Increased Anaplerosis, TCA Cycling, and Oxidative Phosphorylation in the Liver of Dairy Cows with Intensive Body Fat Mobilization during Early Lactation

The onset of milk production lets mammals experience
an enormous
energy and nutrient demand. To meet these requirements, high-yielding
dairy cows mobilize body fat resulting in an augmented hepatic oxidative
metabolism, which has been suggested to signal for depressing hunger
after calving. To examine how the extent of fat mobilization influences
hepatic oxidative metabolism and thus potentially feed intake, blood
and liver samples of 19 Holstein cows were taken throughout the periparturient
period. Retrospectively grouped according to high (H) and low (L)
liver fat content, H cows showed higher fatty acid but lower amino
acid plasma concentrations and lower feed intake than L cows. The
hepatic phospho-AMPK/total AMP ratio was not different between groups
but decreased after parturition. A 2-DE coupled MALDI-TOF-TOF analysis
and qRT-PCR studies revealed H cows having lower expressions of major
enzymes involved in mitochondrial β-oxidation, urea cycling,
and the pentose phosphate pathway but higher expressions of enzymes
participating in peroxisomal and endoplasmic fatty acid degradation,
pyruvate and TCA cycling, amino acid catabolism, oxidative phosphorylation,
and oxidative stress defense. These data indicate that increasing
lipolysis leads to augmenting nutrient catabolism for anaplerosis
and mitochondrial respiration, providing a molecular link between
hepatic oxidative processes and feed intake.