MSACL 2023 Abstract

Plasma Arginine Metabolites in Health and Chronic Kidney Disease

Amy YM Au*(1,2), Kevin Mantik*(3), Forough Bahadory (3), Paul Stathakis (3), Hayley Guiney (4), Jonathan Erlich(1,2), Robert Walker (5), Richie Poulton (4), Andrea Rita Horvath (3), and Zoltan H Endre(1,2) *co-first authors
(1) Department of Nephrology, Prince of Wales Hospital, Sydney, Australia (2) Prince of Wales Clinical School, University of New South Wales, Sydney, Australia (3) Department of Chemical Pathology, New South Wales Health Pathology, Prince of Wales Hospital, Sydney, Australia (4) Department of Psychology, Dunedin Multidisciplinary Health and Development Research Unit, University of Otago, Dunedin, New Zealand (5) Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand

Kevin Mantik, BSc (Presenter) New South Wales Health Pathology, Sydney, Australia >> POSTER (PDF)

Presenter Bio: My current position includes the management of a team at the Clinical Mass Spectrometry section, Chemical Pathology, Prince of Wales Hospital. This role involves the development and validation of clinical assays, and giving oversight to the: technical, operational, quality and regulatory integrity of the department.

Our specialised analyses include: biogenic amines, steroid hormone profiling, vitamins including phylloquinone (Vit K), mercaptopurines, immunosuppressants, and IGF-1. Areas of research and collaboration span from: serum steroid profiling, oncometabolites and TCA cycle intermediates, Nitric Oxide markers in CKD and cardiovascular health, paracetamol metabolites, protein and peptide applications.

Relevant Financial Disclosures (within past 24 months, reported on Dec 01, 2022) No relevant financial relationship(s) to disclose. Conflict mitigation NOT REQUIRED.

Introduction:
Methylated arginines, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), cause aberrant vascular remodelling by inhibition of nitric oxide synthesis and have been shown to predict chronic kidney disease (CKD) and cardiovascular disease (CVD). The occurrence of CKD is underestimated due to the lack of sufficiently sensitive and specific markers that can be used to detect early renal dysfuction.
Objectives: The aim of this study was to validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine ADMA, SDMA, L-Arginine and L-Citrulline, in a large cohort of healthy adults. This method was then applied to a group of CKD patients, and then a high-risk group within the large cohort.

Methods:
We tested 857 men and women aged 45 from the Dunedin Multidisciplinary Health and Development Study (DHMDS) in New Zealand. Within this group we defined a healthy population (n = 376) by excluding smokers, those who use specific medications, self-reported, or tested for heart problems, high blood pressure, diabetes or CKD. We then tested a separate cohort of known CKD patients (n = 38). We also used an estimated glomerular filtration rate (eGFR) trajectory analysis based on plasma cystatin C, and defined study members at higher risk of CKD amongst the individuals in the DMHDS cohort.

Results:
Contrary to previously described methods, specificity was enhanced by complete separation (peak resolution, Rs = 1.8) between the structural isomers, ADMA and SDMA, without the use of derivatisation. We found all analytes were elevated in CKD compared to our healthy cohort (ADMA: 0.61±0.11 μmol/L vs 0.40±0.06 μmol/L, SDMA: 0.65±0.25 vs 0.42±0.06 μmol/L, and citrulline: 42.7±11.8 vs 24.0±5.4 μmol/L), however L-arginine concentration was only slightly higher in the CKD subset. The values from the healthy cohort aligned with previously published reference intervals. Regarding the kidney-function trajectory groups within the DMHD study, significant elevations for ADMA (0.40±0.07 μmol/L), SDMA (0.49±0.08 μmol/L), and L-Citrulline (28.6±7.45 μmol/L), were observed in the high-risk group.

Conclusion:
The LC-MS/MS method developed for simultaneously measuring ADMA, SDMA, Arginine and Citrulline will be used in prospective studies investigating the progression of CKD.