In this WP, we will focus on oxidative stress pathways and lipid metabolites for the identification and quantitation of the proteins and metabolites that are predictive of diabetic neuropathy among well-characterized type 1 and type 2 diabetic neuropathy patients from Denmark and the UK. Candidate oxidative pathways for our studies include nitrotyrosine, oxidized lipids (HODEs, HETEs, isoprostanes), short chain fatty acids, TMAO, and associated metabolites and bile acids. The Feldman Lab is able to monitor stable end products of protein and lipid oxidation and has developed analytical methods to detect these products at the subfemtomole level. These methods combine gas chromatography with isotope dilution and triple quadrapole mass spectrometry. This approach can establish the molecular fingerprints for oxidative damage mediated by different reaction pathways in vivo and based on measures from plasma and urine samples. These oxidation and lipid products may serve as sensitive biomarkers of oxidative stress and potential indicators of disease progression in diabetic neuropathy. The oxidative stress and lipid markers will be measured in a subset of well-phenotyped patients with different degrees of diabetic neuropathy from the ADDITION cohort and a subset of patients both with and without pain from the centers in Denmark and Oxford to identify non-invasive predictors of disease progression of diabetic neuropathy as well as markers for nerve injury pain.