Introduction

The gram-negative bacillus Helicobacter pylori (H. pylori) is the main cause of chronic gastric infection [1]. It is estimated that fifty percent of the world population is infected with H. pylori, with a higher prevalence in the developing countries [2, 3]. It is not only regarded as pathogenic but also a high class carcinogen [4]. While the majority of patients infected with H. pylori tend to develop chronic gastritis, some of them progress to gastric and duodenal ulcers, atrophic gastritis, mucosa-associated lymphoid tissue lymphoma, intestinal metaplasia and gastric cancer [5,6,7].

A number of reports have observed the association between H. pylori and cardiovascular disease and the metabolic syndrome [8, 9]. Furthermore, H. pylori infection has also been indirectly linked to toll-like receptors activation via lipopolysaccharides, leading to metabolic changes culminating in insulin resistance [10]. The association between H. pylori infection and insulin resistance remains controversial. While some studies reported the association between H. pylori infection and insulin resistance [11,12,13,14,15,16], others refuted such a relationship [17,18,19]. Cardaropoli et al. described a strong link between gestational diabetes and H. pylori [20]. Furthermore, few of these studies investigated the association between H. pylori and insulin resistance among pregnant women. Therefore, further research addressing the interplay between H. pylori and insulin resistance is needed.

In Sudan, there is high prevalence of H. pylori among pregnant women regardless of their age and parity [21, 22]. The current study aimed to investigate the association between H. pylori infection and insulin resistance among pregnant Sudanese women.

Main text

A cross-sectional study was conducted at Saad Abuelela hospital, Khartoum, Sudan from the 1st of July 2017 to 31st of January 2018. After signing an informed consent, women with single viable pregnancies were included in the study. Women with twins, diabetes, hypertension, lipid disorders, kidney disease and hemolytic anemia/thalassemia/haemoglobin variants were excluded. Data was collected using a questionnaire that included demographic, obstetrics and clinical data (age, residence, education, occupation, gravidity, parity). The women’s weight and height were measured using standard methods and then their body mass indices were computed.

The glucose tolerance test was performed at 24–28 weeks of gestation. The diagnosis of gestational diabetes mellitus was based on the recommendations of International Association of Diabetes and Pregnancy Study Groups (IADPSG), “fasting blood glucose (FBG) ≥ 92 mg/dl or 1-h blood glucose was ≥ 180 mg/dl and/or 2-h blood glucose ≥ 153 mg/dl, after a 75-g oral glucose load [23].

The glucose level was measured by the glucose oxidase method (Shino-Test Corp. Tokyo, Japan).

The fasting insulin was measured using immunoassay analyzer (AIA 360, Tosoh, Tokyo, Japan. Insulin resistance was calculated using the quantitative insulin sensitivity check index (QUICKI) = 1/[log fasting insulin level (µU/ml) + log fasting glucose level (mg/dl)] [24]. Insulin secretion was indicated by the HOMA of β-cell function (HOMA-β) (%) = 360 × fasting insulin level (µU/ml)/[fasting glucose level (mg/dl) − 63] [25].

Helicobacter pylori IgG antibodies were tested using commercial H. pylori-specific ELISA (Euroimmun, Lu¨beck, Germany). The tests were performed as per the manufacturer’s instructions. Five millilitres of blood were withdrawn in a plain tube, allowed to clot, centrifuged and stored at − 20 °C. Test values of ≥ 1.1 units were regarded as positive. Those ranging between 0.9 and 1.1 units were regarded as weakly positive and those ≤ 0.9 units were considered as negative for H. pylori.

Statistics

SPSS for Windows (version 20.0) was used for data analyses. After checking for normality of distribution of data, the studied variables were described as means, medians and percentages. The difference of medians and proportions were compared between the H. pylori IgG seropositive and IgG seronegative using Mann–Whitney U test and χ2, respectively. All variables were entered into a logistic regression model where the dependent variable was gestational diabetes presence or absence. A P value less than 0.05 was considered statistically significant.

Results

A total number of 166 women were recruited to the study. Respectively, the median age, gravidity and gestational age were 27 years, 2, and 26 weeks. Twenty (12%) of these women had gestational diabetes mellitus, 109 (65.7%) women were H. pylori IgG seropositive. Univariate analysis showed that the mean fasting blood sugar (FBS), the median of first hour post prandial blood sugar (1hpp), the median of the 2 h post prandial blood sugar (2hpp) and the proportion of the H. pylori-positive patients were significantly higher among those who have gestational diabetes mellitus (P value = 0.010, < 0.001, < 0.001, 0.038). The Log HOMA-B% was lower (0.028) respectively. There was no difference between the gestational diabetes mellitus group and the other group in terms of age, education, employment, gravidity, parity, gestational age, BMI, haemoglobin and QUICKI index results. See Table 1.

Table 1 Demographic characteristics of Sudanese pregnant women based on the presence or absence of gestational diabetes mellitus (GDM)
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In multivariate analysis, a higher seropositivity of H. pylori was found to be a risk factor for the development of gestational diabetes mellitus (OR = 2.8, 95% CI 1.1 − 7.5, P = 0.036). See Table 2.

Table 2 Multivariate logistic regression of the predictors of GDM among pregnant Sudanese women
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Discussion

The main finding in the current study was the association between gestational diabetes mellitus and H. pylori IgG seropositivity, where the gestational diabetes group was more likely to be H. pylori IgG seropositive. Wang et al. concluded in their meta-analysis that included 39 studies involving 20,000 subjects that there is an association between H. pylori infection and diabetes mellitus [26]. Cardaropoli et al. found a strong association between GDM and H. pylori among 2820 pregnant women [20]. A large Chinese cohort of more than 30,000 showed an increased association between H. pylori infection and type 2 diabetes mellitus among middle-aged people [27]. In their recent publication of 2016, Bonfigli et al. demonstrated that the elimination of H. pylori infection improved glucose metabolism in patients with type 2 diabetes [28]. On the other hand, a study from Nigeria concluded that type 2 diabetes was not statistically different between H. pylori-infected subjects and controls. However, this study was not powered enough to come out with solid conclusions [29].

In our current study, we found no significant association between the QUICKI index and H. pylori IgG seropositivity among the pregnant Sudanese women. Gerig et al. reported a similar finding among 370 severely obese European subjects from both genders [17]. In the same line, a Lebanese study described no association between H. pylori and insulin resistance among Lebanese adults. In this study, they used stored blood samples of subjects participating in a national non-communicable disease survey [19]. Likewise, no association between H. pylori infection and insulin resistance was documented in a systematic review that included 9 studies with a total number of 2120 subjects [30]. On the other hand, a number of researchers reported the association between H. pylori infection and insulin resistance [11, 12, 18, 31].

The association between H. pylori infection and insulin resistance can be explained by some biological mechanisms. First, changes in glucose metabolism might lead to chemical alterations in the gastric mucosa that facilitates the detection of H. pylori infection [32]. A second explanation is an increase in the proinflammatory cytokines levels in response to H. pylori gastric infection that results in structural alterations to the insulin receptors inhibiting their interaction with insulin [33]. He et al. in their study among mice suggested an interaction between H. pylori and gut microbiota resulting in an increased insulin resistance [34].

Conclusion

The current study concludes that an increased seroprevalence of H. pylori is a risk factor for the development of gestational diabetes mellitus.

Limitations

We acknowledge the need for a larger sample size study.