Hydroxycinnamic acids do not prevent aortic atherosclerosis in hypercholesterolemic golden Syrian hamsters

Abstract

The protective effect of hydroxycinnamic acids, i.e. caffeic acid (CA) and sinapic acid (SA) present in wine, and chlorogenic acid (CHA) present in apple, compared to a red wine phenolic extract (RWPE) was investigated in hamsters fed an atherogenic diet for 12 weeks. Five groups of 8 hamsters fed such a diet received by force-feeding RWPE, CA or SA in water, mimicking a moderate consumption of alcohol-free red wine. Controls received water and CHA force-feeding was extrapolated from apple consumption. Plasma cholesterol concentration was lower in group that received RWPE (−22%) and hydroxycinnamic acids had no effect. Plasma apolipoprotein Apo-A1 concentration was not affected; consumption of RWPE only decreased Apo-B concentration (−46%). Liver superoxide dismutase activity was 33% lower and glutathione peroxidase activity was 67% greater in the group receiving RWPE compared to controls; there was no effect when CA, SA or CHA were given. All the phenolic compounds significantly increased plasma antioxidant capacity (about 28% on average) compared with controls. Aortic fatty streak area was significantly reduced in the group receiving RWPE (−30%) in comparison with controls and hydroxycinnamic acids. Our findings demonstrate that chronic ingestion of the nonalcoholic components of red wine, mainly polyphenols, prevent the development of atherosclerosis in hamster and that wine hydroxycinnamic acids are not the phenolic compounds involved in such a beneficial effect.

Introduction

Phenolic substances are present in large quantities in plant foods. They are important components in the human diet, as their daily intake can reach up to 800 mg depending on the consumption of specific food and beverages such as red wine for exemple (Beecher, 1999). Besides vitamines C, E, A and carotenoids, polyphenols may account for at least part of the health benefits associated with the consumption of fresh fruits, vegetables, tea and red wine (Duthie et al., 2000). A major class of phenolic non flavonoid compounds such as hydroxycinnamic acids is present in human diet in representative amounts Dao and Friedman, 1992, Onyeneho and Hettiarachchy, 1992; they are encountered in wine, coffee, tea leaves, whole grains and in many vegetables and fruits in which they contribute to color and sensory properties such as biterness and astrigency (Macheix et al., 1990). Caffeic acid and sinapic acid are among the major hydroxycinnamic acids present in wine; sinapic acid, which is a potent antioxidant (Andreasen et al., 2001) is present in significant quantities in red wine (up to 2.10⁻³ g/L) (Cabanis et al., 1998); caffeic acid has also been identified as one of the active antioxidant (Abu-Amsha et al., 1996) of red wine (up to 26.10⁻³ g/L) (Cabanis et al., 1998); apples were known to contain up to 510 mg/kg chlorogenic acid (Macheix and Fleuriet, 1998). The potential health benefits of the hydroxycinnamic acids and derivatives have mostly been related to their effective antioxidant capacity. These compounds are of growing interest since they are potent antioxidants and inhibit low-density lipoprotein (LDL) oxydation in vitro Frankel et al., 1993, Nardini et al., 1995, Meyer et al., 1998a, Meyer et al., 1998b, properties which are associated to their ability to scavenge free radicals and chelate metals and which are a known feature of the atherosclerotic plaque where oxidised LDL contribute to the development of fatty lesions (Steinberg et al., 1989). The ability of hydroxycinnamic acids to inhibit oxidation of human LDL decrease in the following order: caffeic acid > sinapic acid > ferulic acid > p-coumaric acid Steinberg et al., 1989, Meyer et al., 1998a, Meyer et al., 1998b, Natella et al., 1999. An increased consumption of phenolics has been correlated with a reduced risk of cardiovascular diseases and certain types of cancers Bravo, 1998, Duthie and Crozier, 2000. Hence it is expected that diseases caused by cholesterol oxidation may be prevented by them Frankel et al., 1993, Laranjinha et al., 1992, Laranjinha et al., 1994, Maxwell et al., 1994, Frankel et al., 1995 and particularly atherosclerosis (Steinberg et al., 1989). It has also been shown that wine phenolic compounds such as resveratrol Belguendouz et al., 1998, Frémont et al., 1999, quercetin Meyer et al., 1998a, Meyer et al., 1998b, Yamamoto et al., 1999, catechins and caffeic acid Meyer et al., 1998a, Meyer et al., 1998b exerted considerable antioxidant potency toward LDL oxidation in vitro. Elsewhere, results from studies of red wine phenolics in humans have also been inconsistent Nigdikar et al., 1998, Abu-Amsha Caccetta et al., 2000; moreover, Revell et al. (2002) reported that resveratrol, catechin, epicatechin and quercetin protect LDL oxidation in vitro but not ex vivo. Such studies reflected in part the use of ex vivo methodologies to assess in vivo effects of phenolics ingestion on LDL oxidation and therefore atherosclerosis. Lipid peroxidation is indeed an initial step in the atherosclerosis pathology and evidence is increasing that oxidative modification of LDL is involved (Steinberg et al., 1989). The early lesions of atherosclerosis consist of subendothelial accumulations of cholesterol-engorged macrophages, called foam cells (Steinberg et al., 1989); accumulation of oxidatively modified LDL in the artery intima contributes significantly to monocyte recruitement and foam cell formation, which form fatty streaks Aqel et al., 1985, Rosenfeld et al., 1987 and which are also present in atherosclerotic plaques Gown et al., 1986, Jonasson et al., 1986, Masuda and Ross, 1990. In humans, such fatty streak lesions can usually be found in the aorta, coronary and cerebral arteries (Lusis, 2000). It has been shown that Golden Syrian hamsters fed a fat-rich diet develop dyslipidemia and atherosclerotic plaques, similar in many respects to human atheroma Filip et al., 1987, Nistor et al., 1987. This model was chosen (i) to overcome such controversy, (ii) because both vitamin E and catechin were reported to inhibit development of aortic lesions in Golden Syrian hamsters (Xu et al., 1998) and (iii) because of its responsiveness to plasma cholesterol lowering and anti-atherogenic interventions Spady and Dietschy, 1985, Spady et al., 1986, Kowala et al., 1991. Moreover hamster has similar plasma lipoprotein distribution to humans and LDL as major plasma cholesterol carrier. Apart from ethanol, the phenolic compounds are involved in the cardioprotective capacity of red wine Das et al., 1999, Agewall et al., 2000 and one possible explanation is that they slow the progression of atherosclerosis by acting as antioxidant toward LDL Frankel et al., 1993, Kinsella et al., 1993, Vinson et al., 2001. This study represents a part of an investigation aiming at determining what class(es) of phenolic compounds is (are) efficient in the prevention of early atherosclerosis. Since, at present, there is no direct evidence that hydroxycinnamic acids exert a beneficial cardioprotective effect in vivo, we have studied their effects and that of a de-alcoholized red wine phenolic extract (RWPE) on this model. For a comparative purpose, chlorogenic acid, the parent compound of caffeic acid, was also tested. In order to induce a peroxidative stress, the high cholesterol and high fat diet was rendered deficient in vitamin C and E and in selenium.

The aim of the present study was to trigger off the arterial wall response to such a stress (fatty streak formation and aortic atherosclerosis emergence) and then to look at the modulation of this effect by RWPE, caffeic acid, sinapic acid and chlorogenic acid.