The time course of salt-induced hypertension, and why it matters

Functional and morphological renal changes in a Göttingen Minipig model of obesity-related and diabetic nephropathy

Obesity-related glomerulopathy and diabetic nephropathy (DN) are serious complications to metabolic syndrome and diabetes. The purpose was to study effects of a fat, fructose and cholesterol-rich (FFC) diet with and without salt in order to induce hypertension on kidney function and morphology in Göttingen Minipigs with and without diabetes. Male Göttingen Minipigs were divided into 4 groups: SD (standard diet, n = 8), FFC (FFC diet, n = 16), FFC-DIA (FFC diet + diabetes, n = 14), FFC-DIA + S (FFC diet with extra salt + diabetes, n = 14). Blood and urine biomarkers, glomerular filtration rate (GFR), blood pressure (BP) and resistive index (RI) were evaluated after 6-7 months (T1) and 12-13 months (T2). Histology, electron microscopy and gene expression (excluding FFC-DIA + S) were evaluated at T2. All groups fed FFC-diet displayed obesity, increased GFR and RI, glomerulomegaly, mesangial expansion (ME) and glomerular basement membrane (GBM) thickening. Diabetes on top of FFC diet led to increased plasma glucose and urea and proteinuria and tended to exacerbate the glomerulomegaly, ME and GBM thickening. Four genes (CDKN1A, NPHS2, ACE, SLC2A1) were significantly deregulated in FFC and/or FFC-DIA compared to SD. No effects on BP were observed. Göttingen Minipigs fed FFC diet displayed some of the renal early changes seen in human obesity. Presence of diabetes on top of FFC diet exacerbated the findings and lead to changes resembling the early phases of human DN.

High-salt diet augments systolic blood pressure and induces arterial dysfunction in outbred, genetically diverse mice

Excess salt consumption contributes to hypertension and arterial dysfunction in humans living in industrialized societies. However, this arterial phenotype is not typically observed in inbred, genetically identical mouse strains that consume a high-salt (HS) diet. Therefore, we sought to determine the effects of HS diet consumption on systolic blood pressure (BP) and arterial function in UM-HET3 mice, an outbred, genetically diverse strain of mice. Male and female UM-HET3 mice underwent a low-salt [LS (1% NaCl)] or HS (4% NaCl) diet for 12 wk. Systolic BP and aortic stiffness, determined by pulse wave velocity (PWV), were increased in HS after 2 and 4 wk, respectively, compared with baseline and continued to increase through week 12 (P < 0.05). Systolic BP was higher from weeks 2-12 and PWV was higher from weeks 4-12 in HS compared with LS mice (P < 0.05). Aortic collagen content was ∼81% higher in HS compared with LS (P < 0.05), whereas aortic elastin content was similar between groups (P > 0.05). Carotid artery endothelium-dependent dilation (EDD) was ∼10% lower in HS compared with LS (P < 0.05), endothelium-independent dilation was similar between groups (P > 0.05). Finally, there was a strong relationship between systolic BP and PWV (r2 = 0.40, P < 0.05), as well as inverse relationship between EDD and systolic BP (r2 = 0.21, P < 0.05) or PWV (r2 = 0.20, P < 0.05). In summary, HS diet consumption in UM-HET3 mice increases systolic BP, which is accompanied by aortic stiffening and impaired EDD. These data suggest that outbred, genetically diverse mice may provide unique translational insight into arterial adaptations of humans that consume an HS diet.NEW & NOTEWORTHY Excess salt consumption is a contributor to hypertension and arterial dysfunction in humans living in industrialized societies, but this phenotype is not observed in inbred, genetically identical mice that consume a high-salt (HS) diet. This study reveals that a HS diet in outbred, genetically diverse mice progressively increases systolic blood pressure and induce arterial dysfunction. These data suggest that genetically diverse mice may provide translational insight into arterial adaptations in humans that consume an HS diet.

How to Improve Awareness, Treatment, and Control of Hypertension in Africa, and How to Reduce Its Consequences: A Call to Action From the World Hypertension League

Hypertension is the leading preventable risk factor for cardiovascular diseases and disability globally. In low- and middle-income countries hypertension has a major social impact, increasing the disease burden and costs for national health systems. The present call to action aims to stimulate all African countries to adopt several solutions to achieve better hypertension management. The following 3 goals should be achieved in Africa by 2030: (1) 80% of adults with high blood pressure in Africa are diagnosed; (2) 80% of diagnosed hypertensives, that is, 64% of all hypertensives, are treated; and (3) 80% of treated hypertensive patients are controlled. To achieve these aims, we call on individuals and organizations from government, private sector, health care, and civil society in Africa and indeed on all Africans to undertake a few specific high priority actions. The aim is to improve the detection, diagnosis, management, and control of hypertension, now considered to be the leading preventable killer in Africa.

Investigation into the Antihypertensive Effects of Diosmetin and Its Underlying Vascular Mechanisms Using Rat Model

OBJECTIVE

Diosmetin is a flavonoid that is found in many important medicinal plants that have antihypertensive therapeutic potential. Diosmetin has been shown to have antiplatelet, anti-inflammatory and antioxidant properties, which suggests that it could be a potential candidate for use in antihypertensive therapy.

METHODS

In vivo and in vitro methods were used for our investigation into the antihypertensive effects of diosmetin.

RESULTS

Diosmetin significantly decreased the mean arterial pressure (MAP). The effects of diosmetin on the MAP and heart rate were more pronounced in hypertensive rats. To explore the involvement of the muscarinic receptors-linked NO pathway, Nω-nitro-L-arginine methyl ester (L-NAME) and atropine were pre-administered in vivo. The pretreatment with L-NAME did not significantly change the effects of diosmetin on the MAP by excluding the involvement of NO. Unlike L-NAME, the atropine pretreatment reduced the effects of diosmetin on the MAP, which demonstrated the role of the muscarinic receptors. In the in vitro study, diosmetin at lower concentrations produced endothelium-dependent and -independent (at higher concentrations) vasorelaxation, which was attenuated significantly by the presence of atropine and indomethacin but not L-NAME. Diosmetin was also tested for high K+-induced contractions. Diosmetin induced significant relaxation (similar to verapamil), which indicated its Ca2+ antagonistic effects. This was further confirmed by diosmetin shifting the CaCl2 CRCs toward the right due to its suppression of the maximum response. Diosmetin also suppressed phenylephrine peak formation, which indicated its antagonist effects on the release of Ca2+. Moreover, BaCl2 significantly inhibited the effects of diosmetin, followed by 4-AP and TEA, which suggested that the K+ channels had a role as well.

CONCLUSIONS

The obtained data showed the Ca2+ channel antagonism, potassium channel activation and antimuscarinic receptor-linked vasodilatory effects of diosmetin, which demonstrated its antihypertensive potential.

Salt sensitivity of blood pressure in childhood and adolescence

Although moderation of sodium intake is recommended population-wide, it remains uncertain who benefits from salt restriction. Salt sensitivity refers to changes in blood pressure in response to sodium intake and may occur with or without hypertension. Unfortunately, there is no practical way to assess salt sensitivity in daily practice. Assessment of salt sensitivity even in research studies is challenging with varying protocols utilized which may contribute to differing results. Building on studies in animals and adults, risk factors and conditions associated with salt sensitivity have been identified in the pediatric and young adult populations. This review presents the limited evidence linking obesity, low birth weight, diabetes, chronic kidney disease, and race/ethnicity with salt sensitivity in children, adolescents, and young adults. The impact of stress on sodium handling is also reviewed. The influence of age on the timing of introduction of dietary salt restriction and the long-term influence of salt sensitivity on risk for hypertension are considered. Lastly, interventions other than salt restriction that may improve salt sensitivity and may inform recommendations to families are reviewed.

Salt-Sensitive Hypertension in GR+/- Rats Is Accompanied with Dysregulation in Adrenal Soluble Epoxide Hydrolase and Polyunsaturated Fatty Acid Pathways

Mutations within the glucocorticoid receptor (GR) gene locus lead to glucocorticoid resistance which is characterized by several clinical symptoms such as adrenal gland hyperplasia and salt-sensitive hypertension, although the underlying mechanisms are still unknown. We studied GR haploinsufficient (GR^+/−) Sprague Dawley rats which, on a standard diet, showed significantly increased plasma aldosterone and corticosterone levels and an adrenocortex hyperplasia accompanied by a normal systolic blood pressure. Following a high salt diet, these rats developed salt-sensitive hypertension and maintained elevated enzyme-soluble epoxide hydrolase (sEH) in adrenal glands, while sEH was significantly decreased in wild-type rats. Furthermore, GR^+/− rats showed dysregulation of the equilibrated linoleic and arachidonic acid pathways, with a significant increase of less active metabolites such as 8,9-DiHETrE. In Sprague Dawley rats, GR haploinsufficiency induced steroid disturbances, which provoked hypertension only in combination with high salt intake, which was accompanied by disturbances in sEH and fatty acid metabolism. Our results suggest that sEH inhibition could be a potential target to treat hypertension in patients with GR haploinsufficiency.

Association between animal source foods consumption and risk of hypertension: a cohort study

PURPOSE

This study assessed the association between animal source foods (ASF) consumption and hypertension, a recognised risk factor for cardiovascular disease. Adverse effects of red and processed meat (RPM) consumption and beneficial effects of the consumption of dairy products and other ASF have been discovered separately; however, the constrained nature of food intake has been typically ignored. We assessed the effects of substituting RPM and other ASF.

METHODS

We followed-up 5394 Chinese adults (age 18-60 years) at baseline using the China Health and Nutrition Survey from 2004 to 2011. Food consumption was assessed using individual-based consecutive 24-h recall and household-based food weighing approaches. Both traditional substitution analysis and substitution analysis based on compositional transformation were used to assess substitution effects.

RESULTS

In total, 1267 participants were newly diagnosed with hypertension during the median follow-up time of 6.81 years (range, 2.97-6.99 years). The traditional substitution analysis found that substituting eggs for RPM was associated with a lower risk of hypertension. The compositional transformation substitution analysis revealed that replacing RPM with any other ASF was associated with a lower risk of hypertension; it implemented substitutions of one or many ASF for RPM; it also revealed different substitution effects of RPM and dairy products, and substituting dairy products for RPM was associated with reduced hypertension risks.

CONCLUSION

The compositional transformation substitution analysis considers the constrained and relative nature of food consumption. It is a flexible approach to estimating substitution effects using different patterns to obtain personalised estimation effects and provide individualised dietary recommendations.

Modelling the Effect of Compliance with Nordic Nutrition Recommendations on Cardiovascular Disease and Cancer Mortality in the Nordic Countries

The objective of this study is to estimate the number of deaths attributable to cardiovascular diseases and diet-related cancers that could be prevented or delayed in the Nordic countries, i.e., Sweden, Denmark, Finland, Norway, and Iceland, if adults adhere to the Nordic Nutrition Recommendations (NNR). A sex- and age-group specific epidemiological macro-simulation model was used to estimate the preventable deaths due to the differences between country specific actual intake and recommended intake of changes in food components. Data included in the model are a baseline scenario (actual dietary intake), a counterfactual scenario (recommended intake), and age-and sex-specific mortality for cardiovascular and diet-related cancer diseases, together with the total population risk of a specific year. Monte Carlo analyses with 5000 iterations were performed to produce the 95% uncertainty intervals. The model predicts that Iceland would benefit the most by adhering to the NNR, followed by Finland. In all the Nordic countries, the highest benefit would be achieved by adhering to the fruits and vegetable intakes, except Denmark, where a lower recommended intake of salt would provide the highest benefit. For men, fruits and vegetables could have saved more lives compared to other dietary components for all the Nordic countries, while for women, dietary fiber was the most prominent factor, except in Iceland. The Nordic Council should consider policies for promoting healthy eating according to the needs of each country.

Prevention of Cardiovascular Disease and Cancer Mortality by Achieving Healthy Dietary Goals for the Swedish Population: A Macro-Simulation Modelling Study

The objective is to estimate the number of deaths attributable to cardiovascular diseases and diet-related cancers that could be prevented or delayed in Sweden if adults adhere to the official dietary recommendations. We used an age-group and sex-specific epidemiological macro-simulation model to estimate preventable deaths due to the discrepancies between actual intake and recommended intake of changes in food components. Data included in the model are a baseline scenario (actual dietary intake), a counterfactual scenario (recommended intake) and age- and sex-specific mortality for cardiovascular and diet-related cancer diseases together compared with the total population risk of a specific year. Monte Carlo analyses with 5000 iterations was performed to produce the 95% uncertainty intervals (UI). The model predicts that 6405 (95% UI: 5086–7086) deaths could be prevented or delayed if the Swedish population could adhere to official dietary recommendations in a year. More deaths would be saved for men than women. The recommendations for fruits and vegetables could have saved 47% of the deaths, followed by fiber intake (32%). For men, fruits and vegetables could have saved more compared to other dietary components, while for women dietary fiber was the prominent factor. Public health policies should consider ensuring healthy eating practices for the Swedish population.

Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension

The thick ascending limb plays a key role in maintaining water and electrolyte balance. The importance of this segment in regulating blood pressure is evidenced by the effect of loop diuretics or local genetic defects on this parameter. Hormones and factors produced by thick ascending limbs have both autocrine and paracrine effects, which can extend prohypertensive signaling to other structures of the nephron. In this review, we discuss the role of the thick ascending limb in the development of hypertension, not as a sole participant, but one that works within the rich biological context of the renal medulla. We first provide an overview of the basic physiology of the segment and the anatomical considerations necessary to understand its relationship with other renal structures. We explore the physiopathological changes in thick ascending limbs occurring in both genetic and induced animal models of hypertension. We then discuss the racial differences and genetic defects that affect blood pressure in humans through changes in thick ascending limb transport rates. Throughout the text, we scrutinize methodologies and discuss the limitations of research techniques that, when overlooked, can lead investigators to make erroneous conclusions. Thus, in addition to advancing an understanding of the basic mechanisms of physiology, the ultimate goal of this work is to understand our research tools, to make better use of them, and to contextualize research data. Future advances in renal hypertension research will require not only collection of new experimental data, but also integration of our current knowledge.

Lack of Suppression of Aldosterone Production Leads to Salt-Sensitive Hypertension in Female but Not Male Balb/C Mice

Clinical studies indicate that salt-sensitive hypertension is more prevalent in women than in men. However, animal models of salt sensitivity have primarily focused on the mechanisms of salt sensitivity in male animals; therefore, elucidation of these mechanisms in female animal models is needed. We have previously shown that female Balb/C mice have higher aldosterone synthase expression and aldosterone production than males. We hypothesized that female Balb/C mice develop salt-sensitive increases in blood pressure. Seven-day feeding of a 4% NaCl high-salt (HS) diet increased blood pressure in female mice without altering blood pressure in males. Females on an HS diet displayed no apparent increases in sodium retention as assessed by 24-hour urine collection, sodium balance measure, and saline loading excretion analysis. Females on an HS diet exhibited lower renin-angiotensin system activity (plasma Ang II [angiotensin II], plasma renin activity, and ACE [angiotensin-converting enzyme] activity) compared with males but developed a salt-induced elevation in adrenal aldosterone synthase expression and retained higher aldosterone levels than males on HS. This resulted in a higher aldosterone/plasma renin activity ratio in females compared with males on HS feeding. Adrenal mRNA expression of angiotensinogen and leptin receptor was increased in female mice on an HS diet. HS impaired endothelium-dependent relaxation in female mice only. MR (mineralocorticoid receptor) inhibition (eplerenone) restored blood pressure and endothelial function in females on an HS diet. Collectively, these data indicate that Balb/C mice develop sex-discrepant salt-sensitive hypertension likely via aldosterone-MR-mediated mechanisms involving impaired endothelium-dependent relaxation in females only. This study presents the first model of spontaneous sex-specific salt sensitivity, which mimics the human pathology.

Total phenolic and flavonoid contents and antihypertensive effect of the crude extract and fractions of Calamintha vulgaris

BACKGROUND

Calamintha vulgaris L., has been used medicinally in the management hypertension.

PURPOSE

To investigate the antihypertensive mechanisms of extract of C. vulgaris L., in Sprague-Dawley (SD) rat.

STUDY DESIGN

Total phenol and total flavonoid contents were determined in the crude extract through HPLC. In vivo and in vitro pharmacological approaches were utilized to test the crude extract and fractions of C. vulgaris in Sprague-Dawley (SD) rats. The effect on mean arterial pressure (MAP) was compared in normotensive and high salt-induced hypertensive rats.

METHODS

Crude extract and nHexane, chloroform, ethylacetate and aqueous fractions of C. vulgaris were tested. In vitro experiments were carried out in isolated rat and rabbit aortae, to probe vascular mechanism(s). Extract was also evaluated for acute toxicity study in mice.

RESULTS

Crude extract and fractions of C. vulgaris induced a fall in MAP in normotensive and high salt-induced hypertensive rats at different doses. The effect was more significant in the hypertensive rats (Max. fall, 38.67 ± 2.17 vs 44.16 ± 4.67 mmHg). Among the fractions, chloroform was more effective (Max. fall, 53.20 ± 1.23 mmHg) and aqueous the least (Max. fall, 38.66 ± 1.12 mmHg). Normotensive rats pretreated with atropine (2 mg/kg) or _L-NAME (100 µg/kg) ablated fall in MAP to the extract and fractions. In isolated rat aorta, extract induced endothelium-dependent vasodilatory effect, which was ablated with atropine (1 µM), _L-NAME (10 µM), atropine + _L-NAME, TEA (10 µM) pretreatment and denudation of aorta. Indomethacin (10 µM) pretreatment ablated vasodilatation at lower concentrations and unmasked a vasoconstrictor effect, followed by relaxation at higher concentrations. Extract and fractions inhibited high K⁺-precontractions and rightward shifted Ca⁺² concentration response curves, similar to verapamil. Total phenolic and flavonoid contents were found 39.41 ± 0.18 (mg of GAE/g) and 12.03 ± 0.23 (mg of QUE/g), respectively. HPLC analysis showed the presence of quercetin and rutin CONCLUSION: Results obtained indicate that the antihypertensive effect of C. vulgaris is the outcome of vasodilation, which is mediated through combination of muscarinic receptor-linked NO, activation of TEA-sensitive K⁺ channels, prostacyclin and Ca⁺² antagonism.

Drinking Water Salinity and Raised Blood Pressure: Evidence from a Cohort Study in Coastal Bangladesh

BACKGROUND

Millions of coastal inhabitants in Southeast Asia have been experiencing increasing sodium concentrations in their drinking-water sources, likely partially due to climate change. High (dietary) sodium intake has convincingly been proven to increase risk of hypertension; it remains unknown, however, whether consumption of sodium in drinking water could have similar effects on health.

OBJECTIVES

We present the results of a cohort study in which we assessed the effects of drinking-water sodium (DWS) on blood pressure (BP) in coastal populations in Bangladesh.

METHODS

DWS, BP, and information on personal, lifestyle, and environmental factors were collected from 581 participants. We used generalized linear latent and mixed methods to model the effects of DWS on BP and assessed the associations between changes in DWS and BP when participants experienced changing sodium levels in water, switched from "conventional" ponds or tube wells to alternatives [managed aquifer recharge (MAR) and rainwater harvesting] that aimed to reduce sodium levels, or experienced a combination of these changes.

RESULTS

DWS concentrations were highly associated with BP after adjustments for confounding factors. Furthermore, for each 100 mg/L reduction in sodium in drinking water, systolic/diastolic BP was lower on average by 0.95/0.57 mmHg, and odds of hypertension were lower by 14%. However, MAR did not consistently lower sodium levels.

CONCLUSIONS

DWS is an important source of daily sodium intake in salinity-affected areas and is a risk factor for hypertension. Considering the likely increasing trend in coastal salinity, prompt action is required. Because MAR showed variable effects, alternative technologies for providing reliable, safe, low-sodium fresh water should be developed alongside improvements in MAR and evaluated in "real-life" salinity-affected settings. https://doi.org/10.1289/EHP659.

Hemodynamic responses to mental stress during salt loading

PURPOSE

The purpose was to examine whether prolonged moderate stress associated with a student exam would increase the blood pressure response to a salt load in young healthy normotensive individuals.

METHODS

Ten healthy young subjects were examined at two different occasions in random order (i) during preparation for a medical exam (prolonged stress) and (ii) outside the exam period (low stress). All subjects consumed a controlled diet for 3 days with low- or high-salt content in randomized order. The subjective stress was measured by Spielberger's State-Trait Anxiety Inventory-Scale, SCL Symptom Checklist for stress and the Visual Analogue Scale. On each level of stress, 24-h ambulatory blood pressure and cardiac output (CO) were measured. Furthermore, plasma norepinephrine (NE), epinephrine (E) and plasma renin activity (PRA) were measured.

RESULTS

Twenty-four-hour ABP, 24-h heart rate, CO as well as plasma levels of NE, E and PRA remained unchanged by changes in stress level. Day-night reduction in SAP was significantly larger during moderate stress and high-salt intake; however, no significant difference was observed during daytime and night-time. Individual increase in mental stress correlated significantly with an individual decrease in PRA (SCL-17, r = -0·80, P<0·05, STAIr = -0·64 P<0·05) during high-salt intake.

CONCLUSION

Moderate stress over a period of time in young healthy normotensive individuals does not lead to changes in 24-h ABP. However, the augmented reduction in day-to-night systolic blood pressure during high-salt intake and moderate stress may indicate that stress affects blood pressure regulation.

The science of salt: a systematic review of clinical salt studies 2013 to 2014

The authors provided a systematic review of the clinical and population health impact of increased dietary salt intake during 1 year. Randomized controlled trials or cohort studies or meta-analyses on the effect of sodium intake were examined from Medline searches between June 2013 to May 2014. Quality indicators were used to select studies that were relevant to clinical and public health. A total of 213 studies were reviewed, of which 11 (n=186,357) were eligible. These studies confirmed a causal relationship between increasing dietary salt and increased blood pressure and an association between several adverse health outcomes and increased dietary salt. A new association between salt intake and renal cell cancer was published. No study that met inclusion criteria found harm from lowering dietary salt. The findings of this systematic review are consistent with previous data relating increased dietary salt to increased blood pressure and adverse health outcomes.

Proposed nomenclature for salt intake and for reductions in dietary salt

There is considerable confusion about what ranges of dietary salt(a) could be considered low, normal, or high and also what ranges of reduction in dietary salt are small or large. The World Hypertension League with other organizations involved in dietary salt reduction have proposed a standardized nomenclature based on normal ancestral levels of salt intake and also on ranges of reduction in salt intake in clinical and population interventions. Low daily salt (sodium) intake where harm due to deficiency would be expected to occur is recommended to remain undefined because of inadequate research but likely <0.25 g (100 mg), normal (physiological) intake <2.5 g (1000 mg), recommended intake <5.0 g (2000 mg), high ≥5.0 g (2000 mg), very high >10 to 15 g (4000-6000 mg), and extremely high >15 g (6000 mg). Reductions in daily salt (sodium) intake are recommended to be called small if <2.5 g (1000 mg), moderate if 2.5 to 5.0 g (1000-2000 mg) and large if >5.0 g (2000 mg). Use of this nomenclature is likely to result in less confusion about salt intake and interventions to reduce dietary sodium.

Global sodium consumption and death from cardiovascular causes

BACKGROUND

High sodium intake increases blood pressure, a risk factor for cardiovascular disease, but the effects of sodium intake on global cardiovascular mortality are uncertain.

METHODS

We collected data from surveys on sodium intake as determined by urinary excretion and diet in persons from 66 countries (accounting for 74.1% of adults throughout the world), and we used these data to quantify the global consumption of sodium according to age, sex, and country. The effects of sodium on blood pressure, according to age, race, and the presence or absence of hypertension, were calculated from data in a new meta-analysis of 107 randomized interventions, and the effects of blood pressure on cardiovascular mortality, according to age, were calculated from a meta-analysis of cohorts. Cause-specific mortality was derived from the Global Burden of Disease Study 2010. Using comparative risk assessment, we estimated the cardiovascular effects of current sodium intake, as compared with a reference intake of 2.0 g of sodium per day, according to age, sex, and country.

RESULTS

In 2010, the estimated mean level of global sodium consumption was 3.95 g per day, and regional mean levels ranged from 2.18 to 5.51 g per day. Globally, 1.65 million annual deaths from cardiovascular causes (95% uncertainty interval [confidence interval], 1.10 million to 2.22 million) were attributed to sodium intake above the reference level; 61.9% of these deaths occurred in men and 38.1% occurred in women. These deaths accounted for nearly 1 of every 10 deaths from cardiovascular causes (9.5%). Four of every 5 deaths (84.3%) occurred in low- and middle-income countries, and 2 of every 5 deaths (40.4%) were premature (before 70 years of age). The rate of death from cardiovascular causes associated with sodium intake above the reference level was highest in the country of Georgia and lowest in Kenya.

CONCLUSIONS

In this modeling study, 1.65 million deaths from cardiovascular causes that occurred in 2010 were attributed to sodium consumption above a reference level of 2.0 g per day. (Funded by the Bill and Melinda Gates Foundation.).

[Is salt sensitive hypertension an inflammatory disease? Role of lymphocytes and macrophages]

High blood pressure is a public health problem. This entity affects 43% of the mexican population and is considered a major risk factor for development of stroke, cardiac failure and chronic kidney disease. Hypertension prevalence has increased over the last decades, mainly because of high salt diet. There is evidence showing that salt-sensitive hypertension develops structural changes as tubular dilation, patchy interstitial fibrosis, osteopontin expression and lymphocytic/macrophage tubulointerstitial infiltrate that blunts urinary sodium excretion and therefore promotes HBP. It has been shown that this structural damage has an inflammatory origin and that immunosuppresant drugs down-regulates tissular injury and improves blood pressure control. In summary, this salt-sentitive hypertension data can be used in development of new and potent blood pressure drugs.

Sodium Consumption: An Individual's Choice?

Excess intake of dietary salt is estimated to be one of the leading risks to health worldwide. Major national and international health organizations, along with many governments around the world, have called for reductions in the consumption of dietary salt. This paper discusses behavioural and population interventions as mechanisms to reduce dietary salt. In developed countries, salt added during food processing is the dominant source of salt and largely outside of the direct control of individuals. Population-based interventions have the potential to improve health and to be cost saving for these countries. In developing economies, where salt added in cooking and at the table is the dominant source, interventions based on education and behaviour change have been estimated to be highly cost effective. Regardless, countries with either developed or developing economies can benefit from the integration of both population and behavioural change interventions.

A 5-component mathematical model for salt-induced hypertension in Dahl-S and Dahl-R rats

Salt-induced hypertension has been demonstrated in a variety of species including rats, monkeys, chimpanzees and humans. Until recently, the multiple phases of this blood pressure increase due to high salt intake had not been closely studied. This work builds upon a recent study, which developed a grey-box multi-component model of salt-induced hypertension in the Dahl-S rat. The previous 3-component model has been extended here to include additional model dynamics to improve the model fit and add new important elements to the model response. The model was optimised using numerical techniques with experimental data from 4 different protocols with Dahl-S, Dahl-R and FF2 hybrid rats. Results show a marked improvement over the previous model and confirm the merit of the 5-component model structure. A comparison between the model dynamics for different rat strains has also been included.

A multi-component model of the dynamics of salt-induced hypertension in Dahl-S rats

BACKGROUND

In humans, salt intake has been suggested to influence blood pressure (BP) on a wide range of time scales ranging from several hours or days to many months or years. Detailed time course data collected in the Dahl salt-sensitive rat strain suggest that the development of salt-induced hypertension may consist of several distinct phases or components that differ in their timing and reversibility. To better understand these components, the present study sought to model the dynamics of salt-induced hypertension in the Dahl salt sensitive (Dahl-S) rat using 3 sets of time course data.

RESULTS

The first component of the model ("Acute-Reversible") consisted of a linear transfer function to account for the rapid and reversible effects of salt on BP (ie. acute salt sensitivity, corresponding with a depressed slope of the chronic pressure natriuresis relationship). For the second component ("Progressive-Irreversible"), an integrator function was used to represent the relatively slow, progressive, and irreversible effect of high salt intake on BP (corresponding with a progressive salt-induced shift of the chronic pressure natriuresis relationship to higher BP levels). A third component ("Progressive-Reversible") consisted of an effect of high salt intake to progressively increase the acute salt-sensitivity of BP (ie. reduce the slope of the chronic pressure natriuresis relationship), amounting to a slow and progressive, yet reversible, component of salt-induced hypertension. While the 3 component model was limited in its ability to follow the BP response to rapid and/or brief transitions in salt intake, it was able to accurately follow the slower steady state components of salt-induced BP changes. This model exhibited low values of mean absolute error (1.92 +/- 0.23, 2.13 +/- 0.37, 2.03 +/- 0.3 mmHg for data sets 1 - 3), and its overall performance was significantly improved over that of an initial model having only 2 components. The 3 component model performed well when applied to data from hybrids of Dahl salt sensitive and Dahl salt resistant rats in which salt sensitivity varied greatly in its extent and character (mean absolute error = 1.11 +/- 0.08 mmHg).

CONCLUSION

Our results suggest that the slow process of development of salt-induced hypertension in Dahl-S rats over a period of many weeks can be well represented by a combination of three components that differ in their timing, reversibility, and their associated effect on the chronic pressure natriuresis relationship. These components are important to distinguish since each may represent a unique set of underlying mechanisms of salt-induced hypertension.