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Randomized Controlled Trial
. 2016 Jul;146(7):1411-9.
doi: 10.3945/jn.115.223909. Epub 2016 Jun 15.

Postprandial Inflammatory Responses and Free Fatty Acids in Plasma of Adults Who Consumed a Moderately High-Fat Breakfast With and Without Blueberry Powder in a Randomized Placebo-Controlled Trial

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Free PMC article
Randomized Controlled Trial

Postprandial Inflammatory Responses and Free Fatty Acids in Plasma of Adults Who Consumed a Moderately High-Fat Breakfast With and Without Blueberry Powder in a Randomized Placebo-Controlled Trial

Kikumi D Ono-Moore et al. J Nutr. .
Free PMC article

Abstract

Background: Saturated fatty acids (FAs) released from triglyceride-rich lipoproteins (TGRLs) activate Toll-like receptor 2 (TLR-2) and induce the expression of proinflammatory cytokines in monocytes. Certain plant polyphenols inhibit TLR-mediated signaling pathways.

Objective: We determined whether plasma free FAs (FFAs) after a moderately high-fat (MHF, 40% kcal from fat) breakfast modulate the inflammatory status of postprandial blood, and whether blueberry intake suppresses FFA-induced inflammatory responses in healthy humans.

Methods: Twenty-three volunteers with a mean ± SEM age and body mass index (in kg/m(2)) of 30 ± 3 y and 21.9 ± 0.4, respectively, consumed an MHF breakfast with either a placebo powder or 2 or 4 servings of blueberry powder in a randomized crossover design. The placebo powder was provided on the first test day and the blueberry powder doses were randomized with a 2-wk washout period. Plasma concentrations of lipids, glucose, and cytokines were determined. To determine whether FFAs derived from TGRL stimulate monocyte activation, and whether this is inhibited by blueberry intake, whole blood was treated with lipoprotein lipase (LPL).

Results: The median concentrations of FFAs and cytokines [tumor necrosis factor-α, interleukin (IL)-6 and IL-8] in postprandial plasma (3.5 h) decreased compared with fasting plasma regardless of the blueberry intake (P < 0.001 for FFAs and P < 0.05 for cytokines). However, concentrations of FFAs and cytokines including IL-1β increased in LPL-treated whole blood compared with untreated blood samples from participants who consumed the placebo powder. Blueberry intake suppressed IL-1β and IL-6 production in LPL-treated postprandial blood compared with the placebo control when fasting changes were used as a covariate.

Conclusions: The plasma FFA concentration may be an important determinant affecting inflammatory cytokine production in blood. Supplementation with blueberry powder did not affect plasma FFA and cytokine concentrations; however, it attenuated the cytokine production induced by ex vivo treatment of whole blood with LPL. This trial was registered at clinicaltrials.gov as NCT01594008.

Keywords: antioxidants; blueberries; cytokines; diet and dietary lipids; lipoprotein lipase; monocyte activation; plasma free fatty acids; postprandial inflammation; postprandial lipemia.

Figures

FIGURE 1
FIGURE 1
CONSORT flow diagram. CONSORT, Consolidated Standards of Reporting Trials.
FIGURE 2
FIGURE 2
Study design and sample allocation. (A) Schematic of the study design. (B) Fasting and postprandial plasma or serum samples were isolated for lipid, insulin, FFAs, and cytokine analyses. (C) Diluted whole blood treated with or without LPL was used to assess monocyte activation induced by endogenously released FFAs from blood TGs. (D) PBMCs isolated from fasting blood were cultured in both 10% heat-inactivated autologous fasting and PP plasma and treated with or without LPL to assess monocyte activation induced by endogenously released FFAs from plasma TGs. (E) Diluted whole blood treated with or without LPL for 120 min to assess expression of adhesion markers by flow cytometry. *, PBMCs and/or data were not collected from one subject because of technician error. BB, blueberry; MHF, moderately high fat; PBMC, peripheral blood mononuclear cell; PP, postprandial.
FIGURE 3
FIGURE 3
Effect of a moderately high-fat breakfast including a placebo control powder or 1 of 2 levels of BB powder on postprandial TGs (A), insulin (B), free FAs (C), and cytokine (D–F) concentrations in healthy adults. Values are medians, n = 23. Data are graphed on box-and-whisker plots by using the Tukey’s method. Tukey outliers are not shown. The variables are displayed on the original scale. The statistical analysis was completed on normalized variables. C, placebo control; PP, postprandial; 2S, 2 servings of BB powder; 4S, 4 servings of BB powder.
FIGURE 4
FIGURE 4
Changes in cytokine (A, B) and FFA (C) concentrations caused by LPL treatment of postprandial whole blood from healthy adults who consumed an MHF breakfast including a placebo control powder or 1 of 2 levels of BB powder. The median differences (Δ) between postprandial +LPL and postprandial −LPL samples are graphed on box-and whisker plots by using the Tukey’s method (n = 23). Tukey outliers are not shown. *Different from 0 (representing no change), P < 0.05. Labeled medians without a common letter differ, P < 0.05. The variables are displayed on the original scale. The statistical analysis was completed on normalized variables. C, placebo control.

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