Metabolomic profiling reveals differential effects of glucagon-like peptide-1 and insulin on nutrient partitioning in ovine liver.

This study was conducted to identify the insulin-independent actions of glucagon-like peptide-1 (GLP-1 (7-36 amide)) in partitioning nutrient metabolism in ovine liver. Four Suffolk wethers (60.0 ± 6.7 kg body weight (BW)) were used in a repeated-measure design under euglycemic--hyperinsulinemic and hyper -GLP-1 clamps for 150 min with intravenous infusion of insulin (0.5 mU/kg BW/min; from 0 to 90 min), GLP-1 (0.5 µg/kg BW/min; from 60 to 150 min) and both hormones co-administered from 60 to 90 min. Liver biopsies were collected at 0, 60, 90 and 150 min to represent the metabolomic profiling of baseline, insulin, insulin plus GLP-1, and GLP-1, respectively, and were analyzed for metabolites using Capillary Electrophoresis Time-of-Flight Mass Spectrometer. Metabolomics analysis reveals 51 metabolites as being significantly altered (P < 0.05) by insulin and GLP-1 infusion compared to baseline values. Insulin infusion enhanced glycolysis, lipogenesis, oxidative stress defense and cell proliferation pathways, but reduced protein breakdown, gluconeogenesis and ketogenesis pathways. Conversely, GLP-1 infusion promoted lipolytic and ketogenic pathways accompanied by a lowered lipid clearance from the liver as well as elevated oxidative stress defense and nucleotide degradation. Despite further research still being warranted, our data suggest that GLP-1 may exert insulin-antagonistic effects on hepatic lipid and nucleotide metabolism in ruminants.