Dietary vitamin B6 could improve the utilization of high carbohydrate diet by promoting carbohydrate degradation and lipid synthesis in Pacific white shrimp (Litopenaeus vannamei)

Abstract

An eight-week feeding trial was carried out to evaluate the impacts of dietary vitamin B₆ on growth performance, antioxidant capacity, carbohydrate metabolism, and lipid metabolism in Pacific white shrimp (Litopenaeus vannamei) under different carbohydrate levels. Six isonitrogenous and isolipid diets were formulated to contain two carbohydrate levels (15 % and 30 %) and three vitamin B₆ levels (0, 120 mg kg⁻¹ and 240 mg kg⁻¹). A total of 540 juvenile Pacific white shrimp (initial weight 1.15 ± 0.02 g) were randomized to six diets with three replicates, and each replication was stocked with 30 shrimp. The results suggested that dietary carbohydrate levels had no significant effect on percent weight gain (PWG) and specific growth rate (SGR), while PWG and SGR were significantly affected by dietary vitamin B₆ levels. The highest PWG and SGR appeared in the groups with 240 mg kg⁻¹ vitamin B₆ supplementation at different carbohydrate levels (P < 0.05). However, the interaction between vitamin B₆ and carbohydrate levels did not show significant differences in PWG and SGR (P > 0.05). Dietary vitamin B₆ and carbohydrates levels had a marked interaction in the content of glutathione (GSH) and concentration of malondialdehyde (MDA) in the hepatopancreas, and dietary vitamin B₆ observably increased the GSH content and decreased the concentration of MDA in 30 % carbohydrates (P < 0.05). Moreover, the contents of insulin-like peptide (INSL), crustacean hyperglycemic hormone (CHH), pyruvic acid (PA) and glucose, and the activities of phosphate fructose kinase (PFK) were markedly impacted by the interaction between dietary vitamin B₆ and carbohydrate levels. Vitamin B₆ supplementation could promote glucose transport, hepatopancreatic glycolysis, and insulin signaling pathway along with the degradation of glycogen in shrimp under high carbohydrate levels. Lipid metabolism results showed that dietary vitamin B₆ supplementation could increase lipid synthesis under 30 % carbohydrate diets. Overall, the finding indicated that vitamin B₆ supplementation could increase antioxidant capacity and regulate glucose metabolism by promoting carbohydrate degradation and lipid deposition in shrimp.