Vascular endothelial growth factor (VEGFA) gene variation in polycystic ovary syndrome in a Tunisian women population
© The Author(s). 2016
Published: 17 October 2016
Polycystic ovary syndrome (PCOS) is characterized by the growth of a number of small cysts on the ovaries which leads to sex hormonal imbalance. Women who are affected by this syndrome suffer from irregular menstrual cycles, decline in their fertility, excessive hair growth, obesity, acne and most importantly cardiac function problems. The vascular endothelial growth factor (VEGF) plays a pivotal role in tissue vascularization in general and in the pathogenesis of many diseases. The PCOS was found to be associated with high expression levels of VEGF. In women who undergo assisted reproductive procedures (ART), VEGF was found to be a key mediator of other factors to control ovary angiogenesis. Here, we set out to examine the association of VEGFA gene polymorphism with PCOS and its components in a population of Tunisia women to enhance our understanding of the genetic background leading angiogenesis and vascularization abnormalities in PCOS.
The association of VEGFA gene with PCOS and its components was examined in a cohort of 268 women from Tunisia involving 118 PCOS patients and 150 controls. VEGFA gene variations were assessed through the analysis of the following SNPs rs699947 (A/C), rs833061 (C/T), rs1570360 (G/A), rs833068 (G/A), rs3025020 (C/T), and rs3025039 (C/T). The linkage disequilibrium between SNPs was assessed using HAPLOVIEW software while combination of SNPs into haplotypes in the population and the reconstruction of the cladogram were carried-out by PHASE and ARLEQUIN programs, respectively. Genetic association and genotype-phenotype correlations were calculated by logistic regression and non-parametric tests (Kruskall-Wallis and Mann–Whitney tests), respectively, using StatView program.
We observed 10 haplotypes in our studied cohort whereH1 (ACGG), H2 (ACAG), H7 (CTGG) and H8 (CTGA) were the most frequent. We observed the association of the genotype CT of the SNP rs30225039 with PCOS phenotype (P = 0.03; OR 95 % CI = 2.05 [1.07–3.90]) and a trend for correlation of the pair of haplotypes H2/H2 with prolactin levels in plasma (P = 0.077; 193.5 ± 94.3 vs 45.7 ± 7.2). These data are consistent with literature and highlight one more time the role of vascularization in the pathogeny of PCOS.
LD pattern in VEGF locus showed a similar LD pattern between the Tunisian population and the CEU. More haplotypes in the Tunisian population than in CEU was observed (22 haplotypes vs 16 haplotypes) suggesting higher recombination rate in Tunisians. The study showed that there was any advantage of using haplotypes compared with SNPs taken alone.
The polycystic ovary syndrome (PCOS) is a disease affecting 6 – 12 % of women at reproductive age and characterized by abnormalities in relation to reproduction, hyperandrogenism as well as metabolic abnormalities like insulin resistance, obesity, impaired fasting glucose (IGF) and metabolic syndrome (MetS) [1, 2].
Knowing the role of blood flow and vascular pattern of an organ in the organ’s morphology and function, previous studies focused on the comparison of blood flow and vascularization between women with PCOS and healthy women showing larger and more vascularized ovaries in PCOS women compared to the control . Moreover, abnormalities in ovarian angiogenesis were involved in the ovarian hyperstimulation syndrome (OHSS) and other disorders of anovulation, subfertility and pathogenic conditions as endometriosis . In this context, the vascular endothelial growth factor (VEGF) system, composed of ligands and receptors plays a pivotal role in tissue vascularization and endothelial cell growth . It was also reported to induce cell proliferation, promote cell migration, inhibit apoptosis and induce permeabilization of blood vessels. It is a major component of the family of angiogenic factors, which includes placental growth factor, angiopoetin, basic fibroblast growth factor and the VEGF family (A, B, C, D and E). VEGFA in particular is a protein encoded by a gene (Gene ID: 7422) located in chromosome 6 and extended on more than 16 kb (GRCh37/hg19; chr6: 43737946–43754224). The gene involves 8 exons and encodes for many VEGFA isoforms as VEGF-165 and VEGF-145.
Previous studies reported the association of VEGFA gene with PCOS through SNPs +9812, +13553, −2578 (rs699947), −460 (rs833061) and +405 [6, 7] and their haplotypes in populations of different origins [6–8]. Moreover, SNPs +405 and −460 were reported as having a trend towards higher insulin resistance . It was suggested the role of some of these SNPs on the regulation of VEGFA gene expression and protein production and secretion .
In this context, we focused on the study of the association of VEGFA gene with PCOS and its components in a population of women from Tunisia well characterized at the phenotypic level. The aim was to better characterize the genetic background responsible for angiogenesis and vascularization abnormalities in PCOS. This will be achieved through testing the association of VEGFA gene in a population where it was previously highlighted the need for haplotyping approach in order to understand better the genetic association in populations with mosaic anthropogenetic components [11, 12].
Subjects and methods
Following an informed consent, a total of 268 unrelated Tunisian women, consisting of 118 PCOS patients and 150 controls. PCOS patients group (mean age: 29.8 ± 0.4 years) were recruited from the outpatient Obstetrics and Gynecology Department, CHU Farhat Hached (Sousse) in Central Tunisia (Table 2). The diagnosis of PCOS was based on the 2003 Rotterdam Criteria . PCOS was then attested when two of the following three conditions are observed: anovulation, hyperandrogenism, and the presence of polycystic ovaries on ultrasound examination. Exclusion criteria were androgen-producing tumors, 21-hydroxylase-deficiency, non-classical adrenal hyperplasia, hyperprolactinemia, active thyroid disease, and Cushing’s syndrome.
Control group consisted of 150 healthy women (mean age: 33.5 ± 0.5 years), with regular menstrual cycles and no evidence of hirsutism, acne, alopecia, or endocrinopathies. None of the controls was on hormonal therapy (including oral contraceptives) for the previous three months or longer, and none of PCOS women or controls was on medication known to affect carbohydrate metabolism or endocrine parameters, at least for the last three months before inclusion in the study. Demographic data and history of hypertension, diabetes, and hypercholesterolemia were recorded for all subjects. Obesity was defined as body-mass index (BMI) ≥30 kg/m2. The protocol of the study was approved by the local ethics committee, and written informed consent was obtained from all subjects.
SNPs genotypingTotal genomic DNA was isolated from peripheral blood lymphocytes by the salting-out method. Six SNPs were selected because of their association with PCOS, angiogenesis and other metabolic components in literature: rs699947 (A/C), rs833061 (C/T), rs1570360 (G/A), rs833068 (G/A), rs3025020 (C/T), andrs3025039 (C/T). The 6 SNPs were genotyped by the allelic discrimination TaqMan SNP Genotyping Assays (Applied Biosystems; Foster City, CA). The PCR primers and TaqManprobes were directly available from Applied Biosystem (predesigned assays) and analyses were done according to the manufacturer’s protocol on a StepOne plus apparatus (Applied Biosystems) (Table 1).Table 1
SNPs probe sequence
Data were expressed as mean ± SE (continuous variables) or as percent of total (categorical variables), and intergroup significance was assessed by χ2 test. Allele frequencies were calculated by gene-counting method; each SNP was tested for Hardy–Weinberg equilibrium using Haploview 4.2 (http://www.broadinstitute.org/haploview). Linkage disequilibrium (LD) was assessed using Haploview 4.2. Genetic association and genotype-phenotype correlation were assessed by logistic regression and non-parametric tests (Mann–Whitney and Kruskall-Walli tests) using StatView program.
Calculation of the power of the study was assessed using SAMPSIZE software (http://sampsize.sourceforge.net).
Results and discussions
Phenotypic features of our women cohort used in the study
(n = 118)
(n = 150)
P (X 2 )a
29.8 ± 0.4
33.5 ± 0.5
28.4 ± 0.7
23.1 ± 0.2
Random glycemia (mmol/L)
7.9 ± 0.2
4.5 ± 0.1
Fasting insulin (mU/L)
15.7 ± 1.2
7.7 ± 0.4
2.9 ± 0.2
1.0 ± 0.1
73.1 ± 11.7
148.8 ± 9.4
1.7 ± 0.1
1.0 ± 0.1
3.1 ± 0.1
1.9 ± 0.2
MetS ATPIII (%)
Allele frequencies of SNPs in PCOS and controls
List of haplotypes resulting from the combination of SNPs rs699947, rs833061, rs1570360 and rs833068 in the Tunisian population
P (χ 2)
Distribution of VEGF genotype in PCOS cases and control women
Deeper investigations of VEGFA gene encompassing larger regions in the locus and using more SNPs need to be envisioned in order to better characterize the gene association in the Tunisian population and to shed light on the genetic/genomic players involved and develop better diagnostic, management and therapeutic approaches.
This work was supported by the recurrent budget from Laboratory of Human genome and multifactorial diseases (LR12ES07) at University of Monastir Tunisia.
This article has been published as part of BMC Genomics Volume 17 Supplement 9, 2016: Proceedings of the 3rd International Genomic Medicine Conference: genomics. The full contents of the supplement are available online at http://bmcgenomics.biomedcentral.com/articles/supplements/volume-17-supplement-9.
Availability of data and material
The data sets supporting the results are included within the article.
TM initiated and designed the study, and is responsible for the facility in which the study is conducted. AB wrote the first draft of the manuscript and was responsible for the genetic analysis, the statistical analysis and interpretation of the data. MA, OK, FHB contributed to the original data collection. FM, MS, SH, FJ contributed to the biological and immunoassay. MAE, MA, MHAQ have read the manuscript, revised it, agreed that the work is ready for publication.
The authors declare that they have no competing interests.
Consent for publication
All patients gave written consent for participating and in the study and for publication including consequences that may result.
Ethics approval and consent to participate
The study was approved by the Medical Ethics and Research Committee of the University Hospital Farhat Hached (Sousse).
Publication fees declaration
The publication charges of this manuscript was paid by the Centre of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
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