Rats Fed Dietary Bioactive Components (Resistant Starch, Whole Grains, and Fat) Undergo Altered Biometrics and Gene Expression as a Result of Gut Fermentation

Abstract

The whole grain and fat content of the diet have been previously shown to affect intestinal fermentation and phenotype conferred by high–amylose maize resistant starch (HAMRS), a form of fermentable dietary fiber. The current studies were designed to compare rodent gut health following consumption of whole grain and non–whole grain prebiotics on moderate fat (MF) and high fat (HF) diets, and to optimize health effect based on dosage of whole grain resistant starch prebiotics. Study 1: Diets were prepared to contain the following factors RS (Present/Absent), WG (Present/Absent), and Fat (HF/MF). A three–way ANOVA was performed with statistical slice on interactions and main effects. Study 2: Isocaloric diets (3.7 kcal/g) were prepared as follows: non–RS non–WG control, non–RS WG control, or with increasing WGRS (5, 10, 15, 20% wt.)]. One–way ANOVA with a priori contrasts (WG vs. all individually) were performed at p<0.05 Both: Diets were fed to Sprague Dawley and lean Zucker Diabetic Fatty rats respectively, for six weeks. After euthanasia, blood, cecal contents and cecal epithelial cells were collected and gastro–intestinal (GI) tract portions and fat pad weights recorded. RT–qPCR was performed to analyze gluconeogenic enzymes, response to oxidative stress, and gut barrier resilience. For study 1, a few interactions were significant, but the RS main effect provided the most substantial changes in biometric and gene expression parameters. WG presence resulted in consistency of fermentation. Results were primarily driven by two major effects: purified RS fermented better on MF than HF diets and diets with RS+WG show similar fermentation on both levels of dietary fat. Although the 10–15% dosages were best for initiating benefits from fermentation in study 2, WG flour alone promoted fermentation with RS1 (a WG kernel component), and WGRS (RS1+RS2) promoted greater fermentation. Replacing traditional starch with a whole grain with resistant starch, as low as 5%, had some beneficial effects. These results suggest that a lower level of intake of fermentable fiber as RS is beneficial, but show that substantial WG (only low RS1) also had beneficial effects.