Thrifty genes for obesity, an attractive but flawed idea, and an alternative perspective: the 'drifty gene' hypothesis

Natural selection shaped the protective effect of the mtDNA lineage against obesity in Han Chinese populations

Mitochondria play a key role in lipid metabolism, and mitochondrial DNA (mtDNA) mutations are thus considered to affect obesity susceptibility by altering oxidative phosphorylation and mitochondrial function. In this study, we investigated mtDNA variants that may affect obesity risk in 2,877 Han Chinese individuals from three independent populations. The association analysis of 16 basal mtDNA haplogroups with body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) revealed that only haplogroup M7 was significantly negatively correlated with all three adiposity-related anthropometric traits in the overall cohort (P=0.003 for BMI, P=1×10-5 for WC, P=0.005 for WHR), which was verified by the analysis of a single population, i.e., the Zhengzhou population. Furthermore, subhaplogroup analysis suggested that M7b1a1 was the most likely haplogroup associated with a decreased obesity risk, and the variation T12811C (causing Y159H in ND5) harbored in M7b1a1 may be the most likely candidate for altering mitochondrial function. Specifically, we found that proportionally more nonsynonymous mutations accumulated in M7b1a1 carriers, indicating that M7b1a1 was either under positive selection or subject to a relaxation of selective constraints. We also found that nuclear variants, especially in DACT2 and PIEZO1, may functionally interact with M7b1a1.

The complex web of obesity: from genetics to precision medicine

INTRODUCTION

Obesity is a growing public health concern affecting both children and adults. Since it involves both genetic and environmental components, the management of obesity requires both, an understanding of the underlying genetics and changes in lifestyle. The knowledge of obesity genetics will enable the possibility of precision medicine in anti-obesity medications.

AREAS COVERED

Here, we explore health complications and the prevalence of obesity. We discuss disruptions in energy balance as a symptom of obesity, examining evolutionary theories, its multi-factorial origins, and heritability. Additionally, we discuss monogenic and polygenic obesity, the converging biological pathways, potential pharmacogenomics applications, and existing anti-obesity medications - specifically focussing on the leptin-melanocortin and incretin pathways. Comparisons between childhood and adult obesity genetics are made, along with insights into structural variants, epigenetic changes, and environmental influences on epigenetic signatures.

EXPERT OPINION

With recent advancements in anti-obesity drugs, genetic studies pinpoint new targets and allow for repurposing existing drugs. This creates opportunities for genotype-informed treatment options. Also, lifestyle interventions can help in the prevention and treatment of obesity by altering the epigenetic signatures. The comparison of genetic architecture in adults and children revealed a significant overlap. However, more robust studies with diverse ethnic representation is required in childhood obesity.

Relation Between Obesity and Type 2 Diabetes: Evolutionary Insights, Perspectives and Controversies

PURPOSE OF REVIEW

Since the mid-twentieth century, obesity and its related comorbidities, notably insulin resistance (IR) and type 2 diabetes (T2D), have surged. Nevertheless, their underlying mechanisms remain elusive. Evolutionary medicine (EM) sheds light on these issues by examining how evolutionary processes shape traits and diseases, offering insights for medical practice. This review summarizes the pathogenesis and genetics of obesity-related IR and T2D. Subsequently, delving into their evolutionary connections. Addressing limitations and proposing future research directions aims to enhance our understanding of these conditions, paving the way for improved treatments and prevention strategies.

RECENT FINDINGS

Several evolutionary hypotheses have been proposed to unmask the origin of obesity-related IR and T2D, e.g., the "thrifty genotype" hypothesis suggests that certain "thrifty genes" that helped hunter-gatherer populations efficiently store energy as fat during feast-famine cycles are now maladaptive in our modern obesogenic environment. The "drifty genotype" theory suggests that if thrifty genes were advantageous, they would have spread widely, but proposes genetic drift instead. The "behavioral switch" and "carnivore connection" hypotheses propose insulin resistance as an adaptation for a brain-dependent, low-carbohydrate lifestyle. The thrifty phenotype theory suggests various metabolic outcomes shaped by genes and environment during development. However, the majority of these hypotheses lack experimental validation. Understanding why ancestral advantages now predispose us to diseases may aid in drug development and prevention of disease. EM helps us to understand the evolutionary relation between obesity-related IR and T2D. But still gaps and contradictions persist. Further interdisciplinary research is required to elucidate complete mechanisms.

Changes in weight status among "Ju/'hoansi" San hunter-gatherers between 1968/69 and 1987-The effects of nutritional transition, sex and age

BACKGROUND

Changes in lifestyle and dietary habits that hunter-gatherer populations have undergone in recent decades have often led to rising obesity rates with disastrous consequences for their health.

OBJECTIVES

The associations between dietary habits and weight status were studied in 238 "Ju/'hoansi" San (93 women and 145 men) aged between 18 and 65 years in northern Namibia in 1987. Weight status was estimated based on the World Health Organization body mass index (BMI) categories, and dietary habits were recorded using food recall methods. Anthropometrics and weight status were compared with those of a sex- and age-matched sample of "Ju/'hoansi" San people collected by Nancy Howell in 1968/69.

RESULTS

Body weight had increased significantly among "Ju/'hoansi" San people from 1968/69 to 1987. The number of underweight people decreased from 1968/69 to 1987. In 1987, most participants (60.9%) were of normal weight. Overweight was found in 1.3% of the women, but not among men. No participants were obese. Less than 4% of the women and less than 2% of the men consumed exclusively traditional hunter-gatherer food. Westernized food products were significantly (p < 0.001) more common among men and younger people. Dietary patterns were significantly associated with weight status. The less traditional the diet, the higher the BMI (p < 0.001).

CONCLUSION

The transition to domestic agricultural and westernized foods was positively associated with increasing BMI. Overweight, however, was still an extremely rare condition in this population in 1987.

Childhood environmental unpredictability and hoarding: Mediating roles of attachment and security

Life history theory provides a unified perspective for understanding human behaviors as adaptive strategies to specific environmental conditions. Within this theoretical framework, hoarding emerges as a behavior reflecting an evolved strategy in response to unpredictable environmental challenges, serving as a buffer against resource scarcity and enhancing survival prospects. This study aimed to explore the key roles of childhood environmental unpredictability, attachment, and sense of security in the development of hoarding. 662 participants completed scales on childhood environmental unpredictability, Revised Experiences in Close Relationships (ECR-R), sense of insecurity, and Savings Inventory-Revised (SI-R). The results showed that childhood environmental unpredictability was significantly positively correlated with hoarding. Attachment anxiety and sense of security individually mediate the effect of childhood environmental unpredictability on hoarding. Additionally, 'attachment anxiety--sense of security' and 'attachment avoidance--sense of security' serve as chain mediators in this relationship separately. This study offers insights into the cognitive-behavioral model of hoarding, highlighting the importance of life history theory in examining childhood environmental unpredictability's relationship with hoarding. It also integrates insights from the psychosocial acceleration theory into our comprehension of hoarding's development. Future research directions are also discussed.

Selection and adaptation in human migration

This article reviews the ways migration shapes human biology. This includes the physiological and genetic, but also socio-cultural aspects such as organization, behavior, and culture. Across disciplines I highlight the multiple levels of cultural and genetic selection whereby individuals and groups adapt to pressures along a migration timeline: the origin, transit, and destination. Generally, the evidence suggests that selective pressures and adaptations occur at the individual, family, and community levels. Consequently, across levels there are negotiations, interactions, and feedbacks that shape migration outcomes and the trajectory of evolutionary change. The rise and persistence of migration-relevant adaptations emerges as a central question, including the maintenance of cumulative culture adaptations, the persistence of "cultures of migration," as well as the individual-level physiological and cognitive adaptations applied to successful transit and settlement in novel environments.

Seeking satiety: From signals to solutions

Remedies for the treatment of obesity date to Hippocrates, when patients with obesity were directed to "reduce food and avoid drinking to fullness" and begin "running during the night." Similar recommendations have been repeated ever since, despite the fact that they are largely ineffective. Recently, highly effective therapeutics were developed that may soon enable physicians to manage body weight in patients with obesity in a manner similar to the way that blood pressure is controlled in patients with hypertension. These medicines have grown out of a revolution in our understanding of the molecular and neural control of appetite and body weight, reviewed here.

Models of body weight and fatness regulation

Body weight and fatness appear to be regulated phenomena. Several different theoretical models are available to capture the essence of this idea. These include the set-point, dynamic equilibrium, adiposity force, control theory-settling point, Hall-Guo, operation point and dual intervention point (DIP) models. The set-point model posits a single reference point around which levels of fat are regulated. The dynamic equilibrium model suggests that the apparent regulation of body fat around a reference point is an illusion owing to the necessary impacts of weight change on energy expenditure. Control theory focuses on the importance of feedback gain and suggests set-point and dynamic equilibrium are ends of a continuum of feedback gain. Control theory models have also been called 'settling point' models. The Hall-Guo, operation point and DIP models also bring together the set-point and dynamic equilibrium ideas into a single framework. The DIP proposes a zone of indifference where dynamic equilibrium 'regulation' predominates, bounded by upper and lower intervention points beyond which physiological mechanisms are activated. The drifty gene hypothesis is an idea explaining where this individual variation in the upper intervention point might come from. We conclude that further experiments to test between the models are sorely required. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

Genetics: A Starting Point for the Prevention and the Treatment of Obesity

Obesity is a common, serious, and costly disease. More than 1 billion people worldwide are obese-650 million adults, 340 million adolescents, and 39 million children. The WHO estimates that, by 2025, approximately 167 million people-adults and children-will become less healthy because they are overweight or obese. Obesity-related conditions include heart disease, stroke, type 2 diabetes, and certain types of cancer. These are among the leading causes of preventable, premature death. The estimated annual medical cost of obesity in the United States was nearly $173 billion in 2019 dollars. Obesity is considered the result of a complex interaction between genes and the environment. Both genes and the environment change in different populations. In fact, the prevalence changes as the result of eating habits, lifestyle, and expression of genes coding for factors involved in the regulation of body weight, food intake, and satiety. Expression of these genes involves different epigenetic processes, such as DNA methylation, histone modification, or non-coding micro-RNA synthesis, as well as variations in the gene sequence, which results in functional alterations. Evolutionary and non-evolutionary (i.e., genetic drift, migration, and founder's effect) factors have shaped the genetic predisposition or protection from obesity in modern human populations. Understanding and knowing the pathogenesis of obesity will lead to prevention and treatment strategies not only for obesity, but also for other related diseases.

The melanocortin action is biased toward protection from weight loss in mice

The melanocortin action is well perceived for its ability to regulate body weight bidirectionally with its gain of function reducing body weight and loss of function promoting obesity. However, this notion cannot explain the difficulty in identifying effective therapeutics toward treating general obesity via activation of the melanocortin action. Here, we provide evidence that altered melanocortin action is only able to cause one-directional obesity development. We demonstrate that chronic inhibition of arcuate neurons expressing proopiomelanocortin (POMC) or paraventricular hypothalamic neurons expressing melanocortin receptor 4 (MC4R) causes massive obesity. However, chronic activation of these neuronal populations failed to reduce body weight. Furthermore, gain of function of the melanocortin action through overexpression of MC4R, POMC or its derived peptides had little effect on obesity prevention or reversal. These results reveal a bias of the melanocortin action towards protection of weight loss and provide a neural basis behind the well-known, but mechanistically ill-defined, predisposition to obesity development.

Understanding the contemporary high obesity rate from an evolutionary genetic perspective

The topic of obesity is gaining increasing popularity globally. From an evolutionary genetic perspective, it is believed that the main cause of the high obesity rate is the mismatch between environment and genes after people have shifted toward a modern high-calorie diet. However, it has been debated for over 60 years about how obesity-related genes become prevalent all over the world. Here, we review the three most influential hypotheses or viewpoints, i.e., the thrifty gene hypothesis, the drifty gene hypothesis, and the maladaptation viewpoint. In particular, genome-wide association studies in the recent 10 years have provided rich findings and evidence to be considered for a better understanding of the evolutionary genetic mechanisms of obesity. We anticipate this brief review to direct further studies and inspire the future application of precision medicine in obesity treatment.

The role of physical activity in the regulation of body weight: The overlooked contribution of light physical activity and sedentary behaviors

The role of physical activity (PA) in the regulation of body weight is still a major topic of debate. This may be because studies have essentially focused on the effects of moderate/vigorous PA (MVPA) on body weight while overlooking the other components of PA, namely, light-intensity PA (LPA, daily life activities) and sedentary behaviors (SB, too much sitting). In this review, we will (i) describe the history of changes in PA behaviors that occurred with modernization; (ii) review data from cross-sectional and longitudinal studies that examined the associations between PA, SB, and measures of obesity; (iii) review interventional studies that investigated the effects of changes in PA and SB on body weight and adiposity; and (iv) discuss experimental studies that addressed potential biological mechanisms underlying the effects of PA and SB on weight regulation. Overall recent findings support the importance of considering all components of PA to better understand the regulation of energy balance and suggest an important role for LPA and SB in addition to MVPA on body weight regulation. Longitudinal large-scale rigorous studies are needed to advance our knowledge of the role of PA/SB in combating the obesity epidemic.

Obesity: an evolutionary context

People completely lacking body fat (lipodystrophy/lipoatrophy) and those with severe obesity both show profound metabolic and other health issues. Regulating levels of body fat somewhere between these limits would, therefore, appear to be adaptive. Two different models might be contemplated. More traditional is a set point (SP) where the levels are regulated around a fixed level. Alternatively, dual-intervention point (DIP) is a system that tolerates fairly wide variation but is activated when critically high or low levels are breached. The DIP system seems to fit our experience much better than an SP, and models suggest that it is more likely to have evolved. A DIP system may have evolved because of two contrasting selection pressures. At the lower end, we may have been selected to avoid low levels of fat as a buffer against starvation, to avoid disease-induced anorexia, and to support reproduction. At the upper end, we may have been selected to avoid excess storage because of the elevated risks of predation. This upper limit of control seems to have malfunctioned because some of us deposit large fat stores, with important negative health effects. Why has evolution not protected us against this problem? One possibility is that the protective system slowly fell apart due to random mutations after we dramatically reduced the risk of being predated during our evolutionary history. By chance, it fell apart more in some people than others, and these people are now unable to effectively manage their weight in the face of the modern food glut. To understand the evolutionary context of obesity, it is important to separate the adaptive reason for storing some fat (i.e. the lower intervention point), from the nonadaptive reason for storing lots of fat (a broken upper intervention point). The DIP model has several consequences, showing how we understand the obesity problem and what happens when we attempt to treat it.

Defining the mammalian coactivation of hepatic 12-h clock and lipid metabolism

The 12-h clock coordinates lipid homeostasis, energy metabolism, and stress rhythms via the transcriptional regulator XBP1. However, the biochemical and physiological bases for integrated control of the 12-h clock and diverse metabolic pathways remain unclear. Here, we show that steroid receptor coactivator SRC-3 coactivates XBP1 transcription and regulates hepatic 12-h cistrome and gene rhythmicity. Mice lacking SRC-3 show abnormal 12-h rhythms in hepatic transcription, metabolic functions, systemic energetics, and rate-limiting lipid metabolic processes, including triglyceride, phospholipid, and cardiolipin pathways. Notably, 12-h clock coactivation is not only preserved, with its cistromic activation priming ahead of the zeitgeber cue of light, but concomitant with rhythmic remodeling in the absence of food. These findings reveal that SRC-3 integrates the mammalian 12-h clock, energy metabolism, and membrane and lipid homeostasis and demonstrates a role for the 12-h clock machinery as an active transcriptional mechanism in anticipating physiological and metabolic energy needs and stresses.

Addressing Structural Racism Is Critical for Ameliorating the Childhood Obesity Epidemic in Black Youth

Racism and childhood obesity are both pervasive factors adversely affecting the health and wellbeing of children and adolescents in the United States. The association between racism and obesity has been touched upon in the literature; yet most work has focused on a few dimensions of intersectionality of these two domains at one time. The renewed focus on structural racism as the primary contributor to distress of Black individuals in the United States has highlighted the urgency of identifying the contributions of racism to the childhood obesity epidemic. The current article is not a complete review of the literature, rather, it is meant to take a broad narrative review of the myriad ways in which racism contributes to the obesity epidemic in Black youth to serve as a call to action for more research, prevention, and intervention. The current article illustrates how a number of mechanisms for the etiology and maintenance of obesity are heavily influenced by racism and how addressing racism is critical for ameliorating the childhood obesity epidemic.

Obesity epidemic through the prism of evolutionary processes

Currently, obesity has become one of the most serious public health problems. It takes millions of lives worldwide every year due to its association with numerous diseases and leads to significant social and economic losses. It is generally accepted that obesity is the result of the interaction of genes and environment, and the predisposition to it lies in our evolutionary past. This review discusses the role of adipose tissue in human evolution, the factors specifying a person’s predisposition to obesity, the main hypotheses for obesity origin, and potential prevention and treatment strategies arising from them. The evolutionary significance of visceral adipose tissue and some ethnic and sex characteristics associated with its distribution are also considered.

An Overview on the Therapeutic Function of Foods Enriched with Plant Sterols in Diabetes Management

Diabetes is one of the most significant health issues across the world. People identified with diabetes are more vulnerable to various infections and are at a greater risk of developing cardiovascular diseases. The plant-based food we consume often contains many sterol-based bioactive compounds. It is well documented that these compounds could effectively manage the processes of insulin metabolism and cholesterol regulation. Insulin resistance followed by hyperglycemia often results in oxidative stress level enhancement and increased reactive oxygen species production. At the molecular level, these changes induce apoptosis in pancreatic cells and hence lead to insulin insufficiency. Studies have proved that plant sterols can lower inflammatory and oxidative stress damage connected with DNA repair mechanisms. The effective forms of phyto compounds are polyphenols, terpenoids, and thiols abundant in vegetables, fruits, nuts, and seeds. The available conventional drug-based therapies for the prevention and management of diabetes are time-consuming, costly, and with life-threatening side effects. Thereby, the therapeutic management of diabetes with plant sterols available in our daily diet is highly welcome as there are no side effects. This review intends to offer an overview of the present scenario of the anti-diabetic compounds from food ingredients towards the therapeutic beneficial against diabetes.

Evolution of Lactase Persistence: Turbo-Charging Adaptation in Growth Under the Selective Pressure of Maternal Mortality?

The emergence of the capacity to digest milk in some populations represents a landmark in human evolution, linking genetic change with a component of niche construction, namely dairying. Alleles promoting continued activity of the enzyme lactase through the life-course (lactase persistence) evolved in several global regions within the last 7,000 years. In some European regions, these alleles underwent rapid selection and must have profoundly affected fertility or mortality. Elsewhere, alleles spread more locally. However, the functional benefits underlying the rapid spread of lactase persistence remain unclear. Here, we set out the hypothesis that lactase persistence promoted skeletal growth, thereby offering a generic rapid solution to childbirth complications arising from exposure to ecological change, or to new environments through migration. Since reduced maternal growth and greater neonatal size both increase the risk of obstructed labour, any ecological exposure impacting these traits may increase maternal mortality risk. Over many generations, maternal skeletal dimensions could adapt to new ecological conditions through genetic change. However, this adaptive strategy would fail if ecological change was rapid, including through migration into new niches. We propose that the combination of consuming milk and lactase persistence could have reduced maternal mortality by promoting growth of the pelvis after weaning, while high calcium intake would reduce risk of pelvic deformities. Our conceptual framework provides locally relevant hypotheses to explain selection for lactase persistence in different global regions. For any given diet and individual genotype, the combination of lactase persistence and milk consumption would divert more energy to skeletal growth, either increasing pelvic dimensions or buffering them from worsening ecological conditions. The emergence of lactase persistence among dairying populations could have helped early European farmers adapt rapidly to northern latitudes, East African pastoralists adapt to sudden climate shifts to drier environments, and Near Eastern populations counteract secular declines in height associated with early agriculture. In each case, we assume that lactase persistence accelerated the timescale over which maternal skeletal dimensions could change, thus promoting both maternal and offspring survival. Where lactase persistence did not emerge, birth weight was constrained at lower levels, and this contributes to contemporary variability in diabetes risk.

Evolutionary forces in diabetes and hypertension pathogenesis in Africans

Rates of type 2 diabetes (T2D) and hypertension are increasing rapidly in urbanizing sub-Saharan Africa (SSA). While lifestyle factors drive the increases in T2D and hypertension prevalence, evidence across populations shows that genetic variation, which is driven by evolutionary forces including a natural selection that shaped the human genome, also plays a role. Here we report the evidence for the effect of selection in African genomes on mechanisms underlying T2D and hypertension, including energy metabolism, adipose tissue biology, insulin action and salt retention. Selection effects found for variants in genes PPARA and TCF7L2 may have enabled Africans to respond to nutritional challenges by altering carbohydrate and lipid metabolism. Likewise, African-ancestry-specific characteristics of adipose tissue biology (low visceral adipose tissue [VAT], high intermuscular adipose tissue and a strong association between VAT and adiponectin) may have been selected for in response to nutritional and infectious disease challenges in the African environment. Evidence for selection effects on insulin action, including insulin resistance and secretion, has been found for several genes including MPHOSPH9, TMEM127, ZRANB3 and MC3R. These effects may have been historically adaptive in critical conditions, such as famine and inflammation. A strong correlation between hypertension susceptibility variants and latitude supports the hypothesis of selection for salt retention mechanisms in warm, humid climates. Nevertheless, adaptive genomics studies in African populations are scarce. More work is needed, particularly genomics studies covering the wide diversity of African populations in SSA and Africans in diaspora, as well as further functional assessment of established risk loci.

Lipid metabolism in adaptation to extreme nutritional challenges

Food shortages represent a common challenge for most animal species. As a consequence, many have evolved metabolic strategies encompassing extreme starvation-resistance capabilities, going without food for months or even years. One such strategy is to store substantial levels of fat when food is available and release these energy-rich lipids during periods of dearth. In this review, we provide an overview of the strategies and pathways underlying the extreme capacity for animals to store and mobilize lipids during nutritionally stressful environmental conditions and highlight accompanying resilience phenotypes that allow these animals to develop and tolerate such profound metabolic phenotypes.

Drosophila as a useful model for understanding the evolutionary physiology of obesity resistance and metabolic thrift

Evolved metabolic thriftiness in humans is a proposed contributor to the obesity epidemic. Insect models have been shown to evolve both 'metabolic thrift' in response to rearing on high-protein diets that promote leanness, and 'obesity resistance' when reared on fattening high-carbohydrate, low-protein foods. Despite the hypothesis that human obesity is caused by evolved metabolic thrift, genetic contributions to this physiological trait remain elusive. Here we conducted a pilot study to determine whether thrift and obesity resistance can arise under laboratory based 'quasi-natural selection' in the genetic model organism Drosophila melanogaster. We found that both these traits can evolve within 16 generations. Contrary to predictions from the 'thrifty genotype/phenotype' hypothesis, we found that when animals from a metabolic thrift inducing high-protein environment are mismatched to fattening high-carbohydrate foods, they did not become 'obese'. Rather, they accumulate less triglyceride than control animals, not more. We speculate that this may arise through as yet un-quantified parental effects - potentially epigenetic. This study establishes that D. melanogaster could be a useful model for elucidating the role of the trans- and inter-generational effects of diet on the genetics of metabolic traits in higher animals.

Assessment of the potential role of natural selection in type 2 diabetes and related traits across human continental ancestry groups: comparison of phenotypic with genotypic divergence

AIMS/HYPOTHESIS

Prevalence of type 2 diabetes differs among human ancestry groups, and many hypotheses invoke differential natural selection to account for these differences. We sought to assess the potential role of differential natural selection across major continental ancestry groups for diabetes and related traits, by comparison of genetic and phenotypic differences.

METHODS

This was a cross-sectional comparison among 734 individuals from an urban sample (none of whom was more closely related to another than third-degree relatives), including 83 African Americans, 523 American Indians and 128 European Americans. Participants were not recruited based on diabetes status or other traits. BMI was calculated, and diabetes was diagnosed by a 75 g oral glucose tolerance test. In those with normal glucose tolerance (n = 434), fasting insulin and 30 min post-load insulin, adjusted for 30 min glucose, were taken as measures of insulin resistance and secretion, respectively. Whole exome sequencing was performed, resulting in 97,388 common (minor allele frequency ≥ 5%) variants; the coancestry coefficient (F_ST) was calculated across all markers as a measure of genetic divergence among ancestry groups. The phenotypic divergence index (P_ST) was also calculated from the phenotypic differences and heritability (which was estimated from genetic relatedness calculated empirically across all markers in 761 American Indian participants prior to the exclusion of close relatives). Under evolutionary neutrality, the expectation is P_ST = F_ST, while for traits under differential selection P_ST is expected to be significantly greater than F_ST. A bootstrap procedure was used to test the hypothesis P_ST = F_ST. RESULTS: With adjustment for age and sex, prevalence of type 2 diabetes was 34.0% in American Indians, 12.4% in African Americans and 10.4% in European Americans (p = 2.9 × 10^-10 for difference among groups). Mean BMI was 36.3, 33.4 and 33.0 kg/m², respectively (p = 1.9 × 10^-7). Mean fasting insulin was 63.8, 48.4 and 45.2 pmol/l (p = 9.2 × 10^-5), while mean 30 min insulin was 559.8, 553.5 and 358.8 pmol/l, respectively (p = 5.7 × 10^-8). F_ST across all markers was 0.130, while P_ST for liability to diabetes, adjusted for age and sex, was 0.149 (p = 0.35 for difference with F_ST). P_ST was 0.094 for BMI (p = 0.54), 0.095 for fasting insulin (p = 0.54) and 0.216 (p = 0.18) for 30 min insulin. For type 2 diabetes and BMI, the maximum divergence between populations was observed between American Indians and European Americans (P_ST-MAX = 0.22, p = 0.37, and P_ST-MAX = 0.14, p = 0.61), which suggests that a relatively modest 22% or 14% of the genetic variance, respectively, can potentially be explained by differential selection (assuming the absence of neutral drift).

CONCLUSIONS/INTERPRETATION

These analyses suggest that while type 2 diabetes and related traits differ significantly among continental ancestry groups, the differences are consistent with neutral expectations based on heritability and genetic distances. While these analyses do not exclude a modest role for natural selection, they do not support the hypothesis that differential natural selection is necessary to explain the phenotypic differences among these ancestry groups. Graphical abstract.

Genetic and Environmental Factors Contributing to Visceral Adiposity in Asian Populations

Obesity-associated metabolic illnesses are increasing at an alarming rate in Asian countries. A common feature observed in the Asian population is a higher incidence of abdominal obesity-the "skinny-fat" Asian syndrome. In this review, we critically evaluate the relative roles of genetics and environmental factors on fat distribution in Asian populations. While there is an upward trend in obesity among most Asian countries, it appears particularly conspicuous in Malaysia. We propose a novel theory, the Malaysian gene-environment multiplier hypothesis, which explains how ancestral variations in feast-and-famine cycles contribute to inherited genetic predispositions that, when acted on by modern-day stressors-most notably, urbanization, westernization, lifestyle changes, dietary transitions, cultural pressures, and stress-contribute to increased visceral adiposity in Asian populations. At present, the major determinants contributing to visceral adiposity in Asians are far from conclusive, but we seek to highlight critical areas for further research.

Health and Diet among People Living in an Isolated Area: Case Study of Pingelap Island in Pohnpei State, the Federated States of Micronesia

Pingelap Island in Pohnpei state is geographically isolated as the nearest island is 70 km away, and such geographical isolation is a challenge for public health due to the limited access to health services. This study aims to reveal the health situation on the island and investigate the influence of geographical isolation on health and diet. For that purpose, the result was compared with those who are living in a community on the main island of Pohnpei state (Mand) with the same ethnic background. Face-to-face interviews were conducted to collect data on demographics, diet, and behavior. Anthropometry and blood pressure measurements were also taken. A total of 98 (Pingelap = 50; Mand = 48) subjects participated in the study. The result showed that females, in particular, had a high prevalence of obesity (80.0% in Pingelap; 75.9% in Mand). However, no significant regional difference was found in both BMI and blood pressure, regardless of gender. Regarding diet, although the geographical location impacted food availability, the consumption of major imported foods did not show a significant regional difference. In conclusion, the geographical isolation did not significantly influence health and diet, but the majority of the study population displayed a high-risk burden of non-communicable diseases.

Vocal Indicators of Size, Shape and Body Composition in Polish Men

OBJECTIVES

From a human evolution perspective, identifying a link between physique and vocal quality could demonstrate dual signaling in terms of the health and biological condition of an individual. In this regard, this study investigates the relationship between men's body size, shape, and composition, and their vocal characteristics.

MATERIALS AND METHODS

Eleven anthropometric measurements, using seven indices, were carried out with 80 adult Polish male participants, while the speech analysis adopted a voice recording procedure that involved phonetically recording vowels /ɑː/, /ɛː/, /iː/, /ɔː/, /uː/ to define the voice acoustic components used in Praat software.

RESULTS

The relationship between voice parameters and body size/shape/composition was found. The analysis indicated that the formants and their derivatives were useful parameters for prediction of height, weight, neck, shoulder, waist, and hip circumferences. Fundamental frequency (F₀) was negatively correlated with neck circumference at Adam's apple level and body height. Moreover neck circumference and F₀ association was observed for the first time in this paper. The association between waist circumference and formant component showed a net effect. In addition, the formant parameters showed significant correlations with body shape, indicating a lower vocal timbre in men with a larger relative waist circumference.

DISCUSSION

Men with lower vocal pitch had wider necks, probably a result of larynx size. Furthermore, a greater waist circumference, presumably resulting from abdominal fat distribution in men, correlated with a lower vocal timbre. While these results are inconclusive, they highlight new directions for further research.

Genetic polymorphisms in neuroendocrine disorder-related candidate genes associated with pre-pregnancy obesity in gestational diabetes mellitus patients by using a stratification approach

Background

Certain candidate genes have been associated with obesity. The goal of this study is to determine the association between thirteen neuroendocrine disorder-related candidate genes and pre-pregnancy obesity among gestational diabetes mellitus (GDM) patients using the stratification approach defined the Asian and International criteria-based body mass index (BMI).

Methods

This was a post-hoc case-control exploratory sub-analysis of a cross-sectional study among GDM women to determine which candidate single nucleotide polymorphisms (SNPs) related to neuroendocrine disorders may be associated with obesity. Factors were adjusted for socio-demographic characteristics and concurrent medical problems in this particular population. Pre-pregnancy BMI and concurrent medical profiles were obtained from maternal health records. Obesity is defined as BMI of ≥27.5 kg/m² for Asian criteria-based BMI and >30 kg/m² for International criteria-based BMI. Thirteen candidate genes were genotyped using Agena^® MassARRAY and examined for association with pre-pregnancy obesity using multiple logistic regression analysis. The significant difference threshold was set at P value <0.05.

Results

Three hundred and twelve GDM women were included in this study; 60.9% and 44.2% of GDM patients were obese using Asian and International criteria-based BMI, respectively. GDM patients with AA or AG genotypes in specific SNP of brain-derived neurotrophic factor (BDNF) (G > A in rs6265) are more likely to be obese (adjusted odd ratio =2.209, 95% CI, 1.305, 3.739, P=0.003) compared to those who carry the GG genotype in the SNP adjusted for parity, underlying with asthma, heart disease, anaemia, education background in the International criteria-based BMI stratification group. On the other hand, there were no associations between other candidate genes (NRG1, FKBP5, RORA, OXTR, PLEKHG1, HTR2C, LHPP, SDK2, TEX51, EPHX2, NPY5R and ANO2) and maternal obesity.

Conclusions

In summary, BDNF rs6265 is significantly associated with pre-pregnancy obesity among GDM patients. The exact role of BDNF adjusted for diet intake and lifestyle factors merits further investigation.

Genetics of Equine Endocrine and Metabolic Disease

A role for a genetic contribution to equine metabolic syndrome (EMS) and pars pituitary intermedia dysfunction (PPID) has been hypothesized. Heritability estimates of EMS biochemical measurements were consistent with moderately to highly heritable traits. Further, genome-wide association analyses have identified hundreds of regions of the genome contributing to EMS and candidate variants have been identified. The genetics of PPID has not yet been proven. Continued research for the specific genetic risk factors for both EMS and PPID is crucial for gaining a better understanding of the pathophysiology of both conditions and allowing development of genetic tests.

Stress hypothesis overload: 131 hypotheses exploring the role of stress in tradeoffs, transitions, and health

Stress is ubiquitous and thus, not surprisingly, many hypotheses and models have been created to better study the role stress plays in life. Stress spans fields and is found in the literature of biology, psychology, psychophysiology, sociology, economics, and medicine, just to name a few. Stress, and the hypothalamic-pituitaryadrenal/interrenal (HPA/I) axis and sympathetic nervous system (SNS), are involved in a multitude of behaviors and physiological processes, including life-history and ecological tradeoffs, developmental transitions, health, and survival. The goal of this review is to highlight and summarize the large number of available hypotheses and models, to aid in comparative and interdisciplinary thinking, and to increase reproducibility by a) discouraging hypothesizing after results are known (HARKing) and b) encouraging a priori hypothesis testing. For this review I collected 214 published hypotheses or models dealing broadly with stress. In the main paper, I summarized and categorized 131 of those hypotheses and models which made direct connections among stress and/or HPA/I and SNS, tradeoffs, transitions, and health. Of those 131, the majority made predictions about reproduction (n = 43), the transition from health to disease (n = 38), development (n = 23), and stress coping (n = 18). Additional hypotheses were classified as stage-spanning or models (n = 37). The additional 83 hypotheses found during searches were tangentially related, or pertained to immune function or oxidative stress, and these are listed separately. Many of the hypotheses share underlying rationale and suggest similar, if not identical, predictions, and are thus not mutually exclusive; some hypotheses spanned classification categories. Some of the hypotheses have been tested multiple times, whereas others have only been examined a few times. It is the hope that multi-disciplinary stress researchers will begin to harmonize their naming of hypotheses in the literature so as to build a clearer picture of how stress impacts various outcomes across fields. The paper concludes with some considerations and recommendations for robust testing of stress hypotheses.

Genome-Wide Selection Scan in an Arabian Peninsula Population Identifies a TNKS Haplotype Linked to Metabolic Traits and Hypertension

Despite the extreme and varying environmental conditions prevalent in the Arabian Peninsula, it has experienced several waves of human migrations following the out-of-Africa diaspora. Eventually, the inhabitants of the peninsula region adapted to the hot and dry environment. The adaptation and natural selection that shaped the extant human populations of the Arabian Peninsula region have been scarcely studied. In an attempt to explore natural selection in the region, we analyzed 662,750 variants in 583 Kuwaiti individuals. We searched for regions in the genome that display signatures of positive selection in the Kuwaiti population using an integrative approach in a conservative manner. We highlight a haplotype overlapping TNKS that showed strong signals of positive selection based on the results of the multiple selection tests conducted (integrated Haplotype Score, Cross Population Extended Haplotype Homozygosity, Population Branch Statistics, and log-likelihood ratio scores). Notably, the TNKS haplotype under selection potentially conferred a fitness advantage to the Kuwaiti ancestors for surviving in the harsh environment while posing a major health risk to present-day Kuwaitis.

Pathophysiological Features of Obesity and its Impact on Cognition: Exercise Training as a Non-Pharmacological Approach

BACKGROUND

The number of individuals with obesity is growing worldwide and this is a worrying trend, as obesity has shown to cause pathophysiological changes, which result in the emergence of comorbidities such as cardiovascular disease, diabetes mellitus type 2 and cancer. In addition, cognitive performance may be compromised by immunometabolic deregulation of obesity. Although in more critical cases, the use of medications is recommended, a physically active lifestyle is one of the main foundations for health maintenance, making physical training an important tool to reduce the harmful effects of excessive fat accumulation.

AIM

The purpose of this review of the literature is to present the impact of immunometabolic alterations on cognitive function in individuals with obesity, and the role of exercise training as a non-pharmacological approach to improve the inflammatory profile, energy metabolism and neuroplasticity in obesity.

METHOD

An overview of the etiology and pathophysiology of obesity to establish a possible link with cognitive performance in obese individuals, with the executive function being one of the most affected cognitive components. In addition, the brain-derived neurotrophic factor (BDNF) profile and its impact on cognition in obese individuals are discussed. Lastly, studies showing regular resistance and/or aerobic training, which may be able to improve the pathophysiological condition and cognitive performance through the improvement of the inflammatory profile, decreased insulin resistance and higher BDNF production are discussed.

CONCLUSION

Exercise training is essential for reestablishment and maintenance of health by increasing energy expenditure, insulin resistance reduction, anti-inflammatory proteins and neurotrophin production corroborating to upregulation of body function.

Ethnic Disparities in Adiposity: Focus on Non-alcoholic Fatty Liver Disease, Visceral, and Generalized Obesity

PURPOSE OF REVIEW

Excessive adiposity has become a public health problem worldwide, contributing to the rise in obesity-related diseases and associated morbidity and mortality. This review details the relative significance of race/ethnicity as it pertains to adiposity and non-alcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Fat distribution remains a more reliable measure of adiposity than anthropometric measures, with visceral adipose tissue (VAT) associated with increased risk of cardiometabolic disease. While obesity is the most common risk factor for NAFLD, the racial/ethnic prevalence of obesity does not completely parallel NAFLD risk. Combating racial/ethnic disparities in obesity requires understanding differential risk among various groups. Hispanics are disproportionally impacted by NAFLD and have high rates of obesity, VAT, and insulin resistance (IR). This contrasts with Blacks, who have high prevalence of obesity and IR, accompanied by a paradoxically favorable lipid profile and low prevalence of VAT and NAFLD. Many features of adiposity and NAFLD are mediated by genetic and environmental factors, the latter being modifiable and the focus of interventions.

Genetics, adaptation to environmental changes and archaic admixture in the pathogenesis of diabetes mellitus in Indigenous Australians

Indigenous Australians are particularly affected by type 2 diabetes mellitus (T2D) due to both their genetic susceptibility and a range of environmental and lifestyle risk factors. Recent genetic studies link predisposition to some diseases, including T2D, to alleles acquired from archaic hominins, such as Neanderthals and Denisovans, which persist in the genomes of modern humans today. Indo-Pacific human populations, including Indigenous Australians, remain extremely underrepresented in genomic research with a paucity of data examining the impact of Denisovan or Neanderthal lineages on human phenotypes in Oceania. The few genetic studies undertaken emphasize the uniqueness and antiquity of Indigenous Australian genomes, with possibly the largest proportion of Denisovan ancestry of any population in the world. In this review, we focus on the potential contributions of ancient genes/pathways to modern human phenotypes, while also highlighting the evolutionary roles of genetic adaptation to dietary and environmental changes associated with an adopted Western lifestyle. We discuss the role of genetic and epigenetic factors in the pathogenesis of T2D in understudied Indigenous Australians, including the potential impact of archaic gene lineages on this disease. Finally, we propose that greater understanding of the underlying genetic predisposition may contribute to the clinical efficacy of diabetes management in Indigenous Australians. We suggest that improved identification of T2D risk variants in Oceania is needed. Such studies promise to clarify how genetic and phenotypic differences vary between populations and, crucially, provide novel targets for personalised medical therapies in currently marginalized groups.

Impact of Early Life or Intrauterine Factors and Socio-Economic Interaction on Diabetes - An Evidence on Thrifty Hypothesis

Diabetes mellitus is one of the most concerning non-communicable diseases worldwide. The prevalence of diabetes increased rapidly by the influence of socioeconomic interactions. The thrifty hypothesis postulates that certain genes that are involved in positive selection promote efficient fat deposition and storage. This is beneficial for the survival of mankind in adverse conditions. However, in this modern society, these genes have become disadvantageous as people are significantly less likely to experience famines and nutrition shortages. The socioeconomic development that has occurred during the 20th century induced abundance of food supplies in almost all regions of the world. This has led to a rapid rise in the prevalence of obesity, and type 2 diabetes as a consequence. Boom of diabetic pandemic in newly developed countries compare with others those who developed gradually can be explain by thrifty hypothesis, as a result of the difference in the exposure to environmental factors and famine by the ancestors leads. The globalization, urbanization, lack of physical activity, intake of high calorie food and migration is major cause of pandemic emergence of diabetes in high as well as middle and low-income countries.

Obesity: Pathophysiology and Management

Obesity continues to be among the top health concerns across the globe. Despite our failure to contain the high prevalence of obesity, we now have a better understanding of its pathophysiology, and how excess adiposity leads to type 2 diabetes, hypertension, and cardiovascular disease. Lifestyle modification is recommended as the cornerstone of obesity management, but many patients do not achieve long-lasting benefits due to difficulty with adherence as well as physiological and neurohormonal adaptation of the body in response to weight loss. Fortunately, 5 drug therapies-orlistat, lorcaserin, liraglutide, phentermine/topiramate, and naltrexone/bupropion-are available for long-term weight management. Additionally, several medical devices are available for short-term and long-term use. Bariatric surgery yields substantial and sustained weight loss with resolution of type 2 diabetes, although due to the high cost and a small risk of serious complications, it is generally recommended for patients with severe obesity. Benefit-to-risk balance should guide treatment decisions.

Positive selection of type 2 diabetes genotypes - the glycaemic threshold hypothesis

The high prevalence of deleterious polygenic type 2 diabetes (T2D) is a paradox requiring explanation beyond food excess, inactivity and the obesity resulting from positive energy balance. Historically, hunting-foraging and later agrarian communities often manifested a converse negative energy balance due to nutritional deficit and/or high physical energy demand - both potentially resulting in hypoglycaemia. Since hypoglycaemia impairs both reproductive fitness and cognitive function, it is proposed that that by expressing resistance to hypoglycaemia, T2D phenotypes were subject to positive selection. The insulin resistance present in often-associated atherosclerotic cardiovascular disease, metabolic syndrome and polycystic ovarian disease may also explain their frequent coexistence and current prevalence.

The evolutionary potential of diet-dependent effects on lifespan and fecundity in a multi-parental population of Drosophila melanogaster

The nutritional conditions experienced by a population have a major role in shaping trait evolution in many taxa. Constraints exerted by nutrient limitation or nutrient imbalance can influence the maximal value that fitness components such as reproduction and lifespan attains, and organisms may shift how resources are allocated to different structures and functions in response to changes in nutrition. Whether the phenotypic changes associated with changes in nutrition represent an adaptive response is largely unknown. Further, it is unclear whether the response of fitness components to diet even has the potential to evolve in most systems. In this study, we use an admixed multi-parental population of Drosophila melanogaster reared in three different diet conditions to estimate quantitative genetic parameters for lifespan and fecundity. We find significant genetic variation for both traits in our population and show that lifespan has moderate to high heritabilities within diets. Genetic correlations for lifespan between diets were significantly less than one, demonstrating a strong genotype by diet interaction. These findings demonstrate substantial standing genetic variation in our population that is comparable to natural populations and highlights the potential for adaptation to changing nutritional environments.

Nutrition and its role in human evolution

Our understanding of human evolution has improved rapidly over recent decades, facilitated by large-scale cataloguing of genomic variability amongst both modern and archaic humans. It seems clear that the evolution of the ancestors of chimpanzees and hominins separated 7-9 million years ago with some migration out of Africa by the earlier hominins; Homo sapiens slowly emerged as climate change resulted in drier, less forested African conditions. The African populations expanded and evolved in many different conditions with slow mutation and selection rates in the human genome, but with much more rapid mutation occurring in mitochondrial DNA. We now have evidence stretching back 300 000 years of humans in their current form, but there are clearly four very different large African language groups that correlate with population DNA differences. Then, about 50 000-100 000 years ago a small subset of modern humans also migrated out of Africa resulting in a persistent signature of more limited genetic diversity amongst non-African populations. Hybridization with archaic hominins occurred around this time such that all non-African modern humans possess some Neanderthal ancestry and Melanesian populations additionally possess some Denisovan ancestry. Human populations both within and outside Africa also adapted to diverse aspects of their local environment including altitude, climate, UV exposure, diet and pathogens, in some cases leaving clear signatures of patterns of genetic variation. Notable examples include haemoglobin changes conferring resistance to malaria, other immune changes and the skin adaptations favouring the synthesis of vitamin D. As humans migrated across Eurasia, further major mitochondrial changes occurred with some interbreeding with ancient hominins and the development of alcohol intolerance. More recently, an ability to retain lactase persistence into adulthood has evolved rapidly under the environmental stimulus of pastoralism with the ability to husband lactating ruminants. Increased amylase copy numbers seem to relate to the availability of starchy foods, whereas the capacity to desaturase and elongate monounsaturated fatty acids in different societies seems to be influenced by whether there is a lack of supply of readily available dietary sources of long-chain polyunsaturated fatty acids. The process of human evolution includes genetic drift and adaptation to local environments, in part through changes in mitochondrial and nuclear DNA. These genetic changes may underlie susceptibilities to some modern human pathologies including folate-responsive neural tube defects, diabetes, other age-related pathologies and mental health disorders.

Genetic Factors Associated With Human Physical Activity: Are Your Genes Too Tight To Prevent You Exercising?

The benefits of physical activity (PA) on health and fitness are well known. It has become apparent from studies of heritability that there is a considerable genetic component to PA. However, PA is such a complex phenotype that the measurement and quantification of it provide a challenge to a clearer understanding of its genetic basis. In this review, we assessed available evidence from family and twin studies that have estimated the heritability of PA. Heritability is greater when evaluated by accelerometry compared with questionnaires, and for questionnaires higher in twin than family studies. Accelerometry studies suggest heritability of PA is 51% to 56%. There have been many genome-wide linkage studies, candidate gene studies, and four genome-wide association studies that have highlighted specific genetic factors linked to different PA levels. These studies have generally failed to replicate identified loci, with the exception of the melanocortin 4 receptor, and this may be because of the variability in the measurement techniques used to characterize the behavior. Future work should aim to standardize the procedures used to measure PA in the context of trying to identify genetic causes. The link of genetics to physical exercise is not so tight that it prevents voluntary interventions.

Genome-Wide Analysis of Starvation-Selected Drosophila melanogaster-A Genetic Model of Obesity

Experimental evolution affords the opportunity to investigate adaptation to stressful environments. Studies combining experimental evolution with whole-genome resequencing have provided insight into the dynamics of adaptation and a new tool to uncover genes associated with polygenic traits. Here, we selected for starvation resistance in populations of Drosophila melanogaster for over 80 generations. In response, the starvation-selected lines developed an obese condition, storing nearly twice the level of total lipids than their unselected controls. Although these fats provide a ∼3-fold increase in starvation resistance, the imbalance in lipid homeostasis incurs evolutionary cost. Some of these tradeoffs resemble obesity-associated pathologies in mammals including metabolic depression, low activity levels, dilated cardiomyopathy, and disrupted sleeping patterns. To determine the genetic basis of these traits, we resequenced genomic DNA from the selected lines and their controls. We found 1,046,373 polymorphic sites, many of which diverged between selection treatments. In addition, we found a wide range of genetic heterogeneity between the replicates of the selected lines, suggesting multiple mechanisms of adaptation. Genome-wide heterozygosity was low in the selected populations, with many large blocks of SNPs nearing fixation. We found candidate loci under selection by using an algorithm to control for the effects of genetic drift. These loci were mapped to a set of 382 genes, which associated with many processes including nutrient response, catabolic metabolism, and lipid droplet function. The results of our study speak to the evolutionary origins of obesity and provide new targets to understand the polygenic nature of obesity in a unique model system.

The Impact of Early Human Migration on Brown Adipose Tissue Evolution and Its Relevance to the Modern Obesity Pandemic

Genetic factors are believed to be primarily responsible for obesity; however, an understanding of how genes for obesity have become so prevalent in modern society has proved elusive. Several theories have attempted to explain the genetic basis for obesity, but none of these appear to factor in the interethnic variation in obesity. Emerging evidence is increasingly pointing to a link between reduced basal metabolism and ineffective brown adipose tissue (BAT) thermogenesis. In fact, BAT presence and function are strongly correlated with metabolic rates and directly influence obesity susceptibility. My colleagues and I recently theorized that ancestral exposure to cold necessitated the evolution of enhanced BAT thermogenesis, which, with today’s hypercaloric and sedentary lifestyle, becomes advantageous, because thermogenesis is energetically wasteful, raising basal metabolism and burning excess calories. The opposite may be true for the descendants of heat-adapted populations. This review further reconciles global evolutionary climatic exposures with obesity demographics to understand the genetic basis for the obesity pandemic, and new insights from the most recent studies are provided, including those assessing archaic human admixture. Key genetic variants influencing BAT thermogenesis are outlined that have also been linked with climatic exposure to cold and appear to support the theory that evolutionary factors relevant to climate may have shaped the modern obesity pandemic.