The Zone-Specific Metabolic Effects of Glucagon Receptor Agonism in the Treatment of Obesity and Metabolic Liver Disease - ABSTRACT Over 40% of Americans are obese and a substantial proportion develop related metabolic diseases such as type 2 diabetes (T2D), metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction- associated steatohepatitis (MASH). Given this public health threat, it is becoming increasingly important to develop effective therapeutics to target metabolic pathways in the liver, as hepatic metabolic dysfunction is a hallmark feature of these diseases. The liver is divided into hexagonal-shaped functional units, lobules, with a central vein in the middle surrounded by six portal triads. The lobule can be further divided into zones based on their proximity to either structure (periportal or pericentral) as well as their functional role, since hepatocytes carry out different metabolic functions in different zones of the lobule. This zonal distribution of hepatocytes has been shown to become disrupted in MASLD, impacting important zonal metabolic functions of the liver. However, whether this altered zonation and disruption of metabolic pathways modulates the safety and efficacy of new obesity therapeutics remains completely unexplored. Incretin hormone-based weight-loss therapies targeting the GLP-1 and GIP receptors (GLP-1R, GIPR) have been shown to be beneficial in treating obesity, improving glycemic control in T2D, and reducing steatosis in MASLD. A new agent targeting GLP-1R, GIPR, and the glucagon receptor (GCGR) is currently demonstrating enhanced weight-loss and liver steatosis results in Phase III clinical trials. These findings, combined with recent rodent studies suggesting that GCG plays a role in liver zonation, has led to a gap in knowledge about the zonal metabolic effects of GCGR agonism in the treatment of obesity and MASLD. Here, we will test the hypothesis that GCGR-based therapeutics mediate their metabolic effects via selectively engaging with the GCGR in distinct zones in the liver with the following Specific Aims: Aim 1 will determine the zonal distribution of GCGR in models of health and metabolic disease, while Aim 2 will define the zonal transcriptional and metabolic effects of chronic GCGR agonism in a mouse model of MASH. Finally, Aim 3 will determine the therapeutic impact of zone-specific GCGR agonism. In the proposed studies, we will utilize novel multi-omics techniques such as spatial transcriptomics, spatial metabolomics, and a novel application of single-nuclei RNA-Seq as the first step towards understanding the zonal metabolic effects of chronic GCGR agonism and determine whether disrupted zonation in disease modulates GCGR signaling. These findings will be significant as they will provide insights that can be leveraged for the development of next- generation therapeutics targeting specific GCGR populations in the liver, mitigating undesired metabolic effects. This training award will also contribute to the rigorous training and development of the applicant in preparation for a career as an independent physician-scientist in the field of metabolic disease.
