SUPPRESSION OF 3-HYDROXY-3-METHYLGLUTARYL-COA REDUCTASE BY LOW-DENSITY LIPOPROTEINS PRODUCED INVITRO BY LIPOPROTEIN-LIPASE ACTION ON NON-SUPPRESSIVE VERY LOW-DENSITY LIPOPROTEINS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 254  (4) , 1007-1009
Abstract
Very low density lipoproteins (VLDL), Sf (Svedberg flotation units) 60-400, from normolipemic individuals do not suppress 3-hydroxy-3-methylglutaryl-CoA reductase activity in cultured normal human fibroblasts at concentrations 20-fold higher than those of low density lipoproteins (LDL) that give total suppression. To determine if these VLDL contain all of the structural elements necessary for receptor-mediated suppression, they were converted in vitro with bovine milk lipoprotein lipase to low density lipoproteins. These LDL-like lipoproteins were as effective in suppression as LDL isolated directly from plasma, with half-maximal and complete suppression at 1 and 4 .mu.g of cholesterol Ml-1. Neither native LDL nor LDL produced in vitro suppressed receptor-negative fibrblasts. The action of lipoprotein lipase on VLDL apparently leads to a rearrangement of lipoprotein components that permits interaction of LDL produced in vitro with the LDL-specific cell surface receptor of fibroblasts and subsequent suppression of 3-hydroxy-3-methylglutaryl-CoA reductase.