Early Life Conditions Research Articles

Sex differences in the antidepressant-like response and molecular events induced by the imidazoline-2 receptor agonist CR4056 in rats

In searching for novel targets to design antidepressants, among the characterized imidazoline receptors (IR), I2 receptors are an innovative therapeutical approach since they are dysregulated in major depressive disorder and by classical antidepressant treatments. In fact, several I2 agonists have been characterized for their antidepressant-like potential, but the results in terms of efficacy were mixed and exclusively reported in male rodents. Since there are well-known sex differences in antidepressant-like efficacy, this study characterized the potential effects induced by two I2 drugs, CR4056 (i.e., most promising drug already in phase II clinical trial for its analgesic properties) and B06 (a compound from a new family of bicyclic α-iminophosphonates) under the stress of the forced-swim test in male and female rats exposed to early-life stress. Moreover, some hippocampal neuroplasticity markers related to the potential effects observed were also evaluated (i.e., FADD, p-ERK/ERK, mBDNF, cell proliferation: Ki-67 + cells). The main results replicated the only prior study reporting the efficacy of CR4056 in male rats, while providing new data on its efficacy in females, which was clearly dependent on prior early-life stress exposure. Moreover, B06 showed no antidepressant-like effects in male or female rats. Finally, CR4056 increased FADD content and decreased cell proliferation in hippocampus, without affecting p-ERK/t-ERK ratio and/or mBDNF content. Interestingly, these effects were exclusively observed in female rats, and independently of early-life conditions, suggesting some distinctive molecular underpinnings participating in the therapeutic response of CR4056 for both sexes. In conjunction, these results present CR4056 with an antidepressant-like potential, especially in female rats exposed to stress early in life, together with some neuronal correlates described in the context of these behavioral changes in females.

Urbanization and depressive symptoms among middle-aged and older adults in China.

Urbanization plays an important role in individuals' health. However, it is difficult to isolate healthy migrant effect between urbanization and health. This study examined the effects of urbanization on depressive symptoms and its possible pathways among Chinese middle-aged and older adults independent of the influence of health-selective migration. Using the baseline survey of the China Health and Retirement Longitudinal Study, this study compared the depressive symptoms among three groups (urbanized rural residents, rural non-migrants and urban non-migrants). The 10-item Center for Epidemiologic Studies Depression Scale (CESD-10) short form was used to measure depressive symptoms. Logistic regression models and Structural Equation Model (SEM) were applied to examine the association between urbanization and depressive symptoms and the corresponding potential mechanisms. Our final sample contained 11,156 respondents with an average age of 58.91 (SD = 9.48), with 5,142 males (46.09%) and 6,014 females (53.91%). Compared with urbanized rural residents, rural residents were more likely to have depressive symptoms (OR = 1.19, 95% CI = 1.07, 1.32), and urban residents were associated with a decreased risk of depressive symptoms (OR = 0.81, 95% CI: 0.70, 0.94). A large proportion of the association between urbanization and depressive symptoms were mainly mediated by social participation, income and living conditions. Planned urbanization had an independent impact on decreased depressive symptoms. Improvements in social participation, income and living conditions are the main drivers behind this relationship. Additionally, urbanization compensates for the negative impact of depressive symptoms from disadvantaged early life conditions, but it cannot eliminate the gap between urbanized rural people and urban non-migrants.

LIFECOURSE DETERMINANTS OF DEPRESSION AMONG OLDER MEXICAN ADULTS

Abstract Older adults’ exposure to poverty, poor health, and negative life events over their lifetime creates cumulative adversity, increasing their risk of depressive symptoms. We hypothesize that those with disadvantaged sociodemographic characteristics like household poverty, chronic health conditions, and negative lifecourse exposures will be more likely to report a high number of depressive symptoms in old age. Three sequential multivariable logistic regression models were estimated using Wave 3 (2012) of the Mexican Health and Aging Study (MHAS). The final sample included 5,610 respondents aged 50 and older, of which 34.3% reported depression measured by a modified 9-item CES-D scale. The sample was mostly female (63.3%) with a mean age of 69. Present-day conditions were measured by quality of the home, consumer durables, chronic health conditions, and health insurance. Early-life conditions were measured by the respondent’s mother’s education and exposure to poverty and illness during childhood. In 2012, older Mexican adults living in homes built with poor construction materials or homes that lack access to water and sanitation (OR=1.24) were more likely to experience high depressive symptoms. In addition, those living in homes without consumer durable goods (OR=1.23) were at increased risk. Older Mexican adults who experienced poverty (OR=1.16) or illness during childhood (OR=1.21) were more likely to report a high number of depressive symptoms in old age. In conclusion, we find evidence of a “long-arm” of childhood, whereas older Mexican adults’ exposure to poverty and illness in childhood increases their likelihood of poor mental health outcomes, regardless of their present-day conditions.

COHORT DIFFERENCES IN EARLY-LIFE SOCIOECONOMIC STATUS AND LATE-LIFE COGNITIVE IMPAIRMENT IN MEXICO

Abstract Socioeconomic characteristics over the life course are associated with late-life cognitive impairment. However, evidence is lacking from countries like Mexico where population aging is occurring in the context of rapidly changing socioeconomic conditions. We used the Mexican Health and Aging Study to investigate differences between participants aged 60-76 in 2001 (n=5085) and 2018 (n=5947) in childhood (home with indoor toilet, parents’ education) and midlife (education, longest held occupation) socioeconomic characteristics and late life cognitive impairment. Cognitive impairment was defined as a low score on >2 out of five assessments. Most participants in the 2018 cohort lived in a home with an indoor toilet as a child (58.1%) and 36.9% had parents who both completed at least some education compared to 41.9% and 28.7% of participants in the 2001 cohort, respectively. Men and women in 2018 had on average 2.34 and 1.83 more years of education than men and women in 2001, respectively. The percentage of women with no main job and men who worked in agriculture were lower in 2018 than 2001 (women: 27.0% vs. 34.6%; men: 23.3% vs. 30.4%). The 2018 cohort had lower odds for cognitive impairment when adjusting for age, sex, marital status, and living in a rural/urban community (OR=0.67 95% CI=0.56-0.81). This difference was reduced after adjusting for childhood socioeconomic measures (OR=0.76 95% CI=0.67-0.86) and was no longer statistically significant after adding midlife socioeconomic measures (OR=0.98 95% CI=0.86-1.12). These findings suggest that improved early-life socioeconomic conditions in Mexico contribute to birth-cohort differences in late-life cognitive impairment.

COHORT DIFFERENCES IN EARLY-LIFE SOCIOECONOMIC STATUS AND LATE-LIFE COGNITIVE IMPAIRMENT IN MEXICO

Abstract Socioeconomic characteristics over the life course are associated with late-life cognitive impairment. However, evidence is lacking from countries like Mexico where population aging is occurring in the context of rapidly changing socioeconomic conditions. We used the Mexican Health and Aging Study to investigate differences between participants aged 60-76 in 2001 (n=5085) and 2018 (n=5947) in childhood (home with indoor toilet, parents’ education) and midlife (education, longest held occupation) socioeconomic characteristics and late life cognitive impairment. Cognitive impairment was defined as a low score on >2 out of five assessments. Most participants in the 2018 cohort lived in a home with an indoor toilet as a child (58.1%) and 36.9% had parents who both completed at least some education compared to 41.9% and 28.7% of participants in the 2001 cohort, respectively. Men and women in 2018 had on average 2.34 and 1.83 more years of education than men and women in 2001, respectively. The percentage of women with no main job and men who worked in agriculture were lower in 2018 than 2001 (women: 27.0% vs. 34.6%; men: 23.3% vs. 30.4%). The 2018 cohort had lower odds for cognitive impairment when adjusting for age, sex, marital status, and living in a rural/urban community (OR=0.67 95% CI=0.56-0.81). This difference was reduced after adjusting for childhood socioeconomic measures (OR=0.76 95% CI=0.67-0.86) and was no longer statistically significant after adding midlife socioeconomic measures (OR=0.98 95% CI=0.86-1.12). These findings suggest that improved early-life socioeconomic conditions in Mexico contribute to birth-cohort differences in late-life cognitive impairment.

CHILDHOOD PHYSICAL ABUSE INCREASES THE RISK OF SUBJECTIVE MEMORY IMPAIRMENT

Abstract Subjective memory impairment, defined as self-reported difficulties in recall and learning, doubles the risk of Alzheimer’s Disease and related dementia, despite being weakly related to objective memory decline. Because of its strong stability over time, it may be possible that subjective memory impairment reflects earlier life risk factors for dementia such as adverse childhood experiences. It is reported that over a fifth of older adults worldwide experienced physical abuse during childhood. Previous cross-sectional studies suggest physical abuse is associated with later cognitive impairment. Still unclear, are the longitudinal associations between childhood abuse and subjective memory impairment in later life. Using a sample of adults drawn from the Health and Retirement Study (n = 19,185, Mage = 67.05, SD = 11.33) we assessed associations between reported physical abuse by a parent before the age of 18 and subjective memory impairment (current memory problems and perceived memory decline) over periods of up to 18 years. Generalized linear mixed models examined longitudinal associations between childhood physical abuse and subjective memory impairment while controlling for depressive symptoms and other empirically relevant covariates. Experiencing childhood physical abuse was associated with increased likelihood of reporting more current memory problems (OR = 1.17, 95% CI 1.04, 1.33) and perceived memory decline in later life (OR = 1.27, 95% CI 1.13, 1.43). Findings suggest childhood physical abuse is associated with subjective memory impairment, a strong predictor of dementia. Understanding early life conditions, including adverse childhood experiences may help explain associations between subjective memory impairment and dementia risk.

CHILDHOOD PHYSICAL ABUSE INCREASES THE RISK OF SUBJECTIVE MEMORY IMPAIRMENT

Abstract Subjective memory impairment, defined as self-reported difficulties in recall and learning, doubles the risk of Alzheimer’s Disease and related dementia, despite being weakly related to objective memory decline. Because of its strong stability over time, it may be possible that subjective memory impairment reflects earlier life risk factors for dementia such as adverse childhood experiences. It is reported that over a fifth of older adults worldwide experienced physical abuse during childhood. Previous cross-sectional studies suggest physical abuse is associated with later cognitive impairment. Still unclear, are the longitudinal associations between childhood abuse and subjective memory impairment in later life. Using a sample of adults drawn from the Health and Retirement Study (n = 19,185, Mage = 67.05, SD = 11.33) we assessed associations between reported physical abuse by a parent before the age of 18 and subjective memory impairment (current memory problems and perceived memory decline) over periods of up to 18 years. Generalized linear mixed models examined longitudinal associations between childhood physical abuse and subjective memory impairment while controlling for depressive symptoms and other empirically relevant covariates. Experiencing childhood physical abuse was associated with increased likelihood of reporting more current memory problems (OR = 1.17, 95% CI 1.04, 1.33) and perceived memory decline in later life (OR = 1.27, 95% CI 1.13, 1.43). Findings suggest childhood physical abuse is associated with subjective memory impairment, a strong predictor of dementia. Understanding early life conditions, including adverse childhood experiences may help explain associations between subjective memory impairment and dementia risk.

Long‐lasting effects of harsh early‐life conditions on adult survival of a long‐lived vertebrate

Early life conditions, especially in long‐lived organisms, can have both immediate and long‐lasting effects in vital traits generating demographic structure across cohorts. Multiple non‐exclusive hypotheses have been proposed to explore this question. For instance, the silver spoon, the viability selection or the predictive adaptive response hypothesis, predict that long lasting effects resulting from harsh early conditions could be negative, positive or vary with current environmental conditions, respectively. We use an 18‐year capture–mark–recapture dataset on adult Audouin's gulls Ichthyaetus audouinii to test for these different hypotheses while accounting for age, breeding experience and large‐scale dispersal. Audouin's gull cohorts experiencing harsh conditions during early life (i.e. nestling period and first winter) are known to experience lower first year survival. Here, we show that early life conditions also explained a large proportion (54%) of adult survival variation among cohorts. However, adulthood cohorts experiencing poor early life conditions had higher adult survival, in accordance with the viability selection hypothesis. Our results also show that apparent inexperienced breeders showed lower survival than experienced ones. Moreover, adult survival decreased with age. These results could suggest an increased cost of reproduction for deferred breeders, individual quality differences or survival senescence in this population. Overall, our study highlights the importance of early development, age and breeding experience as potential factors generating heterogeneity of survival between cohorts. Understanding the mechanisms driving responses to early life conditions at different life stages is fundamental to understanding the long‐term dynamics of wild populations.

How life course socioeconomic conditions shape multimorbidity in old age – a scoping review

Abstract Multimorbidity is the co-existence of two or more chronic conditions in the same individual and is highly prevalent in ageing populations. Inequity in multimorbidity in old age could have socioeconomic roots that can be traced across the life course. It is, however, unclear if adverse socioeconomic conditions (SEC) at different periods of the life course predict the occurrence of multimorbidity in later life. We reviewed, therefore, studies assessing the association between life course SEC, measured at min. two time points, and later-life multimorbidity. We identified four studies (25,209 participants) with the first measure of SEC in childhood. In these four studies, childhood SEC was associated with multimorbidity in old age, and the associations were partially or fully attenuated upon adjustment for later-life SEC. We identified five studies (91,236 participants) with the first measure of SEC in young adulthood, and the associations with multimorbidity in old age as well as the effects of adjustment for later-life SEC differed from one study to the other. In conclusion, SEC in early life could have an effect on multimorbidity, attenuated at least partly by SEC in adulthood. Our results suggest that interventions and health promotion aiming to reduce the risk of multimorbidity in old age should target early-life socioeconomic conditions.

Early life parameters and personality affect oxidative status during adulthood in an altricial rodent

It is increasingly recognized that alterations of the cellular oxidative status might be an important cost underlying challenging early life conditions. For example, an increased litter size can impose challenges as the offspring will face increased competition for maternal resources. Within a litter, individuals with relatively higher starting mass typically show higher growth rates, which can lead to increased oxidative damage. We investigated the long‐term consequences of these early life parameters on the oxidative status in mature mound‐building mice (Mus spicilegus). Individual differences in the animals' exploration tendency were assessed by repeated open field and novel object tests. We predicted less exploratory phenotypes, which typically show a higher stress responsiveness, to be particularly susceptible to possible effects of these early life parameters on oxidative status. We quantified oxidative damage of DNA (8‐hydroxy‐2'‐deoxyguanosine levels, 8‐OHdG) and proteins (protein carbonyl content, PCC), and activities of the antioxidants catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) in liver and skeletal muscle tissue. 8‐OHdG levels were positively associated with CAT and SOD in both tissues, indicating that increased oxidative DNA damage was associated with an upregulation of antioxidant production. Hepatic DNA damage after maturity was increased in animals from larger litters. In less exploratory animals, DNA damage and the activity of CAT and SOD in the muscle were increased, but only in individuals with higher relative starting mass (measured on postnatal day 9). This interaction may be explained by the typically higher adrenocortical activity in less exploratory phenotypes and by the higher growth in relatively heavier pups, two factors known to increase oxidative stress. These findings contribute to enlightening the complex interplay between early life conditions, personality, and oxidative status.

Association of Childhood Trauma with Migraines in Men

Advancements in knowledge are needed to identify the link between childhood trauma and migraines in men. Though migraines are more prevalent in women, research about migraines in men with past traumatic exposure has received little attention. There are9% of men of all ages with migraines in the United States, 12% of adult males in Europe between the ages of 18 and 65 with migraines, and 5 to 29% of males who experienced childhood sexual abuse, in other words, 1 in 6 males; whereby 50% of children who are sex trafficked in the United States are males, while 4% of male victims of significant trauma develop post-traumatic stress disorder. There may be a strong correlation that suggests that male migraine sufferers are more likely to have experienced some form of childhood trauma, in particular sexual abuse. Men’s migraines underrepresentation in research limits understanding of the adverse effects of childhood sexual abuse that often results in post-traumatic stress disorder and other psychiatric and medical conditions. As migraines become more understood, advances in our understanding of the neurobiological effects of trauma on brain structure and function may suggest a possible impact of early-life stress on the onset of migraines. Early-life stress-induced conditions in males may manifest because of sexual abuse often being undetected, fear of speaking out, or fear of being embarrassed. Unlike physical abuse where bruises are visible or neglect where malnourishment is noticeable, sexual abuse may inflict hidden bruises that may contribute to males suffering in silence. An increase in our knowledge may identify sexual abuse as the link between childhood trauma and migraines in men to suggest new treatment strategies.

Association of Childhood Trauma with Migraines in Men

Advancements in knowledge are needed to identify the link between childhood trauma and migraines in men. Though migraines are more prevalent in women, research about migraines in men with past traumatic exposure has received little attention. There are9% of men of all ages with migraines in the United States, 12% of adult males in Europe between the ages of 18 and 65 with migraines, and 5 to 29% of males who experienced childhood sexual abuse, in other words, 1 in 6 males; whereby 50% of children who are sex trafficked in the United States are males, while 4% of male victims of significant trauma develop post-traumatic stress disorder. There may be a strong correlation that suggests that male migraine sufferers are more likely to have experienced some form of childhood trauma, in particular sexual abuse. Men’s migraines underrepresentation in research limits understanding of the adverse effects of childhood sexual abuse that often results in post-traumatic stress disorder and other psychiatric and medical conditions. As migraines become more understood, advances in our understanding of the neurobiological effects of trauma on brain structure and function may suggest a possible impact of early-life stress on the onset of migraines. Early-life stress-induced conditions in males may manifest because of sexual abuse often being undetected, fear of speaking out, or fear of being embarrassed. Unlike physical abuse where bruises are visible or neglect where malnourishment is noticeable, sexual abuse may inflict hidden bruises that may contribute to males suffering in silence. An increase in our knowledge may identify sexual abuse as the link between childhood trauma and migraines in men to suggest new treatment strategies.

Early life environment affects behavior, welfare, gut microbiome composition, and diversity in broiler chickens.

This study aimed to identify whether early-life conditions in broiler chickens could affect their behavior and welfare, and whether or not this was associated with an altered gut microbiome composition or diversity. Broilers were tested in a 2 x 2 factorial design with hatching conditions [home pen (OH) or at the hatchery (HH)] and enrichment (dark brooder (EE) or no brooder (NE) until 14 days of age) as factors (N = 6 per treatment combination). Microbiota composition was measured in the jejunum on days (d) 7, 14, and 35 and in pooled fecal samples on day 14. A novel environment test (NET) was performed on days 1 and 11, and the behavior was observed on days 6, 13, and 33. On day 35, composite asymmetry was determined and footpad dermatitis and hock burn were scored. In their home pen, HH showed more locomotion than OH (P = 0.05), and NE were sitting more and showed more comfort behavior than EE at all ages (P <0.001 and P = 0.001, respectively). On days 6 and 13 NE showed more eating and litter pecking while sitting, but on day 33 the opposite was found (age*enrichment: P = 0.05 and P <0.01, respectively). On days 1 and 11, HH showed more social reinstatement in the NET than OH, and EE showed more social reinstatement than NE (P <0.05). Composite asymmetry scores were lower for EE than NE (P <0.05). EE also had less footpad dermatitis and hock burn than NE (P <0.001). Within OH, NE had a more diverse fecal and jejunal microbiome compared to EE on day 14 (feces: observed richness: P = 0.052; jejunum: observed richness and Shannon: P <0.05); the principal component analysis (PCA) showed differences between NE and EE within both HH and OH in fecal samples on day 14, as well as significant differences in bacterial genera such as Lactobacillus and Lachnospiraceae (P <0.05). On day 35, PCA in jejunal samples only showed a trend (P = 0.068) for differences between NE vs. EE within the OH. In conclusion, these results suggest that especially the dark brooder affected the behavior and had a positive effect on welfare as well as affected the composition and diversity of the microbiome. Whether or not the behavior was modulated by the microbiome or vice versa remains to be investigated.

Phenotypic and environmental correlates of natal dispersal movements in fragmented landscapes

ContextNatal dispersal critically influences eco-evolutionary dynamics and the persistence of spatially structured populations. As both short- and long-distance movements contribute to population persistence in fragmented landscapes, understanding dispersal requires assessing phenotypic and environmental effects on a wide range of distances.ObjectivesTo assess phenotypic and environmental correlates of dispersal movements in fragmented landscapes.MethodsWe radio-tracked juvenile middle spotted woodpeckers in fragmented landscapes to assess phenotypic and environmental effects on emigration age, transfer duration (in days), and transfer distances.ResultsLarge fledglings and those in good condition emigrated earlier than smaller individuals and those in worse condition. Birds in better condition also reduced transfer duration. Overall, females dispersed earlier, remained shorter at transfer and moved further than males. However, while females increased transfer distances with increasing connectivity, males increased distances with decreasing connectivity. Emigration age increased with decreasing patch size and increasing patch quality, and with decreasing population density in patches with soft edges. Both transfer duration and distance increased with decreasing population density.ConclusionsThe correlations between phenotypic traits of fledglings and their posterior movements suggest that early-life conditions influenced dispersal through carry-over effects. Early emigration from low-quality and high-populated patches can be a behavioural mechanism to quickly escape adverse natal conditions, but population density effects were modulated by edge hardness. Finally, because reductions in connectivity led to similar transfer distances between sexes through a reduction in female distances, a lack of sex-biased dispersal can be a previously overlooked effect of habitat isolation that may alter eco-evolutionary dynamics.

Early life environments and cognition in adulthood: New evidence using a semiparametric approach and quantile regression

Theories and empirical evidence document the importance of early life environmental factors on later life cognition. A next question is how and in what dimension associations between early life environments and later life cognition vary. Using data from the UK Biobank in conjunction with time-place-specific infant mortality rates, we assessed heterogeneous and non-linear associations between early life conditions and later life cognition. We found that the association between the infant mortality rate and later life cognition increased once the UK achieved very low infant mortality rates, suggesting that additional decreases in infant mortality rates in an industrialized society continue to improve later life cognition. We also found that infant mortality rates have stronger effects at upper quantiles of the cognition distribution. This implies that adverse early life environments may have an important role for an early manifestation of cognitive aging.

A Scoping Review on Biopsychosocial Predictors of Mental Health among Older Adults.

This review aims to map the available evidence on biopsychosocial predictors of elderly mental health. The articles were independently screened in three selected databases, namely Pubmed, Proquest and Google Scholar. The stages consist of identifying the research questions, seeking and selecting relevant evidence, mapping data, and concluding and reporting results. The PRISMA flowchart was used to show the PEOS evidence search flow. A total of 23,722 articles were obtained from all databases during the initial search, where 458 titles fulfilled the eligibility criteria at the title screening stage. Furthermore, 383 articles passed through abstract screening, where 75 met the inclusion criteria and were included for full-text screening. Based on the full-text screening stage, 28 articles were excluded and the remaining 47 articles that matched the search process were included for data extraction. This review creates biopsychosocial variables related to the mental health of the elderly. The biological factors consist of age, biomarkers, female, health conditions, chronic diseases, and physical function. Variables related to psychological factors are affect, personality traits, and subjective well-being. Meanwhile, social factors include smoking, sleep quality, physical activity, daily living, social support, marital status, loneliness, religiosity, spirituality, and early life conditions.

Early-life adversity predicts performance and fitness in a wild social carnivore.

Studies on humans indicate that encountering multiple sources of adversity in childhood increases the risk of poor long-term health and premature death. Far less is known about cumulative effects of adversity during early life in wildlife. Focusing on the spotted hyena Crocuta crocuta, a social mammal with small litters, extensive maternal care, slow development and access to resources determined by social rank, we determined the contribution of ecological, maternal, social and demographic factors during early life on performance and fitness, and tested whether the impact of early-life adversity is cumulative. Using longitudinal data from 666 female hyenas in the Serengeti National Park, we determined the early growth rate, survival to adulthood, age at first reproduction (AFR), lifetime reproductive success (LRS) and longevity. We fitted multivariate models in which we tested the effects of environmental factors on these performance measures. We then constructed a cumulative adversity index and fitted models to test the effect of this index on each performance measure. Finally, the value of cumulative adversity models was tested by comparing them to multivariate and single-effect models in which the effect of each environmental factor was considered separately. High maternal rank decreased the AFR of daughters. Singleton and dominant cubs had higher growth rate than subordinate cubs, and singletons also had a higher survival chance to adulthood than subordinates. Daughters of prime age mothers had a higher growth rate, longevity and LRS. Little and heavy rainfall decreased survival to adulthood. Increasing numbers of lactating female clan members decreased growth rate, survival to adulthood and LRS. Cumulative adversity negatively affected short-term performance and LRS. Multivariate models outperformed cumulative adversity and single-effect models for all measures except for AFR and longevity, for which single-effect models performed better. Our results suggest that in some wildlife populations the combination of specific conditions in early life may matter more than the accumulation of adverse conditions as such.

Larval diet affects adult reproduction, but not survival, independent of the effect of injury and infection in Drosophila melanogaster

Early-life conditions have profound effects on many life-history traits, where early-life diet affects both juvenile development, and adult survival and reproduction. Early-life diet also has consequences for the ability of adults to withstand environmental challenges such as starvation, temperature and desiccation. However, it is less well known how early-life diet influences the consequences of infection in adults. Here we test whether varying the larval diet of female Drosophila melanogaster (through altering protein to carbohydrate ratio, P:C) influences the long-term consequences of injury and infection with the bacterial pathogen Pseudomonasentomophila. Given previous work manipulating adult dietary P:C, we predicted that adults from larvae raised on higher P:C diets would have increased reproduction, but shorter lifespans and an increased rate of ageing, and that the lowest larval P:C diets would be particularly detrimental for adult survival in infected individuals. For larval development, we predicted that low P:C would lead to a longer development time and lower viability. We found that early-life and lifetime egg production were highest at intermediate to high larval P:C diets, but this was independent of injury and infection. There was no effect of larval P:C on adult survival. Larval development was quickest on intermediate P:C and egg-to-pupae and egg-to-adult viability were slightly higher on higher P:C. Overall, despite larval P:C affecting several measured traits, we saw no evidence that larval P:C altered the consequence of infection or injury for adult survival or early-life and lifetime reproduction. Taken together, these data suggest that larval diets appear to have a limited impact on the adult life history consequences of infection.

Causes and consequences of variation in early-life telomere length in a bird metapopulation.

Environmental conditions during early‐life development can have lasting effects shaping individual heterogeneity in fitness and fitness‐related traits. The length of telomeres, the DNA sequences protecting chromosome ends, may be affected by early‐life conditions, and telomere length (TL) has been associated with individual performance within some wild animal populations. Thus, knowledge of the mechanisms that generate variation in TL, and the relationship between TL and fitness, is important in understanding the role of telomeres in ecology and life‐history evolution. Here, we investigate how environmental conditions and morphological traits are associated with early‐life blood TL and if TL predicts natal dispersal probability or components of fitness in 2746 wild house sparrow (Passer domesticus) nestlings from two populations sampled across 20 years (1994–2013). We retrieved weather data and we monitored population fluctuations, individual survival, and reproductive output using field observations and genetic pedigrees. We found a negative effect of population density on TL, but only in one of the populations. There was a curvilinear association between TL and the maximum daily North Atlantic Oscillation index during incubation, suggesting that there are optimal weather conditions that result in the longest TL. Dispersers tended to have shorter telomeres than non‐dispersers. TL did not predict survival, but we found a tendency for individuals with short telomeres to have higher annual reproductive success. Our study showed how early‐life TL is shaped by effects of growth, weather conditions, and population density, supporting that environmental stressors negatively affect TL in wild populations. In addition, shorter telomeres may be associated with a faster pace‐of‐life, as individuals with higher dispersal rates and annual reproduction tended to have shorter early‐life TL.

Urbanization and Cognitive Function Among Middle-Aged and Old Adults in China.

Our study examined the effect of urbanization on cognitive function and its possible pathways among Chinese middle-aged and older adults independent of the influence of health-selective migration. Using data from the China Health and Retirement Longitudinal Study, we compared cognitive function among three groups (urbanized-rural residents, rural nonmigrants, and urban nonmigrants). Logistic regression and structural equation models were applied to explore the impact of urbanization on cognitive function and the potential mechanisms. Compared with the urbanized-rural group, urban nonmigrants had better cognitive function, with a significant coefficient of 1.56 (95% CI: 1.22, 1.89) for global cognition scores and 0.37 (95% CI: 0.22, 0.53) for episodic memory scores. The rural nonmigrants had the worst cognitive function (β = -0.79, 95% CI: -1.04, -0.55) and lower scores of mental intactness (β = -0.65, 95% CI: -0.84, -0.57) and episodic memory (β = -0.14, 95% CI: -0.26, -0.03). The association between urbanization and cognitive function was mainly mediated by income and living conditions among middle-aged and older adults. Rural people who experienced planned urbanization in China had higher cognitive scores than rural non-migrants. Urbanization could thus have a beneficial and cumulative effect on cognitive function. Improvements in living conditions and changes in income are the main drivers behind the relationship. However, urbanization could compensate for the negative impact on cognitive function from disadvantaged early-life conditions, but it cannot completely eliminate the gap between urbanized-rural people and urban nonmigrants.