β-Glucan: Mode of Action and Its Uses in Fish Immunomodulation

Abstract

β-glucan is considered as an effective immunostimulant because of its binding capacity to different receptors on leukocytes leading to the stimulation of immune responses including bactericidal activity, cytokine productivity, and survival fit ability at cellular levels. In response to immune cell surface receptors, β-glucan stimulates to release cytokines and chemokines. It has been found that these signaling proteins eventually stimulate the immunocompetent cells in fish such as monocytes, macrophages, and neutrophils for killing pathogens by phagocytosis, oxidative burst, and cytotoxic killing activities. They also procreate immunological memories and specific antibodies through activation of T and B lymphocytes. Researchers have proved that β-glucan can modulate some important biochemical (serum hemoglobin, serum protein, and total hemocyte count) and immunological (lysozyme activity, phagocytic activity, oxidative burst activity, and phenoloxidase activity) properties providing more competent immune profile for treating fish and aquatic organisms. β-glucan-supplemented fish showed limited sensitivity of genes involved in acute inflammatory reactions. Findings have shown that β-glucan exerts a positive impact on fish and aquatic organisms’ immunity, enhancing their disease resistance by increasing functional and decreasing deleterious responses. This review focuses on the basic bump of β-glucan on fish and shellfish immunity and recent information on the uses of β-glucan in progressive aquaculture.

A Modeled High-Density Fed-Batch Culture Improves Biomass Growth and β-Glucans Accumulation in Microchloropsis salina

“…They are found as components in plants, fungi, yeasts, and bacteria, among other microorganisms, playing a structural role or as an energy reservoir [ 1 ]. These molecules are known to have several interesting properties, such as anti-cancer activity [ 3 ], antiseptic effects [ 4 ], antioxidant properties [ 5 ], decreasing the risk of cardiovascular disease [ 6 ], and improving immunological responses in several animals [ 7 , 8 , 9 ]. This last observation has been reported in studies carried out on salmon and trout species, whereby supplementing fish diets with β-glucans improve its resistance to pathogens [ 10 , 11 ]…”

The Potential of beta-glucan as feed additives in broiler chickens: A review

“…The growth-promoting effect of β-glucan is attributed to their ability to limit the growth of potentially pathogenic bacteria in the digestive tract of ( Moon et al, 2016) animals then improving intestinal function and gut health via increase in villus uniformity and integrity (Jahanian & Ashnagar, 2015). In response to immune cell, β-glucan stimulates to release cytokines and chemokines as signaling proteins that stimulate the immunocompetent cells (monocytes, neutrophils, and macrophages) for killing pathogens by phagocytosis, oxidative burst, and cytotoxic killing activities (Hadiuzzaman et al, 2022). Thus, the digestive tract remains healthy, functions more efficiently, and more nutrients are available for absorption…”

Hematological changes in Florida pompano (Trachinotus carolinus) supplemented with β‐glucan and Pediococcus acidilactici synbiotic

“…A fortified intestinal barrier may also explain the role of β-glucan prebiotics in preventing the entry and colonization of pathogenic microbes and limiting the absorption of ingested toxicants (Pogue et al, 2021). Their immunomodulatory properties are suspected to be related to their molecular structure (degree of branching) and molecular weight with highmolecular-weight β-glucans, with branching ratios between 0.2 and 0.33, generally being the most potent immunomodulators (Hadiuzzaman et al, 2022;Han et al, 2020;Rieder et al, 2011).…”

“…A fortified intestinal barrier may also explain the role of β‐glucan prebiotics in preventing the entry and colonization of pathogenic microbes and limiting the absorption of ingested toxicants (Pogue et al, 2021). Their immunomodulatory properties are suspected to be related to their molecular structure (degree of branching) and molecular weight with high‐molecular‐weight β‐glucans, with branching ratios between 0.2 and 0.33, generally being the most potent immunomodulators (Hadiuzzaman et al, 2022; Han et al, 2020; Rieder et al, 2011). Because β‐glucans are components of yeast and fungal cell walls (composing 30%–60% of Saccharomyces cerevisiae cell walls), they are recognized by pattern recognition receptors (PRRs), like the C‐type lectin receptor dectin‐1 (also known as β‐glucan receptor) (βGR), scavenger receptor (SR), complement receptor 3 (CR3), and toll‐like receptor (TLR) as pathogen‐associated molecular patterns (PAMPs) and thus trigger both pro‐inflammatory (IL‐1β, IL‐9, IL‐6, and TNF‐α) and anti‐inflammatory (IL‐10 and IL‐11) cytokine release and immunological gene expression (del Valle et al, 2023; Machuca et al, 2022; Meena et al, 2013; Petit et al, 2019; Pogue et al, 2021).…”

“…Because β‐glucans are components of yeast and fungal cell walls (composing 30%–60% of Saccharomyces cerevisiae cell walls), they are recognized by pattern recognition receptors (PRRs), like the C‐type lectin receptor dectin‐1 (also known as β‐glucan receptor) (βGR), scavenger receptor (SR), complement receptor 3 (CR3), and toll‐like receptor (TLR) as pathogen‐associated molecular patterns (PAMPs) and thus trigger both pro‐inflammatory (IL‐1β, IL‐9, IL‐6, and TNF‐α) and anti‐inflammatory (IL‐10 and IL‐11) cytokine release and immunological gene expression (del Valle et al, 2023; Machuca et al, 2022; Meena et al, 2013; Petit et al, 2019; Pogue et al, 2021). Beta‐glucans have proven to be an effective immunostimulant in fish with several papers reviewing the modes of action and beneficial effects in detail (Hadiuzzaman et al, 2022; Machuca et al, 2022; Meena et al, 2013; Petit & Wiegertjes, 2016; Pogue et al, 2021; Rojo‐Cebreros et al, 2018). The antioxidant effects of β‐glucans and other prebiotics likely center around their immunostimulant activity through the activation of immune cells, production of mitochondrial reactive oxygen species, and their role in subsequent expression of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione‐s‐transferase (GST), and glutathione peroxidase (GSH‐Px) (Machuca et al, 2022; Pogue et al, 2021).…”