Hepatic inflammation is a key pathological feature of Nonalcoholic Steatohepatitis (NASH). Natural Killer T-cells (NKT) and CD8+ T-cells are known to play an important role in obesity related adipose tissue inflammation. We hypothesized that these same inflammatory phenotypes would be present in progressive NASH. We used a previously established high fat high carbohydrate (HFHC) murine obesogenic diet model of progressive NASH to investigate the role of NKT cells and CD8+ T-cells in C57Bl6/J mice. Further, to better understand the impact of these cell populations; CD1d-deficient and CD8+ T-cell depleted mice were subjected to HFHC diet for 16 weeks. C57Bl6/J mice fed HFHC diet had increased body weight, liver triglyceride content, serum alanine aminotransferase (ALT) levels and increased NKT cells and CD8+ T-cells infiltration in the liver. In addition human liver sections from patients with NASH showed increased CD8+ T-cells. In comparison, CD1d-deficient and CD8-T cell depleted mice fed HFHC had lower hepatic triglyceride content, lower ALT levels, as well reduced α-smooth muscle actin (αSMA), collagen type 1 alpha 1 (Col1a1), collagen type 1 alpha 2 (Col1a2) mRNA expression, lower activated resident macrophages and infiltrating macrophages and improved NAFLD activity scores. Further, while CD1d-deficient mice were protected against weight gain on the HFHC diet, CD8 T-cell depleted mice gained weight on the HFHC diet. Conclusion We found that NASH has an immunological signature that includes hepatic infiltrating NKT and CD8+ T-Cells. Depletion of these cells resulted in reduced NASH progression and thus presents novel therapeutic avenues for the treatment of NASH.

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Background and Aims The augmenter of liver regeneration (ALR) protein is critical for lipid homeostasis and mitochondrial function. We investigated high‐fat/high‐carbohydrate (HF/HC) diet–induced nonalcoholic fatty liver disease (NAFLD) in wild‐type (WT), hepatocyte‐specific ALR‐knockout (ALR‐H‐KO), and ALR‐heterozygous (ALR‐H‐HET) mice. ALR was measured in serum of human nonalcoholic steatohepatitis (NASH) and NASH‐induced cirrhosis (serum and liver). Approach and Results HF/HC feeding decreased ALR expression in all groups of mice. The otherwise normal ALR‐H‐HET mice gained more weight and steatosis than WT mice when challenged metabolically with the HF/HC diet; ALR‐H‐KO mice gained the least weight and had the least steatosis. These findings were consistent with correspondingly increased triglycerides and cholesterol and altered expression of carnitine palmitoyltransferase 1a, sterol regulatory element‐binding protein, acetyl coenzyme A carboxylase, and fatty acid synthase. All HF/HC‐fed mice developed insulin resistance, the magnitude being lower in ALR‐H‐KO mice. HF/HC‐fed ALR‐H‐HET mice were more resistant to glucose challenge than WT or ALR‐H‐KO mice. The frequency of tumor necrosis factor alpha–producing, interleukin 6 (IL6)–producing, and IL17‐producing cells was greater in ALR‐H‐KO than ALR‐H‐HET and lowest in WT mice. HF/HC feeding did not increase their number in ALR‐H‐KO mice, and the increase in ALR‐H‐HET was greater than that in WT mice except for IL17 cells. Cluster of differentiation 25–positive (CD25+) forkhead box P3–positive CD4+ regulatory T‐cell frequency was lower in ALR‐H‐HET than WT mice and further reduced in ALR‐H‐KO mice; HF/HC reduced regulatory T‐cell frequency only in WT mice. HF/HC‐fed ALR‐H‐HET, but not WT, mice developed fibrosis; and ALR‐H‐KO mice progressed to cirrhosis. White adipose tissue of HF/HC‐fed ALR‐deficient mice developed strong inflammation, indicating bidirectional interactions with the liver. Hepatic and serum ALR levels were significantly reduced in patients with NASH‐cirrhosis. Serum ALR was also significantly lower in patients with NASH. Conclusions Hepatic ALR deficiency may be a critical predisposing factor for aggressive NAFLD progression.

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