Maternal protein restriction leads to hyperinsulinemia and reduced insulin-signaling protein expression in 21-mo-old female rat offspring

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Abstract
Human adult diseases such as cardiovascular disease, hypertension, and type 2 diabetes have been epidemiologically linked to poor fetal growth and development. Male offspring of rat dams fed a low-protein (LP) diet during pregnancy and lactation develop diabetes with concomitant alterations in their insulin-signaling mechanisms. Such associations have not been studied in female offspring. The aim of this study was to determine whether female LP offspring develop diabetes in later life. Control and LP female offspring groups were obtained from rat dams fed a control (20% protein) or an isocaloric (8% protein) diet, respectively, throughout pregnancy and lactation. Both groups were weaned and maintained on 20% normal laboratory chow until 21 mo of age when they underwent intravenous glucose tolerance testing (IVGTT). Fasting glucose was comparable between the two groups; however, LP fasting insulin was approximately twofold that of controls ( P < 0.02). Glucose tolerance during IVGTT was comparable between the two groups; however, LP peak plasma insulin at 4 min was approximately threefold higher than in controls ( P < 0.001). LP plasma insulin area under the curve was 1.9-fold higher than controls ( P < 0.02). In Western blots, both muscle protein kinase C-ζ expression and p110β-associated p85α in abdominal fat were reduced ( P < 0.05) in LPs. Hyperinsulinemia in response to glucose challenge coupled with attenuation of certain insulin-signaling molecules imply the development of insulin resistance in LP muscle and fat. These observations suggest that intrauterine protein restriction leads to insulin resistance in females in old age and, hence, an increased risk of type 2 diabetes.