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Hepatic gene expression of gluconeogenic enzymes and its regulation in Holstein cows under two contrasting feeding strategies.

G. Cañibe




Hepatic gene expression of gluconeogenic enzymes and its regulation in Holstein cows under two contrasting feeding strategies.
G. Cañibe*1, M. Garcia-Roche1,2, D. A. Mattiauda1, A. Cassina2, C. Quijano2, M. Carriquiry1. 1Departamento de Producción Animal y Pasturas, Facultad de Agronomía, Universidad de la República Montevideo, Uruguay, 2Centro de Investigaciones Biomédicas, Departamento de Bioquímica, Facultad de Medicina, Universidad de la República Montevideo, Uruguay.

The aim of the study was to determine the effect of pasture grazing on hepatic gene expression of key gluconeogenic enzymes and its regulation. Multiparous Holstein cows (n = 24, 664 ± 65 kgBW, 3.0 ± 0.4 BCS, spring calving) were assigned in a randomized block design to a total mixed ration (TMR) fed ad libitum (70% forage: 30% concentrate) (G0) or grazing plus supplementation (G1) from 0 to 180 d postpartum (DPP). The G1 cows grazed Festuca arundinacea or Medicago sativa in 2 (18 h) or one session (10 h) depending on heat stress (30 or 20 kgDM/d) and were supplemented with 5.4 kgDM/d of a commercial concentrate or offered TMR (50% of G0 offer). From 180 to 250 DPP, all cows grazed Festuca arundinacea (10 h; 30 kgDM/d) and were offered TMR (50% of G0 offer). Liver biopsies were collected at 35, 110 and 250 DPP. Expression of methylmalonyl-CoA mutase (MCM), pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PCK), glucose-6 phosphatase (G6Pase) and PPAG coactivator 1 α (PGC1A) mRNA was measured by real-time PCR, while AMPK phosphorylation was studied by western-blot. Data was analyzed with a mixed model using repeated measures. Hepatic MCM and PC mRNA was affected by the interaction between treatment and DPP (P < 0.05) as MCM was greater at 35 DPP but less at 110 DPP for G0 than G1 cows (0.93 vs. 0.56 ± 0.24, 0.61 vs. 0.89 ± 0.24, 0.59 vs. 0.65 ± 0.24, for 35, 110 and 250 DPP, G0 and G1, respectively); PC was 1.6-fold greater for G1 than G0 at 35 DPP. Expression of G6Pase and PCK mRNA was 1.6- and 1.9-fold greater (P < 0.05) while PGC1A mRNA tended (P = 0.06) to be 1.9-fold greater in early than mid and late lactation. The pAMPK/AMPK ratio was higher at 35 than 250 DPP (0.88 vs. 0.46 ± 0.08, P < 0.01). Hepatic PGC1A mRNA expression correlated positively with all gluconeogenic genes (r > 0.3, P < 0.06) while pAMPK/AMPK ratio correlated negatively with PC (r = −0.4, P < 0.05) suggesting both of these mechanisms could be regulating gluconeogenesis. Our results indicate cows under pasture-based systems adapt their metabolism to produce glucose from non-propionate when compared with TMR-fed cows.

Keywords: TMR vs. pasture, gluconeogenesis, 5'-AMP-activated protein kinase (AMPK).

Biography: My work is based on elucidating the molecular mechanisms underlying metabolic adaptations during the lactation of dairy cows. I work specifically with energy metabolism, including post-translational modifications, gene expression and enzyme activity