Background Decreased glomerular filtration rate (GFR) leads to reduced production of 1,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D 3 (25[OH]D3). Effects of low GFR on vitamin D catabolism are less well understood. We tested associations of estimated GFR (eGFR) with the circulating concentration of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3), the most abundant product of 25(OH)D 3 catabolism, across populations with a wide range of GFRs. Study Design Cross-sectional study. Setting & Participants 9,596 participants in 5 cohort studies and clinical trials: the Diabetes Control and Complications Trial (N = 1,193), Multi-Ethnic Study of Atherosclerosis (N = 6,470), Cardiovascular Health Study (N = 932), Seattle Kidney Study (N = 289), and Hemodialysis Study (N = 712). Predictor eGFR. Outcome Circulating 24,25(OH) 2D3 concentration. Measurements GFR was estimated from serum creatinine using the Chronic Kidney Disease Epidemiology Collaboration equation. Vitamin D metabolites were measured by mass spectrometry. Results Circulating 24,25(OH)2D3 concentration was correlated with circulating 25(OH)D3 concentration (Pearson r range, 0.64-0.88). This correlation was weaker with lower eGFRs. Moreover, the increment in 24,25(OH)2D3 concentration associated with higher 25(OH)D3 concentration (slope) was lower with lower eGFRs: 2.06 (95% CI, 2.01-2.10), 1.77 (95% CI, 1.74-1.81), 1.55 (95% CI, 1.48-1.62), 1.17 (95% CI, 1.05-1.29), 0.92 (95% CI, 0.74-1.10), 0.61 (95% CI, 0.22-1.00), and 0.37 (95% CI, 0.35-0.39) ng/mL of 24,25(OH)2D3 per 10 ng/mL of 25(OH)D3 for eGFRs ≥ 90, 60-89, 45-59, 30-44, 15-29, and <15 mL/min/1.73 m2 and end-stage renal disease treated with hemodialysis, respectively. As a result, at a 25(OH)D3 concentration of 20 ng/mL, mean 24,25(OH)2D3 concentrations were 2.92 (95% CI, 2.87-2.96), 2.68 (95% CI, 2.64-2.72), 2.35 (95% CI, 2.26-2.45), 1.92 (95% CI, 1.74-2.10), 1.69 (95% CI, 1.43-1.95), 1.14 (95% CI, 0.62-1.66), and 1.04 (95% CI,1.02-1.07) ng/mL for each category, respectively. This interaction was independent of other relevant clinical characteristics. Race, diabetes, urine albumin excretion, and circulating parathyroid hormone and fibroblast growth factor 23 concentrations more modestly modified the association of 24,25(OH)2D3 with 25(OH)D3. Limitations Lack of direct pharmacokinetic measurements of vitamin D catabolism. Conclusions Lower eGFR is associated strongly with reduced vitamin D catabolism, as measured by circulating 24,25(OH)2D3 concentration.
Bibliographical noteFunding Information:
Support: This research was supported by grants R01HL096875, R01HL102214, R01HL080295, and R01HL096851 and contracts N01HC95159 through N01HC95169, HHSN268201200036C, HHSN268200800007C, N01HC55222, N01HC85079 through N01HC85083 , and N01HC85086 from the National Heart, Lung and Blood Institute ; grants R01DK087726 , R01DK088762 , R01DK081473 , and RC4DK090766 from the National Institute of Diabetes and Digestive and Kidney Diseases ; grant AG023629 from the National Institute on Aging ; grants UL1-RR-024156 and UL1-RR-025005 from the National Center for Research Resources ; and grant 0575021N from the American Heart Association . These sponsors had no role in study design; collection, analysis, and interpretation of data; writing the report; or the decision to submit the report for publication.
- 1,25-dihydroxyvitamin D3
- 25-hydroxyvitamin D3
- Decreased renal function
- Index Words
- active vitamin D
- chronic kidney disease (CKD)
- low estimated glomerular filtration rate
- vitamin D catabolism