Elsevier

Cytokine

Volume 107, July 2018, Pages 79-84
Cytokine

Monocyte profile in peripheral blood of gestational diabetes mellitus patients

https://doi.org/10.1016/j.cyto.2017.11.017Get rights and content

Highlights

  • Increased percentage of CD14+ cells in gestational diabetes.

  • Reduced frequency of CD14+CD16+ monocytes in gestational diabetes.

  • Lower percentage of circulating monocytes that express TLR4 in gestational diabetes.

  • Higher serum levels of soluble CD14+ in gestational diabetes.

Abstract

Objective

Gestational diabetes Mellitus has been considered an inflammatory disease involving different cells and mediators in its development. The role of innate immune cells in GDM physiopathology remains unclear, therefore this study was conducted to assess monocyte profile in GDM patients.

Design

This was a case-control study including 20 glucose-tolerant pregnant women (controls) and 18 GDM patients.

Methods

Flow cytometry was used to assess peripheral blood monocytes subsets (classical, intermediate, non-classical), the expression of TLR4 and CCR2 chemokine receptor (CD192) and cytokines (TNFA, IL6, IL10) secretion by monocytes subsets. In addition, sCD14 serum levels were evaluated by ELISA.

Results

We observed increased percentage of CD14+ cells, decreased frequency of intermediate monocytes (CD14+CD16+), and lower percentage of circulating monocytes (classical, intermediate and non-classical) that express TLR4 in the diabetic group compared to controls. Soluble CD14+ serum levels were higher in GDM patients compared to controls. There were no differences in the expression of the CCR2 chemokine receptor and cytokines (TNFA, IL6 and IL10) secretion between the studied groups.

Conclusions

Our results demonstrated that GDM patients present impaired monocyte profile in the peripheral blood, suggesting that these cells are involved in GDM physiopathology.

Introduction

Gestational Diabetes Mellitus (GDM), the main endocrine pathology in pregnancy, is associated with maternal and fetal complications, long term consequences such as type 2 diabetes mellitus (T2DM), and obesity [1], [2]. GDM is known as an inflammatory and insulin resistance (IR) condition [3], [4]. Although its physiopathology remains unclear, it is well known that innate immune factors and mechanisms are involved in the development of GDM [5], [6].

Monocytes are the most important cells of the innate system present in the peripheral blood. It is a heterogeneous population, which has been grouped into three subsets according to the expression of patterns in the lipopolysaccharide receptor (CD14) and the Fcc-III receptor (CD16) [7]. “Classical monocytes”, characterized by high expression of CD14 and lack of CD16 (CD14+CD16), represent 90% to 95% of circulating monocytes, and carry out important phagocytic activity. “Non-classical monocytes” (approximately 5% of the monocytes) express low CD14 and positive CD16 (CD14+CD16++), whereas “intermediate monocytes” (approximately 5% of the monocytes) are characterized by high CD14 and low CD16 (CD14+CD16+) expression [7]. These two small subgroups exhibit different chemokine receptors and act mainly as inflammatory effectors, producing cytokines such as tumor necrosis factor-A (TNFA) and interleukin 1 (IL1). [8].

Toll-like receptors (TLRs) that are mainly expressed in monocytes are critical modulators of the innate and inflammatory response. One of the most studied TLRs is TLR4, the receptor for lipopolysaccharide (LPS) from Gram-negative bacteria, which induces the release of proinflammatory cytokines, and may thereby lead to tissue damage [9]. The interaction of LPS and TLR4 induces the secretion of proinflammatory cytokines by macrophages [10]. In its soluble form (sCD14), the CD14 receptor may interact with LPS, inhibiting the activation of TLR4, and thus indirectly modulating inflammation [11].

Another parameter that has been analyzed is the expression of chemokines and their receptor, due to their critical effect on monocyte migration. Classical monocytes express higher levels of CCR2 and migrate more efficiently to reaction, in comparison to other monocyte subsets. On the other hand, CX3CR1 is expressed highly on intermediate monocytes and seems to support the migration of this specific subtype [8].

Cytokines are also involved in the development of inflammation and IR during pregnancy, especially in women who develop GDM. Different studies have evaluated its production by monocytes in overweight and diabetic patients with controversial results [12]. The unstimulated monocytes of healthy pregnant women have been shown to secrete more [13], less [14], or similar [15] cytokines levels in comparison to the monocytes of non-pregnant women. The type of stimulus may also affect the secretion of cytokines by monocytes. According to Faas et al., after stimulation with LPS, the production of cytokines by monocytes in pregnant women seems to be lower than by monocytes in non-pregnant ones [14].

Several studies have shown that qualitative and quantitative changes in circulating immune cells are usually observed during pregnancy. Some researchers have reported that leukocytosis might be observed in T2DM patients and in pregnant women before GDM was established [16], [17]. Regarding monocyte subpopulations, Melbert et al. have shown that the number of circulating classical monocytes is lower, whereas intermediate monocytes are increased in healthy pregnant women [18]. An increased percentage of the intermediate subset in different inflammatory conditions has also been demonstrated, including in certain obstetric pathologies, such as preeclampsia and preterm birth [19]. Few studies have assessed monocytes in the peripheral blood of GDM patients. However, to the best of our knowledge, the changes in the absolute count of different monocyte subsets in women with GDM have not been studied. Therefore, the purpose of this study was to characterize the profile of circulating monocytes in GDM patients.

Section snippets

Material and methods

This was a case-control study. The patients were recruited from the antenatal care clinic at the Obstetrics Department of the Universidade Federal de São Paulo, São Paulo, Brazil, between 2015 and 2017. The research protocol was approved by the university’s ethics committee and written informed consent was obtained from all participants. The study group was comprised of 18 patients diagnosed with GDM in accordance with the criteria recommended by the International Association for Diabetes and

Results

The main characteristics of the participants are presented on Table 1. There was no significant difference in gestational age at sample collection between glucose-tolerant pregnant women (controls) and GDM groups. However, there were significant differences in ethnicity, pre-pregnancy body mass index (BMI), and maternal age between the two groups. As expected, there were also significant differences in HbA1c levels and glucose concentrations between the groups at the time of sampling. All the

Discussion

Gestational Diabetes Mellitus has been considered an inflammatory condition involving different immune factors in its development. To clarify the role of innate immune cells, the goal of this study was to assess the profile of monocytes in the peripheral blood of GDM patients and compare it to that observed in glucose-tolerant pregnant women (controls).

In accordance with our hypothesis, the monocyte profile seems to be altered in GDM patients compared to that observed in glucose-tolerant

Conclusions

Taken together, our results suggest that women with GDM present an impaired monocyte profile in the peripheral blood, thus supporting the hypothesis that monocytes are involved in the physiopathology of GDM. Our goal is to continue the research by analyzing the functional characteristics of monocytes, including the quantitative evaluation of the cytokines and chemokines produced by these cells when submitted to different conditions.

Declaration of interest

There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Grant Nos. #4,44,174/2014-1 and #3,03,306/2016-5). The funding source had no involvement with the study design, the collection, analysis and interpretation of data, and in the writing of the report and in the decision to submit the article for publication.

Author contributions

S.D. and C.T.C.N. designed the study; A.G.S.A. and T.F.L. performed the laboratory tests; A.G.S.A., T.F.L., R.V.C.G. and E.O. collected the data; S.D. and R.M. collaborated in patient recruitment and made clinical contributions; A.S.G.A. and T.F.L analyzed the data and performed the statistical analysis; S.D. and A.G.S.A. wrote the manuscript; all authors approved the final version of the manuscript.

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