Diet high in monounsaturated fat does not have a different effect on arterial elasticity than a low-fat, high-carbohydrate diet

Objective : To compare the effects of a modified-fat diet high in monounsaturated fat, and a low-fat/high-carbohydrate diet on arterial elasticity.
Design : Randomized crossover design; each diet period was 1 month and a 2-week wash out period occurred in between.
Subjects/setting : Thirty healthy, free-living, nonsmoking men and women were recruited from the Melbourne, Australia, metropolitan region of Australia. Men were aged 35 to 55 years and postmenopausal women were aged 50 to 60 years and were not taking hormone replacement therapy. Twenty-eight subjects completed the study.
Intervention : Two diets of equal energy value: a modified-fat diet and a low-fat/high-carbohydrate diet; the modified-fat diet had 3 times more energy from monounsaturated fat.
Main outcome measures : Arterial elasticity and serum lipoprotein concentrations.
Statistical analysis : The general linear model was used to investigate overall effect and any carryover or order effects. Paired t test and the general linear model were used to compare the results from the 2 diet periods.
Results : High-density lipoprotein cholesterol concentration was significantly higher on the modified-fat diet than on the low-fat/low-carbohydrate diet. Arterial elasticity and concentrations of total cholesterol, low-density lipoprotein cholesterol, and triglycerides were not significantly different on the 2 diets.
Applications/conclusions : There is no evidence to favor a diet high in monounsaturated fat over a low-fat/high-carbohydrate diet because of an effect on arterial elasticity. Other changes in diet may be needed to cause a beneficial effect on arterial elasticity.

Post-prandial remnant lipids impair arterial compliance

OBJECTIVES
We sought to examine the effects of plasma lipids, especially in remnants after a fat meal, on systemic arterial compliance (SAC), a newly recognized cardiovascular risk factor.
BACKGROUND
Post-prandial remnants correlate with coronary heart disease events through mechanisms that may include vascular dysfunction, although the effect on SAC has not been studied.
METHODS
Systemic arterial compliance was measured non-invasively over 6 h after a fat meal in 16 subjects with varying plasma triglyceride levels. Changes were related to rises in plasma lipids and remnant lipids. Systemic arterial compliance was measured in 20 subjects after a control low-fat meal.
RESULTS
The fat meal induced increments in plasma triglyceride and remnant cholesterol and triglyceride (respectively +54%, 50% and 290% at 3 h, analysis of variance <0.001). Systemic arterial compliance fell at 3 h and 6 h by 25% and 27% (analysis of variance <0.001). Baseline SAC correlated significantly with all lipid concentrations at 0, 3 h and 6 h, but only with triglyceride on stepwise regression analysis. The SAC response to the low-fat meal was very small and not significant.
CONCLUSIONS
This is the first demonstration of SAC becoming impaired after a fat meal. Remnant lipids and plasma total triglyceride appeared to contribute to the fall in SAC.

Arterial compliance in obese subjects is improved with dietary plant n-3 fatty acid from flaxseed oil despite increased LDL oxidizability

The compliance or elasticity of the arterial system, an important index of circulatory function, diminishes with increasing cardiovascular risk. Conversely, systemic arterial compliance improves through eating of fish and fish oil. We therefore tested the value of high intake of alpha-linolenic acid, the plant precursor of fish fatty acids. Fifteen obese people with markers for insulin resistance ate in turn four diets of 4 weeks each: saturated/high fat (SHF), alpha-linolenic acid/low fat (ALF), oleic/low fat (OLF), and SHF. Daily intake of alpha-linolenic acid was 20 g from margarine products based on flax oil. Systemic arterial compliance was calculated from aortic flow velocity and aortic root driving pressure. Plasma lipids, glucose tolerance, and in vitro LDL oxidizability were also measured. Systemic arterial compliance during the first and last SHF periods was 0.42 +/- 0.12 (mean +/- SD) and 0.56 +/- 0.21 units based on milliliters per millimeter of mercury. It rose significantly to 0.78 +/- 0.28 (P < .0001) with ALF; systemic arterial compliance with OLF was 0.62 +/- 0.19, lower than with ALF (P < .05). Mean arterial pressures and results of oral glucose tolerance tests were similar during ALF, OLF, and second SHF; total cholesterol levels were also not significantly different. However, insulin sensitivity and HDL cholesterol diminished and LDL oxidizability increased with ALF. The marked rise in arterial compliance at least with alpha-linolenic acid reflected rapid functional improvement in the systemic arterial circulation despite a rise in LDL oxidizability. Dietary n-3 fatty acids in flax oil thus confer a novel approach to improving arterial function.

Isoflavones from red clover improve systemic arterial compliance but not plasma lipids in menopausal women

The possibility that the heightened cardiovascular risk associated with the menopause can be reduced by increasing dietary isoflavone intake was tested in 17 women by measuring arterial compliance, an index of the elasticity of large arteries such as the thoracic aorta. Compliance diminishes with age and menopause. An initial 3- to 4-week run-in period and a 5-week placebo period were followed by two 5-week periods of active treatment with 40 mg and then 80 mg isoflavones derived from red clover containing genistein, daidzein, biochanin, and formononetin in 14 and 13 women, respectively, with 3 others serving as placebo controls throughout. Arterial compliance, measured by ultrasound as a pressure (carotid artery) and volume (outflow into aorta) relationship, was determined after each period; plasma lipids were measured twice during each period. Urinary output of isoflavones was also determined. Arterial compliance rose by 23% relative to that during the placebo period with the 80-mg isoflavone dose and slightly less with the 40-mg dose (mean6SEM: placebo, 19.761.5; 40 mg, 23.760.7; 80 mg, 24.46 1.4). In the three women receiving continuous placebo, compliance was 16 6 2.2, similar to that during the run-in period for the remaining subjects (17 6 2.1). ANOVA showed a significant (P 5 , 0.001) difference between treatments; by Bonferroni multiple comparisons and by paired t test, differences were significant between placebo and 40- and 80-mg isoflavone doses (by paired t test: P50.039 for placebo vs. 40 mg; P 5 0.018 for placebo vs. 80 mg). Plasma lipids were not significantly affected. An important cardiovascular risk factor, arterial compliance, which diminishes with menopause, was significantly improved with red clover isoflavones. As diminished compliance leads to systolic hypertension and may increase left ventricular work, the findings indicate a potential new therapeutic approach for improved cardiovascular function after menopause.

Soy isoflavones improve systemic arterial compliance but not plasma lipids in menopausal and perimenopausal women

The possibility that the heightened cardiovascular risk associated with the menopause, which is said to be ameliorated by soybeans, can be reduced with soy isoflavones was tested in 21 women. Although several were perimenopausal, all have been included. A placebo-controlled crossover trial tested the effects of 80-mg daily isoflavones (45 mg genistein) over 5- to 10-week periods. Systemic arterial compliance (arterial elasticity), which declined with age in this group, improved 26% (P < .001) compared with placebo. Arterial pressure and plasma lipids were unaffected. The vasodilatory capacity of the microcirculation was measured in nine women; high acetylcholine-mediated dilation in the forearm vasculature was similar with active and placebo treatments. LDL oxidizability measured in vitro was unchanged. Thus, one important measure of arterial health, systemic arterial compliance, was significantly improved in perimenopausal and menopausal women taking soy isoflavones to about the same extent as is achieved with conventional hormone replacement therapy.

Arterial compliance, blood pressure, plasma leptin, and plasma lipids in women are improved with weight reduction equally with a meat-based diet and a plant-based diet

Obesity, strongly associated with the risk for coronary heart disease (CHD), is becoming increasingly prevalent. This study was designed to establish first whether systemic arterial compliance (SAC), an index of arterial function, is improved with weight loss and second, whether cardiovascular risk factors that improve with weight loss are reduced equally with lean meat or with an equivalent amount of plant protein in the diet. Thirty-six women, mostly overweight or obess, aged 40 ± 9 years, were allocated nonrandomly to a 16-week parallel-design trial of two equienergetic diets designed to lead to weight loss, with one arm of the study emphasizing red meat and the other soybeans as the major protein source. Body weight, waist and hip circumference, and plasma lipids, glucose, insulin, and leptin levels were measured, and SAC was calculated from ultrasound measurement of aortic flow velocity and aortic root driving pressure. Subjects lost weight (9% of body weight in 16 weeks) and showed decreased plasma total and low-density lipoprotein (LDL) cholesterol (12% and 14%, P < .0001, respectively), triacylglycerol (17%, P < .05), and leptin (24%, P < .01) concentrations. However, lipoprotein(a) [Lp(a)] levels did not change significantly. Mean arterial pressure (MAP) decreased 7% and SAC increased 28% (P < .001 for both). However, only the decrease in arterial pressure correlated significantly with the reduction in the waist to hip ratio (WHR), and the improvement in SAC correlated inversely with the blood pressure reduction (P < .001 for both). Further, weight loss and the metabolic benefits of weight loss occurred equally with the meat-based and plant-based diets. We conclude that moderate weight loss in women leads to a substantial reduction in the cardiovascular risk, including SAC.

Dietary salt loading impairs arterial vascular reactivity 1-3

BACKGROUND: Studies of sodium have shown improvements in vascular function and blood pressure (BP). The effect of chronic sodium loading from a low-sodium diet to a Western diet on vascular function and BP has been less well studied.

OBJECTIVE: The objective was to examine the effects of dietary salt intake on vascular function and BP.

DESIGN: Thirty-five hypertensive volunteers met the inclusion criteria. After a 2-wk run-in with a low-sodium diet (60 mmol/d), the participants maintained their diets and were randomly assigned to receive sequentially 1 of 3 interventions for 4 wk, with a 2-wk washout between interventions: sodium-free tomato juice (A), tomato juice containing 90 mmol Na (B), and tomato juice containing 140 mmol Na (C). The outcomes were changes in pulse wave velocity (PWV), systolic BP (SBP), and diastolic BP (DBP).

RESULTS: The difference in PWV between interventions B and A was 0.39 m/s (95% CI: 0.18, 0.60 m/s; P = 0.001) and between C and A was 0.35 m/s (95% CI: 0.13, 0.57 m/s; P = 0.01). Differences in SBP and DBP between interventions B and A were 4.4 mm Hg (95% CI: 1.2, 7.8 mm Hg; P = 0.01) and 2.4 mm Hg (95% CI: 0.8, 4.1 mm Hg; P = 0.001), respectively, and between interventions C and A were 5.6 mm Hg (95% CI: 2.7, 8.4 mm Hg; P = 0.01) and 3.3 mm Hg (95% CI: 1.5, 5.0 mm Hg; P = 0.001), respectively. Changes in PWV correlated with changes in SBP (r = 0.52) and DBP (r = 0.58).

CONCLUSIONS: Dietary salt loading produced significant increases in PWV and BP in hypertensive volunteers. Correlations between BP and PWV suggest that salt loading may have a BP-independent effect on vascular wall function. This further supports the importance of dietary sodium restriction in the management of hypertension. This trial was registered with the Australian and New Zealand Clinical Trials Registry as ACTRN12609000161224.

Dose-dependent increases in heart rate variability and arterial compliance in overweight and obese adults with DHA-rich fish oil supplementation

Heart rate (HR) variability and large arterial compliance can be improved using fish oils. DHA, a component of fish oil, has cardiovascular health benefits, but its effect on HR variability (HRV) and arterial compliance is yet to be quantified. Sixty-seven overweight or obese adults (thirty-six males and thirty-one females; 53 (sem 2) year; BMI 31·7 (sem 1·1) kg/m²) were randomly allocated to consume either 6 g/d sunola oil (control; n 17), fish oil (260 mg DHA+60 mg EPA per g) at doses of 2 g/d (n 16), 4 g/d (n 17) or 6 g/d (n 17). Blood pressure, HR and compliance of large and small arteries were measured while supine at baseline and after 12 weeks in all participants, and HRV was assessed in a subgroup of forty-six participants. There was no effect of fish oil on blood pressure, small artery compliance or HR. However, the low frequency:high frequency ratio of HRV decreased with increasing doses of fish oil (r − 0·34, P = 0·02), while large artery compliance increased (r 0·34, P = 0·006). Moreover, the changes in these biomarkers were significantly correlated (r − 0·31, P = 0·04) and may reflect fish oil-induced improvements in arterial function and cardiac autonomic regulation.

Exposure to a high-fat diet alters leptin sensitivity and elevates renal sympathetic nerve activity and arterial pressure in rabbits

The activation of the sympathetic nervous system through the central actions of the adipokine leptin has been suggested as a major mechanism by which obesity contributes to the development of hypertension. However, direct evidence for elevated sympathetic activity in obesity has been limited to muscle. The present study examined the renal sympathetic nerve activity and cardiovascular effects of a high-fat diet (HFD), as well as the changes in the sensitivity to intracerebroventricular leptin. New Zealand white rabbits fed a 13.5% HFD for 4 weeks showed modest weight gain but a 2- to 3-fold greater accumulation of visceral fat compared with control rabbits. Mean arterial pressure, heart rate, and plasma norepinephrine concentration increased by 8%, 26%, and 87%, respectively (P<0.05), after 3 weeks of HFD. Renal sympathetic nerve activity was 48% higher (P<0.05) in HFD compared with control diet rabbits and was correlated to plasma leptin (r=0.87; P<0.01). Intracerebroventricular leptin administration (5 to 100 μg) increased mean arterial pressure similarly in both groups, but renal sympathetic nerve activity increased more in HFD-fed rabbits. By contrast, intracerebroventricular leptin produced less neurons expressing c-Fos in HFD compared with control rabbits in regions important for appetite and sympathetic actions of leptin (arcuate: −54%, paraventricular: −69%, and dorsomedial hypothalamus: −65%). These results suggest that visceral fat accumulation through consumption of a HFD leads to marked sympathetic activation, which is related to increased responsiveness to central sympathoexcitatory effects of leptin. The paradoxical reduction in hypothalamic neuronal activation by leptin suggests a marked “selective leptin resistance” in these animals.

A pilot assessment of alpha-stat vs pH-stat arterial blood gas analysis after cardiac arrest

PURPOSE: Resuscitated cardiac arrest (CA) patients typically receive therapeutic hypothermia, but arterial blood gases (ABGs) are often assessed after adjustment to 37°C (alpha-stat) instead of actual body temperature (pH-stat). We sought to compare alpha-stat and pH-stat assessment of PaO2 and PaCO2 in such patients. MATERIALS AND METHODS: Using ABG data obtained during the first 24 hours of intensive care unit admission, we determined the impact of measured alpha vs calculated pH-stat on PaO2 and PaCO2 on patient classification and outcomes for CA patients. RESULTS: We assessed 1013 ABGs from 120 CA patients with a median age of patients 66 years (interquartile range, 50-76). Median alpha-stat PaO2 changed from 122 (95-156) to 107 (82-143) mm Hg with pH-stat and median PaCO2 from 39 (34-46) to 35 (30-41) mm Hg (both P < .001). Using the categories of hyperoxemia, normoxemia, and hypoxemia, pH-stat estimation of PaO2 reclassified approximately 20% of patients. Using the categories of hypercapnia, normocapnia, and hypocapnia, pH stat estimation of PaCO2 reclassified approximately 40% of patients. The mortality of patients in different PaO2 and PaCO2 categories was similar for pH-stat and alpha-stat. CONCLUSIONS: Using the pH-stat method, fewer resuscitated CA patients admitted to intensive care unit were classified as hyperoxemic or hypercapnic compared with alpha-stat. These findings suggest an impact of ABG assessment methodology on PaO2, PaCO2 , and patient classification but not on associated outcomes.