RESUMO
BACKGROUND & AIMS: Non-alcoholic steatohepatitis (NASH) is characterized by steatosis associated with liver inflammation. Steatosis causes recruitment of lymphocytes into the liver and this is worsened by lipopolysaccharides (LPS). As macrophages may be involved in the lymphocyte homing, we studied the role of lipids in determining the phenotype of Kupffer cells (KCs) at the stage of steatosis. METHODS: Steatosis was induced in mice by a high fat diet. The turnover and the recruitment of KCs were analyzed in vivo by flow cytometry. KCs phenotype was assessed by optical and electron microscopy, cell culture and lymphocyte recruitment by in vitro chemotaxis. Lipidomic analysis was carried out by mass-spectrometry and gene expression analysis by TaqMan low density array. RESULTS: Although the number of KCs was not modified in steatotic livers compared to normal livers, their phenotypes were different. Electron microscopy demonstrated that the KCs from fatty livers were enlarged and loaded with lipid droplets. Lipid synthesis and trafficking were dysregulated in fat-laden KCs and toxic lipids accumulated. Fat-laden KCs recruited more CD4+ T and B lymphocytes in response to LPS stimulation than did control KCs and produced high levels of pro-inflammatory cytokines/chemokines, which could be reversed by inhibition of lipogenesis. CONCLUSIONS: Lipid accumulation in fat-laden KCs is due to a dysregulation of lipid metabolism and trafficking. Fat-laden KCs are "primed" to recruit lymphocytes and exhibit a pro-inflammatory phenotype, which is reversible with inhibition of lipogenesis.
Assuntos
Fígado Gorduroso/imunologia , Fígado Gorduroso/metabolismo , Células de Kupffer/imunologia , Células de Kupffer/metabolismo , Acetiltransferases/genética , Animais , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Carnitina O-Palmitoiltransferase/genética , Diacilglicerol O-Aciltransferase/genética , Gorduras na Dieta/metabolismo , Gorduras na Dieta/toxicidade , Ácido Graxo Sintases/genética , Proteínas de Ligação a Ácido Graxo/genética , Fígado Gorduroso/patologia , Expressão Gênica/fisiologia , Células de Kupffer/patologia , Linfócitos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Hepatopatia Gordurosa não Alcoólica , Proteínas Nucleares/genética , Obesidade/imunologia , Obesidade/metabolismo , PPAR gama/genética , Fenótipo , Estearoil-CoA Dessaturase/genética , Fatores de Transcrição/genéticaRESUMO
The increase consumption of fructose in diet is associated with liver inflammation. As a specific fructan substrate, fructose may modify the gut microbiota which is involved in obesity-induced liver disease. Here, we aimed to assess whether fructose-induced liver damage was associated with a specific dysbiosis, especially in mice fed a high fat diet (HFD). To this end, four groups of mice were fed with normal and HFD added or not with fructose. Body weight and glucose sensitivity, liver inflammation, dysbiosis and the phenotype of Kupffer cells were determined after 16 weeks of diet. Food intake was increased in the two groups of mice fed with the HFD. Mice fed with HFD and fructose showed a higher infiltration of lymphocytes into the liver and a lower inflammatory profile of Kupffer cells than mice fed with the HFD without fructose. The dysbiosis associated with diets showed that fructose specifically prevented the decrease of Mouse intestinal bacteria in HFD fed mice and increased Erysipelotrichi in mice fed with fructose, independently of the amount of fat. In conclusion, fructose, used as a sweetener, induced a dysbiosis which is different in presence of fat in the diet. Consequently, the activation of Kupffer cells involved in mice model of HFD-induced liver inflammation was not observed in an HFD/fructose combined diet. These data highlight that the complexity of diet composition could highly impact the development of liver lesions during obesity. Specific dysbiosis associated with the diet could explain that the progressions of liver damage are different.