1883-P: Phosphoproteomics Reveals Mechanistic Insight into Glucagon-Mediated Inhibition of Hepatic Lipogenesis and How MEDI0382, an Oxyntomodulin-Like Peptide with Targeted GLP-1/Glucagon Receptor Activity, Reverses Steatosis

MEDI0382 is an oxyntomodulin-like peptide with targeted GLP-1/glucagon receptor activity that is in clinical development for type 2 diabetes (T2DM), NASH, and obesity and provides glycemic control and weight loss as well as marked improvements of liver outcomes in humans and mice. In mice, reductions in hepatic lipid were independent of weight loss and resulted from improved mitochondrial respiration and turnover and reduced de novo lipogenesis. As hepatocytes lack the GLP-1 receptor, this effect of MEDI0382 is predominantly modulated via glucagon receptors. After treatment with MEDI0382 or g1437, a glucagon analog, isolated hepatocytes showed increased basal and maximal oxygen consumption, increased mitophagosome number, and a ∼6-fold induction in expression of mitochondrial biogenesis regulator PGC-1α (P ≤ 0.0001). We used phosphoproteomics to identify potential mechanisms of action of MEDI0382 and g1437 on lipogenesis inhibition. After g1437 treatment, primary murine hepatocytes exhibited increased phosphorylation on AMPK, GSK3-α, PHK-β, ChREBP, and HSL—all known PKA substrates. We also identified new glucagon-induced phosphorylations on PHK-α2, PYGL, and ChREBP that were not necessarily PKA consensus motifs, implicating involvement of kinases downstream of PKA. In obese mice, MEDI0382 given for 7 days showed time-dependent phosphorylation of the same sites on AMPK, ChREBP, ACC2, ACLY, and DGAT1. These phosphorylation events are predicted to be inhibitory for lipogenesis. To understand translational potential, we treated primary human hepatocytes with g1437 and found 12 homologous phospho sites, including those on AMPK, ACLY, and DGAT1. Thus, MEDI0382 provides unique antisteatotic benefits for obesity/T2DM comorbidities of NASH/NAFLD via enhanced mitochondrial function and novel glucagon-mediated inhibition of lipogenesis.