Insulin resistance biomarkers in small-for-gestational-age infants born to mothers with gestational diabetes mellitus

Abstract

Objective

Early alterations in glucose homeostasis increase the risk of developing insulin resistance (IR) and obesity later in life. The study aimed to ascertain the peripheral blood levels of hormones that controlling glucose homeostasis and inflammatory factors that are correlated with IR and fetal outcomes in small-for-gestational-age (SGA) infants born to mothers with gestational diabetes mellitus (GDM).

Methods

This cohort study included a total of 90 SGA infants born to mothers with GDM (n = 37) and without GDM (n = 53). At birth, blood levels of glucose, insulin, C-peptide, growth hormone (GH), IGFBP3, lipid profiles, fibrinogen, and hypersensitive C-reactive protein (Hs-CRP) were measured; homeostatic model assessment-IR (HOMA-IR) and ponderal index were calculated. All newborns were followed up to the first year of life.

Results

Compared with SGA infants born to mothers without GDM, the levels of low-density lipoprotein-cholesterol (LDL-C), GH, and fibrinogen were significantly higher in the SGA infants born to mothers with GDM (p = .048, .045, and .04, respectively). However, total cholesterol, HDL-C, and apolipoprotein(a) levels were significantly lower in the SGA infants born to mothers with GDM when compared with those in with SGA infants born to mothers without GDM (all p < .05). Weight gain in the first year was higher in the SGA infants born to mothers with GDM group than SGA infants born to mothers without GDM [6644 g (5991–7572) vs. 6032 g (5529–6932)].

Conclusions

Altered biomarkers of IR were observed among SGA infants born to mothers with GDM, suggesting that these infants were more prone to develop IR after birth.

Keywords:

• Gestational diabetes mellitus
• small-for-gestational-age
• insulin resistance
• biomarker
• inflammatory factors

Introduction

The intrauterine environment of gestational diabetes mellitus (GDM) and low birth weight can influence fetal metabolism and long-term growth. Small-for-gestational-age (SGA) is diagnosed by infants with birth weights below the 10th percentile for gestational age. Many epidemiological studies demonstrated that infants born to mothers with GDM and SGA infants had a higher risk of obesity, hypertension, cardiovascular diseases (CVDs), type 2 diabetes, and other metabolic abnormalities in later life [1,2]. The common pathomechanism of these short-term and long-term complications among infants born to mothers with GDM and SGA infants was the development of insulin resistance (IR) and decreased β-cell function [3,4].

GDM can affect 10–28% of all pregnancies and is a common complication of pregnancy [5]. Most of infants born to mothers with GDM are large-for-gestational-age (LGA) infants, but a recent study found that 7% of infants whose mothers had GDM were SGA infants [6]. Previous study demonstrated that perinatal complications and cardiovascular morbidity during adulthood in SGA infants born to mothers with GDM was higher than SGA born to mothers without GDM [6–8]. So these studies indicated that there might be a severe IR status in SGA infants born to mothers with GDM after birth. However, there were limited data on laboratory diagnosis in IR status of these neonates.

IR is a disorder that the peripheral tissues of the human body that have reduced sensitivity to insulin. To date, many approaches have been proposed to use hormones that controlling glucose homeostasis and the inflammatory factors as useful biomarkers of IR; these biomarkers include insulin-like growth factor-1 (IGF-1), C-peptide, hypersensitive C-reactive protein (Hs-CRP), and fibrinogen, etc. [9]. Numerous studies demonstrated that these biomarkers were associated with fetal growth later in life and important determinants of long-term postnatal metabolic health [10,11]. Therefore, the aim of this study was to evaluate peripheral blood levels of biomarkers and to assess their association with the IR and fetal outcomes in SGA infants born to mothers with GDM.

Materials and methods

This study was approved by the research ethical committee of the Guangzhou Women and Children’s Medical Center of Guangzhou Medical University; prior to beginning the protocol, all participants gave informed, written consent.

We evaluated the biomarkers in peripheral blood for full-term infants referred to the department of neonatology, Guangzhou Women and Children’s Medical Center between 25 November 2017 and 14 April 2019. Inclusion criteria: all newborns were in good general health and given normal feeding, infants birth after a term pregnancy (37–42 weeks’ gestation), preterm were excluded from analysis because Chinese children growth trajectories are inapplicable to these infants. Exclusion criteria included the following: newborns with chromosomal aberrations, congenital or acquired infections, metabolic, and genetic syndromes. The neonates were categorized into two groups: SGA infants born to mothers with GDM and SGA infants born to mothers without GDM. All mothers had undergone 75 g oral glucose tolerance test (OGTT) following the standard protocol at the department of obstetrics. All newborns were followed from birth to the end of the first year of life.

GDM was diagnosed by IADPSG criteria published in 2010 [12]. The diagnostic criteria of SGA: infants with birth weights below the 10th percentile for gestational age. Age- and gender-adjusted SD scores for weight were calculated according to the growth reference standard for Chinese children under 7 years of age [13].

Data on mothers and neonates were obtained from medical records. Anthropometrical measurements were taken by trained personnel, and all anthropometric measurements were performed twice. Measurement devices and standards have been previously described in detail [14,15].

All laboratory parameters were determined in the clinical laboratory and endocrine department of Guangzhou Women and Children’s Medical Center. All laboratory methods were carried out by professional clinical laboratorians and followed the standard operating procedures. After a fasting period averaging 3–4 h, blood samples were collected from neonates hospitalized on the 3–7 d of life. Blood samples for the preparation of EDTA-plasma were placed in ice water, and plasma was separated within 2 h. The samples were centrifuged at 3000 rpm for 10 min and then were stored at −80 °C until analysis. Blood glucose was measured using a glucose-oxidase/peroxidase method (Biosino Bio-Technology and Science Inc, Beijing, China), and the content was determined using a glucose oxidase method (Kabi, Stockholm, Sweden), while insulin, IGF-1, IGF1-BP3, cortisol, growth hormone (GH), and C-peptide were analyzed by radioimmunoassay (Pharmacia. Uppsala, Sweden). Fibrinogen was tested using a Sysmex CS5100 automatic blood coagulation analyzer. Blood lipid: total-cholesterol (t-cholesterol), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein(a), apolipoprotein(b), and triglycerides were tested using a OLYMPUS AU5400 automatic biochemical analyzer. Homeostatic model of assessment of insulin resistance (HOMA-IR) was calculated by the formula: [{insulin (mU/l) × glucose (mmol/I)}/22.5].

Data analysis

Statistical calculations were performed using the computer program SPSS version 22 (IBM SPSS Statistics, IBM Corporation, Chicago, IL). For the statistical analysis, the two-sample Wilcoxon rank-sum (Mann–Whitney test) was used for continuous variables that were described with medians and medians and interquartile ranges percentile (25th–75th); for categorical variables, χ² tests were used and variables were described with percentages. Spearman’s correlation analysis was used to determine the association between inflammatory biomarkers levels and maternal gestational OGTT glucose concentration. The statistical significance level was p < .05.

Results

During the collection of samples, 136 neonates were eligible for the study. Seven infants were excluded because of improper blood sampling, 20 infants were excluded because infants did not the inclusion criteria, and 19 infants were excluded because infants could not be reached in the follow-up. Eventually, the final sample consisted of 90 infants: 37 full-term SGA infants born to mothers with GDM, 53 full-term SGA infants born to mothers without GDM. Groups did not differ significantly in infant gestational age at birth, sex, birth weight, or maternal age (all p > .05) (Tables 1 and 2).

Table 1. Maternal characteristics.

	SGA infants born to mother with GDM (n = 37)	SGA infants born to mother without GDM (n = 53)	p Value
Mother’s age, years	31.0 (27.5–36.0)	31.0 (27.0–34.0)	.45
Pre-partum weight, kg	66.0 (55.0–71.5)	60.0 (56.0–74.6)	.10
Pre-partum BMI, kg/m^2	25.0 (23.2–29.6)	24.8 (21.8–26.6)	.08
Fasting plasma glucose at 24–28 weeks’ gestation, mmol/l	4.67 (4.30–5.23)	4.21 (4.09–4.47)	<.001
1-h post-OGTT glucose at 24–28 weeks’ gestation, mmol/l	10.16 (9.12–10.85)	7.32 (6.04–8.22)	<.001
2-h post-OGTT glucose at 24–28 weeks’ gestation, mmol/l	9.31 (8.62–10.01)	6.42 (5.79–7.52)	<.001
Cesarean section, No (%)	12 (32.4)	20 (37.7)	.61

Data are presented as medians and interquartile ranges [p25–p75].

BMI: body mass index; GDM: gestational diabetes mellitus; OGTT: oral glucose tolerance test; SGA: small-for-gestational-age

Table 2. Comparison of SGA infants born to women with and without GDM at birth and first year of life.

	SGA infants born to mother with GDM (n = 37)	SGA infants born to mother without GDM (n = 53)	p Value
Gestational age, weeks	38.3 (37.1–38.9)	38.0 (37.2–38.8)	.52
Sex (boys/girls)	19:18	27:26	.97
Birth weight, g	2416 (2252–2470)	2437 (2319–2448)	.49
Birth length, cm	46 (45–48)	46 (45–47)	.34
BMI, kg/m^2	11.1 (10.5–11.7)	11.2 (10.7–11.5)	.74
Ponderal index, mean (SD)	2.4 (2.2–2.5)	2.4 (2.3–2.5)	.60
Apgar 1′ score	9.0 (9.0–10.0)	9.5 (9.0–10.0)	.10
Apgar 5′ score	10 (9.0–10.0)	9.8 (10.0–10.0)	.17
Hypoglycemia after birth, No, %	3 (8.1)	1 (1.9)	.16
Blood glucose, mmol/l	4.67 (4.18–5.20)	4.55 (3.90–4.92)	.34
Serum insulin, μIU/ml	5.66 (3.30–8.08)	5.40 (3.44–9.14)	1.00
HOMA-IR^a	1.01 (0.62–1.74)	0.80 (0.43–1.22)	.17
t-cholesterol, mmol/l	1.55 (1.35–2.02)	1.92 (1.44–2.33)	.02
LDL-C, nmol/l	0.74 (0.54–1.01)	0.59 (0.52–0.79)	.048
HDL-C, nmol/l	0.63 (0.48–0.99)	0.84 (0.66–1.02)	.03
Triglycerides, mmol/l	0.49 (0.33–0.56)	0.48 (0.33–0.57)	.78
Apolipoprotein(a), g/l	0.56 (0.50–0.69)	0.75 (0.62–0.87)	<.01
Apolipoprotein(b), g/l	0.23 (0.20–0.31)	0.26 (0.21–0.32)	.24
C-peptide, ng/ml	0.68 (0.39–1.04)	0.62 (0.42–0.84)	.15
IGFBP3, ug/ml	0.84 (0.67–0.98)	0.87 (0.70–1.02)	.52
GH, ng/ml	15.95 (11.80–22.02)	22.4 (17.75–31.40)	.045
TSH, μIU/ml	7.84 (3.27–11.05)	8.64 (5.90–14.13)	.15
Cortisol, nmol/l	234.29 (181.01–422.72)	162.05 (117.26–324.22)	.05
Fibrinogen, mean (SD), g/l	1.74 (1.51–2.20)	1.63 (1.45–1.83)	.04
Hs-CRP, mean (SD), mg/l	0.10 (0.06–0.30)	0.30 (0.07–0.30)	.44
Weight gain in 1st year (g)	6644 (5991–7572)	6032 (5529–6932)	.045
Weight at 1 year (g)	9026 (8152–10,313)	8595 (8048–9598)	.24
BMI at 1 year, kg/m^2	16.9 (16.2–18.0)	16.7 (15.9–17.8)	.67

Data are presented as medians and interquartile ranges in parentheses. The nonparametric two-sample Mann–Whitney test was used for the statistical evaluations.

BMI: body mass index; GDM: gestational diabetes mellitus; GH: growth hormone; HDL-C: high-density lipoprotein cholesterol; HOMA-IR: homeostatic model of assessment of insulin resistance; hs-CRP: high sensitivity C-reactive protein; IGFBP3: insulin-like growth factor binding protein-3; LDL-C: low-density lipoprotein cholesterol; SGA: small-for-gestational-age; TSH: thyroid-stimulating hormone

^aHOMA-IR was calculated by the formula: [{insulin (mU/l) × glucose (mmol/I)}/22.5].

Compared with SGA infants born to mothers without GDM, weight gain in the 1st year was higher in the SGA infants born to mothers with GDM group [6644 g (5991–7572) vs. 6032 g (5529–6932), p < .05] (Table 2).

The biomarkers for IR are given in Table 2. Compared with SGA infants born to mothers without GDM, the levels of LDL-C, GH, and fibrinogen were significantly higher in the SGA infants born to mothers with GDM (p = .048, .045, and .04, respectively). However, total cholesterol, HDL-C, and apolipoprotein(a) levels were significantly lower in the SGA infants born to mothers with GDM when compared with those in with SGA infants born to mothers without GDM (all p < .05). There were no between-group differences in HOMA-IR, serum insulin, triglycerides, apolipoprotein(b), C-peptide, IGFBP3, cortisol, and Hs-CRP between two groups (all p > .05).

The results of spearman’s correlation analysis are shown in Table 3. The results shown that apolipoprotein(a) was significantly correlated with 1 and 2 h post-OGTT glucose level (all p < .05).

Table 3. Correlation coefficient between maternal gestational OGTT glucose concentration and inflammatory biomarkers levels.

	Fasting-OGTT glucose level (n = 90)	1 h post-OGTT glucose levels (n = 90)	2 h post-OGTT glucose level (n = 90)
Hs-CRP	0.82*	0.15*	0.08*
Fibrinogen	0.25	0.79	0.12
t-Cholesterol	0.34	0.09	0.04
HDL-C	0.90	0.16	0.07
LDL-C	0.32	0.53	0.25
Apolipoprotein(a)	0.19	0.005	0.003

Hs-CRP: hypersensitive C-reactive protein; HDL-C: high-density lipoprotein cholesterol; LDL-C: low-density lipoprotein cholesterol; OGTT: oral glucose tolerance test

*p Value.

Discussion

The main findings of this study are that there is a significant difference in biomarkers of IR between SGA infants born to mothers with and without GDM; in our study, higher LDL-C, fibrinogen levels, and lower total cholesterol, HDL-C, apolipoprotein(a) levels have been documented in peripheral blood of SGA infants born to mothers with GDM. These findings provide further evidence that IR present in SGA infants born to mothers with GDM after birth, which is not reported by previously published data.

Our study regarding effects of exposure to GDM on offspring IR are correlated with some previous studies [16–18]. Greater IR or lower insulin sensitivity also has been demonstrated among infants born to mothers with GDM immediately after birth [19–21]. However, children included in all these studies did not include SGA infants born to mothers with GDM.

All the biomarkers we selected were confirmed to be related to IR. In agreement with other studies [22–26], higher LDL-C, fibrinogen levels, and lower total cholesterol, HDL-C, apolipoprotein(a) levels have been documented in peripheral blood of SGA infants born to mothers with GDM, so our findings suggest that increased IR is present in SGA infants born to mothers with GDM. However, there were no between-group differences in HOMA-IR, serum insulin, Triglycerides, apolipoprotein(b), C-peptide, IGFBP3, Cortisol, and in our study. Previous studies [17,20,21] also shown that these biomarkers were significantly correlated with body weight, and groups did not differ significantly in birth weight in our study.

Most SGA children and infants exposure to GDM will experience rapid weight gain after birth, and these infants are likely to have excess central fat and abnormal adipocyte function; these changes in weight gain are positively correlated with obesity during puberty and cardiovascular morbidity in adulthood [15,27,28]. Our findings also supported that infants born to GDM mother suffer from rapid weight gain in the first year of life. Further studies shown that the rapid tempo of weight gain in infants was closely associated with early alterations in hormones that controlling glucose homeostasis and inflammatory factors [29–32]. Therefore, our data raise the intriguing possibility that severe IR in SGA infants born to mothers with GDM at birth may lead to their early life accrual of obesity and cardiovascular morbidity in adulthood; further studies are needed to confirm this hypothesis.

The main strength of our study is that it is the first study to show evidence of an independent effect of intrauterine exposure to maternal GDM on increased IR in SGA infants after birth. However, there are some inherent limitations in our study. A limitation of this study is the limited information about health growth trajectories and outcomes later in life in these newborns. Second, the number of samples was relatively modest.

In conclusion, we found significantly higher levels of plasma LDL-C, fibrinogen and lower levels of total cholesterol, HDL-C, and apolipoprotein(a) in SGA infants born to mothers with GDM. These findings suggest that SGA infants born to mothers with GDM more prone to develop IR after birth. Further studies are needed to investigate the importance of these neonatal findings in growth trajectories and outcomes later in life.

Acknowledgments

The authors express our appreciation to all the study participants and members of the department of neonatology, Guangzhou Women and Children’s Medical Centre. The authors are profoundly grateful to the clinic staff who collaborated with us on this study: Jieyi Liang, Liming Lai, and Dabing Huang.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Science and Technology Planning Project of Guangdong Province under Grant 2016A020215177.