Different Sources of Beta-glucan (β-Glucan) Offer Distinct Immunological Benefits for Healthy Dogs

Background

Beta-glucans (β-glucans) are a type of polysaccharide derived from sources such as yeasts, fungi, mushrooms, algae, bacteria, barley, and oats. β-glucans are investigated for use in animals to manage disorders associated with immune-mediated and inflammatory mechanisms, including the chronic diseases Atopic Dermatitis (AD), Osteoarthritis (OA), and Inflammatory Bowel Disease (IBD) in dogs and cats. In aquaculture, they are also used to reduce high, varying, and unpredictable mortality and morbidity in stressed marine life, such as shrimp larvae and trout. β-glucans are valuable as supplements because they are recognized as biological response modifiers possessing immunomodulatory and anti-inflammatory effects. Studies indicate that undenatured, unaltered biological structure, beta-glucans (UDBG) positively influence gene transcription related to overall health, modifying inflammatory responses, protecting from cellular stress, and enhancing immune function without causing immune system over-activity. Additionally, β-glucans function as prebiotics, being selectively fermented by gut bacteria to produce short-chain fatty acids (SCFAs), molceules produced by gut bacteria, that help regulate inflammation, repair mucosal damage, and modulate the intestinal microbiota. Due to its immune-modulating and positive  gut heath properties, β-glucan is becoming a supplement of interest to treat a variety of ailments in animals.

Study objective

Evaluate and compare the effects of β-glucans derived from the unicellular alga Euglena gracilis and yeast, Saccharomyces cerevisiae, on the immune and inflammatory activity of healthy adult dogs.

Methods

Study Design: The study included four experimental diets and was conducted in a randomised block design with two blocks of 16 dogs. For each block, the 16 dogs were split into 4 experimental groups (n=4) and lasted 84 days, with 42 days being a washout where all animals were fed the control diet and another 42 days being fed their respective experimental diets. Samples were collected on Day 42 and Day 84.

Researchers evaluated the following:

Results

No adverse reactions are observed in dogs fed a β-glucan diet

• The β-glucan sources were well-tolerated, and no changes in the clinical condition of the animals were observed during the 42 days of consumption.

The β-glucan diet enhances the immune response 

• The β-glucan source B-S15 (low dose E. gracilis) resulted in the highest monocyte phagocytic index. Both B-Y15 (yeast) and B-S15 (E. gracilis) resulted in a higher neutrophil phagocytic index compared to the control diet.
• Dogs fed B-Y15 (yeast) exhibited higher serum IL-2 concentration than animals fed B-S30 (high dose E. gracilis). No significant differences were found for IL-6, IL-10, TNF-α (serum or faecal), or faecal cytokines

The β-glucan diet may reduce oxidative stress 

• Monocytes from dogs fed E. gracilis diets (B-S15 and B-S30) produced more nitric oxide and less hydrogen peroxide compared to control and B-Y15.

Takeaways

Β-glucan derived from yeast and algae boosted the cellular immune response and may reduce oxidative stress and inflammation when incorporated into the diets of healthy dogs.

1. B-Y15: Yeast-derived β-glucan showed cell-mediated activation of the immune system, indicated by increased serum IL-2 and enhanced neutrophil phagocytic index. These β-glucans are microbial structures often recognized as pathogen-associated molecules, interacting mainly via the Dectin-1 receptor due to their branched molecular structure, leading to innate immune activation and T-cell proliferation regulation (via IL-2).
2. B-S15, B-S30: Algae-derived β-glucan acted differently, increasing monocyte nitric oxide production, monocyte/neutrophil phagocytic indices, and serum CRP. The action mechanism is hypothesized to be distinct from yeast β-glucan, possibly involving receptors other than Dectin-1, such as the Complement Receptor-3 (CR3). The concurrent increase in nitric oxide (an inflammatory mediator) and CRP, combined with the normal range of CRP and stable calprotectin, suggests preparation of the immune system without inducing a detrimental systemic inflammatory state. A simultaneous reduction in hydrogen peroxide supports a balanced immune response.

Limitations

Study Design limited to healthy beagles & ex vivo immune response

• Larger studies with a more diverse population of dog breeds, age, and health need to be conducted to see if there are any sex differences, breed differences, or age differences that may influence the response to treatment.
• Animals did not always reach the target intake of B-glucan. Studies with definitive amounts of b-glucan administered need to be conducted tor reduce variabitly attributed to dogs in teh same group intaking different amounts of food.
• The lack of observable effects on IgG (ex vivo production) and IgA (faecal concentration) may be related to the constraints of the ex vivo methods and the cohort of healthy dogs used. The study also notes that the possible effect of sex on immune responses to prebiotics in dogs remains largely unexplored.