Abstract:
The increasing prevalence of obesity is paralleled by the increasing consumption of sugars, including the simple monosaccharide, fructose. Fructose consumption has been shown to induce insulin resistance, weight gain and hyperlipidaemia. Despite the widespread consumption of fructose-containing foods and beverages and rising incidence of maternal obesity, relatively little attention has been paid to the possible adverse effects of maternal fructose consumption on the developing fetus. The current study aims to investigate the effects of maternal fructose consumption on placental and fetal development. Female rats were time-mated and randomised to either a control (CONT, n=10) diet, or a fructosesupplemented diet (Fr, n=9) throughout pregnancy. On day 21 of pregnancy, maternal and fetal blood samples and placental tissue were collected. Maternal bodyweight, blood glucose and β-hydroxybutyrate (β-HB) levels did not differ between groups, although Fr mothers had elevated plasma fructose levels compared to CONT (p<0.001) and reduced plasma levels of some essential amino acids. Fetal weight was unaffected but Fr placental weights were reduced (p=0.02). Fr female fetuses had higher plasma fructose levels (p<0.05) and higher blood glucose levels (p<0.05), but lower β-HB levels compared to female CONT fetuses (p<0.05). These effects were absent in Fr male fetuses. Plasma levels of nearly all essential amino acids were decreased in Fr fetuses regardless of sex (p<0.001), but interestingly, plasma levels of taurine were increased only in male Fr fetuses (p=0.026). Protein expression of phospho-4E-BP1 (p=0.06) was reduced in the labyrinthine zone of Fr female placentae, associated with decreased SNAT1 (p<0.05) and GLUT1 (p=0.004) protein levels. In Fr male placentae, phospho-mTORC1 protein expression was reduced in the junctional zone (p=0.01), while GLUT3 protein expression was reduced in the labyrinthine zone (p<0.05). Maternal fructose consumption resulted in sex-specific changes in fetal and placental development, whereby female fetuses were apparently more vulnerable to changes in circulating fructose, glucose and β-HB, which may be associated with alterations in placental growth and function. Male fetuses however, appear protected and increased levels of plasma taurine may be suggestive of compensatory mechanisms.