Early origins of inflammation: microbial exposures in infancy predict lower levels of C-reactive protein in adulthood

Exploring the Relationship Between Stress, Salivary C-Reactive Protein, and Embodied Physiological Responses in a Nigerian Population

OBJECTIVES

The impacts of stress on inflammation, although hypothesized, have not been thoroughly examined, especially in relation to social and environmental factors and particularly within Black populations. This study aims to explore the biological mechanisms of embodiment linking stress and health to understand physiological changes in the body's response to psychological stress in a Nigerian population. Through a multidisciplinary approach, this study queries the relationship between stress, cortisol, and salivary C-reactive protein (sCRP), a biomarker of inflammation, while also validating the use of sCRP as a potential and accurate stress indicator in the field.

METHODS

In this cross-sectional study, 138 passive drool saliva samples (nfemale = 89 nmale = 49) were collected and assessed for sCRP and cortisol levels in adults. Participants also completed a short demographic survey and, to measure psychological stress, the General Health Questionnaire 12 (GHQ-12). Relationships between sCRP and stress-related variables (i.e., cortisol, GHQ-12, and demographic data) were assessed using Spearman's correlations, simple regression, multivariable linear regression, and exploratory factor analysis.

RESULTS

sCRP levels ranged from 20.57 to 6879.41 pg/mL across all samples, with significant differences between female and male participants. The GHQ-12 was not a significant predictor of sCRP variability. However, socio-demographic factors such as body mass index (BMI), age, self-reported sex, ethnic identity, and cortisol were significant predictors, collectively explaining 24%-27% of the variation in sCRP.

CONCLUSION

Socio-demographic predictors like BMI, age, sex, and particularly ethnic group experience in Nigeria encapsulate aspects of embodied stress, that significantly affect sCRP variability.

Intimate partner violence, depression, and chronic low-grade inflammation among middle-aged women in Cebu, Philippines

OBJECTIVES

Recent discussions in human biology have highlighted how local ecological contexts shape the relationship between social stressors and health across populations. Chronic low-grade inflammation has been proposed as a pathway linking social stressors to health, with evidence concentrated in high-income Western contexts. However, it remains unclear whether this is an important pathway in populations where prevalence is lower due to lower adiposity and greater infectious exposures. To investigate this further, we tested associations between multiple types of intimate partner violence (IPV), a highly prevalent stressor and health crisis globally, and C-reactive protein (CRP), a commonly used measure of chronic low-grade inflammation, in Cebu, Philippines. For reference, we compared results for CRP to depression, a well-established and consistently observed health outcome of IPV.

METHODS

Data came from 1601 currently partnered women (ages 35-69 years) as part of the Cebu Longitudinal Health and Nutrition Survey. IPV exposures included physical, emotional, and controlling behavior. Depression scores were measured using a modified version of the Center for Epidemiologic Studies-Depression Scale for this population, whereas plasma CRP was measured from overnight-fasted morning blood samples.

RESULTS

All three types of IPV were associated with a higher depression score. However, none of the IPV measures were associated with CRP. In a post hoc interaction test, emotional IPV became positively associated with CRP as waist circumference increased above the mean.

CONCLUSIONS

Our results suggest a complex relationship between social stressors and chronic low-grade inflammation, which is likely dependent on the population-specific context of lifestyle and environmental factors.

Pregnancy is linked to faster epigenetic aging in young women

A central prediction of evolutionary theory is that energy invested into reproduction comes at the expense of somatic maintenance and repair, accelerating biological aging. Supporting this prediction are findings that high fertility among women predicts shorter lifespan and poorer health later in life. However, biological aging is thought to begin before age-related health declines, limiting the applicability of morbidity and mortality for studying the aging process earlier in life. Here, we examine the relationship between reproductive history and biological aging in a sample of young (20 to 22yo) men and women from the Cebu Longitudinal Health and Nutrition Survey, located in the Philippines (n = 1,735). We quantify biological aging using six measures, collectively known as epigenetic clocks, reflecting various facets of cellular aging, health, and mortality risk. In a subset of women, we test whether longitudinal changes in gravidity between young and early-middle adulthood (25 to 31yo) are associated with changes in epigenetic aging during that time. Cross-sectionally, gravidity was associated with all six measures of accelerated epigenetic aging in women (n = 825). Furthermore, longitudinal increases in gravidity were linked to accelerated epigenetic aging in two epigenetic clocks (n = 331). In contrast, the number of pregnancies a man reported fathering was not associated with epigenetic aging among same-aged cohort men (n = 910). These effects were robust to socioecological, environmental, and immunological factors, consistent with the hypothesis that pregnancy accelerates biological aging and that these effects can be detected in young women in a high-fertility context.

Pearl Memorial Lecture. Humans at the extremes: Exploring human adaptation to ecological and social stressors

The field of human biology has long explored how human populations have adapted to extreme environmental circumstances. Yet, it has become increasingly clear that conditions of social stress, poverty, and lifestyle change play equally important roles in shaping human biological variation and health. In this paper, I provide a brief background on the foundational human adaptability research of the International Biological Programme (IBP) from the 1960s, highlighting how its successes and critiques have shaped current research directions in the field. I then discuss and reflect on my own field research that has examined the influence of both environmental and social stresses on human populations living in different ecosystems: the Peruvian Andes, the Siberian arctic, and the Bolivian rainforest. Finally, I consider how the papers in this special issue advance our understanding of human adaptability to extreme conditions and offer directions for future research. Drawing on our field's distinctive evolutionary and biocultural perspectives, human biologists are uniquely positioned to examine how the interplay between social and ecological domains influences the human condition.

Socioeconomic status is negatively associated with immunosenescence but positively associated with inflammation among middle-aged women in Cebu, Philippines

BACKGROUND

Socioeconomic status (SES) gradients in health are well-documented, and while biological pathways are incompletely understood, chronic inflammation and accelerated immune aging (immunosenescence) among lower SES individuals have been implicated. However, previous findings have come from samples in higher income countries, and it is unclear how generalizable they are to lower- and middle-income countries (LMIC) with different infectious exposures and where adiposity-an important contributor to chronic inflammation-might show different SES patterning. To address this gap, we explored associations between SES and inflammation and immunosenescence in a sample of women in Cebu, Philippines.

METHODS

Data came from the mothers of the Cebu Longitudinal Health and Nutrition Survey birth cohort (mean age: 47.7, range: 35-69 years). SES was measured as a combination of annual household income, education level, and assets. Chronic inflammation was measured using C-reactive protein (CRP) in plasma samples from 1,834 women. Immunosenescence was measured by the abundance of exhausted CD8T (CD8 + CD28-CD45RA-) and naïve CD8T and CD4T cells, estimated from DNA methylation in whole blood in a random subsample of 1,028. Possible mediators included waist circumference and a collection of proxy measures of pathogen exposure.

RESULTS

SES was negatively associated with the measures of immunosenescence, with slight evidence for mediation by a proxy measure for pathogen exposure from the household's drinking water source. In contrast, SES was positively associated with CRP, which was explained by the positive association with waist circumference.

CONCLUSIONS

Similar to higher income populations, in Cebu there is an SES-gradient in pathogen exposures and immunosenescence. However, lifestyle changes occurring more rapidly among higher SES individuals is contributing to a positive association between SES and adiposity and inflammation. Our results suggest more studies are needed to clarify the relationship between SES and inflammation and immunosenescence across LMIC.

Three common assumptions about inflammation, aging, and health that are probably wrong

Chronic inflammation contributes to the onset and progression of cardiovascular disease and other degenerative diseases of aging. But does it have to? This article considers the associations among inflammation, aging, and health through the lens of human population biology and suggests that chronic inflammation is not a normal nor inevitable component of aging. It is commonly assumed that conclusions drawn from research in affluent, industrialized countries can be applied globally; that aging processes leading to morbidity and mortality begin in middle age; and that inflammation is pathological. These foundational assumptions have shifted focus away from inflammation as a beneficial response to infection or injury and toward an understanding of inflammation as chronic, dysregulated, and dangerous. Findings from community-based studies around the world-many conducted in areas with relatively high burdens of infectious disease-challenge these assumptions by documenting substantial variation in levels of inflammation and patterns of association with disease. They also indicate that nutritional, microbial, and psychosocial environments in infancy and childhood play important roles in shaping inflammatory phenotypes and their contributions to diseases of aging. A comparative, developmental, and ecological approach has the potential to generate novel insights into the regulation of inflammation and how it relates to human health over the life course.

Association between infectious exposures in infancy and epigenetic age acceleration in young adulthood in metropolitan Cebu, Philippines

OBJECTIVES

The drivers of human life expectancy gains over the past 200 years are not well-established, with a potential role for historical reductions in infectious disease. We investigate whether infectious exposures in infancy predict biological aging using DNA methylation-based markers that forecast patterns of morbidity and mortality later in life.

METHODS

N = 1450 participants from the Cebu Longitudinal Health and Nutrition Survey-a prospective birth cohort initiated in 1983-provided complete data for the analyses. Mean chronological age was 20.9 years when venous whole blood samples were drawn for DNA extraction and methylation analysis, with subsequent calculation of three epigenetic age markers: Horvath, GrimAge, and DunedinPACE. Unadjusted and adjusted least squares regression models were evaluated to test the hypothesis that infectious exposures in infancy are associated with epigenetic age.

RESULTS

Birth in the dry season, a proxy measure for increased infectious exposure in the first year of life, as well as the number of symptomatic infections in the first year of infancy, predicted lower epigenetic age. Infectious exposures were associated with the distribution of white blood cells in adulthood, which were also associated with measures of epigenetic age.

CONCLUSIONS

We document negative associations between measures of infectious exposure in infancy and DNA methylation-based measures of aging. Additional research, across a wider range of epidemiological settings, is needed to clarify the role of infectious disease in shaping immunophenotypes and trajectories of biological aging and human life expectancy.

Birth size and the serum level of biological age markers in men

Previous studies showed that intrauterine growth restrictions, resulting in smaller body size at birth, are associated with altered development and the risk of age-related diseases in adult life. Thus, prenatal development may predict aging trajectories in humans. The study aimed to verify if body size at birth is related to biological age in adult men. The study sample consisted of 159 healthy, non-smoking men with a mean age of 35.24 (SD 3.44) years. Birth weight and length were taken from medical records. The ponderal index at birth was calculated. Biological age was evaluated based on serum levels of s-Klotho, hsCRP, DHEA/S, and oxidative stress markers. Pregnancy age at birth, lifestyle, weight, cortisol, and testosterone levels were controlled. The results showed no relationship between birth size and s-Klotho, DHEA/S level, inflammation, or oxidative stress. Also, men born as small-for-gestational-age (N = 49) and men born as appropriate-for-gestational-age (N = 110) did not differ in terms of biological age markers levels. The results were similar when controlled for pregnancy week at birth, chronological age, BMI, testosterone, or cortisol level. The results suggest that there is no relationship between intrauterine growth and biomarkers of aging in men aged 30-45 years from the affluent population.

Progression of C-reactive protein from birth through preadolescence varies by mode of delivery

Introduction

Delivery via caesarean section (C-section) has been associated with an increased risk of childhood chronic diseases such as obesity and asthma, which may be due to underlying systemic inflammation. However, the impact of specific C-section types may be differential, as emergency C-sections typically involve partial labor and/or membrane rupture. Our objectives were to determine if mode of delivery associates with longitudinal profiles of high sensitivity CRP (hs-CRP) -a marker of systemic inflammation-from birth through preadolescence, and to examine if CRP mediates the association between mode of delivery and preadolescent body mass index (BMI).

Methods

Data from the WHEALS birth cohort (N = 1,258) were analyzed; 564 of the 1,258 children in the cohort had data available for analysis. Longitudinal plasma samples (birth through 10-years of age) from 564 children from were assayed for hs-CRP levels. Maternal medical records were abstracted to obtain mode of delivery. Growth mixture models (GMMs) were used to determine classes of hs-CRP trajectories. Poisson regression with robust error variance was used to calculate risk ratios (RRs).

Results

Two hs-CRP trajectory classes were identified: class 1 (76% of children) was characterized by low hs-CRP, while class 2 (24% of children) was characterized by high and steadily increasing hs-CRP. In multivariable models, children delivered via planned C-section had 1.15 times higher risk of being in hs-CRP class 2, compared to vaginal deliveries (p = 0.028), while no association was found for unplanned C-section deliveries [RR (95% CI) = 0.96 (0.84, 1.09); p = 0.49]. Further, the effect of planned C-section on BMI z-score at age 10 was significantly mediated by hs-CRP class (percent mediated = 43.4%).

Conclusions

These findings suggest potentially beneficial effects of experiencing partial or full labor, leading to a lower trajectory of systemic inflammation throughout childhood and decreased BMI during preadolescence. These findings may have implications for chronic disease development later in life.

Neither environmental unpredictability nor harshness predict reliance on alloparental care among families in Cebu, Philippines

Alloparental caregiving is key to humans' highly flexible reproductive strategies. Across species and across societies, alloparental care is more common in harsh and/or unpredictable environments (HUEs). Currently, however, it is unclear whether HUEs predict intra-population variation in alloparental care, or whether early life HUEs might predict later alloparental care use in adulthood, consistent with adaptive developmental plasticity. We test whether harshness measures (socioeconomic status (SES), environmental hygiene, crowding) and unpredictability measures (parental unemployment, paternal absence, household moves) predicted how much alloparental assistance families in Cebu, Philippines received, in a multigenerational study with data collected across four decades. Though worse environmental hygiene predicted more concurrent alloparental care in 1994, we found little evidence that HUEs predict within-population variation in alloparental care in this large-scale, industrialized society. Indeed, less-crowded conditions and higher SES predicted more alloparental care, not less, in the 1980s and in 2014 respectively, while paternal absence in middle childhood predicted less reliance on alloparental care in adulthood. In this cultural context, our results generally do not provide support for the translation of interspecific or intersocietal patterns linking HUEs and alloparental care to intra-population variation in alloparental care, nor for the idea that a reproductive strategy emphasizing alloparental care use may be preceded by early life HUEs.

Dietary Protein Source Matters for Changes in Inflammation Measured by Urinary C-Reactive Protein in Rural Polish Women

Objectives

Multiple macronutrients have been shown to affect systemic inflammation, a well-known predictor of chronic disease. Less often, varying sources of these macronutrients are examined. Different subsistence environments lead to varying access to protein sources which, combined with physical activity patterns, may lead to different relationships than among more typically studied sedentary, industrialized populations. This study hypothesizes an association between dietary protein intake and urinary C-Reactive Protein (CRP) concentration in women from a rural, agrarian Polish community.

Materials and Methods

We assessed protein intake and their sources for 80 nonsmoking, premenopausal Polish women who were not pregnant, nursing, or on hormonal birth control during the study or within the previous six months. Each participant completed multiple 24-hour dietary recalls during one menstrual cycle. Participants collected morning void urinary samples daily over one menstrual cycle for urinary CRP analysis. We analyzed relationships between plant and animal protein intake and CRP over the menstrual cycle by multiple linear regression.

Results

Plant protein in cereal foods was significantly positively associated with cycle-average urinary CRP concentrations (p<0.05) after controlling for body fat percent, total energy intake, and dietary fiber. Foods containing animal protein were not significantly associated with CRP.

Discussion

Contents of this population's main plant and animal protein sources differ from those of more commonly studied industrialized populations. Within the context of a population's typical diet, more emphasis may need to be placed on particular source of protein consumed, beyond plant versus animal, in order to understand relationships with CRP.

C-reactive protein in adult Samoans: Population variation and physiological correlates

OBJECTIVES

C-reactive protein (CRP) has been associated with adiposity and cardiometabolic disease risk in many populations but remains remarkably understudied in Pacific Islander populations. Here, we provide the first examination of correlates of CRP in adult Samoans (n = 108, ages 35-55 years) to test the hypotheses that CRP exhibits sex-dependent associations with measures of BMI, adiposity, and cardiometabolic disease risks.

METHODS

We analyzed associations between measures of adiposity (total fat mass, visceral fat mass, percent total body fat), body mass index (BMI), cardiometabolic risks, behaviors, demographics, and CRP. Unadjusted analyses of CRP were undertaken using Pearson's pairwise, and Spearman's rank correlations; one-way analysis of variance and Kruskal-Wallis tests assessed variables by CRP quartiles. Adjusted analyses of CRP correlates were examined using generalized linear regression.

RESULTS

Serum CRP ranged from 0.08 to 13.3 mg/L (median 1.4 mg/L) and varied significantly by sex t (108) = -2.47, p = .015. CRP was weakly to moderately associated with measures of adiposity and BMI (r and ρ ranged between 0.25 and 0.50, p < .05) and some cardiometabolic markers (including HbA1c, fasting insulin, and insulin resistance). CRP was significantly associated with percent body fat in women and men, adjusting for other variables.

CONCLUSIONS

These data are among the first to demonstrate CRP correlates in a sample of adult Samoans. CRP differed by sex and was associated with BMI, adiposity, and some cardiometabolic risk markers. These data align with findings in other populations.

Early life, life course and gender influences on levels of C-reactive protein among migrant Bangladeshis in the UK

Background and objectives

Humans co-evolved with pathogens, especially helminths, that educate the immune system during development and lower inflammatory responses. The absence of such stimuli in industrialized countries is associated with higher baseline levels of C-reactive protein (CRP) among adults who appear at greater risk for inflammatory disorders. This cross-sectional study examined effects of early life development on salivary CRP levels in 452 British-Bangladeshis who spent varying periods growing up in Bangladesh or UK. We also analyzed how gender and central obesity modulate effects on CRP. We hypothesized that: (i) first-generation Bangladeshis with higher childhood exposure to pathogens would have chronically lower CRP levels than second-generation British-Bangladeshis; (ii) effects would be greater with early childhoods in Bangladesh; (iii) effects by gender would differ; and (iv) increasing obesity would mitigate early life effects.

Methodology

Saliva samples were assayed for CRP using ELISAs, and anthropometric data collected. Participants completed questionnaires about demographic, socioeconomic, lifestyle and health histories. Data were analyzed using multiple linear regression.

Results

First-generation migrants who spent early childhoods in mostly rural, unhygienic areas, and moved to UK after age 8, had lower salivary CRP compared to the second-generation. Effects differed by gender, while waist circumference predicted higher CRP levels. CRP increased with years in UK, alongside growing obesity.

Conclusions and implications

Our study supports the hypothesis that pathogen exposure in early life lowers inflammatory responses in adults. However, protective effects differed by gender and can be eroded by growing obesity across the life course which elevates risks for other inflammatory disorders.

Lay Summary: Migrants to the UK who spent early childhoods in less hygienic environments in Bangladesh that help to educate their immune systems had lower levels of the inflammatory marker, C-reactive protein (CRP) compared to migrants who grew up in UK. Both gender and increasing obesity were associated with increased levels of CRP.

Adiposity and pathogen exposure: An investigation of response to iron supplementation and hypothesized predictors in anemic pre-school-aged children living in a dual burden environment

OBJECTIVES

Peruvians are experiencing rapid dietary and lifestyle changes, resulting in a phenomenon known as the "dual burden of disease." A common manifestation of the dual burden in individuals is the co-occurrence of overweight and anemia. Despite recent initiatives introduced to address these concerns, rates continue to be public health concerns. This study investigates the relationship between immune activation and lack of response to iron supplementation after 1 month of treatment and explores variation in body fat stores as a potential moderator between immune function and response to treatment.

METHODS

Data come from children, aged 2-5 years (n = 50) from a peri-urban community in Lima, Peru. Multivariate logistic regression models were used to explore the associations between response to treatment (Hb > =11.0 g/dl) after 1 month of treatment), markers of immune activation (C-reactive protein [CRP] and reported morbidity symptoms), and measures of body fat (waist-to-height ratio, triceps skinfold thickness, and body mass index [BMI]).

RESULTS

We found that high CRP is associated with a lack of response to iron supplementation after 1 month of treatment and that BMI z-score may moderate this association. Generally, larger body size is associated with response to iron supplementation whether or not the children in this sample have high immune activation. However, the probability of anemic children responding to iron supplementation treatment differed across adiposity measures.

CONCLUSIONS

Our finding suggesting that adiposity and CRP influence response to iron supplementation, furthers our understanding of the relationship between inflammation and anemia treatment in children and has both theoretical and public health implications.

Challenges in researching the immune pathways between early life adversity and psychopathology

Exposure to childhood adversity is a critical risk factor for the development of psychopathology. A growing field of research examines how exposure to childhood adversity is translated into biological risk for psychopathology through alterations in immune system functioning, most notably heightened levels of inflammation biomarkers. Though our knowledge about how childhood adversity can instantiate biological risk for psychopathology is growing, there remain many challenges and gaps in the field to understand how inflammation from childhood adversity contributes to psychopathology. This paper reviews research on the inflammatory outcomes arising from childhood adversity and presents four major challenges that future research must address: (a) the measurement of childhood adversity, (b) the measurement of inflammation, (c) the identification of mediators between childhood adversity and inflammation, and (d) the identification of moderators of inflammatory outcomes following childhood adversity. We discuss synergies and inconsistencies in the literature to summarize the current understanding of the association between childhood adversity, a proinflammatory phenotype, and the biological risk for psychopathology. We discuss the clinical implications of the inflammatory links between childhood adversity and psychopathology, including possibilities for intervention. Finally, this review conclude by delineates future directions for research, including issues of how best to detect, prevent, and understand these “hidden wounds” of childhood adversity.

Early origins of socioeconomic inequalities in chronic inflammation: Evaluating the contributions of low birth weight and short breastfeeding

The United States is characterized by persistent and widening social inequities in a wide range of adult health outcomes. A life course approach challenges us to consider if, and how, these inequities trace back to early life conditions, and chronic inflammation represents a potentially important mechanism through which early environments may have lasting effects on health in adulthood. Low birth weight (LBW) and shorter durations of breastfeeding both predict increased inflammation in adulthood, which is associated with increased risk for cardiovascular disease, metabolic syndrome, and all-cause mortality. Using data from a large representative sample of young adults in the US (National Longitudinal Study of Adolescent to Adult Health (Add Health)), we document the socioeconomic status (SES) gradient in chronic inflammation, as indicated by concentrations of C-reactive protein (CRP). Using a nested set of structural equation models and marginal standardization techniques, we investigate the extent to which this gradient is explained by patterns of LBW and breastfeeding in infancy. Findings reveal a particularly important role for breastfeeding duration: Based on model predictive margins, increasing breastfeeding duration to three or more months corresponds to a flattening of the SES gradient by 80%, and 83% when LBW is eliminated. This study expands current understandings of the consequential role of developmental environments for population health and for addressing health inequities in future generations.

Measuring attack on self: The need for field-friendly methods development and research on autoimmunity in human biology

BACKGROUND

Autoimmune and inflammatory disorder (AIID) prevalence appears to be increasing in all but the world's poorest regions and countries. Autoimmune diseases occur when there is a breakdown in processes that regulate inflammation and self-recognition by immune cells. Very few field-based studies have been conducted among Indigenous populations and underserved communities with limited access to medical care. This is due, in part, to the fact that autoimmune diseases are difficult to diagnose, even in clinical settings. In remote field settings these difficulties are compounded by the absence of infrastructure necessary for sample storage and analysis, and the lack of hospital/clinic access for more invasive diagnostic procedures. Because of these limitations, little is known about the prevalence of autoimmunity outside wealthy regions and clinical settings.

AIMS

The present paper discusses why AIID are of critical importance in human biology research and why more work needs to be devoted to validating, testing, and utilizing methods for detecting autoantibodies and other biomarkers related to autoimmunity in field-friendly, minimally invasively-collected samples. This paper reviews some of the methods used to diagnose AIIDs in clinical settings, and highlights methods that have been used in studies within human biology and related fields, emphasizing the invasiveness of specific methods and their feasibility in remote field settings.

DISCUSSION AND CONCLUSIONS

Risk for AIID is affected by several reproductive, dietary, environmental, and genetic factors. Human biologists have unique perspectives that they can bring to autoimmunity research, and more population-based studies on autoimmunity are needed within these and related fields.

Variability of C-reactive protein in first-generation Ecuadorian immigrants living in the United States

OBJECTIVES

Establish the variability of C-reactive protein (CRP) within a population of first-generation immigrants living in the United States. Prior work has theorized that individuals with high levels of childhood pathogen exposure may have lower CRP levels in adulthood, and therefore that for these individuals, CRP may not be as accurate an index of chronic disease risk related to low-level inflammation as is presumed based on data from wealthy populations. This potentially has major implications for the interpretation of CRP as a biomarker of chronic inflammation.

METHODS

This longitudinal study collected a total of 125 dried blood spot (DBS) samples from 31 participants (median 4 samples each) and CRP levels in these DBS were assayed by enzyme-linked immunosorbant assay. Surveys were administered to characterize childhood pathogen exposure, and current illness. Variance was estimated using mixed effects regression models.

RESULTS

On average, participants were adults (mean = 41.9 years old) who had immigrated to the United States nearly 20 years prior to the study and had nearly universally experienced childhood helminth infection and other major pathogen exposures. Median serum-equivalent CRP was 0.77 mg/L. Individuals reliably differed in subacute CRP levels, and, depending on whether untransformed or log-transformed CRP was the outcome variable, 45% or 62% of variance in CRP was attributable to between-individual differences.

CONCLUSIONS

The variability of CRP levels in individuals with relatively high childhood pathogen exposure is comparable to previously reported studies in North America and Europe. However, CRP values are relatively low. CRP is an appropriate measure of subacute inflammation in this sample.

Childhood socioeconomic conditions are associated with increased chronic low-grade inflammation over adolescence: findings from the EPITeen cohort study

OBJECTIVE

Early life adversity has been associated with increased risk of inflammation and inflammation-related diseases in adulthood. This study aimed to examine the association of childhood socioeconomic conditions with chronic low-grade inflammation over adolescence.

METHODS

We used information on 2942 members (1507 girls and 1435 boys) of the EPITeen (Epidemiological Health Investigation of Teenagers in Porto) cohort that was established in 2003 in Porto, Portugal, and included 13-year-old adolescents were further evaluated at 17 and 21 years. Mother' and father's education and occupation were used as indicators of childhood socioeconomic conditions. High-sensitivity C reactive protein (hs-CRP) was measured at three points in time (13, 17 and 21 years). hs-CRP levels were categorised in tertiles separately for each wave; chronic low-grade inflammation in adolescence was defined as having hs-CRP levels in the highest tertile in at least two waves and never in the lowest tertile.

RESULTS

Prevalence of chronic low-grade inflammation during adolescence was significantly higher among participants with low parental socioeconomic position. Low parental socioeconomic position was associated with chronic low-grade inflammation in adolescence, after adjustment for sex, perinatal and physical environment factors, health-related behaviours and health status in adolescence OR=1.6; 95% CI: 1.1 to 2.4 for lowest versus highest mother's education and OR=1.6; 95% CI: 1.1 to 2.3 for lowest versus highest father's occupation.

CONCLUSION

Low childhood socioeconomic conditions are associated with chronic low-grade inflammation during adolescence. Our results suggest that the early life socioeconomic environment has an impact on inflammatory processes over adolescence.

Evolutionary life history theory as an organising framework for cohort studies: insights from the Cebu Longitudinal Health and Nutrition Survey

By tracking a group of individuals through time, cohort studies provide fundamental insights into the developmental time course and causes of health and disease. Evolutionary life history theory seeks to explain patterns of growth, development, reproduction and senescence, and inspires a range of hypotheses that are testable using the longitudinal data from cohort studies. Here we review two decades of life history theory-motivated work conducted in collaboration with the Cebu Longitudinal Health and Nutrition Survey (CLHNS), a birth cohort study that enrolled more than 3000 pregnant women in the Philippines in 1983 and has since followed these women, their offspring and grandoffspring. This work has provided evidence that reproduction carries "costs" to cellular maintenance functions, potentially speeding senescence, and revealed an unusual form of genetic plasticity in which the length of telomeres inherited across generations is influenced by reproductive timing in paternal ancestors. Men in Cebu experience hormonal and behavioural changes in conjunction with changes in relationship and fatherhood status that are consistent with predictions based upon other species that practice bi-parental care. The theoretical expectation that early life cues of mortality or environmental unpredictability will motivate a "fast" life history strategy are confirmed for behavioural components of reproductive decision making, but not for maturational tempo, while our work points to a broader capacity for early life developmental calibration of systems like immunity, reproductive biology and metabolism. Our CLHNS findings illustrate the power of life history theory as an integrative, lifecourse framework to guide longitudinal studies of human populations.

Early life microbial exposure, child neurocognition and behaviour at 2 years of age: A birth cohort study

AIM

To investigate the relationship between factors which influence external microbial exposures (FEMEs), previously identified to be protective or to increase the risk of the development of allergic disease, and cognition and behaviour in infants 2 years of age in an Australian population.

METHOD

The Barwon Infant Study is a birth cohort (n = 1074) in Victoria, Australia. Comprehensive questionnaire, clinical and biological measures were collected at multiple time oints. Multiple linear regression was used to evaluate the associations between 56 FEMEs and 3 outcomes; cognition (Bayley Scales of Infant and Toddler Development (BAYLEY-III)) (n = 667, mean (standard deviation) age = 2.45 (0.14) years), internalising and externalising behaviour (Child Behavior Checklist) (n = 666, mean (standard deviation) age = 2.45 (0.14) years).

RESULTS

Overall, there were no consistent patterns or dose response found within an outcome nor across all three outcomes, although there was some evidence for individual associations. Breastfeeding and child care were associated with higher cognitive scores (adjusted mean difference (95% confidence interval) = 3.20 (0.23-6.17) and 0.68 (0.12-1.24), respectively), and increasing sibling number was associated with lower internalising behaviour (adjusted mean difference (95% confidence interval) = -4.13 (-6.34, -1.91)).

CONCLUSION

In contrast to allergic disease, there was an absence of epidemiological evidence to support the association between these FEMEs and cognition and behaviour. Direct investigations into the relationship between exposures which influence gut-microbial composition and cognition and behaviour are now needed.

Early-Life Assets in Oldest-Old Age: Evidence From Primary Care Reform in Early Twentieth Century Sweden

Do early-life effects of investments in public health persist to the oldest-old ages? This article answers this question by using the primary care reform in rural Sweden that between 1890 and 1917 led to the establishment of local health districts, together with openings of hospitals and recruitments of medical personnel, as a natural experiment in early-life environmental conditions. The initiatives undertaken within these districts targeted control of infectious diseases, including various isolation and disinfection measures. This study applies a difference-in-differences method combined with propensity score matching to register-based individual-level data for Sweden from 1968 to 2012 and to multisource, purposely collected data on the reform implementation. Providing pioneering evidence for such a distal relationship (ages 78-95), this study finds that treatment through primary care in the year of birth leads to a significant reduction in all-cause mortality (4 % to 6%) and mortality from cardiovascular diseases (5 % to 6 %) and to an increase in average incomes (2 % to 3 %). The effects are universal and somewhat stronger among individuals from poor socioeconomic backgrounds and at higher baseline levels of disease burden.

Chronic inflammation in the etiology of disease across the life span

Although intermittent increases in inflammation are critical for survival during physical injury and infection, recent research has revealed that certain social, environmental and lifestyle factors can promote systemic chronic inflammation (SCI) that can, in turn, lead to several diseases that collectively represent the leading causes of disability and mortality worldwide, such as cardiovascular disease, cancer, diabetes mellitus, chronic kidney disease, non-alcoholic fatty liver disease and autoimmune and neurodegenerative disorders. In the present Perspective we describe the multi-level mechanisms underlying SCI and several risk factors that promote this health-damaging phenotype, including infections, physical inactivity, poor diet, environmental and industrial toxicants and psychological stress. Furthermore, we suggest potential strategies for advancing the early diagnosis, prevention and treatment of SCI.

Detecting the Effects of Early-Life Exposures: Why Fecundity Matters

Prenatal exposures have meaningful effects on health across the lifecourse. Innovations in causal inference have shed new light on these effects. Here, we motivate the importance of innovation in the characterization of fecundity, and prenatal selection in particular. We argue that such innovation is crucial for expanding knowledge of the fetal origins of later life health. Pregnancy loss is common, responsive to environmental factors, and closely related to maternal and fetal health outcomes. As a result, selection into live birth is driven by many of the same exposures that shape the health trajectories of survivors. Lifecourse effects that are inferred without accounting for these dynamics may be significantly distorted by survival bias. We use a set of Monte Carlo simulations with realistic parameters to examine the implications of prenatal survival bias. We find that even in conservatively specified scenarios, true fetal origin effects can be underestimated by 50% or more. In contrast, effects of exposures that reduce the probability of prenatal survival but improve the health of survivors will be overestimated. The absolute magnitude of survival bias can even exceed small effect sizes, resulting in inferences that beneficial exposures are harmful or vice-versa. We also find reason for concern that moderately sized true effects, underestimated due to failure to account for selective survival, are missing from scientific knowledge because they do not clear statistical significance filters. This bias has potential real-world costs; policy decisions about interventions to improve maternal and infant health will be affected by underestimated program impact.

Revisiting the tuberculosis and leprosy cross-immunity hypothesis: Expanding the dialogue between immunology and paleopathology

OBJECTIVE

Our primary objective is to re-visit the tuberculosis and leprosy cross-immunity. hypothesis through the careful integration of immunology and paleopathology.

METHODS

Using an integrated theoretical analysis that evaluates clinical literature on human innate immunological responses, paleomicrobiology, bioarchaeology, and paleopathology, we develop a multifactorial model.

RESULTS

Past populations do not represent homogeneous immunological landscapes, and therefore it is likely that leprosy in Medieval Europe did not uniformly decline due to cross-immunity.

CONCLUSIONS

We recommend that bioarchaeological reconstructions of past disease experience take into consideration models that include variation in immune function based on past environments and social contexts. This provides a unique opportunity to conduct comprehensive analyses on complex immunological processes.

SIGNIFICANCE

Extrapolating results from experimental immunology to larger populations elucidates complexities of disease cross-immunity and highlights the importance of synthesizing archaeological, social, paleopathological and biological data as a means of understanding disease in the past.

LIMITATIONS

All extrapolations from data produced from in vitro studies to past populations, using living donors, pose significant limitations where, among other factors, the full reconstruction of past environmental and social contexts can frequently be sparse or incomplete.

SUGGESTIONS FOR FUTURE RESEARCH

To reduce the limitations of integrating experimental immunology with bioarchaeological reconstructions (i.e. how to use skeletal samples to reconstruct inflammatory phenotypes), we propose that osteoimmunology, or the study of the interplay between immune cells and bone cells, should be considered a vital discipline and perhaps the foundation for the expansion of paleoimmunology.

Profiles of gene expression in maternal blood predict offspring birth weight in normal pregnancy

The association between lower birth weight and increased disease risk in adulthood has drawn attention to the physiological processes that shape the gestational environment. We implement genome-wide transcriptional profiling of maternal blood samples to identify subsets of genes and associated transcription control pathways that predict offspring birth weight. Female participants (N = 178, mean = 27.0 years) in a prospective observational birth cohort study were contacted between 2009 and 2014 to identify new pregnancies. An in-home interview was scheduled for early in the third trimester (mean = 30.3 weeks) to collect pregnancy-related information and a blood sample, and birth weight was measured shortly after delivery. Transcriptional activity in white blood cells was determined with a whole-genome gene expression direct hybridization assay. Fifty transcripts were differentially expressed in association with offspring birth weight, with 18 up-regulated in relation to lower birth weight, and 32 down-regulated. Examination of transcription control pathways identified increased activity of NF-κB, AP-1, EGR1, EGR4, and Gfi families, and reduced the activity of CEBP, in association with lower birth weight. Transcript origin analyses identified non-classical CD16+ monocytes, CD1c+ myeloid dendritic cells, and neutrophils as the primary cellular mediators of differential gene expression. These results point toward a systematic regulatory shift in maternal white blood cell activity in association with lower offspring birth weight, and they suggest that analyses of gene expression during gestation may provide insight into regulatory and cellular mechanisms that influence birth outcomes.

Regulation of inflammation during gestation and birth outcomes: Inflammatory cytokine balance predicts birth weight and length

OBJECTIVES

The maternal environment during gestation influences offspring health at birth and throughout the life course. Recent research has demonstrated that endogenous immune processes such as dysregulated inflammation adversely impact birth outcomes, increasing the risk for preterm birth and restricted fetal growth. Prior analyses examining this association suggest a relationship between maternal C-reactive protein (CRP), a summary measure of inflammation, and offspring anthropometric outcomes. This study investigates pro- and anti-inflammatory cytokines, and their ratio, to gain deeper insight into the regulation of inflammation during pregnancy.

METHODS

IL6, IL10, TNFɑ, and CRP were quantified in dried blood spots collected in the early third trimester (mean = 29.9 weeks) of 407 pregnancies in Metropolitan Cebu, Philippines. Relationships between these immune markers and offspring anthropometrics (birth weight, length, head circumference, and sum of skinfold thicknesses) were evaluated using multivariate regression analyses. Ratios of pro- to anti-inflammatory cytokines were generated.

RESULTS

Higher maternal IL6 relative to IL10 was associated with reduced offspring weight and length at birth. Individual cytokines did not predict birth outcomes.

CONCLUSIONS

Consistent with the idea that the relative balance of cytokines with pro- and anti-inflammatory effects is a key regulator of inflammation in pregnancy, the IL6:IL10 ratio, but neither cytokine on its own, predicted offspring birth outcomes. Our findings suggest that prior reports of association between CRP and fetal growth may reflect, in part, the balance between pro- and anti-inflammatory cytokines, and that the gestational environment is significantly shaped by cytokine imbalance.

Ankle brachial index (ABI) in a cohort of older women in the Philippines: Prevalence of peripheral artery disease and predictors of ABI

OBJECTIVE

Cardiovascular disease (CVD) is rising in low and middle-income countries, but studies of CVD epidemiology in such settings often focus on risk factors rather than measures of disease progression. Here we use the ankle brachial index (ABI) to assess the prevalence of peripheral artery disease (PAD) among older women living in Metropolitan Cebu, Philippines, and relationships between ABI and CVD risk factors and body composition.

METHODS

ABI was measured using the Doppler technique in 538 female participants in the 2015 Cebu Longitudinal Health and Nutrition Survey (mean age 58 years, range 47-78 years). ABI was related to a panel of CVD risk factors measured in 2005 and 2012, and to 2012 body composition measures.

RESULTS

The prevalence of PAD (1.8%) was among the lowest reported in any comparably-aged sample, and only 9.9% of participants had an ABI indicating borderline PAD risk. Smoking (P < 0.011) and use of CVD medications (P < 0.0001) predicted lower ABI (indicating higher PAD risk), which was also lower in relation to 2012 systolic blood pressure (P < 0.054). ABI was unrelated to other CVD risk factors. An apparent protective relationship between body mass index (BMI) and ABI, noted in previous studies, was found to be confounded by protective relationships between ABI and fat free mass, height, and grip strength (all P < 0.05).

CONCLUSIONS

The prevalence of PAD is low in Cebu Longitudinal Health and Nutrition Survey participants, and ABI was related to few CVD risk factors. Past reports of lower PAD risk in relation to BMI may reflect confounding by lean mass, which has protective relationships with ABI.

Maternal infections during pregnancy and offspring midlife inflammation

Background

Microbial exposures early in life have been found to be associated with lower levels of inflammation in adulthood; however, the role of prenatal exposure to infection on offspring inflammatory profiles is unexplored. The aim was to study if maternal infections during pregnancy are associated with inflammation among offspring in later life and to determine if there are sensitive periods of exposure.

Methods

The study was comprised of 1719 participants in the Copenhagen Aging and Midlife Biobank (CAMB) who were also members of the Copenhagen Perinatal Cohort (CPC). When the CPC was established, information on maternal infections during pregnancy was prospectively collected by a trained medical doctor. The inflammatory measures collected in late midlife included, C-reactive protein (CRP), Interleukin-6 (IL-6), TNF-alpha (TNF-α) and Interleukin-10 (IL-10). Multivariable ordinary least squared regression models were implemented to explore associations between maternal infection and inflammatory measures in offspring, controlling for maternal smoking, pre-pregnancy body mass index, age, marital status and parity.

Results

Maternal infection was associated with a 7% lower CRP level (95% CI, − 17,5%) among offspring compared with offspring born to women without an infection and similarly an 8% lower level of IL-6 (95% CI -15,1%), and a 9% lower level of IL-10 (95% CI, − 23,20%). However, differences did not reach significance. The effects of infection during the first trimester did not differ from infections later in the pregnancy.

Conclusions

Our results suggested that prenatal exposure to infection may be associated with lower levels of inflammatory markers among adult offspring. Additional prospective studies are needed to further explore this finding.

Secondary data analysis to answer questions in human biology

Despite a growing number of publicly available datasets, the use of these datasets for secondary analyses in human biology is less common compared with other fields. Secondary analysis of existing data offers an opportunity for human biologists to ask unique questions through an evolutionary and biocultural lens, allowing for an analysis of cultural and structural nuances that affect health. Leveraging publicly available datasets for human biology research is a way for students and established researchers to complement their data collection, use existing data for master's and doctoral theses, pilot test questions, and use existing data to answer interesting new questions or explore questions at the population level. Here we describe where publicly available data are stored, highlighting some data repositories and how to access them. We then discuss how to decide which dataset is right, depending on the research question. Next, we describe steps to construct datasets, analytical considerations and methodological challenges, best practices, and limitations depending on the structure of the study. We close by highlighting a number of publicly available datasets that have been used by human biologists and other datasets that may be of interest to the community, including research that has been conducted on some example datasets.

Caesarean delivery, immune function and inflammation in early life among Ecuadorian infants and young children

Caesarean delivery has been linked to a number of inflammatory conditions in childhood and adolescence. Yet the mechanisms underlying these associations and their generalizability across contexts with different postnatal feeding and pathogenic exposures remain unclear. This study tests the association between delivery type and three measures of immune function, inflammation, morbidity and leukocyte proportions, in Ecuadorian infants and children aged 6 months to 2 years. Data were collected from mother-child pairs participating in a nationally representative health and nutrition survey Encuesta Nacional de Salud y Nutricion (ENSANUT-ECU) conducted in 2012. The analytic sample includes 828 mothers and infants with delivery information and measured biomarkers. Poisson regression models were used to examine the association between delivery type and markers of immune function, controlling for maternal and infant characteristics, including age, sex, sociodemographic characteristics and medical indications. 40.8% (n=338) of sample infants and children were delivered by caesarean. Compared to those born vaginally, infants born by caesarean were less likely to have elevated C-reactive protein (CRP) [CRP>2 mg/l; risk ratio (RR): 0.76, 95% confidence interval (CI): 0.58-1.00] and more likely to have illness symptoms (RR: 1.22, 95% CI: 1.01-1.46) and elevated basophils (RR: 1.83, 95% CI: 1.03-3.25). No other immune cell proportions differed by delivery type. The results suggest that differences in the perinatal exposures accompanying caesarean delivery may alter immune development and function, particularly in the inflammatory response to infection and in cells involved in the allergic response, across infancy and early childhood. Understanding the pathways linking perinatal exposures to immune development is important for preventing the development of inflammatory conditions.

Early Plasmodium-induced inflammation does not accelerate aging in mice

Aging is associated with a decline of performance leading to reduced reproductive output and survival. While the antagonistic pleiotropy theory of aging has attracted considerable attention, the molecular/physiological functions underlying the early-life benefits/late-life costs paradigm remain elusive. We tested the hypothesis that while early activation of the inflammatory response confers benefits in terms of protection against infection, it also incurs costs in terms of reduced reproductive output at old age and shortened longevity. We infected mice with the malaria parasite Plasmodium yoelii and increased the inflammatory response using an anti-IL-10 receptor antibody treatment. We quantified the benefits and costs of the inflammatory response during the acute phase of the infection and at old age. In agreement with the antagonistic pleiotropy hypothesis, the inflammatory response provided an early-life benefit, since infected mice that were treated with anti-IL-10 receptor antibodies had reduced parasite density and anemia. However, at old age, mice in all treatment groups had similar levels of C-reactive protein, reproductive output, survival rate, and lifespan. Overall, our results do not support the hypothesis that the benefits of a robust response to malaria infection in early life incur longer term fitness costs.

Social and population health science approaches to understand the human microbiome

The microbiome is now considered our 'second genome' with potentially comparable importance to the genome in determining human health. There is, however, a relatively limited understanding of the broader environmental factors, particularly social conditions, that shape variation in human microbial communities. Fulfilling the promise of microbiome research - particularly the microbiome's potential for modification - will require collaboration between biologists and social and population scientists. For life scientists, the plasticity and adaptiveness of the microbiome calls for an agenda to understand the sensitivity of the microbiome to broader social environments already known to be powerful predictors of morbidity and mortality. For social and population scientists, attention to the microbiome may help answer nagging questions about the underlying biological mechanisms that link social conditions to health. We outline key substantive and methodological advances that can be made if collaborations between social and population health scientists and life scientists are strategically pursued.

Variation among populations in the immune protein composition of mother's milk reflects subsistence pattern

LAY SUMMARY

Adaptive immune proteins in mothers' milk are more variable than innate immune proteins across populations and subsistence strategies. These results suggest that the immune defenses in milk are shaped by a mother's environment throughout her life.

BACKGROUND AND OBJECTIVES

Mother's milk contains immune proteins that play critical roles in protecting the infant from infection and priming the infant's developing immune system during early life. The composition of these molecules in milk, particularly the acquired immune proteins, is thought to reflect a mother's immunological exposures throughout her life. In this study, we examine the composition of innate and acquired immune proteins in milk across seven populations with diverse disease and cultural ecologies.

METHODOLOGY

Milk samples (n = 164) were collected in Argentina, Bolivia, Nepal, Namibia, Philippines, Poland and the USA. Populations were classified as having one of four subsistence patterns: urban-industrialism, rural-shop, horticulturalist-forager or agro-pastoralism. Milk innate (lactalbumin, lactoferrin and lysozyme) and acquired (Secretory IgA, IgG and IgM) protein concentrations were determined using triple-quadrupole mass spectrometry.

RESULTS

Both innate and acquired immune protein composition in milk varied among populations, though the acquired immune protein composition of milk differed more among populations. Populations living in closer geographic proximity or having similar subsistence strategies (e.g. agro-pastoralists from Nepal and Namibia) had more similar milk immune protein compositions. Agro-pastoralists had different milk innate immune protein composition from horticulturalist-foragers and urban-industrialists. Acquired immune protein composition differed among all subsistence strategies except horticulturist-foragers and rural-shop.

CONCLUSIONS AND IMPLICATIONS

Our results reveal fundamental variation in milk composition that has not been previously explored in human milk research. Further study is needed to understand what specific aspects of the local environment influence milk composition and the effects this variation may have on infant health outcomes.

Ecological Context and Human Variation: Applying the Principles of Biological Anthropology to Psychoneuroimmunology

There is considerable research interest overlap between biological anthropology and psychoneuroimmunology (PNI), particularly given recent anthropological interest in endocrine and immune system functioning over the life span and in different environmental contexts. In this chapter, I argue that conducting research on non-WEIRD populations and applying an anthropological, evolutionary approach to PNI can greatly strengthen our understanding of immune-endocrine-behavior connections. This chapter reviews population-level variation in the human immune and endocrine systems, as well as genetic and environmental contributions to this variation. The effects of culture on shaping health outcomes and stress responses are also considered. Finally, this chapter discusses some noninvasive sampling methodologies appropriate to field research and alternatives to laboratory-based research designs. By confronting variable social and environmental contexts, PNI can greatly expand on its existing contributions to the treatment and understanding of depression, mood disorders, stress, and other aspects of health and well-being.

Adolescent reserve capacity, socioeconomic status and school achievement as predictors of mortality in Finland - a longitudinal study

Background

Despite robust evidence on the inverse relationship between socioeconomic status (SES) and mortality, deviations from expected results have been observed likely due to school achievement and psychosocial resources, termed as “reserve capacity.” Since adolescence is a critical period in developing sound psychological and behavioural patterns and adolescent markers of SES were seldom used, we determine if family SES in adolescence predicts later mortality. We also study how reserve capacity (perceived health, health-promoting behaviour and social support) and school achievement modify this relationship and reduce the negative effects of low SES.

Methods

A longitudinal study was designed by linking baseline data on 12 to 18 year-old Finns in 1985–95 (N = 41,833) from the Adolescent Health and Lifestyle Surveys with register data on mortality and SES from Statistics Finland. Average follow-up time was 18.4 years with a total of 770,161 person-years. Cox regression models, stratified by sex, were fitted to determine the effects of variables measured during adolescence: family SES, reserve capacity and school achievement on mortality risk.

Results

All reserve capacity dimensions significantly predicted mortality in boys. Perceived health and social support predicted that in girls. Adolescents with the lowest school achievement were more than twice at risk of dying compared to those with better school performance. Low SES increased the risk of death in boys (Hazard ratios: 1.6, 95% CI 1.1–2.4) but not in girls. Reserve capacity and school achievement weakened the effects of low SES on boys’ risk of death.

Conclusions

High reserve capacity and good school achievement in adolescence significantly reduce the risk of mortality. In boys, these also mitigate the negative effect of low SES on mortality. These findings underscore the roles of reserve capacity and school achievement during adolescence as likely causal or modifying factors in SES-health inequalities.

Birth weight and postnatal microbial exposures predict the distribution of peripheral blood leukocyte subsets in young adults in the Philippines

The immune system not only provides protection against infectious disease but also contributes to the etiology of neoplastic, atopic, and cardiovascular and metabolic diseases. Prenatal and postnatal nutritional and microbial environments have lasting effects on multiple aspects of immunity, indicating that immune processes may play important roles in the developmental origins of disease. The objective of this study is to evaluate the association between birth weight and the distribution of leukocyte (white blood cell) subsets in peripheral blood in young adulthood. Postnatal microbial exposures were also considered as predictors of leukocyte distribution. Participants (n=486; mean age=20.9 years) were drawn from a prospective birth cohort study in the Philippines, and analyses focused on the following cell types: CD4 T lymphocytes, CD8 T lymphocytes, B lymphocytes, natural killer cells, monocytes, granulocytes. Higher birth weight was a strong predictor of higher proportion of CD4 T lymphocytes (B=0.12, s.e.=0.041, P=0.003), lower proportion of CD8 T lymphocytes (B=-0.874, s.e.=0.364, P=0.016), higher CD4:CD8 ratio (B=1.964, s.e.=0.658, P=0.003), and higher B lymphocytes (B=0.062, s.e.=0.031, P=0.047). Measures of microbial exposure in infancy were negatively associated with proportions of B lymphocytes and granulocytes, and lower CD4:CD8 ratio. Leukocytes are the key regulators and effectors of innate and specific immunity, but the origins of variation in the distribution of cell type across individuals are not known. Our findings point toward nutritional and microbial exposures in infancy as potentially important determinants of immune-phenotypes in adulthood, and they suggest that leukocyte distribution is a plausible mechanism through which developmental environments have lasting effects on disease risk in adulthood.

Maternal pregnancy C-reactive protein predicts offspring birth size and body composition in metropolitan Cebu, Philippines

The gestational milieu is an important influence on fetal development and long-term disease risk. Here we assess relationships between maternal pregnancy inflammation, indicated by C-reactive protein (CRP), and offspring anthropometric outcomes measured soon after birth. Data come from female participants (n=327, age 24.4-30.2 years) in a longitudinal study located in Metropolitan Cebu, Philippines. Between 2009 and 2014, pregnancy interviews (n=429) were conducted during which questionnaire and anthropometric data were obtained along with dried blood spot cards for CRP measurement. Offspring body weight, length, head circumference and five skinfold thickness measures were obtained soon after birth. Maternal pregnancy CRP was borderline (-1.11±0.64 days/log-mg/l; P<0.1) inversely related to gestational age at delivery, but did not increase the likelihood of preterm delivery. After adjusting for maternal pre-pregnancy body mass index, height, pregnancy adiposity, age, parity and other covariates, CRP was significantly, inversely related to offspring body weight (-0.047±0.017 kg/log-mg/l), length (-0.259±0.092 cm/log-mg/l) and sum of skinfolds (-0.520±0.190 mm/log-mg/l) (all P<0.05), and borderline inversely related to offspring head circumference (-0.102±0.068 cm/log-mg/l; P<0.1). Notably, relationships were continuous across the full CRP range, and not limited to unusually high levels of inflammation. These findings point to an important role of maternal non-specific immune activation as a predictor of offspring birth outcomes. In light of evidence that early life microbial, nutritional and stress experiences influence adult inflammatory regulation, these findings point to inflammation as a potential pathway for the intergenerational transmission of maternal experience to offspring health.

Social and physical environments early in development predict DNA methylation of inflammatory genes in young adulthood

Chronic inflammation contributes to a wide range of human diseases, and environments in infancy and childhood are important determinants of inflammatory phenotypes. The underlying biological mechanisms connecting early environments with the regulation of inflammation in adulthood are not known, but epigenetic processes are plausible candidates. We tested the hypothesis that patterns of DNA methylation (DNAm) in inflammatory genes in young adulthood would be predicted by early life nutritional, microbial, and psychosocial exposures previously associated with levels of inflammation. Data come from a population-based longitudinal birth cohort study in metropolitan Cebu, the Philippines, and DNAm was characterized in whole blood samples from 494 participants (age 20-22 y). Analyses focused on probes in 114 target genes involved in the regulation of inflammation, and we identified 10 sites across nine genes where the level of DNAm was significantly predicted by the following variables: household socioeconomic status in childhood, extended absence of a parent in childhood, exposure to animal feces in infancy, birth in the dry season, or duration of exclusive breastfeeding. To evaluate the biological significance of these sites, we tested for associations with a panel of inflammatory biomarkers measured in plasma obtained at the same age as DNAm assessment. Three sites predicted elevated inflammation, and one site predicted lower inflammation, consistent with the interpretation that levels of DNAm at these sites are functionally relevant. This pattern of results points toward DNAm as a potentially important biological mechanism through which developmental environments shape inflammatory phenotypes across the life course.

Mora‐Faife E, García‐García G, del Valle‐Infante I, Gómez‐Marrero L, Britton J, Fogarty AW. The association of low birth weight with serum C reactive protein in 3-year-old children living in Cuba: A population-based prospective study

OBJECTIVE

Low birthweight is associated with a decreased risk of childhood leukemia and an increased risk of both cardiovascular disease and all-cause mortality in adult life. Possible biological mediators include systemic innate immunity and inflammation. We tested the hypothesis that birthweight was inversely associated with serum high sensitivity C reactive protein assay (hsCRP), a measure of both innate immunity and systemic inflammation.

METHODS

Data on birthweight and current anthropometric measures along with a range of exposures were collected at 1 and 3 years of age in a population-based cohort study of young children living in Havana, Cuba. A total of 986 children aged 3-years-old provided blood samples that were analyzed for serum hsCRP levels.

RESULTS

Nearly 49% of children had detectable hsCRP levels in their serum. Lower birthweight was linearly associated with the natural log of hsCRP levels (beta coefficient -0.70 mg L-1 per kg increase in birthweight, 95% CI: -1.34 to -0.06). This was attenuated but still present after adjustment for the child's sex and municipality (-0.65 mg L-1 per kg birthweight; 95% CI: -1.38 to +0.08). There were no associations between growth from birth or anthropometric measures at 3 years and systemic inflammation.

CONCLUSIONS

Birthweight was inversely associated with serum hsCRP levels in children aged 3 years living in Cuba. These observations provide a potential mechanism that is present at the age of 3 years to explain the association between low birthweight and both decreased childhood leukemia and increased cardiovascular disease in adults.

Associations between male testosterone and immune function in a pathogenically stressed forager-horticultural population

OBJECTIVES

Despite well-known fitness advantages to males who produce and maintain high endogenous testosterone levels, such phenotypes may be costly if testosterone-mediated investment in reproductive effort trade-off against investment in somatic maintenance. Previous studies of androgen-mediated trade-offs in human immune function find mixed results, in part because most studies either focus on a few indicators of immunity, are confounded by phenotypic correlation, or are observational. Here the association between male endogenous testosterone and 13 circulating cytokines are examined before and after ex vivo antigen stimulation with phytohemagglutinin (PHA) and lipopolysaccharides (LPS) in a high pathogen population of Bolivian forager-horticulturalists.

MATERIALS AND METHODS

A Milliplex 13-plex cytokine panel measured cytokine concentration in whole blood samples from 109 Tsimane men aged 40-89 (median = 50 years) before and after antigen stimulation with PHA and LPS. Urinary testosterone was measured via enzyme immunoassay, demographic, and anthropometric data were collected as part of the Tsimane Health and Life History Project.

RESULTS

Higher endogenous testosterone was associated with down-regulated responses in all cytokines after PHA stimulation (but significantly in only 2/13 cytokines), controlling for age and body mass index. In contrast, testosterone was not significantly associated with down-regulation of cytokines after LPS stimulation. MANOVAs indicate that men with higher testosterone showed reduced cytokine responses to PHA compared with LPS (p = 0.0098).

DISCUSSION

Endogenous testosterone appears to be immunomodulatory rather than immunosuppressive. Potentially costlier forms of immune activation like those induced by PHA (largely T-cell biased immune activation) are down-regulated in men with higher testosterone, but testosterone has less impact on potentially less costly immune activation following LPS stimulation (largely B-cell mediated immunity).

Do leprosy and tuberculosis generate a systemic inflammatory shift? Setting the ground for a new dialogue between experimental immunology and bioarchaeology

It is possible that during long lasting chronic infections such as tuberculosis (TB) and leprosy individuals who generate a stronger immune response will produce a chronic shift in the systemic levels of inflammatory proteins. Consequently, the systemic immunological shift could affect inflammatory responses against other persistent pathogens such as Porphyromonas gingivalis associated with periodontal disease (PD).

OBJECTIVE

To determine if in vitro exposure to Mycobacterium tuberculosis or M. leprae lysates impacts subsequent immune responses to P. gingivalis; and to propose a new dialogue between experimental immunology and paleopathology.

MATERIAL AND METHODS

We sequentially (2 days protocol) exposed peripheral blood mononuclear cells (PBMCs) from healthy donors to bacterial lysates either from M. tuberculosis, or M. leprae, or P. gingivalis. After collecting all supernatants, we measured the expression of immune proteins TNFα and IFNγ using an enzyme-linked immunosorbent assay.

RESULTS

Early exposure (day 1) of PBMCs to M. leprae or M. tuberculosis lysates induces an inflammatory shift detected by the increase of TNFα and IFNγ when the same cells are subsequently (day 2) exposed to oral pathogen P. gingivalis.

DISCUSSION

By extrapolating these results, we suggest that chronic infections, such as TB and leprosy, could generate a systemic immunological shift that can affect other inflammatory processes such the one present in PD. We propose that the presence and severity of PD should be explored as a proxy for inflammatory status or competence when reconstructing the health profile in past populations.

The Microbiome of the Built Environment and Human Behavior: Implications for Emotional Health and Well-Being in Postmodern Western Societies

It is increasingly evident that inflammation is an important determinant of cognitive function and emotional behaviors that are dysregulated in stress-related psychiatric disorders, such as anxiety and affective disorders. Inflammatory responses to physical or psychological stressors are dependent on immunoregulation, which is indicated by a balanced expansion of effector T-cell populations and regulatory T cells. This balance is in part driven by microbial signals. The hygiene or "old friends" hypothesis posits that exposure to immunoregulation-inducing microorganisms is reduced in modern urban societies, leading to an epidemic of inflammatory disease and increased vulnerability to stress-related psychiatric disorders. With the global trend toward urbanization, humans are progressively spending more time in built environments, thereby, experiencing limited exposures to these immunoregulatory "old friends." Here, we evaluate the implications of the global trend toward urbanization, and how this transition may affect human microbial exposures and human behavior.

Early developmental exposures shape trade-offs between acquired and innate immunity in humans

BACKGROUND AND OBJECTIVES

Life history theory predicts resource allocation trade-offs between competing functions and processes. We test the hypothesis that relative investment towards innate versus acquired immunity in humans is subject to such trade-offs and that three types of early developmental exposures are particularly salient in shaping adult immunophenotype: (i) pathogen exposure, (ii) nutritional resources; and (iii) extrinsic mortality cues.

METHODOLOGY

We quantified one aspect each of innate and acquired immune function, via C-reactive protein and Epstein-Barr virus antibodies, respectively, in a sample of 1248 men and women from the Philippines (ca. 21.5 years old). Early developmental exposures were assessed via long-term data collected prospectively since participants' birth (1983-4). We calculated a standardized ratio to assess relative bias towards acquired versus innate immune function and examined its relationship to a suite of predictors via multiple regression.

RESULTS

In partial support of our predictions, some of the measures of higher pathogen exposure, greater availability of nutritional resources, and lower extrinsic mortality cues in early life were associated with a bias toward acquired immunity in both men and women. The immune profile of women, in particular, appeared to be more sensitive to early life pathogen exposures than those of men. Finally, contrary to prediction, women exhibited a greater relative investment toward innate, not acquired, immunity.

CONCLUSIONS AND IMPLICATIONS

Early environments can exert considerable influence on the development of immunity. They affect trade-offs between innate and acquired immunity, which show adaptive plasticity and may differ in their influence in men and women.

Late midlife C-reactive protein and interleukin-6 in middle aged danish men in relation to body size history within and across generations

OBJECTIVE

The aim was to estimate the effects of ponderal index at birth and body mass index (BMI) in early adulthood on C-reactive protein (CRP) and interleukin-6 (IL-6) and to quantify the effects through subsequent measures of body size. In a subanalysis, the contributions of maternal BMI to the inflammatory status of offspring were investigated.

METHODS

The study was based on 2,986 Danish males from the Copenhagen Aging and Midlife Biobank. Path analysis was employed to estimate direct and indirect effects.

RESULTS

A 10% higher maternal BMI was associated with 7% higher CRP and 3% higher IL-6 among offspring. A 10% higher ponderal index at birth was associated with 4% lower CRP in late midlife; this effect was only partially mediated by later growth. A 10% higher BMI in early adulthood was associated with 8% higher CRP and 4% higher IL-6 in late midlife. The findings suggest that weight gain in adulthood is associated with low-grade inflammation in late midlife.

CONCLUSIONS

Ponderal index at birth is associated with CRP in later life independently of adult BMI. The findings additionally suggest that preventing weight gain in early adulthood would be beneficial for inflammatory status in later life.