Impact of Age, BMI and Insulin Resistance on Infertile women undergoing Intra cytoplasmic Sperm Injection

 

Manar Alhoda Z. Al-Faqheri, Mohammad O. Selman, Manal T. Al-Obaidi

The High Institute of Infertility Treatment and ART-Al-Nahrain University, Baghdad, Iraq

 

ABSTRACT:

Background: Despite the recent advances in the management of different leading causes of infertility, assisted reproductive techniques are still one of the most popular treatment options. However, the outcome of these procedures is influenced by many factors. Of these, the impact of age and metabolic parameters is still of great concern. Aim: Is to investigate the effect of age related variation in the body mass index and insulin resistanceon the main outcomes of the intracytplasmic injection procedures. Patients and methods: A group of 36 infertile patients were selected randomly for this prospective study from patients attending the high institute for infertility diagnosis and assisted reproductive technologies/Al-Nahrian University and subjected to intra-cytoplasmic sperm injection (ICSI) procedure. Patients were classified into two groups according to their age (<35 and ≥35). BMI was measured for all patients and they were classified according to WHO classification. Fasting plasma level of glucose and insulin was investigated and insulin resistance index (HOMA) was calculated. Gonadotrophins dose and duration of stimulation in addition to the total number of oocytes, M2 oocytes and fertilization rates were noticed and compared between the different BMI, insulin resistance and age categories. Finally, the pregnancy rate, as a primary reproductive endpoint was compared according to the above groups of classification between different study subjects. Results: Of the 36 infertile patients, 24(66.7%) were non obese and 12 (33.3%) were obese, 9(25%) were having HOMA index ≥2 and 15(41.7%) were ≥ 35 years.  Higher BMI was found to be associated with higher HOMA index (R= 0.4 by spearman correlation). Likewise, higher BMI was found to be associated with advanced maternal age (P=0.03). The difference in the median HOMA index between the three BMI groups was significant (p=0.008), unlike the difference between the two age groups in which the relation wasn't significant (P=0.6). Oocyte count was significantly reduced with advancing in age (P= 0.009) and older patients needed a longer stimulation than young age groups (P= 0.01). Pregnancy rate was comparable between the study groups in the various classifications with a significant drop in obese young patients (< 35 years) in comparison to those in the same age group and acceptable BMI( P= 0.04), However, this impact of BMI is diminished after the age of 35 and became non -significant (p=0.4). Conclusion: Higher BMI is associated with relatively higher levels of insulin resistance. Advanced maternal age appeared to be independently and directly associated with poor IVF outcome mainly affecting oocyte count and   the duration to induce ovarian stimulation.

 

 

 

INTRODUCTION:

Obesity is defined as an excess of adiposity in the body. Clinically, obesity is defined as an increased body mass index BMI [weight in kilograms/(height in meters)] [1]. Increased body fat is usually associated with BMI ≥30 kg/m2 [2]. The prevalence of obesity has risen dramatically over the last two decades worldwide. In United States, about 66.7% of women and 75% men of are overweight or obese, out of which, nearly 50% of the women are of reproductive age [3]. In Iraq, the prevalence of obesity may reach up to 52 % in reproductive age women [4]. Despite the fact that,obesity is not a major component in the definition of insulin resistance syndrome or metabolic syndrome, BMI has been shown to be closely associated with some of itscomponents, including elevated insulin resistance and plasma glucose concentration [5]. The underlying promoter of this syndrome, known as insulin resistance (IR) [6], can be assessed by different methods [7], of which, the practical method of homeostasis model assessment of insulin resistance (HOMA-IR) is one of the most important [8]. The negativeimpacts of obesity on reproduction, especially ovulation, are mainly attributable to endocrine disorders [9]. In obese women, gonadotropin secretion is affected by the increased peripheral aromatization of androgens to estrogens while the insulin resistance and hyperinsulinemia lead to hyperandrogenemia [10]. Moreover, fertility in obese women seems to be impaired also in assisted conception programs. In fact, overweight and obesity are suggested to be associated with negative outcomes for patients undergoing in vitro fertilization (IVF) [11]. Likewise, woman’s age is also an important contributor to IVF success [12], and it has been suggested that IVF success rate reduces with increasing age [13]. Furthermore,higher age groups of infertile women are noticed to have impaired response to gonadotrophins in spite of higher doses with fewer oocytes and higher cancelation rates [14]. The pregnancy rate per embryo transfer declined from 26% in patients younger than 30 years to 9% in those aged 37 years, whereas the miscarriage rate increased from 29% in women under the age of 40 to 50% in those ≥ 40 years old [15]. The impact of maternal environment on the differentiation of maturating oocytes is particularly consequential and negative environmental factors (including advancing in age and high BMI) may affect the ability of mature oocytes to be fertilized and support the embryo development [16].

 

The aim of this study is to evaluate the relation between age related variation in these metabolic parameters and their consensual impact of on the main outcomes of assisted reproduction (Intracytoplasmic sperm injection).

 

PATIENT AND METHODS:

36 Iraqi infertile non polycystic ovarian syndrome patients were selected from those attended the high institute for infertility diagnosis and assisted reproductive technologies/Al-Nahrian University-Baghdad and subjected to intra-cytoplasmic sperm injection (ICSI) procedure. The study was approved by the local medical ethical committee of College of Medicine, Al-Nahrain University, and written consent was obtained from patients to participate in the study.

Patients were divided according to their BMI into: Acceptable BMI (<25 Kg/m2), Overweight (25-29.9 Kg/m2) and Obese (30+ Kg/m2), according to their age into: age <35 years and age ≥35 years and lastly according to HOMA index into: < 2 and ≥2.

 

Body mass index (BMI):

The BMI was measured by dividing the weight in kilograms by the height in squared meters (kg/m²). The females with BMI of ≤18.5 considered as underweight, 18.5-24.9 was normal, 25-29.9 as overweight and ≥ 30 as obese [2].

 

Blood sampling:

Venous blood sample (5ml) was collected from each individual after overnight fast at the day of ovum pick up for assessment of fasting glucose, insulin for assessing HOMA.

 

The serum obtained by putting the blood samples in a clean gel tube and allowed to clot at 37°Ċ for 30 minutes before centrifugation. The tubes were centrifuged at 5000 rpm for 10 minutes to isolate plasma from whole blood; serum was stored at -40°Ċ in centrifuge tubes until the time of the assay.

 

Fasting glucose test:

Fasting glucose test is the measurement of glucose level in venous blood in fasting state. The centrifuge tubes of the serum which were collected and stored at day of oocyte retrieval were thawed and analysis done using automated spectrophotometer.

 

Insulin level measurement:

Insulin levels were analyzed through an enzyme linked immunosorbant assay (ELIZA) technique. The kit were purchased from KONO and labelled as human insulin ELIZA kit. Assay range: 0.5mu/L-16mu/L.

 

Homeostatic model assessment (HOMA):

HOMA represents the dynamic relationship between glucose and insulin predicting fasting glucose and insulin concentrations for a wide range of possible combinations of β-cell function and insulin resistance. HOMA is calculated by multiplying fasting plasma insulin (FPI) by fasting plasma glucose (FPG), then dividing by the constant 22.5, i.e. HOMA-IR = (FPI×FPG)/22.5 [8].

 

RESULTS:

Demographic Data:

Patients were divided according their BMI into acceptable, overweight and obese (table 1), age (<35, ≥35) (table 2) and Insulin resistance (<2, ≥2) (table 3).

 

Table 1: Classification of study sample according to BMI category.

 

Table 2: Classification of study sample according to HOMA index

 

Table 3: Classification of study sample according to age

 

Concerning the relationship between BMI and HOMA IR a significant difference was found in the number of cases with HOMA index ≥2 between the 3 BMIgroups (table 4), and when comparison done between pairs another significant results was found: the first was between overweight versus obese and the second one was between the non-obese (acceptable and overweight) versus obese individuals, (table4).

 

Table 4: Relation between BMI and IR

Acceptable * Obese = 0.1

Overweight * Obese = 0.06

Non obese * obese = 0.04

 

When correlation between BMI and HOMA was evaluated, a statistically significant result was found (Figure 1) and when comparison between HOMA indices was done according to the BMI groups (Table 5), all achieved statistical significance except the difference between acceptable versus overweight groups. Another significant correlation was found between age and BMI (Table 6) whereas the correlation between age and HOMA wasn’t significant statistically. (Table7)

 

Table 5: Classification of HOMA according to BMI groups

HOMA IR Acceptable BMI * Overweight = 0.6

HOMA IR Overweight BMI * Obese = 0.04

HOMA IR non obese * Obese = 0.02

 

 

Figure 1: correlation between BMI and insulin resistance. The value of R is 0.44542 and the two-tailed value of P is 0.00648. By normal standards, the association between the two variables would be considered statistically significant.

 

Table 6: Classification of BMI according to age

 

Table 7: classification of HOMA according to age

 

When ICSI outcome and pregnancy rate were predicted according to the 3 BMI categories, there was no statistical significance regarding gonadotropin dose, duration of stimulation, total oocyte number, metaphase 2 oocyte, fertilization rate and pregnancy rate although the number of oocyte was lower in the overweight and obese individuals (table 8A&B).

 

Table 8-A:predicatingICSI outcome and pregnancy rate stratified by BMI categories.

 

Table 8-B: Pregnancy outcome according to BMI categories .

 

Likewise, the effect of insulin resistance on the end points of ICSI appear to non significant. The differences in various ICSI parameters including: duration of stimulation (p=0.8), gonadotrophin dose (p=0.3), oocyte count (p=0.7), M2 oocytes ( p=0.6) and fertilization rate (p=0.06) between the two HOMA groups were non significant. Similar to that, pregnancy rate was not affected by HOMA index (p=0.7).

 

Moreover, when ICSI outcome and pregnancy rate were predicted according to age, a significant increase in the duration of stimulation was found in patients ≥ 35 years, and a significant decrease in the total number of oocytes was also found in the same patients group, Otherwise no significant differences in the gonadotropins dose, metaphase 2 oocyte, fertilization rate and pregnancy rate was found. (table9 A&B)

 

Table 9- A: Predicting ICSI outcome stratified by age categories.

 

Table 9-B: pregnancy outcome according to age groups

 

When comparing the effect of BMI in different age groups regarding pregnancy outcome, no significant differences were found except when comparing between acceptable and obese individuals less than 35 years, in which a statistically significant result was obtained. (table 10).

 

Table 10: Effect of BMI on pregnancy outcome according to age.

 

DISCUSSION:

The present study was mainly concerned about the relation between age, BMI and insulin resistance with the impact of these parameters on Intracytoplasmic sperm injection cycles and pregnancy rates in infertile non-polycystic ovarian syndrome patients.

 

In the first part of this study, the relation between different variables, including: Age, BMI and Insulin resistance was evaluated.

 

The cut-off value for HOMA index defining insulin resistance is variable as it is controlled by many factors and a wide range of variation in this value was suggested according to ethnicity and study sample [17], with the cut-off value of 2 being frequently used [18].

 

When classifying the sample accordingly, it has been found that the number of patients with HOMA insulin resistance index ≥2 is significantly different between the three BMI groups (p=0.01) (Table: 4) and the difference in this number between the obese population and non-obese patients was significant as well (p= 0.04). On the other hand, the difference in median HOMA index was also significant with the higher levels being detected in the obese group (table: 5), Further indicating the effect of higher body weight and higher BMI on insulin resistance and hyperinsulinemia. This association between BMI and HOMA insulin resistance was previously mentioned in many studies supporting the finding of this study [19,20].

 

On the other hand, when classifying the study sample according to age (<35 and ≥35), there was a significant difference in the mean BMI between the two groups (table 6). Additionally, the prevalence of obesity increased significantly from 14 % in the first group to 60 % in the second group, giving an additional evidence for the association between the two variables (table 6). It is well-known that BMI increases with age through the adult years [21]. In fact, age may be the most consistent and predominant factor related to weight variation over the life course [22].

 

Impaired glucose tolerance and insulin resistance are commonly observed among elderly adults. For example, the postprandial glucose is substantially greater and remains elevated longer in nondiabetic elderly adults than in nondiabetic younger adults, which is indicative of age-related decline in insulin sensitivity [23]. However, since the range of ages for this study is narrow (21-40) (table 3), no significant decline of insulin resistance with age is noticed.

 

The second part of this study evaluated the impact of the above mentioned variables on intracytoplasmic sperm injection cycles. Review ofliterature about this impact revealed contradictory rather than conclusive results. In assisted reproduction, however, there are conflicting reports on the effect of obesity on embryo development, oocyte quality, oocyte maturity and pregnancy rates [24-28].

 

In this study, no significant effect for BMI on pregnancy rate or other ICSI parameters was noticed, except for the lower number of oocytes in the overweight and obese groups in comparison to those with acceptable BMI, However, this difference failed to achieve statistical significance. this result is in correspondence to the results of Sathya et al. [29] and Banker et al. [30], but may be in contrary to other studies conducted on the patients undergoing IVF/ICSI and reported the negative impact of BMI on various ICSI parameters [31,32]. On the other hand, Looking at the effect of insulin resistance on IVF outcome in the current as well as previous studies revealed that insulin resistance neither related to hormonal stimulation nor to the outcome [33, 34]. However, most of the previous studies were performed on PCOS patients and the data on the outcome of IVF cycles in insulin resistant non PCOS patients is sparse. It has been found that metformin, an insulin sensitizing agent, is improving pregnancy rate in IVF repeaters without PCOS [35], probably by decreasing insulin resistance, pointing to the importance of further studies about the impact of this variable in non PCOS patients with frequent IVF failure.

 

Other factors that may affect IVF outcome is the age.Among infertile women undergoing IVF, advanced maternal age may cause oocyte aging, resulting in abnormal fertilization and development, such as polyspermy, division arrest, implantation failure and miscarriage [36]. In addition, it has been demonstrated that women over 38 years old had poor IVF outcomes. In this study, patients were classified into 2 groups: <35 and ≥ 35 years based on the classification of advanced maternal age (AMA) [38]. It has been found that those < 35 are producing significantly higher count of oocytes (table 9-A), a result that was previously demonstrated by Yan et al. (36) and Lee et al. [39]. However , the impact of age on the other parameters of ICSI was less significant in this study and fertilization rates were comparable between the groups (table 9-A), a result that is in agreement with Grondahl et al. [40] and Stensen et al. [41] stating that advanced maternal age shows just a negligible impact upon fertilization rate. The second important parameter affected by age is response to stimulation during cycles. In this study, a significant difference was found in the duration of stimulation between the age groups (Table 9-A), demonstrating the early negative effect of age on the ovarian response, and further supporting other studies, including the study of Dicker et al. [42].

 

Lastly, it has been demonstrated that the effect of BMI on IVF cycle appeared to be age related. At younger ages, a higher BMI has a pronounced negative influence on pregnancy rate, but this effect is attenuated as age increases [43]. In this study, When examined as a main variable alone, BMI did not appear to have a significant effect on IVF responses or outcomes (Tables 8-A and B), but when BMI-Age interaction was analyzed, there was a marked decrease in pregnancy rates with increasing BMI for younger patients (table 10). Moreover, Heijnen et al. [44] reported that although BMI has a significant andnegative effect on female fertility, this effect gradually decreases as women approach their mid-thirties and also in younger women receiving IVF. Above the age of 36 years, on the other hand, the effect of BMI on fertility becomes minimal.

 

CONCLUSION:

BMI is directly associated with age and insulin resistance. Increased body mass index and insulin resistance in women does not appear to have direct adverse effect on IVF outcome in non PCOS patients. However, In younger patients undergoing IVF, BMI has a significant negative impact on fertility that diminishes as patients reach their mid thirties. On the other hand advanced maternal age appeared to be independently and directly associated with poor IVF outcome including lower oocytes count and the response to ovarian stimulation.

 

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Accepted on 18.01.2019          © RJPT All right reserved

Research J. Pharm. and Tech 2019; 12(9):4410-4416.