ABSTRACT
OBJECTIVES: The present study was conducted to monitor the expression of pancreas and duodenal homeobox gene (PDX-1) for assessing beta-cell function in islets from patients with chronic pancreatitis (CP). METHODS: Islets isolated from the pancreata of 40 surgical patients categorized as control group, patients with mild CP, and patients with advanced CP were assessed for their yield, size, and glucose-stimulated insulin secretion. Expressions of genes coding for PDX-1, insulin, and glucagon were simultaneously monitored by reverse transcription polymerase chain reaction and confirmed by immunohistochemistry. RESULTS: In comparison with the control group (2673 +/- 592 islet equivalents [IEq]/g), islet yield did not differ much in the patients with mild CP (2344 +/- 738 IEq/g) but was significantly reduced (P < 0.0001) in the patients with advanced CP (731 +/- 167 IEq/g). Although the marginal decrease in islet size observed in the patients with mild CP was not significantly different from that observed in the control group, there was a 58% decrease observed in the patients with advanced CP that was also accompanied by a significant reduction in beta-cell mass (P < 0.05). The expression of insulin and PDX-1 genes, but not of glucagon, was significantly reduced in the patients with advanced CP as confirmed by immunohistochemistry. Islets obtained from the patients with advanced CP retained 53% glucose-stimulated insulin secretion function in comparison with those of the control group. CONCLUSION: The results indicate that beta-cell dysfunction during progression of CP correlates with the decrease in PDX-1 gene expression.
Subject(s)
Gene Expression , Homeodomain Proteins/genetics , Insulin-Secreting Cells/metabolism , Pancreatitis, Chronic/genetics , Trans-Activators/genetics , Adult , Disease Progression , Down-Regulation , Female , Glucagon/genetics , Glucagon/metabolism , Glucose/pharmacology , Homeodomain Proteins/metabolism , Humans , Immunohistochemistry , Insulin/genetics , Insulin/metabolism , Islets of Langerhans/drug effects , Islets of Langerhans/metabolism , Male , Middle Aged , Pancreatitis, Chronic/metabolism , Pancreatitis, Chronic/physiopathology , Reverse Transcriptase Polymerase Chain Reaction , Trans-Activators/metabolism , Young AdultABSTRACT
The inhibition of aflatoxin production by trifluoperazine, an anticalmodulin (CaM) agent and the relevance of Ca(2+)/CaM-dependent phosphorylation and dephosphorylation during aflatoxin biosynthesis was previously reported. To identify proteins that may be regulated by CaM, an in silico analysis for putative CaM-binding domains (CaMBDs) in the aflatoxin-related proteins of Aspergillus parasiticus was performed using the CaM target database. Interestingly, the key regulators of aflatoxin biosynthesis such as AflR and AflJ contained predicted CaMBDs at their C-termini. Furthermore, potential phosphorylation sites for CaM-kinase II were present within these CaMBDs. In addition to other aflatoxin biosynthesis enzymes--such as Vbs, DmtA and OmtA, and the VeA protein (known to regulate the expression of AflJ and AflR)--also showed the presence of putative CaMBDs. Although the present report reaffirms earlier observations on CaM-mediated regulation of aflatoxin biosynthesis, it also opens new avenues for identifying the specific targets of CaM and elucidating the exact mechanism of initiation and regulation of aflatoxin biosynthesis.
