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Intermuscular and perimuscular fat expansion in obesity correlates with skeletal muscle T cell and macrophage infiltration and insulin resistance.

Authors :
Khan, I M
Perrard, X-YD
Brunner, G
Lui, H
Sparks, L M
Smith, S R
Wang, X
Shi, Z-Z
Lewis, D E
Wu, H
Ballantyne, C M
Source :
International Journal of Obesity; Nov2015, Vol. 39 Issue 11, p1607-1618, 12p
Publication Year :
2015

Abstract

<bold>Background/objectives: </bold>Limited numbers of studies demonstrated obesity-induced macrophage infiltration in skeletal muscle (SM), but dynamics of immune cell accumulation and contribution of T cells to SM insulin resistance are understudied. <bold>Subjects/methods: </bold>T cells and macrophage markers were examined in SM of obese humans by reverse transcription-PCR (RT-PCR). Mice were fed high-fat diet (HFD) for 2-24 weeks, and time course of macrophage and T-cell accumulation was assessed by flow cytometry and quantitative RT-PCR. Extramyocellular adipose tissue (EMAT) was quantified by high-resolution micro-computed tomography (CT), and correlation to T-cell number in SM was examined. CD11a-/- mice and C57BL/6 mice were treated with CD11a-neutralizing antibody to determine the role of CD11a in T-cell accumulation in SM. To investigate the involvement of Janus kinase/signal transducer and activator of transcription (JAK/STAT), the major pathway for T helper I (TH1) cytokine interferon-γ, in SM and adipose tissue inflammation and insulin resistance, mice were treated with a JAK1/JAK2 inhibitor, baricitinib. <bold>Results: </bold>Macrophage and T-cell markers were upregulated in SM of obese compared with lean humans. SM of obese mice had higher expression of inflammatory cytokines, with macrophages increasing by 2 weeks on HFD and T cells increasing by 8 weeks. The immune cells were localized in EMAT. Micro-CT revealed that EMAT expansion in obese mice correlated with T-cell infiltration and insulin resistance. Deficiency or neutralization of CD11a reduced T-cell accumulation in SM of obese mice. T cells polarized into a proinflammatory TH1 phenotype, with increased STAT1 phosphorylation in SM of obese mice. In vivo inhibition of JAK/STAT pathway with baricitinib reduced T-cell numbers and activation markers in SM and adipose tissue and improved insulin resistance in obese mice. <bold>Conclusions: </bold>Obesity-induced expansion of EMAT in SM was associated with accumulation and proinflammatory polarization of T cells, which may regulate SM metabolic functions through paracrine mechanisms. Obesity-associated SM 'adiposopathy' may thus have an important role in the development of insulin resistance and inflammation. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
03070565
Volume :
39
Issue :
11
Database :
Complementary Index
Journal :
International Journal of Obesity
Publication Type :
Academic Journal
Accession number :
110833716
Full Text :
https://doi.org/10.1038/ijo.2015.104