Dietary supplementation with olive oil influences iron concentrations in rats

Nutrition Research, Vol. 19, No. 11, pp. 1665-1670.1999 Copyright 0 1999 Elswier Science Inc. Printed in the USA. All rights reserved 0271-5317iW%ee front matter ELSEVIER

PI1 SO271-5317(9!4)001220

DIETARY SUPPLEMBNTATION WITH OLIVE OIL INFLUENCES IRON CONCENTRATIONS IN RATS Kothapa N. Chetty ‘, Ph.D., Ragene Conway, Katrina C. Harris, M.A.T., Waneene C. Dorsey, M.A.T., Dagne Hill, M.A.T., Srikrishna Chetty*, Rajashekar Yerrapragada** and Sushi1lain**, Ph.D. Department of Biological Science, Grambling State University, Grambling, LA 71245; *University of Texas, Austin, Texas; **LSU Medical Center, Shreveport, Louisiana

ABSTRACT We compared the effect of corn oil diet and olive oil diet (5%/wt) on serum iron, total iron binding capacity, transferrin saturation levels, plasma lipid peroxides and liver iron levels of male Sprague Dawley rats. After three weeks, blood and liver samples were collected assayed. Rats fed the olive-oil supplemented diet had significantly lower levels of serum iron and transfertin saturation than controls. Serum total iron binding capacity had no difference in olive oil fed rats compared with controls. Plasma lipid peroxide levels were significantly decreased in olive oil fed rats as compared with controls. There was a significant increase in liver iron concentrations in the olive oil fed groups than in the controls. These findings show that a diet supplemented with olive oil modities iron concentrations in serum and liver tissues. 0 1999 Elswia Scunce Inc Keywords: Serum Iron, Hepatic Iron, Lipid Peroxide, Olive Oil

INTRODUCTION The incidence of coronary heart disease is lower in people of Mediterranean countries compared with people in the northern part of Europe and United States eventhough people of Mediterraneancountries have higher (40% calories) fat intake (1). In Mediterranean countries, the usual diet is high in olive oil. The mechanisms that might contribute to the lower incidence of coronary heart disease (CHD) in Mediterranean population consuming diet rich in olive oil is not clear. Epidemiological studies have suggested different risk factors, such as, increased levels of blood cholesterol and lipid peroxides and lower level of antioxidants in population with the increased incidence of CHD (2,3). Sullivan et al (4,5,6) proposed that higher incidence of CHD in men compared with women may be related to lower iron levels in women. Similarly, Salonen found a positive correlation between serum iron and incidence of acute myocardial infarction (7,8). Iron as Address correspondenceto: KothapaN. Chetty’,Ph.D.,Departmentof Biolo@l Sciences,Grambling State University, P. 0. Box 887, Grambling, Louisiana 71245. Phone: (318) 274-3136; FAX: (318) 274-3741.

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risk factor for CHD has been studied in experimental animals. Myocardial damage caused by anoxia and repertbsion is increased by iron overdose (9,10,11).

The present research was designed to study the concentrations of serum iron, liver iron and plasma lipid peroxide in corn oil (5%) and olive oil (5%) fed rats. We measured serum iron, serum iron binding capacity, and serum transferrin index.

METHODS AND MATERIALS We were granted permissionfrom the Office for Protection from Research Risks (OPRR) of our Animal Welfare Assurance which was submitted in compliance with the Public Health Service (PHS) Policy on Humane Care and Use of Laboratory Animals (Policy). Male Sprague-Dawley rats weighing 175-200 grams were purchased from Harlan Sprague-Dawley, Inc., Indianapolis, Indiana and were housed in a light-cycle room and provided with water and diets with ad libitum access. After 48 hours of arrival animals were randomly assigned to three diierent groups. Experimental diets were prepared by Dyets, Inc. (Bethlehem, PA). The diet formulations were identical in composition except the type of fat. Diets contained either 5% corn oil or 5% olive oil replacing corn oil. There were two groups of rats (1) corn oil (2) olive oil (00). The composition of the diets is shown in Table 1. TABLE 1

(Composition of Control and Experimental Diets.)

Ingredient Casein DL Methionine Corn Starch Sucrose Cellulose Corn Oil Olive Oii AIN- Salt Mix AIN-76 Vitamin Mix Choline Bitartrate

Control 200 3 150 500 50 50 0 35 10 2

Experimental 200 3 150 500 50 50 0 35 10 2

The diets were purchased from Dyets, Inc. (Bethlehem, Pennsylvania). A&r two weeks of dietary regimen, blood was collected from over-night fasted rats by cardiac puncture under phenobarbital anesthesia as described previously (12). Serum was collected by centrifugation in clinical centrifuge for the determination of iron and total iron-binding capacity (TIBC). For determinationof lipid peroxides, vitaminE and vitamin C, plasma from the EDTA-blood was used. Liver specimens were collected to determine the level of the hepatic iron.

OLIVE OIL REDUCES SERUM IRON

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Fe and TIBC Measurements Serum iron and serum total iron-biding capacity (TIBC) were analyzed as per the protocols and instrumentations of Kubena et al (13). HeDatic Iron Hepatic iron was measured as per the procedures of Chareonpong and Yassumoto using Atomic Absorption Spectrophotometer (14). Statistical Analvsis Data were analyzed by one way analysis of variance, with multiple comparison testing Least SignificantDiBkrence(Snedecor and Co&ran, 1980). Differences between the experimental and the control groups were considered significant at the level p
Serum Iron (mg/dL)

TIBC (mg/dL)

Plasma MDA (nmol/mL)

STS%

Hepatic Iron (Ppm)

Corn Oil

126+13* 89+8

461210 453+13

0.18&0.06 0.15+0.06

2721.3* 2og.4

99+4.5* 158k3.5

Olive Oil

Data are presented as mean of:standard error. *Denotes significant difference between corn oil and olive oil @<0.05). Abbreviations: TIBS, total from iron binding capacity; STS, serum transfenin saturation, MDA, malonyl dialdehyde. The lipid peroxide levels was signijkantly lower (P
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decrease in serum iron, serum transfenin saturation, lipid peroxides and increase liver iron levels. Increasing number of studies suggest that generation of free radicals, lipid peroxidation products and oxidative modification of lipoprotein are cytotoxic to cultured fibroblasts and endothelial cells. It has been suggested that oxidatively modiied of LDL could contribute to atherogenesis by disrupting endothelial cells and altering cholesterol metabolism (2,3). Lipid peroxidation and its products such as malondialdehyde, can inhibit certain enzymes and induce changes in cellular permeability, viscosity causeand cellular dysfunctions (15,16,17). All these cellular effects of free radicals and lipid peroxidation might be involved in the pathogenesis of atherosclerosis (2). Iron is known to promote peroxidation of lipids through the Fenton reaction and accumulation of malondialdehyde (MDA) an end product of lipid peroxidation, which in turn also can promote oxidative modification of lipoprotein and cardiovascular disease. Magnusson et. al (18) did not find fenitin to be a risk factor but found an inverse relation between serum ferritin and the risk of myocardial infarction, and determined the total iron-binding capacity (TIBC) to be a strong independent negative risk factor in men. Previous studies have shown an increase in urinary levels of MDA in rats fed polyunsaturated fatty acids (19). A degree of unsaturation of fatty acids determines different levels of susceptibility to lipid peroxidation (20,21). It is known that dietary monounsaturated fatty acids makes isolated LDL resistant to oxidation in vitro (22). In summary, findings of the present study reveal that olive oil, rich in monounsaturated fatty acids reduces blood levels of lipid peroxides and non-heme iron. The mechanisms by which olive oil lower serum iron levels is not known. It could be due to its increased mobilization to the liver. Thus lower level of lipid peroxides in olive oil fed rats could be due to lower circulating iron. The reduced level of lipid peroxidation products in the blood can in turn contribute to lower incidence CHD in people consuming olive oil-rich diet. ACKNOWLEDGEMENTS This study was fbnded by the minority Biomedical Research Support (MBRS), NIH Grant No. S14 GMG4531-10. REFERENCES 1.

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Accepted for publication March 23, 1999.