L-arginine and N-carbamylglutamate (NCG) has been found to play a critical role in regulating the function and volume of the umbilical vein, which provide more nutrients and oxygen from the maternal to the fetus tissue for fetal development and survival and enhance the reproductive performance of sows.

A team of researchers, led by YIN Yulong, at the Institute of Subtropical Agriculture, Chinese Academy of Sciences(ISA) has been able to watch L-arginine or NCG in action as it regulates microRNAs (miR-15b, miR-222) targeting vascular endothelial growth factor A (VEGFA) and endothelial nitric oxide synthase (eNOS) gene expressions in umbilical vein.

“Placenta vascular formation and blood flow are crucial for fetal survival, growth and development, and arginine regulates vascular development and function.” said LIU Xingda, senior author of the research paper, “In our study, we determined the effects of dietary arginine or NCG supplementation during late gestation of sows on the microRNAs, VEGFA and eNOS expression in umbilical vein.”

In their research, twenty-seven landrace × large White sows at day (d) 90 of gestation were assigned randomly to three groups, and fed with the following diets: a control diet and the control diet supplemented with 1.0% L-arginine or 0.10% NCG. Umbilical vein of fetuses with body weight around 2.0 kg (oversized), 1.5 kg (normal) and 0.6 kg (intrauterine growth restriction, IUGR) were obtained immediately after farrowing for miR-15b, miR-16, miR-221, miR-222, VEGFA and eNOS real-time PCR analysis. Compared with the control diets, dietary Arg or NCG supplementation enhanced the reproductive performance of sows, increased (P < 0.05) plasma arginine and decreased (P < 0.05) VEGF and eNOS. The miR-15b expression in the umbilical vein was higher (P < 0.05) in the NCG-supplemented group than in the control group. There was a trend in that the miR-222 expression in the umbilical vein of the oversized fetuses was higher (0.05< P <0.1) than in the normal and IUGR fetuses. The expression of eNOS in both Arg-supplemented and NCG-supplemented group were lower (P < 0.05) than in the control group. The expression of VEGFA was higher (P < 0.05) in the NCG-supplemented group than in the Arg-supplemented and the control group. Meanwhile, the expression of VEGFA of the oversized fetuses was higher (P<0.05) than the normal and IUGR fetuses.

“In a word, our study demonstrated that dietary Arg or NCG supplementation may affect microRNAs (miR-15b, miR-222) targeting VEGFA and eNOS gene expressions in umbilical vein, so as to regulate the function and volume of the umbilical vein, provide more nutrients and oxygen from the maternal to the fetus tissue for fetal development and survival and enhance the reproductive performance of sows.” said LIU, “In the future, it is necessary for us to determine how arginine regulate fetal survival, growth and development through microRNAs.”

This research was jointly supported by grants from the National Basic Research Program of China (2009CB118806), the Chinese Academy of Sciences and Knowledge Innovation Project (KZCX2-EW-412, KZCX2-EW-QN411), NSFC(30901040, 30901041, 30928018, 30828025, 30771558).

The study entitled “Effects of dietary L-arginine or N-carbamylglutamate supplementation during late gestation of sows on the miR-15b/16, miR-221/222, VEGFA and eNOS expression in umbilical vein” has been published online in Amino Acid, DOI: 10.1007/s00726-011-0948-5. (http://www.springerlink.com/content/yv62vv5h7t8l6162/)