Procollagen type III N-terminal peptide (P3NP) and lean mass: a cross-sectional study.

BACKGROUND: Procollagen type III N-terminal peptide (P3NP) is released during collagen synthesis in muscle. Increased circulating P3NP is a marker not only of muscle growth, but also of muscle repair and fibrosis. Thus, P3NP may be a potential biomarker for sarcopenia.

OBJECTIVE: To determine the association between plasma P3NP and lean mass and strength.

DESIGN SETTING AND PARTICIPANTS: A cross-sectional study of men and women from the Framingham Offspring Study. Participants included a convenience sample of 687 members with a measure of plasma P3NP and lean mass, and 806 members with P3NP and quadriceps strength assessment.

MEASUREMENTS: Linear regression was used to estimate the association between total and appendicular lean mass and plasma P3NP, and quadriceps strength and P3NP.

RESULTS: Mean age was 58 years. Median plasma P3NP was similar in men (3.4 mg/L), premenopausal women (3.1 mg/L), and postmenopausal women (3.0 mg/L). In adjusted models, higher P3NP was associated with a modest decrease in total and appendicular lean mass in postmenopausal women [β= -0.13 unit P3NP/kg total lean mass; p=0.003]. A similar trend was found among premenopausal women, although results were not statistically significant [β=-0.10 unit P3NP/kg total lean mass; p=0.41]. No association between P3NP and lean mass was observed in men. P3NP was not associated with strength in men or women.

CONCLUSION: Our results suggest that plasma P3NP might be a useful biomarker of muscle mass in postmenopausal women if longitudinal studies demonstrate that it has adequate sensitivity and specificity to predict muscle loss.