Effect of Irbesartan treatment on plasma and urinary markers of protein damage in patients with type 2 diabetes and microalbuminuria.

Naila Rabbani, Antonysunil Adaikalakoteswari, Kasper Rossing, Peter Rossing, Lise Tarnow, Hans-Henrik Parving, Paul J Thornalley

Index: Amino Acids 42(5) , 1627-39, (2012)

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Abstract

The aim of this study was to assess the effect of the angiotensin II receptor blocker Irbesartan on protein damage by glycation, oxidation and nitration in patients with type 2 diabetes and microalbuminuria. In a double-masked randomised crossover trial of 52 hypertensive type 2 diabetic patients, antihypertensive treatment was replaced with bendroflumethiazide. After 2-months wash-out, patients were treated randomly with Irbesartan 300, 600, and 900 mg o.d., each dose for 2 months in a three-way crossover study. Glycation, oxidation and nitration adduct residues in plasma protein and related urinary free adducts were determined by stable isotopic dilution analysis liquid chromatography-tandem mass spectrometry. Treatment with Irbesartan decreased urinary excretion of advanced glycation endproducts (AGEs)--methylglyoxal- and glyoxal-derived hydroimidazolones, MG-H1 and G-H1. Urinary AGEs were decreased by 30-32%. In plasma protein, treatment with Irbesartan increased content of glycation adducts Nε-fructosyl-lysine, AGEs Nε-carboxymethyl-lysine, Nε-carboxyethyl-lysine and pentosidine, and also increased content of oxidation markers N-formylkynurenine and dityrosine. This was attributed to decreased clearance of plasma protein modified by Nε-fructosyl-lysine and oxidative markers through the glomerular filter tightened by Irbesartan treatment. Treatment of patients with type 2 diabetes with Irbesartan decreased urinary excretion of MG-H1, G-H1 and 3-NT, which may result from decreased exposure to these AGEs. This is likely achieved by blocking angiotensin II signalling and related down-regulation of glyoxalase 1 and may contribute to health benefits of Irbesartan therapy.