Docosahexaenoic acid restores endothelial function in children with hyperlipidemia: results from the EARLY study

OBJECTIVE

The primary objective of this study was to determine whether the National Cholesterol Education Program Step II (NCEP-II) diet or supplementation with docosahexaenoic acid (DHA) with the diet, affects endothelial function in children with familial hypercholesterolemia (FH) or the phenotype of familial combined hyperlipidemia (FCH). As secondary endpoints, the influence of diet and DHA supplementation on lipid profiles as well as biomarkers for oxidative stress and inflammation, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, were all evaluated.

METHODS

In a double-blind, placebo-controlled, randomized, crossover study design, 20 children (ages 9-19 years) with FH (n = 12) and FCH (n = 8) received nutritional counseling based on the National Cholesterol Education Program Step II (NCEP-II) and food guide pyramid dietary guidelines for 6 weeks. They were then randomly assigned to supplementation with docosahexaenoic acid (DHA 1.2 g/d) or placebo for 6 weeks, followed by a washout phase of 6 weeks and crossover phase of 6 weeks while continuing the NCEP-II diet. Endothelium-dependent flow-mediated dilation (FMD) of the brachial artery was determined by high-resolution ultrasound. Plasma levels of total cholesterol, triglycerides and lipoprotein classes (LDL, HDL, VLDL) were measured by ultracentrifugation and enzymatic methods, plasma F2 isoprostanes by gas chromatography/mass spectrometry, urinary 8-OH-2' deoxyguanosine by liquid chromatography, high sensitivity C-reactive protein by immunonephelometry and ADMA by liquid chromatography.

RESULTS

FMD increased significantly after DHA supplementation compared to baseline (p < 0.001), diet alone (p < 0.002), placebo (p < 0.012) and washout (p < 0.001) phases of the study without affecting biomarkers for oxidative stress, inflammation or ADMA. DHA supplementation was associated with increased levels of total cholesterol (p < 0.01), LDL- and HDL cholesterol concentrations (p < 0.001) compared to the NCEP-II diet.

CONCLUSION

This study demonstrates that DHA supplementation restores endothelial-dependent FMD in hyperlipidemic children. The endothelium may thus be a therapeutic target for DHA. This is consistent with a hypothesis of increasing NO bioavailability, with the potential for preventing the progression of early coronary heart disease in high-risk children.

Mechanisms of vasorelaxation induced by eicosapentaenoic acid (20:5n-3) in WKY rat aorta

The vasorelaxant activity of eicosapentaenoic acid (EPA, 20:5n-3), the omega-3 polyunsaturated fatty acid, was investigated in isolated Wistar Kyoto (WKY) rat aortae by measuring isometric tension. Eicosapentaenoic acid (1 - 100 microM) relaxed rat aortae contracted with high K(+) (80 mM) or noradrenaline (NA, 1 microM) in a concentration-dependent manner. Contractions induced by Bay K 8644 or increasing concentrations of calcium were unaffected by EPA. The relaxant effect of EPA (3 - 100 microM) was significantly inhibited by indomethacin (10 microM), the cyclo-oxygenase inhibitor, but not by the nitric oxide (NO) synthesis inhibitor, N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME, 100 microM). Removal of the endothelium did not alter EPA-induced relaxations. In Ca(2+)-free, EGTA 2 mM solution, EPA (10 - 30 microM significantly inhibited NA-sustained contractions. Incubation with EPA (5, 10 microM) diminished both NA-induced (1 microM) phasic and sustained contractions. The vasorelaxant effects of EPA (> or =30 microM) on NA-induced (1 microM) contractions were significantly inhibited by the K(+) channel blocker, glibenclamide (10 microM), but not tetraethylammonium (1 mM). Moreover, indomethacin and glibenclamide combined significantly inhibited EPA-induced (1 - 100 microM) responses. These results indicate EPA exerts its endothelium-independent vasorelaxant effects in WKY rat aortae through production of prostanoids which activate K(+)(ATP) channels. Inhibition of Ca(2+) mobilization from intracellular pools and influx through the non-L-type, but not the L-type, Ca(2+) channel are also possible mechanisms action of EPA's.

Soluble epoxide hydrolase regulates hydrolysis of vasoactive epoxyeicosatrienoic acids

The cytochrome P450-derived epoxyeicosatrienoic acids (EETs) have potent effects on renal vascular reactivity and tubular sodium and water transport; however, the role of these eicosanoids in the pathogenesis of hypertension is controversial. The current study examined the hydrolysis of the EETs to the corresponding dihydroxyeicosatrienoic acids (DHETs) as a mechanism for regulation of EET activity and blood pressure. EET hydrolysis was increased 5- to 54-fold in renal cortical S9 fractions from the spontaneously hypertensive rat (SHR) relative to the normotensive Wistar-Kyoto (WKY) rat. This increase was most significant for the 14,15-EET regioisomer, and there was a clear preference for hydrolysis of 14, 15-EET over the 8,9- and 11,12-EETs. Increased EET hydrolysis was consistent with increased expression of soluble epoxide hydrolase (sEH) in the SHR renal microsomes and cytosol relative to the WKY samples. The urinary excretion of 14,15-DHET was 2.6-fold higher in the SHR than in the WKY rat, confirming increased EET hydrolysis in the SHR in vivo. Blood pressure was decreased 22+/-4 mm Hg (P:<0.01) 6 hours after treatment of SHRs with the selective sEH inhibitor N:, N:'-dicyclohexylurea; this treatment had no effect on blood pressure in the WKY rat. These studies identify sEH as a novel therapeutic target for control of blood pressure. The identification of a potent and selective inhibitor of EET hydrolysis will be invaluable in separating the vascular effects of the EET and DHET eicosanoids.

Docosahexaenoic acid--induced vasorelaxation in hypertensive rats: mechanisms of action

The authors investigated the vasorelaxant properties of the omega-3 fatty acid, docosahexaenoic (DHA, 22:6n-3), and the possible involvement of endothelium-derived nitric oxide, prostanoids, opening of K+ channels, and/or modulation of calcium-mediated events. Isolated aorta from male spontaneously hypertensive rats (SHR) (age 16-17 weeks) were used to measure isometric tension. DHA-induced (1-100 mumol/l) relaxation was examined following contraction to norepinephrine (NE) (10(-6) mol/l) or high-K+ (80 mmol/l) solution in the presence and absence of various inhibitors and calcium-containing solution. DHA acid induced a significant vasorelaxant effect in both NE and high-K(+)-induced contracted SHR aortic rings, although DHA relaxations were greater in high-K(+)-induced contracted rings. In the absence of extracellular calcium, DHA (5-30 mumol/l) inhibited the initial phasic and sustained components of NE-induced contraction under different conditions. Inhibition of nitric oxide synthesis by N omega-nitro-L-arginine methyl ester hydrochloride (100 mumol/l) had no effect on DHA relaxations; however, indomethacin or nifedipine caused significant inhibition at > or = 30 mumol/l DHA. The K+ channel blocker, glibenclamide, but not tetraethyl-ammonium, also had an inhibitory effect on DHA-induced relaxation. These results indicate that DHA's vasorelaxant actions in SHR aorta are independent of endothelium-derived nitric oxide; however, at DHA concentrations > or = 30 mumol/l, vasodilatory prostanoids that activate ATP-sensitive K+ channels (KATP) may be involved. At lower concentrations, DHA-induced relaxation appears to be attributed to modulation of intracellular Ca2+ release and L-type Ca2+ channels in vascular smooth muscle cells. The vasorelaxant properties of DHA may contribute, in part, to the blood pressure-lowering effect of dietary fish oil in this hypertensive model.

Dietary docosahexaenoic acid affects stearic acid desaturation in spontaneously hypertensive rats

Docosahexaenoic acid (DHA, 22:6n-3) is an n-3 polyunsaturated fatty acid which attenuates the development of hypertension in spontaneously hypertensive rats (SHR). The effects of DHA on delta-9-desaturase activity in hepatic microsomes and fatty acid composition were examined in young SHR. Two groups of SHR were fed either a DHA-enriched diet or a control diet for 6 wk. Desaturase activity and fatty acid composition were determined in hepatic microsomes following the dietary treatments. Delta-9-desaturase activity was decreased by 53% in DHA-fed SHR and was accompanied by an increase in 16:0 and a reduction in 16:1n-7 content in hepatic microsomes. The DHA diet also increased the levels of eicosapentaenoic acid (20:5n-3) and DHA. The n-6 fatty acid content was also affected in DHA-fed SHR as reflected by a decrease in gamma-linolenic acid (18:3n-6), arachidonic acid (20:4n-6), adrenic acid (22:4n-6), and docosapentaenoic acid (22:5n-6). A higher proportion of dihomo-gamma-linolenic acid (20:3n-6) and a lower proportion of 20:4n-6 is indicative of impaired delta-5-desaturase activity. The alterations in fatty acid composition and metabolism may contribute to the antihypertensive effect of DHA previously reported.

Calcium-mediated mechanisms of eicosapentaenoic acid-induced relaxation in hypertensive rat aorta

We have previously demonstrated the vasorelaxant properties of the omega-3 fatty acid, eicosapentaenoic acid (EPA), in normotensive and spontaneously hypertensive rat (SHR) aorta, although the mechanism(s) of action are not fully understood. Because endothelial dysfunction and increased intracellular free calcium concentration ([Ca2+]i) are seen in hypertensive rat aorta, we investigated the potential role of Ca2+ signaling, endothelium and derived factors, and the opening of potassium (K+) channels in EPA-induced relaxation. In the presence of extracellular Ca2+, EPA induced significant relaxations at >10 micromol/L (P<.01) in norepinephrine (NE) (10(-6) mol/L)-contracted aortic rings and at 30 micromol/L (P<.001) in high K+ (80 mmol/L)-contracted aortic rings. In the absence of extracellular Ca2+, EPA (10 to 30 micromol/L) inhibits the tonic component of NE-induced contraction (P<.0001). The relaxant properties of EPA in SHR aorta appear specific to Ca2+ release from an internal storage site associated with NE-induced tonic contraction. Further studies with the use of fura-2 to measure [Ca2+]i in cultured vascular smooth muscle (VSM) cells from SHR aorta indicated that EPA (30 micromol/ L)-pretreatment attenuated angiotensin II (50 nmol/ L)-induced Ca2+ transient by 95%, suggesting that an inhibitory effect on the Ca2+ signaling may underlie EPA-induced relaxation of the vessel preparation. In addition, EPA per se induced an increase in [Ca2+li with a duration of approximately 20 min in VSM cells, and the effect was not altered by removal of extracellular Ca2+. There was no increase in the level of inositol-1,4,5-trisphosphate in response to EPA (30 micromol/L). The actions of EPA are independent of endothelium-derived factors, cyclooxygenase metabolites, and activation of K+ channels since endothelium removal, N(omega)-nitro-L-arginine methyl ester hydrochloride, (L-NAME, 100 micromol/L), indomethacin (10 micromol/L), tetraethylammonium (1 mmol/L), and glibenclamide (10 micromol/L) did not affect EPA-induced vasodilation in NE-precontracted aortic rings. These results suggest that EPA directly modulates intracellular Ca2+ signaling in VSM cells, and that this may contribute to the vasorelaxant effect and, at least in part, the blood pressure-lowering effect of fish oil.

The effects of a diet rich in docosahexaenoic acid on organ and vascular fatty acid composition in spontaneously hypertensive rats

Previous research has shown that dietary docosahexaenoic acid (DHA) attenuates the development of high blood pressure in young spontaneously hypertensive rats (SHR). The purpose of this study was to investigate the effects of dietary DHA on organ and vascular fatty acid composition in SHR. Given the important structural and functional role of fatty acids in cell membranes, alterations in fatty acid composition may contribute to the antihypertensive effect of DHA. SHR were fed a purified diet containing either a corn/soybean oil mixture (CSO, control) or a DHA-enriched oil for 6 weeks. The DHA diet markedly increased the levels of DHA in the aorta, renal artery, plasma, liver, heart, kidney, and lung by 5-, 15-, 7-, 6-, 3.8-, 3.5-, and 8.8-fold (P<0.001), respectively. The levels of eicosapentaenoic acid were also increased while there was a concomitant reduction in arachidonic and adrenic acids. Therefore, dietary DHA increases the incorporation of omega-3 polyunsaturated fatty acids in specific organs and vascular tissue in SHR at the expense of omega-6 polyunsaturated fatty acids.

Docosahexaenoic acid is an antihypertensive nutrient that affects aldosterone production in SHR

The effects of dietary docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, on blood pressure and some pressure-regulating systems were measured in young spontaneously hypertensive rats (SHR). Plasma aldosterone and corticosterone levels, adrenal aldosterone production in vitro, and characteristics of adrenal angiotensin receptors were measured after 6 weeks of diet. Renal cytochrome P450 (CYP) 4A gene expression and arachidonic acid metabolism by renal microsomes were also investigated. Plasma cholesterol, triglycerides, and high-density lipoprotein cholesterol were measured. Diets contained either corn/soybean oil alone (CSO), or oil enriched with DHA. After 6 weeks, rats fed DHA had systolic blood pressures averaging 34 mmHg less than controls (P < 0.001). Plasma aldosterone levels were 33% lower in the DHA-fed animals than in controls (22 +/- 3 vs. 33 +/- 3.7 ng/dl, P < 0.05). Plasma levels of corticosterone were 18% lower in animals fed DHA than in controls, but this difference was not statistically significant. Adrenal glomerulosa cells from DHA-fed rats produced less aldosterone in vitro in response to angiotensin II, ACTH, or potassium. The difference was less marked when aldosterone production was stimulated by supplying exogenous corticosterone, suggesting an effect of DHA on postreceptor steps in signal transduction or the early pathway of aldosteronogenesis. We found no significant differences in angiotensin receptor subtype, number, or affinity. Production of arachidonic epoxides by renal microsomes was 17% lower in DHA-fed animals than in controls (P < 0.05). Renal cortical mRNA levels of CYP4A genes and formation of 19- and 20-hydroxyeicosatetraenoic acid (HETE) did not differ between dietary groups. Plasma total cholesterol and high-density-lipoprotein (HDL) levels were significantly reduced in SHR fed the DHA supplement, but triglyceride levels were not significantly different. The effects of DHA on steroid and eicosanoid metabolism may be part of the mechanism by which this fatty acid prevents some of the hypertension in growing SHR.

Age-related changes in plasma and tissue fatty acid composition in Fischer 344 rats

Advancing age is associated with increased risk of coronary artery disease. Changes in fatty acid metabolism affect important cellular membrane properties and functions which may contribute to the vascular pathophysiology of aging. This study was designed to investigate the effects of aging on the fatty acid composition of the plasma, liver, aorta, and renal artery in 4-, 15-, and 24-month old Fischer 344 rats, an animal model for aging. With aging, the levels of total polyunsaturated fatty acids (PUFA) increased in the plasma, aorta, and renal artery. The major changes in the liver fatty acid profile were increases in the levels of 18:2n6 and 18:3n3 and a decrease in the levels of 20:3n6 and 20:5n3. The results indicate that significant shifts occur in the levels of n6 and n3 PUFA in the plasma, liver, and vasculature with aging. The alterations in the fatty acid composition may be a pathogenetic mechanism of the vascular changes associated with aging.

Effects of dietary gamma-linolenic acid on blood pressure and adrenal angiotensin receptors in hypertensive rats

In a previous study, we showed that dietary gamma-linolenic acid (GLA), an omega-6 polyunsaturated fatty acid found in borage oil (BOR), attenuates the development of hypertension in young spontaneously hypertensive rats (SHR). The purpose of this study was to determine the effects of dietary GLA on established hypertension in adult rats, as well as its effects on components of the renin-angiotensin-aldosterone axis. For 5 weeks, male SHR (14-15 weeks old) were fed a basal fat-free diet to which 11% by weight of sesame oil (SES) or BOR was added. Systolic blood pressure (SBP), determined by the tail cuff method, and weight were measured weekly. Plasma renin activity (PRA), aldosterone (PA), and corticosterone (PC) levels were measured at the end of the dietary treatments. The adrenal glands were homogenized, and angiotensin II (ANG II) binding was measured and plotted according to Scatchard. Systolic blood pressure was 12 mmHg lower at Week 5 in SHR fed the BOR diet compared to SES-fed rats (P < 0.005). Weight gains were similar in both dietary groups. Plasma aldosterone was lower, PRA was higher, and the PA/PRA ratio was significantly lower (P < 0.05) in BOR-fed rats. Levels of PC were the same in both groups. The BOR-enriched diet reduced adrenal ANG II receptor density and affinity compared to the SES diet. Results suggest that BOR inhibits adrenal responsiveness to ANG II by an action on adrenal receptors. Our findings demonstrated that dietary GLA lowers SBP in adult SHR. This effect may be mediated, at least in part, by interference with the renin-angiotensin-aldosterone system at the level of adrenal ANG II receptors.

Dietary borage oil alters plasma, hepatic and vascular tissue fatty acid composition in spontaneously hypertensive rats

Dietary borage oil rich in gamma-linolenic acid (GLA) has been shown to lower blood pressure in Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). A potential mechanism for this effect may be attributed to changes in metabolism of GLA to dihomogamma-linolenic (DGLA) and arachidonic acids (AA). We investigated the effects of dietary borage oil on fatty acid composition in the plasma, liver and vascular tissue in WKY and SHR. The diet significantly increased the levels of omega-6 polyunsaturated fatty acids. GLA and DGLA levels in the plasma, liver, aorta and renal artery tissues increased in SHR (P < 0.001) and WKY (P < 0.001). AA levels were also increased in both plasma and liver of SHR (P < 0.05) and WKY (P < 0.05) fed the borage oil enriched diet. The results demonstrate that dietary borage oil produces marked changes in the metabolism of GLA which may contribute to its blood pressure lowering effect in WKY and SHR.

Perceived learning needs of patients with coronary artery disease using a questionnaire assessment tool

OBJECTIVE

To determine the perceived learning needs and their level of importance in patients with angina pectoris or myocardial infarction at hospitalization and follow-up clinic visit and to assess the reliability of a self-administered questionnaire.

DESIGN

Longitudinal, exploratory.

SETTING

West Coast university-affiliated medical center and clinics that serve primarily a veteran population.

PATIENTS

Twenty-eight adults who were admitted with a diagnosis of angina pectoris or myocardial infarction. Age range was 31 to 80 years (mean 61 years).

OUTCOME MEASURES

Learning needs, questionnaire.

INTERVENTION

Data collection was initiated at hospitalization and continued at the first clinic visit after discharge. A self-administered questionnaire and personal data sheet were completed by the patients.

RESULTS

Matched-pair t-tests and Pearson's correlation were used for data analysis. No statistical differences were demonstrated between learning needs at hospitalization and clinic visit. Three content areas including symptom recognition, cardiac anatomy and physiology, and medications were ranked as the most important learning needs of patients at hospitalization and follow-up clinic visit. The least important learning needs at both times were content areas of smoking, work, and sex. No correlation was found between the importance of perceived learning needs and age, occupation, smoking, and marital status. The questionnaire contains 38 items and is self-administered. It was developed on the basis of a previous tool and preliminary study results. Content and validity were supported by clinical experts. The internal consistency reliability alpha coefficients of the questionnaire were 0.96 at hospitalization and 0.93 at the clinic visit.

CONCLUSIONS

The findings of this study suggest that the most important perceived learning needs of patients at hospitalization and follow-up clinic visit are those that affect survival. A self-administered questionnaire can be used as a practical and reliable tool to determine the perceived learning needs of patients with coronary artery disease during the recovery phase of illness. Cardiac educational programs for patients with coronary artery disease can focus on the content areas that patients consider most important.

Influence of aging on the relaxant responses to omega-3 fatty acids in Fischer 344 rat aorta

The effect of age on the vasorelaxant properties of the omega-3 fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA), in isolated rat aortic rings were investigated in 4-, 15- and 24-month-old Fischer 344 rats. Increased aortic wall thickness was seen in both 15- and 24-month-old rats. Maximal contractile responses to norepinephrine (NE) were greater in intact and de-endothelialized (ENDO-) rings from 15- and 24-month-old rats; although increased sensitivity to NE was exhibited in 4-month-old rings. DHA- and EPA-induced (1-100 mumol/l) responses were similar between the three age groups in intact rings. Removal of the endothelium enhanced relaxant responses to both DHA and EPA in all three groups. EPA-induced (1-100 mumol/l) responses ranged from-4 to 28% for both 4- and 15- month ENDO- rings and -1 to -18% in 24-month ENDO-rings. DHA ENDO-ring responses (1-100 mumol/l) were- 4 to -13% in 4 months, -5 to -23% in 15 months, and -0.8 to -16% in 24 months. Age differences were apparent with the ENDO- ring responses to DHA and EPA. These differences were seen with greater relaxant responses to both EPA and DHA in the 4- and 15-month-old aortic rings. Increased sensitivity and a greater maximal relaxant response to acetylcholine (ACH) was noted in the 15-month-old group. Four- and 24-month rings exhibited similar sensitivity and maximal relaxant responses to ACH. However, relaxation was decreased in 24-month rings at low ACH concentrations. These findings suggest that both functional and morphological changes occur with aging. DHA- and EPA-induced responses are not altered by aging in intact rings; however, removal of the endothelium enhances their vasorelaxant properties in all three age groups. This may be related to the direct actions of DHA and EPA on vascular smooth muscle, rather than on mechanisms associated with generation of endothelium-derived relaxing factor.

Assessment of the cardiovascular effects of stress

The stress response increases sympathetic nervous activity, which can adversely affect the cardiovascular system. Cardiovascular disease is due in part to stress-induced mechanisms mediated primarily through increased adrenergic stimulation. These stress-induced mechanisms include elevations in serum lipid levels, alterations in blood coagulation, atherogenesis, vascular changes in hypertension, and myocardial ischemia. Stress management interventions for hypertension are controversial; however, interventions for coronary heart disease-prone behavior patterns have proven successful. Stress management interventions have also reduced cardiovascular events, mortality, and coronary atherosclerosis. Assessment of stress includes individual interviews, which can be complemented by information derived from questionnaires and mental stress testing. Educational and relaxation strategies can prepare patients to understand and cope with stress. These approaches will hopefully decrease the occurrence of stress and, ultimately, the risk for cardiovascular disease.

Vasorelaxant properties of n-3 polyunsaturated fatty acids in aortas from spontaneously hypertensive and normotensive rats

BACKGROUND

Dietary consumption of fish, rich in n-3 polyunsaturated fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), has been shown to reduce blood pressure in both animal studies and clinical trials. Although the antihypertensive mechanisms are not known, the blood-pressure-lowering effect of n-3 polyunsaturated fatty acids may be partially attributed to their vasorelaxant properties.

METHODS

Aortic rings with and without endothelium, from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), 16-17 weeks old, were suspended in tissue baths and isometric tension was measured. Concentration-response curves were generated for DHA and EPA (1-100 mu mol/l) in norepinephrine-contracted rings. Blood pressure was measured using the tail-cuff method and aortic media thickness was determined.

RESULTS

Blood pressure was significantly increased in SHR (n=10; 194 +/- 4.4 mmHg) compared with WKY (n=10; 124 +/- 1.2 mmHg, P < or = 0.0001). DHA (1-100 mu mol/l) relaxed aortic rings f rom WKY (-3.3 +/- 0.7 to -13 +/- 2.3%, P < or = 0.001) and from SHR (-6.5 +/- 1.8 to -22.9 +/- 4%, P < or = 0.01) in a concentration-dependent manner. EPA (1-100 mu mol/l) evoked greater relaxation in SHR (-10.1 +/- 2.0 to -33 +/- 3.9%, P < 0.01) than in WKY (-2.9 +/- 1.1 to -18.3 +/- 2.1%, P < 0.01) aortic rings. The relaxant effect of DHA in both WKY and SHR and of EPA in WKY were not dependent on an intact endothelium. However, EPA (1-10 mu mol/l) induced greater responses in intact SHR rings (-10.1 +/- 2.0 to -14.5 +/- 3.1%) than in de-endothelialized SHR rings (0 to -2.1 +/- 1.7%, P = 0.001).

CONCLUSION

The direct relaxant effects of n-3 fatty acids as seen in WKY and SHR may contribute, in part, toward the blood-pressure-lowering effect of dietary fish and fish-oil supplementation.

Comparative study of diets enriched with evening primrose, black currant, borage or fungal oils on blood pressure and pressor responses in spontaneously hypertensive rats

The effects of oils enriched with gamma-linolenic acid (GLA) on blood pressure and pressor responses were examined in spontaneously hypertensive rats (SHR). Rats were fed purified diets containing evening primrose (EPO), black currant (BCO), borage (BOR) or fungal (FGO) oils for 7 weeks. Significant reductions in blood pressure were obtained in SHR rats maintained on diets enriched with GLA oils. The antihypertensive effect was not associated with enhanced pressor responsiveness to norepinephrine or angiotensin II. Moreover, no differences were found in blood pressure responses to the calcium channel blocker, verapamil. The results suggest that GLA-enriched oils inhibit the development of hypertension in the SHR rat. The blood pressure lowering effect is not mediated by altered pressor responses to vasoconstrictor hormones or intracellular calcium mechanisms.

Exploratory data analysis of hyperlipidemia on the Macintosh: software tools for analysis of biochemical, clinical, and genetic variables in 1677 consecutive lipid clinic patients

Exploratory data analysis (EDA) software facilitates unstructured, iterative open exploration of complex datasets with the aid of multiple linked graphical displays. We are investigating relationships between plasma lipoproteins and coronary artery disease by retrospective analysis of 1677 consecutive UCSF Lipid Clinic patients. Our preliminary experience is with Data Deck 3.0 although several additional software programs (JMP 2.0, Systat 5.1, Minitab 8.0, StatView 4.0) are mentioned. Lipid diagnosis (751 women and 925 men) was 22% primary hypercholesterolemia, 19% combined hyperlipidemia, 3% dysbetalipoproteinemia, 15% endogenous lipemia, 4% mixed lipemia, 5% elevated Lp(a) and 32% with no major lipid abnormality. We found the Macintosh platform (68030) to be flexible and powerful for analysis of moderate size (less than 1 Mb) clinical datasets. High resolution color monitors (1024 x 768 pixels), fast hard disks (< 18 msec) and moderate amounts of system memory (8 + Mb) facilitate exploratory analysis.

Cardiovascular disease prevention: knowledge and attitudes of graduate nursing students

Graduate nursing students were surveyed to determine the knowledge and attitudes of cardiovascular disease prevention. Questionnaires were self-administered to first-year graduate nursing students (n = 50) in a school of nursing prior to and following a physiology course with cardiovascular disease prevention content. In general, the results demonstrated that the respondents were least knowledgeable regarding the prevalence of smoking, the gender differences in high-density lipoprotein (HDL)-cholesterol levels, the influence of body weight on lipids and the recommended percentages of calories from dietary fat. A significant improvement in knowledge was noted after the course. Positive attitudes regarding the importance of cardiovascular disease prevention and the partnership between patients and clinicians necessary to manage risk were identified. These attitudes did not change significantly following the course. These results indicate that graduate education which emphasizes cardiovascular disease prevention increases knowledge. Coupled with positive attitudes and healthy personal lifestyle behaviours, knowledge of cardiovascular disease prevention may enhance the ability of nurses to integrate preventive standards into clinical practice and ultimately decrease the risk of cardiovascular disease.

Dietary gamma-linolenic acid lowers blood pressure and alters aortic reactivity and cholesterol metabolism in hypertension

OBJECTIVE

To determine the effects of dietary gamma-linolenic acid upon blood pressure, aortic reactivity and cholesterol metabolism in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats.

DESIGN

Randomized parallel-group study.

METHODS

SHR and WKY rats were fed a purified diet containing either sesame or borage oil rich in gamma-linolenic acid for 7 weeks. Blood pressure measured by the tail-cuff method and weight were monitored weekly. At the end of the study, intra-arterial pressor responses to norepinephrine and angiotensin II, and reactivity of isolated aortic rings to norepinephrine, angiotensin II, KCl and acetylcholine were determined. Serum cholesterol and triglycerides were measured. Hepatic and intestinal enzymes and receptors of cholesterol metabolism were also measured.

RESULTS

Dietary borage oil significantly decreased blood pressure in SHR and WKY rats compared with sesame oil-fed rats. Pressor responses to norepinephrine and angiotensin II, and aortic reactivity to norepinephrine, angiotensin II, KCl and acetylcholine were not significantly different. The borage oil diet increased serum cholesterol levels in WKY rats and hepatic B-hydroxy-3-methylglutaryl coenzyme A reductase in SHR.

CONCLUSION

These data indicate that dietary borage oil has a blood pressure lowering effect in hypertensive and normotensive rats. However, the effect cannot be explained by altered sensitivity to humoral and neural vasoconstrictors or changes in cholesterol metabolism. Other mechanisms should be investigated.

Ethanol inhalation and dietary n-6, n-3, and n-9 fatty acids in the rat: effect on platelet and aortic fatty acid composition

The effects of 18-carbon n-6, n-3, and n-9 fatty acid diets and ethanol exposure on the fatty acyl composition of platelets and vascular tissue were examined. An experimental design was devised to control the dietary content of 18-carbon fatty acids. The levels of 18:3n6, 18:3n3 and 18:1n9 were varied by a formulation of dietary oils which contained similar proportions of 18:2n6. Male Sprague-Dawley rats were fed a purified diet containing 11% by weight of either borage oil (BOR) rich in 18:3n6, linseed/safflower oil (LSO) rich in 18:3n3, or sesame oil (SES) rich in 18:1n9 for 7 weeks and exposed to ethanol vapors by means of inhalation for the final 6 days of the dietary regimen. Moderate blood ethanol levels of 118 +/- 6.6 mg/dl were obtained. Total lipids were extracted from platelets and aortae, and the fatty acid distributions were analyzed by gas chromatography. BOR feeding resulted in increases in the proportion of n-6 fatty acids (18:3n6, 20:3n6, 20:4n6) in platelets and aorta. Animals fed the LSO diet had increased levels of n-3 fatty acids (18:3n3, 20:5n3, 22:6n3). The SES-based diet resulted in an increase in 18:1n9 in both aorta and platelets. Following ethanol exposure alone, the most marked change in the fatty acid profile was a decrease in 20:4n6 in the platelet. This effect was not observed in rats supplemented with BOR. No significant changes were observed in the aortic fatty acid content at this level of ethanol exposure. The results suggested that, in the rat, a diet enriched with BOR effectively prevented ethanol-induced alterations in platelet fatty acid composition.

The effects of magnetic resonance imaging on intravenous infusion devices

We evaluated the effects of magnetic resonance imaging on the accuracy of three types of intravenous infusion pump devices, IVAC 530, IMED 927 and IMED 960/965. The devices were exposed to a 2,800-gauss static magnetic field at a pulsed radio frequency of 11.9 MHz operating at a maximum power of 1,200 W. Each device was tested at low, medium and fast flow rates in a controlled environment and during magnetic resonance imaging. Intravenous therapy could be carried out normally during magnetic resonance diagnostic imaging only with the IVAC 530 infusion device.

Actuarial analysis of the risk of undergoing repeat cardiac valve replacement

One thousand five hundred ninety-eight patients who underwent cardiac valve replacement were reviewed. One hundred fifty-two patients (10 percent) required a second valve replacement. The indications for repeat valve replacement were prosthetic valve dysfunction in 53 patients (35 percent), development of a new valvular lesion in 46 patients (30 percent), simple closure of a perivalvular leak in 14 patients (9 percent), change of the valve poppet in 13 patients (8 percent), severe hemolysis or emboli in 21 patients (14 percent), and prosthetic valve endocarditis in 5 patients (3 percent). The mean preoperative New York Health Association functional class improved from 3 to 1.5 in the nonreoperated patients and from 2.9 to 1.8 in patients who underwent a second valve replacement. Similarly, the mean cardiac index improved from 2.5 to 2.9 and from 2.5 to 2.8 in nonreoperated and reoperated patients, respectively. The operative mortality rate was 14 percent in the nonreoperated patients and 16 percent at second operation in the reoperated patients. Using actuarial techniques, the risk of repeat valve replacement was 1 to 4 percent per year. Long-term survival was compared between groups. Using actuarial techniques, the estimated survival rates at 1, 5, and 10 years were 89 percent, 69 percent, and 52 percent, respectively in nonreoperated patients and 87 percent, 60 percent, and 37 percent in reoperated patients. This study has documented the excellent improvement in functional and hemodynamic state after second cardiac valve replacement. The operative mortality and long-term survival rates were similar to those of the nonreoperated patients. Patients having repeat cardiac valve replacement can expect good improvement in length and quality of life.