Differential regulation of genes for fetoplacental lipid pathways in pregnancy with gestational and type 1 diabetes mellitus

Experimentally induced gestational androgen excess disrupts glucoregulation in rhesus monkey dams and their female offspring

Discrete fetal androgen excess during early gestation in rhesus monkeys (Macaca mulatta) promotes endocrine antecedents of adult polycystic ovary syndrome (PCOS)-like traits in female offspring. Because developmental changes promoting such PCOS-like metabolic dysfunction remain unclear, the present study examined time-mated, gravid rhesus monkeys with female fetuses, of which nine gravid females received 15 mg of testosterone propionate (TP) subcutaneously daily from 40 to 80 days (first to second trimesters) of gestation [term, mean (range): 165 (155-175) days], whereas an additional six such females received oil vehicle injections over the same time interval. During gestation, ultrasonography quantified fetal growth measures and was used as an adjunct for fetal blood collections. At term, all fetuses were delivered by cesarean section for postnatal studies. Blood samples were collected from dams and infants for glucose, insulin, and total free fatty acid (FFA) determinations. TP injections transiently accelerated maternal weight gain in dams, very modestly increased head diameter of prenatally androgenized (PA) fetuses, and modestly increased weight gain in infancy compared with concurrent controls. Mild to moderate glucose intolerance, with increased area-under-the-curve circulating insulin values, occurred in TP-injected dams during an intravenous glucose tolerance test in the early second trimester. Moreover, reduced circulating FFA levels occurred in PA fetuses during a third trimester intravenous glucagon-tolbutamide challenge (140 days gestation), whereas excessive insulin sensitivity and increased insulin secretion relative to insulin sensitivity occurred in PA infants during an intravenous glucose-tolbutamide test at ∼1.5 mo postnatal age. Data from these studies suggest that experimentally induced fetal androgen excess may result in transient hyperglycemic episodes in the intrauterine environment that are sufficient to induce relative increases in pancreatic function in PA infants, suggesting in this nonhuman primate model that differential programming of insulin action and secretion may precede adult metabolic dysfunction.

Obesity, insulin resistance, and pregnancy outcome

There has been a significant increase over the past few decades in the number of reproductive age women who are either overweight or obese. Overweight and obese women are at increased risk for having decreased insulin sensitivity as compared with lean or average weight women. The combination of obesity and decreased insulin sensitivity increases the long-term risk of these individuals developing the metabolic syndrome and associated problems of diabetes, hypertension, hyperlipidemia, and cardiovascular disorders. Because of the metabolic alterations during normal pregnancy, particularly the 60% decrease in insulin sensitivity, overweight and obese women are at increased risk of metabolic dysregulation in pregnancy, i.e. gestational diabetes, preeclampsia, and fetal overgrowth. Hence, pregnancy can be considered as a metabolic stress test for the future risk of the metabolic syndrome. In this review, we will review the underlying pathophysiology related to these disorders. Most importantly, an understanding of these risks provides an opportunity for prevention. For example, a planned pregnancy offers an opportunity to address weight control prior to conception. At the very least, by avoiding excessive weight gain during pregnancy, this may prevent excessive weight retention post partum. Finally, based on the concept of in utero programming, these lifestyle measures may not only have short- and long-term benefits for the woman but also for her offspring as well.

Obesity, pregnancy, inflammation, and vascular function

Maternal obesity is associated with increased morbidity and mortality for both mother and offspring. The mechanisms underlying the increased risk associated with maternal obesity are not well understood. In non-pregnant populations, many of the complications of obesity are thought to be mediated in part by inflammation and its sequelae. Recent studies suggest that a heightened inflammatory response may also be involved in mediating adverse clinical outcomes during pregnancy. This review summarizes our current knowledge about adipose tissue biology, and its role as an endocrine and inflammatory organ. The evidence for inflammation as a key mediator of adverse pregnancy outcome is also presented, focusing on the role of inflammation in adipose tissue, systemic inflammation, the placenta, and vascular endothelium.

Disturbances in lipid metabolism in diabetic pregnancy - Are these the cause of the problem?

The most common neonatal complication of gestational diabetes (GDM) is macrosomia. During early pregnancy an accumulation of maternal fat depots occurs followed by increased adipose tissue lipolysis and subsequent hyperlipidaemia, which mainly corresponds to increased triglycerides (TG) in all circulating lipoproteins. In GDM women, the enhanced insulin resistance and decreased oestrogens are responsible for the reported wide range of dyslipidaemic conditions. In GDM, decreased proportion of long chain polyunsaturated fatty acids in fetus plasma could result from decreased supply, impaired placental transfer or even altered intrauterine metabolism. A positive correlation between maternal TG and neonatal body weight or fat mass has been found in GDM. Augmented oxidative stress and altered adipokines have also been found, with an adverse outcome even in normoglycaemic conditions. Thus, although additional studies are required, overall these findings indicate that altered maternal lipid metabolism rather than hyperglycaemia constitutes a risk for macrosomia in GDM.

Maternal obesity and fetal metabolic programming: a fertile epigenetic soil

The incidence of obesity and overweight has reached epidemic levels in the United States and developed countries worldwide. Even more alarming is the increasing prevalence of metabolic diseases in younger children and adolescents. Infants born to obese, overweight, and diabetic mothers (even when normal weight) have increased adiposity and are at increased risk of later metabolic disease. In addition to maternal glucose, hyperlipidemia and inflammation may contribute to the childhood obesity epidemic through fetal metabolic programming, the mechanisms of which are not well understood. Pregravid obesity, when combined with normal changes in maternal metabolism, may magnify increases in inflammation and blood lipids, which can have profound effects on the developing embryo and the fetus in utero. Fetal exposure to excess blood lipids, particularly saturated fatty acids, can activate proinflammatory pathways, which could impact substrate metabolism and mitochondrial function, as well as stem cell fate, all of which affect organ development and the response to the postnatal environment. Fetal and neonatal life are characterized by tremendous plasticity and the ability to respond to environmental factors (nutrients, oxygen, hormones) by altering gene expression levels via epigenetic modifications. Given that lipids act as both transcriptional activators and signaling molecules, excess fetal lipid exposure may regulate genes involved in lipid sensing and metabolism through epigenetic mechanisms. Epigenetic regulation of gene expression is characterized by covalent modifications to DNA and chromatin that alter gene expression independent of gene sequence. Epigenetic modifications can be maintained through positive and negative feedback loops, thereby creating stable changes in the expression of metabolic genes and their main transcriptional regulators. The purpose of this article is to review current literature on maternal-fetal lipid metabolism and maternal obesity outcomes and to suggest some potential mechanisms for fetal metabolic programming in key organ systems that regulate postnatal energy balance, with an emphasis on epigenetics and the intrauterine environment.

Lipotoxicity in obese pregnancy and its potential role in adverse pregnancy outcome and obesity in the offspring

Increasing maternal obesity is a challenge that has an impact on all aspects of female reproduction. Lean and obese pregnant women gain similar fat mass, but lean women store fat in the lower-body compartment and obese women in central compartments. In the non-pregnant, central storage of fat is associated with adipocyte hypertrophy and represents a failure to adequately store excess fatty acids, resulting in metabolic dysregulation and ectopic fat accumulation (lipotoxicity). Obese pregnancy is associated with exaggerated metabolic adaptation, endothelial dysfunction and increased risk of adverse pregnancy outcome. We hypothesize that the preferential storage of fat in central rather than ‘safer’ lower-body depots in obese pregnancy leads to lipotoxicity. The combination of excess fatty acids and oxidative stress leads to the production of oxidized lipids, which can be cytotoxic and influence gene expression by acting as ligands for nuclear receptors. Lipid excess and oxidative stress provoke endothelial dysfunction. Oxidized lipids can inhibit trophoblast invasion and influence placental development, lipid metabolism and transport and can also affect fetal developmental pathways. As lipotoxicity has the capability of influencing both maternal endothelial function and placental function, it may link maternal obesity and placentally related adverse pregnancy outcomes such as miscarriage and pre-eclampsia. The combination of excess/altered lipid nutrient supply, suboptimal in utero metabolic environment and alterations in placental gene expression, inflammation and metabolism may also induce obesity in the offspring.

Effects of maternal obesity on fetal growth and body composition: implications for programming and future health

Since the hypothesis linking low birth weight and poor fetal growth with future risk of cardiovascular disease was first proposed, there has been much interest in the early origins of disease. As rates of obesity increase and as maternal obesity has become common, interest has been directed towards the early origins of obesity. It is likely that a complex interaction of inherited gene effects and in-utero environment may interact in the developing fetus to programme pathways leading to future obesity. It is clear that maternal metabolism is disturbed in pregnancy in obese women, and that offspring of obese mothers have a higher percentage of body fat and are insulin resistant. This review discusses the ideas contributing to the current working concept of obesity programming, and discusses several potential mechanisms that may underlie obesity programming and susceptibility to future metabolic and vascular disease.

Perinatal risk factors for childhood obesity and metabolic dysregulation

BACKGROUND

Childhood obesity has increased significantly in recent decades.

OBJECTIVE

The objective was to examine the perinatal risk factors related to childhood obesity.

DESIGN

In a prospective study, 89 women with normal glucose tolerance (NGT) or gestational diabetes mellitus (GDM) and their offspring were evaluated at birth and at 8.8 +/- 1.8 y. At birth, obstetrical data, parental anthropometric measures, and neonatal body composition were assessed; at follow-up, diet and activity were assessed and laboratory studies were conducted. Weight was classified by using weight for age and sex, and body composition was measured by using dual-energy X-ray absorptiometry. In childhood, data were analyzed as tertiles and prediction models were developed by using logistic and stepwise regression.

RESULTS

No significant differences in Centers for Disease Control and Prevention weight percentiles, body composition, and most metabolic measures were observed between children of mothers with NGT and GDM at follow-up. Children in the upper tertile for weight had greater energy intake (P = 0.02), skinfold thickness (P = 0.0001), and leptin concentrations (P < 0.0001) than did those in tertiles 1 and 2. Children in the upper tertile for percentage body fat had greater waist circumference (P = 0.0001), insulin resistance (P = 0.002), and triglyceride (P = 0.009) and leptin (P = 0.0001) concentrations than did children in tertiles 1 and 2. The correlation between body fat at birth and follow-up was r = 0.29 (P = 0.02). The strongest perinatal predictor for a child in the upper tertile for weight was maternal pregravid body mass index (BMI; kg/m(2)) >30 (odds ratio: 3.75; 95% CI: 1.39, 10.10; P = 0.009) and for percentage body fat was maternal pregravid BMI >30 (odds ratio: 5.45; 95% CI: 1.62, 18.41; P = 0.006).

CONCLUSION

Maternal pregravid BMI, independent of maternal glucose status or birth weight, was the strongest predictor of childhood obesity.

Perinatal risk factors for childhood obesity and metabolic dysregulation

BACKGROUND

Childhood obesity has increased significantly in recent decades.

OBJECTIVE

The objective was to examine the perinatal risk factors related to childhood obesity.

DESIGN

In a prospective study, 89 women with normal glucose tolerance (NGT) or gestational diabetes mellitus (GDM) and their offspring were evaluated at birth and at 8.8 +/- 1.8 y. At birth, obstetrical data, parental anthropometric measures, and neonatal body composition were assessed; at follow-up, diet and activity were assessed and laboratory studies were conducted. Weight was classified by using weight for age and sex, and body composition was measured by using dual-energy X-ray absorptiometry. In childhood, data were analyzed as tertiles and prediction models were developed by using logistic and stepwise regression.

RESULTS

No significant differences in Centers for Disease Control and Prevention weight percentiles, body composition, and most metabolic measures were observed between children of mothers with NGT and GDM at follow-up. Children in the upper tertile for weight had greater energy intake (P = 0.02), skinfold thickness (P = 0.0001), and leptin concentrations (P < 0.0001) than did those in tertiles 1 and 2. Children in the upper tertile for percentage body fat had greater waist circumference (P = 0.0001), insulin resistance (P = 0.002), and triglyceride (P = 0.009) and leptin (P = 0.0001) concentrations than did children in tertiles 1 and 2. The correlation between body fat at birth and follow-up was r = 0.29 (P = 0.02). The strongest perinatal predictor for a child in the upper tertile for weight was maternal pregravid body mass index (BMI; kg/m(2)) >30 (odds ratio: 3.75; 95% CI: 1.39, 10.10; P = 0.009) and for percentage body fat was maternal pregravid BMI >30 (odds ratio: 5.45; 95% CI: 1.62, 18.41; P = 0.006).

CONCLUSION

Maternal pregravid BMI, independent of maternal glucose status or birth weight, was the strongest predictor of childhood obesity.