Abstract
Dietary medium chain fatty acids (MCFA) and linoleic acid follow different metabolic routes, and linoleic acid activates PPAR receptors. Both these mechanisms may modify lipoprotein and fatty acid metabolism after dietary intervention. Our objective was to investigate how dietary MCFA and linoleic acid supplementation and body fat distribution affect the fasting lipoprotein subclass profile, lipoprotein kinetics, and postprandial fatty acid kinetics. In a randomized double blind cross-over trial, 12 male subjects (age 51±7 years; BMI 28.5±0.8 kg/m2), were divided into 2 groups according to waist-hip ratio. They were supplemented with 60 grams/day MCFA (mainly C8:0, C10:0) or linoleic acid for three weeks, with a wash-out period of six weeks in between. Lipoprotein subclasses were measured using HPLC. Lipoprotein and fatty acid metabolism were studied using a combination of several stable isotope tracers. Lipoprotein and tracer data were analyzed using computational modeling. Lipoprotein subclass concentrations in the VLDL and LDL range were significantly higher after MCFA than after linoleic acid intervention. In addition, LDL subclass concentrations were higher in lower body obese individuals. Differences in VLDL metabolism were found to occur in lipoprotein lipolysis and uptake, not production; MCFAs were elongated intensively, in contrast to linoleic acid. Dietary MCFA supplementation led to a less favorable lipoprotein profile than linoleic acid supplementation. These differences were not due to elevated VLDL production, but rather to lower lipolysis and uptake rates.
Highlights
The type of fatty acids consumed as dietary fats is known to influence risk factors for cardiovascular disease [1]
Medium-chain fatty acids (MCFAs), being eight to ten carbon atoms long, are used as dietary supplements in weight-loss programs, since they were frequently found to lead to greater weight loss than dietary long-chain fatty acids [2]
Cholesterol concentrations were significantly higher after MCFA supplementation for all subfractions, except the two VLDL subfractions with largest particle diameter and the LDL subfraction with smallest particle diameter
Summary
The type of fatty acids consumed as dietary fats is known to influence risk factors for cardiovascular disease [1]. MCFA, after being absorbed by the intestine, is mostly transported through the portal vein to the liver as free fatty acid In the liver it is packaged in VLDL lipoproteins and distributed further to other target organs [3]. Linoleic acid is generally packaged in large chylomicron particles in the intestine; from there it proceeds directly through the blood to any target organ [5]. Both the role of the liver in the metabolic route and the type of particle used for transport are different for the two types of fatty acid
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