Omega-3 fatty acid supplementation increases 1,25-dihydroxyvitamin D and fetuin-A levels in dialysis patients

Vitamin D deficiency, low levels of fetuin-A, and fibroblast growth factor 23 (FGF-23) are related to vascular calcification, which is associated with cardiovascular disease. We hypothesized that omega-3 fatty acid (FA), which has cardioprotective properties, modifies vitamin D status, fetuin-A, and FGF-23 levels in dialysis patients. In a randomized, open-label, controlled study, a total of 47 patients treated with dialysis for at least 1 year were randomized to treatment for 6 months with omega-3 FAs (Omacor, 3 g/d; Pronova, Sandefjord, Norway) or a control group. Levels of fetuin-A and FGF-23 were measured by enzyme-linked immunoassay, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were measured by radioimmunoassay. The mean age of the enrolled patients was 57.4 ± 10.4 years, and mean dialysis duration was 46.5 ± 28.1 months. Twenty-seven hemodialysis patients and 16 peritoneal dialysis patients finished this trial. After 6 months, the levels of 1,25-dihydroxyvitamin D and fetuin-A were significantly increased in the group taking the omega-3 FA supplement compared with baseline. Levels of calcium, phosphorous, parathyroid hormone, 25-hydroxyvitamin D, FGF-23, and lipid profiles were not significantly changed in the omega-3 FA-supplemented group after 6 months compared with baseline. The erythrocyte membrane contents of eicosapentaenoic acid and docosahexaenoic acid were significantly increased, and oleic acid content was significantly decreased in the omega-3 FA-supplemented group after 6 months compared with baseline. Regarding vascular calcification and cardiovascular disease, omega-3 FA supplementation may have a clinical benefit caused by activating vitamin D, increasing fetuin-A levels, and modifying erythrocyte membrane FA contents in dialysis patients.