The Reproductive Toxicity of Monosodium Glutamate by Damaging GnRH Neurons Cannot Be Relieved Spontaneously Over Time

Abstract

Objective

The present study aims to evaluate the effect of monosodium glutamate on testicular spermatogenesis in mice from the perspective of the hypothalamic-pituitary-testicular axis and whether this destructive effect is alleviated with time.

Methods

Neonatal mice were randomly divided into a monosodium glutamate (MSG) group and a control group, just below the interscapular region after birth with 10 µL MSG to deliver 4 mg/g (body mass), or with equivalent volumes of 0.9% saline. Samples which involved blood, brains and testicles of mice were collected and measured at puberty at 60 days and adulthood at 90 days.

Results

The results show that the fluorescence intensity of GnRH nerve fibers, the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) hormones in the reproductive system, the number of spermatocytes and spermatozoa in testicular sections, the body length, body weight, testicular weight, and testicular index in the 60-day-old mice in monosodium glutamate group (MSG60 group) and the MSG90 group were lower than those in the 60-day-old mice in normal control group (NC60 group) (p < 0.05), but the number of apoptotic cells in the testicular section was higher than in the NC60 group (p < 0.05). When the 90-day-old mice in monosodium glutamate group (MSG90 group) was compared with the MSG60 group, except for body weight and testicular weight increase (p < 0.05), there is no significant difference in the other parameters mentioned above (p > 0.05).

Conclusion

Monosodium glutamate can cause reproductive toxicity to male mice by damaging GnRH neurons, and this reproductive toxicity cannot be relieved spontaneously over time. These findings are supported by observed histological changes.

Keywords:

• monosodium glutamate
• neurotoxicity
• GnRH neurons
• reproductive organs

Acknowledgments

We are particularly grateful to all the people who have given us help on our article.

Abbreviations

MSG, monosodium glutamate; FSH, follicle stimulating hormone; LH, luteinizing hormone; GnRH, Gonadotropin-releasing hormone; T, testosterone; NC60, 60-day-old mice in normal control group; MSG60, 60-day-old mice in monosodium glutamate group; MSG90, 90-day-old mice in monosodium glutamate group; PPARs, peroxisome proliferator-activated receptors.

Ethics Approval and Consent to Participate

All procedures on animals followed Guideline for work on experimental animals approved by Ethic Committee of Faculty of Binzhou Medical University (No:2018-G005-01).

Disclosure

The authors declare that they have no competing interests.

Additional information

Funding

The present study was supported by the Medical Science and Technology development Program of Shandong Province (grant no. 2011QZ002 to Q. C. Li) and Shandong Natural Science Foundation (grant no. ZR2017LH013 to H. L. Sun).