Kidney stone disease affects nearly 10% of the US population and annually adds $5 billion in financial burden to the US healthcare system. Great strides have been made in the extraction of urinary stones, yet little progress has been made in understanding or preventing stone pathogenesis. While we send patient stones and urine for chemical analysis, the results typically have little impact on clinical decision-making. Techniques for stone analysis have not advanced and remain rudimentary, unreliable, and unreproducible. Moreover, traditional 24-hour urine testing does not correctly predict future stone events and thus has limited utility in preventing stone recurrence. The most common (~85%) of kidney stones are calcium-based stones, usually composed of calcium oxalate and/or calcium phosphate. Monitoring urinary calcium can be useful, but does not provide a complete assessment of risk, and modifying calcium intake in order to change whole body calcium homeostasis does not had a significant impact on stone formation. New biomarkers of kidney stone disease are needed to improve the clinical management of kidney stone disease. Our Developmental Center for Interdisciplinary Research in Benign Urology has recently shown that metals other than calcium, including zinc and strontium, play a surprisingly important role in nephrolithiasis, using a Drosophila melanogaster model of stone formation. For example, simply increasing dietary zinc strongly promotes stone formation while chelating zinc or inhibiting zinc transporters dramatically reduces the number of stones. Our proposal to renew funding for the Center aims to translate these findings to human kidney stone disease by focusing on confirming the importance of heavy metals in stone formation in a human cohort of patients and demonstrating the value of comprehensive metallomic and targeted metabolomics analysis of urine and stone samples for predicting symptomatic stone episodes. We will follow a homogenous group of calcium-based stone formers with hyperuricosuria and/or hypocitraturia in our urinary stone clinic at the University of California San Francisco. Stone and urine samples will be collected and analyzed for a broad metallomic and metabolomics panel at our Analytic Core Facility. The combined results of both the metallomic and metabolomic findings from human stones and urine will then allow us to model new diagnostic and therapeutic algorithms to augment or replace the 35-year-old testing method currently in practice. Our goal is to identify the optimal composition of metal and metabolite biomarkers to reveal new aspects of urinary stone pathophysiology and to develop practical diagnostic and therapeutic tools. These methods will create a much-needed modern resource for broad urology community and will provide the necessary scientific foundation to launch a large intervention study in patients with recurrent kidney stone disease
As part of clinical assessment, kidney stone patients routinely provide 24-hour urine collections for analyses. However, such analyses often do not accurately predict stone recurrence and, therefore, have limited value. Better metrics, detailed metallomic and metabolomic testing of urine and kidney stones will be used to help develop new diagnostic and therapeutic algorithms to better predict urinary stone recurrence.
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