Abstract P249: Effects of the Walking Intervention Through Texting Trial on Novel Markers of Vascular Stiffness and Remodeling
Authors: Herbold Jennifer L , Hook Benjamin E , Jarrett Catherine L , Tucker Wesley J , Bhuiyan Nishat , Fernandez Jacqueline A , Todd Michael , Adams Marc A , Angadi Siddhartha S 
Published: March 2022

Introduction:
Improvements in physical activity (PA) are strongly associated with increases in vascular health among inactive populations. The Walking Intervention Through Texting (WalkIT) trial, a 4-month 2x2 factorial randomized controlled trial, examined impacts of goal setting (adaptive vs. static) and financial reward type (small immediate vs. larger delayed) on PA (walking steps/day) in 96 sedentary, overweight and obese adults. An exploratory aim of the trial was to investigate treatment effects on novel biomarkers associated with central arterial stiffness (carotid femoral pulse wave velocity - cfPWV).

Hypothesis:
We hypothesized that adaptive goal and immediate reward groups would show greater pre- to post-trial improvements in biomarkers and cfPWV than static goal and delayed reward groups.

Methods:
Changes in biomarkers were examined for a randomly drawn subsample of 36 participants (n=9 per group; age = 42.3±10.7). Fasting blood plasma samples and cfPWV measurements were taken pre- and post-trial. Markers of vascular remodeling and endothelial function [matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1)] and tumor necrosis factor alpha (TNF-α, an inflammatory cytokine) were quantified in serum and plasma EDTA samples using commercially available enzyme-linked immunosorbent assay kits. cfPWV was measured non-invasively using a Sphygmocor XCELTM device. Linear mixed models were used to assess main effects and interactions for goal, reward, and pre-post change, adjusting for smoking, age, gender, and ethnicity. Partial correlations were used to assess associations between cfPWV and MMP-2, MMP-9, TIMP-1 or TNF-α, controlling for age. Alpha was set at 0.05 but given the exploratory nature of the analyses, 2- and 3-way interactions significant at p < 0.15 were retained for further examination.

Results:
cfPWV improved across all groups but no between group differences were detected. No significant associations were found between cfPWV and MMP-2, MMP-9, TIMP-1 or TNF-α (r < 0.25 and p > 0.25). MMP-9: Significant overall pre-post change (p = 0.001), main effect for goal (p = 0.026), and a main effect trend for reward (p = 0.062) were observed. MMP-2: A trend for pre-post x goal x reward interaction was observed (p = 0.113) with a pre-post decrease in the Static/Delayed group only. TIMP-1: A significant pre-post decrease (p = 0.020) qualified by a trend for a pre-post x reward interaction (p = 0.089; pre-post decreases in the immediate reward groups were larger than the delayed groups). TNF-α: A main effect trend for goal was observed (p = 0.085).

Conclusion:
Physical activity patterns associated with the WalkIT intervention may improve biomarkers associated with vascular remodeling and inflammation; however, we saw no significant associations between changes in biomarkers and improved central arterial stiffness.