PDX-1 was decreased in MIN6N8 cells treated with high glucose or high palmitate, whereas ATF3 was increased, indicating that ATF3 plays a role in hyperglycemia or hyperlipidemia-mediated downregulation of PDX-1 expression.
Hepatic immunoreactive insulin, induced by PDX-1, was processed to mature mI-1 and mI-2 and was biologically active; it ameliorated hyperglycemia in streptozotocin-treated diabetic mice.
At the same time points, high hyperglycemia rats showed a global alteration in gene expression with decreased mRNA for insulin, IAPP, islet-associated transcription factors (pancreatic and duodenal homeobox-1, BETA2/NeuroD, Nkx6.1, and hepatocyte nuclear factor 1 alpha), beta-cell metabolic enzymes (glucose transporter 2, glucokinase, mitochondrial glycerol phosphate dehydrogenase, and pyruvate carboxylase), and ion channels/pumps (Kir6.2, VDCC beta, and sarcoplasmic reticulum Ca(2+)-ATPase 3).
Human BMSCs expressing VEGF and PDX1 reversed hyperglycemia in more than half of the diabetic mice and induced overall improved survival and weight maintenance in all mice.
Hyperglycemia recurred within 24 hours of graft removal and the histological analysis of the retrieved grafts revealed presence of Pdx1-, Nkx6.1- and C-peptide-positive cells.
Patients with mutation in genes encoding the transcription factors, hepatocyte nuclear factor (HNF)- 1alpha, HNF-4alpha, HNF-1beta and insulin promoter factor 1 (IPF-1) have a common progressive beta-cell failure resulting in increasing hyperglycaemia and treatment requirements.
Our data further indicate that hyperglycemia decreases gene expression and increases DNA methylation of PDX-1 because glycosylated hemoglobin (HbA1c) correlates negatively with mRNA expression (rho = -0.50, P = 0.0004) and positively with DNA methylation (rho = 0.54, P = 0.00024) of PDX-1 in the human islets.
While acute exposure to high glucose concentrations causes an increase in PDX-1 binding, and consequently in insulin mRNA levels, chronic hyperglycemia (toxic to the beta-cell) leads to a decrease in PDX-1 and insulin levels.
Compromised Pdx1 mRNA and protein levels in weaned male mutant β-cells were tightly linked with hyperglycemia, decreased β-cell proliferation, reduced β-cell area, and altered expression of Pdx1-bound genes that are important in β-cell replication, endoplasmic reticulum function, and mitochondrial activity.
On the contrary, despite normal pancreas and endocrine development, the FVFPBF<sup>DHom</sup> reporter male animals developed hyperglycemia at weaning age and displayed a reduction in Pdx1 levels in islets, which coincided with alterations in β-cell number and islet architecture.
The suppression of STAT3 signaling, together with exogenously expressed Pdx1, Neurog3, and Mafa, significantly increased the number of reprogrammed β cells in vitro and in vivo, enhanced the formation of islet-like clusters in mice, and ameliorated hyperglycemia in diabetic mice.