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BackgroundMarket integration (MI)-increasing production for and consumption from a market-based economy-is drastically altering traditional ways of life and environmental conditions among indigenous Amazonian peoples. The effects of MI on the biology and health of Amazonian children and adolescents, however, remain unclear.AimThis study examines the impact of MI on sub-adult body size and nutritional status at the population, regional and household levels among the Shuar of Amazonian Ecuador.Subjects and methodsAnthropometric data were collected between 2005-2014 from 2164 Shuar (aged 2-19 years) living in two geographic regions differing in general degree of MI. High-resolution household economic, lifestyle and dietary data were collected from a sub-sample of 631 participants. Analyses were performed to investigate relationships between body size and year of data collection, region and specific aspects of household MI.ResultsResults from temporal and regional analyses suggest that MI has a significant and overall positive impact on Shuar body size and nutritional status. However, household-level results exhibit nuanced and heterogeneous specific effects of MI underlying these overarching relationships.ConclusionThis study provides novel insight into the complex socio-ecological pathways linking MI, physical growth and health among the Shuar and other indigenous Amazonian populations.

Background: Measurements of hormone concentrations in human milk from understudied populations across the world is of growing scientific interest. Due to limited access to suitable laboratory facilities at many research sites, human milk samples are often shipped frozen to distant laboratories for analysis. Shipping and handling exposes samples to the risk of thawing and degradation as the results of delays, mishandling, or other unforeseen circumstances. Similar degradation risk factors are well known in serum samples. However, the vulnerability of hormone degradation in human milk to thawing during transportation is largely unexplored. Leptin and adiponectin are of particular importance due to their roles in feeding behavior and metabolism in infants, hence our focus on these two hormones. In addition, leptin and adiponectin have been shown to be vulnerable to pasteurization temperature degradation in human milk samples. Aims: We tested the degradation of human milk metabolic hormones – leptin and adiponectin – in a controlled environment in response to a variety of freeze/thaw conditions that are reflective of potential temperature fluctuations during transportation. Materials & Methods: Human milk samples were experimentally subjected to thaw durations ranging from 4 to 16 h and assayed for hormonal levels to observe changes from baseline. Samples were also subjected to two additional experimental conditions, re‐freezing after an extended period outside freezers or remaining thawed with additional ice packs, to investigate the impact of common transportation conditions. Results: We found the assayed levels of leptin were not significantly impacted by an extended thaw cycle of 16 h. However, leptin levels were impacted by the extended period of 40 h outside of the freezer. Adiponectin showed a decrease in concentration percentage after the initial 16‐h thaw period, but the increased degradation between 0–16 h and 16–40 h was not as severe as that seen in the leptin samples. Discussion & Conclusion: The results of this experiment can be used to inform hormone measurement consistency given different thawing lengths or freezing conditions during transportation. Additionally, this research informs decisions regarding transportation, storage/handling, and data analysis in human milk research. [ABSTRACT FROM AUTHOR]

Age-related differences in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), salivary testosterone, and 17-[3 estradiol levels are reported for Ache Amerindian males (n = 17; mean age, 37.1 [+ or -] 14.2 SD) of Paraguay in order to explore population variation in patterns of male reproductive senescence in a foraging/agricultural community. Hormone associations were examined to test various hypotheses for age-related differences in hypothalamic-pituitary function. Significant increases in FSH (r = 0.75, P < 0.0005) and LH (r = 0.65, P < 0.01) were noted in association with aging. No significant correlation was observed between morning or evening testosterone and age. Morning and evening estradiol levels were associated with morning and evening testosterone, respectively (morning, r = 0.53, P = 0.05; evening, r = 0.63, P = 0.02). Evening estradiol was also positively associated with LH (r = 0.66, P = 0.02), suggesting testicular production to be an important source of circulating estradiol. Morning estradiol tended to rise with age, but was not significant (r = 0.39, P = 0.15). Anthropometric measurements of height, weight, body mass index, and fat percent did not change significantly with age. In contrast to testosterone, age-related differences in gonadotropin levels may be independent of energetic status, less variant, and more universal among male populations. Implications for gonadotropin function and aging on human male reproductive senescence and life histories are discussed. KEY WORDS gonadotropins; FSH; LH; testosterone; estradiol; male aging

Objective: Associations between leptin and male reproductive hormone levels have been reported in men. However, few of these investigations have focused on associations in healthy men without obesity or overweight or nonindustrial societies. Methods: We test hypotheses that leptin is associated with testosterone, estradiol, luteinizing hormone (LH), and follicle‐stimulating hormone (FSH) within healthy Ache men, an indigenous nonindustrialized South American community using archived data. Results: Archived data of serum FSH, LH, leptin, and salivary testosterone and estradiol levels collected from healthy Ache men (n = 17, mean age = 37.1 ± 14.2) on two separate days revealed leptin was correlated with FSH (D1 p =.07, D2 p =.009) and PM testosterone (TsalPM, D1 p =.05, D2 p =.05). However, controlling for age, associations with FSH were not significant. Mean comparisons and linear regression of values over 2 days resulted in leptin (t = 0.08, p =.94, r2 =.58, p =.0009), LH (t = 1.16, p =.26, r2 =.11, p =.27), FSH (U = 131.5, p =.88, r2 =.63, p =.0002), AM testosterone (TsalAM, t = 4.0, p =.001, r2 =.02, p = 0.75), and TsalPM (t = 2.99, p =.01, r2 =.56, p =.01). Conclusion: We conclude (a) FSH, TsalPM, and leptin levels within individual men are relatively invariant over a span of days; (b) despite small sample sizes, results suggest ecological and lifestyle variation can contribute to variation in leptin associations with male reproductive hormones. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Until recently, the reproductive ecology of human males has not been extensively investigated, primarily as a result of the need for a theoretical framework based on the reproductive constraints and energetics of mammalian males. More specifically, male reproductive ecology has necessitated an integrative interpretation of clinical and anthropological data based on the premise that the evolution of human male life histories has involved selection for physiological mechanisms aimed at optimizing trade-offs between survivorship and reproductive effort. This paper attempts to address this gap in our understanding by presenting the current state of male reproductive ecology, including physiologic data from clinical and anthropological investigations as well as recent theoretical developments. Recent investigations outlining population variation in reproductive endocrine function are discussed within the context of potential sources of variation, including energetic expediture, caloric intake, and developmental canalization during adolescence. Additional summaries of male senescence and behavior are presented to provide a complete overview of male life history. Implications of recent anthropological data on contemporary health issues such as prostate cancer and the development of a male contraceptive are also discussed. Finally, several theories are presented that may contribute to our understanding of the evolution of male life histories and reproductive ecology, including theoretical suggestions involving the role of competition, mate choosiness, and potential constraints on male insemination ability, as well as a theory suggesting that male reproductive ecology may be best understood by analyzing energetic allocation decisions between differing somatic tissues that may be indicative of the competing needs for optimizing survivorship and reproductive effort. Directions for future research are finally considered. Yrbk Phys Anthropol 44:148-176, 2001. KEY WORDS reproductive physiology; testosterone; evolution

Objective: Anemia is an important global health challenge. We investigate anemia prevalence among Indigenous Shuar of Ecuador to expand our understanding of population‐level variation, and to test hypotheses about how anemia variation is related to age, sex, and market integration. Methods: Hemoglobin levels were measured in a total sample of 1650 Shuar participants (ages 6 months to 86 years) from 46 communities between 2008 and 2017 to compare anemia prevalence across regions characterized by different levels of market integration. Results: Shuar anemia rates among children under 15 years (12.2%), adult women (10.5%), and adult men (5.3%) were less than half of those previously documented in other neo‐tropical Indigenous populations. Anemia prevalence did not vary between more traditional and market integrated communities (OR = 0.47, p =.52). However, anemia was negatively associated with body mass index (OR = 0.47, p =.002). Conclusions: Compared to other South American Indigenous populations, anemia prevalence is relatively low among Shuar of Ecuador and invariant with market integration. Understanding this pattern can provide valuable insights into anemia prevention among at‐risk populations. [ABSTRACT FROM AUTHOR]

Objectives: Oxidative stress is hypothesized to contribute to age‐related somatic deterioration. Both reproductive and ecological context may necessitate tradeoffs that influence this outcome. We examined whether measures of lifetime reproductive effort were related to levels of oxidative stress biomarkers in peri‐ and post‐menopausal women and whether associations were moderated by rural or urban residence. Methods: We surveyed 263 healthy women (age 62.1 ± 10.0 SD) from rural (N = 161) and urban Poland (N = 102), collecting sociodemographic data and urine samples to analyze biomarkers of oxidative stress (8‐oxo‐2′‐deoxyguanosine, 8‐OHdG) and antioxidative defense (copper‐zinc superoxide dismutase, Cu‐Zn SOD). Linear regression models, adjusted for residence, were used to test for associations between reproductive effort and 8‐OHdG and Cu‐Zn SOD. Results: Univariate models demonstrated significant associations between gravidity and the biomarkers of oxidative stress (8‐OHdG: R2 = 0.042, P ≤.001; Cu‐Zn SOD: R2 = 0.123, P ≤.001). Multivariate models incorporating potential confounding variables, as well as cross‐product interaction terms, indicated that gravidity was associated with 8‐OHdG (P <.01, R2adj = 0.067) and Cu‐Zn SOD (P =.01, R2adj = 0.159). Residence (ie, urban vs rural) did not significantly moderate the associations between the biomarkers and reproductive effort. Conclusions: Higher lifetime reproductive effort contributes to increases in oxidative stress and antioxidative defenses. Our results provide evidence of potential mechanisms underlying the physiological tradeoffs influencing senescence for women with high reproductive effort. We illustrate the value of applying an evolutionary perspective to elucidate variation in human health and senescence. [ABSTRACT FROM AUTHOR]

Abstract Background Serum leptin variation is commonly associated with fat percentage (%), body mass index (BMI), and activity. In this investigation, we report population differences in mean leptin levels in healthy men as well as associations with fat % and BMI that are independent of these factors and reflect likely variation resulting from chronic environmental conditions. Methods Serum leptin levels, fat %, and BMI were compared between lean American distance runners and healthy Ache Native Americans of Paraguay. Mean levels were compared as were the regressions between fat %, BMI, and leptin. Comparisons were performed between male American distance runners (n = 13, mean age 32.2 ± 9.2 SD) and highly active male New World indigenous population (Ache of Paraguay, n = 20, mean age 32.8 ± 9.2) in order to determine whether significant population variation in leptin is evident in physically active populations living under different ecological circumstances independent of adiposity and BMI. Results While the Ache were hypothesized to exhibit higher leptin due to significantly greater adiposity (fat %, Ache 17.9 ± 1.8 SD; runners 9.7 ± 3.2, p < 0.0001), leptin levels were nonetheless significantly higher in American runners (Ache 1.13 ng/ml ± 0.38 SD; runners 2.19 ± 1.15; p < 0.007). Significant differences in the association between leptin and fat % was also evident between Ache and runner men. Although fat % was significantly related with leptin in runners (r = 0.90, p < 0.0001) fat % was negatively related in Ache men (r = -0.50, p < 0.03). Conclusion These results illustrate that chronic ecological conditions in addition to activity are likely factors that contribute to population variation in leptin levels and physiology. Population variation independent of adiposity should be considered to be an important source of variation, especially in light of ethnic and population differences in the incidence and etiology of obesity, diabetes, and other metabolic conditions.

The analysis explains the consistency of active ghrelin levels across time and describes its associations with leptin, as well as anthropometrics in healthy Ache Amerindian women of Paraguay. The active ghrelin was found to be almost consistent over time in the discussed population.

Male life history trade-offs between immune and reproductive endocrine functions as well as testosterone-immunocompetence relationship was studied. It is found that by suppressing immune response and augmenting anabolic processes, testosterone act as a physiological mechanism regulating the relative amount of energy invested into either reproductive effort or immunocompetence.

An investigation is presented to test the hypothesis that Ache women exhibit leptin levels that are not significantly different from anorectic patients, providing support for the role of chronic environmental differences that might alter leptin physiology. Results revealed that although Ache adiposity was significantly higher than anorectic and control patients, Ache leptin was not significantly different from anorexia patients, lower than controls, and exhibited a very limited range of variation.

Independent of adiposity, significant population variation is demonstrated in serum leptin levels and zinc is shown to be an important regulator of leptins in humans and rodents. It is concluded that zinc is not likely to be a contributing factor in male Ache leptin profiles, and chronic energetic stresses affecting leptin production and perhaps receptor number or sensitivity must be considered.

Leptin is a recently discovered peptide hormone secreted primarily from adipocytes in humans and other mammals; it is a reflection of fat stores, and has been associated with reproductive function. However, few leptin measurements are available from nonindustrialized populations, including contemporary hunter/gatherer communities undergoing the transition to sedentary agriculture. This investigation reports single-sample serum leptin measurements in healthy Ache Amerindian males (n = 21; average age, 32.8 [+ or -] 3.4 SE) and females (n = 12; average age, 31.3 [+ or -] 4.3) in eastern Paraguay. Ache leptin concentrations were much lower than in industrialized populations, although significant sexual dimorphism was evident (female 5.64 ng/ ml [+ or -] 0.91 SE vs. male 1.13 ng/ml [+ or -] 0.08; P [is less than] 0.0001). Indeed, female leptin levels were similar to those of anorexic women, despite apparently adequate adiposity. Controlling for fat percentage, no significant sex difference was evident, suggesting that adiposity was the primary source of leptin variation. Body fat percentage was highly correlated with leptin in females ([r.sup.2] = 0.72; P [is less than] 0.0005) but not males, who exhibited a modest negative correlation ([r.sup.2] = 0.25; P [is less than] 0.03). Weight ([r.sup.2] = 0.45; P = 0.02) and BMI (kg/[m.sup.2]) ([r.sup.2] = 0.81; P [is less than] 0.0001) were also significantly correlated in females but not males. These results suggest that: 1) clinical leptin norms based on industrialized populations may represent the highest range of human variation and may not be representative of most human populations; 2) hormonal priming may underlie population variation in leptin profiles; and 3) the relative importance of leptin as a proximate mechanism regulating reproductive effort during human evolution may have been modest. Am J Phys Anthropol 115:297-303, 2001. KEY WORDS reproductive ecology; body composition; sexual dimorphism; peptide hormone; endocrinology; Indians; South America