Vitamin D Supplementation in CKD - Vascular Function, Structure and Immune Regulation

The study is a single (observer) blinded feasibility pilot randomised study. Study subjects will be recruited from clinics run by St George's Hospital Renal Department and randomised to treatment arm or no treatment arm.

In treatment arm, six doses of vitamin D tablets (cholecalciferol 100,000 IU, five capsules total) will be administered on weeks 0, 4, 8, 12, 16 and 20. In the no-treatment arm the participants receive no cholecalciferol. Participants will have serum calcium levels measured at week 12.

All participants will undergo estimation of endothelial function, carotid intima-media thickness, CD4+CD28null and regulatory T cell frequency in week 0 and week 26. The observer will be blinded to whether the patient is in the treatment or no-treatment arm whilst the following tests are performed:

• Measurement of Brachial Artery Flow Mediated Dilatation
• Measurement of Carotid Intima Media Thickness
• Quantification of CD4+CD28null and regulatory T cell frequency

The pilot study will assess feasibility of the study methods.

Inclusion criteria

• Age 18-80 years
• Calcium < 2.58mmol/l
• On an ACE inhibitor/ARB
• Vitamin D <75nmol/l
• eGFR 15- 60ml/min/1.73m2 and stable
• Informed consent to participate

Exclusion criteria

• Patients already on Vitamin D or calcium supplementation
• Patients with known malignancies
• Patients with autoimmune conditions
• Patients with heart failure (ejection fraction <40%, Plasma NT pro-BNP>500pg/ml)
• Patients with active infection
• Rapidly deteriorating renal function
• Recent Acute coronary syndrome or cerebro-vascular event (within the last 6 months)
• Uncontrolled hypertension (BP>160 systolic)