In:
Arteriosclerosis, Thrombosis, and Vascular Biology, Ovid Technologies (Wolters Kluwer Health), Vol. 22, No. 3 ( 2002-03), p. 476-482
Abstract:
Humans and genetically engineered mice with hypobetalipoproteinemia due to truncation-producing mutations of the apolipoprotein B (apoB) gene frequently have fatty livers, because the apoB defect impairs the capacity of livers to export triglycerides (TGs). We assessed the adaptation of hepatic lipid metabolism in our apoB-38.9-bearing mice. Hepatic TG contents were 2- and 4-fold higher in heterozygous and homozygous mice, respectively, compared with wild-type mice. Respective in vivo hepatic fatty acid synthetic rates were reduced to 40% and 15% of the wild-type rate. Hepatic mRNAs for sterol regulatory element-binding protein (SREBP)-1c, fatty acid synthase (FAS), and stearoyl coenzyme A desaturase-1 were coordinately decreased. FAS and SREBP-1c mRNA levels were strongly and positively correlated with each other and inversely correlated with hepatic TGs, suggesting that impaired TG export is a potent inhibitor of fatty acid synthesis. In contrast, levels of plasma β-hydroxybutyrate and of hepatic carnitine palmitoyl transferase and peroxisome proliferator-activated receptor-α mRNAs were not altered, implying that β-oxidation was not affected. Fasting followed by refeeding increased hepatic fatty acid synthesis 56-fold over fasting in normal and heterozygous mice but only 24-fold in homozygous mice. Parallel changes occurred in FAS and SREBP-1c mRNAs. Thus, impairment of very low density lipoprotein export downregulates hepatic fatty acid synthesis, but the adaptation is incomplete, resulting in fatty livers. The signals mediating suppression of FAS and SREBP-1c levels remain to be identified.
Type of Medium:
Online Resource
ISSN:
1079-5642
,
1524-4636
DOI:
10.1161/hq0302.105271
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2002
detail.hit.zdb_id:
1494427-3
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