Abstract
Summary
In 30 adults, increasing intake of aromatic amino acids increased calcium excretion and serum IGF-1, but not indices of bone turnover, when compared with similar increases in intake of branched-chain amino acids. The mechanisms involved are not certain but these findings suggest a role for the calcium sensor receptor.
Introduction
In contrast to branched-chain amino acids (BCAAs), aromatic amino acids (AAAs) bind to the calcium sensing receptor (CaR) and thus have an increased potential to affect calcium homeostasis. In this study we compare the effects of increased intake of AAAs versus BCAAs on calcium excretion, serum IGF-1, markers of bone turnover, and 4-hr calcium excretion after an oral calcium load.
Methods
After two weeks on low-protein metabolic diets, 30 healthy subjects were randomized to a fivefold increase in intake of AAAs or BCAAs for two weeks. Changes in calcium excretion and other measures were compared in the two groups.
Results
With the increase in amino acid intake, 24-hr calcium excretion (P = 0.027), IGF-1 (P = 0.022), and 4-hr calcium excretion after an oral load (P = 0.023) increased significantly in the AAA relative to the BCAA group. Group changes in turnover markers did not differ significantly.
Conclusion
In comparison with BCAAs, AAAs promoted calcium excretion. The calciuria does not appear to result from increases in bone resorption and may occur by increasing calcium absorption. The AAAs also increased circulating levels of IGF-1. Collectively these findings raise the possibility that AAAs may selectively influence calcium homeostasis through their interactions with the CaR.
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Acknowledgments
We are grateful to the staff of the Metabolic Research Unit at Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University for assistance in carrying out this study. BD-H, SH, HMR, and GED contributed to the design, analysis, and writing of the manuscript. BD-H obtained the funding. None of the authors had any conflicts of interest.
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This material is based on work supported by a Discovery Grant from Dairy Management, Inc. and by the U.S. Department of Agriculture under agreement No. 59-1950-9001. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors, and do not necessarily reflect the view of the U.S. Department of Agriculture.
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Dawson-Hughes, B., Harris, S.S., Rasmussen, H.M. et al. Comparative effects of oral aromatic and branched-chain amino acids on urine calcium excretion in humans. Osteoporos Int 18, 955–961 (2007). https://doi.org/10.1007/s00198-006-0320-x
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DOI: https://doi.org/10.1007/s00198-006-0320-x