Wednesday, June 04, 2014
Female mice deprived of dietary zinc for a relatively short time before conception experienced fertility and pregnancy problems and had smaller, less-developed foetuses than mice that ingested zinc during the same times, according to researchers in Penn State's College of Agricultural Sciences. The findings have implications for human reproduction, scientists suggest.
Defects in placenta development are a major cause of delayed embryo/foetal development because the developing embryos do not get enough nutrients to support normal growth. In the zinc-deficient group, the foetal side of the placenta was much less developed. Consistent with delayed development of the placenta, expression of key placental genes was sharply curtailed in mice with zinc-deficient diets.
Collectively, the findings provide evidence for the importance of preconception zinc in promoting optimal fertility and embryo, foetal and placenta development, explained Francisco Diaz, assistant professor of reproductive biology.
The mineral zinc acts as a catalytic, structural and signalling factor in the regulation of a diverse array of cellular pathways involving hundreds of enzymes and proteins, according to him.
Zinc Deficiency Symptoms
In the six-month study, which was published online in a recent edition of Biology of Reproduction, female mice were fed a control or a zinc-deficient diet for four to five days before ovulation. Then, embryonic and/or placental development was evaluated on days three, six, 10, 12 and 16 of pregnancy. The signs of Zinc deficiency were rather evident.
"We know that dietary restrictions can have an effect on pregnancy and on foetal and placental development, but we are not as familiar with preconception effects that are relatively acute and then seeing the effect later on in pregnancy. That is the most novel aspect of our work here."
One way that zinc may affect egg development is by promoting the epigenetic programming of the DNA of the oocyte, or immature egg cell. During egg development, "methyl groups," or chemical tags, are added at specific locations on the DNA and are essential for that egg to fully support embryo and placenta development later on.
Zinc Deficiency Treatment
"It looks like zinc is similar to folic acid, which is one of the few nutrients that are prescribed before a woman becomes pregnant, because it is needed preconception to ensure the quality of the egg," Diaz said. Zinc is very similar in that it is needed before conception -- so giving multivitamins or supplements to a woman after she has found out that she's pregnant doesn't really address the issue."
"It is certainly important during pregnancy, but if the egg development is already compromised, it may not help that aspect of development. I think our work suggests that you need zinc preconception, just like you need folic acid."
A woman's requirement for zinc is not massive -- unlike for calcium or iron -- but there is a fairly rapid turnover of zinc in the body, so humans need a steady supply, Diaz pointed out.
"Actually, our mice become zinc deficient rather quickly," he said. "Animal studies have shown that some tissues can become zinc deficient within a few days."
X. Tian, K. Anthony, T. Neuberger, F. J. Diaz. Preconception Zinc Deficiency Disrupts Post implantation Foetal and Placental Development in Mice. Biology of Reproduction, 2014; 90 (4): 83