COVID-19 is not a causal risk for miscarriage: evidence from a Mendelian randomization study.

OBJECTIVE: Coronavirus disease 2019 (COVID-19) has caused a global pandemic in the last three years. The lack of reliable evidence on the risk of miscarriage due to COVID-19 has become a concern for patients and obstetricians. We sought to identify rigorous evidence using two-sample Mendelian randomization (MR) analysis. METHODS: Seven single-nucleotide polymorphisms (SNPs) associated with COVID-19 were used as instrumental variables to explore causality by two-sample MR. The summary data of genetic variants were obtained from the Genome Wide Association Study (GWAS) among European populations in the UK Biobank and EBI database. Inverse variance weighting (IVW) method was taken as the gold standard for MR results, and other methods were taken as auxiliary. We also performed sensitivity analysis to evaluate the robustness of MR. RESULTS: The MR analysis showed there was no clear causal association between COVID-19 and miscarriage in the genetic prediction [OR 0.9981 (95% CI, 0.9872-1.0091), p = 0.7336]. Sensitivity analysis suggested that the MR results were robust [horizontal pleiotropy (MR-Egger, intercept = 0.0001592; se = 0.0023; p = 0.9480)]. CONCLUSIONS: The evidence from MR does not support COVID-19 as a causal risk factor for miscarriage in European populations. The small probability of direct placental infection, as well as the inability to stratify the data may explain the results of MR. These findings can be informative for obstetricians when managing women in labor.

Loss of miR-23b/27b/24-1 Cluster Impairs Glucose Tolerance via Glycolysis Pathway in Mice.

Alterations in miRNAs are associated with many metabolic disorders, such as type 2 diabetes (T2DM). The miR-23b/27b/24-1 cluster contains miR-23b, miR-27b, and miR-24-1, which are located within 881 bp on chromosome 9. Studies examining the roles of miR-23b, miR-27b, and miR-24-1 have demonstrated their multifaceted functions in variable metabolic disorders. However, their joint roles in metabolism in vivo remain elusive. To investigate this subject, we constructed miR-23b/27b/24-1 cluster knockout (KO) mice. Compared with wild-type (WT) mice, the KO mice exhibited impaired glucose tolerance, which was accompanied by a reduction in the respiratory exchange rate (RER). These alterations were more noticeable after a high-fat diet (HFD) induction. Hepatic metabolomic results showed decreased expression of reduced nicotinamide adenine dinucleotide (NADH), nicotinamide adenine dinucleotide (NAD), phosphoenolpyruvic acid (PEP), and phosphoric acid, which are involved in the glycolysis pathway. The transcriptomic results indicated that genes involved in glycolysis showed a downregulation trend. qPCR and Western blot revealed that pyruvate kinase (PKLR), the key rate-limiting enzyme in glycolysis, was significantly reduced after the deletion of the miR-23b/27b/24-1 cluster. Together, these observations suggest that the miR-23b/27b/24-1 cluster is involved in the regulation of glucose homeostasis via the glycolysis pathway.

Cellular atlases of ovarian microenvironment alterations by diet and genetically-induced obesity.

Obesity, which can arise from genetic or environmental factors, has been shown to cause serious damages to the reproductive system. The ovary, as one of the primary regulators of female fertility, is a complex organ comprised of heterogeneous cell types that work together to maintain a normal ovarian microenvironment (OME). Despite its importance, the effect of obesity on the entire ovary remains poorly documented. In this study, we performed ovary single-cell and nanoscale spatial RNA sequencing to investigate how the OME changed under different kinds of obesity, including high-fat diet (HFD) induced obesity and Leptin ablation induced obesity (OB). Our results demonstrate that OB, but not HFD, dramatically altered the proportion of ovarian granulosa cells, theca-interstitial cells, luteal cells, and endothelial cells. Furthermore, based on the spatial dynamics of follicular development, we defined four subpopulations of granulosa cell and found that obesity drastically disrupted the differentiation of mural granulosa cells from small to large antral follicles. Functionally, HFD enhanced follicle-stimulating hormone (FSH) sensitivity and hormone conversion, while OB caused decreased sensitivity, inadequate steroid hormone conversion, and impaired follicular development. These differences can be explained by the differential expression pattern of the transcription factor Foxo1. Overall, our study provides a powerful and high-resolution resource for profiling obesity-induced OME and offers insights into the diverse effects of obesity on female reproductive disorders.

Applications of Melatonin in Female Reproduction in the Context of Oxidative Stress.

Oxidative stress has been recognized as one of the causal mediators of female infertility by affecting the oocyte quality and early embryo development. Improving oxidative stress is essential for reproductive health. Melatonin, a self-secreted antioxidant, has a wide range of effects by improving mitochondrial function and reducing the damage of reactive oxygen species (ROS). This minireview illustrates the applications of melatonin in reproduction from four aspects: physiological ovarian aging, vitrification freezing, in vitro maturation (IVM), and oxidative stress homeostasis imbalance associated with polycystic ovary syndrome (PCOS), emphasising the role of melatonin in improving the quality of oocytes in assisted reproduction and other adverse conditions.