Formation of intramuscular collagen cross-links in cattle

牛肌内胶原交联的形成

• 批准号: RGPIN-2021-02714
• 负责人: Bruce, Heather
• 金额: $ 2.91万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=743331
• 关键词: Formation; intramuscular; collagen; cross; links

Collagen is the main protein in connective tissue, and its progressive crosslinking leads to increased meat toughness as animals age. The long-term objectives of this research program are to 1) elucidate the mechanisms controlling the synthesis and crosslinking of intramuscular collagen in food animals, and 2) evaluate the impact of altering these mechanisms on meat quality. Pyridinoline (PYR) and Ehrlich's Chromogen (EC) are two intramuscular collagen crosslinks associated with toughness of meat, with EC predominating in young animals and PYR in old animals. For the preferentially formation of PYR, lysyl hydroxylase 2 (LH2) would need to be more active than lysyl hydroxylase 1 (LH1) because LH2 hydroxylates lysine in the telopeptides of the collagen molecule, a necessary step in the formation of PYR. The activities of LH1 and LH2 are respectively enhanced and inhibited by cyclophilin B (CypB). CypB expression increases when cells experience low oxygen (hypoxia) or when intracellular protein synthesis exceeds cellular capacity to fold proteins into their final structure. CypB expression is controlled through two cytoprotective pathways: the first pathway is through hypoxia-inducible factor 1 (HIF-1) while the second is through the unfolded protein response (UPR). In certain pathologies like cancer, tissues experience hypoxia and exhibit UPR, but whether this occurs in muscle during normal rapid growth is unknown. This research program, therefore, will test the hypotheses that 1) rapid growth of muscle produces endoplasmic reticulum (ER) stress and an unfolded protein response (UPR), 2) rapid growth increases the expression of CypB, 3) increased CypB expression is associated with increased LH1 activity, and 4) increased LH1 activity is associated with an increase in EC in intramuscular collagen. The operative cytoprotective pathways in rapidly growing muscle will be determined by measuring expression of mRNA and proteins associated with ER stress and hypoxia. Active UPR pathways will be determined by measuring mRNA expression and protein levels of ER stress proteins and protein levels of LH1 and LH2 will be determined using Western blot analysis and related to cytoprotective pathway results and concentrations of PYR and EC in intramuscular collagen. Broiler chickens and beef cattle will be used as the animal models in this program as rapid growth in broiler chickens is ensured by provision of unrestricted fed access, while rapid growth in beef cattle will be provoked using commercially-available steroids and the beta-adrenergic agonist ractopamine. Respective comparisons will be made to broiler chickens that are restricted-fed (80% of ad libitum) and slow-growing heritage chickens, and to non-treated cattle. This research will not only benefit control of meat quality but will impact understanding of mechanisms associated with rapid muscle growth and repair in human injury or disease.

胶原蛋白是结缔组织中的主要蛋白质，其进行性交联会导致随着动物的年龄增长而增加肉类韧性。该研究计划的长期目标是1）阐明了控制食用动物肌内胶原蛋白的合成和交联的机制，以及2）评估改变这些机制对肉质质量的影响。吡啶氨酸（Pyr）和Ehrlich的Chomogen（EC）是两个与肉的韧性相关的肌内胶原蛋白交联，在幼小动物中，EC占主导地位。为了优先形成PYR，赖氨酸羟化酶2（LH2）需要比赖氨酸羟化酶1（LH1）更活跃，因为LH2羟基酯在胶原蛋白分子的端主中的LH2羟基赖氨酸，这是Pyr形成的必要步骤。 LH1和LH2的活性分别被环友B（CYPB）增强和抑制。当细胞经历低氧（缺氧）或细胞内蛋白质合成超过细胞的能力时，CYPB表达会增加。 CYPB表达通过两种细胞保护途径进行控制：第一个途径是通过低氧诱导因子1（HIF-1）来控制的，而第二个途径是通过未折叠的蛋白质反应（UPR）。在癌症等某些病理中，组织经历缺氧并表现出UPR，但是在正常快速生长过程中是否发生在肌肉中。因此，该研究计划将测试以下假设：1）肌肉的快速生长产生内质网（ER）应力和展开的蛋白质反应（UPR），2）快速生长增加了CYPB的表达，3）CYPB表达的表达增加与CYPB表达相关。随着LH1活性的增加，4）LH1活性增加与肌内胶原蛋白的EC增加有关。快速生长的肌肉中的手术细胞保护途径将通过测量与ER应激和缺氧相关的mRNA和蛋白质的表达来确定。主动UPR途径将通过测量MRNA表达和ER应激蛋白的蛋白质水平，LH1和LH2的蛋白质水平将使用蛋白质印迹分析确定，并且与肌内胶原蛋白中PYR和EC的浓度有关。肉鸡鸡和牛肉将用作该程序中的动物模型，因为通过提供不受限制的美联储获得肉鸡的快速生长，而肉牛的快速生长将使用商业上可用的类固醇和β-肾上腺素 - 肾上腺素激动剂引起ractopamine。将与受限制的喂食（占多数的80％）和生长缓慢的遗产鸡以及未经处理的牛的肉鸡进行比较。这项研究不仅会受益于对肉质质量的控制，而且会影响对与人类伤害或疾病快速肌肉生长和修复相关机制的理解。