Maternal serum and fetal cord blood irisin levels ingestational diabetes mellitus

Mehmet Aytac Yuksel a,*, Mahmut Oncul a, Abdullah Tuten a,Metehan Imamoglu a, Abdullah Serdar Acikgoz a,Mine Kucur b, Riza Madazli a

aDepartment of Obstetrics and Gynecology, Cerrahpasa School of Medicine, Istanbul University, Istanbul, TurkeybDepartment of Biochemistry, Cerrahpasa School of Medicine, Istanbul University, Istanbul, Turkey

d i a b e t e s r e s e a r c h a n d c l i n i c a l p r a c t i c e 1 0 4 ( 2 0 1 4 ) 1 7 1 – 1 7 5

a r t i c l e i n f o

Article history:

Received 28 August 2013

Received in revised form

10 November 2013

Accepted 21 December 2013

Available online 3 January 2014

Keywords:

Gestational diabetes mellitus

Irisin

Cord blood

Maternal

a b s t r a c t

Aim: To investigate the relationship between maternal and cord blood irisin in gestational

diabetes mellitus (GDM).

Methods: Twenty women with GDM and 20 pregnant women with uncomplicated pregnancies

were recruited for this case–control study. Maternal serum irisin and cord blood irisin levels

were measured by enzyme-linked immunosorbent assay kit at the time of birth. The associa-

tion of maternal serum and cord blood irisin levels with metabolic parameters was analyzed.

Results: Women with GDM had significantly lower mean serum irisin levels compared to

control group (258.3 � 127.9 vs. 393 � 178.9 ng/ml, p < 0.05). Mean cord blood irisin levels for

GDM and control groups were not significantly different (357.2 � 248.0 vs. 333.2 � 173.4 ng/

ml, p > 0.05). No significant differences were found in terms of maternal age, gestational

week at birth, BMI at birth, birth weight, neonatal height, systolic and diastolic blood

pressure between the groups as well (p > 0.05). Serum irisin level was negatively correlated

with BMI at birth and HOMA-IR (r = �0.401, p = 0.010; r = �0.395, p = 0.012, respectively). No

correlations between irisin levels and others parameters were found in both groups.

Conclusions: Maternal serum irisin levels of patients with GDM are significantly lower

compared with non-GDM controls. However, no significant difference was found between

cord blood irisin levels of patients with GDM and healthy pregnant women.

# 2014 Elsevier Ireland Ltd. All rights reserved.

Contents available at ScienceDirect

Diabetes Researchand Clinical Practice

journal homepage: www.elsevier.com/locate/diabres

1. Introduction

GDM (gestational diabetes mellitus) has been defined as any

degree of glucose intolerance with onset or first recognition

during pregnancy [1]. GDM, which affects 16–20% of all

pregnancies has serious adverse perinatal outcomes and

increases long-term risk for the development of obesity, type 2

diabetes and cardiovascular disease in both the mother and

* Corresponding author at: Department of Obstetrics and Gynecology, C34098, Turkey. Tel.: +90 532 601 60 58; fax: +90 2124143000.

E-mail address: maytacyuksel@gmail.com (M.A. Yuksel).

0168-8227/$ – see front matter # 2014 Elsevier Ireland Ltd. All rights

http://dx.doi.org/10.1016/j.diabres.2013.12.025

the offspring [2]. Insulin resistance plays an important role in

the pathogenesis of GDM and despite extensive research, the

mechanisms underlying insulin resistance are not fully

understood [2].

Since it is the largest organ in the body, skeletal muscle

accounts for the majority of glucose uptake in response to

insulin, and is quantitatively the most important site of

insulin resistance. During the past decade, skeletal muscle has

also been identified as a secretory organ and cytokines and

errahpasa School of Medicine, Istanbul University, Fatih, Istanbul

reserved.

d i a b e t e s r e s e a r c h a n d c l i n i c a l p r a c t i c e 1 0 4 ( 2 0 1 4 ) 1 7 1 – 1 7 5172

other peptides produced and secreted by myocytes are

classified as myokines [3]. These myokines function as

endocrine hormones and regulate the function of various

distant organs. Irisin has recently been identified as an

exercise-induced hormone secreted by skeletal muscle and

has been proposed to mediate the beneficial effects of exercise

on metabolism [4]. Sedentary lifestyle is a major risk factor for

type 2 diabetes mellitus. Randomized controlled trials have

demonstrated that physical activity improves glucose toler-

ance and reduces the risk of type 2 diabetes mellitus [5].

Therefore, it has been speculated that physical exercise may

exert its beneficial effects on energy metabolism through

secreted factors from myocytes such as irisin [3].

Recent studies have shown that circulating irisin levels

were significantly lower in patients with type 2 diabetes

compared to people without diabetes [6,7]. Liu and co-workers

demonstrated that irisin might be positively correlated with

most of the well-known markers of insulin resistance in

people without diabetes [6]. These data show that either the

diabetes itself or the metabolic condition that caused

progression to type 2 diabetes is accompanied by lower

circulating irisin levels in circulation. To date, there are a

paucity of data on irisin and human pregnancy. In the current

study, our aim was to investigate maternal and cord serum

irisin levels in women with GDM and women with uncom-

plicated pregnancies.

2. Material and methods

The Ethics Committee of our university approved the study

protocol (dated February 29, 2013, issue no. 83045809/3709) and

all patients were carefully instructed and signed informed

consent before recruitment. 20 pregnant women with GDM

and 20 controls with uncomplicated pregnancies were

recruited for the study. All recruited patients were selected

randomly from women admitted to the antenatal clinic of our

obstetrics department and had a history of prior cesarean

section deliveries and were planned to deliver with cesarean

section. This criterion was established to exclude any possible

effects of labor on the parameters that evaluated in maternal

blood, described below. Exclusion criteria were as follows:

chronic hypertension, preeclampsia, diabetes mellitus, poly-

hydramnios, presence of any acute or chronic disease, fetal

anomalies, prior renal disease, liver disease, multiple gesta-

tion, history of smoking and chronic alcohol consumption. All

women were screened for GDM with 50 g glucose challenge

test (GCT) at 24th gestational week. The 50-g GCT was carried

out independent of the time of day or any previous meal at

about 24 weeks gestation. An oral glucose tolerance test was

recommended to all patients with a 1-h test result � 140 mg/dl

(7.8 mmol/l). Diagnosis of GDM was established according to

results of 100-gram oral glucose tolerance test (OGTT). Patients

with at least two abnormal values above the cutoff values were

determined to be having an abnormal OGTT result: Fas-

ting � 95 mg/dl (5.3 mmol/l); 1 h, �180 mg/dl (10.0 mmol/l);

2 h, �155 mg/dl (8.6 mmol/l); 3 h, �140 mg/dl (7.8 mmol/l) [8].

Control subjects had normal responses to GCT.

20 patients with GDM received various treatment (diet

therapy, self-monitoring of blood glucose or insulin therapy)

in order to maintain control of blood glucose levels

(venous plasma glucose values were targeted to be

105 mg/dl [5.8 mmol/l] or lower before meals and 120 mg/dl

[6.7 mmol/l] or lower 2 h after meals). Insulin therapy was

administered if blood glucose levels remained above target

levels despite strict diet therapy.

Venous blood samples were collected in the fasting state

before delivery. None of the patients were in labor at the time

of sampling. Umbilical cord blood samples were also collected

immediately after delivery. Blood samples were collected in

tubes and were immediately centrifuged after clotting. The

supernatant serum was kept frozen at �80 8C until assay.

Serum irisin levels were measured using enzyme immunoas-

say (EIA). (Catalog # EK-067-16; Phoenix Pharmaceuticals,

Belmont, CA, USA). The lowest detectable concentration of

irisin was 6.8 ng/ml, with intra- and interassay coefficients of

variation were <%10 and %15, respectively. Glucose, insulin,

and HbA1c were determined with standard laboratory

methods. Insulin resistance was estimated by homeostasis

model assessment of insulin resistance (HOMA-IR) [9]. Home-

ostasis model assessment (HOMA) was calculated according to

the following formula: HOMA-IR = [fasting glucose (mmol/

l) � fasting insulin (mU/ml)]/22.5. In women with gestational

diabetes who were on insulin therapy, HOMA-IR was

determined before initiation of insulin therapy. Maternal

body mass index (BMI) values (kg/m2) were calculated prior to

delivery as the ratio of the weight (kg) to the square of the

height (m).

All analyses were performed using the Statistical Package

for the Social Sciences (SPSS) software version 18.0. Kolmo-

gorov–Smirnov test was used to assess normality of distribu-

tion of variables. Data are presented as mean � standard

deviation. Mean values between the groups were compared by

Student t test. Comparison between groups was performed

using Mann–Whitney U-test or independent samples t-test.

Spearman’s correlation coefficient was used to determine the

relationship between the variables. All reported confidence

interval (CI) values are calculated at the 95% level. A p

value < 0.05 was considered statistically significant.

3. Results

Clinical characteristics and biochemical parameters of each

group are shown in Tables 1 and 2. No significant differences

were found between the groups in terms of mean maternal

age, gestational age at birth, BMI, birth weight, neonatal

height, systolic and diastolic blood pressures (p > 0.05).

Mean maternal serum HOMA-IR, fasting glucose and

insulin levels of women with GDM at the time of delivery

were significantly higher than the control group (Table 2).

Mean maternal serum irisin level of women with GDM was

significantly lower than the control group (258.3 � 127.9 vs.

393 � 178.9 ng/ml, p: 0.009) (Table 2 and Fig. 1). Irisin levels in

cord blood were not statistically different among groups

(357.2 � 248.0 vs. 333.2 � 173.4 ng/ml, p: 0.735) (Table 2).

Among women with GDM, 8 had insulin therapy and 12

were treated with diet alone. Clinical and biochemical

characteristics of GDM patients treated with insulin and

managed by diet are shown in Table 3. Mean maternal serum

Table 1 – The clinical characteristics of women diagnosed with gestational diabetes and normal controls.

GDM (n: 20) Control (n: 20) p value

Age (year) 34.8 � 4.11 33.0 � 5.35 0.242

Gestational age at birth (week) 37.4 � 2.7 38.0 � 1.1 0.862

Maternal weight (kg) 82.6 � 11.0 76.4 � 11.1 0.091

Maternal height (cm) 163 � 6.3 164.1 � 7.8 0.758

BMI at birth (kg/m2) 31.4 � 5.3 28.5 � 4.4 0.174

Birth weight (g) 3261 � 755 3366 � 436 0.883

Neonatal height (cm) 49.5 � 4.1 50.2 � 1.6 0.758

SBP (mmHg) 119 � 16.0 109.5 � 10.9 0.060

DBP (mmHg) 73.5 � 8.7 69.0 � 7.8 0.157

Data are presented as mean � standard error of mean (SEM). BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure.

Statistically significant: p < 0.05.

Table 2 – Biochemical characteristics women diagnosed with gestational diabetes and normal controls.

GDM (n: 20) Control (n: 20) p value

Fasting glucose (mg/dl) 90.9 � 21.1 74.5 � 12.9 0.012

HOMA-IR 2.63 � 1.0 1.44 � 0.53 0.000

HbA1c (%) 5.7 � 1.9 5.11 � 0.36 0.367

Insulin (mU/l) 12.4 � 5.1 8.19 � 2.0 0.003

Serum irisin (ng/ml) 258.3 � 127.9 393 � 178.9 0.009

Cord irisin (ng/ml) 357.2 � 248.0 333.2 � 173.4 0.735

Cord glucose (mg/dl) 70.7 � 8.6 67.3 � 9.8 0.217

Data are presented as mean � standard error of mean (SEM). HOMA-IR, homeostatic model assessment of insulin resistance. Statistically

significant: p < 0.05.

d i a b e t e s r e s e a r c h a n d c l i n i c a l p r a c t i c e 1 0 4 ( 2 0 1 4 ) 1 7 1 – 1 7 5 173

irisin and cord irisin levels were not significantly different

between women with GDM on insulin therapy and those

treated with diet alone (p > 0.05) (Table 3).

Maternal serum irisin levels were negatively correlated with

BMI and HOMA-IR values (r = �0.401, p = 0.010; r = �0.395,

p = 0.012, respectively) (Fig. 2). In addition, maternal mean

serum irisin levels were not found to be associated with age,

gestational week at birth, birth weight, HbA1c, glucose, insulin

and cord irisin levels (r = �0.087, p = 0.596; r = �303, p = 0.058;

r = �0.150, p = 0.357; r = 0.063, p = 0.764; r = �0.264, p = 0.100;

r = �0.236, p = 0.142; r = �0.013, p = 0.936, respectively) (Table 4).

Data are pres ented as mean ±

Fig. 1 – Maternal irisin levels in w

4. Discussion

Association between irisin and various diseases such as

obesity, anorexia nervosa, type 2 diabetes, insulin sensitivity

and chronic kidney disease has been studied [6,7,10,11].

However, to the best of our knowledge, this is the first study

to investigate the relationship between irisin and pregnancy.

Maternal serum irisin levels were significantly lower in

pregnant women with GDM compared to control group. This

result suggests that serum irisin levels might be introduced as

sta nda rd error of mean (SEM)

omen with and without GDM.

Table 3 – The clinical and biochemical characteristics of GDM patients treated with insulin and managed by diet.

Management by diet (n: 12) Insulin treatment (n: 8) p value

Age (year) 34.0 � 3.91 35.8 � 4.42 0.258

BMI at birth (kg/m2) 30.5 � 4.46 32.8 � 6.45 0.487

Gestational age at birth (week) 37.3 � 3.39 37.6 � 1.76 0.528

Birth weight (g) 3110.0 � 863.0 3487.5 � 529.3 0.395

Fasting glucose (mg/dl) 87.7 � 21.5 95.6 � 20.9 0.334

HOMA-IR 2.45 � 0.83 2.89 � 1.38 0.512

HbA1c (%) 5.53 � 1.37 6.05 � 2.48 0.954

Insulin (mU/l) 12.1 � 5.07 12.8 � 5.66 0.643

Serum irisin (ng/ml) 267.0 � 110.7 245.3 � 157.5 0.280

Cordon irisin (ng/ml) 387.0 � 250.7 312.5 � 253.5 0.396

Cordon glucose (mg/dl) 68.2 � 9.38 74.5 � 6.07 0.141

Data are presented as mean � standard error of mean (SEM). BMI, body mass index; HOMA-IR, homeostatic model assessment of insulin

resistance. Statistically significant: p < 0.05.

Table 4 – Correlations between maternal serum irisinlevels and all the other parameters in whole groups.

Maternal serum irisin levels

r p

Maternal age �0.087 0.596

BMI at birth �0.401 0.010*

Gestational week at birth �0.303 0.058

Birth weight �0.150 0.357

HbA1c 0.063 0.764

Glucose �0.264 0.100

Insulin �0.236 0.142

HOMA-IR �0.395 0.012*

Cord irisin �0.013 0.936

BMI, body mass index; HOMA-IR, homeostatic model assessment

of insulin resistance. Statistically significant: p < 0.05.* Significant difference.

d i a b e t e s r e s e a r c h a n d c l i n i c a l p r a c t i c e 1 0 4 ( 2 0 1 4 ) 1 7 1 – 1 7 5174

a prospective and novel marker for GDM and decreased levels

of irisin might be indicative of GDM. There was no significant

relationship between GDM and cord irisin levels. Irisin has

been proposed to be involved in mediating the beneficial

effects of exercise on metabolism [4]. In culture and mouse

Fig. 2 – Correlation between maternal serum irisin

models, expression of FNDC5 gene has been proposed to

stimulate the production of irisin, thus leading to an increase

in uncoupling protein 1 (UCP1) levels which induce browning

of subcutaneous adipocytes and thermogenesis [4]. Improve-

ment in glucose tolerance of mice fed a high-fat diet occurs

when circulating levels of irisin increased 3–4 fold [4].

Therefore, brown fat has been demonstrated to induce effects

against diabetes and obesity in murine models [12] as well as

humans [13].

As a PGC-1a activated messenger of myocytes, irisin is

involved in the association between sedentary lifestyle and

obesity and diabetes [3,4,14,15]. The relationship between

irisin and type 2 diabetes has been evaluated in recent studies

[6,7]. It has been suggested that lower levels of circulating

irisin is associated with diabetes itself or the metabolic

condition that caused progression to type 2 diabetes. Previous

studies also investigated the role of PGC-1a in the pathogen-

esis of women with PCOS, type 2 diabetes and their offspring.

Studies in humans revealed that PGC-1a expression and its

activity were significantly down-regulated in skeletal muscles

in type 2 diabetes [16]. Our results show that circulating irisin

levels are significantly lower in women with GDM, and these

levels and BMI and HOMA-IR in all patients.

d i a b e t e s r e s e a r c h a n d c l i n i c a l p r a c t i c e 1 0 4 ( 2 0 1 4 ) 1 7 1 – 1 7 5 175

data are consistent with the available data. Therefore, it is

reasonable to hypothesize that lower level of circulating irisin

observed in our study might be secondary to impaired PGC-1a

expression and function in muscles in patients with GDM.

The effects of irisin on energy metabolism is controversial

[17]. Liu et al. have reported a positive correlation between

circulating irisin levels and BMI values in people without

diabetes. However, the same study also showed no association

between irisin expression from myocytes and BMI, fasting

insulin and fasting blood glucose (FBG) in patients with

diabetes [6]. Positive correlations between circulating irisin

levels and BMI in people without diabetes were shown in the

studies of Stengel et al. and Huh et al. [10,18]. In contrast, a

very recent study suggested that circulating irisin correlated

negatively with BMI, waist–hip ratio and fat mass in men. Even

after adjustment for age, waist–hip ratio and insulin sensi-

tivity; circulating irisin was still lower in overweight and obese

men without diabetes [19]. Our study showed that maternal

serum irisin levels were negatively correlated with BMI and

insulin resistance. Reasons for these discrepancies could be

the gender-differences, but this paradox might also the result

of a disassociation between FNDC5 expression and circulating

irisin under some conditions.

Irisin in fetal cord blood has not been evaluated so far. We

found no significant difference in cord blood irisin levels of

patients with GDM compared to control group. In fact, we have

no data about the placental absorption of maternal irisin. In

addition to this, normal maternal glucose levels were

successfully achieved in women with GDM in this study.

These facts may explain fetal irisin levels. Indeed, further

evaluation of fetal irisin in GDM patients with uncontrolled

glycemic profiles may contribute to an elaboration of fetal

irisin and its association with GDM.

The inability to measure the effect of fetal insulin concen-

trations on fetal irisin levels and the relatively small population

can be listed as the limitations of the study. Therefore, further

studies are needed to investigate the role of irisin in the

pathogenesis of GDM. In conclusion, maternal serum irisin

levels are lower in the patients with GDM. It remains possible

that GDM may affect PGC-1a expression or functions in

muscles. Furthermore, maternal plasma irisin levels are

negatively associated with BMI and insulin resistance.

Conflict of interest

No conflict of interest.

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