosphorus levels increased to .4.5 mg/dL.
Coronary Artery Calcification Coronary artery calcification (CAC) was evaluated at baseline and after 18 months by multislice computed tomography scan (LightSpeed Pro 16; GE Healthcare, Milwaukee, WI), using a gantry rotation of 0.4 s, collimation of 2.5 mm (slice thickness), and reconstruction time of 6 frames per second. A calcium threshold of 130 HU was used. The images were scored by a single radiologist who was blinded to the clinical and biochemical information of the patients. As described by Agatston et al.,18 the calcium score was determined by multiplying the area of each calcified lesion by a weighting factor corresponding to the peak pixel intensity for each lesion. The sum of each lesion of all coronary arteries was used for the analysis. The presence of CAC was defined as calcium score $10 AU. Biochemical Assessments Blood samples were drawn in a 12-h fasting state for the evaluation of serum creatinine (automated biochemistry
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analyzer, Olympus AU400), hemoglobin (automated hematology analyzer, Abbott Cell-Dyn 3200), ionized calcium (electrolyte analyzer, Roche 9180), phosphorus (automated biochemistry analyzer, Olympus AU400), iPTH (reference values, 10-65 pg/mL, chemiluminescence; DPC Medlab), 25(OH)D (reference values, 30100 ng/mL, chemiluminescent immunoassay; DiaSorin, Stillwater, MN), serum albumin, lipid profile, and highsensitivity C-reactive protein (reference value, ,0.11 mg/dL; immunonephelometry). Urinary protein level was measured by 24-h urine collection. Glomerular filtration rate was estimated by creatinine clearance in 24-h urine volume and corrected for body surface area. Calcium and phosphorus levels were obtained monthly, whereas serum 25(OH)D level, creatinine clearance, iPTH level, and other laboratory parameters were measured at 3, 6, 12, and 18 months. Vitamin D deficiency and insufficiency were defined according to KDOQI.12 Dyslipidemia was defined according to the National Cholesterol Education Program—Adult Treatment Panel III guidelines.19 Participants who did not practice at least 150 min per week of moderate physical activity were considered sedentary.20 Changes in creatinine clearance, calcium score, and 25(OH)D level were defined as the difference between values at the 18th month and those at baseline.
Statistical Analysis Data are reported as mean and standard deviation, median and interquartile range, or frequency. The comparisons of continuous variables between groups were performed using Student’s independent t-test and Mann– Whitney U test for normal and skewed data, respectively. Comparisons of proportions were performed using c2 analysis or Fischer’s exact test, as appropriate. Analyses within each group were performed using paired-samples t-test for continuous normal data, Wilcoxon signed-rank test for skewed continuous data, and McNemar test for categorical data. The Spearman correlation was used to determine the relationship between calcium score change and cumulative cholecalciferol dose, creatinine clearance change, and 25(OH)D level change. A generalized estimating equation was used to analyze the longitudinal correlation between cholecalciferol supplementation and VC. The multivariate model was adjusted for age, iPTH level, ionized calcium level, creatinine clearance, and presence of diabetes. A Tweedie distribution was assumed in the model because the calcium score had an asymmetric distribution and many values with zeros. A P value of 0.05 was considered statistically significant. This pilot study used a convenience sample given the absence of studies evaluating the impact of vitamin D supplementation on VC at the time of the protocol. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) for Windows version 18.0 (SPSS Inc., Chicago, IL).
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Results Demographic, biochemical, and clinical data at baseline and after 18 months in the vitamin D–insufficient and vitamin D–deficient groups are shown in Tables 1 and 2, respectively.
Vitamin D Insufficient Groups: Treated and Placebo Forty-four patients were randomized 1:1 to the treated and placebo groups. Demographic and clinical characteristics of both groups were similar at baseline, except for lower serum ionized calcium level and higher coronary calcium score in the treated group. There were no significant differences in 25(OH)D, phosphorus, and iPTH levels and creatinine clearance. Bone mineral metabolism parameters during the study are shown in Figure 2. Compared with the placebo group, 25(OH) levels were greater at 6, 12,
and 18 months and iPTH levels were lower at 12 and 18 months in the treated group. Ionized calcium and phosphorous levels were similar and did not change over time. At 18 months, there was a significant increase in 25(OH) D levels in both groups, although it was higher in the treated group (18 6 8 vs. 8 6 9 ng/mL, P 5 .001). In the treated group, 86% of patients had 25(OH)D level $ 30 ng/mL after 18 months, the cumulative cholecalciferol dose was 900,000 IU, and the standardized change in 25(OH)D level was 1.9 (0.9–2.4) ng/mL/100,000 IU of cholecalciferol. In the placebo group, at the 18th month, 41% of patients had 25(OH)D level $ 30 ng/mL. CAC score and iPTH levels remained stable in the treated group, whereas in the placebo group, these parameters significantly increased. In the treated insufficient group, but not in the placebo group, calcium score change was inversely correlated with 25(OH)D change (r 5 20.45, P 5 .037;
Table 1. Baseline and Follow-up Data of Treated and Placebo Insufficient Groups Variables
Treated, N 5 22
Demographic data Age (years) Men, n (%) White skin, n (%) Hypertension, n (%) Diabetes, n (%) Dyslipidemia, n (%) Sedentary, n (%) Body mass index (kg/m2) Smokers, n (%)
69 (61-76) 9 (41) 14 (64) 22 (100) 12 (54) 18 (82) 14 (64) 27 6 4 1 (4) Baseline
18 months
P
Placebo, N 5 22
Between Groups, P
64 (53-73) 13 (59) 13 (59) 21 (95) 7 (32) 17 (77) 12 (54) 27 6 4 1 (4)
.11 .23 .76 1.00 .13 .71 .54 .80 1.00
Baseline
18 months
P
p0
Laboratory parameters 35 (27-44) 37 (29-48) .25 31 (26-41) 41 (20-48) .42 .36 CRCL (mL/min/1.73 m2) Proteinuria (g/24h) 0 (0-0.24) 0 (0-0.65) .008 0.20 (0-0.64) 0.23 (0-0.83) .19 .07 Hemoglobin (g/dL) 13.1 6 1.5 12.8 6 8 .29 13.9 6 1.9 12.9 6 1.9 .003 .11 Glycemia (mg/dL) 92 (86-102) 91 (79-115) .99 86 (76-107) 87 (79-105) .18 .15 HDL cholesterol (mg/dL) 40 (38-44) 39 (34-48) .39 44 (38-50) 42 (35-51) .35 .24 LDL cholesterol (mg/dL) 96 (78-113) 99 (83-119) .58 105 (83-132) 105 (72-115) .45 .49 Triglycerides (mg/dL) 146 (103-188) 136 (102-220) .58 155 (119-220) 137 (92-206) .45 .49 Albumin (g/dL) 4.3 6 0.2 4.2 6 0.3 .08 4.4 6 0.3 4.3 6 0.3 .21 .28 Ionized calcium (mmol/L) 1.30 (1.28-1.33) 1.28 (1.24-1.33) .06 1.33 (1.30-1.35) 1.30 (1.27-1.34) .26 .047 Phosphorus (mg/dL) 3.5 (3.1-3.8) 3.4 (3.1-3.7) .45 3.2 (3.0-3.8) 3.2(2.8-3.9) .92 .29 Phosphaturia (mg/24h) 414 (314-522) 502 (331-599) .42 422 (326-501) 474 (381-617) .17 .77 P-binder use, n (%) 0 (0) 2 (9) .50 1 (4) 4 (18) .25 .23 iPTH (pg/mL) 92 (73-119) 105 (75-169) .10 91 (57-153) 142 (100-200) .003 .82 25(OH)D (ng/mL) 20 6 3 38 6 9 ,.001 22 6 4 30 6 9 ,.001 .10 Spring or summer collect, n (%) 8 (36) 12 (55) .50 11 (50) 14 (64) .58 .36 C-reactive protein (mg/dL) 0.39 (0.18-1.24) 0.33 (0.14-1.41) .38 0.35 (0.14-0.89) 0.32 (0.16-1.06) .47 .51 Coronary calcium score (AU) All patients* 256 (81-611) 280 (38-627) .23 35 (0-310) 47 (0-288) .01 .02 Calcified patients† 418 (109-918) 364 (232-817) .25 118 (37-421) 199 (49-490) .01 .03 Noncalcified patients‡ 0 (0-0) 0 (0-1) .32 0 (0-0) 0 (0-0) .32 .48
p18
.69 .23 .84 .74 .79 .80 .80 .30 .19 .73 .69 .38 .08 .006 .54 .87 .04 .09 .16
Data are given as mean 6 standard deviation and median (interquartile range). p0 denotes intergroup comparisons at baseline, and p18 denotes intergroup comparisons at the 18th month. 25(OH)D, 25-hydroxyvitamin D; AU, Agatston units; CRCL, creatinine clearance; iPTH, intact parathormone; HDL, high density lipoproteins; LDL, low density lipoproteins. *N 5 22 in the treated group, and N 5 22 in the placebo group. †Baseline calcium score $ 10AU: N 5 18 in the treated group, and N 5 14 in the placebo group. ‡Baseline calcium score , 10AU: N 5 4 in the treated group, and N 5 8 in the placebo group.
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VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION Table 2. Baseline and Follow-up Data of the Deficient Group (N 5 24) Variables Demographic Data Age (years) Men, n (%) White skin, n (%) Hypertension, n (%) Diabetes, n (%) Dyslipidemia, n (%) Sedentary, n (%) Body mass index (kg/m2) Smokers, n (%) Laboratory parameters Creatinine clearance (mL/min/1.73 m2) Proteinuria (g/24h) Hemoglobin (g/dL) Glycemia (mg/dL) HDL cholesterol (mg/dL) LDL cholesterol (mg/dL) Triglycerides (mg/dL) Albumin (g/dL) Ionized calcium (mmol/L) Phosphorus (mg/dL) Phosphaturia (mg/24h) P-binder use, n (%) iPTH (pg/mL) 25(OH)D (ng/mL) Spring or summer collect, n (%) C-reactive protein (mg/dL) Coronary calcium score (AU) All patients (N 5 24) Calcified patients (N 5 18) Noncalcified patients (N 5 6)
Baseline
18 Months
P
33 (26-43) 0.40 (0-1.28) 12.8 6 1.5 92 (83-130) 50 (36-55) 84 (73-104) 136 (101-231) 4.2 6 0.3 1.29 (1.26-1.32) 3.6 (3.2-4.1) 456 (342-574) 0 (0) 140 (74-165) 11 6 2.5 8 (33) 0.26 (0.11-0.60)
23 (17-49) 0.29 (0-1.34) 12.5 6 1.5 94 (79-111) 40 (36-48) 91 (71-111) 127 (95-190) 4.1 6 0.3 1.27 (1.23-1.31) 3.7 (3.4-3.9) 404 (321-676) 6 (25) 133 (89-190) 43 6 15 16 (67) 0.20 (0.11-0.58)
.036 .98 .35 .13 .030 .82 .41 .74 .08 .83 .74 .031 .09 ,.001 .13 .88
223 (10-498) 265 (84-733) 0 (0-1)
306 (27-547) 333 (157-745) 0 (0-4)
69 (61-74) 11 (46) 13 (54) 24 (100) 17 (71) 21 (87) 15 (62) 27 6 5 2 (8)
.005 .006 .65
25(OH)D, 25-hydroxyvitamin D; AU, Agatston units; iPTH, intact parathormone; HDL, high density lipoproteins; LDL, low density lipoproteins. Data are given as mean 6 standard deviation and median (interquartile range).
Fig. 3). A similar number of patients did not have VC in the treated and placebo groups at baseline (4 [18%] and 8 [36%], respectively; P 5 .32). Both groups experienced stabilization of creatinine clearance. Increased urinary protein level in the treated group and decreased hemoglobin level in the placebo group were observed. Blood glucose level, lipid profile, ionized calcium level, serum phosphorus level, and the requirement of phosphorus binders were similar in both groups. In the multivariate analysis, there was no significant difference in CAC progression between both groups (group effect P 5.001; time effect P 5.82; interaction P 5.92; Fig. 4A). Similar results were obtained when only patients with CAC (calcium score $10 AU) were analyzed (group effect P 5.002; time effect P 5.65; interaction P 5.92; Fig. 4B). No patients had ionized calcium level .1.40 mmol/L or 25(OH)D level .150 ng/mL during the study.
Vitamin D–Deficient Group Twenty-four individuals constituted the deficient group. All patients had hypertension, diabetes (71%), dyslipidemia (87%), and VC (75%) at baseline. Bone mineral metabolism
parameters with respect to time are shown in Figure 5. Serum 25(OH)D concentrations significantly increased at the third month and remained elevated up to the 18th month. iPTH, ionized calcium, and phosphorous levels did not change. After 18 months, there was a significant increase in 25(OH)D levels (absolute change of 32 6 15 ng/mL), and 83% of the patients achieved normal levels of 25(OH)D. The median cumulative cholecalciferol dose was 2,375,000 IU (2,262,500–2,725,000 IU). The standardized change in 25(OH)D level was 1.2 (0.8-1.8) ng/mL/100,000 IU of cholecalciferol. Of note, there was a significant decrease in creatinine clearance and HDL (high density lipoproteins) cholesterol level. The CAC score increased significantly at the end of the study. The CAC score change was inversely correlated with the change in creatinine clearance (r 5 20.43, P 5 .03; Fig. 6A) and cumulative cholecalciferol dose (r 5 20.41, P 5 .048; Fig. 6B), but not with the change in 25(OH)D level (r 5 0.08, P 5.69). No patients had ionized calcium level .1.40 mmol/L or 25(OH)D .150 ng/mL during the study. The change in 25(OH)D level per unit of
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Figure 2. Bone mineral metabolism parameters in the insufficient groups over the 18-month study course. iPTH, intact parathormone.
cholecalciferol in the deficient group was lower [1.2 (0.81.8) vs. 1.9 (0.9-2.4) ng/mL/100,000 IU, P 5 .01] than that in the insufficient group.
Discussion
Figure 3. Correlation between the CAC score change and 25(OH)D change in the (A) treated and (B) placebo insufficient groups. CAC, coronary artery calcification.
The cholecalciferol supplementation protocol used in the present study was able to restore 25(OH)D levels in the majority of patients. Nevertheless, this study did not demonstrate any benefit of vitamin D therapy on VC in CKD patients with hypovitaminosis D. Studies in patients with CKD with different vitamin D– supplementation protocols have shown that 25–100% of the subjects could achieve the target 25(OH)D level.14,15,21 In the present study, considering all treated patients, we observed that 85% of them achieved the normal 25(OH) D levels. We could hypothesize that this successful result is explained by some characteristics of our protocol, such as the high cumulative dose of vitamin D, long duration of therapy, and use of cholecalciferol instead of ergocalciferol. In fact, some studies could give support to this assumption. First, there is a dose-dependent increase in 25(OH)D concentration in the general population and in patients with CKD after vitamin D supplementation.15,22 Thimachai et al.15 have found that 60% of patients with CKD responded to ergocalciferol supplementation by doubling the KDOQI recommended dose, whereas only 19% responded to the standard regime. Trials have demonstrated that the response to vitamin D– supplementation peaks at 3 months, whereas others have observed this effect only at 6 months.22 Therefore, short-
VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION
Figure 4. CAC progression in the insufficient groups in (A) all patients and (B) those with calcification. CAC, coronary artery calcification.
duration studies might be inappropriate to evaluate the impact of vitamin D supplementation on 25(OH)D levels. Second, the type of vitamin D used may play a role as cholecalciferol seems to be more efficacious than ergocalciferol in increasing the serum 25(OH)D level.16 Moreover, characteristics of the patient, such as the presence of
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CKD, baseline 25(OH)D levels, ethnicity, and comorbidity, could affect the response to vitamin D supplementation.18,22,23 Whereas, in the population without CKD, the lower the baseline 25(OH)D level, the higher the change in 25(OH)D levels after a given dose of vitamin D supplementation.22 In the present study, the deficient group had lower change in the 25(OH)D level per unit of cholecalciferol than the insufficient group. This finding could be partially explained by the decline in kidney function (P 5.02) and higher proteinuria (P 5.01) in the deficient group as compared to the treated insufficient group (data not shown). It has been demonstrated that both conditions are risk factors for resistance to vitamin D– replacement therapy.23 A cross-sectional analysis have demonstrated a positive correlation between low 25(OH)D levels and VC in both dialysis and nondialysis patients.7,8 Nevertheless, two clinical trials performed in patients on hemodialysis showed no impact on the progression of VC after 6 and 12 months of cholecalciferol supplementation, which was evaluated by plain radiographs.24,25 These negative results might be explained by the irreversibility of the VC present in the later stages of CKD.26 Even considering an adequate supply of ergocholecalciferol and 25(OH)D synthesis, patients on hemodialysis demonstrated a markedly impaired uptake of 25(OH)D by the extrarenal tissue.27 Thus, the cardioprotective properties of 25(OH)D might be less pronounced in this population. Moreover, periods longer than 12 months could be required to evaluate the impact of a pharmacological intervention or a risk factor exposure on VC progression.28 Finally, lumbar, pelvic, and hand radiographs to evaluate VC are all less sensitive Figure 5. Bone mineral metabolism parameters in the deficient group over the 18-month study course. iPTH, intact parathormone.
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ing high doses of vitamin D supplementation. Moreover, the decrease in kidney function has probably overcome the benefit of vitamin D in this group. In fact, the decrease in kidney function is closely related to the incidence and severity of VC.30 Some limitations of this study should be acknowledged. The relatively small sample size, absence of a deficient control group, unexpected increase in 25(OH)D level in the placebo group, and difference in the baseline calcium score between the randomized groups could all have interfered with the results. In addition, FGF23, an important regulator of vitamin D synthesis, was not evaluated in the present study. Despite this, the use of a gold standard image method, a long-term vitamin D–supplementation protocol, and the absence of confounders such as patients with late stages of CKD or those using calcitriol, vitamin D analogs, or calcium-based phosphate binders may be considered the strengths of this study.32 In conclusion, long-term cholecalciferol supplementation was safe and effective in restoring 25(OH)D levels in predialysis patients with CKD. Nevertheless, vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D. Figure 6. Correlation of calcium score change with (A) creatinine clearance change and (B) cholecalciferol cumulative dose in the deficient group.
and accurate than coronary computed tomography.29 Our study is the first to evaluate the impact of long-term cholecalciferol supplementation on VC progression, using the gold standard image method, in the earlier stages of CKD. In the univariate analysis, we observed stabilization of CAC in the treated insufficient group compared with an increase in the placebo group. This possible attenuation of VC, if any, occurred in a group at high risk for VC progression as it had a greater baseline calcium score. It is well known that the greater the baseline CAC, the greater the CAC progression.30 In the same treated insufficient group, the protective effect of vitamin D could be further suggested as patients with higher increment of 25(OH)D levels had lower VC progression. Moreover, better control of the PTH level by vitamin D in this group might have attenuated VC progression, as suggested elsewhere.31 Unfortunately, the beneficial effect of vitamin D supplementation on VC progression could not be confirmed by the multivariate analysis. As expected, the vitamin D–deficient group had higher prevalence of diabetes and proteinuria than the insufficient group. Consequently, they had a significant decline in kidney function compared with stabilization of the glomerular filtration rate in other groups. Although cholecalciferol replacement did not prevent VC progression in this group, patients with higher cholecalciferol cumulative doses had lesser CAC changes, suggesting a potential advantage of us-
Practical Application The long-term use of cholecalciferol, vitamin D in the nutritional form, is safe and effective in restoring 25(OH) D levels in predialysis patients with CKD. Nevertheless, vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D.
References 1. Gaksch M, Jorde R, Grimnes G, et al. Vitamin D and mortality: Individual participant data meta-analysis of standardized 25-hydroxyvitamin D in 26916 individuals from a European consortium. PLoS One. 2017;12:e0170791. 2. Sch€ ottker B, Ball D, Gellert C, Brenner H. Serum 25-hydroxyvitamin D levels and overall mortality. A systematic review and meta-analysis of prospective cohort studies. Ageing Res Rev. 2013;12:708-718. 3. Mehrotra R, Kermah DA, Salusky IB, et al. Chronic kidney disease, hypovitaminosis D, and mortality in the United States. Kidney Int. 2009;76:977-983. 4. Pilz S, Tomaschitz A, Friedl C, et al. Vitamin D status and mortality in chronic kidney disease. Nephrol Dial Transpl. 2011;26:3603-3609. 5. Drechsler C, Pilz S, Obermayer-Pietsch B, et al. Vitamin D deficiency is associated with sudden cardiac death, combined cardiovascular events, and mortality in haemodialysis patients. Eur Heart J. 2010;31:2253-2261. 6. Wolf M, Shah A, Gutierrez O, et al. Vitamin D levels and early mortality among incident hemodialysis patients. Kidney Int. 2007;72:1004-1013. 7. Garcia-Canton C, Bosch E, Ramirez A, et al. Vascular calcification and 25-hydroxyvitamin D levels in non-dialysis patients with chronic kidney disease stages 4 and 5. Nephrol Dial Transpl. 2011;26:2250-2256. 8. Wang F, Wu S, Ruan Y, Wang L. Correlation of serum 25hydroxyvitamin D level with vascular calcification in hemodialysis patients. Int J Clinexp Med. 2015;8:15745-15751. 9. de Boer IH, Kestenbaum B, Shoben AB, Michos ED, Sarnak MJ, Siscovick DS. 25-Hydroxyvitamin D levels inversely associate with risk for developing coronary artery calcification. J Am Soc Nephrol. 2009;20:18051812.
VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION 10. Kassi E, Adamapoulos C, Basdra EK, Papavassiliou AG. Role of vitamin D in Atherosclerosis. Circulation. 2013;128:2517-2531. 11. Norman PE, Powell JT. Vitamin D and cardiovascular disease. Circ Res. 2014;114:379-393. 12. National Kidney Foundation, Kidney Disease-Dialysis Outcome Quality Initiative. K/DOQI Clinical Practice Guidelines for bone metabolism and disease in chronic kidney disease. Am J Kidney Dis. 2003;42:S1S202. 13. Kidney Disease: Improving Global Outcomes (KDIGO) CKD-MBD Work Group. KDIGO 2017 clinical practice guideline update for the diagnosis, evaluation, prevention, and treatment of Chronic Kidney DiseaseMineral and Bone Disorder (CKD-MBD). Kidney Int Suppl. 2017;7:S1-S59. 14. Qunibi WY, Abdellatif A, Sankar S. Treatment of vitamin D deficiency in CKD patients with ergocalciferol: are current K/DOQI treatment guidelines adequate? Clin Nephrol. 2010;73:276-285. 15. Thimachai P, Supasyndh O, Chaiprasert A, Satirapoj B. Efficacy of high vs. Conventional ergocalciferol dose for increasing 25-hydroxyvitamin D and Suppressing parathyroid hormone levels in stage III-IV CKD with vitamin D deficiency/insufficiency: a randomized controlled trial. J Med Assoc Thai. 2015;98:643-648. 16. Tripkovic L, Lambert H, Hart K, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clinnutr. 2012;95:1357-1364. 17. Sanchez I, Mangoo-Karim R, Stubbs JR, Yanev GP, Wetmore JB. Ethnic differences in 25-hydroxyvitamin D levels and response to treatment in CKD. Int Urol Nephrol. 2013;45:181-189. 18. Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Detrano R. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol. 1990;15:827-832. 19. Third Report of the National cholesterol Education Program (NCEP) Expert Panel on Detection, evaluation, and treatment of high blood cholesterol in Adults (Adult treatment Panel III). Third Report of the National cholesterol Education Program (NCEP) Expert Panel on Detection, evaluation, and treatment of high blood cholesterol in Adults (Adult treatment Panel III) final Report. Circulation. 2002;106:3143-3421.
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20. World Health Organization. Global recommendations on physical activity for health. Genebra: WHO. 2010. http://whqlibdoc.who.int/publications/ 2010/9789241599979_eng.pdf. Accessed September 10, 2014. 21. Ponda MP, Breslow JL. Vitamin D3 Repletion in chronic kidney disease stage 3: effects on blood Endotoxin activity, Inflammatory Cytokines and Intestinal Permeability. Ren Fail. 2013;35:497-503. 22. Mazahery H, Von Hurst PR. Factors affecting 25-hydroxyvitamin D concentration in response to vitamin D supplementation. Nutrients. 2015;7:5111-5142. 23. Parikh A, Chase HS, Vernocchi L, Stern L. Vitamin D resistance in chronic kidney disease (CKD). BMC Nephrol. 2014;15:47. 24. Delanaye P, Weekers L, Warling X, et al. Cholecalciferol in hemodialysis patients: a randomized, double-blind, proof-of-concept and safety study. Nephrol Dial Transpl. 2013;28:1779-1786. 25. Kidir V, Ersoy I, Altuntas A, et al. Effect of cholecalciferol replacement on vascular calcification and left ventricular mass index in dialysis patients. Ren Fail. 2015;37:635-639. 26. Bhan I, Thadhani R. Vascular calcification and ESRD: a hard target. Clin J Am Soc Nephrol. 2009;4(Suppl 1):S102-S105. 27. Gallieni M, Kamimura S, Ahmed A, et al. Kinetics of monocyte 1- alpha-hydroxylase in renal failure. Am J Physiol. 1995;268:F746-F753. 28. McCullough PA, Chinnaiyan KM. Annual progression of coronary calcification in trials of preventive Therapies. Arch Intern Med. 2009;169:2064-2070. 29. Disthabanchong S, Boongird S. Role of different imaging modalities of vascular calcification in predicting outcomes in chronic kidney disease. World J Nephrol. 2017;6:100-110. 30. Tuttle KR, Short RA. Longitudinal relationships among coronary artery calcification, serum phosphorus, and kidney function. Clin J Am Socnephrol. 2009;4:1968-1973. 31. Huber BC, Grabmaier U, Brunner S. Impact of parathyroid hormone on bone marrow-derived stem cell mobilization and migration. World J Stem Cells. 2014;6:637-643. 32. Razzaque MS. The dualistic role of vitamin D in vascular calcifications. Kidney Int. 2011;79:708-714.
The Effect of Long-Term Cholecalciferol Supplementation on Vascular Calcification in Chronic Kidney Disease Patients With Hypovitaminosis D Farid Samaan, MD, PhD,* Aluızio B. Carvalho, MD, PhD,* Roberta Pillar, MD,* Lillian A. Rocha, MD, PhD,* Jose L. Cassiolato, MD,† Lilian Cuppari, PhD,* and Maria Eug^enia F. Canziani, MD, PhD* Objective: The role of vitamin D supplementation on vascular calcification (VC) in patients with chronic kidney disease (CKD) is controversial. The objective of this study was to evaluate the effects of long-term cholecalciferol supplementation on VC in nondialysis patients with CKD stages 3–4 with hypovitaminosis D. Design and Methods: Eighty patients aged 18–85 years with creatinine clearance between 15 and 60 mL/min/1.73 m2 and serum 25(OH)D level , 30 ng/mL were enrolled in a 18-month prospective study. Individuals with vitamin D insufficiency (25-hydroxyvitamin D [25(OH)D] level between 16 and 29 ng/mL) were included in a randomized, double-blind, two-arm study to receive cholecalciferol or placebo. Patients with vitamin D deficiency [25(OH)D , 15 ng/mL] were included in an observational study and mandatorily received cholecalciferol. The coronary artery calcium score was obtained by multislice computed tomography at baseline and the 18th month. Results: During the study, VC did not change in the treated insufficient group (418 [81–611] to 364 [232–817] AU, P 5 0.25) but increased in the placebo group (118 [37–421] to 199 [49–490] AU, P 5 0.01). The calcium score change was inversely correlated with 25(OH)D change (r 5 20.45; P 5 0.037) in the treated insufficient group but not in the placebo group. Renal function did not change in the insufficient, treated, and placebo groups. In multivariate analysis, there was no difference in VC progression between the treated and placebo insufficient groups (interaction P 5 0.92). In the deficient group, VC progressed (265 [84–733] to 333 [157–745] AU; P 5 0.006) and renal function declined (33 [26–43] to 23 [17–49] mL/min/1.73 m2; P 5 0.04). The calcium score change was inversely correlated with cholecalciferol cumulative doses (r 5 20.41; P 5 0.048) and kidney function change (r 5 20.43; P 5 0.033) but not with 25(OH)D change (r 5 20.08; P 5 0.69). Conclusion: Vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D. Conclusion: Vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D. Ó 2018 by the National Kidney Foundation, Inc. All rights reserved.
Introduction
H
YPOVITAMINOSIS D HAS been associated with higher cardiovascular morbidity and mortality in the general population and in patients with chronic kidney disease (CKD).1-6 Among the cardiovascular abnormalities in patients with CKD, vascular calcification (VC) is of major interest. Cross-sectional studies have demonstrated a positive correlation between low levels of 25-hydroxyvitamin D (25(OH)D) and VC in both dialysis and nondialysis CKD *
Nephrology Division, Federal University of S~ao Paulo, S~ao Paulo, Brazil. Cardios Research Institute, S~ao Paulo, Brazil. Support: Foundation for Research Support of the State of S~ao Paulo (FAPESP) and Coordination of Improvement of Higher Level Personnel (CAPES). Financial Disclosure: The authors declare that they have no conflict of interest. Address correspondence to Maria Eug^enia F. Canziani, MD, PhD, Rua Pedro de Toledo 282, CEP 04039-000, S~ao Paulo, SP Brazil. E-mail: dialisefor@ †
uol.com.br Ó
2018 by the National Kidney Foundation, Inc. All rights reserved. 1051-2276/$36.00 https://doi.org/10.1053/j.jrn.2018.12.002
Journal of Renal Nutrition, Vol -, No - (-), 2019: pp 1-9
patients.7,8 Furthermore, in a prospective study, de Boer et al.9 showed a strong association between low 25(OH)D levels and development of VC in patients with CKD. This relationship may arise from vitamin D actions on cells of the blood vessels, which are relevant to cardiovascular physiology and pathology.10 Supporting this, studies have shown that hypovitaminosis D is related to endothelial dysfunction and osteochondrogenic transformation of vascular smooth muscle cells, both of which are key processes for VC.11 As hypovitaminosis D is a frequent finding in patients with CKD, Kidney Disease Outcomes Quality Initiative (KDOQI) and Kidney Disease: Improving Global Outcomes (KDIGO) recommend to assess and restore 25(OH)D concentrations by vitamin D supplementation in this population.12,13 Restoration of 25(OH)D levels remains a challenge in these patients as most of the previous randomized controlled trials of vitamin D supplementation have shown conflicting results due to short-term protocols (,6 months) and variable doses and types of vitamin D.14-16 Cholecalciferol, also known as vitamin D3, is a type of vitamin D frequently used in 1
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clinical practice. It has high affinity to hepatic 25-hydroxylase, vitamin D–binding protein, and vitamin D receptor.16 Data on the impact of vitamin D supplementation on VC in patients with CKD are scarce and controversial. Thus, this study aimed to evaluate the effects of long-term cholecalciferol supplementation on VC in stage 3-4 CKD patients with hypovitaminosis D.
Methods Patients Eighty patients with creatinine clearance between 15 and 60 mL/min/1.73 m2 and serum 25(OH)D , 30 ng/mL were selected from the CKD outpatient clinic of the Federal University of S~ao Paulo, Brazil. The exclusion criteria were age ,18 and .85 years; nephrotic syndrome; immobilization in the last 3 months; liver, autoimmune, infectious, or neoplastic diseases; positive serology for HIV; previous use of cholecalciferol or multivitamin containing vitamin D; previous or current use of active vitamin D analogs or bisphosphonates; use of corticosteroids and immunosuppressive drugs in the last 3 months; hypercalcemia (ionized calcium .1.40 mmol/L); and serum intact parathormone (iPTH) level .500 pg/mL. The study was reviewed and approved by the Ethics Advisory Committee of the Federal University of S~ao Paulo, and each patient signed the informed consent form. This study was
registered at the Brazilian Clinical Trials Registry (ReBec—www.ensaiosclinicos.gov.br) under the number RBR-95j5pm.
Study Design and Supplementation Protocol In this 18-month prospective study, 80 CKD patients with hypovitaminosis D were included. During the follow-up, 12 patients did not complete the study due to withdrawal (5 patients), dialysis onset (2), prolonged hospitalization (2), and death (3). These patients had similar 25(OH)D levels, creatinine clearance, bone mineral profile, blood pressure, and coronary calcium score at baseline to those who finished the study. Therefore, 68 patients were considered in the final analysis (Fig. 1). Forty-four individuals with vitamin D insufficiency (25(OH)D level between 16 and 29 ng/mL) were included in the randomized, double-blind, two-arm study to receive 1:1 cholecalciferol or placebo. An independent researcher generated a computerized random list, and the allocation sequence of 20 patients was concealed in a closed box. The twenty-four patients with vitamin D deficiency (25(OH)D level # 15 ng/mL) were separately analyzed and mandatorily received cholecalciferol. Cholecalciferol was supplemented orally with a concentration of 1,000 IU/drop (Magister Handling Pharmacy Ltd., S~ao Paulo, Brazil). The placebo solution was identical in appearance, smell, and flavor to cholecalciferol. The duration of vitamin D supplementation was
Figure 1. Study design and patient distribution.
VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION
18 months in all study groups. The treated insufficient group received a fixed dose of 50,000 IU/month of cholecalciferol for 18 months without adjustment. The placebo insufficient group received 50,000 IU/month in the same manner. The deficient group was initially treated with 50,000 IU of cholecalciferol weekly for 12 weeks. After this period, the maintenance dose was adjusted according to serum 25(OH)D levels. Patients with vitamin D deficiency who had achieved 25(OH)D levels $ 30 ng/mL received a monthly dose of 50,000 IU, whereas in those with 25(OH)D levels , 30 ng/ mL, the weekly regime was maintained until the next serum 25(OH)D measurement. Vitamin D discontinuation criteria were serum ionized calcium level .1.40 mmol/L or 25(OH)D level .150 ng/mL. Responsiveness to cholecalciferol was evaluated by the percentage of patients that achieved 25(OH)D level $ 30 ng/mL at the 18th month and by the standardized change in 25(OH)D level (25(OH)D level at 18 months – baseline/100,000 IU of cholecalciferol administered over time) as described previously.17 For patients under the monthly cholecalciferol regime, compliance with the treatment was ensured by drug administration at the research center. For patients under weekly regime, adherence was ensured by returning of empty bottles at the visits. Patients were given sunscreen protector (SPF 30) and instructed to use it 20 min before and every 3 h of sun exposure during the study period to minimize the effects of skin production of vitamin D. No control of types of clothes or dietary intake of vitamin D–rich foods was performed. A noncalcium phosphate binder was prescribed if serum phosphorus levels increased to .4.5 mg/dL.
Coronary Artery Calcification Coronary artery calcification (CAC) was evaluated at baseline and after 18 months by multislice computed tomography scan (LightSpeed Pro 16; GE Healthcare, Milwaukee, WI), using a gantry rotation of 0.4 s, collimation of 2.5 mm (slice thickness), and reconstruction time of 6 frames per second. A calcium threshold of 130 HU was used. The images were scored by a single radiologist who was blinded to the clinical and biochemical information of the patients. As described by Agatston et al.,18 the calcium score was determined by multiplying the area of each calcified lesion by a weighting factor corresponding to the peak pixel intensity for each lesion. The sum of each lesion of all coronary arteries was used for the analysis. The presence of CAC was defined as calcium score $10 AU. Biochemical Assessments Blood samples were drawn in a 12-h fasting state for the evaluation of serum creatinine (automated biochemistry
3
analyzer, Olympus AU400), hemoglobin (automated hematology analyzer, Abbott Cell-Dyn 3200), ionized calcium (electrolyte analyzer, Roche 9180), phosphorus (automated biochemistry analyzer, Olympus AU400), iPTH (reference values, 10-65 pg/mL, chemiluminescence; DPC Medlab), 25(OH)D (reference values, 30100 ng/mL, chemiluminescent immunoassay; DiaSorin, Stillwater, MN), serum albumin, lipid profile, and highsensitivity C-reactive protein (reference value, ,0.11 mg/dL; immunonephelometry). Urinary protein level was measured by 24-h urine collection. Glomerular filtration rate was estimated by creatinine clearance in 24-h urine volume and corrected for body surface area. Calcium and phosphorus levels were obtained monthly, whereas serum 25(OH)D level, creatinine clearance, iPTH level, and other laboratory parameters were measured at 3, 6, 12, and 18 months. Vitamin D deficiency and insufficiency were defined according to KDOQI.12 Dyslipidemia was defined according to the National Cholesterol Education Program—Adult Treatment Panel III guidelines.19 Participants who did not practice at least 150 min per week of moderate physical activity were considered sedentary.20 Changes in creatinine clearance, calcium score, and 25(OH)D level were defined as the difference between values at the 18th month and those at baseline.
Statistical Analysis Data are reported as mean and standard deviation, median and interquartile range, or frequency. The comparisons of continuous variables between groups were performed using Student’s independent t-test and Mann– Whitney U test for normal and skewed data, respectively. Comparisons of proportions were performed using c2 analysis or Fischer’s exact test, as appropriate. Analyses within each group were performed using paired-samples t-test for continuous normal data, Wilcoxon signed-rank test for skewed continuous data, and McNemar test for categorical data. The Spearman correlation was used to determine the relationship between calcium score change and cumulative cholecalciferol dose, creatinine clearance change, and 25(OH)D level change. A generalized estimating equation was used to analyze the longitudinal correlation between cholecalciferol supplementation and VC. The multivariate model was adjusted for age, iPTH level, ionized calcium level, creatinine clearance, and presence of diabetes. A Tweedie distribution was assumed in the model because the calcium score had an asymmetric distribution and many values with zeros. A P value of 0.05 was considered statistically significant. This pilot study used a convenience sample given the absence of studies evaluating the impact of vitamin D supplementation on VC at the time of the protocol. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) for Windows version 18.0 (SPSS Inc., Chicago, IL).
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Results Demographic, biochemical, and clinical data at baseline and after 18 months in the vitamin D–insufficient and vitamin D–deficient groups are shown in Tables 1 and 2, respectively.
Vitamin D Insufficient Groups: Treated and Placebo Forty-four patients were randomized 1:1 to the treated and placebo groups. Demographic and clinical characteristics of both groups were similar at baseline, except for lower serum ionized calcium level and higher coronary calcium score in the treated group. There were no significant differences in 25(OH)D, phosphorus, and iPTH levels and creatinine clearance. Bone mineral metabolism parameters during the study are shown in Figure 2. Compared with the placebo group, 25(OH) levels were greater at 6, 12,
and 18 months and iPTH levels were lower at 12 and 18 months in the treated group. Ionized calcium and phosphorous levels were similar and did not change over time. At 18 months, there was a significant increase in 25(OH) D levels in both groups, although it was higher in the treated group (18 6 8 vs. 8 6 9 ng/mL, P 5 .001). In the treated group, 86% of patients had 25(OH)D level $ 30 ng/mL after 18 months, the cumulative cholecalciferol dose was 900,000 IU, and the standardized change in 25(OH)D level was 1.9 (0.9–2.4) ng/mL/100,000 IU of cholecalciferol. In the placebo group, at the 18th month, 41% of patients had 25(OH)D level $ 30 ng/mL. CAC score and iPTH levels remained stable in the treated group, whereas in the placebo group, these parameters significantly increased. In the treated insufficient group, but not in the placebo group, calcium score change was inversely correlated with 25(OH)D change (r 5 20.45, P 5 .037;
Table 1. Baseline and Follow-up Data of Treated and Placebo Insufficient Groups Variables
Treated, N 5 22
Demographic data Age (years) Men, n (%) White skin, n (%) Hypertension, n (%) Diabetes, n (%) Dyslipidemia, n (%) Sedentary, n (%) Body mass index (kg/m2) Smokers, n (%)
69 (61-76) 9 (41) 14 (64) 22 (100) 12 (54) 18 (82) 14 (64) 27 6 4 1 (4) Baseline
18 months
P
Placebo, N 5 22
Between Groups, P
64 (53-73) 13 (59) 13 (59) 21 (95) 7 (32) 17 (77) 12 (54) 27 6 4 1 (4)
.11 .23 .76 1.00 .13 .71 .54 .80 1.00
Baseline
18 months
P
p0
Laboratory parameters 35 (27-44) 37 (29-48) .25 31 (26-41) 41 (20-48) .42 .36 CRCL (mL/min/1.73 m2) Proteinuria (g/24h) 0 (0-0.24) 0 (0-0.65) .008 0.20 (0-0.64) 0.23 (0-0.83) .19 .07 Hemoglobin (g/dL) 13.1 6 1.5 12.8 6 8 .29 13.9 6 1.9 12.9 6 1.9 .003 .11 Glycemia (mg/dL) 92 (86-102) 91 (79-115) .99 86 (76-107) 87 (79-105) .18 .15 HDL cholesterol (mg/dL) 40 (38-44) 39 (34-48) .39 44 (38-50) 42 (35-51) .35 .24 LDL cholesterol (mg/dL) 96 (78-113) 99 (83-119) .58 105 (83-132) 105 (72-115) .45 .49 Triglycerides (mg/dL) 146 (103-188) 136 (102-220) .58 155 (119-220) 137 (92-206) .45 .49 Albumin (g/dL) 4.3 6 0.2 4.2 6 0.3 .08 4.4 6 0.3 4.3 6 0.3 .21 .28 Ionized calcium (mmol/L) 1.30 (1.28-1.33) 1.28 (1.24-1.33) .06 1.33 (1.30-1.35) 1.30 (1.27-1.34) .26 .047 Phosphorus (mg/dL) 3.5 (3.1-3.8) 3.4 (3.1-3.7) .45 3.2 (3.0-3.8) 3.2(2.8-3.9) .92 .29 Phosphaturia (mg/24h) 414 (314-522) 502 (331-599) .42 422 (326-501) 474 (381-617) .17 .77 P-binder use, n (%) 0 (0) 2 (9) .50 1 (4) 4 (18) .25 .23 iPTH (pg/mL) 92 (73-119) 105 (75-169) .10 91 (57-153) 142 (100-200) .003 .82 25(OH)D (ng/mL) 20 6 3 38 6 9 ,.001 22 6 4 30 6 9 ,.001 .10 Spring or summer collect, n (%) 8 (36) 12 (55) .50 11 (50) 14 (64) .58 .36 C-reactive protein (mg/dL) 0.39 (0.18-1.24) 0.33 (0.14-1.41) .38 0.35 (0.14-0.89) 0.32 (0.16-1.06) .47 .51 Coronary calcium score (AU) All patients* 256 (81-611) 280 (38-627) .23 35 (0-310) 47 (0-288) .01 .02 Calcified patients† 418 (109-918) 364 (232-817) .25 118 (37-421) 199 (49-490) .01 .03 Noncalcified patients‡ 0 (0-0) 0 (0-1) .32 0 (0-0) 0 (0-0) .32 .48
p18
.69 .23 .84 .74 .79 .80 .80 .30 .19 .73 .69 .38 .08 .006 .54 .87 .04 .09 .16
Data are given as mean 6 standard deviation and median (interquartile range). p0 denotes intergroup comparisons at baseline, and p18 denotes intergroup comparisons at the 18th month. 25(OH)D, 25-hydroxyvitamin D; AU, Agatston units; CRCL, creatinine clearance; iPTH, intact parathormone; HDL, high density lipoproteins; LDL, low density lipoproteins. *N 5 22 in the treated group, and N 5 22 in the placebo group. †Baseline calcium score $ 10AU: N 5 18 in the treated group, and N 5 14 in the placebo group. ‡Baseline calcium score , 10AU: N 5 4 in the treated group, and N 5 8 in the placebo group.
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VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION Table 2. Baseline and Follow-up Data of the Deficient Group (N 5 24) Variables Demographic Data Age (years) Men, n (%) White skin, n (%) Hypertension, n (%) Diabetes, n (%) Dyslipidemia, n (%) Sedentary, n (%) Body mass index (kg/m2) Smokers, n (%) Laboratory parameters Creatinine clearance (mL/min/1.73 m2) Proteinuria (g/24h) Hemoglobin (g/dL) Glycemia (mg/dL) HDL cholesterol (mg/dL) LDL cholesterol (mg/dL) Triglycerides (mg/dL) Albumin (g/dL) Ionized calcium (mmol/L) Phosphorus (mg/dL) Phosphaturia (mg/24h) P-binder use, n (%) iPTH (pg/mL) 25(OH)D (ng/mL) Spring or summer collect, n (%) C-reactive protein (mg/dL) Coronary calcium score (AU) All patients (N 5 24) Calcified patients (N 5 18) Noncalcified patients (N 5 6)
Baseline
18 Months
P
33 (26-43) 0.40 (0-1.28) 12.8 6 1.5 92 (83-130) 50 (36-55) 84 (73-104) 136 (101-231) 4.2 6 0.3 1.29 (1.26-1.32) 3.6 (3.2-4.1) 456 (342-574) 0 (0) 140 (74-165) 11 6 2.5 8 (33) 0.26 (0.11-0.60)
23 (17-49) 0.29 (0-1.34) 12.5 6 1.5 94 (79-111) 40 (36-48) 91 (71-111) 127 (95-190) 4.1 6 0.3 1.27 (1.23-1.31) 3.7 (3.4-3.9) 404 (321-676) 6 (25) 133 (89-190) 43 6 15 16 (67) 0.20 (0.11-0.58)
.036 .98 .35 .13 .030 .82 .41 .74 .08 .83 .74 .031 .09 ,.001 .13 .88
223 (10-498) 265 (84-733) 0 (0-1)
306 (27-547) 333 (157-745) 0 (0-4)
69 (61-74) 11 (46) 13 (54) 24 (100) 17 (71) 21 (87) 15 (62) 27 6 5 2 (8)
.005 .006 .65
25(OH)D, 25-hydroxyvitamin D; AU, Agatston units; iPTH, intact parathormone; HDL, high density lipoproteins; LDL, low density lipoproteins. Data are given as mean 6 standard deviation and median (interquartile range).
Fig. 3). A similar number of patients did not have VC in the treated and placebo groups at baseline (4 [18%] and 8 [36%], respectively; P 5 .32). Both groups experienced stabilization of creatinine clearance. Increased urinary protein level in the treated group and decreased hemoglobin level in the placebo group were observed. Blood glucose level, lipid profile, ionized calcium level, serum phosphorus level, and the requirement of phosphorus binders were similar in both groups. In the multivariate analysis, there was no significant difference in CAC progression between both groups (group effect P 5.001; time effect P 5.82; interaction P 5.92; Fig. 4A). Similar results were obtained when only patients with CAC (calcium score $10 AU) were analyzed (group effect P 5.002; time effect P 5.65; interaction P 5.92; Fig. 4B). No patients had ionized calcium level .1.40 mmol/L or 25(OH)D level .150 ng/mL during the study.
Vitamin D–Deficient Group Twenty-four individuals constituted the deficient group. All patients had hypertension, diabetes (71%), dyslipidemia (87%), and VC (75%) at baseline. Bone mineral metabolism
parameters with respect to time are shown in Figure 5. Serum 25(OH)D concentrations significantly increased at the third month and remained elevated up to the 18th month. iPTH, ionized calcium, and phosphorous levels did not change. After 18 months, there was a significant increase in 25(OH)D levels (absolute change of 32 6 15 ng/mL), and 83% of the patients achieved normal levels of 25(OH)D. The median cumulative cholecalciferol dose was 2,375,000 IU (2,262,500–2,725,000 IU). The standardized change in 25(OH)D level was 1.2 (0.8-1.8) ng/mL/100,000 IU of cholecalciferol. Of note, there was a significant decrease in creatinine clearance and HDL (high density lipoproteins) cholesterol level. The CAC score increased significantly at the end of the study. The CAC score change was inversely correlated with the change in creatinine clearance (r 5 20.43, P 5 .03; Fig. 6A) and cumulative cholecalciferol dose (r 5 20.41, P 5 .048; Fig. 6B), but not with the change in 25(OH)D level (r 5 0.08, P 5.69). No patients had ionized calcium level .1.40 mmol/L or 25(OH)D .150 ng/mL during the study. The change in 25(OH)D level per unit of
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Figure 2. Bone mineral metabolism parameters in the insufficient groups over the 18-month study course. iPTH, intact parathormone.
cholecalciferol in the deficient group was lower [1.2 (0.81.8) vs. 1.9 (0.9-2.4) ng/mL/100,000 IU, P 5 .01] than that in the insufficient group.
Discussion
Figure 3. Correlation between the CAC score change and 25(OH)D change in the (A) treated and (B) placebo insufficient groups. CAC, coronary artery calcification.
The cholecalciferol supplementation protocol used in the present study was able to restore 25(OH)D levels in the majority of patients. Nevertheless, this study did not demonstrate any benefit of vitamin D therapy on VC in CKD patients with hypovitaminosis D. Studies in patients with CKD with different vitamin D– supplementation protocols have shown that 25–100% of the subjects could achieve the target 25(OH)D level.14,15,21 In the present study, considering all treated patients, we observed that 85% of them achieved the normal 25(OH) D levels. We could hypothesize that this successful result is explained by some characteristics of our protocol, such as the high cumulative dose of vitamin D, long duration of therapy, and use of cholecalciferol instead of ergocalciferol. In fact, some studies could give support to this assumption. First, there is a dose-dependent increase in 25(OH)D concentration in the general population and in patients with CKD after vitamin D supplementation.15,22 Thimachai et al.15 have found that 60% of patients with CKD responded to ergocalciferol supplementation by doubling the KDOQI recommended dose, whereas only 19% responded to the standard regime. Trials have demonstrated that the response to vitamin D– supplementation peaks at 3 months, whereas others have observed this effect only at 6 months.22 Therefore, short-
VITAMIN D, CHRONIC KIDNEY DISEASE, AND CORONARY CALCIFICATION
Figure 4. CAC progression in the insufficient groups in (A) all patients and (B) those with calcification. CAC, coronary artery calcification.
duration studies might be inappropriate to evaluate the impact of vitamin D supplementation on 25(OH)D levels. Second, the type of vitamin D used may play a role as cholecalciferol seems to be more efficacious than ergocalciferol in increasing the serum 25(OH)D level.16 Moreover, characteristics of the patient, such as the presence of
7
CKD, baseline 25(OH)D levels, ethnicity, and comorbidity, could affect the response to vitamin D supplementation.18,22,23 Whereas, in the population without CKD, the lower the baseline 25(OH)D level, the higher the change in 25(OH)D levels after a given dose of vitamin D supplementation.22 In the present study, the deficient group had lower change in the 25(OH)D level per unit of cholecalciferol than the insufficient group. This finding could be partially explained by the decline in kidney function (P 5.02) and higher proteinuria (P 5.01) in the deficient group as compared to the treated insufficient group (data not shown). It has been demonstrated that both conditions are risk factors for resistance to vitamin D– replacement therapy.23 A cross-sectional analysis have demonstrated a positive correlation between low 25(OH)D levels and VC in both dialysis and nondialysis patients.7,8 Nevertheless, two clinical trials performed in patients on hemodialysis showed no impact on the progression of VC after 6 and 12 months of cholecalciferol supplementation, which was evaluated by plain radiographs.24,25 These negative results might be explained by the irreversibility of the VC present in the later stages of CKD.26 Even considering an adequate supply of ergocholecalciferol and 25(OH)D synthesis, patients on hemodialysis demonstrated a markedly impaired uptake of 25(OH)D by the extrarenal tissue.27 Thus, the cardioprotective properties of 25(OH)D might be less pronounced in this population. Moreover, periods longer than 12 months could be required to evaluate the impact of a pharmacological intervention or a risk factor exposure on VC progression.28 Finally, lumbar, pelvic, and hand radiographs to evaluate VC are all less sensitive Figure 5. Bone mineral metabolism parameters in the deficient group over the 18-month study course. iPTH, intact parathormone.
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SAMAAN ET AL
ing high doses of vitamin D supplementation. Moreover, the decrease in kidney function has probably overcome the benefit of vitamin D in this group. In fact, the decrease in kidney function is closely related to the incidence and severity of VC.30 Some limitations of this study should be acknowledged. The relatively small sample size, absence of a deficient control group, unexpected increase in 25(OH)D level in the placebo group, and difference in the baseline calcium score between the randomized groups could all have interfered with the results. In addition, FGF23, an important regulator of vitamin D synthesis, was not evaluated in the present study. Despite this, the use of a gold standard image method, a long-term vitamin D–supplementation protocol, and the absence of confounders such as patients with late stages of CKD or those using calcitriol, vitamin D analogs, or calcium-based phosphate binders may be considered the strengths of this study.32 In conclusion, long-term cholecalciferol supplementation was safe and effective in restoring 25(OH)D levels in predialysis patients with CKD. Nevertheless, vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D. Figure 6. Correlation of calcium score change with (A) creatinine clearance change and (B) cholecalciferol cumulative dose in the deficient group.
and accurate than coronary computed tomography.29 Our study is the first to evaluate the impact of long-term cholecalciferol supplementation on VC progression, using the gold standard image method, in the earlier stages of CKD. In the univariate analysis, we observed stabilization of CAC in the treated insufficient group compared with an increase in the placebo group. This possible attenuation of VC, if any, occurred in a group at high risk for VC progression as it had a greater baseline calcium score. It is well known that the greater the baseline CAC, the greater the CAC progression.30 In the same treated insufficient group, the protective effect of vitamin D could be further suggested as patients with higher increment of 25(OH)D levels had lower VC progression. Moreover, better control of the PTH level by vitamin D in this group might have attenuated VC progression, as suggested elsewhere.31 Unfortunately, the beneficial effect of vitamin D supplementation on VC progression could not be confirmed by the multivariate analysis. As expected, the vitamin D–deficient group had higher prevalence of diabetes and proteinuria than the insufficient group. Consequently, they had a significant decline in kidney function compared with stabilization of the glomerular filtration rate in other groups. Although cholecalciferol replacement did not prevent VC progression in this group, patients with higher cholecalciferol cumulative doses had lesser CAC changes, suggesting a potential advantage of us-
Practical Application The long-term use of cholecalciferol, vitamin D in the nutritional form, is safe and effective in restoring 25(OH) D levels in predialysis patients with CKD. Nevertheless, vitamin D supplementation did not attenuate VC progression in CKD patients with hypovitaminosis D.
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