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This study evaluated the effects of dietary myo-inositol (MI) on growth performance, antioxidant status and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis) fed different percentage of lipid. Crabs (4·58 (sem 0·05) g) were fed four diets including a normal lipid diet (N, containing 7 % lipid and 0 mg/kg MI), N with MI supplementation (N + MI, containing 7 % lipid and 1600 mg/kg MI), a high lipid diet (H, containing 13 % lipid and 0 mg/kg MI) and H with MI supplementation (H + MI, containing 13 % lipid and 1600 mg/kg MI) for 8 weeks. The H + MI group showed higher weight gain and specific growth rate than those in the H group. The dietary MI could improve the lipid accumulations in the whole body, hepatopancreas and muscle as a result of feeding on the high dietary lipid (13 %) in crabs. Besides, the crabs fed the H + MI diets increased the activities of antioxidant enzymes but reduced the malondialdehyde content in hepatopancreas compared with those fed the H diets. Moreover, dietary MI enhanced the expression of genes involved in lipid oxidation and exportation, yet reduced lipid absorption and synthesis genes expression in the hepatopancreas of crabs fed the H diet, which might be related to the activation of inositol 1,4,5-trisphosphate receptor (IP3R)/calmodulin-dependent protein kinase kinase-β (CaMKKβ)/adenosine 5'-monophosphate-activated protein kinase (AMPK) signalling pathway. This study demonstrates that MI could increase lipid utilisation and reduce lipid deposition in the hepatopancreas of E. sinensis fed a high lipid diet through IP3R/CaMKKβ/AMPK activation. This work provides new insights into the function of MI in the diet of crustaceans. [ABSTRACT FROM AUTHOR]

Zinc (Zn) is an essential trace mineral element in organisms and is involved in physiological processes. This study investigates the effects of dietary Zn on the growth, antioxidant capacity, non‐specific immunity and disease resistance of juvenile Chinese mitten crab. Zn was supplemented, respectively, at 0 (control), 25, 50, 100, 200 and 400 mg/kg to the basal diet to form six diets as Zn0, Zn25, Zn50, Zn100, Zn200 and Zn400. Each diet was separately used to feed the crabs (0.40 ± 0.01 g) for 56 days. Diet without Zn supplementation led to a higher feed intake rate, a lower Zn content in the hepatopancreas and a lower non‐specific immune enzyme activity than other groups with Zn supplement. The results also showed that compared with the control group: (1) The final weight, weight gain rate, specific growth rate, Zn in the hepatopancreas, body crude protein and the activities of serum alkaline phosphatase (AKP), acid phosphatase (ACP) and copper‐zinc superoxidase (CuZnSOD) were significantly increased in the Zn100 group. (2) Moreover, Zn accumulation in the hepatopancreas and body ash were significantly increased in the Zn200 group, and the antioxidant enzyme activities such as CuZnSOD and glutathione peroxidase (GSH‐Px) in the hepatopancreas were significantly increased. (3) In addition, the addition of Zn can activate the TLRs/NF‐κB pathway after the lipopolysaccharide (LPS) injection, resulting in upregulation of the relative mRNA expression of antimicrobial peptide (ALFs). This study demonstrates that dietary Zn supplements can significantly improve growth performance, antioxidant capacity, non‐specific immunity and disease resistance of juvenile crabs. The regression analysis showed that the optimal dietary Zn level was 94.87 mg/kg for weight gain and 96.96 mg/kg for specific growth. [ABSTRACT FROM AUTHOR]

Amino acids are not only substrates of collagen synthesis, but also signal molecules to participate in regulation of collagen metabolism. In this paper, we reviewed the nutritional regulation of collagen metabolism from collagen synthesis and catabolism. The effects of glycine (Gly), proline (Pro) and hydroxyproline (Hyp) on collagen metabolism, as well as the potential signaling pathways and molecular mechanisms involved in mediating collagen metabolism were summarized. Future research directions were also forecasted. [ABSTRACT FROM AUTHOR]

In aquaculture, it is necessary to determine of the diurnal biological variations in the intestines to determine an appropriate feeding schedule. The present study aimed to examine the transcriptomes of the Pelteobagrus vachellii intestines at four time points (0 h, 6 h, 12 h, and 18 h) within a light/dark cycle. In comparison with the zeitgeber time 0 (ZT0) transcriptomes, we identified 37,842 unigenes with significant differential expression, including 6,638; 9,626; and 7,938 that genes upregulated, and 3,507; 4,703; and 5,412 genes that were down regulated at 4, 12, and 24 h respectively. The differentially expressed unigenes were subjected to enrichment analysis, which indicated the involvement of the major digestive pathways, including digestion of protein, lipid and carbohydrate, catabolic process (protein, carbohydrate and lipid), and circadian rhythm. We selected 73 key differentially expressed genes (DEGs) from among these pathways and identified DEGs that showed increased expression at night, including those encoding trypsin-3, chymotrypsinogen 2, amino acid transporter, maltase-glucoamylase, facilitated glucose transporter, lipase, phospholipase, fatty acid-binding protein, fatty acid synthase, long-chain fatty acid transport protein, and apolipoprotein. Moreover, DEGs involved of circadian rhythm were identified, including brain-muscle-Arnt-like 1 (BMAL1), cryptochrome-1, circadian locomoter output cycles protein kaput (CLOCK) and period circadian protein homolog 1–3. Finally, the expression levels of 12 unigenes were analyzed using quantitative real-time PCR, which were in accordance with RNA-sequencing analysis. In general, the expression of genes related to the digestion of proteins, lipids, and carbohydrates showed upregulated expression at night; however, the peak time of expression of transporters for different nutrition molecules showed more diversification within the light/dark cycle. [ABSTRACT FROM AUTHOR]

Hydroxyproline (Hyp) may play an important role in collagen metabolism, as it is almost exclusively found in collagen. To examine this possibility, a 56‐day feeding trial was conducted to evaluate the effect of graded supplementaries of Hyp (0, 2.5, 5, 7.5, 10 and 12.5 g/kg dry diet weight) on growth performance, feed utilization, biochemical composition and collagen synthesis of chu's croaker, Nibea coibor (13.6 ± 0.28 g). The growth performance and feed utilization were improved with increased levels of dietary Hyp, reaching a maximum at 5 g/kg (diet H2) followed by a slight decrease. Polynomial regression analysis showed that the maximum specific growth rate (SGR) was attained at 7.177 g/kg dietary Hyp. Increasing levels of Hyp did not affect body composition of juvenile Nibea coibor. However, dietary Hyp supplementation significantly affected the levels of Leu, Ile, Met, Lys, Ser, Glu and Pro in muscle and the levels of Met, Lys, Glu, Pro and Gly in swim bladder. The serum calcium (SC) level decreased significantly with increasing levels of dietary Hyp. However, the triglycerides (TG) and total cholesterol (T‐CH) levels in serum and liver were relatively stable. Importantly, the acid‐soluble collagen (ASC) and total collagen (TC) levels in swim bladder increased significantly initially and then decreased after reaching a maximum. Polynomial regression analysis revealed that the maximum TC level in swim bladder was attained at 9.736 g/kg of dietary Hyp. Collectively, these results suggest that the appropriate provision of hydroxyproline is essential for maximal collagen synthesis and growth. [ABSTRACT FROM AUTHOR]

Vitamin D 3 (vit-D 3 ), as an indispensable and fat-soluble nutrient, is associated with skeletal mineralization and health in mammals. However, such associations have not been well studied in economically important crustaceans. Six levels of vit-D 3 with isonitrogenous and isolipidic diets were used to feed Eriocheir sinensis . The range of optimal vit-D 3 requirements is 5685.43-10,000 IU/kg based on growth. The crabs fed 9000 IU/kg vit-D 3 showed the best growth performance. This vit-D 3 dose significantly increased antioxidant capacity in the hepatopancreas and intestine and was optimal for molting and innate immunity via quantitative polymerase chain reaction analysis. Transcriptomics analyses indicate that vit-D 3 could alter protein processing in the endoplasmic reticulum, steroid biosynthesis, and antigen processing and presentation. As shown by the enzyme-linked immunosorbent assay, vit-D 3 could improve vitamin D receptor, retinoic acid receptor, and C-type lectins concentrations. The 1α,25-dihydroxy vit-D 3 content in serum was significantly higher in 3000-9000 IU/kg vit-D 3 . The study suggests that dietary vit-D 3 and its metabolites can regulate molting and innate immunity in crabs.