Serum selenium level and 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.

A prospective cohort study of multimetal exposure and risk of gestational diabetes mellitus

The relationship between co-exposure to multiple metals and gestational diabetes mellitus (GDM) and the mechanisms involved are poorly understood. In this nested case-control study, 228 GDM cases and 456 matched controls were recruited, and biological samples were collected at 12-14 gestational weeks. The urinary concentrations of 10 metals and 8-hydroxydeoxyguanosine (8-OHdG) as well as the serum levels of malondialdehyde (MDA) and advanced glycation end products (AGEs) were determined to assess the association of metals with GDM risk and the mediating effects of oxidative stress. Urinary Ti concentration was significantly and positively associated with the risk of GDM (odds ratio [OR]:1.45, 95 % confidence interval [CI]: 1.12, 1.88), while Mn and Fe were negatively associated with GDM risk (OR: 0.67, 95 % CI: 0.50, 0.91 or OR: 0.61, 95 % CI: 0.47, 0.80, respectively). A significant negative association was observed between Mo and GDM risk, specifically in overweight and obese pregnant women. Bayesian kernel machine regression showed a significant negative joint effect of the mixture of 10 metals on GDM risk. The adjusted restricted cubic spline showed a protective role of Mn and Fe in GDM risk (P < 0.05). A significant negative association was observed between essential metals and GDM risk in quantile g-computation analysis (P < 0.05). Mediation analyses showed a mediating effect of MDA on the association between Ti and GDM risk, with a proportion of 8.7 % (P < 0.05), and significant direct and total effects on Ti, Mn, and Fe. This study identified Ti as a potential risk factor and Mn, Fe, and Mo as potential protective factors against GDM, as well as the mediating effect of lipid oxidation.

Selenium Deficiency Exacerbates Hyperoxia-Induced Lung Injury in Newborn C3H/HeN Mice

Extremely preterm infants are often treated with supraphysiological oxygen, which contributes to the development of bronchopulmonary dysplasia (BPD). These same infants exhibit compromised antioxidant capacities due in part to selenium (Se) deficiency. Se is essential for basal and inducible antioxidant responses. The present study utilized a perinatal Se deficiency (SeD) mouse model to identify the combined effects of newborn hyperoxia exposure and SeD on alveolarization and antioxidant responses, including the identification of affected developmental pathways. Se-sufficient (SeS) and SeD C3H/HeN breeding pairs were generated, and pups were exposed to room air or 85% O2 from birth to 14 d. Survival, antioxidant protein expression, and RNA seq analyses were performed. Greater than 40% mortality was observed in hyperoxia-exposed SeD pups. Surviving SeD pups had greater lung growth deficits than hyperoxia-exposed SeS pups. Gpx2 and 4 protein and Gpx activity were significantly decreased in SeD pups. Nrf2-regulated proteins, Nqo1 and Gclc were increased in SeD pups exposed to hyperoxia. RNA seq revealed significant decreases in the Wnt/β-catenin and Notch pathways. Se is a biologically relevant modulator of perinatal lung development and antioxidant responses, especially in the context of hyperoxia exposure. The RNA seq analyses suggest pathways essential for normal lung development are dysregulated by Se deficiency.

Toxicological effects of selenium nanoparticles in laboratory animals: A review

This paper provides a comprehensive summary of the main toxicological studies conducted on selenium nanoparticles (NPs) using laboratory animals, up until February 28, 2023. A literature search revealed 17 articles describing experimental studies conducted on warm-blooded animals. Despite some uncertainties, in vivo studies have demonstrated that selenium NPs have an adverse effect on laboratory animals, as evidenced by several indicators of general toxic action. These effects include reductions of body mass, changes in hepatotoxicity indices (increased enzyme activity and accumulation of selenium in the liver), and the possibility of impairment of fatty acid, protein, lipid, and carbohydrate metabolisms. However, no specific toxic action attributable solely to selenium has been identified. The LOAEL and NOAEL values are contradictory. The NOAEL was 0.22 mg/kg body weight per day for males and 0.33 mg/kg body weight per day for females, while the LOAEL was assumed to be a dose of 0.05 mg/kg of nanoselenium. This LOAEL value is much higher for rats than for humans. The relationship between the adverse effects of selenium NPs and exposure dose is controversial and presents a wide typological diversity. Further research is needed to clarify the absorption, metabolism, and long-term toxicity of selenium NPs, which is critical to improving the risk assessment of these compounds.

The effect of selenium supplementation in pregnant women on maternal, fetal, and newborn outcomes: a systematic review and meta-analysis

OBJECTIVE

Low maternal selenium status has been associated with poor pregnancy outcomes, including preterm birth. This study aimed to evaluate available evidence of the effects of selenium supplementation during pregnancy on preterm birth and related maternal, fetal, and newborn outcomes.

DATA SOURCES

MEDLINE, Embase, CINAHL, Global Index Medicus, and the Cochrane Library were systematically searched on June 23, 2022, without language or time restrictions.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials and nonrandomized interventional studies were included if they compared the effects of selenium supplementation with placebo or no treatment among pregnant women. The review protocol was registered in the International Prospective Register of Systematic Reviews (identification number: CRD42022383669).

METHODS

For outcomes reported by ≥1 study, a meta-analysis was conducted. Because of the small number of studies and high clinical heterogeneity between populations, random-effects models were used. The Risk of Bias 2 and Risk Of Bias In Non-randomized Studies - of Interventions tools were used to assess study quality, and Grading of Recommendations Assessment, Development, and Evaluation analysis was used to determine the certainty of evidence for each outcome.

RESULTS

Literature searches identified 5105 unique records, and 32 studies met the eligibility criteria. Of note, 11 reports were not included for analysis following research integrity assessments. Moreover, 10 trials and 3 observational studies met the inclusion criteria; however, only 8 trials (1851 women) and 1 prospective cohort study (71,728 women) reported on at least 1 review outcome. Our results could not determine the effect of selenium supplementation on preterm birth at <37 weeks of gestation (relative risk, 0.65; 95% confidence interval, 0.26-1.63; very low certainty evidence) and <34 weeks of gestation (relative risk, 1.05; 95% confidence interval, 0.59-1.44; very low certainty evidence).

CONCLUSION

There is limited evidence on the effects of selenium supplementation during pregnancy. Further trials, with larger sample sizes, more representative populations, and reliable assessment of maternal selenium status at trial entry, are required.

The Association Between the Imbalance of Single-Carbon Nutrients in Early Pregnancy and Gestational Diabetes Mellitus Risk is Influenced by Serum Selenium Status: A Cohort Study

Purpose

The role of imbalanced one-carbon nutrients in gestational diabetes mellitus (GDM) risk has garnered significant interest, yet existing studies yield inconsistent results. Our objective was to assess whether the association between an unbalanced ratio of folate to vitamin B12 and GDM risk is influenced by the status of other micronutrients.

Methods

This cohort study included 366 singleton-pregnancy Han women enrolled at the Shunyi District Maternal and Child Health Hospital in Beijing, China. During the first trimester of pregnancy, we measured red blood cell (RBC) folate, serum levels of vitamin B12, vitamin D, and selenium. We examined the association between the imbalanced status of RBC folate and vitamin B12 and GDM risk using logistic regression, stratified by serum selenium or vitamin D status.

Results

Among the 366 women, 67 (18.3%) were diagnosed with GDM, 201 (54.9%) had vitamin D deficiency, and 245 (66.9%) had selenium deficiency. Overall, women with higher RBC folate/vitamin B12 ratios did not exhibit a significantly higher risk of GDM compared to those in reference tertile (all P > 0.05). Subsequently, we divided women into deficient and non-deficient groups based on serum selenium or vitamin D levels. In women with selenium deficiency, those in the highest tertile of the RBC folate/vitamin B12 ratio had the highest odds of GDM [OR: 3.40 (1.16-9.97), P=0.026] after adjusting for covariates. However, similar findings were not observed in pregnancies with normal selenium status. Irrespective of vitamin D status, women with higher RBC folate/vitamin B12 ratios did not exhibit a significantly increased risk of GDM.

Conclusion

Micronutrient deficiencies are common in early pregnancy. Women with a higher folate/vitamin B12 ratio coupled with selenium deficiency in early pregnancy have a higher GDM risk. These findings underscore the importance of micronutrient assessment in early pregnancy and subsequent interventions for micronutrient deficiencies.

Role of Oxidative Stress and Inflammation in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications. It is related to several gestational and fetal adverse outcomes. Moreover, women with GDM and their infants have a high risk of developing type 2 diabetes in the future. The pathogenesis of GDM is not completely understood; nevertheless, two factors that contribute to its development are oxidative stress and inflammation. Oxidative stress and inflammation are related; reactive oxygen species (ROS) production can activate inflammatory cells and enhance the production of inflammatory mediators. Inflammation, in turn, leads to an increased ROS release, causing a vicious circle to ensue. Inflammatory responses can be achieved via the activation of the NF-κB signaling pathway. Herein, we review the English literature regarding oxidative stress and inflammation evaluated simultaneously in the same population, attempting to identify mechanisms through which these factors contribute to the development of GDM. Furthermore, the modulation of oxidative stress and inflammation by different therapies used in women with GDM and in cell models of GDM is included in the review. Probiotics and nutrient supplementations have been shown to reduce biomarkers of inflammation and oxidative stress in vitro and in women with GDM.

Association of Selenium Levels with Preeclampsia: A Systematic Review and Meta-analysis

Several observational studies have shown inconclusive findings on the association between selenium levels and preeclampsia. This systematic review and meta-analysis was conducted to clarify the association between selenium levels and preeclampsia. The databases PubMed, Google Scholar, ScienceDirect, and the Cochrane Library were searched for studies which investigated selenium levels with preeclampsia and which were published up to April 2022. The overall standardized mean differences (SMD) of selenium levels between cases and controls were measured. Sensitivity analysis, reporting bias, subgroup analysis, and meta-regression were performed for the estimate. The meta-analysis was calculated using the "meta" package in the open-source software R. A total of 26 studies with 1855 preeclampsia cases compared with 3728 healthy pregnant controls were included. The level of selenium was significantly lower in cases of preeclampsia compared with the controls [SMD =  - 0.85; 95% confidence interval (CI): (- 1.46, - 0.25); P =  < 0.01). As there was significant heterogeneity [I² = 96%, Cochran's Q = 620.47; P =  < 0.01], the random effects model was used. A stratified meta-analysis revealed that selenium levels were significantly lower in the cases compared with the controls among pregnant women from the African continent [SMD =  - 1.15 (- 1.65, - 0.65); P =  < 0.01]. Likewise, the same pattern was observed among women from middle- and low-income countries [SMD =  - 1.32 (- 2.22, - 0.42); P =  < 0.01]. None of the investigated factors (Modified Newcastle-Ottawa Scale quality score, year of publication, and sample size) showed significant association with the selenium SMD. The level of certainty of this evidence is "low certainty," as calculated by the GRADEpro GDT online tool. This meta-analysis with low level of evidence certainty revealed that low selenium level is associated significantly with preeclampsia. This pattern is also observed in women from the African continent and women from low- or middle-income countries. Further studies with different prospective designs and detailed patient characteristics are needed to consolidate this evidence.

Review on the health-promoting effect of adequate selenium status

Selenium is an essential microelement involved in various biological processes. Selenium deficiency increases the risk of human immunodeficiency virus infection, cancer, cardiovascular disease, and inflammatory bowel disease. Selenium possesses anti-oxidant, anti-cancer, immunomodulatory, hypoglycemic, and intestinal microbiota-regulating properties. The non-linear dose-response relationship between selenium status and health effects is U-shaped; individuals with low baseline selenium levels may benefit from supplementation, whereas those with acceptable or high selenium levels may face possible health hazards. Selenium supplementation is beneficial in various populations and conditions; however, given its small safety window, the safety of selenium supplementation is still a subject of debate. This review summarizes the current understanding of the health-promoting effects of selenium on the human body, the dietary reference intake, and evidence of the association between selenium deficiency and disease.

A machine learning approach for early prediction of gestational diabetes mellitus using elemental contents in fingernails

The aim of this pilot study was to predict the risk of gestational diabetes mellitus (GDM) by the elemental content in fingernails and urine with machine learning analysis. Sixty seven pregnant women (34 control and 33 GDM patient) were included. Fingernails and urine were collected in the first and second trimesters, respectively. The concentrations of elements were determined by inductively coupled plasma-mass spectrometry. Logistic regression model was applied to estimate the adjusted odd ratios and 95% confidence intervals. The predictive performances of multiple machine learning algorithms were evaluated, and an ensemble model was built to predict the risk for GDM based on the elemental contents in the fingernails. Beryllium, selenium, tin and copper were positively associated with the risk of GDM while nickel and mercury showed opposite result. The trained ensemble model showed larger area under curve (AUC) of receiver operating characteristic curve (0.81) using fingernail Ni, Cu and Se concentrations. The model was validated by external data set with AUC = 0.71. In summary, the results of the present study highlight the potential of fingernails, as an alternative sample, together with machine learning in human biomonitoring studies.

Association of Serum Antioxidant Minerals and Type 2 Diabetes Mellitus in Chinese Urban Residents

Antioxidant minerals including zinc, copper and selenium play critical roles in the maintenance of the redox balance in the body. However, their influences on type 2 diabetes mellitus (T2DM) are still inconclusive in Chinese populations. To elucidate the relationship between antioxidant minerals and T2DM, serum zinc, copper and selenium concentrations were measured in 1443 Chinese urban residents using a 1:2 matched case-control study. Conditional logistic regression models (CLR) were used to obtain the odds ratios (ORs) and 95% confidence intervals (CIs), and restricted cubic splines (RCS) were used to examine their dose−response associations. Serum zinc (OR = 0.52 [0.35, 0.77]) and copper concentrations (OR = 0.25 [0.17, 0.37]) were negatively associated with T2DM in a fully adjusted model. An L-shaped zinc-T2DM association (Poverall association = 0.003, and Pnonlinearity = 0.005) and a negative linear copper-T2DM association (Poverall association < 0.0001, and Pnonlinearity = 0.395) were observed. No association was found between serum selenium and T2DM in fully adjusted CLR or RCS models. In addition, joint associations with T2DM were identified between serum zinc and copper and between serum selenium and copper. In conclusion, our study emphasizes the importance of an adequate intake of antioxidant minerals for T2DM prevention in the Chinese population.

Association between blood selenium levels and gestational diabetes mellitus: A systematic review and meta-analysis

Introduction

The association between blood (serum or plasma) selenium concentrations and gestational diabetes mellitus (GDM) has been evaluated in some studies. However, the reported findings are debatable, and only case-control and cross-sectional studies were included.

Objective

This research aimed to assess the association between blood selenium levels and GDM by analyzing existing literature. To provide a reference for the prevention and treatment of GDM, we included prospective studies which are not included in previous studies to collate more high-quality evidence and better test the etiological hypothesis between blood Se concentrations and GDM.

Methods

The PubMed, EMBASE, and Web of Science databases were retrieved for literature up to September 2022, and relevant references were manually searched. Raw data from relevant studies were extracted, and a random effect model was adopted for meta-analysis. The total effects were reported as weighted mean differences. All data were analyzed using Stata 16.0 software.

Results

Fourteen studies involving 890 pregnant women with GDM and 1618 healthy pregnant women were incorporated in the meta-analysis. Pregnancies with GDM had significantly lower blood selenium levels than those with normal glucose tolerance (weighted mean difference = -8.11; 95% confidence interval: -12.68 to -3.54, P = 0.001). Subgroup analyses showed that the association between blood selenium levels and GDM was consistent in the residents of Asia and Africa, but not in European. This trend was significant in the second and third trimester subgroups, but not in the first trimester subgroup. Articles published in 2006-2015 also showed this trend, but those published before 2005 and 2016-2019 did not show significant results. This difference was evident in non-prospective studies, but not significant in prospective studies. Studies using the Carpenter and Coustan diagnostic criteria were consistent with this trend, whereas studies using other diagnostic criteria found no differences. In addition, in terms of blood selenium measurement methods, atomic absorption spectrometry showed more significant differences than other methods. In the subgroup analysis based on the sample size of included studies and the quality of the studies, each subgroup showed statistical differences.

Conclusion

Lower blood selenium concentrations are associated with GDM as shown in our study. Therefore, supplementing an appropriate amount of selenium may be helpful for GDM prevention and treatment.

Plasma and vitreous selenium concentrations in patients with type 2 diabetes and diabetic retinopathy

BACKGROUND

This work aimed to determine and compare plasma and vitreous selenium (Se) concentrations in patients with type 2 diabetes and diabetic retinopathy (DR).

METHODS

A total of 60 type-2-diabetes patients including 20 without DR, 20 with non-proliferative DR (NPDR), and 20 with proliferative diabetic retinopathy (PDR), were involved in this study. Blood plasma samples were collected from above 60 patients and 20 normal controls (without diabetes). Twenty control vitreous samples were obtained from the eyes presenting a macular hole and epimacular membrane. Vitreous samples were also collected from PDR patients receiving one-week intravitreal anti-VEGF therapy or not. Plasma and vitreous Se concentrations were determined by inductively coupled plasma mass spectrometry.

RESULTS

Plasma Se concentrations in PDR patients (163.74 ± 32.68 μg/L) were significantly higher than those in normal control patients (121.59 ± 28.33 μg/L), NPDR patients (130.34 ± 29.11 μg/L), and the patients without DR (81.23 ± 20.59 μg/L) (all P < .001). Similarly, Se concentrations in vitreous samples of PDR patients (56.30 ± 12.03 μg/L) were consistently higher than those in control vitreous samples (26.26 ± 6.53 μg/L). In addition, vitreous Se concentrations in PDR patients decreased to 47.76 ± 9.72 μg/L after intravitreal injection of the anti-VEGF drug ranibizumab for one week, which was significantly lower than those before injection (P = .02). Plasma VEGF levels of diabetic patients were lower than those of the normal controls (P < .001). On the contrary, the vitreous VEGF level in the PDR group (913.61 ± 193.32 pg/mL) was significantly higher than that of the normal control group (101.23 ± 21.33 pg/mL) (P < .001).

CONCLUSION

The elevation of Se concentrations may be an important risk factor in plasma and vitreous with diabetic retinopathy among type-2-diabetes patients. The elevated VEGF may be also closely related to the intraocular Se concentration in PDR patients.

Association of Selenium Levels with Gestational Diabetes Mellitus: An Updated Systematic Review and Meta-Analysis

Several studies have investigated the association between selenium levels and gestational diabetes mellitus (GDM); however, their results are not conclusive. This systematic review and meta-analysis aimed to update and draw conclusions regarding the evidence from published studies that investigated selenium levels in relation to GDM. PubMed, Google Scholar, Cochrane Library and ScienceDirect were searched for studies related to selenium and GDM, published from the inception of each database through to July 2022. The meta-analysis was conducted by measuring the standardized mean difference (SMD) between the selenium levels of women with GDM and those pregnant without GDM (control group). Stratified meta-analysis, meta-regression analysis and reporting bias were applied. The "meta" package in the open-access software R was used to analyze all of the data. A total of 12 studies, including 940 pregnant women with GDM and 1749 controls met this study's inclusion criteria. The selenium levels were significantly lower in women with GDM compared with the control group (SMD = -0.66; 95% confidence interval (CI): (-1.04, -0.28); p ≤ 0.001). Due to significant heterogeneity (I2 = 94%, Cochrane Q = 186.7; p ≤ 0.0001), the random-effects model was followed. The stratified meta-analysis showed that the selenium levels were lower in the cases compared with the normal controls in the third trimester (SMD = -1.85 (-3.03, -0.66); p ≤ 0.01). The same trend was observed in the studies published before the year 2014 (SMD = -0.99 (-1.70, -0.28); p ≤0.01) and those published in or after 2014 (SMD = -0.45 (-0.90, 0.00); p = 0.05). None of the investigated covariates in the meta-regression analysis (each study's geographic location, trimester of selenium quantification, World Bank economic classification, method of selenium determination, study design, study quality score, publication year and study's sample size) were significantly associated with the selenium SMD. The current evidence indicates that selenium levels are lower among women with GDM in comparison to those without GDM; however, after the correction of the reporting bias, the result was no longer significant. Further studies with more prospective designs are needed to confirm this evidence and explain the function of selenium in GDM throughout pregnancy.

Association between whole blood metallic elements concentrations and gestational diabetes mellitus in Japanese women: The Japan environment and Children's study

BACKGROUND

Exposure to several metallic elements has been suggested as a risk factor for gestational diabetes mellitus (GDM), but inconsistent findings have been reported. This study aimed to examine the association between the maternal whole blood concentration of metallic elements (Hg, Pb, Cd, Mn, and Se) and GDM using the dataset of the Japan Environment and Children's Study (JECS), a nationwide birth cohort study, which was designed to examine the adverse effects of pre/post-natal exposure to hazardous environment.

METHODS

The data of 78,964 pregnant women who were participants of JECS were used. Blood samples were collected from the pregnant women at second/third trimester of gestation. We employed logistic regression analysis, quantile g-computation (QGC) and a distributed lag nonlinear model (DLNM) to examine the association between the blood concentration of metallic elements and the risk of GDM.

RESULTS

The prevalence of GDM was 2.1%. In the logistic regression analyses, maternal blood Hg was associated with an increased risk of GDM. In QGC analysis, although metallic elements mixtures were not related to an increased risk of GDM, Hg (52.6%) may be the main contributor. According to the results of DLNM, for maternal exposure to Hg, 4.99 ng/g was identified as its susceptible minimum window for elevated risk of GDM.

CONCLUSIONS

Our findings highlighted an association between Hg exposure and an increased risk of GDM. Studies of the underlying mechanisms and potential contributing factors, including fish intake, of this association are warranted.

Selenium Prevents Inflammation in Human Placenta and Adipose Tissue In Vitro: Implications for Metabolic Diseases of Pregnancy Associated with Inflammation

Gestational diabetes mellitus (GDM) and maternal obesity are significant metabolic complications increasingly prevalent in pregnancy. Of major concern, both GDM and maternal obesity can have long-term detrimental impacts on the health of both mother and offspring. Recent research has shown that increased inflammation and oxidative stress are two features central to the pathophysiology of these metabolic conditions. Evidence suggests selenium supplementation may be linked to disease prevention in pregnancy; however, the specific effects of selenium on inflammation and oxidative stress associated with GDM and maternal obesity are unknown. Therefore, this study aimed to investigate the effect of selenium supplementation on an in vitro model of GDM and maternal obesity. Human placental tissue, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were stimulated with either the bacterial product lipopolysaccharide (LPS) or the pro-inflammatory cytokine TNF-α. Selenium pre-treatment blocked LPS and TNF-α induced mRNA expression and secretion of pro-inflammatory cytokines and chemokines, while increasing anti-inflammatory cytokine and antioxidant mRNA expression in placenta, VAT and SAT. Selenium pre-treatment was also found to inhibit LPS- and TNF-α induced phosphorylation of ERK in placenta, VAT and SAT. These findings indicate that selenium may be able to prevent inflammation and oxidative stress associated with GDM and maternal obesity. Additional in vivo studies are required to identify the efficacy of selenium supplementation in preventing inflammatory pathways activated by GDM and maternal obesity and to elucidate the mechanism involved.

Associations between Circulating SELENOP Level and Disorders of Glucose and Lipid Metabolism: A Meta-Analysis

Selenoprotein P (SELENOP) is an extracellular antioxidant, selenium transporter, and hepatokine interfering with glucose and lipid metabolism. To study the association between the circulating SELENOP concentration and glucose and lipid metabolic diseases (GLMDs), including gestational diabetes (GD), metabolic syndrome (MetS), non-alcoholic fatty liver disease, obesity, and type 2 diabetes, as well as the individual markers, a meta-analysis was conducted by searching multiple databases from their establishment through March 2022 and including 27 articles published between October 2010 and May 2021, involving 4033 participants. Participants with GLMDs had higher levels of SELENOP than those without GLMDs (standardized mean difference = 0.84, 95% CI: 0.16 to 1.51), and the SELENOP levels were positively correlated with the markers of GLMDs (pooled effect size = 0.09, 95% CI: 0.02 to 0.15). Subgroup analyses showed that the SELENOP concentrations were higher in women with GD and lower in individuals with MetS than their counterparts, respectively. Moreover, SELENOP was positively correlated with low-density lipoprotein cholesterol, but not with the other markers of GLMDs. Thus, the heterogenicity derived from diseases or disease markers should be carefully considered while interpreting the overall positive association between SELENOP and GLMDs. Studies with a larger sample size and advanced design are warranted to confirm these findings.

The association between serum selenium level and gestational diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

The relationship between serum selenium level and gestational diabetes mellitus (GDM) is controversial. The purpose is to update and summarize previous studies to understand the relationship in more detail.

METHODS

PubMed, The Cochrane Library, EMBASE, Web of science, CNKI, WANFANG DATA and Cqvip were searched for studies published up to 3 September 2021. The random-effects model was used to measure the combined estimation. The overall effect was reported in a standard mean difference (SMD) and 95% confidence interval (95% CI). All data were analysed by Review Manager 5.4.

RESULTS

Twenty-seven studies involving 1588 patients with GDM and 2450 healthy pregnant women contributed to this meta-analysis. Selenium level was significantly lower in women with GDM than those without GDM (SMD = -1.29; 95% CI: -1.60 to -0.97, p < 0.00001). Subgroup analyses showed that such trend was consistent within the non-European population (Asia: SMD = -1.44; 95% CI: -1.79 to -1.08, p < 0.00001; Africa: SMD = -2.62; 95% CI: -4.50 to -0.74, p = 0.006) and in the second and third trimesters (the second trimester: SMD = -1.41; 95% CI: -1.82 to -0.99, p < 0.00001; the third trimester: SMD = -1.54; 95% CI: -2.09 to -0.98, p < 0.00001), but not within the European population (SMD = -0.47; 95% CI: -1.09 to 0.16, p = 0.14) or in the first trimester (SMD = -0.52; 95% CI: -1.13 to 0.10, p = 0.10).

CONCLUSIONS

This meta-analysis showed that the serum selenium level of patients with GDM was lower than that in healthy pregnant women, especially within the non-European population and in the second and third trimesters.

Selenoproteins in the Human Placenta: How Essential Is Selenium to a Healthy Start to Life?

Selenium is an essential trace element required for human health, and selenium deficiency has been associated with many diseases. The daily recommended intake of selenium is 60 µg/day for adults, which increases to 65 µg/day for women when pregnant. Selenium is incorporated into the 21st amino acid, selenocysteine (sec), a critical component of selenoproteins that plays an important role in a variety of biological responses such as antioxidant defence, reactive oxygen species (ROS) signalling, formation of thyroid hormones, DNA synthesis and the unfolded protein response in the endoplasmic reticulum (ER). Although 25 selenoproteins have been identified, the role of many of these is yet to be fully characterised. This review summarises the current evidence demonstrating that selenium is essential for a healthy pregnancy and that poor selenium status leads to gestational disorders. In particular, we focus on the importance of the placental selenoproteome, and the role these proteins may play in a healthy start to life.

Early pregnancy essential and non-essential metal mixtures and gestational glucose concentrations in the 2nd trimester: Results from project viva

Metals are involved in glucose metabolism, and some may alter glycemic regulation. However, joint effects of essential and non-essential metals on glucose concentrations during pregnancy are unclear. This study explored the joint associations of pregnancy exposures to essential (copper, magnesium, manganese, selenium, zinc) and non-essential (arsenic, barium, cadmium, cesium, lead, mercury) metals with gestational glucose concentrations using 1,311 women enrolled 1999-2002 in Project Viva, a Boston, MA-area pregnancy cohort. The study measured erythrocyte metal concentrations from 1st trimester blood samples and used glucose concentrations measured 1 h after non-fasting 50-gram glucose challenge tests (GCT) from clinical gestational diabetes screening at 26-28 weeks gestation. Bayesian Kernel Machine Regression (BKMR) and quantile-based g-computation were applied to model the associations of metal mixtures-including their interactions-with glucose concentrations post-GCT. We tested for reproducibility of BKMR results using generalized additive models. The BKMR model showed an inverse U-shaped association for barium and a linear inverse association for mercury. Specifically, estimated mean glucose concentrations were highest around 75th percentile of barium concentrations [2.1 (95% confidence interval: -0.2, 4.4) mg/dL higher comparing to the 25th percentile], and each interquartile range increase of erythrocyte mercury was associated with 1.9 mg/dL lower mean glucose concentrations (95% credible interval: -4.2, 0.4). Quantile g-computation showed joint associations of all metals, essential-metals, and non-essential metals on gestational glucose concentrations were all null, however, we observed evidences of interaction for barium and lead. Overall, we found early pregnancy barium and mercury erythrocytic concentrations were associated with altered post-load glucose concentrations in later pregnancy, with potential interactions between barium and lead.

Evidence-Based Recommendations for an Optimal Prenatal Supplement for Women in the U.S., Part Two: Minerals

The levels of many essential minerals decrease during pregnancy if un-supplemented, including calcium, iron, magnesium, selenium, zinc, and possibly chromium and iodine. Sub-optimal intake of minerals from preconception through pregnancy increases the risk of many pregnancy complications and infant health problems. In the U.S., dietary intake of minerals is often below the Recommended Dietary Allowance (RDA), especially for iodine and magnesium, and 28% of women develop iron deficiency anemia during their third trimester. The goal of this paper is to propose evidence-based recommendations for the optimal level of prenatal supplementation for each mineral for most women in the United States. Overall, the evidence suggests that optimal mineral supplementation can significantly reduce a wide range of pregnancy complications (including anemia, gestational hypertension, gestational diabetes, hyperthyroidism, miscarriage, and pre-eclampsia) and infant health problems (including anemia, asthma/wheeze, autism, cerebral palsy, hypothyroidism, intellectual disability, low birth weight, neural tube defects, preterm birth, rickets, and wheeze). An evaluation of 180 commercial prenatal supplements found that they varied widely in mineral content, often contained only a subset of essential minerals, and the levels were often below our recommendations. Therefore, there is a need to establish recommendations on the optimal level of mineral supplementation during pregnancy.

Maternal selenium deficiency during gestation is positively associated with the risks for LBW and SGA newborns in a Chinese population

BACKGROUND

Maternal selenium (Se) deficiency is associated with some adverse pregnant outcomes. However, it remains controversial whether maternal Se deficiency during gestation enhances the risks for low-birth-weight (LBW) and small-for-gestational-age (SGA) newborns.

METHODS

For our cohort study, total 3133 mother-and-infant pairs were selected. Maternal serum Se concentration was detected by graphite furnace atomic absorption spectrometry. According to international references for maternal serum Se concentration, subjects were divided into Se deficiency (<45.0 μg/L), Se insufficiency (45.0-94.9 μg/L) and Se sufficiency (≥95.0 μg/L).

RESULTS

There was a positive relation of maternal serum Se concentration in gestation and neonatal birth weight. Further analysis showed that the risks for LBW and SGA in SD group were significantly higher than that in SI and SS group, the adjusted ORs for LBW and SGA newborns were 1.87 (95%CI: 1.02, 3.45; P = 0.04) and 1.47 (95%CI: 1.07, 2.02; P = 0.02) in SI group, and 3.92 (95%CI: 2.03, 7.57; P < 0.001) and 2.77 (95%CI: 1.92, 4.02; P < 0.001) in SD group compared to SS group. In different gender subgroup, positive relations were observed between maternal Se deficiency and the risk for LBW girls, as well as the risks for both SGA girls and boys.

CONCLUSION

Maternal Se deficiency in gestation was positively associated with the risk for LBW girls, as well as the risks for both SGA girls and boys.

Neonatal Selenoenzyme Expression Is Variably Susceptible to Duration of Maternal Selenium Deficiency

Maternal selenium (Se) deficiency is associated with decreased neonatal Se levels, which increases the risk for neonatal morbidities. There is a hierarchy to selenoprotein expression after Se deficiency in adult rodents, depending on the particular protein and organ evaluated. However, it is unknown how limited Se supply during pregnancy impacts neonatal selenoprotein expression. We used an Se-deficient diet to induce perinatal Se deficiency (SeD), initiated 2–4 weeks before onset of breeding and continuing through gestation. Neonatal plasma, liver, heart, kidney, and lung were collected on the day of birth and assessed for selenoproteins, factors required for Se processing, and non-Se containing antioxidant enzymes (AOE). Maternal SeD reduced neonatal circulating and hepatic glutathione peroxidase (GPx) activity, as well as hepatic expression of Gpx1 and selenophosphate synthetase 2 (Sps2). In contrast, the impact of maternal SeD on hepatic thioredoxin reductase 1, hepatic non-Se containing AOEs, as well as cardiac, renal, and pulmonary GPx activity, varied based on duration of maternal exposure to SeD diet. We conclude that the neonatal liver and circulation demonstrate earlier depletion in selenoenzyme activity after maternal SeD. Our data indicate that prolonged maternal SeD may escalate risk to the neonate by progressively diminishing Se-containing AOE across multiple organs.

Associations of Serum Selenium Levels in the First Trimester of Pregnancy with the Risk of Gestational Diabetes Mellitus and Preterm Birth: a Preliminary Cohort Study

Women with gestational diabetes mellitus (GDM) may have lower serum selenium levels than healthy controls, which may be associated with preterm birth. We explored the association of serum selenium levels in early pregnancy with the risk of GDM and preterm birth among Chinese women. We included 398 women with a singleton pregnancy, who were followed up prospectively from the first prenatal visit until delivery. Serum selenium levels were measured in the first trimester. After delivery, data concerning mothers and their children were sourced from medical records by researchers who were blind to the participants' selenium status. Of the 398 women, 71 (17.8%) had GDM, 21(5.3%) had preterm birth, and 266 (66.8%) had selenium deficiency (serum selenium < 70 μg/L). Women in the upper three quartiles of serum selenium level did not have a significantly lower risk of GDM or preterm birth than those in the lowest quartile after adjustment for covariates (all p > 0.05). When serum selenium levels were classified as normal or deficient, the risk of GDM or preterm birth among women with normal serum selenium levels was still not lower than that of women with deficient serum selenium levels after adjustment for covariates (all p > 0.05). Although selenium deficiency was common in the Chinese women in our cohort, our results indicate that low serum selenium level during early pregnancy may not be a strong predictor of the risk of GDM and preterm birth. However, our sample size was small, and future studies with larger populations are warranted.

Early Pregnancy Exposure to Rare Earth Elements and Risk of Gestational Diabetes Mellitus: A Nested Case-Control Study

OBJECTIVE

The extensive use of rare earth elements (REEs) in many technologies was found to have effects on human health, but the association between early pregnancy exposure to REEs and gestational diabetes mellitus (GDM) is still unknown.

METHODS

This nested case-control study involved 200 pregnant women with GDM and 200 healthy pregnant women from the Peking University Birth Cohort in Tongzhou. We examined the serum concentrations of 14 REEs during early pregnancy and analyzed their associations with the risk of GDM.

RESULTS

When the elements were considered individually in the logistic regression model, no significant associations were found between REEs and GDM, after adjusting for confounding variables (P > 0.05). In weighted quantile sum (WQS) regression, each quartile decrease in the mixture index for REEs resulted in a 1.67-fold (95% CI: 1.12-2.49) increased risk of GDM. Neodymium (Nd), Praseodymium (Pr), and Lanthanum (La) were the most important contributors in the mixture.

CONCLUSION

The study findings indicated that early pregnancy exposure to lower levels of REE mixture was associated with an increased risk of GDM, and Nd, Pr, and La exhibited the strongest effects in the mixture.

Maternal, placental and cordonal metallomic profiles in gestational diabetes mellitus

76 pregnant women, among them 38 affected by gestational diabetes mellitus (GDM) and 38 control subjects, were recruited at the University Hospital of Padua (Italy). Placenta samples, maternal whole blood and umbilical cord whole blood were collected after delivery and analysed via ICP-MS to determine the metallome, i.e. the whole elemental content. Results were statistically evaluated to evidence the correlation between the elemental concentrations in all samples and the presence of the disease. The results obtained in whole cord blood showed that many elements were correlated with GDM: Ca, Cu, Na, and Zn were present in higher concentration in GDM cord blood than in control samples, whereas Fe, K, Mn, P, Rb, S and Si showed an opposite trend. It was also highlighted that the cord blood from GDM patients exhibited an elemental composition more similar to that of the mother blood compared with the cord blood from control subjects. These results, in part interpreted in the light of the literature, open the possibility to use cord blood as a GDM marker, thus helping to delineate more accurate nutritional guidelines for pregnant women and to explain the biochemical processes occurring in the fetus and placenta during GDM.

The Effects of Selenium Supplementation on Gene Expression Related to Insulin and Lipid Metabolism, and Pregnancy Outcomes in Patients with Gestational Diabetes Mellitus: a Randomized, Double-Blind, Placebo-Controlled Trial

This study was performed to evaluate the effects of selenium supplementation on gene expression related to insulin and lipid metabolism, and pregnancy outcomes in patients with gestational diabetes mellitus (GDM). The current randomized, double-blind, placebo-controlled clinical trial was conducted in 36 patients with GDM. Participants were randomly divided into two groups to intake either 200 μg/day selenium supplements as selenium yeast or placebo (n = 18 each group) for 6 weeks. Selenium supplementation upregulated peroxisome proliferator-activated receptor gamma (P = 0.03) and glucose transporter 1 (GLUT-1) (P = 0.01) in lymphocytes of subjects with GDM compared with the placebo. Selenium supplementation did not affect gene expression of low-density lipoprotein receptor (LDLR) and lipoprotein(a) [Lp(a)]. Supplementation with selenium had a significant decrease in incidence of newborns' hyperbilirubinemia (5.6% vs. 33.3%, P = 0.03) and newborns' hospitalization (5.6% vs. 33.3%, P = 0.03) compared with the placebo. Overall, we found that selenium supplementation for 6 weeks among patients with GDM significantly increased PPAR-γ and GLUT-1 expression, but did not affect gene expression of LDLR and LP(a). It also reduced incidence of newborns' hyperbilirubinemia and newborns' hospitalization. Clinical trial registration number: http://www.irct.ir: IRCT20170513033941N35.

First Trimester Microelements and their Relationships with Pregnancy Outcomes and Complications

Microelements involved in the oxidative balance have a significant impact on human health, but their role in pregnancy are poorly studied. We examined the relationships between first trimester levels of selenium (Se), iron (Fe), zinc (Zn), and copper (Cu), as well as maternal characteristics and pregnancy results. The data came from a Polish prospective cohort of women in a single pregnancy without chronic diseases. A group of 563 women who had a complete set of data, including serum microelements in the 10–14th week was examined, and the following were found: 47 deliveries <37th week; 48 cases of birth weight <10th and 64 newborns >90th percentile; 13 intrauterine growth restriction (IUGR) cases; 105 gestational hypertension (GH) and 15 preeclampsia (PE) cases; and 110 gestational diabetes mellitus (GDM) cases. The microelements were quantified using mass spectrometry. The average concentrations (and ranges) of the elements were as follows: Se: 60.75 µg/L (40.91–125.54); Zn: 618.50 µg/L (394.04–3238.90); Cu: 1735.91 µg/L (883.61–3956.76); and Fe: 1018.33 µg/L (217.55–2806.24). In the multivariate logistic regression, we found that an increase in Se of 1 µg/L reduces the risk of GH by 6% (AOR = 0.94; p = 0.004), the risk of IUGR by 11% (AOR = 0.89; p = 0.013), and the risk of birth <34th week by 7% (but close to the significance) (AOR = 0.93; p = 0.061). An increase in Fe of 100 µg/L reduces the risk of PE by 27% (AOR = 0.73; p = 0.009). In the multivariable linear regression, we found negative strong associations between prepregnancy BMI, Se (β = −0.130; p = 0.002), and Fe (β = −0.164; p < 0.0001), but positive associations with Cu (β = 0.320; p < 0.000001). The relationships between Se and maternal age (β = 0.167; p < 0.0001), Se and smoking (β = −0.106; p = 0.011) and Cu, and gestational age from the 10–14th week (β = 0.142; p < 0.001) were also found. Secondary education was associated with Zn (β = 0.132; p = 0.004) and higher education was associated with Cu (β = −0.102; p = 0.023). A higher financial status was associated with Fe (β = 0.195; p = 0.005). Other relationships were statistically insignificant. Further research is needed to clarify relationships between first trimester microelements and pregnancy complications. In addition, attention should be paid to lifestyle-related and socioeconomic factors that affect microelement levels.

Trace elements in type 2 diabetes mellitus and their association with glycemic control

Background

Alterations in serum levels of trace elements reported in type 2 diabetes mellitus (T2DM) have been linked with induction of T2DM and associated complications.

Objectives

To assess serum levels of copper (Cu), zinc (Zn) and selenium (Se) in T2DM patients with adequate and poor glycemic control.

Patients and methods

This study was performed at King Khalid University Hospital, Riyadh. A total of 100 consenting T2DM patients comprising of 50 patients with glycated hemoglobin (HbA1c) less than 6.5% and 50 patients with HbA1c more than 6.5% along with a group of 50 normal healthy individuals were included in the study. Serum levels of Cu, Zn and Se were measured by inductively coupled plasma-mass spectrometry (ICP-MS) instrument.

Results

Among T2DM patients with HbA1c <6.5%, mean serum Cu levels (13.4+4.3µmol/L) were not different from the controls (14.5+1.92µmol/L) whereas Zn (9.9+2.7µmol/Lvs15+3.2µmol/L;p<0.0001) and Se levels (1+0.2µmol/Lvs1.62+0.2µmol/L; p<0.0004) were lower than the controls. Among T2DM patients with HbA1c >6.5% mean serum Cu (18.1+4.1µmol/Lvs14.5+1.9µmol/L; p<0.0001), Zn (15+3.2µmol/Lvs13.5+1.9µmol/L; p<0.009) and Se (1.62+0.2µmol/Lvs1.17+0.16µmol/L;p<0.0001) were significantly higher than the controls. HbA1c% negatively correlated with HbA1c >6.5% (r = -0.302; p<0.03).

Conclusion

Cu, Zn and Se homeostasis was altered in T2DM patients and varied with glycemic control.

Maternal Selenium Deficiency in Mice Alters Offspring Glucose Metabolism and Thyroid Status in a Sexually Dimorphic Manner

Selenium is an essential micronutrient commonly deficient in human populations. Selenium deficiency increases the risks of pregnancy complications; however, the long-term impact of selenium deficiency on offspring disease remains unclear. This study investigates the effects of selenium deficiency during pregnancy on offspring metabolic function. Female C57BL/6 mice were allocated to control (>190 μg selenium/kg, n = 8) or low selenium (<50 μg selenium/kg, n = 8) diets prior to mating and throughout gestation. At postnatal day (PN) 170, mice underwent an intraperitoneal glucose tolerance test and were culled at PN180 for biochemical analysis. Mice exposed to selenium deficiency in utero had reduced fasting blood glucose but increased postprandial blood glucose concentrations. Male offspring from selenium-deficient litters had increased plasma insulin levels in conjunction with reduced plasma thyroxine (tetraiodothyronine or T4) concentrations. Conversely, females exposed to selenium deficiency in utero exhibited increased plasma thyroxine levels with no change in plasma insulin. This study demonstrates the importance of adequate selenium intake around pregnancy for offspring metabolic health. Given the increasing prevalence of metabolic disease, this study highlights the need for appropriate micronutrient intake during pregnancy to ensure a healthy start to life.

Systems Biology of Selenium and Complex Disease

Selenium is an essential trace element for maintenance of overall health, whose deficiency and dyshomeostasis have been linked to a variety of diseases and disorders. The majority of previous researches focused on characterization of genes encoding selenoproteins or proteins involved in selenium metabolism as well as their functions. Many studies in humans also investigated the relationship between selenium and complex diseases, but their results have been inconsistent. In recent years, systems biology and "-omics" approaches have been widely used to study complex and global variations of selenium metabolism and function in physiological and different pathological conditions. The present paper reviews recent progress in large-scale and systematic analyses of the relationship between selenium status or selenoproteins and several complex diseases, mainly including population-based cohort studies and meta-analyses, genetic association studies, and some other omics-based studies. Advances in ionomics and its application in studying the interaction between selenium and other trace elements in human health and diseases are also discussed.

A Prospective Study of Early Pregnancy Essential Metal(loid)s and Glucose Levels Late in the Second Trimester

CONTEXT

Studies suggest many essential trace metal(loid)s are involved in glucose metabolism, but the associations among pregnant women are unclear.

OBJECTIVE

To assess associations between early pregnancy plasma zinc, selenium, copper, and molybdenum levels and blood glucose levels later in the second trimester.

DESIGN

The Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies‒Singleton Cohort is a prospective cohort study conducted between July 2009 and January 2013.

SETTING

Twelve academic research hospitals in the United States.

PATIENTS

A total of 1857 multiracial, nonobese, healthy women.

MAIN OUTCOME MEASURE

Blood glucose levels from 1-hour 50-g gestational load test (GLT) at 24 to 28 weeks of gestation.

RESULTS

Higher concentrations of first-trimester copper were associated with higher glucose levels from the GLT (i.e., every 50% increase in copper concentration was related to 4.9 mg/dL higher glucose level; 95% CI: 2.2, 7.5 mg/dL) adjusted for maternal sociodemographic characteristics and reproductive history. In contrast, every 50% increase in molybdenum concentration was associated with 1.2 mg/dL lower mean glucose level (95% CI: -2.3, -0.1 mg/dL). The magnitude of these associations was greater at the upper tails of glucose level distribution based on quantile regressions of the 10th, 50th, and 90th percentiles.

CONCLUSIONS

Higher copper and lower molybdenum concentrations could increase the risk of glucose dysregulation during pregnancy, with women at higher risk of gestational diabetes mellitus potentially affected to a greater extent. Further work is needed to understand the mechanisms involved with early pregnancy essential metal(loid)s to inform clinical diagnosis and prevention of glucose intolerance during pregnancy.

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.

Trace element profiles in pregnant women's sera and umbilical cord sera and influencing factors: Repeated measurements

In utero exposure to toxic heavy metals and deficient or excessive essential trace elements during pregnancy may have adverse effects on pregnant women and their offsprings, which are of great concern. The objective of the present study was to characterize serum concentrations of multiple trace elements at multiple time points during pregnancy in Chinese women. Three thousand four hundred and sixteen pregnant women in total were included from MABC (Ma'anshan Birth Cohort) study. Fasting sera in the morning and questionnaires were obtained at three separate follow-up visits. Nineteen trace elements from serum samples were analyzed, including aluminum (Al), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), barium (Ba), thallium (Tl), lead (Pb), calcium (Ca), magnesium (Mg), mercury (Hg) and molybdenum (Mo). The total detection rates for most elements were 100% rather than Ni (99.98%), As (99.97%), Cd (99.6%), Ba (99.9%), Pb (99.8%), Hg (99.8%). The concentration distributions of 19 elements varied vastly. Median concentrations for all trace elements ranged from 38.5 ng/L to 102.9 mg/L. The moderate interclass correlation coefficients (ICCs) were observed for Co, Cu, Se and Hg, ranging from 0.40 to 0.62; the lower ICCs, ranging from 0.13 to 0.32 were for Fe, Zn, Cd, Ba, Tl, Mg and Mo. The intraclass correlation effects were not observed for the remaining elements, such as Al, V, Cr, Mn, Ni, As and Pb. The concentrations of each element between three time points were significantly different; significant differences were also found between any two time points except for Ni, Cd and Mo. Many factors could affect the levels of trace elements, and a very important factor of them was season. Consequently, a single measurement of elements in sera seems not enough to describe exposure levels throughout pregnancy; additionally, season affected exposure levels of trace elements with moderate ICCs showed certain regularity. Future analyses should take sampling seasons into consideration carefully.

Relationship between pre-pregnancy body mass index and mineral concentrations in serum and amniotic fluid in pregnant women during labor

The aim of the study was to determine the correlations between body mass index (BMI) values before pregnancy and the concentrations of selected elements (Mg, Co, Cu, Zn, Sr, Cd, Ba, Pb, U, Ca, Cr, Al, Mn, V, Fe) in blood serum and amniotic fluid (AF) in pregnant women. Elemental analysis of serum and amniotic fluid in 225 Polish women (Caucasian/white) showed a relationship between the concentration of minerals in the above-mentioned samples and the pre-pregnancy BMI. Analysis of blood serum was performed by using ICP-MS and it demonstrated that iron concentration was significantly lower in overweight and obese women. Being underweight in pregnant women was associated with a significantly lower concentration of magnesium and cobalt in the blood serum. Both underweight and overweight women were associated with significantly lower concentrations of calcium and strontium in the blood serum. The concentration of cobalt was significantly higher in underweight women. The concentration of lead in the blood serum of overweight and obese women was significantly higher than in other groups. Analysis of the AF showed that the concentration of copper was significantly lower in overweight and obese women, and the concentration of manganese and vanadium significantly higher than in other groups of women. A deficiency in essential minerals and an excess of heavy metals in women may be associated with abnormal body weight and this is important in the etiopathogenesis of pregnancy and fetal development disorders.