Abstract
BackgroundWe previously identified the urinary biomarkers to diagnose calcium deficiency and nutritional rickets by ultra-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF MS/MS). To find biomarkers of calcium deficiency and further confirm these biomarkers in serum, we performed serum metabolomics analysis of calcium-deficient rats.MethodsA calcium-deficient rat model was established with a low-calcium diet for 12 weeks. Serum metabolomics based UPLC/Q-TOF MS/MS and multivariate statistical analysis was performed to identify the alterations in metabolites associated with calcium deficiency in rats.ResultsBone mineral density, serum parathyroid hormone and alkaline phosphatase were significantly decreased in the low-calcium diet group (LCG) compared to the normal calcium diet group (NCG). Serum metabolic-profiling analysis could definitively distinguish between the LCG and NCG and identified 24 calcium-deficient biomarkers. Three metabolites (indoxyl sulfate, phosphate, and taurine) of the 24 biomarkers were found in our previous urinary metabolomics study of rats with a calcium deficiency and nutritional rickets. The areas under the curve (AUCs) of these three biomarkers were greater than 0.8, and the combination of any two biomarkers was higher than 0.95.ConclusionDietary calcium deficiency induced the alterations of metabolites in the serum of rats, and the three identified biomarkers had relatively high diagnostic values for calcium deficiency in rats.
Highlights
Calcium is a major constituent of bones and teeth and plays an essential role as a second messenger in cellsignaling pathways [1]
Biochemical analysis and bone mineral density (BMD) Compared with the normal calcium diet group (NCG), significant differences for serum parathyroid hormone (PTH), alkaline phosphatase (AP) and BMD were observed in the low-calcium diet group (LCG) (Table 1)
The serum samples of rats were analyzed by ultra-performance liquid chromatography/quadrupole time-offlight tandem mass spectrometry (UPLC/Q-TOF MS/ MS) in the positive (electrospray ionization (ESI)+) and negative ion (ESI−) modes
Summary
Calcium is a major constituent of bones and teeth and plays an essential role as a second messenger in cellsignaling pathways [1]. Calcium deficiency is a worldwide nutritional-deficiency public-health problem [2]. Meng et al Nutr Metab (Lond) (2020) 17:99 diagnosis and discovery of calcium deficiency is necessary for therapy. The above methods have their limitations and cannot be widely used in population research, especially for slight calcium deficiency [14, 15]. Decreased BMD is the result of long-term calcium deficiency. When serum calcium and BMD change significantly, the body’s calcium deficiency is already severe, causing some irreversible pathological changes to the body. It is necessary to find new calcium-deficient biomarkers and establish a rapid, sensitive and specific method for evaluation of calcium nutritional status. We previously identified the urinary biomarkers to diagnose calcium deficiency and nutritional rickets by ultra-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF MS/MS). To find biomarkers of calcium deficiency and further confirm these biomarkers in serum, we performed serum metabolomics analysis of calcium-deficient rats
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