Effects Of Maternal Dietary Energy Intake Pattern On Placental Nutrient Transfer And Fetal Growth In Uterine In Rats

Human epidemiological and animal study showed that maternal nutritional status could program the postnatal growth performance and incidence of metabolic syndrome in adulthood, however, few studies have dressed the mechanisms mediating the maternal nutritional effects on the intrauterine growth, therefore, two experiments were conducted to evaluate the effects of maternal dietary energy patterns on the placental nutrients transfer and fetal growth in uterine.In experiment 1, effects of high-energy diet on the placental nutrients transfer, fetal growth, and gene expressions in fetal liver were investigated. Thirty SD rats (90 days age and weighed 250g) were fed high energy (HE) or low energy (LE) diets ad libitum immediately after the confirmation of pregnancy untill being sacrificed on day 20 of pregnancy for sample collection. Results:1. He diet resulted in 25% higher average daily energy intake than low-fat diet (P< 0.05), and fetal growth on day 20 of pregnancy was higher in HE diets (P<0.05)2. Placental nutrient transporter mRNA expressions of Slc2al, Slc2a3, Slc38al, Slc38a4 and Slc7al were not affected by HE diet (P> 0.05), but placental Slc38a2 expressions were up-regulated by HE diet (P< 0.05)3. HF resulted in higher circulating triglyceride concentration, but not glucose, total cholesterol and free fatty acid concentrations. HE diets induced higher fetal growth was associated with higher Leptin concentration and upregualted Leptin-target gene STAT3 expression.4. PPARy, GR, Na-K-ATPase mRNA expression in fetal liver tended to be up-regulated by HE diet (P>0.05). DNMT1 mRNA expression was up-regulated (P< 0.05), whereas DNMT3a mRNA expression (P<0.01) was down-regulated by HE.In experiment 2, effects of dietary energy types on fetal growth, the placental nutrient transporter and fetal energy metabolism related gene expressions were evaluated. Eighty rats (1 months' age) were allocated to four dietary treatment groups according to 22 experimental design. Treatment effects were high (25%) and low (5%) level, as well as high fiber (51%) and low fiber (0%). High-fat was mixed with soybean oil(5%), swine lard(10%) and rapeseed oil(10%). Fiber was provided by oat bran, wheat bran and carrot with the ratio of 1:1:1. Therefore, four dietary treatment groups were estabolished, Low fat-low fiber (Energy provided by starch, L-L), low fat-high fiber (Energy provided by starch and fiber, L-H), high fat-low fiber (Energy provided by starch and fat, H-L), high fat-high fiber (H-H). Rats were fed treatment diets 4 weeks prior to mating and continued in pregnancy until sample collection were performed on day 14 and 18 of pregnancy.Results:1. Placental weight and placental efficiency on d 14 and 18 of pregnancy were not affected by dietary energy types (P>0.05). Fetal weight on d 18 of pregnancy was affected by the interaction between fat and fiber (P<0.01). Fetal weight in L-L diet was significantly lower than that in H-L diets (P<0.05).2. High fat and high fiber elevated circulating glucose on day 14 of pregnancy (P< 0.05), and glucose concentration was the highest in H-L on d 14 of pregnancy. Maternal circulating concentrations of FFA, TC, Igf-2, Leptin and corticosterone were not affected on day 14 and 18 of pregnancy (P>0.05).3. Placental nutrient transporter mRNA expression was affected by dietary energy types on day 14 and 18 of pregnancy. Placental Slc2a3and Slc7al mRNA was upregualted by H-L diet compared with L-L diet (P<0.05). However, placental Slc2al and Slc38a4 mRNA expressions were adaptively upregualted by L-L diet (P<0.05). Placental Slc38al and Slc38a2 mRNA expressions were not affected by dietary energy types (P> 0.05).4. Placental imprinted gene Igf-2 and H19 expressions were affected by dietary energy types (P<0.05). H-L resulted in higher placental Igf-2 expression than L-L diet (P<0.05) on d14 of pregnancy, but H19 expression in H-L was down-regulated compared with L-L diets. Fetal imprinted genes Igf-2 and H19 expressions were not affected by dietary energy types (P>0.05). 5. Fetal DNMT1 and DNMT3a expressions on day 18 of pregnancy were not affected by maternal dietary energy types (P>0.05). Fiber and fat fiber interaction affected fetal DNMT1 and DNMT3a expression (P<0.05). High fiber up-regulated fetal DNMT1 expression compared with low fiber in the low-fat fed rats (P<0.05). Fetal DNMT3a expression was affected by fat fiber interaction (P<0.05), and H-L diets significantly upregulated DNMT3a expression compared with other groups (P<0.05).PPARa and PPARy expressions of fetal sample from d 14 and d18 of pregnancy were not affected by maternal dietary energy types, whereas GR on d 18 of pregnancy were down-regulated by high fiber treatment.Conclusion:Pregnant rats fed HE diets ad libitum promoted fetal growth upregulated placental nutrient transporter expression. Under similar dietary energy intake, maternal dietary energy type could affect the placental nutrient transfer and fetal growth via the regulation of placental imprinted gene Igf-2 and H19. Different energy intake patterns in uterine were associated with altered gene expression related to DNA methylation and energy metabolism.