In vivo study of metabolic dynamics and heterogeneity in brown and beige fat by label‐free multiphoton redox and fluorescence lifetime microscopy

• Published in: Journal of biophotonics 2020-02, Vol.13 (2), p.e201960057-n/a
• Main Authors: He, Sicong, Wei, Xiuqing, Qin, Zhongya, Chen, Congping, Wu, Zhenguo, Qu, Jianan Y.
• Format: Article
• Language: English
• Subjects: Adipocytes; Adipose tissue; Animal tissues; beige fat; Cellular structure; Coenzymes; Fluorescence; fluorescence lifetime; Heterogeneity; Imaging; In vivo methods and tests; Lifetime; Lipids; Metabolism; optical redox ratio; Subgroups; Technology assessment; Thermogenesis
• ISSN: 1864-063X; 1864-0648
• DOI: 10.1002/jbio.201960057

In this work, the metabolic characteristics of adipose tissues in live mouse model were investigated using a multiphoton redox ratio and fluorescence lifetime imaging technology. By analyzing the intrinsic fluorescence of metabolic coenzymes, we measured the optical redox ratios of adipocytes in vivo and studied their responses to thermogenesis. The fluorescence lifetime imaging further revealed changes in protein bindings of metabolic coenzymes in the adipocytes during thermogenesis. Our study uncovered significant heterogeneity in the cellular structures and metabolic characteristics of thermogenic adipocytes in brown and beige fat. Subgroups of brown and beige adipocytes were identified based on the distinct lipid size distributions, redox ratios, fluorescence lifetimes and thermogenic capacities. The results of our study show that this label‐free imaging technique can shed new light on in vivo study of metabolic dynamics and heterogeneity of adipose tissues in live organisms. Metabolic characterization of thermogenic adipocytes provides remarkable insight into the mechanism of obesity‐related diseases. This paper presents a label‐free method to assess the metabolism and thermogenesis of mouse adipose tissues in vivo. The optical redox ratio and fluorescence lifetime are used as biomarkers to determine the thermogenic response of brown, beige and white adipose tissues to different physiological stimulations. This technique may be used to study the recruitment and activation of thermogenic adipocytes.