Effects of adenosine monophosphate‐activated kinase activators on bovine oocyte nuclear maturation in vitro

Abstract

The purpose of this study was to examine the effects of an activator of AMPK (5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR)) on bovine oocyte nuclear maturation in vitro. After 7 hr of culture, AICAR (1 mM) significantly increased the percentages of cumulus-enclosed oocytes (CEO) and denuded oocytes (DO) remaining at the germinal vesicle stage. After 22 hr of culture, AICAR significantly reduced the percentage of CEO reaching metaphase II (MII). AICAR at 1.0 mM also increased the inhibitory effect of the adenylate cyclase activator forskolin in CEO; however, at 0.05 mM, AICAR increased the percentage of oocytes at MII after 22 hr of culture compared to forskolin alone. The adenosine kinase inhibitor 5'-aminodeoxyadenosine reversed the effect of AICAR in CEO and DO showing that phosphorylation of AICAR by adenosine kinase is required for its inhibitory activity. GMP, but not AMP, inhibited meiosis in CEO and DO; however, inhibition of guanyl and adenyl nucleotides synthesis did not reverse the effect of AICAR suggesting that the inhibitory effect of AICAR is not due to increased synthesis of these nucleotides. Metformin, another activator of AMPK, also inhibited GVBD in CEO and DO. The alpha-1 isoform of the catalytic subunit of AMPK was detected in oocytes and cumulus cells, and reverse transcription-polymerase chain reaction experiments showed the presence of transcripts for alpha-1, alpha-2, beta-1, and gamma-3 isoforms of the regulatory subunits in cumulus cells and oocytes. These data show that the AMPK activator AICAR is inhibitory to nuclear maturation in bovine oocytes due to activation of AMPK.

Potential upstream regulators and downstream targets of AMP-activated kinase signaling during oocyte maturation in a marine worm

“…Accordingly, various analyses have shown that AMPK triggers GVBD in denuded or cumulus-enclosed oocytes of mice (Chen et al 2006, LaRosa & Downs 2006, Chen & Downs 2008. Alternatively, AMPK agonists can block GVBD in other cumulus-enclosed mammalian oocytes (Bilodeau-Goeseels et al 2007, Mayes et al 2007, Tosca et al 2007, although such blockage is apparently due to effects on follicle cells and/or to non-AMPK-mediated pathways (Mayes et al 2007, Tosca et al 2007, Bilodeau-Goeseels et al 2010. However, oocytes of nemertean worms lack follicle cells , and AMPK activations nevertheless inhibit nemertean GVBD (Stricker et al 2010a(Stricker et al , 2010b, indicating that intraoocytic AMPK can stimulate or block MPF activation in different animals.…”

“…For example, recent studies of intraoocytic AMPK in mice have assessed the relationship between diabetes and AMPK-mediated targets in glucose metabolism (Ratchford et al 2007), the activation of AMPK by FSH and amphiregulin (Chen & Downs 2008), and the interconnections between AMPK and fatty acid oxidative pathways (Downs et al 2009). Moreover, how AMPK interacts with MAPK and other signals has been evaluated in oocytes of cows and pigs (Bilodeau-Goeseels et al 2007, Mayes et al 2007, Tosca et al 2007.…”

The Control of Meiotic Arrest and Resumption in Mammalian Oocytes

“…Contrary to results obtained with mouse oocytes where AMPK activation led to meiotic resumption (see section 2.3), meiosis was inhibited when bovine oocytes were cultured with the AMPK activator 5'-aminoimidazole-4-carboxamide 1--D-ribofuranoside (AICAR, Bilodeau-Goeseels et al, 2007). The inhibitory effect of AICAR was observed in cumulusenclosed and denuded oocytes, was reversible, increased the inhibitory effect of the AC activator FSK, was dependent on its phosphorylation by adenosine kinase and was not due to increased cAMP levels or to increased purine nucleotide synthesis (Bilodeau-Goeseels et al, 2007).…”

“…The inhibitory effect of AICAR was observed in cumulusenclosed and denuded oocytes, was reversible, increased the inhibitory effect of the AC activator FSK, was dependent on its phosphorylation by adenosine kinase and was not due to increased cAMP levels or to increased purine nucleotide synthesis (Bilodeau-Goeseels et al, 2007). Metformin [MET, one of the most widely used drugs for the treatment of type 2 diabetes and an AMPK activator (Zhou et al, 2001)], was also reported to inhibit GVBD in bovine CEO and DO by Bilodeau-Goeseels et al (2007). In a subsequent study, however, the AMPK inhibitor Compound C (CC) did not reverse the effect of AICAR and MET and even had a significant inhibitory effect itself on bovine oocyte meiosis (Bilodeau-Goeseels et al, 2011).…”

The effect of nutrition and metabolic status on the development of follicles, oocytes and embryos in ruminants

“…In cattle, similar to the pig, pharmacological activation of AMPK blocked nuclear maturation of the oocyte (at prophase of the first meiotic division or at the germinal vesicle stage (Bilodeau-Goeseels et al, 2007;Tosca et al, 2007b), whereas in mice AMPK improved the resumption of meiosis by accelerating rupture of the nuclear membrane (Bilodeau-Goeseels, 2011) or breakdown of the germinal vesicle (Downs and Chen, 2006). Although there are some differences among species, AMPK appears to be important for the breakdown of the germinal vesicle during nuclear maturation of the oocyte.…”