Title:Role of Tyrosine Isomers in Acute and Chronic Diseases Leading to Oxidative Stress - A Review
Volume: 23
Issue: 7
Author(s): Gergő A. Molnár, Szilárd Kun, Eszter Sélley, Melinda Kertész, Lívia Szélig, Csaba Csontos, Katalin Böddi, Lajos Bogár, Attila Miseta and István Wittmann
Affiliation:
Keywords:
Meta-tyrosine, ortho-tyrosine, para-tyrosine, sepsis, inflammation, oxidative stress, hormone resistance,
carbohydrate metabolism.
Abstract: Oxidative stress plays a major role in the pathogenesis of a variety of acute and
chronic diseases. Measurement of the oxidative stress-related end products may be performed,
e.g. that of structural isomers of the physiological para-tyrosine, namely meta- and
ortho-tyrosine, that are oxidized derivatives of phenylalanine. Recent data suggest that in sepsis, serum level
of meta-tyrosine increases, which peaks on the 2nd and 3rd days (p<0.05 vs. controls), and the kinetics follows
the intensity of the systemic inflammation correlating with serum procalcitonin levels. In a similar study subset,
urinary meta-tyrosine excretion correlated with both need of daily insulin dose and the insulin-glucose
product in non-diabetic septic cases (p<0.01 for both). Using linear regression model, meta-tyrosine excretion,
urinary meta-tyrosine/para-tyrosine, urinary ortho-tyrosine/para-tyrosine and urinary (meta- + orthotyrosine)/
para-tyrosine proved to be markers of carbohydrate homeostasis.
In a chronic rodent model, we tried to compensate the abnormal tyrosine isomers using para-tyrosine, the
physiological amino acid. Rats were fed a standard high cholesterol-diet, and were given para-tyrosine or vehicle
orally. High-cholesterol feeding lead to a significant increase in aortic wall meta-tyrosine content and a
decreased vasorelaxation of the aorta to insulin and the glucagon-like peptide-1 analogue, liraglutide, that
both could be prevented by administration of para-tyrosine.
Concluding, these data suggest that meta- and ortho-tyrosine are potential markers of oxidative stress in acute
diseases related to oxidative stress, and may also interfere with insulin action in septic humans. Competition
of meta- and ortho-tyrosine by supplementation of para-tyrosine may exert a protective role in oxidative
stress-related diseases.
