title: Calcium-deficiency assessment and biomarker identification by an integrated urinary metabonomics analysis.
abstract: BACKGROUND
  Calcium deficiency is a global public-health problem. Although the initial stage of calcium deficiency can lead to metabolic alterations or potential pathological changes, calcium deficiency is difficult to diagnose accurately. Moreover, the details of the molecular mechanism of calcium deficiency remain somewhat elusive. To accurately assess and provide appropriate nutritional intervention, we carried out a global analysis of metabolic alterations in response to calcium deficiency.
  
  
  METHODS
  The metabolic alterations associated with calcium deficiency were first investigated in a rat model, using urinary metabonomics based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and multivariate statistical analysis. Correlations between dietary calcium intake and the biomarkers identified from the rat model were further analyzed to confirm the potential application of these biomarkers in humans.
  
  
  RESULTS
  Urinary metabolic-profiling analysis could preliminarily distinguish between calcium-deficient and non-deficient rats after a 2-week low-calcium diet. We established an integrated metabonomics strategy for identifying reliable biomarkers of calcium deficiency using a time-course analysis of discriminating metabolites in a low-calcium diet experiment, repeating the low-calcium diet experiment and performing a calcium-supplement experiment. In total, 27 biomarkers were identified, including glycine, oxoglutaric acid, pyrophosphoric acid, sebacic acid, pseudouridine, indoxyl sulfate, taurine, and phenylacetylglycine. The integrated urinary metabonomics analysis, which combined biomarkers with regular trends of change (types A, B, and C), could accurately assess calcium-deficient rats at different stages and clarify the dynamic pathophysiological changes and molecular mechanism of calcium deficiency in detail. Significant correlations between calcium intake and two biomarkers, pseudouridine (Pearson correlation, r = 0.53, P = 0.0001) and citrate (Pearson correlation, r = -0.43, P = 0.001), were further confirmed in 70 women.
  
  
  CONCLUSIONS
  To our knowledge, this is the first report of reliable biomarkers of calcium deficiency, which were identified using an integrated strategy. The identified biomarkers give new insights into the pathophysiological changes and molecular mechanisms of calcium deficiency. The correlations between calcium intake and two of the biomarkers provide a rationale or potential for further assessment and elucidation of the metabolic responses of calcium deficiency in humans.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, 150081, PR China.
authors.forename: Maoqing
authors.initials: M
authors.lastname: Wang
authors.forename: Xue
authors.initials: X
authors.lastname: Yang
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
authors.forename: Ran
authors.initials: R
authors.lastname: Li
authors.forename: Hua
authors.initials: H
authors.lastname: Ning
authors.forename: Lixin
authors.initials: L
authors.lastname: Na
authors.forename: Yifan
authors.initials: Y
authors.lastname: Huang
authors.forename: Yue
authors.initials: Y
authors.lastname: Song
authors.forename: Liyan
authors.initials: L
authors.lastname: Liu
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Pan
authors.forename: Qiuju
authors.initials: Q
authors.lastname: Zhang
authors.forename: Lijun
authors.initials: L
authors.lastname: Fan
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Changhao
authors.initials: C
authors.lastname: Sun
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000652:urine*; D002118:Calcium / Q000172:deficiency*; D002853:Chromatography, Liquid; D005260:Female; D006801:Humans; D008297:Male; D055442:Metabolome; D055432:Metabolomics / Q000379:methods; D008875:Middle Aged; D051381:Rats; D017208:Rats, Wistar; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014556:Urine / Q000737:chemistry*
chemical_list: D015415:Biomarkers; D002118:Calcium
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