Author(s): Shaul ME, Bennett G, Strissel KJ, Greenberg AS, Obin MS
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Abstract OBJECTIVE: To identify, localize, and determine M1/M2 polarization of epidydimal adipose tissue (eAT) macrophages (Phis) during high-fat diet (HFD)-induced obesity. RESEARCH DESIGN AND METHODS: Male C57BL/6 mice were fed an HFD (60\% fat kcal) or low-fat diet (LFD) (10\% fat kcal) for 8 or 12 weeks. eATMPhis (F4/80(+) cells) were characterized by in vivo fluorescent labeling, immunohistochemistry, fluorescence-activated cell sorting, and quantitative PCR. RESULTS: Recruited interstitial macrophage galactose-type C-type lectin (MGL)1(+)/CD11c(-) and crown-like structure-associated MGL1(-)/CD11c(+) and MGL1(med)/CD11c(+) eATMPhis were identified after 8 weeks of HFD. MGL1(med)/CD11c(+) cells comprised approximately 65\% of CD11c(+) eATMPhis. CD11c(+) eATMPhis expressed a mixed M1/M2 profile, with some M1 transcripts upregulated (IL-12p40 and IL-1beta), others downregulated (iNOS, caspase-1, MCP-1, and CD86), and multiple M2 and matrix remodeling transcripts upregulated (arginase-1, IL-1Ra, MMP-12, ADAM8, VEGF, and Clec-7a). At HFD week 12, each eATMPhi subtype displayed an enhanced M2 phenotype as compared with HFD week 8. CD11c(+) subtypes downregulated IL-1beta and genes mediating antigen presentation (I-a, CD80) and upregulated the M2 hallmark Ym-1 and genes promoting oxidative metabolism (PGC-1alpha) and adipogenesis (MMP-2). MGL1(med)/CD11c(+) eATMPhis upregulated additional M2 genes (IL-13, SPHK1, CD163, LYVE-1, and PPAR-alpha). MGL1(med)/CD11c(+) ATMPhis expressing elevated PGC-1alpha, PPAR-alpha, and Ym-1 transcripts were selectively enriched in eAT of obese mice fed pioglitazone for 6 days, confirming the M2 features of the MGL1(med)/CD11c(+) eATMPhi transcriptional profile and implicating PPAR activation in its elicitation. CONCLUSIONS: These results 1) redefine the phenotypic potential of CD11c(+) eATMPhis and 2) suggest previously unappreciated phenotypic and functional commonality between murine and human ATMPhis in the development of obesity and its complications.
This article was published in Diabetes
and referenced in Journal of Clinical & Cellular Immunology