Effect of fish oil supplementation on aortic compliance in rats: role of the endothelium

Vascular compliance is reduced in vascular dementia and not in Alzheimer's disease

OBJECTIVE

to determine whether functional changes in the vasculature differ between Alzheimer's disease (AD) and vascular dementia (VAD).

DESIGN

we determined vascular stiffness in patients with a clinical and radiological diagnosis of either AD or VAD and compared them to normal age- and sex-matched controls.

METHODS

In all, 16 patients with late onset AD, 13 subjects with VAD and 16 age- and sex-matched controls were recruited to this study. Central arterial compliance (CAC), augmentation index (AI) and pulse wave velocity (PWV) (measures of arterial stiffness) were measured.

RESULTS

the mean age was 77.7 +/- 8.3 years (mean +/- SD) in the AD group, 79.7 +/- 8.9 years in the VAD group and 76.4 +/- 6.9 in the controls (P = 0.44). CAC was significantly lower in subjects with VAD compared to both the AD and the control groups (0.57 +/- 0.46 ml/mm Hg versus 1.12 +/- 0.57 and 1.1 +/- 0.47 ml/mm Hg respectively, P = 0.01). AI was significantly higher in the subjects with VAD compared to both the AD and the control groups (13.3 +/- 9.0 versus 3.5 +/- 11.4 and 4.2 +/- 9.7% respectively, P = 0.03). PWV in the muscular and elastic arteries were not statistically different between the three groups but tended to be highest in the VAD group for carotid-radial measurements.

CONCLUSIONS

the reduced CAC and increased AI in VAD subjects indicate that the disease process is associated with less vascular compliance of the large elastic arteries in these patients, but not in patients with AD.

Effect of hyperhomocysteinemia induced by methionine administration on flow-mediated dilatation of the brachial artery in healthy subjects

Homocysteine may contribute to systolic hypertension and cardiac events by decreasing conduit artery compliance and inducing endothelial dysfunction. The effects of the experimental induction of hyperhomocysteinemia on systemic arterial compliance and pulsewave velocity are unclear, with contradictory results from previous studies. The investigators tested whether oral methionine impairs brachial artery compliance in addition to endothelial function.

Depressed prostanoid-induced contractility of the gut in spontaneously hypertensive rats (SHR) is not affected by the level of dietary fat

Dietary saturated fat (SF) has adverse effects on cardiac and vascular smooth muscle (VSM) contractility. Furthermore, VSM of spontaneously hypertensive rats (SHR) is overreactive to various biological stimuli. The aim of this study was to investigate the effects of increasing dietary fat as lard on gut contractility in SHR. Control Wistar-Kyoto (WKY) rats and SHR (13 wk old) were fed for 12 wk a diet containing 3% sunflower oil [low fat (LF), 3% total fat] or diets supplemented with 7% lard [medium fat (MF), 10% total fat] or 27% lard [high fat (HF), 30% total fat]. For ileal and colonic tissues (WKY and SHR), there was a lower total phospholipid PUFA (n-6)/(n-3) ratio with increased dietary SF (P < 0.003). For WKY, increasing SF led to lower levels of the major SCFA and lower total SCFA levels in cecal digesta (P < 0.01). This trend was evident in SHR but significant only for butyrate (P < 0.01). Contractility responses were unaltered in ileum. In colon, there was a change of sensitivity (50% effective concentration) to angiotensin II in WKY (P < 0.05) due to increased SF and a change of sensitivity to prostaglandin (PG)E(2) and carbachol in SHR (P < 0.05). When the 3 dietary groups were combined, there was lower sensitivity (P < 0.01) and lower maximal contraction (P < 0.05) in ileum and lower maximal contraction in colon of SHR in response to PGF(2alpha) (P < 0.05) and PGE(2) (P < 0.01) compared with WKY. Unlike (n-3) PUFA, dietary SF had little overall effect on gut contractility. However, this is the first report of a defect in PG responsiveness from gut tissue from hypertensive rats.

Influence of estrogen on aortic stiffness and endothelial function in female rats

Mechanisms underlying cardioprotective properties of estrogens are not fully understood. We evaluated effects of ovariectomy and estrogen replacement on arterial distensibility and endothelial function in rats. Sprague-Dawley rats were sham operated (Sham) or ovariectomized and treated with 17beta-estradiol (OVX-E(2)) or vehicle (OVX) for 3 wk. Anesthetized rats were instrumented for measurement of central and peripheral arterial blood pressures and carotid and hindquarters blood flows. Arterial distensibility was evaluated in anesthetized rats on the basis of changes in thoracoabdominal pressure pulse wave velocity (PWV). PWV was calculated as the distance between the two central and peripheral cannula tips divided by transit time. Ovariectomy significantly reduced PWV (390 +/- 19 and 472 +/- 42 cm/s in OVX and Sham, respectively). Estrogen treatment completely normalized PWV (490 +/- 37 cm/s). Estrogen-treated rats were associated with left ventricular hypertrophy and increased pulse pressure. Resting hemodynamic parameters were similar in all groups. Estrogen replacement significantly potentiated bradykinin vasodilatory responses in the hindlimb, but not in the carotid vascular bed. Hemodynamic responses to sodium nitroprusside and ANG II were similar in all groups. In conclusion, our results demonstrate for the first time that aortic stiffness determined by PWV is decreased in estrogen-deficient rats. Estrogen treatment increases aortic stiffness and potentiates endothelial vasodilator function in the hindquarters, but not in the carotid vascular bed, suggesting a regional heterogeneity in the modulatory influence of estrogen on vasomotor function.