The role of testosterone in coordinating male life history strategies: The moderating effects of the androgen receptor CAG repeat polymorphism

Partnered fathers often have lower testosterone than single non-parents, which is theorized to relate to elevated testosterone (T) facilitating competitive behaviors and lower T contributing to nurturing. Cultural- and individual-factors moderate the expression of such psychobiological profiles. Less is known about genetic variation's role in individual psychobiological responses to partnering and fathering, particularly as related to T. We examined the exon 1 CAG (polyglutamine) repeat (CAGn) within the androgen receptor (AR) gene. AR CAGn shapes T's effects after it binds to AR by affecting AR transcriptional activity. Thus, this polymorphism is a strong candidate to influence individual-level profiles of "androgenicity." While males with a highly androgenic profile are expected to engage in a more competitive-oriented life history strategy, low androgenic men are at increased risk of depression, which could lead to similar outcomes for certain familial dynamics, such as marriage stability and parenting. Here, in a large longitudinal study of Filipino men (n=683), we found that men who had high androgenicity (elevated T and shorter CAGn) or low androgenicity (lower T and longer CAGn) showed elevated likelihood of relationship instability over the 4.5-year study period and were also more likely be relatively uninvolved with childcare as fathers. We did not find that CAGn moderated men's T responses to the fatherhood transition. In total, our results provide evidence for invested fathering and relationship stability at intermediate levels of androgenicity and help inform our understanding of variation in male reproductive strategies and the individual hormonal and genetic differences that underlie it.

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.

Androgen receptor CAG repeat polymorphism and hypothalamic-pituitary-gonadal function in Filipino young adult males

OBJECTIVES

Testosterone (T), the primary androgenic hormone in males, is stimulated through pulsatile secretion of LH and regulated through negative feedback inhibition at the hypothalamus and pituitary. The hypothalamic-pituitary-gonadal (HPG) axis also controls sperm production through the secretion of follicle-stimulating hormone (FSH). Negative feedback in the HPG axis is achieved in part through the binding of T to the androgen receptor (AR), which contains a highly variable trinucleotide repeat polymorphism (AR-CAGn). The number of repeats in the AR-CAGn inversely correlates with transcriptional activity of the AR. Thus, we predicted longer AR-CAGn to be associated with higher T, LH, and FSH levels.

METHODS

We examined the relationship between AR-CAGn and total plasma T, LH, and FSH, as well as "bioavailable" morning (AM-T) and evening (PM-T) testosterone in 722 young (21.5 ± 0.5 years) Filipino males.

RESULTS

There was no relationship between AR-CAGn and total T, AM-T, or LH (P > .25 for all). We did observe a marginally non-significant (P = .066) correlation between AR-CAGn and PM-T in the predicted direction, and a negative correlation between AR-CAGn and FSH (P = .005).

CONCLUSIONS

Our results both support and differ from previous findings in this area, and study parameters that differ between our study and others, such as participant age, sample time, and the role of other hormones should be considered when interpreting our findings. While our data point to a modest effect of AR-CAGn on HPG regulation at best, the AR-CAGn may still affect somatic traits by regulating androgenic activity at peripheral tissues.

Adiposity and Chronic Inflammation in Young Women Predict Inflammation during Normal Pregnancy in the Philippines

BACKGROUND

Rates of overweight and obesity are on the rise globally, and excess adipose tissue may contribute to elevations in inflammation during pregnancy, leading to pregnancy complications and adverse birth outcomes.

OBJECTIVE

The purpose of this study was to evaluate adiposity and inflammation in young women as predictors of inflammation in the third trimester of pregnancy in a community-based sample of healthy women.

METHODS

Female participants (24-30 y) in a prospective observational cohort study (Cebu Longitudinal Health and Nutrition Survey) were contacted between 2009 and 2014 to identify new pregnancies. A total of 309 women provided data from 409 pregnancies. An in-home interview was scheduled for the third trimester to collect pregnancy information, anthropometric measurements, and a blood sample. Circulating C-reactive protein (CRP) was measured with a high-sensitivity immunoassay. Data collected from assessments in 2005 and 2009 were used to assess body mass index (BMI) and CRP in young adulthood, before pregnancy. Robust regression models were implemented to evaluate BMI and CRP in young adulthood as predictors of pregnancy CRP.

RESULTS

Pre-pregnancy BMI was a stronger predictor of third-trimester circulating CRP than BMI in the third trimester. No association was found between pregnancy weight gain and CRP. Pre-pregnancy CRP was a significant predictor of CRP in pregnancy, independent of BMI.

CONCLUSIONS

Levels of overweight/obesity and inflammation in young adulthood, before pregnancy, are important predictors of inflammation in the third trimester of pregnancy. These results may have implications for addressing the growing concern about the contribution of obesity to adverse birth outcomes, and they suggest that factors that influence the regulation of inflammation, before pregnancy and independent of adiposity, may be important in shaping the inflammatory response to pregnancy.

Trade-offs between acquired and innate immune defenses in humans

Immune defenses provide resistance against infectious disease that is critical to survival. But immune defenses are costly, and limited resources allocated to immunity are not available for other physiological or developmental processes. We propose a framework for explaining variation in patterns of investment in two important subsystems of anti-pathogen defense: innate (non-specific) and acquired (specific) immunity. The developmental costs of acquired immunity are high, but the costs of maintenance and activation are relatively low. Innate immunity imposes lower upfront developmental costs, but higher operating costs. Innate defenses are mobilized quickly and are effective against novel pathogens. Acquired responses are less effective against novel exposures, but more effective against secondary exposures due to immunological memory. Based on their distinct profiles of costs and effectiveness, we propose that the balance of investment in innate versus acquired immunity is variable, and that this balance is optimized in response to local ecological conditions early in development. Nutritional abundance, high pathogen exposure and low signals of extrinsic mortality risk during sensitive periods of immune development should all favor relatively higher levels of investment in acquired immunity. Undernutrition, low pathogen exposure, and high mortality risk should favor innate immune defenses. The hypothesis provides a framework for organizing prior empirical research on the impact of developmental environments on innate and acquired immunity, and suggests promising directions for future research in human ecological immunology.

No association between blood telomere length and longitudinally assessed diet or adiposity in a young adult Filipino population

PURPOSE

Telomeres, DNA-protein structures that cap and protect chromosomes, are thought to shorten more rapidly when exposed to chronic inflammation and oxidative stress. Diet and nutritional status may be a source of inflammation and oxidative stress. However, relationships between telomere length (TL) and diet or adiposity have primarily been studied cross-sectionally among older, overweight/obese populations and yielded inconsistent results. Little is known about the relationship between diet or body composition and TL among younger, low- to normal-weight populations. It also remains unclear how cumulative exposure to a specific diet or body composition during the years of growth and development, when telomere attrition is most rapid, may be related to TL in adulthood.

METHODS

In a sample of 1459 young adult Filipinos, we assessed the relationship between blood TL at ages 20.8-22.5 and measures of BMI z-score, waist circumference, and diet collected between the ages of 8.5 and 22.5. TL was measured using monochrome multiplex quantitative PCR, and diet was measured using multiple 24-h recalls.

RESULTS

We found no associations between blood TL and any of the measures of adiposity or between blood TL and the seven dietary factors examined: processed meats, fried/grilled meats and fish, non-fried fish, coconut oil, fruits and vegetables, bread and bread products, and sugar-sweetened beverages.

CONCLUSIONS

Considering the inconsistencies in the literature and our null results, small differences in body composition and consumption of any single pro- or anti-inflammatory dietary component may not by themselves have a meaningful impact on telomere integrity, or the impact may differ across distinct ecological circumstances.

High-throughput RNA sequencing reveals structural differences of orthologous brain-expressed genes between western lowland gorillas and humans

The human brain and human cognitive abilities are strikingly different from those of other great apes despite relatively modest genome sequence divergence. However, little is presently known about the interspecies divergence in gene structure and transcription that might contribute to these phenotypic differences. To date, most comparative studies of gene structure in the brain have examined humans, chimpanzees, and macaque monkeys. To add to this body of knowledge, we analyze here the brain transcriptome of the western lowland gorilla (Gorilla gorilla gorilla), an African great ape species that is phylogenetically closely related to humans, but with a brain that is approximately one-third the size. Manual transcriptome curation from a sample of the planum temporale region of the neocortex revealed 12 protein-coding genes and one noncoding-RNA gene with exons in the gorilla unmatched by public transcriptome data from the orthologous human loci. These interspecies gene structure differences accounted for a total of 134 amino acids in proteins found in the gorilla that were absent from protein products of the orthologous human genes. Proteins varying in structure between human and gorilla were involved in immunity and energy metabolism, suggesting their relevance to phenotypic differences. This gorilla neocortical transcriptome comprises an empirical, not homology- or prediction-driven, resource for orthologous gene comparisons between human and gorilla. These findings provide a unique repository of the sequences and structures of thousands of genes transcribed in the gorilla brain, pointing to candidate genes that may contribute to the traits distinguishing humans from other closely related great apes.

Improving qPCR telomere length assays: Controlling for well position effects increases statistical power

OBJECTIVES

Telomere length (TL) is commonly measured using quantitative PCR (qPCR). Although, easier than the southern blot of terminal restriction fragments (TRF) TL measurement method, one drawback of qPCR is that it introduces greater measurement error and thus reduces the statistical power of analyses. To address a potential source of measurement error, we consider the effect of well position on qPCR TL measurements.

METHODS

qPCR TL data from 3,638 people run on a Bio-Rad iCycler iQ are reanalyzed here. To evaluate measurement validity, correspondence with TRF, age, and between mother and offspring are examined.

RESULTS

First, we present evidence for systematic variation in qPCR TL measurements in relation to thermocycler well position. Controlling for these well-position effects consistently improves measurement validity and yields estimated improvements in statistical power equivalent to increasing sample sizes by 16%. We additionally evaluated the linearity of the relationships between telomere and single copy gene control amplicons and between qPCR and TRF measures. We find that, unlike some previous reports, our data exhibit linear relationships. We introduce the standard error in percent, a superior method for quantifying measurement error as compared to the commonly used coefficient of variation. Using this measure, we find that excluding samples with high measurement error does not improve measurement validity in our study.

CONCLUSIONS

Future studies using block-based thermocyclers should consider well position effects. Since additional information can be gleaned from well position corrections, rerunning analyses of previous results with well position correction could serve as an independent test of the validity of these results.

Maternal characteristics associated with milk leptin content in a sample of Filipino women and associations with infant weight for age

BACKGROUND

Human milk contains many metabolic hormones that may influence infant growth. Milk leptin is positively associated with maternal adiposity and inversely associated with infant growth. Most research has been conducted in populations with higher leptin levels; it is not well understood how milk leptin may vary in lean populations or the associations that reduced leptin may have with infant size for age. It is also largely unknown if associations between maternal body composition and milk leptin persist past 1 year of age.

OBJECTIVES

We investigated the association between maternal body composition and milk leptin content in a sample of lean Filipino women and the association between milk leptin content and infant size for age.

METHODS

Milk samples were collected at in-home visits from 113 mothers from Cebu, Philippines. Milk leptin content was measured using EIA techniques; anthropometric data, dietary recalls, and household information were also collected.

RESULTS

Mean ± standard deviation (SD) milk leptin in this sample was 300.7 ± 293.6 pg/mL, among the lowest previously reported. Mean ± SD maternal percentage body fat was 24.8% ± 3.5%. Mean ± SD infant age was 9.9 ± 7.0 months, and mean ± SD weight for age z-score was -0.98 ± 1.06. Maternal percentage body fat was a significant, positive predictor of milk leptin content. Milk leptin was a significant, inverse predictor of infant weight and body mass index z-scores in infants 1 year old or younger.

CONCLUSION

The association between maternal body composition, milk leptin, and infant growth persists in mothers with lean body composition. Milk leptin is not associated with growth in older infants.

Slow early growers have more muscle in relation to adult activity: evidence from Cebu, Philippines

Background/objectives

Adult skeletal muscle mass (SMM) protects against type 2 diabetes but little is known about its developmental antecedents. We examined whether pace of early weight gain predicted adult SMM in a birth cohort from Cebu City, Philippines. Additionally, we examined whether increases in SMM associated with adult muscle-building exercise varied according to early growth.

Subjects/methods

Data came from 1472 participants of the Cebu Longitudinal Health and Nutrition Survey. Weight was measured at birth and at 6-month intervals through age 24 months. Adult SMM was estimated from anthropometric measurements when participants were 20-22 years old. Interviews provided information on adult exercise/lifestyle habits.

Results

SMM (mean ± SD) was 20.8 ± 3.9 kg (men) and 13.6 ± 3.4 kg (women). Faster early weight gain predicted higher adult SMM. After adjustment for height and lifestyle factors, strongest associations with SMM were found for 6-12 months growth in men (β=0.17, p=0.001) and for birth weight in women (β=0.14, p=0.001). Individuals who had grown slowly displayed greater SMM in association with adult weight lifting, basketball playing, and physically demanding forms of employment (men) or household chores (women).

Conclusions

These results suggest heightened sensitivity of activity-induced muscle hypertrophy among adults who were born light or who gained weight slowly as infants. Future research should test this finding by comparing responses of muscle mass to an intervention in slow v. fast early growers. Findings suggest that adults who display reduced SMM following suboptimal early growth may be good candidates for new anti-diabetes interventions that promote muscle-building activities.

C-reactive protein response to influenza vaccination as a model of mild inflammatory stimulation in the Philippines

BACKGROUND

C-reactive protein (CRP) is increasingly measured as a marker of systemic inflammation that predicts elevated risk for cardiovascular disease. Influenza vaccination is a mild pro-inflammatory stimulus, and the CRP response to vaccination may provide additional information on individual differences in inflammatory response and risk for disease.

AIM

To document the pattern of CRP response to influenza vaccination among a large sample of older women in the Philippines. The Philippines exemplifies current global trends toward increasing rates of overweight/obesity, but also maintains relatively high rates of infectious disease. The secondary aim of the study is to investigate the impact of infectious symptoms on the pattern of response to vaccination.

METHODS

A community-based sample of 934 women (mean age=55.4 years) received the influenza vaccine. CRP was assessed at baseline and 72h post-vaccination. Descriptive, non-parametric, and parametric analyses were implemented to assess the magnitude of CRP response, and to investigate whether responses were associated with baseline CRP or the presence of infectious symptoms prior to vaccination.

RESULTS

Influenza vaccination resulted in a statistically significant CRP response of 0.35mg/L (p<0.001), representing a 30.2% increase from baseline. For individuals with symptoms of infectious disease at baseline, the CRP response was smaller (12.9%) and not statistically significant (p=0.77). Lower CRP at baseline was associated with larger CRP response to vaccination in the entire sample, and among participants without recent symptoms of infection.

CONCLUSIONS

Influenza vaccination produces a mild CRP response in the Philippines. This study extends prior research in US and European populations validating influenza vaccination as an in vivo model for investigating the dynamics of inflammation, but also raises potential complications in settings where rates of infectious disease are elevated.

Developmental origins of flatter cortisol rhythms: socioeconomic status and adult cortisol activity

OBJECTIVE

Low socioeconomic status (SES) is associated with increased psychosocial stress among low-income persons, which could contribute to differences in activity of the HPA axis (assessed by diurnal cortisol profiles). The current article investigates associations of SES from different developmental stages with cortisol profiles.

METHODS

Using data from a large, socioeconomically diverse birth cohort (N = 1,490) in Cebu, Philippines, the current study compares the relative and joint contributions of SES from five developmental periods, between the prenatal/birth period and early adulthood, to adult cortisol, and examines the effects of chronic exposure to low SES.

RESULTS

Chronically low SES from infancy through early adulthood predicts the highest bedtime cortisol levels, lowest cortisol awakening responses (CARs), lowest total cortisol levels across the day (area under curve or AUC), and the flattest cortisol rhythms between wake up and bedtime, a profile associated with poorer health. Results indicate that cumulative economic strain (between the prenatal period and early adulthood) predicts flatter cortisol rhythms more consistently than SES from any particular period.

CONCLUSION

Interventions focusing on the psychosocial stressors associated with economic deprivation during any period from infancy to adulthood may be helpful, but targeting interventions across multiple periods may have the greatest impact. Interventions aimed at improving economic conditions between infancy and early adulthood may have implications for long-term changes in HPA axis functioning.

Ethnic discrimination predicts poor self-rated health and cortisol in pregnancy: insights from New Zealand

Despite growing research emphasis on understanding the health effects of ethnic discrimination, little work has focused on how such exposures may influence a woman's biology and health during pregnancy. Understanding such effects is important given evidence that maternal stress experience in pregnancy can have long term effects on offspring health. Here we present data evaluating the relationship between perceived discrimination, self-rated health, and the stress hormone cortisol measured in late pregnancy among a diverse sample of women living in Auckland, New Zealand (N = 55). We also evaluated possible intergenerational impacts of maternal discrimination on stress reactivity in a subset of offspring (N = 19). Pregnant women were recruited from two antenatal care clinics in Auckland. Women were met in their homes between 34 and 36 weeks gestation, during which time a prenatal stress questionnaire was administered and saliva samples (morning and evening from two days) were obtained. Offspring cortisol reactivity was assessed at the standard six week postnatal vaccination visit. We found that 34% of women reported having experienced ethnic discrimination, with minority and immigrant women being more likely to report being angry or upset in response to discrimination experience compared with NZ-born women of European descent. Women reporting discrimination experience had worse self-rated health, higher evening cortisol and gave birth to infants with higher cortisol reactivity, all independent of ethnicity and material deprivation. These findings suggest that discrimination experience can have biological impacts in pregnancy and across generations, potentially contributing to the ethnic gradient in health.

Metabolic costs and evolutionary implications of human brain development

The high energetic costs of human brain development have been hypothesized to explain distinctive human traits, including exceptionally slow and protracted preadult growth. Although widely assumed to constrain life-history evolution, the metabolic requirements of the growing human brain are unknown. We combined previously collected PET and MRI data to calculate the human brain's glucose use from birth to adulthood, which we compare with body growth rate. We evaluate the strength of brain-body metabolic trade-offs using the ratios of brain glucose uptake to the body's resting metabolic rate (RMR) and daily energy requirements (DER) expressed in glucose-gram equivalents (glucosermr% and glucoseder%). We find that glucosermr% and glucoseder% do not peak at birth (52.5% and 59.8% of RMR, or 35.4% and 38.7% of DER, for males and females, respectively), when relative brain size is largest, but rather in childhood (66.3% and 65.0% of RMR and 43.3% and 43.8% of DER). Body-weight growth (dw/dt) and both glucosermr% and glucoseder% are strongly, inversely related: soon after birth, increases in brain glucose demand are accompanied by proportionate decreases in dw/dt. Ages of peak brain glucose demand and lowest dw/dt co-occur and subsequent developmental declines in brain metabolism are matched by proportionate increases in dw/dt until puberty. The finding that human brain glucose demands peak during childhood, and evidence that brain metabolism and body growth rate covary inversely across development, support the hypothesis that the high costs of human brain development require compensatory slowing of body growth rate.

Parental childhood growth and offspring birthweight: pooled analyses from four birth cohorts in low and middle income countries

Objective

Associations between parental and offspring size at birth are well established, but the relative importance of parental growth at different ages as predictors of offspring birthweight is less certain. Here we model parental birthweight and postnatal conditional growth in specific age periods as predictors of offspring birthweight.

Methods

We analyzed data from 3,392 adults participating in four prospective birth cohorts and 5,506 of their offspring.

Results

There was no significant heterogeneity by study site or offspring sex. 1SD increase in maternal birthweight was associated with offspring birthweight increases of 102 g, 1SD in maternal length growth 0–2 year with 46 g, and 1SD in maternal height growth Mid-childhood (MC)-adulthood with 27 g. Maternal relative weight measures were associated with 24 g offspring birth weight increases (2 year- MC) and 49 g for MC-adulthood period but not with earlier relative weight 0–2 year. For fathers, birthweight, and linear/length growth from 0–2 year were associated with increases of 57 and 56 g in offspring birthweight, respectively but not thereafter.

Conclusions

Maternal and paternal birthweight and growth from birth to 2 year each predict offspring birthweight. Maternal growth from MC-adulthood, relative weight from 2-MC and MC-adulthood also predict offspring birthweight. These findings suggest that shared genes and/or adequate nutrition during early life for both parents may confer benefits to the next generation, and highlight the importance of maternal height and weight prior to conception. The stronger matrilineal than patrilineal relationships with offspring birth weight are consistent with the hypothesis that improving the early growth conditions of young females can improve birth outcomes in the next generation. Am. J. Hum. Biol. 27:99–105, 2015. © 2014 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.

Preterm delivery as a predictor of diurnal cortisol profiles in adulthood: evidence from Cebu, Philippines

OBJECTIVES

Fetal exposure to elevated maternal cortisol can permanently modify hypothalamic-pituitary-adrenal (HPA) axis function, and thereby have long-term health impacts. Maternal cortisol steadily increases throughout normal pregnancy, but is abnormally high in preterm deliveries (<37 weeks). Prematurity remains a widespread public health problem, yet little is known about its potential long-term effects on adult HPA function. Here we test the hypothesis that diurnal cortisol profiles measured in young adulthood will vary based upon an individual's preterm status.

METHODS

Diurnal salivary cortisol profiles, a marker of HPA-axis function, were measured in 1,403 young adults (ages 21-23 years) participating in the Cebu Longitudinal Health and Nutrition Survey, located in Metropolitan Cebu City, Philippines.

RESULTS

Males who had been born preterm exhibited lower morning cortisol and non-significantly elevated evening cortisol, resulting in a more adverse, flatter rate of decline across the day. In contrast, there were no significant differences by preterm status in cortisol measured at any time of day in females.

CONCLUSIONS

These findings point to potential long-term effects of having been born preterm on adult HPA-axis function, and add to evidence from this and other populations for sex differences in the biological and health impacts of prenatal stress exposure.

Early origins of health disparities: material deprivation predicts maternal evening cortisol in pregnancy and offspring cortisol reactivity in the first few weeks of life

OBJECTIVES

Maternal hypothalamic pituitary adrenal-axis function regulates production of the stress hormone cortisol, which during pregnancy can cross the placenta and have lasting impacts on fetal growth and development. This article provides a preliminary test of the hypothesis that a woman's socioeconomic status (SES) predicts her cortisol during pregnancy and her offspring's cortisol during the early postnatal period among an ethnically diverse sample in Auckland, New Zealand to evaluate whether differences in cortisol contribute to the intergenerational inheritance of health disparities within this population.

METHODS

Maternal saliva samples were collected at waking and prior to sleep on 2 days in late pregnancy (34-36 weeks gestation; N = 55), and a subset of offspring saliva was collected before (N = 48) and 20 min after a standard vaccination at 6 weeks of age (N = 19). SES was quantified using a locally validated index of material deprivation, the NZ Deprivation Index for individuals (NZiDep).

RESULTS

We found that, after controlling for ethnicity and other covariates, women with higher NZiDep scores had significantly higher evening but similar morning cortisol, consistent with a pattern of chronic strain. Infants of women reporting greater material deprivation had elevated cortisol response to vaccination.

CONCLUSIONS

These findings suggest that maternal SES experience impacts maternal cortisol in pregnancy and offspring cortisol reactivity soon after birth, with potential long-term effects on offspring biology and health. Additional research is needed to clarify how biological and behavioral factors in both the prenatal and postnatal period facilitate this relationship.

Salivary estradiol and testosterone in Filipino men: Diurnal patterns and relationships with adiposity

OBJECTIVES

We used detailed saliva sampling procedures to test for diurnal changes in men's salivary estradiol (E2) and testosterone (T) and assessed whether greater adiposity predicted higher E2 and T.

METHODS

We drew on a subsample of young adults enrolled in a long-running birth cohort study in Metro Cebu, Philippines. Subjects provided saliva samples at four time points during the day (waking, waking +40 min, early evening, and bedtime), which were assayed for E2 and T. Using these detailed hormonal data, we calculated E2 (n = 29) and T (n = 44) area-under-the-curve values, which provide insights on hormonal production over the study period.

RESULTS

While T declined immediately after waking and reached a nadir in the early evening, E2 did not show significant diurnal change (P ≥ 0.1) but was positively correlated to T at multiple time points (P ≤ 0.05). Subjects with higher adiposity (BMI, waist circumference, skinfolds) had elevated E2 secretion throughout the day (P ≤ 0.01), but adiposity was not related to salivary T.

CONCLUSIONS

Consistent with past research, our results indicate that adipose tissue is a significant site of E2 production in males but differ from a limited number of prior studies of young men in that we did not find lower T with increasing adiposity. Given E2's role in male hypothalamic-pituitary-gonadal function and complex interfaces with the immune system, these results have important implications for models of male life history as rates of overweight and obesity rise in populations around the world.

Birth status, child growth, and adult outcomes in low- and middle-income countries

OBJECTIVE

To assess the impact of being born preterm or small for gestational age (SGA) on several adult outcomes.

STUDY DESIGN

We analyzed data for 4518 adult participants in 5 birth cohorts from Brazil, Guatemala, India, the Philippines, and South Africa.

RESULTS

In the study population, 12.8% of males and 11.9% of females were born preterm, and 26.8% of males and 22.4% of females were born term but SGA. Adults born preterm were 1.11 cm shorter (95% CI, 0.57-1.65 cm), and those born term but SGA were 2.35 cm shorter (95% CI, 1.93-2.77 cm) compared with those born at term and appropriate size for gestational age. Blood pressure and blood glucose level did not differ by birth category. Compared with those born term and at appropriate size for gestational age, schooling attainment was 0.44 years lower (95% CI, 0.17-0.71 years) in those born preterm and 0.41 years lower (95% CI, 0.20-0.62 years) in those born term but SGA.

CONCLUSION

Being born preterm or term but SGA is associated with persistent deficits in adult height and schooling, but is not related to blood pressure or blood glucose level in low- and middle-income settings. Increased postnatal growth is associated with gains in height and schooling regardless of birth status, but not with increases in blood pressure or blood glucose level.

Do testosterone declines during the transition to marriage and fatherhood relate to men's sexual behavior? Evidence from the Philippines

Testosterone (T) is thought to help facilitate trade-offs between mating and parenting in humans. Across diverse cultural settings married men and fathers have lower T than other men and couples' sexual activity often declines during the first years of marriage and after having children. It is unknown whether these behavioral and hormonal changes are related. Here we use longitudinal data from a large study in the Philippines (n=433) to test this model. We show that among unmarried non-fathers at baseline (n=153; age: 21.5 ± 0.3 years) who became newly married new fathers by follow-up (4.5 years later), those who experienced less pronounced longitudinal declines in T reported more frequent intercourse with their partners at follow-up (p<0.01) compared to men with larger declines in T. Controlling for duration of marriage, findings were similar for men transitioning from unmarried to married (without children) (p<0.05). Men who remained unmarried and childless throughout the study period did not show similar T-sexual activity outcomes. Among newly married new fathers, subjects who had frequent intercourse both before and after the transition to married fatherhood had more modest declines in T compared to peers who had less frequent sex (p<0.001). Our findings are generally consistent with theoretical expectations and cross-species empirical observations regarding the role of T in male life history trade-offs, particularly in species with bi-parental care, and add to evidence that T and sexual activity have bidirectional relationships in human males.