title: Measurement of 1,5-anhydroglucitol in blood and saliva: from non-targeted metabolomics to biochemical assay.
abstract: Diabetes testing using saliva, rather than blood and urine, could facilitate diabetes screening in public spaces. We previously identified 1,5-anhydro-D-glucitol (1,5-AG) in saliva as a diabetes biomarker. The Glycomark™ assay kit is FDA approved for 1,5-AG measurement in blood. Here we evaluated its applicability for 1,5-AG quantification in saliva.
  
  
  
  Using pooled saliva samples, we validated Glycomark™ assay use with a RX Daytona(+) clinical chemistry analyser. We then used this set-up to analyse 82 paired blood and saliva samples from a diabetes case-control study, for which broad mass spectrometry-based characterization of the blood and saliva metabolome was also available. Osmolality was measured to account for potential variability in saliva samples.
  
  
  
  The technical variability of the read-outs for the pooled saliva samples (CV = 2.05 %) was comparable to that obtained with manufacturer-provided blood surrogate quality controls (CV = 1.38-1.8 %). We found a high correlation between Glycomark assay and mass spectrometry measurements of serum 1,5-AG (r(2) = 0.902), showing reproducibility of the non-targeted metabolomics results. The significant correlation between the osmolality measurements performed at two independent platforms with the time interval of 2 years (r(2) = 0.887), also indicates the sample integrity. The assay read-out for saliva was not correlated with the mass spectrometry-based 1,5-AG saliva measurements. Comparison with the full saliva metabolome revealed a high correlation of the saliva assay read-outs with galactose.
  
  
  
  Glycomark™ assay read-outs for saliva were stable and replicable. However, the signal was dominated by galactose, which is biochemically similar to 1,5-AG and absent in blood. Adapting the 1,5-AG kit for saliva analysis will require enzymatic depletion of galactose. This should be feasible, since the assay already includes a similar step for glucose depletion from blood samples.
authors.affiliation: Department of Physiology and Biophysics, Weill Cornell Medicine-Qatar, Qatar-Foundation, P.O Box: 24144, Doha, Qatar.
authors.forename: Anna
authors.initials: A
authors.lastname: Halama
authors.affiliation: Translational Research Institute, Academic Health System, Hamad Medical Corporation, PO Box 3050, Doha, Qatar.
authors.forename: Michal
authors.initials: M
authors.lastname: Kulinski
authors.affiliation: Department of Physiology and Biophysics, Weill Cornell Medicine-Qatar, Qatar-Foundation, P.O Box: 24144, Doha, Qatar.
authors.forename: Sara Abdul
authors.initials: SA
authors.lastname: Kader
authors.affiliation: Department of Physiology and Biophysics, Weill Cornell Medicine-Qatar, Qatar-Foundation, P.O Box: 24144, Doha, Qatar.
authors.forename: Noothan J
authors.initials: NJ
authors.lastname: Satheesh
authors.affiliation: Department of Internal Medicine, Hamad Medical Corporation, Doha, Qatar.
authors.forename: Abdul Badi
authors.initials: AB
authors.lastname: Abou-Samra
authors.affiliation: Department of Physiology and Biophysics, Weill Cornell Medicine-Qatar, Qatar-Foundation, P.O Box: 24144, Doha, Qatar. karsten@suhre.fr.|Institute of Bioinformatics and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany. karsten@suhre.fr.
authors.forename: Karsten
authors.initials: K
authors.lastname: Suhre
authors.affiliation: Translational Research Institute, Academic Health System, Hamad Medical Corporation, PO Box 3050, Doha, Qatar.
authors.forename: Ramzi M
authors.initials: RM
authors.lastname: Mohammad
mesh_terms: D000328:Adult; D000368:Aged; D001681:Biological Assay / Q000379:methods*; D003847:Deoxyglucose / Q000097:blood*; D005260:Female; D005690:Galactose / Q000378:metabolism; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D055442:Metabolome; D055432:Metabolomics / Q000379:methods*; D008875:Middle Aged; D009994:Osmolar Concentration; D012463:Saliva / Q000378:metabolism*
chemical_list: C006584:1,5-anhydroglucitol; D003847:Deoxyglucose; D005690:Galactose