Efficacy of omega-3 fatty acids in children and adults with IgA nephropathy is dosage- and size-dependent.

Previous studies that have evaluated fish oil preparations in patients with IgA nephropathy (IgAN) have produced a wide range of conclusions. Proposed explanations for these discordant results have not provided a unifying hypothesis. Results from two clinical trials were analyzed to examine whether there is a dosage-dependent effect of Omacor, a purified preparation of omega-3 fatty acids, in patients with IgAN. Whether changes in the level of proteinuria and plasma phospholipid fatty acid profiles were dependent on the dose of Omacor factored by body size was determined. In a post hoc analysis of the first trial results, correlations were found between (1) phospholipid eicosapentaenoic acid (EPA)/arachidonic acid (AA) and docosahexaenoic acid (DHA)/AA ratios and the dosage of Omacor, expressed as milligrams per kilogram of body weight (r = 0.78, P < 0.001 for EPA/AA; r = 0.86, P < 0.001 for DHA/AA), (2) phospholipid EPA/AA and DHA/AA levels and percentage change in urine protein/creatinine ratio after 21 to 24 mo of therapy (r = -0.50, P = 0.02 for EPA/AA; r = -0.52, P = 0.01 for DHA/AA), and (3) dosage of Omacor per kilogram of body weight and change in proteinuria after 21 to 24 mo (r = -0.50, P = 0.02). A similar relationship was observed between urine protein/creatinine ratio and dosage of Omacor per kilogram of body weight in trial 2 (r = -0.38, P < 0.001). It is concluded from these data that the effect of Omacor on proteinuria in patients with IgAN is dosage dependent and is associated with a dosage-dependent effect of Omacor on plasma phospholipid EPA and DHA levels.