The effect of different treatments for early-lactation hyperketonemia on liver triglycerides, glycogen, and expression of key metabolic enzymes in dairy cattle

摘要

ABSTRACTDespite the widespread use of treatments for postpartum hyperketonemia in dairy cows, there is currently a lack of evidence comparing their effects on both the resolution of hyperketonemia and the potential effects on the liver of affected animals. The objective of our work was to investigate the effect of commonly used hyperketonemia treatments on hepatic triglyceride and glycogen content as well as on the mRNA and protein abundance of key enzymes involved in gluconeogenesis, ketogenesis, and lipid metabolism. Multiparous Holstein cows between 3 and 9 d in milk were screened 3 times per week and enrolled in the study when whole-blood β-hydroxybutyrate concentrations measured ≥1.2 mmol/L. Cows were randomly allocated to 1 of 4 groups: (1) 500 mL of a 50%d-glucose solution intravenously once a day for 3 d (n = 8), (2) 300 mL of propylene glycol orally once a day for 3 d (n = 8), (3) 500 mL of a 50%d-glucose solution intravenously and 300 mL of propylene glycol orally once a day for 3 d (n = 8), or (4) an untreated control group (n = 8). Liver biopsies were taken on the day of enrollment as well as on the day following completion of treatments. Liver triglyceride and glycogen content were determined by colorimetric and fluorometric methods, respectively. Gene and protein expression of pyruvate carboxylase, phosphoenolpyruvate carboxykinase 1, glucose-6-phosphatase, 3-hydroxy-3-methylglutaryl-CoA synthase 2, acetyl-CoA carboxylase, and carnitine palmitoyltransferase 1A were compared between groups and time points using quantitative reverse transcriptase PCR and Western blotting techniques, respectively. In addition, the ratio of light chain 3B II:I was determined by Western blotting. Plasma samples from both time points for each enrolled cow were submitted for chemistry analysis. Data were analyzed using a repeated-measures ANOVA taking into account the paired nature of the data, and differences between all groups and time points were controlled for multiple comparisons using the Tukey procedure. No difference was found in triglyceride or glycogen concentration between treatment groups. The gene expression of pyruvate carboxylase decreased in the group receiving both treatments, whereas protein expression of this enzyme increased in all groups over time. The autophagy marker light chain 3B II:I decreased in the group receiving both glucose and propylene glycol. No other changes in gene or protein expression of key hepatic enzymes were associated with treatments. We conclude that intravenous glucose and oral propylene glycol, commonly used treatments for ketosis in postpartum dairy cows, administered alone or in combination for a duration of 3 d did not have important beneficial or detrimental effects on selected indicators of liver composition and function in cows with hyperketonemia.