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Re-evaluation of fatty acid metabolism-related gene expression in nonalcoholic fatty liver disease.
Int J Mol Med. 2007 Sep; 20(3):351-8.IJ

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 alpha (HADHalpha), uncoupling protein 2 (UCP2), straight-chain acyl-CoA oxidase (ACOX), branched-chain acyl-CoA oxidase (BOX), cytochrome P450 2E1 (CYP2E1), CYP4A11, and peroxisome proliferator-activated receptor (PPAR)alpha 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), PPARgamma, 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, HADHalpha, UCP2, ACOX, BOX, CYP2E1, and CYP4A11, were all overexpressed, indicating that oxidation was enhanced in NAFLD, whereas the expression of CTP1a and PPARalpha 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 PPARgamma 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 (beta-oxidation), peroxisomal (beta-oxidation) and microsomal (omega-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.

Authors+Show Affiliations

Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 812-8582 Fukuoka, Japan.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

17671740

Citation

Kohjima, Motoyuki, et al. "Re-evaluation of Fatty Acid Metabolism-related Gene Expression in Nonalcoholic Fatty Liver Disease." International Journal of Molecular Medicine, vol. 20, no. 3, 2007, pp. 351-8.
Kohjima M, Enjoji M, Higuchi N, et al. Re-evaluation of fatty acid metabolism-related gene expression in nonalcoholic fatty liver disease. Int J Mol Med. 2007;20(3):351-8.
Kohjima, M., Enjoji, M., Higuchi, N., Kato, M., Kotoh, K., Yoshimoto, T., Fujino, T., Yada, M., Yada, R., Harada, N., Takayanagi, R., & Nakamuta, M. (2007). Re-evaluation of fatty acid metabolism-related gene expression in nonalcoholic fatty liver disease. International Journal of Molecular Medicine, 20(3), 351-8.
Kohjima M, et al. Re-evaluation of Fatty Acid Metabolism-related Gene Expression in Nonalcoholic Fatty Liver Disease. Int J Mol Med. 2007;20(3):351-8. PubMed PMID: 17671740.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Re-evaluation of fatty acid metabolism-related gene expression in nonalcoholic fatty liver disease. AU - Kohjima,Motoyuki, AU - Enjoji,Munechika, AU - Higuchi,Nobito, AU - Kato,Masaki, AU - Kotoh,Kazuhiro, AU - Yoshimoto,Tsuyoshi, AU - Fujino,Tatsuya, AU - Yada,Masayoshi, AU - Yada,Ryoko, AU - Harada,Naohiko, AU - Takayanagi,Ryoichi, AU - Nakamuta,Makoto, PY - 2007/8/3/pubmed PY - 2007/10/12/medline PY - 2007/8/3/entrez SP - 351 EP - 8 JF - International journal of molecular medicine JO - Int J Mol Med VL - 20 IS - 3 N2 - 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 alpha (HADHalpha), uncoupling protein 2 (UCP2), straight-chain acyl-CoA oxidase (ACOX), branched-chain acyl-CoA oxidase (BOX), cytochrome P450 2E1 (CYP2E1), CYP4A11, and peroxisome proliferator-activated receptor (PPAR)alpha 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), PPARgamma, 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, HADHalpha, UCP2, ACOX, BOX, CYP2E1, and CYP4A11, were all overexpressed, indicating that oxidation was enhanced in NAFLD, whereas the expression of CTP1a and PPARalpha 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 PPARgamma 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 (beta-oxidation), peroxisomal (beta-oxidation) and microsomal (omega-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. SN - 1107-3756 UR - https://www.unboundmedicine.com/medline/citation/17671740/Re_evaluation_of_fatty_acid_metabolism_related_gene_expression_in_nonalcoholic_fatty_liver_disease_ L2 - http://www.spandidos-publications.com/ijmm/20/3/351 DB - PRIME DP - Unbound Medicine ER -