Bone marrow adipocytes drive the development of tissue invasive Ly6Chigh monocytes during obesity
Parastoo Boroumand, David Prescott, Tapas Mukherjee, Philip J. Bilan, Michael D. Wong, Jeff Shen, Ivan Tattoli, Yuhuan Zhou, Angela Li, Tharini Sivasubramaniyam, Nancy Shi, Lucie Y. Zhu, Zhi Liu, Clinton S. Robbins, Dana J. Philpott, Stephen E. Girardin, Amira Klip
Abstract
During obesity and high fat-diet (HFD) feeding in mice, sustained low-grade inflammation includes not only increased pro-inflammatory macrophages in the expanding adipose tissue, but also bone marrow (BM) production of invasive Ly6C high monocytes. As BM adiposity also accrues with HFD, we explored the relationship between the gains in BM white adipocytes and invasive Ly6C high monocytes by in vivo and ex vivo paradigms. We find a temporal and causal link between BM adipocyte whitening and the Ly6C high monocyte surge, preceding the adipose tissue macrophage rise during HFD in mice. Phenocopying this, ex vivo treatment of BM cells with conditioned media from BM adipocytes or bona fide white adipocytes favoured Ly6C high monocyte preponderance. Notably, Ly6C high skewing was preceded by monocyte metabolic reprogramming towards glycolysis, reduced oxidative potential and increased mitochondrial fission. In sum, short-term HFD changes BM cellularity, resulting in local adipocyte whitening driving a gradual increase and activation of invasive Ly6C high monocytes.