Maternal Under- and Over-Nutrition during Gestation Causes Islet Hypertrophy and Sex-Specific Changes to Pancreas DNA Methylation in Fetal Sheep

Abstract

The mechanisms by which fetal programming predisposes offspring to reduced β-cell function later in life are poorly understood. We hypothesized that maternal under- and over-nutrition during gestation would negatively affect offspring pancreas development and alter DNA methylation patterns. Pregnant ewes (n = 78) were fed 100, 60, or 140% of NRC requirements beginning at d 30.2 ± 0.2 of gestation. The fetuses are referred to as CON, RES, and OVER, respectively. Fetal pancreas tissue was collected at d 90 or 135 of gestation or within 24 h of birth. Tissue was preserved for histological (n = 8 to 9 offspring per treatment per time point) and DNA methylation analyses (n = 3 to 4 fetuses per treatment per sex). At d 135, OVER exhibited an increased islet size, reduced islet number, and greater insulin positive area compared with CON (p ≤ 0.03). An increased islet size was also observed at d 135 in RES (p ≤ 0.03) compared with CON. Cellular proliferation was reduced at birth in OVER vs. CON (p = 0.01). In the RES vs. CON females, 62% of the differentially methylated regions (DMRs) were hypomethylated (p ≤ 0.001). In the RES vs. CON males, 93% of the DMRs were hypermethylated (p ≤ 0.001). In OVER, 66 and 80% of the DMRs were hypermethylated in the female and male offspring compared with CON (p ≤ 0.001). In conclusion, changes to maternal diet during pregnancy affects the islet hypertrophy and cellular proliferation of the offspring at early post-natal time points. Additionally, changes in DNA methylation patterns appear to be in a diet-specific and sex-dependent manner.