Postprandial lipid metabolism and vascular function: impact of sex and age
Date
2023
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
The Western diet is low in nutrient density and abundant in high-fat foods which has been linked to cardiovascular disease (CVD) development. The resulting hyperlipidemia which comes with increases in dietary fat has been associated with endothelial dysfunction, a non-traditional risk factor for atherosclerosis and subsequent CVD and this is thought to occur via increased oxidative stress. Premenopausal women have been shown to exhibit less endothelial dysfunction following the intake of a high-fat meal (HFM) compared to age-matched men. While the mechanisms behind this phenomenon are not clearly understood, two potential mechanisms indicate a potential cardioprotective effect of estrogen, while other data suggest that premenopausal women clear plasma lipids more efficiently than age-matched men leading to a reduced postprandial (PP) lipemic response. Moreover, if estrogen affords premenopausal women a cardioprotective effect following consumption of a HFM, little is known pertaining to postmenopausal women and their response to a HFM as data indicates older individuals have a heightened PP lipemic response. Purpose: To investigate the vascular effects of HFMs on men and women, both young and old and the role of oxidative stress. And second, to determine whether women clear lipids more efficiently than age-matched men. Hypothesis: Consumption of a HFM will result in greater endothelial dysfunction and oxidative stress levels in young men (YM) compared to young women (YM), and old men (OM) and women (OW) will have greater dysfunction and oxidative stress than the young participants. Lastly, we hypothesized that the YW will exhibit increased rates of lipid clearance in comparison to the YM, with no differences between the older individuals. Methods: We compared the effects of a HFM to a low-fat meal (LFM) to isolate the effects of fat in the postprandial period. Specifically, participants consumed a milkshake as the HFM on one study visit day and an isocaloric bowl of cereal to serve as the LFM on the other study visit day. During the lab visits, endothelial function was assessed by brachial artery flow-mediated dilation, oxidative stress was assessed by measuring the concentration of reactive oxygen species in whole blood via electron paramagnetic resonance spectroscopy, and lipid clearance was assessed as the concentration of serum lipoproteins before the test meals, as well as two, four, and six-hours postprandially. Results: Twenty-nine (10 YM, 8 YW, 6 OM, 5 OW) participants completed both interventions. Participants were generally healthy with normal blood work, non-obese, and normotensive. The younger women had higher FMD values than the younger men at all time points, and the younger participants had higher FMD values than the older adults at all time points, regardless of meal. Levels of oxidative stress increased over time in all groups after consuming both the HFM and LFM, without there being any specific sex or age differences present. Lastly, while every group experienced significant increases in plasma TGs after consuming the HFM, there were no main effects of sex or age in the clearance of plasma lipids. Conclusions: The main novel findings of this single-blind randomized crossover design study is that while we did not observe any meaningful sex differences in vascular function and lipid metabolism following the consumption of a HFM, age played the biggest role in determining the postprandial vascular response. More specifically, the young men and women displayed the least amount of vascular dysfunction in comparison to both the older men and older women. Mechanistically, while there was not a specific effect of age or sex on postprandial oxidative stress levels, to some extent oxidative stress plays a role in the ensuing vascular dysfunction in the postprandial period because every group exhibited heightened levels after consuming both meals.
Description
Keywords
Aging differences, Lipemia, Lipids, Postprandial, Sex differences, Triglycerides