http://informahealthcare.com/gye ISSN: 0951-3590 (print), 1473-0766 (electronic) Gynecol Endocrinol, Early Online: 1–4 ! 2014 Informa UK Ltd. DOI: 10.3109/09513590.2014.920006
ORIGINAL ARTICLE
Serum irisin concentration in women with gestational diabetes Mariusz Kuzmicki1, Beata Telejko2, Danuta Lipinska2, Justyna Pliszka1, Michal Szamatowicz1, Juliusz Wilk2, Monika Zbucka-Kretowska3, Piotr Laudanski4, Adam Kretowski2, Maria Gorska2, and Jacek Szamatowicz1 Department of Gynecology, 2Department of Endocrinology, Diabetology and Internal Medicine, 3Department of Re-productiveness and Gynecological Endocrinology, and 4Department of Perinatology, Medical University of Bialystok, Bialystok, Poland
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1
Abstract
Keywords
Irisin is a novel myokine and adipokine which induces an increase in total body energy expenditure, improving insulin sensitivity and glucose tolerance in experimental animals. In the present study, serum irisin concentration was measured by an enzyme immunoassay in 130 women with gestational diabetes mellitus (GDM) and 140 BMI-matched patients with normal glucose tolerance (NGT). Median irisin level was significantly lower in the patients with GDM than in the NGT subjects (1703.3 [1354.8–2097.9 ng/ml] versus 1873.8 [1519.8– 2294.8 ng/ml], p ¼ 0.01); however, 3 months after childbirth its concentrations did not differ markedly between the two groups (1165.9 [872.1–1497.5] ng/ml versus 1139.0 [984.0–1376.7] ng/ml). In the whole group, irisin concentration correlated negatively with 2 h glucose level (R ¼ 0.14, p ¼ 0.03). In the women with NGT, irisin concentration correlated positively with ISOGTT (R ¼ 0.22, p ¼ 0.04) and the disposition index (DI120) (R ¼ 0.24, p ¼ 0.03), as well as negatively with 2 h insulin level (R ¼ 0.23, p ¼ 0.03) and HOMA-IR (R ¼ 0.24, p ¼ 0.02). Multiple regression analysis revealed that 2 h glucose and DI120 were the only variables significantly influencing serum irisin ( ¼ 0.158, p ¼ 0.03 and ¼ 0.159, p ¼ 0.02, respectively). Our results suggest that serum irisin concentration increases markedly in pregnant women, but this increase seems to be significantly lower in patients with GDM.
Adipokine, gestational diabetes, insulin resistance, irisin, myokine, pregnancy
Introduction Irisin is a novel myokine [1], adipokine [2] and neurokine [3] consisting of 112 amino acid residues, with a molecular weight of 12 587 kDa [1,4]. Irisin is proteolytically processed from the product of fibronectin type III domain containing 5 (FNDC5) gene in response to the activation of peroxisome proliferatoractivated receptor g (PPARg) co-activator-1a (PGC-1a) [1]. Studies in mice have shown that FNDC5/irisin overexpression induces browning of white adipose tissue, thereby increasing total body energy expenditure and protecting from diet induced obesity and diabetes [1,5]. Thus, experimental data suggest that a decrease in circulating irisin may be associated with the development of insulin resistance and impaired glucose tolerance. Indeed, clinical studies have shown decreased expression of FNDC5 gene in muscle and subcutaneous adipose tissue [6], as well as lower serum irisin concentration in patients with type 2 diabetes as compared with healthy individuals [6–8]. A decrease in circulating irisin was also observed in patients with gestational diabetes mellitus (GDM) [9], which is regarded to be a prediabetic state or a transient unmasking of the metabolic syndrome, characterized by an enormous insulin resistance and inadequate beta-cell compensation [10]. However, changes in circulating
Address for correspondence: Mariusz Kuzmicki, Department of Gynecology, Medical University of Bialystok, M. Curie-Sklodowskiej 24A, 15-276 Bialystok, Poland. Tel: +48857468502. E-mail: [email protected]
History Received 30 January 2014 Revised 24 March 2014 Accepted 28 April 2014 Published online 22 May 2014
irisin in GDM seem still controversial since two other studies did not show significant differences between subjects with GDM and BMI-matched healthy pregnant women [3,11]. Moreover, an association between irisin and insulin sensitivity in humans is still far from clear [3,6–9,11–16]. Therefore, the aim of the present study was to analyze serum irisin concentrations during and after pregnancy in relation to the disturbances of glucose tolerance and various indices of insulin sensitivity and insulin secretion.
Materials and methods Study population From the population of 972 pregnant women routinely tested for GDM with a 75 g 2-h oral glucose tolerance test (OGTT) at the gynecological out-patient clinic of the Medical University of Bialystok, 130 patients with GDM and 140 women with normal glucose tolerance (NGT), matched for age, gestational age and BMI, were recruited for this cross-sectional study. GDM was diagnosed on the basis of the following threshold glucose levels: fasting 100 mg/dl (5.5 mmol/l), 1 h 180 mg/dl (10.0 mmol/l) and 2 h 140 mg/dl (7.8 mmol/l). Patients with multiple pregnancy, pre-existing glucose intolerance, pregnancy-induced hypertension, preeclampsia, acute or chronic inflammation, as well as active smokers were not included. Written informed consent was obtained from all participants before enrollment, and the protocol was approved by the local ethics committee (Medical University of Bialystok). All women were invited to undergo reexamination 10–12 weeks after childbirth and 88 patients with prior GDM, as well as 76 women with NGT during pregnancy reported for a control visit 3 months postpartum.
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Analytical methods The OGTT was performed after an overnight fast and blood samples were collected at 0, 30, 60 and 120 min after glucose load and plasma glucose concentration was measured using oxidase method (CORMAY, Warsaw, Poland). Plasma insulin was assayed by immunoradiometric method (Biosource Europe SA, Nivelle, Belgium), glycated hemoglobin (HbA1c) was evaluated by a high performance liquid chromatography technique (BIO-RAD Laboratories, Munchen, Germany) and lipid concentrations were measured by enzymatic methods (ANALCO-GBG, Warsaw, Poland). Serum sex hormone binding globulin (SHBG) was estimated by an immunoradiometric assay (ZenTech s.a, Angleur, Belgium). Serum irisin concentration was measured using an enzyme immunoassay (Phoenix Pharmaceuticals, Inc., CA, Cat. No. EK-067-29) with a minimal detectable concentration of 1.1 ng/ml and intra- and inter-assay coefficients of variation of less than 10% and less than 15%, respectively. Before the assay serum samples were diluted 1:50, as recommended by the manufacturer, to ensure that determined irisin levels are within the linear range of the standard curve. The absorbance at 450 nm was measured using a mQuant microtiter plate reader (BIOTEK Instruments Inc., Winooski, VT). The following indices of insulin sensitivity and secretion were calculated: – the Matsuda and de Fronzo index (ISOGTT), defined as 10 000/ˇ[(FPG FPI) (G I)], where FPG ¼ fasting plasma glucose, FPI ¼ fasting plasma insulin, G ¼ mean glucose and I ¼ mean insulin during the OGTT (both calculated from glucose and insulin levels at 0, 30 and 120 min of the OGTT) [17]; – the disposition index as the products of insulin sensitivity and insulin secretion: DI30 ¼ ISOGTT AUCIns30/AUCGlu30 and DI120 ¼ ISOGTT AUCIns120/AUCGlu120, where AUCIns30/ AUCGlu30 ¼ the ratio of the area under the insulin curve (AUC) to the glucose AUC during 0–30 min of the OGTT and AUCIns120/AUCGlu120 ¼ the ratio of insulin
–
AUC to glucose AUC during 0–120 min of the OGTT) [18,19]. the homeostasis model assessment of insulin resistance (HOMA-IR ¼ FPG FPI/22.5) [20].
Statistical analysis The data were analyzed by the STATISTICA 10.0 for Windows Software (StatSoft. Inc, Tulsa, OK). Before analysis, data were tested for normality of distribution using the Shapiro–Wilk test. Differences between the groups were compared by the Mann– Whitney U-test, and relationships between variables were tested by Spearman’s rank correlations. The Wilcoxon test was used to compare the differences in irisin concentrations during and after pregnancy. Linear multiple regression was applied to establish the variables independently related to serum irisin level. p Value less than 0.05 was regarded as statistically significant.
Results Clinical characteristics of the groups studied The patients with GDM had significantly higher fasting and postload glucose (by definition, p50.00001), higher insulin at 0 and 120 min of the OGTT (p ¼ 0.02 and p50.00001, respectively), higher HbA1c (p50.00001), triglyceride concentration (p ¼ 0.001) and HOMA-IR (p ¼ 0.0007), as well as lower ISOGTT (p50.00001), DI30 (p ¼ 0.01) and DI120 (p50.00001) than had the women with NGT (Table 1). Three months postpartum, the patients with previous GDM had still higher glucose levels at 30 (p ¼ 0.02), 60 (p ¼ 0.01) and 120 min (p ¼ 0.02) of the OGTT, as well as lower triglyceride concentration (p ¼ 0.02) than had the women without GDM (Table 2). Serum irisin concentration Serum irisin levels were significantly lower in the patients with GDM than in the women with NGT (p ¼ 0.01, Table 1). Three months postpartum its concentrations were markedly
Table 1. Clinical characteristics of the groups studied.
n Age (years) Parity Gestational age (week) Prepregnancy BMI (kg/m2) Current BMI (kg/m2) Weight gain (kg) Fasting glucose (mmol/l) Glucose 30’ (mmol/l) Glucose 60’ (mmol/l) Glucose 120’ (mmol/l) Fasting insulin (pmol/l) Insulin 30’ (pmol/l) Insulin 60’ (pmol/l) Insulin 120’ (pmol/l) HOMA-IR ISOGTT DI30 DI120 HbA1c (%) Total cholesterol (mmol/l) HDL-cholesterol (mmol/l) LDL-cholesterol (mmol/l) Triglycerides (mmol/l) SHBG (nmol/l) Irisin (ng/ml)
NGT
GDM
p Value
140 30 (28–34) 2 (1–2) 28 (26–29) 23.3 (21.9–26.8) 27.2 (24.8–30.4) 8.0 (6.5–12.0) 4.4 (4.1–4.6) 7.2 (6.5–7.8) 7.1 (6.0–7.9) 5.8 (5.1–6.3) 93.1 (64.8–121.7) 571.3 (428.0–761.6) 607.7 (459.9–865.9) 423.5 (303.5–559.6) 2.6 (1.8–3.5) 4.24 (3.29–5.34) 250.9 (201.6–334.9) 331.2 (257.9–410.3) 4.8 (4.5–5.1) 6.1 (5.5–6.9) 1.9 (1.6–2.2) 3.3 (2.6–4.0) 2.0 (1.6–2.5) 336.9 (294.3–376.6) 1873.8 (1519.8–2294.8)
130 31 (28–35) 2 (1–2) 28 (26–30) 24.3 (20.9–28.1) 28.2 (24.4–31.5) 9.0 (6.0–11.3) 4.8 (4.4–5.2) 8.5 (7.9–9.4) 9.9 (8.8–10.6) 8.3 (7.8–8.9) 105.9 (75.9–143.2) 489.2 (380.7–714.3) 761.9 (450.7–984.8) 698.6 (508.3–989.9) 3.3 (2.3–4.5) 2.93 (2.11–4.29) 201.1 (127.4–411.8) 232.6 (176.4–285.3) 5.1 (4.8–5.3) 6.5 (5.6–7.1) 1.9 (1.6–2.2) 3.4 (2.5–4.2) 2.2 (1.9–3.0) 332.7 (284.1–367.5) 1703.3 (1354.8–2097.9)
0.21 0.22 0.08 0.87 0.90 0.59 50.00001 50.00001 50.00001 50.00001 0.02 0.057 0.39 50.00001 0.0007 50.00001 0.01 50.00001 50.00001 0.09 0.99 0.52 0.001 0.27 0.01
Data are shown as medians (interquartile range); NGT, normal glucose tolerance; GDM, gestational diabetes mellitus; differences between NGT and GDM groups were analyzed by the Mann-Whitney U-test.
Irisin in pregnant women
DOI: 10.3109/09513590.2014.920006
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Table 2. Clinical characteristics of the groups studied three months postpartum.
n Age (years) Current BMI (kg/m2) Newborns’ weight (g) Fasting glucose (mmol/l) Glucose 30’ (mmol/l) Glucose 60’ (mmol/l) Glucose 120’ (mmol/l) Fasting insulin (pmol/l) Insulin 30’ (pmol/l) Insulin 60’ (pmol/l) Insulin 120’ (pmol/l) HOMA-IR ISOGTT DI30 DI120 HbA1c (%) Total cholesterol (mmol/l) HDL-cholesterol (mmol/l) LDL-cholesterol (mmol/l) Triglycerides (mmol/l) SHBG (nmol/l) Irisin (ng/ml)
NGT
GDM
p Value
76 33 (29–35) 24.1 (23.0–27.3) 3500 (2950–3700) 4.8 (4.5–5.1) 7.2 (6.4–8.4) 6.5 (5.5–8.1) 4.9 (4.2–5.7) 83.6 (47.8–106.4) 301.2 (245.5–583.0) 308.4 (178.9–436.7) 204.4 (153.2–351.7) 2.7 (1.3–3.4) 5.96 (3.93–8.70) 207.2 (144.4–241.3) 238.6 (174.7–351.2) 5.3 (5.0–5.5) 4.4 (3.9–5.4) 1.6 (1.5–1.9) 2.4 (1.8–3.1) 1.0 (0.8–1.6) 44.9 (35.9–80.0) 1139.0 (984.0–1376.7)
88 31 (27–35) 24.2 (21.9–27.6) 3475 (2950–3700) 4.9 (4.6–5.4) 8.1 (7.3–9.3) 8.0 (6.7–9.0) 5.7 (4.7–6.9) 78.2 (46.9–107.5) 330.3 (224.8–548.4) 394.5 (226.1–625.1) 210.2 (158.1–367.6) 2.6 (1.4–3.4) 5.23 (3.74–7.76) 168.3 (132.2–223.0) 223.5 (163.8–276.1) 5.2 (5.0–5.5) 4.7 (4.3–5.3) 1.6 (1.3–1.8) 2.6 (2.2–3.2) 0.8 (0.6–1.1) 45.8 (26.9–63.5) 1165.9 (872.1–1497.5)
0.46 0.99 0.87 0.34 0.02 0.01 0.02 0.98 0.87 0.23 0.77 0.84 0.43 0.14 0.17 0.69 0.56 0.67 0.32 0.03 0.41 0.97
Data are shown as medians (interquartile range); NGT, normal glucose tolerance; GDM, gestational diabetes mellitus; differences between NGT and GDM groups were analyzed using the Mann-Whitney U-test.
lower than during pregnancy (p50.00001) and did not differ significantly between the two groups (Table 2). In the whole group of pregnant women, serum irisin concentration correlated negatively with glucose level at 120 min of the OGTT (R ¼ 0.14, p ¼ 0.03). In the subjects with NGT, irisin concentration correlated positively with ISOGTT (R ¼ 0.22, p ¼ 0.04) and DI120 (R ¼ 0.24, p ¼ 0.03), as well as negatively with insulin level at 120 min of the OGTT (R ¼ 0.23, p ¼ 0.03) and HOMA-IR (R ¼ 0.24, p ¼ 0.02). Three months after childbirth serum irisin was not associated with any of the anthropometric or metabolic variables studied. Multiple regression analysis revealed that 2 h glucose and DI120 were the only variables significantly influencing serum irisin level ( ¼ 0.158, p ¼ 0.03 and ¼ 0.159, p ¼ 0.02, respectively), each of them explaining about 3% of its variability.
Discussion The present study showed that serum irisin levels were significantly lower in the patients with GDM than in the healthy pregnant women, although 3 months postpartum its concentrations did not differ markedly between the two groups. Our results are consistent with the findings of Yuksel et al. [9], who also reported a decrease in circulating irisin in women with GDM; however, in this study irisin levels were measured in late pregnancy. In contrast, Ebert et al. [11] found no difference in circulating irisin between pregnant women with and without GDM, although 4 years after childbirth irisin concentrations were significantly higher in patients with previous GDM than in women with NGT. Conversely, Aydin et al. [21] showed decreased serum irisin in lactating women with prior GDM in comparison with healthy lactating women. No significant differences in serum irisin between non-obese, obese and GDM subjects at term were recently reported by Piya et al. [3]. However, further analysis revealed that after adjusting for BMI, lipids and glucose, irisin levels were significantly lower in non-obese pregnant women as compared with obese and GDM groups. The authors suggested that these findings may reflect irisin resistance developing
together with insulin resistance. The concept of irisin resistance with compensatory hyperirisinemia was also proposed by Hee Park et al. [12], who showed that high irisin levels were associated with an increased risk of the metabolic syndrome and cardiovascular disease. However, an association between irisin and insulin resistance, in particular during pregnancy, seems still controversial. Piya et al. [3] demonstrated that in pregnant women serum irisin was positively correlated with fasting glucose, insulin and HOMA-IR. Ebert et al. [11] also found a positive association between circulating irisin and insulin, but only in the subgroup with GDM. In contrast, Yuksel et al. [9] reported that serum irisin level was negatively correlated with HOMA-IR. In the present study, irisin concentration in the non-diabetic women correlated positively with ISOGTT and DI120, used as the measures of insulin sensitivity and beta cell compensation, as well as negatively with HOMA-IR and insulin level at 120 min of the OGTT. A positive association of circulating irisin with insulin sensitivity, measured by the frequently sampled i.v. glucose tolerance test, was also reported by Moreno-Navarette et al. [6] in individuals with various degree of obesity. Additionally, we observed that in the whole group of pregnant women serum irisin concentration correlated negatively with glucose level at 120 min of the OGTT, which is consistent with the results of Choi et al. [7], who found that 2 h plasma glucose was an independent negative predictor of irisin concentration in the patients with newly-diagnosed type 2 diabetes. All these discrepancies may result from differences in clinical characteristics of the subjects studied and various diagnostic criteria; however, the possible influence of BMI or weight gain during pregnancy and gestational week at sampling seems unclear since a positive correlation between serum irisin and BMI at the 28th week of gestation [11] and a negative one at term [3], were reported by various authors. In the present study, no associations between circulating irisin and BMI or gestational age were observed. Moreover, controversial results, i.e. higher irisin concentration in pregnant than in non-pregnant women [11] or no significant differences during and after pregnancy [3], have been found in different studies. Our results showed that irisin levels in the 24th–30th week of pregnancy were markedly higher
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than three months postpartum, which may suggest a compensation for a physiologic increase in insulin resistance or a stimulating effect of high estrogens levels [22], or conceivably its additional secretion by the placenta, although the contribution of placental tissue to circulating irisin seems insignificant [11,22]. In conclusion, our results suggest that serum irisin concentration increases markedly during pregnancy and that this increase is significantly lower in women with GDM; however, further investigations are needed to fully explore the association between this new myokine/adipokine and glucose intolerance in pregnancy.
Declaration of interest The authors report no conflict of interest. The study was supported by the State Committee for Scientific Research (Grant No. N N407 141 937).
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References 1. Bostro¨m P, Wu J, Jedrychowski MP, et al. PGC1-a-dependent myokine that drives brown-fat-like development of white fat and thermogenesis. Nature 2012;481:463–8. 2. Roca-Rivada A, Castelao C, Senin LL, et al. FNDC5/irisin is not only a myokine but also an adipokine. PLoS One 2013;8:e60563. doi: 10.1371/journal.pone.0060563. 3. Piya MK, Harte AL, Sivakumar K, et al. The identification of irisin in human cerebrospinal fluid: influence of adiposity, metabolic markers and gestational diabetes. Am J Physiol Endocrinol Metab 2014;306:E512–E518. 4. Schumacher MA, Chinnam N, Ohashi T, et al. The structure of irisin reveals a novel intersubunit b-sheet fibronectin (FNIII) dimer; implications for receptor activation. J Biol Chem 2013;288: 33738–44. 5. Zhang Y, Li R, Meng Y, et al. Irisin stimulates browning of white adipocytes through mitogen-activated protein kinase p38 MAP kinase and ERK MAP kinase signaling. Diabetes 2014;63:514–25. 6. Moreno-Navarrete JM, Ortega F, Serrano M, et al. Irisin is expressed and produced by human muscle and adipose tissue in association with obesity and insulin resistance. J Clin Endocrinol Metab 2013; 98:E769–78. 7. Choi YK, Kim MK, Bae KH, et al. Serum irisin levels in new-onset type 2 diabetes. Diabetes Res Clin Pract 2013;100:96–101. 8. Liu JJ, Wong MD, Toy WC, et al. Lower circulating irisin is associated with type 2 diabetes mellitus. J Diabetes Complications 2013;27:365–9.
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9. Yuksel MA, Oncul M, Tuten A, et al. Maternal serum and fetal cord blood irisin levels in gestational diabetes mellitus. Diabetes Res Clin Pract 2014;104:171–175. 10. Buchanan TA, Xiang A, Kjos SL, Watanabe R. What is gestational diabetes? Diabetes Care 2007;30:S105–11. 11. Ebert T, Stepan H, Schrey S, et al. Serum levels of irisin in gestational diabetes mellitus during pregnancy and after delivery. Cytokine 2014;652:153–8. 12. Hee Park K, Zaichenko L, Brinkoetter M, et al. Circulating irisin in relation to insulin resistance and the metabolic syndrome. J Clin Endocrinol Metab 2013;98:4899–907. 13. Stengel A, Hofmann T, Goebel-Stengel M, et al. Circulating levels of irisin in patients with anorexia nervosa and different stages of obesity –correlation with body mass index. Peptides 2013;39: 125–30. 14. Staiger H, Bo¨hm A, Scheler M, et al. Common genetic variation in the human FNDC5 locus, encoding the novel muscle-derived ‘browning’ factor irisin, determines insulin sensitivity. PLoS One 2013;8:e61903. doi:10.1371/journal.pone.0061903. 15. Pekkala S, Wiklund PK, Hulmi JJ, et al. Are skeletal muscle FNDC5 gene expression and irisin release regulated by exercise and related to health? J Physiol 2013;591:5393–400. 16. Hecksteden A, Wegmann M, Steffen A, et al. Irisin and exercise training in humans – results from a randomized controlled training trial. BMC Med 2013;11:235. doi:10.1186/1741-7015-11-235. 17. Matsuda M, DeFronzo R. Insulin sensitivity indices obtained from oral glucose tolerance testing: comparison with the euglycemic insulin clamp. Diabetes Care 1999;22:1462–70. 18. Retnakaran R, Qi Y, Goran MI, Hamilton JK. Evaluation of proposed oral disposition index measures in relation to the actual disposition index. Diabet Med 2009;26:1198–203. 19. Stanca´kova´ A, Javorsky´ M, Kuulasmaa T, et al. Changes in insulin sensitivity and insulin release in relation to glycemia and glucose tolerance in 6,414 Finnish men. Diabetes 2009;58:1212–21. 20. Matthews DR, Hosker JP, Rudenski AS, et al. Homeostasis model assessment: insulin resistance and b-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia 1985;28:412–19. 21. Aydin S, Kuloglu T, Aydin S. Copeptin, adropin and irisin concentrations in breast milk and plasma of healthy women and those with gestational diabetes mellitus. Peptides 2013;47: 66–70. 22. Huh JY, Panagiotou G, Mougios V, et al. FNDC5 and irisin in humans: I. Predictors of circulating concentrations in serum and plasma and II. mRNA expression and circulating concentrations in response to weight loss and exercise. Metabolism 2012;61: 1725–38.
ORIGINAL ARTICLE
Serum irisin concentration in women with gestational diabetes Mariusz Kuzmicki1, Beata Telejko2, Danuta Lipinska2, Justyna Pliszka1, Michal Szamatowicz1, Juliusz Wilk2, Monika Zbucka-Kretowska3, Piotr Laudanski4, Adam Kretowski2, Maria Gorska2, and Jacek Szamatowicz1 Department of Gynecology, 2Department of Endocrinology, Diabetology and Internal Medicine, 3Department of Re-productiveness and Gynecological Endocrinology, and 4Department of Perinatology, Medical University of Bialystok, Bialystok, Poland
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1
Abstract
Keywords
Irisin is a novel myokine and adipokine which induces an increase in total body energy expenditure, improving insulin sensitivity and glucose tolerance in experimental animals. In the present study, serum irisin concentration was measured by an enzyme immunoassay in 130 women with gestational diabetes mellitus (GDM) and 140 BMI-matched patients with normal glucose tolerance (NGT). Median irisin level was significantly lower in the patients with GDM than in the NGT subjects (1703.3 [1354.8–2097.9 ng/ml] versus 1873.8 [1519.8– 2294.8 ng/ml], p ¼ 0.01); however, 3 months after childbirth its concentrations did not differ markedly between the two groups (1165.9 [872.1–1497.5] ng/ml versus 1139.0 [984.0–1376.7] ng/ml). In the whole group, irisin concentration correlated negatively with 2 h glucose level (R ¼ 0.14, p ¼ 0.03). In the women with NGT, irisin concentration correlated positively with ISOGTT (R ¼ 0.22, p ¼ 0.04) and the disposition index (DI120) (R ¼ 0.24, p ¼ 0.03), as well as negatively with 2 h insulin level (R ¼ 0.23, p ¼ 0.03) and HOMA-IR (R ¼ 0.24, p ¼ 0.02). Multiple regression analysis revealed that 2 h glucose and DI120 were the only variables significantly influencing serum irisin ( ¼ 0.158, p ¼ 0.03 and ¼ 0.159, p ¼ 0.02, respectively). Our results suggest that serum irisin concentration increases markedly in pregnant women, but this increase seems to be significantly lower in patients with GDM.
Adipokine, gestational diabetes, insulin resistance, irisin, myokine, pregnancy
Introduction Irisin is a novel myokine [1], adipokine [2] and neurokine [3] consisting of 112 amino acid residues, with a molecular weight of 12 587 kDa [1,4]. Irisin is proteolytically processed from the product of fibronectin type III domain containing 5 (FNDC5) gene in response to the activation of peroxisome proliferatoractivated receptor g (PPARg) co-activator-1a (PGC-1a) [1]. Studies in mice have shown that FNDC5/irisin overexpression induces browning of white adipose tissue, thereby increasing total body energy expenditure and protecting from diet induced obesity and diabetes [1,5]. Thus, experimental data suggest that a decrease in circulating irisin may be associated with the development of insulin resistance and impaired glucose tolerance. Indeed, clinical studies have shown decreased expression of FNDC5 gene in muscle and subcutaneous adipose tissue [6], as well as lower serum irisin concentration in patients with type 2 diabetes as compared with healthy individuals [6–8]. A decrease in circulating irisin was also observed in patients with gestational diabetes mellitus (GDM) [9], which is regarded to be a prediabetic state or a transient unmasking of the metabolic syndrome, characterized by an enormous insulin resistance and inadequate beta-cell compensation [10]. However, changes in circulating
Address for correspondence: Mariusz Kuzmicki, Department of Gynecology, Medical University of Bialystok, M. Curie-Sklodowskiej 24A, 15-276 Bialystok, Poland. Tel: +48857468502. E-mail: [email protected]
History Received 30 January 2014 Revised 24 March 2014 Accepted 28 April 2014 Published online 22 May 2014
irisin in GDM seem still controversial since two other studies did not show significant differences between subjects with GDM and BMI-matched healthy pregnant women [3,11]. Moreover, an association between irisin and insulin sensitivity in humans is still far from clear [3,6–9,11–16]. Therefore, the aim of the present study was to analyze serum irisin concentrations during and after pregnancy in relation to the disturbances of glucose tolerance and various indices of insulin sensitivity and insulin secretion.
Materials and methods Study population From the population of 972 pregnant women routinely tested for GDM with a 75 g 2-h oral glucose tolerance test (OGTT) at the gynecological out-patient clinic of the Medical University of Bialystok, 130 patients with GDM and 140 women with normal glucose tolerance (NGT), matched for age, gestational age and BMI, were recruited for this cross-sectional study. GDM was diagnosed on the basis of the following threshold glucose levels: fasting 100 mg/dl (5.5 mmol/l), 1 h 180 mg/dl (10.0 mmol/l) and 2 h 140 mg/dl (7.8 mmol/l). Patients with multiple pregnancy, pre-existing glucose intolerance, pregnancy-induced hypertension, preeclampsia, acute or chronic inflammation, as well as active smokers were not included. Written informed consent was obtained from all participants before enrollment, and the protocol was approved by the local ethics committee (Medical University of Bialystok). All women were invited to undergo reexamination 10–12 weeks after childbirth and 88 patients with prior GDM, as well as 76 women with NGT during pregnancy reported for a control visit 3 months postpartum.
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M. Kuzmicki et al.
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Analytical methods The OGTT was performed after an overnight fast and blood samples were collected at 0, 30, 60 and 120 min after glucose load and plasma glucose concentration was measured using oxidase method (CORMAY, Warsaw, Poland). Plasma insulin was assayed by immunoradiometric method (Biosource Europe SA, Nivelle, Belgium), glycated hemoglobin (HbA1c) was evaluated by a high performance liquid chromatography technique (BIO-RAD Laboratories, Munchen, Germany) and lipid concentrations were measured by enzymatic methods (ANALCO-GBG, Warsaw, Poland). Serum sex hormone binding globulin (SHBG) was estimated by an immunoradiometric assay (ZenTech s.a, Angleur, Belgium). Serum irisin concentration was measured using an enzyme immunoassay (Phoenix Pharmaceuticals, Inc., CA, Cat. No. EK-067-29) with a minimal detectable concentration of 1.1 ng/ml and intra- and inter-assay coefficients of variation of less than 10% and less than 15%, respectively. Before the assay serum samples were diluted 1:50, as recommended by the manufacturer, to ensure that determined irisin levels are within the linear range of the standard curve. The absorbance at 450 nm was measured using a mQuant microtiter plate reader (BIOTEK Instruments Inc., Winooski, VT). The following indices of insulin sensitivity and secretion were calculated: – the Matsuda and de Fronzo index (ISOGTT), defined as 10 000/ˇ[(FPG FPI) (G I)], where FPG ¼ fasting plasma glucose, FPI ¼ fasting plasma insulin, G ¼ mean glucose and I ¼ mean insulin during the OGTT (both calculated from glucose and insulin levels at 0, 30 and 120 min of the OGTT) [17]; – the disposition index as the products of insulin sensitivity and insulin secretion: DI30 ¼ ISOGTT AUCIns30/AUCGlu30 and DI120 ¼ ISOGTT AUCIns120/AUCGlu120, where AUCIns30/ AUCGlu30 ¼ the ratio of the area under the insulin curve (AUC) to the glucose AUC during 0–30 min of the OGTT and AUCIns120/AUCGlu120 ¼ the ratio of insulin
–
AUC to glucose AUC during 0–120 min of the OGTT) [18,19]. the homeostasis model assessment of insulin resistance (HOMA-IR ¼ FPG FPI/22.5) [20].
Statistical analysis The data were analyzed by the STATISTICA 10.0 for Windows Software (StatSoft. Inc, Tulsa, OK). Before analysis, data were tested for normality of distribution using the Shapiro–Wilk test. Differences between the groups were compared by the Mann– Whitney U-test, and relationships between variables were tested by Spearman’s rank correlations. The Wilcoxon test was used to compare the differences in irisin concentrations during and after pregnancy. Linear multiple regression was applied to establish the variables independently related to serum irisin level. p Value less than 0.05 was regarded as statistically significant.
Results Clinical characteristics of the groups studied The patients with GDM had significantly higher fasting and postload glucose (by definition, p50.00001), higher insulin at 0 and 120 min of the OGTT (p ¼ 0.02 and p50.00001, respectively), higher HbA1c (p50.00001), triglyceride concentration (p ¼ 0.001) and HOMA-IR (p ¼ 0.0007), as well as lower ISOGTT (p50.00001), DI30 (p ¼ 0.01) and DI120 (p50.00001) than had the women with NGT (Table 1). Three months postpartum, the patients with previous GDM had still higher glucose levels at 30 (p ¼ 0.02), 60 (p ¼ 0.01) and 120 min (p ¼ 0.02) of the OGTT, as well as lower triglyceride concentration (p ¼ 0.02) than had the women without GDM (Table 2). Serum irisin concentration Serum irisin levels were significantly lower in the patients with GDM than in the women with NGT (p ¼ 0.01, Table 1). Three months postpartum its concentrations were markedly
Table 1. Clinical characteristics of the groups studied.
n Age (years) Parity Gestational age (week) Prepregnancy BMI (kg/m2) Current BMI (kg/m2) Weight gain (kg) Fasting glucose (mmol/l) Glucose 30’ (mmol/l) Glucose 60’ (mmol/l) Glucose 120’ (mmol/l) Fasting insulin (pmol/l) Insulin 30’ (pmol/l) Insulin 60’ (pmol/l) Insulin 120’ (pmol/l) HOMA-IR ISOGTT DI30 DI120 HbA1c (%) Total cholesterol (mmol/l) HDL-cholesterol (mmol/l) LDL-cholesterol (mmol/l) Triglycerides (mmol/l) SHBG (nmol/l) Irisin (ng/ml)
NGT
GDM
p Value
140 30 (28–34) 2 (1–2) 28 (26–29) 23.3 (21.9–26.8) 27.2 (24.8–30.4) 8.0 (6.5–12.0) 4.4 (4.1–4.6) 7.2 (6.5–7.8) 7.1 (6.0–7.9) 5.8 (5.1–6.3) 93.1 (64.8–121.7) 571.3 (428.0–761.6) 607.7 (459.9–865.9) 423.5 (303.5–559.6) 2.6 (1.8–3.5) 4.24 (3.29–5.34) 250.9 (201.6–334.9) 331.2 (257.9–410.3) 4.8 (4.5–5.1) 6.1 (5.5–6.9) 1.9 (1.6–2.2) 3.3 (2.6–4.0) 2.0 (1.6–2.5) 336.9 (294.3–376.6) 1873.8 (1519.8–2294.8)
130 31 (28–35) 2 (1–2) 28 (26–30) 24.3 (20.9–28.1) 28.2 (24.4–31.5) 9.0 (6.0–11.3) 4.8 (4.4–5.2) 8.5 (7.9–9.4) 9.9 (8.8–10.6) 8.3 (7.8–8.9) 105.9 (75.9–143.2) 489.2 (380.7–714.3) 761.9 (450.7–984.8) 698.6 (508.3–989.9) 3.3 (2.3–4.5) 2.93 (2.11–4.29) 201.1 (127.4–411.8) 232.6 (176.4–285.3) 5.1 (4.8–5.3) 6.5 (5.6–7.1) 1.9 (1.6–2.2) 3.4 (2.5–4.2) 2.2 (1.9–3.0) 332.7 (284.1–367.5) 1703.3 (1354.8–2097.9)
0.21 0.22 0.08 0.87 0.90 0.59 50.00001 50.00001 50.00001 50.00001 0.02 0.057 0.39 50.00001 0.0007 50.00001 0.01 50.00001 50.00001 0.09 0.99 0.52 0.001 0.27 0.01
Data are shown as medians (interquartile range); NGT, normal glucose tolerance; GDM, gestational diabetes mellitus; differences between NGT and GDM groups were analyzed by the Mann-Whitney U-test.
Irisin in pregnant women
DOI: 10.3109/09513590.2014.920006
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Table 2. Clinical characteristics of the groups studied three months postpartum.
n Age (years) Current BMI (kg/m2) Newborns’ weight (g) Fasting glucose (mmol/l) Glucose 30’ (mmol/l) Glucose 60’ (mmol/l) Glucose 120’ (mmol/l) Fasting insulin (pmol/l) Insulin 30’ (pmol/l) Insulin 60’ (pmol/l) Insulin 120’ (pmol/l) HOMA-IR ISOGTT DI30 DI120 HbA1c (%) Total cholesterol (mmol/l) HDL-cholesterol (mmol/l) LDL-cholesterol (mmol/l) Triglycerides (mmol/l) SHBG (nmol/l) Irisin (ng/ml)
NGT
GDM
p Value
76 33 (29–35) 24.1 (23.0–27.3) 3500 (2950–3700) 4.8 (4.5–5.1) 7.2 (6.4–8.4) 6.5 (5.5–8.1) 4.9 (4.2–5.7) 83.6 (47.8–106.4) 301.2 (245.5–583.0) 308.4 (178.9–436.7) 204.4 (153.2–351.7) 2.7 (1.3–3.4) 5.96 (3.93–8.70) 207.2 (144.4–241.3) 238.6 (174.7–351.2) 5.3 (5.0–5.5) 4.4 (3.9–5.4) 1.6 (1.5–1.9) 2.4 (1.8–3.1) 1.0 (0.8–1.6) 44.9 (35.9–80.0) 1139.0 (984.0–1376.7)
88 31 (27–35) 24.2 (21.9–27.6) 3475 (2950–3700) 4.9 (4.6–5.4) 8.1 (7.3–9.3) 8.0 (6.7–9.0) 5.7 (4.7–6.9) 78.2 (46.9–107.5) 330.3 (224.8–548.4) 394.5 (226.1–625.1) 210.2 (158.1–367.6) 2.6 (1.4–3.4) 5.23 (3.74–7.76) 168.3 (132.2–223.0) 223.5 (163.8–276.1) 5.2 (5.0–5.5) 4.7 (4.3–5.3) 1.6 (1.3–1.8) 2.6 (2.2–3.2) 0.8 (0.6–1.1) 45.8 (26.9–63.5) 1165.9 (872.1–1497.5)
0.46 0.99 0.87 0.34 0.02 0.01 0.02 0.98 0.87 0.23 0.77 0.84 0.43 0.14 0.17 0.69 0.56 0.67 0.32 0.03 0.41 0.97
Data are shown as medians (interquartile range); NGT, normal glucose tolerance; GDM, gestational diabetes mellitus; differences between NGT and GDM groups were analyzed using the Mann-Whitney U-test.
lower than during pregnancy (p50.00001) and did not differ significantly between the two groups (Table 2). In the whole group of pregnant women, serum irisin concentration correlated negatively with glucose level at 120 min of the OGTT (R ¼ 0.14, p ¼ 0.03). In the subjects with NGT, irisin concentration correlated positively with ISOGTT (R ¼ 0.22, p ¼ 0.04) and DI120 (R ¼ 0.24, p ¼ 0.03), as well as negatively with insulin level at 120 min of the OGTT (R ¼ 0.23, p ¼ 0.03) and HOMA-IR (R ¼ 0.24, p ¼ 0.02). Three months after childbirth serum irisin was not associated with any of the anthropometric or metabolic variables studied. Multiple regression analysis revealed that 2 h glucose and DI120 were the only variables significantly influencing serum irisin level ( ¼ 0.158, p ¼ 0.03 and ¼ 0.159, p ¼ 0.02, respectively), each of them explaining about 3% of its variability.
Discussion The present study showed that serum irisin levels were significantly lower in the patients with GDM than in the healthy pregnant women, although 3 months postpartum its concentrations did not differ markedly between the two groups. Our results are consistent with the findings of Yuksel et al. [9], who also reported a decrease in circulating irisin in women with GDM; however, in this study irisin levels were measured in late pregnancy. In contrast, Ebert et al. [11] found no difference in circulating irisin between pregnant women with and without GDM, although 4 years after childbirth irisin concentrations were significantly higher in patients with previous GDM than in women with NGT. Conversely, Aydin et al. [21] showed decreased serum irisin in lactating women with prior GDM in comparison with healthy lactating women. No significant differences in serum irisin between non-obese, obese and GDM subjects at term were recently reported by Piya et al. [3]. However, further analysis revealed that after adjusting for BMI, lipids and glucose, irisin levels were significantly lower in non-obese pregnant women as compared with obese and GDM groups. The authors suggested that these findings may reflect irisin resistance developing
together with insulin resistance. The concept of irisin resistance with compensatory hyperirisinemia was also proposed by Hee Park et al. [12], who showed that high irisin levels were associated with an increased risk of the metabolic syndrome and cardiovascular disease. However, an association between irisin and insulin resistance, in particular during pregnancy, seems still controversial. Piya et al. [3] demonstrated that in pregnant women serum irisin was positively correlated with fasting glucose, insulin and HOMA-IR. Ebert et al. [11] also found a positive association between circulating irisin and insulin, but only in the subgroup with GDM. In contrast, Yuksel et al. [9] reported that serum irisin level was negatively correlated with HOMA-IR. In the present study, irisin concentration in the non-diabetic women correlated positively with ISOGTT and DI120, used as the measures of insulin sensitivity and beta cell compensation, as well as negatively with HOMA-IR and insulin level at 120 min of the OGTT. A positive association of circulating irisin with insulin sensitivity, measured by the frequently sampled i.v. glucose tolerance test, was also reported by Moreno-Navarette et al. [6] in individuals with various degree of obesity. Additionally, we observed that in the whole group of pregnant women serum irisin concentration correlated negatively with glucose level at 120 min of the OGTT, which is consistent with the results of Choi et al. [7], who found that 2 h plasma glucose was an independent negative predictor of irisin concentration in the patients with newly-diagnosed type 2 diabetes. All these discrepancies may result from differences in clinical characteristics of the subjects studied and various diagnostic criteria; however, the possible influence of BMI or weight gain during pregnancy and gestational week at sampling seems unclear since a positive correlation between serum irisin and BMI at the 28th week of gestation [11] and a negative one at term [3], were reported by various authors. In the present study, no associations between circulating irisin and BMI or gestational age were observed. Moreover, controversial results, i.e. higher irisin concentration in pregnant than in non-pregnant women [11] or no significant differences during and after pregnancy [3], have been found in different studies. Our results showed that irisin levels in the 24th–30th week of pregnancy were markedly higher
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M. Kuzmicki et al.
than three months postpartum, which may suggest a compensation for a physiologic increase in insulin resistance or a stimulating effect of high estrogens levels [22], or conceivably its additional secretion by the placenta, although the contribution of placental tissue to circulating irisin seems insignificant [11,22]. In conclusion, our results suggest that serum irisin concentration increases markedly during pregnancy and that this increase is significantly lower in women with GDM; however, further investigations are needed to fully explore the association between this new myokine/adipokine and glucose intolerance in pregnancy.
Declaration of interest The authors report no conflict of interest. The study was supported by the State Committee for Scientific Research (Grant No. N N407 141 937).
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