Asymmetric dimethylarginine concentrations are elevated in women with gestational diabetes

Mechanisms of Homoarginine: Looking Beyond Clinical Outcomes

PURPOSE

Homoarginine (hArg) is an arginine metabolite that has been known for years, but its physiological role in the body remains poorly understood. For instance, it is well known that high hArg concentrations in the blood are protective against several disease states, yet the mechanisms behind these health benefits are unclear. This review compiles what is known about hArg, namely its synthetic pathways, its role in different diseases and conditions, and its proposed mechanisms of action in humans and experimental animals.

FINDINGS

Previous work has identified multiple pathways that control hArg synthesis and degradation in the body. Furthermore, endogenous hArg can modulate the cardiovascular system, with decreased hArg being associated with cardiovascular complications and increased mortality. Studies also suggest that hArg could serve as a diagnostic biomarker for a variety of immune, pancreatic, renal, and hepatic dysfunctions. Finally, in women, hArg concentrations rapidly increase throughout pregnancy and there are suggestions that alterations in hArg could indicate pregnancy complications like pre-eclampsia.

SUMMARY

Homoarginine is an under-appreciated amino acid with potential wide-ranging roles in systemic health, pregnancy, and pathophysiology. Although recent research has focused on its health or disease associations, there is a need for more investigations into understanding the mechanistic pathways by which hArg may operate. This could be aided using metabolomics, which provides a comprehensive approach to correlating multiple metabolites and metabolic pathways with physiological effects. Increasing our knowledge of hArg's roles in the body could pave the way for its routine use as both a diagnostic and therapeutic molecule.

Nutritional Approaches Targeting Gut Microbiota in Oxidative-Stress-Associated Metabolic Syndrome: Focus on Early Life Programming

Metabolic syndrome (MetS) denotes a constellation of risk factors associated with the development of cardiovascular disease, with its roots potentially traced back to early life. Given the pivotal role of oxidative stress and dysbiotic gut microbiota in MetS pathogenesis, comprehending their influence on MetS programming is crucial. Targeting these mechanisms during the early stages of life presents a promising avenue for preventing MetS later in life. This article begins by examining detrimental insults during early life that impact fetal programming, ultimately contributing to MetS in adulthood. Following that, we explore the role of oxidative stress and the dysregulation of gut microbiota in the initiation of MetS programming. The review also consolidates existing evidence on how gut-microbiota-targeted interventions can thwart oxidative-stress-associated MetS programming, encompassing approaches such as probiotics, prebiotics, postbiotics, and the modulation of bacterial metabolites. While animal studies demonstrate the favorable effects of gut-microbiota-targeted therapy in mitigating MetS programming, further clinical investigations are imperative to enhance our understanding of manipulating gut microbiota and oxidative stress for the prevention of MetS.

Asymmetric dimethylarginine and gestational diabetes mellitus: a systematic review and meta-analysis

PURPOSE

Emerging evidence demonstrates that asymmetric dimethylarginine (ADMA) levels are elevated in patients with or at risk of cardiovascular disease (CVD). Since women with gestational diabetes mellitus (GDM) are at high risk of future CVD, we conducted a systematic review and meta-analysis to compare ADMA concentrations between women with and without GDM during pregnancy and postpartum.

METHODS

PubMed, Google Scholar, EMBASE, and CINAHL databases were searched. The review protocol is registered in PROSPERO (CRD42021276796). Study selection, data extraction, and data analyses were performed in accordance with PRISMA guidelines. Random-effects model was used to quantify ADMA levels in the study groups.

RESULTS

Eleven studies provided data on 1148 women. Mean plasma ADMA concentration was 0.04 μmol/L (95% confidence interval (CI) -0.06-0.15) higher in pregnant women with GDM than those without GDM, but no significant difference was observed. In contrast, our meta-analysis demonstrated a significant increase in postpartum mean ADMA concentration (Mean Difference (MD) 0.11 μmol/L; 95% CI 0.05-0.16) among women with previous GDM compared to women without previous GDM.

CONCLUSION

Elevated ADMA levels in GDM may be a CVD risk factor, suggesting that ADMA may be a potential biomarker for early CVD risk prediction in women with GDM.

Metabolic Syndrome Programming and Reprogramming: Mechanistic Aspects of Oxidative Stress

Metabolic syndrome (MetS) is a worldwide public health issue characterized by a set of risk factors for cardiovascular disease. MetS can originate in early life by developmental programming. Increasing evidence suggests that oxidative stress, which is characterized as an imbalance between reactive oxygen species (ROS), nitric oxide (NO), and antioxidant systems, plays a decisive role in MetS programming. Results from human and animal studies indicate that maternal-derived insults induce MetS later in life, accompanied by oxidative stress programming of various organ systems. On the contrary, perinatal use of antioxidants can offset oxidative stress and thereby prevent MetS traits in adult offspring. This review provides an overview of current knowledge about the core mechanisms behind MetS programming, with particular focus on the occurrence of oxidative-stress-related pathogenesis as well as the use of potential oxidative-stress-targeted interventions as a reprogramming strategy to avert MetS of developmental origins. Future clinical studies should provide important proof of concept for the effectiveness of these reprogramming interventions to prevent a MetS epidemic.

High Folate, Perturbed One-Carbon Metabolism and Gestational Diabetes Mellitus

Folate is a dietary micronutrient essential to one-carbon metabolism. The World Health Organisation recommends folic acid (FA) supplementation pre-conception and in early pregnancy to reduce the risk of fetal neural tube defects (NTDs). Subsequently, many countries (~92) have mandatory FA fortification policies, as well as recommendations for periconceptional FA supplementation. Mandatory fortification initiatives have been largely successful in reducing the incidence of NTDs. However, humans have limited capacity to incorporate FA into the one-carbon metabolic pathway, resulting in the increasingly ubiquitous presence of circulating unmetabolised folic acid (uFA). Excess FA intake has emerged as a risk factor in gestational diabetes mellitus (GDM). Several other one-carbon metabolism components (vitamin B12, homocysteine and choline-derived betaine) are also closely entwined with GDM risk, suggesting a role for one-carbon metabolism in GDM pathogenesis. There is growing evidence from in vitro and animal studies suggesting a role for excess FA in dysregulation of one-carbon metabolism. Specifically, high levels of FA reduce methylenetetrahydrofolate reductase (MTHFR) activity, dysregulate the balance of thymidylate synthase (TS) and methionine synthase (MTR) activity, and elevate homocysteine. High homocysteine is associated with increased oxidative stress and trophoblast apoptosis and reduced human chorionic gonadotrophin (hCG) secretion and pancreatic β-cell function. While the relationship between high FA, perturbed one-carbon metabolism and GDM pathogenesis is not yet fully understood, here we summarise the current state of knowledge. Given rising rates of GDM, now estimated to be 14% globally, and widespread FA food fortification, further research is urgently needed to elucidate the mechanisms which underpin GDM pathogenesis.

Endothelial Dysfunction in Pregnancy Complications

The endothelium, which constitutes the inner layer of blood vessels and lymphatic structures, plays an important role in various physiological functions. Alterations in structure, integrity and function of the endothelial layer during pregnancy have been associated with numerous gestational complications, including clinically significant disorders, such as preeclampsia, fetal growth restriction, and diabetes. While numerous experimental studies have focused on establishing the role of endothelial dysfunction in pathophysiology of these gestational complications, their mechanisms remain unknown. Numerous biomarkers of endothelial dysfunction have been proposed, together with the mechanisms by which they relate to individual gestational complications. However, more studies are required to determine clinically relevant markers specific to a gestational complication of interest, as currently most of them present a significant overlap. Although the independent diagnostic value of such markers remains to be insufficient for implementation in standard clinical practice at the moment, inclusion of certain markers in predictive multifactorial models can improve their prognostic value. The future of the research in this field lies in the fine tuning of the clinical markers to be used, as well as identifying possible therapeutic techniques to prevent or reverse endothelial damage.

Decreased nitric oxide content mediated by asymmetrical dimethylarginine and protein l-arginine methyltransferase 3 in macrophages induces trophoblast apoptosis: a potential cause of recurrent miscarriage

STUDY QUESTION

Is the protein l-arginine methyltransferase 3 (PRMT3)/asymmetrical dimethylarginine (ADMA)/nitric oxide (NO) pathway involved in the development of recurrent miscarriage (RM), and what is the potential mechanism?

SUMMARY ANSWER

Elevated levels of PRMT3 and ADMA inhibit NO formation in the decidua, thereby impairing the functions of trophoblast cells at the maternal-foetal interface.

WHAT IS KNOWN ALREADY

Decreased NO bioavailability is associated with RM. ADMA, an endogenous inhibitor of nitric oxide synthase (NOS), is derived from the methylation of protein arginine residues by PRMTs and serves as a predictor of mortality in critical illness.

STUDY DESIGN, SIZE, DURATION

A total of 145 women with RM and 149 healthy women undergoing elective termination of an early normal pregnancy were enrolled. Ninety-six female CBA/J, 24 male DBA/2 and 24 male BALB/c mice were included. CBA/J × DBA/2 matings represent the abortion group, while CBA/J × BALB/c matings represent the normal control group. The CBA/J pregnant mice were then categorised into four groups: (i) normal + vehicle group (n = 28), (ii) abortion + vehicle group (n = 28), (iii) normal + SGC707 (a PRMT3 inhibitor) group (n = 20) and (iv) abortion + SGC707 group (n = 20). All injections were made intraperitoneally on Days 0.5, 3.5 and 6.5 of pregnancy. Decidual tissues were collected on Days 8.5, 9.5 and 10.5 of gestation. The embryo resorption rates were calculated on Day 9.5 and Day 10.5 of gestation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

NO concentration, ADMA content, NOS activity, expression levels of NOS and PRMTs in decidual tissues were determined using conventional assay kits or western blotting. PRMT3 expression was further analysed in decidual stromal cells, macrophages and natural killer cells. A co-culture system between decidual macrophages (DMs) and HTR-8/SVneo trophoblasts was constructed to study the roles of the PRMT3/ADMA/NO signalling pathway. Trophoblast apoptosis was analysed via Annexin V-fluorescein isothiocyanate/propidium iodide staining. CBA/J × DBA/2 mouse models were used to investigate the effects of SGC707 on embryo resorption rates.

MAIN RESULTS AND THE ROLE OF CHANCE

Our results show that NO concentration and NOS activity were decreased, but ADMA content and PRMT3 expression were increased in the decidua of RM patients. Moreover, compared with the normal control subjects, PRMT3 expression was significantly up-regulated in the macrophages but not in the natural killer cells or stromal cells of the decidua from RM patients. The inhibition of PRMT3 results in a significant decrease in ADMA accumulation and an increase in NO concentration in macrophages. When co-cultured with DMs, which were treated with SGC707 and ADMA, trophoblast apoptosis was suppressed and induced, respectively. In vivo experiments revealed that the administration of SGC707 reduced the embryo resorption rate of CBA/J × DBA/2 mice.

LIMITATIONS, REASONS FOR CAUTION

All sets of experiments were not performed with the same samples. The main reason is that each tissue needs to be reserved for clinical diagnosis and only a small piece of each tissue can be cut and collected for this study.

WIDER IMPLICATIONS OF THE FINDINGS

Our results indicate that the PRMT3/ADMA/NO pathway is a potential marker and target for the clinical diagnosis and therapy of RM.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Key Research and Development Program of China (2017YFC1001401), National Natural Science Foundation of China (81730039, 82071653, 81671460, 81971384 and 82171657) and Shanghai Municipal Medical and Health Discipline Construction Projects (2017ZZ02015). The authors have declared no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Homocysteine level and gestational diabetes mellitus: a systematic review and meta-analysis

AIMS

It is reported that elevated homocysteine (Hcy) level represents an independent risk factor for gestational diabetes mellitus (GDM). However, the relationship between Hcy level and GDM remains controversial. Our study aimed to systematically review available literature linking Hcy to GDM for a comprehensive understanding of the relationship between circulating Hcy level and GDM in humans.

METHODS

PubMed, The Cochrane Library, and Web of Science were searched for studies published up to January 2021. Manual searches of references of the relevant studies were also conducted. Standard mean difference (SMD) with 95% confidence interval (95%CI) were calculated to evaluate the relationship between Hcy level and GDM using the Review Manager 5.3 and Stata 12.0.

RESULTS

Of 106 references reviewed, 12 studies with a total of 712 GDM patients contributed to the present meta-analysis. Hcy level was significantly elevated in women with GDM compared with those without GDM (SMD = 0.55; 95% CI: 0.25-0.85, p = .0003). In the subgroup meta-analyses, this evidence was more consistent among women with Hcy sampling during the second trimester (SMD = 0.76, 95% CI: 0.34-1.18, p = .0004) and with average age ≥30 years (SMD = 0.69, 95% CI: 0.25-1.12, p = .002).

CONCLUSION

The evidence indicated that the level of circulating Hcy was significantly elevated among women with GDM compared with those with normal glucose tolerance, especially with mean age ≥30 years and in the second trimester.

The diagnostic indicators of gestational diabetes mellitus from second trimester to birth: a systematic review

BACKGROUND

Gestational diabetes mellitus (GDM) is glucose intolerance first recognised during pregnancy. Both modalities and thresholds of the GDM diagnostic test, the Oral Glucose Tolerance Test (OGTT), have varied widely over time and among countries. Additionally, OGTT limitations include inconsistency, poor patient tolerability, and questionable diagnostic reliability. Many biological parameters have been reported to be modified by GDM and could potentially be used as diagnostic indicators. This study aimed to 1) systematically explore biomarkers reported in the literature as differentiating GDM from healthy pregnancies 2) screen those indicators assessed against OGTT to propose OGTT alternatives.

MAIN BODY

A systematic review of GDM diagnostic indicators was performed according to PRISMA guidelines (PROSPERO registration CRD42020145499). Inclusion criteria were full-text, comprehensible English-language articles published January 2009-January 2021, where a biomarker (from blood, ultrasound, amniotic fluid, placenta) was compared between GDM and normal glucose tolerance (NGT) women from the second trimester onward to immediately postpartum. GDM diagnostic method had to be clearly specified, and the number of patients per study higher than 30 in total or 15 per group. Results were synthesised by biomarkers.

RESULTS

Of 13,133 studies identified in initial screening, 174 studies (135,801 participants) were included. One hundred and twenty-nine studies described blood analytes, one amniotic fluid analytes, 27 ultrasound features, 17 post-natal features. Among the biomarkers evaluated in exploratory studies, Adiponectin, AFABP, Betatrophin, CRP, Cystatin-C, Delta-Neutrophil Index, GGT, TNF-A were those demonstrating statistically and clinically significant differences in substantial cohorts of patients (> 500). Regarding biomarkers assessed versus OGTT (i.e. potential OGTT alternatives) most promising were Leptin > 48.5 ng/ml, Ficolin3/adiponectin ratio ≥ 1.06, Chemerin/FABP > 0.71, and Ultrasound Gestational Diabetes Score > 4. These all demonstrated sensitivity and specificity > 80% in adequate sample sizes (> / = 100).

CONCLUSIONS

Numerous biomarkers may differentiate GDM from normoglycaemic pregnancy. Given the limitations of the OGTT and the lack of a gold standard for GDM diagnosis, advanced phase studies are needed to triangulate the most promising biomarkers. Further studies are also recommended to assess the sensitivity and specificity of promising biomarkers not yet assessed against OGTT.

TRIAL REGISTRATION

PROSPERO registration number CRD42020145499.

Discovery of metabolic biomarkers for gestational diabetes mellitus in a Chinese population

Background

Gestational diabetes mellitus (GDM), one of the most common pregnancy complications, can lead to morbidity and mortality in both the mother and the infant. Metabolomics has provided new insights into the pathology of GDM and systemic analysis of GDM with metabolites is required for providing more clues for GDM diagnosis and mechanism research. This study aims to reveal metabolic differences between normal pregnant women and GDM patients in the second- and third-trimester stages and to confirm the clinical relevance of these new findings.

Methods

Metabolites were quantitated with the serum samples of 200 healthy pregnant women and 200 GDM women in the second trimester, 199 normal controls, and 199 GDM patients in the third trimester. Both function and pathway analyses were applied to explore biological roles involved in the two sets of metabolites. Then the trimester stage-specific GDM metabolite biomarkers were identified by combining machine learning approaches, and the logistic regression models were constructed to evaluate predictive efficiency. Finally, the weighted gene co-expression network analysis method was used to further capture the associations between metabolite modules with biomarkers and clinical indices.

Results

This study revealed that 57 differentially expressed metabolites (DEMs) were discovered in the second-trimester group, among which the most significant one was 3-methyl-2-oxovaleric acid. Similarly, 72 DEMs were found in the third-trimester group, and the most significant metabolites were ketoleucine and alpha-ketoisovaleric acid. These DEMs were mainly involved in the metabolism pathway of amino acids, fatty acids and bile acids. The logistic regression models for selected metabolite biomarkers achieved the area under the curve values of 0.807 and 0.81 for the second- and third-trimester groups. Furthermore, significant associations were found between DEMs/biomarkers and GDM-related indices.

Conclusions

Metabolic differences between healthy pregnant women and GDM patients were found. Associations between biomarkers and clinical indices were also investigated, which may provide insights into pathology of GDM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00606-8.

Impact of Arginine Nutrition and Metabolism during Pregnancy on Offspring Outcomes

By serving as a precursor for the synthesis of nitric oxide, polyamines, and other molecules with biological importance, arginine plays a key role in pregnancy and fetal development. Arginine supplementation is a potential therapy for treating many human diseases. An impaired arginine metabolic pathway during gestation might produce long-term morphological or functional changes in the offspring, namely, developmental programming to increase vulnerability to developing a variety of non-communicable diseases (NCDs) in later life. In contrast, reprogramming is a strategy that shifts therapeutic interventions from adulthood to early-life, in order to reverse the programming processes, which might counterbalance the rising epidemic of NCDs. This review presented the role of arginine synthesis and metabolism in pregnancy. We also provided evidence for the links between an impaired arginine metabolic pathway and the pathogenesis of compromised pregnancy and fetal programming. This was followed by reprogramming strategies targeting the arginine metabolic pathway, to prevent the developmental programming of NCDs. Despite emerging evidence from experimental studies showing that targeting the arginine metabolic pathway has promise as a reprogramming strategy in pregnancy to prevent NCDs in the offspring, these results need further clinical application.

Endothelial dysfunction in pregnancy metabolic disorders

In recent years, the vascular endothelium has gained attention as a key player in the initiation and development of pregnancy disorders. Endothelium acts as an endocrine organ that preserves the homeostatic balance by responding to changes in metabolic status. However, in metabolic disorders, endothelial cells adopt a dysfunctional function, losing their normal responsiveness. During pregnancy, several metabolic changes occur, in which endothelial function decisively participates. Similarly, when pregnancy metabolic disorders occur, endothelial dysfunction plays a key role in pathogenesis. This review outlines the main findings regarding endothelial dysfunction in three main metabolic pathological conditions observed during pregnancy: gestational diabetes, hypertensive disorders, and obesity and hyperlipidemia. Organ, histological and cellular characteristics were thoroughly described. Also, we focused in discussing the underlying molecular mechanisms involved in the cellular signaling pathways that mediate responses in these pathological conditions.

Expression of intercellular adhesion molecule-1 in umbilical vascular of pregnant women with gestational diabetes mellitus and the clinical significance

The purpose of this study was to investigate the expression of intercellular adhesion molecule-1 (ICAM-1) in umbilical vascular of pregnant women with gestational diabetes mellitus (GDM) and the clinical significance. A total of 103 pregnant women with GDM were selected in the First Hospital of Lanzhou University and the Second Affiliated Hospital of Xi'an Jiaotong University from January 2016 to December 2016 as GDM group. At the same time, 106 normal pregnant women were selected as control group. i) General information of the two groups of pregnant women including age, gestational age, gravida, parity, BMI, systolic blood pressure and diastolic blood pressure were compared; ii) the laboratory indicators of the two groups of pregnant women including fasting blood glucose, glycosylated hemoglobin (HbA1c), umbilical cord arterial pH, partial pressure of oxygen (pO₂) and carbon dioxide (pCO₂) in umbilical artery were compared; iii) expression of ICAM-1 in umbilical vascular was detected by immunohistochemistry; iv) expression levels of ICAM-1 in umbilical vascular of the two groups of patients were compared. i) There was no significant difference in the age, smoking, gestational age, gravida, parity, BMI, systolic blood pressure and diastolic blood pressure between the two groups (p>0.05); ii) no significant differences in HbA1c, umbilical cord arterial pH, pO₂ and pCO₂ were found between the groups (p>0.05); iii) ICAM-1 was expressed in umbilical vessels of both groups of pregant women; iv) no significant differences in expression levels of ICAM-1 in umbilical artery and umbilical vein endothelial cells were found between the groups (p>0.05). Therefore, GDM patients with good blood glucose control have no umbilical cord endothelial cell damage.

Serum homocysteine level and gestational diabetes mellitus: A meta-analysis

Aims/Introduction

Homocysteine levels during pregnancy in women with gestational diabetes mellitus (GDM) have been studied; however, it remains unclear whether hyperhomocysteinemia is a useful predictor of insulin resistance. The present study aimed to evaluate the relationship between homocysteine level and GDM.

Materials and Methods

PubMed, Elsevier, Web of Science and CNKI were searched for relevant studies published up to January 2015. Manual searches of references of the relevant original studies were carried out. Meta‐analysis was used to assessed the relationship between homocysteine level and GDM using the stata 12.0 software.

Results

Homocysteine levels were significantly elevated in women with GDM compared with those without GDM (weighted mean difference 0.77, 95% confidence interval 0.44–1.10). This evidence was more consistent during the second trimester measurement of homocysteine (weighted mean difference 0.95, 95% confidence interval 0.67–1.23) and for women aged older than 30 years (weighted mean difference 0.90, 95% confidence interval 0.63–1.17).

Conclusions

The present meta‐analysis shows that homocysteine level is significantly elevated among women with GDM compared with women with normal glucose tolerance, and this finding persists more during the second trimester.

Intercellular Adhesion Molecule and Endogenous NOS Inhibitor: Asymmetric Dimethylarginine in Pregnant Women with Gestational Diabetes Mellitus

OBJECTIVE

The aim of the study was to evaluate the concentrations of soluble intercellular adhesion molecule-1 (s-ICAM-1) and endogenous NOS inhibitor, asymmetric dimethylarginine (ADMA), as markers of endothelium dysfunction in patients with gestational diabetes mellitus (GDM).

PATIENTS AND METHODS

The levels of s-ICAM-1 and ADMA were analysed in the group of 56 patients with GDM and compared to 25 healthy pregnant women. The concentrations of s-ICAM-1 and ADMA were measured in serum using ELISA tests.

RESULTS

The groups did not differ by baseline descriptors: age (30.75 ± 6.32 versus 28.50 ± 4.95 years, NS) and gestational age (28.96 ± 2.85 versus 29.12 ± 2.96 hbd, NS). The patients with GDM were more obese (BMI 27.93 ± 7.02 versus 22.34 ± 4.21 kg/m(2), p = 0.032) and had higher concentration of C-reactive protein (6.46 ± 6.03 versus 3.18 ± 3.83 mg/L, p = 0.029). In the GDM group the level of ADMA was lower (0.38 ± 0.17 versus 0.60 ± 0.28 μmol/L, p = 0.001) and the level of s-ICAM-1 was significantly higher (289.95 ± 118.12 versus 232.56 ± 43.31 ng/mL, p = 0.036) compared to controls.

CONCLUSIONS

The pregnant women with GDM are characterized by higher concentration of s-ICAM-1 that reflects the activation and dysfunction of the endothelial cells. The decreased ADMA level in GDM patients seems to be preventive in the limitation of NO synthesis caused by the impaired insulin action and the endothelial dysfunction.

Asymmetric dimethylarginine is associated with high-sensitivity C-reactive protein and early carotid atherosclerosis in women with previous gestational diabetes mellitus

Asymmetric dimethylarginine (ADMA) is increased in subjects with previous gestational diabetes mellitus (GDM). The aim of this study was to investigate the relationship between serum ADMA levels and early carotid atherosclerosis in women with history of GDM. A total of 42 normoglycemic women with previous GDM and 42 age-matched healthy controls were enrolled. Serum levels of ADMA, lipids, insulin, fasting and 2-h glucose following 75-g oral glucose tolerance test, and high sensitivity C-reactive protein (hsCRP) were measured. Carotid atherosclerosis was evaluated by ultrasonographically determined intima-media thickness (IMT). Serum ADMA and hsCRP were higher in women with previous GDM compared to the healthy controls (0.72 ± 0.16 vs. 0.41 ± 0.15 μmol/L, p < 0.001; 1.81 ± 0.32 vs. 1.05 ± 0.26 mg/L, p < 0.001; respectively). Carotid IMT was also increased in the previous GDM group (0.77 ± 0.14 vs. 0.52 ± 0.13 mm, p < 0.001). In women with previous GDM, ADMA was positively correlated with hsCRP (r = 41, p < 0.001) and carotid IMT (r = 0.38, p < 0.001). Multiple linear regression analysis revealed that ADMA was a significant predictor for elevated carotid IMT in subjects with previous GDM after adjusting for traditional risk factors (β = 0.26, p = 0.017). Our data demonstrated that serum ADMA was associated with hsCRP and carotid IMT in normoglycemic women with previous GDM.

A systematic review of metabolite profiling in gestational diabetes mellitus

AIMS/HYPOTHESIS

Gestational diabetes mellitus is associated with adverse maternal and fetal outcomes during, as well as subsequent to, pregnancy, including increased risk of type 2 diabetes and cardiovascular disease. Because of the importance of early risk stratification in preventing these complications, improved first-trimester biomarker determination for diagnosing gestational diabetes would enhance our ability to optimise both maternal and fetal health. Metabolomic profiling, the systematic study of small molecule products of biochemical pathways, has shown promise in the identification of key metabolites associated with the pathogenesis of several metabolic diseases, including gestational diabetes. This article provides a systematic review of the current state of research on biomarkers and gestational diabetes and discusses the clinical relevance of metabolomics in the prediction, diagnosis and management of gestational diabetes.

METHODS

We conducted a systematic search of MEDLINE (PubMed) up to the end of February 2014 using the key term combinations of 'metabolomics,' 'metabonomics,' 'nuclear magnetic spectroscopy,' 'mass spectrometry,' 'metabolic profiling' and 'amino acid profile' combined (AND) with 'gestational diabetes'. Additional articles were identified through searching the reference lists from included studies. Quality assessment of included articles was conducted through the use of QUADOMICS.

RESULTS

This systematic review included 17 articles. The biomarkers most consistently associated with gestational diabetes were asymmetric dimethylarginine and NEFAs. After QUADOMICS analysis, 13 of the 17 included studies were classified as 'high quality'.

CONCLUSIONS/INTERPRETATION

Existing metabolomic studies of gestational diabetes present inconsistent findings regarding metabolite profile characteristics. Further studies are needed in larger, more racially/ethnically diverse populations.

Role of equilibrative adenosine transporters and adenosine receptors as modulators of the human placental endothelium in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a diseases that alters human placenta macro and microvascular reactivity as a result of endothelial dysfunction. The human placenta is a highly vascularized organ which lacks innervation, so blood flux is governed by locally released vasoactive molecules, including the endogenous nucleoside adenosine and the free radical nitric oxide (NO). Altered adenosine metabolism and uptake by the endothelium leads to increased NO synthesis which then turns-off the expression of genes coding for a family of nucleoside membrane transporters belonging to equilibrative nucleoside transporters, particularly isoforms 1 (hENT1) and 2 (hENT2). This mechanism leads to increased extracellular adenosine and, as a consequence, activation of adenosine receptors to further sustain a tonic activation of NO synthesis. This is a phenomenon that seems operative in the placental macro and microvascular endothelium in GDM. We here summarize the findings available in the literature regarding these mechanisms in the human feto-placental circulation. This phenomenon is altered in the feto-placental vasculature, which could be crucial for understanding GDM deleterious effects in fetal growth and development.

The association of adipose-derived dimethylarginine dimethylaminohydrolase-2 with insulin sensitivity in experimental type 2 diabetes mellitus

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS), which can be hydrolyzed by dimethylarginine-dimethylaminohydrolase (DDAH). It has been reported that adipocytes can produce DDAH/ADMA, but its role remains unknown. In the present study, we examined the effects of adipocyte-derived DDAH/ADMA on insulin sensitivity using animal and cell models. Results showed that in adipose tissue of high fat diet-fed diabetic rats, as well as in high glucose (25 mM) plus insulin (100 nM)-treated 3T3-L1 adipocytes, expression levels of insulin receptor substance-1 (IRS-1), glucose transporter-4 (GLUT-4), and DDAH isoform-2 (DDAH-2) were down-regulated compared with control, although DDAH-1 expression showed no significant changes. We also observed that nitric oxide bioavailability, DDAH and NOS activities were subsequently decreased, while the local ADMA content was elevated in diabetic adipose tissue. Transfection of human DDAH-2 gene into high glucose- and insulin-treated 3T3-L1 adipocytes significantly ameliorated DDAH activity, reduced ADMA contents, and up-regulated the mRNA expression levels of IRS-1 and GLUT-4. These findings suggested that in the development of type 2 diabetes mellitus, local DDAH-2 in adipocytes might play an important role in regulating insulin sensitivity.

Biological significance of a thyroid hormone-regulated secretome

The thyroid hormone, 3,3,5-triiodo-L-thyronine (T3), modulates several physiological processes, including cellular growth, differentiation, metabolism and proliferation, via interactions with thyroid hormone response elements (TREs) in the regulatory regions of target genes. Several intracellular and extracellular protein candidates are regulated by T3. Moreover, T3-regulated secreted proteins participate in physiological processes or cellular transformation. T3 has been employed as a marker in several disorders, such as cardiovascular disorder in chronic kidney disease, as well as diseases of the liver, immune system, endocrine hormone metabolism and coronary artery. Our group subsequently showed that T3 regulates several tumor-related secretory proteins, leading to cancer progression via alterations in extracellular matrix proteases and tumor-associated signaling pathways in hepatocellular carcinomas. Therefore, elucidation of T3/thyroid hormone receptor-regulated secretory proteins and their underlying mechanisms in cancers should facilitate the identification of novel therapeutic targets. This review provides a detailed summary on the known secretory proteins regulated by T3 and their physiological significance. This article is part of a Special Issue entitled: An Updated Secretome.

Roles of nitric oxide and asymmetric dimethylarginine in pregnancy and fetal programming

Nitric oxide (NO) regulates placental blood flow and actively participates in trophoblast invasion and placental development. Asymmetric dimethylarginine (ADMA) can inhibit NO synthase, which generates NO. ADMA has been associated with uterine artery flow disturbances such as preeclampsia. Substantial experimental evidence has reliably supported the hypothesis that an adverse in utero environment plays a role in postnatal physiological and pathophysiological programming. Growing evidence suggests that the placental nitrergic system is involved in epigenetic fetal programming. In this review, we discuss the roles of NO and ADMA in normal and compromised pregnancies as well as the link between placental insufficiency and epigenetic fetal programming.

Asymmetric dimethylarginine level in hyperglycemic gestation

We aimed to evaluate plasma asymmetric dimethylarginine (ADMA) concentrations and its relation with insulin sensitivity/resistance indices in pregnant women with different degrees of carbohydrate intolerance. This study included a two step approach; 50 g glucose challenge test (GCT) followed by 100 g oral glucose tolerance test (OGTT) was used for diagnosis of carbohydrate intolerance within 24-28th weeks of gestation. Pregnant women with positive GCT but negative OGTT (AGCT group, n=30) and gestational diabetics (GDM group, n=58) were compared to healthy pregnant controls (n=50). Plasma ADMA concentration and its relationship with glucose and insulin levels and insulin sensitivity/resistance indices (HOMA-IR, QUICKI, ISIOGTT) were evaluated. Both AGCT and GDM groups were found to have similarly higher plasma ADMA levels than control subjects (3.60±1.21; 4.00±1.70; 2.65±0.82 μmol/l, respectively, P=0.001). ADMA was significantly but slightly correlated with insulin sensitivity/resistance indices and moderately correlated with 2-h insulin level. The 2-h insulin value of the OGTT was the independent influencing constant for ADMA (R=0.57, P=0.0001). In conclusion, plasma asymmetric dimethylarginine level was higher in cases with abnormal glucose challenge test but normal OGTT as well as in gestational diabetics, compared to pregnant women with normal glucose tolerance. The elevated ADMA level in pregnant women with carbohydrate intolerance may possibly be due to elevated insulin level.

Relationships between serum levels of thyroid hormones and serum concentrations of asymmetric dimethylarginine (ADMA) and N-terminal-pro-B-type natriuretic peptide (NT-proBNP) in patients with Graves' disease

Endothelial dysfunction as well as abnormal thyroid hormone levels may be responsible for increased cardiovascular risk in Graves' disease (GD). Asymmetric dimethylarginine (ADMA) and N-terminal-pro-B-type natriuretic peptide (NT-proBNP) are new markers of endothelial and myocardial dysfunction, respectively. The purpose of this study was to investigate the relationship among the serum levels of ADMA, NT-proBNP, and thyroid hormones in GD patients. This was a cross-sectional investigation conducted in a university teaching hospital. Two hundred and thirty-nine GD (Female: 182, Male: 57) patients and 81 normal controls were enrolled in this study. Serum levels of ADMA were positively related with FT3 (r = 0.584, P < 0.001), FT4 (r = 0.551, P < 0.001), and TRAb levels (r = 0.502, P < 0.001). Serum NT-proBNP levels were positively associated with FT3 (r = 0.243, P < 0.001) and FT4 levels (r = 0.274, P < 0.001), as well as heart rate (r = 0.271, P < 0.03). The elevation of serum ADMA and NT-proBNP levels were also observed in patients with controlled hyperthyroidism. It is thus concluded that serum ADMA and NT-proBNP levels were increased in GD patients. Future studies may determine the usefulness of these two biomarkers to detect early signs of endothelial dysfunction, vascular stiffness, and fluid volume in GD patients.

Review: Differential placental macrovascular and microvascular endothelial dysfunction in gestational diabetes

Human endothelial dysfunction is a common feature in many diseases of pregnancy, such as gestational diabetes (GD). Metabolic changes include abnormal synthesis of nitric oxide (NO) and abnormal membrane transport of l-arginine and adenosine in primary cultures of human umbilical vein (HUVEC, macrovascular) and placental microvillus (hPMEC, microvascular) endothelial cells. These alterations are associated with modifications in the expression and activity of endothelial (eNOS) and inducible (iNOS) NO synthases, respectively, an effect that is maintained at least up to passage 5 in culture. HUVEC and hPMEC exhibit expression and activity of the human cationic amino acid transporter 1 (hCAT-1), equilibrative nucleoside transporters 1 (hENT1) and hENT2, as well as the corresponding SLC7A1, SLC29A1 and SLC29A2 gene promoter activities. Altered gene expression results from increased NO level, protein kinase C, mitogen-activated protein kinases, and hCHOP-C/EBPα transcription factor activation. Reduced ENT-mediated adenosine transport in GD is associated with stimulation of the l-arginine/NO pathway, and mainly due to reduced expression and activity of hENT1. In addition, hENT2 activity seems able to restore the reduced adenosine transport in GD. Additionally, insulin exerts a differential modulation of endothelial cells from macrocirculation compared with microcirculation, possibly due to expression of different insulin receptor isoforms. It is suggested that a common functional characteristic leading to changes in the bioavailability of adenosine and metabolism of l-arginine is evidenced by human fetal micro and macrovascular endothelium in GD.