Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP)

Mechanism of dietary salt-mediated increase in intravascular production of TGF-beta1

Clinical and preclinical studies have demonstrated an important effect of arterial pathobiology on the progressive loss of renal function that occurs in chronic kidney disease. Chronic kidney disease, in turn, promotes alterations in vascular function. A modulating role for dietary salt has been suggested, with the amount of salt intake regulating endothelial cell production of transforming growth factor-beta1 (TGF-beta1), a fibrogenic growth factor that promotes arteriosclerosis and glomerulosclerosis. The purpose of the present studies was to determine how the interaction between dietary salt intake and vasculature promoted the production of TGF-beta1 in rats. Two different vascular tissues, aortic rings and glomeruli, were chosen for study. Dietary salt induced, in a dose-dependent fashion, activation of proline-rich tyrosine kinase-2 (Pyk2) and further identified c-Src as an important binding partner of Pyk2 in these tissues. Use of pharmacological inhibitors and dominant negative strategies confirmed that dietary salt induced complex formation of Pyk2 and c-Src with downstream activation of p38 and p42/44 mitogen-activated protein kinases and generation of TGF-beta1. The experiments defined the molecular signaling events that promoted the production of TGF-beta1, a key growth factor involved in the vascular response to increased salt intake.

Lifestyle modifications to lower or control high blood pressure: is advice associated with action? The behavioral risk factor surveillance survey

Routine lifestyle modification advice for managing high blood pressure (BP) is of questionable effectiveness. Using data from the 2005 Behavior Risk Factor Surveillance System, we examined whether receipt of advice is associated with reported adoption of lifestyle modifications. We determined proportions of hypertensive adults taking action to change eating habits, reduce salt intake, exercise, or decrease alcohol consumption to control high BP. We then determined associations between reports of advice given and corresponding actions being taken: 70.1% of respondents reported changing eating habits, 78.7% reported reducing salt intake, 67.1% reported exercising, and 57.9% of those who drank alcohol reported decreasing their consumption. Compared with those who did not recall being given advice, hypertensive adults who recalled being given advice were more likely to change their eating habits (prevalence ratio [PR], 1.62; 95% confidence interval [CI], 1.56-1.67), reduce salt (PR, 1.53; 95% CI, 1.48-1.58), exercise (PR, 1.41; 95% CI, 1.36-1.47), and reduce alcohol consumption (PR, 1.78; 95% CI, 1.70-1.87).

Optimal treatment of hypertension with diastolic heart failure

Approximately 5 million people in the United States have heart failure. Epidemiologic studies have demonstrated that at least one half of patients who have clinically overt heart failure have diastolic heart failure (DHF), or heart failure with preserved ejection fraction. DHF is characterized by concentric remodeling with normal left ventricular end-diastolic volume, abnormalities of active relaxation, and increased passive ventricular stiffness. Diuretics are an essential component of therapy for most patients who have DHF, and treatment of hypertension is a cornerstone of therapy designed to prevent or to treat DHF. Several antihypertensive agents have been shown to effectively reduce wave reflection, including angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, calcium antagonists, and nitrates. Lifestyle changes may also be helpful.

Lifestyle and Risk of Cardiovascular Disease and Type 2 Diabetes in Women: A Review of the Epidemiologic Evidence

Cardiovascular disease is the leading cause of death among both women and men in the United States, accounting for nearly half of all deaths and considerable morbidity. Type 2 diabetes is a major risk factor for cardiovascular disease and one that is particularly potent in women; its prevalence has increased dramatically in recent years. Epidemiologic data indicate that cardiovascular disease and type 2 diabetes share common risk factors and are largely preventable; indeed, findings from the Nurses' Health Study suggest that 74% of cardiovascular disease cases, 82% of coronary heart disease cases, and 91% of diabetes cases in women could be prevented by not smoking, engaging in regular physical activity, maintaining a healthy weight, eating healthier food, and drinking moderate amounts of alcohol. This article reviews lifestyle risk factors and preventive strategies for cardiovascular disease and type 2 diabetes among women.

Salt: its role in chronic kidney disease

Few controversies in medicine have such a long history as that of whether salt is identifiably dangerous or not dangerous. The most common reported association between excess dietary salt intake and clinical outcome has been in the field of hypertension, but dietary sodium intake mediates effects that go far beyond, and are independent of, extracellular fluid expansion and elevation in blood pressure. For nephrologists, clinical trials that demonstrate no negative outcome of a high salt diet in the general population are thus not particularly assuasive, because patients with chronic kidney disease (CKD) represent an entity that is by no means comparable to the general population. This review takes a look at the challenges associated with salt balance in CKD patients (particularly at K/DOQI stage 5), followed by a summary of current concepts believed to play a part in salt-mediated pathophysiology, and the conclusion, based on the present state of scientific knowledge, that it appears advisable to advocate low dietary salt intake in this patient population.

Pathogenesis of essential hypertension: historical paradigms and modern insights

Since its first identification in the late 1800s, a variety of etiologies for essential hypertension have been proposed. In this paper we review the primary proposed hypotheses in the context of both the time in which they were proposed as well as the subsequent studies performed over the years. From these various insights, we propose a current paradigm to explain the renal mechanisms underlying the hypertension epidemic today. Specifically, we propose that hypertension is initiated by agents that cause systemic and intrarenal vasoconstriction. Over time intrarenal injury develops with microvascular disease, interstitial T cell and macrophage recruitment with the induction of an autoimmune response, with local angiotensin II formation and oxidant generation. These changes maintain intrarenal vasoconstriction and hypoxia with a change in local vasoconstrictor-vasodilator balance favoring sodium retention. Both genetic and congenital (nephron number) mechanisms have profound influence on this pathway. As blood pressure rises, renal ischemia is ameliorated and sodium balance restored completely (in salt-resistant) or partially (in salt-sensitive) hypertension, but at the expense of a rightward shift in the pressure natriuresis curve and persistent hypertension.

A call for higher standards of evidence for dietary guidelines

Dietary guidelines, especially those designed to prevent the diseases of dietary excess, are a relatively new phenomenon in the United States. National dietary guidelines have been promulgated based on scientific reasoning and indirect evidence. In general, weak evidentiary support has been accepted as adequate justification for these guidelines. This low standard of evidence is based on several misconceptions, most importantly the belief that such guidelines could not cause harm. Using guidelines against dietary fat as a case in point, an analysis is provided that suggests that harm indeed may have been caused by the widespread dissemination of and adherence to these guidelines, through their contribution to the current epidemic of obesity and overweight in the U.S. An explanation is provided of what may have gone wrong in the development of dietary guidelines, and an alternative and more rigorous standard is proposed for evidentiary support, including the recommendation that when adequate evidence is not available, the best option may be to issue no guideline.

Normal-sodium diet compared with low-sodium diet in compensated congestive heart failure: is sodium an old enemy or a new friend?

The aim of the present study was to evaluate the effects of a normal-sodium (120 mmol sodium) diet compared with a low-sodium diet (80 mmol sodium) on readmissions for CHF (congestive heart failure) during 180 days of follow-up in compensated patients with CHF. A total of 232 compensated CHF patients (88 female and 144 male; New York Heart Association class II–IV; 55–83 years of age, ejection fraction <35% and serum creatinine <2 mg/dl) were randomized into two groups: group 1 contained 118 patients (45 females and 73 males) receiving a normal-sodium diet plus oral furosemide [250–500 mg, b.i.d. (twice a day)]; and group 2 contained 114 patients (43 females and 71 males) receiving a low-sodium diet plus oral furosemide (250–500 mg, b.i.d.). The treatment was given at 30 days after discharge and for 180 days, in association with a fluid intake of 1000 ml per day. Signs of CHF, body weight, blood pressure, heart rate, laboratory parameters, ECG, echocardiogram, levels of BNP (brain natriuretic peptide) and aldosterone levels, and PRA (plasma renin activity) were examined at baseline (30 days after discharge) and after 180 days. The normal-sodium group had a significant reduction (P<0.05) in readmissions. BNP values were lower in the normal-sodium group compared with the low sodium group (685±255 compared with 425±125 pg/ml respectively; P<0.0001). Significant (P<0.0001) increases in aldosterone and PRA were observed in the low-sodium group during follow-up, whereas the normal-sodium group had a small significant reduction (P=0.039) in aldosterone levels and no significant difference in PRA. After 180 days of follow-up, aldosterone levels and PRA were significantly (P<0.0001) higher in the low-sodium group. The normal-sodium group had a lower incidence of rehospitalization during follow-up and a significant decrease in plasma BNP and aldosterone levels, and PRA. The results of the present study show that a normal-sodium diet improves outcome, and sodium depletion has detrimental renal and neurohormonal effects with worse clinical outcome in compensated CHF patients. Further studies are required to determine if this is due to a high dose of diuretic or the low-sodium diet.

Modified MyPyramid for Older Adults

In 1999 we proposed a Modified Food Guide Pyramid for adults aged 70+ y. It has been extensively used in a variety of settings and formats to highlight the unique dietary challenges of older adults. We now propose a Modified MyPyramid for Older Adults in a format consistent with the MyPyramid graphic. It is not intended to substitute for MyPyramid, which is a multifunctional Internet-based program allowing for the calculation of individualized food-based dietary guidance and providing supplemental information on food choices and preparation. Pedagogic issues related to computer availability, Web access, and Internet literacy of older adults suggests a graphic version of MyPyramid is needed. Emphasized are whole grains and variety within the grains group; variety and nutrient density, with specific emphasis on different forms particularly suited to older adults' needs (e.g. frozen) in the vegetables and fruits groups; low-fat and non-fat forms of dairy products including reduced lactose alternatives in the milk group; low saturated fat and trans fat choices in the oils group; and low saturated fat and vegetable choices in the meat and beans group. Underlying themes stress nutrient- and fiber-rich foods within each group and food sources of nutrients rather than supplements. Fluid and physical activity icons serve as the foundation of MyPyramid for Older Adults. A flag to maintain an awareness of the potential need to consider supplemental forms of calcium, and vitamins D and B-12 is placed at the top of the pyramid. Discussed are newer concerns about potential overnutrition in the current food landscape available to older adults.

Chronic disease prevention: health effects and financial costs of strategies to reduce salt intake and control tobacco use

In 2005, WHO set a global goal to reduce rates of death from chronic (non-communicable) disease by an additional 2% every year. To this end, we investigated how many deaths could potentially be averted over 10 years by implementation of selected population-based interventions, and calculated the financial costs of their implementation. We selected two interventions: to reduce salt intake in the population by 15% and to implement four key elements of the WHO Framework Convention on Tobacco Control (FCTC). We used methods from the WHO Comparative Risk Assessment project to estimate shifts in the distribution of risk factors associated with salt intake and tobacco use, and to model the effects on chronic disease mortality for 23 countries that account for 80% of chronic disease burden in the developing world. We showed that, over 10 years (2006-2015), 13.8 million deaths could be averted by implementation of these interventions, at a cost of less than US$0.40 per person per year in low-income and lower middle-income countries, and US$0.50-1.00 per person per year in upper middle-income countries (as of 2005). These two population-based intervention strategies could therefore substantially reduce mortality from chronic diseases, and make a major (and affordable) contribution towards achievement of the global goal to prevent and control chronic diseases.

Cardiovascular health disparities: a systematic review of health care interventions

Racial and ethnic disparities in cardiovascular health care are well documented. Promising approaches to disparity reduction are increasingly described in literature published since 1995, but reports are fragmented by risk, condition, population, and setting. The authors conducted a systematic review of clinically oriented studies in communities of color that addressed hypertension, hyperlipidemia, physical inactivity, tobacco, and two major cardiovascular conditions, coronary artery disease and heart failure. Virtually no literature specifically addressed disparity reduction. The greatest focus has been African American populations, with relatively little work in Hispanic, Asian, and Native American populations. The authors found 62 interventions, 27 addressing hypertension, 9 lipids, 18 tobacco use, 8 physical inactivity, and 7 heart failure. Only 1 study specifically addressed postmyocardial infarction care. Data supporting the value of registries, multidisciplinary teams, and community outreach were found across several conditions. Interventions addressing care transitions, using telephonic outreach, and promoting medication access and adherence merit further exploration.

Risk of cardiovascular events among women with high normal blood pressure or blood pressure progression: prospective cohort study

OBJECTIVE

To compare cardiovascular risk among women with high normal blood pressure (130-9/85-9 mm Hg) against those with normal blood pressure (120-9/75-84 mm Hg) and those with baseline hypertension.

DESIGN

Prospective cohort study.

SETTING

Women's health study, United States.

PARTICIPANTS

39 322 initially healthy women classified into four categories according to self reported baseline blood pressure and followed for a median of 10.2 years.

MAIN OUTCOME MEASURES

Time to cardiovascular death, myocardial infarction, or stroke (major cardiovascular event-primary end point); progression to hypertension.

RESULTS

982 (2.5%) women developed a major cardiovascular event, and 8686 (30.1%) women without baseline hypertension progressed to hypertension. The age adjusted event rate for the primary end point was 1.6/1000 person years among women with normal blood pressure, 2.9/1000 person years among those with high normal blood pressure, and 4.3/1000 person years among those with baseline hypertension. Compared with women with high normal blood pressure (reference group), those with normal blood pressure had a lower risk of a major cardiovascular event (adjusted hazard ratio 0.61, 95% confidence interval 0.48 to 0.76) and of incident hypertension (0.42, 0.40 to 0.44). The hazard ratio for a major cardiovascular event in women with baseline hypertension was 1.30 (1.08 to 1.57). Women who progressed to hypertension (reference group) during the first 48 months of the study had a higher cardiovascular risk than those who remained normotensive (adjusted hazard ratio 0.64, 0.50 to 0.81). Women with high normal blood pressure at baseline who progressed to hypertension (reference group) had similar outcome rates to women with baseline hypertension (adjusted hazard ratio 1.17, 0.88 to 1.55).

CONCLUSION

The cardiovascular risk of women with high normal blood pressure is higher than that of women with normal blood pressure. The cardiovascular risk of women who progress to hypertension is increased shortly after a diagnosis of hypertension has been made.

TRIAL REGISTRATION

Clinical trials NCT00000479 [ClinicalTrials.gov].

Salt, the kidneys, and arterial hypertension

The kidneys play a major role in the regulation of the salt balance and thereby regulate blood pressure. Salt sensitivity is acquired or genetically-induced and is noted in about 50% of patients with essential hypertension. This property leads to a high cardiovascular risk. In this situation, the benefit of salt restriction is significant, and this dietary change should be associated with a high potassium intake. In patients treated by antihypertensive drugs, salt restriction improves the blood pressure control, which can permit a reduction of the number of drugs required to achieve a normal blood pressure. The recommended maximal salt intake should not exceed 6 grams/day (NaCl). Because most dietary salt comes from processed foods, the help of the food industry is crucial for a long-term compliance with a reduced salt intake, which could yield an additional important benefit in the reduction of cardiovascular risk.

Renal hemodynamics in overweight and obesity: pathogenetic factors and targets for intervention

Weight excess is a risk factor for progressive renal function loss, not only in subjects with renal disease or renal transplant recipients, but also in the general population. Considering the increasing prevalence of obesity worldwide, weight excess may become the main renal risk factor on a population basis, all the more so because the risk is not limited to morbid obesity, but is already apparent in the overweight range. The mechanism of the renal risk is multifactorial. In addition to the role of comorbid conditions such as hypertension and diabetes, current evidence supports a pathogenetic role for renal hemodynamics, specifically glomerular hyperfiltration, and also glomerular hypertension. Weight excess is associated with an elevated glomerular filtration rate and a less pronounced rise in renal plasma flow, resulting in an elevated filtration fraction. This suggests glomerular hypertension due to afferent-efferent dysbalance, which impairs glomerular protection from systemic hypertension. Data in renal transplant recipients support the pathogenetic role of elevated glomerular pressure for long-term renal prognosis. Blockade of the renin-angiotensin-aldosterone system can reverse the renal hemodynamic abnormalities. The obesity-associated renal risk is unfavourably affected by high sodium intake. This may be due to the effects of sodium on blood pressure, which is often sodium-sensitive in obesity, but direct renal effects are also present. Interestingly, sodium restriction ameliorates overweight-associated hyperfiltration in overweight subjects. More focus on weight excess as a renal risk factor is warranted. Preventive measures should focus on weight excess as well as on specific protection against renal damage, by renin-angiotensin-aldosterone system-blockade and moderate sodium restriction.

Salt and cardiovascular disease

Legislation to cut levels of salt in processed food is necessary and justified