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Published on: July 6, 2022
Effect of 5-aminoimidazole-4-carboxamide ribonucleoside on the mitochondrial function and developmental ability of
Shun Takeo1, Takahito Abe1, Koumei Shirasuna1
1Department of Animal Science, Tokyo University of Agriculture, Atsugi City, Kanagawa, Japan.
Abstract:
Oocyte nuclear maturation depends on sufficient energy supply through oxidative phosphorylation and β-oxidation. AMP-activated protein kinase (AMPK) is an energy sensor controlling the oocyte energy metabolism. The main aim of this study was to examine the effect of 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a potent activator of AMPK, on the ATP content and mitochondrial DNA copy number (Mt-number) of bovine oocytes and on their developmental ability. Oocytes were collected from slaughterhouse-derived bovine ovaries. When these oocytes were cultured in a maturation medium containing 0-, 50-, 250-, and 500-μM AICAR, higher AICAR concentrations reduced the rate of meiotic maturation and the ATP content in oocytes, whereas lower AICAR increased the ATP content in oocytes without affecting the maturation rate. Supplementation of the maturation medium with a low concentration of AICAR (50 and 250 μM) increased phospho-AMPK expression level, as determined by immunostaining. In addition, AICAR treatment increased the ATP content in oocytes, which remained elevated for as long as 2 days after fertilization. On culturing the oocytes with AICAR (250 μM), the fertilization outcome, rate of blastulation, and total cell number of the blastocysts significantly improved. When the proteosomal mitochondrial degradation was inhibited by supplementing the maturation medium with MG132, the Mt-number, as determined by real-time polymerase chain reaction, significantly increased. However, the treatment of oocytes with AICAR did not affect the Mt-number in the presence or absence of MG132. From these data, we conclude that low concentrations of AICAR improved the embryonic developmental ability, presumably via the upregulation of the ATP content in oocytes, but the increase in the ATP content was not due to the upregulation of mitochondrial biogeneration.
Insights
Low concentrations of 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) enhance bovine oocyte developmental potential by increasing ATP content. This improvement in embryonic development was observed without affecting mitochondrial DNA copy number.
Area of Science:
- Reproductive biology
- Cellular metabolism
- Biochemistry
Background:
- Oocyte maturation requires significant energy, primarily from oxidative phosphorylation and beta-oxidation.
- AMP-activated protein kinase (AMPK) acts as a key cellular energy sensor, regulating oocyte metabolism.
Purpose of the Study:
- To investigate the impact of AICAR, an AMPK activator, on bovine oocyte ATP content, mitochondrial DNA copy number, and developmental competence.
- To elucidate the mechanisms by which AICAR influences oocyte energy metabolism and subsequent embryonic development.
Main Methods:
- Bovine oocytes were cultured with varying concentrations of AICAR (0, 50, 250, 500 μM).
- ATP content, meiotic maturation rates, and mitochondrial DNA copy number (Mt-number) were assessed.
- Phospho-AMPK expression was evaluated using immunostaining.
- Fertilization, blastulation rates, and blastocyst cell numbers were analyzed after AICAR treatment.
Main Results:
- Low AICAR concentrations (50 and 250 μM) increased oocyte ATP content and phospho-AMPK levels without impairing maturation.
- AICAR treatment improved fertilization rates, blastulation rates, and blastocyst cell numbers.
- AICAR did not alter mitochondrial DNA copy number, even when proteasomal degradation was inhibited.
Conclusions:
- Low-dose AICAR enhances bovine oocyte developmental ability by boosting ATP levels, independent of mitochondrial biogenesis.
- The findings suggest a potential therapeutic strategy for improving oocyte quality and embryonic development.
