Dietary Epigenetics
Arizona, who have the world’s highest incidence and prevalence of diabetes, showed a genetic transmission component (Knowler et al. 1978). The study also revealed that the cycle of inter-generational diabetes can be explained by environmental factors, since the strongest single risk factor for type 2 diabetes mellitus was exposure to maternal diabetes in utero (Dabelea et al. 1998). Children born to diabetic mothers showed a 10-fold increase in the prevalence of diabetes by early adulthood compared with children whose mothers did not develop diabetes until after delivery (Heerwagen et al. 2010). This inheritance could be in part due to exposure to a diabetic intrauterine environment (Dabelea et al. 2000). In another study, individuals whose cord blood or amniotic fluid insulin levels were elevated had a three to fourfold risk of developing glucose intolerance and type 2 diabetes mellitus during childhood (Pinney and Simmons 2012). This suggests that persistent fetal exposure to hyperinsulinaemia in the uterine environment contributes to the development of diabetes through epigenetic mechanisms. This notion is supported by studies showing that impaired glucose tolerance of adolescent offspring is associated with maternal hyperglycemia and not with the specific type of diabetes of the mother (Silverman et al. 1995). A study in rats also showed that although an intrauterine environment that provides normal glucose concentration cannot overcome a genetic predisposition to diabetes, a hyperglycaemic intrauterine environment significantly increases the risk of diabetes in the adult life of the offspring (Gill-Randall et al. 2004). 4.3.3 Maternal Diabetes and Offspring Obesity Obesity and type 2 diabetes mellitus are closely related; consequently, there are many studies where maternal diabetes seems to predispose offspring to obesity. One study showed that newborn infants of women with gestational diabetes have 20% more body fat than infants of women with normal glucose 89