Elevated iron status and risk of gestational diabetes mellitus: A systematic review and meta-analysis

Dietary management of gestational diabetes: A review

Gestational diabetes mellitus (GDM) is a common condition in pregnant women that can affect the health of both the mother and the fetus. A healthy diet reduces the risk of GDM, while on the contrary, an unhealthy diet can increase the risk of developing GDM. Dietary interventions remain an important way to control GDM at this time. However, real-life diets are complex and varied, and the effect of these diets on gestational diabetes is unknown. This article summarizes research related to dietary control of GDM. Hopefully, this will help with dietary interventions for people with GDM.

Scientific opinion on the tolerable upper intake level for iron

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for iron. Systematic reviews were conducted to identify evidence regarding high iron intakes and risk of chronic diseases, adverse gastrointestinal effects and adverse effects of iron supplementation in infancy, young childhood and pregnancy. It is established that systemic iron overload leads to organ toxicity, but no UL could be established. The only indicator for which a dose-response could be established was black stools, which reflect the presence of large amounts of unabsorbed iron in the gut. This is a conservative endpoint among the chain of events that may lead to systemic iron overload but is not adverse per se. Based on interventions in which black stools did not occur at supplemental iron intakes of 20-25 mg/day (added to a background intake of 15 mg/day), a safe level of intake for iron of 40 mg/day for adults (including pregnant and lactating women) was established. Using allometric scaling (body weight0.75), this value was scaled down to children and adolescents and safe levels of intakes between 10 mg/day (1-3 years) and 35 mg/day (15-17 years) were derived. For infants 7-11 months of age who have a higher iron requirement than young children, allometric scaling was applied to the supplemental iron intakes (i.e. 25 mg/day) and resulted in a safe level of supplemental iron intake of 5 mg/day. This value was extended to 4-6 month-old infants and refers to iron intakes from fortified foods and food supplements, not from infant and follow-on formulae. The application of the safe level of intake is more limited than a UL because the intake level at which the risk of adverse effects starts to increase is not defined.

Bioinformatics Prediction and Experimental Validation of the Role of Macrophage Polarization and Ferroptosis in Gestational Diabetes Mellitus

Purpose

Gestational diabetes mellitus (GDM) is a common metabolic disorder during pregnancy that is associated with placental inflammation and adverse pregnancy outcomes. However, the mechanisms of inflammation in GDM are still unclear.

Methods

Bulk transcriptome, single-cell transcriptome, clinical information, and samples were collected from GSE154414, GSE70493, GSE173193 and a retrospective cohort. Bioinformatics prediction was used to explore the mechanisms of placental inflammation, and multiplex immunofluorescence was used to validate the results.

Results

First, we found that GDM is characterized by low-grade inflammation and is linked to several adverse pregnancy outcomes, as supported by our collected clinical data. Additionally, we identified ten hub genes (FCGR3B, CXCR1, MMP9, ITGAX, CCL5, GZMB, S100A8, LCN2, TGFB1, and LTF) as potential therapy targets and confirmed the binding of corresponding predictive therapeutic agents by molecular docking. Transcriptome sequencing analysis has shown that macrophages are primarily responsible for the emergence of placental inflammation, and that M1 macrophage polarization increased while M2 macrophage polarization decreased in GDM when compared to the control sample. Multiplex immunofluorescence staining of CD68, CD80, and ACSL4 was performed and suggested that ferroptosis of macrophages may contribute to placental inflammation in GDM.

Conclusion

In conclusion, our findings provide a better understanding of the mechanisms of inflammation in GDM and suggest potential therapeutic targets for this condition.

Iron salt supplementation during gestation and gestational diabetes mellitus

OBJETIVE

To evaluate the association between the use of iron salts during the first two trimesters of gestation in non-anemic women and the development of gestational diabetes mellitus.

METHODS

The study used maternal data from the 2015 Pelotas Birth Cohort. All non-anemic women at the 24th week of gestation (n = 2,463) were eligible for this study. Gestational diabetes mellitus was self-reported by women. Crude and adjusted logistic regression were performed considering level of significance = 0.05.

RESULTS

Among the women studied, 69.7% were exposed to prophylactic iron supplementation in the first two trimesters of gestation. The prevalence of gestational diabetes mellitus among those exposed was 8.7% (95%CI: 7.4–10.1) and 9.3% (95%CI: 7.4–11.6) among those who were not exposed. Iron supplementation was not associated with increased risk of gestational diabetes mellitus in crude (OR = 0.9; 95%CI: 0,7–1,3) and adjusted analysis (OR = 1.1; 95%CI :0,8–1,6).

CONCLUSIONS

The results suggest that routine iron use in non-anemic pregnant women does not increase the risk of developing gestational diabetes. This evidence supports the existing national and international guidelines, in which prophylactic iron supplementation is recommended for all pregnant women as soon as they initiate antenatal care in order to prevent iron deficiency anemia.

Hemoglobin at the first visit of pregnancy and developing gestational diabetes mellitus: Results of a prospective registry cohort study

BACKGROUND AND AIM

Gestational diabetes mellitus (GDM) is associated with a considerable risk of diabetes in the future. Few studies focused on the association between hemoglobin levels and developing gestational diabetes. This study aimed to determine the association of hemoglobin in early pregnancy and developing gestational diabetes mellitus.

METHODS

A prospective registry cohort study was designed for the recall of women with gestational diabetes mellitus. The registry was implemented in the health centers of Ahvaz City in 2019. Biological and clinical assessments were done, and interviewer-administered questionnaires were used to collect data on socio-demographic Features, medical and obstetric history, and risk factors of GDM. SPSS used for data analysis. The optimal hemoglobin cut-off point, its sensitivity, and specificity for the prediction of GDM were estimated using ROC analysis.

RESULTS

The prevalence of anemia was 17.1% in pregnant women (8.1% in women with gestational diabetes versus %24.2% in the healthy group, p < 0.001). The hemoglobin mean in women with GDM was significantly higher than in healthy women (P < 0.001). Hemoglobin at the first visit was significantly associated with a greater risk of gestational diabetes (OR = 3.80, 95% CI: 3.05-4.74). The area under the curve (AUC) was 0.76 (95% CI 0.73-79), and the optimal cut-off point for hemoglobin was 11.90 g/dL, with a sensitivity of 75% and a specificity of 68%. Women with a higher hemoglobin level had a 3.8- more risk of developing GDM.

CONCLUSION

Measurement of hemoglobin can be a relatively good tool for predicting gestational diabetes in the first months of pregnancy. The combination of hemoglobin with fasting blood sugar and BMI improves the predictive value for gestational diabetes incidence.

Maternal hemoglobin change from early pregnancy to second trimester is associated with risk of gestational diabetes mellitus: a retrospective cohort study

Introduction

The accrual of iron that is reflected in high maternal hemoglobin (Hb) status is increasingly recognized as a risk factor for gestational diabetes mellitus (GDM). Changes in maternal Hb level could also implicate glycemic status in pregnancy. This study aimed to determine the associations between maternal Hb levels and their changes with GDM.

Methods

In this retrospective cohort study, a total of 1,315 antenatal records of mothers with singleton pregnancies from eight health clinics of a district in the northern region of Peninsular Malaysia who delivered between 1st January 2016-31st December 2017 were analyzed. Data extracted from the records were socio-demographic, anthropometric, obstetrical, and clinical data. Hb levels were extracted at booking (<14 weeks) and second trimester (14-28 weeks). Change in Hb was determined by subtracting the Hb level in the second trimester from the booking Hb level and was categorized as decreased, unchanged, and increased Hb. The associations between maternal Hb levels and their changes with GDM risk were analyzed using multiple regression, adjusting for covariates in four different models. Model 1: maternal age and height. Model 2: covariates of Model 1 added with parity, history of GDM, and family history of diabetes. Model 3: covariates of Model 2 added with iron supplementation at booking. Model 4: covariates of Model 3 added with Hb level at booking.

Results and Discussions

Unchanged Hb level from booking to second trimester was significantly associated with GDM risk in Model 1 (AOR: 2.55; 95% CI: 1.20, 5.44; p < 0.05), Model 2 (AOR: 2.45, 95% CI: 1.13, 5.34; p < 0.05) Model 3 (AOR: 2.42; 95% CI: 1.11, 5.27; p < 0.05), and Model 4 (AOR: 2.51; 95% CI: 1.15, 5.49; p < 0.05). No significant associations were observed between maternal Hb levels and GDM in the study.

Conclusion

Unchanged Hb levels from the booking (<14 weeks of gestation) to the second trimester (14-28 weeks) increased GDM risk. Further investigation is warranted to evaluate the associations between changes in maternal Hb and GDM risk and to identify potential factors influencing this relationship.

Iron deficiency and iron overload in men and woman of reproductive age, and pregnant women

Iron is an essential micronutrient for human biology and health, but high iron levels can be dangerous. Both iron deficiency and iron overload have been linked to reproductive health. This review summarizes the effects of iron deficiency and iron overload on men of reproductive age, women of reproductive age, and pregnant women. In addition, appropriate iron levels and the need for iron and nutritional supplements at different stages of life and pregnancy are discussed. In general, men should be aware of the risk of iron overload at any stage of life; women should take appropriate iron supplements before menopause; postmenopausal women should pay attention to the risk of iron overload; and pregnant women should receive reasonable iron supplementation in middle and late pregnancy. By summarizing evidence on the relationship between iron and reproductive health, this review aims to promote the development of strategies to optimize reproductive capacity from the perspective of nutrition. However, additional detailed experimental investigations and clinical studies are needed to assess the underlying causes and mechanisms of the observed associations between iron and reproductive health.

Iron Supplementation in Pregnancy and Risk of Gestational Diabetes: A Narrative Review

Pregnant women frequently supplement their diets with iron to treat any cryptic anemia, on the assumption that if anemia is not present, there will be no negative consequences. However, in women who are already iron-replete, it has been suggested that this can lead to iron overload and an increased risk of certain pregnancy complications. One such complication is gestational diabetes. Fourteen clinical trials, case-control or cohort studies (found using Pubmed/Scopus/Web of Science) have investigated links between iron supplementation in pregnancy and risk of gestational diabetes, several of them finding significant associations with increased risk. Potential mechanisms include increased oxidative stress leading to insulin resistance and inadequate compensatory insulin secretion. Current evidence suggests that dietary supplementation with iron in pregnancy may increase a pregnant woman's chance of developing gestational diabetes, although available evidence is somewhat contradictory, and the magnitude of any increased risk appears relatively small. Meta-analyses have suggested the presence of significant heterogeneity in results between studies, urging a degree of caution in interpreting these results. It is currently suggested that advice to pregnant women about whether to supplement their diets with iron or not should consider both their current iron status and their other established risk factors for gestational diabetes.

Iron Salts, High Levels of Hemoglobin and Ferritin in Pregnancy, and Development of Gestational Diabetes: A Systematic Review

OBJECTIVE

 The aim of this study was to systematically review literature on the use of iron supplements (not including iron derived from diet), increased levels of hemoglobin and/or ferritin, and the risk of developing gestational diabetes mellitus (GDM).

DATA SOURCE

 The following databases were searched, from the study's inception to April 2021: PUBMED, Cochrane, Web of Science, Scopus, Embase, Cinahl and Lilacs.

SELECTION OF STUDIES

 A total of 6,956 titles and abstracts were reviewed, 9 of which met the final inclusion criteria, with 7,560 women in total.

DATA COLLECTION

 Data extraction was performed by two independent reviewers and disagreements were resolved by a third researcher.

DATA SYNTHESIS

 Methodological quality in controlled trials were assessed according to the Cochrane Collaboration tools (ROB-2 and ROBINS-1) and for the observational studies, the National Institutes of Health's (NIH) quality assessment tool was used. Among the 5 observational studies, women with a higher hemoglobin or ferritin level were more likely to develop GDM when compared with those with lower levels of these parameters. Among the 3 randomized clinical trials, none found a significant difference in the incidence of GDM among women in the intervention and control groups. However, we identified many risks of bias and great methodological differences among them.

CONCLUSION

 Based on the studies included in this review, and due to the important methodological problems pointed out, more studies of good methodological quality are needed to better establish the association between iron supplementation and GDM.

Hemoglobin concentration and iron supplement during pregnancy were associated with an increased risk of gestational diabetes mellitus

BACKGROUND

Hemoglobin (Hb) measurement is a conventional test during perinatal visits. Hb concentration is related to iron supplement. However, studies focusing on Hb levels, iron supplement, and pregnancy outcomes are scarce. This study aimed to determine whether Hb levels and iron supplement were associated with the risk of gestational diabetes mellitus (GDM).

METHODS

A running hospital-based cohort was conducted from August, 2011. The demographic data and medical information were collected individually through questionnaires and patient medical records. Multiple linear regression was applied for the association between Hb levels, iron supplement, and blood glucose. Multiple logistic regression was used for evaluating odds ratios between Hb levels, iron supplement, and GDM.

RESULTS

Hb levels during first (T1) and second trimester (T2) of pregnancy were significantly and positively associated with blood glucose and GDM risk. After adjusting for age, prepregnancy body mass index, and other risk factors, pregnant women with Hb ≥ 11 g/dL and iron supplement had higher postprandial blood glucose at 1 hour (Hb ≥ 11 g/dL in T2 and iron supplement in T1: β = 0.860，P = <0.001; Hb ≥ 11 g/dL in T2 and iron supplement in T2: β = 0.960，P < 0.001; Hb ≥ 11 g/dL in T1 and iron supplement in T2: β = 1.133, P = 0.033) and GDM risks (odds ratio [OR] = 1.53, 95% confidence interval [CI]: 1.05-2.24; OR = 1.92, 95% CI: 1.13-3.35; OR = 2.15, 95% CI: 1.07-4.34, respectively), compared with those with Hb < 11 g/dL and without iron supplement.

CONCLUSION

High Hb concentration and iron supplements without anemia increased postprandial blood glucose and risks for GDM. It indicates that pregnant women with good Hb levels should not be advised to take iron supplements during pregnancy.

tRNA Biology in the Pathogenesis of Diabetes: Role of Genetic and Environmental Factors

The global rise in type 2 diabetes results from a combination of genetic predisposition with environmental assaults that negatively affect insulin action in peripheral tissues and impair pancreatic β-cell function and survival. Nongenetic heritability of metabolic traits may be an important contributor to the diabetes epidemic. Transfer RNAs (tRNAs) are noncoding RNA molecules that play a crucial role in protein synthesis. tRNAs also have noncanonical functions through which they control a variety of biological processes. Genetic and environmental effects on tRNAs have emerged as novel contributors to the pathogenesis of diabetes. Indeed, altered tRNA aminoacylation, modification, and fragmentation are associated with β-cell failure, obesity, and insulin resistance. Moreover, diet-induced tRNA fragments have been linked with intergenerational inheritance of metabolic traits. Here, we provide a comprehensive review of how perturbations in tRNA biology play a role in the pathogenesis of monogenic and type 2 diabetes.

Prepregnancy hemoglobin levels and gestational diabetes mellitus in pregnancy

AIM

To identify the influence of prepregnancy hemoglobin levels on gestational diabetes mellitus.

MATERIALS AND METHODS

Korean women who had given birth between January 1st, 2006 and December 31st, 2015 and who had undergone a biannual national health screening examination within 6 months prior to pregnancy were enrolled. Subjects were divided into three groups according to their hemoglobin levels. Multivariate logistic regression analysis was used to estimate the adjusted odds ratio and 95% confidence interval for GDM.

RESULTS

Of the 366,122 participants, GDM developed in 14,799 (4%) women. More specifically, GDM developed in 3.6% of women with prepregnancy anemia (hemoglobin < 11 g/dL), 3.57% with normal hemoglobin levels, and 4.47% with hemoglobin levels higher than 13 g/dL. We did not find any association between prepregnancy anemia and the risk of developing GDM (OR 1.002 [95% CI 0.90-1.11]). After adjusting for potential confounding factors (adjusted odds ratio 1.41; 95% CI 1.29-1.54), high hemoglobin levels were associated with insulin requiring GDM.

CONCLUSIONS

Our study identified an association between high prepregnancy hemoglobin levels and GDM risk.

Reliability of glycosylated hemoglobin in the diagnosis of gestational diabetes mellitus

Background

Oral glucose tolerance test (OGTT) performed at 24‐28 weeks gestation is the current recommended method to the diagnosis of gestational diabetes mellitus (GDM). Many recent studies investigating HbA1c in detecting GDM yield different results. There are no published data on HbA1c in the diagnosis of GDM in Sub‐Saharan countries including Sudan.

Methods

A cross‐sectional study was carried out at the antenatal care of Saad Abuelela Maternity Hospital, Khartoum, Sudan during the period from February to November 2018 to assess the reliability of HbA1c in the diagnosis of GDM. GDM was diagnosed according to the International Association of Diabetes and Pregnancy Study Groups using a 75‐g oral glucose tolerance test.

Results

Three hundred and forty‐eight women were enrolled. The mean (SD) of the age, gravidity, and gestational age of the enrolled women were 27.8 (5.6) years, 2.36 (2.2) and 26.26 (2.43) weeks, respectively. Sixty‐eight women (19.5%) had GDM. A poor productively for HbA1c in diagnosis GDM was shown (AUC = 0.62, 95% CI = 0.55‐0.69). At HbA1c level of 4.150%, the sensitivity and specificity of the diagnosis for GDM were 76.51% and 37.85%, respectively. At HbA1c level of 5.850%, the sensitivity and specificity of the diagnosis for GDM were 13.24% and 91.43%, respectively. While there was no significant (Spearman) correlation between fasting blood glucose and HbA1c, there were significant correlations between HbA1c and OGTT 1 and 2 hours of OGTT.

Conclusion

In this study, HbA1c has a poor reliability, insufficient sensitivity or specificity for use to diagnose GDM.

High haemoglobin levels in early pregnancy and gestational diabetes mellitus among Sudanese women

A longitudinal study was carried out to investigate the prevalence and risk factors (including haemoglobin levels) for gestational diabetes mellitus (GDM) in Khartoum, Sudan. The study was carried out at Saad Abuelela Hospital (Khartoum, Sudan) during February to November 2017. Pregnant women in early pregnancy (gestational age <14 weeks) were enrolled in the study. The detailed medical and obstetrics history was recorded for each participant using a questionnaire. The women were then followed up, where a 75-g oral glucose tolerance test was performed at 24 - 28 weeks of gestation. Of 290 women, 259 (89.3%) completed the follow-up. The mean (standard deviation [SD]) of the age, gravidity and gestational age at enrolment were 28.02 (5.7) years, 2.37 (2.42) and 10.86 (2.63) weeks, respectively. Forty-eight women (18.5%) had GDM. Binary regression showed that while age, parity, residence, education and body mass index (BMI) were not associated with GDM, a high haemoglobin level was the only factor associated with GDM (OR = 1.52, 95% confidence interval [CI] = 1.07 - 2.16, p = .019). Women with haemoglobin > 10.8 g/dl were at a higher risk of GDM (OR = 2.52, 95% CI = 1.02 - 6.27, p = .044). There is a high prevalence of GDM, especially among women with high haemoglobin levels.Impact statementWhat is already known on this subject? Gestational diabetes mellitus (GDM) is one of the most common complications during pregnancy, contributing significantly to maternal, perinatal morbidity and mortality and can lead to adverse consequences for the health of both mother and offspring later in life. The rate of GDM varies with the various settings and populations, and a prevalence of 1-14% has been reported depending on the population studied. High haemoglobin levels were recently reported to be associated with GDM.What do the results of this study add? There is a high prevalence of GDM in Khartoum, Sudan, especially among women with high haemoglobin levels in early pregnancy.What are the implications of these findings for clinical practice and/or further research? Haemoglobin levels could be used as reliable markers to detect GDM. These markers could be used in the prevention of GDM.

Association between Serum Ferritin and Blood Lipids: Influence of Diabetes and hs-CRP Levels

This study is aimed at exploring the relationship between serum ferritin and blood lipids and the influence of diabetes and different hs-CRP levels. A total of 8163 subjects were analyzed. Participators were classified according to serum ferritin, diabetes, and two hs-CRP levels. Blood lipids were determined using standardized methods and conditions. Except for HDL-C, there was a significant increase in blood lipids in the progressive ferritin group with normal hs-CRP levels (P < 0.05). But HDL-C was just the opposite (P < 0.0001). In nondiabetic patients, TG, TC, and LDL-C were significantly elevated in the progressive ferritin group (P < 0.05). And, HDL-C was just the opposite (P < 0.05). The generalized linear model and the parsimonious model showed that serum TG was positively correlated with ferritin, and LDL-C was negatively correlated with ferritin (P < 0.05). But the correlation between LDL-C and ferritin was broken (P > 0.05). After a sufficient adjustment, there was a positive correlation between serum TG and ferritin and a negative correlation between LDL-C and ferritin. Nonetheless, a negative correlation between LDL-C and ferritin is influenced by diabetes frailly. And, there was no change of relationship between lipids and ferritin in different hs-CRP levels. We found a real relationship between ferritin and lipids after sufficient adjustment for confounders.

Effects of prophylactic iron supplementation on outcome of nonanemic pregnant women: A non-randomized clinical trial

BACKGROUND

The aim of the current study was to investigate the effects of prophylactic iron supplementation on the pregnancy outcome of nonanemic pregnant women in a sample of Iranian population.

METHODS

This non-randomized clinical trial was conducted during a 2-year period in obstetrics clinics of Shiraz, southern Iran. We included a sample of singleton pregnancies registered in our clinics. Those with comorbidities were excluded. Serum ferritin was measured at baseline and participants were classified accordingly: those with normal serum ferritin levels (≥30 µg/dL) who received standard prophylactic iron supplementation during the pregnancy (Group 1); those who had minor thalassemia and elevated serum ferritin levels (≥30 µg/dL) who did not receive prophylactic iron supplementation or those with normal ferritin levels (≥30 µg/dL) who refused to receive iron supplementation due to gastrointestinal upset (Group 2); and those with iron deficiency anemia with low serum ferritin levels (<30 µg/dL) who received standard iron supplementation during pregnancy (Group 3). All the participants were followed to the delivery and maternal and neonatal outcomes were recorded and compared between three study groups.

RESULTS

Overall we included 30 pregnant women in each group with mean age of the participants was 28.66 ± 6.02 years. There was no significant difference between three study groups regarding gestational age at delivery (p = 0.250), birthweight (p = 0.893), Apgar at 1 (p = 0.532) and 5 (p = 0.590) minutes, and route of delivery (p = 0.590). The overall rate of maternal complication of the pregnancy was comparable between the three study groups (p = 0.188). However, those in group 1, had significantly higher rate of gestational diabetes mellitus (GDM) when compared to other two groups (p = 0.038).

CONCLUSION

Prophylactic iron supplementation in pregnant women with normal ferritin levels is associated with increased risk of GDM. Other pregnancy and neonatal outcomes are not affected by the prophylactic iron supplementation.

Risk factors for gestational diabetes: An umbrella review of meta-analyses of observational studies

BACKGROUND/OBJECTIVE

Gestational diabetes mellitus (GDM) is a common pregnancy complication, with complex disease mechanisms, and several risk factors may contribute to its onset. We performed an umbrella review to summarize the evidence from meta-analyses of observational studies on risk factors associated with GDM, evaluate whether there are indications of biases in this literature and identify which of the previously reported associations are supported by convincing evidence.

METHODS

We searched PubMed and ISI Web of Science from inception to December 2018 to identify meta-analyses examining associations between putative risk factors for GDM. For each meta-analysis we estimated the summary effect size, the 95% confidence interval, the 95% prediction interval, the between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias.

RESULTS

Thirty eligible meta-analyses were identified, providing data on 61 associations. Fifty (82%) associations had nominally statistically significant findings (P<0.05), while only 15 (25%) were significant at P<10-6 under the random-effects model. Only four risk factors presented convincing evidence:, low vs. normal BMI (cohort studies), BMI ~30-35 kg/m2 vs. normal BMI, BMI >35 kg/m2 vs. normal BMI, and hypothyroidism.

CONCLUSIONS

The compilation of results from synthesis of observational studies suggests that increased BMI and hypothyroidism show the strongest consistent evidence for an association with GDM. Diet and lifestyle modifications in pregnancy should be tested in large randomized trials. Our findings suggest that women with known thyroid disease may be offered screening for GDM earlier in pregnancy.

Role of ethnicity and environment on lifestyle and cardiometabolic profile in the Native American Mapuche population: Protocol for a systematic review and meta-analysis

INTRODUCTION

Cardiometabolic risk factors contribute to increase the incidence of some of the most widespread noncommunicable diseases today. The propensity to present an elevated cardiometabolic risk appears to especially affect non-Caucasians ethnic groups, such as the Native American Mapuche population. In addition, urbanization process has also a great impact on lifestyle and cardiometabolic profile. Therefore, a systematic review and meta-analysis will be conducted to summarize the relevant evidence regarding lifestyle and cardiometabolic profile in Mapuche population, and to assess the role of the ethnicity and the urbanization process on the lifestyle and cardiometabolic profile in Mapuche people with respect to European descendants.

METHODS

A comprehensive search until 2019 will be performed using PubMed/MEDLINE, SciELO, Web of Science and Scopus. Observational studies, carried out in general population of Mapuche ethnicity living in rural and urban areas, with data of lifestyle and/or cardiometabolic profile, will be selected. A qualitative summary, as well as meta-analyzes when possible, will be done to present the information. Random effects meta-analyzes will be performed using the generic inverse variance method. Pooled effect size will be expressed as mean difference with 95% confidence intervals. Heterogeneity will be assessed using the Cochran Q-statistic and the I statistic. Stratified analyzes, meta-regressions, and sensitivity analyzes will be performed to evaluate potential sources of heterogeneity. In addition, random effects meta-regressions and stratified analyzes will also be used to examine the impact of covariates on the effect size estimated. Publication bias will be investigated using Egger and Begg test, and risk of bias will be assessed using the Research Triangle Institute Item Bank (RTI-IB). Finally, the quality of evidence will be evaluated through the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines.

RESULTS

The results of meta-analyzes will provide important information about differences in lifestyle and cardiometabolic profile between Mapuche people and European descendants, as well as between Mapuche people living in urban and rural areas.

CONCLUSION

This systematic review and meta-analysis will be helpful to obtain a more reliable understanding of lifestyle and cardiometabolic profile in Mapuche population compared to European descendants, and the impact of the transition from rural to urban areas in this ethnic group.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.

Correlation between plasma ferritin level and gestational diabetes mellitus and its impact on fetal macrosomia

Aims/Introduction

To explore the relationship between plasma iron levels and gestational diabetes mellitus, as well as its impact on macrosomia.

Materials and Methods

We retrospectively compared ferritin level and other characteristics between pregnant women with gestational diabetes mellitus (GDM) and pregnant women without GDM. The correlation between the levels of plasma ferritin, glucose and hemoglobin was explored. Meanwhile, we assessed the risk factors of macrosomia. Furthermore, we explored the relationship between ferritin level and the incidence of macrosomia.

Results

A total of 793 pregnant women were enrolled in the present study, of which 92 pregnant women had GDM and 701 pregnant women were healthy. Meanwhile, 51 pregnant women gave birth to infants with macrosomia and another 742 women had normal infants. Compared with non‐GDM women, pregnant women with GDM were older, with higher pre‐pregnancy body mass index, plasma ferritin, fasting plasma glucose, 1‐h postprandial glucose, 2‐h plasma glucose and hemoglobin. In addition, our results showed a significant positive correlation between the levels of ferritin and fasting plasma glucose when ferritin levels were >70 ng/mL. Our results also showed that pre‐pregnancy overweight or obesity, a high concentration of ferritin, as well as abnormal levels of fasting plasma glucose, 1‐h plasma glucose and 2 h plasma glucose were risk factors for macrosomia. Furthermore, as the level of ferritin increased, so did the incidence of macrosomia.

Conclusions

The current study provides evidence that pregnant women with high levels of ferritin might be prone to GDM. In addition, a high level of ferritin might be an independent risk factor for macrosomia. Therefore, the negative effect of iron supplementation in non‐anemic pregnant women might be noteworthy.

Iron Status and Gestational Diabetes-A Meta-Analysis

A meta-analysis of the association of iron overload with gestational diabetes mellitus (GDM) may inform the health debate. We performed a meta-analysis investigating the association of iron biomarkers and dietary iron exposure with GDM. We identified 33 eligible studies (N = 44,110) published in 2001–2017. The standardized mean differences (SMD) in women who had GDM compared to pregnant women without were 0.25 µg/dL (95% CI: 0.001–0.50) for iron, 1.54 ng/mL (0.56–2.53) for ferritin, 1.05% (0.02 to 2.08) for transferrin saturation, and 0.81 g/dL (0.40–1.22) for hemoglobin. Adjusted odds ratio for GDM were 1.58 (95% CI: 1.20–2.08) for ferritin, 1.30 (1.01–1.67) for hemoglobin, and 1.48 (1.29–1.69) for dietary heme intake. We did not find any differences in TIBC or transferrin concentration in women with and without GDM. We also did not find any association of increased transferrin receptor or increased intake of total dietary iron, non-heme iron or supplemental iron, with increased odds ratios for GDM. Considerable heterogeneity was present among the studies (0–99%), but no evidence of publication bias. Accumulating evidence suggests that circulating and dietary iron biomarkers among pregnant women are associated with GDM, but the results should be interpreted with caution due to the high heterogeneity of analyses. Randomized trials investigating the benefits of iron reduction in women at high risk for GDM are warranted.

Maternal and neonatal outcomes related to iron supplementation or iron status: a summary of meta-analyses

BACKGROUND

Iron deficiency is the most abundant nutritional deficiency in the world and is discussed to be associated with adverse pregnancy outcomes. The objective of this review was to perform an umbrella summary of meta-analyses to evaluate the effects and associations of iron supplementation or iron status on maternal and birth/neonatal outcomes.

METHODS

A literature search was conducted on PubMed and Scopus by two reviewers without temporal restriction. Systematic reviews and meta-analyses of studies evaluating (1) the effects of multimicronutrient compared to iron + folic acid supplementations on maternal and birth/neonatal outcomes (2), the association of dietary iron intake or hemoglobin or ferritin status regarding the risk for maternal (gestational diabetes mellitus (GDM)) and birth/neonatal outcomes, and (3) the effects of iron supplementation on pregnancy and birth/neonatal outcomes, were included in this review.

RESULTS

Overall, 16 meta-analyses were included. Multimicronutrient supplements had significant risk reducing effects on low birth weight and small for gestational age compared to iron/folic acid supplements as controls. Furthermore, most of the meta-analyses showed that higher levels of hemoglobin or ferritin increased the risk for GDM. On the other hand, maternal anemia (low hemoglobin levels) was associated with adverse birth/neonatal outcomes. Finally, iron supplementation reduced the risk of iron deficiency and iron deficiency anemia and had some risk reducing effects on low birth weight newborns.

CONCLUSIONS

Our summary of meta-analyses showed that multimicronutrient supplementation had beneficial effects on some neonatal outcomes. Furthermore, higher ferritin levels seem to increase the risk for GDM whereas maternal anemia was associated with adverse birth/neonatal outcomes.

Elevated iron status and risk of gestational diabetes mellitus: A systematic review and meta-analysis

The aim of this systematic review and meta-analysis of observational studies was to assess the relationship between elevated iron status, measured as hemoglobin and ferritin levels, and the risk of gestational diabetes mellitus (GDM). The present study was recorded in PROSPERO (2013:CRD42013005717). The selected studies were identified through a systematic review of scientific literature published in The Cochrane Library and PubMed/MEDLINE databases from their inception until March 10, 2016, in addition to citation tracking and hand-searches. The search strategy of original articles combined several terms for hemoglobin, ferritin, pregnancy, and GDM. OR and 95% CI of the selected studies were used to identify associations between hemoglobin and/or ferritin levels with the risk of GDM. Summary estimates were calculated by combining inverse-variance using fixed-effects model. 2468 abstracts were initially found during the search. Of these, 11 with hemoglobin and/or ferritin data were selected for the meta-analyses. We observed that high hemoglobin (OR = 1.52; 95% CI: 1.23-1.88), as well as ferritin (OR = 2.09; 95% CI: 1.48-2.96) levels were linked to an increased risk of GDM. Low heterogeneity was observed in hemoglobin (I²  = 33.3%, P = 0.151) and ferritin (I²  = 0.7%, P = 0.418) meta-analyses, respectively. Publication bias was not appreciated. High hemoglobin or ferritin levels increase the risk of GDM by more than 50% and more than double, respectively, in the first and third trimester. Therefore, determining of hemoglobin or ferritin concentration in early pregnancy might be a useful tool for recognizing pregnant women at risk of GDM.