Brown Adipose Tissue and Metabolic Markers Differ Between Greenlanders and Danes With Cold Activation.

Abstract

Brown adipose tissue (BAT) is a thermogenic tissue that converts energy into heat in response to cold exposure, and is therefore a promising target for improving cardiometabolic health. Habitually cold-exposed Arctic people represent a unique model of metabolic adaptation to cold. We investigated cold-induced BAT activation in Greenlanders in comparison to Danes. A comparative crossover study was conducted of 13 Greenlanders and 11 Danes, with 2 experimental sessions conducted 2 weeks apart: A, a thermoneutral session; and B, a cooling session. BAT volume and activity were assessed using 2-deoxy-2-[18F]-fluoro-D-glucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) imaging. Serial measurement of metabolic markers associated with BAT activity was performed by blood sampling. Both for Greenlanders and Danes, core temperature decreased 0.5 °C during cooling, and the volume of active BAT increased, yet with a higher increase in active BAT volume of 16 917% in Greenlanders compared to 4541% in Danes (P = .046). Marked differences in glucose levels were seen in Greenlanders and Danes in response to cooling (Danes: 0.30 mmol/L, P = .013; Greenlanders: 0.16 mmol/L, P = .12), insulin (Danes: 2.43 pmol/L, P = .32; Greenlanders: 6.65 pmol/L, P = .001), triglycerides (Danes: -0.59 mmol/L, P < .001; Greenlanders: -0.16 pmol/L, P = .21), and total cholesterol (Danes: 0.39 mmol/L, P < .001; Greenlanders: 0.02 mmol/L, P = .89). The larger increase in BAT activity in response to cooling and the dampened response in metabolic parameters in Greenlanders compared to Danes leads to a hypothesis of preparedness for rapid thermogenic response to cold exposure in populations with active BAT.