Dietary Mono- and polyunsaturated fatty acids similarly increase plasma apoliprotein A-IV concentrations in healthy men and women.
Dietary Mono- and polyunsaturated fatty acids similarly increase plasma apoliprotein A-IV concentrations in healthy men and women.
Year: 2003
Authors: M Kratz, U Wahrburg, A Eckardstein, B Ezeh, G Assmann, F Kronenberg.
Publication Name: J Nutr
Publication Details: Volume 133; Page 1821
Abstract:
Apolipoprotein (apo) A-IV is a glycoprotein found in the small intestine synthesized in response to the absorption of dietary or biliary fat. Evidence suggests that apo A-IV is involved in a multitude of functions including reverse cholesterol transport, the control of food intake (suppression of food intake), modulation of gastric acid secretion and gastric emptying, as well as an antioxidant effect in inhibiting lipid peroxidation. These findings suggest that apo A–IV may be considered an anti-atherogenic factor. Previous animal studies have demonstrated considerable protection against atherosclerotic lesions in response to over expression of the apo A–IV gene. Similarly, human studies have revealed an inverse association between plasma apo A–IV concentrations and coronary artery disease. Although dietary fat stimulates the synthesis of apo A–IV, no studies to date have fully delineated the effect of specific dietary fatty acids on plasma apo A–IV concentrations. The purpose of this study was to investigate the effect of different fat sources rich in monounsaturated fat (MUFA), alpha-linolenic acid (ALA), and linoleic acid (LA), on LDL oxidizability. Forty-eight participants (23 men and 25 women) were involved in this 6-week parallel design study. All participants consumed a high fat diet rich in saturated fat (SFA) for a 2-week period. Participants were then randomly divided into one of three high fat dietary treatment groups for a remaining 4-week period: 1) refined olive oil (rich in MUFA; 8 men, 9 women); 2) canola oil (rich in MUFA and ALA; 6 men, 7 women); or 3) sunflower oil (rich in linoleic acid; 9 men, 9 women). All diets were identical in every respect except for the dietary fatty acid content. Venous blood samples were obtained at the beginning of the study, following the baseline period, and at week 2 and 4 of the treatment period. Plasma apo A–IV concentrations were determined using ELISA, and all statistical calculations were performed using the Statistical Package for the Social Sciences (SPSS). Results demonstrated that plasma apo A–IV concentrations decreased during the baseline diet period by 14% or 13.6 mg/L. However, an opposite effect was observed in the dietary treatment groups as a whole, demonstrating a 16% increase in apo A–IV plasma concentrations. Although at first the increase appeared to be greater in subjects consuming the canola oil and sunflower oil diets, there was no effect of dietary consumption. Furthermore, gender or apo A–IV genotype did not appear to be a factor in the diet-induced increases in apo A–IV concentrations. Finally, the increase in plasma apo A–IV concentrations in subjects consuming the treatment diets was not linear, with the increase in plasma apo A–IV concentrations occurring in the last 2-weeks of the treatment phase. The researchers concluded that diets rich in unsaturated fatty acids increase plasma concentrations of apo A–IV when compared to a diet high in SFA. Although the mechanism by which unsaturated fat produces this increase remains unknown, the authors state it may be attributed to the effect of unsaturated fat on apo A–IV catabolism in terms of hepatic clearance rate. However, further studies are required to establish whether or not an increase in plasma apo A–IV concentrations lowers the risk of coronary heart disease. The results, however preliminary, do suggest that the inclusion of oils rich in unsaturated fatty acids, such as canola oil and flax oil, in the diet may have a number of anti-atherogenic effects including a potential increase in apo A-IV, an strong antioxidant with regard to lipid oxidation.
