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BACKGROUND Adiponectin is an important vascular protective adipocytokine that possesses antidiabetic, antiatherogenic, and anti-inflammatory properties. The aim of this study was to evaluate the effect of various antihypertensive drugs on the production and secretion of adiponectin from adipocytes. METHODS 3T3-L1 adipocytes were incubated for 6 h with increased doses of the following drugs: hydrochlorothiazide, atenolol, losartan, telmisartan, captopril, and nifedipine. Adiponectin levels, as well as adiponectin-mRNA expression, were measured in the medium and cells. RESULTS Significant increases of adiponectin were induced by telmisartan: 56% with a dose of 0.1 micromol/l (P < 0.05), 131% with 10 micromol/l (P < 0.05), and 125% with 100 micromol/l (P < 0.01). Losartan (100 micromol/l) also increased adiponectin by 65% (P < 0.05). Conversely, hydrochlorothiazide, 0.1 micromol/l, reduced adiponectin by 37% (P < 0.01). Captopril, atenolol, and nifedipine had no effect on adiponectin. Gene expression of adiponectin correlated with these results: with telmisartan, it increased by 27%, and with hydrochlorothiazide it decreased by 38% (P < 0.05 for both compared to the control). CONCLUSION In this comparative model, telmisartan, and to a lesser extent, losartan, increased production and secretion of adiponectin from 3T3-L1 adipocytes compared to the other antihypertensive drugs.

BACKGROUND Melatonin, the primary hormone of the pineal gland, is a known modulator of various physiological processes. The aim of this study was to evaluate the role of melatonin in the pathogenesis of hypertension in rats with metabolic syndrome and to assess whether melatonin supplementation prevents the development of hypertension in this model. METHODS Twenty male Sprague-Dawley (SD) rats were fed either a high fructose diet (n = 10) or a regular diet (control; n = 10) for 5 weeks. Urinary excretion of 6-hydroxymelatoninsulfate (a metabolite of melatonin) was measured at the beginning and the end of the study. An additional 20 SD rats were fed with the same diets but with a supplementation of melatonin (30 mg/kg/day) in their drinking water. Blood pressure (BP) was measured every week. RESULTS BP increased significantly in rats fed with a high fructose diet and remained unchanged in the control group. The BP rise was associated with a significant decrease in melatonin secretion during sleep. Melatonin supplementation prevented the BP rise in fructose fed rats. BP increased by 14.6 +/- 1.0 mm Hg in the fructose fed rats, whereas it increased by only 3 +/- 2.6 mm Hg in rats fed with fructose and melatonin (P < 0.001 between groups). CONCLUSIONS Melatonin secretion decreased in fructose fed rats that developed hypertension. Administration of melatonin blunted this BP rise. These data suggested that melatonin plays a role in the pathogenesis of hypertension in rats with metabolic syndrome.

The health hazard of the metabolic syndrome (MS) is increasing, yet there is no effective pharmacologic treatment to this entity as a whole. Recently, hypoadiponectinemia was found to play an important role in the development of MS. We studied the effect of the PPAR-gamma agonist rosiglitazone on adiponectin and the metabolic profile in the fructose-induced hypertensive, hyperinsulinemic, hypertriglyceridemic rat model.Thirty male Sprague-Dawley rats were divided into three groups. Ten were fed standard rat chow for 5 weeks, 10, a fructose-enriched diet for 5 weeks, and 10, a fructose-enriched diet for 5 weeks, with rosiglitazone 10 mg/kg/d added during the last 2 weeks. Blood pressure (BP), oral glucose tolerance test (OGTT), plasma insulin, triglycerides, and adiponectin were recorded, as well as mRNA levels of the adiponectin gene in visceral adipose tissue.Fructose-fed rats developed MS as manifested by the increase in systolic BP (from 139 +/- 3 to 158 +/- 4 mm Hg, P.05), insulin (from 26 +/- 1.6 to 40 +/- 2.5 muU/mL, P.05), triglycerides (from 91 +/- 9 to 304 +/- 24 mg/dL, P.05), and impaired OGTT (area under the curve from 13,894 +/- 246 to 17,725 +/- 700 mg/dL/min). Treatment with rosiglitazone reversed these effects and reduced BP to 133 +/- 7 mm Hg, insulin levels to 30 +/- 2.8 muU/mL, triglycerides to 116 +/- 9 mg/dL, and the OGTT to 15,415 +/- 372 mg/dL/min (P.05 for all variables). In addition, rosiglitazone increased plasma levels of adiponectin fourfold from 4.3 +/- 0.1 to 18.4 +/- 0.6 mug/mL (P.05). This increase was coupled with 3.8-fold increase in adiponectin mRNA in visceral adipose tissue.This study shows for the first time that in an animal model of MS, the insulin sensitizer, rosiglitazone, improves the metabolic profile and increases plasma levels of adiponectin and its gene expression. It is possible therefore that rosiglitazone exerts its beneficial effects by increasing the levels of adiponectin.

Background Reactive oxygen species play a key role in the formation of endothelial dysfunction accompanying diabetes mellitus, hypertension, and other cardiovascular diseases. Methods This study compares oxidative stress (OS) in Wistar-Kyoto rats (WKY), spontaneously hypertensive rats (SHR), non–insulin-dependent Cohen Diabetic rats (CDR), and Cohen Rosenthal diabetic hypertensive rats (CRDH), a unique animal model of both diabetes and hypertension. The OS was evaluated with a newly developed thermochemiluminiscence (TCL) analyzer (Lumitest Ltd., Nesher, Israel) that measures the oxidizability (ie, susceptibility to oxidation) of a test sample. Results The TCL oxidizability test results of sera from the different rats groups showed a time-dependent increase in TCL of up to 145% ± 7% for WKY, 160% ± 8% for SHR, 179% ± 12% for CDR, and 226% ± 15% for CRDH. These results were significant: P < .001 for SHR and CDR and P < .0001 for CRDH in comparison to WKY. Lipid peroxide levels also increased in each strain of rats: to 80 ± 7.8 nmol/mL in WKY, 104 ± 10.1 nmol/mL in SHR, 110 ± 9.4 nmol/mL in CDR, and 167 ± 11.7 nmol/mL in CRDH. These results were also significant: P < .001 for SHR, CDR and CRDH in comparison to WKY. Conclusion The combination of hypertension and diabetes is accompanied by higher oxidative stress than that seen with either disorder alone.

Background Commercially available garlic preparations in the form of garlic oil, garlic powder and pills are widely used for certain therapeutic purposes, including lowering blood pressure and improving lipid profile. Despite the impressive effects of garlic most studies are limited by lack of controlled methods and suitable double-blinding, and by the use of preparations with unknown amounts and chemical identification of the active ingredient. Allicin, a synthetic preparation of an active constituent of garlic, was found to lower blood pressure, insulin, and triglycerides levels in fructose-fed rats. Thus, it was considered important to assess its effect on the weight of the animals. Methods Male Sprague-Dawley rats weighing 240 to 250 g were fed a fructose-enriched diet consisting of 21% protein, 5% fat, 60% carbohydrate, 0.49% sodium and 0.49% potassium for 5 weeks, which produced hyperinsulinemia, hypertension, and hypertriglyceridemia. Group I (controls) rats were fed a diet enriched by fructose only; group II was given allicin the last 2 weeks, and group III was given allicin the first 3 weeks. The three groups consumed the same amount of food. Weight was measured at the beginning of the experiment and after 3 and 5 weeks on the diet. Results Weight in the control group rose from 249.4 ± 10.04 g to 274.5 ± 15.5 g after 3 weeks and to 306.9 ± 22.2 g after 5 weeks. Weight in group II rose from baseline 259.1 ± 12.1 g to 306.9 ± 22.2 g after 3 weeks on fructose alone, and declined slightly to 282.4 ± 17.4 g after 2 weeks of allicin (P < .02). In group III, in which the protocol was reversed, the baseline weight of 260.4 ± 13.25 g rose only to 269.8 ±15.3 g (P < .431) after 3 weeks on fructose and allicin. Conclusions The control group that was fed a diet enriched by fructose alone continued to gain weight, whereas the groups fed allicin did not. The difficulty of preventing weight gain after reaching the nadir of weight loss underscores the practical value of allicin for weight control.

The effects of a synthetic preparation of an active constituent of garlic, allicin, were studied on blood pressure (BP), triglycerides, and insulin levels in Sprague-Dawley rats in which high fructose feeding elicited hyperinsulinemia, hypertension, and hypertriglyceridemia. Results were compared with those of the antihypertensive drug enalapril. Three groups of male Sprague-Dawley rats were fed a fructose-enriched diet for 5 weeks. During the last 2 weeks 10 animals received only fructose, 10 received allicin, and 10 received enalapril. Blood pressure, insulin level, and triglyceride levels were measured at the beginning of the experiment and after 3 and 5 weeks on the fructose diet, fructose/allicin diet, or fructose/enalapril diet. Allicin lowered BP from the maximal level (after 3 weeks of fructose) of 153.4 +/- 8 mm Hg to 139.7 +/- 12 mm Hg after 2 weeks on allicin; insulin from 11.7 +/- 3.7 ng/mL on fructose diet to 6.92 +/- 3.3 ng/mL on allicin; and triglycerides from 132.8 +/- 18 mg/dL on fructose to 59.6 +/- 27 mg/dL on allicin. The similar effect of allicin and enalapril on BP, insulin, and triglycerides reinforces the trend toward combining the nonpharmacologic approach with drug therapy.

Allylmercaptocaptopril (CPSSA) was synthesized by reacting captopril with pure allicin. Fructose-induced hypertensive groups of rats were fed a fructose-rich diet for 3 weeks, and then received the diet plus either CPSSA (40 to 56 mg or 138 to 194 micromol/L/kg/d) or captopril (80 mg or 369 micromol/L/kg/d) for 2 more weeks. CPSSA (both doses) significantly lowered blood pressure (BP) from 153.4 to 120.8 mm Hg (P

BACKGROUND Premenopausal women have lower blood pressure (BP) levels than men of similar age. Adiponectin has been shown to play a role in the pathogenesis of hypertension. The aim of the present study was to compare the effect of various stress stimuli on BP and plasma adiponectin levels in male and female Sprague Dawley (SD) rats. METHODS In three experimental models of hypertension, fructose-enriched diet, high salt diet, or L-NAME, were administered for up to 4 weeks. BP, metabolic parameters, and plasma adiponectin were measured at baseline and during the studies. The fructose diet protocol was repeated in female rats for 2 weeks with the addition of testosterone injections or vehicle. RESULTS Females, in contrast to males, did not develop fructose-induced hypertension. Total plasma triglycerides (TGs) were half in females at baseline (P < 0.001) and a third at 4 weeks (P < 0.05). Plasma insulin levels were 23% lower in females than in males at baseline (P < 0.05) and 42% lower after 4 weeks of fructose-enriched diet (P = 0.001). Plasma adiponectin levels were 65% higher in females than in males at baseline (P = 0.001) and 45% higher after 4 weeks of fructose-enriched diet (P < 0.05). Furthermore, female rats showed blunted BP response and elevated plasma adiponectin in the salt-induced and L-NAME-induced hypertension models. Testosterone injection to female rats reduced plasma adiponectin and reversed the blunted BP response. CONCLUSIONS Elevated plasma adiponectin levels, perhaps due to lack of suppression by testosterone, are associated with a blunting of BP response in female compared to male SD rats.

Losartan (DuP 753) is a novel orally active angiotensin II antagonist that lowers blood pressure. The present study evaluates the hemodynamic and humoral effects of losartan in essential hypertension. Fifteen patients (12 men, 3 women; mean age, 46 +/- 2 years; range, 33 to 64 years) with a diastolic blood pressure (DBP) between 95 and 115 mm Hg after 2 weeks of placebo participated in the study. Initially the patients were treated with losartan (50 mg) once daily for 1 month. Then, if the trough DBP was > or = 93 mm Hg, hydrochlorothiazide (HCTZ), 6.25 to 12.5 mg daily, and nifedipine, 30 to 60 mg daily, were added as needed. Ten patients completed 12 months of treatment. Trough blood pressure, heart rate, plasma creatinine, potassium, uric acid, cholesterol, renin activity (PRA), aldosterone, and norepinephrine were measured at baseline and after 1 and 12 months of treatment. Losartan lowered mean arterial pressure significantly from 119 +/- 2 mm Hg at baseline to 113 +/- 2 mm Hg (P < .05) after 1 month of treatment. Coadministration of HCTZ and nifedipine further decreased the mean arterial pressure to 103 +/- 2 mm Hg after 12 months of treatment. Plasma levels of creatinine, potassium, uric acid, cholesterol, and norepinephrine remained unchanged. PRA increased and plasma aldosterone decreased significantly (P < .05). The decrease in mean arterial pressure was related to baseline PRA (r = 0.53, P < .05). and to the change in PRA (r = 0.52, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Slow breathing practiced routinely using an interactive device has demonstrated a sustained reduction in high blood pressure (BP). We reevaluated the BP response of hypertensives (n = 13) to this daily treatment for 8 weeks using 24-h ambulatory, home, and office BP measurements. A clinically significant BP reduction of similar magnitude was observed in all BP monitoring modalities during the daytime. Greater BP reductions were found for older patients and higher baseline BP. The results provide additional support for the efficacy of the device as an adjunctive lifestyle modification for treating hypertension.

Background The etiology of the metabolic syndrome (MS) includes both genetic and environmental factors. The two most commonly studied animal models of the MS are the high-sucrose diet given to spontaneously hypertensive rats (SHRs) and high-fructose diet given to Sprague Dawley rats (SDRs). This study compares between these two models. Methods The two rat strains were examined; within each group, the rats were assigned to either the high-sugar diet (SDRs with fructose-enriched diet and SHRs with sucrose-enriched diet) or standard rat chow (control group). The rats were followed for 7 weeks. The main MS components (obesity, hypertension, impaired glucose tolerance, hyperinsulinemia, hypertriglyceridemia, and hypercholesterolemia) were measured. Results At baseline systolic blood pressure (SBP), fasting blood levels of triglycerides and insulin, as well as glucose intolerance, were significantly higher among the SHRs compared to SDRs. Following fructose enrichment, SDRs became hyperinsulinemic, hypertriglyceridemic, hypercholesterolemic, hypertensive, and insulin resistant, whereas SHRs responded to sucrose supplementation by a significant elevation in blood pressure and mild worsening of insulin resistance. Endpoint results revealed superiority of sucrose--SHR model in terms of hypertension and superiority of fructose--SDR model in terms of hyperinsulinemia, hypertriglyceridemia, and hypercholesterolemia. Both models showed similar postintervention degree of glucose tolerance. Conclusions The fructose-fed SDR model represents a predominantly environmentally acquired MS, whereas the SHR model is less affected by dietary intervention and better displays the predominantly genetic spontaneous appearance of the syndrome. This fundamental difference should be taken into consideration when choosing an animal model to study the MS.

Background Pheochromocytoma, a rare and usually curable cause of hypertension, is characterized by symptoms and signs related to increased catecholamine secretion. Pregnancy can elicit clinical manifestations of otherwise unrecognized pheochromocytoma. Methods and Results Four women, ranging in age from 27 to 37 years, were referred to the hypertension clinic with the following presentations: 1) a 35-year-old woman, diagnosed with gestational hypertension and headaches during the third trimester of her pregnancy and 5 months after delivery, was hospitalized with pulmonary edema. Echocardiography revealed severe dilated left ventricular (LV) dysfunction. Cardiac function was normalized after surgical resection of a pheochromocytoma from her left adrenal; 2) a 37-year-old woman suffered from preeclampsia, persistent hypertension and orthostatic hypotension after a cesarean section. A diagnostic work-up revealed a catecholamine-secreting paraganglioma in the retroperitoneum. The patient underwent a laparosopic resection of the tumor; 3) a 27-year-old woman suffered from hypertension and episodes of palpitations, sweating, and dyspnea in the first trimester of her pregnancy. An ultrasound revealed a 5-cm mass in the left adrenal. She underwent a left adrenalectomy at the 17th week of pregnancy, which confirmed the diagnosis of pheochromocytoma; 4) a 34-year-old woman, at the 26th week of pregnancy, presented with an acute loss of vision and blood pressure of 230/140 mm Hg. Fundoscopy showed papilledema with soft exudates in both eyes. Chemical studies were positive and imaging revealed a left adrenal pheochromocytoma. Despite aggressive medical treatment, fetal distress mandated a laparotomy at the end of the 28th week of pregnancy. A healthy newborn was delivered and resection of the adrenal tumor confirmed the diagnosis of pheochromocytoma. Conclusions Although rare, pheochromocytoma can cause severe peripartum hypertension. Screening for pheochromocytoma, ideally with plasma-free metanephrines, should be considered in cases of peripartum hypertension.

Background In view of the demonstrated interaction between endothelin and the renin-angiotensin system, the antihypertensive effect of combined therapy with an endothelin antagonist LU-135252 and the angiotensin converting enzyme inhibitor trandolapril, was studied in fructose-induced hypertensive, hyperinsulinemic, hypertriglyceridemic male Sprague-Dawley rats. Methods Forty animals were fed a fructose-enriched diet (Tekled, Harlan) for 5 weeks, as follows: group A, fructose only; group B, trandolapril 0.1 mg/kg/day added during the last 2 weeks; group C, LU-135252 100 mg/kg/day added during the last 2 weeks; group D, both trandolapril and LU-135252 added the last 2 weeks. Systolic blood pressure (BP) was measured weekly in conscious rats by the indirect tail–cuff method. Blood samples from a retro-orbital sinus puncture were taken at the beginning of the experiment and after 3 and 5 weeks and examined for insulin and triglyceride concentrations. Results Systolic BP decreased in group B (trandolapril) from 148.8 ± 9.8 at 3 weeks to 138.3 ± 8.7 mm Hg after 5 weeks; in group C (endothelin antagonist) from 155.1 ± 5.5 to 142.5 ± 10.6 mm Hg; and in group D (combination) from 154.6 ± 10.9 to 121.2 ± 8.9 mm Hg. Triglyceride levels decreased only in the combined trandolapril/endothelin antagonist group from 167.6 ± 55.3 in the third week to 134.9 ± 53.7 mg/dL after 5 weeks. Insulin levels decreased only on combination therapy from 7.4 ± 3.6 to 5.3 ± 3.8 ng/mL during the same period. The BP decrease was additive compared with the respective individual substances. Conclusions The trandolapril/endothelin antagonist combination appears to offer a rational antihypertensive combination that is superior to that of either drug alone. This finding applies to the specific rat model studied in which BP, insulin, and triglycerides were increased by fructose diet.

Adrenalectomized, spontaneously hypertensive rats (SHR) were used to test the hypertensinogenic property of recently synthesized 18,19-dihydroxycorticosterone (18,19-Di-OH-B). The steroid was given via Alzet miniosmotic pump, with and without aldosterone. Neither 18,19-Di-OH-B (5 micrograms) nor aldosterone (5 micrograms) increased blood pressure in SHR when given alone; when administered together they resulted in a significant rise in blood pressure. Results indicate a high probability that certain mineralocorticoids, which are inactive by themselves, might play a role in the etiology of hypertension when acting together under physiological conditions.

Because the potential impact of habitual caffeine intake on blood pressure is a controversial issue, a study was carried out to explore the relationship between caffeine and various humoral factors that could account for a coffee-induced rise in blood pressure. Twenty-three hypertensive patients who refrained from caffeine for 2 to 3 weeks were given 250 mg oral caffeine powder dissolved in water. Blood pressure was recorded every 15 min by blood pressure monitor. Caffeine blood level, renin and endothelin were measured before and 1, 2, 3, and 6 h after caffeine intake. Urinary electrolytes and catecholamines were measured under caffeine influence (period I), and for the next 6 h (period II). A significant increase in systolic (P = .017) and diastolic blood pressure (P = .023) occurred in 13 subjects who were 58 +/- 10.4 years old. Nonresponders were younger (44.5 +/- 15.8 years). A statistically significant decrease in heart rate was seen during the first hour after caffeine intake in both responders (P = .008) and nonresponders (P = .004). Marked diuresis and natriuresis were observed during period I in both groups. Renin and endothelin levels were unchanged. Although chronic studies point to development of tolerance to long-term caffeine ingestion, acute studies like the one described are essential to obtain data on the immediate effects that can be of practical importance, especially in the elderly.

The effect of 20 mg of enalapril with and without 12.5 mg of hydrochlorothiazide on glucose metabolism insulin sensitivity and lipids was evaluated in hypertensive non-insulin-dependent diabetes. Ten mild to moderate hypertensive patients with non-insulin-dependent diabetes mellitus were treated for 8 weeks with 20 mg enalapril once a day, and then divided into two groups of 5 patients each for a second 8 weeks of treatment with enalapril alone or in combination with hydrochlorothiazide, 12.5 mg once a day. Blood pressure, fasting plasma glucose, lipids and insulin, glycosylated hemoglobin, and insulin sensitivity were measured at baseline and after 8 and 16 weeks. Results were analyzed by the ANOVA test for repeated measures and all values are given as mean ± SD. Diastolic blood pressure decreased significantly after the first and second period of enalapril and after the combination of enalapril and hydrochlorothiazide. Glycosylated hemoglobin dropped significantly after the first and second period of enalapril monotherapy. Plasma triglycerides and fasting plasma insulin decreased significantly after the 16 weeks of enalapril. Insulin-mediated glucose uptake increased significantly after 8 and 16 weeks of monotherapy with enalapril. No significant difference was observed in any of the metabolic characteristics, including insulin sensitivity, between the values after 8 weeks of enalapril alone and the final values of the enalapril-treated and the enalapril/hydrochlorothiazide-treated groups. It is concluded that enalapril improves some of the metabolic parameters, including insulin sensitivity, of hypertensive diabetic patients. Despite the small number of hydrochlorothiazide patients, these results lead us to suggest that the coadministration of low-dose hydrochlorothiazide may not adversely affect these parameters, and that enalapril may have blunted the metabolic adverse effect of the diuretic.

Recent studies showed that supplementation of a large dose of fish oil is effective in lowering blood pressure. Whether supplementation of a low dose of fish oil is also effective in lowering blood pressure is controversial. The present study evaluates the hemodynamic and humoral effects of low-dose dietary fish oil supplementation in patients with mild hypertension. Eleven patients with mild hypertension were given 3 g/day of n-3 polyunsaturated fatty acids for 6 week. Twenty-four hour blood pressure monitoring and humoral parameters were recorded before and during fish oil treatment. In five patients, blood pressure response to angiotensin II (AII) infusion (1, 2, 3, 6, 9 ng/kg/min) was also recorded before and during treatment. Casual mean arterial pressure was unchanged (111 +/- 1 mm Hg v 109 +/- 3 mm Hg; P = NS). Average 24-h mean arterial pressure (MAP) also did not change during fish oil treatment (98 +/- 2 mm Hg v 99 +/- 3 mm Hg; P = NS). Fish oil supplementation did not attenuate the vascular reactivity to AII infusion. Maximal MAP following AII infusion (9 ng/kg/min) was 128 +/- 5 mm Hg before and 129 +/- 7 mm Hg during fish oil treatment (P = NS). Plasma levels of norepinephrine, renin activity, aldosterone, and atrial natriuretic peptide remained unchanged during treatment. Plasma levels of total cholesterol slightly increased from 200 +/- 10 mg/dL to 211 +/- 9 mg/dL (P < .05), but plasma levels of high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)