Age-related decrease in the activity of UDP-xylose:core protein xylosyltransferase in rat costal cartilage

Area of Science:

• Biochemistry
• Connective Tissue Research
• Aging Biology

Background:

• Cartilage aging involves changes in extracellular matrix composition and enzyme activity.
• UDP-xylose:core protein xylosyltransferase (XT) is crucial for proteoglycan synthesis.

Purpose of the Study:

• To investigate the age-related changes in XT activity in rat costal cartilage.
• To determine the relationship between XT activity and proteoglycan content in young versus old rats.

Main Methods:

• Enzyme activity assays for UDP-xylose:core protein xylosyltransferase (EC 2.4.2.26).
• Quantification of galactosamine-containing proteoglycans using 4 M guanidinium chloride extraction.
• Comparison of enzyme activity and proteoglycan levels in young (3 months) and old (36 months) rats.

Main Results:

• XT activity was significantly higher in young rats (3370 Bq h-1 mg-1 DNA) compared to old rats (1090 Bq h-1 mg-1 protein).
• Proteoglycan content was substantially greater in young rats (29.1 nmol GalN/mg) than in old rats (5.8 nmol GalN/mg).
• When normalized to proteoglycan content, XT activity was similar between young (80 Bq h-1 µmol-1 GalN) and old rats (85 Bq h-1 µmol-1 GalN).

Conclusions:

• The synthesis of proteochondroitin sulfate is reduced in the costal cartilage of old rats.
• A diminished activity of UDP-xylose:core protein xylosyltransferase is a key mechanism contributing to age-related decline in cartilage synthesis.