Low sodium diet after DASH: has the situation changed? Dietary Approaches to Stop Hypertension

Pharmacological characterization of the diuretic effect of Hibiscus sabdariffa Linn (Malvaceae) extract

ETHNOPHARMACOLOGICAL RELEVANCE

Hibiscus sabdariffa L. (Malvaceae) populary known in Mexico as "Jamaica", "flor de Jamaica", has widely used in Mexican Traditional Medicine as antihypertensive and diuretic, although the latter activity has been reported the present work show evidence about the diuretic, natriuretic and potassium-sparing effects.

AIM OF THE STUDY

To evaluate the diuretic activity of Hibiscus sabdariffa aqueous extract on in vivo and in situ models.

MATERIALS AND METHODS

The Hibiscus sabdariffa aqueous extract was administrated in increasing doses and evaluated the diuresis produced and disposal of electrolytes. Moreover, in isolated kidney was determined the renal filtration rate with plant extract, furosemide and amiloride.

RESULTS

The yield of Hibiscus sabdariffa aqueous extraction was 28.3% and the chemical standardization from 1 g of extract was: 56.5 mg delphinidin-3-O-sambubioside, 20.8 mg/g cyanidin-3-O-sambubioside, 3.2 mg/g quercetin, 2.1 mg/g rutin and 2.7 mg/g chlorogenic acid. The diuretic and natriuretic effect of Hibiscus sabdariffa aqueous extract showed a dose-dependent behavior. The pharmacological constants of natriuretic effect was ED50=86 mg/kg and Emax=0.9 mEq/100 g/5 h. In the model of kidney in situ was observed that renal filtration increased 48% with the aqueous extract of Hibiscus sabdariffa and an additive effect when was perfuse with furosemide.

CONCLUSION

The compound presents in Hibiscus sabdariffa as quercetin had effect on the vascular endothelium causing oxide nitric release, increasing renal vasorelaxation by increasing kidney filtration. Therefore, the diuretic effect of Hibiscus sabdariffa may be mediated by nitric oxide release.

Dietary salt restriction and blood pressure in clinical trials

Dietary salt has long been recognized as a major factor affecting blood pressure such that sodium intake is a component of lifestyle modification guidelines for control of high blood pressure. These recommendations are based on results from epidemiologic observational studies and clinical trials of various sodium diets among normotensives and hypertensives. Nonetheless, results from the different studies vary such that specific recommendations regarding sodium intake are difficult to interpret. The results from several recent major trials indicated greater associations of blood pressure and sodium intake than earlier studies as well as meta-analyses of numerous clinical trials. The studies of sodium intake and blood pressures are complicated by measurements of intake, salt sensitivity, hypertension treatment, effects of sodium independent of blood pressure, and length of interventions. Limitations in the methodology of different studies have reduced the value of the results to provide specific and reliable sodium intake levels essential for clinical and lifestyle guidelines.

Renal dysfunction and ischemic heart disease mortality in a hypertensive population

OBJECTIVE

While recent studies indicate that renal dysfunction may be predictive of all-cause mortality and cardiovascular disease (CVD) outcomes in hypertensive individuals, there has been little attention to the specific association of ischemic heart disease (IHD) mortality and renal function. This study examines the relationship between IHD mortality and baseline glomerular filtration rate (GFR) (estimated by the Cockcroft and Gault formula) among treated hypertensive subjects.

DESIGN

A prospective cohort study of participants in a worksite-based antihypertensive treatment program in New York City (1981-1999).

PATIENTS

We studied 9929 subjects who had at least 6 months follow-up (mean 9.6 years) with a baseline serum creatinine.

MAIN OUTCOME MEASURES

IHD death outcomes (n=343) ascertained from the National Death Index.

RESULTS

Multivariate Cox proportional hazard models were constructed adjusting for known cardiovascular risk factors. Mean GFR of the cohort was 91.6 ml/min per 1.73 m. Those with lower GFR were more likely to be older, female, White, report a history of cardiovascular disease, have higher cholesterol and blood urea nitrogen values, and lower hemoglobin and body mass index than those with highest GFR. After adjustment for known cardiovascular risk factors, the risk of IHD death increased progressively as the GFR decreased. Hazard ratio for IHD mortality for each 10-unit reduction of estimated GFR below the normal threshold of >or=90 ml/min per 1.73 m was 1.33 (95% confidence interval 1.17, 1.50; P<0.001).

CONCLUSIONS

The results of this study suggest an independent inverse association between estimated GFR and IHD mortality among treated hypertensive individuals.

Lifestyle and dietary modification for prevention of heart failure

This article discusses the factors that contribute most to systolic and diastolic heart failure (HF): ischemic heart disease, hypertension,obesity, diabetes, and nephropathy. Diabetes often follows the insulin resistance syndrome in which obesity and hypertension are combined with dyslipidemia, and obesity is likely causal. Diabetes and hypertension are common causes of nephropathy, which in turn is a common precursor to HF. Insulin resistance, obesity,dyslipidemia, diabetes, and hypertension are risk factors for atherosclerotic coronary disease and left ventricular ischemia. Each is also a risk factor for diastolic dysfunction.

Pharmacogenomics of primary hypertension--the lessons from the past to look toward the future

A number of recent reviews have addressed the issue of the pharmacogenomics of primary hypertension and related complications by considering the data on the genotype-drug response relationship. Here we mainly discuss the methodological aspects of this issue, trying to integrate 'traditional' clinical and experimental pathophysiology and therapy-pharmacology with the 'new' genetics. Such integration is indispensable to: a). define the appropriate 'context' (genetic background, environment, age, gender, phase of hypertension, previous therapy etc.) in which a given genotype-drug response relationship should be tested (it is indeed likely that many discrepancies among published data originate from context's interference); b). assign the correct clinical meaning to the results obtained by statistics and functional genetics methodologies; c). define a novel clinical entity caused by a disease favoring allele, alone or in combination with other alleles, with a consistent clinical picture, prognosis and responsiveness to the appropriate drug; d). estimate the size of the population target amenable to benefit from a therapeutic intervention developed according to the pharmacogenomics' principles; e). develop a novel drug that selectively interferes with the sequence of events triggered by the genetic mechanism(s) underlying the clinical entity. Peculiar to this strategy is to look for consistency among findings gathered from different 'contexts' after having properly accounted for the context's dependency of the results.

Dopamine and the kidney: a role in hypertension?

PURPOSE OF REVIEW

Defective transduction of the dopamine receptor signal in the kidney has been shown to be important in the pathogenesis of hypertension This review will discuss the genetic mechanism for the defective renal dopaminergic function and the interaction with other gene variant products in the pathogenesis of salt sensitivity and essential hypertension.

RECENT FINDINGS

Single nucleotide polymorphisms of G protein-coupled receptor kinase type 4 (GRK4) phosphorylate, desensitize, and diminish the inhibitory action of D receptors on sodium transport in the kidney. Inhibition of GRK4 expression normalizes renal proximal tubule D receptor function in humans and rodents and ameliorates the hypertension in genetically hypertensive rats. Expression of the GRK4 variant, GRK4gammaA142V, produces hypertension and impairs the natriuretic effect of D receptor stimulation in mice. In humans, GRK4 single nucleotide polymorphisms are associated with essential hypertension, particularly salt sensitive hypertension. The prediction of the hypertensive phenotype is most accurate when elements of the renin-angiotensin system and GRK4 are included in the analysis.

SUMMARY

GRK4 single nucleotide polymorphisms, by preventing the natriuretic function of the dopaminergic system and by allowing the antinatriuretic function of angiotensin II type 1 receptors to predominate, may be responsible for salt sensitivity. Hypertension develops with additional perturbations caused by the variants of other genes (e.g., alpha-adducin, angiotensin converting enzyme, angiotensinogen, angiotensin II type 1 receptor, aldosterone synthase, 11beta-hydroxysteroid dehydrogenase type 2), the quantitative interaction of which may vary depending upon the genetic background.