PPARγ regulates exocrine pancreas lipase

Aim: Pancreatic lipase (triacylglycerol lipase EC 3.1.13) is an essential enzyme in hydrolysis of dietary fat. Dietary fat, especially polyunsaturated fatty acids (PUFA), regulate pancreatic lipase (PNLIP); however, the molecular mechanism underlying this regulation is mostly unknown. As PUFA are known to regulate expression of proliferator-activated receptor gamma (PPAR gamma), and as we identified in-silico putative PPAR gamma binding sites within the putative PNLIP promoter sequence, we hypothesized that PUFA regulation of PNLIP might be mediated by PPAR gamma. Materials and methods: We used in silico bioinformatics tools, reporter luciferase assay, PPAR gamma agonists and antagonists, PPAR gamma overexpression in exocrine pancreas AR42J and primary cells to study PPAR gamma regulation of PNLIP. Results: Using in silico bioinformatics tools we mapped PPAR gamma binding sites (PPRE) to the putative promoter region of PNLIP. Reporter luciferase assay in AR42J rat exocrine pancreas acinar cells transfected with various constructs of the putative PNLIP promoter showed that PNLIP transcription is significantly enhanced by PPAR gamma dose-dependently, reaching maximal levels with multi PPRE sites. This effect was significantly augmented in the presence of PPAR gamma agonists and reduced by PPAR gamma antagonists or mutagenesis abrogating PPRE sites. Over-expression of PPAR gamma significantly elevated PNLIP transcript and protein levels in AR42J cells and in primary pancreas cells. Moreover, PNLIP expression was up-regulated by PPAR gamma agonists (pioglitazone and 15dPGJ2) and significantly down-regulated by PPAR gamma antagonists in non-transfected rat exocrine pancreas AR42J cell line cells. Conclusion: PPAR gamma transcriptionally regulates PNLIP gene expression. This transcript regulation resolves part of the missing link between dietary PUFA direct regulation of PNLIP. (C) 2016 Elsevier B.V. All rights reserved.