Indication of mixed glucose and fatty acid use by inferred brown adipose tissue activity in Samoans

Abstract

ObjectivesDespite the growing rates of global obesity and the known positive associations between brown adipose tissue (BAT) and cardiovascular health, little is known about the metabolic effects of BAT activity in Samoans, a population at high risk of obesity and type II diabetes. Here we assessed the potential effects of inferred BAT activity on metabolic health markers in Samoan adults exposed to mild cold.MethodsUsing point‐of‐care finger prick technology we measured fasting glucose, total cholesterol, high‐density lipoprotein (HDL), and low‐density lipoprotein (LDL) levels before and after 30 min of cold exposure among 61 individuals (38 females, 23 males, ages 31–54) from ‘Upolu Island, Samoa. Respiratory quotient was measured by indirect calorimetry to determine substrate metabolism at room temperature and cold exposure.ResultsFasting glucose levels decreased significantly (p < .001) after cold exposure while neither total cholesterol (p = .88), HDL (p = .312), nor LDL (p = .089) changed. Respiratory quotient decreased significantly (p = .009) between exposures, suggesting an increased preference for lipid metabolism as a response to cold.ConclusionsThe observed effects of inferred BAT activity on biomarkers suggest BAT activity utilizes both glucose and lipid‐derived fatty acids as fuel for thermogenesis. Our work provides evidence for the beneficial metabolic effects of BAT and emphasizes the need for the population‐specific development of metabolic treatments involving BAT to ensure the successful and equitable minimization of extreme consequences of obesity and metabolic health.

Pearl Memorial Lecture. Humans at the extremes: Exploring human adaptation to ecological and social stressors

“…Niclou et al (2024) explicitly examine the influence of adaptation to cold exposure on biomarkers of cardiometabolic health in a sample of Samoan adults. They find that cold‐activation of BAT metabolism is associated with the utilization of both fatty acids and glucose as metabolic fuel to support increased energy expenditure.…”

“…Since 2007, research has documented that adult humans vary markedly in the amounts of BAT they possess (Cypress et al, 2009) and the extent to which BAT influences energy metabolism in response to cold stress (e.g., Muzik et al, 2013; van der Lans et al, 2013). Recent field‐based studies of energy expenditure and BAT activity among non‐western populations of Siberia (Levy et al, 2018, 2022), Finland (Ocobock et al, 2020, 2022), and Samoa (Niclou et al, 2022, 2024) have highlighted the diversity in physiological responses to cold stress across human populations. Ocobock also notes the growing interest in better understanding how aspects of cold adaptation may shape variation in risks of cardiometabolic health outcomes.…”

The now and future of human biology at the extremes: An introduction to the special issue

“…Further, redefining the concepts of the extremes with an emphasis on connecting them to the foundational study of human adaptability (albeit with a broader biocultural lens) allows for a more robust examination of human physiological and behavioral variation and resilience. This more holistic perspective of human adaptability has immense potential for benefitting Indigenous and marginalized populations who may be at greater risk of climate‐related transformation to their environment (Pisor & Jones, 2021), reducing the detrimental mental and physical health effects experienced by disenfranchised groups (Kim et al, 2019), and preventing disparities in medical and social interventions to infectious and noncommunicable diseases (Kim, 2023; Niclou et al, 2023; see Special Issue: Human Biologists Confront the COVID‐19 Pandemic in the American Journal of Human Biology ). Furthermore, there are contributions to be made even in currently unknowable settings, like spaceflight (Sarma & Shelhamer, 2023).…”

“…While excess weight gain is well understood to contribute to metabolic disease, the physiological effects of weight gain alone do not suffice to create the extreme consequences of obesity in society. Niclou et al stipulate that the interconnected social, economic, and environmental factors contributing to obesity foster the extremes of obesity (Niclou et al, 2023). In their work for this special issue, the authors demonstrate how a population‐specific approach to obesity and health can help parse out the biological and environmental factors affecting metabolism.…”