Free radicals and oxidants play a dual role as both toxic and beneficial compounds, since they can be either harmful or helpful to the body. They are produced either from normal cell metabolisms in situ or from external sources (pollution, cigarette smoke, radiation, medication). When an overload of free radicals cannot gradually be destroyed, their accumulation in the body generates a phenomenon called oxidative stress. This process plays a major part in the development of chronic and degenerative illness such as cancer, autoimmune disorders, aging, cataract, rheumatoid arthritis, cardiovascular and neurodegenerative diseases. The human body has several mechanisms to counteract oxidative stress by producing antioxidants, which are either naturally produced in situ, or externally supplied through foods and/or supplements. This mini-review deals with the taxonomy, the mechanisms of formation and catabolism of the free radicals, it examines their beneficial and deleterious effects on cellular activities, it highlights the potential role of the antioxidants in preventing and repairing damages caused by oxidative stress, and it discusses the antioxidant supplementation in health maintenance.

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Free Radicals, Antioxidants in Disease and Health

Hyperglycemia and Adverse Pregnancy Outcomes

Oxidative stress (OS), a state characterized by an imbalance between pro-oxidant molecules including reactive oxygen and nitrogen species, and antioxidant defenses, has been identified to play a key role in the pathogenesis of subfertility in both males and females. The adverse effects of OS on sperm quality and functions have been well documented. In females, on the other hand, the impact of OS on oocytes and reproductive functions remains unclear. This imbalance between pro-oxidants and antioxidants can lead to a number of reproductive diseases such as endometriosis, polycystic ovary syndrome (PCOS), and unexplained infertility. Pregnancy complications such as spontaneous abortion, recurrent pregnancy loss, and preeclampsia, can also develop in response to OS. Studies have shown that extremes of body weight and lifestyle factors such as cigarette smoking, alcohol use, and recreational drug use can promote excess free radical production, which could affect fertility. Exposures to environmental pollutants are of increasing concern, as they too have been found to trigger oxidative states, possibly contributing to female infertility. This article will review the currently available literature on the roles of reactive species and OS in both normal and abnormal reproductive physiological processes. Antioxidant supplementation may be effective in controlling the production of ROS and continues to be explored as a potential strategy to overcome reproductive disorders associated with infertility. However, investigations conducted to date have been through animal or in vitro studies, which have produced largely conflicting results. The impact of OS on assisted reproductive techniques (ART) will be addressed, in addition to the possible benefits of antioxidant supplementation of ART culture media to increase the likelihood for ART success. Future randomized controlled clinical trials on humans are necessary to elucidate the precise mechanisms through which OS affects female reproductive abilities, and will facilitate further explorations of the possible benefits of antioxidants to treat infertility.

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The effects of oxidative stress on female reproduction: a review

Oxidative stress has been proven to be related to the onset of a large number of health disorders. This chemical stress is triggered by an excess of free radicals, which are generated in cells because of a wide variety of exogenous and endogenous processes. Therefore, finding strategies for efficiently detoxifying free radicals has become a subject of a great interest, from both an academic and practical points of view. Melatonin is a ubiquitous and versatile molecule that exhibits most of the desirable characteristics of a good antioxidant. The amount of data gathered so far regarding the protective action of melatonin against oxidative stress is overwhelming. However, rather little is known concerning the chemical mechanisms involved in this activity. This review summarizes the current progress in understanding the physicochemical insights related to the free radical-scavenging activity of melatonin. Thus far, there is a general agreement that electron transfer and hydrogen transfer are the main mechanisms involved in the reactions of melatonin with free radicals. However, the relative importance of other mechanisms is also analyzed. The chemical nature of the reacting free radical also has an influence on the relative importance of the different mechanisms of these reactions. Therefore, this point has also been discussed in detail in the current review. Based on the available data, it is concluded that melatonin efficiently protects against oxidative stress by a variety of mechanisms. Moreover, it is proposed that even though it has been referred to as the chemical expression of darkness, perhaps it could also be referred to as the chemical light of health.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-079X.2011.00916.x

Melatonin as a natural ally against oxidative stress: a physicochemical examination

Objective  To develop a practical evidence based list of clinical risk factors that can be assessed by a clinician at ≤16 weeks’ gestation to estimate a woman’s risk of pre-eclampsia. Design  Systematic review and meta-analysis of cohort studies. Data sources  PubMed and Embase databases, 2000-15. Eligibility criteria for selecting studies  Cohort studies with ≥1000 participants that evaluated the risk of pre-eclampsia in relation to a common and generally accepted clinical risk factor assessed at ≤16 weeks’ gestation. Data extraction  Two independent reviewers extracted data from included studies. A pooled event rate and pooled relative risk for pre-eclampsia were calculated for each of 14 risk factors. Results  There were 25 356 688 pregnancies among 92 studies. The pooled relative risk for each risk factor significantly exceeded 1.0, except for prior intrauterine growth restriction. Women with antiphospholipid antibody syndrome had the highest pooled rate of pre-eclampsia (17.3%, 95% confidence interval 6.8% to 31.4%). Those with prior pre-eclampsia had the greatest pooled relative risk (8.4, 7.1 to 9.9). Chronic hypertension ranked second, both in terms of its pooled rate (16.0%, 12.6% to 19.7%) and pooled relative risk (5.1, 4.0 to 6.5) of pre-eclampsia. Pregestational diabetes (pooled rate 11.0%, 8.4% to 13.8%; pooled relative risk 3.7, 3.1 to 4.3), prepregnancy body mass index (BMI) >30 (7.1%, 6.1% to 8.2%; 2.8, 2.6 to 3.1), and use of assisted reproductive technology (6.2%, 4.7% to 7.9%; 1.8, 1.6 to 2.1) were other prominent risk factors. Conclusions  There are several practical clinical risk factors that, either alone or in combination, might identify women in early pregnancy who are at “high risk” of pre-eclampsia. These data can inform the generation of a clinical prediction model for pre-eclampsia and the use of aspirin prophylaxis in pregnancy.

https://www.bmj.com/content/bmj/353/bmj.i1753.full.pdf

Clinical risk factors for pre-eclampsia determined in early pregnancy: systematic review and meta-analysis of large cohort studies

Aims: The objectives of this study were to determine the role of oxidative stress in intrauterine growth restriction (IUGR) and to investigate the possible molecular mechanism(s) le

Role of oxidative stress in intrauterine growth restriction.

Oxidant Status in Maternal and Cord Plasma and Placental Tissue in Gestational Diabetes

Aim. This study was designed to examine the relationship between homocysteine (Hcy), lipoprotein levels and insulin resistance in obese and non-obese patients with polycystic ovary syndrome (PCOS).Materials and methods. Eighty-five patients (38 obese, 47 non-obese) with PCOS and 50 healthy subjects (25 obese, 25 non-obese) were included in the study. PCOS was defined according to the Homburg criterion. Serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), dehydroepiandrosterone sulfate (DHEA-S), insulin, 17-hydroxyprogesterone, free testosterone, androstenedione, vitamin B12 and folate were measured. Also, serum concentrations of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), lipoprotein (a) (Lp(a)), apoprotein B (Apo B) and apoprotein A (Apo A) were determined. Plasma Hcy levels were measured. Insulin resistance was evaluated by homeostasis model assessment (HOMA).Results. Plasma Hcy levels wer...

Levels of lipoprotein and homocysteine in non-obese and obese patients with polycystic ovary syndrome

Aim: The aim of this study was to assess the effects of metformin and rosiglitazone on insulin resistance and serum androgen levelsin both obese and lean patients with polycystic ovary syndrome (PCOS). Materials and methods: Forty lean [body mass index (BMI) ²5 kg/m2) patients were included in the study. Waist and hip measurements, serum sex steroid levels, insulin response to 75-g oral glucose tolerance test, fasting insulin, fasting C-peptide levels and homeostasis modelassessment of insulin resistance (HOMA-IR) were determined in all patients. The degree of hirsutism was determined by the Ferriman-Gallwey scoring system. Patients were divided into two groups, with 40 (20 overweight and obese; 20 non-obese) patients each. One group was treated with metformin (MET group) 850 mg bid while the other received rosiglitazone (ROSI group) 4 mg/day for 12 weeks. All measurements were repeated at the end of this period. Results: After the 12-week treatment period, HOMA-IR, area under the curve of insulin, fasting insulin and C-peptide levels were observed to have be decreased significantly in all groups. The decrease in the parameters mentioned above was similar in the four groups. The serum levels of free testosterone, androstenedione and DHEA-S decreased in all groups, but the decrease was statistically significant only in the ROSI groups. Within the lean MET group one patient became pregnant and was hence excluded from the final data analysis. Menstruations became regular after metformin therapy in 41.6% of lean and 35.7% of obese patients who had menstrual disturbance prior to the study. Rosiglitazone therapy improved menstrual disturbance in 61.5 % of lean and 53.8% of obese patients. Conclusions: Our data showed that both metformin and rosiglitazone increased insulin sensitivity in obese patients with PCOS as expected, and in lean patients as well. Rosiglitazone seemed to be more effective in decreasing the androgen levels and in achieving slightly greater improvement in menstrual disturbance than metformin.

Aydan Biri

Papers

Role of oxidative stress in intrauterine growth restriction.

Oxidant Status in Maternal and Cord Plasma and Placental Tissue in Gestational Diabetes

Levels of lipoprotein and homocysteine in non-obese and obese patients with polycystic ovary syndrome

The effects of rosiglitazone and metformin on insulin resistance and serum androgen levels in obese and lean patients with polycystic ovary syndrome.

An investigation of relationships between hypoxia-inducible factor-1α gene polymorphisms and ovarian, cervical and endometrial cancers