Effects of a One-Year Physical Activity Program on Serum C-Terminal Agrin Fragment (CAF) Concentrations among Mobility-Limited Older Adults

Abstract

Objectives: C-terminal Agrin Fragment (CAF) has been proposed as a potential circulating biomarker for predicting changes in physical function among older adults. To determine the effect of a one-year PA intervention on changes in CAF concentrations and to evaluate baseline and longitudinal associations between CAF concentrations and indices of physical function.

Design: Ancillary study to the Lifestyle Interventions and Independence for Elders Pilot (LIFE-P), a multi-site randomized clinical trial designed to evaluate the effects of chronic exercise on the physical function of older adults at risk for mobility disability.

Setting: Four academic research centers within the U.S.

Participants: Three hundred thirty three older adults aged 70 to 89 with mild to moderate impairments in physical function.

Intervention: A 12-month intervention of either structured physical activity (PA) or health education promoting successful aging (SA).

Measurements: Serum CAF concentrations and objectives measures of physical function - i.e. gait speed and performance on the Short Physical Performance Battery (SPPB).

Results: The group*time interaction was not significant for serum CAF concentrations (p=0.265), indicating that the PA intervention did not significantly reduce serum CAF levels compared to SA. Baseline gait speed was significantly correlated with baseline CAF level (r = -0.151, p= 0.006), however the association between CAF and SPPB was not significant. Additionally, neither baseline nor the change in CAF concentrations strongly predicted the change in either performance measure following the PA intervention.

Conclusion: In summary, the present study shows that a one-year structured PA program did not reduce serum CAF levels among mobility-limited older adults. However, further study is needed to definitively determine the utility of CAF as a biomarker of physical function.

Figure 1

Figure 1A. Serum CAF levels according to randomized groups at baseline and during follow-up. Means estimated from repeated measures analysis of covariance adjusted for gender, intervention assignment and visit. p-value indicates that for the group*time interaction. Figure 1B. Scatterplot demonstrating the linear relationships between baseline serum CAF levels and self-selected gait speed. Correlation coefficient indicates bivariate associations. Figure 1C. Scatterplot demonstrating the linear relationships between baseline serum CAF levels and score on the Short Physical Performance Battery. Correlation coefficient indicates bivariate associations.