The Role of Pancreatic Preproglucagon in Regulating Local Inflammation in Mice

Data suggest that both pancreatic and intestinally produced glucagon-like peptide-1 (GLP-1) increases in response to inflammation. Here, we set out to determine the tissue-specific function of increased GLP-1 during inflammatory stimuli. Using our innovative mouse model of tissue-specific Gcg (the gene that encodes GLP-1) expression, we explored the function of GLP-1 under severe inflammatory conditions induced by lipopolysaccharide (LPS) administration in lean and obese mice. High-fat diet (HFD) increased the LPS-induced suppression of feeding and increased the plasma levels of pro-inflammatory cytokines and GLP-1. Both pancreatic and intestinal Gcg expression contribute to LPS-induced increases in GLP-1, but Gcg was not necessary for the glucoregulatory or suppressed feeding responses to LPS. While Gcg was not necessary for systemic cytokine increases with LPS in either chow- or HFD-fed mice, whole-body Gcg-null animals had increased macrophage accumulation and an increased expression of genes reflecting pro-inflammatory signaling in the pancreas. We then performed flow cytometry on the pancreas from mice expressing a fluorescent marker on the GLP-1 receptor (GLP-1R). In response to LPS, we found that pancreatic CD64+/CD11b+ macrophages expressed the GLP-1R. We conclude that under severe inflammatory conditions, pancreatic production of GLP-1 functions in an immunological rather than a metabolic role to directly regulate local macrophage accumulation.