Comparison of Endothelial Function in Pre‐ and Post‐exercise States between Obese and Normal‐weight Children

Background and Rationale Microangiopathy is a common comorbidity associated with adult obesity. We hypothesize that microvascular function may be altered following an age‐specific pattern in pediatric obesity, occurring well before any clinical sign of vascular impairment. As exercise provides a strong, relatively homogeneous vasodilatory stimulus, these early alterations in endothelial function may be more easily detected in the post‐exercise state. We therefore designed the present study with the objective to detect differences between obese (Ob) and normal‐weight (Nw) children in endothelial function, via Laser Doppler Flowmetry (LDF), both at rest and following a standard incremental exercise test to exhaustion. Methods Thirteen Ob children (13 ± 2 yrs, 97 ± 0.8 BMI%, 6F) and 11 Nw children (14 ± 2 yrs, 61 ± 14 BMI%, 6F) participated in the study. An optical probe connected with a Periflux 5000 Laser Doppler system (Perimed, Sweden) was placed on the base of the middle finger, and LDF measurements of skin perfusion were obtained before, during, and after a 1‐min occlusion induced at the wrist with a blood pressure cuff inflated at 200 mmHg. Subjects then performed a standard incremental cycling exercise test to exhaustion, using a commercial metabolic cart/cycle ergometer system (Carefusion, San Diego, USA). The incremental phase of the test was tailored to last ~ 10 min after 2 min of unloaded pedaling. LDF measurements were then repeated 8 min after exercise cessation. Baseline pre‐occlusive perfusion (Plat1), post‐occlusive hyperemic peak (pMax), and the time from release of occlusion to reach pMax (PkT) were obtained from perfusion tracings. Comparisons were made using two‐tailed, independent Student's t‐tests. Results Perfusion variables (in arbitrary perfusion Units) were greater in Ob throughout the study (Plat1, pre‐exercise 76 ± 13 vs. 43 ± 12 in Nw, p = 0.068; post‐exercise, 86 ± 13 vs. 41 ± 6 in Nw, p<0.05; pMax, pre‐exercise, 165 ± 16 vs. 99 ± 21, p<0.05, post‐exercise, 164 ± 16 vs. 117 ± 13, p<0.05). The magnitude of the hyperemic peak relative to baseline, while quantitatively larger in Nw in the pre‐exercise state, only reached significance in the post‐exercise state (pMax/Plat1, post‐exercise, 3.0 ± 0.3 vs. 2.1 ± 0.2, p<0.05). In general, therefore, a similar pattern of differences was present in all studies, but significance was more clearly delineated in the post exercise state. PkT was similar across weight groups, and unchanged by prior exercise. Conclusions Overall, our cohort of Ob children displayed characteristic perfusion alterations relative to Nw children, possibly including a state of chronic baseline vascular dilation, and reduced responsiveness to additional vasodilatory stimuli, such as physical exercise. Our findings are consistent with the concept that obesity, even in its very early stages in pediatric populations, is associated with microvascular dysfunction. Support or Funding Information NIH NICHD P01HD048721 & UL1 TR000153