Background: Excess fructose consumption contributes to the development of obesity, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD). Uric acid, a metabolite of fructose metabolism, may have a direct role in the development of NAFLD, bu...
Background: Excess fructose consumption contributes to the development of obesity, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD). Uric acid, a metabolite of fructose metabolism, may have a direct role in the development of NAFLD, but the mechanism is unclear. Therefore, to evaluate the contributions of fructose and uric acid on NAFLD development, the effects of uric acid lowering treatment on fatty liver was examined using a high fructose diet-induced fatty liver rat model.
Methods: Thirty-week-old OLETF male rats were divided into three groups: (1) normal chow-diet OLETF rats (NC group, n=10); (2) high fructose-diet OLETF rats (HFrD group, n=10); and (3) high fructose-diet OLETF rats with allopurinol treatment (HFrDAL group, n=10). After 16 weeks of treatment, an intraperitoneal glucose tolerance test (IPGTT) was performed to measure glucose metabolism parameters. After sacrifice, liver tissue was processed to assess histological characteristics and real-time polymerase chain reaction (PCR) was performed to evaluate expression of genes involved in lipid metabolism and inflammation. Endoplasmic reticulum (ER) stress pathway modulation was evaluated by Western blot.
Results: The HFrD group had significantly elevated body weight, as well as higher serum uric acid and triglyceride concentrations compared to the NC group (P<0.05). In the IPGTT, blood glucose concentrations at 2 hours were significantly increased in the HFrD and HFrDAL groups compared with the NC group (P<0.05). The mean NAFLD activity score was significantly increased in the HFrD group versus the NC group (P<0.05). Allopurinol treatment significantly reduced body weight, decreased serum uric acid concentrations, and ameliorated hepatic lipid accumulation in the HFrDAL group compared with the HFrD group (P<0.05). High fructose diet significantly suppressed hepatic expression of fat oxidation genes in the HFrD group, which was ameliorated by allopurinol treatment in the HFrDAL group. Hepatic expression of pro-inflammatory cytokine genes was significantly elevated in the HFrD group, but not in the HFrDAL group (P<0.05). Furthermore, high fructose diet-induced hepatic ER stress pathway activation was inhibited by allopurinol treatment.
Conclusions: Allopurinol ameliorates high fructose diet-induced hepatic steatosis through modulation of hepatic lipid metabolism and pro-inflammatory cytokines expression. Allopurinol also partially affects ER stress pathway induction. Therefore, uric acid may have a direct role in the development of fructose-induced hepatic steatosis, and uric acid lowering therapy could be a candidate for the prevention or treatment of NAFLD.