Abstract
This study investigated effects of dietary glycerol supplementation on liver, muscle, and adipose gene expression related with gluconeogenesis and lipid metabolism and association of gene expression levels with marbling score in Korean cattle steers. Fourteen Korean cattle steers (average age 28.4 months; average body weight 733 kg) were equally assigned to two groups (0 and 5% glycerol supplementation). Glycerol was provided with glycerol (63%)-adsorbed ground wheat bran (37%, DM) by top dressing during roughage feeding. A concentrate (1.2% of body weight) and 1.0 kg of ryegrass were individually fed twice daily. After four months of study, steers were slaughtered, and marbling score was evaluated. Longissimus thoracis (LT) and subcutaneous adipose tissue at the 13th thoracic vertebra area and liver were collected and analyzed for mRNA levels by quantitative real-time PCR. Statistical significance was analyzed by analysis of variance. Correlations were analyzed using Pearson’s correlation analysis. Glycerol supplementation increased (P = 0.01) marbling score. In the LT, glycerol supplementation tended to increase (0.05 < P ≤ 0.10) lipid uptake CD36 and lipoprotein lipase (LPL) mRNA levels. In subcutaneous adipose tissues, glycerol supplementation increased (P ≤ 0.05) LPL, adipogenic sterol regulatory element binding protein 1 (SREBP1), and lipogenic acetyl CoA carboxylase (ACC) mRNA levels and tended to increase (0.05 < P < 0.10) CD36, adipogenic peroxisome proliferator-activated gamma (PPARG), and lipogenic fatty acid synthase (FASN) expression. It did not affect (P > 0.05) mRNA levels of hepatic gluconeogenesis genes. Marbling score showed significant positive correlations (0.57 < r < 0.68; P < 0.05) with mRNA levels of several genes including LPL, PPARG, SREBP1, and ACC in adipose tissues, but not with any genes examined in the LT. Our study demonstrates that lipid uptake, adipogenesis and lipogenesis may mainly contribute to the increased marbling score by glycerol supplementation.
Up-regulation of bone morphogenetic protein and its signaling molecules following castration of bulls and their association with intramuscular fat content in Korean cattle
