Omega-3 polyunsaturated fatty acids improve intestinal barrier integrity-albeit to a lesser degree than short-chain fatty acids: an exploratory analysis of the randomized controlled LIBRE trial

Abstract

Purpose: Adherence to the Mediterranean diet is associated with beneficial health effects, including gastrointestinal disorders. Preclinical studies suggest that omega-3 polyunsaturated fatty acids (n-3 PUFAs), found in Mediterranean foods like nuts and fish, improve intestinal barrier integrity. Here, we assessed possible effects of n-3 PUFAs on barrier integrity in a randomized controlled trial.

Methods: We studied 68 women from the open-label LIBRE trial (clinicaltrials.gov: NCT02087592) who followed either a Mediterranean diet (intervention group, IG) or a standard diet (control group, CG). Study visits comprised baseline, month 3, and month 12. Barrier integrity was assessed by plasma lipopolysaccharide binding protein (LBP) and fecal zonulin; fatty acids by gas chromatography with mass spectrometry. Median and interquartile ranges are shown.

Results: Adherence to the Mediterranean diet increased the proportion of the n-3 docosahexaenoic acid (DHA) (IG + 1.5% [0.9;2.5, p < 0.001]/ + 0.3% [- 0.1;0.9, p < 0.050] after 3/12 months; CG + 0.9% [0.5;1.6, p < 0.001]/ ± 0%) and decreased plasma LBP (IG - 0.3 µg/ml [- 0.6;0.1, p < 0.010]/ - 0.3 µg/ml [- 1.1; - 0.1, p < 0.001]; CG - 0.2 µg/ml [- 0.8; - 0.1, p < 0.001]/ ± 0 µg/ml) and fecal zonulin levels (IG - 76 ng/mg [- 164; - 12, p < 0.010]/ - 74 ng/mg [- 197;15, p < 0.001]; CG - 59 ng/mg [- 186;15, p < 0.050]/ + 10 ng/mg [- 117;24, p > 0.050]). Plasma DHA and LBP (R²: 0.14-0.42; all p < 0.070), as well as plasma DHA and fecal zonulin (R²: 0.18-0.48; all p < 0.050) were found to be inversely associated in bi- and multivariate analyses. Further multivariate analyses showed that the effect of DHA on barrier integrity was less pronounced than the effect of fecal short-chain fatty acids on barrier integrity.

Conclusions: Our data show that n-3 PUFAs can improve intestinal barrier integrity.

Trial registration number: The trial was registered prospectively at ClinicalTrials.gov (reference: NCT02087592).

Keywords: Gut barrier; Gut permeability; Intestinal barrier; Mediterranean diet; Omega 3 fatty acids; PUFAs.

Fig. 1

Effect of the intervention on dietary habits. a–e Shown are data for baseline (BL), as well as after month 3 (V1) and month 12 (V2) for the intake of typical Mediterranean foods. Tukey boxplots with median, whiskers (1.5 × interquartile ranges), and outliers are shown in green (intervention group; BL: n = 31, V1, V2: n = 26) and orange (control group; BL: n = 33, V1: n = 31, V2: n = 29). Within group difference to baseline is indicated by asterisks (*p < 0.05; **p < 0.1; ***p < 0.001; Wilcoxon signed-rank test). This figure summarizes data shown in Supplementary Table 1

Fig. 2

Effect of the intervention on plasma fatty acid composition and intestinal barrier biomarkers Shown are data for baseline (BL), as well as after month 3 (V1) and month 12 (V2) for the proportion (%) of docosahexaenoic acid (DHA), arachidonic acid (ARA), oleic acid (OA), and total saturated fatty acids (SFAs) in the total plasma fatty acid composition (plasma FAs) (a–e), and for the intestinal barrier biomarkers plasma lipopolysaccharide binding protein (LBP) and fecal zonulin (f, g). Tukey boxplots with median, whiskers (1.5 × interquartile ranges), and outliers are shown in green (intervention group; BL: n = 33, V1: n = 26–33, V2: n = 23–29) and orange (control group; BL: n = 35, V1: n = 29–35, V2: n = 28–32). Within group difference to baseline is indicated by asterisks (*p < 0.05; **p < 0.1; ***p < 0.001; Wilcoxon signed-rank test). This figure summarizes data shown in Supplementary Table 2

Fig. 3

Omega-3 polyunsaturated fatty acids improve intestinal barrier integrity. Shown are the correlations between the proportion (%) of saturated fatty acids (SFAs) in the total plasma fatty acid composition (plasma FAs) and plasma levels of lipopolysaccharide binding protein (LBP) (a); the proportion of the omega-3 polyunsaturated docosahexaenoic acid (DHA) and plasma levels of LBP (b); and the proportion of DHA and fecal levels of zonulin (c). Spearman correlations were conducted for the intervention and the control groups (n = 33/35) using shift values (baseline [BL] values subtracted from the respective values after month 3 [V1] and month 12 [V2]. This figure summarizes the main findings shown in detail in Table 2

Fig. 4

Omega-3 polyunsaturated fatty acids improve intestinal barrier integrity—albeit to a lesser degree than fecal short-chain fatty acids. Shown are the comparisons of the effect sizes (R²) of the correlation between the proportion (%) of the omega-3 polyunsaturated fatty acid (n-3 PUFA) docosahexaenoic acid (DHA) in the total plasma fatty acid composition and the fecal short-chain fatty acids (SCFAs) propionate and butyrate with plasma lipopolysaccharide binding protein (LBP) (a), and fecal zonulin (b). Panels c, d show the comparisons of the effect sizes of the multiple linear regressions (MLR) between the proportion of DHA and the fecal SCFAs propionate and butyrate with plasma LBP (c) and fecal zonulin (d). #p < 0.07; *p < 0.05; **p < 0.01; ***p < 0.001; n.s. not significant. This figure summarizes the main findings shown in detail in Table 2 and Supplementary Table 3