Amino acid racemization reveals differential protein turnover in osteoarthritic articular and meniscal cartilages.
Abstract
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.
Type
Journal articleSubject
AdultAge Factors
Aged
Aged, 80 and over
Amino Acids
Cartilage, Articular
Chromatography, High Pressure Liquid
Dentin
Humans
Isomerism
Menisci, Tibial
Middle Aged
Osteoarthritis, Knee
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https://hdl.handle.net/10161/10861Published Version (Please cite this version)
10.1186/ar2639Publication Info
Stabler, Thomas V; Byers, Samuel S; Zura, Robert D; & Kraus, Virginia Byers (2009). Amino acid racemization reveals differential protein turnover in osteoarthritic articular
and meniscal cartilages. Arthritis Res Ther, 11(2). pp. R34. 10.1186/ar2639. Retrieved from https://hdl.handle.net/10161/10861.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Virginia Byers Kraus
Professor of Medicine
My special area of expertise is as a clinician scientist investigating osteoarthritis.
Osteoarthritis is the most common form of joint disease in man and its incidence increases
with age. It is a problem of increasing concern to the medical community due to the
increasing longevity of the population. Trained as a molecular biologist and a Rheumatologist,
I endeavor to study this disease from bedside to bench. The work in this laboratory
focuses on osteoarthritis and deals w
Robert Douglas Zura
Associate Professor of Orthopaedic Surgery
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