Free amino acids in plasma have been associated with risk of cancer, metabolic syndrome, diabetes and low levels are observed in frail, elderly persons (2). Branched chain amino acids (BCAA; Leu, Ile and Val) are associated with insulin resistance, diabetes type 2, cardiovascular disease and early kidney disease (2, 3), and the valine catabolites, 3-hydroxyisobutyrate (3HIB) is belived to play a key role in the development of insulin resistance (3).
Patient/subject: Prandial status affects concentration, which increases slightly after a protein rich meal.
Matrix: Serum or EDTA plasma.
Volume: Minimum volume is 50 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: Most amino acids are stable.
Reported values: Orn: 30-90 µmol/L; Asp: 0-26 µmol/L; Glu: 20-140 µmol/L; Lys: 120-290 µmol/L; Ala: 230-510 µmol/L; Phe: 26-85 µmol/L; Ile: 40-140 µmol/L; Leu: 70-170 µmol/L; Pro: 110-360 µmol/L; Val: 150-350 µmol/L; Asn: 20-130 µmol/L; Gln: 390-700 µmol/L; Thr: 70-240 µmol/L; Tyr: 40-110 µmol/L.
Intraclass correlation coefficient (ICC): na.
1. Midttun, Ø., McCann, A., Aarseth, O., Krokeide, M., Kvalheim, G., Meyer, K., and Ueland, P.M. (2016). Combined measurement of 6 fat-soluble vitamins and 26 water-soluble functional vitamin markers and amino acids in 50 μL of serum or plasma by high-throughput mass spectrometry. Anal Chem 88, 10427-436.
2. Nagao, K., & Kimura, T. (2020). Use of plasma-free amino acids as biomarkers for detecting and predicting disease risk. Nutr Rev, 78(12 Suppl 2), 79-85.
3. Arany, Z., and Neinast, M. (2018). Branched chain amino acids in metabolic disease. Curr Diab Rep 18, 76.