Effects of glucagon, glycerol, and glucagon plus glycerol on gluconeogenesis, lipogenesis, and lipolysis in periparturient Holstein cows

The objective of this study was to investigate the effect of daily glucagon subcutaneous injections of 15 mg and oral administration of 400 mL glycerol during the first 14 d postpartum on the rates of gluconeogenesis in liver and lipogenesis and lipolysis in adipose tissues obtained from dairy cows with fatty liver syndrome (FLS). To induce FLS, 16 multiparous cows with body condition score of ≥ 3.5 (1-5 scale) cows were daily fed dry-cow ration plus 6 kg of cracked corn during the last 6 weeks of dry period. Cows were assigned equally and randomly to 4 treatment groups: saline, glycerol, glucagon, and glucagon plus glycerol. Liver and adipose tissue slices were incubated with 10 nM glucagon and 1 nM tumor necrosis factor-alpha (TNF-alpha). Glucose synthesis rates from propionic acid and alanine were measured in liver, and glycerol release rates and fatty acid synthesis rates were measured in adipose tissues. Glucagon injections and glycerol oral administration did not affect the rates of gluconeogensis or lipolysis. Lipogenesis rates tended to decrease with glucagon and glycerol treatments. Incubation of adipose and liver tissues with TNF-alpha and glucagon did not affect glucose synthesis rates or fatty acid breakdown or synthesis in adipose tissue. We conclude that glucagon and glycerol treatments alleviate the symptoms of FLS by long-term effects rather than direct effects on liver or adipose metabolic pathways.