Abstract
Human milk fat contains high concentrations of medium-chained fatty acids (MCFA) and triacylglycerols emulsified by a sphingomyelin-rich phospholipid membrane (milk phospholipids, MPL). Infant formula comprises mainly long-chained fatty acids (LCFA) emulsified with dairy proteins and soy lecithin (SL) lacking sphingomyelin. Sphingomyelin content and saturation level of phospholipids affect the gut lipase activity, which alters the concentrations of lipid hydrolysis products in ileum and colon, and hereby putatively affects the competitive advantage of specific gut bacteria. Thus, differences in phospholipid and FA composition may modulate the establishment of the gut microbiota. We investigated effects of fatty acid (FA) composition and emulsification (MPL vs SL) ingested during establishment of human gut microbiota in germ-free mice, and found that cecal microbiotas from mice given MCFA-rich emulsions were characterized by high relative abundances of Bacteroidaceae and Desulfovibrionaceae, while LCFA-rich emulsions caused higher abundances of Enterobacteriaceae, Erysipelotrichaceae, Coriobacteriaceae and Enterococcaceae. Consumption of SL-emulsified lipids skewed the community towards more Enterococcaceae and Enterobacteriaceae, while MPL increased Bacteroidaceae, Desulfovibrionaceae, Rikkenellaceae and Porphyromonadaceae. Intake of SL increased cecal concentrations of iso-valeric and iso-butyric acids. This suggests that fat-type and emulsifiers applied in infant formula may have distinct effects on the establishment of the gut microbiota in formula-fed infants.
Highlights
The composition of the gut microbiota is an important factor in human health, and has been suggested to affect host metabolism and immune homeostasis[1, 2]
This study aimed to investigate whether intake of oil types characterized by either medium-chained fatty acids (MCFA) or long-chained fatty acids (LCFA), and of emulsions based on soy lecithin (SL) or MPLs during infant microbiota establishment led to differences in the bacterial composition
Several in vitro studies have demonstrated that certain C18-fatty acid (FA) are capable of improving the growth of Lactobacillus[46, 47], while we recently showed that MCFA given as free FAs and monoacylglycerol promoted growth of both Lactobacillus and Bifidobacterium during in vitro fermentation by human infant fecal microbiota[31]
Summary
The composition of the gut microbiota is an important factor in human health, and has been suggested to affect host metabolism and immune homeostasis[1, 2]. The intestinal microbiota is highly dynamic during early life, and its development depends on many different factors including diet, environment and host metabolic processes[4,5,6]. The core of the MFG contains the TAG, and the entire MFG is enveloped by a milk fat globule membrane (MFGM) consisting of phospholipids (PLs), glycolipids, proteins and cholesterol. This MFGM acts as emulsifier, and stabilizes the lipid droplets in the emulsion. The predominant difference between the PL content in human milk and infant formula is the high content of SM and more saturated PLs found in milk
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