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The effect of a high-fat meal on sympathetic vasoconstrictor responsiveness in healthy young males and females

  • Author / Creator
    Justin J. Duong
  • Consumption of a high-fat (HF) meal has been linked to diminished vascular function, evidenced by decreased postprandial flow mediated dilation (FMD). This is thought to occur through a decrease in nitric oxide bioavailability. A postprandial decline in nitric oxide bioavailability may also increase sympathetic vasoconstrictor responsiveness; however, this has not been studied. There is also evidence that premenopausal females show a cardio-protective effect against the effects of HF meal ingestion. Therefore, the purpose of the present study was to investigate the hypotheses that 1) a HF meal would heighten sympathetic vasoconstrictor responsiveness and impair flow mediated vasodilation (FMD) in healthy young adults and 2) females would have reduced sympathetic vasoconstrictor responsiveness and maintained FMD after a HF meal compared to males. In a randomized cross-over design, young males (n=15) and females (n=15) consumed either a HF or an iso-caloric low-fat (LF) meal on separate days. Two hours postprandial, subjects underwent brachial artery FMD and cold-pressor (CPT) tests to measure endothelial function and sympathetic vasoconstrictor responsiveness, respectively. Beat-by-beat blood pressure was measured by finger photoplethysmography and mean arterial pressure (MAP) was calculated. Forearm blood flow (FBF) was measured by Doppler ultrasound at the brachial artery and forearm vascular conductance (FVC) was calculated as FBF/MAP. FMD was calculated as the percentage increase in brachial artery diameter from baseline and normalized for cumulative shear rate. Sympathetic vasoconstrictor responsiveness was calculated as the percentage decrease in FVC (%∆FVC) in response to the CPT compared to resting baseline values. FMD was found to be lower (p<0.05) following the HF meal compared to the LF meal (LF: 7.1 ± 2.1%; HF: 6.1 ± 1.8%). Shear rate area under the curve (AUC) was also significantly different (p<0.05) between meals (HF: 4.5 ± 1.2.1 s-1.s x 104; LF: 4.1 ± 0.9 s-1.s x 104). However, FMD normalized to shear AUC was not different (p>0.05) between meal conditions (LF: 1.6 ± 0.5 s-1.s x10-4, AUC; HF: 1.6 ± 0.6 s-1.s x10-4, AUC). Similarly, a HF meal did not alter (p>0.05) sympathetic vasoconstrictor responsiveness (LF: -27.9 ± 18.4 %∆FVC; HF: -27.3 ± 15.8 %∆FVC) The increase in blood pressure in response to the CPT was also not different (p>0.05) between meal condition (LF: 32.0±17.1 mmHg; HF: 35.4±17.9 mmHg). Absolute (p>0.05) and relative VO2max (p>0.05) were not correlated to FMD, normalized FMD, or sympathetic vasoconstrictor responsiveness in males or females for either meal condition. Brachial artery diameter was positively correlated (p<0.05) with absolute VO2max in males. Relative VO2max was positively correlated (p<0.05) with baseline diameter in the LF condition but not the HF condition in males (p>0.05). Baseline brachial diameter was not significantly correlated to absolute (p>0.05) or relative VO2max (p>0.05) in females. FMD was greater (p<0.05) in females (LF: 8.1± 2.1%; HF: 7.4± 1.4%) compared to males (LF: 6.3± 1.5%; HF: 5.1± 1.2%). Shear rate was also found to be significantly higher (p<0.05) in females (LF: 5.0± 1.2 s-1.s x 104; HF: 4.4 ± 1.1 s-1.s x 104) compared to males (LF: 4.1 ± 0.9 s-1.s x 104; HF: 3.7 ± 0.6 s-1.s x 104). However, when FMD was normalized to shear rate AUC, there was no significant difference between males (LF: 1.6 ± 0.4; HF: 1.4 ± 0.4 s-1.s x10-4, AUC) and females (LF: 1.7 ± 0.5; HF: 1.8 ± 0.6 s-1.s x10-4, AUC) (p>0.05). Blood pressure response to CPT in males (LF: 25.1 ± 13.9; HF: 26.7 ± 11.1 mmHg) and females (LF: 22.7 ± 13.9; HF: 25.4 ± 15.2 mmHg) was similar (p>0.05). ∆%FVC was also not significantly different in males (LF: -28.3 ± -22.6; HF: -26.3 ± 16.6%) or females (LF: -27.1 ± 13.8; HF: -30.4 ± 15.2%) (p>0.05). These data suggest that a HF meal may reduce endothelial function in both males and females as measured by FMD. However, when normalized to shear rate, this difference appears to be abolished. Furthermore, our data indicate a HF meal does not heighten sympathetic vasoconstrictor responsiveness in healthy young males and females.

  • Subjects / Keywords
  • Graduation date
    Spring 2020
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-eanm-0612
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.