Urinary Metabolomic Markers of Protein Glycation, Oxidation, and Nitration in Early-Stage Decline in Metabolic, Vascular, and Renal Health.

Jinit Masania,Johanna Grabher,Hildegard Hafner-Giessauf,Beate Tiran,Johannes M Roob,Barbara Obermayer-Pietsch,Brigitte M Winklhofer-Roob,Kashif Rajpoot,Gernot Faustmann,Nasir Rajpoot,Attia Anwar,Naila Rabbani,Paul J Thornalley

doi:10.1155/2019/4851323

Abstract

Glycation, oxidation, nitration, and crosslinking of proteins are implicated in the pathogenic mechanisms of type 2 diabetes, cardiovascular disease, and chronic kidney disease. Related modified amino acids formed by proteolysis are excreted in urine. We quantified urinary levels of these metabolites and branched-chain amino acids (BCAAs) in healthy subjects and assessed changes in early-stage decline in metabolic, vascular, and renal health and explored their diagnostic utility for a noninvasive health screen. We recruited 200 human subjects with early-stage health decline and healthy controls. Urinary amino acid metabolites were determined by stable isotopic dilution analysis liquid chromatography-tandem mass spectrometry. Machine learning was applied to optimise and validate algorithms to discriminate between study groups for potential diagnostic utility. Urinary analyte changes were as follows: impaired metabolic health—increased Nε-carboxymethyl-lysine, glucosepane, glutamic semialdehyde, and pyrraline; impaired vascular health—increased glucosepane; and impaired renal health—increased BCAAs and decreased Nε-(γ-glutamyl)lysine. Algorithms combining subject age, BMI, and BCAAs discriminated between healthy controls and impaired metabolic, vascular, and renal health study groups with accuracy of 84%, 72%, and 90%, respectively. In 2-step analysis, algorithms combining subject age, BMI, and urinary Nε-fructosyl-lysine and valine discriminated between healthy controls and impaired health (any type), accuracy of 78%, and then between types of health impairment with accuracy of 69%-78% (cf. random selection 33%). From likelihood ratios, this provided small, moderate, and conclusive evidence of early-stage cardiovascular, metabolic, and renal disease with diagnostic odds ratios of 6 – 7, 26 – 28, and 34 – 79, respectively. We conclude that measurement of urinary glycated, oxidized, crosslinked, and branched-chain amino acids provides the basis for a noninvasive health screen for early-stage health decline in metabolic, vascular, and renal health.

Highlights

Diabetes mellitus, cardiovascular disease (CVD), and chronic kidney disease (CKD) are major noncommunicable chronic diseases in adults linked to premature death and loss of productive life in Westernised countries
Advanced glycation end products (AGEs), formed by the degradation of proteins glycated by glucose and by the direct reaction of proteins with reactive dicarbonyl compounds such as methylglyoxal, have been proposed as both mediators of health decline leading to Type 2 diabetes mellitus (T2DM), CVD, and CKD [6,7,8]
Positive likelihood ratios suggested that the use of urinary excretion of branched-chain amino acids (BCAAs) and FL as features in diagnostic algorithms gave small, moderate, and conclusive evidence of increased likelihood of earlystage cardiovascular, metabolic, and renal disease, respectively

Summary

Introduction

Cardiovascular disease (CVD), and chronic kidney disease (CKD) are major noncommunicable chronic diseases in adults linked to premature death and loss of productive life in Westernised countries. Advanced glycation end products (AGEs), formed by the degradation of proteins glycated by glucose and by the direct reaction of proteins with reactive dicarbonyl compounds such as methylglyoxal, have been proposed as both mediators of health decline leading to T2DM, CVD, and CKD [6,7,8]. Examples of the latter are association of fructosamine-derived AGE, glucosepane, with development of T2DM [6] and association of increased formation of the methylglyoxal-derived AGE, hydroimidazolone MG-H1, with insulin resistance, risk of CVD, and development of CKD [9,10,11]. Measurement of urinary fluxes of oxidized and glycated amino acids gives an estimate of total body exposure to these adducts—except for Nε-fructosyl-lysine (FL) which may be further metabolised enzymatically [14]

Methods

Results

Conclusion