The ability of liver to respond to changes in nutrient availability is essential for the maintenance of metabolic homeostasis. Autophagy encompasses mechanisms of cell survival, including capturing, degrading, and recycling of intracellular
proteins and organelles in lysosomes. During negative nutrient status, autophagy provides substrates to sustain cellular metabolism and hence, tissue function. Severe negative energy balance in dairy cows is associated with
fatty liver. The aim of this study was to investigate the hepatic autophagy status in dairy cows with severe
fatty liver and to determine associations with
biomarkers of liver function and
inflammation. Liver and blood samples were collected from multiparous cows diagnosed as clinically healthy (n = 15) or with severe
fatty liver (n = 15) at 3 to 9 d in milk. Liver tissue was biopsied by needle
puncture, and serum samples were collected on 3 consecutive days via jugular venipuncture. Concentrations of
free fatty acids and β-hydroxybutyrate were greater in cows with severe
fatty liver. Milk production, dry matter intake, and concentration of
glucose were all lower in cows with severe
fatty liver. Activities of serum
aspartate aminotransferase,
alanine aminotransferase,
glutamate dehydrogenase, and γ-glutamyl
transferase were all greater in cows with severe
fatty liver. Serum concentrations of
haptoglobin and
serum amyloid A were also markedly greater in cows with severe
fatty liver. The
mRNA expression of autophagosome formation-related gene ULK1 was lower in the liver of dairy cows with severe
fatty liver. However, the expression of other autophagosome formation-related genes,
beclin 1 (BECN1),
phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3), autophagy-related gene (ATG) 3, ATG5, and ATG12, did not differ. More important,
ubiquitinated proteins,
protein expression of sequestosome-1 (SQSTM1, also called p62), and
microtubule-associated protein 1 light chain 3 (MAP1LC3, also called LC3)-II was greater in cows with severe
fatty liver. Transmission electron microscopy revealed an increased number of autophagosomes in the liver of dairy cows with severe
fatty liver. Taken together, these results indicate that excessive
lipid infiltration of the liver impairs autophagic activity that may lead to cellular damage and
inflammation.