Non-alcoholic fatty liver disease: more than just ectopic fat accumulation

Tyrphostin AG17 inhibits adipocyte differentiation in vivo and in vitro

Background

Excessive subcutaneous adiposity in obesity is associated to positive white adipocyte tissue (WAT) differentiation (adipogenesis) and WAT expandability. Here, we hypothesized that supplementation with the insulin inhibitor and mitochondrial uncoupler, Tyrphostin (T-AG17), in vitro and in vivo inhibits adipogenesis and adipocyte hypertrophy.

Methods

We used a 3T3-L1 proadipocyte cell line to identify the potential effect of T-AG17 on adipocyte differentiation and fat accumulation in vitro. We evaluated the safety of T-AG17 and its effects on physiological and molecular metabolic parameters including hormonal profile, glucose levels, adipogenesis and adipocyte hypertrophy in a diet-induced obesity model using C57BL/6 mice.

Results

We found that T-AG17 is effective in preventing adipogenesis and lipid synthesis in the 3T3-L1 cell line, as evidenced by a significant decrease in oil red staining (p < 0.05). In obese C57BL/6 mice, oral administration of T-AG17 (0.175 mg/kg for 2 weeks) lead to decreased fat accumulation and WAT hypertrophy. Further, T-AG17 induced adipocyte apoptosis by activating caspase-3. In the hepatocytes of obese mice, T-AG17 promoted an increase in the size of lipid inclusions, which was accompanied by glycogen accumulation. T-AG17 did not alter serum biochemistry, including glucose, insulin, leptin, free fatty acids, creatinine, and aspartate aminotransferase.

Conclusion

T-AG17 promotes adipocyte apoptosis in vivo and is an effective modulator of adipocyte differentiation and WAT hypertrophy in vitro and in vivo. Therefore, T-AG17 may be useful as a pharmacological obesity treatment.

Somatotropic Axis Dysfunction in Non-Alcoholic Fatty Liver Disease: Beneficial Hepatic and Systemic Effects of Hormone Supplementation

Background: Somatotropic axis dysfunction associated with non-alcoholic fatty liver disease (NAFLD) has potential multisystemic detrimental effects. Here, we analysed the effects of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) supplementation on liver histology, adipokine profile and muscle function in an NAFLD model. Methods: C57BL/6 mice were fed with a high fat diet (HFD) for 12 weeks and were separated into three groups treated for 4 weeks with: (1) High fat diet (HFD) (n = 10); (2) HFD + GH 9 μg/g/d (n = 10); (3) HFD + IGF-1 0.02 µg/g/d (n = 9). A control group fed a chow diet was included (n = 6). Liver histology, liver triglycerides content, serum alanine aminotransferase (ALT) activity, adiponectin and leptin serum levels, in vivo muscle strength, tetanic force and muscle fibre cross-sectional area (CSA) were measured. Results: HFD + GH and HFD + IGF-1 groups showed significantly lower ALT activity compared to HFD (p < 0.01). Liver triglyceride content in HFD + GH was decreased compared to HFD (p < 0.01). Histologic steatosis score was increased in HFD and HFD + GH group (p < 0.01), whereas HFD + IGF-1 presented no difference compared to the chow group (p = 0.3). HFD + GH group presented lower serum leptin and adiponectin levels compared to HFD. GH and IGF-1 supplementation therapy reverted HFD-induced reduction in muscle strength and CSA (sarcopenia). Conclusions: GH and IGF-1 supplementation induced significant improvement in liver steatosis, aminotransferases and sarcopenia in a diet-induced NAFLD model.

Association of UCP2 -866G>A Polymorphism With Nonalcoholic Fatty Liver Disease in Patients From North-West of Iran

OBJECTIVE

To investigate the association of uncoupling protein-2 (UCP2) -866G > A gene polymorphism (rs659366) with nonalcoholic fatty liver disease (NAFLD).

METHODS

We performed a case-control study with a cohort of 75 patients with NAFLD (of Iranian ethnicity) and 76 healthy individuals of Iranian ethnicity. The UCP2 -866G > A polymorphism (rs659366) was determined using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Patients with AA and AG genotypes were 71% and 68%, respectively, more likely to have NAFLD, compared with individuals with the GG genotype (reference group). In subjects with a GG genotype, serum triglyceride (TG) concentration was significantly higher in patients with NAFLD (P = .04). Serum alanine aminotransferase (ALT) concentrations in all 3 genotypes and serum aspartate aminotransferase (AST) concentrations in AG and GG genotypes of UCP2 gene polymorphism were significantly higher in patients (P <.05).

CONCLUSION

Our results revealed a modest modifier effect of -866G>A UCP2 polymorphism in patients with NAFLD.

Practical approaches to the nutritional management of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and a serious health burden worldwide which increases risk of cirrhosis, type 2 diabetes mellitus (T2DM), and cardiovascular complications. Current epidemics of obesity, unhealthy dietary patterns, and sedentary lifestyles, all contribute to the high prevalence of NAFLD. Dietary patterns and nutrients are important contributors to the development, progression, and treatment of NAFLD. A healthy diet is beneficial for all NAFLD patients beyond weight reduction. Generally, hypercaloric diets, especially rich in trans/saturated fat and cholesterol, high consumption of red and processed meat, and fructose-sweetened beverages seem to increase the risk of progression toward nonalcoholic steatohepatitis (NASH), whereas reducing caloric intake and high-glycemic index (GI) foods, increasing consumption of monounsaturated fatty acids, omega-3 fatty acids, fibers, and specific protein sources such as fish and poultry have preventive and therapeutic effects. Therefore, nutrition serves as a major route of prevention and treatment of NAFLD, and patients with NAFLD should have an individualized diet recommendation. In this review, the evidence linking macronutrients to NAFLD are discussed.

The role of diet and nutritional intervention for the management of patients with NAFLD

During the last few decades, the prevalence of obesity, insulin resistance and non-alcoholic fatty liver disease (NAFLD) have dramatically increased. Nutrition and modern lifestyle habits are intimately involved in this epidemiological change. Although lifestyle intervention can theoretically revert the metabolic disturbances and prevent the long term complications of NAFLD, its efficacy is diminished in clinical practice by poor implementation and reduced adherence to lifestyle intervention programs. In this article we summarize the main elements of dietary interventions for NAFLD, describe practical strategies to optimize efficacy and review potential nutritional strategies under development that hopefully will improve outcomes in the future.

Current management of patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) and its progressive form, nonalcoholic steatohepatitis (NASH) are the most common causes of chronic liver disease in industrialized countries. NAFLD has also been strongly associated with type II diabetes and cardiovascular diseases. This study was a multipurposed review, which included discussion of recent studies investigating the cellular and genetic basis of these diseases, the pathogenesis of NAFLD and the current treatment and management of nonalcoholic steatohepatitis. Currently, maintaining a healthy weight through dietary changes and exercise, the use of insulin-modulating pharmacologic agents for diabetes control and the use of lipid-lowering, anti-oxidants have been the most widely recommended treatments. Inclusion of pathogenic mechanisms in treatment design will allow future therapies to target-specific pathways involved in NAFLD pathogenesis.