Frequent extreme cold exposure and brown fat and cold-induced thermogenesis: A study in a monozygotic twin

INTRODUCTION: Mild cold acclimation is known to increase brown adipose (BAT) activity and cold-induced thermogenesis (CIT) in humans. We here effect of a lifestyle with frequent exposure to extreme cold on BAT and Dutch man known as 'the Iceman', who has multiple world records in extreme cold challenges. Furthermore, his monozygotic twin brother who 'normal' sedentary lifestyle without extreme cold exposures was METHODS: The Iceman (subject A) and his brother (subject B) were studied mild cold (13 degrees C) and thermoneutral conditions (31 degrees C). Measurements included BAT activity and respiratory muscle activity by [18F]FDG-PET/CT imaging and energy expenditure through indirect addition, body temperatures, cardiovascular parameters, skin perfusion, thermal sensation and comfort were measured. Finally, we determined for uncoupling protein-1 and beta3-adrenergic receptor. RESULTS: comparable BAT activity (A: 1144 SUVtotal and B: 1325 SUVtotal), within previously observed in young adult men. They were genotyped with the for uncoupling protein-1 (G/G). CIT was relatively high (A: 40.1% and B: but unlike during our previous cold exposure tests in young adult men, subjects practiced a g-Tummo like breathing technique, which involves respiratory muscle activity. This was confirmed by high [18F]FDG-uptake respiratory muscle. CONCLUSION: No significant differences were found two subjects, indicating that a lifestyle with frequent exposures to does not seem to affect BAT activity and CIT. In both subjects, BAT was higher compared to earlier observations, whereas CIT was very high, that g-Tummo like breathing during cold exposure may cause additional production by vigorous isometric respiratory muscle contraction. The be interpreted with caution given the low subject number and the fact participants practised the g-Tummo like breathing technique.