Mannan: The Therapeutic Potential


Mannan is a generic name for a linear polymer of linked mannose residues or a polysaccharide moiety of glycoproteins, and also refers to the polysaccharide cell wall found in yeasts. 

Mannan can be isolated from plants such as algae, mushrooms and yeast. It is used in nutrition and medicine due to its low toxicity, minimal side effects, low cost, and broad spectrum of therapeutic uses.

Mannan Structure & Function

The therapeutic potential of mannan is linked to its function as a regulator of macrophage activation. Macrophages are a type of immune system white blood cell that engulfs and digests unhealthy body cells such as cancer cells, microbes, cellular debris and foreign substances. 

Mannan has been shown to cause an in vivo (inside the body) increase of liver lysosomes density. Researchers demonstrated this by using isopycnic centrifugation in a sucrose gradient along with a distribution of several reference enzymes, revealing a shift in the distribution of cathepsin C  and lysosomal enzymes arylsulfatase to higher-density fractions of liver macrophages. This was observed without changes in marker enzymes in either mitochondria or peroxisomes.

Hypolipidemic Effects of Mannan

Mannans have been reported to stimulate macrophages as immunomodulators in vivo via their interaction with the mannose receptor. In addition, studies demonstrated that mannans can participate by involving macrophages in the elimination of circulating atherogenic lipoproteins. 

Since both adaptive and innate immune responses have a role in every phase of atherosclerosis, the latter is tightly regulated. Therefore, through their immunomodulatory features, polysaccharides such as mannan can be employed to develop new ways to treat and prevent hyperlipidemia and atherosclerosis.

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Effects of Mannans on Tumors

Mannans and other polysaccharides such as β-glucans have been reported to have antimetastatic and antitumor effects in research experiments. The studies suggest that a brief treatment of lymphocytes with galactomannan – a galectin antagonist – reduces cell surface motility, prevents glycosylated receptors binding when present on the membrane of tumor-infiltrating lymphocytes, and has a corrective function of these cells. In addition, it was suggested that a mannan-modified adenovirus that encodes vascular endothelial growth factor receptor 2 may induce antitumor immunity.

Macrophages associated with tumours perform critical functions such as tumor angiogenesis, metastasis, and immune evasion. Recent research suggests that a conjugate of alendronate-glucomannan – known to reduce tumor-associated macrophages – may have some effect for cancer immunotherapy. This was shown in both in vitro and in vivo assays where the conjugate accumulated preferentially in macrophages and induced apoptosis. Thus, the researchers demonstrated that therapeutic agents may eliminate tumor-associated macrophages and could present a strategy for cancer immunotherapy.

Action of the Mannose Receptor

Macrophages contain a mannose receptor that has been shown to be expressed by dendritic cells, macrophages and endothelial cells. The receptor has an essential role in the scavenging of mannoglycoproteins through a process called endocytosis.

Evidence strongly suggests that the mannose receptor plays a role in pathogen clearance through an action that binds it to mannose-containing and fucose-containing microorganisms. This is accomplished through carbohydrate recognition domains. The subsequent stimulation and binding of phagocytosis by the macrophage mannose receptor results in the trigger of products that further enhance the antigen clearance.

Role in immune response

Since the mannose receptor has a broad binding specificity, its ligand specificity and cellular distribution give it a critical function in immune responses and homeostasis. 

Many pathogenic microbes have mannose-containing structures on their surface. The receptor interacts with those pathogens, functions in endocytosis and phagocytosis, and scavenges unwanted mannoglycoproteins through its role in immune homeostasis.

Regulation of inflammatory responses

Mannose receptors are critical to the regulation of inflammatory responses through their regulation of the level of molecules released by inflammatory processes. These receptors are found at low levels during inflammation and increase at the end of the inflammation process. 

Action in the brain

The expression of the mannose receptor in the brain has been observed through mannose receptor mediation in vitro pinocytosis by astrocytes and microglia  – glial cells capable of conversion to immunocompetent cells. In addition, astrocytes and microglia represent the main sites of expression of mannose receptor in vivo and in vitro. Expression and endocytic activities in these cells by the mannose receptor are regulated by various cytokines. Finally, it should be noted that this receptor is often used by adapted intracellular pathogens and can recognize a wide variety of microorganisms. 


Mannans have been shown to offer numerous health benefits, including weight control, obesity control,  management of diverticular disease, prebiotic benefits, diarrhea prevention, constipation alleviation, and the inhibition of inflammation due to gut-related conditions. In addition, research suggests that mannans balance intestinal microbiota, offer immune-system modulation, and reduce colorectal cancer risk. 

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Mannan FAQ

Mannan is found in the cell walls of plants. In addition, some derivatives of mannan are found in nature in instances where the repeating sugar unit alternates between mannose and glucose to form glucomannan.

Mannan oligosaccharides are prebiotics, derived from the outer cell wall of S. cerevisiae and composed of complex carbohydrate molecules.

Galactans are the polysaccharides that are composed of galactose derivatives while mannans are also polysaccharides that are composed of mannose.

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Works Cited

Korolenko, Tatiana A., et al. “Glucan and Mannan—Two Peas in a Pod.” International Journal of Molecular Sciences, vol. 20, no. 13, 29 June 2019,  Accessed 27 July 2021.

Mannan – an Overview – ScienceDirect Topics.” . Accessed 27 July 2021.