Key result
Cholesterol-enriched chylomicrons showed no significant difference in triglyceride hydrolysis rate by heart lipoprotein lipase compared to controls, and a slightly lower rate (84%) with adipose tissue lipase.
Cholesteryl ester content of chylomicrons does not have a major effect on their rate of triglyceride hydrolysis by lipoprotein lipase.
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Cholesteryl ester content may not regulate chylomicron lipolysis in this model; leaves open primary determinants of tissue-specific LPL activity in vivo.
The chemical and biochemical properties of cholesterol-enriched and cholesterol-poor chylomicrons from rat lymph have been compared. The enriched particles, prepared from cholesterol-containing lipid dispersions, passed into the duodenum, had four to ten times the cholesteryl ester content of the control chylomicrons but had the same content of total "core" (cholesteryl ester + triglyceride) lipid. Both chylomicron species had the same protein composition, the same phospholipid composition, and the same composition of triglyceride fatty acids. The rate of hydrolysis of chylomicron triglyceride for enriched and control particles was determined using both soluble and membrane-supported lipoprotein lipase (LPL) species from heart and adipose tissues. The lipase that was functional in the isolated perfused heart showed no significant difference in initial catabolic rate with cholesterol-enriched and control chylomicrons. The same result was obtained with this isolated LPL species in vitro. The lipase that was functional in isolated perfused epididymal adipose tissue showed a slightly lower catabolic rate with cholesterol-enriched particles (84% of that obtained with control chylomicrons). The same result was obtained with isolated adipose tissue LPL. It is concluded that cholesteryl ester content of chylomicrons under these conditions neither affects their protein composition nor has a major effect on their rate of reaction with lipoprotein lipase.
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Fielding et al. (1978) studied this question. Cholesterol-enriched chylomicrons vs. Cholesterol-poor (control) chylomicrons was evaluated on Rate of hydrolysis of chylomicron triglyceride by lipoprotein lipase. Cholesterol-enriched chylomicrons showed no significant difference in triglyceride hydrolysis rate by heart lipoprotein lipase compared to controls, and a slightly lower rate (84%) with adipose tissue lipase.
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