Urinary ortho-tyrosine excretion in diabetes mellitus and renal failure: Evidence for hydroxyl radical production

Abstract

The difference between para-tyrosine levels of the groups is probably due to renal impairment, while there is indirect evidence for an increased tubular secretion or production of ortho-tyrosine in the kidney in diabetic patients with or without CKD.

Incorporation of Ortho- and Meta-Tyrosine Into Cellular Proteins Leads to Erythropoietin-Resistance in an Erythroid Cell Line

“…The supernatant was filtered by a syringe filter (0.2 µm) before analysis. Finally para-, ortho- and meta -tyrosine levels were determined using reverse phase-HPLC (C 18 silica column, 250x4 mm) with fluorescence detection (λ EX =275 nm; λ EM =305 nm) as described earlier [19]. Concentrations were calculated using an external standard.…”

“…Using immunoblot analysis, they found impaired ERK and STAT3 activation in the presence of meta-tyrosine [18]. Molnar et al found significantly lower para-tyrosine level, and also a non-significant, but obviously higher plasma ortho-tyrosine level in patients with CKD [19]. According to the recent work of our group, on the one hand para-tyrosine level was significantly lower, on the other hand meta- and ortho-tyrosine levels were significantly higher in dialyzed patients compared to control groups (data under publication).…”

Microalbuminuria, Indicated by Total versus Immunoreactive Urinary Albumins, in Acute Ischemic Stroke Patients

“…3,[13][14][15][16][17][18][19][20][21] In many disease conditions, endothelial dysfunction and increased permeability is caused by increased oxidative stress, [22][23][24] which is indicated by an increased urinary level of amino acid oxidation products, such as ortho-tyrosine (o-Tyr), a stable and specific marker of free radical production. 25,26 In the urine, total albumin (t-uAlb) has 2 forms, [27][28][29][30] immunologically intact albumin (immunoreactive albumin [ir-uAlb]) and the modified form of albumin without epitopes (nonimmunoreactive albumin [nir-uAlb]). 27,[31][32][33] In clinical practice, standard immunochemical urinary albumin assays include immunoturbidimetry (IT), which detects ir-uAlb and is used to establish the diagnosis of microalbuminuria.…”

Assessment of microvascular reactivity and oxidative stress in hypertensive adolescents and hemodialysis patients

“…Such modifications can be detected in cardiovascular (e.g. hypertension, obesity and atherosclerosis), renal (chronic kidney disease (CKD) and end-stage renal disease (ESRD)) and pulmonary diseases (for example asthma and cystic fibrosis), and also in cancer and diabetes [1][2][3][4][5][6][7]. These modified molecules can serve as representative biomarkers of the oxidative/nitrosative damage involved in the pathophysiology of the diseases [4].…”

“…ROS also attack polyunsaturated fatty acid residues of phospholipids, resulting in a decreased membrane fluidity, increased leakiness of the membrane, and inactivation of receptors and ion channels, as well as the formation of lipid peroxides and their by-products malondialdehyde (MDA), 4-hydroxy-2-nonenal (both mutagenic and toxic) and F 2 -isoprostanes ( Figure 1) [1][2][3]. Additionally, ROS and RNS may induce damage to proteins, either reversible (such as the formation of mixed disulfides between protein thiol groups and low-molecular-weight thiols, in particular GSH (S-glutathionylation)) or irreversible (carbonylation, nitrosylation and hydroxylation, resulting in generation of carbonylated proteins, nitrotyrosine, 3,4-dihydroxy-phenylalanine, ortho-tyrosine and meta-tyrosine) [1, 5,6]. Such modifications can be detected in cardiovascular (e.g.…”