The Effects of n-3 Long-Chain Polyunsaturated Fatty Acid Supplementation on Biomarkers of Kidney Injury in Adults With Diabetes: Results of the GO-FISH trial

OBJECTIVE: Long-chain n-3 polyunsaturated fatty acid (n-3 PUFA) supplements may have renoprotective effects in patients with diabetes, but previous trials have been inconsistent. We performed a randomized controlled trial of n-3 PUFA supplementation on urine albumin excretion and markers of kidney injury in adults with type 2 diabetes. RESEARCH DESIGN AND METHODS: We conducted a randomized, placebo-controlled, two-period crossover trial to test the effects of 4 g/day of n-3 PUFA supplementation on markers of glomerular filtration and kidney injury in adults with adult-onset diabetes and greater than or equal to trace amounts of proteinuria. Each period lasted 6 weeks and was separated by a 2-week washout. The main outcome was urine albumin excretion and, secondarily, markers of kidney injury (kidney injury molecule-1, N-acetyl β-d-glucosaminidase [NAG], neutrophil gelatinase-associated lipocalin [NGAL], and liver fatty acid–binding protein [LFABP]), serum markers of kidney function (cystatin C, β(2)-microglobulin, and creatinine), and estimated glomerular filtration rate (eGFR). RESULTS: Of the 31 participants, 29 finished both periods. A total of 55% were male, and 61% were African American; mean age was 67 years. At baseline, mean BMI was 31.6 kg/m(2), median eGFR was 76.9 mL/min/1.73 m(2), and median 24-h urine albumin excretion was 161 mg/day. Compared with placebo, n-3 PUFA had nonsignificant effects on urine albumin excretion (−7.2%; 95% CI −20.6 to 8.5; P = 0.35) and significant effects on urine NGAL excretion (−16% [−29.1 to −0.5%]; P = 0.04). There was no effect on serum markers of kidney function or eGFR. In subgroup analyses, there were significant decreases in 24-h urinary excretion of albumin, NGAL, LFABP, and NAG among participants taking medications that block the renin-angiotensin-aldosterone system (RAAS). CONCLUSIONS: These results suggest a potential effect of n-3 PUFA supplementation on markers of kidney injury in patients with diabetes and early evidence of kidney disease. In the context of prior studies, these results provide a strong rationale for long-term trials of n-3 PUFA on chronic kidney disease progression.