Month: June 2022

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Proud to introduce Dr. Alexandra Niclou

It has been a wonderful and fruitful journey (not without its troubles thanks to COVID and my changing institutions), but I am so VERY PROUD to say that my student, Alexandra Niclou, is now Dr. Alexandra Niclou.

Alex (right) and I (left) after the hooding ceremony.

Alex is beyond brilliant, and I consider myself exceptionally lucky to have been a part of this process. Watching her grow, manage so many obstacles, and surpass me has truly been an honor and humbling experience.

Alex’s dissertation work focused on brown adipose tissue (BAT) among individuals in Samoa. This work is not only fascinating, but unique and groundbreaking, as it is the first time BAT has been measured among an adult tropical population. This work provides critical insight into the question, “Do all humans have BAT?” and, if so, “How does BAT function differently in different populations?” In order to conduct this work successfully, she developed collaborations with colleagues who work in Samoa. This includes Dr. Nicola Hawley from Yale and the Samoan Obesity, Lifestyle and Genetic Adaptations Study (OLaGA) team.

Alex found the cold adaptive BAT among the tropical Samoans. This unexpected finding suggests that BAT may be present in all humans. However, she also found that it functioned differently than among the Albany population she worked with previously and work conducted among cold climate populations by other researchers. By examining the presence or absence of this tissue in a tropical population, she has greatly added to our understanding of the role brown adipose tissue plays in human evolution and adaptation as well as addressing human variation and the unique morphologies exhibited by Polynesian populations. Furthermore, this work has the potential to reveal a therapeutic role for BAT in treating the global obesity epidemic and diabetes given the metabolic and glucose disposal properties. This is all to say that Alex’s work is not only exceptional within the field of human biology and anthropology, but also has real world implications.

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

Yes, I am WAY behind on updating my website with various things! Here is another brown adipose tissue article recently out. This one is done in collaboration with Drs. Päivi Soppela, Minna Turunen, Ville Stenbäck, and Karl-Heinz Herzig.

We measured brown adipose tissue activity (using indirect calorimetry, thermal imaging, and mild cold exposure) among reindeer herders in Finland. We found that herders do indeed have active brown adipose tissue (BAT). When activated, resting metabolic rates increase significantly by 8.7%, warmer supraclavicular temperatures (BAT positive region) relative to sternum temperatures (BAT negative regions), and BAT among this sample preferentially uses fatty acids for fuel (a low RQ – respiratory quotient). This is different from other studies that have shown a preference for glucose or mixed glucose-fatty acid as fuel among other populations.

Resting metabolic rate at room temperature and during cold exposure when BAT is activated.

There were no correlations of BAT with any anatomical or physiological variables with the exception of a negative correlation between a change in RQ and the change in supraclavicular surface temperatures. Based on work by Dr. Stephanie Levy, this lack of correlation with various anatomical and physiological variables might be due to BAT activity being determined or at the very least influenced by cold exposure during key developmental periods in childhood.

Supraclavicular (BAT positive) and Sternal (BAT negative) surface temperatures during room temperature and mild cold exposure. The supraclavicular region stayed significantly warmers than the sternal region.

This study shows that BAT activity is highly variable even among different cold climate populations, and that like high altitude populations, there are often different ways the body copes and adapts to similar environments.

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Weather Permitting: Increased seasonal efficiency of nonshivering thermogenesis through brown adipose tissue activation in the winter

Very proud to share this new article written by the newly minted Dr. Alexandra Niclou (my now former PhD student).

This work looked at brown adipose tissue activation between summer and winter among folks in Albany, New York. We compared changes in metabolic rate, respiratory quotient, & supraclavicular heat dissipation between room and mild cold temperatures in summer & winter. The participant pool was largely the same between the two seasons.

During cold exposure – when brown fat is activated – supraclavicular temperatures were greater in winter compared to summer while metabolic rate did not change. RQ – an index for substrate utilization – significantly increased in winter compared to summer, suggesting increase in preference for carbohydrates as fuel in winter.

This demonstrates that inferred brown fat activity is greater, more efficient, & increases glucose use in winter. Brown adipose tissue may play a role in seasonal cold acclimatization and glucose disposal in humans.

These figures show the metabolic rates, respiratory quotients, and supraclavicular temperatures for females, males, and the sample overall for summer and winter measures of brown adipose tissue.