Abstract
Obesity leads to a switch in subsets of CD4+ T cell in adipose tissue, characterized by an increase in IFNγ producing Th1 cells and a decrease in anti-inflammatory regulatory T (Treg) cells, which impairs systemic insulin sensitivity. What signals these changes is unknown. Herein we demonstrate that genetic deficiency of adipocyte MHCII decreases adipose IFNγ expression and increases adipose Treg abundance in obese mice, leading to reduced obesity-induced adipose inflammation and reduced insulin resistance without affecting weight gain. The preserved insulin sensitivity of high fat diet (HFD)-fed adipocyte-specific MHCII knockout (aMHCII−/−) mice was substantially attenuated by adipose-specific Treg ablation. Adipocytes of aMHCII−/− mice exhibit decreased capacity to stimulate IFNγ production in Th1 cells, whereas HFD-fed IFNγR1−/− mice were more insulin sensitive and had similarly high levels of Tregs in adipose tissue as aMHCII−/− mice. We further show that IFNγ strongly inhibits IL-33 effects to promote adipose Treg proliferation. Our results identify MHCII in adipocyte as a critical determinant of the obesity-induced adipose T cell subset switch and insulin resistance.
Highlights
Obesity leads to a switch in subsets of CD4 þ T cell in adipose tissue, characterized by an increase in IFNg producing Th1 cells and a decrease in anti-inflammatory regulatory T (Treg) cells, which impairs systemic insulin sensitivity
H2-Ab1 expression was reduced in adipocytes but not stromal vascular fractions (SVFs), bone marrow derived macrophages (BMDMs), peritoneal macrophages (PMs) or spleen dendritic cells (DCs) of aMHCII À / À mice (Fig. 1d), while MHCI gene expression did not differ
Our previous work uncovered a dialogue between adipocytes and CD4 þ T cells, whereby an increase in leptin within days of high fat diet (HFD) increases adipose-resident T cell (ART) expression of the Th1 marker Tbet and IFNg, which increases adipocyte MHCII expression[10]
Summary
Obesity leads to a switch in subsets of CD4 þ T cell in adipose tissue, characterized by an increase in IFNg producing Th1 cells and a decrease in anti-inflammatory regulatory T (Treg) cells, which impairs systemic insulin sensitivity. Tbet null mice have more adipose Tregs than WT mice, and this increase is strongly implicated in their improved metabolic profile[7,8] Despite these studies, little is known about the specific mechanisms that activate pro-inflammatory T cell changes in obesity. Adipocyte MHCII may be a target to prevent adipose inflammation and its metabolic complications
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