Low- and high-thermogenic brown adipocyte subpopulations coexist in murine adipose tissue
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
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
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Research Article Metabolism

Low- and high-thermogenic brown adipocyte subpopulations coexist in murine adipose tissue

Abstract

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 brown adipocyte subpopulation with low thermogenic activity coexisting with the classical high-thermogenic brown adipocytes within the BAT. Compared with the high-thermogenic brown adipocytes, these low-thermogenic brown adipocytes had substantially lower Ucp1 and Adipoq expression, larger lipid droplets, and lower mitochondrial content. Functional analyses showed that, unlike the high-thermogenic brown adipocytes, the low-thermogenic brown adipocytes have markedly lower basal mitochondrial respiration, and they are specialized in fatty acid uptake. Upon changes in environmental temperature, the 2 brown adipocyte subpopulations underwent dynamic interconversions. Cold exposure converted low-thermogenic brown adipocytes into high-thermogenic cells. A thermoneutral environment had the opposite effect. The recruitment of high-thermogenic brown adipocytes by cold stimulation is not affected by high-fat diet feeding, but it does substantially decline with age. Our results revealed a high degree of functional heterogeneity of brown adipocytes.

Authors

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

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Figure 5

The brown adipocyte subpopulations have distinct metabolic profiles.

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The brown adipocyte subpopulations have distinct metabolic profiles. (A)...
(A) Ucp1-GFP mice, the inducible real-time labeling system of Ucp1 promoter activity, derived from interbreeding 2 transgenic strains, Ucp1-rtTA and TRE-GFP, which allows inducible real-time labeling of the Ucp1 promoter activity. At the basal level, Ucp1-GFP mice do not express GFP in any cell type. When these mice are treated with dox, GFP expression is induced based on the Ucp1 promoter activity. (B) Fluorescent images of isolated BA-H and BA-L subpopulations from the BAT of Ucp1-GFP mice. Scale bar: 50 μm. These images are representative of 4 independent experiments. (C–E) OCR in freshly isolated primary cells treated with the different compounds. Primary brown adipocytes (BA-H and BA-L) were from male WT mice housed in 6°C for 7 days. As controls, primary white adipocytes and SVF from BAT were from male WT mice housed at room temperature. (C) Plot of OCR to time measured by Seahorse. (D and E) Calculated basal and maximum respiration levels of different cell types. n = 8 mice (BA-H and BA-L); n = 5 mice (WA and SVF). (F) Plot of OCR to time measured by Seahorse in primary brown adipocytes (BA-H and BA-L) treated with the different compounds. These cells were freshly isolated from male AdipoChaser-mT/mG mice housed in 6°C for 7 days through EasySep Magnet (Stem Cell Technologies). (G) Fatty acid uptake rate in the 2 brown adipocyte subpopulations. n = 8 mice (BA-H and BA-L). For each group, cells from all mice were pooled together, and data represent mean ± SD of experimental replicates, normalized to cell numbers. **P < 0.01. Statistical significance was assessed using a 1-way ANOVA followed by Tukey’s multiple comparisons test (D and E), or a 2-tailed Student’s t test (G). (H) Ten-week-old Ucp1-GFP mice were treated with dox-containing diet for 4 days before tissue harvest. PACT-cleared BAT from Ucp1-GFP mice and immunolabeled with GFP (green) and sympathetic neuron marker tyrosine hydroxylase (TH) (purple) antibody. Scale bar: 30 μm. Images are representative of 3 independent experiments.