Impact of Vitamin D on Diabetic Kidney Disease in African Americans

This purpose of this project is to evaluate the effectiveness of vitamin D supplementation over 12 months in vitamin D deficient African American adults with type 2 diabetes.

Diabetic kidney disease is increasing in prevalence and is associated with significant morbidity and mortality. Health disparities exist in the progression of diabetic kidney disease, with minorities being more affected even when adjusting for treatment, glycemic and hypertensive control, and medical coverage. Secondary prevention of the progression of diabetic kidney disease is hindered by a lack of easily modifiable risk factors. Based on animal and observational human studies, vitamin D deficiency is potentially a novel, modifiable risk factor that may interrupt or delay the progression of diabetic kidney disease through direct effects as well as by helping to ameliorate kidney disease risk factors, such as hyperglycemia, hypertension and inflammation. In addition, based on minorities having a higher prevalence of vitamin D deficiency, it may also potentially impact the differential progression of diabetic kidney disease in minorities. However, clinical trials evaluating the impact of vitamin D supplementation on diabetic kidney disease are lacking. Thus, this pilot study funded as an R03 through the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) has the following specific aims: (1): To evaluate the impact of vitamin D supplementation (vitamin D3 at 400 IU/d versus 4000 IU/d) on the proportion of individuals with progression of albuminuria over 12 months in a sample of African American participants with vitamin D deficiency in a randomized controlled trial. (2): To identify whether kidney disease risk factors such as blood pressure and glycemic control mediate the impact of vitamin D supplementation on the progression of albuminuria over 12 months in a sample of African American participants with vitamin D deficiency in a randomized controlled trial.

Vitamin D3 supplementation of 400 IU/D or 4000 IU/D with combined calcium carbonate supplementation of 1000 mg/day

Vitamin D3 supplementation of 4000 IU/D or 4000 IU/D with combined calcium carbonate supplementation of 1000 mg/day

Patients receive vitamin D 400 IU/d with calcium carbonate (1000 mg) once per day for 15 months (3 month run in phase with 12 month follow up)

Patients receive vitamin D 4000 IU/d with calcium carbonate (1000 mg) once per day for 15 months (3 month run in phase with 12 month follow up)

Urinary Albumin:Creatinine Ratio (ACR) is a well-established, sensitive marker of nephropathy progression (urine albumin (mg/dL) to urine creatinine (g/dL) ratio).

Estimated Glomerular Filtration Rate (eGFR) will be evaluated every 6 months, since changes in eGFR and ACR may occur independently and represent different pathways to the development of renal insufficiency. eGFR will be calculated via the Modification of Diet in Renal Disease (MDRD) equation of 4 variables (Cr level, age, sex, race) per NKF recommendations, with serum creatinine (Cr) measured using the SYNCHRON® System by means of the Jaffe rate method. For the purposes of this study, a decrease in eGFR will serve as a secondary outcome measure.

Inclusion Criteria: African American race Diagnosis of Type 2 Diabetes Stage 1 or 2 Kidney Disease with detectable microalbuminuria >4.0 (mg/g) 25(OH)D level <20 ng/ml Exclusion Criteria: Type 1 diabetes --> Stage 3 Kidney Disease, or history of dialysis, kidney transplantation or nephrolithiasis Unable to provide informed consent or contact information Pre-existing calcium or parathyroid condition, including serum calcium >10.2 mg/dL Sarcoidosis, active tuberculosis, or malignancy Known hypersensitivity to vitamin D or any of its analogues and derivatives Current pregnancy or planning to become pregnant in next 15 months