Assessment of the Genotoxic Potential of Repeatedly Heated Cooking Oil In Wistar Rats

Repeated heating of edible oils at high temperatures and its use in cooking food generates polycyclic aromatic hydrocarbons (PAHs) that have carcinogenic potential. The use of repeatedly heated cooking oils (RHCO) is a common practice in India. The present investigation in Wistar rats was done to determine the genotoxic potential of consumption of food cooked in sunflower oil that has been repeatedly heated to boiling. The rats were fed a diet cooked-fried in such oil. The biomarkers of genotoxicity, comet assay, micronucleus test, and chromosomal aberrations in peripheral blood lymphocytes (PBL) of Wistar rats were used. Results of the present investigation reveal that rats fed on food cooked in oil that was 5 times repeatedly boiled induced significant Deoxy ribonucleic acid (DNA) damage in PBL and liver homogenate. Increased frequency of micronuclei and chromosomal aberrations in blood and bone marrow of rats were also observed. A similar observation was found in rats that were fed food cooked in oil that was boiled 3 times. However, the results of genotoxicity in rats that ate food cooked in oil heated only once were not statistically significant in comparison to the control rats that fed on food made in heated oil (not boiled). Intake of food cooked in repeatedly heated oil of different heating grades induced significant genotoxicity in rats evident by increased DNA damage and frequency of micronuclei and chromosomal aberrations. The presence of PAHs in heated oils triggers the generation of free radicals which could be the possible causative factor for the induced genetic damage. This study sheds light on the potential link between dietary habits involving the use of degraded oils and long-term health consequences.

Gynura procumbens ethanol extract improves vascular dysfunction by suppressing inflammation in postmenopausal rats fed a high-fat diet

CONTEXT

Gynura procumbens (Lour.) Merr. (Asteraceae) has been reported to have various pharmacological activities including anti-inflammatory effects.

OBJECTIVE

This study sought to determine whether Gynura procumbens (GP) could improve vascular reactivity by suppressing inflammation in postmenopausal rats fed with five-times heated palm oil (5HPO) diet.

MATERIALS AND METHODS

Forty-eight female Sprague-Dawley rats were randomly divided into sham [non-ovariectomized; grouped as control, GP extracts (250 and 500 mg/kg), atorvastatin (ATV, 10 mg/kg)] and postmenopausal (PM) groups [ovariectomized rats fed with 5HPO; grouped as PM, GP extracts (250 and 500 mg/kg) and ATV (10 mg/kg)]. Each group (n = 6) was either supplemented with GP extract or ATV orally once daily for 6 months.

RESULTS

In comparison with the untreated PM group, 250 and 500 mg/kg GP supplementation to PM groups reduced the systolic blood pressure (103 ± 2.7, 86 ± 2.4 vs. 156 ± 7.83 mmHg, p < 0.05), intima-media thickness (101.28 ± 3.4, 93.91 ± 2.93 vs. 143.78 ± 3.31 µM), vasoconstriction percentage induced by phenylephrine (102.5%, 88.3%, vs. 51.8%), sICAM-1 (0.49, 0.26 vs. 0.56 pg/mL) and sVCAM-1 (0.39, 0.25 vs. 0.45 pg/mL). GP extract supplementation increased vasorelaxation percentage induced by acetylcholine (78.4% vs. 47.3%) and sodium nitroprusside (84.2% vs. 53.7%), increased changes in plasma nitric oxide level (1.25%, 1.31% vs. 1.9%), and suppressed the elevation of TNF-α (0.39 vs. 1.02 pg/mL), IL-6 (0.43 vs. 0.77 pg/mL) and CRP (0.29 vs. 0.69 ng/mL) in the PM groups.

CONCLUSIONS

GP extract might improve vascular dysfunction by suppressing the inflammatory response, consequently preventing blood pressure elevation.

Repeatedly heated palm olein disrupts male reproductive system of rat: A histological and biochemical study

The aim of this study was to investigate the effect of heated and unheated palm olein in different doses on the male reproductive system of rats. Forty male rats were randomly classified into five groups (n = 8) including Control, Low palm, High palm, Heated low palm and Heated high palm. The palm olein was administrated orally for 6 months. Histological and biochemical parameters of the male reproductive system were measured. There was a significant reduction in sexual hormones, serum levels of superoxide dismutase, high-density lipoprotein, testis weight and sperm parameters in the high dose and heated palm olein groups compared to the other group (p < 0.05). The levels of malondialdehyde, apoptosis rate, proteins levels (TNF-α, IL-1β, IL-6), low-density lipoprotein, cholesterol, triglyceride and the weight of the rats were significantly higher in the high dose and heated palm olein groups than the others (p < 0.05). High dose and heated palm olein treatment could damage the male rat's reproductive indices that were related to increased inflammatory markers, decreased sex hormone levels, and negative effects on testicular tissue and sperm parameters.

Reused palm oil from frying pork or potato induced expression of cytochrome P450s and the SLCO1B1 transporter in HepG2 cells

Deep frying degrades the oil and generates harmful products. This study evaluated effects of reused palm oil (from frying pork or potato) on expression of cytochrome P450s (CYPs), the transporter (SLCO1B1), and lipid metabolism regulators; proliferator-activated receptors (PPAR) and sterol regulatory element binding protein (SREBP). Human hepatic carcinoma cell line (HepG2) cells were incubated with oleic acid (OA), new palm oil, or reused palm oils for 24 hr. Fatty acid accumulation was examined by Nile red staining. Total RNA was extracted, followed by RT/qPCR of the target genes. Fatty acid accumulation was significantly different between the new and the reused oils. Expression of CYP1A2, CYP2C19, CYP2E1, CYP3A4, CYP4A11, and SLCO1B1 was induced by reused oils. Expression of PPAR-α was strongly increased in all treatments while SREBP-1a and SREBP-1c were suppressed. Modification of CYPs, PPAR-α, and SLCO1B1 by palm oil might increase the risk of fatty acid accumulation with associated oxidative stress. Therefore, consumption of palm oil or reused oil should be limited. PRACTICAL APPLICATIONS: Deep frying degrades the oil and generates harmful products. This study evaluated effects of reused palm oil (from frying pork or potato) on expression of cytochrome P450s (CYPs), the transporter (SLCO1B1), and lipid metabolism regulators; PPAR and SREBP in HepG2 cells. Both of the reused oils-induced profiles of all CYP and SLCO1B1, but the new oil upregulated CYP2E1, CYP3A4, and CYP4A11. PPAR-α was induced while SREBP-1a and SREBP-1c were suppressed by all treatments. Inductions of CYPs with suppression of SREBP-1a and SREBP-1c might contribute to an increased risk of fatty acid accumulation. These findings revealed the impacts of reused palm oil on metabolism via CYPs which related to oxidative stress for further study. Hence, consumption of palm oil or reused cooking oil should be of concern.

Gynura procumbens Standardised Extract Reduces Cholesterol Levels and Modulates Oxidative Status in Postmenopausal Rats Fed with Cholesterol Diet Enriched with Repeatedly Heated Palm Oil

Gynura procumbens (Lour.) Merr. (GP) has been reported in previous studies to possess antihyperlipidaemic, antioxidative, and cardioprotective properties. This study was aimed to determine the effect of standardised 80% ethanol extract of GP on lipid profiles and oxidative status of hypercholesterolemic rats. Postmenopausal (PM) Sprague-Dawley rats were ovariectomised and fed with 2% cholesterol diet fortified with five times heated palm oil to develop hyperlipidaemia status. Two doses of the extract (250 and 500 mg/kg) and atorvastatin (10 mg/kg) were administered once daily via oral gavage for 24 weeks. Systolic blood pressure (SBP) was increased during the first month in the postmenopausal group and decreased with GP supplementation. Lipid droplets accumulation was shown at the tunica media (TM) area of the aorta in the postmenopausal group and reduced with GP supplementation. Total cholesterol (TC), total triglycerides (TG), low-density lipoprotein (LDL), and malondialdehyde (MDA) levels increased (p < 0.05) at 3 and 6 months in the postmenopausal group and were reduced with GP supplementation. GP also increased high-density lipoprotein (HDL) level in the postmenopausal group. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were reduced in the postmenopausal group compared to control in the sham group but increased (p < 0.05) with GP supplementation. The results showed that the higher dose of GP (500 mg/kg) gave better effect. GP has the ability to reduce oxidative stress and prevent membrane cell damage through antioxidant enzyme activity modification and lipid profile changes in postmenopausal rats related to atherosclerosis.

The protective activity of nanomicelle curcumin in bisphenol A-induced cardiotoxicity following subacute exposure in rats

Bisphenol A (BPA), an estrogenic compound, is used in manufacture of polycarbonate plastics and epoxy resins. Curcumin, the active ingredient of turmeric, is a potent protective compound against cardiac diseases. In this study the protective effect of nanomicelle curcumin on BPA-induced subchronic cardiotoxicity in rats was evaluated. Rats were divided into 6 groups including control, nanomicelle curcumin (50 mg/kg, gavage), BPA (50 mg/kg, gavage), nanomicelle curcumin (10, 25, and 50 mg/kg) plus BPA. The treatments were continued for 4 weeks. Results revealed that BPA significantly induced histophatological injuries including focal lymphatic inflammation, nuclear degenerative changes and cytoplasmic vacuolation, increased body weight, systolic and diastolic blood pressures, malondialdehyde and Creatine phosphokinase-MB level and decreased glutathione content in comparison with control group. In addition, in electrocardiographic graph, RR, QT, and PQ intervals were increased by BPA. Western blot analysis showed that BPA up-regulated phosphorylated p38 (p38-mitogen-activated protein kinase) and JNK (c-jun NH2 terminal kinases), while down-regulated phosphorylated AKT (Protein Kinase B) and ERK1/2 (extracellular signal-regulated protein kinases 1 and 2). However, nanomicelle curcumin (50 mg/kg) significantly improved these toxic effects of BPA in rat heart tissue. The results provide evidence that nanomicelle curcumin showed preventive effects on subchronic exposure to BPA induced toxicity in the heart tissue in rats.

Effects of citrus leaf extract on aortic vascular reactivity in hypertensive rats fed repeatedly heated vegetable oil

The prolonged intake of diet containing repeatedly heated vegetable oil can cause hypertension in the long run. In this study, the effects of citrus leaf extract (CLE) supplementation on vascular reactivity, plasma nitrite, and aortic structure in hypertensive rats were investigated by the consumption of repeatedly heated vegetable oil [corrected]. Male Sprague Dawley rats (n = 56) were divided into 7 groups corresponding to the respective diets. For 16 weeks, 1 group was given standard rat chow (control) while other groups were given diets containing 15% w/w of palm oil, fresh palm oil (FPO), palm oil heated 5 times (5HPO), and palm oil heated 10 times (10HPO), with or without the incorporation of 0.15% w/w CLE (FPO+CLE, 5HPO+CLE, or 10HPO+CLE). Plasma nitrite levels were measured before and at 16 weeks of treatment. After 16 weeks, the rats were sacrificed and aortae were harvested for measuring vascular reactivity and for microscopic study. CLE supplementation had significantly reduced the loss of plasma nitrite and attenuated the vasoconstriction response to phenylephrine in the 5HPO group but not in the 10HPO group. However, CLE had no significant effect on the vasorelaxation response to acetylcholine and sodium nitroprusside. The elastic lamellae of tunica media in 5HPO, 10HPO, and 10HPO+CLE groups appeared disorganised and disrupted. Obtained findings suggested that CLE was able to enhance nitric oxide bioavailability that might dampen the vasoconstriction effect of phenylephrine.

Altered Potassium Ion Channel Function as a Possible Mechanism of Increased Blood Pressure in Rats Fed Thermally Oxidized Palm Oil Diets

Intake of thermally oxidized palm oil leads to cytotoxicity and alteration of the potassium ion channel function. This study investigated the effects of fresh and thermally oxidized palm oil diets on blood pressure and potassium ion channel function in blood pressure regulation. Male Wistar rats were randomly divided into three groups of eight rats. Control group received normal feed; fresh palm oil (FPO) and thermally oxidized palm oil (TPO) groups were fed a diet mixed with 15% (weight/weight) fresh palm oil and five times heated palm oil, respectively, for 16 weeks. Blood pressure was measured; blood samples, hearts, and aortas were collected for biochemical and histological analyses. Thermally oxidized palm oil significantly elevated basal mean arterial pressure (MAP). Glibenclamide (10^-5 mmol/L) and tetraethylammonium (TEA; 10^-3 mmol/L) significantly raised blood pressure in TPO compared with FPO and control groups. Levcromakalim (10^-6 mmol/L) significantly (p < .01) reduced MAP by 32.0% in FPO and by 5.4% in TPO. NS1619 (10 mmol/L) significantly (p < .01) decreased MAP by 19.5% in FPO and by 8% in TPO. The TPO significantly (p < 0.01) increased the tissue levels of peroxide, total cholesterol, triglyceride, and low-density lipoprotein cholesterol while catalase and superoxide dismutase activities were significantly (p < .01) decreased compared with control and FPO groups. Histological alterations were prominent in aortas and hearts of rats in the TPO group. These results suggest that prolonged consumption of repeatedly heated palm oil increases MAP probably due to the attenuation of adenosine triphosphate-sensitive potassium (K_ATP) and large-conductance calcium-dependent potassium (BK_Ca) channels, tissue peroxidation, and altered histological structures of the heart and blood vessels.

Predictors of Hypertension in a Population of Undergraduate Students in Sierra Leone

We report on the first survey of hypertension in undergraduates in Sierra Leone. Levels of hypertension (12%) and obesity (4%) appear low compared to the general population but given the rapid increase of both and the expectation that many graduates will enter the formal employment sector and a sedentary lifestyle, there is still cause for concern. We measured their BMI (body mass index) and used a questionnaire to investigate demographic and lifestyle choices. In agreement with most authorities, we found that BMI and age were statistically significant predictors of systolic and diastolic blood pressure but that the explanatory power was low (r = 0.21 to 0.27). Men may be more sensitive than women to an increase in BMI on blood pressure (p < 0.1). We failed to find statistically significant relationships with ethnicity, religion, stress, course of study, levels of physical activity, diet, smoking, or consumption of caffeine and alcohol. Family history of hypertension, consumption of red palm oil, and self-diagnosed attacks of typhoid fever were close to conventional levels of significance (p < 0.1). We intend to use this as a baseline for longitudinal studies to assess risks and suggest appropriate public health action.

Serum selenium levels, the selenoprotein glutathione peroxidase and vascular protection: The SABPA study

Selenium is an important co-factor for the optimal functioning of the antioxidant enzyme, glutathione peroxidase (GPx). Studies investigating the associations of selenium with blood pressure (BP) and hemodynamic measures are sparse. This study investigated whether 24h blood pressure, vascular resistance, arterial compliance and arterial stiffness relate to both serum selenium and GPx activity. In this cross-sectional study selenium levels, GPx activity, ambulatory blood pressure and arterial stiffness of 200 black and 209 white school teachers from South Africa were measured. Serum selenium levels were significantly lower in black compared to white teachers (p<0.001), independent of sex. One in 10 black men and one in five black women were selenium deficient (<8μg/100ml). Only in white men inverse independent associations of 24h systolic BP (β=-0.19; p=0.039) and 24h diastolic BP (β=-0.21; p=0.029) with selenium were found. In the same group, an inverse association between carotid-dorsalis pedis pulse wave velocity (cd-PWV) and GPx activity (β=-0.23; p=0.017) were also found. To conclude, lower serum selenium levels in black populations from the same geographical region as their white counterparts may impact on the loss of the vasculoprotective effects of selenium and selenoproteins such as GPx.

Evaluation of the deleterious health effects of consumption of repeatedly heated vegetable oil

Consumption of repeatedly heated cooking oil (RHCO) has been a regular practice without knowing the harmful effects of use. The present study is based on the hypothesis that, heating of edible oils to their boiling points results in the formation of free radicals that cause oxidative stress and induce damage at the cellular and molecular levels. Peroxide value of heated oil, histopathological alterations, antioxidant enzyme levels and blood biochemistry were determined in Wistar rats treated with the RHCO. RHCO revealed higher peroxide value in comparison to oil that has been unheated or singly heated. Histopathological observation depicted significant damage in jejunum, colon and liver of animals that received oil heated repeatedly for 3 times. The altered antioxidant status reflects an adaptive response to oxidative stress. Alteration in the levels of these enzymes might be due to the formation of reactive oxygen species (ROS) through auto oxidation or enzyme catalyzed oxidation of electrophilic components within RHCO. Analysis of blood samples revealed elevated levels of glucose, creatinine and cholesterol with declined levels of protein and albumin in repeatedly heated cooking oil group. Hematological parameters did not reveal any statistically significant difference between treated and control groups. Results of the present study confirm that the thermal oxidation of cooking oil generates free radicals and dietary consumption of such oil results in detrimental health effects.

Thyroid Hormones, Oxidative Stress, and Inflammation

Inflammation and oxidative stress (OS) are closely related processes, as well exemplified in obesity and cardiovascular diseases. OS is also related to hormonal derangement in a reciprocal way. Among the various hormonal influences that operate on the antioxidant balance, thyroid hormones play particularly important roles, since both hyperthyroidism and hypothyroidism have been shown to be associated with OS in animals and humans. In this context, the nonthyroidal illness syndrome (NTIS) that typically manifests as reduced conversion of thyroxine (T₄) to triiodothyronine (T₃) in different acute and chronic systemic conditions is still a debated topic. The pathophysiological mechanisms of this syndrome are reviewed, together with the roles of deiodinases, the enzymes responsible for the conversion of T₄ to T₃, in both physiological and pathological situations. The presence of OS indexes in NTIS supports the hypothesis that it represents a condition of hypothyroidism at the tissue level and not only an adaptive mechanism to diseases.

The role of dietary coconut for the prevention and treatment of Alzheimer's disease: potential mechanisms of action

Coconut, Cocos nucifera L., is a tree that is cultivated to provide a large number of products, although it is mainly grown for its nutritional and medicinal values. Coconut oil, derived from the coconut fruit, has been recognised historically as containing high levels of saturated fat; however, closer scrutiny suggests that coconut should be regarded more favourably. Unlike most other dietary fats that are high in long-chain fatty acids, coconut oil comprises medium-chain fatty acids (MCFA). MCFA are unique in that they are easily absorbed and metabolised by the liver, and can be converted to ketones. Ketone bodies are an important alternative energy source in the brain, and may be beneficial to people developing or already with memory impairment, as in Alzheimer's disease (AD). Coconut is classified as a highly nutritious 'functional food'. It is rich in dietary fibre, vitamins and minerals; however, notably, evidence is mounting to support the concept that coconut may be beneficial in the treatment of obesity, dyslipidaemia, elevated LDL, insulin resistance and hypertension - these are the risk factors for CVD and type 2 diabetes, and also for AD. In addition, phenolic compounds and hormones (cytokinins) found in coconut may assist in preventing the aggregation of amyloid-β peptide, potentially inhibiting a key step in the pathogenesis of AD. The purpose of the present review was to explore the literature related to coconut, outlining the known mechanistic physiology, and to discuss the potential role of coconut supplementation as a therapeutic option in the prevention and management of AD.

Animal Models in Cardiovascular Research: Hypertension and Atherosclerosis

Hypertension and atherosclerosis are among the most common causes of mortality in both developed and developing countries. Experimental animal models of hypertension and atherosclerosis have become a valuable tool for providing information on etiology, pathophysiology, and complications of the disease and on the efficacy and mechanism of action of various drugs and compounds used in treatment. An animal model has been developed to study hypertension and atherosclerosis for several reasons. Compared to human models, an animal model is easily manageable, as compounding effects of dietary and environmental factors can be controlled. Blood vessels and cardiac tissue samples can be taken for detailed experimental and biomolecular examination. Choice of animal model is often determined by the research aim, as well as financial and technical factors. A thorough understanding of the animal models used and complete analysis must be validated so that the data can be extrapolated to humans. In conclusion, animal models for hypertension and atherosclerosis are invaluable in improving our understanding of cardiovascular disease and developing new pharmacological therapies.

The role of oxidative stress, antioxidants and vascular inflammation in cardiovascular disease (a review)

The concept of mild chronic vascular inflammation as part of the pathophysiology of cardiovascular disease, most importantly hypertension and atherosclerosis, has been well accepted. Indeed there are links between vascular inflammation, endothelial dysfunction and oxidative stress. However, there are still gaps in our understanding regarding this matter that might be the cause behind disappointing results of antioxidant therapy for cardiovascular risk factors in large-scale long-term randomised controlled trials. Apart from the limitations of our knowledge, limitations in methodology and assessment of the body's endogenous and exogenous oxidant-antioxidant status are a serious handicap. The pleiotropic effects of antioxidant and anti-inflammation that are shown by some well-established antihypertensive agents and statins partly support the idea of using antioxidants in vascular diseases as still relevant. This review aims to provide an overview of the links between oxidative stress, vascular inflammation, endothelial dysfunction and cardiovascular risk factors, importantly focusing on blood pressure regulation and atherosclerosis. In view of the potential benefits of antioxidants, this review will also examine the proposed role of vitamin C, vitamin E and polyphenols in cardiovascular diseases as well as the success or failure of antioxidant therapy for cardiovascular diseases in clinical trials.

Cardioprotective effect of virgin coconut oil in heated palm oil diet-induced hypertensive rats

CONTEXT

Virgin coconut oil (VCO) contains high antioxidant activity which may have protective effects on the heart in hypertensive rats.

OBJECTIVES

The study investigated the effects of VCO on blood pressure and cardiac tissue by measuring angiotensin-converting enzyme (ACE) activity and its histomorphometry in rats fed with a heated palm oil (HPO) diet.

MATERIALS AND METHODS

Thirty-two male Sprague-Dawley rats were randomly divided into four groups: (i) control, (ii) orally given VCO (1.42 ml/kg), (iii) fed with a HPO (15%) diet, and (iv) fed with a HPO diet and supplemented with VCO (1.42 ml/kg, po) (HPO+VCO) for 16 weeks. Blood pressure was measured monthly. After 16 weeks, rat hearts were dissected for lipid peroxidation (TBARS) and ACE activity measurement and histomorphometric study.

RESULTS

Systolic blood pressure was significantly increased in the HPO group compared with the control starting at week eight (112.91 ± 1.32 versus 98.08 ± 3.61 mmHg, p < 0.05) which was prevented by VCO supplementation (91.73 ± 3.42 mmHg). The consumption of HPO increased TBARS and ACE activity in heart, which were inhibited by VCO supplementation. The increases in the myofiber width and area as well as nuclear size reduction in the HPO group were significantly prevented by VCO supplementation.

CONCLUSION

These results suggested that VCO supplementation possesses a cardioprotective effect by preventing the increase in blood pressure via an antioxidant mechanism and remodeling in rats fed repeatedly with a HPO diet.

Heated vegetable oils and cardiovascular disease risk factors

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.

Early endothelial nitrosylation and increased abdominal adiposity in Wistar rats after long-term consumption of food fried in canola oil

OBJECTIVE

The aim of this study was to establish whether the long-term consumption of reused canola oil contributes to the development of dyslipidemia, obesity, and endothelial function.

METHODS

Canola oil was used for one frying cycle (1 FC) of corn flour dough or reused 10 times (10 FC). Rats received chow diet (control) or supplemented with 7% raw oil (RO), 1 FC or 10 FC oil (n = 10 per group). Food consumption, blood pressure (BP), and body weight plasma glucose, plasma lipids were monitored. Vascular reactivity was analyzed using aorta rings stimulated with phenylephrine and acetylcholine. Nitrotyrosine presence in aorta rings was analyzed by immunohistochemistry.

RESULTS

After 10 wk of follow-up, visceral adipose tissue was significantly more abundant in 1 FC (7.4 ± 0.6 g) and 10 FC (8.8 ± 0.7 g) than the RO (5.0 ± 0.2 g; P = 0.05 versus 10 FC group) or control group (2.6 ± 0.3 g; P = 0.05 versus all groups). Despite similar plasma cholesterol, triglycerides, and BP among groups, a significantly reduced acetylcholine-induced vascular relaxation was observed in the three groups receiving the oil-supplemented diet (47.2% ± 3.6%, 27.2% ± 7.7%, and 25.9% ± 7.6% of relaxation, for the RO, 1 FC, and 10 FC, respectively; P < 0.05 for all versus 62.4% ± 9.7% of the control group). Endothelial dysfunction was concomitant with the presence of nitrotyrosine residues at a higher extent in the groups that received heated oils compared with the RO group.

CONCLUSION

High canola oil intake over 10 wk was associated with increased adipose tissue and early endothelial dysfunction probably induced by peroxinitrite formation. Such deleterious effects were significantly potentiated when the consumed oil had been used repeatedly for frying.

Virgin coconut oil prevents blood pressure elevation and improves endothelial functions in rats fed with repeatedly heated palm oil

This study was performed to explore the effects of virgin coconut oil (VCO) in male rats that were fed with repeatedly heated palm oil on blood pressure, plasma nitric oxide level, and vascular reactivity. Thirty-two male Sprague-Dawley rats were divided into four groups: (i) control (basal diet), (ii) VCO (1.42 mL/kg, oral), (iii) five-times-heated palm oil (15%) (5HPO), and (iv) five-times-heated palm oil (15%) and VCO (1.42 mL/kg, oral) (5HPO + VCO). Blood pressure was significantly increased in the group that was given the 5HPO diet compared to the control group. Blood pressure in the 5HPO + VCO group was significantly lower than the 5HPO group. Plasma nitric oxide (NO) level in the 5HPO group was significantly lower compared to the control group, whereas in the 5HPO + VCO group, the plasma NO level was significantly higher compared to the 5HPO group. Aortic rings from the 5HPO group exhibited attenuated relaxation in response to acetylcholine and sodium nitroprusside as well as increased vasoconstriction to phenylephrine compared to the control group. Aortic rings from the 5HPO + VCO group showed only attenuated vasoconstriction to phenylephrine compared to the 5HPO group. In conclusion, VCO prevents blood pressure elevation and improves endothelial functions in rats fed with repeatedly heated palm oil.

Involvement of inflammation and adverse vascular remodelling in the blood pressure raising effect of repeatedly heated palm oil in rats

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.

Association of elevated blood pressure and impaired vasorelaxation in experimental Sprague-Dawley rats fed with heated vegetable oil

Background

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.

Methods

Forty-two male Sprague-Dawley rats were equally divided into six groups: Group I (control) - normal rat chow, Group II - fresh soy oil, Group III - soy oil heated once, Group IV - soy oil heated twice, Group V - soy oil heated five times, Group VI - soy oil heated ten times. Blood pressure was measured at the baseline level and at a monthly interval for six months. Plasma nitric oxide, heme oxygenase and angiotensin-converting enzyme levels were measured prior to treatment, at month-three and month-six later. At the end of treatment, the rats were sacrificed and thoracic aortas were taken for measurement of vascular reactivity.

Results

Blood pressure increased significantly (p < 0.01) in the repeatedly heated oil groups compared to the control and fresh soy oil groups. Consumption of diet containing repeatedly heated oil resulted higher plasma angiotensin-converting enzyme level and lower nitric oxide content and heme oxygenase concentration. Reheated soy oil groups exhibited attenuated relaxation in response to acetylcholine or sodium nitroprusside, and greater contraction to phenylephrine.

Conclusion

As a result of consumption of repeatedly heated soy oil, an elevation in blood pressure was observed which may be due to the quantitative changes in endothelium dependent and independent factors including enzymes directly involved in the regulation of blood pressure.