Serum Uric Acid-Lowering Effects of Combined Glycine and Tryptophan Treatments in Subjects with Mild Hyperuricemia: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

Abstract

We determined the serum uric acid-lowering effects of combined daily supplementation of glycine and tryptophan in patients with mild hyperuricemia using a randomized, double-blind, placebo-controlled, crossover clinical trial design. Japanese healthy adult males and females with mild hyperuricemia (fasting serum uric acid of 6.6–7.9 mg/dL) ingested a powder mixture containing 3.0 g of glycine and 0.2 g of tryptophan or a placebo powder once daily at bedtime for 6 weeks. Combined supplementation with glycine and tryptophan significantly decreased serum uric acid levels (from 7.1 mg/dL to 6.7 mg/dL, p = 0.004) before and after the trial. Serum uric acid concentrations significantly decreased in the subjects supplemented with the amino acid mixture compared with those in placebo-treated subjects (p = 0.028). In addition, the combination treatment with glycine and tryptophan decreased serum triglyceride levels (from 119 mg/dL to 86 mg/dL, p = 0.002). Increased solubility of uric acid caused by urinary pH were likely contributors to the serum uric acid-lowering effects of the amino acid mixture.

Combined Supplementation with Glycine and Tryptophan Reduces Purine-Induced Serum Uric Acid Elevation by Accelerating Urinary Uric Acid Excretion: A Randomized, Single-Blind, Placebo-Controlled, Crossover Study

“…This study examined whether the combined administration of 6.0 g of glycine and 0.4 g of tryptophan suppressed the elevation in serum uric acid levels induced by purine ingestion and increased urinary uric acid excretion. The amino acid doses used for single ingestion were based on those used in continual supplementation [14]. Both glycine and tryptophan are present in dietary proteins that are ingested in normal daily living.…”

“…In agreement with previous reports [11,12], glycine increased urinary uric acid excretion and enhanced urate clearance in the current study. The authors previously reported that continual supplementation with glycine and tryptophan led to an increase in urinary pH [14]. Glycine exhibits a buffering action and it is often used as an antacid.…”

“…Therefore, the authors subsequently conducted a clinical trial to confirm the serum uric acid-lowering effects of continual combined supplementation with glycine and tryptophan under mild hyperuricemia. The results revealed that combined treatment with 3.0 g of glycine and 0.2 g of tryptophan daily for 6 weeks significantly decreased serum uric acid concentrations in subjects with mild hyperuricemia [14]. The mixture of amino acids enhanced urate clearance, except in subjects with abnormally high urate clearance.…”

Enhancing effect of glycine and tryptophan mixture on estimated glomerular filtration rate in healthy participants: A randomized, double-blind, placebo-controlled parallel study

“…In our two previous clinical trials, the oral administration of the combined dose of glycine and tryptophan led to a decreased concentration of serum uric acid because of the increased urate excretion into the urine [20,21]. A recent prospective cohort study suggested that serum uric acid levels are independently associated with the incidence of impaired renal function and renal progression [22], and a meta-analysis reported that uric acid-lowering therapy effectively regards CKD progression [23].…”

The influence of dietary interventions on paraclinical parameters in patients with metabolic syndrome

“…Uric acid has been found to be strongly associated with triglycerides, regardless of age, sex, smoking, alcohol consumption, obesity and insulin resistance, in a study published in China 26 . Uric acid and triglyceride levels have also been linked to oxidative stress and mitochondrial dysfunction 27 , but there was also a decrease in the level of uric acid and triglycerides following the administration of glycine and tryptophan without diet therapy [28][29][30] .…”