Microbiota accessible carbohydrates
Microbiota-accessible carbohydrates (MACs) are carbohydrates that are resistant to digestion by a host's metabolism, and are made available for gut microbes, as prebiotics, to ferment or metabolize into beneficial compounds, such as short chain fatty acids.[1] The term, ‘‘microbiota-accessible carbohydrate’’ contributes to a conceptual framework for investigating and discussing the amount of metabolic activity that a specific food or carbohydrate can contribute to a host's microbiota.[1]
MACs may come from plants, fungi, animal tissues, or food-borne microbes, and must be metabolized by the microbiome.[1] A significant quantity of the cellulose humans consume is not metabolized by gut microbes and therefore cannot be considered a MAC.[2] The amount of dietary MACs found within a food source will differ for each individual, since which carbohydrates are metabolized depends upon the composition of each person’s microbiota. For example, many Japanese individuals possess the genes for the consumption of the algal polysaccharide porphyran in their microbiomes, which are rarely found in North American and European individuals.[3][4] For individuals who harbor such a porphyran-degrading strain, porphyran would be a MAC. However, porphyran would not be a MAC for those without a microbiota adaptation to seaweed. In similar fashion, germ-free mice without a microbiota might consume a diet with large quantities of potential MACs, but none of the carbohydrates would be considered MACs, since they would escape the digestive tract without being metabolized by microbes.[1]
Lack of dietary MACs results in a microbiota reliant upon endogenous host-derived MACs, such as mucin glycans.[5] Different host genotypes can influence the identity of MACs available to the microbiota in multiple ways. For example, a host's genes may affect the level of mucus structures, such as the absence of alpha-1-2 fucose residues in the mucus of nonsecretor individuals who lack alpha-1-2- fucosyltransferase activity in the intestine.[6] Similarly, a host may have genes that can determine the efficiency of digestion and absorption of carbohydrates in the small intestine. For example, lactose is accessible to the microbiota in people who are lactose intolerant, and should therefore be considered a MAC for those individuals. For nursing infants, dietary MACs that are naturally found in breast milk are known as human milk oligosaccharides (HMOs).[7][8][9] For formula-fed infants, dietary MACs, such as galacto-oligosaccharides, are artificially added to formula.[10] Therefore the research, discussion and quantification of MACs and their impact on a host's microbiota may be critical to determining their impact on human health.[1]
References
- 1 2 3 4 5 Sonnenburg, Erica D.; Sonnenburg, Justin L. (2014). "Starving our Microbial Self: The Deleterious Consequences of a Diet Deficient in Microbiota-Accessible Carbohydrates". Cell Metabolism 20: 779–786. doi:10.1016/j.cmet.2014.07.003. ISSN 1550-4131.
- ↑ Chassard, Christophe; Delmas, Eve; Robert, Céline; Bernalier-Donadille, Annick (2010). "The cellulose-degrading microbial community of the human gut varies according to the presence or absence of methanogens". FEMS Microbiology Ecology 74 (1): 205–213. doi:10.1111/j.1574-6941.2010.00941.x. ISSN 0168-6496.
- ↑ Hehemann, Jan-Hendrik; Correc, Gaëlle; Barbeyron, Tristan; Helbert, William; Czjzek, Mirjam; Michel, Gurvan (2010). "Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota". Nature 464 (7290): 908–912. doi:10.1038/nature08937. ISSN 0028-0836. PMID 20376150.
- ↑ Hehemann, J.-H.; Kelly, A. G.; Pudlo, N. A.; Martens, E. C.; Boraston, A. B. (2012). "Bacteria of the human gut microbiome catabolize red seaweed glycans with carbohydrate-active enzyme updates from extrinsic microbes". Proceedings of the National Academy of Sciences 109 (48): 19786–19791. doi:10.1073/pnas.1211002109. ISSN 0027-8424.
- ↑ Sonnenburg, J. L. (2005). "Glycan Foraging in Vivo by an Intestine-Adapted Bacterial Symbiont". Science 307 (5717): 1955–1959. doi:10.1126/science.1109051. ISSN 0036-8075.
- ↑ Kashyap, P. C.; Marcobal, A.; Ursell, L. K.; Smits, S. A.; Sonnenburg, E. D.; Costello, E. K.; Higginbottom, S. K.; Domino, S. E.; Holmes, S. P.; Relman, D. A.; Knight, R.; Gordon, J. I.; Sonnenburg, J. L. (2013). "Genetically dictated change in host mucus carbohydrate landscape exerts a diet-dependent effect on the gut microbiota". Proceedings of the National Academy of Sciences 110 (42): 17059–17064. doi:10.1073/pnas.1306070110. ISSN 0027-8424.
- ↑ Bode, L. (2012). "Human milk oligosaccharides: Every baby needs a sugar mama". Glycobiology 22 (9): 1147–1162. doi:10.1093/glycob/cws074. ISSN 0959-6658.
- ↑ Marcobal, Angela; Barboza, Mariana; Sonnenburg, Erica D.; Pudlo, Nicholas; Martens, Eric C.; Desai, Prerak; Lebrilla, Carlito B.; Weimer, Bart C.; Mills, David A.; German, J. Bruce; Sonnenburg, Justin L. (2011). "Bacteroides in the Infant Gut Consume Milk Oligosaccharides via Mucus-Utilization Pathways". Cell Host & Microbe 10 (5): 507–514. doi:10.1016/j.chom.2011.10.007. ISSN 1931-3128.
- ↑ Marcobal, A; Kashyap, P C; Nelson, T A; Aronov, P A; Donia, M S; Spormann, A; Fischbach, M A; Sonnenburg, J L (2013). "A metabolomic view of how the human gut microbiota impacts the host metabolome using humanized and gnotobiotic mice". The ISME Journal 7 (10): 1933–1943. doi:10.1038/ismej.2013.89. ISSN 1751-7362.
- ↑ Alliet, Philippe; Scholtens, Petra; Raes, Marc; Hensen, Karen; Jongen, Hanne; Rummens, Jean-Luc; Boehm, Guenther; Vandenplas, Yvan (2007). "Effect of prebiotic galacto-oligosaccharide, long-chain fructo-oligosaccharide infant formula on serum cholesterol and triacylglycerol levels". Nutrition 23 (10): 719–723. doi:10.1016/j.nut.2007.06.011. ISSN 0899-9007.