Maternal exercise during pregnancy ameliorates the postnatal neuronal impairments induced by prenatal restraint stress in mice

Exercise reduces physical alterations in a rat model of fetal alcohol spectrum disorders

BACKGROUND

Prenatal alcohol exposure (PAE) has serious physical consequences for children such as behavioral disabilities, growth disorders, neuromuscular problems, impaired motor coordination, and decreased muscle tone. However, it is not known whether loss of muscle strength occurs, and which interventions will effectively mitigate physical PAE impairments. We aimed to investigate whether physical alteration persists during adolescence and whether exercise is an effective intervention.

RESULTS

Using paradigms to evaluate different physical qualities, we described that early adolescent PAE animals have significant alterations in agility and strength, without alterations in balance and coordination compared to CTRL animals. We evaluated the effectiveness of 3 different exercise protocols for 4 weeks: Enrichment environment (EE), Endurance exercise (EEX), and Resistance exercise (REX). The enriched environment significantly improved the strength in the PAE group but not in the CTRL group whose strength parameters were maintained even during exercise. Resistance exercise showed the greatest benefits in gaining strength, and endurance exercise did not.

CONCLUSION

PAE induced a significant decrease in strength compared to CTRL in PND21. Resistance exercise is the most effective to reverse the effects of PAE on muscular strength. Our data suggests that individualized, scheduled, and supervised training of resistance is more beneficial than endurance or enriched environment exercise for adolescents FASD.

Physically active pregnancies: Insights from the placenta

Physical activity (PA) positively influences pregnancy, a critical period for health promotion, and affects placental structure and function in ways previously overlooked. Here, we summarize the current body of literature examining the association between PA, placenta biology, and physiology while also highlighting areas where gaps in knowledge exist. PA during pregnancy induces metabolic changes, influencing nutrient availability and transporter expression in the placenta. Hormones and cytokines secreted during PA contribute to health benefits, with intricate interactions in pro- and anti-inflammatory markers. Extracellular vesicles and placental "-omics" data suggest that gestational PA can shape placental biology, affecting gene expression, DNA methylation, metabolite profiles, and protein regulation. However, whether cytokines that respond to PA alter placental proteomic profiles during pregnancy remains to be elucidated. The limited research on placenta mitochondria of physically active gestational parents (gesP), has shown improvements in mitochondrial DNA and antioxidant capacity, but the relationship between PA, placental mitochondrial dynamics, and lipid metabolism remains unexplored. Additionally, PA influences the placenta-immune microenvironment, angiogenesis, and may confer positive effects on neurodevelopment and mental health through placental changes, vascularization, and modulation of brain-derived neurotrophic factor. Ongoing exploration is crucial for unraveling the multifaceted impact of PA on the intricate placental environment.

A Baldwin interpretation of adult hippocampal neurogenesis: from functional relevance to physiopathology

Hippocampal adult neurogenesis has been associated to many cognitive, emotional, and behavioral functions and dysfunctions, and its status as a selected effect or an "appendix of the brain" has been debated. In this review, we propose to understand hippocampal neurogenesis as the process underlying the "Baldwin effect", a particular situation in evolution where fitness does not rely on the natural selection of genetic traits, but on "ontogenetic adaptation" to a changing environment. This supports the view that a strong distinction between developmental and adult hippocampal neurogenesis is made. We propose that their functions are the constitution and the lifelong adaptation, respectively, of a basic repertoire of cognitive and emotional behaviors. This lifelong adaptation occurs through new forms of binding, i.e., association or dissociation of more basic elements. This distinction further suggests that a difference is made between developmental vulnerability (or resilience), stemming from dysfunctional (or highly functional) developmental hippocampal neurogenesis, and adult vulnerability (or resilience), stemming from dysfunctional (or highly functional) adult hippocampal neurogenesis. According to this hypothesis, developmental and adult vulnerability are distinct risk factors for various mental disorders in adults. This framework suggests new avenues for research on hippocampal neurogenesis and its implication in mental disorders.

Effect of Maternal Exercise on Diet-induced Redox Imbalance in Hippocampus of Adult Offspring

Physical exercise practice has been increasingly recommended in the prevention and treatment of chronic diseases, causing a positive effect from body weight/fat loss to improved cognitive function. Maternal exercise seems to induce the same positive lifelong adaptations to the offspring. We hypothesized that maternal exercise can prevent redox imbalance in adult offspring's hippocampus exposed to a high-fat diet (HFD). Female Wistar rats were divided into three groups before and during pregnancy: (1) sedentary, (2) swimming exercise, and (3) swimming exercise with overload. On 60 days of age, the male pups were divided into standard diet or HFD for one month, yielding normal and HFD subgroups for each maternal condition. Maternal interventions did not alter gestational parameters, birth outcomes, and offspring weight gain from weaning to 90 days of age. The HFD consumption increased body fat, which was not prevented by maternal exercise. Serum glucose levels were increased by HFD, an effect that was prevented by unload maternal exercise. In the hippocampus, both maternal exercise intensities could increase antioxidant defense. Hippocampal redox homeostasis was impaired by HFD, causing increased superoxide levels, which was prevented by exercise without load, while overload caused only a reduction of the effect. In summary, the practice of swimming exercise without overload during pregnancy seems to be more beneficial when evaluated in animal model, preventing HFD induced redox imbalance and increasing antioxidant defense while overload swimming exercise during pregnancy demonstrated a negative effect on offspring submitted to HFD consumption.

Sex-dependent metabolic effects of pregestational exercise on prenatally stressed mice

Stressful events during the prenatal period have been related to hyperactive hypothalamic-pituitary-adrenal (HPA) axis responses as well as metabolic changes in adult life. Moreover, regular exercise may contribute to the improvement of the symptoms associated with stress and stress-related chronic diseases. Therefore, this study aims to investigate the effects of exercise, before the gestation period, on the metabolic changes induced by prenatal stress in adult mice. Female Balb/c mice were divided into three groups: control (CON), prenatal restraint stress (PNS) and exercise before the gestational period plus PNS (EX + PNS). When adults, the plasmatic biochemical analysis, oxidative stress, gene expression of metabolic-related receptors and sex differences were assessed in the offspring. Prenatal stress decreased neonatal and adult body weight when compared to the pregestational exercise group. Moreover, prenatal stress was associated with reduced body weight in adult males. PNS and EX + PNS females showed decreased hepatic catalase. Pregestational exercise prevented the stress-induced cholesterol increase in females but did not prevent the liver mRNA expression reduction on the peroxisome proliferator-activated receptors (PPARs) α and γ in PNS females. Conversely, PNS and EX + PNS males showed an increased PPARα mRNA expression. In conclusion, pregestational exercise prevented some effects of prenatal stress on metabolic markers in a sex-specific manner.

Wheel-running exercise before and during gestation against acute and sensitized cocaine psychomotor-activation in offspring

While animal research has consistently reported preventive effects of exercise against drug abuse vulnerability, little is known about the influence of the developmental stage during which exercise is displayed on addictive drugs responsiveness. This study aimed to determine whether prenatal exercise could attenuate acute cocaine reactivity and psychomotor sensitization in youth offspring. We used a split-plot factorial design where C57BL/6 J females were randomly assigned into sedentary or exercised (wheel-running) conditions before and during gestation, the wheels being removed on gestational day 18. Offspring were weaned, gendered and individually housed on 24-28 days old. At 38-42 days old, they were tested for their acute psychomotor responsiveness to 8 mg/kg cocaine and their initiation of sensitization over 8 additional once-daily administrations, the long-term expression of sensitization occurring 30 days later. Adolescent females born from exercised mothers were much less responsive to the acute psychomotor-stimulating effect of cocaine than those born from sedentary mothers (d = 0.75, p = 0.02), whereas there was no evidence for such a difference in males (d = 0.34, p = 0.17). However, we did not find sizeable attenuating effects of prenatal exercise on the initiation and the long-term expression of the psychomotor-activating effect of cocaine, in either sex (Cohen's ds varying from -0.13 to 0.39). These results suggest that prenatal exercise may induce initial protection against cocaine responsiveness in youth females, a finding that warrants further research.

Nrg1 deficiency modulates the behavioural effects of prenatal stress in mice

Little is known about the exact genes that confer vulnerability or resilience to environmental stressors during early neurodevelopment. Partial genetic deletion of neuregulin 1 (Nrg1) moderates the neurobehavioural effects of stressors applied in adolescence and adulthood, however, no study has yet examined its impact on prenatal stress. Here we examined whether Nrg1 deficiency in mice modulated the impact of prenatal stress on various behaviours in adulthood. Male heterozygous Nrg1 mice were mated with wild-type female mice who then underwent daily restraint stress from days 13 to 19 of gestation. Surprisingly, prenatal stress had overall beneficial effects by facilitating sensorimotor gating, increasing sociability, decreasing depressive-like behaviour, and improving spatial memory in adulthood. Such benefits were not due to any increase in maternal care, as prenatal stress decreased nurturing of the offspring. Nrg1 deficiency negated the beneficial behavioural effects of prenatal stress on all measures except sociability. However, Nrg1 deficiency interacted with prenatal stress to trigger locomotor hyperactivity. Nrg1 deficiency, prenatal stress or their combination failed to alter acute stress-induced plasma corticosterone concentrations. Collectively these results demonstrate that Nrg1 deficiency moderates the effects of prenatal stress on adult behaviour, but it does so in a complex, domain-specific fashion.

Swimming exercise before and during pregnancy: Promising preventive approach to impact offspring´s health

Several environmental factors affect child development, such as the intrauterine environment during the embryonic and fetal development and early postnatal environment provided by maternal behavior. Although mechanistic effects of maternal exercise on offspring health improvement are not yet completely understood, the number of reports published demonstrating the positive influence of maternal exercise have increase. Herein, we addressed issues related to early postnatal environment provided by maternal behavior and early developmental physical landmarks, sensorimotor reflexes, and motor movements ontogeny. In brief, adult female rats underwent involuntary swimming exercise, in a moderated intensity, one week before mating and throughout pregnancy, 30 min a day, 5 days a week. Maternal exercised dams have unchanged gestational outcomes compared to sedentary dams. We found no differences concerning the frequency of pup-directed behavior displayed by dams. However, sedentary dams displayed a poorer pattern of maternal care quality during dark cycle than exercised dams. Physical landmarks and sensorimotor reflexes development of female and male littermates did not differ between maternal groups. Developmental motor parameters such as immobility, lateral head movements, head elevation, pivoting, rearing with forelimb support and crawling frequencies did not differ between groups. Pups born to exercised dams presented higher frequency of walking and rearing on the hind legs. These data suggest that female and male littermates of exercised group present a high frequency of exploratory behavior over sedentary littermates. Taken together, the present findings reinforce that maternal exercise throughout pregnancy represent a window of opportunity to improve offspring's postnatal health.

Intergenerational Sex-Specific Transmission of Maternal Social Experience

The social environment is a major determinant of individual stress response and lifetime health. The present study shows that (1) social enrichment has a significant impact on neuroplasticity and behaviour particularly in females; and (2) social enrichment in females can be transmitted to their unexposed female descendants. Two generations (F0 and F1) of male and female rats raised in standard and social housing conditions were examined for neurohormonal and molecular alterations along with changes in four behavioural modalities. In addition to higher cortical neuronal density and cortical thickness, social experience in mothers reduced hypothalamic-pituitary-adrenal (HPA) axis activity in F0 rats and their F1 non-social housing offspring. Only F0 social mothers and their F1 non-social daughters displayed improved novelty-seeking exploratory behaviour and reduced anxiety-related behaviour whereas their motor and cognitive performance remained unchanged. Also, cortical and mRNA measurements in the F1 generation were affected by social experience intergenerationally via the female lineage (mother-to-daughter). These findings indicate that social experience promotes cortical neuroplasticity, neurohormonal and behavioural outcomes, and these changes can be transmitted to the F1 non-social offspring in a sexually dimorphic manner. Thus, a socially stimulating environment may form new biobehavioural phenotypes not only in exposed individuals, but also in their intergenerationally programmed descendants.

Exercise and epigenetic inheritance of disease risk

Epigenetics is the study of gene expression changes that occur in the absence of altered genotype. Current evidence indicates a role for environmentally induced alterations to epigenetic modifications leading to health and disease changes across multiple generations. This phenomenon is called intergenerational or transgenerational epigenetic inheritance of health or disease. Environmental insults, in the form of toxins, plastics and particular dietary interventions, perturb the epigenetic landscape and influence the health of F1 through to F4 generations in rodents. There is, however, the possibility that healthy lifestyles and environmental factors, such as exercise training, could lead to favourable, heritable epigenetic modifications that augment transcriptional programmes protective of disease, including metabolic dysfunction, heart disease and cancer. The health benefits conferred by regular physical exercise training are unquestionable, yet many of the molecular changes may have heritable health implications for future generations. Similar to other environmental factors, exercise modulates the epigenome of somatic cells and researchers are beginning to study exercise epigenetics in germ cells. The germ cell epigenetic modifications affected by exercise offer a molecular mechanism for the inheritance of health and disease risk. The aims of this review are to: (i) provide an update on the expanding field of exercise epigenetics; (ii) offer an overview of data on intergenerational/transgenerational epigenetic inheritance of disease by environmental insults; (iii) to discuss the potential of exercise-induced intergenerational inheritance of health and disease risk; and finally, outline potential mechanisms and avenues for future work on epigenetic inheritance through exercise.

Ancestral Exposure to Stress Generates New Behavioral Traits and a Functional Hemispheric Dominance Shift

In a continuously stressful environment, the effects of recurrent prenatal stress (PS) accumulate across generations and generate new behavioral traits in the absence of genetic variation. Here, we investigated if PS or multigenerational PS across 4 generations differentially affect behavioral traits, laterality, and hemispheric dominance in male and female rats. Using skilled reaching and skilled walking tasks, 3 findings support the formation of new behavioral traits and shifted laterality by multigenerational stress. First, while PS in the F1 generation did not alter paw preference, multigenerational stress in the F4 generation shifted paw preference to favor left-handedness only in males. Second, multigenerational stress impaired skilled reaching and skilled walking movement abilities in males, while improving these abilities in females beyond the levels of controls. Third, the shift toward left-handedness in multigenerationally stressed males was accompanied by increased dendritic complexity and greater spine density in the right parietal cortex. Thus, cumulative multigenerational stress generates sexually dimorphic left-handedness and dominance shift toward the right hemisphere in males. These findings explain the origins of apparently heritable behavioral traits and handedness in the absence of DNA sequence variations while proposing epigenetic mechanisms.

Homage to the ‘H’ in developmental origins of health and disease

Abundant evidence exists linking maternal and paternal environments from pericopconception through the postnatal period to later risk to offspring diseases. This concept was first articulated by the late Sir David Barker and as such coined the Barker Hypothesis. The term was then mutated to Fetal Origins of Adult Disease and finally broadened to developmental origins of adult health and disease (DOHaD) in recognition that the perinatal environment can shape both health and disease in resulting offspring. Developmental exposure to various factors, including stress, obesity, caloric-rich diets and environmental chemicals can lead to detrimental offspring health outcomes. However, less attention has been paid to date on measures that parents can take to promote the long-term health of their offspring. In essence, have we neglected to consider the ‘H’ in DOHaD? It is the ‘H’ component that should be of primary concern to expecting mothers and fathers and those seeking to have children. While it may not be possible to eliminate exposure to all pernicious factors, prevention/remediation strategies may tip the scale to health rather than disease. By understanding disruptive DOHaD mechanisms, it may also illuminate behavioral modifications that parents can adapt before fertilization and throughout the neonatal period to promote the lifelong health of their male and female offspring. Three possibilities will be explored in the current review: parental exercise, probiotic supplementation and breastfeeding in the case of mothers. The ‘H’ paradigm should be the focus going forward as a healthy start can indeed last a lifetime.

Behavioral benefits of maternal swimming are counteracted by neonatal hypoxia-ischemia in the offspring

Hypoxia-ischemia (HI) represents one of the most common causes of neonatal encephalopathy. The central nervous system injury comprises several mechanisms, including inflammatory, excitotoxicity, and redox homeostasis unbalance leading to cell death and cognitive impairment. Exercise during pregnancy is a potential therapeutic tool due to benefits offered to mother and fetus. Swimming during pregnancy elicits a strong metabolic programming in the offspring's brain, evidenced by increased antioxidant enzymes, mitochondrial biogenesis, and neurogenesis. This article aims to evaluate whether the benefits of maternal exercise are able to prevent behavioral brain injury caused by neonatal HI. Female adult Wistar rats swam before and during pregnancy (30min/day, 5 days/week, 4 weeks). At 7(th) day after birth, the offspring was submitted to HI protocol and, in adulthood (60(th) day), it performed the behavioral tests. It was observed an increase in motor activity in the open field test in HI-rats, which was not prevented by maternal exercise. The rats subjected to maternal swimming presented an improved long-term memory in the object recognition task, which was totally reversed by neonatal HI encephalopathy. BDNF brain levels were not altered; suggesting that HI or maternal exercise effects were BDNF-independent. In summary, our data suggest a beneficial long-term effect of maternal swimming, despite not being robust enough to protect from HI injury.

Stress exposure during the preimplantation period affects blastocyst lineages and offspring development

We found retardation of preimplantation embryo growth after exposure to maternal restraint stress during the preimplantation period in our previous study. In the present study, we evaluated the impact of preimplantation maternal restraint stress on the distribution of inner cell mass (ICM) and trophectoderm (TE) cells in mouse blastocysts, and its possible effect on physiological development of offspring. We exposed spontaneously ovulating female mice to restraint stress for 30 min three times a day during the preimplantation period, and this treatment caused a significant increase in blood serum corticosterone concentration. Microscopic evaluation of embryos showed that restraint stress significantly decreased cell counts per blastocyst. Comparing the effect of restraint stress on the two blastocyst cell lineages, we found that the reduction in TE cells was more substantial than the reduction in ICM cells, which resulted in an increased ICM/TE ratio in blastocysts isolated from stressed dams compared with controls. Restraint stress reduced the number of implantation sites in uteri, significantly delayed eye opening in delivered mice, and altered their behavior in terms of two parameters (scratching on the base of an open field test apparatus, time spent in central zone) as well. Moreover, prenatally stressed offspring had significantly lower body weights and in 5-week old females delivered from stressed dams, fat deposits were significantly lower. Our results indicate that exposure to stress during very early pregnancy can have a negative impact on embryonic development with consequences reaching into postnatal life.

The janus face of stress on reproduction: from health to disease

Parenthood is a fundamental feature of all known life. However, infertility has been recognized as a public health issue worldwide. But even when the offspring are conceived, in utero problems can lead to immediate (abortion), early (birth), and late (adulthood) consequences. One of the most studied factors is stress. However, stress response is, per se, of adaptive nature allowing the organism to cope with challenges. Stressors lead to deterioration if one is faced with too long lasting, too many, and seemingly unsolvable situations. In stress adaptation the hypothalamus-pituitary-adrenocortical axis and the resulting glucocorticoid elevation are one of the most important mechanisms. At cellular level stress can be defined as an unbalance between production of free radicals and antioxidant defenses. Oxidative stress is widely accepted as an important pathogenic mechanism in different diseases including infertility. On the other hand, the goal of free radical production is to protect the cells from infectious entities. This review aims to summarize the negative and positive influence of stress on reproduction as a process leading to healthy progeny. Special emphasis was given to the balance at the level of the organism and cells.

Prenatal stress and inhibitory neuron systems: implications for neuropsychiatric disorders

Prenatal stress is a risk factor for several psychiatric disorders in which inhibitory neuron pathology is implicated. A growing body of research demonstrates that inhibitory circuitry in the brain is directly and persistently affected by prenatal stress. This review synthesizes research that explores how this early developmental risk factor impacts inhibitory neurons and how these findings intersect with research on risk factors and inhibitory neuron pathophysiology in schizophrenia, anxiety, autism and Tourette syndrome. The specific impact of prenatal stress on inhibitory neurons, particularly developmental mechanisms, may elucidate further the pathophysiology of these disorders.

Prenatal stress inhibits hippocampal neurogenesis but spares olfactory bulb neurogenesis

The dentate gyrus (DG) and the olfactory bulb (OB) are two regions of the adult brain in which new neurons are integrated daily in the existing networks. It is clearly established that these newborn neurons are implicated in specific functions sustained by these regions and that different factors can influence neurogenesis in both structures. Among these, life events, particularly occurring during early life, were shown to profoundly affect adult hippocampal neurogenesis and its associated functions like spatial learning, but data regarding their impact on adult bulbar neurogenesis are lacking. We hypothesized that prenatal stress could interfere with the development of the olfactory system, which takes place during the prenatal period, leading to alterations in adult bulbar neurogenesis and in olfactory capacities. To test this hypothesis we exposed pregnant C57Bl/6J mice to gestational restraint stress and evaluated behavioral and anatomic consequences in adult male offspring.

We report that prenatal stress has no impact on adult bulbar neurogenesis, and does not alter olfactory functions in adult male mice. However, it decreases cell proliferation and neurogenesis in the DG of the hippocampus, thus confirming previous reports on rats. Altogether our data support a selective and cross-species long-term impact of prenatal stress on neurogenesis.

Evidences that maternal swimming exercise improves antioxidant defenses and induces mitochondrial biogenesis in the brain of young Wistar rats

Physical exercise during pregnancy has been considered beneficial to mother and child. Recent studies showed that maternal swimming improves memory in the offspring, increases hippocampal neurogenesis and levels of neurotrophic factors. The objective of this work was to investigate the effect of maternal swimming during pregnancy on redox status and mitochondrial parameters in brain structures from the offspring. Adult female Wistar rats were submitted to five swimming sessions (30 min/day) prior to mating with adult male Wistar rats, and then trained during the pregnancy (five sessions of 30-min swimming/week). The litter was sacrificed when 7 days old, when cerebellum, parietal cortex, hippocampus, and striatum were dissected. We evaluated the production of reactive species and antioxidant status, measuring the activities of superoxide-dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GPx), as well as non-enzymatic antioxidants. We also investigated a potential mitochondrial biogenesis regarding mitochondrion mass and membrane potential, through cytometric approaches. Our results showed that maternal swimming exercise promoted an increase in reactive species levels in cerebellum, parietal cortex, and hippocampus, demonstrated by an increase in dichlorofluorescein oxidation. Mitochondrial superoxide was reduced in cerebellum and parietal cortex, while nitrite levels were increased in cerebellum, parietal cortex, hippocampus, and striatum. Antioxidant status was improved in cerebellum, parietal cortex, and hippocampus. SOD activity was increased in parietal cortex, and was not altered in the remaining brain structures. CAT and GPx activities, as well as non-enzymatic antioxidant potential, were increased in cerebellum, parietal cortex, and hippocampus of rats whose mothers were exercised. Finally, we observed an increased mitochondrial mass and membrane potential, suggesting mitochondriogenesis, in cerebellum and parietal cortex of pups subjected to maternal swimming. In conclusion, maternal swimming exercise induced neurometabolic programing in the offspring that could be of benefit to the rats against future cerebral insults.