Maternal obesity in ewes results in reduced fetal pancreatic β-cell numbers in late gestation and decreased circulating insulin concentration at term.

About 30% of U.S. women of reproductive age are obese, a condition linked to offspring obesity and diabetes. This study utilized an ovine model of maternal obesity in which ewes are overfed to induce obesity at conception and throughout gestation. At mid-gestation, fetuses from these obese ewes are macrosomic, hyperglycemic, and hyperinsulinemic, and they exhibited markedly increased pancreatic weight and β-cell numbers compared with fetuses of ewes fed to requirements. This study was conducted to establish fetal pancreatic phenotype and function in late gestation and at term in this ovine model. Multiparous ewes were fed a control (C, 100% National Research Council [NRC] recommendations) or obesogenic (OB, 150% NRC) diet from 60 days before conception to necropsy at day 135 of gestation or to lambing. No differences were observed in fetal size or weight on day 135 or in lamb birth weights between C and OB ewes. In contrast to our previously published results at mid-gestation, pancreatic weights (P < 0.01) and β-cell numbers (P < 0.05) of OB fetuses were markedly lower than those from C fetuses, whereas the β-cell apoptotic rate was increased (P < 0.05) in day 135 OB versus C fetuses. At birth, blood insulin concentration was lower (P < 0.05) and glucose level was higher (P < 0.05) in newborn lambs from OB versus C ewes. These data demonstrate differential impacts of maternal obesity on fetal pancreatic growth and β-cell numbers during early and late gestation. During the first half of gestation there was a marked increase in pancreatic growth, β-cell proliferation, and insulin secretion, followed by a reduction in pancreatic growth and β-cell numbers in late gestation, resulting in reduced circulating insulin at term. It is speculated that the failure of the pancreas to return to a normal cellular composition and function postnatally could result in glucose/insulin dysregulation, leading to obesity, glucose intolerance, and diabetes in postnatal life.