Selective amino acid deficiency in patients with impaired glucose tolerance and type 2 diabetes

IntroductionAmino acids are important modulators of glucose metabolism, insulin secretion and insulin sensitivity. However, little is known about the changes in amino acid metabolism in patients with diabetes.Patients and methodsThe circulating amino acid levels were determined in 17 patients with type 2 diabetes, 17 individuals with impaired glucose tolerance (IGT), and 14 control subjects.ResultsTotal amino acid concentrations were 2850 ± 57 µmol/l in patients with type 2 diabetes, 2980 ± 77 µmol/l in individuals with IGT, and 2886 ± 74 µmol/l in control subjects (p = 0.38). Patients with type 2 diabetes exhibited significant reductions in the concentrations of gamma-aminobutyric acid (GABA), arginine, glutamine and phosphoethanolamine (p < 0.05), whereas valine levels were higher than in controls (p = 0.008). In IGT subjects, GABA levels were reduced, while tyrosine concentrations were increased (p < 0.05). The plasma levels of essential amino acids were positively related to fasting and post-challenge glucose levels, fasting C-peptide, HOMA insulin resistance and fasting glucagon levels (p < 0.05).ConclusionsTotal amino acid levels are similar in patients with diabetes, IGT subjects and controls, but the individual levels of several amino acids differ significantly between these groups. These alterations may contribute to the disturbances in insulin secretion and action in diabetic patients and may provide a rationale for offering specific amino acid supplementations to diabetic patients.