Inflammatory Gene Variants in the Tsimane, an Indigenous Bolivian Population with a High Infectious Load

Abstract

The Tsimane of lowland Bolivia are an indigenous forager-farmer population living under conditions resembling pre-industrial European populations, with high infectious morbidity, high infection and inflammation, and shortened life expectancy. Analysis of 917 persons ages 5 to 60+ showed that allele frequencies of 9 SNPs examined in the apolipoprotein E (apoE), C-reactive protein (CRP), and interleukin-6 (IL-6) genes differed from some European, African, and north Asian-derived populations. The apoE2 allele was absent, whereas four SNPs related to CRP and IL-6 were monomorphic: CRP (rs1800947, rs3093061, and rs3093062) and IL-6 (rs1800795). No significant differences in apoE, CRP, and IL-6 variants across age were found CRP levels were higher in carriers of two CRP proinflammatory SNPs, whereas they were lower in carriers of apoE4. Taken together, the evidence for (1) different allele frequencies between the Tsimane and other populations and (2) the correlations of CRP and apoE alleles with blood CRP may suggest that these variants are under selection in response to a high infection environment.

Immune function in Amazonian horticulturalists

“…Moreover, some differences between Tsimane and industrialised populations may be due to genetic, rather than environmental differences. Analysis of a handful of Tsimane genes do show differences in the frequencies of some immune related genes, though how these link to phenotypes is somewhat unclear (Vasunilashorn et al, 2011). Future analysis of both genetic and environmental variance will be needed to elucidate how genes and environments interact to produce Tsimane immunological patterns.…”

Low mineral density of a weight‐bearing bone among adult women in a high fertility population

“…For example, high IL-6 gene transcription contributes to lean body mass (Wernstedt et al 2004) and potentially reduced bone mass. A promoter SNP (position −174) underlying IL-6 production is monomorphic among Tsimane (Vasunilashorn et al 2011), suggesting a potential mechanism linking genetic history, high infectious burden, reduced body mass, and reduced BMD. Future studies will examine these possibilities to understand why, throughout life, Tsimane female BMD is noticeably lower than that of Ecuadorian Shuar females, who similarly engage in a foraging-horticultural lifestyle but also experience greater market access, reduced pathogen burden, and have lower fertility and higher BMI (Madimenos et al 2012).…”

“…Tsimane total fertility rate is 9 births per woman, mean inter-birth interval (IBI) is 30 months, breastfeeding is on-demand, and mean weaning age is 19 months (Mcallister et al 2012; Veile et al 2014). Tsimane also experience high pathogen burden and lack public health infrastructure, which leads to greater immune activation throughout life (Blackwell et al 2011; Vasunilashorn et al 2010, 2011). In addition, Tsimane regularly experience risk of food shortfalls associated with a mixed foraging and horticultural economy (Gurven et al 2012; Stieglitz et al 2014).…”

Depression as sickness behavior? A test of the host defense hypothesis in a high pathogen population

“…Moreover, depression risk alleles identified by candidate gene and genome-wide association studies are associated with alleles promoting innate and adaptive immunity (12). The types of pro-inflammatory genotypes that are over-represented in depressed samples may, in fact, confer enhanced survivorship in high pathogen environments while reducing survivorship when pathogenic exposures are minimized (24, 25). Although direct evidence that depression induces greater immune activation in response to infection or injury is scant, immune profiles of clinically depressed individuals show strong similarities to the acute phase response that is characterized by an activated innate immune system including elevated blood concentrations of inflammatory biomarkers (18, 26).…”