Effects of rumen-protected guanidinoacetic acid on fat deposition, antioxidant capacity, fatty acid profiles in subcutaneous adipose of Tibetan sheep: integrated RNA-seq and LC-MS/MS analysis.

INTRODUCTION: The subcutaneous fat exerts energy storage and protective effects. However, excessive fat deposition results in waste of biological resources and compromises meat quality. According to the biological function, we hypothesized that GAA's could reduce subcutaneous fat deposition in Tibetan sheep. METHODS: A total of 120 healthy weaned male lambs (2 months old) with similar body weight (17.33 ± 0.21 kg) were randomly divided into four groups, each receiving a basal diet or diet containing 0.08%, 0.10%, or 0.12% GAA. The experimental period lasted 90 days. RESULTS: Our results showed that 0.10% GAA significantly reduced subcutaneous fat thickness (P < 0.05). Antioxidant capacity was improved, as evidenced by a reduced MDA (P, P-linear, P-quadratic < 0.05), while increased SOD and T-AOC (P, P-linear, P-quadratic < 0.05). The contents of C18:3(n-3) (P, P-quadratic < 0.05) and C18:2(n-6) (P, P-linear < 0.05) was significantly increased when supplementing 0.10% GAA, while those of C16:0 (P < 0.05) and C22:2(n-6) (P, P-linear < 0.05) was significantly decreased. Pearson correlation analysis revealed that the differential genes including ANGPT2, PLA2G4A, PIK3CB, IDNK, MAPKAPK5 and the differential metabolites including DG (16:0/20:4), TG (16:0/16:0/18:1), DG (16:1/18:1), DG (16:0/18:2), Cer (d18:1/18:1) were closely associated with the antioxidant capacity and fat deposition. CONCLUSION: In summary, 0.10% GAA reduced subcutaneous fat thickness, improved the fatty acid profile, and maintained redox homeostasis in Tibetan sheep.