Calcium bioavailability of functional foods and discovery of novel bone biomarkers using serum proteomic approach
Abstract
Osteoporosis is a serious threat to public health. The quantity and quality of dietary calcium intake play important roles in osteoporosis prevention. Functional foods containing active components promoting calcium absorption or high-quality calcium are useful sources to maximize calcium utilization through dietary modification. In the first study, the acute and chronic effects of whey proteins on calcium and bone metabolism were evaluated in growing rats. In acute studies, whey protein concentrates significantly enhanced calcium absorption. However, in a subsequent chronic feeding study, the acute calcium absorption enhancing effect disappeared, likely through an adaptation. In the second study, calcium (Ca) bioavailability from Ca carbonate fortified soymilk and tricalcium phosphate (TCP) fortified soymilk was compared with cow's milk in young healthy women using the dual stable isotope technique. Fractional Ca absorption determined from 24-h urine samples showed that Ca carbonate fortified soymilk had similar Ca bioavailability as that of cow's milk, but both were significantly higher than that of TCP fortified soymilk. In addition to the direct measurement of calcium metabolism, treatments can be evaluated by bone markers including tracers and biomarkers specific to bone. In the third study, we tested two tracers, 45Ca and 3H-tetracycline, for their utility as bone resorption markers. Bone resorption rates determined from urinary 45Ca and 3 H-tetracycline using kinetic modeling were similar. 45 Ca and 3H labeling efficiencies were significantly higher in trabecular-rich bones than cortical-rich bones. In the fourth study, serum proteomics was used to discover novel bone biomarkers with hindlimb unloaded (HU) rats. Bisphosphonate plus HU (HUA) was used to separate bone biomarkers from non-specific changes to bone. Unloading significantly decreased femur BMD and BNIC and increased bone resorption rate (urinary 3H-tetracycline) compared to control. Two-dimensional gels were performed on serum samples and analyzed by PDQuest for spot matching. A total of 53 spots were differentially expressed among the 3 groups. Thirty protein spots that had significantly different quantities in the HU group than either the control and the HUA groups followed the changes observed from bone and urine results. However, cross-examination of potential biomarkers on other established bone models is essential to confirm the findings.
Degree
Ph.D.
Advisors
Weaver, Purdue University.
Subject Area
Nutrition
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