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ARS Home » Northeast Area » Beltsville, Maryland (BHNRC) » Beltsville Human Nutrition Research Center » Diet, Genomics and Immunology Laboratory » Research » Research Project #436294

Research Project: Polyphenol-Rich Foods and Promotion of Intestinal Health

Location: Diet, Genomics and Immunology Laboratory

2020 Annual Report

Objective 1: Determine if polyphenol rich diets prevent microbiome dysbiosis, inappropriate activation of Toll and NOD-like receptor (TLR/NOD-like receptors) and reduce the severity of colitis in pigs. [NP107, C3, PS3B] Objective 2: Compare consumption of polyphenol-rich foods combined with probiotics early in life for amelioration of systemic inflammation induced by a westernized high fat diet. [NP107, C3, PS3B, C4, PS4A] Objective 3: Establish if consumption of polyphenol-rich foods will normalize westernized high fat diet-induced microbiome dysbiosis and prevent generalized inflammation. [NP107, C3, PS3B C4, PS4A]

The overall goal of the proposed research is to understand the complex interactions between diet, gut microbiome and host responses that are critical for the prevention of diseases associated with poor diet choices. The objective is to use a human-relevant pig model to understand mechanisms of intestinal dysregulation during consumption of a westernized-diet, which is strongly associated with obesity and related metabolic diseases, and to evaluate the incorporation of dietary probiotics, fruits and vegetables as an approach to attenuate the adverse consequences of consuming a westernized-diet. To achieve this goal, we propose to study the time-dependent changes in broad host health biomarkers within the immunome, microbiome and metabolome, and the dietary interventions that modulate these biomarkers. Our central hypothesis is that a modified westernized dietary pattern that contains recommended levels of fruits and vegetables will promote a healthier host microbiome due a polyphenol-induced prebiotic effect and anti-inflammatory responses.

Progress Report
Partial progress was made on Objective 1. A 21-pig pilot study was conducted to test a range of dextran sodium sulfate (DSS) doses for inducing clinical colitis and separately evaluate the impact of fruit and vegetable supplementation on microbiome composition. Refinement of the initial seven-day, DSS-induced colitis protocol with sixteen pigs was required to consistently replicate the occurrence of expected lesions with clinical signs. Histopathology analysis of a subset of pigs showed intestinal crypt and goblet cell hyperplasia with enhanced mucus production on the DSS-treated groups relative to the controls without a clear DSS-dose-dependent effect, suggesting that lower doses can be safely used to induce colitis without exacerbated clinical signs in the main study. Five additional pigs were fed a standard 16% protein diet containing macro and micronutrient requirements for growing pigs and lyophilized fruits and vegetables with an equivalent amount to half the daily dietary guideline recommendation for the consumption of fruits and vegetables for Americans. A fresh vegetable mix derived from 3.5 cups wet volume with equal parts of vegetables (spinach, kale, broccoli and celery) and a fruit mix derived from 2.5 cups wet volume containing equal parts of green grapes, strawberries, red apples, blackberries, and blueberries were prepared in-house and lyophilized in advance for a three-week dietary intervention. Complete analysis to identify longitudinal responsive bacterial taxa in intestinal contents and transcriptome changes in immune reactive tissues is underway. Bacterial diversity analysis showed decreased alpha diversity in proximal colon contents of DSS-treated pigs with a time-dependent separation of bacterial communities (beta-diversity) after fruit and vegetable consumption. Additional taxonomic analysis and its impact on predicted metabolic function is underway. Two new collaborative projects to study the impact of dietary interventions on brain health are also underway. Brain samples (hypothalamus, hippocampus) derived from a porcine study of diet-induced cardiovascular disease from the previous project plan have been processed and sequenced for transcriptome analysis. Additional processing of frontal cortex has started. This project relates directly to the current Objective 2 of the current project by examining modulatory effects of polyphenols at brain level. Transcriptome and metabolome analysis of brain samples (hippocampus, cortex) and liver derived from pigs fed two doses of mushroom-supplemented diets is also underway, and will contribute to better understand diet-brain axis modulation.

1. Blood brain barrier (BBB) permeability of flavanol metabolites can facilitate interaction with neurogenic compounds. Flavanols, including flavan-3-ols (F3O), are abundant in fruits, cocoa and pulses and have been recognized as promising dietary compounds for the prevention of chronic diseases including neurodegenerative ones. F3O are poorly absorbed along the intestine, but are structurally changed by gut bacteria to yield smaller metabolites like phenyl-y-valerolactones (PVL) that then appear in the bloodstream shortly after F3O intake. There is a lack of information concerning the effective permeability of BBB by major F3O metabolites coming from the intestine. Mass spectrometry analysis of several sections of brains derived from pigs fed a flavanol-rich cocoa extract confirmed the presence of PVL in brain cortex. Other have shown that amyloid-ß oligomers are associated with Alzheimer's disease and that PVL interferes with their ability to generate toxic aggregates that can cause memory deterioration and brain inflammation in a mouse model of Alzheimer’s disease. Our study in pigs highlights the BBB permeability of one of the main cocoa-derived metabolites from dietary cocoa that can improve neuro-degenerative outcomes.

Review Publications
Angelino, D., Carregora, D., Domenech-Coca, C., Savi, M., Figueira, I., Brindani, N., Jang, S., Lakshman, S., Molokin, A., Urban Jr, J.F., Davies, C.D., Britto, M.A., Kim, K.S., Brighenti, F., Curti, C., Blade, C., Del Bas, J.M., Stilli, D., Solano Aguilar, G., Nunes Del Santos, C., Del Rio, D., Mena, P. 2019. 5-(Hydroxyphenyl)-y-valerolactone-sulfate, a key microbial metabolite of flavan-3-ols, is able to reach the brain: evidence from different in silico, in vitro and in vivo experimental models. Nutrients. 11(11). pii: E2678.
Liu, F., Smith, A.D., Solano Aguilar, G., Wang, T.T., Pham, Q., Tang, Q., Urban Jr, J.F., Xue, C., Li, R.W. 2020. Mechanistic insights into the attenuation of intestinal inflammation and modulation of the gut microbiome by krill oil using in vitro and in vivo models. Microbiome. 8:83.