Generation of Maternal Obesity Models in Studies of Developmental Programming in Rodents.

Mother-child cohort studies have established that both pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) are independently associated with cardio-metabolic risk factors in juvenile and adult offspring, including systolic and diastolic blood pressure. In rodent studies maternal obesity confers many facets of the metabolic syndrome including a persistent sympathy-excitatory hyperresponsiveness and hypertension acquired in the early stages of development. Insight from these animal models raises the possibility that early life exposure to the nutritional and hormonal environment of obesity in pregnancy in humans may lead to early onset of metabolic syndrome and/or essential hypertension. This chapter will address the development of rodent models of maternal overnutrition and obesity, which have proved invaluable in generating testable hypotheses for clinical translation and the development of intervention strategies to stem the swelling tide of obesity and its comorbidities predicted for future generations.

Sucrose feeding in mouse pregnancy leads to hypertension, and sex-linked obesity and insulin resistance in female offspring.

Eating an unbalanced diet during pregnancy may induce long-term health consequences in offspring, in particular obesity, insulin resistance, and hypertension. We tested the hypothesis that a maternal diet rich in simple sugars predispose mouse offspring to obesity, glucose intolerance, and cardiovascular diseases in adulthood. Female C57BL/6J mice were fed either a standard chow or a sucrose-rich diet (26% of total energy) 6 weeks prior to mating, throughout pregnancy and lactation. Offspring of control dams (OC) and high sucrose fed dams (OSF) were weaned onto standard control chow, and metabolic and cardiovascular parameters determined at 3 months of age. Both male and female OSF were hyperphagic by 4 weeks of age and females were heavier than OC at 6 weeks. At 3 months, female OSF showed a significant increase in inguinal fat pad mass, whereas skeletal muscle mass (tibialis anterior) and locomotor activity were decreased relative to OC. A 10-fold increase in fasting serum insulin in female OSF vs. OC at 3 months (Insulin [pmol/L] mean ± SEM, OSF, 200.3 ± 16.1, vs. OC, 20.3 ± 1.8, n = 6 P < 0.001), was associated with impaired glucose tolerance (AUC [mmol/L min] mean ± SEM, OSF 1437.4 ± 124.2 vs. OC, 1076.8 ± 83.9, n = 6, P < 0.05). Both male and female OSF were hypertensive as assessed by radiotelemetry (night-time systolic arterial pressure (SAP) [mmHg] mean ± SEM, male OSF, 128 ± 1 vs. OC, 109 ± 1, n = 6, P < 0.01; female OSF, 130 ± 1 vs. OC, 118 ± 1, n = 6, P < 0.05). Analysis of heart rate variability (HRV) demonstrated an increased low:high frequency ratio in male and female OSF (P < 0.05), indicative of heightened sympathetic efferent tone. Renal tissue noradrenaline (NA) content was markedly raised in the OSF vs. OC (NA [pg/ml/mg tissue] mean ± SEM, male OSF, 2.28 ± 0.19 vs. OC 0.84 ± 0.09, n = 6, P < 0.01). Exposure to a maternal diet rich in sucrose led to obesity and glucose intolerance in female mice offspring, and hypertension in both sexes.

Fostering in mice induces cardiovascular and metabolic dysfunction in adulthood.

Cross-fostering is widely used in developmental programming studies to determine the relative contribution of the in utero and suckling periods in establishing the adult offspring phenotype in response to an environmental challenge. We have investigated whether the process of fostering per se influences cardiovascular and metabolic function in adult offspring of C57BL/6J mice in comparison with animals suckled by their biological dams. Cross-fostered (CF) mice demonstrated juvenile onset hyperphagia and significantly higher body weight (from weaning to 12 weeks: male control (CON) vs. CF: P < 0.01, female CON vs. CF: P < 0.001; RM ANOVA) accompanied by increased abdominal adiposity in males only (white adipose tissue mass (mg): CON 280.5 ± 13.4 [mean ± SEM] (n = 7) vs. CF, 549.8 ± 99.3 (n = 8), P < 0.01). Both male and female CF mice demonstrated significantly enhanced glucose tolerance. A marked increase in systolic blood pressure (SBP) was observed in male CF mice (SBP (mmHg), day: CON 100.5 ± 1.4 (n = 6) vs. CF 114.3 ± 0.7 (n = 6), P < 0.001; night: CON 108.0 ± 2.0 (n = 6) vs. CF 123.2 ± 1.1 (n = 6), P < 0.001). Endothelium-dependent relaxation was enhanced in male CF mice, and renal noradrenaline was increased in female CF mice. Concentration of serum triglycerides, cholesterol, insulin and leptin were increased in CF vs. CON. The process of cross-fostering profoundly affects cardiovascular and metabolic phenotype in mice. The findings have implications for the inclusion of appropriate controls in the design of future studies and in the interpretation of previous cross-fostering studies in mice.

Role of thyroid hormones in the developmental control of tissue glycogen in fetal sheep near term.

Developmental and glucocorticoid-induced changes in tissue glycogen content occur in the fetus near term coincident with an increase in plasma triiodothyronine (T(3)), although the role of thyroid hormones in mediating these changes is unknown. This study investigated glycogen content in the liver, heart and skeletal muscle of sheep fetuses after experimental manipulation of thyroid hormone concentration in utero by T(3) infusion and fetal thyroidectomy (TX). At 130 days of gestation (term 145 +/- 2 days), hepatic glycogen was greater, and muscle glycogen was lower, in the TX fetuses than in the intact fetuses. However, between 130 and 144 days of gestation the normal increment in hepatic glycogen, and decrement in cardiac glycogen, seen in intact fetuses was abolished when the prepartum rise in T(3), but not cortisol, was prevented by TX. At 144 days of gestation, hepatic glycogen was lower, and cardiac glycogen was higher, in the TX compared with intact fetuses. In intact fetuses at 130 days of gestation, 5 days of intravenous T(3) infusion (8-12 microg kg(-1) day(-1)) caused a small but significant increase in hepatic glycogen, although the concentration achieved was not as great as that observed in intact fetuses infused with cortisol (2-3 mg kg(-1) day(-1)) for 5 days. Infusion of T(3) reduced cardiac glycogen to the level observed in mature fetuses near term and immature fetuses infused with cortisol for 5 days. Glycogen content in fetal skeletal muscle increased between 100 and 115 days of gestation, but was unaffected by cortisol or T(3) infusion. Therefore, thyroid hormones are important in the developmental control of hepatic and cardiac glycogen content in the ovine fetus near term and may mediate, in part, the maturational effects of cortisol.

Diet-induced obesity in female mice leads to offspring hyperphagia, adiposity, hypertension, and insulin resistance: a novel murine model of developmental programming.

Maternal obesity is increasingly prevalent and may affect the long-term health of the child. We investigated the effects of maternal diet-induced obesity in mice on offspring metabolic and cardiovascular function. Female C57BL/6J mice were fed either a standard chow (3% fat, 7% sugar) or a palatable obesogenic diet (16% fat, 33% sugar) for 6 weeks before mating and throughout pregnancy and lactation. Offspring of control (OC) and obese dams (OO) were weaned onto standard chow and studied at 3 and 6 months of age. OO were hyperphagic from 4 to 6 weeks of age compared with OC and at 3 months locomotor activity was reduced and adiposity increased (abdominal fat pad mass; P<0.01). OO were heavier than OC at 6 months (body weight, P<0.05). OO abdominal obesity was associated with adipocyte hypertrophy and altered mRNA expression of beta-adrenoceptor 2 and 3, 11 beta HSD-1, and PPAR-gamma 2. OO showed resistance artery endothelial dysfunction at 3 months, and were hypertensive, as assessed by radiotelemetry (nighttime systolic blood pressure at 6 months [mm Hg] mean+/-SEM, male OO, 134+/-1 versus OC, 124+/-2, n=8, P<0.05; female OO, 137+/-2 versus OC, 122+/-4, n=8, P<0.01). OO skeletal muscle mass (tibialis anterior) was significantly reduced (P<0.01) OO fasting insulin was raised at 3 months and by 6 months fasting plasma glucose was elevated. Exposure to the influences of maternal obesity in the developing mouse led to adult offspring adiposity and cardiovascular and metabolic dysfunction. Developmentally programmed hyperphagia, physical inactivity, and altered adipocyte metabolism may play a mechanistic role.