Dysregulation in the Unfolded Protein Response in the FGR Rat Pancreas

Accumulating evidence suggests that fetal growth restriction (FGR) leads to the development of diabetes mellitus in adults. The aim of this study was to investigate the effect of protein malnutrition in utero on the pancreatic unfolded protein response (UPR) pathway in FGR offspring. An FGR model was developed by feeding a low-protein diet to pregnant rats throughout gestation. Eighty-four UPR pathway components in the pancreas were investigated by quantitative PCR arrays and confirmed by qPCR and western blotting. Activating transcription factor (Atf4 and Atf6), herpud1, protein kinase R-like endoplasmic reticulum kinase (Perk), X-box binding protein 1 (Xbp1), and the phosphorylation of eIF2α were upregulated, while cyclic AMP-responsive element-binding protein 3-like protein was markedly downregulated in FGR fetuses compared with controls. Investigation in adult offspring revealed temporal changes, for most UPR factors restored to normal, except that dysregulation of Atf6 and Creb3l3 maintained until adulthood. Moreover, autophagy was suppressed in FGR fetal pancreas and may be associated with decreased activation of AMP-activated protein kinase (Ampk). Apoptosis regulators Bax and cleaved-caspase 3 and 9 were upregulated in FGR fetal pancreas. Given that islet size and number were decreased in FGR fetus, we speculated that the aberrant intrauterine milieu impaired UPR signaling in fetal pancreas development. Whether these alterations early in life contribute to the predisposition of FGR fetuses to adult metabolic disorders invites further exploration.