High sodium-low potassium environment and hypertension

Modifying Dietary Sodium and Potassium Intake: An End to the 'Salt Wars'?

Excessive salt intake raises blood pressure, but the implications of this observation for human health have remained contentious. It has also been recognized for many years that potassium intake may mitigate the effects of salt intake on blood pressure and possibly on outcomes such as stroke. Recent large randomized intervention trials have provided strong support for the benefits of replacing salt (NaCl) with salt substitute (75% NaCl, 25% KCl) on hard outcomes, including stroke. During the same period of time, major advances have been made in understanding how the body senses and tastes salt, and how these sensations drive intake. Additionally, new insights into the complex interactions between systems that control sodium and potassium excretion by the kidneys, and the brain have highlighted the existence of a potassium switch in the kidney distal nephron. This switch seems to contribute importantly to the blood pressure-lowering effects of potassium intake. In recognition of these evolving data, the United States Food and Drug Administration is moving to permit potassium-containing salt substitutes in food manufacturing. Given that previous attempts to reduce salt consumption have not been successful, this new approach has a chance of improving health and ending the 'Salt Wars'.

Research trends and hotpots on the relationship between high salt and hypertension: A bibliometric and visualized analysis

INTRODUCTION

A high salt diet is a significant risk factor for hypertension, and scholarly investigations into this relationship have garnered considerable attention worldwide. However, bibliometric analyses in this field remain underdeveloped. This study aimed to conduct a bibliometric and visual analysis of research progress on the link between high salt and hypertension from 2011 to 2022 with the goal of identifying future research trends and providing valuable insights for this field.

METHODS

High salt and hypertension data were obtained from the Web of Science Core Collection database. Microsoft Excel, Scimago Graphica, CiteSpace, and VOSviewer software were employed to analyze publication output trends, the most productive countries or regions, journals, authors, co-cited references, and keywords.

RESULTS

After screening, 1470 papers met the inclusion criteria. Relevant publications increased annually by 3.66% from 2011 to 2022. The United States led in research productivity, with The Journal of Hypertension publishing the most papers, and David L. Mattson as the most prolific author. Oxidative stress has emerged as a prominent research topic, and extensive investigations have been conducted on related mechanisms. "Oxidative stress," "gut microbiota," and "kidney injury" are recent hotspots that are expected to remain so, and this study carefully characterizes the mechanism of high salt-induced hypertension based on these hotspots.

CONCLUSION

This study utilized bibliometric and visualization analysis to identify the development trends and hotspots of publications related to high salt and hypertension. The findings of this study offer valuable insights into the forefront of emerging trends and future directions in this field.

Eating behaviour of Indonesian adolescents: a systematic review of the literature

OBJECTIVES

Global evidence has shown that behaviour acquired during adolescence often lasts into adulthood. Diet quality of and malnutrition in Indonesian adolescents is a neglected area of research. The current study reviews all studies related to eating behaviour in Indonesian adolescents to support evidence-based policy to improve diets.

DESIGN

We searched electronic databases (six international and one local), from January 2000 to April 2018. The search terms used were (1) prevalence (prevalence OR number* OR case*, incidence OR survey), (2) adolescents (adolescen* OR school-age OR young adult), (3) Indonesia (Indonesia*) and (4) eating pattern (eat* OR fruit OR vegetable OR food recall OR food OR frequenc* OR consumption OR dietary intake). Articles were assessed against a critical appraisal tool.

SETTING

Indonesia.

PARTICIPANTS

10-19 years.

RESULTS

We discovered 15 studies related to eating behaviour, 5 of which were secondary analyses of nationally representative surveys and one was a nationwide survey. Of the nine studies, one study was conducted in multiple cities, and the rest were conducted in a single city or smaller area. There were seven main topics from the included studies: nutrient adequacy, fruit and vegetable consumption, water and beverage intake, Na intake, breakfast habit, snacking frequency and western fast food consumption.

CONCLUSIONS

Adolescents consume inadequate amounts of protein, fruits and vegetables, and excessive amounts of Na and western fast food. Measures are needed to improve and motivate adolescents to adopt healthier eating patterns. Furthermore, there is a need to have one standard definition and measurement of eating behaviour in Indonesia.

Effects of extreme potassium stress on blood pressure and renal tubular sodium transport

We characterized mouse blood pressure and ion transport in the setting of commonly used rodent diets that drive K⁺ intake to the extremes of deficiency and excess. Male 129S2/Sv mice were fed either K⁺-deficient, control, high-K⁺ basic, or high-KCl diets for 10 days. Mice maintained on a K⁺-deficient diet exhibited no change in blood pressure, whereas K⁺-loaded mice developed an ~10-mmHg blood pressure increase. Following challenge with NaCl, K⁺-deficient mice developed a salt-sensitive 8 mmHg increase in blood pressure, whereas blood pressure was unchanged in mice fed high-K⁺ diets. Notably, 10 days of K⁺ depletion induced diabetes insipidus and upregulation of phosphorylated NaCl cotransporter, proximal Na⁺ transporters, and pendrin, likely contributing to the K⁺-deficient NaCl sensitivity. While the anionic content with high-K⁺ diets had distinct effects on transporter expression along the nephron, both K⁺ basic and KCl diets had a similar increase in blood pressure. The blood pressure elevation on high-K⁺ diets correlated with increased Na⁺-K⁺-2Cl^- cotransporter and γ-epithelial Na⁺ channel expression and increased urinary response to furosemide and amiloride. We conclude that the dietary K⁺ maneuvers used here did not recapitulate the inverse effects of K⁺ on blood pressure observed in human epidemiological studies. This may be due to the extreme degree of K⁺ stress, the low-Na⁺-to-K⁺ ratio, the duration of treatment, and the development of other coinciding events, such as diabetes insipidus. These factors must be taken into consideration when studying the physiological effects of dietary K⁺ loading and depletion.

The association of estimated salt intake with blood pressure in a Viet Nam national survey

OBJECTIVE

To evaluate the association of salt consumption with blood pressure in Viet Nam, a developing country with a high level of salt consumption.

DESIGN AND SETTING

Analysis of a nationally representative sample of Vietnamese adults 25-65 years of age who were surveyed using the World Health Organization STEPwise approach to Surveillance protocol. Participants who reported acute illness, pregnancy, or current use of antihypertensive medications were excluded. Daily salt consumption was estimated from fasting mid-morning spot urine samples. Associations of salt consumption with systolic blood pressure and prevalent hypertension were assessed using adjusted linear and generalized linear models. Interaction terms were tested to assess differences by age, smoking, alcohol consumption, and rural/urban status.

RESULTS

The analysis included 2,333 participants (mean age: 37 years, 46% male, 33% urban). The average estimated salt consumption was 10g/day. No associations of salt consumption with blood pressure or prevalent hypertension were observed at a national scale in men or women. The associations did not differ in subgroups defined by age, smoking, or alcohol consumption; however, associations differed between urban and rural participants (p-value for interaction of urban/rural status with salt consumption, p = 0.02), suggesting that higher salt consumption may be associated with higher systolic blood pressure in urban residents but lower systolic blood pressure in rural residents.

CONCLUSIONS

Although there was no evidence of an association at a national level, associations of salt consumption with blood pressure differed between urban and rural residents in Viet Nam. The reasons for this differential association are not clear, and given the large rate of rural to urban migration experienced in Viet Nam, this topic warrants further investigation.

Plasma Lycopene Is Associated with Pizza and Pasta Consumption in Middle-Aged and Older African American and White Adults in the Southeastern USA in a Cross-Sectional Study

BACKGROUND

The role of dietary lycopene in chronic disease prevention is not well known.

METHODS

This study examined intake of lycopene and other antioxidants from lycopene-rich foods (e.g., pizza and pasta) simultaneously with plasma levels of lycopene and other antioxidants in a representative cross-sectional sample (187 Blacks, 182 Whites, 40-79 years old) from the Southern Community Cohort Study (SCCS). The SCCS is an ongoing study conducted in populations at high risk for chronic diseases living in Southeastern United States. Dietary intake was assessed using a validated food frequency questionnaire (FFQ), and plasma levels of lycopene and other antioxidants were measured at baseline (2002-2005). The participants were classified into tertiles according to consumption of pizza and pasta food groups.

RESULTS

Lycopene dietary intake and plasma lycopene concentrations were significantly higher in the highest (tertile 3) compared to tertiles 1 and 2 (both P < 0.01). Total energy intake ranged from 1964.3 ± 117.1 kcal/day (tertile 1) to 3277.7 ± 115.8 kcal/day (tertile 3) (P<0.0001). After adjusting for age and energy intake, total dietary fat, saturated fatty acids, trans-fatty acids, and sodium intakes were significantly higher in tertile 3 than tertiles 2 and 1 (all P <0.01). Vitamin C intake was significantly lower in tertile 3 than tertiles 1 and 2 (P = 0.003). Except for γ-tocopherol being higher in tertile 3 than tertiles 1 and 2 (P = 0.015), the plasma concentrations of antioxidants were lower in tertile 3 than tertiles 1 and 2 (β-carotene, α-carotene, lutein and zeaxanthin, all P<0.05).

CONCLUSIONS

In the SCCS population, pizza and pasta were the main sources of dietary lycopene and their intake was associated with plasma lycopene concentration. Diets with frequent pizza and pasta consumption were high in energy, saturated fatty acids, trans-fatty acids, sodium and low in other antioxidants. Future studies of lycopene as a protective dietary factor against chronic disease should consider the overall nutritional quality of lycopene-containing foods.

Dietary intake of metals by the young adult population of Eastern Poland: Results from a market basket study

Dietary intake of macro-, trace and toxic elements was determined among the young adult population of Eastern Poland. The study was performed in 2011-2013 and involved 583 participants living in Lublin and its province. Dietary intakes of metals were determined using a 24h dietary recall technique and a market basket method. The analytical quantification of As, Ca, Cd, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Se and Zn was performed using ICP-MS technique, whereas the content of mercury was determined using the Mercury Analyzer. Performed investigations revealed that daily dietary intakes of the majority of the study elements (macro- and trace) and toxic elements such as As, Pb or Hg are within the range of reference values. However, high consumption of Na and improper Na/K ratio combined with low intake of Mg may be harmful to the health of the population. Moreover, obtained data suggest that the risk of developing diseases among population in Eastern Poland related to high exposure to Ni and Cd absorbed from foodstuffs was high.

Liver Fibrosis Can Be Induced by High Salt Intake through Excess Reactive Oxygen Species (ROS) Production

High salt intake has been known to cause hypertension and other side effects. However, it is still unclear whether it also affects fibrosis in the mature or developing liver. This study demonstrates that high salt exposure in mice (4% NaCl in drinking water) and chick embryo (calculated final osmolality of the egg was 300 mosm/L) could lead to derangement of the hepatic cords and liver fibrosis using H&E, PAS, Masson, and Sirius red staining. Meanwhile, Desmin immunofluorescent staining of mouse and chick embryo livers indicated that hepatic stellate cells were activated after the high salt exposure. pHIS3 and BrdU immunohistological staining of mouse and chick embryo livers indicated that cell proliferation decreased; as well, TUNEL analyses indicated that cell apoptosis increased in the presence of high salt exposure. Next, dihydroethidium staining on the cultured chick hepatocytes indicated the excess ROS was generated following high salt exposure. Furthermore, AAPH (a known inducer of ROS production) treatment also induced the liver fibrosis in chick embryo. Positive Nrf2 and Keap1 immunohistological staining on mouse liver suggested that Nrf2/Keap1 signaling was involved in high salt induced ROS production. Finally, the CCK8 assay was used to determine whether or not the growth inhibitory effect induced by high salt exposure can be rescued by antioxidant vitamin C. Meanwhile, the RT-PCR result indicated that the Nrf2/Keap1 downsteam genes including HO-1, NQO-1, and SOD2 were involved in this process. In sum, these experiments suggest that high salt intake would lead to high risk of liver damage and fibrosis in both adults and developing embryos. The pathological mechanism may be the result from an imbalance between oxidative stress and the antioxidant system.

Environmental origins of hypertension: phylogeny, ontogeny and epigenetics

Hypertension and renal parenchymal disease are intricately linked. Primary renal parenchymal disease can impact on sodium and volume regulation and lead to hypertension, while arterial hypertension can induce renal parenchymal injury and precipitate renal dysfunction. The examination for clues to the environmental origins of renal disease and hypertension necessitates an approach that integrates epidemiology, clinical medicine, developmental biology, environmental science and epigenetics, such that the manner in which genes and the environment interact can be better understood to pave the way for innovative management paradigms with regards to prevention, diagnosis and treatment. This review summarizes the extant literature and provides cogent arguments for the need to evaluate chronic adult onset disease models such as hypertension and renal disease from the modern perspective that takes into account prenatal exposures, the intrauterine environment and development, postnatal growth and transgenerational epigenetic modifications with their attendant future disease risk from the individual to the population level.

Dietary contributors to hypertension in adults reviewed

Recent national surveys which measured respondents' blood pressure (BP) levels have shown a high prevalence of hypertension amongst the Irish population, with approximately two-thirds of men and over half of women aged 45 years and over affected. Higher prevalence rates are observed with advancing age. Established diet- and lifestyle-related risk factors for hypertension such as high salt intake, high alcohol consumption and physical inactivity are pervasive in Ireland and are believed to contribute significantly to the high national prevalence of this condition. Additional dietary deficits have been implicated in the development of hypertension, however, including low fruit and vegetable intake, low dairy food consumption and low intake of oily fish. Deficiencies of single micro-nutrients such as folate, riboflavin, vitamin C and vitamin D have also been recently recognised as risk factors for hypertension. For each of these factors, there is evidence that the food and nutrient intakes of many Irish adults fall short of the ideal. These dietary and nutritional deficits, when superimposed on Ireland's existing health-subversive behaviours and escalating rates of obesity, constitute a potent constellation of risk factors for hypertension. However, they also represent viable and potentially effective targets for health promotion initiatives. This review aims to describe the main nutritional, dietary and lifestyle contributors to hypertension in Ireland with a view to informing future interventions aimed at alleviating Ireland's burden of hypertensive disease.

High energy diets-induced metabolic and prediabetic painful polyneuropathy in rats

To establish the role of the metabolic state in the pathogenesis of polyneuropathy, an age- and sex-matched, longitudinal study in rats fed high-fat and high-sucrose diets (HFSD) or high-fat, high-sucrose and high-salt diets (HFSSD) relative to controls was performed. Time courses of body weight, systolic blood pressure, fasting plasma glucose (FPG), insulin, free fatty acids (FFA), homeostasis model assessment-insulin resistance index (HOMA-IR), thermal and mechanical sensitivity and motor coordination were measured in parallel. Finally, large and small myelinated fibers (LMF, SMF) as well as unmyelinated fibers (UMF) in the sciatic nerves and ascending fibers in the spinal dorsal column were quantitatively assessed under electron microscopy. The results showed that early metabolic syndrome (hyperinsulinemia, dyslipidemia, and hypertension) and prediabetic conditions (impaired fasting glucose) could be induced by high energy diet, and these animals later developed painful polyneuropathy characterized by myelin breakdown and LMF loss in both peripheral and central nervous system. In contrast SMF and UMF in the sciatic nerves were changed little, in the same animals. Therefore the phenomenon that high energy diets induce bilateral mechanical, but not thermal, pain hypersensitivity is reflected by severe damage to LMF, but mild damage to SMF and UMF. Moreover, dietary sodium (high-salt) deteriorates the neuropathic pathological process induced by high energy diets, but paradoxically high salt consumption, may reduce, at least temporarily, chronic pain perception in these animals.

Flutamide increases aldosterone levels in gonadectomized male but not female Wistar rats

BACKGROUND

Sex-specific differences in blood pressure (BP) suggest an important modulating role of testosterone in the kidney. However, little is known about the interaction between androgens and the mineralocorticoid aldosterone. Our objective was to determine the effects of testosterone in gonadectomized male and female rats on a low-salt diet, and to determine the effect of androgen receptor (AR) blockade by flutamide on BP and on aldosterone levels.

METHODS

Normotensive male and female Wistar rats were gonadectomized and put on a low-salt diet. They were treated for 16 days with testosterone or placebo. In addition, the animals received the AR antagonist flutamide or placebo, respectively. BP was measured by tail-cuff method, 24-h urine samples were collected in metabolic cages and blood was collected for hormonal measurements.

RESULTS

Testosterone increased BP in males and females, and this effect could be blocked by flutamide. Flutamide treatment itself significantly increased aldosterone levels in male but not in female rats. These elevated aldosterone levels could be lowered by testosterone treatment during AR blockade. Accordingly to aldosterone levels, flutamide increased in males the serum sodium/potassium to urinary sodium/potassium ratio, an in vivo indicator of renal aldosterone action.

CONCLUSIONS

Testosterone regulates BP in male and female gonadectomized rats via the AR. Flutamide by itself exerts influence over aldosterone in the absence of gonadal steroid replacement suggesting AR involvement in renal sodium handling. These flutamide effects were sex-specific and not seen in female rats.

Habitual dietary sodium intake is inversely associated with coronary flow reserve in middle-aged male twins

BACKGROUND

Evidence links dietary sodium to hypertension and cardiovascular disease (CVD), but investigation of its influence on cardiovascular function is limited.

OBJECTIVE

We examined the relation between habitual dietary sodium and coronary flow reserve (CFR), which is a measure of overall coronary vasodilator capacity and microvascular function. We hypothesized that increased sodium consumption is associated with lower CFR.

DESIGN

Habitual daily sodium intake for the previous 12 mo was measured in 286 male middle-aged twins (133 monozygotic and dizygotic pairs and 20 unpaired twins) by using the Willett food-frequency questionnaire. CFR was measured by positron emission tomography [N(13)]-ammonia, with quantitation of myocardial blood flow at rest and after adenosine stress. Mixed-effects regression analysis was used to assess the association between dietary sodium and CFR.

RESULTS

An increase in dietary sodium of 1000 mg/d was associated with a 10.0% lower CFR (95% CI: -17.0%, -2.5%) after adjustment for demographic, lifestyle, nutritional, and CVD risk factors (P = 0.01). Across quintiles of sodium consumption, dietary sodium was inversely associated with CFR (P-trend = 0.03), with the top quintile (>1456 mg/d) having a 20% lower CFR than the bottom quintile (<732 mg /d). This association also persisted within pairs: a 1000-mg/d difference in dietary sodium between brothers was associated with a 10.3% difference in CFR after adjustment for potential confounders (P = 0.02).

CONCLUSIONS

Habitual dietary sodium is inversely associated with CFR independent of CVD risk factors and shared familial and genetic factors. Our study suggests a potential novel mechanism for the adverse effects of dietary sodium on the cardiovascular system. This trial was registered at clinicaltrials.gov as NCT00017836.

The central mechanism underlying hypertension: a review of the roles of sodium ions, epithelial sodium channels, the renin-angiotensin-aldosterone system, oxidative stress and endogenous digitalis in the brain

The central nervous system has a key role in regulating the circulatory system by modulating the sympathetic and parasympathetic nervous systems, pituitary hormone release, and the baroreceptor reflex. Digoxin- and ouabain-like immunoreactive materials were found >20 years ago in the hypothalamic nuclei. These factors appeared to localize to the paraventricular and supraoptic nuclei and the nerve fibers at the circumventricular organs and supposed to affect electrolyte balance and blood pressure. The turnover rate of these materials increases with increasing sodium intake. As intracerebroventricular injection of ouabain increases blood pressure via sympathetic activation, an endogenous digitalis-like factor (EDLF) was thought to regulate cardiovascular system-related functions in the brain, particularly after sodium loading. Experiments conducted mainly in rats revealed that the mechanism of action of ouabain in the brain involves sodium ions, epithelial sodium channels (ENaCs) and the renin-angiotensin-aldosterone system (RAAS), all of which are affected by sodium loading. Rats fed a high-sodium diet develop elevated sodium levels in their cerebrospinal fluid, which activates ENaCs. Activated ENaCs and/or increased intracellular sodium in neurons activate the RAAS; this releases EDLF in the brain, activating the sympathetic nervous system. The RAAS promotes oxidative stress in the brain, further activating the RAAS and augmenting sympathetic outflow. Angiotensin II and aldosterone of peripheral origin act in the brain to activate this cascade, increasing sympathetic outflow and leading to hypertension. Thus, the brain Na(+)-ENaC-RAAS-EDLF axis activates sympathetic outflow and has a crucial role in essential and secondary hypertension. This report provides an overview of the central mechanism underlying hypertension and discusses the use of antihypertensive agents.

The meaning of hypokalemia in heart failure

Maintenance of normal potassium (K(+)) homeostasis has become an increasingly important limiting factor in the therapy of heart failure (HF). With the application of loop diuretics and digoxin, hypokalemia has become a frequent and feared side effect of treatment. Low serum K(+) in HF may be also a marker of increased neurohormonal activity and disease progression. To gain the maximum benefit from treatment, we need to individualize drug use and carefully monitor electrolytes. Symptomatic HF patients (New York Heart Association class III-IV) should be prescribed the lowest dose of diuretic necessary to maintain euvolemia. Mild hypokalemia may be corrected by the use of aldosterone receptor antagonists such as spironolactone or eplerenone. However, a more severe hypokalemia should preferably be corrected using K(+) supplement. Serum K levels should be frequently checked and maintained between 4.0 and 5.5 mEq/l (mmol/l).

Taste mixture interactions: suppression, additivity, and the predominance of sweetness

Most of what is known about taste interactions has come from studies of binary mixtures. The primary goal of this study was to determine whether asymmetries in suppression between stimuli in binary mixtures predict the perception of tastes in more complex mixtures (e.g., ternary and quaternary mixtures). Also of interest was the longstanding question of whether overall taste intensity derives from the sum of the tastes perceived within a mixture (perceptual additivity) or from the sum of the perceived intensities of the individual stimuli (stimulus additivity). Using the general labeled magnitude scale together with a sip-and-spit procedure, we asked subjects to rate overall taste intensity and the sweetness, sourness, saltiness and bitterness of approximately equi-intense sucrose, NaCl, citric acid and QSO(4) stimuli presented alone and in all possible binary, ternary and quaternary mixtures. The results showed a consistent pattern of mixture suppression in which sucrose sweetness tended to be both the least suppressed quality and the strongest suppressor of other tastes. The overall intensity of mixtures was found to be predicted best by perceptual additivity. A second experiment that was designed to rule out potentially confounding effects of the order of taste ratings and the temperature of taste solutions replicated the main findings of the first experiment. Overall, the results imply that mixture suppression favors perception of sweet carbohydrates in foods at the expense of other potentially harmful ingredients, such as high levels of sodium (saltiness) and potential poisons or spoilage (bitterness and sourness).

High-salt diet during pregnancy and angiotensin-related cardiac changes

OBJECTIVES

High-salt intake has been demonstrated in link to hypertension, and cardiovascular diseases could be programmed in fetal origins. We determined the influence of high-salt diet during pregnancy on the development of the heart.

METHODS

Fetal cardiac structures, cell cycle, renin-angiotensin system (RAS), and epigenetic alternations in the heart following maternal high salt intake during pregnancy were examined.

RESULTS

Following exposure to high salt, disorganized myofibrillae and mitochondria cristae loss were found in the fetus, S-phase for cardiac cells was enhanced, plasma angiotensin II decreased, and cardiac angiotensin II increased in the fetus. Angiotensin II-increased S-phase in the fetal cardiac cells was primarily via AT1 receptor mechanisms. AT2 receptor mRNA and protein in the fetal heart were not affected, whereas AT1 receptor protein, AT1a, and AT1b mRNA were increased. DNA methylation was found at the CpG sites that were related to AT1b receptors in the fetal heart. Cardiac AT1 receptor protein in the adult offspring was also higher following exposure to prenatal high salt.

CONCLUSION

The results suggest a relationship between high-salt diet in pregnancy and developmental changes of the cardiac cells and renin-angiotensin system.

Carotid chemoreceptor reflexes following dietary salt loading in rats

There is a strong association between salt intake and hypertension. Alterations in baroreceptor activity, which precede and contribute to the elevation in blood pressure, have also been shown to affect chemoreceptor reflex response. Dietary salt loading with 8% sodium chloride was carried out in Sprague Dawley rats aged 8 weeks for a period of 5-6 weeks. Blood pressure was thereafter recorded under anaesthesia from the common carotid artery with a Grass Polygraph 7D model, whereas serum Na and K concentrations were measured using a flame photometer. Salt loading resulted in elevated arterial blood pressure as well as hypokalaemia. Stimulation of the carotid chemoreceptor by injection of sodium dithionite resulted in elevated arterial blood pressure, decreased heart rate and hyperventilation in both control and salt-loaded rats. However, the bradycardic response as estimated by the difference in percentage reduction in heart rate was significantly higher in salt rats (36%) than in the control rats (10%). The results indicate that a high-salt diet results in enhanced bradycardic response to carotid chemoreceptor stimulation and that this observation may be related to the attendant hypokalaemia.

Hydrochlorothiazide and potassium chloride in comparison with hydrochlorothiazide and amiloride in the treatment of mild hypertension

A randomized, double-blind, cross-over study comparing 50 mg hydrochlorothiazide plus 5 mg amiloride (HCTZ/A) with 50 mg hydrochlorothiazide plus 26 mmol potassium chloride (HCTZ/K) was conducted in 18 patients with mild essential hypertension (diastolic pressure 90-105 mmHg). The sequence of treatment was: placebo for 2 weeks, one active drug for 3 weeks, placebo for 2 weeks, the other active drug for 3 weeks. The two agents were significantly and equally efficacious in lowering the systolic and diastolic blood pressure. Baseline vs. treatment mean serum potassium levels were 3.82 vs. 3.78 mmol/l for HCTZ/A and 3.82 vs. 3.70 mmol/l for HCTZ/K. The decrease in serum potassium level from baseline was significant for both agents but not significantly different when the two treatment forms were compared. Both treatment forms elevated fasting serum cholesterol and glucose. Serum triglycerides and uric acid rose significantly with HCTZ/K. Amiloride may affect the tubular handling of uric acid causing increased uric acid excretion, thus counteracting thiazide-induced hyperuricemia. During 3 weeks' extension of the main study, 5 patients received HCTZ/A in double the original dose (100 mg/10 mg) and 6 patients received HCTZ/K in double the original dose (100 mg/52 mmol). No further blood pressure reduction was observed on treatment with these doses. The mean serum potassium levels did not decrease further on doubling the HCTZ/A dose, while a significant fall was observed for HCTZ/K (3.60 vs. 3.42 mmol/l) (p less than 0.05, single tailed t-test). Both drug combinations were well tolerated and side-effects were not significantly different from those during placebo administration. This study demonstrates that 50 mg hydrochlorothiazide plus 26 mmol potassium chloride are as effective as 50 mg hydrochlorothiazide plus 5 mg amiloride, both in reducing blood pressure and preventing hypokalaemia in the treatment of essential hypertension. A small extension study indicates that amiloride might be more effective than potassium chloride in preventing hypokalaemia when high doses (100 mg/day) of hydrochlorothiazide are administered.

Comparison of energy and nutrient intakes in women with high and low blood pressure levels

The present study found no link between the intake of energy and various nutrients, on the one hand, and high or low blood pressure (BP) in women, on the other. Sixty women not on treatment for hypertension were selected from a defined population and examined, applying the duplicate portion technique, with respect to the relationships between BP and the intake of energy and nutrients. They were selected from above the 95th percentile for BP (group A) and from below the 30th (group B). The two groups were age-matched. The food sampling comprised six days, divided into three periods of two consecutive days within a period of four weeks. Twenty-four hour urine specimens were collected in each period and on two other occasions. The mean values for intake of energy, fat, protein, carbohydrates, minerals and electrolytes did not differ between the two groups despite the large differences in BP and obesity. The mean values for urinary excretion of minerals, electrolytes and nitrogen (calculated as crude protein) did not differ between groups. The present findings for the effect of salt on BP do not justify restriction of the salt intake as a means for decreasing BP in the population.

Effect of potassium-enriched salt on cardiovascular mortality and medical expenses of elderly men

BACKGROUND

The beneficial effects of potassium-enriched salt on blood pressure have been reported in a few short-term trials. The long-term effects of potassium-enriched salt on cardiovascular mortality have not been carefully studied.

OBJECTIVE

The objective was to examine the effects of potassium-enriched salt on cardiovascular disease (CVD) mortality and medical expenditures in elderly veterans.

DESIGN

Five kitchens of a veteran retirement home were randomized into 2 groups (experimental or control) and veterans assigned to those kitchens were given either potassium-enriched salt (experimental group) or regular salt (control group) for approximately 31 mo. Information on death, health insurance claims, and dates that veterans moved in or out of the home was gathered.

RESULTS

Altogether, 1981 veterans, 768 in the experimental [x (+/-SD) age: 74.8 +/- 7.1 y] and 1213 in the control (age: 74.9 +/- 6.7 y) groups, were included in the analysis. The experimental group had better CVD survivorship than did the control group. The incidence of CVD-related deaths was 13.1 per 1000 persons (27 deaths in 2057 person-years) and 20.5 per 1000 (66 deaths in 3218 person-years) for the experimental and control groups, respectively. A significant reduction in CVD mortality (age-adjusted hazard ratio: 0.59; 95% CI: 0.37, 0.95) was observed in the experimental group. Persons in the experimental group lived 0.3-0.90 y longer and spent significantly less (approximately US Dollars 426/y) in inpatient care for CVD than did the control group, after control for age and previous hospitalization expenditures.

CONCLUSIONS

This study showed a long-term beneficial effect on CVD mortality and medical expenditure associated with a switch from regular salt to potassium-enriched salt in a group of elderly veterans. The effect was likely due to a major increase in potassium and a moderate reduction in sodium intakes.

Pathogenesis and etiology of essential hypertension: role of dietary carbohydrate

The development of essential hypertension (EH) is proposed to be the result of a cascade of metabolic alterations, with high insulin levels/hyperinsulinemia and an abnormal reaction to the vasodilatory effect of insulin as the initiating factors. It is well established that insulin causes vasodilatation of peripheral resistance vessels. In normal subjects, this insulin-induced vasodilatation and decrease of the peripheral vascular resistance (PVR) is compensated by an SNS-mediated re-vasoconstriction in order to avoid hypotension, with the net effect of a slight decrease in blood pressure and no significant effect on peripheral vascular resistance. In contrast, in genetically predisposed subjects, prone to the development of essential hypertension, the insulin-induced vasodilatation is compensated by an increased heart rate and cardiac output (to avoid hypotension), mediated by an abnormal sympathetic overactivity, (characterised by high norepinephrine spillover rates and (frequently) a hyperdynamic circulation), while the PVR remains low during the early phase of developing EH. During the course of chronic hypertension, the SNS-overactivity leads to progressive trophic alterations of vessel walls, and structural and functional vascular remodeling, with narrowing of arterial resistance vessels and an increasing PVR. Vascular remodeling and lumen narrowing not only affect peripheral resistance vessels, but also kidney vessels. Narrowing and decreased distensibility of preglomerular kidney vessels lead to chronic activation of the Renin-Angiotensin-Aldosterone-System, with reinforcement and fixation of hypertension. High-glycemic index nutrition is suggested to play a key role in the etiology of hypertension: The chronic stimulus of pancreatic beta-cells due to high-glycemic index nutrition may cause cell hypertrophy and dysfunction, resulting in postprandial hyperinsulinemia, and -- in susceptible subjects -- the development of EH. Since significant evidence suggests that hyperinsulinemia also represents a key factor for the development of obesity, insulin resistance and the metabolic syndrome, the well-known common association of EH and these metabolic alterations becomes quite understandable.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure; production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells; as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure;production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells;as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

What is the optimal serum potassium level in cardiovascular patients?

Humans are prone to sodium overload and potassium depletion. This electrolyte imbalance is important in the pathogenesis of cardiovascular disease and sudden cardiac death. Avoiding hypokalemia is beneficial in several cardiovascular disease states including acute myocardial infarction, heart failure, and hypertension. The evidence highlighting the importance of potassium homeostasis in cardiovascular disease and possible mechanisms explaining potassium's benefits are reviewed. Targets for serum potassium concentration are suggested.

IGF-I activity may be a key determinant of stroke risk--a cautionary lesson for vegans

IGF-I acts on vascular endothelium to activate nitric oxide synthase, thereby promoting vascular health; there is reason to believe that this protection is especially crucial to the cerebral vasculature, helping to ward off thrombotic strokes. IGF-I may also promote the structural integrity of cerebral arteries, thereby offering protection from hemorrhagic stroke. These considerations may help to explain why tallness is associated with low stroke risk, whereas growth hormone deficiency increases stroke risk--and why age-adjusted stroke mortality has been exceptionally high in rural Asians eating quasi-vegan diets, but has been declining steadily in Asia as diets have become progressively higher in animal products. There is good reason to suspect that low-fat vegan diets tend to down-regulate systemic IGF-I activity; this effect would be expected to increase stroke risk in vegans. Furthermore, epidemiology suggests that low serum cholesterol, and possibly also a low dietary intake of saturated fat--both characteristic of those adopting low-fat vegan diets--may also increase stroke risk. Vegans are thus well advised to adopt practical countermeasures to minimize stroke risk--the most definitive of which may be salt restriction. A high potassium intake, aerobic exercise training, whole grains, moderate alcohol consumption, low-dose aspirin, statin or policosanol therapy, green tea, and supplementation with fish oil, taurine, arginine, and B vitamins--as well as pharmacotherapy of hypertension if warranted--are other practical measures for lowering stroke risk. Although low-fat vegan diets may markedly reduce risk for coronary disease, diabetes, and many common types of cancer, an increased risk for stroke may represent an 'Achilles heel'. Nonetheless, vegans have the potential to achieve a truly exceptional 'healthspan' if they face this problem forthrightly by restricting salt intake and taking other practical measures that promote cerebrovascular health.

A preliminary fast may potentiate response to a subsequent low-salt, low-fat vegan diet in the management of hypertension - fasting as a strategy for breaking metabolic vicious cycles

Although a salted diet appears to be a sine qua non for the development of essential hypertension, low-salt diets often have a modest or even negligible impact on the blood pressure of hypertensives; this suggests that salt, perhaps often acting in concert with other aspects of a modern, rich diet, may set in place certain metabolic vicious cycles that sustain blood pressure elevation even when dietary salt is eliminated. Therapeutic fasting is known to lower elevated blood pressure - presumably in large part because it minimizes insulin secretion - and may have the potential to break some of these vicious cycles. Goldhamer has recently reported that a regimen comprised of a water-only fast of moderate duration, followed by a transition to a low-fat, low-salt, whole-food vegan diet, achieves dramatic reductions in the blood pressure of hypertensives, such that the large majority of patients can be restored to normotensive status, in the absence of any drug therapy. Although long-term follow-up of these subjects has been sporadic, the available data suggest that these large reductions is blood pressure can be conserved in patients who remain compliant with the follow-up diet - in other words, a 'cure' for hypertension may be feasible. If a protein-sparing modified fast can be shown to be virtually as effective as a total fast for achieving these benefits, it may be possible to implement this regimen safely on an outpatient basis. The ability of therapeutic fasts to break metabolic vicious cycles may also contribute to the efficacy of fasting in the treatment of type 2 diabetes and autoimmune disorders. As a general principle, if a metabolic disorder is susceptible to prevention - but not reversal - by a specific diet, and therapeutic fasting has a temporary favorable impact on this disorder, then a more definitive therapy may consist of a therapeutic fast, followed up by the protective diet as a maintenance regimen.

Sodium-induced rise in blood pressure is suppressed by androgen receptor blockade

Our objective was to test the hypothesis that 1) a high Na (HNa, 3%) diet would increase blood pressure (BP) in male Wistar-Kyoto (WKY) and spontaneously hypertensive Y chromosome (SHR/y) rat strains in a territorial colony; 2) sympathetic nervous system (SNS) blockade using clonidine would lower BP on a HNa diet; and 3) prepubertal androgen receptor blockade with flutamide would lower BP on a HNa diet. A 2 x 4 factorial design used rat strains (WKY, SHR/y) and treatment [0.3% normal Na (NNa), 3% HNa, HNa/clonidine, and HNa/flutamide]. BP increased in both strains on the HNa diet (P < 0.0001). There was no significant decrease in BP in either strain with clonidine treatment. Androgen receptor blockade with flutamide significantly decreased BP in both strains (P < 0.0001) and normalized BP in the SHR/y colony. Neither heart rate nor activity could explain these BP differences. In conclusion, a Na sensitivity was observed in both strains, which was reduced to normotensive values by androgen blockade but not by SNS blockade.

Up-regulation of endothelial nitric oxide activity as a central strategy for prevention of ischemic stroke - just say NO to stroke!

Nitric oxide (NO) produced by the endothelium of cerebral arterioles is an important mediator of endothelium-dependent vasodilation (EDV), and also helps to prevent thrombosis and vascular remodeling. A number of risk factors for ischemic stroke are associated with impaired EDV, and this defect is usually at least partially attributable to a decrease in the production and/or stability of NO. These risk factors include hypertension, high-sodium diets, homocysteine, diabetes, visceral obesity, and aging. Conversely, many measures which may provide protection from ischemic stroke - such as ample dietary intakes of potassium, arginine, fish oil, and selenium - can have a favorable impact on EDV. Protection afforded by exercise training, estrogen replacement, statin drugs, green tea polyphenols, and cruciferous vegetables may reflect increased expression of the endothelial NO synthase. IGF-I activity stimulates endothelial NO production, and conceivably is a mediator of the protection associated with higher-protein diets in Japanese epidemiology and in hypertensive rats. These considerations prompt the conclusion that modulation of NO availability is a crucial determinant of risk for ischemic stroke. Multifactorial strategies for promoting effective cerebrovascular NO activity, complemented by measures that stabilize platelets and moderate blood viscosity, should minimize risk for ischemic stroke and help maintain vigorous cerebral perfusion into ripe old age. The possibility that such measures will also diminish risk for Alzheimer's disease, and slow the normal age-related decline in mental acuity, merits consideration. A limited amount of ecologic epidemiology suggests that both stroke and senile dementia may be extremely rare in cultures still consuming traditional unsalted whole-food diets. Other lines of evidence suggest that promotion of endothelial NO activity may decrease risk for age-related macular degeneration.

Ontogenetic aspects of hypertension development: analysis in the rat

In this review, we attempt to outline the age-dependent interactions of principal systems controlling the structure and function of the cardiovascular system in immature rats developing hypertension. We focus our attention on the cardiovascular effects of various pharmacological, nutritional, and behavioral interventions applied at different stages of ontogeny. Several distinct critical periods (developmental windows), in which particular stimuli affect the further development of the cardiovascular phenotype, are specified in the rat. It is evident that short-term transient treatment of genetically hypertensive rats with certain antihypertensive drugs in prepuberty and puberty (at the age of 4-10 wk) has long-term beneficial effects on further development of their cardiovascular apparatus. This juvenile critical period coincides with the period of high susceptibility to the hypertensive effects of increased salt intake. If the hypertensive process develops after this critical period (due to early antihypertensive treatment or late administration of certain hypertensive stimuli, e.g., high salt intake), blood pressure elevation, cardiovascular hypertrophy, connective tissue accumulation, and end-organ damage are considerably attenuated compared with rats developing hypertension during the juvenile critical period. As far as the role of various electrolytes in blood pressure modulation is concerned, prohypertensive effects of dietary Na+ and antihypertensive effects of dietary Ca2+ are enhanced in immature animals, whereas vascular protective and antihypertensive effects of dietary K+ are almost independent of age. At a given level of dietary electrolyte intake, the balance between dietary carbohydrate and fat intake can modify blood pressure even in rats with established hypertension, but dietary protein intake affects the blood pressure development in immature animals only. Dietary protein restriction during gestation, as well as altered mother-offspring interactions in the suckling period, might have important long-term hypertensive consequences. The critical periods (developmental windows) should be respected in the future pharmacological or gene therapy of human hypertension.

Endothelial membrane potential regulates production of both nitric oxide and superoxide--a fundamental determinant of vascular health

There is recent evidence that the membrane potential of vascular endothelium regulates not only nitric oxide (NO) synthesis, but also superoxide generation, such that hyperpolarization stimulates NO production while suppressing that of superoxide. Given that NO works in a variety of ways to inhibit atherothrombotic disease and hypertension, whereas superoxide not only vetoes the benefits of NO but also disrupts endothelial metabolism and promotes LDL oxidation through its oxidant activity, it is thus evident that endothelium membrane potential is a crucial determinant of cardiovascular risk. Membrane polarization can be enhanced by measures which increase the synthesis or availability of the Na+-K+-ATPase, moderately enhance serum K+ and increase the conductance of membrane K+ channels. Such measures may include high-K+/low-Na+ natural diets, insulin sensitizing modalities, 'euthyroid replacement therapy' and ACE inhibitors. Epidemiological correlations of insulin resistance with hypertension and cardiovascular risk may reflect the low membrane potential of insulin-resistant vascular endothelium. Adjunctive measures for suppressing the generation or half-life of endothelial superoxide are suggested.

Elemental analysis of blood of Nigerian hypertensive subjects

Proton-induced X-ray emission (PIXE) has been used to obtain the concentrations of 11 elements (P, S, Cl, K, Ca, Fe, Cu, Zn, Br, Rb, and Cd) in whole-blood samples of 16 hypertensive subjects (mean age: 52.5 +/- 0.5 yr) and 18 age-matched controls (mean age: 51.5 +/- 0.5 yr) in a Nigerian population. The results of the study indicate that the hypertensive subjects have significantly higher mean concentration of Cl, Cd, Cu, and Zn when compared with the controls, and the mean concentration of P, K, and Ca was found to be significantly lower in the hypertensive group in comparison to the controls. Furthermore, the Zn:Cd ratio was found to be significantly higher in the controls than in the hypertensives, and the Cu:Zn ratio was significantly higher in the hypertensives.

The effects of potassium depletion and supplementation on blood pressure: a clinical review

Nonpharmacologic treatment currently is recognized as an important part in the treatment of hypertension, and the role of dietary potassium intake in blood pressure (BP) control is becoming quite evident. Clinical studies have examined the mechanism by which hypokalemia can increase BP and the benefit of a large potassium intake on BP control. Epidemiologic data suggest that potassium intake and BP are correlated inversely. In normotensive subjects, those who are salt sensitive or who have a family history of hypertension appear to benefit most from the hypotensive effects of potassium supplementation. The greatest hypotensive effect of potassium supplementation occurs in patients with severe hypertension. This effect is pronounced with prolonged potassium supplementation. The antihypertensive effect of increased potassium intake appears to be mediated by several factors, which include enhancing natriuresis, modulating baroreflex sensitivity, direct vasodilation, or lowering cardiovascular reactivity to norepinephrine or angiotensin II. Potassium repletion in patients with diuretic-induced hypokalemia improves BP control. An increase in potassium intake should be included in the nonpharmacologic management of patients with uncomplicated hypertension.

Up-regulation of intracellular signalling pathways may play a central pathogenic role in hypertension, atherogenesis, insulin resistance, and cancer promotion--the 'PKC syndrome'

The modern diet is greatly different from that of our paleolithic forebears' in a number of respects. There is reason to believe that many of these dietary shifts can up-regulate intracellular signalling pathways mediated by free intracellular calcium and protein kinase C, particularly in vascular smooth muscle cells; this disorder of intracellular regulation is given the name 'PKC syndrome'. PKC syndrome may entail either a constitutive activation of these pathways, or a sensitization to activation by various agonists. The modern dietary perturbations which tend to induce PKC syndrome may include increased dietary fat and sodium, and decreased intakes of omega-3 fats, potassium, calcium, magnesium and chromium. Insulin resistance may be both a cause and effect of PKC syndrome, and weight reduction and aerobic training should act to combat this disorder. PKC syndrome sensitizes vascular smooth muscle cells to both vasoconstrictors and growth factors, and thus promotes both hypertension and atherogenesis. In platelets, it induces hyperaggregability, while in the microvasculature it may be a mediator of diabetic microangiopathy. In vascular endothelium, intimal macrophages, and hepatocytes, increased protein kinase C activity can be expected to increase cardiovascular risk. Up-regulation of protein kinase C in stem cells may also play a role in the promotion of 'Western' fat-related cancers. Practical guidelines for combatting PKC syndrome are suggested.

Effect of dietary sodium chloride on the development of renal glomerular and vascular lesions in hypertensive rats

1. The hypothesis that high levels of NaCl in the diet aggravates hypertension-associated renal vascular lesions was examined in unilaterally nephrectomized deoxycorticosterone acetate treated (DOCA) and two kidney one clip (2K1C) hypertensive rats, as well as normotensive controls. 2. High NaCl diet significantly increased systolic blood pressure (SBP) in DOCA rats, but had little effect on SBP in normal control rats, and did not affect the rise of SBP in 2K1C rats. 3. High NaCl diet was associated with a higher percentage of glomerular lesions and renal arterial and arteriolar lesions in DOCA and 2K1C rats (P < 0.05). 4. Thus high NaCl intake exacerbated renal arterial and arteriolar and glomerular lesions in both DOCA and 2K1C hypertensive rats. In 2K1C rats this effect may be in part independent of blood pressure.

Renal disease and black Americans: selected issues

Black Americans compared with their white counterparts are disproportionately hypertensive and have a greater incidence of end-stage renal disease (ESRD). Renal disease is a frequent end point of accelerated hypertension. The reasons why black Americans have a higher incidence of ESRD relative to white Americans are explored. As transplantation is a preferred mode of treatment for chronically ill ESRD patients, the paper examines some of the reasons why blacks are more reluctant than whites to donate their organs (e.g. kidneys) for transplantation. Although various reasons affect organ donation, altruism is explored as a possible factor that may influence the willingness of blacks to donate their organs.