Larraine Presley

Fetuses of Obese Mothers Develop Insulin Resistance in Utero

OBJECTIVE Offspring of obese mothers have an increased risk for obesity and diabetes. The purpose of this study was to determine whether fetuses of obese women have increased obesity, insulin resistance, and markers of inflammation, supporting the concept of fetal programming. RESEARCH DESIGN AND METHODS Fifty-three lean and 68 obese women with singleton term pregnancies were evaluated at elective cesarean delivery. Maternal and umbilical cord blood was obtained for measures of insulin resistance and cytokines. Neonatal body composition was estimated using anthropometric measurements within 24 h of delivery. RESULTS The fetuses of obese mothers had greater percent body fat (13.1 ± 3.4 vs. 11.6 ± 2.9%, P = 0.02), homeostasis model assessment of insulin resistance (1.51 ± 0.86 vs. 1.06 ± 0.70, P = 0.003), cord leptin (14.5 ± 13.5 vs. 8.2 ± 4.7 ng/ml, P = 0.001), and interleukin-6 (3.5 ± 2.3 vs. 2.4 ± 1.4 pg/ml, P = 0.02) than fetuses of lean women. There was a strong positive correlation between fetal adiposity and insulin resistance (r = 0.32, P = 0.0008) as well as maternal pregravid BMI and fetal insulin resistance (r = 0.31, P = 0.007) even with adjustment for potential confounders. Cord leptin had a significant correlation with fetal insulin resistance (r = 0.30, P = 0.001), but there was no significant correlation between any other umbilical cord cytokines and fetal insulin resistance. CONCLUSIONS These data suggest that maternal obesity creates a significant risk for the next generations with metabolic compromise already apparent at birth. Therefore, if prevention of obesity is the goal rather than treatment, the perinatal period may be an important focus of future research.

Pregravid obesity associates with increased maternal endotoxemia and metabolic inflammation.

Obese pregnant women develop severe insulin resistance and enhanced systemic and placental inflammation, suggesting associated modifications of endocrine and immune functions. Activation of innate immunity by endotoxins/lipopolysaccharides (LPS) has been proposed as a mechanism for enhancing metabolic alterations in disorders with insulin resistance. The aim of this study was to characterize the immune responses developed by the adipose tissue (AT) and their potential links to maternal endotoxemia in pregnancy with obesity. Blood and subcutaneous abdominal AT were obtained from 120 lean and obese women (term pregnancy) recruited at delivery. Gene expression was assessed in AT and stromal vascular cells isolated from a subset of 24 subjects from the same cohort. Doubling of plasma endotoxin concentrations indicated subclinical endotoxemia in obese compared with lean women. This was associated with significant increase in systemic C‐reactive protein and interleukin‐6 (IL‐6) but not tumor necrosis factor‐α (TNF‐α) concentrations. AT inflammation was characterized by accumulation of CD68+ macrophages with a threefold increased gene expression of the macrophage markers CD68, EMR1, and CD14. Gene expression for cytokines IL‐6, TNF‐α, IL‐8, and monocyte chemotactic protein‐1 (MCP1) and for LPS—sensing CD14, toll‐like receptor 4 (TLR4), translocating chain‐associated membrane protein 2 was 2.5‐5‐fold higher in stromal cells of obese compared to lean. LPS‐treated cultured stromal cells of obese women expressed a 5–16‐fold stimulation of the same cytokines upregulated in vivo. Our data demonstrate that subclinical endotoxemia is associated with systemic and AT inflammation in obese pregnant women. Recognition of bacterial pathogens may contribute to the combined dysfunction of innate immunity and the metabolic systems in AT.

Increased Skeletal Muscle Tumor Necrosis Factor-α and Impaired Insulin Signaling Persist in Obese Women With Gestational Diabetes Mellitus 1 Year Postpartum

OBJECTIVE—Women with gestational diabetes mellitus (GDM) demonstrate chronic and progressive insulin resistance and a markedly increased risk of converting to type 2 diabetes after pregnancy. However, the cellular mechanisms underlying this insulin resistance are unknown. RESEARCH DESIGN AND METHODS—We investigated the progression of insulin resistance in nine obese women with GDM during late pregnancy (30–36 weeks) and 1 year postpartum. Skeletal muscle biopsies were obtained at each visit, and insulin resistance was determined by the hyperinsulinemic-euglycemic clamp technique. RESULTS—Insulin resistance was not significantly improved in GDM women (4.1 ± 0.4 vs. 5.8 ± 1.1 10−2 mg · kg FFM · min−1/μU · ml−1). Subjects did not experience significant weight loss postpartum. Body weight, fat mass, fasting glucose, and plasma tumor necrosis factor (TNF)-α remained higher 1 year postpartum than seen in previously studied normal glucose-tolerant women. Skeletal muscle TNF-α mRNA was elevated five- to sixfold in GDM women and remained higher 1 year postpartum. While levels of insulin receptor (IR), IR substrate (IRS)-1, and p85α improved postpartum, insulin-stimulated IR tyrosine phosphorylation and receptor tyrosine kinase activity did not significantly improve postpartum in GDM. The levels of 312Ser-IRS-1 also did not improve postpartum and correlated with TNF-α mRNA (r2 = 0.19, P < 0.03), consistent with a state of subclinical inflammation and chronic skeletal muscle insulin resistance. CONCLUSIONS—These results suggest the mechanisms underlying chronic insulin resistance in GDM women may be driven by increased inflammation that impinges on the IR and IRS-1 signaling cascade in skeletal muscle. These findings have important implications for the health of GDM women during subsequent pregnancies and their risk for progression to type 2 diabetes.

Increased Death of Adipose Cells, a Path to Release Cell‐Free DNA Into Systemic Circulation of Obese Women

Remodeling of adipose tissue is required to support the expansion of adipose mass. In obesity, an increased death of adipocytes contributes to the accelerated cellular turnover. We have shown that obesity in pregnancy is associated with metabolic and immune alterations in the adipose tissue. In this study, we characterized the mechanisms responsible for increased death of adipose cells of pregnant obese women and its functional consequences. We postulated that a higher turnover of dead cells in white adipose tissue of obese women would translate into release of cell‐free DNA (cfDNA) into their systemic circulation. Increase in adipose mass of obese compared to lean women results from a lesser number of hypertrophic adipocytes and an accumulation of macrophages in the stromal vascular fraction (SVF). The adipocytes of obese displayed enhanced necrosis with a loss of perilipin staining at the plasma membrane. Apoptosis was prominent in SVF cells with an increased expression of caspase 9 and caspase 3 and a higher rate of terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate nick end‐labeling (TUNEL) positive CD68 macrophages in obese vs. lean. Whereas circulating fetal cfDNA concentrations were not changed, there was a twofold increase in circulating glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) cfDNA and adipose tissue GAPDH mRNA in obese women. The maternal systemic GAPDH cfDNA was positively correlated with BMI and gestational weight gain. These data suggest that the active remodeling of adipose tissue of obese pregnant women results in an increased release of cfDNA of maternal origin into the circulation.

High Molecular Mass Multimer Complexes and Vascular Expression Contribute to High Adiponectin in the Fetus

CONTEXT High plasma adiponectin concentrations in human fetuses and neonates are unique features of early developmental stages. Yet, the origins of the high adiponectin concentrations in the perinatal period remain elusive. OBJECTIVE This study was undertaken to identify the sources and functional properties of adiponectin in utero. DESIGN AND METHODS Tissue specimens were obtained at autopsy from 21- to 39-wk-old stillborn human fetuses. Adipose tissue and placenta were obtained at term elective cesarean section. Adiponectin complexes and expression were measured by immunodetection and real-time PCR. RESULTS Adiponectin mRNA transcripts were detected in fetal sc and omental adipose depots at lower concentrations than in maternal adipose tissue. Immunoreactive adiponectin was also observed in vascular endothelial cells of fetal organs, including skeletal muscle, kidney, and brain. The absence of adiponectin in all placental cell types and lack of correlation between maternal and umbilical adiponectin indicate that umbilical adiponectin reflects its exclusive production by fetal tissues. The most prominent forms of adiponectin in fetal plasma were high and low molecular mass (HMW and LMW) multimers of 340 and 160 kDa, respectively. The proportion of the HMW complexes was 5-fold (P < 0.001) higher in umbilical plasma than in adult. The high HMW and total adiponectin levels were associated with lower insulin concentration and lower homeostasis model of assessment of insulin resistance indices in umbilical plasma, reflecting higher insulin sensitivity of the fetus compared with adult. CONCLUSIONS The abundance of HMW adiponectin and its vascular expression are characteristics of human fetal adiponectin. Combined with high insulin sensitivity, fetal adiponectin may be a critical determinant of in utero growth.

Longitudinal changes in infant body composition: association with childhood obesity

Rapid weight gain in infancy has been established as a risk factor for the development of later obesity.

Patterns of Adiponectin Expression in Term Pregnancy: Impact of Obesity

CONTEXT Adiponectin (adpN) production is down-regulated in several situations associated with insulin resistance. The hypoadiponectinemia, which develops in late pregnancy, suggests a role of adpN in pregnancy-induced insulin resistance. OBJECTIVE In obese pregnancy there is a decreased systemic adpN, which results from down-regulation of gene expression in adipose tissue. SETTING AND DESIGN One hundred and thirty-three women with uncomplicated pregnancies and a wide range in pre-gravid body mass index (18-62 kg/m(2)) were recruited at term for a scheduled cesarean delivery. Maternal blood, placenta, and sc abdominal adipose tissue were obtained in the fasting state. DNA methylation was analyzed by MBD-based genome-wide methylation sequencing and methyl-specific PCR of placenta and maternal adipose tissue. mRNA and protein expression were characterized by real-time RT-PCR and immunodetection. Plasma adpN, leptin, and insulin were assayed by ELISA. RESULTS Maternal adipose tissue was the prominent site of adpN gene expression with no detectable mRNA or protein in placenta. In obese women, adipose tissue adpN mRNA was significantly decreased (P < .01) whereas DNA methylation was significantly increased (P < .001) compared with lean women. The decreased adipose tissue expression resulted in normal-weight women having significantly greater plasma adpN compared with the severely obese (12.8 ± 4.3 ng/mL vs 8.6 ± 3.1, P < .001). Plasma adpN was negatively correlated with maternal body mass index (r = -0.28, P < .001) and homeostasis model assessment indices of insulin sensitivity (r = -0.32, P < .001) but not with gestational weight gain. CONCLUSIONS Maternal adipose tissue is the primary source of circulating adpN during pregnancy. Further, based on our results, the placenta does not synthesize adiponectin at term. Obesity in pregnancy is associated with negative regulation of adpN adipose expression with increase in adpN DNA methylation associated with lower mRNA concentrations and hypoadiponectinemia. Maternal hypoadiponectinemia may have functional consequences in down-regulating biological signals transmitted by adpN receptors in various tissues, including the placenta.

Molecular inflammation and adipose tissue matrix remodeling precede physiological adaptations to pregnancy

Changes in adipose tissue metabolism are central to adaptation of whole body energy homeostasis to pregnancy. To gain insight into the molecular mechanisms supporting tissue remodeling, we have characterized the longitudinal changes of the adipose transcriptome in human pregnancy. Healthy nonobese women recruited pregravid were followed in early (8-12 wk) and in late (36-38 wk) pregnancy. Adipose tissue biopsies were obtained in the fasting state from the gluteal depot. The adipose transcriptome was examined via whole genome DNA microarray. Expression of immune-related genes and extracellular matrix components was measured using real-time RT-PCR. Adipose mass, adipocyte size, and cell number increased in late pregnancy compared with pregravid measurements (P < 0.001) but remained unchanged in early pregnancy. The adipose transcriptome evolved during pregnancy with 10-15% of genes being differently expressed compared with pregravid. Functional gene cluster analysis revealed that the early molecular changes affected immune responses, angiogenesis, matrix remodeling, and lipid biosynthesis. Increased expression of macrophage markers (CD68, CD14, and the mannose-6 phosphate receptor) emphasized the recruitment of the immune network in both early and late pregnancy. The TLR4/NF-κB signaling pathway was enhanced specifically in relation to inflammatory adipokines and chemokines genes. We conclude that early recruitment of metabolic and immune molecular networks precedes the appearance of pregnancy-related physiological changes in adipose tissue. This biphasic pattern suggests that physiological inflammation is an early step preceding the development of insulin resistance, which peaks in late pregnancy.

In utero gender dimorphism of adiponectin reflects insulin sensitivity and adiposity of the fetus.

Circulating adiponectin reflects the degree of energy homeostasis and insulin sensitivity of adult individuals. Low abundance of the high molecular weight (HMW) multimers, the most active forms mediating the insulin‐sensitizing effects of adiponectin, is indicative of impaired metabolic status. The increase in fetal adiponectin HMW compared with adults is a distinctive features of human neonates. To further understand the functional properties of adiponectin during fetal life, we have evaluated the associations of adiponectin with insulin sensitivity, body composition, and gender. Umbilical cord adiponectin, adiponectin complexes, and metabolic parameters were measured at term by elective cesarean delivery. The associations between adiponectin, measures of body composition, and insulin sensitivity were evaluated in relation to fetal gender in 121 singleton neonates. Higher total adiponectin concentrations in female compared with male fetuses (34.3 ± 9.5 vs. 24.9 ± 8.6, P < 0.001) were associated with a 3.2‐fold greater abundance in circulating HMW complexes (0.20 ± 0.03 vs. 0.08 ± 0.03, P < 0.001, n = 9). Adiponectin was positively correlated with neonatal fat mass (r = 0.27, P < 0.04) and percent body fat in female fetuses (r = 0.28, P < 0.03) and with lean mass in males (r = 0.28, P < 0.03). There was no significant correlation between cord adiponectin and fasting insulin concentrations or fetal insulin sensitivity as estimated by homeostasis model assessment of insulin resistance (HOMA‐IR). The gender dimorphism for plasma adiponectin concentration and complex distribution first appears in utero. In sharp contrast to the inverse correlation found in adults, the positive relationship between adiponectin and body fat is a specific feature of the fetus.

Perinatal factors relating to changes in maternal body fat in late gestation

Objective:To examine changes in skinfolds in late gestation in healthy women.Study Design:Skinfold measures were performed in 39 women at 30.8 (mean) and 37.7 weeks gestation. Fat mass (kg) and sum of three skinfolds were calculated.Results:A decrease in skinfold thickness was observed in 21 women (−3.1±2.1 mm) in late gestation, whereas 18 women had an increase (4.3±3.2 mm), P<0.001. The group of women who lost body fat (decrease in skinfold thickness) had a trend toward greater pregravid body mass index (BMI, 25 vs 22 kg/m2, P=0.06), and gained less weight in late gestation (3.0 vs 4.3 kg, P=0.042). On multiple regression, maternal age and gestational weight gain were positively correlated with fat mass accrual, whereas pregravid BMI and dietary fiber were negative determinants of late gestational fat mass.Conclusion:Increases in maternal fat mass in late gestation were related to maternal age and gestational weight gain, whereas decreases were related to increased pregravid BMI and dietary fiber.