(A–C) glutamine, alanine, and N-acetylamine-alanine, (D–F) leucine-isoleucine, threonine, and proline, (G–I) 1-methyl-histidine, phenylalanine, and indole-3-carboxylic acid levels. n≥3 forHC, T1DM, and T2DM corneal buttons. Error bars represent standard error of the mean. A one-way ANOVA was performed and P≤0.05 considered statistically significant. Each data point corresponds to an individual patient.