Downregulated IRS-1 and PPARgamma in obese women with gestational diabetes: relationship to FFA during pregnancy

Adipose Tissue Insulin Resistance in Gestational Diabetes

BACKGROUND

Gestational diabetes mellitus (GDM) is a metabolic disorder characterized by insulin resistance (IR) and altered glucose-lipid metabolism. We propose that ectonucleotide pyrophosphate phosphodiesterase-1 (ENPP1), a protein known to induce adipocyte IR, is a determinant of GDM. Our objective was to study ENPP1 expression in adipose tissue (AT) of obese pregnant women with or without GDM, as well as glucose tolerance in pregnant transgenic (Tg) mice with AT-specific overexpression of human ENPP1.

METHODS

AT biopsies and blood were collected from body mass index-matched obese pregnant women non-GDM (n = 6), GDM (n = 7), and nonpregnant controls (n = 6) undergoing cesarian section or elective surgeries, respectively. We measured the following: (1) Expression of key molecules involved in insulin signaling and glucose-lipid metabolism in AT; (2) Plasma glucose and insulin levels and calculation of homeostasis model assessment of IR (HOMA-IR); (3) Intraperitoneal glucose tolerance test in AtENPP1 Tg pregnant mice.

RESULTS

We found that: (1) Obese GDM patients have higher AT ENPP1 expression than obese non-GDM patients, or controls (P = 0.01-ANOVA). (2) ENPP1 expression level correlated negatively with glucose transporter 4 (GLUT4) and positively with insulin receptor substrate-1 (IRS-1) serine phosphorylation, and to other adipocyte functional proteins involved in glucose and lipid metabolism (P < 0.05 each), (3) AT ENPP1 expression levels were positively correlated with HOMA-IR (P = 0.01-ANOVA). (4) Pregnant AT ENPP1 Tg mice showed higher plasma glucose than wild type animals (P = 0.046-t test on area under curve [AUC]_glucose).

CONCLUSIONS

Our results provide evidence of a causative link between ENPP1 and alterations in insulin signaling, glucose uptake, and lipid metabolism in subcutaneous abdominal AT of GDM, which may mediate IR and hyperglycemia in GDM.

Peroxisome proliferator activated receptor gamma 2 modulates late pregnancy homeostatic metabolic adaptations

Pregnancy requires the adaptation of maternal energy metabolism including expansion and functional modifications of adipose tissue. Insulin resistance (IR), predominantly during late gestation, is a physiological metabolic adaptation that serves to support the metabolic demands of fetal growth. The molecular mechanisms underlying these adaptations are not fully understood and may contribute to gestational diabetes mellitus. Peroxisome proliferator-activated receptor gamma (PPARγ) controls adipogenesis, glucose and lipid metabolism and insulin sensitivity. The PPARγ2 isoform is mainly expressed in adipocytes and is thus likely to contribute to adipose tissue adaptation during late pregnancy. In the present study, we investigated the contribution of PPARγ2 to the metabolic adaptations occurring during the late phase of pregnancy in the context of IR. Using a model of late pregnancy in PPARγ2 knockout (KO) mice, we found that deletion of PPARγ2 exacerbated IR in association with lower serum adiponectin levels, increased body weight and enhanced lipid accumulation in liver. Lack of PPARγ2 provoked changes in the distribution of fat mass and preferentially prevented the expansion of the perigonadal depot while at the same time exacerbating inflammation. PPARγ2KO pregnant mice presented adipose tissue depot-dependent decreased expression of genes involved in lipid metabolism. Collectively, these data indicate that PPARγ2 is essential to promote healthy adipose tissue expansion and immune and metabolic functionality during pregnancy, contributing to the physiological adaptations that lead gestation to term.

Expression and correlation of sex hormone-binding globulin and insulin signal transduction and glucose transporter proteins in gestational diabetes mellitus placental tissue

OBJECTIVE

The aim of the present study was to investigate the probable pathogenesis of gestational diabetes mellitus (GDM) by analyzing the correlation between sex hormone-binding globulin (SHBG) secreted by the placenta during pregnancy and insulin signaling components and glucose transporter proteins (GLUTs) in the placental tissue.

DESIGN AND METHODS

Placental tissue was collected from full-term and non-obese [body mass index <25kg/m(2)] pregnant women; 10 diagnosed with GDM and 10 with normal pregnancy. We used real-time polymerase chain reaction (PCR), immunohistochemistry and western blotting to detect expression of protein and mRNA of SHBG and insulin signaling components and GLUTs in placental tissue.

RESULTS

In the placental tissue of non-obese women, there was a decrease in expression of SHBG protein and mRNA, with a concurrent decrease in expression of GLUT-4 protein and mRNA in women with GDM compared with normal controls. There was a decrease in GLUT-3 and insulin receptor substrate (IRS)-1 protein expression and lower IRS-2 mRNA expression was also observed in GDM placental tissue. Linear correlation analyses showed a positive correlation between SHBG and IRS-2 mRNA (P=0.038, R(2)=0.2178, y=0.249x+1.4208); positive correlation between SHBG and phosphatidylinositol 3-kinase (PI3K) p85α mRNA (P=0.035, R(2)=0.224, y=0.3506x+0.7433); positive correlation between SHBG and GLUT-4 mRNA (P=0.000, R(2)=0.5174, y=1.3822+1.7811x); positive correlation between IRS-2 and GLUT-4 mRNA (P=0.002, R(2)=0.4064, y=-0.8272+2.9592x); negative correlation between IRS-1 and PI3K p85α mRNA (P=0.005, R(2)=0.366, y=2.4492-0.1929x); negative correlation between IRS-1 and GLUT-3 mRNA (P=0.027, R(2)=0.243, y=0.9254-0.0714x); and positive correlation between IRS-2 and GLUT-1 mRNA (P=0.004, R(2)=0.3794, y=0.0225+0.6298x).

CONCLUSION

The results confirm that defective receptors for insulin signal transduction and GLUT proteins are present in GDM placental tissue. Decreasing expression of SHBG may participate in regulation of insulin signaling, leading to a concomitant decrease in expression of relevant insulin signaling components in placental tissue, implying insulin resistance and eventual development of GDM.

Association of maternal prepregnancy BMI with metabolomic profile across gestation

BACKGROUND/OBJECTIVES

Elevated prepregnancy body mass index (pBMI) and excess gestational weight gain (GWG) constitute important prenatal exposures that may program adiposity and disease risk in offspring. The objective of this study is to investigate the influence of pBMI and GWG on the maternal metabolomic profile across pregnancy, and to identify associations with birth weight.

SUBJECTS/METHODS

This is a longitudinal prospective study of 167 nondiabetic women carrying a singleton pregnancy. Women were recruited between March 2011 and December 2013 from antenatal clinics affiliated to the University of California, Irvine, Medical Center. Seven women were excluded from analyses because of a diagnosis of diabetes during pregnancy. A total of 254 plasma metabolites known to be related to obesity in nonpregnant populations were analyzed in each trimester using targeted metabolomics. The effects of pBMI and GWG on metabolites were tested through linear regression and principle component analysis, adjusting for maternal sociodemographic factors, diet, and insulin resistance. A Bonferroni correction was applied for multiple comparison testing.

RESULTS

pBMI was significantly associated with 40 metabolites. Nonesterified fatty acids (NEFA) showed a strong positive association with pBMI, with specificity for mono-unsaturated and omega-6 NEFA. Among phospholipids, sphingomyelins with two double bonds and phosphatidylcholines containing 20:3 fatty acid chain, indicative of omega-6 NEFA, were positively associated with pBMI. Few associations between GWG, quality and quantity of the diet, insulin resistance and the maternal metabolome throughout gestation were detected. NEFA levels in the first and, to a lesser degree, in the second trimester were positively associated with birth weight percentiles.

CONCLUSIONS

Preconception obesity appears to have a stronger influence on the maternal metabolic milieu than gestational factors such as weight gain, dietary intake and insulin resistance, highlighting the critical importance of preconception health. NEFA in general, as well as monounsaturated and omega-6 fatty acid species in particular, represent key metabolites for a potential mechanism of intergenerational transfer of obesity risk.

Positive Correlation between Enhanced Expression of TLR4/MyD88/NF-κB with Insulin Resistance in Placentae of Gestational Diabetes Mellitus

Insulin resistance (IR) is a critical factor of the pathophysiology of Gestational diabetes mellitus (GDM). Studies on key organs involved in IR, such as livers and adipose tissues, showed that Toll-like receptor 4 (TLR4) can regulate insulin sensitivity. As a maternal-fetal interface with multi-functions, placentae could contribute to the development of IR for GDM. Thus, we investigated the expressions of TLR4/Myeloid Differentiation factor 88 (MyD88)/Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-kB) in term placentae from 33 GDM women and 36 healthy pregnant women with normal glucose tolerance, evaluated local and systemic IR and furthermore identified the association between placental TLR4 and IR. TLR4 protein was expressed in various cells of term placenta, particularly in syncytiotrophoblast of villi. Compared with normal pregnancy, the expression of TLR4/MyD88/NF-kB pathway increased in the placenta of GDM (p<0.05), and these differences were more pronounced in the maternal section of the placenta and the syncytiotrophoblast of villi. In addition, more severe IR was observed in the placenta of GDM patients than the control group, evidenced with higher pIRS-1(ser312) (p<0.001) and lower IRS-1 (p<0.05) as well as pAkt proteins (p<0.01). The expression of TLR4 in placentae is positively correlated with local IR (pIRS-1: r = 0.76, p <0.001 and pAkt: r = -0.47, p <0.001) and maternal fasting (r = 0.42, p <0.01), one-hour (r = 0.52, p <0.01) and two-hour glucose (r = 0.54, p <0.01) at OGTT. We found an that enhanced expression of the TLR4-MyD88-NF-kB pathway occurs in GDM placentae, which positively correlates with heightened local IR in placentae and higher maternal hyperglycemia. The TLR4/MyD88/NF-kB pathway may play a potential role in the development of IR in placentae of GDM.

Insulin receptor isoforms: an integrated view focused on gestational diabetes mellitus

The human insulin receptor (IR) exists in two isoforms that differ by the absence (IR-A) or the presence (IR-B) of a 12-amino acid segment encoded by exon 11. Both isoforms are functionally distinct regarding their binding affinities and intracellular signalling. However, the underlying mechanisms related to their cellular functions in several tissues are only partially understood. In this review, we summarize the current knowledge in this field regarding the alternative splicing of IR isoform, tissue-specific distribution and signalling both in physiology and disease, with an emphasis on the human placenta in gestational diabetes mellitus (GDM). Furthermore, we discuss the clinical relevance of IR isoforms highlighted by findings that show altered insulin signalling due to differential IR-A and IR-B expression in human placental endothelium in GDM pregnancies. Future research and clinical studies focused on the role of IR isoform signalling might provide novel therapeutic targets for treating GDM to improve the adverse maternal and neonatal outcomes.

Proximity to Delivery Alters Insulin Sensitivity and Glucose Metabolism in Pregnant Mice

In late pregnancy, maternal insulin resistance occurs to support fetal growth, but little is known about insulin-glucose dynamics close to delivery. This study measured insulin sensitivity in mice in late pregnancy at day 16 (D16) and near term at D19. Nonpregnant (NP) and pregnant mice were assessed for metabolite and hormone concentrations, body composition by DEXA, tissue insulin signaling protein abundance by Western blotting, glucose tolerance and utilization, and insulin sensitivity using acute insulin administration and hyperinsulinemic-euglycemic clamps with [(3)H]glucose infusion. Whole-body insulin resistance occurred in D16 pregnant dams in association with basal hyperinsulinemia, insulin-resistant endogenous glucose production, and downregulation of several proteins in hepatic and skeletal muscle insulin signaling pathways relative to NP and D19 values. Insulin resistance was less pronounced at D19, with restoration of NP insulin concentrations, improved hepatic insulin sensitivity, and increased abundance of hepatic insulin signaling proteins. At D16, insulin resistance at whole-body, tissue, and molecular levels will favor fetal glucose acquisition, while improved D19 hepatic insulin sensitivity will conserve glucose for maternal use in anticipation of lactation. Tissue sensitivity to insulin, therefore, alters differentially with proximity to delivery in pregnant mice, with implications for human and other species.

Maternal Glucose and Fatty Acid Kinetics and Infant Birth Weight in Obese Women With Type 2 Diabetes

The objectives of this study were 1) to describe maternal glucose and lipid kinetics and 2) to examine the relationships with infant birth weight in obese women with pregestational type 2 diabetes during late pregnancy. Using stable isotope tracer methodology and mass spectrometry, maternal glucose and lipid kinetic rates during the basal condition were compared in three groups: lean women without diabetes (Lean, n = 25), obese women without diabetes (OB, n = 26), and obese women with pregestational type 2 diabetes (OB+DM, n = 28; total n = 79). Glucose and lipid kinetics during hyperinsulinemia were also measured in a subset of participants (n = 56). Relationships between maternal glucose and lipid kinetics during both conditions and infant birth weight were examined. Maternal endogenous glucose production (EGP) rate was higher in OB+DM than OB and Lean during hyperinsulinemia. Maternal insulin value at 50% palmitate Ra suppression (IC50) for palmitate suppression with insulinemia was higher in OB+DM than OB and Lean. Maternal EGP per unit insulin and plasma free fatty acid concentration during hyperinsulinemia most strongly predicted infant birth weight. Our findings suggest maternal fatty acid and glucose kinetics are altered during late pregnancy and might suggest a mechanism for higher birth weight in obese women with pregestational diabetes.

The early origins of obesity and insulin resistance: timing, programming and mechanisms

Maternal obesity is associated with an increased risk of developing gestational diabetes mellitus and it also results in an increased risk of giving birth to a large baby with increased fat mass. Furthermore, it is also contributes to an increased risk of obesity and insulin resistance in the offspring in childhood, adolescence and adult life. It has been proposed that exposure to maternal obesity may therefore result in an 'intergenerational cycle' of obesity and insulin resistance. There is significant interest in whether exposure to maternal obesity around the time of conception alone contributes directly to poor metabolic outcomes in the offspring and whether dieting in the obese mother before pregnancy or around the time of conception has metabolic benefits for the offspring. This review focusses on experimental and clinical studies that have investigated the specific impact of exposure to maternal obesity during the periconceptional period alone or extending beyond conception on adipogenesis, lipogenesis and on insulin signalling pathways in the fat, liver and muscle of the offspring. Findings from these studies highlight the need for a better evidence base for the development of dietary interventions in obese women before pregnancy and around the time of conception to maximize the metabolic benefits and minimize the metabolic costs for the next generation.

Serum YKL-40 levels in gestational diabetes mellitus

OBJECTIVE

Serum YKL-40 levels are elevated in patients with type 1 and 2 diabetes. However, the correlation between YKL-40 and gestational diabetes mellitus (GDM) remains unknown. The present study compared serum YKL-40 levels in pregnant women with GDM and those with normal glucose tolerance and evaluated the relationship between YKL-40 and insulin-resistant syndrome.

METHODS

Thirty-five patients with GDM and 43 age-matched healthy pregnant women at 24-28 weeks of gestation were studied. In addition to anthropometric assessments, serum glucose, insulin, YKL-40, total cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein and glycated hemoglobin were measured in all subjects. All subjects underwent a 2-h 75-g oral glucose tolerance test (OGTT). Body mass index (BMI) and the homeostasis model assessment of insulin resistance (HOMA-IR) were calculated.

RESULTS

Fasting and 2 h serum YKL-40 levels were significantly higher in pregnant women with GDM compared with controls (77.3 ± 29.3 versus 50.9 ± 16.7 ng/mL, p < 0.001, fasting concentrations; 63.5 ± 20.1 versus 40.6 ± 10.7 ng/mL, p = 0.009, 2 h concentrations). OGTT had no effect on YKL-40 levels in either group (p > 0.05). There were significant correlations between YKL-40 and glycated hemoglobin (β = 0.37, p = 0.006), fasting insulin (β = 0.49, p = 0.001) and HOMA-IR (β = 0.18, p = 0.015) in the GDM group.

CONCLUSIONS

Serum YKL-40 levels are elevated in patients with GDM but are unaffected by OGTT. YKL-40 levels are related to glycated hemoglobin, fasting insulin and HOMA-IR. These results suggest that YKL-40 may be a major contributor to GDM.

Maternal Serum Resistin Is Reduced in First Trimester Preeclampsia Pregnancies and Is a Marker of Clinical Severity

OBJECTIVE

To examine whether resistin levels in first trimester maternal serum are associated with insulin resistance or preeclampsia (PE).

METHODS

A case-control study of maternal serum resistin concentration conducted using 285 normal pregnancies and 123 PE pregnancies matched for gestational age, parity and maternal age. Samples were taken in gestational weeks 10⁺⁰-13⁺⁶.

RESULTS

There was a negative correlation between resistin and clinical severity of PE, but no correlation with IS, TNF-α, body mass index, birth weight and pregnancy length.

CONCLUSIONS

Resistin is reduced in first trimester of PE pregnancies, particularly in severe PE. Inflammation and IS cannot explain this phenomenon.

Pro-inflammatory Macrophages suppress PPARγ activity in Adipocytes via S-nitrosylation

Peroxisome proliferator-activated receptor-γ (PPARγ) is a ligand-activated nuclear receptor and plays an essential role in insulin signaling. Macrophage infiltration into adipose tissue is a character of metabolic inflammation and closely related to insulin resistance in type 2 diabetes. The mechanism by which pro-inflammatory macrophages cause insulin resistance remains to be elucidated. Here we showed that co-culture with macrophages significantly suppressed the transcriptional activity of PPARγ on its target genes in 3T3-L1 preadipocytes and diabetic primary adipocytes, depending on inducible nitric oxide synthase (iNOS). We further showed that PPARγ underwent S-nitrosylation in response to nitrosative stress. Mass-spectrometry and site-directed mutagenesis revealed that S-nitrosylation at cysteine 168 was responsible for the impairment of PPARγ function. Extended exposure to NO instigated the proteasome-dependent degradation of PPARγ. Consistently, in vivo evidence revealed an association of the decreased PPARγ protein level with increased macrophage infiltration in visceral adipose tissue (VAT) of obese diabetic db/db mice. Together, our results demonstrated that pro-inflammatory macrophages suppressed PPARγ activity in adipocytes via S-nitrosylation, suggesting a novel mechanism linking metabolic inflammation with insulin resistance.

Pandemic of Pregnant Obese Women: Is It Time to Re-Evaluate Antenatal Weight Loss?

The Obesity pandemic will afflict future generations without successful prevention, intervention and management. Attention to reducing obesity before, during and after pregnancy is essential for mothers and their offspring. Preconception weight loss is difficult given that many pregnancies are unplanned. Interventions aimed at limiting gestational weight gain have produced minimal maternal and infant outcomes. Therefore, increased research to develop evidence-based clinical practice is needed to adequately care for obese pregnant women especially during antenatal care. This review evaluates the current evidence of obesity interventions during pregnancy various including weight loss for safety and efficacy. Recommendations are provided with the end goal being a healthy pregnancy, optimal condition for breastfeeding and prevent the progression of obesity in future generations.

Gestational diabetes mellitus is associated with increased leukocyte peroxisome proliferator-activated receptor γ expression

INTRODUCTION

Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-activated transcription factor of the nuclear receptor superfamily that is involved in lipid and carbohydrate metabolism as well as inflammation; thereby it participates in metabolic diseases including diabetes. Although PPARγ expression has been observed in different tissues of diabetic patients, its level in leukocytes from subjects affected by gestational diabetes mellitus (GDM) has not yet been reported. This study aimed to investigate leukocyte PPARG expression in GDM patients at 24-33 weeks of gestation and, in turn, to correlate these alterations with anthropometric and metabolic parameters of patients.

MATERIAL AND METHODS

Leukocytes were isolated from the blood of normal glucose tolerant (NGT; n = 34) and GDM (n = 77) pregnant women between 24 and 33 weeks of gestation. Leukocyte PPARG mRNA expression was determined by semi-quantitative polymerase chain reaction. Univariate correlation analysis was performed to investigate associations between PPARG expression and clinical characteristics of patients.

RESULTS

Leukocyte PPARG mRNA level was significantly higher in GDM than NGT women (p < 0.05). In the whole study group, PPARG expression positively correlated with plasma glucose concentrations at 1 h (r = 0.222, p = 0.049) and 2 h (r = 0.315, p = 0.020) of 75 g oral glucose tolerance test (OGTT), and negatively correlated with plasma HDL cholesterol concentration (r = -0.351, p = 0.010).

CONCLUSIONS

The correlation between leukocyte PPARG overexpression and hyperglycaemia suggests that PPARG mRNA expression in these cells might be up-regulated in high-glucose conditions in GDM patients at 24-33 weeks of gestation.

Double stranded viral RNA induces inflammation and insulin resistance in skeletal muscle from pregnant women in vitro

OBJECTIVE

Maternal peripheral insulin resistance and increased inflammation are two features of pregnancies complicated by pre-existing maternal obesity and gestational diabetes mellitus (GDM). There is now increasing evidence that activation of Toll-like receptor (TLR) signalling pathways by viral products may play a role in the pathophysiology of diabetes. Thus, the aim of this study was to assess the effect of the TLR3 ligand and viral dsRNA analogue polyinosinic polycytidilic acid (poly(I:C)) on inflammation and the insulin signalling pathway in skeletal muscle from pregnant women.

MATERIALS/METHODS

Human skeletal muscle tissue explants were performed to determine the effect of poly(I:C) on the expression and secretion of markers of inflammation, and the insulin signalling pathway and glucose uptake.

RESULTS

Poly(I:C) significantly increased the expression of a number of inflammatory markers in skeletal muscle from pregnant women. Specifically, there was an increase in the expression and/or secretion of the pro-inflammatory cytokines TNF-α, and IL-6 and the pro-inflammatory chemokines IL-8 and MCP-1. These effect of poly(I:C) appear to mediated via a number of signalling molecules including the pro-inflammatory transcription factor NF-κB, and the serine threonine kinases GSK3 and AMPKα. Additionally, poly(I:C) decreased insulin stimulated GLUT-4 expression and glucose uptake in skeletal muscle from pregnant women.

CONCLUSIONS

The in vitro data presented in this study suggests that viral infection may contribute to the pathophysiology of pregnancies complicated by pre-existing maternal obesity and/or GDM. It should be noted that the in vitro studies cannot be directly used to infer the same outcomes in the intact subject.

Insulin-like growth factor-binding protein 1 and 7 concentrations are lower in obese pregnant women, women with gestational diabetes and their fetuses

OBJECTIVE

To determine the effect of pre-existing maternal obesity and gestational diabetes mellitus (GDM) on the circulating levels of insulin growth factor-binding protein (IGFBPs) in cord and maternal plasma.

STUDY DESIGN

IGFBP-1-7 levels were measured on maternal and cord plasma from women with normal glucose tolerance (NGT) (30 non-obese and 36 obese) and GDM (44 non-obese and 26 obese) at the time of term elective cesarean section.

RESULT

Maternal plasma IGFBP-1, IGFBP-6 and IGFBP-rP1 concentrations were significantly lower in NGT obese compared with NGT non-obese women and in non-obese GDM women compared with non-obese NGT women. In cord plasma, IGFBP-1-3 and IGFBP-rP1 concentrations were significantly lower in NGT obese compared with NGT non-obese women and in non-obese GDM women compared with non-obese NGT women. Significant positive correlations were observed between maternal and cord plasma IGFBP-1 and IGFBP-rP1 levels and maternal insulin resistance. In cord plasma, significant positive correlations were observed between IGFBP-1-3 and IGFBP-rP1 levels and fetal insulin resistance. Fetal birthweight was inversely correlated with maternal plasma IGFBP-1 levels and cord plasma IGFBP-1 and IGFBP-2 levels. When corrected for maternal body mass index, the only significant relationship that still existed was between cord plasma IGFBP-1 concentrations and fetal birthweight.

CONCLUSION

At the time of term cesarean section, pre-existing maternal obesity and GDM are associated with lower IGFBP levels in maternal and cord plasma. Alterations in circulating IGF and IGFBPs may alter birthweight and/or neonatal adiposity. This may lead to alterations in optimal growth trajectory and lead to metabolic disorders later in life.

GSK3β is increased in adipose tissue and skeletal muscle from women with gestational diabetes where it regulates the inflammatory response

Infection and inflammation, through their ability to increase pro-inflammatory cytokines and chemokines and adhesion molecules, are thought to play a central role in the pathophysiology of insulin resistance and type 2 diabetes. Recent studies have shown that glycogen synthase kinase 3 (GSK3) plays a central role in regulating this inflammation. There are, however, no studies on the role of GSK3 in pregnancies complicated by gestational diabetes mellitus (GDM). Thus, the aims of this study were (i) to determine whether GSK3 is increased in adipose tissue and skeletal muscle from women with GDM; and (ii) to investigate the effect of GSK3 inhibition on inflammation in the presence of inflammation induced by bacterial endotoxin lipopolysaccharide (LPS) or the pro-inflammatory cytokine IL-1β. Human omental adipose tissue and skeletal muscle were obtained from normal glucose tolerant (NGT) women and BMI-matched women with diet-control GDM at the time of Caesarean section. Western blotting was performed to determine GSK3 protein expression. Tissue explants were performed to determine the effect of the GSK3 inhibitor CHIR99021 on markers of inflammation. When compared to women with NGT, omental adipose tissue and skeletal muscle obtained from women with diet-controlled GDM had significantly higher GSK3β activity as evidenced by a decrease in the expression of GSK3β phosphorylated at serine 9. The GSK3 inhibitor CHIR99021 significantly reduced the gene expression and secretion of the pro-inflammatory cytokines TNF-α, IL-1β and IL-6; the pro-inflammatory chemokines IL-8 and MCP-1; and the adhesion molecules ICAM-1 and VCAM-1 in tissues stimulated with LPS or IL-1β. In conclusion, GSK3 activity is increased in GDM adipose tissue and skeletal muscle and regulates infection- and inflammation-induced pro-inflammatory mediators.

The Role of Metformin in Metabolic Disturbances during Pregnancy: Polycystic Ovary Syndrome and Gestational Diabetes Mellitus

Maintenance of gestation implicates complex function of multiple endocrine mechanisms, and disruptions of the global metabolic environment prompt profound consequences on fetomaternal well-being during pregnancy and postpartum. Polycystic Ovary Syndrome (PCOS) and gestational diabetes mellitus (GDM) are very frequent conditions which increase risk for pregnancy complications, including early pregnancy loss, pregnancy-induced hypertensive disorders, and preterm labor, among many others. Insulin resistance (IR) plays a pivotal role in the pathogenesis of both PCOS and GDM, representing an important therapeutic target, with metformin being the most widely prescribed insulin-sensitizing antidiabetic drug. Although traditional views neglect use of oral antidiabetic agents during pregnancy, increasing evidence of safety during gestation has led to metformin now being recognized as a valuable tool in prevention of IR-related pregnancy complications and management of GDM. Metformin has been demonstrated to reduce rates of early pregnancy loss and onset of GDM in women with PCOS, and it appears to offer better metabolic control than insulin and other oral antidiabetic drugs during pregnancy. This review aims to summarize key aspects of current evidence concerning molecular and epidemiological knowledge on metformin use during pregnancy in the setting of PCOS and GDM.

Gestational diabetes is characterized by reduced mitochondrial protein expression and altered calcium signaling proteins in skeletal muscle

The rising prevalence of gestational diabetes mellitus (GDM) affects up to 18% of pregnant women with immediate and long-term metabolic consequences for both mother and infant. Abnormal glucose uptake and lipid oxidation are hallmark features of GDM prompting us to use an exploratory proteomics approach to investigate the cellular mechanisms underlying differences in skeletal muscle metabolism between obese pregnant women with GDM (OGDM) and obese pregnant women with normal glucose tolerance (ONGT). Functional validation was performed in a second cohort of obese OGDM and ONGT pregnant women. Quantitative proteomic analysis in rectus abdominus skeletal muscle tissue collected at delivery revealed reduced protein content of mitochondrial complex I (C-I) subunits (NDUFS3, NDUFV2) and altered content of proteins involved in calcium homeostasis/signaling (calcineurin A, α1-syntrophin, annexin A4) in OGDM (n = 6) vs. ONGT (n = 6). Follow-up analyses showed reduced enzymatic activity of mitochondrial complexes C-I, C-III, and C-IV (−60–75%) in the OGDM (n = 8) compared with ONGT (n = 10) subjects, though no differences were observed for mitochondrial complex protein content. Upstream regulators of mitochondrial biogenesis and oxidative phosphorylation were not different between groups. However, AMPK phosphorylation was dramatically reduced by 75% in the OGDM women. These data suggest that GDM is associated with reduced skeletal muscle oxidative phosphorylation and disordered calcium homeostasis. These relationships deserve further attention as they may represent novel risk factors for development of GDM and may have implications on the effectiveness of physical activity interventions on both treatment strategies for GDM and for prevention of type 2 diabetes postpartum.

CTRP5 ameliorates palmitate-induced apoptosis and insulin resistance through activation of AMPK and fatty acid oxidation

Lipotoxicity resulting from a high concentration of saturated fatty acids is closely linked to development of insulin resistance, as well as apoptosis in skeletal muscle. CTRP5, an adiponectin paralog, is known to activate AMPK and fatty acid oxidation; however, the effects of CTRP5 on palmitate-induced lipotoxicity in myocytes have not been investigated. We found that globular domain of CTRP5 (gCTRP5) prevented palmitate-induced apoptosis and insulin resistance in myocytes by inhibiting the activation of caspase-3, reactive oxygen species accumulation, and IRS-1 reduction. These beneficial effects of gCTRP5 are mainly attributed to an increase in fatty acid oxidation through phosphorylation of AMPK. These results provide a novel function of CTRP5, which may have preventive and therapeutic potential in management of obesity, insulin resistance, and type 2 diabetes mellitus.

NOD1 expression is increased in the adipose tissue of women with gestational diabetes

Maternal peripheral insulin resistance and increased inflammation are two features of pregnancies, complicated by gestational diabetes mellitus (GDM). The nucleotide-binding oligomerisation domain (NOD) intracellular molecules recognise a wide range of microbial products, as well as other intracellular danger signals, thereby initiating inflammation through activation of nuclear factor κB (NFκB). The aim of this study was to determine whether levels of NOD1 and NOD2 are increased in adipose tissue of women with GDM. The effect of NOD1 and NOD2 activation on inflammation and the insulin signalling pathway was also assessed. NOD1, but not NOD2, expression was higher in omental and subcutaneous adipose tissues obtained from women with GDM when compared with those from women with normal glucose tolerance (NGT). In both omental and subcutaneous adipose tissues from NGT and GDM women, the NOD1 ligand g-d-glutamyl-meso-diaminopimelic acid (iE-DAP) significantly induced the expression and secretion of the pro-inflammatory cytokine interleukin 6 (IL6) and chemokine IL8; COX2 (PTGS2) gene expression and subsequent prostaglandin production; the expression and secretion of the extracellular matrix remodelling enzyme matrix metalloproteinase 9 (MMP9) and the gene expression and secretion of the adhesion molecules ICAM1 and VCAM1. There was no effect of the NOD2 ligand muramyl dipeptide on any of the endpoints tested. The effects of the NOD1 ligand iE-DAP were mediated via NFκB, as the NFκB inhibitor BAY 11-7082 significantly attenuated iE-DAP-induced expression and secretion of pro-inflammatory cytokines, COX2 gene expression and subsequent prostaglandin production, MMP9 expression and secretion and ICAM1 and VCAM1 gene expression and secretion. In conclusion, the present findings describe an important role for NOD1 in the development of insulin resistance and inflammation in pregnancies complicated by GDM.

Gestational diabetes mellitus alters apoptotic and inflammatory gene expression of trophobasts from human term placenta

AIM

Increased placental growth secondary to reduced apoptosis may contribute to the development of macrosomia in GDM pregnancies. We hypothesize that reduced apoptosis in GDM placentas is caused by dysregulation of apoptosis related genes from death receptors or mitochondrial pathway or both to enhance placental growth in GDM pregnancies.

METHODS

Newborn and placental weights from women with no pregnancy complications (controls; N=5), or with GDM (N=5) were recorded. Placental villi from both groups were either fixed for TUNEL assay, or snap frozen for gene expression analysis by apoptosis PCR microarrays and qPCR.

RESULTS

Maternal, placental and newborn weights were significantly higher in the GDM group vs. Controls. Apoptotic index of placentas from the GDM group was markedly lower than the Controls. At a significant threshold of 1.5, seven genes (BCL10, BIRC6, BIRC7, CASP5, CASP8P2, CFLAR, and FAS) were down regulated, and 13 genes (BCL2, BCL2L1, BCL2L11, CASP4, DAPK1, IκBκE, MCL1, NFκBIZ, NOD1, PEA15, TNF, TNFRSF25, and XIAP) were unregulated in the GDM placentas. qPCR confirmed the consistency of the PCR microarray. Using Western blotting we found significantly decreased placental pro-apoptotic FAS receptor and FAS ligand (FASL), and increased mitochondrial anti-apoptotic BCL2 post GDM insult. Notably, caspase-3, which plays a central role in the execution-phase of apoptosis, and its substrate poly (ADP-ribose) polymerase (PARP) were significantly down regulated in GDM placentas, as compared to non-diabetic Control placentas.

CONCLUSION

Maternal GDM results in heavier placentas with aberrant placental apoptotic and inflammatory gene expression that may account, at least partially, for macrosomia in newborns.

The role of exercise in reducing the risks of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is the most common medical complication of pregnancy and is particularly prevalent among obese women. Both GDM and obesity confer significant comorbidities for the mother and her offspring, including perinatal complications, excessive fetal growth and long-term risks for maternal and offspring obesity and diabetes. Exercise has well-documented health benefits and reduces peripheral insulin resistance in nonpregnant individuals, a major risk factor for the development of diabetes. Observational studies conducted in large population-based cohorts suggest that women who are the most active before pregnancy are less insulin-resistant in late pregnancy and have lower rates of GDM. This article will review the evidence supporting a role for exercise in the prevention of GDM, the management of glycemic control in women with established GDM, and the reduction of GDM-associated maternal and offspring health consequences. Wherever possible, the discussion will focus on studies carried out on obese women. However, there are many areas where strong evidence is lacking in obese populations, and it may be inferred from similar studies performed in normal weight pregnant women.

Induction of miR-29a by saturated fatty acids impairs insulin signaling and glucose uptake through translational repression of IRS-1 in myocytes

MicroRNAs have been shown to play an important role in insulin signaling but their biological function in insulin resistance induced by saturated fatty acids (SFA) remains largely unknown. Here, we report that SFA palmitate and high fat diet (HFD) significantly increase expression of miR-29a in myocytes. miR-29a targets IRS-1 3'UTR directly and represses IRS-1 expression at the translational level. Furthermore, the ectopic expression of miR-29a impairs insulin signaling and glucose uptake in myocytes through a substantial decrease in IRS-1. These findings suggest that the up-regulation of miR-29a by SFA is causally related to the development of insulin resistance in myocytes.

Pregnancy in obese mice protects selectively against visceral adiposity and is associated with increased adipocyte estrogen signalling

Maternal obesity is linked with increased adverse pregnancy outcomes for both mother and child. The metabolic impact of excessive fat within the context of pregnancy is not fully understood. We used a mouse model of high fat (HF) feeding to induce maternal obesity to identify adipose tissue-mediated mechanisms driving metabolic dysfunction in pregnant and non-pregnant obese mice. As expected, chronic HF-feeding for 12 weeks preceding pregnancy increased peripheral (subcutaneous) and visceral (mesenteric) fat mass. However, unexpectedly at late gestation (E18.5) HF-fed mice exhibited a remarkable normalization of visceral but not peripheral adiposity, with a 53% reduction in non-pregnant visceral fat mass expressed as a proportion of body weight (P<0.001). In contrast, in control animals, pregnancy had no effect on visceral fat mass proportion. Obesity exaggerated glucose intolerance at mid-pregnancy (E14.5). However by E18.5, there were no differences, in glucose tolerance between obese and control mice. Transcriptomic analysis of visceral fat from HF-fed dams at E18.5 revealed reduced expression of genes involved in de novo lipogenesis (diacylglycerol O-acyltransferase 2 - Dgat2) and inflammation (chemokine C-C motif ligand 2 - Ccl2) and upregulation of estrogen receptor α (ERα) compared to HF non pregnant. Attenuation of adipose inflammation was functionally confirmed by a 45% reduction of CD11b⁺CD11c⁺ adipose tissue macrophages (expressed as a proportion of all stromal vascular fraction cells) in HF pregnant compared to HF non pregnant animals (P<0.001). An ERα selective agonist suppressed both de novo lipogenesis and expression of lipogenic genes in adipocytes in vitro. These data show that, in a HF model of maternal obesity, late gestation is associated with amelioration of visceral fat hypertrophy, inflammation and glucose intolerance, and suggest that these effects are mediated in part by elevated visceral adipocyte ERα signaling.

The G1057D polymorphism of insulin receptor substrate-2 associated with gestational diabetes mellitus

OBJECTIVE

The Gly1057D polymorphism in the insulin receptor substrate-2 (IRS-2) gene has been reported to be associated with insulin resistance, obesity and type 2 diabetes; little is known about its possible association with gestational diabetes mellitus (GDM). To investigate this association we determined the distribution of its genotypes and frequency of alleles in GDM patients.

MATERIALS AND METHODS

The study population consisted of 94 subjects; among them were 44 patients with GDM and 50 healthy controls without diabetes. Genomic DNA was extracted from the leukocyte by high pure polymerase chain reaction (PCR) template preparation kit. Genetic polymorphism of IRS-2 G1057D was detected by using PCR-based restriction fragment-length polymorphism (RFLP).

RESULTS

For IRS-2 G1057D polymorphism, there was no significant difference in genotype distribution between GDM patients and controls. The risk for GDM was 2.97 times higher (95% CI: 0.89-9.93, p = 0.076) in the individuals with the IRS-2 DD genotype compared to the GG genotype. Also individuals with the IRS-2 D allele had a significantly higher risk of GDM compared with individuals with the IRS-2 G allele, with a relative risk of 1.86 (95% CI: 1.02-3.37, p = 0.042) for cases compared with population controls.

CONCLUSION

These results suggest that IRS-2 1057D allele may be associated with GDM.

Effect of pre-existing maternal obesity, gestational diabetes and adipokines on the expression of genes involved in lipid metabolism in adipose tissue

OBJECTIVE

To determine the effect of maternal obesity, gestational diabetes mellitus (GDM) and adipokines on the expression of genes involved in fatty acid uptake, transport, synthesis and metabolism.

MATERIALS/METHODS

Human subcutaneous and omental adipose tissues were obtained from lean, overweight and obese normal glucose tolerant (NGT) women and women with GDM. Quantitative RT-PCR (qRT-PCR) was performed to determine the level of expression. Adipose tissue explants were performed to determine the effect of the adipokines TNFα, IL-1β and leptin on adipose tissue gene expression.

RESULTS

Pre-existing maternal obesity and GDM are associated with decreased expression in genes involved in fatty acid uptake and intracellular transport (LPL, FATP2, FATP6, FABPpm and ASCL1), triacylglyceride (TAG) biosynthesis (MGAT1,7 MGAT2 and DGAT1), lipogenesis (FASN) and lipolysis (PNPLA2, HSL and MGLL). Decreased gene expression was also observed for the transcription factors involved in lipid metabolism (LXRα, PPARα, PPARδ, PPARγ, RXRα and SREBP1c). On the other hand, the gene expression of the adipokines TNFα, IL-1β and or leptin was increased in adipose tissue from obese and GDM women. Functional in vitro studies revealed that these adipokines decreased the gene expression of LPL, FATP2, FATP6, ASCL1, PNPLA2, PPARδ, PPARγ and RXRα.

CONCLUSIONS

Pregnancies complicated by pre-existing maternal obesity and GDM are associated with abnormal adipose tissue lipid metabolism, which may play a role in the pathogenesis of these diseases.

Activation of inflammasomes in adipose tissue of women with gestational diabetes

Gestational diabetes mellitus (GDM) is characterised by maternal peripheral insulin resistance, increased inflammation, and increasing levels of circulating free fatty acids (FFAs) and advanced glycation endproducts (AGEs). Caspase-1 is a key component of the inflammasome, which is activated upon cellular infection or stress to trigger the maturation IL-1β, a pro-inflammatory cytokine that mediated insulin resistance. The aim of this study was to determine whether the inflammasome is activated in adipose tissue from women with gestational diabetes mellitus (GDM) and if it interferes with the insulin signalling pathway leading to the insulin resistance that is evident in GDM. Protein expression of active caspase-1 and mature IL-1β secretion was increased in adipose tissue of women with GDM. Treatment of adipose tissue with IL-1β decreased insulin-stimulated phosphorylation of IRS-1, GLUT-4 expression and glucose uptake. Low-grade inflammation (induced by LPS), the FFA palmitate and AGE conjugated to BSA (AGE-BSA), induced IL-1β secretion via inflammasome activation. In conclusion, the present findings describe an important role for adipose tissue inflammasome activation in the development of insulin resistance associated in pregnancies complicated by GDM.

Long term intake of 0.1% ethanol decreases serum adiponectin by suppressing PPARγ expression via p38 MAPK pathway

Light alcohol consumption was reported to be negatively associated with insulin resistance and risk of cardiovascular diseases; however, the results were inconsistent. We here investigate whether long term intake of low-concentration ethanol can affect adiponectin levels. Male Wistar rats were exposed to 0.1% ethanol in drinking water for 26weeks. Visceral adipose tissue (VAT) was cultured and treated with ethanol, SB203580, GW9662, or rosiglitazone. Adiponectin in serum and culture supernatant were measured by ELISA, mRNA levels of adiponectin and PPARγ were determined by RT-PCR, and protein expressions of PPARγ, p38 MAPK and phospho-p38 MAPK were determined by Western blot. In vivo, ethanol decreased the mRNA of adiponectin in VAT and serum adiponectin significantly. Decreased PPARγ and increased activation of p38 MAPK were observed in ethanol treated group. In vitro, SB203580 increased the adiponectin and PPARγ levels in normal DMEM cultured VAT and ameliorated ethanol-induced decrease of adiponectin and PPARγ expressions. GW9662 also decreased the adiponectin levels; Both ethanol and GW9662 weakened the rosiglitazone-induced elevation of adiponectin levels in cultured VAT. These data suggest that long term intake of 0.1% ethanol down-regulated adiponectin levels, and the regulation of PPARγ via p38 MAPK pathway plays an important role in the mechanism underneath.

Maternal leptin, adiponectin, resistin, visfatin and tumor necrosis factor-alpha in normal and gestational diabetes

Gestational diabetes mellitus (GDM) is a common medical complication associated with pregnancy. The present study evaluates the changes in maternal adipocytokines (leptin, adiponectin, resistin, visfatin and tumor necrosis factor-alpha; TNF-α) in pregnancy complicated with GDM compared to normal pregnancy at 2nd and 3rd trimesters. The study included total number of 142 pregnant women classified into 4 groups: normal pregnancy (n = 33) and pregnancy with GDM (n = 24) both at 2nd trimester and normal pregnancy (n = 38) and GDM (n = 47) at 3rd trimester. Both GDM groups were significantly presented with elevated body mass index, fasting blood sugar and abnormal oral glucose tolerance test compared to their matched control. Results indicated reduction in maternal serum leptin and adiponectin in GDM compared to normal pregnancy at 3rd trimester. Elevated resistin and TNF-α were evident among pregnancy complicated with GDM at both tested trimesters. On the other hand, significant elevation in maternal visfatin was noted between GDM and matched control at 2nd trimester only. Significant increase in maternal leptin and visfatin and resistin was noted by advances in gestational period in healthy pregnancy. On the other hand, reduced adiponectin and elevated visfatin mean values were noticed in GDM at 3rd compared to 2nd trimester. It could be concluded that increased insulin resistance accompanies GDM is associated with suppressed leptin and adiponectin and increased resistin and TNF-α which might suggest their involvement in the development of GDM.

The concurrent validity between leptin, BMI and skin folds during pregnancy and the year after

Background:

From a public health perspective it is important to know which of the currently used methods to estimate changes in maternal body fat during pregnancy and the year thereafter is the most adequate.

Objectives:

To evaluate the concurrent validity between leptin and surrogates of fat measures: body mass index (BMI) and the sum of four skin folds.

Design:

Data from the New Life(style) intervention study were analysed as a cohort study.

Setting:

Midwife practices in The Netherlands.

Population:

Healthy pregnant nulliparous women.

Methods:

Anthropometric measurements were done and blood was collected at 15, 25 and 35 weeks of pregnancy and at 6, 26 and 52 weeks after delivery. Data were used if at least 4 out of the 6 measurements were available, leaving 87 women in the analyses. Spearman's correlation coefficients between leptin and BMI and between leptin and the sum of skin folds were calculated for each time point and for the changes between the time points.

Results:

Correlations between leptin and BMI varied from 0.69 to 0.81. Correlations between leptin and the sum of skin folds were comparable, varying between 0.65 and 0.81.

Correlations between changes in leptin and changes in BMI and the sum of skin folds, respectively, were much lower compared with cross-sectional correlations.

Conclusion:

Because of the high correlation among the three methods and because of the overlapping intervals, all methods seem to be equally adequate to estimate changes in maternal body fat during pregnancy and the year thereafter.

Differential effects of maternal obesity and weight loss in the periconceptional period on the epigenetic regulation of hepatic insulin-signaling pathways in the offspring

Our aim was to determine the effect of exposure to maternal obesity or to maternal weight loss around conception on the programming of hepatic insulin signaling in the offspring. We used an embryo transfer model in sheep to investigate the effects of exposure to either maternal obesity or to weight loss in normal and obese mothers preceding and for 1 wk after conception on the expression of hepatic insulin-signaling and gluconeogenic factors and key miRNAs involved in insulin signaling in the offspring. We found that exposure to maternal obesity resulted in increased hepatic miR-29b (P<0.05), miR-103 (P<0.01), and miR-107 (P<0.05) expression, a decrease in IR (P<0.05), phopsho-Akt (P<0.01), and phospho-FoxO1 (P<0.01) abundance, and a paradoxical decrease in 11βHSD1 (P<0.05), PEPCK-C (P<0.01), and PEPCK-M (P<0.05) expression in lambs. These changes were ablated by a period of moderate dietary restriction imposed during the periconceptional period. Maternal dietary restriction alone also resulted in decreased abundance of a separate subset of hepatic insulin-signaling molecules, namely, IRS1 (P<0.05), PDK1 (P<0.01), phospho-PDK1 (P<0.05), and aPKCζ (P<0.05) and in decreased PEPCK-C (P<0.01) and G6Pase (P<0.01) expression in the lamb. Our findings highlight the sensitivity of the epigenome to maternal nutrition around conception and the need for dietary interventions that maximize metabolic benefits and minimize metabolic costs for the next generation.

High fat diet induced obesity alters ovarian phosphatidylinositol-3 kinase signaling gene expression

Insulin regulates ovarian phosphatidylinositol-3-kinase (PI3 K) signaling, important for primordial follicle viability and growth activation. This study investigated diet-induced obesity impacts on: (1) insulin receptor (Insr) and insulin receptor substrate 1 (Irs1); (2) PI3K components (Kit ligand (Kitlg), kit (c-Kit), protein kinase B alpha (Akt1) and forkhead transcription factor subfamily 3 (Foxo3a)); (3) xenobiotic biotransformation (microsomal epoxide hydrolase (Ephx1), Cytochrome P450 isoform 2E1 (Cyp2e1), Glutathione S-transferase (Gst) isoforms mu (Gstm) and pi (Gstp)) and (4) microRNA's 184, 205, 103 and 21 gene expression. INSR, GSTM and GSTP protein levels were also measured. Obese mouse ovaries had decreased Irs1, Foxo3a, Cyp2e1, MiR-103, and MiR-21 but increased Kitlg, Akt1, and miR-184 levels relative to lean littermates. These results support that diet-induced obesity potentially impairs ovarian function through aberrant gene expression.

Mild gestational hyperglycemia in rat induces fetal overgrowth and modulates placental growth factors and nutrient transporters expression

Mild gestational hyperglycemia is often associated with fetal overgrowth that can predispose the offspring to metabolic diseases later in life. We hypothesized that unfavorable intrauterine environment may compromise the development of placenta and contribute to fetal overgrowth. Therefore, we developed a rat model and investigated the effects of maternal dysglycemia on fetal growth and placental gene expression. Female rats were treated with single injection of nicotinamide plus streptozotocin (N-STZ) 1-week before mating and were studied at gestational day 21. N-STZ pregnant females displayed impaired glucose tolerance that is associated with a lower insulin secretion. Moderate hyperglycemia induced fetal overgrowth in 40% of newborns, from pregnancies with 10 to 14 pups. The incidence of macrosomia was less than 5% in the N-STZ pregnancies when the litter size exceeds 15 newborns. We found that placental mass and the labyrinthine layer were increased in macrosomic placentas. The expression of genes involved in placental development and nutrient transfer was down regulated in the N-STZ placentas of macrosomic and normosomic pups from pregnancies with 10 to 14 ones. However, we observed that lipoprotein lipase 1 (LPL1) gene expression was significantly increased in the N-STZ placentas of macrosomic pups. In pregnancies with 15 pups or more, the expression of IGFs and glucose transporter genes was also modulated in the control placentas with no additional effect in the N-STZ ones. These data suggest that placental gene expression is modulated by gestational conditions that might disrupt the fetal growth. We described here a new model of maternal glucose intolerance that results in fetal overgrowth. We proposed that over-expression of LPL1 in the placenta may contribute to the increased fetal growth in the N-STZ pregnancies. N-STZ model offers the opportunity to determinate whether these neonatal outcomes may contribute to developmental programming of metabolic diseases in adulthood.

The induction of miR-96 by mitochondrial dysfunction causes impaired glycogen synthesis through translational repression of IRS-1 in SK-Hep1 cells

MicroRNA (miRNA) is a class of endogenous small noncoding RNA that negatively regulates gene expression at the post-transcriptional level and plays an important role in the pathogenesis of various diseases. However, the identity and role of miRNAs involved in the development of insulin resistance resulting from mitochondrial dysfunction are largely unknown. In this study, mitochondrial dysfunction by genetic or metabolic inhibition induced an impairment of insulin signaling in SK-Hep1 cells via a reduction in the expression of IRS-1 protein. Significant up-regulation of miR-96, which was presumed to target IRS-1 3'UTR, was found in SK-Hep1 cells with mitochondrial dysfunction. Using reporter gene assay we confirmed that miR-96 authentically targeted IRS-1 3'UTR. Furthermore, the ectopic expression of miR-96 caused a substantial decrease in IRS-1 protein expression, and a consequent impairment in insulin signaling. These findings suggest that the up-regulation of miR-96 by mitochondrial dysfunction contributes to the development of insulin resistance by targeting IRS-1 in SK-Hep1 cells.

Green tea polyphenols reduced fat deposits in high fat-fed rats via erk1/2-PPARγ-adiponectin pathway

Objective

Hypoadiponectinemia contributes to the development of obesity and related disorders such as diabetes, hyperlipidemia, and cardiovascular diseases. In this study we investigated the effects of green tea polyphenols (GTPs) on adiponectin levels and fat deposits in high fat (HF) fed rats, the mechanism of signaling pathway was explored as well.

Methods and Results

Male Wistar rats were fed with high-fat diet. GTPs (0.8, 1.6, 3.2 g/L) were administered via drinking water. Serum adiponectin and insulin were measured by ELISA, mRNA levels of adiponectin and PPARγ in visceral adipose tissue (VAT) were determined by Real-time PCR, protein levels of PPARγ, phospho (p) - PPARγ, extracellular signal regulated kinase (erk) 1/2 and p-erk1/2 in VAT were determined by western blot. GTPs treatment attenuated the VAT accumulation, hypoadiponectinemia and the decreased mRNA level of adiponectin in VAT induced by HF. Decreased expression and increased phosphorylation of PPARγ (the master regulator of adiponectin), and increased activation of erk1/2 were observed in HF group, and these effects could be alleviated by GTPs treatment. To explore the underlying mechanism, VAT was cultured in DMEM with high glucose to mimic the hyperglycemia condition in vitro. Similar to the results of in vivo study, decreased adiponectin levels, decreased expression and increased phosphorylation of PPARγ, and elevated erk1/2 phosphorylation in cultured VAT were observed. These effects could be ameliorated by co-treatment with GTPs or PD98059 (a selective inhibitor of erk1/2).

Conclusion

GTPs reduced fat deposit, ameliorated hypoadiponectinemia in HF-fed rats, and relieved high glucose-induced adiponectin decrease in VAT in vitro. The signaling pathway analysis indicated that PPARγ regulation mediated via erk1/2 pathway was involved.

2D-DIGE to identify proteins associated with gestational diabetes in omental adipose tissue

Gestational diabetes mellitus (GDM) is a significant risk factor for the type 2 diabetes epidemic in many populations. Maternal adipose tissue plays a central role in the pathophysiology of GDM. Thus, the aim of this study was to determine the effect of GDM on the proteome of adipose tissue. Omental adipose tissue was obtained at the time of term Caesarean section from women with normal glucose tolerance (NGT) or GDM. 2D-difference gel electrophoresis (DIGE), followed by mass spectrometry, was used to identify protein spots (n = 6 patients per group). Western blotting was used for confirmation of six of the spot differences (n = 6 patients per group). We found 14 proteins that were differentially expressed between NGT and GDM adipose tissue (≥ 1.4-fold, P < 0.05). GDM was associated with an up-regulation of four proteins: collagen alpha-2(VI) chain (CO6A2 (COL6A2)), fibrinogen beta chain (FIBB (FGB)), lumican (LUM) and S100A9. On the other hand, a total of ten proteins were found to be down-regulated in adipose tissue from GDM women. These were alpha-1-antitrypsin (AIAT (SERPINA 1)), annexin A5 (ANXA5), fatty acid-binding protein, adipocyte (FABP4), glutathione S-transferase P (GSTP (GSTP1)), heat-shock protein beta-1 (HSP27 (HSPB1)), lactate dehydrogenase B chain (LDHB), perilipin-1 (PLIN1), peroxiredoxin-6 (PRX6 (PRDX6)), selenium-binding protein 1 (SBP1) and vinculin (VINC (VCL)). In conclusion, proteomic analysis of omental fat reveals differential expression of several proteins in GDM patients and NGT pregnant women. This study revealed differences in expression of proteins that are involved in inflammation, lipid and glucose metabolism and oxidative stress and added further evidence to support the role of visceral adiposity in the pathogenesis of GDM.

Activation of PPARγ by restores mast cell numbers and reactivity in alloxan-diabetic rats by reducing the systemic glucocorticoid levels

Mast cell function and survival have been shown to be down-regulated under diabetic conditions. This study investigates the role of the peroxisome proliferator-activated receptor (PPAR)-γ in reducing mast cell number and reactivity in diabetic rats. The effect of rosiglitazone on mast cell apoptosis was also evaluated. Diabetes was induced by intravenous injection of alloxan into fasted rats and PPARγ agonist rosiglitazone and/or specific antagonist 2-chloro-5-nitrobenzanilide (GW9662) were administered 3 day after diabetes induction, once daily for 18 consecutive days. Mast cell apoptosis and plasma corticosterone levels were evaluated by TUNEL and radioimmunoassay, respectively. Treatment with rosiglitazone restored mast cell numbers in the pleural cavity and mesenteric tissue of diabetic rats. Rosiglitazone also significantly reversed the diabetes-induced reduction of histamine release by mast cells, as measured by fluorescence, following activation with the antigen in vitro. Increased apoptosis in mast cells from diabetic rats were inhibited by rosiglitazone. Moreover, we noted that the increase in plasma corticosterone levels in diabetic rats was inhibited by rosiglitazone. In addition, GW9662 blocked the ability of rosiglitazone to restore baseline numbers of mast cells and plasma corticosterone in diabetic rats. In conclusion, our findings showed that rosiglitazone restored the number and reactivity of mast cells in diabetic rats, accompanied with a suppression of apoptosis, in parallel with impairment of diabetes hypercorticolism, indicating that PPARγ has an important role in these phenomena.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Pregnancy augments hepatic glucose storage in response to a mixed meal

Studies were carried out on conscious female non-pregnant (NP) and pregnant (P; third-trimester) dogs (n 16; eight animals per group) to define the role of the liver in mixed meal disposition with arteriovenous difference and tracer techniques. Hepatic and hindlimb substrate disposal was assessed for 390 min during and after an intragastric mixed meal infusion labelled with [¹⁴C]glucose. The P dogs exhibited postprandial hyperglycaemia compared with NP dogs (area under the curve (AUC; change from basal over 390 min) of arterial plasma glucose: 86 680 (sem 12 140) and 187 990 (sem 33 990) mg/l in NP and P dogs, respectively; P < 0·05). Plasma insulin concentrations did not differ significantly between the groups (AUC: 88 230 (sem 16 314) and 69 750 (sem 19 512) pmol/l in NP and P dogs, respectively). Net hepatic glucose uptake totalled 3691 (sem 508) v. 5081 (sem 1145) mg/100 g liver in NP and P dogs, respectively (P = 0·38). The AUC of glucose oxidation by the gut and hindlimb were not different in NP and P dogs, but hepatic glucose oxidation (84 (sem 13) v. 206 (sem 30) mg/100 g liver) and glycogen synthesis (0·4 (sem 0·5) v. 26 (sem 0·7) g/100 g liver) were greater in P dogs (P < 0·05). The proportion of hepatic glycogen deposited via the direct pathway did not differ between the groups. Hindlimb glucose uptake and skeletal muscle glycogen synthesis was similar between the groups, although final glycogen concentrations were higher in NP dogs (9·6 (sem 0·6) v. 70 (sem 0·6) mg/g muscle; P < 0·05). Thus, hepatic glucose oxidation and glycogen storage were augmented in late pregnancy. Enhanced hepatic glycogen storage following a meal probably facilitates the maintenance of an adequate glucose supply to maternal and fetal tissues during the post-absorptive period.

Adipokines: new emerging roles in fertility and reproduction

Adipose tissue is a specialized endocrine and paracrine organ producing specific factors called adipokines. It is well known that adipokines balance is fundamental to prevent obesity, metabolic syndrome, and cardiovascular diseases. During the last years, new roles of adipokines have been emerging in the field of fertility and reproduction. Although the literature is still quite controversial, this review serves to resume current knowledge on this topic. Alterations in adipokine levels or in their mechanism of action are associated with fertility impairment and pregnancy diseases, as well as with obesity, metabolic syndrome, and cardiovascular diseases. Normal levels of adipokines are fundamental to maintain integrity of hypothalamus-pituitary-gonadal axis, regular ovulatory processes, successful embryo implantation, and physiologic pregnancy. More efforts are needed to understand the mechanisms and to the extent to which adipokine changes are involved in the impairment of fertility and pregnancy outcome, to find possible medical treatments.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians Learning Objectives: After completion of this educational activity, the obstetrician/gynecologist should be better able to demonstrate current knowledge in the research field of adipokines in fertility and reproduction; evaluate the central role of metabolism balance in good pregnancy outcome; and apply new perspectives of studies.

Is it time to revisit the Pedersen hypothesis in the face of the obesity epidemic?

The Pedersen hypothesis was formulated more than 50 years ago. Jorgen Pedersen primarily cared for women with type 1 diabetes. He suggested that fetal overgrowth was related to increased transplacental transfer of glucose, stimulating the release of insulin by the fetal beta cell and subsequent macrosomia. Optimal maternal glucose control decreased perinatal mortality and morbidity. However, over the ensuing decades, there have been increases in maternal obesity and subsequently gestational diabetes mellitus (GDM) and type 2 diabetes. The underlying pathophysiology of type 1 and GDM/type 2 diabetes are fundamentally different, type 1 diabetes being primarily a disorder of beta cell failure and type 2 diabetes/GDM including both insulin resistance and beta cell dysfunction. As such the metabolic milieu in which the developing fetus is exposed may be quite different in type 1 diabetes and obesity. In this review we examine the metabolic environment of obese diabetic women and lipid metabolism affecting fetal adiposity. The importance of understanding these issues relates to the increasing trends of obesity worldwide with perinatal programming of metabolic dysfunction in the offspring.

The induction of microRNA targeting IRS-1 is involved in the development of insulin resistance under conditions of mitochondrial dysfunction in hepatocytes

Background

Mitochondrial dysfunction induces insulin resistance in myocytes via a reduction of insulin receptor substrate-1 (IRS-1) expression. However, the effect of mitochondrial dysfunction on insulin sensitivity is not understood well in hepatocytes. Although research has implicated the translational repression of target genes by endogenous non-coding microRNAs (miRNA) in the pathogenesis of various diseases, the identity and role of the miRNAs that are involved in the development of insulin resistance also remain largely unknown.

Methodology

To determine whether mitochondrial dysfunction induced by genetic or metabolic inhibition causes insulin resistance in hepatocytes, we analyzed the expression and insulin-stimulated phosphorylation of insulin signaling intermediates in SK-Hep1 hepatocytes. We used qRT-PCR to measure cellular levels of selected miRNAs that are thought to target IRS-1 3′ untranslated regions (3′UTR). Using overexpression of miR-126, we determined whether IRS-1-targeting miRNA causes insulin resistance in hepatocytes.

Principal Findings

Mitochondrial dysfunction resulting from genetic (mitochondrial DNA depletion) or metabolic inhibition (Rotenone or Antimycin A) induced insulin resistance in hepatocytes via a reduction in the expression of IRS-1 protein. In addition, we observed a significant up-regulation of several miRNAs presumed to target IRS-1 3′UTR in hepatocytes with mitochondrial dysfunction. Using reporter gene assay we confirmed that miR-126 directly targeted to IRS-1 3′UTR. Furthermore, the overexpression of miR-126 in hepatocytes caused a substantial reduction in IRS-1 protein expression, and a consequent impairment in insulin signaling.

Conclusions/Significance

We demonstrated that miR-126 was actively involved in the development of insulin resistance induced by mitochondrial dysfunction. These data provide novel insights into the molecular basis of insulin resistance, and implicate miRNA in the development of metabolic disease.

Longitudinal study of prepregnancy cardiometabolic risk factors and subsequent risk of gestational diabetes mellitus: The CARDIA study

This study examined prepregnancy cardiometabolic risk factors and gestational diabetes mellitus (GDM) in subsequent pregnancies. The authors selected 1,164 women without diabetes before pregnancy who delivered 1,809 livebirths between 5 consecutive examinations from 1985 to 2006 in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. The authors measured prepregnancy cardiometabolic risk factors and performed multivariate repeated-measures logistic regression to compute the odds of GDM adjusted for race, age, parity, birth order, and other covariates. Impaired fasting glucose (100-125 vs. <90 mg/dL), elevated fasting insulin (>15-20 and >20 vs. <10 μU/mL), and low levels of high-density lipoprotein cholesterol (<40 vs. >50 mg/dL) before pregnancy were directly associated with GDM: The odds ratios = 4.74 (95% confidence interval (CI): 2.14, 10.51) for fasting glucose, 2.19 (95% CI: 1.15, 4.17) for middle insulin levels and 2.36 (95% CI: 1.20, 4.63) for highest insulin levels, and 3.07 (95% CI: 1.62, 5.84) for low levels of high-density lipoprotein cholesterol among women with a negative family history of diabetes; all P < 0.01. Among overweight women, 26.7% with 1 or more cardiometabolic risk factors developed GDM versus 7.4% with none. Metabolic impairment exists before GDM pregnancy in nondiabetic women. Interconceptual metabolic screening could be included in routine health assessments to identify high-risk women for GDM in a subsequent pregnancy and to potentially minimize fetal exposure to metabolic abnormalities that program future disease.

Critical issues in setting micronutrient recommendations for pregnant women: an insight

The European Micronutrient Recommendations Aligned (EURRECA) Network aims to provide standardized approaches to reveal and beneficially influence variability within the European Union in micronutrient recommendations for vulnerable population groups. Characterization of the 'vulnerability' together with the 'variability' of micronutrient needs represents the first step to creating guidelines for setting micronutrient recommendations within target populations. This paper describes some of the key factors and characteristics relevant to assess micronutrient requirements and formulate recommendations of micronutrients in pregnancy. Nutritional requirements during pregnancy increase to support fetal growth and development as well as maternal metabolism and tissue accretion. Micronutrients are involved in both embryonal and fetal organ development and overall pregnancy outcomes. Several factors may affect directly or indirectly fetal nourishment and the overall pregnancy outcomes, such as the quality of diet including intakes and bioavailability of micronutrients, maternal age, and the overall environment. The bioavailability of micronutrients during pregnancy varies depending on specific metabolic mechanisms because pregnancy is an anabolic and dynamic state orchestrated via hormones acting for both redirection of nutrients to highly specialized maternal tissues and transfer of nutrients to the developing fetus. The timing of prenatal intakes or supplementations of specific micronutrients is also crucial as pregnancy is characterized by different stages that represent a continuum, up to lactation and beyond. Consequently, nutrition during pregnancy might have long-lasting effects on the well-being of the mother and the fetus, and may further influence the health of the baby at a later age.