on October 27, 2005
Published online before print October 27, 2005, doi: 10.1161/01.ATV.0000193620.98587.40
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Submitted on February 18, 2005
Accepted on October 5, 2005
Stimulation of Liver-Directed Cholesterol Flux in Mice by Novel N-Acetylgalactosamine-Terminated Glycolipids With High Affinity for the Asialoglycoprotein Receptor
Patrick C.N. Rensen *;
From the Division of Biopharmaceutics (P.C.N.R., L.A.J.M.S., P.J.v.S., M.F., S.H.v.L., T.J.C.v.B., E.A.L.B.), Leiden/Amsterdam Center for Drug Research, University of Leiden, Gorlaeus Laboratory, Leiden; the Department of Industrial Design (H.N.J.S.), Delft University of Technology, Delft; Central Clinical Chemical Laboratory of the Leiden University Medical Center (J.H.M.S.), Leiden; and the Department of General Internal Medicine (P.C.N.R. current address), Leiden University Medical Center, Leiden, The Netherlands.
* To whom correspondence should be addressed. E-mail: P.C.N.Rensen{at}lumc.nl.
Objective--Interventions that promote liver-directed cholesterol flux can suppress atherosclerosis, as demonstrated for scavenger receptor-BI overexpression in hypercholesterolemic mice. In analogy, we speculate that increasing lipoprotein flux to the liver via the asialoglycoprotein receptor (ASGPr) may be of therapeutic value in hypercholesterolemia.
Methods and Results--A bifunctional glycolipid (LCO-Tyr-GalNAc3) with a high-nanomolar affinity for the ASGPr (inhibition constant 2.1±0.2 nmol/L) was synthesized that showed rapid association with lipoproteins on incubation with serum. Prior incubation of LCO-Tyr-GalNAc3 with radiolabeled low-density lipoprotein or high-density lipoprotein (0.5 µg/µg of protein) resulted in a dramatic induction of the liver uptake of these lipoproteins when injected intravenously into mice (70±3% and 78±1%, respectively, of the injected dose at 10 minutes of low-density lipoprotein and high-density lipoprotein), as mediated by the ASGPr on hepatocytes. Intravenously injected LCO-Tyr-GalNAc3 quantitatively incorporated into serum lipoproteins and evoked a strong and persistent (
48 hour) cholesterol-lowering effect in normolipidemic mice (37±2% at 6 hours) and hyperlipidemic apoE-/- mice (32±2% at 6 hours). The glycolipid was also effective on subcutaneous administration.
Conclusions--LCO-Tyr-GalNAc3 is very effective in promoting cholesterol uptake by hepatocytes and, thus, may be a promising alternative for the treatment of those hyperlipidemic patients who do not respond sufficiently to conventional cholesterol-lowering therapies.
Key words: cholesterol-lowering drugs • hyperlipoproteinemia • lipoproteins • receptors • transgenic models