NAFLD is caused by excessive hepatic lipid accumulation and associated with activation of macrophage/Kupffer cells and oxidative stress, resulting in nonalcoholic steatohepatitis (NASH) with advanced fibrosis. Placental extracts have been used to treat various chronic diseases due to their antioxidative effect. However, the effects of the extracts on the development of NASH have yet to be elucidated. Here, we investigated the effect of porcine placental extract (PPE) in a lipotoxicity-induced NASH model. C57BL/6 mice were fed a high-cholesterol, high-fat (CL) diet or a CL diet containing 0.1% PPE (CL+0.1%PPE) or 0.3% PPE (CL+0.3%PPE). Liver histology and fibrogenesis were examined. In addition, intrahepatic immune cell numbers were quantified by flow cytometry. After 15 weeks of administration, PPE alleviated lipid accumulation by reducing hepatic TG, TC and NEFA levels, as well as lipid peroxidation, which was assessed by TBARS. PPE improved glucose intolerance and enhanced the insulin signal, assessed by IRβ and Akt phosphorylation, in the liver, which was associated with the attenuation of MAPK (ERK/p38MAPK) and NF-kB activation. Flow cytometry analysis revealed that PPE reduced CD11c+CD206−(M1) by 44.2%, whereas it increased CD11c-CD206+(M2) by 1.4-fold, resulting in a predominance of M2 over M1 macrophage populations in the liver of NASH mice. In addition, PPE downregulated LPS-induced M1 marker mRNA expression in isolated murine peritoneal macrophages, but augmented IL-4-induced M2 marker mRNA expression in a dose-dependent manner. Furthermore, the PPE reduced the hepatic stellate cell (HSC) activation associated with the attenuated transforming growth factor-β/Smad3 signaling, both in the liver of NASH mice and in HSC line. Thus, PPE may be a potential approach to prevent NASH by limiting lipid peroxidation, promoting M2 macrophage polarization, and attenuating HSC activation.
G. Chen: None. L. Xu: None. N. Nagata: None. M. Nagashimada: None. T. Ota: None.