Modulation of Nuclear Receptor 4A1 Expression Improves Insulin Secretion in a Mouse Model of Chronic Pancreatitis

Abstract

Objectives Diabetes secondary to chronic pancreatitis (CP) presents clinical challenges due to lack of understanding on factor(s) triggering insulin secretory defects. Therefore, we aimed to delineate the molecular mechanism of β-cell dysfunction in CP. Materials and Methods Transcriptomic analysis was conducted to identify endocrine-specific receptor expression in mice and human CP on microarray. The identified receptor (NR4A1) was overexpressed in MIN6 cells using PEI linear transfection. RNA-Seq analysis of NR4A1-overexpressed (OE) MIN6 cells on NovaSeq6000 identified aberrant metabolic pathways. Upstream trigger for NR4A1OE was studied by InBio Discover and cytokine exposure, whereas downstream effect was examined by Fura2 AM-based fluorimetric and imaging studies. Mice with CP were treated with IFN-γ-neutralizing monoclonal antibodies to assess NR4A1 expression and insulin secretion. Results Increased expression of NR4A1 associated with decreased insulin secretion in islets (humans: controls 9 ± 0.2, CP 3.7 ± 0.2, mice: controls 8.5 ± 0.2, CP 2.1 ± 0.1 μg/L). NR4A1OE in MIN6 cells (13.2 ± 0.1) showed reduction in insulin secretion (13 ± 5 to 0.2 ± 0.1 μg/mg protein per minute, P = 0.001) and downregulation of calcium and cAMP signaling pathways. IFN-γ was identified as upstream signal for NR4A1OE in MIN6. Mice treated with IFN-γ–neutralizing antibodies showed decreased NR4A1 expression 3.4 ± 0.11-fold (P = 0.03), showed improved insulin secretion (4.4 ± 0.2-fold, P = 0.01), and associated with increased Ca2+ levels (2.39 ± 0.06-fold, P = 0.009). Conclusions Modulating NR4A1 expression can be a promising therapeutic strategy to improve insulin secretion in CP.