Determination of asymmetric and symmetric dimethylarginines in human plasma by HPLC with electrochemical detection.

A new HPLC method was developed and validated for the determination of asymmetric and symmetric dimethylarginines and l-arginine in human plasma. After SPE and evaporation of the eluate, the samples were derivatised with an o-phthaldialdehyde reagent containing 3-mercaptopropionic acid. The derivatives formed were analysed by isocratic RP-HPLC with electrochemical detection at +320 mV. The mobile phase consisted of 50 mM phosphate buffer (pH 6.1) containing 10% v/v acetonitrile, the flow rate was 1 mL/min. The retention times of all compounds including monomethylarginine (internal standard) were <24 min. The LODs (S/N 3:1) were 0.012 µM for both dimethylarginines and 0.013 µM for L-arginine; the linearity of the method was from 0.1 to 20 µM for both dimethylarginines and from 1 to 200 µM for L-arginine. Absolute extraction recoveries measured for all analytes ranged from 85 to 88%.

ADMA, SDMA and L-arginine/ADMA ratio but not DDAH genetic polymorphisms are reliable predictors of diabetic nephropathy progression as identified by competing risk analysis.

BACKGROUND/AIMS: Complex interplay of genetic and (patho)physiological factors influence availability of nitric oxide during the development and progression of diabetic complications. We assessed predictive value of commonly studied methylated asymmetric and symmetric dimethylarginines (ADMA and SDMA) and selected single nucleotide polymorphisms (SNPs) in dimethylarginine dimethylaminohydrolase (DDAH) 1 and 2 genes for the progression of diabetic nephropathy (DN). METHODS: A total of 341 type 1 and type 2 diabetes patients with variable degree of kidney disease were included at baseline. Plasma levels of ADMA, SDMA and L-arginine were measured and six tagging SNPs in DDAH1 and 2 were determined. Progression of DN was defined as a transition from any given stage to a more advanced stage of albuminuria. Competing risk analysis was applied. RESULTS: Plasma levels of ADMA and SDMA significantly correlated with GFR. No significant genotype-phenotype relationship was ascertained for ADMA and DDAH variants, but SNP rs805304 exhibited marginally significant association with DN. ADMA, SDMA and L-arginine/ADMA ratio standardised to GFR were identified as significant predictors of DN progression but not GFR decline using multivariate competing risk analysis. CONCLUSIONS: In our study we confirmed potentially significant role of ADMA and SDMA for the assessment of risk of DN progression in European diabetic population.