Figure 2.

Plasma levels of arginine, citrulline, dehydroxycarnitine, and glutamic γ-semialdehyde are elevated in DR patients. Metabolites enriched in the pathway analyses were further analyzed with a Wilcoxon rank sum test and using LC-MS/MS, revealing arginine, citrulline, dehydroxycarnitine, and glutamic γ-semialdehyde levels are significantly increased in DR patients compared with diabetic controls. DC, diabetic controls. *Confidence level 1 by MSI standards, identities verified via LC-MS/MS with authentic standards. †Confidence level 2 by MSI standards, putative annotation based on MS/MS spectral matching using MetFrag and mzCloud.