Juan Gao,Xueshan Li,Kangle Lu,Kai Song,Jian Zhang,Ling Wang,Chunxiao Zhang
This study investigated the effects of dietary protein levels on growth performance, antioxidant capacity, digestive enzyme activity, and metamorphosis rate of the bullfrog ( Lithobates catesbeianus ) tadpoles. Seven isolipidic and isoenergetic diets were formulated with 24.61%, 28.49%, 33.74%, 37.50%, 44.06%, 48.39% and 53.92% crude protein. Triplicate replicates of tadpoles (growth stage 25 and 0.009 g) were fed with experimental diets two times daily for 11 weeks, and the daily feeding amount was 6.50% of the tadpole's body weight. Weight gain (WG), specific growth rate (SGR), the total antioxidant capacity (T-AOC) and catalase (CAT) activity in the liver, the intestinal trypsin activity (TPS) and metamorphosis rate at stage 42 of bullfrog tadpoles all increased with increasing dietary protein level from 24.61% to 44.06% and then decreased. Based on the second-order polynomial regression analysis of the weight gain and metamorphosis rate at stage 41 vs. dietary protein level, the optimal dietary protein level for bullfrog tadpoles was 42.49% and 46.50%, respectively. In conclusion, the optimum dietary protein level of bullfrog tadpoles was estimated to be 42.49%–46.50% of the diet.
Jia Ran,Zeyuan Yu,Xia Liu,Mingqian Wang,Yuxin Tang,Fujian Chen,Xiaodong Yu,Qiyi He
Dipeptidyl peptidase-IV (DPP-IV) is a key therapeutic target for type 2 diabetes, and food-derived inhibitory peptides are promising alternatives to synthetic drugs. In this study, bullfrog muscle protein hydrolysates were prepared using different proteases, among which the compound protease hydrolysate showed the strongest DPP-IV inhibitory activity. Ultrafiltration revealed that the <3 kDa fraction exhibited the highest potency. Three peptides (VPVG, LPVQ, and VPLG) were identified by LC–MS/MS combined with in silico screening. Among them, synthesized VPVG showed the strongest inhibitory activity (IC 50 = 128.91 μM). Enzyme kinetics indicated a mixed-type inhibition mechanism, while molecular docking and molecular dynamics simulations demonstrated stable interactions with the DPP-IV active site. The peptides showed good stability under heat treatment, varying pH conditions, and simulated gastrointestinal digestion. They exhibited no cytotoxicity in Caco-2 cells, inhibited cellular DPP-IV activity, and significantly reduced blood glucose levels in a hyperglycemic zebrafish model.
Jibin Lin,Chunxiao Zhang,Kangle Lu,Kai Song,Ling Wang
This study was carried out to evaluate the impacts and interactions of guanidinoacetic acid (GAA) and betaine (BT) supplementation of soybean-meal-based diets on the growth, meat quality, and methionine utilization in the bullfrog Lithobates catesbeianus . A basal diet was supplemented with 0 or 4 g/kg of BT and/or 0, 0.4, or 4 g/kg GAA to formulate six experimental diets, designated Control (BT/GAA: 0/0), B0G0.4 (0/0.4), B0G4 (0/4), B4G0 (4/0), B4G0.4 (4/0.4) and B4G4 (4/4). Each diet was fed to three individual bullfrogs (initially weighing 51.70 ± 0.33 g) for 8 weeks. As a result, bullfrogs fed diets with GAA showed greater weight gain than the control group ( P < 0.05). The addition of GAA or BT to the diets increased whole-body protein deposition and the hind leg index ( P < 0.05). Diets supplemented with GAA led to reduced muscle glycolysis, which increased the muscle pH value 24 h after euthanasia ( P < 0.05). However, a combination of BT and GAA had an insignificant effect on the expression of betaine homocysteine methyltransferase mRNA compared with the diets supplemented with GAA-only ( P > 0.05). The findings of this study suggest that dietary GAA supplementation improves bullfrog growth performance and muscle energy metabolism after slaughter, but GAA combined BT supplementation does not improve methionine utilization for bullfrog.
危险品化学品经营许可证（带存储）