OXIDATIVE STRESS BIOMARKERS IN THE CARDIAC AND HEPATIC TISSUES OF RAINBOW TROUT (ONCORHYNCHUS MYKISS WALBAUM) FED THE Β-GLUCAN-SUPPLEMENTED DIET

Abstract

Treatment with β-glucans has been found to stimulate various aspects of immune responses such as resistance to infections and resistance to environmental stress. The effects of dietary β-glucans on the general health status of rainbow trout, as well as oxidative stress biomarkers in different tissues specifically should be explored. This prompted us to investigate the effects of dietary yeast β-1,3/1,6-D-glucans supplemented for a 14-day feeding period on liver and heart function and the oxidative mechanisms underlying these effects. We assessed the levels of lipid peroxidation, derivatives of the oxidatively modified proteins (OMP), and the total antioxidant capacity (TAC) in the hepatic and cardiac tissue of rainbow trout (Oncorhynchus mykiss Walbaum) after a 14-day period of oral supplementation with β-glucans. Thirty healthy rainbow trout weighing 55.9 ± 2.1 g were used in the experiments. The fish were fed with a commercial basal diet at a rate of 1.5% body weight four times a day. After acclimation, the fish were randomly divided into two groups. The groups were fed for 14 days as follows: the control group comprising rainbow trout (n = 15) received a control basal diet and the β-glucan group (n = 15) was fed with the Yestimun® food product at a dose of 1% of the basal feed (with 85% of β-1.3/1.6-glucans, Leiber GmbH, Bramsche, Germany). The basal feed was supplemented with 1% of Yestimun® powder (dose: 1 kg per 99 kg, w/w). This insoluble and highly purified preparation contains natural polysaccharides, e.g. β-1,3/1,6-D-glucans derived from Spent Brewers’ Yeast (Saccharomyces cerevisiae). Yeast cell walls typically contain approximately 30% of β-glucans of dry weight. Our results showed that feeding with low doses of β-glucans induced a statistically non-significant decrease in TBARS levels in the hepatic and cardiac tissues of rainbow trout. The feeding with low doses of β-glucans induced non-significant changes in the TAC levels both in the hepatic and cardiac tissues of rainbow trout. Levels of aldehydic and ketonic derivatives of OMP in the cardiac and hepatic tissues of rainbow trout fed the β-glucan-supplemented diet were at the same levels as in the untreated controls. In conclusion, our results unambiguously showed that β-glucan did not induce oxidative stress in the hepatic and cardiac tissues of rainbow trout.