Abstract

   This study elucidated the regulatory mechanisms of age-related meat
   flavor precursors in naturally grazed Sunit sheep of different ages (6,
   18, and 30 months) by analyzing their metabolite and mRNA profiles. The
   longissimus dorsi muscle was sampled from each group and subjected to
   metabolomics and transcriptomics analyses. A total of 395 differential
   metabolites (DMs) and 1482 differentially expressed genes (DEGs) were
   detected across the age groups. As the age increased, the expression
   levels of GOT1 and GLUL increased, activating arginine biosynthesis and
   alanine, aspartate, and glutamate metabolism pathways, which promoted
   the accumulation of umami compounds (L-glutamate and L-glutamine).
   Meanwhile, the expression level of LPIN1 increased with age, promoting
   glycerophospholipid metabolism and contributing to the development of
   lipid-related aroma. FADS1 and FADS2 expressed the highest levels at
   age Mth_18. This pattern influenced the unsaturated fatty acid
   biosynthesis pathway and consequently had a regulatory effect on the
   DHA levels. An amino acid metabolic regulatory network that involved
   arginine biosynthesis, alanine, aspartate and glutamate metabolisms,
   and arginine and proline metabolisms was established. This study
   provided insights into the variations in meat flavor precursors among
   sheep of different ages and elucidated the underlying regulatory
   mechanisms.

   Keywords: Sunit sheep, flavor precursor, age, regulation mechanism

1. Introduction

   Meat quality, including the tenderness, flavor, color, and juiciness,
   influences consumer preferences and choices. Flavor is considered a