Effect of Angiotensin II Type 2 Receptor-Interacting Protein on Adipose Tissue Function via Modulation of Macrophage Polarization

<div><p>We demonstrated that angiotensin II type 2 (AT₂) receptor-interacting protein (ATIP) 1 ameliorates inflammation-mediated vascular remodeling independent of the AT₂ receptor, leading us to explore the possibility of whether ATIP1 could exert anti-inflammatory effects and play a role in other pathophysiological conditions. We examined the possible anti-inflammatory effects of ATIP1 in adipose tissue associated with amelioration of insulin resistance. In mice fed a high-cholesterol diet, adipose tissue macrophage (ATM) infiltration and M1-to-M2 ratio were decreased in ATIP1 transgenic mice (ATIP1-Tg) compared with wild-type mice (WT), with decreased expression of inflammatory cytokines such as tumor necrosis factor-α and monocyte chemoattractant protein-1 in white adipose tissue (WAT), but an increase in interleukin-10, an anti-inflammatory cytokine. Moreover, 2-[³H]deoxy-d-glucose (2-[³H]DG) uptake was significantly increased in ATIP1-Tg compared with WT. Next, we examined the roles of ATIP1 in BM-derived hematopoietic cells, employing chimeric mice produced by BM transplantation into irradiated type 2 diabetic mice with obesity, KKAy, as recipients. ATM infiltration and M1-to-M2 ratio were decreased in ATIP1 chimera (ATIP1-tg as BM donor), with improvement of insulin-mediated 2-[³H]DG uptake and amelioration of inflammation in WAT. Moreover, serum adiponectin concentration in ATIP1 chimera was significantly higher than that in WT chimera (WT as BM donor) and KKAy chimera (KKAy as BM donor). These results indicate that ATIP1 could exert anti-inflammatory effects in adipose tissue via macrophage polarization associated with improvement of insulin resistance, and ATIP1 in hematopoietic cells may contribute to these beneficial effects on adipose tissue functions in type 2 diabetes.</p> </div

WAT in ATIP1-Tg and WT after treatment with high-cholesterol diet for 18 weeks.

<p>(<b>A</b>) Ratio of WAT weight to body weight in epididymal and retroperitoneal tissue. (<b>B</b>) Morphological comparison of epididymal WAT. Representative photomicrographs at ×100 magnification and histogram of adipocyte number per field. n = 7–8 for each group.</p

Macrophage infiltration and polarization in ATIP1-Tg and WT after treatment with high-cholesterol diet.

<p>Cells in the stromal vascular fraction (SVF) of the epididymal fat pad from each mouse were analyzed by flow cytometry as described in “Methods”. (<b>A</b>) Representative results of flow cytometry. F4/80-positive cells were further analyzed with anti-CD11c and anti-CD206 antibodies. Blue dots show M1 macrophages and purple dots show M2 macrophages. Red dots represent both CD11c- and CD206-negative fraction evaluated using isotype controls. (<b>B</b>) Percentage of F4/80-positive cells in SVF. n = 5 for each group. (<b>C</b>) Ratio of M1 to M2 fraction in F4/80-positive cells. Light gray squares; M1 fraction, dark gray squares; M2 fraction. n = 5 for each group.</p

Cytokine levels and glucose uptake in WAT of ATIP1-Tg and WT after treatment with high-cholesterol diet.

<p>(<b>A</b>) Expression of TNF-α, MCP-1 and IL-10 in epididymal (Epi) and retroperitoneal (Retro) WAT. Open squares; WT, closed squares; ATIP1-Tg. n = 7–8 for each group. *p<0.05 vs. WT. (<b>B</b>) Rate constant of 2-[³H] DG uptake in epididymal and retroperitoneal WAT was determined with and without insulin (1.0 U/kg) injection. Open squares; WT, closed squares; ATIP1-Tg. n = 6 for each group.</p

Glucose uptake and cytokines levels in white adipose tissue and serum levels of TNF-α and adiponectin in each chimeric mouse.

<p>(A) Rate constant of 2-[³H] DG uptake in epididymal (Epi) and retroperitoneal (Retro) WAT were determined with and without insulin (1.0 U/kg) injection. n = 6 for each group. (B) Expression of TNF-α, MCP-1 and IL-10 in epididymal and retroperitoneal WAT. n = 6 for each group. (C) Serum TNF-α and adiponectin concentrations measured by ELISA. n = 8–10 for each group. *p<0.05 vs. KKAy chimera and WT chimera.</p

Change in mRNA expression of inflammatory cytokines and NADPH oxidase subunits in hippocampus of AD model mice by CH-3 treatment.

<p>mRNA expression of MCP-1 (<b>A</b>), TNF-α (<b>B</b>), IL-6 (<b>C</b>), iNOS (<b>D</b>), eNOS (<b>E</b>), p22^phox (<b>F</b>), p47^phox (<b>G</b>), p67^phox (<b>H</b>) and gp91^phox (I) in hippocampus. n = 8–12 mice in each group. †<i>P</i><0.05 vs. control, *<i>P</i><0.05 or **<i>P</i><0.01 vs. Aβ1–42 (+).</p

Mouse characteristics in early training stage.

<p>Mouse characteristics in early training stage.</p

Improvement of cognitive decline by MKP treatment in AD model mice.

<p>(<b>A</b>) Swim latency in Morris water maze test. (<b>B</b>) Time spent in target quadrant including the former platform position in Morris water maze test. (<b>C</b>) Cerebral blood flow measured by laser speckle flowmetry after Morris water maze test. MKP was orally administered to mice every day at 0.5 mg/kg/day starting 2 days before Aβ1–42 injection. n = 5–8 mice in each group. †<i>P</i><0.05 vs. control, *<i>P</i><0.05 or **<i>P</i><0.01 vs. Aβ1–42 (+).</p

Composition of CH-3.

<p>Composition of CH-3.</p

Misclassification matrix in 6-class model.

<p>Misclassification matrix in 6-class model.</p