Effects of a β-glucan-enriched diet on biomarkers of oxidative stress, energy metabolism and lysosomal function in muscle tissue of European grayling (Thymallus thymallus L.).

Introduction: The grayling (Thymallus thymallus L.) has several advantages over other fish species that make it attractive for aquaculture and invest it with importance for food security. The study assessed the effects of a β-glucan-enriched diet on biomarkers of oxidative stress, energy metabolism and lysosomal function in muscle tissue of European grayling (Thymallus thymallus L.).

Material and methods: Sixty-six grayling weighing approximately 34 g were divided into equal control and experimental groups. A basal diet was fed to the control group and a β-glucan-enriched one was fed to the experimental group for 45 d. Lipid peroxidation (LP) level; oxidative protein modification (OPM); total antioxidant status (TAS); and superoxide dismutase (SOD), catalase (CAT), glutathione reductase, glutathione peroxidase (GPx), alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate (LDH), succinate dehydrogenase (SDH), alanyl aminopeptidase, leucyl aminopeptidase, acid phosphatase (AcP) and β-N-acetylglucosaminidase (NAG) activities were assessed in the muscle tissue of fish euthanised after 15, 30 and 45 d of feeding.

Results: The β-glucan supplementation reduced LP, attenuated OPM and improved the TAS in muscle tissue. Increased SOD and CAT activity and maintenance of GPx activity in muscle tissue were the main mediators of these effects. They also affected energy metabolism through modulation of key enzymes and metabolites, including ALT, AST, LDH, SDH, AcP and NAG activity, and altered lactate and pyruvate levels. Multivariate analysis of variance, supported by high F-values and low P-values indicating statistical significance, highlighted the significant effect of β-glucans and feeding duration on markers of oxidative stress, antioxidant defences and TAS.

Conclusion: B-glucans altered the balance between aerobic and anaerobic metabolism, reduced OPM and modulated the transaminase response, affecting amino acid metabolism and the production of Krebs cycle intermediates.