Ezetimibe as a potential treatment for non-alcoholic fatty liver disease: is the intestine a modulator of hepatic insulin sensitivity and hepatic fat accumulation?

Identification of hepatic NPC1L1 as an NAFLD risk factor evidenced by ezetimibe-mediated steatosis prevention and recovery

Non-alcoholic fatty liver disease (NAFLD) is a serious global public health concern. Nevertheless, there are no specific medications for treating the associated abnormal accumulation of hepatic lipids such as cholesterol and triglycerides. While seminal findings suggest a link between hepatic cholesterol accumulation and NAFLD progression, the molecular bases of these associations are not well understood. Here, we experimentally demonstrate that hepatic Niemann-Pick C1-Like 1 (NPC1L1), a cholesterol re-absorber from bile to the liver, can cause steatosis, an early stage of NAFLD using genetically engineered L1-Tg mice characterized by hepatic expression of NPC1L1 under the control of ApoE promoter. Contrary to wild-type mice that have little expression of hepatic Npc1l1, the livers of L1-Tg mice fed a high-fat diet became steatotic within only a few weeks. Moreover, hepatic NPC1L1-mediated steatosis was not only prevented, but completely rescued, by orally administered ezetimibe, a well-used lipid-lowering drug on the global market, even under high-fat diet feedings. These results indicate that hepatic NPC1L1 is an NAFLD-exacerbating factor amendable to therapeutic intervention and would extend our understanding of the vital role of cholesterol uptake from bile in the development of NAFLD. Furthermore, administration of a TLR4 inhibitor also prevented the hepatic NPC1L1-mediated steatosis formation, suggesting a latent link between physiological roles of hepatic NPC1L1 and regulation of innate immune system. Our results revealed that hepatic NPC1L1 is a novel NAFLD risk factor contributing to steatosis formation that is rescued by ezetimibe; additionally, our findings uncover feasible opportunities for repositioning drugs to treat NAFLD in the near future.

Ezetimibe reduces cholesterol content and NF-kappaB activation in liver but not in intestinal tissue in guinea pigs

Background

Statins (HMG CoA reductase inhibitors), in addition to reducing circulating cholesterol and incidence of coronary heart disease, also have pleiotropic, anti-inflammatory effects. Patients with chronic liver diseases, non-alcoholic fatty liver disease (NAFLD) or hepatitis C are often excluded from statin therapy because of adverse effects in a small cohort of patients despite increased cardiovascular risk cholesterol. Ezetimibe, which inhibits cholesterol absorption by inhibition of Niemann-Pick C1 like 1 (NPC1L1) protein in the brush border of intestinal cells, has been suggested as a new therapeutic option in these patients.

Methods

Effects of ezetimibe on lipoprotein metabolism, hepatic and intestinal lipid content in guinea pigs, an animal model with a lipoprotein profile and pattern similar to humans were investigated. In order to investigate a possible effect of ezetimibe on cholesterol induced inflammation NF-kappaB activation as an indicator for inflammatory processes in liver and gut tissue was measured.

Results

Lipid enriched diet led to accumulation of lipids in hepatic tissue which caused strong hepatic NF-kappaB activation. Ezetimibe reduced lipid diet induced increase of circulating cholesterol by about 77% and prevent hepatic NF-kappaB activation almost completely. In contrast in intestinal cells Ezetimibe, though lowering diet induced cholesterol accumulation, increased triglyceride content and subsequent NF-kappaB activation.

Conclusion

In summary these data show, that ezetimibe effectively reduced diet induced circulating cholesterol levels, hepatic lipid accumulation and inflammatory response in our guinea pig model. However this drug elicited a local inflammatory response in intestinal tissue. Whether these diverse effects of ezetimibe on inflammatory parameters such as NF-kappaB have clinical relevance remains to be determined.

The effect of ezetimibe on NAFLD

NAFLD has become the most common liver disorder in countries, where obesity, type 2 diabetes mellitus, dyslipidemia, and metabolic syndrome are common. The strong association between these conditions and the risk of cardiovascular disease make treatment crucial. Possible interventions for NAFLD target excess body weight, insulin resistance, inflammation, oxidative stress or intestinal lipid absorption. Administration of combination therapy with a statin plus ezetimibe, associated with lifestyle changes, may represent an effective strategy because of the strong reduction in low-density lipoprotein cholesterol levels. Combination therapy is often more effective, especially when complementary mechanisms of action are involved. Ezetimibe is effective and well tolerated in combination with a number of lipid lowering therapies, including statins, orlistat, and insulin-sensitizing agents. There is strong evidence from preclinical models to supporting the use of ezetimibe in this setting. Larger controlled trials are needed to confirm its effectiveness in patients with NAFLD, to establish the most efficacious combinations and to determine whether treatment can reverse fibrosis.

Management of nonalcoholic fatty liver disease: an evidence-based clinical practice review

AIM

To build a consensus among Chilean specialists on the appropriate management of patients with nonalcoholic fatty liver disease (NAFLD) in clinical practice.

METHODS

NAFLD has now reached epidemic proportions worldwide. The optimal treatment for NAFLD has not been established due to a lack of evidence-based recommendations. An expert panel of members of the Chilean Gastroenterological Society and the Chilean Hepatology Association conducted a structured analysis of the current literature on NAFLD therapy. The quality of the evidence and the level of recommendations supporting each statement were assessed according to the recommendations of the United States Preventive Services Task Force. A modified three-round Delphi technique was used to reach a consensus among the experts.

RESULTS

A group of thirteen experts was established. The survey included 17 open-ended questions that were distributed among the experts, who assessed the articles associated with each question. The levels of agreement achieved by the panel were 93.8% in the first round and 100% in the second and third rounds. The final recommendations support the indication of lifestyle changes, including diet and exercise, for all patients with NAFLD. Proven pharmacological therapies include only vitamin E and pioglitazone, which can be used in nondiabetic patients with biopsy-proven nonalcoholic steatohepatitis (the progressive form of NAFLD), although the long-term safety and efficacy of these therapies have not yet been established.

CONCLUSION

Current NAFLD management is rapidly evolving, and new pathophysiology-based therapies are expected to be introduced in the near future. All NAFLD patients should be evaluated using a three-focused approach that considers the risks of liver disease, diabetes and cardiovascular events.

Bariatric surgery as potential treatment for nonalcoholic fatty liver disease: a future treatment by choice or by chance?

Morbid obesity is strongly associated with nonalcoholic fatty liver disease (NAFLD) which is one of the most common causes of chronic liver disease worldwide. The current best treatment of NAFLD and NASH is weight reduction through life style modifications, antiobesity medication, and bariatric surgery. Importantly, bariatric surgery is the best alternative option for weight reduction if lifestyle modifications and pharmacological therapy have not yielded long-term success. Bariatric surgery is an effective treatment option for individuals who are grossly obese and associated with marked decrease in obesity-related morbidity and mortality. The most common performed bariatric surgery is Roux-en-Y gastric bypass (RYGB). The current evidence suggests that bariatric surgery in these patients will decrease the grade of steatosis, hepatic inflammation, and fibrosis. NAFLD per se is not an indication for bariatric surgery. Further research is urgently needed to determine (i) the benefit of bariatric surgery in NAFLD patients at high risk of developing liver cirrhosis (ii) the role of bariatric surgery in modulation of complications of NAFLD like diabetes and cardiovascular disease. The outcomes of the future research will determine whether bariatric surgery will be one of the recommended choice for treatment of the most progressive type of NAFLD.

Dorothy Hodgkin Lecture 2012: non-alcoholic fatty liver disease, insulin resistance and ectopic fat: a new problem in diabetes management

Non-alcoholic fatty liver disease is now recognized as the hepatic component of the metabolic syndrome. Non-alcoholic fatty liver disease is a spectrum of fat-associated liver conditions that can result in end-stage liver disease and the need for liver transplantation. Simple steatosis, or fatty liver, occurs early in non-alcoholic fatty liver disease and may progress to non-alcoholic steatohepatitis, fibrosis and cirrhosis with increased risk of hepatocellular carcinoma. Prevalence estimates for non-alcoholic fatty liver disease range from 17 to 33% in the general populations and it has been estimated that non-alcoholic fatty liver disease exists in up to 70% of people with Type 2 diabetes. Non-alcoholic fatty liver disease increases risk of Type 2 diabetes and cardiovascular disease. In people with Type 2 diabetes, non-alcoholic fatty liver disease is the most frequent cause (∼80%) of fatty liver diagnosed by ultrasound. As non-alcoholic fatty liver disease is strongly associated with insulin resistance, the presence of non-alcoholic fatty liver disease with diabetes often contributes to poor glycaemic control. Consequently, strategies that decrease liver fat and improve whole-body insulin sensitivity may both contribute to prevention of Type 2 diabetes and to better glycaemic control in people who already have developed diabetes. This review summarizes the Dorothy Hodgkin lecture given by the author at the 2012 Diabetes UK annual scientific conference, proposing that fatty acid fluxes through the liver are crucial for the pathogenesis of non-alcoholic fatty liver disease and for increasing insulin resistance.

Non-alcoholic fatty liver disease and cardiovascular risk: metabolic aspects and novel treatments

Non-alcoholic fatty liver disease (NAFLD) is usually a silent disease that occurs in a very high proportion of people with features of the metabolic syndrome, including overweight, insulin resistance and type 2 diabetes. Because obesity and type 2 diabetes are now extremely common in Westernised societies, it is likely that the prevalence of NAFLD increases markedly in the future. Although previously it was thought that NAFLD was harmless, it is now recognised that NAFLD can be a progressive liver condition that increases risk of cirrhosis, end-stage liver disease and hepatocellular carcinoma. Additionally, liver fat accumulation causes insulin resistance and increases risk of type 2 diabetes. Increasing evidence now shows NAFLD is a risk factor for cardiovascular disease (CVD). The purpose of this review is to briefly discuss the pathogenesis of NAFLD, to describe the relationship between NAFLD and CVD and the mechanisms linking both conditions and to discuss some of the treatment options (including lifestyle, nutrition and drugs) that may influence both NAFLD and risk of CVD.

Statin-based treatment for cardiovascular risk and non-alcoholic fatty liver disease. Killing two birds with one stone?

Cardiovascular disease (CVD) and non-alcoholic fatty liver disease (NAFLD) share common risk factors and may have a parallel course. Statin treatment alone or in combination with other drugs has a substantially beneficial effect on CVD morbidity and mortality. The question was if these regimens were harmful for the liver. Mounting data suggest that statin monotherapy or statin-based treatments are safe in patients with NAFLD and can improve liver tests and liver ultrasonographic evidence of NAFLD. Recent data suggest that statin-based therapies are beneficial to the liver and at the same time reduce CVD morbidity and mortality in patients with NAFLD more than in subjects without it. These findings suggest that with statins we are able to get two birds with one stone.