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Open Access Research article

Calcium-deficiency assessment and biomarker identification by an integrated urinary metabonomics analysis

Maoqing Wang1, Xue Yang1, Fan Wang2, Ran Li3, Hua Ning1, Lixin Na1, Yifan Huang1, Yue Song1, Liyan Liu1, Hongzhi Pan1, Qiuju Zhang4, Lijun Fan4, Ying Li1* and Changhao Sun1*

Author Affiliations

1 Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, 150081, P. R. China

2 Department of Epidemiology, School of Public Health, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, 150081, P. R. China

3 Department of Public Health Surveillance, Harbin Center for Disease Control and Prevention, 30 Weixing Road, Daowai District, 150056, Harbin, P. R. China

4 Department of Epidemiology and Biostatistics, School of Public Health, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, 150081, P. R. China

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BMC Medicine 2013, 11:86  doi:10.1186/1741-7015-11-86

Published: 28 March 2013

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.

Keywords:
biomarkers; calcium deficiency; metabonomics; UPLC/Q-TOF MS/MS; urine