title: Circulating vitamin D metabolites and kidney disease in type 1 diabetes.
abstract: BACKGROUND
  Impaired vitamin D metabolism may contribute to the development and progression of diabetic kidney disease.
  
  
  OBJECTIVE
  The aim of the study was to test associations of circulating vitamin D metabolites with risks of incident microalbuminuria, impaired glomerular filtration rate (GFR), and hypertension in type 1 diabetes.
  
  
  METHODS
  We performed a cohort study of 1193 participants in the Diabetes Control and Complications Trial (DCCT), a randomized clinical trial of intensive diabetes therapy, and its observational follow-up, the Epidemiology of Diabetes Interventions and Complications (EDIC) Study. We measured plasma concentrations of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D, and 24,25-dihydroxyvitamin D by mass spectrometry at the end of the DCCT and tested associations with incident microalbuminuria, impaired GFR, and hypertension over up to 16 yr of EDIC follow-up.
  
  
  RESULTS
  At the time metabolites were measured, mean age was 32.4 yr; mean duration of diabetes, 7.5 yr; mean iothalamate GFR, 132.9 ml/min/1.73 m(2); and geometric mean albumin excretion rate, 11.8 mg/24 h. Over follow-up, 166 cases of microalbuminuria, 54 cases of impaired GFR, and 541 cases of hypertension were observed. Compared with 25(OH)D of at least 30 ng/ml, 25(OH)D below 20 ng/ml was associated with a 65% higher risk of microalbuminuria (95% confidence interval, 7 to 154%) in adjusted analyses. Low concentrations of 24,25-dihydroxyvitamin D, but not 1,25-dihydroxyvitamin D, were also associated with increased risk of microalbuminuria. No circulating vitamin D metabolite was associated with risk of impaired GFR or hypertension.
  
  
  CONCLUSIONS
  Low plasma concentrations of 25(OH)D and 24,25-dihydroxyvitamin D are associated with increased risk of microalbuminuria in type 1 diabetes. In contrast, we did not find evidence linking impaired vitamin D metabolism to early GFR loss or the development of hypertension.
authors.affiliation: Kidney Research Institute and Division of Nephrology, University of Washington, Box 359606, 325 Ninth Avenue, Seattle, Washington 98104, USA.
authors.forename: Ian H
authors.initials: IH
authors.lastname: de Boer
authors.forename: Michael C
authors.initials: MC
authors.lastname: Sachs
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Cleary
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Hoofnagle
authors.forename: John M
authors.initials: JM
authors.lastname: Lachin
authors.forename: Mark E
authors.initials: ME
authors.lastname: Molitch
authors.forename: Michael W
authors.initials: MW
authors.lastname: Steffes
authors.forename: Wanjie
authors.initials: W
authors.lastname: Sun
authors.forename: Bernard
authors.initials: B
authors.lastname: Zinman
authors.forename: John D
authors.initials: JD
authors.lastname: Brunzell
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000097:blood / Q000150:complications / Q000453:epidemiology / Q000378:metabolism; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000150:complications / Q000453:epidemiology / Q000378:metabolism*; D003928:Diabetic Nephropathies / Q000097:blood* / Q000150:complications / Q000453:epidemiology / Q000378:metabolism*; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000150:complications / Q000453:epidemiology / Q000378:metabolism; D015994:Incidence; D008297:Male; D016032:Randomized Controlled Trials as Topic; D014807:Vitamin D / Q000032:analysis / Q000097:blood* / Q000378:metabolism
chemical_list: D014807:Vitamin D