Characterisation of Protein-damage-markers in the Plasma of Patients With Chronic-periodontitis

Objectives: Periodontitis is the most common inflammatory condition of man and has been shown to have significant inflammatory and oxidative stress components in its pathobiology. The aim of this study was to identify and quantify protein damage markers in plasma proteins of patients with periodontitis and healthy control subjects using gold standard techniques.
Methods: Plasma was collected from patients with chronic periodontitis (CP, n = 17, 9 males and 8 females; mean age 43 ± 11 years), defined by a minimum of two sites per quadrant with pocketing or interproximal attachment loss of >6 mm and one-third radiographic bone loss, and healthy controls (n = 16, 9 males and 7 female; mean age 50 ± 8 years). CP samples used in this study were from the ENERGISE study (NCT00952536, ethics approval 05/Q2707/252) in the unsupplemented arm. Plasma protein glycation, oxidation and nitration markers were analyzed using gold standard analytical liquid chromatography tandem mass spectrometric detection (LC-MS/MS) with stable isotope dilution analysis. Confidence score and ANOVA tests for all proteins were determined.
Results: Plasma protein content of early glycation adduct Nε-fructosyl-lysine (FL) was decreased 61% in periodontitis, with respect to health controls (p<0.001). Plasma protein advanced glycation endproducts (AGEs) were also changed with respect to health controls: Nε-carboxymethyl-lysine (CML) decreased 64% (p<0.001), 3-deoxyglucosone-derived hydroimidazolone increased by 93% (P<0.001). Markers of oxidative damage were increased: N-formylkynurenine (0.360 ± 0.378 vs 2.94 ± 0.45 mmol/mol trp, increased 8-fold; p<0.001) was highly significant in patients with periodontitis (p<0.001) and 3-nitrotyrosine (0.0053 ± 0.0033 vs 0.010 ± 0.002 mmol/mol tyr, increased 2-fold; p<0.01). No change was observed in the levels of methylglyoxal-derived AGEs, hydroimidazolone MG-H1 and Nε-(1-carboxyethyl) lysine.
Conclusions: Plasma protein glycation, oxidation and nitration of patients with periodontitis were apparent and may reflect increased oxidative stress, increased dicarbonyl glycation and increased albumin transcapillary escape.