Fatty Acids of Microbial Origin in the Perirenal Fat of Rats (Rattus norvegicus domestica) and Guinea Pigs (Cavia porcellus) Fed Various Diets

Abstract

Guinea pigs are assumed to practice caecotrophy to a higher degree than rats. Studies from leporids suggest that through the practice of caecotrophy, hindgut fermenting species could build up microbial fatty acids (FA) in body tissues. We hypothesized that microbial FA would be detectable in the body tissue of guinea pigs and rats, and this to a higher degree in guinea pigs. Twenty‐four rats and guinea pigs were fed with four different pelleted diets (lucerne‐, meat‐, meat‐bone‐, insect‐based) in groups of six animals for 8 weeks. Perirenal adipose tissue differed in FA composition between the species in spite of the common diets. FA typically associated with microbial activity (saturated FA (SFA; typically 18:0), monounsaturated FA (MUFA; typically trans‐fatty acids TFA), and odd‐ and branched‐chain FA (Iso‐FA)), were all detected. Guinea pigs had higher SFA levels than rats except on the lucerne diet. Concentrations of 18:0 were higher for guinea pigs on the meat and bone diet. Iso‐FA concentrations in guinea pigs exceeded those of rats on all diets. FA profiles with a microbial fingerprint appear—although in low proportions—in the body tissue of both species, and this seemingly to a higher extent in guinea pigs. With respect to whether consumption of rodent meat rich in microbial FA has particular effects on human health as shown for ruminant products, microbial FA concentrations are probably too low to cause any distinct effects.

Nitrogen isotopes in tooth enamel record diet and trophic level enrichment: Results from a controlled feeding experiment

“…This behavior has been explicitly demonstrated in rats (Sperber et al 1983) and guinea pigs (Holtenius and Björnhag 1985;Takahashi and Sakaguchi 2006). Indeed, evidence for microbe-related fatty acids in the body fat of the experimental animals from this study suggests that the guinea pigs relied more on this mechanism than did the rats (De Cuyper et al 2020). Unknown nitrogen isotope fractionation during metabolism of nutrients by gut microbes and differential uptake of the resulting microbiallyderived protein could therefore contribute to species differences in diet-to-tissue fractionation.…”

Teeth and the gastrointestinal tract in mammals: when 1 + 1 = 3

“…This could include the secretion of phosphorus (a major nutrient required for microbe growth) into [139], and the removal of calcium (that might render phosphorus unavailable by complexation) from the digesta [140]; the modulation of the microbiome by the degree of digesta washing [86] or peristalsis [141]; or any mechanism that determines the heritability of the GIT microbiome [142]. Possibly, ranking species by their urinary concentrations of purine derivates (from digestion and metabolism of nucleic acid-rich microbiota) [143,144], their adipose tissue concentrations of fatty acids of microbial origin [145], or microbial contribution to the isotope pattern of the essential amino acids in their red blood cells [146] could indicate the extent of microbe farming, but additional proxies would be welcome. Similarly, species could be ranked by quantifying adaptations to microbiota digestion, such as ribonuclease and lysozyme secretion in the GIT [76,77]; this could include assessing whether mammalian chitinases are involved in digesting the fungal parts of the GIT microbiome.…”