The consumption of monosodium glutamate during the periconceptional period can impair preimplantation embryo development

Abstract

Monosodium glutamate (MSG) is one of the most commonly used food additives and is consumed worldwide as part of commercially processed foods. To study the possible reproductive risks of consuming monosodium glutamate during the periconceptional period (comprising oocyte maturation and the earliest stages of embryo development), we administered MSG (at doses of 500, 200 or 50 mg/kg body weight, by oral gavage) to female mice in this period. Preimplantation embryos were then isolated at D4 of gestation and analyzed. In blastocysts developed from female mice fed with MSG, we found a reduced proportion of blastocysts, a lower number of cells, and an increased proportion of dead cells. The expression of the proapoptotic gene Bak1 and active caspase-3 were significantly increased and telomeres were shorter in blastocysts isolated from MSG-fed females. The results of our previous in vitro study revealed that glutamate receptors are involved in the negative effects of glutamate on mouse blastocysts. In silico analysis of RNA-seq datasets containing data from human preimplantation embryos performed in this study revealed that NMDA receptors (formed from the GRIN2D or GRIN2B and GRIN3B subunits) and the GRM4 and GRM8 metabotropic receptors are expressed in human blastocysts. These results indicate that glutamate receptors could mediate the effects of MSG in human blastocyst cells. In summary, our results show that oral intake of relatively low doses of MSG during the periconception period can adversely affect early embryonic development and embryo quality and may pose a risk to successful conception and subsequent embryo development.