ABSTRACT
BACKGROUND: ACAT-related enzyme 2 required for viability 1 (ARV1) is a putative lipid transporter of the endoplasmic reticulum that is conserved across eukaryotic species. The ARV1 protein contains a conserved N-terminal cytosolic zinc ribbon motif known as the ARV1 homology domain, followed by multiple transmembrane regions anchoring it in the ER. Deletion of ARV1 in yeast results in defective sterol trafficking, aberrant lipid synthesis, ER stress, membrane disorganization and hypersensitivity to fatty acids (FAs). We sought to investigate the role of Arv1 in mammalian lipid metabolism. METHODS: Homologous recombination was used to disrupt the Arv1 gene in mice. Animals were examined for alterations in lipid and lipoprotein levels, body weight, body composition, glucose tolerance and energy expenditure. RESULTS: Global loss of Arv1 significantly decreased total cholesterol and high-density lipoprotein cholesterol levels in the plasma. Arv1 knockout mice exhibited a dramatic lean phenotype, with major reductions in white adipose tissue (WAT) mass and body weight on a chow diet. This loss of WAT is accompanied by improved glucose tolerance, higher adiponectin levels, increased energy expenditure and greater rates of whole-body FA oxidation. CONCLUSIONS: This work identifies Arv1 as an important player in mammalian lipid metabolism and whole-body energy homeostasis.
ABSTRACT
The hypothesis that hepatitis B infection is etiologically related to hepatoma has been investigated by studying the interrelationships between hepatitis B surface antigen (HBsAg, Australia antigen) and the fast-moving 5'-nucleotide phosphodiesterase Band V isoenzyme (5'-NPDase-V). Sera from 58 patients with viral hepatitis were tested for 5'-NPDase-V and HBsAg. The isoenzyme was found in 34 of 37 patients who were also positive for HBsAg but in only 4 of 21 hepatitis patients who were HBsAg negative. Five patients convalescing from hepatitis were negative for both HBsAg and the isoenzyme. Preparative gel electrophoresis showed that these 2 markers were different proteins. Of 34 hepatoma patients, 29 were positive for 5'-NPDase-V. Only 1 isoenzyme-positive patient was positive for HBsAg by counterimmunoelectrophoresis. However, of 16 isoenzyme-positive hepatoma patients available for radioimmunoassay, 8 were NBsAg positive (50%). None of 21 hepatoma samples tested for antibody to NBsAg was positive. Of 21 "normal" carriers of HBsAg and 10 carriers with Down's syndrome, 4 persons were detected with the isoenzyme. The results suggest that HBsAg and 5'-NPDase-V in the presence of liver damage are associated and thus provide a new marker enzyme between hepatitis B infection and hepatoma.
