日粮碳水化合物促进猪肌内和皮下脂肪形成的差异及调控机制研究

Intramuscular fat is a major contributor to meat flavor, meanwhile, it also influences meat color, tenderness and juiciness. Dietary carbohydrate, which is the main substrate of lipogenesis for pigs, regulates expression of adipogenesis through insulin and glucose metabolite, however, their molecular mechanisms were unclear. Bamei pigs, one native breed located in the northwest part of China, are characterized by a high subcutaneous (SC) fat content and intramuscular (IM) fat content. In this study, changes of number and size of preadipocytes and adipocytes are determined using frozen section staining and immunohistochemical techniques, and expressions of lipogenic genes detected by molecular biotechnology in longissimus dorsi and subcutaneous adipose tissue from Bamei and Landrace pigs at different ages, to study the cytological basis of adipogenesis and mechanism and differences for de novo lipogenesis regulated by dietary carbohydrate in these tissues; Moreover, porcine Gene Expression Microarrays are employed to investigate the effect of dietary carbohydrate on gene expression profiles in IM and SC adipse tissue, and screen potentially differential expression genes related to lipid metabolism, furtherly, of which role and signal pathway in adipogenesis induced by glucose are to be studied in primary cultured IM and SC adipocytes with RNAi to elucidate molecular mechanism underlying regulation of glucose in adipocytes lipogenisis and fat deposition. This study would be important to expore regulating pathway of fat deposition by nutrion and improving the meat quality, also establish the theoretical basis for utilization of the advantage genetic resources of local pig breeds.

肌内脂肪直接参与肉质嫩度、风味和多汁性的形成，皮下脂肪影响胴体品质；日粮碳水化合物是猪主要的能量来源和生脂底物，也通过胰岛素及葡萄糖代谢产物调控脂肪形成，但其调控机制尚不清楚。本项目立足我国地方猪种体脂含量高、肉质好的特性，利用免疫组化法和冰冻切片染色，分析生长早期不同阶段八眉、长白猪背最长肌和皮下脂肪组织前体脂肪细胞及脂肪细胞数量、大小的变化，以分子生物学方法分析生脂基因表达，研究日粮碳水化合物调控肌内和皮下脂肪形成的细胞学基础和脂肪从头合成的分子机制及差异；采用基因表达谱芯片分析，研究碳水化合物对肌内和皮下脂肪组织基因表达谱的影响，筛选脂肪代谢相关差异表达基因，并利用分离培养的猪肌内和皮下脂肪细胞及RNAi技术研究其在葡萄糖诱导脂肪形成中的作用和调控通路，揭示调控肌内和皮下脂肪生成和沉积的机制，探讨通过营养调控猪脂肪沉积的途径，为改善猪肉品质及挖掘地方猪种优势遗传资源提供理论基础。

肌内脂肪直接参与肉质嫩度、风味和多汁性的形成，脂肪酸组成与消费者健康密切相关。日粮碳水化合物和脂肪是猪主要的能量物质，也通过不同的途径调控猪脂肪形成。本项目采用不同日粮处理，研究了高碳水化合物日粮对猪生产性能、肉质性状及健康相关性状的影响。结果表明，相对于添加植物油日粮，高碳水化合物日粮不影响猪生产性能和肉品质，但添加亚油酸、亚麻酸含量不同的植物油显著提高了肌内脂肪含量及皮下脂肪和肌内脂肪n-3 PUFA含量；利用RNA-seq研究日粮对猪基因转录谱的影响，高碳水化合物日粮与富含亚油酸和亚麻酸日粮处理相比，在脂肪组织分别发现361个和54个DEGs，肌肉分别发现394和179个DEGs。DEGs显著富集的GO条目包括免疫系统过程、代谢过程、生长等；利用KEEG等数据库，鉴定了影响脂肪沉积、脂肪酸组成包括碳水化合物代谢、脂质代谢调控、信号转导、PPAR信号等通路的DEGs，以及影响体液免疫和抗氧化性能的DEGs；利用切片染色，分析7日龄、120日龄八眉猪、长白猪背最长肌和皮下脂肪组织脂肪细胞数量、大小的变化，研究了脂肪形成的细胞学基础；利用细胞培养技术，研究了葡萄糖和胰岛素调控脂肪生成的分子机制。结果证明，葡萄糖主要通过ChREBP和LXRα或LXRα/SREBP-1c调控猪脂肪细胞生脂及生脂基因表达，而胰岛素主要通过SREBP-1c及LXRα或LXRα/SREBP-1c调控生脂。研究结果为进一步研究深入研究营养调控的分子机制提供了丰富的依据。