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Table 1 Association of D/D+L amino acid ratios with age in tooth dentin, normal cartilage, and paired osteoarthritic articular and meniscal cartilages

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

   Amino acid
   Asx Ser Leu Ile Glx Ala
Tooth
dentin
Mean D/D+L ratio 0.0599 0.0198 0.0105 0.0077 0.0137 0.0135
  r 2 0.961 0.827 0.349 0.018 0.014 0.002
  Slope e-105 65.2 30.5 6.9 -3.4 0.5 0.6
  P value <0.0001a <0.0001a 0.0019a 0.5246 0.5740 0.8497
Normal articular cartilage Mean D/D+L ratio 0.0463 0.0142 0.0117 0.0125 0.0125 0.0283
  r 2 0.778 0.470 0.287 0.060 0.194 0.001
  Slope e-105 35.2 18.4 11.6 0.7 2.3 -0.6
  P value <0.0001a 0.0012a 0.0181a 0.3136 0.0590 0.9410
OA
articular cartilage
Mean D/D+L ratio 0.0506 0.0120 0.0105    
  r 2 0.126 0.173 0.053    
  Slope e-105 16.0 7.0 6.0    
  P value 0.081 0.055 0.221    
OA
meniscal cartilage
Mean D/D+L ratio 0.0506 0.0127 0.0099    
  r 2 0.021 0.002 0.0099    
  Slope e-105 8.0 1.0 -3.0    
  P value 0.442 0.802 0.595    
  1. Dentin: n = 25 human tooth samples from subjects ranging in age from 13 to 80 years. Normal cartilage: n = 19 human surgical waste and autopsy samples from subjects ranging in age from 17 to 83 years. Osteoarthritic (OA) articular and meniscal cartilages: n = 30 paired human surgical waste samples from subjects ranging in age from 43 to 85 years. aDenotes significant age-related increase at P < 0.05. Ala, alanine; Asx, asparagine + aspartate; Glx, glutamate + glutamine; Ile, isoleucine; Leu, leucine; Ser, serine.