The severity of rat liver injury by fructose and high fat depends on the degree of respiratory dysfunction and oxidative stress induced in mitochondria.

BACKGROUND: High fat or fructose induces non-alcoholic fatty liver disease (NAFLD) accompanied of mitochondrial dysfunction and oxidative stress. Controversy remains about whether fructose or fat is more deleterious for NAFLD development. To get more insights about this issue and to determine if the severity of liver disease induced by fructose or fat is related to degree of mitochondrial dysfunction, we compared the effects of diets containing high fat (HF), fructose (Fr) or high fat plus fructose (HF + Fr) on NAFLD development, mitochondrial function, ROS production and lipid peroxidation. METHODS: Wistar rats were assigned to four groups: Control, fed with standard rodent chow; High fat (HF), supplemented with lard and hydrogenated vegetable oil; Fructose (Fr), supplemented with 25% fructose in the drinking water; High fat plus fructose group (HF + Fr), fed with both HF and Fr diets. Rats were sacrificed after 6 weeks of diets consumption and the liver was excised for histopathological analysis by hematoxylin and eosin staining and for mitochondria isolation. Mitochondrial function was evaluated by measuring both mitochondrial respiration and complex I activity. Lipid peroxidation and ROS production were evaluated in mitochondria by the thiobarbituric acid method and with the fluorescent ROS probe 2,4-H2DCFDA, respectively. RESULTS: Fr group underwent the lower degree of both liver damage and mitochondrial dysfunction that manifested like less than 20% of hepatocytes with microvesicular steatosis and partial decrease in state 3 respiration, respectively. HF group displayed an intermediate degree of damage as it showed 40% of hepatocytes with microvesicular steatosis and diminution of both state 3 respiration and complex I activity. HF + Fr group displayed more severe damage as showed microvesicular steatosis in 60% of hepatocytes and inflammation, while mitochondria exhibited fully inhibited state 3 respiration, impaired complex I activity and increased ROS generation. Exacerbation of mitochondrial lipid peroxidation was observed in both the Fr and HF + Fr groups. CONCLUSION: Severity of liver injury induced by fructose or fat was related to the degree of dysfunction and oxidative damage in mitochondria. Attention should be paid on the serious effects observed in the HF + Fr group as the typical Western diet is rich in both fat and carbohydrates.

Protective effect of supplementation with biotin against high-fructose-induced metabolic syndrome in rats.

Several reports have demonstrated that pharmacological concentrations of biotin reduce hyperglycemia, hypertriglyceridemia, and hypertension. We hypothesized that biotin could exert a protective effect on some illness-associated metabolic syndrome. To test this hypothesis, male Wistar rats were fed a diet containing 30% fructose in drinking water and classified into four groups: C, the control group; B, the group receiving biotin (intraperitoneal injection, 2 mg/kg); F, the group receiving fructose (30% w/v); and FB, the group receiving fructose-biotin. The administration of biotin began after the rats had been on a high-fructose diet for 12 weeks and continued for 4 weeks. Our results showed that food and fluid intake were diminished in the F and FB groups. However, the final body weights were similar between the groups. A significant increase in hepatic triglyceride and cholesterol content, plasma cholesterol, triglycerides, transaminases, low-density lipoprotein cholesterol (LDL-c), systolic blood pressure, and vasocontraction, as well as a decrease in high-density lipoprotein cholesterol (HDL-c) were observed in the F group. Glucose tolerance and insulin tolerance were also impaired in the F group. The administration of biotin ameliorated all these changes. Hepatic oxidative stress as well as macrovesicular fatty changes in hepatocytes caused by a high-fructose diet were also improved by biotin. Our findings demonstrate that biotin has a protective role against metabolic syndrome by improving insulin resistance associated with normal hepatic and serum levels of triglyceride and cholesterol, blood pressure, and the prevention of steatosis and hepatic oxidative damage. Therefore, biotin could be used as a therapeutic strategy in the pharmacological treatment of metabolic syndrome.