S-Propyl-Cysteine Sulfoxide and DL-Methionine Sulfoxide Inhibit the Secretion of Apolipoprotein B100 and Lipids in HepG2 Cells

Abstract

It is known that high levels of apolipoprotein B100 (apoB100) and lipids in the serum are risk factors for atherosclerosis. In the present study, we evaluated the effects of four sulfur-containing amino compounds, S-propyl-cysteine sulfoxide, DL-methionine sulfoxide, S-carboxymethyl cysteine, and S-carboxyethyl cysteine, found in Allium species on lipid metabolism and apoB100 secretion in human liver model cells, HepG2. Both S-propyl-cysteine Sulfoxide and DL-methionine sulfoxide inhibited apoB100 secretion into the medium in vitro and reduced the secretion of newly synthesized triacylglycerol (TAG) and cholesterol without affecting cellular lipid synthesis from [14C]acetate. S-Carboxymethyl cysteine and S-carboxyethyl cysteine also reduced the secretion of newly synthesized TAG and cholesterol into the medium. A correlation between the hypolipidemic activity and the length of alkyl chain bound to cysteine was observed. These compounds had no effect on MTT activity and intracellular protein concentration compared with the untreated cells. These results suggest that sulfur-containing amino compounds in onion and garlic reduce the secretion of apoB100, TAG and cholesterol in human liver model cells, by inhibiting apoB100-containing lipoprotein assembly and secretion. Thus, these components of Allium species may be beneficial to reduce risk factors for atherosclerosis.