214-LB: Activating and Disrupting the Liver–Alpha-Cell Axis Respectively Enhances and Impairs Amino Acid Metabolism and Alpha-Cell Growth
Authors: CHRISTENSEN EMILIE E. , GALSGAARD KATRINE D. , JOHANSEN CHRISTIAN D. , TRAMMELL SAMUEL , BOMHOLT ANNA B. , HUNT JENNA , KRUSE THOMAS , LAU JESPER F. , GREVENGOED TRISHA , HOLST JENS J. , WEWER ALBRECHTSEN NICOLAI J. 
Published: May 2022

Amino acids control alpha cell secretion and growth, while glucagon stimulates hepatic amino acid uptake and ureagenesis, forming the liver-alpha cell axis. Patients with nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes have increased levels of glucagon and amino acids pointing to a disrupted liver-alpha cell axis. Both glucagon agonism and antagonism are explored for diabetes and NAFLD therapy but their effects on the axis are unclear. Female C57Bl/6JRj mice were treated with a long-acting glucagon analogue (GCGA, NNC9204-0043, Novo Nordisk A/S) or PBS twice daily, or once weekly with a GCGR antibody (GCGR Ab, REGN1193, Regeneron) or control antibody (Ctl. Ab, REGN1945, Regeneron) . After four weeks, total plasma amino acids were decreased by 48% in GCGA mice (P=0.0006) and increased by 285% in GCGR Ab mice (P&lt;0.0001) versus week 0. At week 4, 18 of 19 amino acids were reduced in GCGA mice and increased in GCGR Ab mice. Asparagine changed the most in both groups, with a mean fold change of 0.21 and 7.50 in GCGA and GCGR Ab mice, respectively. Plasma urea index ([urea]/[amino acids]) was increased by 36% in GCGA mice (P=0.055) and decreased by 61% in GCGR Ab mice (P=0.001) . Liver RNA-sequencing revealed opposite effects of GCGA and GCGR Ab on expression of amino acid transporters (e.g. Slc43a) and ureagenesis genes (e.g. Ass1) . Activity of carbamoyl phosphate synthetase 1 was increased by 27% in GCGA versus PBS mice (P=0.007) and decreased by 33% in GCGR Ab mice versus Ctl. Ab (P=0.002) . GCGA lowered pancreas weight and glucagon content by 15% (P=0.004) and 95% (P&lt;0.0001) compared to PBS. Conversely, GCGR Ab mice had a 34% increase in pancreas weight versus Ctl. Ab (P=0.0009) . Thus, chronically increased GCGR signaling leads to hypoaminoacidemia and decreased alpha cell mass, while chronically decreased GCGR signaling leads to hyperaminoacidemia and increased alpha cell mass. These changes must be considered when developing glucagon-based therapeutics.

Disclosure
E. E. Christensen: None. J. J. Holst: Advisory Panel; Novo Nordisk, Board Member; Antag Therapeutics, Bainan Biotech. N. J. Wewer albrechtsen: Research Support; Mercodia AB, Novo Nordisk, Regeneron Pharmaceuticals Inc., Speaker's Bureau; Merck & Co., Inc., Mercodia AB. K. D. Galsgaard: None. C. D. Johansen: None. S. Trammell: None. A. B. Bomholt: None. J. Hunt: None. T. Kruse: Employee; Novo Nordisk. J. F. Lau: Employee; Novo Nordisk A/S, Stock/Shareholder; Novo Nordisk A/S. T. Grevengoed: None.

Funding
Nicolai J. Wewer Albrechtsen is supported by NNF Excellence Emerging Investigator Grant ? Endocrinology and Metabolism (Application No. NNF19OC0055001) , EFSD Future Leader Award (NNF21SA0072746) and DFF Sapere Aude (1052-00003B) . Novo Nordisk Foundation Center for Protein Research is supported financially by the Novo Nordisk Foundation (grant agreement NNF14CC0001) .