Adipose tissue, possibly in combination with obesity associated comorbidities, are responsible for the production of many inflammatory mediators and adipocytokines. As a consequence, obese individuals often have a low-grade chronic inflammatory status. Weight loss is an effective solution to reduce the secretion of the inflammatory cytokines.
Even without performing a weight loss program in the dog trial, 90 days supplementation with MacroGard® resulted in lower serum TNF-α concentrations in the obese dogs, an important pro-inflammatory cytokine. Although not significant, other inflammatory markers IL-6 and C-reactive protein were also lower in the obese dogs after supplementation and became closer to the reference values found in lean dogs. Controlling the effects of low grade inflammation is noticed in other studies with MacroGard® as well, including trials on periodontitis (3) (5), osteoarthritis (6) and atopic dermatitis (7).
Weight loss is the recommended treatment for obese animals. However, caloric restriction of pets is difficult, as it consequently leads to the animal seeking and begging for food and this behaviour may often compromise the owner and their compliance for restricted feeding. Dietary strategies to stimulate satiety without additional calories are of great interest for managing weight reduction of companion animals.
The release of appetite-regulating hormones plays an important role in controlling the caloric intake by pet animals. Both PYY and GLP-1 prolong the gastric emptying time and the small intestine transit time, and are known to reduce appetite and promote satiety.
In the obese dogs from the trial, MacroGard® seemed to increase the release of PYY. Despite the large numerical difference between the mean PYY value before and after supplementation in the overweighted dogs, the observed difference was not significant.
However, appetite regulating hormone GLP-1 increased significantly in obese dogs after receiving beta-1,3/1,6-glucans in their diet. The increase of satiety hormones could correlate to the practical observations in this study, where four out of the seven obese dogs were eating more slowly, presented food leftovers as the study progressed and why none of the dogs showed begging behaviour attempting to obtain more food.
Beta-1,3/1,6-glucans have proven to be beneficial for overweight dogs. Inclusion of 0.1% of highly purified beta-1,3/1,6-glucans from yeast in the diet can improve glucose and lipid homeostasis, inflammatory status and satiety in obese dogs with insulin resistance. These results are in line with studies in other animal species. Although the mechanisms require further investigations, cereal and yeast beta-glucans could be complimentary to each other in a weight control diet, as the carbohydrate structures have different physiological properties in the digestive tract. MacroGard® is a natural ingredient that has proven to be beneficial for weight loss programs and in diets for obese pet animals.
Glucose and cholesterol control by beta-1,3/1,6-glucans in other species
Not only is a large part of the pet population overweight, obesity and diabetes are also a main public health issue in humans and many research projects with laboratory animals as human models are focussing on nutritional solutions. A Brazilian research group of the Federal University of Lavras evaluated the use of highly purified beta-1,3/1,6-glucans from yeast (MacroGard®) in different settings and occasions of obesity and diabetes. In type 2 diabetic rats receiving a high fat diet, the effects of exercise and beta-1,3/1,6-glucans consumption were investigated. Independent of the physical exercise, ingestion of beta-1,3/1,6-glucans significantly optimized glycaemic parameters like lower fasting blood glucose and HbA1c levels. The beta-1,3/1,6-glucans also reduced predisposition to atherosclerosis, by significantly lowering levels of triacylglycerols, total cholesterol and LDL-C in the blood, while increasing HDL-C (also known as the ‘good’ cholesterol), resulting in an improved atherogenic index (2).
Completely in line with these results, in another rat study, consumption of highly purified beta-1,3/1,6-glucans (MacroGard®) lowered blood glucose, total cholesterol and triacylglycerols in diabetic animals with and without periodontal disease (3). Furthermore, in this study treatment with this beta-1,3/1,6-glucan source reduced the release of degradative enzymes and inflammatory markers (e.g. COX-2, NF-kB). Independent of the diabetic status, alveolar bone loss was reduced in animals with gingivitis that received beta-1,3/1,6-glucans. Attenuated alveolar bone loss is also demonstrated in other studies with beta-1,3/1,6-glucans in Wistar rats (8) and cats (5). All these promising results promote further research into the effects of beta-1,3/1,6-glucans in pet animals with excess of body weight or other comorbidities.
Cereal or yeast beta-glucans?
For centuries, cereal and fungal beta-glucans have been used for medicinal and cosmetic purposes. Beta-glucans are natural components of the cell walls of plants, some bacteria and yeasts. Glucans are polymers that contain glucose as the only building block. The specific way of how glucose molecules are connected to each other, influences the physiological properties of each specific glucan structure. Figure 3 shows a glucose molecule, and the numbers refer to the location where one glucose molecule can be linked to the next glucose molecule.
Beta-glucans found in plants and cereals are predominantly linear and have branches with ß-1,3/1,4-type linkages. These ß-1,3/1,4-type glucans are soluble with low molecular weight. In contrast, beta-glucans from yeast and fungi are insoluble, and have a linear ß(1,3) backbone with side ß(1,6) branches (Figure 3).