1. Hepatocyte cholesterol content modulates glucagon receptor signalling
- Author
-
Wanling Song, Alejandra Tomas, Ben Jones, Tricia Tan, T. B. Ansell, Mark S.P. Sansom, Emma Rose McGlone, David Carling, Stephen R. Bloom, and C. Dunsterville
- Subjects
medicine.medical_specialty ,Simvastatin ,0601 Biochemistry and Cell Biology ,Glucagon receptor ,Glucagon ,chemistry.chemical_compound ,Mice ,Internal medicine ,Type 2 diabetes mellitus ,medicine ,Receptors, Glucagon ,Animals ,Humans ,Receptor ,Molecular Biology ,Chemistry ,Cholesterol ,Cholesterol binding ,Fatty liver ,Cell Biology ,0606 Physiology ,medicine.disease ,Endocrinology ,medicine.anatomical_structure ,Glucose ,Hepatocyte ,Hepatocytes ,lipids (amino acids, peptides, and proteins) ,Cell membrane ,Non-alcoholic fatty liver disease ,medicine.drug - Abstract
Objective To determine whether glucagon receptor (GCGR) actions are modulated by cellular cholesterol levels. Methods We determined the effects of experimental cholesterol depletion and loading on glucagon-mediated cAMP production, ligand internalisation and glucose production in human hepatoma cells, mouse and human hepatocytes. GCGR interactions with lipid bilayers were explored using coarse-grained molecular dynamic simulations. Glucagon responsiveness was measured in mice fed a high cholesterol diet with or without simvastatin to modulate hepatocyte cholesterol content. Results GCGR cAMP signalling was reduced by higher cholesterol levels across different cellular models. Ex vivo glucagon-induced glucose output from mouse hepatocytes was enhanced by simvastatin treatment. Mice fed a high cholesterol diet had increased hepatic cholesterol and a blunted hyperglycaemic response to glucagon, both of which were partially reversed by simvastatin. Simulations identified likely membrane-exposed cholesterol binding sites on the GCGR, including a site where cholesterol is a putative negative allosteric modulator. Conclusions Our results indicate that cellular cholesterol content influences glucagon sensitivity and indicate a potential molecular basis for this phenomenon. This could be relevant to the pathogenesis of non-alcoholic fatty liver disease, which is associated with both hepatic cholesterol accumulation and glucagon resistance. more...
- Published
- 2022