Dietary Protein in a Challenge Meal Does Not Alleviate Postprandial Impairments in Vascular Endothelial Function in Healthy Older Adults with Cardiometabolic Risk: A Randomized Crossover-Controlled Trial

Abstract

Background: Postprandial vascular endothelial dysfunction is an early marker of atherosclerosis. Meal protein has been reported to reduce endothelial dysfunction in adults, and the effect could be mediated by the amino acid content.

Objectives: This trial aims to assess the effect of a specifically designed plant-protein blend that contains high leucine, arginine, and cysteine on postprandial endothelial function in the elderly.

Methods: In a randomized, double-blind, 3-period crossover (2-wk washout), controlled trial, we compared the vascular effects of 3 high-saturated-fat high-sucrose (HFHS) meals containing either our specific plant-protein blend, or milk protein, or without added protein. The trial was conducted on 29 healthy adults aged >65 y presenting ≥2 cardiometabolic risk factors. Postprandial vascular function was evaluated at fasting, 3 h, and 5 h postprandially, using brachial flow-mediated dilation (FMD), hand microvascular reactivity (using Flowmetry Laser Doppler, FLD), and finger reactive hyperemia index (using Peripheral Arterial Tonometry, RHI). Immune cell count and gene expression in peripheral blood mononuclear cells (PBMCs) were also assessed postprandially. Data were analyzed using mixed linear models with repeated measurements on participants for meal composition and time of sampling. This trial was registered at clinicaltrials.gov as NCT04923555.

Results: FMD incremental AUC value decreased after meals (time effect P < 0.01), with no significant differences between meals. RHI also decreased with time (P < 0.01). PBMC count and monocyte chemoattractant protein-1 (MCP1), IL-1β, and IL-6 expression increased after meals showing postprandial endothelial activation (P < 0.05). Overall, meal composition had no effect on any of the postprandial changes (Ps>0.10).

Conclusions: In healthy adults aged >65 y presenting cardiometabolic risk, adding protein to an HFHS challenge meal does not mitigate postprandial impairments in vascular endothelial function and inflammatory activation. Further studies are needed to explore the potential differences with younger adults.

Keywords: FMD; RT-QPCR; blood plasma; elderly people; low-grade inflammation; milk protein; oxidative stress; plant protein blend; vascular function.