Objective: Obesity is a health concern. Resistant starch (RS) type 2 from high-amylose maize (HAM-RS2) and dietary sodium butyrate (SB) reduce abdominal fat in rodents. RS treatment is associated with increased gut hormones peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), but it is not known if SB increases these hormones. Design and Methods: This was investigated in a 2 3 2 rat study with HAM-RS2 (0 or 28% weight) and dietary sodium butyrate (0 and 3.2%) resulting in isocaloric treatments: energy control (EC), sodium butyrate (SB), HAM-RS2 (RS), and the combination (SBRS). Results: RS and SB reduced abdominal fat and the combination reduced abdominal fat compared to SB and RS. RS was associated with increased fermentation in the cecum. Serum PYY and GLP-1 total were increased with RS treatment. RS treatment was associated with increased cecal butyrate produced from fermentation of RS, but there was no cecal increase for dietary SB. Conclusions: SB after its absorption into the blood appears to not affect production of PYY and GLP-1, while butyrate from fermentation in the cecum promotes increased PYY and GLP-1. Future studies with lower doses of RS and SB are warranted and the combination may be beneficial for human health.

In our previous studies, ingestion of prebiotics in low fat diets resulted in decreased cecal pH from 8 to about 6 indicating robust fermentation. However, in some preliminary studies this effect on fermentation was not seen when rodents were fed a high fat diet. Therefore, this comprehensive high fat diet study was conducted to determine which sources and combinations of prebiotics would enhance fermentation. The effects of prebiotics in a high fat diet (44% energy) on pH, cecal weights, abdominal fat, and body weight were studied in mature male C57Bl/6 mice fed one of 9 isocaloric diets (4 kcal/g) for 12 weeks. A control (C) was compared to 4 prebiotics: Hi‐Maize® RS2 (R), Novelose® RS3 (N), Nutraflora® fructooligosaccharide (F), Orafti HP gel® inulin (I) fed individually and combined (F+I, R+F, R+I, and R+N). Results were significant at p<0.05. Fermentation (lower pH of 7) occurred with F and I diets. All prebiotic diets had larger empty ceca, but only F and I had greater full ceca than the RS groups. It is proposed that dietary fat modulates monogastric fermentation and microbiota similar to the effect it has in ruminants. This agrees with our previous data showing that high fat diets reduce the number of specific bacteria that ferment prebiotics. Beneficial health effects of prebiotic ingestion may be most effective if consumed with a low fat diet. Funding: LSU AgCenter, GTC Nutrition and National Starch.

Resistant starch (RS) resists digestion in the small intestine thus increasing the amount of starch available for microbial fermentation producing short chain fatty acids in the colon. Additionally, RS has been shown to reduce body fat in rodent models through mechanisms possibly related to colonic fermentation pathways. Acarbose, an α‐glucosidase inhibitor used to treat Type 2 diabetes, inhibits starch digestion in the small intestines, thus undigested starch reaches the colon mimicking the effects of RS. In this study, we compared changes in fermentation and body fat in rats fed diets with RS or acarbose (AC). Thirty female retired breeder rats were placed in 3 treatment groups (control, 30% RS, 0.4% AC) and fed energy balanced diets (20% fat, 3.7kcal/g) for 12 weeks. Dietary RS and AC reduced body weight and body fat gain. The control group gained 20g, compared to no gain for AC and a 20g loss for RS. Both RS and AC had larger full GI tracts, indicating reduced starch digestion; however, only RS had lower pH of cecal contents indicating only RS increased colonic fermentation. Acarbose seems to prevent starch digestion in the small intestine and starch fermentation in the large intestine. At the doses used, both RS and AC were effective in preventing weight gain, but the greater effect of weight loss with RS may be due to fermentation. Funding by LSU AgCenter.

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