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This study was performed to investigate the effect of melatonin on bovine oocyte maturation and subsequent embryonic development in vitro. The endogenous melatonin concentration in bovine follicular fluid is approximately 10(-11) M. To examine the potential beneficial effects of melatonin on bovine oocyte maturation in vitro, germinal vesicle (GV) oocytes were incubated with different concentrations of melatonin (10(-11), 10(-9), 10(-7), 10(-5), 10(-3) M). Melatonin supplementation at suitable concentrations significantly promoted oocyte maturation. The development of embryos and the mean cell number/blastocyst produced after in vitro fertilization were remarkably improved. The most effective melatonin concentrations obtained from the studies ranged from 10(-9) to 10(-7) M. The expression of melatonin receptor MT1 and MT2 genes was identified in cumulus cells, granulosa cells, and oocytes using reverse transcription PCR, immunofluorescence, and Western blot. The mechanistic studies show that the beneficial effects of melatonin on bovine oocyte maturation are mediated via melatonin membrane receptors as the melatonin receptor agonist (IIK7) promotes this effect while the melatonin receptor antagonist (luzindole) blocks this action. Mechanistic explorations revealed that melatonin supplementation during bovine oocyte maturation significantly up-regulated the expressions of oocyte maturation-associated genes (GDF9, MARF1, and DNMT1a) and cumulus cells expansion-related gene (PTX3, HAS1/2) and that LHR1/2, EGFR are involved in signal transduction and epigenetic reprogramming. The results obtained from the studies provide new information regarding the mechanisms by which melatonin promotes bovine oocyte maturation in vitro and provide an important reference for in vitro embryo production of bovine and the human-assisted reproductive technology.

When a defect occurs in the in vitro development of a pronuclear embryo, the interruption of the subsequent implantation limits the success of assisted conception. This common problem remains to be solved. In this study, we observed that melatonin at its physiological concentration (10(-7)  m) significantly promoted the in vitro development of murine pronuclear embryos. This was indicated by the increased blastocyst rate, hatching blastocyst rate, and blastocyst cell number with melatonin treatment. In addition, when these blastocysts were implanted into female recipient mice, the pregnancy rates (95.0% versus control 67.8%), litter sizes (4.1 pups/litter versus control 2.7 pups/litter), and postnatal survival rates of offspring (96.84% versus control 81.24%) were significantly improved compared with their non-melatonin-treated counterparts. Mechanistic studies revealed that melatonin treatment upregulates gene expression of the antioxidant enzyme, superoxide dismutase (SOD), and the anti-apoptotic factor bcl-2 while downregulating the expression of pro-apoptotic genes p53 and caspase-3. Due to these changes, melatonin treatment reduces ROS production and cellular apoptosis during in vitro embryo development and improves the quality of blastocysts. The implantation of blastocysts with higher quality leads to more healthy offspring and increased pup survival.

Female fertility irreversibly declines with aging, and this is primarily associated with the decreased quality and quantity of oocytes. To evaluate whether a long‐term of melatonin treatment would improve the fertility of aged mice, different concentrations of melatonin (10−3, 10−5, 10−7 mol/L) were supplemented into drinking water. Melatonin treatments improved the litter sizes of mice at the age of 24 weeks. Mice treated with 10−5 mol/L melatonin had the largest litter size among other concentrations. At this optimal concentration, melatonin not only significantly increased the total number of oocytes but also their quality, having more oocytes with normal morphology that could generate more blastocyst after in vitro fertilization in melatonin (10−5 mol/L)‐treated group than that in the controls. When these blastocysts were transferred to recipients, the litter size was also significantly larger in melatonin treated mice than that in controls. The increases in TAOC and SOD level and decreases in MDA were detected in ovaries and uterus from melatonin‐treated mice compared to the controls. Melatonin reduced ROS level and maintained mitochondrial membrane potential in the oocytes cultured in vitro. Mechanistically studies revealed that the beneficial effects of melatonin on oocytes were mediated by MT1 receptor and AMPK pathway. Thereafter, MT1 knocking out (MT1‐KO) were generated and shown significantly reduced number of oocytes and litter size. The expression of SIRT1, C‐myc, and CHOP were downregulated in the ovary of MT1‐KO mice, but SIRT1 and p‐NF‐kB protein level were elevated in response to disturbed redox balance. The results have convincingly proven that melatonin administration delays ovary aging and improves fertility in mice via MT1/AMPK pathway.

The gut microbiota, identified as the target for vegetables, can affect the development of obesity and associated metabolic syndromes. As a medicinal and edible plant, Luffa cylindrica (L.) Roem (LC) has abundant nutrients that can effectively reduce obesity risk. However, the interaction between the prevention effects of LC against obesity and the modulating gut microbiota of LC remain obscure. This study demonstrated LC supplementation improved high‐fat diet (HFD)–induced gut microbiota dysbiosis and significantly enhanced short‐chain fatty acid (SCFA)–producing bacteria (e.g., Blautia) along with SCFA content accumulation in the gut. Meanwhile, LC supplementation substantially restored gut barrier damage in long‐term HFD treatment Moreover, LC supplementation improved HFD‐induced overweight, hyperlipidemia, insulin resistance, and chronic inflammation. Gene expression profiles showed that LC displayed an important impact on hepatic lipid transport and lipid synthesis (sterol regulatory element binding transcriptional factor 1c–peroxisome proliferator‐activated receptor γ signaling pathway). More importantly, an antibiotic treatment experiment demonstrated that the beneficial effects of LC in reducing obesity risk largely depended on the gut microbiota, especially SCFA‐producing bacteria (e.g., Blautia). Therefore, LC supplementation improved gut microbiota dysbiosis via enhancing SCFA‐producing bacteria (e.g., Blautia), maintained gut barrier integrity, and alleviated the development of obesity. Overall, LC would provide a potential dietary intervention strategy against obesity and enteral homeostasis dysbiosis through modulating the gut microbiota.—Zhang, L., Shi, M., Ji, J., Hu, X., Chen, F. Gut microbiota determines the prevention effects of Luffa cylindrica (L.) Roem supplementation against obesity and associated metabolic disorders induced by high‐fat diet. FASEB J. 33, 10339–10352 (2019). http://www.fasebj.org