Origins of lifetime health around the time of conception: causes and consequences.

Both obesity and overweight are increasing worldwide and have detrimental influences on several human body functions including the reproductive health. In particular, obese women undergo perturbations of the ‘hypothalamic pituitary ovarian axis’, and frequently suffer of menstrual dysfunction leading to anovulation and infertility. Besides the hormone disorders and subfertility that are common in the polycystic ovary syndrome (PCOS), in obesity the adipocytes act as endocrine organ. The adipose tissue indeed, releases a number of bioactive molecules, namely adipokines, that variably interact with multiple molecular pathways of insulin resistance, inflammation, hypertension, cardiovascular risk, coagulation, and oocyte differentiation and maturation. Moreover, endometrial implantation and other reproductive functions are affected in obese women with complications including delayed conceptions, increased miscarriage rate, reduced outcomes in assisted conception treatments. On the contrary, weight loss programs through lifestyle modification in obese women, have been proven to restore menstrual cyclicity and ovulation and improve the likelihood of conception.

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Obesity as disruptor of the female fertility.

In the United States, 36.5% of women between the ages of 20 and 39 years are obese. This obesity results in not only metabolic disorders including type II diabetes and cardiovascular disease, but also impaired female fertility. Systemic and tissue-specific chronic inflammation and oxidative stress are common characteristics of obesity. This is also true in the ovary. Several studies have demonstrated that pro-inflammatory cytokines and reactive oxygen species alter estrous cyclicity, steroidogenesis and ovulation. Inflammation and oxidative stress also impair meiotic and cytoplasmic maturation of the oocyte which reduces its developmental competence for fertilization and pre-implantation embryo development. Interestingly, there is recent evidence that obesity- and/or polycystic ovary syndrome (PCOS)-dependent changes to the gut microbiome contributes to ovarian inflammation, steroidogenesis and the expression of mRNAs in the oocyte. However, several gaps remain necessitating future studies to identify inflammation, oxidative stress and gut microbiome mechanisms that reduce ovarian function and oocyte quality.

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Obesity induces ovarian inflammation and reduces oocyte quality

Obesity is a disorder characterized by a disproportionate increase in body weight in relation to height, mainly due to the accumulation of fat, and is considered a pandemic of the present century by many international health institutions. It is associated with several non-communicable chronic diseases, namely, metabolic syndrome, type 2 diabetes mellitus (T2DM), cardiovascular diseases (CVD), and cancer. Metabolomics is a useful tool to evaluate changes in metabolites due to being overweight and obesity at the body fluid and cellular levels and to ascertain metabolic changes in metabolically unhealthy overweight and obese individuals (MUHO) compared to metabolically healthy individuals (MHO). We aimed to conduct a systematic review (SR) of human studies focused on identifying metabolomic signatures in obese individuals and obesity-related metabolic alterations, such as inflammation or oxidative stress. We reviewed the literature to identify studies investigating the metabolomics profile of human obesity and that were published up to May 7th, 2019 in SCOPUS and PubMed through an SR. The quality of reporting was evaluated using an adapted of QUADOMICS. Thirty-three articles were included and classified according to four types of approaches. (i) studying the metabolic signature of obesity, (ii) studying the differential responses of obese and non-obese subjects to dietary challenges (iii) studies that used metabolomics to predict weight loss and aimed to assess the effects of weight loss interventions on the metabolomics profiles of overweight or obese human subjects (iv) articles that studied the effects of specific dietary patterns or dietary compounds on obesity-related metabolic alterations in humans. The present SR provides state-of-the-art information about the use of metabolomics as an approach to understanding the dynamics of metabolic processes involved in human obesity and emphasizes metabolic signatures related to obesity phenotypes.

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Are we close to defining a metabolomic signature of human obesity? A systematic review of metabolomics studies

The ovary is perhaps the most dynamic organ in the human body, only rivaled by the uterus. The molecular mechanisms that regulate follicular growth and regression, ensuring ovarian tissue homeostasis, remain elusive. We have performed single-cell RNA-sequencing using human adult ovaries to provide a map of the molecular signature of growing and regressing follicular populations. We have identified different types of granulosa and theca cells and detected local production of components of the complement system by (atretic) theca cells and stromal cells. We also have detected a mixture of adaptive and innate immune cells, as well as several types of endothelial and smooth muscle cells to aid the remodeling process. Our results highlight the relevance of mapping whole adult organs at the single-cell level and reflect ongoing efforts to map the human body. The association between complement system and follicular remodeling may provide key insights in reproductive biology and (in)fertility. In the ovary, follicular degeneration occurs after folliculogenesis, with one dominant follicle reaching maturity every month. Here, by performing single cell RNA-seq of adult human follicles, the authors identify subclasses of granulosa and theca cell lineages, which correlate with the growth or degeneration of the follicles.

https://biblio.ugent.be/publication/8679771/file/8679772.pdf

Single-cell reconstruction of follicular remodeling in the human adult ovary.

Context It is hypothesized that obesity adversely affects the ovarian environment, which can disrupt oocyte maturation and embryonic development. Objective This study aimed to compare oocyte gene expression profiles and follicular fluid (FF) content from overweight/obese (OW) women and normal-weight (NW) women who were undergoing fertility treatments. Design Using single-cell transcriptomic analyses, we investigated oocyte gene expression using RNA sequencing. Patients or Other Participants Eleven OW women and 13 NW women undergoing fertility treatments were enrolled. Main Outcome Measures Oocyte messenger RNA profiles as well as serum and FF hormone and lipid levels were assessed. Results OW women had significantly higher body mass index, body fat percentage, and serum homeostatic model assessment-insulin resistance index compared with NW women (P < 0.01). Serum leptin and C-reactive protein (CRP) levels as well as FF leptin, CRP, and triglyceride levels were increased (P < 0.05) in OW compared with NW women. Oocytes from OW women had increased expression of proinflammatory (CXCL2; P = 0.071) and oxidative stress-related (DUSP1; P = 0.051) genes but had decreased expression of GAS7 (fat metabolism; P = 0.065), TXNIP (oxidative stress; P = 0.055), and transcription factors ID3 (P = 0.075) and TWIST1 (P = 0.099) compared with NW women. Conclusions These findings provide evidence for the significant influence of body composition on oocyte transcript abundance in women undergoing hormonal induction to retrieve oocytes. They further identify the potential for maternal diet to influence oocyte gene expression. The preconception period is, therefore, an important window of opportunity to consider for lifestyle interventions.

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Obesity Modulates Inflammation and Lipid Metabolism Oocyte Gene Expression: A Single-Cell Transcriptome Perspective.

Although obesity negatively influences the metabolic homeostasis of cells within a broad range of tissues, its impact on oocyte metabolism is not fully understood. Prior evidence suggests that obes...

Dean M. Moutos

Papers

Obesity Modulates Inflammation and Lipid Metabolism Oocyte Gene Expression: A Single-Cell Transcriptome Perspective.

Obesity leads to distinct metabolomic signatures in follicular fluid of women undergoing in vitro fertilization