Dietary resistant starch preserved through mild extrusion of grain alters fecal microbiome metabolism of dietary macronutrients while increasing immunoglobulin A in the cat.

Juan J Loor,Matthew I Jackson,Christopher Waldy,Dennis E Jewell

doi:10.1371/journal.pone.0241037

Abstract

Dietary digestion-resistant starch (RS) provides health benefits to the host via gut microbiome-mediated metabolism. The degree to which cats manifest beneficial changes in response to RS intake was examined. Healthy cats (N = 36) were fed identically formulated foods processed under high (n = 17) or low (n = 19) shear extrusion conditions (low and high RS levels [LRS and HRS], respectively). Fecal samples collected after 3 and 6 weeks' feeding were assayed for stool firmness score, short-chain fatty acids, ammonia, and changes to the global metabolome and microbiome; fecal immunoglobulin A (IgA) was analyzed at week 6. Few differences were seen in proximate analyses of the foods; stool firmness scores did not differ. In cats consuming HRS food, concentrations of fecal butyrate and the straight chain:branched chain fatty acid ratio were significantly greater in feces at both weeks 3 and 6, while fecal ammonia was reduced at week 6 relative to feces from LRS-fed cats. Fecal IgA concentrations were significantly higher at week 6 with HRS food. RS consumption altered 47% of the fecal metabolome; RS-derived sugars and metabolites associated with greater gut health, including indoles and polyamines, increased in the cats consuming HRS food relative to those fed the LS food, while endocannabinoid N-acylethanolamines decreased. Consumption of HRS food increased concentrations of the ketone body 3-hydroxybutyrate in feces and elevated concentrations of reduced members of NADH-coupled redox congeners and NADH precursors. At the microbiome genus-level, 21% of operational taxonomic units were significantly different between food types; many involved taxa with known saccharolytic or proteolytic proclivities. Microbiome taxa richness and Shannon and Simpson alpha diversity were significantly higher in the HRS group at both weeks. These data show that feline consumption of grain-derived RS produces potentially beneficial shifts in microbiota-mediated metabolism and increases IgA production.

Highlights

The lower gut of monogastric animals harbors communities of microbiota
These results indicate that the low shear extrusion conditions led to a food that contained less cooked starch with likely more resistant starch (RS) and that its starch content was of a higher molecular weight
This study examined the effects of feline consumption of RS produced through different extrusion conditions on gut microbiome metabolism of dietary carbohydrate, protein, and fat

Summary

Introduction

The lower gut of monogastric animals harbors communities of microbiota (ie, the microbiome). In this mutualistic relationship, dietary nutrients escaping host digestion and absorption become available to the microbiome while the microbiome concomitantly generates a number of small molecule metabolites (postbiotics) that act locally in the gastrointestinal tract and are reabsorbed across the colon to systemic circulation [1]. Food processing through extrusion can increase the digestibility and bioavailability of nutrients to the host while restricting their access to the colonic microbiota. Grains are prominent sources of dietary starch and serve as a source of energy, fiber, and protein for companion animals and enable formation of a dry, extruded pet food kibble with appropriate expansion

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Results

Conclusion