Helminth infection, fecundity, and age of first pregnancy in women

American J Phys Anthropol

Blackwell

Stieglitz

et al. 2016

Self Cite

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 phytohaemagglutinin (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 to 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).

Section: Study Goals and Hypothesesmentioning

confidence: 76%

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

American J Phys Anthropol

Blackwell

Stieglitz

et al. 2016

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“…With effects on energy balance, pathogen stress may counteract obesity. Inflammation may also be better regulated, as helminths and other parasites induce regulatory and T H 2 responses (McDade et al, 2012; Blackwell et al, 2015). …”

Section: Discussionmentioning

confidence: 99%

“…Characterisation of immune function in Amazonians is important both for documenting human biological diversity and for understanding and addressing the health challenges facing Amazonian peoples. Understanding how immune function responds to ecological conditions also bears on questions of human life history evolution, as immune responses and disease impact profiles of growth, reproduction, senescence and mortality (McDade, 2003; Blackwell et al, 2010, 2015; Pisor et al, 2013). …”

Section: Introductionmentioning

confidence: 99%

“…In general, Tsimane are short and lean, but not undernourished (Foster et al, 2005). Tsimane are predominately a natural fertility population, with a total fertility rate of 9.1 births per woman (Gurven et al, 2007; McAllister et al, 2012; Blackwell et al, 2015). Tsimane breastfeed their infants on-demand, with a mean weaning age of 19 months (Veile et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Immune function in Amazonian horticulturalists

Blackwell

Annals of Human Biology

Suarez³

et al. 2016

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131

Background Amazonian populations are exposed to diverse parasites and pathogens, including protozoal, bacterial, fungal, and helminthic infections. Yet much of our understanding of the immune system is based on industrialised populations where these infections are relatively rare. Aim We examine distributions and age-related differences in 22 measures of immune function for Bolivian forager-horticulturalists and US and European populations. Subjects and Methods Subjects were 6,338 Tsimane aged 0–90 years. Blood samples collected between 2004–2014 were analysed for 5-part blood differentials, C-reactive protein, erythrocyte sedimentation rate (ESR), and total immunoglobulins E, G, A, and M. Flow cytometry was used to quantify naive and non-naïve CD4 and CD8 T cells, natural killer cells, and B cells. Results Compared to reference populations, Tsimane have elevated levels of most immunological parameters, particularly immunoglobulins, eosinophils, ESR, B cells, and natural killer cells. However, monocytes and basophils are reduced and naïve CD4 cells depleted in older age groups. Conclusion Tsimane ecology leads to lymphocyte repertoires and immunoglobulin profiles that differ from those observed in industrialised populations. These differences have consequences for disease susceptibility and co-vary with patterns of other life history traits, such as growth and reproduction.

“…WBCs also decline with age among Tsimane, particularly lymphocytes and eosinophils, suggesting increasing maintenance costs because older adults are not less likely to experience infection than younger adults (Gurven et al 2009). Systemic immunity shows many indications of chronic activation from infection with helminths, with 70% of Tsimane infected at any given time (Blackwell et al 2011; Blackwell et al 2013; Blackwell et al 2015; Blackwell et al 2016); coinfection is not uncommon (Blackwell et al 2013; Martin et al 2013). Serum immunoglobulins are two orders of magnitude higher than among US adults, especially for IgE (highly indicative of infection with helminths) (Blackwell et al 2011).…”

Section: Methodsmentioning

confidence: 99%

High resting metabolic rate among Amazonian forager‐horticulturalists experiencing high pathogen burden

Gurven

American J Phys Anthropol

Stieglitz

et al. 2016

Self Cite

101

Objectives Resting metabolic rate (RMR) reflects energetic costs of homeostasis and accounts for 60-75% of total energy expenditure (TEE). Lean mass and physical activity account for much RMR variability, but the impact of prolonged immune activation from infection on human RMR is unclear in naturalistic settings. We evaluate the effects of infection on mass-corrected RMR among Bolivian forager-horticulturalists, and assess whether RMR declines more slowly with age than in hygienic sedentary populations, as might be expected if older adults experience high pathogen burden. Materials and Methods RMR was measured by indirect calorimetry (Fitmate MED, Cosmed) in 1,300 adults aged 20-90 and TEE was measured using doubly labeled water (n= 40). Immune biomarkers, clinical diagnoses and anthropometrics were collected by the Tsimane Health and Life History Project. Results Tsimane have higher RMR and TEE than people in sedentary industrialized populations. Tsimane RMR is 18-47% (women) and 22-40% (men) higher than expected using six standard prediction equations. Tsimane mass-corrected TEE is similarly elevated compared to Westerners. Elevated leukocytes and helminths are associated with excess RMR in multivariate regressions, and jointly result in a predicted excess RMR of 10-15%. After age 40, RMR declines by 69 kcal/decade (p<0.0001). Controlling for lean mass and height accounts for 71% of age-related RMR decline, and adding indicators of infection minimally affects the age slope. The residual level of age-related decline from age 40 is 1.2% per decade. Conclusion High pathogen burden may lead to higher metabolic costs, which may be offset by smaller body mass or other energy-sparing mechanisms.