Astaxanthin Alleviates Oxidative Stress in Mouse Preantral Follicles and Enhances Follicular Development Through the AMPK Signaling Pathway

This study investigates the effects of astaxanthin on oxidative stress, mitochondrial function, and follicular development in mouse preantral follicles, with a focus on the involvement of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Astaxanthin (2.5 nM) significantly enhanced both the antrum formation (from 85.96% in the control group to 94.38% in the astaxanthin group) and maturation rates (from 79.15% to 85.12%) of oocytes (<i>p</i> < 0.05). From day 4 of in vitro culture, astaxanthin notably increased the area of follicle attachment (from 0.06 µm² to 0.32 µm²) and the secretion of estradiol (from 32.10 ng/L to 49.73 ng/L) (<i>p</i> < 0.05). Additionally, it significantly decreased malondialdehyde content (from 80.54 μM to 62.65 μM) within the follicles while increasing the mRNA expression levels of glutathione and superoxide dismutase 1 (<i>p</i> < 0.05). Astaxanthin also reduced reactive oxygen species levels in oocytes (<i>p</i> < 0.05). Notably, astaxanthin enhanced the expression of p-AMPK and PGC-1α, which are key proteins for the AMPK pathway; NRF1 and TFAM, which are crucial for mitochondrial biogenesis; NRF2 and HO-1, which protect against oxidative stress; CO1, CO2, CO3, ATP6, ATP8, and TOM20, which are essential for electron transport chain activity and ATP synthesis; PINK1, Parkin, and LC3-II, which are involved in mitophagy; Bcl-2, which inhibits cell apoptosis; and StAR and P450scc, which promote estrogen synthesis (<i>p</i> < 0.05). Furthermore, astaxanthin improved mitochondrial membrane potential and decreased the expression of cleaved caspase 3, Bax, and P53, which promotes cell apoptosis (<i>p</i> < 0.05). However, these changes induced by astaxanthin were completely reversed by AMPK inhibitors, indicating the involvement of the AMPK pathway. Conclusively, astaxanthin enhances the in vitro development of follicles, alleviates oxidative stress in preantral follicles, and promotes mitochondrial function during in vitro culture, which may be mediated by the AMPK pathway.