Hyperuricemia impairs PAX4 protein expression and plasticity in pancreatic β-cells

Abstract

Uric Acid (UA) is a product produced from the metabolic breakdown of purines that is highly associated with several signaling pathways in pancreatic β-cells. High plasma uric acid (hyperuricemia) is associated with gout, insulin resistance, and type 2 diabetes mellitus (T2DM). Hyperuricemia can lead to pancreatic β-cell death and decreased insulin sensitivity; thus, it could be considered a novel risk factor for the development of T2DM. Expression of the transcription factor, Paired Box 4 (PAX4), in pancreatic endocrine progenitor cells plays a critical role in inducing β-cell differentiation, and therefore, β-cell plasticity. It has been shown that overexpression of PAX4 in pancreatic α-cells caused a conversion of α-β-cell lineage. However, the effects of hyperuricemia on PAX4 expression in pancreatic β-cells and their consequences are currently unknown. Therefore, this led to my hypothesis that hyperuricemia leads to a decrease in PAX4 expression in pancreatic β-cells, which in turn results in a change in β-cell plasticity and function.

Human (1.1B4) pancreatic β-cells were used to achieve the aims of this project. We investigated how applying hyperuricemic conditions for days affects the expression of PAX4. The cells were subjected to an MTT assay (β-cell viability and proliferation), western blot analyses (protein expression), RT-qPCR (mRNA expression), and fluorescence immunocytochemistry (protein expression detection). We report that 1.1B4 cells had a significant decrease in PAX4 protein expression under hyperuricemic conditions (P < 0.05), suggesting a loss in β-cell plasticity and function. Furthermore, the transcription factor ARX induces pancreatic α-cell differentiation and during β-cell differentiation it is inhibited by PAX4. We observed a significant increase in ARX mRNA expression in 1.1B4 cells exposed to hyperuricemic conditions (P < 0.05), which indicates a loss in β-cell plasticity, suggesting a switch/transdifferentiation to an α-like cell function.

In this study, it has been identified that hyperuricemia reduces PAX4 protein expression and enhances ARX mRNA expression. Ultimately, this affects the β-cell plasticity inducing transdifferentiation to α-like cells. Therefore, PAX4 gene is a potential target that may help prevent the progression and development of T2DM.