Preoperative Short‐Term Restriction of Sulfur‐Containing Amino Acid Intake for Prevention of Acute Kidney Injury After Cardiac Surgery: A Randomized, Controlled, Double‐Blind, Translational Trial

BACKGROUND: Acute kidney injury (AKI) is a major risk factor for chronic kidney disease and increased mortality. Until now, no compelling preventive or therapeutic strategies have been identified. Dietary interventions have been proven highly effective in organ protection from ischemia reperfusion injury in mice and restricting dietary intake of sulfur‐containing amino acids (SAA) seems to be instrumental in this regard. The UNICORN trial aimed to evaluate the protective impact of restricting SAA intake before cardiac surgery on incidence of AKI. METHODS AND RESULTS: In this single‐center, randomized, controlled, double‐blind trial, 115 patients were assigned to a SAA‐reduced formula diet (LowS group) or a regular formula diet (control group) in a 1:1 ratio for 7 days before scheduled cardiac surgery. The primary end point was incidence of AKI within 72 hours after surgery, secondary end points included increase of serum creatinine at 24, 48, and 72 hours as well as safety parameters. Quantitative variables were analyzed with nonparametric methods, while categorical variables were evaluated by means of Chi‐square or Fisher test. SAA intake in the group with SAA reduced formula diet was successfully reduced by 77% (group with SAA reduced formula diet, 7.37[6.40–7.80] mg/kg per day versus control group, 32.33 [28.92–33.60] mg/kg per day, P<0.001) leading to significantly lower serum levels of methionine. No beneficial effects of SAA restriction on the rate of AKI after surgery could be observed (group with SAA reduced formula diet, 23% versus control group, 16%; P=0.38). Likewise, no differences were recorded with respect to secondary end points (AKI during hospitalization, creatinine at 24, 48, 72 hours after surgery) as well as in subgroup analysis focusing on age, sex, body mass index and diabetes. CONCLUSIONS: SAA restriction was feasible in the clinical setting but was not associated with protective properties in AKI upon cardiac surgery. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique Identifier: NCT03715868.