Plasma endothelin-1, homocysteine, and nitric oxide levels in a multiethnic hypertensive cohort from the United Arab Emirates

Hypertension is a major cause of morbidity and mortality in the United Arab Emirates [UAE]. However, little is known regarding vasoactive biomarkers and lipid profiles in hypertensives versus normotensives in this heterogeneous ethnic population. This study aimed to evaluate plasma endothelin-1 [ET-1], homocysteine [Hcy], nitric oxide [NO], and lipid parameters among hypertensive subjects and normotensives controls in a heterogeneous ethnic population from the UAE. We collected venous samples from 164 hypertensive and 112 normotensive subjects matched for age, gender and ethnicity to determine their plasma levels of ET-1, Hcy and NO as well as their lipid profile. Hypertensive subjects displayed significantly higher plasma levels of ET-1 [p < 0.001] and NO [p < 0.001] but lower insulin levels [P<0.006] than normotensives. In contrast, there was no statistically significant difference with regard to Hcy concentrations. Very low-density lipoprotein [VLDL] and triglycerides [TG] levels were significantly [p < 0.01] higher in hypertensives than controls. Total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], and non-esterified fatty acids [NEFA] were significantly lower [p < 0.01] in hypertensives than normotensives. In our heterogeneous ethnic population, levels of ET-1 and NO, but not of Hcy, were found to be associated with hypertension and may possibly contribute to an increased systemic vascular resistance among hypertensives. Whether the elevated ET-1 results are because of overproduction or decreased clearance remains to be ascertained Elevated levels of TG and VLDL, alongside with unaltered TC levels, seem to indicate the presence of type IV hypertriglyceridaemia

Ciruculating levels of endothelin-1 in a homogenous Gulf Arab population with untreated essential hypertension.

Racial variations are reported in the natural history of hypertension. For example, hypertension is significantly more prevalent in blacks than whites. Endothelial cells are important regulators of vascular tone and homeostasis, in part through secretions of vasoactive substances including endothelin-1 [ET-1], a small peptide with potentvasopressor actions. In black hypertensives, ET-1 levels are higher than in normotensive blacks and in both hypertensive and normotensive whites. Since ET-1 might play a significant role in the development and severity of hypertension in the indigenous Arab population of the United Arab Emirates, we investigated the circulating levels of ET-1 in this homogenous population. ET-1 levels were measured in plasma samples from 60 untreated hypertensive Arabs and compared with 60 ageand sex-matched normotensive controls. ET-1 levels were significantly higher in hypertensives [mean 10.1 +/- 1 pmol/L] than normotensives [mean 2.2 +/- 0.5 pmol/L]. Body mass index [BMI] was slightly higher among the hypertensives. For all subjects these levels significantly [P < 0.001] correlated with systolic blood pressure and less significantly [P < 0.05] with diastolic blood pressure and body weight. The correlation between ET-1 and both systolic and diastolic blood pressure was persistently significant after adjusting for BMI. Plasma concentrations of ET-1 are significantly higher in hypertensive Gulf Arabs as compared with reported levels in white hypertensives and ET-1 could be a risk factor for cardiovascular diseases in this population. The endothelial system might be particularly important with respect to hypertension in this racial group and merits further study

Plasma concentrations of non-esterified fatty acids in chronic renal failure in the United Arab Emirates

In end-stage renal failure, dyslipoproteinemia is linked to risk of cardiovascular disease. Increased concentrations of triacylglycerol-rich, very low density lipoproteins [VLDL] and decreased concentrations of high density lipoproteins [HDL] are usual, whilst total cholesterol and low density lipoprotein [LDL] concentrations are not increased. Non-esterified fatty acids [NEFA] are not transported by lipoproteins, but increased concentrations may also be associated with cardiovascular disease risk. In this study, plasma concentrations of NEFA and other lipids were compared in healthy subjects and patients with end-stage chronic renal failure who were either undialyzed or undergoing peritoneal dialysis or hemodialysis. Fasted blood samples for measurement of albumin, total, free and HDL-cholesterol, triacylglycerols and NEFA were taken from 56 apparently healthy subjects and from 48, 28 and 46 patients from the United Arab Emirates during 2002 who were either untreated or on peritoneal or hemodialysis. Hemodialysis subjects were studied immediately before and after a single treatment session. For all groups of patients, total, and LDL-cholesterol were unchanged, triacylglycerols and free cholesterol were raised and HDL-cholesterol concentrations and the percentage of esterified cholesterol were significantly decreased compared to controls. Plasma NEFA concentrations for untreated patients were similar to controls, but were decreased in peritoneal dialysis patients and markedly increased both before and, even more so, after dialysis in hemodialysis patients. Patients with end-stage renal failure share common features of dyslipoproteinemia irrespective of whether they are untreated or on peritoneal dialysis or hemodialysis. However, only hemodialysis patients show significantly increased concentrations of NEFA