Sex-specific increase in susceptibility to metabolic syndrome in adult offspring after prenatal ethanol exposure with post-weaning high-fat diet

Prenatal ethanol exposure and changes in fetal neuroendocrine metabolic programming

Prenatal ethanol exposure (PEE) (mainly through maternal alcohol consumption) has become widespread. However, studies suggest that it can cause intrauterine growth retardation (IUGR) and multi-organ developmental toxicity in offspring, and susceptibility to various chronic diseases (such as neuropsychiatric diseases, metabolic syndrome, and related diseases) in adults. Through ethanol's direct effects and its indirect effects mediated by maternal-derived glucocorticoids, PEE alters epigenetic modifications and organ developmental programming during fetal development, which damages the offspring health and increases susceptibility to various chronic diseases after birth. Ethanol directly leads to the developmental toxicity of multiple tissues and organs in many ways. Regarding maternal-derived glucocorticoid-mediated IUGR, developmental programming, and susceptibility to multiple conditions after birth, ethanol induces programmed changes in the neuroendocrine axes of offspring, such as the hypothalamus-pituitary-adrenal (HPA) and glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axes. In addition, the differences in ethanol metabolic enzymes, placental glucocorticoid barrier function, and the sensitivity to glucocorticoids in various tissues and organs mediate the severity and sex differences in the developmental toxicity of ethanol exposure during pregnancy. Offspring exposed to ethanol during pregnancy have a "thrifty phenotype" in the fetal period, and show "catch-up growth" in the case of abundant nutrition after birth; when encountering adverse environments, these offspring are more likely to develop diseases. Here, we review the developmental toxicity, functional alterations in multiple organs, and neuroendocrine metabolic programming mechanisms induced by PEE based on our research and that of other investigators. This should provide new perspectives for the effective prevention and treatment of ethanol developmental toxicity and the early prevention of related fetal-originated diseases.

Fatty acid metabolism changes in association with neurobehavioral deficits in animal models of fetal alcohol spectrum disorders

Fetal alcohol spectrum disorders (FASD) show behavioral problems due to prenatal alcohol exposure (PAE). A previous study reports changes in gene expressions linked to fatty acid (FA) metabolism in the cerebral cortex of the PAE mouse model. We find an increase of palmitic acid and arachidonic acid in phospholipid in the cerebral cortex of PAE at postnatal day 30. The increase of palmitic acid is consistent with increase of the producing enzyme, Fasn (fatty acid synthase). Decrease of 26:6 FA is also consistent with the increase of the enzyme which uses 26:6 as a substrate for making very long chain FAs, Elovl4 (elongation of very long chain fatty acids protein 4). However, there is no increase in the elongated products. Rather, lipid droplets (LDs) accumulated in the brain. Although FA-associated metabolic measurements are not affected by PAE, the abundance of FA-related gut microbiota is altered. This suggests that the gut microbiome could serve as a tool to facilitate uncovering the brain pathophysiology of FASD and a potential target to mitigate neurobehavioral problems.

Fetal alcohol spectrum disorder predisposes to metabolic abnormalities in adulthood

Prenatal alcohol exposure (PAE) affects at least 10% of newborns globally and leads to the development of fetal alcohol spectrum disorders (FASDs). Despite its high incidence, there is no consensus on the implications of PAE on metabolic disease risk in adults. Here, we describe a cohort of adults with FASDs that had an increased incidence of metabolic abnormalities, including type 2 diabetes, low HDL, high triglycerides, and female-specific overweight and obesity. Using a zebrafish model for PAE, we performed population studies to elucidate the metabolic disease seen in the clinical cohort. Embryonic alcohol exposure (EAE) in male zebrafish increased the propensity for diet-induced obesity and fasting hyperglycemia in adulthood. We identified several consequences of EAE that may contribute to these phenotypes, including a reduction in adult locomotor activity, alterations in visceral adipose tissue and hepatic development, and persistent diet-responsive transcriptional changes. Taken together, our findings define metabolic vulnerabilities due to EAE and provide evidence that behavioral changes and primary organ dysfunction contribute to resultant metabolic abnormalities.

Prenatal ethanol exposure induced disorder of hypothalamic-pituitary-adrenal axis-associated neuroendocrine metabolic programming alteration and dysfunction of glucose and lipid metabolism in 40-week-old female offspring rats

This study was designed to demonstrate disorder of hypothalamic-pituitary-adrenal (HPA) axis-associated neuroendocrine metabolic programming alteration and dysfunction of glucose and lipid metabolism induced by prenatal ethanol exposure (PEE) in postnatal week 40 (PW40) female offspring rats. Pregnant Wistar rats were administrated 4  g/kg·d ethanol intragastrically from gestational day 11 until term delivery. After weaning, the female offspring were fed with high-fat diet until PW24, and suffered to unpredictable chronic stress (UCS) during PW38-40. Animal serum was collected to examine the changes in hypothalamic-pituitary-adrenal (HPA) axis activity, glucose and lipid metabolic phenotypes before and after UCS. We found that pups in the PEE group manifested a low birthweight at PW1 and an early catch-up growth pattern. Furthermore, a low basal activity of HPA axis continued to PW38 in the PEE group. On the basal condition, serum low-density lipoprotein-cholesterol (LDL-C) level was significantly increased and high-density lipoprotein-cholesterol (HDL-C) level was significantly decreased in the PEE group, while serum triglyceride, total cholesterol (TCH), glucose and insulin levels were not significantly changed. Under unpredictable chronic stress, serum insulin in the PEE group was significantly decreased, while the levels of serum triglyceride, TCH, LDL-C, and the ratio of LDL-C/HDL-C were significantly higher than those in the control. These results suggest that PEE increases the dysfunction of glucose and lipid metabolism in PW40 female offspring, which is related to the disorder of HPA axis-associated neuroendocrine metabolic programming alteration.

Fetal and postnatal zinc restriction: Sex differences in metabolic alterations in adult rats

OBJECTIVE

Intrauterine and postnatal micronutrient malnutrition may program metabolic diseases in adulthood. We examined whether moderate zinc restriction in male and female rats throughout fetal life, lactation, or postweaning growth induces alterations in liver, adipose tissue, and intermediate metabolism.

METHODS

Female Wistar rats were fed low-zinc or control zinc diets from pregnancy to offspring weaning. After weaning, male and female offspring were fed either a low-zinc or a control zinc diet. At 74 d of life, oral glucose tolerance tests were performed and serum metabolic profiles were evaluated. Systolic blood pressure and oxidative stress and morphology of liver and retroperitoneal adipose tissue were evaluated in 81 d old offspring.

RESULTS

Zinc restriction during prenatal and postnatal life induced an increase in systolic blood pressure, hyperglycemia, hypertriglyceridemia, higher serum glucose levels at 180 min after glucose overload, and greater insulin resistance indexes in male rats. Hepatic histologic studies revealed no morphologic alterations, but an increase in lipid peroxidation and catalase activity were identified in zinc-deficient male rats. Adipose tissue from zinc-deficient male rats had adipocyte hypertrophy, an increase in lipid peroxidation, and a reduction in catalase and glutathione peroxidase activity. Adequate dietary zinc content during postweaning growth reversed basal hyperglycemia, hypertriglyceridemia, insulin resistance indexes, hepatic oxidative stress, and adipocyte hypertrophy. Female rats were less sensitive to the metabolic effects of zinc restriction.

CONCLUSIONS

This study strengthens the importance of a balanced intake of zinc during growth to ensure adequate lipid and carbohydrate metabolism in adult life.

Sex-specific deficits in biochemical but not behavioral responses to delay fear conditioning in prenatal alcohol exposure mice

BACKGROUND

Studies in clinical populations and preclinical models have shown that prenatal alcohol exposure (PAE) is associated with impairments in the acquisition, consolidation and recall of information, with deficits in hippocampal formation-dependent learning and memory being a common finding. The glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and extracellular signal-regulated kinase 2 (ERK2) are key regulators of hippocampal formation development, structure and functioning and, thus, are potential mediators of PAE's effects on this brain region. In the present studies, we employed a well-characterized mouse model of PAE to identify biochemical mechanisms that may underlie activity-dependent learning and memory deficits associated with PAE.

METHODS

Mouse dams consumed either 10% (w/v) ethanol in 0.066% (w/v) saccharin (SAC) or 0.066% (w/v) SAC alone using a limited (4-h) access, drinking-in-the-dark paradigm. Male and female offspring (∼180-days of age) were trained using a delay conditioning procedure and contextual fear responses (freezing behavior) were measured 24 h later. Hippocampal formation tissue and blood were collected from three behavioral groups of animals: 20 min following conditioning (conditioning only group), 20 min following the re-exposure to the context (conditioning plus re-exposure group), and behaviorally naïve (naïve group) mice. Plasma corticosterone levels were measured by enzyme immunoassay. Immunoblotting techniques were used to measure protein levels of the GR, MR, ERK1 and ERK2 in nuclear and membrane fractions prepared from the hippocampal formation.

RESULTS

Adult SAC control male and female mice displayed similar levels of contextual fear. However, significant sex differences were observed in freezing exhibited during the conditioning session. Compared to same-sex SAC controls, male and female PAE mice demonstrated context fear deficits While plasma corticosterone concentrations were elevated in PAE males and females relative to their respective SAC naïve controls, plasma corticosterone concentrations in the conditioning only and conditioning plus re-exposure groups were similar in SAC and PAE animals. Relative to the respective naïve group, nuclear GR protein levels were increased in SAC, but not PAE, male hippocampal formation in the conditioning only group. In contrast, no difference was observed between nuclear GR levels in the naïve and conditioning plus re-exposure groups. In females, nuclear GR levels were significantly reduced by PAE but there was no effect of behavioral group or interaction between prenatal treatment and behavioral group. In males, nuclear MR levels were significantly elevated in the SAC conditioning plus re-exposure group compared to SAC naïve mice. In PAE females, nuclear MR levels were elevated in both the conditioning only and conditioning plus re-exposure groups relative to the naïve group. Levels of activated ERK2 (phospho-ERK2 expressed relative to total ERK2) protein were elevated in SAC, but not PAE, males following context re-exposure, and a significant interaction between prenatal exposure group and behavioral group was found. No main effects or interactions of behavioral group and prenatal treatment on nuclear ERK2 were found in female mice. These findings suggest a sex difference in which molecular pathways are activated during fear conditioning in mice.

CONCLUSIONS

In PAE males, the deficits in contextual fear were associated with the loss of responsiveness of hippocampal formation nuclear GR, MR and ERK2 to signals generated by fear conditioning and context re-exposure. In contrast, the contextual fear deficit in PAE female mice does not appear to be associated with activity-dependent changes in GR and MR levels or ERK2 activation during training or memory recall, although an overall reduction in nuclear GR levels may play a role. These studies add to a growing body of literature demonstrating that, at least partially, different mechanisms underlie learning, memory formation and memory recall in males and females and that these pathways are differentially affected by PAE.

Effects of ethanol and varenicline on female Sprague-Dawley rats in a third trimester model of fetal alcohol syndrome

Perinatal ethanol exposure disrupts a variety of developmental processes in neurons important for establishing a healthy brain. These ethanol-induced impairments known as fetal alcohol spectrum disorder (FASD) are not fully understood, and currently, there is no effective treatment. Further, growing evidence suggests that adult females are more susceptible to ethanol, with the effects of perinatal ethanol exposure also being sexually divergent. Female models have been historically underutilized in neurophysiological investigations, but here, we used a third-trimester binge-ethanol model of FASD to examine changes to basal forebrain (BF) physiology and behavior in female Sprague-Dawley rats. We also tested varenicline as a potential cholinomimetic therapeutic. Rat pups were gavage-treated with binge-like ethanol, varenicline and ethanol, and varenicline alone. Using patch-clamp electrophysiology in BF slices, we observed that binge-ethanol exposure increased spontaneous post-synaptic current (sPSC) frequency. Varenicline exposure alone also enhanced sPSC frequency. Varenicline plus ethanol co-treatment prevented the sPSC frequency increase. Changes in BF synaptic transmission persisted into adolescence after binge-ethanol treatment. Behaviorally, binge-ethanol treated females displayed increased anxiety (thigmotaxis) and demonstrated learning deficits in the water maze. Varenicline/ethanol co-treatment was effective at reducing these behavioral deficits. In the open field, ethanol-treated rats displayed longer distances traveled and spent less time in the center of the open field box. Co-treated rats displayed less anxiety, demonstrating a possible effect of varenicline on this measure. In conclusion, ethanol-induced changes in both BF synaptic transmission and behavior were reduced by varenicline in female rats, supporting a role for cholinergic therapeutics in FASD treatment.

The expressional disorder of the renal RAS mediates nephrotic syndrome of male rat offspring induced by prenatal ethanol exposure

This study aimed to prove that prenatal ethanol exposure (PEE) can induce nephrotic syndrome in male rat offspring and to explore the underlying intrauterine programming mechanisms. Pregnant Wistar rats were intragastrically administered ethanol (4 g/kg d) from gestational day (GD) 9 to GD 20, and the male fetuses were delivered by cesarean section at GD20 and the male adult offspring were euthanized at postnatal week (PW) 24. In vitro, the primary metanephric mesenchyme cells were treated with ethanol at concentrations of 15-60 mM. The results indicated that the kidneys of adult offspring in the PEE group exhibited glomerulosclerosis as well as interstitial fibrosis. The levels of serum creatinine and urine protein were elevated; the serum total cholesterol level was increased and the serum albumin concentration was reduced. In the fetal kidney, developmental retardation was presented in the PEE group via pathological examinations, accompanied by the expressional inhibition of the glial-cell-line-derived neurotrophic factor/c-ret tyrosine kinase receptor (GDNF/c-ret) signaling pathway. Although serum angiotensin II (Ang II) level and the gene expression of renal angiotensin-converting enzyme (ACE) were increased in the PEE group, the expression of renal angiotensin II type 2 receptor (AT₂R) was significantly inhibited, accompanied by a reduction in the H3K27ac level on the AT₂R gene promoter. In the non-classical renin-angiotensin system (RAS), the expression of renal angiotensin converting enzyme 2 (ACE2) and Mas receptor (MasR) were inhibited in the PEE group. The above changes of the classical and non-classical RAS all sustained from utero to adulthood. In vitro, ethanol elevated the gene expression of ACE and angiotensin II type 1a receptor (AT_1aR) whereas it reduced the expression of AT₂R, ACE2, and MasR, accompanied by a reduction in the H3K27ac level on AT₂R gene promoter. Taken together, these results suggested that PEE can induce fetal kidney developmental retardation and adult nephrotic syndrome, and direct regulation of ethanol to the renal RAS was involved in the mechanism of nephrotic syndrome induced by PEE.

Fetal Alcohol Exposure Alters Blood Flow and Neurological Responses to Transient Cerebral Ischemia in Adult Mice

BACKGROUND

Prenatal alcohol exposure (PAE) can result in physical and neurocognitive deficits that are collectively termed "fetal alcohol spectrum disorders" (FASD). Although FASD is associated with lifelong intellectual disability, the mechanisms mediating the emergence of secondary mental health and physical disabilities are poorly understood. Based on our previous data showing that maternal ethanol (EtOH) exposure in mice resulted in an immediate reduction in cranially directed fetal blood flow, we hypothesized that such exposure would also result in persistent alterations in cranially directed blood flow in the prenatally alcohol-exposed (PAE) adult. We also hypothesized that PAE adults exposed to an acute cerebrovascular insult would exhibit more brain damage and neurobehavioral impairment compared to non-PAE adult controls.

METHODS

Pregnant C57BL/6 mice were exposed to EtOH, 3 g/kg, or water by intragastric gavage. Blood flow in carotid, renal, and femoral arteries was assessed by ultrasound imaging in PAE and control adults at 3, 6, and 12 months of age. To mimic ischemic stroke in young adult populations, 3-month-old PAE and control animals were subject to transient middle cerebral artery occlusion (MCAo) and subsequently assessed for behavioral recovery, stroke infarct volume, and brain cytokine profiles.

RESULTS

PAE resulted in a significant age-related decrease in blood acceleration in adult mice, specifically in the carotid artery. A unilateral transient MCAo resulted in equivalent cortico-striatal damage in both PAE and control adults. However, PAE adult mice exhibited significantly decreased poststroke behavioral recovery compared to controls.

CONCLUSIONS

Our data collectively show that PAE adult mice exhibit a persistent, long-term loss of cranially directed blood flow, and decreased capacity to compensate for brain trauma due to acute-onset adult diseases like ischemic stroke.