Serum Adiponectin Level in Women of Reproductive Age Group with Poly Cystic Ovarian Syndrome: A Case-Control Study

Roshni H Babua, Soja Vb, Sreekumari Rc

a. Department of Biochemistry, ESIC Medical College, Paripally, Kerala, India; b. Department of Biochemistry, Palakkad Medical College, Palakkad, Kerala, India; c. Department of Obstetrics and Gynaecology, Sree Avittom Thirunal Hospital, Government Medical College, Thiruvananthapuram, Kerala, India

Corresponding Author: Roshni H Babu, Assistant Professor, Department of Biochemistry, ESIC Medical College, Paripally, Kerala, India. Phone: +91-9496351062, Email: roshni.babu@gmail.com

Abstract

Poly cystic ovarian syndrome (PCOS) is the most common heterogeneous endocrine and metabolic disorder affecting women of reproductive age group. Adiponectin, the adipocytokine secreted by adipose tissue is a possible link between insulin resistance and gonadal dysfunction in PCOS. Hence, the aim of this study was to assess the serum adiponectin level in women with PCOS and without PCOS. The study also evaluated the association of adiponectin with lipid profile and fasting plasma glucose. For this, we have selected 48 women of reproductive age group (15-44 years) with PCOS as cases. Age and body mass index (BMI) matched 48 healthy women were taken as controls. The mean serum adiponectin level was significantly low (P<0.05) in PCOS group compared to control group. The PCOS group had significantly higher triglyceride levels (P<0.05) and lower mean high-density lipoprotein level (P<0.05). In conclusion, our study confirms that, irrespective of BMI, serum adiponectin level is significantly low in women with PCOS compared to healthy controls. Yet another important finding of the study was the association of dyslipidemia with hypoadiponectinemia in PCOS patients.

Key words: Adiponectin, PCOS, BMI, Insulin Resistance, CAD

 

Introduction

Polycystic ovarian syndrome (PCOS) is one of the most common endocrine-metabolic diseases affecting 6-10% of women of reproductive age group.1 It is characterized by chronic anovulation, polycystic ovaries and hyperandrogenism. Hyperandrogenism can either be clinical or biochemical. It is also often found to be associated with insulin resistance (IR) and obesity. Disturbances in the functioning of hypothalamus, pituitary, ovaries, adrenals, pancreas, liver, and adipose tissue are due to the endocrine abnormalities that occur in this syndrome.2 Women with PCOS have a number of risk factors for coronary artery disease (CAD), like type 2 diabetes, metabolic syndrome, elevated triglyceride to high-density lipoprotein (HDL) ratio, IR and vascular dysfunction.3

Women with PCOS are insulin resistant above and beyond that determined by their body mass index (BMI). Hence, obesity as such may not be the primary driver of PCOS but the adipose tissue dysfunction as well may play a role in IR, subclinical inflammation and metabolic and vascular consequences of the disorder. Adipose tissue, functions as a specialized endocrine organ producing a group of proteins with hormone-like functions, called adipocytokines or adipokines. Adiponectin, an adipocytokine is a 244 amino acid protein that is produced exclusively by adipocytes. It plays a role in preventing or counteracting the development of IR.4

Adiponectin has a molecular weight of 30 kDa, and is also referred to as adipocyte complement-related protein 30 kDa. Adiponectin expression is down-regulated by adipose tissue. Plasma adiponectin concentrations correlate inversely with obesity, cardiovascular disease, dyslipidemia and IR.5 IR and the resultant hyperinsulinism in PCOS, place patients at risk of long-term metabolic disorders, such as impaired glucose tolerance, type 2 diabetes and cardiovascular disease. As per recent studies, it is found that there is decreased circulating adiponectin level in obese, insulin-resistant women with PCOS.6,7 Those PCOS women with low adiponectin concentrations are more likely to develop type 2 diabetes and CAD. Hence monitoring of serum adiponectin level can be used as a tool to identify PCOS patients who are at a greater risk for developing type 2 diabetes mellitus and CAD. As the prevalence of diabetes, coronary heart disease and other related disorders in Indian population has assumed epidemic proportions, this study aims at early identification of patients at risk of developing these complications and helps to provide an effective intervention for the same.

 

Objectives

  1. To assess the association of adiponectin levels in women of reproductive age group with and without PCOS.

  2. To evaluate the association of adiponectin with lipid profile and fasting plasma glucose (FPG).

 

Materials and Methods

Study Design

This case-control study was conducted in the Department of Biochemistry, Government Medical College, Thiruvananthapuram, Kerala, India. The subjects chosen for the study were those women who came on an outpatient basis in the Infertility Clinic, Department of Obstetrics and Gynecology, SAT Hospital, Government Medical College, Thiruvananthapuram. The study was conducted in accordance with the Declaration of Helsinki and subsequent revisions and was conducted only after the approval of the Institutional Ethical Committee.

In this study, 48 women with PCOS in the reproductive age group (15-44 years) were taken as cases. The diagnosis of PCOS was made according to criteria by Rotterdam ESHRE/ASRM sponsored PCOS consensus workshop group.8 The diagnosis was based on the presence of any 2 out of the 3 criteria:

  1. Oligo-and/or anovulation (≤8 menstrual periods annually)

  2. Clinical signs of hyperandrogenism (such as hirsutism, acne, acanthosis nigricans)

    Subjects were assessed for hirsutism by using modified Ferryman Gallaway score. A score of ≥8 is taken as hirsutism.

  3. Polycystic ovaries with the exclusion of other etiologies.

The morphology of polycystic ovary is defined as an ovary with 12 or more follicles measuring 2-9 mm in diameter and/or increased ovarian volume (more than 10 cm3) in ultrasonogram.

Age and BMI-matched 48 healthy women with regular menstrual cycles, no known medication and no clinical signs of hyperandrogenism were taken as controls. Women with disorders such as thyroid dysfunction, hyperprolactinemia, diabetes mellitus, Cushing syndrome, late-onset congenital adrenal hyperplasia or androgen-secreting tumors were excluded.

In all subjects, after getting written informed consent, demographic data, a detailed history including menstrual history, past medical history, family history, and drug history was obtained. The anthropometric parameters like weight and height were recorded for all patients and controls. BMI was calculated from the following formula.

BMI=Body weight in kg/height in meters square

 

Methods

A volume of 5 ml blood was drawn in the fasting condition under aseptic precautions from the cubital vein and one part of blood collected was transferred to bottles containing sodium fluoride, for FPG estimation. From the remaining blood, serum was separated by centrifugation and kept at −20°C until analysis was carried out.

We estimated Serum adiponectin using RayBio Human Adiponectin ELISA Kit as per the guidelines.9-11 Plasma glucose was assayed by the glucose oxidase method,12 serum cholesterol by the end point enzymatic method13 and triglyceride by end point method (GPO Trinder method).14 Estimation of HDL was by enzymatic method. From the values of total cholesterol, HDL and triglyceride, the value of low-density lipoprotein (LDL) was determined by using the Friedewald’s formulae.15

 

Statistical Analysis

The statistical analysis was performed using SPSS version 17.0. For each variable, the mean and standard deviation were estimated for both cases and control groups. Differences in proportion were tested using Chi-square test or Fisher’s exact test. Fisher’s exact test was done due to the smaller group of population. Group means were compared by t-test. P<0.05 was considered as significant. Receiver operating characteristic (ROC) curve was drawn to find out the cut-off value of adiponectin in our population. Multiple regression analysis was done to study the difference in serum adiponectin levels between two study groups adjusting for other independent factors.

 

Results

The results of this study showed that the PCOS group had significantly higher mean Triglyceride level (P<0.05) and lower mean HDL level (P<0.05) than the control group. No significant difference in means of total cholesterol and LDL cholesterol was noted between cases and control groups. The mean FPG level (P<0.05) was high in PCOS group compared to control group. The mean serum adiponectin level was significantly low (P<0.05) in PCOS group compared to control group (Table 1).

Table 1. Demographic characteristics, serum adiponectin, and biochemical parameters in PCOS and control groups

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ROC curve was employed to obtain a cut-off value of adiponectin in our study population, as adiponectin do not have a normal value or range in our population. The area under the curve was found to be 0.768, which is significant, and the value of adiponectin, which gave the maximum sensitivity and specificity was 7.3 (Figure 1). Thus, 7.3 was taken as the cut-off value from ROC curve for our study population.

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Figure 1. Receiver operating characteristic (ROC) curve for adiponectin. Area under the ROC curve = 0.768

The value of adiponectin that gave maximum sensitivity and specificity is 7.30 (Table 2).

Table 2. Adiponectin

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The percentage distribution of adiponectin levels in case and controls was also done with the cut-off value obtained from ROC curve. The distribution of adiponectin values showed that 37.5% cases and 85.4% controls have adiponectin values ≥7.3 whereas, 62.5% cases and 14.6% controls have adiponectin value <7.3. Pearson’s Chi-square test was done with P<0.05, which indicates that serum adiponectin value is significantly low in cases compared to controls (Figure 2).

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Figure 2. Comparison of adiponectin levels between cases and controls

Variables that were statistically significant in univariate analysis were subjected to multivariate analysis (Table 3). Finally when all the parameters were included, only adiponectin, triglycerides, and HDL cholesterol were significant (P=0.05).

Table 3. Multivariate analysis

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Discussion

Women with PCOS are at increased risk of reproductive abnormalities and metabolic dysfunction. So, they are prone to develop type 2 diabetes mellitus and cardiovascular disease. Adiponectin is a possible link between obesity, IR and gonadal axis dysfunction in PCOS.

In our case-control study to assess the serum adiponectin levels in women with PCOS compared to women without PCOS, we found out that serum adiponectin level was significantly low in PCOS group compared to control group. This is in accordance with several epidemiological studies which have shown that hypoadiponectinemia is seen in PCOS.16,17 A meta-analysis of 16 studies and a review of 31 studies (Toulis KA et al18) evaluated the adiponectin levels in women with PCOS having similar BMI. Adiponectin levels seem to be lower in women with PCOS compared with controls even after eliminating BMI related effects. A similar study in 2011 by Yasar L et al,22 in which serum adiponectin levels in teenage girls with PCOS was studied also concluded that adiponectin levels were lower in PCOS patients when compared to BMI matched controls.

However, as per the studies by Spranger J et al19 in 2004 and Olszanecka-Glinianowicz M et al2 in 2010, adiponectin levels were lower in overweight or obese women than in normal-weight women, without any difference between PCOS and controls after adjustment for BMI.

PCOS patients have increased triglyceride level and LDL level and decreased HDL level compared to controls. Hence, our study has shown that PCOS women have low adiponectin level and dyslipidemia. This finding is comparable with studies by Matsubara et al20 and Gulcelik NE et al.21

 

Conclusion

Our study confirms that adiponectin acts as a risk factor in PCOS. In our study, irrespective of BMI, serum adiponectin level is significantly low in PCOS patients compared to healthy controls. PCOS patients have dyslipidemia associated with hypoadiponectinemia. So by assessing the serum adiponectin levels we can take effective interventions to screen and monitor women with PCOS who are at higher risk for developing type 2 diabetes mellitus and CAD.

 

End Note

Author Information

  1. Roshni H Babu, Assistant Professor, Department of Biochemistry, ESIC Medical College, Paripally, Kerala, India. Email: roshni.babu@gmail.com

  2. V Soja, Department of Biochemistry, Palakkad Medical College, Palakkad, Kerala, India. Email: spiritual1240@gmail.com

  3. R Sreekumari, Department of Obstetrics and Gynaecology, Sree Avittom Thirunal Hospital, Government Medical College, Thiruvananthapuram, Kerala, India. Email: anilsree83@gmail.com

 

Acknowledgements

The authors gratefully acknowledge Dr.Saboora Beegum M, Professor and Head, Department of Biochemistry, Government Medical College, Thiruvananthapuram, for providing technical help. We also acknowledge Dr.Nirmala, Professor and Head Department of Obstetrics and Gynecology, Government Medical College, Thiruvananthapuram for providing clinical support. We are also thankful to Dr.Shankara Sharma, Associate Professor, Medical Statistics, Sree Chitra Thirunal Institute for helping us with statistical work of the paper.

 

Conflict of Interest

The authors declare that there is no conflict of interest.

 

List of Abbreviations

  • PCOS: Poly cystic ovarian syndrome

  • CAD: Coronary artery disease

  • HDL: High-density lipoprotein

  • LDL: Low-density lipoprotein

  • FPG: Fasting plasma glucose

  • BMI: Body mass index

  • IR: Insulin resistance

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