Abstract
Long chain n-3 fatty acids present in fish oils have been shown to reduce fasting plasma triglyceride and very low density lipoprotein levels in normal and hyperlipidemic human subjects. The present studies were designed to examine whether dietary n-3 fatty acids influence chylomicron formation and metabolism in healthy volunteers. In the first study seven subjects were fed either saturated fat, vegetable oil, or fish oil-based diets for 4 weeks each, and test meals containing 50 g of the background fat were administered after the second week of each diet. The postprandial rise in triglyceride levels was significantly lower following the fish oil test meal as compared to the saturated fat or vegetable oil test meals. In the second study, six subjects eating their usual home diets were given two fat tolerance tests. The first contained saturated fat and the second, given 1 week later, contained fish oil. There was no difference in the postprandial triglyceride response between the fish oil and the saturated fat meals. A third study was then conducted with eight volunteers in which saturated fat and fish oil test meals were administered during saturated fat and fish oil background diets in a crossover design. The presence of fish oil in the background diet reduced postprandial lipemia regardless of the type of fat in the test meal. Although there was no effect of the fish oil diet on the lipoprotein lipase and hepatic lipase activity of postheparin plasma measured in vitro, stimulation of in vivo lipolysis was not ruled out. Our results suggest that chronic (but not acute) intake of fish oil may inhibit the synthesis or secretion of chylomicrons from the gut. However, accelerated clearance due to decreased VLDL competition cannot be excluded.
Highlights
Long chain n-3 fatty acids present in fish oils have been shown to reduce fasting plasma triglyceride and very low density lipoprotein levels in normal and hyperlipidemic human subjects.The present studies were designed to examine whether dietary n-3 fatty acids influence chylomicron formation and metabolism in healthy volunteers
We have previously shown that a diet rich in fish oil caused a dramatic blunting of the normal rise in plasma triglyceride levels followinga fatty meal [3].To determine whether this effect was the result of the presence of fish oil in the test meal or in the background diet, we have examined the effects of n-3 fatty acids on postprandial triglyceride levels
Our results suggest that the presence of n-3 fatty acids in the background diet alone will reduce postprandial triglyceride levels regardless of the type of fat administered in the meal itself
Summary
Long chain n-3 fatty acids present in fish oils have been shown to reduce fasting plasma triglyceride and very low density lipoprotein levels in normal and hyperlipidemic human subjects.The present studies were designed to examine whether dietary n-3 fatty acids influence chylomicron formation and metabolism in healthy volunteers. The two enzymes responsible for the intravascular hydrolysis of triglycerideare lipoprotein lipase(LPL)and hepatic triglyceridelipase ('7, 8).To assesswhether dietary fish oils may influence triglyceride removal from VLDL and chylomicrons, we have measured the activities of both of these enzymes in postheparin plasma after a diet high in n-3 fatty acids. We have previously shown that a diet rich in fish oil caused a dramatic blunting of the normal rise in plasma triglyceride levels followinga fatty meal [3].To determine whether this effect was the result of the presence of fish oil in the test meal or in the background diet, we have examined the effects of n-3 fatty acids on postprandial triglyceride levels. Our results suggest that the presence of n-3 fatty acids in the background diet alone will reduce postprandial triglyceride levels regardless of the type of fat administered in the meal itself.
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