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The hypochylomicronemic effect of beta,beta'-methyl-substituted hexadecanedioic acid (MEDICA 16) is mediated by a
B Frenkel1, N Mayorek, R Hertz
1Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
The Journal of Biological Chemistry
|June 15, 1988
Summary
MEDICA 16 significantly reduces plasma chylomicrons and triacylglycerols in rats by enhancing their clearance. This hypochylomicronemic effect is linked to reduced apoC-III, suggesting a potential treatment for hyperlipidemia.
Area of Science:
- Biochemistry
- Pharmacology
- Lipid Metabolism
Background:
- Hyperlipidemia is a significant risk factor for cardiovascular disease.
- Chylomicrons are key carriers of dietary lipids, and their accumulation contributes to hyperlipidemia.
- Understanding mechanisms to enhance chylomicron clearance is crucial for developing lipid-lowering therapies.
Purpose of the Study:
- To investigate the effects of beta,beta'-tetramethyl-substituted hexadecanedioic acid (MEDICA 16) on plasma chylomicron levels in rats.
- To elucidate the mechanism by which MEDICA 16 influences chylomicron metabolism and clearance.
- To explore the potential of MEDICA 16 as a therapeutic agent for hyperlipidemic conditions.
Main Methods:
- Rats were administered MEDICA 16 and fed a standard diet.
- Plasma chylomicron-triacylglycerols and cholesterol ester levels were measured.
- Chylomicron clearance rates were determined using tracers.
- ApoC-III content in plasma chylomicrons was analyzed.
- Hepatic receptors and lipoprotein lipase activity were assessed.
Main Results:
- MEDICA 16 treatment caused a sustained 70-80% decrease in plasma chylomicrons-triacylglycerols.
- The hypochylomicronemic effect was due to enhanced plasma clearance, not altered intestinal production or absorption.
- Fractional clearance rates for chylomicrons-triacylglycerols and cholesterol ester were significantly increased in MEDICA 16-treated rats.
- This enhanced clearance was attributed to increased hepatic uptake and extrahepatic catabolism, linked to a 10-fold decrease in plasma apoC-III.
- No changes were observed in hepatic apoB,E or apoE receptors, or lipoprotein lipase capacity.
Conclusions:
- MEDICA 16 effectively reduces plasma chylomicrons by accelerating their clearance.
- The drug's action is primarily mediated by enhanced catabolism, potentially via reduced apoC-III levels.
- Pharmacological reduction of plasma apoC-III presents a promising therapeutic strategy for specific hyperlipidemic states.