Effect of a diet based on the dietary guidelines for americans on inflammation markers in women at risk for cardiometabolic disease: results of a randomized, controlled trial

Abstract

Objective: To evaluate the effect of a diet pattern based on Dietary Guidelines for Americans (DGA), in a controlled feeding setting, on plasma markers of inflammation and on cytokine production by peripheral blood mononuclear cells (PBMC).

Design: Women (n = 44) with one or more risk factors of metabolic syndrome (and BMI: 25.2-39.8 kg/m²) completed an 8-wk controlled feeding study. They were randomized to either a group following a diet based on DGA 2010 (DGA), or a group given a 'typical American diet' (TAD), based largely on a Western diet pattern. By design, women maintained their body weight. Fasting plasma and PBMC were collected at wk. 0 (baseline) and at wk. 8 (post-intervention). Sixteen plasma markers of inflammation and eight PBMC cytokines were measured at both time points, to evaluate if the diet had a significant effect on concentrations of these inflammatory markers. Data were analyzed using ANCOVA, followed by multiple-comparison adjustment using Benjamini-Hochberg method.

Results: Significant changes observed in Serum Amyloid A (SAA) and Matrix Metalloproteinase 3 (MMP3) in plasma did not retain significance upon multiple comparison adjustment. SAA: p = 0.044, adj p = 0.450; DGA mean change [95% CI] = - 12.6[- 32.3 to 7.04]; TAD mean change [95% CI] = - 2.24 [- 9.99 to 5.51]. MMP3: p = 0.014, adj p = 0.35; DGA mean change [95% CI] = 2.72[- 4.16 to 9.59]; TAD mean change [95% CI] = - 0.98[- 16.7 to 14.7]). Other inflammation markers were not differently altered by DGA relative to TAD. Effect size of change (Cohens d) indicated a large/medium-large effect of intervention on MMP3 and CRP, and medium effect on IL-6.

Conclusions: No statistically significant changes were observed in the immune markers examined in this study. The biological roles and magnitude of the non-significant differences seen with two variables, CRP and MMP3, suggest that they be examined in future studies.

Trial registration: Clinicaltrials.gov identifier NCT02298725.

Keywords: C-reactive protein; Dietary guidelines for americans; Matrix metalloproteinase-3.

Fig. 1

A Difference between Wk8 and Wk0 for all fasting cytokine parameters measured in plasma and derived from PBMCs with p-values and Benjamini-Hochberg adjusted p-values inset. One-way ANCOVA with adjustment for baseline values indicated no significant differences between DGA and TAD groups. Values are mean ± SEM. J-Su – Johnson normalizing, unbounded (Su), J. Sb – Johnson normalizing bounded (Sb) Log – logarithmic transformation, CR – cube root transformation; B Difference between Wk8 and Wk0 for all fasting cytokine parameters measured in PBMCs stimulated with anti-CD3 and anti-CD28 antibody, with p-values and Benjamini-Hochberg adjusted p-values inset. One-way ANCOVA with adjustment for baseline values indicated no significant differences between DGA and TAD groups. Values are mean ± SEM. J. Su – Johnson normalizing unbounded (Su), SR – square root transformation, CR – cube root transformation; C Difference between Wk8 and Wk0 for all fasting cytokine parameters measured in PBMCs stimulated with LPS with p-values and Benjamini-Hochberg adjusted p-values inset. One-way ANCOVA with adjustment for baseline values indicated no significant differences between DGA and TAD groups. Vales are mean ± SEM. J. Su – Johnson normalizing unbounded (Su), SR – square root transformation

Fig. 2

The lower and upper CI and mean change between wk8-wk0 in TAD (black bars) and DGA (grey bars), inset with effect size of change (ES) calculated as mean /pooled standard deviation on the right corner are shown in panels A – D. Panels A and B show data from fasting plasma, while C and D show data from PBMC’s, with the exception of IP-10 in panel D (which was graphed with other variables that could share the x-axis). The upper and lower CI are depicted at the ends of the bars, and the mean is represented by the while line/space at the center of each bar. Large intervals were noticed in several immunological parameters, suggesting low power. Based on effect size of change observed, both MMP3 and CRP have medium to large effect sizes (denoted by black dotted rectangles), trailed by IL-6 and IP-10. LPS-IL-6 also had slightly more than low effect size (at 0.31). While MMP3 and IP-10 increased following DGA, and decreased following TAD, and the reverse was true in CRP and IL-6