Olive leaf powder prevents nonalcoholic steatohepatitis in Sprague–Dawley rats fed a high-fat and high-cholesterol diet

Abstract

<h2>Summary</h2><h3>Background and aims</h3> The pathogenesis of nonalcoholic steatohepatitis (NASH) is multifactorial, and oxidative stress and the activation of inflammatory cytokines may play an important role in the progression of NASH. Olive leaves contain polyphenols, such as oleuropein, and have been reported to possess a wide range of pharmacological properties, including anti-oxidative and anti-inflammatory effects. Thus, we hypothesized that olive leaf extract might have a preventive effect on NASH progression. <h3>Methods</h3> Nine-week-old male Sprague–Dawley rats were fed a high-fat and high-cholesterol (HFC) diet with or without olive leaf powder (OLP; n = 6–7/group) for 9 weeks. The histopathology, serology, and expression of cholesterol/lipid metabolism-, fibrosis-, inflammation-, and oxidative stress-related genes in the liver were evaluated. <h3>Results</h3> The rats fed a HFC diet supplemented with 0.8% (w/w) of OLP showed lower levels of serum total cholesterol and alanine aminotransferase, a lower concentration of hepatic cholesterol, and a significantly higher level of adiponectin than the rats fed a HFC diet without OLP. Histopathologically, rats fed a HFC diet supplemented with 0.8% (w/w) of OLP showed less hepatic inflammation, fibrosis, and thioredoxin than rats fed a HFC diet without OLP. <h3>Conclusions</h3> Our results suggest that OLP possesses a preventive effect against NASH progression, presumably due to the elevated serum adiponectin levels and its anti-oxidative properties. Because this preventive effect was not dose-dependent, further studies are needed to investigate the optimal dose of OLP for obtaining the maximum preventive effects against NASH, and to elucidate the detailed pharmacological mechanism(s) of OLP.