Impact of a High-Fat or High-Fiber Diet on Intestinal Microbiota and Metabolic Markers in a Pig Model

Abstract

To further elaborate interactions between nutrition, gut microbiota and host health, an animal model to simulate changes in microbial composition and activity due to dietary changes similar to those in humans is needed. Therefore, the impact of two different diets on cecal and colonic microbial gene copies and metabolic activity, organ development and biochemical parameters in blood serum was investigated using a pig model. Four pigs were either fed a low-fat/high-fiber (LF), or a high-fat/low-fiber (HF) diet for seven weeks, with both diets being isocaloric. A hypotrophic effect of the HF diet on digestive organs could be observed compared to the LF diet (p < 0.05). Higher gene copy numbers of Bacteroides (p < 0.05) and Enterobacteriaceae (p < 0.001) were present in intestinal contents of HF pigs, bifidobacteria were more abundant in LF pigs (p < 0.05). Concentrations of acetate and butyrate were higher in LF pigs (p < 0.05). Glucose was higher in HF pigs, while glutamic pyruvic transaminase (GPT) showed higher concentrations upon feeding the LF diet (p < 0.001). However, C-reactive protein (CRP) decreased with time in LF pigs (p < 0.05). In part, these findings correspond to those in humans, and are in support of the concept of using the pig as human model.

Establishing a model for childhood obesity in adolescent pigs

“…Adolescent pigs fed a 5‐week HFD developed an obese phenotype, having increased body weight and 46% greater back‐fat depth compared with pigs consuming a LFD, which is in agreement with previous findings . Back fat thickness is commonly used as a measure of obesity in pigs , and increased fat deposition is associated with dysregulated gene expression (such as TCF7L2 and leptin) that are high risk susceptibility genes for type 2 diabetes and obesity .…”

“…In contrast, a recent study in conventional pigs found increased Bacteroidetes ( Bacteroides group and Prevotella spp.) in both cecum and colon of pigs fed a HFD . In obese Ossabaw minipigs, reduced abundance of genera Prevotella and increased abundance of Clostridium were observed in the colon compared with their lean counterparts, analogous to findings in the current study .…”

“…In previous studies, feeding a HFD (~20%, w / w ) to pigs for 7 or 11 weeks was insufficient to observe changes in weight, but these studies neglected to characterize glucose tolerance, which is often impaired with obesity. Whereas, the present study found 5‐week HFD feeding was adequate to induce obesity, including impaired glucose tolerance.…”

Gastrointestinal (GI) Tract Microbes and Microbial Neurotoxins in the Human Central Nervous System (CNS) in Alzheimer’s Disease (AD)

“…Generally microbial Bacteroidetes species such as Bacteroides fragilis (B. fragilis) appear to be generally beneficial to human health via their ability to cleave dietary fiber into digestible short-chain fatty acids, their production of useful polysaccharides, vitamins and their precursors, volatile fatty acids and other nutrients, however, when they escape the confines of a healthy GI tract microbiome they elicit inflammatory systemic pathology with substantial morbidity and mortality [15,[22][23][24]26]. It is well known that diet has a role in regulating the composition, complexity and speciation of the GI tract microbiome -for example species of Bacteroidetes proliferate in animal models fed high fat-cholesterol (HF-C) diets deprived of dietary fiber [25]. Besides their prodigious output of LPS, endotoxins generated by B. fragilis are a leading cause of anaerobic bacteremia and systemic inflammatory distress through the production of the highly pro-inflammatory zinc metalloproteinase B. fragilis toxin (BFT) fragilysin [24,26].…”

“…Related to the points above, overall the GI tract microbiome of AD patients was found to exhibit highly selective abundance and compositional differences in genus and species from control age-and sex-matched individuals and exhibited phylum-and genus-wide differences in bacterial abundance including a significantly increased abundance of Bacteroidetes and decreased abundance of Firmicutes and Bifidobacterium in the AD-affected brain [9,[14][15][16][17][23][24][25][26]. Very recently, at least 2 independent publications have shown an enrichment of LPS within the neocortex or hippocampus of ADaffected brain [6,[27][28][29].…”