Randomized Controlled Trial of Vitamin D3 in Diabetic Kidney Disease

Randomized Controlled Trial of Vitamin D3 in Diabetic Kidney Disease

This study will assess the effects of vitamin D3 supplementation (cholecalciferol; 2000 IU daily) on serum calcium levels, circulating vitamin D levels, and markers of kidney disease and cardiovascular risk among people with diabetes mellitus and early kidney disease. Eligibility criteria include type 2 diabetes and stage 1-2 chronic kidney disease, defined by a urine albumin-creatinine ratio 30-300 mg/g and an estimated glomerular filtration rate ≥ 60 mL/min. Participants will be randomly assigned to treatment with vitamin D3 or placebo, each taken by mouth once daily for a study duration of one year. Study medications will be added to standard treatment, including an angiotensin converting enzyme inhibitor and/or angiotensin II receptor blocker. We hypothesize that vitamin D3, compared with placebo: (1) is well-tolerated and safe among people with diabetes and kidney disease; (2) results in adequate attained circulating vitamin D levels; and (3) positively affects markers of kidney disease and cardiovascular risk.

Inclusion Criteria:

• Clinical diagnosis of type 2 diabetes mellitus
• Urine albumin-creatinine ratio 30-1000 mg/g
• Estimated glomerular filtration rate greater than or equal to 60 mL/min
• Treatment with angiotensin converting enzyme inhibitor and/or angiotensin II receptor blocker for greater than or equal to 6 months, with a stable dose for greater than or equal to 3 months
• Blood pressure less than 140/90 (assessed while taking medications)
• Hemoglobin A1c less than 9% (assessed while taking medications)
• 25-hydroxyvitamin D less than 30 ng/mL

Exclusion Criteria:

• Prior dialysis or kidney transplantation
• Known cause of albuminuria other than diabetes
• Planning to leave the area within 12 months
• Life expectancy less than 12 months
• Participation in another clinical trial within 6 months
• Osteoporosis or other established indication for vitamin D therapy
• Vitamin D3 supplement intake greater than 400 IU/day at screening visit
• History of nephrolithiasis
• Serum calcium greater than 10.2 mg/dL
• Dementia, not fluent in English, or unable to provide informed consent without proxy respondent
• Incontinent of urine
• Failure to take greater than or equal to 80% of placebo pills during study run-in