Effects of genetics and in utero diet on murine pancreatic development

Abstract

Malnutrition in utero (IU) could alter pancreatic development. Reported here are the effects of high fat diet (HFD) during pregnancy on fetal growth and pancreatic morphology in an “At Risk” animal model of metabolic disease, the glucose transporter 4 heterozygous mouse (G4+/−). Wild type (WT) female mice mated with G4+/− males were fed HFD or control (CD) diet for 2 weeks prior to mating and throughout pregnancy. At embryonic day18.5 fetuses were sacrificed and pancreata isolated for analysis of morphology and expression of genes involved in insulin-cell development, proliferation, apoptosis, glucose transport and function. Compared to WT CD, WT HFD fetal pancreata had a 2.4 fold increase in the number of glucagon cells (p=0.023). HFD also increased glucagon cell size by 18% in WT pancreata compared to WT CD. Compared to WT CD, G4+/− CD had an increased number of insulin cells, and decreased insulin and glucagon cell size. Compared to G4+/− CD, G4+/− HFD fetuses had increased pancreatic gene expression of Igf2, a mitogen and inhibitor of apoptosis. Expression of genes involved in proliferation, apoptosis, glucose transport and insulin secretion were not altered in WT HFD compared with G4+/− HFD pancreata. In contrast to WT HFD pancreata, HFD exposure did not alter pancreatic islet morphology in fetuses with GLUT4 haploinsufficiency; this may be mediated in part by increased Igf2 expression. Thus, interactions between IU diet and fetal genetics may play a critical role in the developmental origins of health and disease.

Critical periods of increased fetal vulnerability to a maternal high fat diet

“…Females were bred to non-littermate glucose transporter 4 heterozygous (G4+/−) males, a model of insulin resistance [ 27 ]. In contrast to WT male offspring from WT pregnancies, WT male offspring of WT female and G4+/− male exposed to a maternal HF IU are programmed to develop characteristics of the MetS [ 9 , 10 , 23 ].…”

“…Fetal Study: Pregnant mothers and fetuses were sacrificed at e18.5 of pregnancy, as previously described [ 9 , 10 , 23 ]. Litter number, placental and fetal weights, and crown-rump length (CRL) were recorded, as well as the number of abnormal or dead pups per litter.…”

“…Quantitative Real Time-PCR Analysis: The cDNA of fetal livers was analyzed with qRT PCR for mRNA gene expression (n = 4-6 per diet) as previously described [ 10 , 23 ]. The RNA was checked for DNA contamination, using PCR with control primers as described previously [ 29 ].…”

“…For quantitative analysis, all samples were normalized to the genes described above using the ΔCT value method; the control (C) group was used as the reference group. Each sample was measured in triplicate for each gene to assess technical variability [ 10 , 23 , 29 ]. The selection of genes was based on a literature search for genes associated with an altered IU milieu [ 10 ].…”

“…Poor prenatal growth, an inflammatory-oxidative stress response, lipotoxicity in the liver and dysregulation in the hepatic expression of genes involved in gluconeogenesis (GNG) have also been observed in non-human primates as well as rodent models exposed to HF IU [ 9 , 10 , 21 , 22 ]. Similarly, our laboratory has previously reported that WT mice exposed to HF IU are born small, have altered pancreatic islet morphology [ 23 ] and develop features of MetS compared to mice exposed to control (C) diet IU and during lactation [ 9 ]. Fetal liver of mice exposed to HF IU have increased expression of genes involved in GNG, inflammation and oxidative stress [ 10 ] that were associated with functional alterations to fetal hepatic histone modifications [ 24 ].…”