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Re: N-Glycosylation Critically Regulates Function of Oxalate Transporter SLC26A6
Urological Survey Urolithiasis/Endourology Re: Molecular Modifiers Reveal a Mechanism of Pathological Crystal Growth Inhibition J. Chung, I. Granja, M. G. Taylor, G. Mpourmpakis, J. R. Asplin and J. D. Rimer Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, Litholink Corp., Laboratory Corp. of America Holdings, Chicago, Illinois, and Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania Nature 2016; 536: 446e450. doi: 10.1038/nature19062
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27501150 Editorial Comment: These investigators demonstrated that in in vitro studies citrate and hydroxycitrate can inhibit the nucleation of calcium oxalate monohydrate via crystal dissolution even in supersaturated conditions. This action is thought to be due to a reduction in strain in the crystal lattice. Hydroxycitrate is not normally detected in urine. This group administered Garcinia cambogia, a fruit with a high content of hydroxycitrate, to nonkidney stone forming humans, which resulted in hydroxycitrate detection in the urine. These investigators demonstrated a new mechanism of crystal inhibition and a potential agent to prevent stone formation. Studies to assess the metabolism of hydroxycitrate and its safety profile are needed. Dean G. Assimos, MD
Suggested Reading Grases F, Rodriguez A and Costa-Bauza A: Efficacy of mixtures of magnesium, citrate and phytate as calcium oxalate crystallization inhibitors in urine. J Urol 2015; 194: 812. Bergsland KJ, Kinder JM, Asplin JR et al: Influence of gender and age on calcium oxalate crystal growth inhibition by urine from relatives of stone forming patients. J Urol 2002; 167: 2372. Bouropoulos K, Bouropoulos N, Melekos M et al: The inhibition of calcium oxalate monohydrate crystal growth by maleic acid copolymers. J Urol 1998; 159: 1755.
Re: N-Glycosylation Critically Regulates Function of Oxalate Transporter SLC26A6 R. B. Thomson, C. L. Thomson and P. S. Aronson Yale School of Medicine Am J Physiol Cell Physiol 2016; Epub ahead of print. doi: 10.1152/ajpcell.00171.2016
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27681177 Editorial Comment: SLC26A6 (PAT1) is a chloride oxalate transporter that promotes intestinal oxalate secretion. When this gene is knocked out in mice, it results in increased plasma oxalate levels and hyperoxaluria. These investigators showed in cell culture experiments that the function of this transporter is impacted by glycosylation. This finding has significant translational implications and
0022-5347/17/1972-0411/0 THE JOURNAL OF UROLOGY® Ó 2017 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
AND
RESEARCH, INC.
http://dx.doi.org/10.1016/j.juro.2016.11.015 Vol. 197, 411-413, February 2017 Printed in U.S.A.
www.jurology.com
j
411
UROLITHIASIS/ENDOUROLOGY
412
may explain differences in net intestinal oxalate absorption in humans. There is also a potential link to the fecal microbiome, which has organisms that may promote deglycosylation. This may prove to be a significant translational research platform. Dean G. Assimos, MD
Suggested Reading Voss S, Hesse A, Zimmermann DJ et al: Intestinal oxalate absorption is higher in idiopathic calcium oxalate stone formers than in healthy controls: measurements with the [13C2]oxalate absorption test. J Urol 2006; 175: 1711. von Unruh GE, Voss S, Sauerbruch T et al: Reference range for gastrointestinal oxalate absorption measured with a standardized [13C2]oxalate absorption test. J Urol 2003; 169: 687.
Re: Patients Attending Shared Medical Appointments for Metabolic Stone Prevention have Decreased Stone Risk Factors R. A. Jhagroo, S. Y. Nakada and K. L. Penniston Department of Medicine, Division of Nephrology and Department of Urology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin J Endourol 2016; Epub ahead of print. doi: 10.1089/end.2016.0500
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27673722 Editorial Comment: This group previously reported on the shared medical appointments for stone prevention and found that patients were satisfied with this approach. In this study they analyzed changes in 24-hour urinary stone risk parameters in those who had individualized appointments and those who participated in shared visits. Improvements were seen in both groups, and patient satisfaction was for the most part similar. Shared appointments have been used for other urological disease processes and are an efficient way of providing access to care. Differences in stone recurrence between these 2 approaches need to be assessed. Dean G. Assimos, MD
Suggested Reading Jhagroo RA, Nakada SY and Penniston KL: Shared medical appointments for patients with kidney stones new to medical management decrease appointment wait time and increase patient knowledge. J Urol 2013; 190: 1778. Pearle MS, Goldfarb DS, Assimos DG et al: Medical management of kidney stones: AUA guideline. J Urol 2014; 192: 316.
Re: Response of Germ-Free Mice to Colonization with O. formigenes and Altered Schaedler Flora X. Li, M. L. Ellis, A. E. Dowell, R. Kumar, C. D. Morrow, T. R. Schoeb and J. Knight Department of Urology, Center for Clinical and Translational Science, and Department of Cell, Developmental and Integrative Biology, Genetics Research Division, University of Alabama at Birmingham, Birmingham, Alabama Appl Environ Microbiol 2016; Epub ahead of print. doi: 10.1128/AEM.02381-16
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27663026 Editorial Comment: Oxalobacter formigenes is an anaerobic bacterium whose main carbon source is oxalate. Lack of fecal colonization with this organism is a risk factor for recurrent calcium oxalate stone formation. The authors studied the biology of O. formigenes in germ-free and altered Schaedler flora (ASF) mice. They demonstrated that this organism effectively degrades oxalate in the intestine and ASF bacteria do not. They also showed that ASF bacteria may bolster the integrity of the intestinal epithelium and perhaps limit paracellular oxalate transport. They also found that O. formigenes may survive in an aerobic environment. This is an excellent model to study the biological impact of this organism. Dean G. Assimos, MD
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27501150 Editorial Comment: These investigators demonstrated that in in vitro studies citrate and hydroxycitrate can inhibit the nucleation of calcium oxalate monohydrate via crystal dissolution even in supersaturated conditions. This action is thought to be due to a reduction in strain in the crystal lattice. Hydroxycitrate is not normally detected in urine. This group administered Garcinia cambogia, a fruit with a high content of hydroxycitrate, to nonkidney stone forming humans, which resulted in hydroxycitrate detection in the urine. These investigators demonstrated a new mechanism of crystal inhibition and a potential agent to prevent stone formation. Studies to assess the metabolism of hydroxycitrate and its safety profile are needed. Dean G. Assimos, MD
Suggested Reading Grases F, Rodriguez A and Costa-Bauza A: Efficacy of mixtures of magnesium, citrate and phytate as calcium oxalate crystallization inhibitors in urine. J Urol 2015; 194: 812. Bergsland KJ, Kinder JM, Asplin JR et al: Influence of gender and age on calcium oxalate crystal growth inhibition by urine from relatives of stone forming patients. J Urol 2002; 167: 2372. Bouropoulos K, Bouropoulos N, Melekos M et al: The inhibition of calcium oxalate monohydrate crystal growth by maleic acid copolymers. J Urol 1998; 159: 1755.
Re: N-Glycosylation Critically Regulates Function of Oxalate Transporter SLC26A6 R. B. Thomson, C. L. Thomson and P. S. Aronson Yale School of Medicine Am J Physiol Cell Physiol 2016; Epub ahead of print. doi: 10.1152/ajpcell.00171.2016
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27681177 Editorial Comment: SLC26A6 (PAT1) is a chloride oxalate transporter that promotes intestinal oxalate secretion. When this gene is knocked out in mice, it results in increased plasma oxalate levels and hyperoxaluria. These investigators showed in cell culture experiments that the function of this transporter is impacted by glycosylation. This finding has significant translational implications and
0022-5347/17/1972-0411/0 THE JOURNAL OF UROLOGY® Ó 2017 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
AND
RESEARCH, INC.
http://dx.doi.org/10.1016/j.juro.2016.11.015 Vol. 197, 411-413, February 2017 Printed in U.S.A.
www.jurology.com
j
411
UROLITHIASIS/ENDOUROLOGY
412
may explain differences in net intestinal oxalate absorption in humans. There is also a potential link to the fecal microbiome, which has organisms that may promote deglycosylation. This may prove to be a significant translational research platform. Dean G. Assimos, MD
Suggested Reading Voss S, Hesse A, Zimmermann DJ et al: Intestinal oxalate absorption is higher in idiopathic calcium oxalate stone formers than in healthy controls: measurements with the [13C2]oxalate absorption test. J Urol 2006; 175: 1711. von Unruh GE, Voss S, Sauerbruch T et al: Reference range for gastrointestinal oxalate absorption measured with a standardized [13C2]oxalate absorption test. J Urol 2003; 169: 687.
Re: Patients Attending Shared Medical Appointments for Metabolic Stone Prevention have Decreased Stone Risk Factors R. A. Jhagroo, S. Y. Nakada and K. L. Penniston Department of Medicine, Division of Nephrology and Department of Urology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin J Endourol 2016; Epub ahead of print. doi: 10.1089/end.2016.0500
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27673722 Editorial Comment: This group previously reported on the shared medical appointments for stone prevention and found that patients were satisfied with this approach. In this study they analyzed changes in 24-hour urinary stone risk parameters in those who had individualized appointments and those who participated in shared visits. Improvements were seen in both groups, and patient satisfaction was for the most part similar. Shared appointments have been used for other urological disease processes and are an efficient way of providing access to care. Differences in stone recurrence between these 2 approaches need to be assessed. Dean G. Assimos, MD
Suggested Reading Jhagroo RA, Nakada SY and Penniston KL: Shared medical appointments for patients with kidney stones new to medical management decrease appointment wait time and increase patient knowledge. J Urol 2013; 190: 1778. Pearle MS, Goldfarb DS, Assimos DG et al: Medical management of kidney stones: AUA guideline. J Urol 2014; 192: 316.
Re: Response of Germ-Free Mice to Colonization with O. formigenes and Altered Schaedler Flora X. Li, M. L. Ellis, A. E. Dowell, R. Kumar, C. D. Morrow, T. R. Schoeb and J. Knight Department of Urology, Center for Clinical and Translational Science, and Department of Cell, Developmental and Integrative Biology, Genetics Research Division, University of Alabama at Birmingham, Birmingham, Alabama Appl Environ Microbiol 2016; Epub ahead of print. doi: 10.1128/AEM.02381-16
Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27663026 Editorial Comment: Oxalobacter formigenes is an anaerobic bacterium whose main carbon source is oxalate. Lack of fecal colonization with this organism is a risk factor for recurrent calcium oxalate stone formation. The authors studied the biology of O. formigenes in germ-free and altered Schaedler flora (ASF) mice. They demonstrated that this organism effectively degrades oxalate in the intestine and ASF bacteria do not. They also showed that ASF bacteria may bolster the integrity of the intestinal epithelium and perhaps limit paracellular oxalate transport. They also found that O. formigenes may survive in an aerobic environment. This is an excellent model to study the biological impact of this organism. Dean G. Assimos, MD