在不同階段飼喂低蛋白日糧對生長豬骨骼肌內游離氨基酸組成和蛋白質合成途徑的調控

畜牧編輯 · 發表于 2017-2-13 10:26:30

　　2016. J. Anim. Sci. 94(12):5192-5205

　　在不同階段飼喂低蛋白日糧對生長豬骨骼肌內游離氨基酸組成和蛋白質合成途徑的調控

　　Y. H. Li, H. K. Wei, F. N. Li , S. W. Kim,C. Y. Wen, Y. H. Duan, Q. P. Guo, W. L. Wang, H. N. Liu and Y. L. Yin

　　本試驗旨在探究保證生長豬肌蛋白沉積量不變的情況下日糧粗蛋白水平可降低的程度及其相關機制，以及試驗豬對日糧蛋白受限所產生的反應是否受到后期飼養環節的影響而發生劇烈變化。選取36頭試驗豬（初始重為9.57±0.64 kg）分為兩組置于獨立的限位欄飼養10天或者是25天。每組豬只再分為3個小組，不同小組日糧的粗蛋白水平分別為20%、17%和14%。其中粗蛋白水平為17%和14%的日糧均補充Lys、Met、Thr和Trp，使日糧中以上四種氨基酸濃度與20%粗蛋白水平日糧相一致。試驗結果表明與飼喂20%和17%粗蛋白水平日糧的豬只相比，飼喂14%粗蛋白日糧10天和25天后豬只的生長狀況均受到顯著抑制（P < 0.05）。

　　飼喂20%粗蛋白水平日糧25天后豬只血漿中尿素氮含量比飼喂17%和14%粗蛋白水平日糧的豬只要高。另外，飼喂低蛋白水平日糧25天后豬只骨骼肌中游離氨基酸水平有顯著變化（P < 0.05）；值得注意的是，14%粗蛋白日糧與20%粗蛋白日糧相比可顯著提高肌肉中游離氨基酸濃度。同時，日糧中粗蛋白水平的降低也影響了試驗結束時骨骼肌內某些氨基酸轉運載體的mRNA水平，尤其是14%和20%兩種粗蛋白水平日糧組間存在極顯著的差異。

　　最重要的是，我們發現給豬只飼喂14%粗蛋白日糧后其骨骼肌中雷帕霉素靶蛋白復合物1（mTORC1）通路相關基因得到全面的激活（P <0.05）。飼喂17%粗蛋白日糧的豬只與飼喂20%粗蛋白日糧的豬只相比只有部分基因受到抑制。然而，給豬只飼喂低蛋白水平日糧十天后我們發現血漿指標、肌肉中游離氨基酸濃度和肌肉中mTORC1 通路的變化極小。

　　總的來說，本試驗的研究結果表明在14%粗蛋白日糧中補充限制性氨基酸并不能有效恢復豬只蛋白合成和肌肉生長，然而17%粗蛋白日糧可能會維持豬只的肌肉水平，而肌肉水平在部分程度上受到氨基酸轉運載體表達量、游離氨基酸水平和mTORC1信號通路激活程度的調節。

　　Regulation in free amino acid profile and protein synthesis pathway of growing pig skeletal muscles by low-protein diets for different time periods

　　Y. H. Li, H. K. Wei, F. N. Li , S. W. Kim,C. Y. Wen, Y. H. Duan, Q. P. Guo, W. L. Wang, H. N. Liu and Y. L. Yin

　　The objective of the study was to explore the extent to which the dietary CP level can be reduced for maintaining muscle protein deposition in growing pigs as well as the related mechanism and whether the response to dietary protein restriction is diversely modified throughout the 2 trial periods. A total of 36 pigs (9.57 ± 0.64 kg initial BW) were individually penned and fed 1 of 3 diets for 10 or 25 d. During each period, the diets contained 20, 17, and 14% CP, respectively. Both the 17% CP diet and the 14% CP diet were supplemented with Lys, Met, Thr, and Trp to provide the same total concentrations as those in the 20% CP diet. Results showed that feeding the 14% CP diet for 10 or 25 d seriously impaired (P < 0.05) growth performance of the pigs compared with those fed the 20 or 17% CP diets. Pigs fed the 20% CP diet for 25 d had a higher (P < 0.05) serum content of urea nitrogen than those fed the 17 and 14% CP diets. In addition, the free AA (FAA) profile in skeletal muscle of the pigs was evidently changed (P < 0.05) by the low-protein diets for 25 d; of note, the 14% CP diet increased (P <0.05) the size of muscle FAA pool compared with the 20% CP diet. Meanwhile, ond 25, reducing dietary CP levels also influenced (P < 0.05) mRNA levels of specific AA transceptors expressed in skeletal muscle, especially revealing the striking differences between the 14 and 20% CP diet–fed pigs. Most importantly, we observed a globally decreased (P < 0.05) activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway in skeletal muscle of pigs fed the 14% CP diet, whereas only partial inhibition was observed for those fed the 17% CP diet compared with those fed the 20% CP diet. However, feeding the low-protein diets for 10 d had minimal effects on serum parameters, muscle FAA profile, and muscle mTORC1 pathway of the pigs. Taken together, our results indicate that supplementing with limiting AA to the 14% CP diet is not highly effective for the pigs in restoring protein synthesis and muscle growth, whereas the 17% CP diet likely maintains the pigs’ muscle mass, which were regulated, at least in part, by mediating AA transceptors expression, FAA profile, and activation of the mTORC1 pathway。

翻譯：李光燃來源：豬營養國際論壇CSIS