Methionine- and Choline-Deficient Diet-Induced Nonalcoholic Steatohepatitis Is Associated with Increased Intestinal Inflammation.

Inflammation drives the pathogenesis of nonalcoholic steatohepatitis (NASH). The current study examined changes in intestinal inflammation during NASH. In male C57BL/6J mice, feeding a methionine- and choline-deficient diet (MCD) resulted in severe hepatic steatosis and inflammation relative to feeding a chow diet (CD). MCD-fed mice exhibited characteristics of mucosal and submucosal inflammatory responses compared with CD-fed mice. Moreover, intestinal phosphorylation states of c-Jun N-terminal protein kinase p46 and mRNA levels of IL-1B, IL-6, tumor necrosis factor alpha, and monocyte chemoattractant protein-1 were significantly higher and intestinal mRNA levels of IL-4 and IL-13 were significantly lower in MCD-fed mice compared with those in CD mice. Surprisingly, upon treatment with MCD-mimicking media, the proinflammatory responses in cultured intestinal epithelial CMT-93 cells did not differ significantly from those in CMT-93 cells treated with control media. In contrast, in RAW264.7 macrophages, MCD-mimicking media significantly increased the phosphorylation states of c-Jun N-terminal protein kinase p46 and mitogen-activated protein kinases p38 and mRNA levels of IL-1B, IL-6, IL-10, and tumor necrosis factor alpha under either basal or lipopolysaccharide-stimulated conditions. Collectively, these results suggest that increased intestinal inflammation is associated with NASH phenotype. Thus, elevated proinflammatory responses in macrophages likely contribute to, in large part, increased intestinal inflammation in NASH.