👤 Richard E Pratley

Type 1 diabetes (T1D) is an autoimmune disease resulting in the destruction of pancreatic β-cells leading to insulin deficiency and hyperglycemia. Single cell transcriptomic analysis of human islets demonstrated profound β-cell changes and revealed heterogeneity in endocrine and exocrine cells in T1D. Pancreatic stellate cells (PSCs), the resident mesenchymal cells of the pancreas, regulate extracellular matrix homeostasis and drive fibrosis in aging, pancreatitis, and pancreatic cancer. By secreting cytokines and growth factors, PSCs contribute to local immunity and inflammation that affect pancreatic exocrine and endocrine functions. However, cell-cell communication from single cell transcriptomics analyzing the role of PSCs in T1D has not been explored. We analyzed single-cell RNA sequencing data from human pancreatic islets of 20 donors with and without T1D from the Human Pancreas Analysis Program database using the CellChat R package, focusing on activated-PSCs (aPSCs) signaling pathways. In addition, we performed aPSCs differential expression gene and gene set enrichment analyses. CellChat analysis revealed aPSCs demonstrated major changes increasing the number and strength of cellular communications in T1D compared to control pancreata. Signaling pathways upregulated in cell-to-cell communication involving aPSCs include TGFB, FGF, CXCL, ANGPTL, and NGF, and their respective ligands TGFB1/3, FGF7, CXCL12, ANGPTL4 and NGF. In contrast, PTN signaling from aPSCs was blunted in T1D. Our study revealed novel intercellular communication signatures involving aPSCs in T1D. Identification of the changes in cellular communication between aPSCs and other cells in T1D suggest a role in T1D pathogenesis or progression which might lead to the development of novel therapeutics. Show less

Incretin hormone dysregulation contributes to reduced insulin secretion and hyperglycemia in patients with type 2 diabetes mellitus (T2DM). Resistance to glucose-dependent insulinotropic polypeptide (GIP) action may occur through desensitization or downregulation of β-cell GIP receptors (GIP-R). Studies in rodents and cell lines show GIP-R expression can be regulated through peroxisome proliferator-activated receptor γ (PPARγ) response elements (PPREs). Whether this occurs in humans is unknown. To test this, we conducted a randomized, double-blind, placebo-controlled trial of pioglitazone therapy on GIP-mediated insulin secretion and adipocyte GIP-R expression in subjects with well-controlled T2DM. Insulin sensitivity improved, but the insulinotropic effect of infused GIP was unchanged following 12 weeks of pioglitazone treatment. In parallel, we observed increased GIP-R mRNA expression in subcutaneous abdominal adipocytes from subjects treated with pioglitazone. Treatment of cultured human adipocytes with troglitazone increased PPARγ binding to GIP-R PPREs. These results show PPARγ agonists regulate GIP-R expression through PPREs in human adipocytes, but suggest this mechanism is not important for regulation of the insulinotropic effect of GIP in subjects with T2DM. Because GIP has antilipolytic and lipogenic effects in adipocytes, the increased GIP-R expression may mediate accretion of fat in patients with T2DM treated with PPARγ agonists. Show less