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Response to different dietary carbohydrate and protein levels of pearl oysters (Pinctada fucata martensii) as revealed by GC–TOF/MS-based metabolomics

Yang, Chuangye, Hao, Ruijuan, Du, Xiaodong, Wang, Qingheng, Deng, Yuewen, Sun, Ruijiao
The Science of the total environment 2019 v.650 pp. 2614-2623
Chlorella, Pinctada fucata, acid phosphatase, alanine, alkaline phosphatase, amylases, antioxidant activity, aspartic acid, beta oxidation, biochemical pathways, catalase, dietary carbohydrate, disasters, energy, enzyme activity, fatty acids, food availability, food safety, glutamic acid, glutathione peroxidase, malondialdehyde, metabolites, metabolomics, monophenol monooxygenase, oysters, pollution, powders, protein content, protein synthesis, proteinases, proteins, serine, shellfish, starch, sucrose, superoxide dismutase, threonine, yeasts
Land-based culturing can avoid the effects of environmental pollution and natural disasters, thus ensuring food safety for shellfish. However, food availability, in this case, is limited. To achieve the optimum balance of dietary carbohydrates and proteins and explore the mechanisms behind the phenomenon, we formulated five isoenergetic and isolipidic diets (C30P40, C35P35, C40P30, C45P25, and C50P20) with different levels of carbohydrates (C) and proteins (P). There were five experimental groups (C30P40, C35P35, C40P30, C45P25, and C50P20) and two control groups (CG1 and CG2). CG1 was fed with mixed powders of yeast and Chlorella sp., and CG2 was cultured in natural sea. After 60-day feeding, the highest rates of survival and absolute growth appeared in C45P25. C45P25 exhibited significantly higher activities of amylase, protease, alkaline phosphatase, acid phosphatase, superoxide dismutase, catalase, glutathione peroxidase, and phenoloxidase and significantly lower malondialdehyde content than C30P40, C35P35, C40P30, C50P20, and CG1. No significant differences were observed between C45P25 and CG2. Furthermore, the total antioxidant capacity of the pearl oysters in C45P25 was significantly higher than that in C30P40, C35P35, C40P30, and C50P20. On the basis of these results, the optimal balance of proteins and carbohydrates for pearl oysters was the C45P25 diet. Metabolomics-based profiling of the pearl oysters fed with high-carbohydrate/low-protein diet (C45P25) and low-carbohydrate/high-protein diet (C30P40) revealed 80 significantly different metabolites (VIP > 1 and P < 0.05). Furthermore, integrated key metabolic pathway analysis showed that C45P25 regulated starch and sucrose metabolism, alanine, aspartate and glutamate metabolism and glycine, serine and threonine metabolism to meet the energy demand and increase the glucogenic amino acid, thereby promoting protein synthesis and reducing fatty acid β-oxidation in comparison with C30P40. This finding helps elucidate the underlying mechanisms leading to the high-carbohydrate/low-protein diet characteristic of the optimal dietary carbohydrate and protein levels of P. f. martensii.