Lipid atherogenic risk markers can be more favourably influenced by thecis-9,trans-11-octadecadienoate isomer than a conjugated linoleic acid mixture or fish oil in hamsters

Abstract

The aim of our present study was to compare the efficiency of conjugated linoleic acids (CLA) and fish oil in modulating atherogenic risk markers. Adult male hamsters were given a cholesterol-rich diet (0·6 g/kg) for 8 weeks; the diet was supplemented with 5 g cis-9,trans-11-CLA isomer/kg, 12 g CLA mixture (CLA-mix)/kg, 12 g fish oil/kg or 12 g fish oil þ 12 g CLA-mix/kg. The plasma cholesterol status was improved only with the cis-9,trans-11-CLA (HDL-cholesterol and HDL-cholesterol:LDL-cholesterol ratio, P,0·05), but was of borderline significance for CLA-mix (HDL-cholesterol:LDL-cholesterol ratio, P¼ 0·06), with an increase (33 -40 %) in the liver lipoprotein receptors (scavenger receptor-type I and LDL ApoB/E receptor) and HDL-binding protein 2 (P,0·05). A 100 % pigment gallstones incidence and a slight insulin resistance (homeostatic model assessment index) were observed in the CLA-mix-fed hamsters (P¼ -0·031). In comparison, fish-oil feeding alone improved merely the scavenger receptor-type I and HDL-binding protein 2 liver status and faeces sterol output. For most of our present observations, the concomitant intake of fish oil and CLA-mix gave dominant effects that were exclusive and specific to one or the other oil. In conclusion, part of the beneficial effects of CLA in the present study can be ascribed to the cis-9,trans-11-isomer, and these did not generally overlap with those of fish oil. In addition, the CLA-mix effects are clearly affected by the marine (n-3) fatty acids. Conjugated linoleic acid: Rumenic acid: Fish oil: Lipid atherosclerosis risk markers: HamstersConjugated linoleic acid (CLA) is a collective term describing positional and geometrical isomers of linoleic acid. Among them, the cis-9,trans-11-isomer, so-called rumenic acid, occurs naturally in foodstuffs from ruminant animal fat sources. CLA have received growing attention in the past 10 years because of their pleiotropic biological activities. For instance, these fatty acids are effective anti-carcinogens, anti-atherosclerotic agents and potent modulators of the immune function (Pariza et al. 2001;Martin & Valeille, 2002). Studies dealing with the anti-atherosclerotic properties of CLA are scarce but promising. For instance, a CLA mixture (CLA-mix; 94·0 % (range 1-10 g/kg cis-9,trans-11 and trans-10,cis-12 isomers/kg of diet) decreased early aortic atherosclerosis when given to male hamsters receiving a pro-atherogenic diet (F 1 B strain; Wilson et al. 2000), and even caused regression of pre-established atherosclerosis in the male rabbit (New Zealand White; Kritchevsky et al. 2000) (10 g/kg diet). On the other hand, a detrimental effect on early aortic lesions outcome of a similar CLA-mix (5 g/kg diet) has been observed in C57Bl/6 mice fed a pro-atherogenic diet (Munday et al. 1999). Nevertheless, the studies dealing with the effect of CLA on the plasma lipid profile are less clear. Animal studies and studies with human subjects have had discordant results, as reviewed in Roche et al. (2001). In addition, animal experiments (hamste...

Adverse effects of conjugated alpha-linolenic acids (CLnA) on lipoprotein profile on experimental atherosclerosis in hamsters

“…These results suggest that RA or CLnA do not beneficially modify the lipoprotein profile or fatty streak formation in F 1 B hamsters fed an HC diet. Our results differ from other data on hamsters supplemented with RA (Nicolosi et al, 1997;Valeille et al, 2004). In this study, the pronounced atherogenic status of hamsters fed one of the HC diet compared with the animals fed the control diet may explain in part the discrepancy of our results compared with other literature.…”

“…The high fat content of the HC diets may also have induced an early propensity to atherosclerosis as seen by the high CE in liver and the fatty streaks. This result has not been noticed in other studies such as that of Valeille et al (2004) showing beneficial effects of RA on atherosclerosis. This may explain in part the different potential of RA to influence proatherogenic TC concentrations and aortic fatty streaks formation.…”

“…This may relate in part to the housing conditions (two by two) used in this experiment, which seems to have affected plasma lipid concentrations and early atherogenesis as previously reported by Yoganathan et al (1998). However, it can also be related to the amount of other fats in the diet, which could largely modify the lipoprotein profile when supplemented with CLA (Valeille et al, 2004). In this context, the introduction of 20% lard in our HC diet instead of 20% coconut oil may have created an important fatty-acid modification interfering with CLA properties.…”

“…In fact, the overall activity of a CLnA mixture may be directed by one of the two isomers as demonstrated in a previous study (Plourde et al, 2006). Only the c-9, t-11, c-15 18:3 isomer is metabolised to conjugated 20:5n-3 and 22:6n-3 isomers and this may have a greater role in biochemical and signalisation pathways as was hypothesised for other conjugated fatty acids (Valeille et al, 2004). It has already been shown that CLA isomers can also be elongated and desaturated, then further metabolised to produce various CLAderived eicosanoids and other novel mediators that may exhibit biological activities in their own right (Pariza et al, 2000).…”

“…Moreover, RA may be more active in preventing atherosclerosis in animals (Valeille et al, 2004;Lock et al, 2005). A diet containing 18:2 trans-10, cis-12 appears to have a profound proatherogenic effect, while RA impeded the development of atherosclerosis in mice (Arbones-Mainar et al, 2006), an effect possibly explained by increased epithelial permeability with trans-10, cis-12 but not with RA (Roche et al, 2001).…”