Original Paper Ann Nutr Metab 2012;61:74–82 DOI: 10.1159/000339618
Received: November 14, 2011 Accepted after revision: May 21, 2012 Published online: August 7, 2012
Cholecalciferol Supplementation in Chronic Kidney Disease: Restoration of Vitamin D Status and Impact on Parathyroid Hormone Miriam G. Garcia-Lopes a Roberta Pillar b Maria Ayako Kamimura a, b Lillian A. Rocha b Maria Eugênia F. Canziani b Aluízio B. Carvalho b Lilian Cuppari a, b a
Nutrition Program and b Division of Nephrology, Federal University of São Paulo, São Paulo, Brazil
Key Words Adiposity ⴢ Cholecalciferol ⴢ Chronic kidney disease ⴢ Parathyroid hormone ⴢ Vitamin D
dose of 50,000 IU of cholecalciferol for 3 months restored the vitamin D status of most patients and led to a reduction in PTH. The monthly dose of 50,000 IU appears not to be sufficient to maintain the levels of 25(OH)D. Copyright © 2012 S. Karger AG, Basel
Abstract Background/Aims: Hypovitaminosis D is highly prevalent among patients with chronic kidney disease (CKD) and has been associated with poor outcome. We aimed to test the effect of a protocol of cholecalciferol supplementation on the restoration of vitamin D status and on parathyroid hormone (PTH) levels in patients with CKD. Methods: This was a prospective interventional study of 6 months. Forty-five CKD patients (stages 3 and 4) with 25-hydroxyvitamin D deficiency [25(OH)D !15 ng/ml] were included. Patients received a weekly dose of 50,000 IU of cholecalciferol during 3 months, and 50,000 IU/month thereafter for those who had achieved 25(OH)D 630 ng/ml. Results: At 3 months, 78% of the patients restored their vitamin D status. At 6 months, only 43% of those patients maintained adequate vitamin D status. PTH decreased at 3 months (p = 0.02) but returned to baseline levels after 6 months. Fibroblast growth factor 23 increased at 3 months (p = 0.001) and returned to initial levels at 6 months. No changes were found in serum 1,25(OH)2D, ionized calcium and phosphorus. Conclusions: A weekly
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Introduction
Hypovitaminosis D is highly prevalent among patients with chronic kidney disease (CKD) and has been associated with mortality even in the earlier stages of the disease [1, 2]. Studies have documented that 40–100% of CKD patients are vitamin D deficient or insufficient [3–8]. The knowledge that extrarenal sites, including the parathyroid glands, are able to synthesize 1,25-dihydroxyvitamin D [1,25(OH)2D] locally via its precursor 25-hydroxyvitamin D [25(OH)D] has renewed interest in the restoration and maintenance of adequate vitamin D status in CKD. Earlier [9] and more recent [10] guidelines on the management of CKD-related bone and mineral disorders point out the importance of treating hypovitaminosis D. Although an increasing number of studies on vitamin D supplementation in CKD have been conducted in recent years [11–15], evidence is still lacking in several aspects, Lilian Cuppari Department of Medicine, Division of Nephrology Federal University of São Paulo, Rua Pedro de Toledo 282 São Paulo, SP 04039-000 (Brazil) Tel. +55 11 5904 8499, E-Mail lcuppari @ uol.com.br
namely, a protocol of treatment to restore vitamin D status with the greatest benefit for the patients. Moreover, the potential factors that may influence the response to vitamin D supplementation in CKD patients, and finally, the impact of replenishing vitamin D on outcomes have been poorly investigated. In the present study, in a group of CKD patients with deficiency in vitamin D [25(OH)D !15 ng/ml], we aimed: (1) to evaluate the effectiveness of a treatment protocol with cholecalciferol in the restoration of vitamin D status, (2) to examine the factors that affect the response to treatment, and (3) to investigate the impact of replenishing vitamin D on parathyroid hormone (PTH) as well as on markers of mineral metabolism.
Methods Participants Between March 2007 and July 2009, 319 patients with CKD (stages 3 and 4) from a single renal outpatient clinic of the Federal University of São Paulo (São Paulo, Brazil) underwent assessment of vitamin D status. Vitamin D deficiency [25(OH)D !15 ng/ml] was found in 68 patients (21%), and 46 of them were eligible for participating in the study. Exclusion criteria were age !18 years, CKD stages 1, 2 or 5, serum ionized calcium 11.40 mmol/l, intact PTH 1500 pg/ml, urinary protein 13 g/24 h, liver disease, active malignancy, autoimmune or infectious disease, and use of any type of vitamin D compounds, calcium salts, corticosteroids or immunosuppressive drugs in the previous 3 months. The Human Investigation Review Committee of the Federal University of São Paulo approved the study protocol, and informed consent was obtained from each patient. Study Protocol This was a 6-month prospective interventional study. At baseline and at the end of 3 and 6 months, the following laboratory parameters were determined: 25(OH)D, 1,25(OH)2D, serum ionized calcium, serum phosphorus, intact PTH, intact fibroblast growth factor 23 (FGF-23), creatinine, albumin, C-reactive protein (CRP) and 24-hour urinary creatinine, protein, calcium and phosphorus. Body composition analysis and nutritional assessment were performed at baseline. During the period of treatment, patients had monthly visits to monitor ionized calcium, phosphorus and PTH. A non-calcium phosphate binder was prescribed if serum phosphorus increased to values 1 4.6 mg/dl. Patients were discontinued from the study if serum ionized calcium, PTH or 25(OH)D increased to values 11.40 mmol/l, 500 pg/ml and 150 ng/ml, respectively.
dose of 50,000 IU/month for a further 3 months. For the others, the dose of 50,000 IU/week was maintained. In order to assess compliance, all patients brought along the empty bottle of the supplement at each monthly visit. In order to minimize the effects of skin production of vitamin D, all patients received a sunscreen (SPF 30) and were instructed to use it during the study period. Laboratory Parameters Blood samples were obtained after an overnight fasting. All the procedures performed with the blood samples for the determination of 25(OH)D and 1,25(OH)2D were protected from light. The serum samples obtained were frozen at a temperature of –80 ° C. 25(OH)D (chemiluminescence) and 1,25(OH)2D (radioimmunoassay) were determined by using a commercial kit (DiaSorin Inc., Stillwater, Minn., USA). Intact PTH (Abbott Architect i2000 assay, chemiluminescence; normal range 15–68 pg/ml), intact FGF-23 by ELISA (Kainos, Tokyo, Japan; normal range 8.2– 54.3 pg/ml), albumin (bromcresol green), and high-sensitivity CRP (chemiluminescence) were determined. Serum phosphorus and ionized calcium (normal range 1.12–1.40 nmol/l) were measured using a standard autoanalyzer and serum bicarbonate by automated potentiometer. Patients were carefully instructed to collect 24-hour urine to measure creatinine, protein, calcium and phosphorus. Fractional excretion of phosphorus was calculated as (urine phosphorus ! serum creatinine !100)/(serum phosphorus ! 24-hour urinary creatinine). Glomerular filtration rate was estimated by creatinine clearance corrected for body surface area.
Nutritional Status and Body Composition The body mass index (BMI) was calculated as body weight divided by squared height. Nutritional status was evaluated by the 7-point subjective global assessment [16]. Body composition was assessed by dual energy X-ray absorptiometry using a scanner DPX model (Lunar Radiation Corporation, Madison, Wisc., USA). Total body fat and truncal fat were divided by squared height and stratified according to the median values of the sample according to gender (body fat index: 10.7 kg/m2 for women and 6.7 kg/m2 for men; truncal fat index: 5.8 kg/m2 for women and 4.1 kg/m2 for men).
Supplementation Protocol The patients underwent oral supplementation of cholecalciferol (1,000 IU/drop; Magister Handling Pharmacy Ltd., São Paulo, Brazil). During the first 3 months, they were instructed to take 50 drops once a week (50,000 IU/week). After this period, the patients who had achieved 25(OH)D levels 630 ng/ml received a
Statistical Analysis Data were expressed as the mean 8 SD or frequency. Nonnormally distributed variables such as 25(OH)D, 1,25(OH)2D, PTH, FGF-23, CRP, serum creatinine, creatinine clearance, urinary protein and urinary calcium were log transformed (natural base). Analysis of variance or paired t test was used for analysis of follow-up data. Pearson’s linear correlation coefficients were calculated to evaluate associations among changes of variables. Independent Student’s t test or the 2 test was performed for comparing the baseline characteristics between non-responder patients, defined as those who have not achieved serum 25(OH)D 630 ng/ml after 3 months of 50,000 IU cholecalciferol supplementation, with the responders [25(OH)D 130 ng/ml]. Using the variables that were significantly different between the groups (responders vs. non-responders) and adjusting for known factors that interfere with the response (age, sex and proteinuria), a multiple logistic regression analysis was performed using the groups (responders vs. non-responders) as the dependent variable.
Cholecalciferol Supplementation in CKD
Ann Nutr Metab 2012;61:74–82
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Table 1. Laboratory parameters during the follow-up (n = 45)
25(OH)D, ng/ml Intact PTH, pg/ml 1,25(OH)2D, pg/ml Serum ionized calcium, mmol/l Serum phosphorus, mg/dl FGF-23, pg/ml Serum bicarbonate, mmol/l Serum albumin, g/dl CRP, mg/dl Serum creatinine, mg/dl Creatinine clearance, ml/min Urinary calcium, mg/24 h Urinary protein, g/24 h Fractional excretion phosphorus, % Urinary phosphorus, g/24 h
Baseline
Month 3
Month 6
p
11.282.5 136.4876.4 42.1820.7 1.2980.05 3.880.8 99.98103.5 23.284.1 4.280.3 0.5880.78 2.380.8 34.5811.7 40.1833.9 0.880.9 28.188.4 477.38173.6
43.4816.4a 118.2876.6a 45.9826.6 1.2980.06 3.980.6 123.6892.2a, b 22.584.4 4.180.3 0.3780.41 2.580.9 a 32.9814.1 59.9849.3a 0.781.0 29.888.9 485.28197.8
38.1816.0a 138.38118.6 46.9825.4 1.2880.05 3.880.8 98.68113.5 22.584.2 4.280.3 0.4880.63 2.581.0a 32.3813.2 53.4849.2 a 0.881.0 29.889.9 476.58183.2
0.001 0.02 0.55 0.33 0.62 0.001 0.38 0.05 0.16 0.01 0.09 0.001 0.55 0.19 0.9
Data are presented as the mean 8 SD. To convert 25(OH)D in ng/ml to nmol/l, multiply by 2.496. a p < 0.01 vs. baseline. b p < 0.01 vs. month 6.
All tests were two-sided, and a p value !0.05 was considered significant. All analyses were performed using SPSS software, version 15.0 (SPSS Inc., Chicago, Ill., USA).
Results
Forty-five patients completed the study (age 60.1 8 15.6 years, 58% women, 42% diabetics, and 56% dark skin colored). According to the 7-point subjective global assessment criteria, the majority of patients (73%) was classified as well nourished, and the BMI was indicative of overweight (27.1 8 5.7 kg/m2). The main etiologies of kidney disease were diabetic (27%) and hypertensive (27%) nephropathies. Proteinuria was found in 28 patients (62%). No patient was in use of calcium supplements or phosphate binders at baseline. The laboratory parameters during follow-up are summarized in table 1. There was a significant increase in 25(OH)D levels at 3 and 6 months when compared to baseline. At 3 months, in which the cumulative dose of cholecalciferol was 656,444 8 114,239 IU, 78% of the patients reached levels of 25(OH)D 630 ng/ml. At 6 months, in which the cumulative dose of cholecalciferol was reduced to 310,000 8 222,741 IU, restoration of vitamin D was observed in 58% of the patients. Of note, from those patients who normalized vitamin D levels at 3 months and underwent dose adjustment (from 50,000 IU/week to 76
Ann Nutr Metab 2012;61:74–82
50,000 IU/month), only 43% were able to maintain adequate 25(OH)D levels thereafter. In order to investigate the factors associated with poor response to cholecalciferol supplementation, baseline characteristics of the patients who restored 25(OH)D to normal levels (n = 35) were compared to those who did not normalize vitamin D status (n = 10) after 3 months, a period in which all patients underwent the same protocol of cholecalciferol supplementation (table 2). In the group of patients who did not restore vitamin D status (non-responders), 25(OH)D increased only from 11.5 8 2.9 to 23.9 8 5.0 ng/ml (p ! 0.001), while in the group of patients who restored vitamin D status (responders), the increase in 25(OH)D was from 11.1 8 2.4 to 48.9 8 14.1 ng/ml (p ! 0.001). The non-responder group had a lower creatinine clearance (p = 0.04), greater truncal fat index (p ! 0.01), and a greater proportion of patients with a BMI 625 kg/m2 (table 2). The multivariate logistic regression analysis adjusted for sex, age, baseline urinary protein and changes in serum creatinine pointed out increased adiposity as the main factor associated with lower response to vitamin D supplementation (table 3). As can be seen in table 1, PTH decreased at 3 months, but at 6 months, the hormone returned to levels similar to baseline. The monthly measurement of PTH depicted in figure 1 allows visualizing that the significant reductions in PTH occurred after 3 and 4 months, which corresponds to the period in which patients received the Garcia-Lopes /Pillar /Kamimura /Rocha / Canziani /Carvalho /Cuppari
Table 2. Baseline characteristics of the patients according to restoration of vitamin D status at 3 months
Non-responders (n = 10) 25(OH)D, ng/ml, 3 months Women Age, years Diabetes Stage of CKD Stage 3 Stage 4 BMI BMI ≥25.0 kg/m2 Truncal fat index kg/m2 Higher than median value Total fat index kg/m2 Higher than median value 25(OH)D, ng/ml 1,25(OH)2D, pg/ml Intact PTH, pg/ml FGF-23, pg/ml Serum ionized calcium, nmol/l Serum phosphorus, mg/dl Serum creatinine, mg/dl Creatinine clearance, ml/min Urinary protein, g/24 h
Responders (n = 35)
p
23.985.0 6 (60) 60.2813.1 5 (50)
48.9814.1 20 (57) 60.0816.4 14 (40)
