Retinal vessel functional responses between South Africans living with and without HIV: The EndoAfrica-NWU study

Abstract

Introduction: Childhood obesity is associated with increased risk of metabolic complications such as pre-diabetes, hyperten-sion, dyslipidemia, and ectopic fat deposition already from a young age. While obesity has been associated with vascular endothelial dysfunction, little is known about the effect of obesity on skeletal muscle microvascular function in children. We hypothesized that microvascular function, across tibialis anterior (TA), soleus (SO) and gastrocnemius (GM), is impaired in children with obesity compared with normal-weight children. Method and Material: Children (9-16 yrs of age) were recruited for 2 groups: Normal-weight (iso-BMI = 19-25kg/m 2 ; n=18) and obese (iso-BMI>30 kg/m 2 ; n=22). Participants were positioned supine in a 3T MR scanner with a pressure cuff around the thigh. Blood oxygen level dependent (BOLD) images from the lower leg were acquired continuously during 5 minutes of cuff occlusion and 3 minutes of reperfusion. From the time series of BOLD images, and within each of the 3 muscle groups, the hyperemic response to ischemia-reperfusion was assessed via peak magnitude (BOLDPeak; % of baseline) and time-to-peak (BOLDTTP, seconds). Two-way (muscle, group), repeated measures ANOVAs were used to analyze BOLDpeak and BOLDTTP. Bonferroni-corrected post hoc tests were performed, where appropriate. Results: For BOLDpeak, there was a muscle-by-group interaction (p=0.03). Compared with normal-weight, obese had lower BOLDpeak in TA (101.1±2.9 vs. 108.3±4.4; p<0.001), SO (107.7±3.3 vs. 114.5±6.6; p<0.001) and GM (105.1±3.1 vs. 108.7±4.8; p=0.008). In obese, BOLDpeak was lower in TA than SO (p<0.001) and GM (p<0.001), and lower in GM than SO (p=0.02). In normal-weight, BOLDpeak was lower in TA than SO (p<0.001) and lower in GM than SO (p=0.002). For BOLDTTP, there was no effect of group, but a main effect of muscle (p<0.001), such that BOLDTTP was shorter in TA than SO (p<0.001) and GM (p<0.001), and shorter in SO compared with GM (p<0.001). Conclusion: Compared to normal-weight, children with obesity exhibit lower BOLDpeak across all muscle groups in the lower leg, reflecting blunted tissue oxygenation in response to an ischemia-reperfusion paradigm. These results indicate that skeletal muscle microvascular function is impaired in children with obesity, which may have implications for overall muscle and metabolic function.