Pre- and postnatal dietary protein deficiency influences anxiety, memory and social behaviour in the African striped mouse Rhabdomys dilectus chakae

Unraveling the Molecular Mechanisms of the Neurodevelopmental Consequences of Fetal Protein Deficiency: Insights From Rodent Models and Public Health Implications

Fetal brain development requires increased maternal protein intake to ensure that offspring reach their optimal cognitive potential in infancy and adulthood. While protein deficiency remains a prevalent issue in developing countries, it is also reemerging in Western societies due to the growing adoption of plant-based diets, some of which are monotonous and may fail to provide sufficient amino acids crucial for the brain's critical developmental phase. Confounding variables in human nutritional research have impeded our understanding of the precise impact of protein deficiency on fetal neurodevelopment, as well as its implications for childhood neurocognitive performance. Moreover, it remains unclear whether such deficiency could predispose to mental health problems in adulthood, mirroring observations in individuals exposed to prenatal famine. In this review, we sought to evaluate mechanistic data derived from rodent models, placing special emphasis on the involvement of neuroendocrine axes, the influence of sex and timing, epigenetic modifications, and cellular metabolism. Despite notable progress, critical knowledge gaps remain, including understanding the long-term reversibility of effects due to fetal protein restriction and the interplay between genetic predisposition and environmental factors. Enhancing our understanding of the precise mechanisms that connect prenatal nutrition to brain development in future research endeavors can be significantly advanced by integrating multiomics approaches and utilizing additional alternative models such as nonhuman primates. Furthermore, it is crucial to investigate potential interventions aimed at alleviating adverse outcomes. Ultimately, this research has profound implications for guiding public health strategies aimed at raising awareness about the crucial role of optimal maternal nutrition in supporting fetal neurodevelopment.

Perinatal diet and offspring anxiety: A scoping review

Health behaviors during pregnancy have an impact on the developing offspring. Dietary factors play a role in the development of mental illness: however, less is known about the impact of diet factors during pre-conception, gestation, and lactation on anxiety levels in offspring. This scoping review sought to systematically map the available research involving human and animal subjects to identify nutritional interventions which may have a harmful or protective effect, as well as identify gaps. Studies investigating an association between any perinatal diet pattern or diet constituent and offspring anxiety were included. The number of studies reporting an association with increased or decreased levels of anxiety were counted and presented in figures. A total of 55,914 results were identified as part of a larger scoping review, and 120 articles met the criteria for inclusion. A greater intake of phytochemicals and vitamins were associated with decreased offspring anxiety whereas maternal caloric restriction, protein restriction, reduced omega-3 consumption, and exposure to a high fat diet were associated with higher levels of offspring anxiety. Results were limited by a very large proportion of animal studies. High quality intervention studies involving human subjects are warranted to elucidate the precise dietary factors or constituents that modulate the risk of anxiety in offspring.

Impaired social cognition caused by perinatal protein malnutrition evokes neurodevelopmental disorder symptoms and is intergenerationally transmitted

Nutritional inadequacy before birth and during postnatal life can seriously interfere with brain development and lead to persistent deficits in learning and behavior. In this work, we asked if protein malnutrition affects domains of social cognition and if these phenotypes can be transmitted to the next generation. Female mice were fed with a normal or hypoproteic diet during pregnancy and lactation. After weaning, offspring were fed with a standard chow. Social interaction, social recognition memory, and dominance were evaluated in both sexes of F1 offspring and in the subsequent F2 generation. Glucose metabolism in the whole brain was analyzed through preclinical positron emission tomography. Genome-wide transcriptional analysis was performed in the medial prefrontal cortex followed by gene-ontology enrichment analysis. Compared with control animals, malnourished mice exhibited a deficit in social motivation and recognition memory and displayed a dominant phenotype. These altered behaviors, except for dominance, were transmitted to the next generation. Positron emission tomography analysis revealed lower glucose metabolism in the medial prefrontal cortex of F1 malnourished offspring. This brain region showed genome-wide transcriptional dysregulation, including 21 transcripts that overlapped with autism-associated genes. Our study cannot exclude that the lower maternal care provided by mothers exposed to a low-protein diet caused an additional impact on social cognition. Our results showed that maternal protein malnutrition dysregulates gene expression in the medial prefrontal cortex, promoting altered offspring behavior that was intergenerationally transmitted. These results support the hypothesis that early nutritional deficiency represents a risk factor for the emergence of symptoms associated with neurodevelopmental disorders.

A resource-poor developmental diet reduces adult aggression in male Drosophila melanogaster

Aggressive behaviours occur throughout the animal kingdom and agonistic contests often govern access to resources. Nutrition experienced during development has the potential to influence aggressive behaviours in adults through effects on growth, energy budgets and an individual’s internal state. In particular, resource-poor developmental nutrition might decrease adult aggression by limiting growth and energy budgets, or alternatively might increase adult aggression by enhancing motivation to compete for resources. However, the direction of this relationship—and effects of developmental nutrition experienced by rivals—remains unknown in most species, limiting understanding of how early-life environments contribute to variation in aggression. We investigated these alternative hypotheses by assessing male-male aggression in adult fruit flies, Drosophila melanogaster, that developed on a low-, medium- or high-resource diet, manipulated via yeast content. We found that a low-resource developmental diet reduced the probability of aggressive lunges in adults, as well as threat displays against rivals that developed on a low-resource diet. These effects appeared to be independent of diet-related differences in body mass. Males performed relatively more aggression on a central food patch when facing rivals of a low-resource diet, suggesting that developmental diet affects aggressive interactions through social effects in addition to individual effects. Our finding that resource-poor developmental diets reduce male-male aggression in D. melanogaster is consistent with the idea that resource budgets mediate aggression and in a mass-independent manner. Our study improves understanding of the links between nutrition and aggression.

Significance statement

Early-life nutrition can influence social behaviours in adults. Aggression is a widespread social behaviour with important consequences for fitness. Using the fruit fly, Drosophila melanogaster, we show that a poor developmental diet reduces aspects of adult aggressive behaviour in males. Furthermore, males perform more aggression near food patches when facing rivals of poor nutrition. This suggests that early-life nutrition affects aggressive interactions through social effects in addition to individual effects.

Problem Solving in Animals: Proposal for an Ontogenetic Perspective

Simple Summary

Animals must be able to solve problems to access food and avoid predators. Problem solving is not a complicated process, often relying only on animals exploring their surroundings, and being able to learn and remember information. However, not all species, populations, or even individuals, can solve problems, or can solve problems in the same way. Differences in problem-solving ability could be due to differences in how animals develop and grow, including differences in their genetics, hormones, age, and/or environmental conditions. Here, we consider how an animal’s problem-solving ability could be impacted by its development, and what future work needs to be done to understand the development of problem solving. We argue that, considering how many different factors are involved, focusing on individual animals, and individual variation, is the best way to study the development of problem solving.

Abstract

Problem solving, the act of overcoming an obstacle to obtain an incentive, has been studied in a wide variety of taxa, and is often based on simple strategies such as trial-and-error learning, instead of higher-order cognitive processes, such as insight. There are large variations in problem solving abilities between species, populations and individuals, and this variation could arise due to differences in development, and other intrinsic (genetic, neuroendocrine and aging) and extrinsic (environmental) factors. However, experimental studies investigating the ontogeny of problem solving are lacking. Here, we provide a comprehensive review of problem solving from an ontogenetic perspective. The focus is to highlight aspects of problem solving that have been overlooked in the current literature, and highlight why developmental influences of problem-solving ability are particularly important avenues for future investigation. We argue that the ultimate outcome of solving a problem is underpinned by interacting cognitive, physiological and behavioural components, all of which are affected by ontogenetic factors. We emphasise that, due to the large number of confounding ontogenetic influences, an individual-centric approach is important for a full understanding of the development of problem solving.

Hyperlipidic diet affects body composition and induces anxiety-like behaviour in intrauterine growth-restricted adult mice

NEW FINDINGS

What is the central question of this study? What is the effect in male and female offspring of a protein-deficient diet producing intrauterine growth restriction (IUGR) in maternal mice on morphometric, metabolic and behavioural parameters before and after a challenge with a fat diet? What is the main finding and its importance? Male and female mice presented different growth trajectories after birth. IUGR favoured increased adiposity in male mice, and high-fat diet-induced anxiety-like behaviour in female mice.

ABSTRACT

As there is sexual dimorphism in the response to maternal manipulations, we aimed to analyse the effects of intrauterine growth restriction (IUGR) in both sexes on morphometric, metabolic and behavioural parameters throughout postnatal development, and after challenge with a hyperlipidic diet. Female Swiss mice (n = 59) were distributed into two groups (SD: standard diet, n = 26; and PDD: isocaloric protein-deficient diet, n = 33), 2 weeks before mating and during the gestational period. After birth, offspring from SD and PDD dams were cross-fostered and nurtured by SD dams until postnatal day (PND) 28. At PND 60 all animals were challenged with a hypercaloric diet for 4 weeks. Offspring birth weight was significantly reduced in the PDD group compared to the SD group (P = 0.0001), but only male offspring presented a rapid catch-up during the first 21 days of development. Although no differences in body weight were observed between groups after the challenge with the hyperlipidic diet, an increase in the relative perigonadal white adipose tissue (P = 0.009) and a decrease in gross gastrocnemius muscle weight (P = 0.010) were observed in the PDD males. In relation to behavioural tests, there was an increase in locomotion in both sexes (P = 0.0001), and a decrease in female grooming (P = 0.006) in the PDD group. Additionally, females from the PDD group showed increased hyperlipidic food intake. In conclusion, IUGR affected both sexes, with females showing prominent behavioural modifications and males presenting altered body composition elicited by a hyperlipidic diet.

Sons benefit from paternal care in African striped mice

Mammalian paternal care is rare and is often linked to enhanced fitness under particular ecological conditions. The proximate consequences of paternal care on offspring are lacking, however. Here, we tested whether levels of paternal care predict the behavioural, cognitive and physiological development of sons in the naturally paternal African striped mouse (Rhabdomys pumilio). We focused on sons raised in two treatments: biparental (both parents) or uniparental (mother alone) families. We recorded levels of interactions between pups with both parents, and later assessed the behaviour, cognition and physiology of sons at three developmental stages: juvenile, sub-adult and adult (sexual maturity). Sons from biparental families showed (a) reduced anxiety as juveniles; (b) greater exploration and social interaction at different stages; (c) better cognition; and (d) reduced corticosterone concentrations than sons from uniparental families. In contrast, sons from uniparental families showed greater levels of paternal care, although prolactin concentrations did not differ between treatments. Paternal care in striped mice enhances fitness of males. Here, we also show that sons benefit psychologically and physiologically through interactions with their fathers. However, sons also trade-off such benefits against their own paternal care behaviour, suggesting that fathers influence the development of their son's phenotype in complex ways.

Perinatal Nutrition and Programmed Risk for Neuropsychiatric Disorders: A Focus on Animal Models

Maternal nutrition is critically important for fetal development. Recent human studies demonstrate a strong connection between diet during pregnancy and offspring risk for neuropsychiatric disorders including depression, anxiety, and attention-deficit/hyperactivity disorder. Animal models have emerged as a crucial tool for understanding maternal nutrition's contribution to prenatal programming and the later development of neuropsychiatric disorders. This review highlights preclinical studies examining how maternal consumption of the three macronutrients (protein, fats, and carbohydrates) influence offspring negative-valence behaviors relevant to neuropsychiatric disorders. We highlight the translational aspects of animal models and so examine exposure periods that mirror the neurodevelopmental stages of human gestation. Because of our emphasis on programmed changes in neurobehavioral development, studies that continue diet exposure until assessment in adulthood are not discussed. The presented research provides a strong foundation of preclinical evidence of nutritional programming of neurobehavioral impairments. Alterations in risk assessment and response were observed alongside neurodevelopmental impairments related to neurogenesis, synaptogenesis, and synaptic plasticity. To date, the large majority of studies utilized rodent models, and the field could benefit from additional study of large-animal models. Additional future directions are discussed, including the need for further studies examining how sex as a biological variable affects the contribution of maternal nutrition to prenatal programming.

Protein deficiency decreases stereotypic behavior frequency and prevalence and activity in the striped mouse Rhabdomys dilectus chakae

Diverse motivational triggers, including diet, elicit stereotypic behavior. We investigated whether diets comprised of different protein levels but similar levels of energy were associated with the occurrence of locomotor stereotypies in the striped mouse Rhabdomys dilectus chakae. In a first experiment, 20 stereotypic and 20 non-stereotypic (10 subjects per sex and per group) juvenile (40 days old) subjects were placed on baseline (BP), high (HP) or low protein (LP) diet treatments (120 subjects in total). All subjects initially identified as stereotypic displayed stereotypic behavior in the BP and HP treatments on Days 60-63 and Days 80-83 compared to 35% and 12.5% of LP subjects, respectively. Moreover, LP subjects displayed lower levels of activity and stereotypic behavior than BP and HP subjects. Those identified as non-stereotypic never displayed stereotypy. In a second experiment, 48 individuals, bred and reared on LP and whose parents were stereotypic, were assigned to either HP (13 males, 12 females) or LP (12 males, 11 females) treatments at 50 days of age for 30 days. Stereotypy was three times less likely to occur in the LP than the HP treatment, and activity was greater in LP-HP individuals than LP-LP individuals. In both experiments, LP individuals had the lowest body mass. Striped mice adjusted their behaviors in response to dietary protein levels. Protein deficiency reduced activity and stereotypic behavior and prevalence, possibly related to an energy or neurological deficit.