Equine maternal aging affects oocyte health

We all know that as animals age fertility goes down. In this study one of the reasons in mares is elucidated. It was found that the older mare’s eggs were not as metabolically active as younger mare’s eggs resulting in a significant decline in developing into a blastocyte when fertilized.
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Equine maternal aging affects oocyte lipid content, metabolic function and developmental potential
Reproduction. 2021 Apr;161(4):399-409. doi: 10.1530/REP-20-0494.
Authors
Giovana D Catandi 1 , Yusra M Obeidat 2 , Corey D Broeckling 3 , Thomas W Chen 4 , Adam J Chicco 5 , Elaine M Carnevale 1
Affiliations

1 Equine Reproduction Laboratory, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
2 Electronic Engineering Department, Hijjawi Faculty for Engineering Technology, Yarmouk University, Irbid, Jordan.
3 Proteomics and Metabolomics Facility, Colorado State University, Fort Collins, Colorado, USA.
4 Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado, USA.
5 Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.

PMID: 33539317
PMCID: PMC7969451 (available on 2022-04-01)
DOI: 10.1530/REP-20-0494

Abstract

Advanced maternal age is associated with a decline in fertility and oocyte quality. We used novel metabolic microsensors to assess effects of mare age on single oocyte and embryo metabolic function, which has not yet been similarly investigated in mammalian species. We hypothesized that equine maternal aging affects the metabolic function of oocytes and in vitro-produced early embryos, oocyte mitochondrial DNA (mtDNA) copy number, and relative abundance of metabolites involved in energy metabolism in oocytes and cumulus cells. Samples were collected from preovulatory follicles from young (≤14 years) and old (≥20 years) mares. Relative abundance of metabolites in metaphase II oocytes (MII) and their respective cumulus cells, detected by liquid and gas chromatography coupled to mass spectrometry, revealed that free fatty acids were less abundant in oocytes and more abundant in cumulus cells from old vs young mares. Quantification of aerobic and anaerobic metabolism, respectively measured as oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in a microchamber containing oxygen and pH microsensors, demonstrated reduced metabolic function and capacity in oocytes and day-2 embryos originating from oocytes of old when compared to young mares. In mature oocytes, mtDNA was quantified by real-time PCR and was not different between the age groups and not indicative of mitochondrial function. Significantly more sperm-injected oocytes from young than old mares resulted in blastocysts. Our results demonstrate a decline in oocyte and embryo metabolic activity that potentially contributes to the impaired developmental competence and fertility in aged females.