Prenatal Glucocorticoid Overexposure Research Articles

Dissecting the networks underlying diverse brain disorders after prenatal glucocorticoid overexposure.

New human life begins in the uterus in a period of both extreme plasticity and sensitivity to environmental disturbances. The fetal stage is also a vital period for central nervous system development, with experiences at this point profoundly and permanently shaping brain structure and function. As such, some brain disorders may originate in utero. Glucocorticoids, a class of essential stress hormones, play indispensable roles in fetal development, but overexposure may have lasting impacts on the brain. In this review, we summarize data from recent clinical and non-clinical studies regarding alterations in fetal brains due to prenatal glucocorticoid overexposure that are associated with nervous system disorders. We discuss relevant changes to brain structure and cellular functions and explore the underlying molecular mechanisms. In addition, we summarize factors that may cause differential outcomes between varying brain regions, and outline clinically feasible intervention strategies that are expected to minimize negative consequences arising from fetal glucocorticoid overexposure. Finally, we highlight the need for experimental evidence aided by new technologies to clearly determine the effects of excessive prenatal glucocorticoid exposure. This review consolidates diverse findings to help researchers better understand the relationship between the prenatal glucocorticoid overexposure and the effects it has on various fetal brain regions, promoting further development of critical intervention strategies.

Developmental programming of mitochondrial substrate metabolism in skeletal muscle of adult sheep by cortisol exposure before birth.

Prenatal glucocorticoid overexposure causes adult metabolic dysfunction in several species but its effects on adult mitochondrial function remain largely unknown. Using respirometry, this study examined mitochondrial substrate metabolism of fetal and adult ovine biceps femoris (BF) and semitendinosus (ST) muscles after cortisol infusion before birth. Physiological increases in fetal cortisol concentrations pre-term induced muscle- and substrate-specific changes in mitochondrial oxidative phosphorylation capacity in adulthood. These changes were accompanied by muscle-specific alterations in protein content, fibre composition and abundance of the mitochondrial electron transfer system (ETS) complexes. In adult ST, respiration using palmitoyl-carnitine and malate was increased after fetal cortisol treatment but not with other substrate combinations. There were also significant increases in protein content and reductions in the abundance of all four ETS complexes, but not ATP synthase, in the ST of adults receiving cortisol prenatally. In adult BF, intrauterine cortisol treatment had no effect on protein content, respiratory rates, ETS complex abundances or ATP synthase. Activity of citrate synthase, a marker of mitochondrial content, was unaffected by intrauterine treatment in both adult muscles. In the ST but not BF, respiratory rates using all substrate combinations were significantly lower in the adults than fetuses, predominantly in the saline-infused controls. The ontogenic and cortisol-induced changes in mitochondrial function were, therefore, more pronounced in the ST than BF muscle. Collectively, the results show that fetal cortisol overexposure programmes mitochondrial substrate metabolism in specific adult muscles with potential consequences for adult metabolism and energetics.

The effects of prenatal dexamethasone exposure and fructose challenge on pituitary-adrenocortical activity and anxiety-like behavior in female offspring

Prenatal glucocorticoid overexposure could largely influence pituitary-adrenal activity and anxiety-like behavior in offspring. Our aim was to study the possible potentiating effect of moderate dose of fructose – common ingredient of today’s diet – on prenatal glucocorticoid treatment-induced hypothalamo-pituitary-adrenal (HPA) axis changes. Pregnant female rats were treated with multiple dexamethasone (Dx) doses (3 x 0.5 mg/kg/b.m. Dx; 16th-18th gestational day). Half of female offspring from control and Dx treated dams were supplemented with 10% fructose solution, from weaning till adulthood. Immunohistochemistry, unbiased stereological evaluation and hormonal analysis are used to provide the morpho-functional state of pituitary and adrenal gland. Anxiety-like behavior was assessed using the light/dark box test and the elevated plus maze test. Prenatally Dx exposed females, with or without fructose consumption, had markedly reduced adrenocortical volume (p < 0.05) comparing to controls. Increased basal plasma ACTH level in these females (p < 0.05) maintained corticosterone concentration at control level produced by smaller adrenal glands. In parallel, anxiety-like behavior was shown by both tests used. In conclusion, prenatal Dx exposure cause negative psychophysiological outcome reflected in increased HPA axis activity and anxiety behavior in female offspring, while moderately increased fructose consumption failed to evoke any alteration or to potentiate effects of prenatal Dx exposure.

Postnatal High-Fat Diet Increases Liver Steatosis and Apoptosis Threatened by Prenatal Dexamethasone through the Oxidative Effect.

The objective of this study was to investigate cellular apoptosis in prenatal glucocorticoid overexposure and a postnatal high fat diet in rats. Pregnant Sprague-Dawley rats at gestational days 14 to 21 were administered saline (vehicle) or dexamethasone and weaned onto either a normal fat diet or a high fat diet for 180 days; in total four experimental groups were designated, i.e., vehicle treated group (VEH), dexamethasone treated group (DEX), vehicle treated plus high-fat diet (VHF), and dexamethasone treated plus high-fat diet (DHF). Chronic effects of prenatal liver programming were assessed at postnatal day 180. The apoptotic pathways involved proteins were analyzed by Western blotting for their expressions. Apoptosis and liver steatosis were also examined by histology. We found that liver steatosis and apoptosis were increased in the DHF, DEX, and VHF treated groups, and that the DHF treated group was increased at higher levels than the DEX and VHF treated groups. The expression of leptin was decreased more in the DHF treated group than in the DEX and VHF treated groups. Decreased peroxisome proliferator-activated receptor-gamma coactivator 1α, phosphoinositide-3-kinase, manganese superoxide dismutase and increased malondialdehyde expression levels were seen in DHF treated group relative to the DEX treated group. The DHF treated group exhibited higher levels of oxidative stress, apoptosis and liver steatosis than the DEX treated group. These results indicate that the environment of high-fat diet plays an important role in the development of liver injury after prenatal stress.

Melatonin in the regulation of liver steatosis following prenatal glucocorticoid exposure.

Nonalcoholic fatty liver disease patients are characterized by hepatic steatosis. Prenatal glucocorticoid overexposure can result in steatosis. In this study, we aimed to determine the mechanism and cellular apoptosis of prenatal glucocorticoid overexposure in rats and whether melatonin can rescue the prenatal glucocorticoid-induced steatosis and apoptosis in neonatal rats. Pregnant Sprague-Dawley rats at gestational days 14 to 21 were administered dexamethasone. Acute effects of prenatal programming liver were assessed at postnatal day 7. The expression of proteins involved in the apoptotic and methylation pathways was analyzed by RT-PCR and Western blotting. Apoptosis and steatosis were examined by histology staining. The liver steatosis and apoptosis were increased in prenatal glucocorticoid group more than in control group and decreased in melatonin group. The expression of leptin decreased in prenatal glucocorticoid and increased in melatonin group by liver RT-PCR and Western blot study. Caspase 3, TNF-α proteins expression, and TUNEL stains increased in prenatal glucocorticoid compared with control and decreased in melatonin group. The liver histone deacetylase, DNA methyltransferase activity, and DNA methylation were increased in prenatal glucocorticoid and decreased in melatonin group. The present study showed that the prenatal glucocorticoid induced programming liver steatosis at day 7 after delivery, possibly via altered leptin expression. Melatonin can reverse the methylation of leptin and decreased liver steatosis.

Altered placental methyl donor transport in the dexamethasone programmed rat

There is increasing evidence for a role for epigenetic modifications in early life ‘programming’ effects. Altered placental methyl donor transport may impact on the establishment of epigenetic marks in the fetus. This study investigated the effects of prenatal glucocorticoid overexposure on placental methyl donor transport. Glucocorticoids increased folate but decreased choline transport and reduced fetal plasma methionine levels. There was no change in global DNA methylation in fetal liver. These data suggest prenatal glucocorticoid overexposure causes complex alterations in the placental transport of key methyl donors which may have important implications for maternal diet and nutrient supplementation in pregnancy.

Multigenerational programming in the glucocorticoid programmed rat is associated with generation-specific and parent of origin effects

Exposure to an adverse early life environment is associated with increased cardio-metabolic disease risk, a phenomenon termed "programming." The effects of this are not limited to the exposed first (F1) generation but can be transmissible to a second generation (F2) through male and female lines. Using a three generation animal model of programming by initial prenatal glucocorticoid overexposure we have identified effects on fetal and placental weight in both the F1 and F2 offspring. However, the expression of candidate imprinted genes in the fetus and placenta differed between the F1 and F2, with marked parent-of-origin effects in F2. Since DNA methylation at imprinted genes is maintained at fertilization, they are potential templates for the transmission of programming effects across generations. Although we detected alterations in DNA methylation at differentially methylated regions (DMRs) of the key prenatal growth factor Igf2 in F1 and F2 fetal liver, the changes in DNA methylation at these DMRs do not appear to underlie the transmission of effects on Igf2 expression through sperm. Thus, multigenerational programming effects on birth weight and disease risk is associated with different processes in F1 and F2. These findings have implications for the pathogenesis and future attempts to stratify therapies for the ‘developmental component’ of cardiometabolic disease.

Prenatal Dexamethasone Programs Expression of Genes in Liver and Adipose Tissue and Increased Hepatic Lipid Accumulation But Not Obesity on a High-Fat Diet

The association between low birth weight and cardiovascular disease is amplified by the development of obesity. We explored the effects of postnatal high-fat (HF) feeding in dexamethasone (Dex)-programmed rats, in which prenatal glucocorticoid overexposure is associated with reduced birth weight and adult glucose intolerance. Male Wistar rats exposed to Dex or vehicle (Veh) during the last week of gestation were weaned onto HF or control diets for 6 months. Dex-exposed animals were of lower birth weight and showed catch-up growth by 7 wk. There were no differences in obesity or hyperinsulinaemia between Dex-HF and Veh-HF animals. However, Dex-HF animals had increased hepatic triglyceride content compared with Veh-HF animals. mRNA transcript profiles in adipose tissue revealed depot-specific changes in the expression of genes involved in fatty acid esterification and triglyceride synthesis and storage with prenatal Dex exposure. Thus, antenatal glucocorticoid overexposure in rats does not confer increased sensitivity to HF diet-induced obesity, but increases susceptibility to fatty liver. This may be due to depot-specific-programmed alterations in fat metabolism in adipose tissue.

Predictive value of maternal bodyweight, postnatal weight gain and prenatal dexamethasone overexposure for the development of obesity in adult marmoset monkeys

In rats, adult bodyweight is modulated by the intrauterine environment as well as early postnatal nutritional conditions. Along with fetal glucocorticoid overexposure or postnatal overfeeding persistent increases of bodyweight, blood pressure, liver enzymes (PEPCK) and a decrease in glucose tolerance are observed. Moreover, there is also evidence for a resistance against satiety signals in distinct brain regions. Whether prenatal glucocorticoid overexposure promotes obesity in primates is still matter of debate. We therefore investigated in offspring of marmoset monkeys the effect of intrauterine overexposure with the synthetic glucocorticoid dexamathasone (DEX) either during early or late pregnancy on weight gain, blood pressure and biochemical measures in a two year follow-up study. Marmoset monkeys (Callithrix jacchus) are small (˜400g) non-endangered South American non-human primates. They are of increasing interest in biomedical research because they share many similarities with humans and are easy to handle and to breed under standardized laboratory housing conditions. Three groups of pregnant marmoset monkeys were treated orally for one week with vehicle (CON; N=10) or with dexamethasone (5mg/kg daily) during early (E-DEX; pregnancy day 42–48; N=10) or late pregnancy (L-DEX; pregnancy day 90–96; N=10), respectively. In male offspring (N=30 experimental animals in total) bodyweight was recorded in weekly to monthly intervals. Blood pressure was measured and blood samples were collected at 6, 12, 18 and 24 months of age. Triglycerides, HDL-cholesterol, total cholesterol, fasting glucose, glucose after an oral glucose load (OGTT) and HbA1c were determined. In newborns, weight did not differ between groups. During the first two months after birth L-DEX offspring gained significantly (p<0.02) more weight than E-DEX and CON. In adulthood bodyweight correlated directly with maternal non-pregnant bodyweight (p<0.05) and the weight gain during two months after birth (p=0.01). Metabolic parameters and blood pressure correlated significantly (p<0.005) with bodyweight (negative correlation for HDL-cholesterol, positive correlation for all other parameters). As a consequence, offspring that showed rapid early weight gain and had an obese mother were likely to develop obesity with symptoms of metabolic syndrome, i.e. increased blood pressure, triglycerides, total cholesterol, fasting glucose, HbA1c and decreased HDL-cholesterol. Epidemiological studies in humans are consistent with these results showing that an obese mother and rapid early weight gain are risk factors for the development of obesity in later life. In contrast to the findings in rats, prenatal DEX overexposure seems to play a less important role for bodyweight development in marmosets. Due to the similarities to humans the marmoset monkey seems to be an ideal model for further studies on the regulation of early postnatal weight gain and its role for the development of metabolic disorders in adulthood. Supported by a European Commission Grant (QLRI-CT-2002–02758, EUPEAH).

Effects of prenatal glucocorticoid exposure on cardiac calreticulin and calsequestrin protein expression during early development and in adulthood.

Overexpression of the conserved Ca(2+)-binding proteins calreticulin and calsequestrin impairs cardiac function, leading to premature death. Calreticulin is vital for embryonic development, but also impairs glucocorticoid action. Glucocorticoid overexposure during late fetal life causes intra-uterine growth retardation and programmed hypertension in adulthood. To determine whether intra-uterine growth retardation or programmed hypertension was associated with altered calreticulin or calsequestrin expression, effects of prenatal glucocorticoid overexposure (maternal dexamethasone treatment on days 15-21 of pregnancy) were examined during fetal life and postnatal development until adulthood (24 weeks). Dexamethasone (100 or 200 microg/kg of maternal body weight) was administered via osmotic pump. Calreticulin was detected as a 55 kDa band and calsequestrin as 55 and 63 kDa bands in 21 day fetal hearts. Only the 55 kDa calsequestrin band was detected postnatally. Prenatal glucocorticoid overexposure at the higher dose decreased calreticulin protein expression (26%; P <0.05) but increased calsequestrin protein expression, both 55 and 63 kDa bands, by 87% ( P <0.01) and 78% ( P <0.01); only the 55 kDa calsequestrin band was increased at the lower dose (66%; P <0.05). Offspring of dams treated at the lower dexamethasone dose were studied further. In control offspring, cardiac calreticulin protein expression declined between 2 and 3 weeks of age, and remained suppressed until adulthood. Cardiac calsequestrin protein expression increased 2-fold between fetal day 21 and postnatal day 1 and continued to increase until adulthood, at which time it was 3.4-fold higher ( P <0.001). Prenatal dexamethasone exposure minimally affected postnatal calsequestrin protein expression, but the postnatal decline in calreticulin protein expression was abrogated and calreticulin protein expression in adulthood was 2.2-fold increased ( P <0.001) compared with adult controls. In view of the known associations between cardiac calreticulin overexpression and impaired cardiac function, targeted up-regulation of calreticulin may contribute to the increased risk of adult heart disease introduced as a result of prenatal overexposure to glucocorticoids.