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Heated vegetable oils and cardiovascular disease risk factors

Ng CY, Leong XF, Masbah N, Adam SK, Kamisah Y, Jaarin K

Vascul. Pharmacol., 2014 Apr;61(1):1-9.
PMID: 24632108 DOI: 10.1016/j.vph.2014.02.004

Cardiovascular disease (CVD) is one of the leading major causes of morbidity and mortality worldwide. It may result from the interactions between multiple genetic and environmental factors including sedentary lifestyle and dietary habits. The quality of dietary oils and fats has been widely recognised to be inextricably linked to the pathogenesis of CVD. Vegetable oil is one of the essential dietary components in daily food consumption. However, the benefits of vegetable oil can be deteriorated by repeated heating that leads to lipid oxidation. The practice of using repeatedly heated cooking oil is not uncommon as it will reduce the cost of food preparation. Thermal oxidation yields new functional groups which may be potentially hazardous to cardiovascular health. Prolonged consumption of the repeatedly heated oil has been shown to increase blood pressure and total cholesterol, cause vascular inflammation as well as vascular changes which predispose to atherosclerosis. The harmful effect of heated oils is attributed to products generated from lipid oxidation during heating process. In view of the potential hazard of oxidation products, therefore this review article will provide an insight and awareness to the general public on the consumption of repeatedly heated oils which is detrimental to health.
Reprint of "heated vegetable oils and cardiovascular disease risk factors"

Ng CY, Leong XF, Masbah N, Adam SK, Kamisah Y, Jaarin K

Vascul. Pharmacol., 2014 Jul;62(1):38-46.
PMID: 24846858 DOI: 10.1016/j.vph.2014.05.003

Cardiovascular disease (CVD) is one of the leading major causes of morbidity and mortality worldwide. It may result from the interactions between multiple genetic and environmental factors including sedentary lifestyle and dietary habits. The quality of dietary oils and fats has been widely recognised to be inextricably linked to the pathogenesis of CVD. Vegetable oil is one of the essential dietary components in daily food consumption. However, the benefits of vegetable oil can be deteriorated by repeated heating that leads to lipid oxidation. The practice of using repeatedly heated cooking oil is not uncommon as it will reduce the cost of food preparation. Thermal oxidation yields new functional groups which may be potentially hazardous to cardiovascular health. Prolonged consumption of the repeatedly heated oil has been shown to increase blood pressure and total cholesterol, cause vascular inflammation as well as vascular changes which predispose to atherosclerosis. The harmful effect of heated oils is attributed to products generated from lipid oxidation during heating process. In view of the potential hazard of oxidation products, therefore this review article will provide an insight and awareness to the general public on the consumption of repeatedly heated oils which is detrimental to health.
Intake of repeatedly heated palm oil causes elevation in blood pressure with impaired vasorelaxation in rats

Leong XF, Najib MN, Das S, Mustafa MR, Jaarin K

Tohoku J. Exp. Med., 2009 Sep;219(1):71-8.
PMID: 19713687

Oxidization of dietary cooking oil increases the risk of cardiovascular diseases such as hypertension by increasing the formation oxidative oxygen radicals. The aim of study was to investigate the effects of repeatedly heated palm oil on blood pressure, plasma nitrites, and vascular reactivity. Nitrites were measured, as an indirect marker for nitric oxide production. Male Sprague-Dawley rats were divided into four groups: control group fed with basal diet and other three groups fortified with 15% weight/weight fresh palm oil (FPO), palm oil heated five times (5HPO) or palm oil heated ten times (10HPO) for 24 weeks. The oil was heated to 180 degrees C for 10 min. Blood pressure was measured at baseline and at intervals of four weeks for 24 weeks using non-invasive tail-cuff method. Following 24 weeks, the rats were sacrificed and thoracic aortas were dissected for measurement of vascular reactivity. Blood pressure was elevated significantly (p < 0.05) in 5HPO and 10HPO groups, with the 10HPO group showing higher values. Aortic rings from animals fed with heated oil showed diminished relaxation in response to acetylcholine or sodium nitroprusside, and greater contraction to phenylephrine. Acetylcholine and sodium nitroprusside cause endothelium-dependent and endothelium-independent relaxation, respectively. Relaxation responses remained unaltered in the FPO group, with the attenuated contractile response to phenylephrine, compared to control group. FPO increased plasma nitrites by 28%, whereas 5HPO and 10HPO reduced them by 25% and 33%, respectively. Intake of repeatedly heated palm oil causes an increase in blood pressure, which may be accounted for by the attenuated endothelium-dependent vasorelaxant response.
Consumption of repeatedly heated soy oil increases the serum parameters related to atherosclerosis in ovariectomized rats

Adam SK, Das S, Soelaiman IN, Umar NA, Jaarin K

Tohoku J. Exp. Med., 2008 Jul;215(3):219-26.
PMID: 18648182

Repeated heating of soy oil may promote lipid peroxidation. Oxidized unsaturated fatty acids may contribute to the pathogenesis of atherosclerosis, especially in estrogen-deficient states. This study was performed to explore the deleterious effects of repeatedly heated soy oil on the development of atherosclerosis using ovariectomized rats, which represent an estrogen-deficient state. Twenty-four female Sprague-Dawley rats were ovariectomized and were divided equally into four groups. The control group was fed with 2% cholesterol diet without any oil. The three treatment groups each received 2% cholesterol diet fortified with fresh, once-heated or five-times-heated (repeatedly heated) soy oil, respectively. Serum thiobarbituric acid reactive substances (TBARS), lipid profile and homocysteine levels were measured prior to ovariectomy and at the end of four months. Ovariectomized rats treated with repeatedly heated soy oil showed significant increases in lipid peroxidation and low-density lipoprotein (LDL) levels. Treatment with once-heated or repeatedly heated soy oil caused a significant increase in total cholesterol, while fresh soy oil caused significant reduction in homocysteine level as compared to other groups. Repeatedly heated soy oil caused significant increases in TBARS and LDL as compared to fresh oil. The higher level of homocysteine in the ovariectomized rats fed with repeatedly heated oil, as compared to those fed with fresh oil, also suggests the repeatedly heated oil contributes to the development of atherosclerosis. Importantly, the protective effect of the soy oil may be lost once it was being repeatedly heated. In conclusion, the consumption of repeatedly heated oil may predispose to atherosclerosis in estrogen-deficient states.
Fulltext Level of knowledge, attitude and practice of night market food outlet operators in Kuala Lumpur regarding the usage of repeatedly heated cooking oil

Azman A, Mohd Shahrul S, Chan SX, Noorhazliza AP, Khairunnisak M, Nur Azlina MF, et al.

Med J Malaysia, 2012 Feb;67(1):91-101.
PMID: 22582556 MyJurnal

Consumption of repeatedly heated oil can be detrimental to health. The objective of this study was to determine the level of knowledge, attitude and practice of night market food outlet operators in Kuala Lumpur regarding the usage of repeatedly heated cooking oil. The quality of cooking oil was also investigated. A cross-sectional study involving pretested questionnaire was undertaken in April 2009. The questionnaire was designed as a tool to collect data from the respondents (n=100) by face-to-face interview. The results showed that majority of respondents had only moderate (53.0%) or low (18.0%) level of knowledge regarding this issue. Most respondents (67.0%) agreed that it is not a good practice. The majority (69.0%) agreed that the usage of repeatedly heated cooking oil is detrimental to health. Despite that, most respondents (63.0%) admitted that they had used cooking oil repeatedly. Most (62.0%) of the cooking oil samples taken from the night market food outlets were considered fit for human consumption. In conclusion, the level of knowledge of night market food outlet operators in Kuala Lumpur regarding this issue needs to be improved in order to ensure the safety of fried food purchased from such establishments.
Deep-fried keropok lekors Increase Oxidative Instability in Cooking Oils

Kamisah Y, Shamil S, Nabillah MJ, Kong SY, Hamizah NA, Qodriyah HM, et al.

Malays J Med Sci, 2012 Oct;19(4):57-62.
PMID: 23613649

BACKGROUND: This study was performed to compare the oxidative quality of repeatedly heated palm and soybean oils, which were used to fry keropok lekors and potato chips.
METHODS: A kilogramme of keropok lekors or potato chips was fried in 2.5 L of palm or soybean oil at 180 °C for 10 minutes. The frying process was repeated once and four times to obtain twice-heated and five-times-heated oils. The peroxide value and fatty acid composition of the oils were measured.
RESULTS: Frequent heating significantly increased the peroxide values in both oils, with the five-times-heated oils having the highest peroxide values [five-times-heated palm: 14.26 ± 0.41 and 11.29 ± 0.58 meq/kg vs fresh: 2.13 ± 0.00, F (3,12) = 346.80, P < 0.001; five-times-heated soybean: 16.95 ± 0.39 and 12.90 ± 0.21 meq/kg vs fresh: 2.53 ± 0.00 oils, F (3,12) = 1755, P < 0.001, when used to fry keropok lekors and potato chips, respectively]. Overall, both oils showed significantly higher peroxide values when keropok lekors were fried in them compared with when potato chips were fried. In general, the heated soybean oil had significantly higher peroxide values than the heated palm oil. Fatty acid composition in the oils remained mostly unaltered by the heating frequency.
CONCLUSION: keropok lekors, when used as the frying material, increased the peroxide values of the palm and soybean oils. Fatty acid composition was not much affected by the frequency of frying or the fried item used.
Effect of repeatedly heated palm olein on blood pressure-regulating enzymes activity and lipid peroxidation in rats

Leong XF, Salimon J, Mustafa MR, Jaarin K

Malays J Med Sci, 2012 Jan;19(1):20-9.
PMID: 22977371

BACKGROUND: Oxidative stress is associated with the pathogenesis of cardiovascular diseases. The process of deep-fat frying in dietary cooking oil plays a role in the generation of free radicals. In this study, palm olein heated to 180 °C was tested for its effect on the activity of blood pressure-regulating enzymes and lipid peroxidation.
METHODS: Forty-two adult male Sprague-Dawley rats were equally assigned into 6 groups.The first group was fed with normal rat chow as the control group, and the subsequent groups were fed with rat chow fortified with 15% weight/weight of the following: fresh palm olein, palm olein heated once, palm olein heated twice, palm olein heated 5 times, or palm olein heated 10 times. The duration of feeding was 6 months. Fatty acid analyses of oil were performed using gas chromatography. Peroxide values were determined using standard titration. Plasma was collected for biochemical analyses.
RESULTS: Repeatedly heated palm olein increased the levels of peroxide, angiotensin-converting enzyme, and lipid peroxidation as well as reduced the level of heme oxygenase. Fresh palm olein and palm olein heated once had lesser effects on lipid peroxidation and a better effect on the activity of blood pressure-regulating enzymes than repeatedly heated palm olein.
CONCLUSION: Repeatedly heated palm olein may negatively affect the activity of blood pressure-regulating enzymes and increase lipid peroxidation.
Influence of dietary fat on plasma lipid profiles of Malaysian adolescents

Marzuki A, Arshad F, Razak TA, Jaarin K

Am J Clin Nutr, 1991 04;53(4 Suppl):1010S-1014S.
PMID: 1901440 DOI: 10.1093/ajcn/53.4.1010S

We studied the effects of saturated (palm olein) and polyunsaturated (soybean oil) cooking oils on the lipid profiles of Malaysian male adolescents eating normal Malaysian diets for 5 wk. Diets cooked with palm olein did not significantly alter plasma total-cholesterol, LDL cholesterol, and HDL cholesterol concentrations or the ratio of total cholesterol to HDL cholesterol compared with diets cooked with soybean oil. However, the diet cooked with palm olein significantly increased apolipoprotein A-I (11%) and apolipoprotein B (9%) concentrations. Unexpectedly, soybean-oil-cooked diets caused a significant increase (47%) in plasma triglycerides compared with palm-olein-cooked diets. We conclude that palm olein, when used as cooking oil, has no detrimental effects on plasma lipid profiles in Malaysian adolescents.
Fulltext Palm vitamin E and glucosamine sulphate in the treatment of osteoarthritis of the knee

Haflah NH, Jaarin K, Abdullah S, Omar M

Saudi Med J, 2009 Nov;30(11):1432-8.
PMID: 19882056

OBJECTIVE: To assess the efficacy of oral palm vitamin E in reducing symptoms of patients with osteoarthritis (OA) of the knee compared to oral glucosamine sulphate.
METHODS: This open study was carried out at the Universiti Kebangsaan Malaysia Medical Center, Kuala Lumpur, Malaysia between March 2006 and November 2007. Seventy-nine patients were recruited to receive either 1.5 g oral glucosamine sulphate or 400 mg oral palm vitamin E for 6 months. Symptoms were assessed using the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index and visual analogue scale (VAS).
RESULTS: Sixty-four patients completed the trial (vitamin E n=33, glucosamine sulfate n=31). After 6 months of treatment, both groups showed a significant improvement in WOMAC scale and significant reduction in the VAS score during standing and walking. There was no significant difference in WOMAC scale and VAS score between the 2 groups. Except for mild allergic reaction and abdominal discomfort in one patient, there were no other serious adverse effects reported. Serum malondialdehyde was significantly higher in the glucosamine group compared to palm vitamin E treated group at the end of the study. Serum of vitamin E was significantly higher in the palm vitamin E group compared to glucosamine.
CONCLUSION: The finding of this study suggests that oral palm vitamin E in a dose of 400 mg taken daily has a potential role in reducing symptoms of patients with OA of the knee. It may be just as effective as glucosamine sulphate in reducing the symptoms and free from serious side effects. Further study is required to ascertain the mechanism of action beside its antioxidant effect.
Effects of nicardipine on lipid peroxidation in rabbits given 2% cholesterol diet

Ismail NM, Jaarin K, Vasudevan SK, Hashim S

Pharmacol. Toxicol., 1995 Jul;77(1):10-5.
PMID: 8532606

Nicardipine has been shown to have an anti-atherogenic effect in rabbits given a 2% cholesterol diet. Current evidence suggests that lipid peroxidation plays an important role in atherogenesis. This study examines the effect of nicardipine on lipid peroxidation in rabbits given a 2% cholesterol diet, 8 of these rabbits given nicardipine 0.5 mg/kg twice daily intramuscularly for ten weeks while the remaining untreated 6 were controls. After ten weeks, serum malondialdehyde in the control group was significantly higher compared to their baseline levels (P < 0.05). However, there was no increase in serum malondialdehyde in the nicardipine group after 10 weeks. The area of Sudan IV positive intimal lesions (atherosclerotic plaques) were significantly decreased (P < 0.01) in the treated group compared to the control group. The aortic tissue content of cholesterol and diene conjugates were also decreased in the nicardipine group (P < 0.01). These findings suggest a possible link between nicardipine and lipid peroxidation in mediating its antiatherogenic effects.
Cardioprotective effect of virgin coconut oil in heated palm oil diet-induced hypertensive rats

Kamisah Y, Periyah V, Lee KT, Noor-Izwan N, Nurul-Hamizah A, Nurul-Iman BS, et al.

Pharm Biol, 2015;53(9):1243-9.
PMID: 25853965 DOI: 10.3109/13880209.2014.971383

Virgin coconut oil (VCO) contains high antioxidant activity which may have protective effects on the heart in hypertensive rats.
Changes in blood pressure, vascular reactivity and inflammatory biomarkers following consumption of heated corn oil

Das S, Hamsi MA, Kamisah Y, Qodriyah HMS, Othman F, Emran A, et al.

Pak J Pharm Sci, 2017 Sep;30(5):1609-1615.
PMID: 29084680

Consumption of corn oil for cooking purpose is gaining popularity. The present study examined the effect of heated corn oil on blood pressure and its possible mechanism in experimental rats. Thirty male Sprague-Dawley rats were randomly divided into 5 groups and were fed with the following diets, Group I was fed with basal diet only; whereas group II,III,IV and V were fed with basal diet fortified with 15% (w/w) either fresh, once-heated, five-times-heated or ten-times-heated corn oil, respectively for 16 weeks. Body weight, blood pressure were measured at baseline and weekly interval for 16 weeks. Inflammatory biomarkers which included soluble intracellular adhesion molecules (sICAM), soluble vascular adhesion molecules (sVCAM) and C reactive protein (CRP), were measured at baseline and the end of 16 weeks. The rats were sacrificed and thoracic aorta was taken for measurement of vascular reactivity. There was significant increase in the blood pressure in the groups fed with heated once, five-times (5HCO) and ten-times-heated corn oil (10-HCO) compared to the control. The increase in the blood pressure was associated with an increase in CRP, sICAM and sVCAM, reduction in vasodilatation response to acetylcholine and greater vasoconstriction response to phenylephrine. The results suggest that repeatedly heated corn oil causes elevation in blood pressure, vascular inflammation which impairs vascular reactivity thereby predisposing to hypertension. There is a need to educate people not to consume corn oil in a heated state.
Effects of repeatedly heated palm oil on serum lipid profile, lipid peroxidation and homocysteine levels in a post-menopausal rat model

Adam SK, Soelaiman IN, Umar NA, Mokhtar N, Mohamed N, Jaarin K

Mcgill J Med, 2008 Jul;11(2):145-51.
PMID: 19148313

Oxidized unsaturated fatty acids may contribute to the pathogenesis of atherosclerosis. In the present study, we examined the effects of heated palm oil mixed with 2% cholesterol diet on serum lipid profile, homocysteine and thiobarbituric acid reactive substances (TBARS) levels in estrogen-deficient rats. Twenty-four female Sprague Dawley rats were ovariectomized and then were divided equally into four groups. The control group was given 2% cholesterol diet only throughout the study period. The three treatment groups received 2% cholesterol diet fortified with fresh, once-heated or five-times-heated palm oil, respectively. Serum TBARS, lipid profile and homocysteine levels were measured prior to ovariectomy and at the end of four months of the study. Five-times-heated palm oil caused a significant increase in TBARS and total cholesterol (TC) compared to control (F=22.529, p<0.05). There was a significant increase in serum homocysteine in the control as well as five-times heated palm oil group compared to fresh and once-heated palm oil groups (F=4.432, p<0.05). The findings suggest that repeatedly heated palm oil increase lipid peroxidation and TC. Ovariectomy increases the development of atherosclerosis as seen in this study. Feeding with fresh and once-heated palm oil does not cause any deleterious effect but repeatedly heated oil may be harmful because it causes oxidative damage thereby predisposing to atherosclerosis.
Fulltext Association of elevated blood pressure and impaired vasorelaxation in experimental Sprague-Dawley rats fed with heated vegetable oil

Leong XF, Mustafa MR, Das S, Jaarin K

Lipids Health Dis, 2010;9:66.
PMID: 20573259 DOI: 10.1186/1476-511X-9-66

Poor control of blood pressure leads to hypertension which is a major risk factor for development of cardiovascular disease. The present study aimed to explore possible mechanisms of elevation in blood pressure following consumption of heated vegetable oil.
Enzymatic and microstructural changes in the liver of experimental rats fed with fatty diet and fresh or heated soy oil concurrently

Jaarin K, Hwa TC, Umar NA, Siti Aishah MA, Das S

Clin Ter, 2010;161(5):429-33.
PMID: 21057734

Consumption of heated edible oils may be harmful. The present study aimed to observe the histological changes due to concurrent consumption of soy oil (either fresh or heated) and fatty diet and the changes in the level of alanine transaminase (ALT) and alkaline phosphatase (ALP).
Fulltext Involvement of inflammation and adverse vascular remodelling in the blood pressure raising effect of repeatedly heated palm oil in rats

Ng CY, Kamisah Y, Faizah O, Jubri Z, Qodriyah HM, Jaarin K

Int J Vasc Med, 2012;2012:404025.
PMID: 22778962 DOI: 10.1155/2012/404025

Oil thermoxidation during deep frying generates harmful oxidative free radicals that induce inflammation and increase the risk of hypertension. This study aimed to investigate the effect of repeatedly heated palm oil on blood pressure, aortic morphometry, and vascular cell adhesion molecule-1 (VCAM-1) expression in rats. Male Sprague-Dawley rats were divided into five groups: control, fresh palm oil (FPO), one-time-heated palm oil (1HPO), five-time-heated palm oil (5HPO), or ten-time-heated palm oil (10HPO). Feeding duration was six months. Blood pressure was measured at baseline and monthly using tail-cuff method. After six months, the rats were sacrificed and the aortic arches were dissected for morphometric and immunohistochemical analyses. FPO group showed significantly lower blood pressure than all other groups. Blood pressure was increased significantly in 5HPO and 10HPO groups. The aortae of 5HPO and 10HPO groups showed significantly increased thickness and area of intima-media, circumferential wall tension, and VCAM-1 than other groups. Elastic lamellae were disorganised and fragmented in 5HPO- and 10HPO-treated rats. VCAM-1 expression showed a significant positive correlation with blood pressure. In conclusion, prolonged consumption of repeatedly heated palm oil causes blood pressure elevation, adverse remodelling, and increased VCAM-1, which suggests a possible involvement of inflammation.
Vitamin E and factors affecting atherosclerosis in rabbits fed a cholesterol-rich diet

Ismail NM, Abdul Ghafar N, Jaarin K, Khine JH, Top GM

Int J Food Sci Nutr, 2000;51 Suppl:S79-94.
PMID: 11271860

The present study aims to examine the effects of a palm-oil-derived vitamin E mixture containing tocotrienol (approximately 70%) and tocopherol (approximately 30%) on plasma lipids and on the formation of atherosclerotic plaques in rabbits given a 2% cholesterol diet. Eighteen New Zealand White rabbits (2.2-2.8 kg) were divided into three groups; group 1 (control) was fed a normal diet, group 2 (AT) was fed a 2% cholesterol diet and group 3 (PV) was fed a 2% cholesterol diet with oral palm vitamin E (60 mg/kg body weight) given daily for 10 weeks. There were no differences in the total cholesterol and triacylglycerol levels between the AT and PV groups. The PV group had a significantly higher concentrations of HDL-c and a lower TC/HDL-c ratio compared to the AT group (P < 0.003). The aortic tissue content of cholesterol and atherosclerotic lesions were comparable in both the AT and PV groups. However, the PV group had a lower content of plasma and aortic tissue malondialdehyde (P < 0.005). Our findings suggest that despite a highly atherogenic diet, palm vitamin E improved some important plasma lipid parameters, reduced lipid peroxidation but did not have an effect on the atherosclerotic plaque formation.
Effect of palm vitamin E on the healing of ethanol-induced gastric injury in rats

Jaarin K, Renuvathani M, Nafeeza MI, Gapor MT

Int J Food Sci Nutr, 2000;51 Suppl:S31-41.
PMID: 11271855

The effect of palm vitamin E on the healing of ethanol-induced gastric lesions and various biochemical parameters were investigated. The study was divided into two phases. In the first phase of the study, 42 rats of Sprague Dawley species (200-250 gm weight) were randomly divided into two groups fed with a normal diet (control) or palm vitamin E enriched diet (150 mg/kg) for 3 weeks. The rats were killed after 3 weeks of feeding. Gastric tissue contents of malondialdehyde (MDA), prostaglandin E2 and acid were measured. In the second phase of the study 42 rats were divided into two groups. Group 1 was fed normal rat pellets (control) and group 2 was fed palm vitamin E enriched pellets (150 mg/kg food) for 3 weeks. After 3 weeks of feeding gastric mucosal injury was induced by an orogastric tube administration of 0.5 ml 100% ethanol. The rats were killed at 1 hour, 4 hours and 1 week after ethanol exposure for semiquantitative determination of ulcer index and gastric acid concentration. Gastric tissue MDA and mucus were measured only at 1 week after ethanol exposure. In the first phase of the study we found that palm vitamin E only caused a significant reduction in gastric MDA. However, it showed no significant effects on prostaglandin E2 and gastric acid concentration. In the second phase of the study, the mean ulcer index of palm vitamin E supplemented group killed after 1 week of ethanol exposure was significantly lower compared to the respective control. However, there was no significant difference in ulcer index in rats killed at 1 hour and 24 hours after ethanol exposure. The gastric acid concentration was significantly higher in the group treated with palm vitamin E killed 1 week after ethanol exposure compared to control. The gastric tissue MDA was significantly lower in the palm vitamin E supplemented group compared to control. There was no significant difference in gastric mucus content of the both groups. The ulcer healing which occurred in the presence of a high gastric acid suggests that the effect of palm vitamin E on the healing of gastric lesions was not mediated via a reduction in gastric acid nor was it mediated through increasing prostaglandin E2 or mucus production. The most probable mechanism is via reducing lipid peroxidation as reflected by a significant decreased in gastric tissue MDA content.
Fulltext The role of repeatedly heated soybean oil in the development of hypertension in rats: association with vascular inflammation

Ng CY, Kamisah Y, Faizah O, Jaarin K

Int J Exp Pathol, 2012 Oct;93(5):377-87.
PMID: 22974219 DOI: 10.1111/j.1365-2613.2012.00839.x

Thermally oxidized oil generates reactive oxygen species that have been implicated in several pathological processes including hypertension. This study was to ascertain the role of inflammation in the blood pressure raising effect of heated soybean oil in rats. Male Sprague-Dawley rats were divided into four groups and were fed with the following diets, respectively, for 6 months: basal diet (control); fresh soybean oil (FSO); five-time-heated soybean oil (5HSO); or 10-time-heated soybean oil (10HSO). Blood pressure was measured at baseline and monthly using tail-cuff method. Plasma prostacyclin (PGI(2) ) and thromboxane A(2) (TXA(2) ) were measured prior to treatment and at the end of the study. After six months, the rats were sacrificed, and the aortic arches were dissected for morphometric and immunohistochemical analyses. Blood pressure was increased significantly in the 5HSO and 10HSO groups. The blood pressure was maintained throughout the study in rats fed FSO. The aortae in the 5HSO and 10HSO groups showed significantly increased aortic wall thickness, area and circumferential wall tension. 5HSO and 10HSO diets significantly increased plasma TXA(2) /PGI(2) ratio. Endothelial VCAM-1 and ICAM-1 were significantly increased in 5HSO, as well as LOX-1 in 10HSO groups. In conclusion, prolonged consumption of repeatedly heated soybean oil causes blood pressure elevation, which may be attributed to inflammation.
Fulltext A detailed microscopic study of the changes in the aorta of experimental model of postmenopausal rats fed with repeatedly heated palm oil

Adam SK, Das S, Jaarin K

Int J Exp Pathol, 2009 Jun;90(3):321-7.
PMID: 19563614 DOI: 10.1111/j.1365-2613.2009.00658.x

Hypercholesterolaemia, increase in lipid peroxidation and hyperhomocysteinaemia may contribute to the pathogenesis of atherosclerosis. This study was performed to examine the effects of repeatedly heated palm oil mixed with 2% cholesterol diet on atherosclerosis in oestrogen-deficient postmenopausal rats. Ovariectomy causes disruption of tunica intima layer of the rat aorta simulating a postmenopausal condition in females. Twenty-four ovariectomized female Sprague-Dawley rats were divided into four groups. The control group received 2% cholesterol diet without palm oil. A diet with 2% cholesterol content fortified with fresh, once-heated and five-times-heated palm oil was given to the other treatment groups. The rats were sacrificed at the end of 4 months of study and the aortic arch tissue was processed for histomorphometry and electron microscopy. On observation, there was disruption of the intimal layer of the ovariectomized rat aorta. There was no obvious ultrastructural change in the aorta of the rats fed with fresh palm oil. The ultrastructural changes were minimal with once-heated palm oil, in which there was a focal disruption of the endothelial layer. The focal disruption was more pronounced with five-times-heated palm oil. The results of this study show that the ingestion of fresh palm oil may have a protective effect on the aorta but such a protective action may be lost when the palm oil is repeatedly heated. The study may be clinically important for all postmenopausal women who are susceptible to atherosclerosis.

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