Lifetime socioeconomic status and early life microbial environments predict adult blood telomere length in the Philippines.

OBJECTIVES: Psychosocial stress is postulated to hasten senescence in part by accelerating the shortening of telomere length (TL). One pathway through which this may happen is via increasing inflammation and innate immune system activation-a pathway which recent studies suggest acts more strongly for those who grew up in low microbial environments. Thus, we hypothesized that: (1) Psychosocial stress will be inversely associated with TL, (2) early life microbial environments will predict TL, and (3) microbial environments will moderate the association between psychosocial stress and TL. METHODS: We utilized data from the Cebu Longitudinal Health and Nutrition Survey based in the Philippines (N = 1410). We determined early life microbial environments by season of birth and exposure to animal feces. Psychosocial stress measures included perceived stress in adulthood, lifetime socioeconomic status (SES), and parental instability in childhood. TL was measured in blood from young adults by qPCR. RESULTS: Contrary to predictions, we found that higher SES was associated with shorter TL and no association of TL with the other stress variables. Individuals born in the higher microbial exposure season had shorter TL, but early life microbial environments did not moderate the association between psychosocial stress and TL. CONCLUSIONS: The unexpected inverse association between SES and TL suggests that higher SES, while indexing lower psychosocial stress, may impact TL more strongly through nonstress factors in the Philippines, such as unhealthy behavior. The inverse association between microbial environments and TL is consistent with other evidence connecting early life infections to decreased life expectancies.

Androgen receptor polyglutamine repeat length (AR-CAGn) modulates the effect of testosterone on androgen-associated somatic traits in Filipino young adult men.

OBJECTIVES: The androgen receptor (AR) mediates expression of androgen-associated somatic traits such as muscle mass and strength. Within the human AR is a highly variable glutamine short-tandem repeat (AR-CAGn), and CAG repeat number has been inversely correlated to AR transcriptional activity in vitro. However, evidence for an attenuating effect of long AR-CAGn on androgen-associated somatic traits has been inconsistent in human populations. One possible explanation for this lack of consistency is that the effect of AR-CAGn on AR bioactivity in target tissues likely varies in relation to circulating androgen levels. MATERIALS AND METHODS: We tested whether relationships between AR-CAGn and several androgen-associated somatic traits (waist circumference, lean mass, arm muscle area, and grip strength) were modified by salivary (waking and pre-bed) and circulating (total) testosterone (T) levels in young adult males living in metropolitan Cebu, Philippines (n = 675). RESULTS: When men's waking T was low, they had a reduction in three out of four androgen-associated somatic traits with lengthening AR-CAGn (p < .1), consistent with in vitro research. However, when waking T was high, we observed the opposite effect-lengthening AR-CAGn was associated with an increase in these same somatic traits. DISCUSSION: Our finding that longer AR-CAGn predicts greater androgen-associated trait expression among high-T men runs counter to in vitro work, but is generally consistent with the few prior studies to evaluate similar interactions in human populations. Collectively, these results raise questions about the applicability of findings derived from in vitro AR-CAGn studies to the receptor's role in maintaining androgen-associated somatic traits in human populations.

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.

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.

Progesterone and estrogen responsiveness to father-toddler interaction.

OBJECTIVES: We assessed the responsiveness of salivary progesterone (P4) and estradiol (E2) to father-child interaction, including testing for differences in short-term hormonal change based on paternal characteristics. We also predicted that P4 exposure during the study period would relate positively to post-interaction paternal mood. METHODS: We conducted an in-home intervention study in which fathers (n = 44) played with their toddlers. Subjects provided saliva samples before interacting with their children, with additional collections 40 and 70 min later. RESULTS: E2 did not significantly change over the study period (P > 0.4). P4 declined significantly from baseline to 40 min (P < 0.05) and 70 min (P < 0.001). Men reporting that the interaction made them feel very happy/relaxed had greater P4 exposure from baseline through 70 min (area under the curve) compared with men reporting less positive post-interaction mood (P < 0.05). This relationship persisted after controlling for cortisol. Men's % decrease in P4 (baseline to 40 min) was significantly greater if they had an infant (P < 0.05), while fathers' % decline in E2 (baseline to 70 min) was larger if they had more children (P < 0.05). CONCLUSIONS: These results require replication but could indicate that grouping fathers with different levels of experience obscures meaningful variation in hormonal responses to child interaction. Our findings appear consistent with the effects of P4 as a mood enhancer and suggest future research should explore the possible role of P4 as hormonal mechanism that could reinforce or facilitate paternal investment.

Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines.

Because cross-species evidence suggests that high testosterone (T) may interfere with paternal investment, the relationships between men's transition to parenting and changes in their T are of growing interest. Studies of human males suggest that fathers who provide childcare often have lower T than uninvolved fathers, but no studies to date have evaluated how nighttime sleep proximity between fathers and their offspring may affect T. Using data collected in 2005 and 2009 from a sample of men (n = 362; age 26.0 ± 0.3 years in 2009) residing in metropolitan Cebu, Philippines, we evaluated fathers' T based on whether they slept on the same surface as their children (same surface cosleepers), slept on a different surface but in the same room (roomsharers), or slept separately from their children (solitary sleepers). A large majority (92%) of fathers in this sample reported practicing same surface cosleeping. Compared to fathers who slept solitarily, same surface cosleeping fathers had significantly lower evening (PM) T and also showed a greater diurnal decline in T from waking to evening (both p<0.05). Among men who were not fathers at baseline (2005), fathers who were cosleepers at follow-up (2009) experienced a significantly greater longitudinal decline in PM T over the 4.5-year study period (p<0.01) compared to solitary sleeping fathers. Among these same men, baseline T did not predict fathers' sleeping arrangements at follow-up (p>0.2). These results are consistent with previous findings indicating that daytime father-child interaction contributes to lower T among fathers. Our findings specifically suggest that close sleep proximity between fathers and their offspring results in greater longitudinal decreases in T as men transition to fatherhood and lower PM T overall compared to solitary sleeping fathers.

Age at menarche and parity are independently associated with Anti-Müllerian hormone, a marker of ovarian reserve, in Filipino young adult women.

OBJECTIVES: Despite ample evidence of variation in timing of menopause, little is known about the extent or underlying causes of individual variation in ovarian reserve and age-related follicular decline. Anti-Müllerian hormone (AMH), a hormonal marker of ovarian reserve, may be a useful tool to clarify these questions. We describe AMH in a cohort of Filipino young adult women, and evaluate whether ovarian reserve in early adulthood relates to measures of life history scheduling (menarcheal age) and reproductive effort (parity). METHODS: Data and samples are obtained from 294 nonpregnant participants (21.5 years ± 0.3) in the Cebu Longitudinal Health and Nutrition Survey. Plasma AMH was assayed using an enzyme immunoassay and relationships between AMH, menarcheal age, and parity were examined. RESULTS: Mean AMH was 4.3 ng/mL. In multiple regression models, women who experienced menarche earlier had significantly higher AMH as young adults (P < 0.05). Women with two (P < 0.05) and three or more (P < 0.01) children had significantly lower AMH than those with no children. These associations were independent of age, smoking, and body mass index. CONCLUSIONS: These findings suggest that individual variation in life history scheduling and reproductive history could contribute to variation in ovarian reserve. Moreover, they demonstrate the utility of AMH as a tool for human reproductive ecology, and highlight the need for further research clarifying the extent of human population variation in ovarian reserve and the behavioral and ecological influences underlying this variation.

Short-term changes in fathers' hormones during father-child play: impacts of paternal attitudes and experience.

Hormonal differences between fathers and non-fathers may reflect an effect of paternal care on hormones. However, few studies have evaluated the hormonal responses of fathers after interacting with their offspring. Here we report results of a 30-minute in-home experiment in which Filipino fathers played with their toddlers and consider whether paternal experience and men's perceptions of themselves as fathers affect hormonal changes. Fathers provided saliva and dried blood spot samples at baseline (B) and 30 (P30) and 60 (P60, saliva only) minutes after the interaction. We tested whether testosterone (T), cortisol (CORT), and prolactin (PRL) shifted after the intervention. In the total sample, T did not vary over the study period, while CORT declined from B to P30 and P60, and PRL also declined from B to P30. Fathers who spent more time in daily caregiving and men who thought their spouses evaluated them positively as parental caregivers experienced a larger decline in PRL (B to P30) compared to other fathers. First-time fathers also had larger declines in PRL compared to experienced fathers. Experienced fathers also showed a greater decline in CORT (B to P60) compared to first-time fathers. These results suggest that males' paternal experience and age of offspring affect hormonal responses to father-child play and that there is a psychobiological connection between men's perceptions of themselves as fathers and their hormonal responsivity to childcare.

Testosterone, physical activity, and somatic outcomes among Filipino males.

Testosterone (T) facilitates male investment in reproduction in part through its anabolic effects on skeletal muscle. Traits like muscle and strength are energetically costly but are believed to enhance competitive ability in humans and other mammals. However, there are limited data on relationships between T and somatic outcomes in lean, non-western populations. We evaluate relationships between waking and pre-bed salivary T and adiposity, fat-free mass (FFM), arm muscle area (AMA), and grip strength (GS) in a large, population-based birth cohort of young adult Filipino males (20.8-22.6 years, n = 872). Data were collected as part of the Cebu Longitudinal Health and Nutrition Survey. Neither waking nor evening T predicted FFM, AMA, or GS. However, there were borderline or significant interactions between T and basketball playing (the most common team sport) and weight lifting as predictors of outcomes: higher waking T predicted higher FFM (activity x T interaction P < 0.01), AMA (interaction P < 0.1), and GS (interaction P < 0.02) among frequent basketball players, and GS (interaction P < 0.09) among the smaller sample of weight lifters. In contrast to clinical studies, but consistent with findings in several subsistence-level populations, T was positively related to adiposity in these lean young males, suggesting that energy status might regulate circulating T. Our findings support a role of the prewaking rise in T as a determinant of energetic allocation to lean mass and strength in the context of repeated muscular use and support the hypothesized role of T as a mediator of investment in costly somatic traits in human males.