Development of novel rat model for high-fat and high-cholesterol diet-induced steatohepatitis and severe fibrosis progression in SHRSP5/Dmcr

Abstract

Objectives: Patients with nonalcoholic fatty liver disease are increasing worldwide, and preventive measures are an urgent need and primary concern today.

Aim: This study aimed to develop and clarify the usefulness of the SHRSP5/Dmcr rat, derived from a stroke-prone spontaneously hypertensive rat, as a novel animal model for time-course analysis of steatohepatitis and the severe fibrosis progression often observed in the disease.

Methods: Ten-week-old male SHRSP5/Dmcr rats were divided into six groups: half were fed a high-fat and high-cholesterol-containing diet (HFC diet), and the others the control, stroke-prone (SP) diet for 2, 8, and 14 weeks.

Results: The HFC diet significantly increased serum transaminase and gamma glutamyl transpeptidase activities, tumor necrosis factor alpha levels, and serum and hepatic total cholesterol levels over time. In contrast, this diet decreased serum albumin, glucose, and adiponectin levels throughout or the later stage of the feeding period, but did not influence serum insulin levels. Histopathologically, the HFC diet increased microvesicular steatosis, and focal or spotty necrosis with lymphocyte infiltrations were observed in the liver at 2 weeks, macrovesicular steatosis, ballooned hepatocytes with Mallory-Denk body formation in some, and multilobular necrosis and fibrosis at 8 weeks. Interestingly, this fibrosis formed a honeycomb network at 14 weeks. These changes are very similar to those observed in patients with non-alcoholic steatohepatitis.

Conclusions: SHRSP5/Dmcr rats appear to be a useful model for analyzing the time-dependent changes of HFC diet-induced steatohepatitis and fibrosis progression.

Fig. 1

Macroscopic photos of liver in rats fed SP diet for 2 weeks (a), 8 weeks (b), and 14 weeks (c), or HFC diet for 2 weeks (d), 8 weeks (e), and 14 weeks (f)

Fig. 2

H&E staining of liver in rats fed SP and HFC diets [original magnifications were ×100 (a–f) and ×400 (g–l)]. Liver from rats fed SP diet for 2 (a, g), 8 (b, h) and 14 weeks (c, i); liver from rats fed HFC diet for 2 (d, j), 8 (e, k), and 14 weeks (f, l). Lipid deposition (microvesicular steatosis predominantly) and focal or spotty necrosis with lymphocyte infiltrations (arrows) were observed in the liver of rats fed the HFC diet for 2 weeks (d, j). Extensive lipid deposition (macrovesicular steatosis predominantly) and multilobular necrosis in the liver of rats fed the HFC diet for 8 weeks (e, k). In addition to these findings, fibrosis was suspected in the liver of rats fed the HFC diet for 14 weeks (f, l). Mallory-Denk bodies (yellow arrows) were also observed in ballooned hepatocytes from rats fed the HFC diet for 8 and 14 weeks (k, l)

Fig. 3

Azan staining of liver sections from each group (original magnifications ×100). The livers of rats fed the SP diet for 2 (a), 8 (b), and 14 weeks (c), and HFC diet for 2 (d), 8 (e), and 14 weeks (f). Extensive fibrosis (arrows) was evident in the liver of the rats fed the HFC diet for 8 weeks (e), and fiber septa of honeycomb fibrosis (arrows) was evident in the liver of the rats fed the diet for 14 weeks (f)

Fig. 4

TG (a) and TC (b) levels in the liver. Open square shows rats fed the SP diet, and closed square shows rats fed the HFC diet. Values are expressed as the mean ± SD (n = 6). *Significant differences were observed between rats fed SP and HFC diets (p < 0.05)