Independent of their inflammatory phenotype, macrophages are key orchestrators of hepatic metabolism. Non-alcoholic fatty liver disease (NAFLD) often occurs in obese individuals and is among the most common causes of cirrhosis, the terminal chronic liver disease that may necessitate liver transplantation. While multiple populations of macrophages have been described in the human liver, their function and turnover in obese patients at high risk of developing NAFLD and cirrhosis is currently unknown. Herein we identified a specific human population of resident liver myeloid cells that protects against the metabolic impairment associated with obesity. By studying the turnover of liver myeloid cells in individuals undergoing liver transplantation using markers of donor-recipient mismatch, we made the novel discovery that liver myeloid cell turnover differs between humans and mice. Using single cell techniques and flow cytometry we determined that the proportion of the protective resident liver myeloid cells, denoted liver myeloid cells 2 (LM2), decreases during obesity. Functional ... (Show More)

Independent of their inflammatory phenotype, macrophages are key orchestrators of hepatic metabolism. Non-alcoholic fatty liver disease (NAFLD) often occurs in obese individuals and is among the most common causes of cirrhosis, the terminal chronic liver disease that may necessitate liver transplantation. While multiple populations of macrophages have been described in the human liver, their function and turnover in obese patients at high risk of developing NAFLD and cirrhosis is currently unknown. Herein we identified a specific human population of resident liver myeloid cells that protects against the metabolic impairment associated with obesity. By studying the turnover of liver myeloid cells in individuals undergoing liver transplantation using markers of donor-recipient mismatch, we made the novel discovery that liver myeloid cell turnover differs between humans and mice. Using single cell techniques and flow cytometry we determined that the proportion of the protective resident liver myeloid cells, denoted liver myeloid cells 2 (LM2), decreases during obesity. Functional validation approaches using human 2D and 3D cultures revealed that the presence of LM2 ameliorates the oxidative stress associated with obese conditions. Our study indicates that resident myeloid cells could be a therapeutic target to decrease the oxidative stress associated with NAFLD.

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