05, p<0.05, respectively; Fig. 5a), and similar to the numbers observed in LDLR?/?/MPO+/+ mice on chow. Moreover, additional analyses of LDLR?/?/MPO?/?tp animals consistently revealed a strongly reduced expression of pro-inflammatory genes previously implicated in the pathogenesis of NASH (Fig. 5b). For new example, tumor necrosis factor-�� (TNF-��) and IL-1�� mRNA expression were almost two-fold lower in the liver of LDLR?/?/MPO?/?tp mice compared with LDLR?/?/MPO+/+tp mice (p<0.05, p<0.01, respectively). In addition, hepatic IL-6 expression tended to be reduced in LDLR?/?/MPO?/?tp mice relative to LDLR?/?/MPO+/+tp mice, although the difference was not statistically significant. Hepatic monocyte chemoattractant protein-1 (Mcp-1) mRNA expression was over two-fold lower in LDLR?/?/MPO?/?tp mice (p<0.
01), and, consistent with this, their CD68 mRNA expression was also significantly reduced. Taken together, these results show that MPO plays an important role in high-fat diet-induced inflammation of the liver, promoting both inflammatory cell recruitment and cytokine/chemokine expression. Figure 5 General reduction of diet-induced hepatic inflammation in LDLR?/?/MPO?/?tp mice. Reduced High-fat Diet-induced Adipose Tissue Inflammation in LDLR?/?/MPO?/?tp Mice The pathogenesis of NASH is mediated by cross-talk between inflamed adipose tissue and the liver . In order to investigate the potential contribution of adipose tissue-derived factors to the reduced hepatic inflammation in LDLR?/?/MPO?/?tp mice, several inflammatory parameters were investigated.
First of all, Ly-6G staining revealed an absence of neutrophils in visceral adipose tissue in both groups (data not shown). Next, visceral adipose tissue was stained for the macrophage marker F4/80. High-fat diet-induced obesity is characterized by infiltration of macrophages into adipose tissue, where they organize into so-called ��crown-like structures�� surrounding dead adipocytes . Interestingly, adipose tissue of LDLR?/?/MPO?/?tp mice was completely devoid of such crown-like structures, whereas they were readily identifiable in adipose tissue of LDLR?/?/MPO+/+tp mice (Fig. 6a). Quantitative PCR analysis of adipose tissue Mac-1 expression, another macrophage marker, was in line with these results, showing a marked reduction in LDLR?/?/MPO?/?tp animals (p<0.05; Fig. 6b).
Similarly, Cilengitide expression of Mcp-1, a potent chemo-attractant for monocytes, was strongly reduced in the LDLR?/?/MPO?/?tp group (p<0.05; Fig. 6b). Furthermore, adipose tissue expression of the pro-inflammatory adipokines leptin and TNF-�� was lower in LDLR?/?/MPO?/?tp animals, whereas expression of adiponectin, which has anti-inflammatory properties, was higher (Fig. 6c). Thus, MPO deficiency protects adipose tissue from high-fat diet-induced inflammation, which may contribute to the attenuation of inflammation in the liver of LDLR?/?/MPO?/?tp mice.