Manifestly Altered MicroRNAs in Poly Cystic Ovary Syndrome

http Introduction Polycystic ovarian syndrome (PCOS) is a common heterogeneous endocrine disorder in women during reproductive ages. Principally, there are three diagnostic criteria proposed by different groups including the National Institute of Health/National Institute of Children’s Health and Disease (1), the European Society of Human Reproduction and Embryology/the American Society of Reproductive Medicine (2), and the Excessive Androgen Association and PCOS (3). The prevalence of PCOS ranges from 6 to 20% given the type of the applied criteria (4-6). According to all available criteria, the diagnosis of PCOS is usually based on dysmenorrhea, hyperandrogenism, and polycystic ovary detected by sonography. The typical symptoms of PCOS include oligomenorrhea, amenorrhea, hirsutism, acne, overweight or diabetes, and infertility. Currently, the exact cause of PCOS is unknown. Epidemiological studies suggested that the PCOS profile risk relies on familial history, overweight and obesity (7-9), and diabetes (10). Post-transcription regulation by microRNAs (miRNAs) has been important research over the past 10 years. miRNAs constitute a large family of small noncoding RNAs with a length of 19-25 nucleotides (11,12). The production and function of miRNAs are shown in Figure 1. miRNA genes are usually transcribed by the RNA polymerase II/III and bound to pri-miRNA. They are then processed by Drosha in order to convert to pre-microRNAs. Next, they migrate to the cytoplasm and are changed into mature miRNAs by the Dicer. In addition, miRNAs attach to the 3’ UTR region of target genes causing the total or partial inhibition of gene transcription (13). The total inhibition of miRNA relies on the extent that miRNA complements mRNA and is rarely observed in animals. Thus, the effect of miRNA on mRNA transcription mostly occurs through suppressing and reducing transcription (14). The regulatory mechanisms of miRNAs have been extensively studied in the development of diseases, especially cancers. However, the possible regulatory patterns of miRNAs in PCOS have been poorly examined and require further studies. Different studies have reported contradictory results on miRNAs in various samples of blood, plasma, serum, ovaries, and to the same extent, in different ovarian components including follicular fluid, granulosa cells, blastocyte, and oocyte (15-18).


Introduction
Polycystic ovarian syndrome (PCOS) is a common heterogeneous endocrine disorder in women during reproductive ages. Principally, there are three diagnostic criteria proposed by different groups including the National Institute of Health/National Institute of Children's Health and Disease (1), the European Society of Human Reproduction and Embryology/the American Society of Reproductive Medicine (2), and the Excessive Androgen Association and PCOS (3). The prevalence of PCOS ranges from 6 to 20% given the type of the applied criteria (4-6). According to all available criteria, the diagnosis of PCOS is usually based on dysmenorrhea, hyperandrogenism, and polycystic ovary detected by sonography. The typical symptoms of PCOS include oligomenorrhea, amenorrhea, hirsutism, acne, overweight or diabetes, and infertility. Currently, the exact cause of PCOS is unknown. Epidemiological studies suggested that the PCOS profile risk relies on familial history, overweight and obesity (7)(8)(9), and diabetes (10).
Post-transcription regulation by microRNAs (miRNAs) has been important research over the past 10 years. miRNAs constitute a large family of small noncoding RNAs with a length of 19-25 nucleotides (11,12). The production and function of miRNAs are shown in Figure 1. miRNA genes are usually transcribed by the RNA polymerase II/III and bound to pri-miRNA. They are then processed by Drosha in order to convert to pre-microRNAs. Next, they migrate to the cytoplasm and are changed into mature miRNAs by the Dicer. In addition, miRNAs attach to the 3' UTR region of target genes causing the total or partial inhibition of gene transcription (13). The total inhibition of miRNA relies on the extent that miRNA complements mRNA and is rarely observed in animals. Thus, the effect of miRNA on mRNA transcription mostly occurs through suppressing and reducing transcription (14). The regulatory mechanisms of miRNAs have been extensively studied in the development of diseases, especially cancers. However, the possible regulatory patterns of miRNAs in PCOS have been poorly examined and require further studies.
Different studies have reported contradictory results on miRNAs in various samples of blood, plasma, serum, ovaries, and to the same extent, in different ovarian components including follicular fluid, granulosa cells, blastocyte, and oocyte (15)(16)(17)(18).

Investigating the miRNAs Affecting Hormonal
Pathways miRNAs have a more stable expression in the serum that makes them suitable noninvasive biomarkers for diagnosis and prognosis. Hence, various studies selected

Manifestly Altered MicroRNAs in Poly Cystic Ovary Syndrome
iejm.hums.ac.ir http blood samples as the source of the miRNAs profile. For example, a case-control study indicated that miR-21, miR-27b, miR-103, and miR-155 diminished in the total blood. Further, bioinformatic analyses proposed that these miRNAs can be involved in the metabolism of hormones, especially testosterone (19). In another study, the expression of miRNAs in PCOS patients was compared against control through microarray ad qPCR methods, and the findings revealed that miR-30c, miR-146a, and miR-222 increased significantly in PCOS patients. Relevant analyses indicated that miR-146a was negatively associated with the serum testosterone level. This study also showed that the differentiated miRNAs expressed in ovarian tissues did not match different types in the blood (15,16,20). The androgen synthesis in the ovary usually increases in PCOS patients. The ovarian cycle is also impaired due to the abnormal secretion of the hypothalamus-pituitary-ovary axis hormone. In addition, insulin inhibits the hepatic synthesis of sexual hormonebinding globulin, resulting in elevated free testosterone concentration, which leads to the emergence of PCOS symptoms. Some studies examined the relationship between miRNAs and the level of sexual hormone (21,22). They also showed that miRNAs are involved in the homeostatic modification of steroid hormones, as well as target steroid receptors or steroid synthesis enzymes. miR-222, which was largely expressed in the follicular liquid and serum of PCOS patients (23), is an estrogen receptor regulator 1 (24). It was further reported that miR-320 targets the steroidogenic factor 1 (SF-1) gene although the expression of this miRNA was discrepant across different studies (17).

Investigating the MicroRNAs Affecting Insulin Pathways
In their study, Ding et al found that miRNA is heavily involved in intrinsic immunity, apoptosis, angiogenesis, oxidative stress, as well as the signaling pathway of P53 and mitogen-activated protein kinase/AKT (25).
Subsequent tests indicated that miR-6767-5p was negatively correlated with fasting blood sugar and directly related to the severity of dysmenorrhea (26). Furthermore, PCOS is usually associated with the severe incidence of insulin resistance. In type I diabetes, it was found that the patients with PCOS had an increased risk of developing the disease by around 15.4% as compared to the control group (27). A previous study also showed that the prevalence of PCOS in types I and II diabetes was 24% and 8.3%, respectively (18). In a study by Amini et al (28), these numbers differed from 4.5%-13.4% to 26.7% in a study by Peppard et al (29). Based on the findings of another study, dysregulation in miRNAs can be a target for the key molecules of the insulin signaling pathway (24). Moreover, the role of insulin in the synthesis of androgens can indicate the relationship between these two diseases as the cause and effect (30). Glucose transporter protein type-4 (GLUT-4) is a major insulin-dependent glucose transporter (31) and miR-93 can target GLUT-4. According to previous evidence, the mRNA level of GLUT-4 diminishes by the elevation of miR-93 (30,32). Additionally, insulin receptor substrates 1 and 2 (IRS1 and IRS2) are considered as cytoplasmic signaling molecules that mediate insulin effects (33). Finally, another previous study reported that IRS2 significantly suppressed through the overexpression of miR-135a, miR-18b, and miR-9 (34).

Conclusion
In general, a close association was observed between the PCOS and many diseases including diabetes, complicating its treatment. Previous studies on miRNAs mostly addressed tissue or cell culture while recent studies have mainly focused on serum samples because the serum miRNA profile may have the potential for providing a good noninvasive biomarker for the diagnosis and prognosis of PCOS or the possibility of the incidence of its associated diseases.
It seemed that changes in the miRNAs involved in steroid and insulin signaling pathways may have a significant relationship with the pathogenesis of PCOS and its associated diseases, which can be candidates for future studies. In addition, the study of miRNAs may set the ground for the emergence of new pharmacologic targets in PCOS and its related diseases.
Although miRNAs and their target genes have been   (Table 1), it seems that extensive studies are required so that to create a panel of microRNAs which can be used with high sensitivity and specificity in creating the kits to diagnose PCOS and the probability of the incidence of its associated diseases. Accordingly, it provides the chance for determining the prognosis of the PCOS spectrum and the stage of the disease, and eventually, specifying the degree of the success of therapeutic strategies. It is also possible that by knowing the changes in the expression profile of this group of molecules, its pathogenesis mechanisms would become clear and new drugs apart from hormone therapy could emerge for its treatment or control.

Conflict of Interest Disclosures
The authors declare that they have no conflict of interests.

Acknowledgment
This research was partially supported by Hormozgan University of Medical Science. We thank our colleagues from the Student Research Committee for providing insight and expertise that greatly assisted the research although they may not agree with all the conclusions of this paper.

Ethical Statement
Not applicable.

Authors' Contribution
MM wrote the manuscript. MR, PM, and KM collected the data, revised the literature, and contributed to the conception and design of the study. Eventually, all authors contributed to the critical revision, edition, and final approval of the manuscript.

Funding/Support
There is no funding for this article.