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Symmetric dimethylarginine, an endogenous marker of glomerular filtration rate, and the risk for microalbuminuria in young people with type 1 diabetes
  1. M Loredana Marcovecchio1,
  2. R Neil Dalton2,
  3. Charles Turner2,
  4. A Toby Prevost3,
  5. Barry Widmer1,
  6. Rakesh Amin1,
  7. David B Dunger1
  1. 1Department of Paediatrics and Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge, UK
  2. 2WellChild Laboratory, King’s College London, Evelina Children’s Hospital, London, UK
  3. 3Centre for Applied Medical Statistics, Institute of Public Health, University of Cambridge, Cambridge, UK
  1. Correspondence to Professor David B Dunger, University Department of Paediatrics, Level 8, Box 116, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 0QQ, UK; dbd25{at}cam.ac.uk

Abstract

Objectives To perform a cross-sectional comparison of endogenous markers of glomerular filtration rate (GFR) (plasma symmetric dimethylarginine (SDMA) and estimated GFR (eGFR)) with a direct measure of GFR (using the plasma clearance of Inutest (In-GFR)), and a longitudinal evaluation of these markers in relation to the development of microalbuminuria, in young people with type 1 diabetes (T1D).

Methods Longitudinal stored blood samples (n=1105) were available from 417 young people from the Oxford Regional Prospective Study (an inception cohort of 527 children followed for a median of 10.3 (interquartile range 7.1–12.3) years), for measurement of SDMA and creatinine. Additional annually collected data on anthropometric parameters, HbA1c, insulin dose and three early morning albumin:creatinine ratios were available. In-GFR was measured in a representative subgroup of 183 subjects.

Main outcome measures SDMA and eGFR.

Results SDMA and eGFR were significantly and similarly associated with In-GFR (r=−0.38 and r=0.36, p<0.001). Overall SDMA levels were lower in microalbuminuric (n=116) than normoalbuminuric subjects (n=301) (0.385±0.063 vs 0.412±0.059 µmol/l, p<0.001), probably reflecting hyperfiltration. The pattern of change in SDMA levels with age differed between microalbuminuric and normoalbuminuric subjects. Whereas SDMA levels declined in both groups until the age of 16 years, thereafter they tended to rise only in microalbuminuric subjects, probably reflecting a decline in renal function.

Conclusions In this longitudinal study of young people with T1D, measurement of SDMA, in contrast to eGFR, proved to be a reliable marker in identifying changes in filtration rates associated with the development of microalbuminuria (MA).

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Footnotes

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the district ethics committee in the Oxford region.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Funding The Oxford Regional Prospective Study is funded by Diabetes UK. In addition, this study was supported (in part) by a European Society for Pediatric Endocrinology Research Fellowship, sponsored by Novo Nordisk A/S (to MLM).

  • Patient consent Obtained.

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