Objective

7,8-Dihydroxyflavone (7,8-DHF), a small molecular mimetic of brain-derived neurotrophic factor (BDNF), alleviates high-fat diet-induced obesity in female mice in a sex-specific manner by activating muscular tropomyosin-related kinase B (TrkB). However, the underlying molecular mechanism for this sex difference is unknown. Moreover, muscular estrogen receptor α (ERα) plays a critical role in metabolic diseases. Impaired ERα action is often accompanied by metabolic syndrome (MetS) in postmenopausal women. This study investigated whether muscular ERα is involved in the metabolic effects of 7,8-DHF.

Methods

For the in vivo studies, 72 female C57BL/6J mice were given a low-fat diet or high-fat diet, and both received daily intragastric administration of vehicle or 7,8-DHF for 24 weeks. The hypothalamic-pituitary-ovarian (HPO) axis function was assessed by investigating typical sex-related serum hormones and the ovarian reserve. Indicators of menopausal MetS, including lipid metabolism, insulin sensitivity, bone density, and serum inflammatory cytokines, were also evaluated. The expression levels of ERα and other relevant signaling molecules were also examined. In vitro, the molecular mechanism involved in the interplay of ERα and TrkB receptors was verified in differentiated C2C12 myotubes using several inhibitors and a lentivirus short hairpin RNA-knockdown strategy.

Results

Long-term oral administration of 7,8-DHF acted as a protective factor for the female HPO axis function, protecting against ovarian failure, earlier menopause, and sex hormone disorders, which was paralleled by the alleviation of MetS coupled with the production of ERα-rich, TrkB-activated, and uncoupling protein 1 (UCP1) high thermogenic skeletal muscle tissues. 7,8-DHF-stimulated transactivation of ERα at serine 118 (S118) and tyrosine 537 (Y537), which was crucial to activate the BDNF/TrkB signaling cascades. In turn, activation of BDNF/TrkB signaling was also required for the ligand-independent activation of ERα, especially at the Y537 phosphorylation site. In addition, Src family kinases played a core role in the interplay of ERα and TrkB, synergistically activating the signaling pathways related to energy metabolism.

Conclusions

These findings revealed a novel role of 7,8-DHF in protecting the function of the female HPO axis and activating tissue-specific ERα, which improves our understanding of this sex difference in 7,8-DHF-mediated maintenance of metabolic homeostasis and provides new therapeutic strategies for managing MetS in women.

中文翻译：

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肌肉雌激素受体 α 和 BDNF/TrkB 信号之间的串扰通过雌性小鼠的 7,8-二羟基黄酮缓解代谢综合征

客观的

7,8-二羟基黄酮 (7,8-DHF) 是一种脑源性神经营养因子 (BDNF) 的小分子模拟物，通过激活肌肉原肌球蛋白相关，以性别特异性方式减轻雌性小鼠高脂饮食引起的肥胖激酶 B (TrkB)。然而，这种性别差异的潜在分子机制尚不清楚。此外，肌肉雌激素受体α（ERα）在代谢疾病中起着关键作用。ERα 作用受损通常伴有绝经后妇女的代谢综合征 (MetS)。该研究调查了肌肉 ERα 是否参与了 ​​7,8-DHF 的代谢作用。

方法

对于体内研究，72只雌性C57BL / 6J小鼠给予低脂肪饮食或高脂肪饮食，并且两个接收到的车辆或7,8-DHF的每日灌胃给药24周。通过研究典型的性相关血清激素和卵巢储备来评估下丘脑-垂体-卵巢 (HPO) 轴功能。还评估了更年期 MetS 的指标，包括脂质代谢、胰岛素敏感性、骨密度和血清炎性细胞因子。还检查了 ERα 和其他相关信号分子的表达水平。在体外，使用几种抑制剂和慢病毒短发夹 RNA 击倒策略在分化的 C2C12 肌管中验证了参与 ERα 和 TrkB 受体相互作用的分子机制。

结果

长期口服 7,8-DHF 作为女性 HPO 轴功能的保护因素，防止卵巢功能衰竭、更年期提前和性激素紊乱，同时缓解 MetS 并产生 ERα富含 TrkB 激活的解偶联蛋白 1 (UCP1) 高产热骨骼肌组织。7,8-DHF 刺激 ERα 在丝氨酸 118 (S118) 和酪氨酸 537 (Y537) 的反式激活，这对于激活 BDNF/TrkB 信号级联至关重要。反过来，BDNF/TrkB 信号传导的激活也是 ERα 的配体非依赖性激活所必需的，尤其是在 Y537 磷酸化位点。此外，Src 家族激酶在 ERα 和 TrkB 的相互作用中发挥核心作用，协同激活与能量代谢相关的信号通路。

结论

这些发现揭示了 7,8-DHF 在保护女性 HPO 轴功能和激活组织特异性 ERα 方面的新作用，这提高了我们对 7,8-DHF 介导的代谢稳态维持中这种性别差异的理解，并提供了管理女性 MetS 的新治疗策略。