Regulatory effects of soy isoflavones on ovarian development in female Chinese mitten crabs (Eriocheir sinensis)

Soy isoflavones are phytoestrogens that exhibit both estrogenic and/or antiestrogenic effects. This research investigated the potential of soy isoflavones as functional feed additives to promote ovarian development in female Chinese mitten crabs (Eriocheir sinensis). One hundred ninety-two crabs (101.52 ± 4.57 g) were randomly assigned to four groups (six replicates per group and eight crabs per replicate), and fed diets supplemented with 0.00, 32.51, 70.83, or 369.03 mg/kg soy isoflavones for 11 weeks. Compared to the control group, supplementation with 32.51 mg/kg soy isoflavones significantly increased the gonadosomatic index, hemolymph vitellogenin content, and the vtg mRNA levels in the hepatopancreas and ovary (P < 0.05). Moreover, supplementation with 32.51 and 70.83 mg/kg soy isoflavones significantly promoted yolk granule formation (P < 0.05). At the molecular level, soy isoflavones modulated estradiol levels and activated the estrogen-related receptor signaling. They also upregulated the expression levels of esrrb, hsd3b2, and hsd17b6 genes (P < 0.05), compared to the control group. Additionally, they increased estradiol synthesis through activating the cyclic adenosine monophosphate/PKA/CREB protein signaling pathway. High dose supplementation (369.03 mg/kg) did not significantly affect ovarian development (P > 0.05). Therefore, soy isoflavones exhibit a U-shaped effect on ovarian development of E. sinensis, with 32.51 mg/kg being an effective dose for promoting ovarian maturation.