Rapid onset vasodilation in response to forearm muscle contraction in Hispanic American and Caucasian American Adults
Authors: Perez Justo , Liu Randy , Van Wagoner Tyler , Nyarko Ruby , Dalve Ashlesha , Appiah Crystal , Kaur Jasdeep 
Published: May 2023

Hispanic Americans (HA) are the fastest growing ethnic populations in the U.S., estimated to double in the next four decades. According to NHANES 2013-2016 data, prevalence of type 2 diabetes (T2D) is 15.1% in HA men and 14.1% in HA women, compared to 9.4 and 7.3% in non-Hispanic Caucasian American (CA) men and women, respectively. Even HA children have a 5-fold higher rate of T2D compared to their age-matched CA counterparts. Impaired vascular function is a hallmark of T2D however, limited number of studies have investigated the effect of ethnicity on vascular function at rest and during exercise. To our knowledge, only one study has reported a higher flow-mediated dilation at rest in healthy HA compared to CA adults. Hence, the purpose of this study was to investigate the rapid onset vasodilation in response to a single muscle contraction of the forearm at progressively increasing intensity (20, 40, and 60% of maximum voluntary contraction (MVC)) in young, healthy HA compared to age- and weight-matched CA individuals. A single muscle contraction model was chosen to isolate the robust local vasodilatory responsiveness of the vasculature without increases in sympathetic nerve activity or large hemodynamic changes. We hypothesized that HA would demonstrate an attenuated forearm vascular conductance (FVC) and forearm blood flow (FBF) in response to skeletal muscle contractions, compared to CA group. Young, healthy HA (n=4) and CA (n=4) adults performed skeletal muscle contractions at 20%, 40 % and 60% of their maximum voluntary contraction (MVC). To isolate the effect of mechanical compression during muscle contractions, FBF and FVC responses to a brachial cuff inflation were also measured. Heart rate (ECG), mean arterial pressure (MAP; finger photoplethysmography) and forearm blood flow (FBF; duplex Doppler ultrasound) were measured. FVC was calculated as FBF/MAP. Baseline FBF (CA: 115.21 ± 48.9 and HA: 68.89 ± 21.9 ml/min; p=0.27), MAP (CA: 82 ± 7.48 and HA: 81 ± 2.87 mmHg; p=0.77), FVC (p=0.15), and MVCs (CA: 67 ± 26.8 and HA: 70 ± 7.4 kg; p=0.82) were similar between the groups. Following single muscle contractions, both groups exhibited an intensity dependent increase in FVC and FBF, however, there was no difference between HA and CA groups. For instance, following muscle contraction at 40% MVC, peak FVC (%Δ) was 251% ± 46.35 in HA and 189% ± 34.98 in CA (race effect p = 0.23, time effect = 0.01, interaction p = 0.029). Similarly, peak %Δ FBF or %Δ FVC following 60% contractions were similar between the groups (FVC: 327% ± 84.36 in HA vs. 286% ± 74.45 in CA (race effect p=0.62, time effect p<0.01, interaction effect p=0.01)). Both groups exhibited a similar response to brachial cuff inflation for peak FVC (p=0.21) and peak FBF (p=0.30). Our preliminary findings indicate that HA have a preserved rapid onset vasodilation in response to a single forearm contraction when compared to CA adults. Supported by Kinesiology and Health Education UT Austin Start-up Account 19-2635-91 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.