Maternal insulin therapy does not restore foetoplacental endothelial dysfunction in gestational diabetes mellitus

KLF4 down-regulation underlies placental angiogenesis impairment induced by maternal glucose intolerance in late pregnancy

Maternal glucose intolerance in late pregnancy can easily impair pregnancy outcomes and placental development. The impairment of placental angiogenesis is closely related to the occurrence of glucose intolerance during pregnancy, but the mechanism remains largely unknown. In this study, the pregnant mouse model of maternal high-fat diet and endothelial injury model of porcine vascular endothelial cells (PVECs) was used to investigate the effect of glucose intolerance on pregnancy outcomes and placental development. Feeding pregnant mice, a high-fat diet was shown to induce glucose intolerance in late pregnancy, and significantly increase the incidence of resorbed fetuses. Moreover, a decrease was observed in the proportion of blood sinusoids area and the expression level of CD31 in placenta, indicating that placental vascular development was impaired by high-fat diet. Considering that hyperglycemia is an important symptom of glucose intolerance, we exposed PVECs to high glucose (50 mM), which verified the negative effects of high glucose on endothelial function. Bioinformatics analysis further emphasized that high glucose exposure could significantly affect the angiogenesis-related functions of PVECs and predicted that Krüppel-like factor 4 (KLF4) may be a key mediator of these functional changes. The subsequent regulation of KLF4 expression confirmed that the inhibition of KLF4 expression was an important reason why high glucose impaired the endothelial function and angiogenesis of PVECs. These results indicate that high-fat diet can aggravate maternal glucose intolerance and damage pregnancy outcome and placental angiogenesis, and that regulating the expression of KLF4 may be a potential therapeutic strategy for maintaining normal placental angiogenesis.

Case Report: Abruptio placentae and epileptic seizure after occurrence of perinatal hyperglycaemia in woman with gestational diabetes mellitus and hypertriglyceridemia-induced acute pancreatitis

Hypertriglyceridemia-induced acute pancreatitis seldom occurs in the second trimester of pregnancy with gestational diabetes mellitus. For these patients, the existing knowledge on concomitant hyperglycemia is not sufficient. We report a case of abruptio placentae and epileptic seizure following perinatal hyperglycaemia in woman with gestational diabetes mellitus and hypertriglyceridemia-induced acute pancreatitis. The occurrence of abruptio placentae and epileptic seizure may be associated with concomitant hyperglycemia, and the epileptic seizure was terminated after she underwent treatment with insulin. We should pay more attention to the adverse effects of perinatal hyperglycemia and continue to give appropriate insulin treatment even if patients have passed the acute phase of hypertriglyceridemia-induced acute pancreatitis.

Gestational Diabetes-Placental Expression of Human Equilibrative Nucleoside Transporter 1 (hENT1): Is Delayed Villous Maturation an Adaptive Pattern?

Gestational diabetes mellitus (GDM) is a metabolic disease that can affect placental villous maturation and villous vascularity. The main effects of GDM on placental growth are a delay of villous maturation (DVM) and decreased formation of vasculo-syncytial membranes (VSM). Human equilibrative nucleoside transporter-1 (hENT1) is an adenosine transporter expressed in the human umbilical vein endothelial cells (HUVEC) and human placental microvascular endothelium cells (hPMEC). Its role is crucial in maintaining physiological fetal adenosine levels during pregnancy, and its reduction has been described in GDM. Twenty-four placentas from pregnancies with a confirmed diagnosis of GDMd and twenty-four matched non-GDM placentas (controls) were retrospectively analyzed to investigate the immunohistochemical expression of hENT1 in HUVEC and hPMEC. The study included the quantitative evaluation of VSM/mm² in placental tissue and the immunohistochemical quantitative evaluation of Ki-67, PHH3, and p57 in villous trophoblast. hENT1 expression was higher in all the vascular districts of the control cases compared to the GDMd placentas (p < 0.0001). The VSM/mm² were lower in the GDMd cases, while the Ki-67, PHH3, and p57 were higher when compared to the control cases. To our knowledge, this is the first report of hENT1 expression in the human placentas of GDM patients. The absence/low expression of hENT1 in all the GDMd patients may indicate a potential role in microvascular adaptative mechanisms. The trophoblasts' proliferative/antiapoptotic pattern (high Ki-67, high PHH3, and high p57 count) may explain the statistically significant lower number of VSM/mm² found in the GDMd cases.

Platelets and endothelial dysfunction in gestational diabetes mellitus

The prevalence of gestational diabetes mellitus (GDM) has increased in recent years, along with the higher prevalence of obesity in women of reproductive age. GDM is a pathology associated with vascular dysfunction in the fetoplacental unit. GDM-associated endothelial dysfunction alters the transfer of nutrients to the foetus affecting newborns and pregnant women. Various mechanisms for this vascular dysfunction have been proposed, of which the most studied are metabolic alterations of the vascular endothelium. However, different cell types are involved in GDM-associated endothelial dysfunction, including platelets. Platelets are small, enucleated cell fragments that actively take part in blood haemostasis and thrombus formation. Thus, they play crucial roles in pathologies coursing with endothelial dysfunction, such as atherosclerosis, cardiovascular diseases, and diabetes mellitus. Nevertheless, platelet function in GDM is understudied. Several reports show a potential relationship between platelet volume and mass with GDM; however, platelet roles and signaling mechanisms in GDM-associated endothelial dysfunction are unclear. This review summarizes the reported findings and proposes a link among altered amount, volume, mass, reactivity, and function of platelets and placenta development, resulting in fetoplacental vascular dysfunction in GDM.

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.

Increased Fetal Cardiovascular Disease Risk: Potential Synergy Between Gestational Diabetes Mellitus and Maternal Hypercholesterolemia

Cardiovascular diseases (CVD) remain a major cause of death worldwide. Evidence suggests that the risk for CVD can increase at the fetal stages due to maternal metabolic diseases, such as gestational diabetes mellitus (GDM) and maternal supraphysiological hypercholesterolemia (MSPH). GDM is a hyperglycemic, inflammatory, and insulin-resistant state that increases plasma levels of free fatty acids and triglycerides, impairs endothelial vascular tone regulation, and due to the increased nutrient transport, exposes the fetus to the altered metabolic conditions of the mother. MSPH involves increased levels of cholesterol (mainly as low-density lipoprotein cholesterol) which also causes endothelial dysfunction and alters nutrient transport to the fetus. Despite that an association has already been established between MSPH and increased CVD risk, however, little is known about the cellular processes underlying this relationship. Our knowledge is further obscured when the simultaneous presentation of MSPH and GDM takes place. In this context, GDM and MSPH may substantially increase fetal CVD risk due to synergistic impairment of placental nutrient transport and endothelial dysfunction. More studies on the separate and/or cumulative role of both processes are warranted to suggest specific treatment options.

Exposome and foetoplacental vascular dysfunction in gestational diabetes mellitus

A balanced communication between the mother, placenta and foetus is crucial to reach a successful pregnancy. Several windows of exposure to environmental toxins are present during pregnancy. When the women metabolic status is affected by a disease or environmental toxin, the foetus is impacted and may result in altered development and growth. Gestational diabetes mellitus (GDM) is a disease of pregnancy characterised by abnormal glucose metabolism affecting the mother and foetus. This disease of pregnancy associates with postnatal consequences for the child and the mother. The whole endogenous and exogenous environmental factors is defined as the exposome. Endogenous insults conform to the endo-exposome, and disruptors contained in the immediate environment are the ecto-exposome. Some components of the endo-exposome, such as Selenium, vitamins D and B₁₂, adenosine, and a high-fat diet, and ecto-exposome, such as the heavy metals Arsenic, Mercury, Lead and Copper, and per- and polyfluoroakyl substances, result in adverse pregnancies, including an elevated risk of GDM or gestational diabesity. The impact of the exposome on the human placenta's vascular physiology and function in GDM and gestational diabesity is reviewed.

Gestational diabesity and foetoplacental vascular dysfunction

Gestational diabetes mellitus (GDM) shows a deficiency in the metabolism of D-glucose and other nutrients, thereby negatively affecting the foetoplacental vascular endothelium. Maternal hyperglycaemia and hyperinsulinemia play an important role in the aetiology of GDM. A combination of these and other factors predisposes women to developing GDM with pre-pregnancy normal weight, viz. classic GDM. However, women with GDM and prepregnancy obesity (gestational diabesity, GDty) or overweight (GDMow) show a different metabolic status than women with classic GDM. GDty and GDMow are associated with altered l-arginine/nitric oxide and insulin/adenosine axis signalling in the human foetoplacental microvascular and macrovascular endothelium. These alterations differ from those observed in classic GDM. Here, we have reviewed the consequences of GDty and GDMow in the modulation of foetoplacental endothelial cell function, highlighting studies describing the modulation of intracellular pH homeostasis and the potential implications of NO generation and adenosine signalling in GDty-associated foetal vascular insulin resistance. Moreover, with an increase in the rate of obesity in women of childbearing age worldwide, the prevalence of GDty is expected to increase in the next decades. Therefore, we emphasize that women with GDty and GDMow should be characterized with a different metabolic state from that of women with classic GDM to develop a more specific therapeutic approach for protecting the mother and foetus.

High total cholesterol and triglycerides levels increase arginases metabolism, impairing nitric oxide signaling and worsening fetoplacental endothelial dysfunction in gestational diabetes mellitus pregnancies

During human pregnancy, maternal physiological dyslipidemia (MPD) supports fetal development. However, some women develop maternal supraphysiological dyslipidemia (MSPD: increased total cholesterol (TC) and triglycerides (TG) levels). MSPD is present in normal and pregnancies with gestational diabetes mellitus (GDM). Both pathologies associate with fetoplacental endothelial dysfunction, producing alterations in nitric oxide (NO)-L-arginine/arginase metabolism. Nevertheless, the effect of MSPD on GDM, and how this synergy alters fetoplacental endothelial function is unknown, which is the aim of this study. 123 women at term of pregnancy were classified as MPD (n=40), MSPD (n=35), GDM with normal lipids (GDM- MPD, n=23) and with increased lipids (GDM-MSPD, n=25). TC ≥291 mg/dL and TG ≥275 mg/dL were considered as MSPD. Endothelial NO synthase (eNOS), human cationic amino acid transporter 1 (hCat1), and arginase II protein abundance and activity, were assayed in umbilical vein endothelial cells. In MSPD and MSPD-GDM, TC and TG increased respect to MPD and MPD-GDM. eNOS activity was reduced in MSPD and MSPD-GDM, but increased in MPD-GDM compared with MPD. No changes were observed in eNOS protein. However, decreased tetrahydrobiopterin levels were observed in all groups compared with MPD. Increased hCat1 protein and L-arginine transport were observed in both GDM groups compared with MPD. However, the transport was higher in GDM-MSPD compared to GDM-MPD. Higher Arginase II protein and activity were observed in MSPD-GDM compared with MPD. Thus, MSPD in GDM pregnancies alters fetal endothelial function associated with NO metabolism.

Reduced mechanical function of the left atrial predicts adverse outcome in pregnant women with clustering of metabolic risk factors

INTRODUCTION

The left atrial (LA) strain and strain rate are sensitive indicators of LA function. However, they are not widely used for the evaluation of pregnant women with metabolic diseases. The aim of this study was to assess the LA strain and strain rate of pregnant women with clustering of metabolic risk factors and to explore its prognostic effect on adverse pregnancy outcomes.

MATERIALS AND METHODS

Sixty-three pregnant women with a clustering of metabolic risk factors (CMR group), fifty-seven women with pregnancy-induced hypertension (PIH group), fifty-seven women with gestational diabetes mellitus (GDM group), and fifty matched healthy pregnant women (control group) were retrospectively evaluated. LA function was evaluated with two-dimensional speckle-tracking imaging. Iatrogenic preterm delivery caused by severe preeclampsia, placental abruption, and fetal distress was regarded as the primary adverse outcome.

RESULTS

The CMR group showed the lowest LA strain during reservoir phase (LASr), strain during contraction phase (LASct) and peak strain rate during conduit phase (pLASRcd) among the three groups (P < 0.05). LA strain during conduit phase (LAScd) and peak strain rate during reservoir phase (pLASRr) in the CMR group were lower than those in the control and GDM groups (P < 0.05). Multivariable Cox regression analysis demonstrated systolic blood pressure (HR = 1.03, 95% CI 1.01-1.05, p = 0.001) and LASr (HR = 0.86, 95% CI 0.80-0.92, p < 0.0001) to be independent predictors of iatrogenic preterm delivery. An LASr cutoff value ≤ 38.35% predicted the occurrence of iatrogenic preterm delivery.

CONCLUSIONS

LA mechanical function in pregnant women with metabolic aggregation is deteriorated. An LASr value of 38.35% or less may indicate the occurrence of adverse pregnancy outcomes.

Oral L-glutamine rescues fructose-induced poor fetal outcome by preventing placental triglyceride and uric acid accumulation in Wistar rats

BACKGROUND

Metabolic adaptation of pregnant mothers is crucial for placental development and fetal growth/survival. However, evidence exists that indiscriminate consumption of fructose-enriched drink (FED) during pregnancy disrupts maternal-fetal metabolic tolerance with attendant adverse fetal outcomes. Glutamine supplementation (GLN) has been shown to exert a modulatory effect in metabolic disorders. Nevertheless, the effects of GLN on FED-induced poor fetal outcome, and in particular the impacts on placental uric acid/lipid accumulation are unknown. The present study was conducted to test the hypothesis that oral GLN improves fetal outcome by attenuating placental lipid accumulation and uric acid synthesis in pregnant rats exposed to FED.

MATERIALS AND METHODS

Pregnant Wistar rats (160-180 g) were randomly allotted to control, GLN, FED and FED + GLN groups (6 rats/group). The groups received vehicle by oral gavage, glutamine (1 g/kg) by oral gavage, fructose (10%; w/v) and fructose + glutamine, respectively, through gestation.

RESULTS

Data showed that FED during pregnancy caused placental inefficiency, reduced fetal growth, and caused insulin resistance with correspondent increase in fasting blood glucose and plasma insulin. FED also resulted in an increased placental triglyceride, total cholesterol and de novo uric acid synthesis by activating adenosine deaminase and xanthine oxidase activities. Moreover, FED during pregnancy led to increased lipid peroxidation, lactate production with correspondent decreased adenosine and glucose-6-phosphate dehydrogenase-dependent antioxidant defense. These alterations were abrogated by GLN supplementation.

CONCLUSION

These findings implicate that high FED intake during pregnancy causes poor fetal outcome via defective placental uric acid/triglyceride-dependent mechanism. The findings also suggest that oral GLN improves fetal outcome by ameliorating placental defects through suppression of uric acid/triglyceride accumulation.

Insulin Therapy in Pregnancy Hypertensive Diseases and its Effect on the Offspring and Mother Later in Life

Pregnancy hypertensive disorders such as Preeclampsia (PE) are strongly correlated with insulin resistance, a condition in which the metabolic handling of D-glucose is deficient. In addition, the impact of preeclampsia is enhanced by other insulin-resistant disorders, including polycystic ovary syndrome and obesity. For this reason, there is a clear association between maternal insulin resistance, polycystic ovary syndrome, obesity and the development of PE. However, whether PE is a consequence or the cause of these disorders is still unclear. Insulin therapy is usually recommended to pregnant women with diabetes mellitus when dietary and lifestyle measures have failed. The advantage of insulin therapy for Gestational Diabetes Mellitus (GDM) patients with hypertension is still controversial; surprisingly, there are no studies in which insulin therapy has been used in patients with hypertension in pregnancy without or with an established GDM. This review is focused on the use of insulin therapy in hypertensive disorders in the pregnancy and its effect on offspring and mother later in life. PubMed and relevant medical databases have been screened for literature covering research in the field especially in the last 5-10 years.

Gestational Diabetes Mellitus Treatment Schemes Modify Maternal Plasma Cholesterol Levels Dependent to Women´s Weight: Possible Impact on Feto-Placental Vascular Function

: Gestational diabetes mellitus (GDM) associates with fetal endothelial dysfunction (ED), which occurs independently of adequate glycemic control. Scarce information exists about the impact of different GDM therapeutic schemes on maternal dyslipidemia and obesity and their contribution to the development of fetal-ED. The aim of this study was to evaluate the effect of GDM-treatments on lipid levels in nonobese (N) and obese (O) pregnant women and the effect of maternal cholesterol levels in GDM-associated ED in the umbilical vein (UV). O-GDM women treated with diet showed decreased total cholesterol (TC) and low-density lipoproteins (LDL) levels with respect to N-GDM ones. Moreover, O-GDM women treated with diet in addition to insulin showed higher TC and LDL levels than N-GDM women. The maximum relaxation to calcitonin gene-related peptide of the UV rings was lower in the N-GDM group compared to the N one, and increased maternal levels of TC were associated with even lower dilation in the N-GDM group. We conclude that GDM-treatments modulate the TC and LDL levels depending on maternal weight. Additionally, increased TC levels worsen the GDM-associated ED of UV rings. This study suggests that it could be relevant to consider a specific GDM-treatment according to weight in order to prevent fetal-ED, as well as to consider the possible effects of maternal lipids during pregnancy.

Placental structure in gestational diabetes mellitus

The placenta is a transitory organ, located between the mother and the foetus, which supports intrauterine life. This organ has nutritional, endocrine and immunologic functions to support foetal development. Several factors are related to the correct functioning of the placenta including foetal and maternal blood flow, appropriate nutrients, expression and function of receptors and transporters, and the morphology of the placenta itself. Placental morphology is crucial for understanding the pathophysiology of the organ as represents the physical structure where nutrient exchange occurs. In pathologies of pregnancy such as diabetes mellitus in humans and animal models, several changes in the placental morphology occur, related mainly with placental size, hypervascularization, higher branching capillaries of the villi and increased glycogen deposits among others. Gestational diabetes mellitus is associated with modifications in the structure of the human placenta including changes in the surface area and volume, as well as histological changes including an increased volume of intervillous space and terminal villi, syncytiotrophoblast number, fibrinoid areas, and glycogen deposits. These modifications may result in functional changes in this organ thus limiting the wellbeing of the developing foetus. This review gives an overview of recurrent morphological changes at macroscopic and histological levels seen in the placenta from gestational diabetes in humans and animal models. This article is part of a Special Issue entitled: Membrane Transporters and Receptors in Pregnancy Metabolic Complications edited by Luis Sobrevia.

Neonates from women with pregestational maternal obesity show reduced umbilical vein endothelial response to insulin

OBJECTIVE

Pregestational maternal obesity (PGMO) associates with foetoplacental vascular endothelial dysfunction and higher risk for insulin resistance in the neonate. We characterised the PGMO consequences on the insulin response of the human foetoplacental vasculature.

METHODS

Umbilical veins were from pregnancies where the mother was with PGMO (body mass index 30-42.3 kg/m², n = 33) or normal pregestational weight (PGMN) (body mass index 19.5-24.4 kg/m², n = 21) with total gestational weight gain within the physiological range. Umbilical vein ring segments were mounted in a myograph for isometric force measurements. Primary cultures of human umbilical vein endothelial cells were used in passage 3. Vessel rings and cells were exposed to 1 nmol/L insulin (20 min) in the absence or presence of 100 μmol/L N^G-nitro-l-arginine methyl ester (inhibitor of nitric oxide synthase, NOS).

RESULTS

Vessel rings from PGMO showed reduced nitric oxide synthase-activity dependent dilation to insulin or calcitonin-gene related peptide compared with PGMN. PGMO associated with higher inhibitor phosphorylation of the insulin receptor substrate 1 (IRS-1) and lower activator phosphorylation of protein kinase B/Akt (Akt). Cells from PGMO also showed lower nitric oxide level and reduced activator serine¹¹⁷⁷ but increased inhibitor threonine⁴⁹⁵ phosphorylation of endothelial nitric oxide synthase (eNOS) and saturable transport of l-arginine. HUVECs from PGMO were not responsive to insulin.

CONCLUSION

The lack of response to insulin by the foetoplacental endothelium may result from reduced IRS-1/Akt/eNOS signalling in PGMO. These findings may result in higher risk of insulin resistance in neonates to PGMO pregnancies.

Adenosine kinase and cardiovascular fetal programming in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a detrimental condition for human pregnancy associated with endothelial dysfunction and endothelial inflammation in the fetoplacental vasculature and leads to increased cardio-metabolic risk in the offspring. In the fetoplacental vasculature, GDM is associated with altered adenosine metabolism. Adenosine is an important vasoactive molecule and is an intermediary and final product of transmethylation reactions in the cell. Adenosine kinase is the major regulator of adenosine levels. Disruption of this enzyme is associated with alterations in methylation-dependent gene expression regulation mechanisms, which are associated with the fetal programming phenomenon. Here we propose that cellular and molecular alterations associated with GDM can dysregulate adenosine kinase leading to fetal programming in the fetoplacental vasculature. This can contribute to the cardio-metabolic long-term consequences observed in offspring after exposure to GDM.

Role of insulin, adenosine, and adipokine receptors in the foetoplacental vascular dysfunction in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a disease of pregnancy associated with maternal and foetal hyperglycaemia and altered foetoplacental vascular function. Human foetoplacental microvascular and macrovascular endothelium from GDM pregnancy show increased maximal l-arginine transport capacity via the human cationic amino acid transporter 1 (hCAT-1) isoform and nitric oxide (NO) synthesis by the endothelial NO synthase (eNOS). These alterations are paralleled by lower maximal transport activity of the endogenous nucleoside adenosine via the human equilibrative nucleoside transporter 1 (hENT1) and activation of adenosine receptors. A causal relationship has been described for adenosine-activation of A_2A adenosine receptors, hCAT-1, and eNOS activity (i.e. the Adenosine/l-Arginine/Nitric Oxide, ALANO, signalling pathway). Insulin restores these alterations in GDM via activation of insulin receptor A (IR-A) form in the macrovascular but IR-A and IR-B forms in the microcirculation of the human placenta. Adipokines are secreted from adipocytes influencing the foetoplacental metabolic and vascular function. Various adipokines are dysregulated in GDM, with adiponectin and leptin playing major roles. Abnormal plasma concentration of these adipokines and the activation or their receptors are involved in the pathophysiology of GDM. However, involvement of adipokines, adenosine, and insulin receptors and membrane transporters in the aetiology of this disease of pregnancy is unknown. This review focuses on the pathophysiology of insulin and adenosine receptors and l-arginine and adenosine membranes transporters giving an overview of the key adipokines leptin and adiponectin in the foetoplacental vasculature in GDM. This article is part of a Special Issue entitled: Membrane Transporters and Receptors in Pregnancy Metabolic Complications edited by Luis Sobrevia.

Endoplasmic reticulum stress and development of insulin resistance in adipose, skeletal, liver, and foetoplacental tissue in diabesity

Diabesity is an abnormal metabolic condition shown by patients with obesity that develop type 2 diabetes mellitus. Patients with diabesity present with insulin resistance, reduced vascular response to insulin, and vascular endothelial dysfunction. Along with the several well-described mechanisms of insulin resistance, a state of endoplasmic reticulum (ER) stress, where the primary human targets are the adipose tissue, liver, skeletal muscle, and the foetoplacental vasculature, is apparent. ER stress characterises by the activation of the unfolded protein response via three canonical ER stress sensors, i.e., the protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6. Slightly different cell signalling mechanisms preferentially enable in diabesity in the ER stress-associated insulin resistance for adipose tissue (IRE1α/X-box binding protein 1 mRNA splicing/c-jun N-terminal kinase 1 activation), skeletal muscle (tribbles-like protein 3 (TRB3)/proinflammatory cytokines activation), and liver (PERK/activating transcription factor 4/TRB3 activation). There is no information in human subjects with diabesity in the foetoplacental vasculature. However, the available literature shows that pregnant women with pre-pregnancy obesity or overweight that develop gestational diabetes mellitus (GDM) and their newborn show insulin resistance. ER stress is recently reported to be triggered in endothelial cells from the human umbilical vein from mothers with pre-pregnancy obesity. However, whether a different metabolic alteration to obesity in pregnancy or GDM is present in women with pre-pregnancy obesity that develop GDM, is unknown. In this review, we summarised the findings on diabesity-associated mechanisms of insulin resistance with emphasis in the primary targets adipose, skeletal muscle, liver, and foetoplacental tissues. We also give evidence on the possibility of a new GDM-associated metabolic condition triggered in pregnancy by maternal obesity, i.e. gestational diabesity, leading to ER stress-associated insulin resistance in the human foetoplacental vasculature.

Pre-pregnancy maternal obesity associates with endoplasmic reticulum stress in human umbilical vein endothelium

Obesity associates with the endoplasmic reticulum (ER) stress-induced endothelial dysfunction. Pregnant women with pre-pregnancy maternal obesity (PGMO) may transfer this potential risk to their offspring; however, whether ER stress occurs and associates with foetoplacental endothelial dysfunction in PGMO is unknown. We studied the l-arginine transport and nitric oxide (NO) synthesis in human umbilical vein endothelial cells (HUVECs) from women with PGMO or with a normal pre-pregnancy weight. We analysed the expression and activation of the ER stress sensors protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6). PGMO associated with lower endothelial NO synthase activity due to increased Thr⁴⁹⁵-inhibitor and decreased Ser¹¹⁷⁷-stimulator phosphorylation. However, higher expression and activity of the human cationic amino acid transporter 1 was found. PGMO caused activation of PERK and its downstream targets eukaryotic initiation factor 2 (eIF2α), C/EBP homologous protein 10 (CHOP), and tribbles-like protein 3 (TRB3). Increased IRE1α protein abundance (but not its phosphorylation or X-box binding protein 1-mRNA splicing) and increased c-Jun N-terminal kinase 1 phosphorylation was seen in PGMO. A preferential nuclear location of the activating transcription factor 6 (ATF6) was found in HUVECs from PGMO. All the changes seen in PGMO were blocked by TUDCA but unaltered by tunicamycin. Thus, PGMO may determine a state of ER stress via upregulation of the PERK-eIF2α-CHOP-TRB3 axis signalling in HUVECs. This phenomenon results in foetoplacental vascular endothelial dysfunction at birth.

Insulin therapy and its consequences for the mother, foetus, and newborn in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a disease characterised by glucose intolerance and first diagnosed in pregnancy. This condition relates to an anomalous placental environment and aberrant placental vascular function. GDM-associated hyperglycaemia changes the placenta structure leading to abnormal development and functionality of this vital organ. Aiming to avoid the GDM-hyperglycaemia and its deleterious consequences in the mother, the foetus and newborn, women with GDM are firstly treated with a controlled diet therapy; however, some of the women fail to reach the recommended glycaemia values and therefore they are passed to the second line of treatment, i.e., insulin therapy. The several protocols available in the literature regarding insulin therapy are variable and not a clear consensus is yet reached. Insulin therapy restores maternal glycaemia, but this beneficial effect is not reflected in the foetus and newborn metabolism, suggesting that other factors than d-glucose may be involved in the pathophysiology of GDM. Worryingly, insulin therapy may cause alterations in the placenta and umbilical vessels as well as the foetus and newborn additional to those seen in pregnant women with GDM treated with diet. In this review, we summarised the variable information regarding indications and protocols for administration of the insulin therapy and the possible outcomes on the function and structure of the foetoplacental unit and the neonate parameters from women with GDM.

Maternal supraphysiological hypercholesterolemia associates with endothelial dysfunction of the placental microvasculature

Maternal physiological or supraphysiological hypercholesterolemia (MPH, MSPH) occurs during pregnancy. MSPH is associated with foetal endothelial dysfunction and atherosclerosis. However, the potential effects of MSPH on placental microvasculature are unknown. The aim of this study was to determine whether MSPH alters endothelial function in the placental microvasculature both ex vivo in venules and arterioles from the placental villi and in vitro in primary cultures of placental microvascular endothelial cells (hPMEC). Total cholesterol < 280 mg/dL indicated MPH, and total cholesterol ≥280 mg/dL indicated MSPH. The maximal relaxation to histamine, calcitonin gene-related peptide and adenosine was reduced in MSPH venule and arteriole rings. In hPMEC from MSPH placentas, nitric oxide synthase (NOS) activity and L-arginine transport were reduced without changes in arginase activity or the protein levels of endothelial NOS (eNOS), human cationic amino acid 1 (hCAT-1), hCAT-2A/B or arginase II compared with hPMEC from MPH placentas. In addition, it was shown that adenosine acts as a vasodilator of the placental microvasculature and that NOS is active in hPMEC. We conclude that MSPH alters placental microvascular endothelial function via a NOS/L-arginine imbalance. This work also reinforces the concept that placental endothelial cells from the macro- and microvasculature respond differentially to the same pathological condition.

Fetoplacental endothelial exosomes modulate high d-glucose-induced endothelial dysfunction

INTRODUCTION

Gestational diabetes mellitus (GDM) is associated with fetoplacental endothelial dysfunction, which may be induced by hyperglycemia. We hypothesized that endothelial exosomes, which are extracellular nanovesicles affecting endothelial function, play a role in the high glucose (HG)-induced endothelial dysfunction.

METHODS

Exosomes were isolated from HUVECs incubated with basal glucose (5.5 mmol/L; HUVEC- BG; exo-BG) and from HUVECs incubated with HG for 24 h (25 mmol/L; HUVEC-HG; exo-HG) in exosome-free medium. Exosomes were isolated and characterized by ultracentrifugation, sucrose gradient, electron microscopy, nanotracking analysis and Western blotting. HUVEC-BG and HUVEC-HG were exposed to exo-BG and exo-HG in two different concentrations: 5 μg and 1 μg exosome protein/mL. The exosomal effect on endothelial cell function was determined by wound healing assay, expression of endothelial nitric oxide synthase (eNOS), human cationic amino acid transporter type 1 (hCAT-1), vascular endothelial growth factor (VEGF) and intracellular adhesion molecule type 1 (ICAM-1) by Western blotting, qPCR or flow cytometry.

RESULTS

HG increased the exosomal release from HUVECs, endothelial wound healing and expression of phosphorylated (P∼Ser¹¹⁷⁷)-eNOS, hCAT-1, VEGF and ICAM-1. Exo-HG also increased endothelial cell wound healing, P∼Ser¹¹⁷⁷-eNOS, hCAT-1 and ICAM-1 expression in HUVEC-BG. Exo-BG reverted the effect of HG on endothelial cell wound healing and hCAT-1 mRNA expression to normal values.

DISCUSSION

Our results show that HG may induce endothelial dysfunction in HUVECs and that exosomes from HUVEC-HG mimicked some of the effects of HG. This study contributes to the unraveling of the mechanism by which hyperglycemia affects the fetoplacental vasculature in GDM.

Akt/mTOR Role in Human Foetoplacental Vascular Insulin Resistance in Diseases of Pregnancy

Insulin resistance is characteristic of pregnancies where the mother shows metabolic alterations, such as preeclampsia (PE) and gestational diabetes mellitus (GDM), or abnormal maternal conditions such as pregestational maternal obesity (PGMO). Insulin signalling includes activation of insulin receptor substrates 1 and 2 (IRS1/2) as well as Src homology 2 domain-containing transforming protein 1, leading to activation of 44 and 42 kDa mitogen-activated protein kinases and protein kinase B/Akt (Akt) signalling cascades in the human foetoplacental vasculature. PE, GDM, and PGMO are abnormal conditions coursing with reduced insulin signalling, but the possibility of the involvement of similar cell signalling mechanisms is not addressed. This review aimed to determine whether reduced insulin signalling in PE, GDM, and PGMO shares a common mechanism in the human foetoplacental vasculature. Insulin resistance in these pathological conditions results from reduced Akt activation mainly due to inhibition of IRS1/2, likely due to the increased activity of the mammalian target of rapamycin (mTOR) resulting from lower activity of adenosine monophosphate kinase. Thus, a defective signalling via Akt/mTOR in response to insulin is a central and common mechanism of insulin resistance in these diseases of pregnancy. In this review, we summarise the cell signalling mechanisms behind the insulin resistance state in PE, GDM, and PGMO focused in the Akt/mTOR signalling pathway in the human foetoplacental endothelium.