# Transglutaminase 2-expressing macrophages modulate adipose tissue inflammation

## TL;DR

Transglutaminase 2-expressing macrophages in fat tissue reduce inflammation and insulin resistance in obese mice.

## Contribution

Identifies TGM2+ macrophages as anti-inflammatory regulators in obesity-related adipose tissue.

## Key findings

- TGM2+ macrophages are upregulated in high-fat diet-induced obesity.
- TGM2 silencing increases inflammation in macrophages and worsens insulin resistance.
- Recombinant TGM2 promotes anti-inflammatory IL-10 in fat cells but not in T cells.

## Abstract

We investigated Transglutaminase 2 (TGM2) in high fat diet (HFD) obese mice, finding upregulated TGM2+ adipose tissue macrophages (ATMs) in HFD epididymal white adipose tissue (eWAT) compared to chow diet (CD) eWAT. Using Tgm2 CRISPR silencing, we examined TGM2 modulation of inflammation in vitro within bone marrow-derived macrophages (BMMs), as well as in co-cultured eWAT stromal vascular fraction (SVF) cells. Tgm2 silencing in BMMs led to increased pro-inflammation, compared to control. In contrast, in vitro exposure of eWAT SVF to recombinant TGM2 increased anti-inflammatory IL-10 secretion. However, IL-10 was not induced by recombinant TGM2 in CD activated CD4 + T cells, or in HFD-derived SVF CD4 + T cells. In vivo Tgm2 silencing in CD11b+ cells in HFD mice resulted in pro-inflammation in eWAT and serum, and increased adiposity and insulin resistance, suggesting that TGM2 + ATMs possess an anti-inflammatory role in obesity that is insufficient to reverse obesity-induced inflammation.

Low-grade chronic inflammation is linked to obesity-driven insulin resistance. Transglutaminases 2-expressing macrophages are increased in obesity and modulate adipose tissue inflammation, growth and insulin sensitivity in diet-induced obese mice.