Plasma levels of carboxylic acids are markers of early kidney dysfunction in young people with type 1 diabetes

Background We compared plasma metabolites of amino acid oxidation and the tricarboxylic acid (TCA) cycle in youth with and without type 1 diabetes mellitus (T1DM) and related the metabolites to glomerular filtration rate (GFR), renal plasma flow (RPF), and albuminuria. Metabolites associated with impaired kidney function may warrant future study as potential biomarkers or even future interventions to improve kidney bioenergetics. Methods Metabolomic profiling of fasting plasma samples using a targeted panel of 644 metabolites and an untargeted panel of 19,777 metabolites was performed in 50 youth with T1DM <= 10 years and 20 controls. GFR and RPF were ascertained by iohexol and p-aminohippurate clearance, and albuminuria calculated as urine albumin to creatinine ratio. Sparse partial least squares discriminant analysis and moderated t tests were used to identify metabolites associated with GFR and RPF. Results Adolescents with and without T1DM were similar in age (16.1 +/- 3.0 vs. 16.1 +/- 2.9 years) and BMI (23.4 +/- 5.1 vs. 22.7 +/- 3.7 kg/ m(2)), but those with T1DM had higher GFR (189 +/- 40 vs. 136 +/- 22 ml/min) and RPF (820 +/- 125 vs. 615 +/- 65 ml/min). Metabolites of amino acid oxidation and the TCA cycle were significantly lower in adolescents with T1DM vs. controls, and the measured metabolites were able to discriminate diabetes status with an AUC of 0.82 (95% CI: 0.71, 0.93) and error rate of 0.21. Lower glycine (r:-0.33, q= 0.01), histidine (r:-0.45, q < 0.001), methionine (r: -0.29, q = 0.02), phenylalanine (r: -0.29, q = 0.01), serine (r: -0.42, q < 0.001), threonine (r: -0.28, q= 0.02), citrate (r: -0.35, q = 0.003), fumarate (r: -0.24, q = 0.04), and malate (r: -0.29, q= 0.02) correlated with higher GFR. Lower glycine (r: -0.28, q= 0.04), phenylalanine (r: -0.3 q= 0.03), fumarate (r: -0.29, q= 0.04), and malate (r: -0.5, q < 0.001) correlated with higher RPF. Lower histidine (r: -0.28, q= 0.02) was correlated with higher mean ACR. Conclusions In conclusion, adolescents with relatively short T1DM duration exhibited lower plasma levels of carboxylic acids that associated with hyperfiltration and hyperperfusion.