What is Lacto-N-Tetraose (LNT)?

November 02, 2023 7 min read

What is Lacto-N-Tetraose (LNT)?

More than 200 Types of HMOs

Current scientific research has identified human milk oligosaccharides (HMOs) as having many benefits for human health. There are over 200 of these glycans (sugars), and they are the third most abundant part of human breast milk[i].

One of the handful is lacto-N-tetraose (LNT), one of the most abundant HMOs present in human breast milk, and the one we are going to observe in this article. So, join us as once again we enter this fantastic world of biological magic.

What is Lacto-N-tetraose? 

Lacto-N-tetraose or LNT has noteworthy importance in the HMO world. In research studies, it has been seen to have multiple functions, as a prebiotic (food) for the gut microbiota, antiadhesive properties that ultimately protect the gut cells from attachment by pathogenic bacteria, anti-viral protection, and immune-modulating processes that enhance the immune system against disease[ii].

Structure of Lacto-N-tetraose

LNT is composed of four monosaccharides, meaning it is classed as a tetra-saccharide. The monosaccharide units are galactose, N-acetylglucosamine, an additional galactose, and glucose. Being the least soluble of the glycans, and because of its binding pattern, LNT components can combine and create an almost solid structure, a composition that has been seen to have immunomodulatory and metabolic properties, these processes may help fight disease[iv].

 

 

Structure of LNT

 

Figure 1. Structure of LNT: the orange circles represent galactose, the blue square is the N-acetylglucosamine and the blue circle is glucose. (Adapted from James et al., 2016)[iii].

 

LNT and LNnT are isomers. That means they have the same molecular formula, but their atoms are arranged in different formations. LNT and its derivatives constitute more than half of HMOs. LNT is classified as a type I HMO and LNnT is a type II HMO. They are identical except for their glycosidic linkage, β1-3 vs β1-4. Interestingly, it is this structural difference that is hypothesised as the reason for the differential phenotypes in bifidobacterial utilisation in these two HMOs. We’ll explore LNnT in more depth shortly.

What are the functions of lacto-N-tetraose?

Lacto-N-tetraose is a prebiotic because it encourages the growth of healthy gut bacteria. Its presence in human breast milk means that LNT is one of the first functional foods you encounter as babies, feeding the first colonisers of your gut microbiome, including Bifidobacteria.

LNT and Bifidobacteria

    Bifidobacterium longum infantis (B. infantis) is particularly fond of LNT. B. infantisis a typical resident of the infant gut, taking full advantage of HMOs like LNT to bolster its abundance. Being present in large numbers is of uppermost importance for your good gut microbes. Once in your colon, it thrives and contributes to an optimum environment where good gut bacteria can become abundant.

    LNT versus LNnT

      Research shows that B. infantis grows more efficiently while utilising LNT rather than LNnT. A further study by Li et al (2023) also demonstrated that B. infantiscan use N-acetylglucosamine-containing HMOs, including LNT, as nitrogen sources[v].

      Postbiotics 

        The metabolism of LNT by strains such as B. infantisyields SCFAs like acetate and lactate, powerful postbiotics that have been shown to regulate the immune system and improve the integrity of the gut barrier function[vi].  For example, Groeger et al., (2013) found that oral administration of B. infantissignificantly reduced plasma C-reactive protein (CRP) levels in patients with both gastrointestinal and non-gastrointestinal inflammatory disorders (ulcerative colitis, chronic fatigue syndrome, and psoriasis). CRP is an inflammatory biomarker produced by the liver and increases when there’s inflammation in the body.

        Inflammation Regulation 

          The results of the study revealed that B. infantisfeeding reduced CRP levels in all three inflammatory states and lowered other pro-inflammatory messenger levels in healthy subjects, including TNF-α and IL-6. Therefore, demonstrating that this microbial strain could have positive benefits on the systemic immune system[vii].

          Furthermore, a literature review by Clarke et al., (2012) found that B. infantismay also help to relieve the symptoms of irritable bowel syndrome (IBS), like abdominal pain, bloating, and gas.

          How B. infantis utilise LNT? 

            B. infantisinteraction sees its genome encode a series of hydrolases (set of enzymes) that lead to additional enzyme and oligosaccharide transporters, initiating LNT into the chain of chemical events, and feeding it into the Bifidobacteriumfermentation pathway. This means B. infantisgenerates ATP (energy) and other substrates required for anabolic processes such as lactate (muscle energy), NAD+ crucial coenzymes found in every cell, and acetate, another energy producer, through the utilisation of HMOs like LNT[viii].

            It is the production of these metabolites that may reduce the circulation of pro-inflammatory messengers and cytokines. Whereas SCFAs such as acetate may benefit specific cardio-metabolic diseases by lowering visceral fat levels[ix].

            Promote Butyrate-Producing Bacteria  

              Acetate is also the preferred energy source of the butyrate producer Faecalibacterium prausnitzii.So, B.infantismay inadvertently help increase butyrate production by feeding on LNT, transforming it into acetate, and cross-feeding other beneficial gut microbes.

              Other Properties of LNT

                As well as its interaction with beneficial gut microbes, LNT offers other health benefits through its anti-microbial, anti-adhesion, and anti-viral properties[x].

                In studies with other HMOs, LNT has been shown to interact with the cells that line the gut, called epithelial cells. Here, LNT becomes a decoy for potential pathogenic bacteria, drawing pathogens away from binding to the colon cells via a process of secretions that almost compel these pathogens to bind elsewhere. This action renders the pathogen unable to establish itself let alone a colony. Without numbers, the risk of disease is reduced, thus providing much-needed protection, important at any stage of life, but probably none more so when we are in our infancy[xi][xii].

                With the gut cells left to go about their intended duties, HMOs like LNT then go even further, being a source of food for the gut microbiota comes with a rich reward, the production of postbiotics. These are the result of probiotics (bacteria) consuming prebiotics (food). All of these participate in day-to-day chemical reactions that keep us ticking along and include:

                • Vitamins:B and K, are essential in the activity of metabolic pathways and critical for oxygen transport and cell metabolism.
                • Amino acids:There are nine essential amino acids which must be acquired from our diet, some of which are produced during bacterial fermentation.
                • Enzymes: The catalysts that make reactions happen.
                • Bacterial lysates:These are bacterial cells that can be broken down and used for their medicinal properties.
                • Cell-free supernatants: A mixture of bacterial-produced metabolites, that when bacteria are removed, leaves behind a health-promoting liquid.
                • Short-chain-fatty-acids (SCFA’s): Perhaps the most famous of the bacterial postbiotics and produced during the fermentation of complex carbs, dietary fibres, and other prebiotics[xiii] 

                Conclusion

                LNT is a complex carbohydrate molecule that is an important constituent of human breast milk. It is an example of a human milk oligosaccharide (HMO). As we’ve witnessed in this article, LNT has several important functions for human health, including nourishing and supporting the growth of important health-promoting bacteria, particularly Bifidobacteria, and protecting the body from potential pathogens.

                LNT is one of the first functional foods we encounter as babies. Like other HMOs, LNT isn’t digested by our digestive system, instead, the good gut bacteria do it for us, transforming it into useful postbiotic molecules that help to maintain, regulate, and promote our health. But emerging research shows that HMOs are not just important in our infancy, but throughout our lifetime. Why not explore our range of HMO products to see how you can support your gut microbiome and beyond?

                 

                Written byLeanne Edermaniger, M.Sc.Leanne is a professional science writer who specializes in human health and enjoys writing about all things related to the gut microbiome. 

                Sources

                [i] Corona L, Lussu A, Bosco A, Pintus R, Cesare Marincola F, Fanos V, Dessì A. Human Milk Oligosaccharides: A Comprehensive Review towards Metabolomics. Children (Basel). 2021 Sep 14;8(9):804. doi: 10.3390/children8090804. PMID: 34572236; PMCID: PMC8465502.

                [ii] Hu M, Miao M, Li K, Luan Q, Sun G, Zhang T. Human milk oligosaccharide lacto-N-tetraose: Physiological functions and synthesis methods. Carbohydr Polym. 2023 Sep 15;316:121067. doi: 10.1016/j.carbpol.2023.121067. Epub 2023 May 25. PMID: 37321746.

                [iii] James K, Motherway MO, Bottacini F, van Sinderen D. Bifidobacterium breve UCC2003 metabolises the human milk oligosaccharides lacto-n-tetraose and lacto-n-neo-tetraose through overlapping, yet distinct pathways. Scientific Reports. 2016;6(1). doi:10.1038/srep38560

                [iv] Caseiro C, Dias JNR, de Andrade Fontes CMG, Bule P. From Cancer Therapy to Winemaking: The Molecular Structure and Applications of β-Glucans and β-1, 3-Glucanases. Int J Mol Sci. 2022 Mar 15;23(6):3156. doi: 10.3390/ijms23063156. PMID: 35328577; PMCID: PMC8949617.

                [v] Li S, You X, Rani A, Özcan E, Sela DA. Bifidobacterium infantis utilizes N-acetylglucosamine-containing human milk oligosaccharides as a nitrogen source. Gut Microbes. 2023 Dec;15(2):2244721. doi: 10.1080/19490976.2023.2244721. PMID: 37609905; PMCID: PMC10448974.

                [vi] Chichlowski M, Shah N, Wampler JL, Wu SS, Vanderhoof JA. Bifidobacterium longum Subspecies infantis (B. infantis) in Pediatric Nutrition: Current State of Knowledge. Nutrients. 2020 May 28;12(6):1581. doi: 10.3390/nu12061581. PMID: 32481558; PMCID: PMC7352178.

                [vii] Groeger D, O’Mahony L, Murphy EF, Bourke JF, Dinan TG, Kiely B, et al. bifidobacterium infantis35624 modulates host inflammatory processes beyond the gut. Gut Microbes. 2013;4(4):325–39. doi:10.4161/gmic.25487

                [viii] Özcan E, Sela DA. Inefficient metabolism of the human milk oligosaccharides lacto-n-tetraose and lacto-n-neotetraose shifts bifidobacterium longum subsp. infantis physiology. Frontiers in Nutrition. 2018;5. doi:10.3389/fnut.2018.00046

                [ix] Nogal A, Louca P, Zhang X, Wells PM, Steves CJ, Spector TD, Falchi M, Valdes AM, Menni C. Circulating Levels of the Short-Chain Fatty Acid Acetate Mediate the Effect of the Gut Microbiome on Visceral Fat. Front Microbiol. 2021 Jul 15;12:711359. doi: 10.3389/fmicb.2021.711359. PMID: 34335546; PMCID: PMC8320334.

                [x] Hu M, Miao M, Li K, Luan Q, Sun G, Zhang T. Human milk oligosaccharide lacto-N-tetraose: Physiological functions and synthesis methods. Carbohydrate Polymers. 2023;316:121067. doi:10.1016/j.carbpol.2023.121067

                [xi] Wiciński M, Sawicka E, Gębalski J, Kubiak K, Malinowski B. Human Milk Oligosaccharides: Health Benefits, Potential Applications in Infant Formulas, and Pharmacology. Nutrients. 2020 Jan 20;12(1):266. doi: 10.3390/nu12010266. PMID: 31968617; PMCID: PMC7019891.

                [xii] Cheng L, Kong C, Wang W, Groeneveld A, Nauta A, Groves MR, Kiewiet MBG, de Vos P. The Human Milk Oligosaccharides 3-FL, Lacto-N-Neotetraose, and LDFT Attenuate Tumor Necrosis Factor-α Induced Inflammation in Fetal Intestinal Epithelial Cells In Vitro through Shedding or Interacting with Tumor Necrosis Factor Receptor 1. Mol Nutr Food Res. 2021 Apr;65(7):e2000425. doi: 10.1002/mnfr.202000425. Epub 2021 Mar 3. PMID: 33465830; PMCID: PMC8047892.

                [xiii] Thorakkattu P, Khanashyam AC, Shah K, Babu KS, Mundanat AS, Deliephan A, Deokar GS, Santivarangkna C, Nirmal NP. Postbiotics: Current Trends in Food and Pharmaceutical Industry. Foods. 2022 Oct 5;11(19):3094. doi: 10.3390/foods11193094. PMID: 36230169; PMCID: PMC9564201.


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