肌纤维类型是影响肉品质的重要因素之一。申请人前期发现，日粮补充胍基乙酸可以改善猪肉品质，促进肌纤维类型的转化，但其中的相关机制尚不清楚。研究发现线粒体功能和CaN/NFAT信号通路对骨骼肌肌纤维类型转化有重要的调控作用。因此，本项目拟在前期工作基础上，以育肥猪为研究对象，研究胍基乙酸对育肥猪肉质和骨骼肌能量状态的影响，采用RT-PCR和Western-Blot等技术，探讨胍基乙酸促进线粒体的合成与功能改善的生物学机制，明确CaN/NFAT信号通路中关键基因及蛋白表达的规律；在此基础上，采用体外细胞模型，进一步探讨胍基乙酸通过CaN/NFAT信号通路调控肌纤维类型转化的分子机制。研究结果有望阐明胍基乙酸对肌纤维类型转化的影响及其调控机制，为通过营养调控技术改善猪肉品质提供重要理论依据。

The muscle fiber type is one of the main factors to affect the meat quality. In our previous research, we found that dietary guanidinoacetic acid supplementation could improve the meat quality, and regulate the transformation of muscle fiber type in finishing pigs. However, the relevant mechanism is still unclear. Several studies have found that mitochondrial function and CaN/NFAT signaling pathway have important regulatory effects on the skeletal muscle fiber type transformation. This project intends to investigate the effects of dietary guanidinoacetic acid supplementation on meat quality and energy reserves of skeletal muscle in finishing pigs, and explore the biological mechanism to promote the synthesis and function of mitochondria, and clarify the regulation of key genes and proteins in CaN/NFAT signaling pathway by RT-PCR and Western-Blot techniques. On this basis, the in vitro experiment is used to further explore the molecular mechanism of muscle fiber type transformation by guanidinoacetic acid supplementation through CaN/NFAT signaling pathway. The results are expected to clarify the effect and the regulatory mechanism of guanidinoacetic acid on muscle fiber type transformation in finishing pigs, which may provide important theoretical basis for improving pork quality through nutritional techniques.