Obese ZDF rats fermented resistant starch with effects on gut microbiota but no reduction in abdominal fat

Abstract

Scope To determine if whole-grain (WG) flour with resistant starch (RS) will produce greater fermentation than isolated RS in obese Zucker Diabetic Fatty (ZDF) rats, and whether greater fermentation results in different microbiota, reduced abdominal fat, and increased insulin sensitivity. Methods and results This study utilized four groups fed diets made with either isolated digestible control starch, WG control flour (6.9% RS), isolated RS-rich corn starch (25% RS), or WG corn flour (25% RS). ZDF rats fermented RS and RS-rich WG flour to greatest extent among groups. High-RS groups had increased serum glucagon-like peptide 1 (GLP-1) active. Feeding isolated RS showed greater Bacteroidetes to Firmicutes phyla among groups, and rats consuming low RS diets possessed more bacteria in Lactobacillus genus. However, no differences in abdominal fat were observed, but rats with isolated RS had greatest insulin sensitivity among groups. Conclusions Data demonstrated ZDF rats (i) possess a microbiota that fermented RS, and (ii) WG high-RS fermented better than purified RS. However, fermentation and microbiota changes did not translate into reduced abdominal fat. The defective leptin receptor may limit ZDF rats from responding to increased GLP-1 and different microbiota for reducing abdominal fat, but did not prevent improved insulin sensitivity.

CD Obesity‐Prone Rats, but not Obesity‐Resistant Rats, Robustly Ferment Resistant Starch Without Increased Weight or Fat Accretion

“…We conclude that increases in M. smithii and S24‐7 are markers of bacterial fermentation of RS because both rat phenotypes had similar amounts of these potential markers in phase 1 when no RS was fed. We previously observed increased S24‐7 in Zucker diabetic fatty (ZDF) rats with obesity that robustly fermented RS , and we hypothesize that we would have observed an increase in M. smithii if these were measured in other studies. Increases in S24‐ 7 and M. smithii may be under a homeostatic mechanism of host dynamics that regulates the gut community responses to promote host fermentation.…”

“…Cecal contents were frozen in liquid nitrogen and stored at −80°C. Fermentation (cecum weights, cecal content pH and short‐chain fatty acids [SCFAs], and serum glucagon‐like peptide 1 [GLP‐1] active) was measured as described .…”

“…Amplification, sequencing, and bioinformatics of bacterial DNA from phase 2 were performed at the LSU Microbial Genomics Resource Group by using V3 2 × 300 bp kits as described previously . Analysis using the UPARSE process was with 97% identity for operational taxonomic units .…”

Novel Resistant Starch Type 4 Products of Different Starch Origins, Production Methods, and Amounts Are Not Equally Fermented when Fed to Sprague‐Dawley Rats

“…Rats were humanely euthanized by isoflurane induction and cardiac exsanguination after 3 weeks on the diets. Blood was collected in tubes containing DPP‐4 inhibitor for measurement of active GLP‐1 using ALPCO ELISA kit (Salem, NH) as was previously reported . The stomach, small intestine, cecum, and large intestine were separated and weighed individually full and empty.…”

“…Our research group has found that RS2, a high‐amylose maize starch, is robustly fermented by several different rodent models, including young, male Sprague‐Dawley rats when fed a moderate‐ or low‐fat diet . Although there has been phenotypic variation in body weight changes and fat accretion, male Sprague‐Dawley, obese Zucker Diabetic Fatty (ZDF), and CD obese‐prone rat models have distinctly demonstrated robust fermentation of Hi‐Maize 260 high amylose starch as indicated by enlarged ceca, decreased cecal pH, and increased production of SCFAs . Martinez et al.…”