Adipose tissue-specific ablation of PGC-1 beta impairs thermogenesis in brown fat

Impaired thermogenesis observed in mice with whole-body ablation of peroxisome proliferator-activated receptor-gamma coactivator-1 beta (PGC-1 beta; officially known as PPARGC1B) may result from impaired brown fat (brown adipose tissue; BAT) function, but other mechanism(s) could be involved. Here, using adipose-specific PGC-1 beta knockout mice (PGC-1 beta-AT-KO mice) we aimed to learn whether specific PGC-1 beta ablation in adipocytes is sufficient to drive cold sensitivity. Indeed, we found that warm-adapted (30 degrees C) mutant mice were relatively sensitive to acute cold exposure (6 degrees C). When these mice were subjected to cold exposure for 7 days (7-day-CE), adrenergic stimulation of their metabolism was impaired, despite similar levels of thermogenic uncoupling protein 1 in BAT in PGC-1 beta-AT-KO and wild-type mice. Gene expression in BAT of mutant mice suggested a compensatory increase in lipid metabolism to counteract the thermogenic defect. Interestingly, a reduced number of contacts between mitochondria and lipid droplets associated with low levels of L-form of optic atrophy 1 was found in BAT of PGC-1 beta-AT-KO mice. These genotypic differences were observed in warm-adapted mutant mice, but they were partially masked by 7-day-CE. Collectively, our results suggest a role for PGC-1 beta in controlling BAT lipid metabolism and thermogenesis. This article has an associated First Person interview with the first author of the paper.