The Mediterranean diet pattern is increasingly associated with improved metabolic health. Two mechanisms by which consuming a Mediterranean diet pattern may contribute to improved metabolic health are modulation of the gastrointestinal (GI) microbiota and reduction of metabolic endotoxemia. Metabolic endotoxemia, defined as a 2- to 3-fold increase in circulating levels of bacterial endotoxin, has been proposed as a cause of inflammation during metabolic dysfunction. As the largest source of endotoxins in the human body, the GI microbiota represents a crucial area for research on strategies for reducing endotoxemia. Diets high in saturated fat and low in fiber contribute to metabolic endotoxemia through several mechanisms, including changes in the GI microbiome and bacterial fermentation end products, intestinal physiology and barrier function, and enterohepatic circulation of bile acids. Thus, the Mediterranean diet pattern, rich in unsaturated fats and fiber, may be one dietary strategy to reduce metabolic endotoxemia. Preclinical studies have demonstrated the differential effects of dietary saturated and unsaturated fats on the microbiota and metabolic health, but human studies are lacking. The role of dietary fiber and the GI microbiome in metabolic endotoxemia is underinvestigated. Clinical research on the effects of different types of dietary fat and fiber on the GI microbiota and GI and systemic inflammation is necessary to determine efficacious dietary strategies for reducing metabolic endotoxemia, inflammation, and subsequent metabolic disease.

Background Avocados are rich in dietary fiber and monounsaturated fatty acids (MUFAs), nutrients that have been independently connected to metabolic health benefits and the gastrointestinal microbiota. Objectives We aimed to evaluate the impact of avocado consumption on the gastrointestinal microbiota and microbial metabolites, secondary outcomes of the Persea americana for Total Health (PATH) study, and conduct exploratory analyses to assess relations between the fecal microbiota, fecal metabolites, and health markers. Methods Adults [n = 163, 25–45 y, BMI (kg/m2) ≥ 25.0] were enrolled in the PATH study, a 12-wk investigator-blinded trial where participants were batch randomized to match the 2 groups by age, sex, visceral adiposity, and fasting glucose concentrations. Participants consumed isocaloric meals with or without avocado (175 g, men; 140 g, women) once daily for 12 wk. The fecal microbiota was assessed with 16S ribosomal RNA gene (V4 region) sequencing and analysis using DADA2 and QIIME2. Fecal fatty acid and bile acid concentrations were quantified using GC and LC-MS. Per-protocol (≥80% meal consumption) and intent-to-treat analyses were conducted using univariate ANOVA and Mann-Whitney U tests. Bivariate correlations were conducted between fecal microbiota, fecal metabolites, and health measures. Results The avocado treatment increased ɑ diversity and enriched Faecalibacterium, Lachnospira, and Alistipes between 26% and 65% compared with the control group. The avocado group had 18% greater fecal acetate, 70% greater stearic acid, and 98% greater palmitic acid concentrations than the control group, while the concentrations of the bile acids cholic and chenodeoxycholic acid were 91% and 57% lower, respectively. Conclusions Daily avocado consumption resulted in lower fecal bile acid concentrations, greater fecal fatty acid and SCFAs, and greater relative abundances of bacteria capable of fiber fermentation, providing evidence that this nutrient-dense food affects digestive physiology, as well as the composition and metabolic functions of the intestinal microbiota. This trial was registered at www.clinicaltrials.gov as NCT02740439.

No abstract

No abstract

No abstract

Background: Consuming adequate dietary fiber is a promising strategy for reducing systemic inflammation. Objective: To evaluate relationships between dietary fiber intake, markers of metabolic endotoxemia, and systemic inflammation in adults. Methods: This was a cross-sectional study of 129 healthy participants (age 33.6 ± 6.1 years, BMI 30.5 ± 6.9 kg/m2). Dietary fiber intake was assessed by food frequency questionnaire. Adiposity was measured using dual energy X-ray absorptiometry (DXA). Fecal short chain fatty acids (SCFA) were quantified using gas chromatography mass spectrometry. Fecal microbiota sequence data (V4 region, 16S rRNA gene) were analyzed using DADA2 and QIIME2. Inflammatory cytokines were assessed with enzyme-linked immunosorbent assays; flow cytometry was conducted for monocyte surface marker quantification. Bivariate correlations and generalized step-wise linear modeling were used for statistical analyses. Results: Plasma C-reactive protein (CRP) and interleukin (IL)-6 concentrations were positively related to whole-body (CRP r = 0.45, p = <0.0001; IL-6 r = 0.34, p = 0.0002) and visceral adiposity (CRP r = 0.33, p = 0.0003; IL-6 r = 0.38, p = 0.0002). Plasma lipopolysaccharide binding protein (LBP) concentrations were inversely related to dietary fiber intake (r = -0.22, p = 0.03) and fecal SCFA (acetate r = -0.25, p = 0.01; propionate r = -0.28, p = 0.003; butyrate r = -0.23, p = 0.02). Whole-body adiposity, dietary fiber, and fecal SCFA were the most predictive of plasma LBS-BP concentrations. Conclusions: Novel findings included associations between dietary fiber intake, the gastrointestinal microbiota, and systemic inflammation.

Objectives Excess fat mass has been associated with poorer cognitive function. Elevated visceral adiposity (VAT) has also been associated with cardiometabolic risk factors including chronic systemic low-grade inflammation. Whereas the cognitive implications of inflammation have been extensively studied in preclinical models, the influence of inflammatory cytokines on human cognition is unclear. Thus, this study aimed to investigate the relations among VAT, inflammatory cytokines and cognitive control. We hypothesized that elevated VAT and inflammation would be related to poorer performance during a cognitive control task. Methods Participants between 25–45 years (N = 77 48 females) with overweight/obesity (BMI ≥ 25 kg/m2) underwent a DXA scan to quantify VAT. A Flanker Task was used to assess cognitive control while Event-Related Potentials were recorded. Following an overnight fast, blood was collected to quantify plasma C-reactive protein (CRP) and Interleukin-6 (IL-6) concentrations using ELISAs. Spearman's correlations were used to analyze relations using a 1-tailed approach. Results Greater VAT was related to lower congruent (r = −.19, P = .05) and incongruent trial accuracy (r = −.26, P = .01), as well as lower congruent P3 peak amplitude (r = −.23, P = .02) and slower latency (r = .37, P < .001). Similarly, elevated CRP and IL-6 were associated with poorer congruent (rCRP = −.22 pCRP = .03; rIL6 = −.20 pIL6 = .03), and incongruent (rCRP = −.33 pCRP = .002; rIL6 = −.32 pIL6 = .002) accuracy. Additionally, CRP was related to slower incongruent P3 peak latency (r = .22, P = .02). Partial correlations controlling for CRP and IL-6 showed that VAT was no longer associated with cognitive performance (all p's > 0.07); however, the association between VAT and P3 peak amplitude (r = −.26, P = .01) and latency (r = .35, P = .001) persisted even following adjustment for CRP and IL-6. Conclusions This work replicates previous research indicating that VAT is related to poorer attentional abilities; however, we extend the literature by elucidating the role of low-grade inflammation as a contributing factor in this relationship in adults with excess fat mass. Funding Sources This work was supported by funds provided by the Dept of Kinesiology & Community Health at UIUC & the USDA National Institute of Food and Agriculture, Hatch Project 1009249. Partial support provided by the Hass Avocado Board.

No abstract