Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0015695 (fatty liver)
 13,941 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The development of cholesterol-lowering drugs, including a statins, bile acid sequestrants and cholesterol absorption inhibitors has expanded the options for cardiovascular prevention. Recent treatment guidelines emphasise that individuals at substantial risk for atherosclerotic coronary heart disease should meet defined lipid targets. Combination therapy with drugs that have different and complementary mechanisms of action is often needed to achieve these goals. Existing approaches to the treatment of hypercholesterolaemia are still ineffective in halting the progression of coronary artery disease in some patients despite combination therapies. Other patients are resistant to, or intolerant of, conventional pharmacotherapy and remain at high-risk of atherosclerotic cardiovascular disease, so that alternative approaches are needed. New agents, including inhibitors of microsomal triglyceride transfer protein (MTP), may play a future role, either alone or in combination, in the treatment of hyperlipidaemias. This review focuses on novel approaches to treat dyslipidaemias via the inhibition of MTP. Patients most suitable for use of MTP inhibitors include those with hepatic hypersecretion of apoB, including the metabolic syndrome, Type 2 diabetes mellitus and familial combined hyperlipidaemia, as well as homozygous and heterozygous familial hypercholesterolaemia. However, certain safety issues with these agents need resolving, particularly fatty liver disease.
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PMID:MTP inhibition as a treatment for dyslipidaemias: time to deliver or empty promises? 1722 33

Although the vast majority of heavy drinkers and individuals with obesity, insulin resistance, and the metabolic syndrome have steatosis, only a minority ever develop steatohepatitis, fibrosis, and cirrhosis. Genetic and environmental risk factors for advanced alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) seem likely to include factors that influence the severity of steatosis and oxidative stress, the cytokine milieu, the magnitude of the immune response, and/or the severity of liver fibrosis. For ALD, the dose and pattern of alcohol intake, coffee intake, and dietary and other lifestyle factors leading to obesity are the most important environmental determinants of disease risk. For NAFLD, dietary saturated fat and antioxidant intake, small bowel bacterial overgrowth, and obstructive sleep apnea syndrome may play a role. Family studies and interethnic variations in susceptibility suggest that genetic factors are important in determining disease risk. For ALD, functional polymorphisms in the ADH and ALDH alcohol metabolizing genes play a role in determining susceptibility in Oriental populations. No genetic associations with advanced NAFLD have been replicated in large studies. Preliminary data suggest that polymorphisms in the genes encoding microsomal triglyceride transfer protein, superoxide dismutase 2, the CD14 endotoxin receptor, tumor necrosis factor alpha, transforming growth factor beta, and angiotensinogen may be associated with steatohepatitis or hepatic fibrosis or both.
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PMID:Genetics of alcoholic liver disease and nonalcoholic fatty liver disease. 1729 76

Hepatocyte growth factor (HGF) has various effects especially on epithelial cells. However, the precise role of HGF on lipogenesis is still not fully understood. A high-fat diet was administered to HGF transgenic mice and wild-type control mice in vivo. Furthermore, recombinant human HGF (rhHGF) was administered to HepG2 cell line in vitro. We performed an analysis regarding the factors relating to lipid metabolism. An overexpression of HGF dramatically ameliorates a high-fat diet-induced fatty liver. HGF transgenic mice showed an apparently reduced lipid accumulation in the liver. The activation of microsomal triglyceride transfer protein (MTP) and apolipoprotein B (ApoB) accompanying higher triglyceride levels in the serum were found in HGF transgenic mice on a normal diet. Interestingly, this upregulation of the MTP activation became more apparent in the high-fat diet. In addition, the administration of rhHGF stimulated MTP and ApoB expression while reducing reduced the intracellular lipid content in HepG2 cell line. However, this induction of MTP and ApoB by HGF was clearly inhibited by PD98059 (MAPK inhibitor). In conclusion, the data presented in this study indicated that HGF ameliorates a high-fat diet-induced fatty liver via the activation of MTP and ApoB.
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PMID:HGF ameliorates a high-fat diet-induced fatty liver. 1739 3

It has been shown that the hepatitis C virus (HCV) core protein reduces the activity of the microsomal triglyceride transfer protein (MTP) and could lead to steatosis in HCV-infected patients. Experimentally, apolipoprotein-AII (apoAII), which restores triglyceride secretion altered by the HCV core protein, could be protective against HCV steatosis. On the other hand, increasing plasma concentrations of mouse apoAII in transgenic mice produced several aspects of insulin-resistance syndrome, which also is implicated in the pathogenesis of HCV steatosis. This study was designed to investigate the role of apoAII in HCV-related steatosis in humans. Sixty-five hospitalized patients with chronic HCV were included in this study to assess the effects of apoAII, body mass index (BMI), age, insulin sensibility (HOMA), and leptin level on steatosis. Steatosis was observed in 55.3% of patients. Apo-AII was significantly associated with HOMA and with leptin concentrations. In univariate analyses, age, BMI, increased leptin level, increased HOMA, and increased apoAII concentration were associated with steatosis. In multivariate analysis, steatosis was associated with apoAII concentration, age, gender, and BMI. Contrary to previous hypotheses, apoAII is not a protective factor against HCV steatosis but is significantly associated with the development of liver steatosis. The fact that the plasma levels of apoAII correlate with HOMA and leptin levels in HCV-infected patients suggests that apoAII may contribute to hepatic steatosis progression in relationship to visceral obesity, insulin resistance, and metabolism of triglyceride-rich lipoproteins.
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PMID:Apolipoprotein-AII concentrations are associated with liver steatosis in patients with chronic hepatitis C. 1743 96

We evaluated the effects of a potent NO donor, S-nitroso-N-acetylcysteine (SNAC), on microsomal triglyceride transfer protein (MTP) expression in ob/ob mice. NAFLD was induced in male ob/ob mice using a methionine-choline deficient diet (MCD) concomitantly with oral SNAC fed solution (n=5) or vehicle (control; n=5) by gavage daily for 4 weeks. Livers were collected for histology and for assessing MTP by RT-qPCR, Western blot, immunohistochemistry and immunogold electron microscopy analyses. Histological analysis showed diffuse macro and microvesicular steatosis, moderate hepatocellular ballooning and moderate inflammatory infiltrate in ob/ob mice fed the MCD diet. With SNAC, mice showed a marked reduction in liver steatosis (p<0.01), in parenchymal inflammation (p=0.02) and in MTP protein immunoexpression in zone III (p=0.05). Moreover, SNAC caused reduction of MTP protein in Western blot analysis (p<0.05). In contrast, MTP mRNA content was significantly higher (p<0.05) in mice receiving SNAC. Immuno-electron microscopy showed MTP localized in the rough endoplasmic reticulum of hepatocytes in both treated and untreated groups. However with SNAC treatment, MTP was also observed surrounding fat globules. Histological improvement mediated by a nitric oxide donor is associated with significantly altered expression and distribution of MTP in this animal model of fatty liver disease. Further studies are in progress to examine possible mechanisms and to develop SNAC as a possible therapy for human fatty liver disease.
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PMID:Modulation of hepatic microsomal triglyceride transfer protein (MTP) induced by S-nitroso-N-acetylcysteine in ob/ob mice. 1752 68

Worldwide approximately 200 million people are chronically infected with hepatitis C virus (HCV). Chronic HCV infection represents the leading cause of liver cirrhosis and the main indication for liver transplantation in the western world. In addition, chronic HCV infection is associated with numerous clinical manifestations, including type 2 diabetes. An obvious and frequently suggested explanation for the connection between HCV infection and type 2 diabetes is that cirrhosis by itself causes insulin resistance. However, the prevalence of type 2 diabetes in HCV cirrhosis is higher than in HBV cirrhosis (23.6% vs 9.4%). This suggests that HCV infection by itself can lead to insulin resistance and predispose to the onset of type 2 diabetes. First, HCV core protein induces hepatic steatosis by inhibition of microsomal triglyceride transfer protein and hepatic steatosis causes insulin resistance. Secondly, HCV core protein inhibits, through elevation of TNF-alfa and other factors, the insulin-signalling pathways causing insulin resistance. Moreover, recent data strongly suggest that insulin resistance is an important predictor of poor response to antiviral therapy in chronic hepatitis patients treated with peginterferon plus ribavirin.
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PMID:Hepatitis C and insulin resistance: mutual interactions. A review. 1754 92

The antiretroviral nucleoside reverse-transcriptase inhibitor (NRTI) stavudine (d4T) can induce mild to severe liver injuries such as steatosis (i.e. triglyceride accumulation), steatohepatitis and liver failure. NRTI-induced toxicity has been ascribed to the inhibition of mitochondrial DNA (mtDNA) replication causing mtDNA depletion and respiratory chain dysfunction. This can secondarily impair the tricarboxylic acid cycle and fatty acid oxidation (FAO), thus leading to lactic acidosis and hepatic steatosis. However, NRTIs could also impair mitochondrial function and induce hepatic steatosis through other mechanisms. In this study, we sought to determine whether d4T could inhibit mitochondrial FAO and induce triglyceride accumulation through a mtDNA-independent mechanism. Since human tumoral and non-tumoral hepatic cell lines were unable to efficiently oxidize palmitic acid, the effects of d4T on mitochondrial FAO were assessed on cultured rat hepatocytes. Our results showed that 750 microM of d4T significantly inhibited palmitic acid oxidation after 48 or 72 h of culture, without inducing cell death. Importantly, high concentrations of zidovudine and zalcitabine (two other NRTIs that can induce hepatic steatosis), or beta-aminoisobutyric acid (a d4T metabolite), did not impair FAO in rat hepatocytes. D4T-induced FAO inhibition was observed without mtDNA depletion and lactate production, and was fully prevented with l-carnitine or clofibrate coincubation. l-carnitine also prevented the accretion of neutral lipids within rat hepatocytes. High concentrations of d4T were unable to inhibit FAO on freshly isolated liver mitochondria. Moreover, a microarray analysis was performed to clarify the mechanism whereby d4T can inhibit mitochondrial FAO and induce triglyceride accumulation in rat hepatocytes. The microarray data, confirmed by quantitative real-time PCR analysis, showed that d4T increased the expression of sterol regulatory element-binding protein-1c (SREBP1c) and reduced that of microsomal triglyceride transfer protein (MTP). Finally, d4T-induced alteration of SREBP1c and MTP expression was partially prevented by l-carnitine. Thus, short-term incubation with high concentrations of d4T can rapidly induce accumulation of neutral lipids within rat hepatocytes, which can be fully prevented by l-carnitine. Furthermore, our investigations suggested that lipid accumulation could be the consequence of a dual mechanism, namely a mtDNA-independent impairment of mitochondrial FAO and a reduction of lipid export from the hepatocytes.
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PMID:High concentrations of stavudine impair fatty acid oxidation without depleting mitochondrial DNA in cultured rat hepatocytes. 1829 83

Whereas most individuals with nonalcoholic fatty liver disease (NAFLD) will have steatosis, only a minority will ever develop progressive disease. Family studies and interethnic variations in susceptibility suggest that genetic factors may be important in determining disease risk. Although no genetic associations with advanced NAFLD have been replicated in large studies, preliminary data suggest that polymorphisms in the genes encoding microsomal triglyceride transfer protein, superoxide dismutase 2, the CD14 endotoxin receptor, tumor necrosis factor-alpha, transforming growth factor-beta, and angiotensinogen may be associated with steatohepatitis and/or fibrosis. With the advent of high-throughput gene analyses and the reduced cost of whole genome-wide scans, it seems likely that genes contributing to inherited susceptibility to this common disease will be identified in the near future.
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PMID:Genes and nonalcoholic fatty liver disease. 1844 59

The liver secretes triglyceride-rich VLDLs, and the triglycerides in these particles are taken up by peripheral tissues, mainly heart, skeletal muscle, and adipose tissue. Blocking hepatic VLDL secretion interferes with the delivery of liver-derived triglycerides to peripheral tissues and results in an accumulation of triglycerides in the liver. However, it is unclear how interfering with hepatic triglyceride secretion affects adiposity, muscle triglyceride stores, and insulin sensitivity. To explore these issues, we examined mice that cannot secrete VLDL [due to the absence of microsomal triglyceride transfer protein (Mttp) in the liver]. These mice exhibit markedly reduced levels of apolipoprotein B-100 in the plasma, along with reduced levels of triglycerides in the plasma. Despite the low plasma triglyceride levels, triglyceride levels in skeletal muscle were unaffected. Adiposity and adipose tissue triglyceride synthesis rates were also normal, and body weight curves were unaffected. Even though the blockade of VLDL secretion caused hepatic steatosis accompanied by increased ceramides and diacylglycerols in the liver, the mice exhibited normal glucose tolerance and were sensitive to insulin at the whole-body level, as judged by hyperinsulinemic euglycemic clamp studies. Normal hepatic glucose production and insulin signaling were also maintained in the fatty liver induced by Mttp deletion. Thus, blocking VLDL secretion causes hepatic steatosis without insulin resistance, and there is little effect on muscle triglyceride stores or adiposity.
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PMID:Blocking VLDL secretion causes hepatic steatosis but does not affect peripheral lipid stores or insulin sensitivity in mice. 1851 9

Hepatic apolipoprotein B (apoB) lipoprotein production is metabolically regulated via the phosphoinositide 3-kinase cascade; however, the role of the key negative regulator of this pathway, the tumor suppressor phosphatase with tensin homology (PTEN), is unknown. Here, we demonstrate that hepatic protein levels of apoB100 and microsomal triglyceride transfer protein (MTP) are significantly down-regulated (73% and 36%, respectively) in the liver of PTEN liver-specific knockout (KO) mice, and this is accompanied by increased triglyceride (TG) accumulation and lipogenic gene expression, and reduced hepatic apoB secretion in freshly isolated hepatocytes. MTP protein mass and lipid transfer activity were also significantly reduced in liver of PTEN KO mice. Overexpression of the dominant negative mutant PTEN C/S124 (adenovirus expressing PTEN C/S mutant [AdPTENC/S]) possessing constitutive phospoinositide 3-kinase activity in HepG2 cells led to significant reductions in both secreted apoB100 and cellular MTP mass (76% and 34%, respectively), and increased messenger RNA (mRNA) levels of sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC). Reduced apoB100 secretion induced by AdPTENC/S was associated with increased degradation of newly-synthesized cellular apoB100, in a lactacystin-sensitive manner, suggesting enhanced proteasomal degradation. AdPTENC/S also reduced apoB-lipoprotein production in McA-RH7777 and primary hamster hepatocytes. Our findings suggest a link between PTEN expression and hepatic production of apoB-containing lipoproteins. We postulate that perturbations in PTEN not only may influence hepatic insulin signaling and hepatic lipogenesis, but also may alter hepatic apoB-lipoprotein production and the MTP stability. On loss of PTEN activity, increased lipid substrate availability in the face of reduced hepatic lipoprotein production capacity can rapidly lead to hepatosteatosis and fatty liver.
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PMID:Phosphatase and tensin homolog (PTEN) regulates hepatic lipogenesis, microsomal triglyceride transfer protein, and the secretion of apolipoprotein B-containing lipoproteins. 1902 12


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