Circumpolar adaptation, social change, and the development of autoimmune thyroid disorders among the Yakut (Sakha) of Siberia

Human cold adaptation: An unfinished agenda v2.0

BACKGROUND

Research on human extreme cold climate adaptations has benefitted from a recent resurgence since Ted Steegmann laid out his Human Cold Adaptation Agenda in 2007. Human biologists have drastically expanded our knowledge in this area during the last 15 years, but we still have a great deal more work to do to fulfill the cold climate adaptation agenda.

METHODS

Here, I follow Steegmann's example by providing a review of cold climate adaptations and setting forth a new, expanded agenda.

RESULTS

I review the foundational work on cold climate adaptations including classic Bergmann, Allen, and Thomson rules as well as early work assessing metabolic differences among Indigenous cold climate populations. From there, I discuss some of the groundbreaking work currently taking place on cold climate adaptations such as brown adipose tissue (a heat generating organ), physical activity levels, metabolic rates, and behavioral/cultural mechanisms. Finally, I present a path forward for future research with a focus on some of the basic extreme cold adaptations as well as how human biologists should approach the effects of climate change on human health and well-being, particularly within a cold climate context.

CONCLUSION

The Arctic has felt the dramatic effects of climate change sooner and more acutely than other parts of the world, making it an ideal location for studying both cold climate adaptations and climate change resilience. Human biologists have a great deal to contribute to the conversation on not only adaptations to extreme cold, but also the ways in which climate change is being embodied by cold climate populations.

To the extreme! How biological anthropology can inform exercise physiology in extreme environments

The fields of biological anthropology and exercise physiology are closely related and can provide mutually beneficial insights into human performance. These fields often use similar methods and are both interested in how humans function, perform, and respond in extreme environments. However, these two fields have different perspectives, ask different questions, and work within different theoretical frameworks and timescales. Biological anthropologists and exercise physiologists can greatly benefit from working together when examining human adaptation, acclimatization, and athletic performance in the extremes of heat, cold, and high-altitude. Here we review the adaptations and acclimatizations in these three different extreme environments. We then examine how this work has informed and built upon exercise physiology research on human performance. Finally, we present an agenda for moving forward, hopefully, with these two fields working more closely together to produce innovative research that improves our holistic understanding of human performance capacities informed by evolutionary theory, modern human acclimatization, and the desire to produce immediate and direct benefits.

No association of BMI and body adiposity with cardiometabolic biomarkers among a small sample of reindeer herders of sub-Arctic Finland

The rising global obesity rate is alarming due to its real health and socioeconomic consequences. Finland, like other circumpolar regions, is also experiencing a rise in obesity . Here we assess BMI, body adiposity, and measures of cardiometabolic health among a small population of reindeer herders in sub-Arctic Finland. We collected anthropometric and biomarker measures at two different time points: October 2018 (N = 20) and January 2019 (N = 21) with a total of 25 unique individuals across the data collection periods (ages 20-64). Anthropometric measures included height, weight, age, and body composition. Biomarkers included measures of cholesterol, fasting glucose, HDL cholesterol, LDL cholesterol, and triglyceride levels. Over 70% of this sample was classified as "overweight" and "obese" as categorised by BMI and 64% classified as "overfat" based on body fat percentage. However, there was no significant relationship between BMI and body fat percentage with any of the measured biomarkers. Although the sample size is small, the results of this study suggest there might not be a strong correlation between BMI, body adiposity, and cardiometabolic health indices within this population - a pattern that has been documented elsewhere. However, further study is needed to confirm this lack of a correlation.

Brown adipose tissue thermogenesis among a small sample of reindeer herders from sub-Arctic Finland

Introduction

Interest in human physiological responses to cold stress have seen a resurgence in recent years with a focus on brown adipose tissue (BAT), a mitochondria dense fat specialized for heat production. However, a majority of the work examining BAT has been conducted among temperate climate populations.

Methods

To expand our understanding of BAT thermogenesis in a cold climate population, we measured, using indirect calorimetry and thermal imaging, metabolic rate and body surface temperatures of BAT-positive and BAT-negative regions at room temperature, and mild cold exposure of resting participants from a small sample of reindeer herders (N = 22, 6 females) from sub-Arctic Finland.

Results

We found that most herders experienced a significant mean 8.7% increase in metabolic rates, preferentially metabolized fatty acids, and maintained relatively warmer body surface temperatures at the supraclavicular region (known BAT location) compared to the sternum, which has no associated BAT. These results indicate that the herders in this sample exhibit active BAT thermogenesis in response to mild cold exposure.

Conclusions

This study adds to the rapidly growing body of work looking at the physiological and thermoregulatory significance of BAT and the important role it may play among cold stressed populations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-022-00290-4.

Minimally invasive biomarkers in human population biology research, part 2: An introduction to the special issue

Over the past several decades, biomarkers have become indispensable tools in human biology, allowing researchers to investigate biocultural and evolutionary questions and to generate basic data on health and well-being. Human biologists are central players in biomarker methods development, pioneering the creation of "field friendly," minimally invasively collected biomarker approaches, as well as leading the innovative use of biomarkers, most notably to map the complex pathways from social and environmental conditions to altered physiology to health effects. This special issue, Part 2 of a collection focused on minimally invasively collected biomarkers, is comprised of nine papers that jointly contribute to driving the science of biomarker methods development and application. This compilation of papers engages with topics such as biological normalcy, ecoimmunology, and the ethics of working with vulnerable and underserved populations. It also focuses attention on research areas at present not emphasized in human biology such as bone turnover markers as a window onto osteoporosis and osteoarthritis and the use of cancer-related biomarkers in population screening and epidemiology. Taken together, these papers help draw the roadmap for future biomarker work, emphasizing: (1) the need for systematic and transparent approaches to assay validation, with open access publication; (2) simultaneous measurement of multiple biomarkers and expanded use of instrument platforms that increase the range of physiological, genomics, and omics markers available to researchers; and, (3) increased attention to ethics and researcher responsibilities, encouraging a mindset that recognizes our obligation to provide benefits to individuals and communities and to help redress past abuses.

Minimally invasive biomarkers in human and non-human primate evolutionary biology: Tools for understanding variation and adaptation

BACKGROUND

The use of minimally invasive biomarkers (MIBs - physiological biomarkers obtained from minimally invasive sample types) has expanded rapidly in science and medicine over the past several decades. The MIB approach is a methodological strength in the field of human and non-human primate evolutionary biology (HEB). Among humans and our closest relatives, MIBs provide unique opportunities to document phenotypic variation and to operationalize evolutionary hypotheses.

AIMS

This paper overviews the use of MIBs in HEB. Our objectives are to (1) highlight key research topics which successfully implement MIBs, (2) identify promising yet under-investigated areas of MIB application, and (3) discuss current challenges in MIB research, with suggestions for advancing the field.

DISCUSSION AND CONCLUSIONS

A range of MIBs are used to investigate focal topics in HEB, including energetics and life history variation/evolution, developmental plasticity, and social status and dominance relationships. Nonetheless, we identify gaps in existing MIB research on traits such as physical growth and gut function that are central to the field. Several challenges remain for HEB research using MIBs, including the need for additional biomarkers and methods of assessment, robust validations, and approaches that are standardized across labs and research groups. Importantly, researchers must provide better support for adaptation and fitness effects in hypothesis testing (e.g., by obtaining complementary measures of energy expenditure, demonstrating redundancy of function, and performing lifetime/longitudinal analyses). We point to continued progress in the use of MIBs in HEB to better understand the past, present, and future of humans and our closest primate relatives.

Commentary—fat but fit…and cold? Potential evolutionary and environmental drivers of metabolically healthy obesity

As global obesity rates continue to rise, it is important to understand the origin, role and range of human variation of body mass index (BMI) in assessing health and healthcare. A growing body of evidence suggests that BMI is a poor indicator of health across populations, and that there may be a metabolically healthy obese phenotype. Here, we review the reasons why BMI is an inadequate tool for assessing cardiometabolic health. We then suggest that cold climate adaptations may also render BMI an uninformative metric. Underlying evolutionary and environmental drivers may allow for heat conserving larger body sizes without necessarily increasing metabolic health risks. However, there may also be a potential mismatch between modern obesogenic environments and adaptations to cold climates, highlighting the need to further investigate the potential for metabolically healthy obese phenotypes among circumpolar and other populations as well as the broader meaning for metabolic health.

Measuring attack on self: The need for field-friendly methods development and research on autoimmunity in human biology

BACKGROUND

Autoimmune and inflammatory disorder (AIID) prevalence appears to be increasing in all but the world's poorest regions and countries. Autoimmune diseases occur when there is a breakdown in processes that regulate inflammation and self-recognition by immune cells. Very few field-based studies have been conducted among Indigenous populations and underserved communities with limited access to medical care. This is due, in part, to the fact that autoimmune diseases are difficult to diagnose, even in clinical settings. In remote field settings these difficulties are compounded by the absence of infrastructure necessary for sample storage and analysis, and the lack of hospital/clinic access for more invasive diagnostic procedures. Because of these limitations, little is known about the prevalence of autoimmunity outside wealthy regions and clinical settings.

AIMS

The present paper discusses why AIID are of critical importance in human biology research and why more work needs to be devoted to validating, testing, and utilizing methods for detecting autoantibodies and other biomarkers related to autoimmunity in field-friendly, minimally invasively-collected samples. This paper reviews some of the methods used to diagnose AIIDs in clinical settings, and highlights methods that have been used in studies within human biology and related fields, emphasizing the invasiveness of specific methods and their feasibility in remote field settings.

DISCUSSION AND CONCLUSIONS

Risk for AIID is affected by several reproductive, dietary, environmental, and genetic factors. Human biologists have unique perspectives that they can bring to autoimmunity research, and more population-based studies on autoimmunity are needed within these and related fields.

Development and validation of an ELISA for a biomarker of thyroid dysfunction, thyroid peroxidase autoantibodies (TPO-Ab), in dried blood spots

BACKGROUND

The prevalence of allergic and autoimmune conditions has been steadily increasing in wealthy nations over the past century. One hypothesis put forward to explain this is the Old Friends Hypothesis, which posits that increased hygiene, urbanization, and lifestyle changes have reduced our exposure to parasites and microbes that we co-evolved with, resulting in immune dysregulation. However, research in traditionally living populations, who are exposed to greater parasite and pathogen loads such as those encountered during our evolution, is limited, in part due to a lack of minimally invasive, field-friendly biomarkers of autoimmune disorders. We therefore developed an ELISA to assess positivity for thyroid peroxidase autoantibody (TPO-Ab), an indicator of autoimmune thyroid disease, based on dried blood spot (DBS) samples.

RESULTS

We used the Accubind anti-thyroid peroxidase test system to screen our validation samples comprising matched fingerprick DBS, venous DBS, and plasma samples from 182 adults. After confirming that we had TPO-Ab-positive individuals in our validation sample (n = 12), we developed an indirect ELISA to measure TPO-Ab levels from one 3-mm DBS punch. The sensitivity and specificity of our assay for DBS samples ranged from 91.7-100% and 98.2-98.8%, respectively, using a cut-off value of ≥ 26 IU/mL. Intra-assay reliability for duplicate quality control DBS punches was 5.2%, while inter-assay reliability ranged from 11.5-24.4% for high, medium, and low DBS controls. Dilutional linearity ranged from 80 to 120%, and spike and recovery experiments indicated that the DBS matrix does not interfere with the detection of TPO-Ab. TPO-Ab levels remained stable in DBS samples stored at - 28 °C or - 80 °C, but decreased over time in DBS samples kept at 22 °C or at 37 °C.

CONCLUSIONS

We developed an in-house, kit-independent indirect ELISA assay to determine individuals' TPO-Ab positivity based on dried blood spots, representing a cost-effective method with potential applications in a range of research settings.

Recent Advances in Autoimmune Thyroid Diseases

Autoimmune thyroid disease (AITD) includes hyperthyroid Graves disease, hypothyroid autoimmune thyroiditis, and subtle subclinical thyroid dysfunctions. AITD is caused by interactions between genetic and environmental predisposing factors and results in autoimmune deterioration. Data on polymorphisms in the AITD susceptibility genes, related environmental factors, and dysregulation of autoimmune processes have accumulated over time. Over the last decade, there has been progress in the clinical field of AITD with respect to the available diagnostic and therapeutic methods as well as clinical consensus. The updated clinical guidelines allow practitioners to identify the most reasonable and current approaches for proper management. In this review, we focus on recent advances in understanding the genetic and environmental pathogenic mechanisms underlying AITD and introduce the updated set of clinical guidelines for AITD management. We also discuss other aspects of the disease such as management of subclinical thyroid dysfunction, use of levothyroxine plus levotriiodothyronine in the treatment of autoimmune hypothyroidism, risk assessment of long-standing antithyroid drug therapy in recurrent Graves' hyperthyroidism, and future research needs.

The Pathogenesis of Hashimoto's Thyroiditis: Further Developments in our Understanding

Hashimoto's thyroiditis (HT) is part of a spectrum of thyroid autoimmune conditions and this review provides an update on the latest developments in the field. HT has a genetic predisposition with a number of immune-related and thyroid-specific genes conferring disease susceptibility. However, disentangling genes with protective and predisposing effect is a complex process that requires further work. The recent increase in the incidence of HT implicates environmental factors in disease pathogenesis including improved hygiene, increased dietary iodine intake, new treatment modalities and chemical agents. Additional unmodifiable predisposing factors include stress, climate, age and gender. Both cellular and humoral immunity play a role in HT pathogenesis. Defects in T regulatory cells and increased activation of follicular helper T cells may have a role in disease initiation/perpetuation. Infiltrating lymphocytes can be directly cytotoxic to thyroid follicular cells (TFC) or may affect cell viability/function indirectly through cytokine production, which alters TFC integrity and modulates their metabolic and immune function. Thyroid peroxidase and thyroglobulin antibodies are present in the majority of HT patients and help with management decisions. Antibodies against the sodium iodide symporter and pendrin are present in a minority with little known about their clinical relevance. In addition to immune cells, recent work has identified DNA fragments, generated following cell death, and micro RNA as potential factors in HT pathogenesis. Despite the large number of studies, the mechanistic pathways in HT are still not fully understood and further work is required to enhance our knowledge and identify novel preventative and therapeutic clinical targets.

Socio-demographic predictors of sleep complaints in indigenous Siberians with a mixed economy

OBJECTIVES

Socio-demographic indicators closely relate to sleep in industrialized populations. However we know very little about how such factors impact sleep in populations undergoing industrialization. Within populations transitioning to the global economy, the preliminary evidence has found an inconsistent relationship between socio-demographics and sleep complaints across countries and social strata.

MATERIALS AND METHODS

Surveys were conducted on a sample of rural Sakha (Yakut) adults (n = 168) during the autumn of 2103 to assess variation in socio-demographics and sleep complaints, including trouble sleeping and daytime sleepiness. Socio-demographic variables included age, gender, socioeconomic measures, and markers of traditional/market-based lifestyle. We tested whether the socio-demographic variables predicted sleep complaints using bivariate analyses and multiple logistic regressions.

RESULTS

Trouble sleeping was reported by 18.5% of the participants and excessive daytime sleepiness (EDS) by 17.3%. Trouble sleeping was significantly predicted by older age, female gender, and mixing traditional and market-based lifestyles. EDS was not significantly predicted by any socio-demographic variable.

DISCUSSION

These findings support the few large-scale studies that found inconsistent relationships between measures of socioeconomic status and sleep complaints in transitioning populations. Employing a mix of traditional and market-based lifestyles may leave Sakha in a space of vulnerability, leading to trouble sleeping.

Seasonal variation in basal metabolic rates among the Yakut (Sakha) of Northeastern Siberia

OBJECTIVES

Previous research has shown that indigenous circumpolar populations have elevated basal metabolic rates (BMRs), yet few studies have explored whether metabolic rates increase during the winter. This study addresses this gap by examining seasonal variation in BMR and its associations with thyroid function and lifestyle factors among the Yakut (Sakha) of Siberia.

METHODS

Anthropometric dimensions, BMR, and thyroid hormone levels (free triiodothyronine [fT3], free thyroxine [fT4], thyroid-stimulating hormone [TSH]) were measured on two occasions (July/August, 2009 and January 2011) on a sample of 94 Yakut (Sakha) adults (35 men, 59 women) from the rural village of Berdygestiakh, Sakha Republic, Russia.

RESULTS

Seasonal changes in BMR varied by age. Younger Yakut adults (19-49 years) showed significant elevations in winter-time BMR of 6% (P < 0.05), whereas older individuals (≥50 years) showed modest declines (2%; n.s.). Both younger and older Yakut men and women showed increased respiratory quotients during the winter. FT3 and fT4 levels significantly declined during the winter in both younger and older Yakut men and women (P < 0.05). Lifestyle factors were significant predictors of BMR variation, particularly among older men and women.

CONCLUSIONS

Among the Yakut, increased wintertime BMR was observed among younger but not older adults, whereas all adults showed sharp reductions in free thyroid hormone levels during the winter. Among men, greater participation in subsistence activities was associated with increased BMRs and greater fat oxidation. Among women, variation in food use had the strongest impact on metabolic function.

Objectively measured physical activity and sedentary behaviour of Yakut (Sakha) adults

BACKGROUND

Circumpolar regions are undergoing social and economic transition, which often corresponds to a behavioural transition. Yet, physical activity and sedentary behaviour are rarely objectively measured within these groups.

AIM

This study aimed to characterize objectively measured physical activity and sedentary behaviour in a sample of indigenous Siberians.

SUBJECTS AND METHODS

Yakut (Sakha) adults (n = 68, 32 men) underwent anthropometry, interviews and wore a triaxial accelerometer for two days. Time spent in moderate-to-vigorous physical activity (MVPA) or sedentary behaviour was calculated using a single axis and also all three axes.

RESULTS

Men spent significantly more time in MVPA than women, although no sex difference was found in sedentary behaviour. Participants were far more active and less sedentary when classified using all three axes (vector magnitude) than a single axis. Television viewing time significantly related to sedentary behaviour in men only.

CONCLUSION

The Yakut have gender differences in amount and predictors of physical activity and sedentary behaviour. Triaxial accelerometry is more sensitive to daily physical activity in free living populations than single axis.

The immunopathogenesis of chronic autoimmune thyroiditis one century after hashimoto

Hakaru Hashimoto described 4 patients with a hitherto unknown cause for goitre, struma lymphomatosa, a century ago. He was careful to distinguish this from Riedel thyroiditis but it has become clear that fibrosis and atrophy of the thyroid are indeed components of Hashimoto thyroiditis, and in rare cases IgG4-related sclerosing disease may be an outcome. Although the cause of the lymphocytic infiltration was unknown to Hashimoto, we now know through the pioneering studies of N.R. Rose and E. Witebsky [J Immunol 1956;76:417-427] that this condition is the archetype for autoimmune destruction as a disease mechanism. In the last two decades in particular, there has been huge interest in unravelling the genetic basis for this and related autoimmune disorders. The list of polymorphisms associated with autoimmune thyroid disease grows each year, and in the case of vitiligo, which is frequently found in association with thyroid autoimmunity, we know that 27 separate susceptibility loci account for less than 20% of the heritability of this condition. Environmental and existential factors may turn out to be just as complex in number and in interactions. We can thus imagine a 'Swiss cheese' model for the causation of autoimmune thyroid disease, in which the effects of cumulative weaknesses line up - like the holes in slices of cheese - to allow the catastrophic event of autoimmune destruction to occur.