Transcriptomic analysis elucidates the enhanced skeletal muscle mass, reduced fat accumulation, and metabolically benign liver in human follistatin-344 transgenic pigs

Follistatin (FST) is an important regulator of skeletal muscle growth and adipose deposition through its ability to bind to several members of the transforming growth factor-β (TGF-β) superfamily, and thus may be a good candidate for future animal breeding programs. However, the molecular mechanisms underlying the phenotypic changes have yet to be clarified in pig. We generated transgenic (TG) pigs that express human FST specifically in skeletal muscle tissues and characterized the phenotypic changes compared with the same tissues in wild-type pigs. The TG pigs showed increased (P<0.05) skeletal muscle growth, decreased adipose deposition, and improved metabolism status. Transcriptome analysis detected important roles of the PIK3-AKT signaling pathway, calcium-mediated signaling pathway, and amino acid metabolism pathway in FST-induced skeletal muscle hypertrophy, and depot-specific oxidative metabolism changes in psoas major muscle. Furthermore, the lipid metabolism-related process was changed in adipose tissue in the TG pigs. Gene set enrichment analysis revealed that genes related to lipid synthesis, lipid catabolism, and lipid storage were down-regulated (P<0.01) in the TG pigs for subcutaneous fat, whereas genes related to lipid catabolism were significantly up-regulated (P<0.05) in the TG pigs for retroperitoneal fat compared with their expression levels in wild-type pigs. In liver, genes related to the TGF-β signaling pathway were over-represented in the TG pigs, which is consistent with the inhibitory role of FST in regulating TGF-β signaling. Together, these results provide new insights into the molecular mechanisms underlying the phenotypic changes in pig.