1154
Interaction among energy status, retinol- binding protein and retinoids status in periparturient dairy cows: hepatic and adipose gene expression
An objective of this study was to determine the effect of feeding various amounts of dietary vitamin A (0 or 110 IU/kg BW), crude protein (CP: 12.5% or 16%), and an ionophore (monensin at 0 or 400 mg/d per head) prepartum on bovine hepatic and adipose tissue gene expression of selected markers of inflammation and gluconeogenesis during transition period. Multiparous Holstein dairy cows (n=80) were studied from -35 to +21 relative to expected parturition in a complete randomized block design with a 2×2×2 factorial arrangement. Hepatic and adipose tissue (subcutaneous) were collected on day -35, -3, +3, +10, +21 and frozen in liquid nitrogen. Total RNA was isolated from each tissue samples, and complementary DNA analyzed for relative mRNA expression of retinol binding protein (RBP), peroxisome proliferator-activated receptor (PPAR)-γ, and tumor necrosis factor (TNF)-α (adipose tissue) and phosphoenolpyruvate carboxykinase, pyruvate carboxylase, TNF-α, and RBP (liver). Ribosomal protein S9 and GAPDH were used as house-keeping genes. Results were analyzed using mixed model repeated measures ANOVA. In adipose tissue, PPAR-γ was affected by dietary CP × vitamin A interaction (ΔCt of 2.23, 1.93, 2.14, and 2.54 for no vitamin A- high protein, vitamin A- high CP, no vitamin A- low CP, and vitamin A- low CP; P = 0.06). In addition, TNF-α was affected by monensin × vitamin A interaction (ΔCt of 8.76, 8.82, 8.87, and 8.12 for no vitamin A- no monensin, vitamin A- no monensin, no vitamin A- monensin, and vitamin A- monensin; P = 0.04). Moreover, RBP gene expression was affected by dietary CP × vitamin A interaction (ΔCt of -0.49, -1.27 ,-0.63, and 0.09 for no vitamin A- high CP, vitamin A- high CP, no vitamin A- low CP, and vitamin A- low CP; P = 0.06). In contrast, dietary treatments did not affect hepatic expression of genes tested. Overall, the combined effect of dietary protein and vitamin A may alter RBP and PPAR-γ status, potentially increasing circulating retinol and adipogenesis in adipose tissue. Also, the combined effect of dietary monensin and vitamin A may increase adipose TNF-α expression, which may affect inflammatory reactions in periparturient dairy cows.
Keywords: gene expression, retinol-binding protein, transition cows