Seasonal variation of metabolic activity in visceral, subcutaneous and brown adipose tissues: a positron emission tomography study

Abstract

Glucose metabolism in human brown adipose tissue (BAT) varies by season due to the activating effects of cold acclimation on BAT nonshivering thermogenesis. Elevated metabolic activity in BAT may affect systemic metabolic health. However, potential alterations in BAT fatty acid metabolism during cold seasons are not known. The purpose of this study was to examine whether thermal seasons affect the metabolic activity in visceral, subcutaneous and brown adipose tissues.

We studied seasonal variation in fatty acid metabolism by analyzing 40 (26 females, 14 males) healthy subjects, to whom PET scans were performed between years 2011 and 2013 using fatty acid tracer 18F-FTHA and 15O-H2O to measure tissue perfusion. Outdoor temperatures and thermal season criteria were collected from the open data of the Finnish Meteorological Institute (FMI).

BAT non-esterified fatty acid (NEFA) uptake and perfusion during acute cold exposure were similar in winter and in summer in both sexes. In women, BAT NEFA uptake and perfusion in room temperature correlated with current day, current month, next month and previous week mean outdoor temperature (P always ≤ 0.04).

BAT metabolic activity measured by fatty acid uptake and perfusion in room temperature correlates negatively with outdoor temperature of the current day and month, next month and previous week in women while men display nonsignificant correlation with outdoor temperature. Additionally, BAT activity during acute cold exposure is not significantly affected by outdoor temperature. These findings could be taken into account when treating obesity or doing BAT-related research in the future.