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Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages

INTRODUCTION: Certain amino acids within proteins have been reported to change from the L form to the D form over time. This process is known as racemization and is most likely to occur in long-lived low-turnover tissues such as normal cartilage. We hypothesized that diseased tissue, as found in an...

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Autores principales: Stabler, Thomas V, Byers, Samuel S, Zura, Robert D, Kraus, Virginia Byers
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2009
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2688179/
https://www.ncbi.nlm.nih.gov/pubmed/19267899
http://dx.doi.org/10.1186/ar2639
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author Stabler, Thomas V
Byers, Samuel S
Zura, Robert D
Kraus, Virginia Byers
author_facet Stabler, Thomas V
Byers, Samuel S
Zura, Robert D
Kraus, Virginia Byers
author_sort Stabler, Thomas V
collection PubMed
description INTRODUCTION: Certain amino acids within proteins have been reported to change from the L form to the D form over time. This process is known as racemization and is most likely to occur in long-lived low-turnover tissues such as normal cartilage. We hypothesized that diseased tissue, as found in an osteoarthritic (OA) joint, would have increased turnover reflected by a decrease in the racemized amino acid content. METHODS: Using high-performance liquid chromatography methods, we quantified the L and D forms of amino acids reported to racemize in vivo on a biological timescale: alanine, aspartate (Asp), asparagine (Asn), glutamate, glutamine, isoleucine, leucine (Leu), and serine (Ser). Furthermore, using a metabolically inactive control material (tooth dentin) and a control material with normal metabolism (normal articular cartilage), we developed an age adjustment in order to make inferences about the state of protein turnover in cartilage and meniscus. RESULTS: In the metabolically inactive control material (n = 25, ages 13 to 80 years) and the normal metabolizing control material (n = 19, ages 17 to 83 years), only Asp + Asn (Asx), Ser, and Leu showed a significant change (increase) in racemization with age (P < 0.01). The age-adjusted proportions of racemized to total amino acid (D/D+L expressed as a percentage of the control material) for Asx, Ser, and Leu when compared with the normal articular cartilage control were 97%, 74%, and 73% in OA meniscal cartilage and 97%, 70%, and 78% in OA articular cartilage. We also observed lower amino acid content in OA articular and meniscal cartilages compared with normal articular cartilage as well as a loss of total amino acids with age in the OA meniscal but not the OA articular cartilage. CONCLUSIONS: These data demonstrate comparable anabolic responses for non-lesioned OA articular cartilage and OA meniscal cartilage but an excess of catabolism over anabolism for the meniscal cartilage.
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spelling pubmed-26881792009-05-29 Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages Stabler, Thomas V Byers, Samuel S Zura, Robert D Kraus, Virginia Byers Arthritis Res Ther Research Article INTRODUCTION: Certain amino acids within proteins have been reported to change from the L form to the D form over time. This process is known as racemization and is most likely to occur in long-lived low-turnover tissues such as normal cartilage. We hypothesized that diseased tissue, as found in an osteoarthritic (OA) joint, would have increased turnover reflected by a decrease in the racemized amino acid content. METHODS: Using high-performance liquid chromatography methods, we quantified the L and D forms of amino acids reported to racemize in vivo on a biological timescale: alanine, aspartate (Asp), asparagine (Asn), glutamate, glutamine, isoleucine, leucine (Leu), and serine (Ser). Furthermore, using a metabolically inactive control material (tooth dentin) and a control material with normal metabolism (normal articular cartilage), we developed an age adjustment in order to make inferences about the state of protein turnover in cartilage and meniscus. RESULTS: In the metabolically inactive control material (n = 25, ages 13 to 80 years) and the normal metabolizing control material (n = 19, ages 17 to 83 years), only Asp + Asn (Asx), Ser, and Leu showed a significant change (increase) in racemization with age (P < 0.01). The age-adjusted proportions of racemized to total amino acid (D/D+L expressed as a percentage of the control material) for Asx, Ser, and Leu when compared with the normal articular cartilage control were 97%, 74%, and 73% in OA meniscal cartilage and 97%, 70%, and 78% in OA articular cartilage. We also observed lower amino acid content in OA articular and meniscal cartilages compared with normal articular cartilage as well as a loss of total amino acids with age in the OA meniscal but not the OA articular cartilage. CONCLUSIONS: These data demonstrate comparable anabolic responses for non-lesioned OA articular cartilage and OA meniscal cartilage but an excess of catabolism over anabolism for the meniscal cartilage. BioMed Central 2009 2009-03-06 /pmc/articles/PMC2688179/ /pubmed/19267899 http://dx.doi.org/10.1186/ar2639 Text en Copyright © 2009 Stabler et al.; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an open access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Stabler, Thomas V
Byers, Samuel S
Zura, Robert D
Kraus, Virginia Byers
Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
title Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
title_full Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
title_fullStr Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
title_full_unstemmed Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
title_short Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
title_sort amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2688179/
https://www.ncbi.nlm.nih.gov/pubmed/19267899
http://dx.doi.org/10.1186/ar2639
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