Modulation of Cystathionine β-Synthase Level Regulates Total Serum Homocysteine in Mice

Elevated total plasma homocysteine is an independent risk factor in the development of vascular disease in humans. Cystathionine β-synthase (CBS) is an enzyme that condenses homocysteine with serine to form cystathionine. In this article, we describe the effects of modulating CBS activity using a transgenic mouse that contains the human CBS cDNA under control of the zinc-inducible metallothionein promoter (Tg–CBS). In the presence of zinc, Tg–CBS mice have a 2- to 4-fold increase in liver and kidney CBS activity compared with nontransgenic littermates. Transgenic mice on standard mouse chow had a 45% decrease in their serum homocysteine (12.1 to 7.2 μmol/L; P