Label-Free Proteomics of the Fetal Pancreas Identifies Deficits in the Peroxisome in Rats with Intrauterine Growth Restriction

Abstract

Aim The objective of the present study was to identify differentially expressed proteins (DEPs) in the pancreas of a fetus with intrauterine growth restriction (IUGR) and to investigate the molecular mechanisms leading to adulthood diabetes in IUGR. Methods The IUGR rat model was induced by maternal protein malnutrition. The fetal pancreas was collected at embryonic day 20 (E20). Protein was extracted, pooled, and subjected to label-free quantitative proteomic analysis. Bioinformatics analysis (GO and IPA) was performed to define the pathways and networks associated with DEPs. LC-MS results were confirmed by western blotting and/or quantitative PCR (q-PCR). The principal parameters of oxidative stress-superoxide dismutase (Sod) were determined in blood samples of fetal rats. Results A total of 57 DEPs (27 upregulated, 30 downregulated) were identified with a 1.5-fold change threshold and a p value ≤ 0.05 between the IUGR and the control pancreas. Bioinformatics analysis revealed that these proteins play important roles in peroxisome biogenesis and fission, fatty acid beta-oxidation (FAO), mitotic cell cycle, and histone modification. The peroxin Pex14 was downregulated in the IUGR pancreas as confirmed by western blotting and q-PCR. Pmp70, a peroxisomal membrane protein involved in the transport of fatty acids, was upregulated. Hsd17b4 and Acox1/2, which catalyze different steps of peroxisomal FAO, were dysregulated. Sod plasma concentrations in the IUGR fetus were higher than those in the control, suggesting partial compensation for oxidative stress. Multiple DEPs were related to the regulation of the cell cycle, including reduced Cdk1, Mcm2, and Brd4. The histone acetylation regulators Hdac1/2 were downregulated, whereas Sirt1/3 and acetylated H3K56 were increased in the IUGR fetal pancreas. Conclusion The present study identified DEPs in the fetal pancreas of IUGR rats by proteomic analysis. Downregulation of pancreas peroxins and dysregulation of enzymes involved in peroxisomal FAO may impair the biogenesis and function of the peroxisome and may underlie the development of T2 diabetes mellitus in adult IUGR rats. Disorders of cell cycle regulators may induce cell division arrest and lead to smaller islets. The present data provide new insight into the role of the peroxisome in the development of the pancreas and may be valuable in furthering our understanding of the pathogenesis of IUGR-induced diabetes.

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Peroxisome Deficiency Dysregulates Fatty Acid Oxidization and Exacerbates Lipotoxicity in β Cells

“…IUGR increases the susceptibility to T2D and impairs glucose tolerance in adults [ 12 , 13 ]. We previously reported that maternal protein malnutrition leads to aberrant expression of Pex14 and FA metabolic enzymes in the fetal pancreas using an IUGR rat model [ 14 ]. Our knockdown assays using Pex14 siRNA support the hypothesis that downregulation of Pex14 lead to programed cell death and reduced resistance to lipotoxicity in the β cell.…”

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The peroxisome: an update on mysteries 3.0

“…In contrast, a complete loss of peroxisome function (through PEX14 silencing) has been shown to exacerbate lipotoxic phenotypes in response to palmitate treatment (Guan et al 2021 ), suggesting some level of peroxisomal β-oxidation is required to protect cells from the deleterious effects of accumulated VLCFAs, the most lipotoxic form of free fatty acids to β-cells (Plötz et al 2019 ). Furthermore, PEX14 protein expression is significantly downregulated in the foetal pancreas in a mouse model of intrauterine growth restriction, which predisposes animals to developing T2DM later in life (Liu et al 2019 ). Beyond β-oxidation, peroxisome-dependent synthesis of ether phospholipids has recently been demonstrated to support β-cell function under conditions where fatty acids are in excess.…”