Pivotal role of the Keap1-Nrf2 pathway in the pathogenesis and prevention of non-alcoholic steatohepatitis induced cirrhosis

Keap1-Nrf2通路在非酒精性脂肪性肝炎肝硬化发病机制和预防中的关键作用

• 批准号: MR/J001465/1
• 负责人: John Hayes
• 金额: $ 75.53万
• 依托单位: University of Dundee
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FJ001465%2F1
• 关键词: Pivotal; role; Keap1; Nrf2; pathway

Non-alcoholic steatohepatitis (NASH) is a common disease that involves fat accumulation in liver cells and inflammation of the liver. Its incidence is increasing rapidly because it is prevalent in individuals with diabetes and those who are obese; it has been estimated that approximately 2.0% of the adult population in the UK may have NASH. This trend is alarming, and has huge cost implications for the National Health Service, because NASH can give rise to liver fibrosis, cirrhosis and cancer, none of which are treatable. It is thought that NASH arises in certain individuals because their livers do not cope with metabolic changes produced by diet, diabetes or the environment. In each of these cases, it is envisaged that oxidative stress represents a common consequence of the physiological and environmental insults that produce liver disease. The activity of a protein known as Nrf2 is emerging as the most important determinant of susceptibility to NASH for three reasons: (i) it keeps fat production and storage in the liver low; (ii) it helps maintain high levels of anti-inflammatory proteins and (iii) it is a vital component in maintaining high levels of natural anti-oxidant agents in the liver. We hypothesize that Nrf2 normally functions to minimise the likelihood of NASH arising, and that by increasing its activity using drugs will protect 'at risk' individuals of developing NASH and the disease progressing further. To date, experiments that have implicated Nrf2 in determining susceptibility to NASH or prevention of the disease have used a specialized, non-standard diet (deficient in certain key molecules), which is not relevant to the human disease. Unfortunately, no standard animal model exists that recapitulates the entire spectrum of liver pathology (i.e., from steatosis, to NASH, to fibrosis, to cirrhosis and to hepatoma), which we can use to test the role of Nrf2 in this disease. In a pilot study, we have found that feeding a 'Western' high fat (HF) diet to mice for 24 weeks produced mild NASH, whereas feeding the same diet to mice totally deficient of Nrf2 for the same period produced full-blown NASH with fibrosis and cirrhosis. We now wish to confirm these preliminary findings by studying a larger number of animals on the HF diet, and by examining the time-course of the disease using biomarkers (i.e. monitoring levels of certain disease-associated molecules in the blood).In order to prove whether Nrf2 is important in the development of NASH and its progression to fibrosis and cirrhosis, we first require at least one reliable animal model that reflects the human disease. To this end, we will generate two models, which we anticipate will develop liver disease at different rates: firstly, we will feed normal mice a 'Western' high fat (HF) diet; secondly, we will feed normal mice a 'Western' high fat + fructose (i.e. high levels of sugar; HFF) diet. A detailed time course of the development of fatty liver, NASH, fibrosis and cirrhosis in mice fed these two diets will be established using clinical chemistry, histology and biochemical measurements of pathological changes associated with development of the disease. Once the rate of progression of the disease has been established in the normal mice placed on the 'Western' HF and HFF diets, we will examine the contribution that Nrf2 makes to protection against NASH by testing whether removal of this protein results in an accelerated appearance of NASH, fibrosis and cirrhosis when these mice are fed the same diets. Lastly, we will examine whether activation of Nrf2, either by genetic means or by treatment with a certain type of drug, inhibits the appearance of NASH, fibrosis, or cirrhosis when the animals are fed the same 'Western' HF and HFF diets.

非酒精性脂肪性肝炎（NASH）是一种常见疾病，涉及肝细胞脂肪堆积和肝脏炎症。它的发病率正在迅速增加，因为它在糖尿病患者和肥胖者中普遍存在；据估计，英国大约有 2.0% 的成年人可能患有 NASH。这一趋势令人震惊，并且对国家卫生服务产生巨大的成本影响，因为 NASH 会导致肝纤维化、肝硬化和癌症，而这些都是无法治疗的。人们认为，某些人之所以会出现 NASH，是因为他们的肝脏无法应对饮食、糖尿病或环境产生的代谢变化。在这些情况下，氧化应激被认为是导致肝脏疾病的生理和环境损伤的常见后果。一种被称为 Nrf2 的蛋白质的活性正在成为 NASH 易感性的最重要决定因素，原因有以下三个：(i) 它使肝脏中的脂肪产生和储存保持在较低水平； (ii) 它有助于维持高水平的抗炎蛋白，(iii) 它是维持肝脏中高水平的天然抗氧化剂的重要组成部分。我们假设 Nrf2 的正常功能是最大限度地减少 NASH 发生的可能性，并且通过使用药物增加其活性将保护处于发生 NASH 和疾病进一步进展的“风险”个体。迄今为止，涉及 Nrf2 确定 NASH 易感性或预防该疾病的实验都使用了专门的非标准饮食（缺乏某些关键分子），这与人类疾病无关。不幸的是，没有标准的动物模型能够概括整个肝脏病理学范围（即从脂肪变性到 NASH，到纤维化，到肝硬化和肝癌），我们可以用它来测试 Nrf2 在这种疾病中的作用。在一项初步研究中，我们发现给小鼠喂食“西方”高脂肪 (HF) 饮食 24 周会产生轻度 NASH，而在同一时期给完全缺乏 Nrf2 的小鼠喂食相同的饮食会产生全面的 NASH，并伴有纤维化和肝硬化。我们现在希望通过研究大量HF饮食的动物，并使用生物标志物检查疾病的时间进程（即监测血液中某些疾病相关分子的水平）来证实这些初步发现。为了证明Nrf2在NASH的发展及其向纤维化和肝硬化的进展中是否重要，我们首先需要至少一个反映人类疾病的可靠动物模型。为此，我们将生成两个模型，我们预计它们将以不同的速度发展为肝病：首先，我们将给正常小鼠喂食“西方”高脂肪（HF）饮食；其次，我们将给正常小鼠喂食“西方”高脂肪+果糖（即高水平糖；HFF）饮食。将使用与疾病发展相关的病理变化的临床化学、组织学和生化测量来确定饲喂这两种饮食的小鼠脂肪肝、NASH、纤维化和肝硬化发展的详细时间过程。一旦确定了接受“西方”HF 和 HFF 饮食的正常小鼠的疾病进展速度，我们将通过测试在给这些小鼠喂食相同饮食时，去除这种蛋白质是否会导致 Nrf2 加速出现 NASH、纤维化和肝硬化，来研究 Nrf2 对预防 Nrf2 的贡献。最后，我们将检查当动物被喂食相同的“西方”HF 和 HFF 饮食时，通过遗传手段或通过某种类型的药物治疗来激活 Nrf2 是否会抑制 NASH、纤维化或肝硬化的出现。

项目成果

Susceptibility of Nrf2-null mice to steatohepatitis and cirrhosis upon consumption of a high-fat diet is associated with oxidative stress, perturbation of the unfolded protein response, and disturbance in the expression of metabolic enzymes but not with insulin resistance.

• DOI: 10.1128/mcb.00677-14
• 发表时间: 2014-09
• 期刊: Molecular and cellular biology
• 影响因子: 5.3
• 作者: Meakin PJ;Chowdhry S;Sharma RS;Ashford FB;Walsh SV;McCrimmon RJ;Dinkova-Kostova AT;Dillon JF;Hayes JD;Ashford ML
• 通讯作者: Ashford ML

Mechanisms of activation of the transcription factor Nrf2 by redox stressors, nutrient cues, and energy status and the pathways through which it attenuates degenerative disease.

• DOI: 10.1016/j.freeradbiomed.2015.06.021
• 发表时间: 2015-11
• 期刊: Free radical biology & medicine
• 影响因子: 7.4
• 作者: Tebay LE;Robertson H;Durant ST;Vitale SR;Penning TM;Dinkova-Kostova AT;Hayes JD
• 通讯作者: Hayes JD