Deleterious mutation V369M in the mouse GCGR gene causes abnormal plasma amino acid levels indicative of a possible liver-α-cell axis

Absence of PNET formation and normal longevity in a mouse model of Mahvash disease

Mahvash disease, a rare autosomal recessive metabolic disorder characterized by biallelic loss-of-function mutations in the glucagon receptor gene (GCGR), induces significant pancreatic hyperglucagonemia, resulting in α-cell hyperplasia and occasional hypoglycemia. Utilizing CRISPR-Cas9 technology, we engineered a mouse model, designated as Gcgr V369M/V369M, harboring a homozygous V369M substitution in the glucagon receptor (GCGR). Although wild-type (WT) and Gcgr V369M/V369M mice exhibited no discernible difference in appearance or weight, adult Gcgr V369M/V369M mice, approximately 12 months of age, displayed a notable decrease in fasting blood glucose levels and elevated the levels of cholesterol and low-density lipoprotein-cholesterol. Moreover, plasma amino acid levels such as alanine (Ala), proline (Pro) and arginine (Arg) were elevated in Gcgr V369M/V369M mice contributing to α-cell proliferation and hyperglucagonemia. Despite sustained α-cell hyperplasia and increased circulating glucagon levels in Gcgr V369M/V369M mice, metabolic disparities between the two groups gradually waned with age accompanied by a reduction in α-cell hyperplasia. Throughout the lifespan of the mice (up to approximately 30 months), pancreatic neuroendocrine tumors (PNETs) did not manifest. This prolonged observation of metabolic alterations in Gcgr V369M/V369M mice furnishes valuable insights for a deeper comprehension of mild Mahvash disease in humans.

Hypoglycemia, Vascular Disease and Cognitive Dysfunction in Diabetes: Insights from Text Mining-Based Reconstruction and Bioinformatics Analysis of the Gene Networks

Hypoglycemia has been recognized as a risk factor for diabetic vascular complications and cognitive decline, but the molecular mechanisms of the effect of hypoglycemia on target organs are not fully understood. In this work, gene networks of hypoglycemia and cardiovascular disease, diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, cognitive decline, and Alzheimer's disease were reconstructed using ANDSystem, a text-mining-based tool. The gene network of hypoglycemia included 141 genes and 2467 interactions. Enrichment analysis of Gene Ontology (GO) biological processes showed that the regulation of insulin secretion, glucose homeostasis, apoptosis, nitric oxide biosynthesis, and cell signaling are significantly enriched for hypoglycemia. Among the network hubs, INS, IL6, LEP, TNF, IL1B, EGFR, and FOS had the highest betweenness centrality, while GPR142, MBOAT4, SLC5A4, IGFBP6, PPY, G6PC1, SLC2A2, GYS2, GCGR, and AQP7 demonstrated the highest cross-talk specificity. Hypoglycemia-related genes were overrepresented in the gene networks of diabetic complications and comorbidity; moreover, 14 genes were mutual for all studied disorders. Eleven GO biological processes (glucose homeostasis, nitric oxide biosynthesis, smooth muscle cell proliferation, ERK1 and ERK2 cascade, etc.) were overrepresented in all reconstructed networks. The obtained results expand our understanding of the molecular mechanisms underlying the deteriorating effects of hypoglycemia in diabetes-associated vascular disease and cognitive dysfunction.