Schisandrin B ameliorates non-alcoholic liver disease through anti-inflammation activation in diabetic mice

Abstract

Type 2 diabetes mellitus (T2DM) is a metabolic risk factor associated with non-alcoholic liver disease (NAFLD). Schisandrin B (Sch B) is a promising agent for NAFLD. However, the actions of Sch B on diabetes-associated NAFLD and the underlying mechanisms are not characterized. This study aimed to assess whether Sch B has beneficial effects on T2DM-associated NAFLD. Sch B (50 mg/kg, gavage) was administrated to C57BL/KSJ db/db mice for 2 weeks. Body weight, liver weight, blood glucose, and insulin resistance were measured. Serum lipid level and liver function were detected using the biochemistry analyzer. Quantitative Real-Time PCR assay was used to evaluate mRNA levers of lipid metabolism genes. Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) staining was performed to measure apoptosis in the liver. Pathological analysis and immunohistochemistry assessment were used to analyze hepatic steatosis and inflammatory infiltration. Sch B supplementation significantly decrease body weight, related liver weight, blood glucose, and serum insulin, and improved insulin resistance in db/db mice. Sch B obviously corrected NAFLD phenotypes including lipid deposition, steatohepatitis, and high levels of hepatic enzymes and serum lipid. In addition, mRNA levels of Sterol response element-bind protein 1c (SREBP-1c), fatty acid synthetase (Fasn), and acetyl-CoA carboxylase (ACC) were markedly downregulated by Sch B treatment. TUNEL-positive cells were also decreased by Sch B. Furthermore, Sch B inhibited the Kupffer cells, IL-1β, and TNF-α infiltration to the liver. Sch B ameliorated insulin resistance and lipid accumulation under high glucose conditions, which was partly associated with its inhibition of apoptosis and anti-inflammatory actions.

Keywords: Schisandrin B; inflammatory infiltration; insulin resistance; non-alcoholic fatty liver disease; type 2 diabetes mellitus.

Figure 1

Improvements of body weight, relative liver weight, and insulin resistance by Sch B treatment in db/db mice. Ten‐week‐old db/m mice and db/db mice were administrated with Sch B (50 mg/kg/day) or normal saline by gavage. The administration period lasted for 2 weeks. Body weight (a), relative weight of liver (b), blood glucose (c), and serum insulin (d) were detected after Sch B treatment. GTT assay (e) and ITT (g) assay were used to measure blood glucose at different time‐points. (f, h) The corresponding area under curve (AUC) was calculated. The data are presented as mean ± SEM, n = 6, *P < .05 versus db/m, ^# P < .05 versus db/db

Figure 2

Improvements of hepatic pathology and hepatic function by Sch B treatment in db/db mice. (a–d) representative images of hepatic H&E staining (magnification, 200×). The black arrow pointed to the lipid droplet and asterisk was used to draw inflammatory cells. Scale bar, 100 μm. Histopathological analysis of steatosis (e), hepatocyte ballooning (f), lobular inflammation (g), and the total NAFLD activity (h). Changes of serum ALT (i), and AST (j) were detected. The data are presented as mean ± SEM, n = 6, *P < .05 versus db/m, ^# P < .05 versus db/db

Figure 3

Attenuation of hepatic steatosis by Sch B treatment in db/db mice. (a–d) Representative images of oil red O staining (magnification, 200×). Scale bar, 100 μm. Levels of total cholesterol in serum (e), triglyceride in serum (f), total cholesterol in livers (g), and triglyceride in livers (h) were measured. The data are presented as mean ± SEM, n = 6, *P < .05 versus db/m, ^# P < .05 versus db/db

Figure 4

Effects of Sch B on apoptosis in the liver of db/db mice. (a–c) Representative images of TUNEL staining (magnification, 200×). Scale bar, 100 μm. (d) the number of TUNEL‐positive cells were calculated. The data are presented as mean ± SEM, n = 6, *P < .05 versus db/m, ^# P < .05 versus db/db

Figure 5

Alleviation of inflammatory infiltration by Sch B treatment in the liver tissues of db/db mice. Liver sections were stained with CD68 (a‐c), F4/80 (d‐f), IL‐1β (g‐i), or TNF‐α (j‐l) to monitor inflammatory infiltration (magnification, 200×). Scale bar, 100 μm. (m) the bar graph showed that Sch B treatment significantly downregulated the infiltration of inflammatory cells and inflammatory cytokines in the liver tissues. (n) Concentrations of IL‐1β and TNF‐α in the liver tissues were measured using ELISA kits. The data are presented as mean ± SEM, n = 6, *P < .05 versus db/m, ^# P < .05 versus db/db