Hyperglycemia‐induced apoptosis affects sex ratio of bovine and murine preimplantation embryos

Abstract

The effect of glucose in the medium used during in vitro culture on both cell death by apoptosis and the sex ratio of bovine blastocysts derived from in vitro-matured and in vitro-fertilized oocytes was evaluated. Oocytes were matured, inseminated, and cultured in vitro in mSOF medium with 10% FCS with or without glucose supplementation. Exposure to high concentrations of glucose (10, 20, and 30 mM) during bovine embryo development in vitro from zygote to blastocyst resulted in a decrease in the number of cells per embryo and an increase in the frequency of apoptotic cells. A significantly higher proportion of females was found among those embryos that developed under hyperglycemic conditions in vitro. Moreover, both murine and bovine blastocysts incubated for 6 hr in 20 mM glucose had a significantly higher number of apoptotic cells in comparison to control. In this study, we also determined whether blastocyst production of the X-linked inhibitor of apoptosis protein (XIAP) differs between the sexes. Our results show that female bovine blastocysts produce significantly higher amounts of XIAP mRNA than males and this could be crucial in explaining the higher proportion of female blastocysts observed following in vitro culture under hyperglycemic conditions which induce apoptosis. Moreover, a higher proportion of female murine blastocysts cultured under hyperglycemic conditions were implanted in the uterus (65.3 of implantations from embryos cultured with 20 mM of glucose are females vs. 49% in control). This mechanism provides an explanation for the significant reduction of male children born to diabetic mothers.

Transcriptional sexual dimorphism during preimplantation embryo development and its consequences for developmental competence and adult health and disease

“…Higher pyruvate and glucose uptake were also found for male human embryos (Ray et al 1995). Transcriptional studies have observed a higher expression of the X-linked gene G6PD in bovine (Gutierrez-Adan et al 2000, Wrenzycki et al 2002, Jimenez et al 2003 and human (Taylor et al 2001) embryos. G6PD is the first and key PPP regulatory enzyme and therefore may be responsible for these metabolic differences, which may be responsible for altered sex ratio, as discussed below.…”

“…However, during the preimplantation period, X inactivation is a reversible dynamic process; both X-chromosomes are active after embryonic genome activation and XCI is not fully accomplished during early development, which leads to a higher expression of X-linked genes in female embryos (Kobayashi et al 2006, Bermejo-Alvarez et al 2010a. In this sense, a higher expression of selected X-linked genes such as XIST, glucose-6-phosphate dehydrogenase (G6PD), HPRT1, PGK, XIAP and MAOA was reported for mouse (Kay et al 1994, Hartshorn et al 2002, bovine (Gutierrez-Adan et al 2000, Peippo et al 2002, Wrenzycki et al 2002, Jimenez et al 2003, Morton et al 2007) and human (Taylor et al 2001) embryos. The developmental stage at which XCI is accomplished is not clear and may differ greatly between species (Okamoto & Heard 2009), but two global transcriptional studies reported that many X-linked genes are upregulated in female blastocysts in mice (Kobayashi et al 2006) and especially in cattle, where most of them (w90%) are highly expressed in females (Bermejo-Alvarez et al 2010a).…”

“…Surprisingly, the sex ratio changes were not accompanied by a sex-specific embryo loss, as survival rates were not altered (Kimura et al 2005). In contrast, higher glucose concentrations during bovine and murine IVC reduced the percentage of males (Jimenez et al 2003), and maternal diabetes in humans was suggested to result in a higher proportion of daughters (reviewed in Gutierrez-Adan et al (2006)). Furthermore, the optimal glucose concentration may depend largely on the basal medium composition (Biggers & McGinnis 2001), which may confound any interpretation of its putative sex-specific effects.…”

New insights into human pre-implantation metabolism in vivo and in vitro

“…the presence of sulfur amino acids and derivatives, neutralizing the ROS. In the bovine system, an excess of glucose increases apoptosis and induces shifts in sex ratio towards the female [29]: the female embryo has a more effective antiapoptotic mechanism than the male (XIAP, X-linked inhibitor of apoptosis). Indeed, an increase in monozygotic twinning (MZT) may be due to the quality of culture media/conditions and an excessively high level of glucose, rather than to prolonged culture time [30].…”

Suboptimal in vitro culture conditions: an epigenetic origin of long‐term health effects

“…The preferential inactivation is exclusive of Xp, and is confined to the cells of extraembryonic lineages. Interestingly, it has been shown that in the mouse, some essential genes are able to escape this mechanism of chromatin inactivation (Gutierrez-Adan et al, 2000;Jimenez et al, 2003;Perez-Crespo et al, 2005;Kobayashi et al, 2006). It has been reported that about 15% permanently escape inactivation and are thus expressed at twice the level in females as in males (Carrel and Willard, 2005).…”