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Beneficial Metabolic Effects of TREM2 in Obesity are Uncoupled from its Expression on Macrophages

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posted on 24.02.2021, 20:08 by Omar Sharif, Julia Stefanie Brunner, Ana Korosec, Rui Martins, Alexander Jais, Berend Snijder, Andrea Vogel, Michael Caldera, Anastasiya Hladik, Karin Lakovits, Simona Saluzzo, Benedikta Boehm, Anna-Dorothea Gorki, Ildiko Mesteri, Josefine Lindroos-Christensen, Katharina Tillmann, Dagmar Stoiber, Jörg Menche, Gernot Schabbauer, Martin Bilban, Giulio Superti-Furga, Harald Esterbauer, Sylvia Knapp
Obesity-induced white adipose tissue (WAT) hypertrophy is associated with elevated adipose tissue macrophage (ATM) content. Overexpression of the triggering receptor expressed on myeloid cells 2 (TREM2) reportedly increases adiposity, worsening health. Paradoxically, using insulin resistance, elevated fat mass and hypercholesterolemia as hallmarks of unhealthy obesity, a recent report demonstrated ATM-expressed TREM2 promoted health. Here, we identified that in mice TREM2 deficiency aggravated diet-induced insulin resistance and hepatic steatosis independently of fat and cholesterol levels. Metabolomics linked TREM2 deficiency with elevated obesity-instigated serum ceramides that correlated with impaired insulin sensitivity. Remarkably, while inhibiting ceramide synthesis exerted no influences on TREM2-dependent ATM remodeling, inflammation or lipid load, it restored insulin tolerance, reversing adipose hypertrophy and secondary hepatic steatosis of TREM2-deficient animals. Bone marrow transplantation experiments revealed unremarkable influences of immune cell-expressed TREM2 on health instead demonstrating that WAT-intrinsic mechanisms impinging on sphingolipid metabolism dominate in TREM2’s systemic protective effects on metabolic health.

Funding

This work was funded by the Austrian Science Fund (FWF P25801 and FWF P31568 to OS) and the special research programs (SFB) Immunothrombosis of the Austrian Science Fund (F5410-B21 to SK).

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