Abstract. Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent causes of abnormal liver dysfunction, and its prevalence has markedly increased. We previously evaluated the expression of fatty acid metabolism-related genes in NAFLD and reported changes in expression that could contribute to increased fatty acid synthesis. In the present study, we evaluated the expression of additional fatty acid metabolism-related genes in larger groups of NAFLD (n=26) and normal liver (n=10) samples. The target genes for real-time PCR analysis were as follows: acetyl-CoA carboxylase (ACC) 1, ACC2, fatty acid synthase (FAS), sterol regulatory element-binding protein 1c (SREBP-1c), and adipose differentiation-related protein (ADRP) for evaluation of de novo synthesis and uptake of fatty acids; carnitine palmitoyltransferase 1a (CPT1a), long-chain acyl-CoA dehydrogenase (LCAD), long-chain L-3-hydroxyacylcoenzyme A dehydrogenase α (HADHα), uncoupling protein 2 (UCP2), straight-chain acyl-CoA oxidase (ACOX), branched-chain acyl-CoA oxidase (BOX), cytochrome P450 2E1 (CYP2E1), CYP4A11, and peroxisome proliferatoractivated receptor (PPAR)α for oxidation in the mitochondria, peroxisomes and microsomes; superoxide dismutase (SOD), catalase, and glutathione synthetase (GSS) for antioxidant pathways; and diacylglycerol O-acyltransferase 1 (DGAT1), PPARγ, and hormone-sensitive lipase (HSL) for triglyceride synthesis and catalysis. In NAFLD, although fatty acids accumulated in hepatocytes, their de novo synthesis and uptake were up-regulated in association with increased expression of ACC1, FAS, SREBP-1c, and ADRP. Fatty acid oxidation-related genes, LCAD, HADHα, UCP2, ACOX, BOX, CYP2E1, and CYP4A11, were all overexpressed, indicating that oxidation was enhanced in NAFLD, whereas the expression of CTP1a and PPARα was decreased. Furthermore, SOD and catalase were also overexpressed, indicating that antioxidant pathways are activated to neutralize reactive oxygen species (ROS), which are overproduced during oxidative processes. The expression of DGAT1 was up-regulated without increased PPARγ expression, whereas the expression of HSL was decreased. Our data indicated the following regarding NAFLD: i) increased de novo synthesis and uptake of fatty acids lead to further fatty acid accumulation in hepatocytes; ii) mitochondrial fatty acid oxidation is decreased or fully activated; iii) in order to complement the function of mitochondria (ß-oxidation), peroxisomal (ß-oxidation) and microsomal (ω-oxidation) oxidation is up-regulated to decrease fatty acid accumulation; iv) antioxidant pathways including SOD and catalase are enhanced to neutralize ROS overproduced during mitochondrial, peroxisomal, and microsomal oxidation; and v) lipid droplet formation is enhanced due to increased DGAT expression and decreased HSL expression. Further studies will be needed to clarify how fatty acid synthesis is increased by SREBP-1c, which is under the control of insulin and AMP-activated protein kinase. IntroductionNonalcoholic fatty liver disease...

Abstract. Nonalcoholic fatty liver disease (NAFLD) is a common liver disease whose prevalence has increased markedly. We reported previously that fatty acid synthesis was enhanced in NAFLD with the accumulation of fatty acids. To clarify the disorder, we evaluated the expression of genes regulating fatty acid synthesis by real-time PCR using samples from NAFLD (n=22) and normal liver (control; n=10). A major regulator of fatty acids synthesis is sterol regulatory element-binding protein-1c (SREBP-1c). Its expression was significantly higher in NAFLD, nearly 5-fold greater than the controls. SREBP-1c is positively regulated by insulin signaling pathways, including insulin receptor substrate (IRS)-1 and -2. In NAFLD, IRS-1 expression was enhanced and correlated positively with SREBP-1c expression. In contrast, IRS-2 expression decreased by 50% and was not correlated with SREBP-1c. Forkhead box protein A2 (Foxa2) is a positive regulator of fatty acid oxidation and is itself negatively regulated by IRSs. Foxa2 expression increased in NAFLD and showed a negative correlation with IRS-2, but not with IRS-1, expression. It is known that SREBP-1c is negatively regulated by AMPactivated protein kinase (AMPK) but expression levels of AMPK in NAFLD were almost equal to those of the controls. These data indicate that, in NAFLD, insulin signaling via IRS-1 causes the up-regulation of SREBP1-c, leading to the increased synthesis of fatty acids by the hepatocytes; negative feedback regulation via AMPK does not occur and the activation of Foxa2, following a decrease of IRS-2, upregulates fatty acid oxidation. IntroductionNonalcoholic fatty liver disease (NAFLD) is one of the most frequent causes of liver dysfunction (1-3) and its prevalence has been increasing markedly (4-6). Furthermore, nonalcoholic steatohepatitis (NASH), a severe form of NAFLD accompanied by hepatitis and fibrosis, may progress to cirrhosis and hepatic failure (7,8). NAFLD is often found in patients with obesity and/or insulin resistance, however, its precise cause remains unclear. Therefore, it is important to understand the features of lipid metabolism, particularly fatty acid metabolism, in NAFLD. Previously, we evaluated the expression levels of genes involved in fatty acid metabolism in the liver with NAFLD and found that the expression of those genes including acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), was up-regulated, indicating that fatty acid synthesis was enhanced in hepatocytes, leading to the accumulation of fatty acids (9,10).Sterol regulatory element-binding proteins (SREBPs) are membrane-bound transcription factors that regulate the expression of genes involved in lipid synthesis, and SREBP-1c positively regulates the expression of genes encoding lipogenic enzymes including ACC and FAS (11,12). Insulin is a well-known stimulator of lipogenesis and activates the hepatic expression of 14). Insulin receptor substrate (IRS) proteins, a family of docking molecules, connect insulin receptor activation to essential downstream cascad...

These findings suggest that LXR acts as one of the main regulators of lipid metabolism by regulating SREBP-1c expression in NAFLD.

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Abstract. Non-alcoholic fatty liver disease (NAFLD) is considered a hepatic manifestation of metabolic syndrome, which is known to be associated with insulin resistance (IR). NAFLD occurs when the rate of hepatic fatty acid uptake from plasma and de novo fatty acid synthesis is greater than the rate of fatty acid oxidation and excretion as very low-density lipoprotein (VLDL). To estimate the effects of IR on hepatic lipid excretion, mRNA expression levels of genes involved in VLDL assembly were analyzed in NAFLD liver. Twenty-two histologically proven NAFLD patients and 10 healthy control subjects were enrolled in this study. mRNA was extracted from liver biopsy samples and real-time PCR was performed to quantify the expression levels of apolipoprotein B (apoB), microsomal triglyceride transfer protein (MTP) and liver fattyacid binding protein (L-FABP). Hepatic expression levels of the genes were compared between NAFLD patients and control subjects. In NAFLD patients, we also examined correlations between expression levels of the genes and metabolic factors, including IR, and the extent of obesity and hepatic lipid accumulation. Hepatic expression levels of apoB, MTP and L-FABP were significantly up-regulated in NAFLD patients compared to control subjects. The expression levels of MTP were correlated with those of apoB, but not with those of L-FABP. In the NAFLD liver, the expression levels of MTP were significantly reduced in patients with HOMA-IR >2.5. In addition, a significant reduction in MTP expression was observed in livers with advanced steatosis. Enhanced expression of genes involved in VLDL assembly may be promoted to release excess lipid from NAFLD livers. However, the progression of IR and hepatic steatosis may attenuate this compensatory process.

Branched-chain amino acids (BCAAs) have a potential to improve glucose metabolism in cirrhotic patients; however, the contribution of liver in this process has not been clarified. To estimate the effect of BCAA on glucose metabolism in liver, we evaluated the mRNA expression levels of glucose-sensing apparatus genes in HepG2 cells and in rat liver after oral administration of BCAA. HepG2 cells were cultured in low glucose (100 mg/dl) or high glucose (400 mg/dl) in the absence or presence of BCAA. The mRNA expression levels and protein levels of GLUT2 and liver-type glucokinase (L-GK) were estimated using RT-PCR and immunoblotting. The expression levels of transcriptional factors, including SREBP-1c, ChREBP, PPAR-gm and LXRa, were estimated. The mRNA expression levels of transcriptional factors, glycogen synthase, and genes involved in gluconeogenesis were evaluated in rat liver at 3 h after the administration of BCAA. BCAA accelerated the expression of GLUT2 and L-GK in HepG2 cells in high glucose. Expression levels of ChREBP, SREBP-1c, and LXRa were also increased in this condition. BCAA administration enhanced the mRNA expression levels of L-GK, SREBP-1c, and LXRa and suppressed the expression levels of G-6-Pase in rat liver, without affecting the expression levels of glycogen synthase or serum glucose concentrations. BCAA administration enhanced the bioactivity of the glucose-sensing apparatus, probably via the activation of a transcriptional mechanism, suggesting that these amino acids may improve glucose metabolism through the accelerated utility of glucose and glucose-6-phosphate in the liver.

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Background Previous studies have suggested an association between the use of direct‐acting antiviral agents (DAAs) for treating hepatitis C virus (HCV) infection and the resulting decrease in the incidence of hepatocellular carcinoma (HCC); however, it is unclear whether DAAs prevent the recurrence of HCC after curative treatment for HCC. This study aimed to prospectively investigate HCC recurrence and its predictors after curative treatment for HCC. Methods A total of 3012 patients with chronic HCV infection, with or without cirrhosis, who were treated with DAAs were enrolled between January 1, 2015 and January 31, 2017 as per the institutional review board approved study protocol at 15 institutions, including 10 university hospitals and five high‐volume centers in the Kyusyu area of Japan. Of the 3012 patients, 459 patients who had HCC but were cured with surgery or ablation therapy (curative treatment) before the use of DAAs were included in the analysis. Results During a mean follow‐up period of 29.4 months, 217 (47.2%) patients developed HCC recurrence. The median time to recurrence was 34.0 months, and the 1‐, 2‐, and 3‐year cumulative HCC recurrence rates were 27.1%, 43.4%, and 50.8%, respectively. The risk factors for HCC recurrence were the α‐fetoprotein (AFP) level before DAA therapy ( P = 0.0047) and the number of curative treatments for HCC before DAA therapy ( P < 0.0001). Conclusions A high AFP level and multiple occurrences of HCC before DAA therapy are associated with a high risk for HCC recurrence after curative treatment. Follow‐up after DAA therapy should include special attention to the abovementioned risk factors.