Dose‐ and Duration‐Dependent Effects of Propylene Glycol on Lipid Metabolism‐Related <scp>mRNAs</scp> , Proteins, and Fatty Acids in the Adipose Tissue of Fattening Akkaraman Lambs

Propylene glycol (PG) is incorporated into ruminant diets to boost glucogenic energy availability, yet its precise effects on adipose tissue development remain incompletely defined. The study was designed as a 3 × 3 factorial experiment with two independent variables: dose of PG and duration of fattening. Three groups were formed, including a dose group of PG 1.5 mL/kg live weight (PG1.5), a dose group of PG 3 mL/kg live weight (PG3), and a group without PG (PG0). Gluteal adipose tissues were collected from animals slaughtered on days 60, 90, and 120. mRNA, protein, and fatty acid profiles were analyzed. Protein-protein interaction and gene set enrichment analysis were also performed. On day 60, FABP4 was approximately 3-fold higher at both mRNA and protein levels in PG3 compared to PG0, nearly 2-fold higher at the protein level in PG1.5, and SREBP-1c protein levels were reduced in PG1.5 compared to PG0. On day 120, FABP4, PPARγ, C/EBPα exhibited an increasing trend at both mRNA and protein levels in PG groups, whereas SREBP-1c was decreased in PG3. Fatty acid profiling revealed C16:0, C18:0, and C18:1 comprised over 70% of total lipids. PG supplementation shifted the profile toward unsaturated species, reducing saturated fatty acid proportions and enhancing nutritional indices, particularly in PG1.5. Findings at the bioinformatics levels demonstrate PG exerts clear dose- and time-dependent modulation of adipogenic transcription factors, fatty acid composition, and molecular interaction networks in lamb adipose tissue. Early PG3 feeding elevates FABP4 and suppresses SREBP-1c, whereas prolonged supplementation enhances PPARγ and C/EBPα and drives a favorable shift in lipid profiles. Network and pathway analyses reveal coordinated regulation via NR1H3/RXR and PPAR axes, suggesting PG not only optimizes energy partitioning but also supports cellular homeostasis. These results could contribute to the development of potential strategies aimed at supporting adipose tissue quality and metabolic health in sheep.