title: Macrophage polarization in obesity and type 2 diabetes: weighing down our understanding of macrophage function?
abstract: Obesity and type 2 diabetes are now recognized as chronic pro-inflammatory diseases. In the last decade, the role of the macrophage in particular has become increasingly implicated in their pathogenesis. Abundant literature now establishes that monocytes get recruited to peripheral tissues (i.e., pancreas, liver, and adipose tissue) to become resident macrophages and contribute to local inflammation, development of insulin resistance, or even pancreatic dysfunction. Furthermore, an accumulation of evidence has established an important role for macrophage polarization in the development of metabolic diseases. The general view in obesity is that there is an imbalance in the ratio of M1/M2 macrophages, with M1 "pro-inflammatory" macrophages being enhanced compared with M2 "anti-inflammatory" macrophages being down-regulated, leading to chronic inflammation and the propagation of metabolic dysfunction. However, there is emerging evidence revealing a more complex scenario with the spectrum of macrophage states exceeding well beyond the M1/M2 binary classification and confused further by human and animal models exhibiting different macrophage profiles. In this review, we will discuss the recent findings regarding macrophage polarization in obesity and type 2 diabetes.
authors.affiliation: Cellular and Molecular Metabolism Laboratory, Baker IDI Heart and Diabetes Institute , Melbourne, VIC , Australia ; Haematopoiesis and Leukocyte Biology Laboratory, Baker IDI Heart and Diabetes Institute , Melbourne, VIC , Australia.
authors.forename: Michael James
authors.initials: MJ
authors.lastname: Kraakman
authors.affiliation: Haematopoiesis and Leukocyte Biology Laboratory, Baker IDI Heart and Diabetes Institute , Melbourne, VIC , Australia ; Department of Immunology, Monash University , Melbourne, VIC , Australia.
authors.forename: Andrew James
authors.initials: AJ
authors.lastname: Murphy
authors.affiliation: Diabetic Complications Laboratory, Baker IDI Heart and Diabetes Institute , Melbourne, VIC , Australia ; Department of Medicine, Central Clinical School, Monash University , Melbourne, VIC , Australia.
authors.forename: Karin
authors.initials: K
authors.lastname: Jandeleit-Dahm
authors.affiliation: Cellular and Molecular Metabolism Laboratory, Baker IDI Heart and Diabetes Institute , Melbourne, VIC , Australia.
authors.forename: Hélène L
authors.initials: HL
authors.lastname: Kammoun
keywords: M1/M2; inflammation; macrophage; obesity; polarization; type 2 diabetes