Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.2.1.22 (cystathionine beta-synthase)
 965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hyperhomocysteinemia (HHCY) is a consequence of impaired methionine/cysteine metabolism and is caused by deficiency of vitamins and/or enzymes such as cystathionine beta-synthase (CBS). Although HHCY is an important and independent risk factor for cardiovascular diseases that are commonly associated with hepatic steatosis, the mechanism by which homocysteine promotes the development of fatty liver is poorly understood. CBS-deficient (CBS(-/-)) mice were previously generated by targeted deletion of the Cbs gene and exhibit pathological features similar to HHCY patients, including endothelial dysfunction and hepatic steatosis. Here we show abnormal lipid metabolism in CBS(-/-) mice. Triglyceride and nonesterified fatty acid levels were markedly elevated in CBS(-/-) mouse liver and serum. The activity of thiolase, a key enzyme in beta-oxidation of fatty acids, was significantly impaired in CBS(-/-) mouse liver. Hepatic apolipoprotein B100 levels were decreased, whereas serum apolipoprotein B100 and very low density lipoprotein levels were elevated in CBS(-/-) mice. Serum levels of cholesterol/phospholipid in high density lipoprotein fractions but not of total cholesterol/phospholipid were decreased, and the activity of lecithin-cholesterol acyltransferase was severely impaired in CBS(-/-) mice. Abnormal high density lipoprotein particles with higher mobility in polyacrylamide gel electrophoresis were observed in serum obtained from CBS(-/-) mice. Moreover, serum cholesterol/triglyceride distribution in lipoprotein fractions was altered in CBS(-/-) mice. These results suggest that hepatic steatosis in CBS(-/-) mice is caused by or associated with abnormal lipid metabolism.
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PMID:Abnormal lipid metabolism in cystathionine beta-synthase-deficient mice, an animal model for hyperhomocysteinemia. 1546 79

We previously reported that hyperhomocysteinemia (HHcy), an independent risk factor of coronary artery disease (CAD), is associated with increased atherosclerosis and decreased plasma high-density lipoprotein cholesterol (HDL-C) in cystathionine beta-synthase-/apolipoprotein E-deficient (CBS(-/-)/apoE(-/-)) mice. We observed that plasma homocysteine (Hcy) concentrations are negatively correlated with HDL-C and apolipoprotein A1 (apoA-I) in patients with CAD. We found the loss of large HDL particles, increased HDL-free cholesterol, and decreased HDL protein in CBS(-/-)/apoE(-/-) mice, and attenuated cholesterol efflux from cholesterol-loaded macrophages to plasma in CBS(-/-)/apoE(-/-) mice. ApoA-I protein was reduced in the plasma and liver, but hepatic apoA-I mRNA was unchanged in CBS(-/-)/apoE(-/-) mice. Moreover, Hcy (0.5 to 2 mmol/L) reduced the levels of apoA-I protein but not mRNA and inhibited apoA-1 protein synthesis in mouse primary hepatocytes. Further, plasma lecithin:cholesterol acyltransferase (LCAT) substrate reactivity was decreased, LCAT specific activity increased, and plasma LCAT protein levels unchanged in apoE(-/-)/CBS(-/-) mice. Finally, the clearance of plasma HDL cholesteryl ester, but not HDL protein, was faster in CBS(-/-)/apoE(-/-) mice, correlated with increased scavenger receptor B1, and unchanged ATP-binding cassette transporter A1 protein expression in the liver. These findings indicate that HHcy inhibits reverse cholesterol transport by reducing circulating HDL via inhibiting apoA-I protein synthesis and enhancing HDL-C clearance.
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PMID:Hyperhomocysteinemia decreases circulating high-density lipoprotein by inhibiting apolipoprotein A-I Protein synthesis and enhancing HDL cholesterol clearance. 1697 11