Brown adipose tissue (BAT), as the main site of adaptive thermogenesis, exerts beneficial metabolic effects on obesity and insulin resistance. BAT has been previously assumed to contain a homogeneous population of brown adipocytes. Utilizing multiple mouse models capable of genetically labeling different cellular populations, as well as single-cell RNA sequencing, and 3D tissue profiling, we discovered a new brown adipocyte subpopulation with low thermogenic activity co-existing with the classical high thermogenic brown adipocytes within the BAT. These low thermogenic brown adipocytes had significantly lower Ucp1 and Adipoq expression, larger lipid droplets, and lower mitochondrial content. Functional analyses showed that the low thermogenic brown adipocytes have significant lower basal mitochondrial respiration, and they are specialized in fatty acid uptake. Upon changes in environmental temperature, the two brown adipocyte subpopulations underwent dynamic inter-conversions. Cold exposure converted low thermogenic brown adipocytes into high thermogenic cells, and a thermoneutral environment had the opposite effect. This recruitment of high thermogenic brown adipocytes by cold stimulation is not affected by high fat diet feeding, but significantly declined with age. Our results revealed a high degree of functional heterogeneity of brown adipocytes.
Anying Song, Wenting Dai, Min Jee Jang, Leonard Medrano, Zhuo Li, Hu Zhao, Mengle Shao, Jiayi Tan, Aimin Li, Tinglu Ning, Marcia M. Miller, Brian Armstrong, Janice M. Huss, Yi Zhu, Yong Liu, Viviana Gradinaru, Xiwei Wu, Lei Jiang, Philipp E. Scherer, Qiong A. Wang