Nonhypertensive cardiac effects of a high salt diet

Increased Oxidative Stress, Altered Trace Elements, and Macro-Minerals Are Associated with Female Obesity

Generally female individuals are more prone to obesity due to their lifestyle and physiology. However, female individuals have got little attention in this aspect. This pioneering study designed to find the level of serum malondialdehyde (MDA), non-enzymatic antioxidant (vitamin C), other trace elements (zinc and iron), and macro-minerals (sodium, potassium, and calcium) for female obesity determining its role and action in disease diagnosis along with propagation. For this prospective case-control study, 70 female obese and 70 healthy individuals were evaluated. Serum lipid peroxidation product malondialdehyde (MDA) concentration was measured to determine the level of lipid peroxidation. UV spectrophotometric method was implemented for vitamin C concentration to measure serum ascorbic acid. Atomic absorption spectroscopy (AAS) was implemented to determine serum macro-minerals (Na, K, and Ca), and trace elements (Zn and Fe) were estimated. For statistical analysis, student's t-test and Pearson's correlation test were executed. A significantly higher concentration of serum MDA (p < 0.001) and low concentration of antioxidants (vitamin C) (p < 0.001) are observed in patient than control group. We found a lower concentration of trace elements (zinc, iron) and macro-minerals (sodium, potassium, and calcium) in patients compared to control except sodium. The mean concentrations for serum Zn, Fe, Na, K, and Ca were 0.34 ± 0.01, 0.25 ± 0.01, 3828.91 ± 205.09, 90.42 ± 6.45, and 43.04 ± 2.38 mg/L and 0.78 ± 0.08, 0.84 ± 0.08, 2600.97 ± 99.79, 223.79 ± 14.64, and 86.43 ± 2.78 mg/L, respectively, for female obese patients and control subjects (p < 0.001). We can suggest from our study that there is a strong association of female obesity with increased serum concentrations of MDA and reduced non-enzymatic antioxidant vitamin C and different serum trace metals and macro-minerals.

Increased concentration of serum MDA, decreased antioxidants and altered trace elements and macro-minerals are linked to obesity among Bangladeshi population

BACKGROUND AND OBJECTIVE

Obesity is an emerging public health concern in Bangladesh. This study aimed to find the levels of the serum malondialdehyde (MDA), non-enzymatic antioxidants (vitamin A, C and E), trace elements (zinc and iron) and macro-minerals (calcium, potassium and sodium) in obesity and its action in disease advancement.

METHODS

Level of lipid peroxidation was estimated by measurement of the serum concentrations of malondialdehyde (MDA). Vitamin A and E concentration was found by RP-HPLC method and vitamin C was assessed for serum ascorbic acid by UV spectrophotometric method. Serum trace elements (Zn and Fe) and macro-minerals (Na, K and Ca) were estimated by Atomic Absorption Spectroscopy (AAS).

RESULTS

Our study observed significantly elevated concentrations of MDA (p < 0.001) and depleted concentrations of antioxidants (vitamin A, E and C) (p < 0.05) in the patient than control group. Analysis of serum trace elements (Zn and Fe) and macro-minerals (Na, K and Ca) and found that the mean values of Zn, Fe, Na, K and Ca were 0.39 ± 0.02 and 0.43 ± 0.03, 3284.81 ± 34.51, 162.18 ± 3.72, 44.62 ± 2.13 mg/L for the patient and 0.91 ± 0.13, 0.88 ± 0.06, 2562.74 ± 95.92, 243.58 ± 8.97, 87.66 ± 2.10 mg/L for the controls, consequently. There was a substantial difference in trace elements and macro-minerals between the patients and controls (p < 0.001).

CONCLUSION

Our study proposes that increased serum concentrations of MDA and decreased non-enzymatic antioxidant and altered trace elements and macro-minerals are powerfully related with obesity.

TRPV1 Activation Attenuates High-Salt Diet-Induced Cardiac Hypertrophy and Fibrosis through PPAR-δ Upregulation

High-salt diet-induced cardiac hypertrophy and fibrosis are associated with increased reactive oxygen species production. Transient receptor potential vanilloid type 1 (TRPV1), a specific receptor for capsaicin, exerts a protective role in cardiac remodeling that resulted from myocardial infarction, and peroxisome proliferation-activated receptors δ (PPAR-δ) play an important role in metabolic myocardium remodeling. However, it remains unknown whether activation of TRPV1 could alleviate cardiac hypertrophy and fibrosis and the effect of cross-talk between TRPV1 and PPAR-δ on suppressing high-salt diet-generated oxidative stress. In this study, high-salt diet-induced cardiac hypertrophy and fibrosis are characterized by significant enhancement of HW/BW%, LVEDD, and LVESD, decreased FS and EF, and increased collagen deposition. These alterations were associated with downregulation of PPAR-δ, UCP2 expression, upregulation of iNOS production, and increased oxidative/nitrotyrosine stress. These adverse effects of long-term high-salt diet were attenuated by chronic treatment with capsaicin. However, this effect of capsaicin was absent in TRPV1^−/− mice on a high-salt diet. Our finding suggests that chronic dietary capsaicin consumption attenuates long-term high-salt diet-induced cardiac hypertrophy and fibrosis. This benefit effect is likely to be caused by TRPV1 mediated upregulation of PPAR-δ expression.

Cardiovascular effects of dietary salt intake in aged healthy cats: a 2-year prospective randomized, blinded, and controlled study

High salt dry expanded diets are commercially available for cats to increase water intake and urine volume, as part of the prevention or treatment of naturally occurring urinary stone formation (calcium oxalates and struvites). However, chronic high salt intake may have potential cardiovascular adverse effects in both humans, especially in aging individuals, and several animal models. The objective of this prospective, randomized, blinded, and controlled study was to assess the long-term cardiovascular effects of high salt intake in healthy aged cats. Twenty healthy neutered cats (10.1±2.4 years) were randomly allocated into 2 matched groups. One group was fed a high salt diet (3.1 g/Mcal sodium, 5.5 g/Mcal chloride) and the other group a control diet of same composition except for salt content (1.0 g/Mcal sodium, 2.2 g/Mcal chloride). Clinical examination, systolic and diastolic arterial blood pressure measurements, standard transthoracic echocardiography and conventional Doppler examinations were repeatedly performed on non-sedated cats by trained observers before and over 24 months after diet implementation. Radial and longitudinal velocities of the left ventricular free wall and the interventricular septum were also assessed in systole and diastole using 2-dimensional color tissue Doppler imaging. Statistics were performed using a general linear model. No significant effect of dietary salt intake was observed on systolic and diastolic arterial blood pressure values. Out of the 33 tested imaging variables, the only one affected by dietary salt intake was the radial early on late diastolic velocity ratio assessed in the endocardium of the left ventricular free wall, statistically lower in the high salt diet group at 12 months only (P = 0.044). In conclusion, in this study involving healthy aged cats, chronic high dietary salt intake was not associated with an increased risk of systemic arterial hypertension and myocardial dysfunction, as observed in some elderly people, salt-sensitive patients and animal models.

Postprandial effects of a high salt meal on serum sodium, arterial stiffness, markers of nitric oxide production and markers of endothelial function

AIM

The aim of the study was to determine if a high salt meal containing 65 mmol Na causes a rise in sodium concentrations and a reduction in plasma nitrate/nitrite concentrations (an index of nitric oxide production). Secondary aims were to determine the effects of a high salt meal on augmentation index (AIx) a measure of arterial stiffness and markers of endothelial function.

METHODS AND RESULTS

In a randomised cross-over study 16 healthy normotensive adults consumed a low sodium soup containing 5 mmol Na and a high sodium soup containing 65 mmol Na. Sodium, plasma nitrate/nitrite, endothelin-1 (ET-1), C-reactive protein (CRP), vasopressin (AVP) and atrial natriuretic peptide (ANP) concentrations before and every 30 min after the soup for 2 h. Blood pressure (BP) and AI were also measured at these time points. There were significant increases in serum sodium, osmolality and chloride in response to the high sodium meal. However plasma nitrate/nitrite concentrations were not different between meals (meal p = 0.812; time p = 0.45; meal × time interaction p = 0.50). Plasma ANP, AVP and ET-1 were not different between meals. AI was significantly increased following the high sodium meal (p = 0.02) but there was no effect on BP.

CONCLUSIONS

A meal containing 65 mmol Na increases serum sodium and arterial stiffness but does not alter postprandial nitrate/nitrite concentration in healthy normotensive individuals. Further research is needed to explore the mechanism by which salt affects vascular function in the postprandial period. This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12611000583943http://www.anzctr.org.au/trial_view.aspx?ID=343019.

High urinary sodium is associated with increased carotid intima-media thickness in normotensive overweight and obese adults

BACKGROUND

Increased dietary sodium has been reported to increase cardiovascular disease (CVD) risk, perhaps through blood pressure (BP)-independent vascular remodeling. Carotid intima-media thickness (IMT) is an accepted measure of structural vascular remodeling and a strong predictor of CVD. This study aimed to determine whether urinary sodium is positively associated with carotid IMT in normotensive overweight and obese adults.

METHODS

We evaluated baseline data from 258 participants in the Slow Adverse Vascular Effects (SAVE) clinical trial. Urinary sodium was measured from one 24-h urine collection from each individual. Carotid IMT was measured using high-resolution B-mode ultrasonography. Participants were categorized into quartiles of urinary sodium.

RESULTS

There was a significant positive trend with greater IMT associated with increasing urinary sodium quartile in univariate linear regression (P = 0.047). This trend was significant when adjusting for age, sex, race, and systolic BP (SBP) (P = 0.03) as well as in a fully adjusted model (P = 0.04). In pairwise comparisons, the highest urinary sodium quartile had a significantly greater mean IMT (0.62 mm) than the lowest urinary sodium quartile (0.59 mm) after adjustment for age, sex, race, and SBP (P = 0.04). This comparison lost significance after the addition of BMI.

CONCLUSIONS

In our community-based sample of normotensive overweight and obese adults, we observed a significant positive trend in carotid IMT with increasing quartile of urinary sodium. If the ongoing clinical trial confirms this relationship between sodium and carotid IMT, it would lend support to efforts to decrease sodium intake in overweight and obese individuals.

The relationship between nutrient intake and cognitive performance in people at risk of dementia

BACKGROUND

There is evidence of a link between nutrient intake and cognitive impairment and decline in old age. There has been no study of nutrient intake in Irish subjects at risk of dementia.

AIM

To investigate the possible link between nutrient intake and cognitive performance in a group of Irish adults at risk of dementia, and to compare the nutrient intake in these adults stratified by the absence or presence of the apolipoprotein E (APOE) epsilon4 allele.

METHOD

Forty-four subjects, who were first-degree blood relatives of people with Alzheimer's disease, were recruited. Cognitive performance and nutritional intake were assessed and apolipoprotein E (APOE) genotype determined.

RESULTS

The intakes of cholesterol (P < 0.037) and Na (P < 0.037) were significantly higher in subjects with altered cognitive performance. There was no significant difference in nutrient intakes between APOE epsilon-4 allele positive and APOE epsilon-4 allele negative subjects.

CONCLUSION

The findings of this work suggest that dietary cholesterol and sodium intake may be linked to cognitive impairment.

Single-Nucleotide Polymorphisms for Diagnosis of Salt-Sensitive Hypertension

Background: Salt-sensitive (SS) hypertension affects &gt;30 million Americans and is often associated with low plasma renin activity. We tested the diagnostic validity of several candidate genes for SS and low-renin hypertension.

Methods: In Japanese patients with newly diagnosed, untreated hypertension (n = 184), we studied polymorphisms in 10 genes, including G protein–coupled receptor kinase type 4 (GRK4), some variations of which are associated with hypertension and impair D1 receptor (D1R)-inhibited renal sodium transport. We used the multifactor dimensionality reduction method to determine the genotype associated with salt sensitivity (≥10% increase in blood pressure with high sodium intake) or low renin. To determine whether the GRK4 genotype is associated with impaired D1R function, we tested the natriuretic effect of docarpamine, a dopamine prodrug, in normotensive individuals with or without GRK4 polymorphisms (n = 18).

Results: A genetic model based on GRK4 R65L, GRK4 A142V, and GRK4 A486V was 94.4% predictive of SS hypertension, whereas the single-locus model with only GRK4 A142V was 78.4% predictive, and a 2-locus model of GRK4 A142V and CYP11B2 C-344T was 77.8% predictive of low-renin hypertension. Sodium excretion was inversely related to the number of GRK4 variants in hypertensive persons, and the natriuretic response to dopaminergic stimulation was impaired in normotensive persons having ≥3 GRK4 gene variants.

Conclusions: GRK4 gene variants are associated with SS and low-renin hypertension. However, the genetic model predicting SS hypertension is different from the model for low renin, suggesting genetic differences in these 2 phenotypes. Like low-renin testing, screening for GRK4 variants may be a useful diagnostic adjunct for detection of SS hypertension.

Functional genomics of the dopaminergic system in hypertension

Abnormalities in dopamine production and receptor function have been described in human essential hypertension and rodent models of genetic hypertension. Under normal conditions, D(1)-like receptors (D(1) and D(5)) inhibit sodium transport in the kidney and intestine. However, in the Dahl salt-sensitive and spontaneously hypertensive rats (SHRs) and in humans with essential hypertension, the D(1)-like receptor-mediated inhibition of epithelial sodium transport is impaired because of an uncoupling of the D(1)-like receptor from its G protein/effector complex. The uncoupling is receptor specific, organ selective, nephron-segment specific, precedes the onset of hypertension, and cosegregates with the hypertensive phenotype. The defective transduction of the renal dopaminergic signal is caused by activating variants of G protein-coupled receptor kinase type 4 (GRK4: R65L, A142V, A486V). The GRK4 locus is linked to and GRK4 gene variants are associated with human essential hypertension, especially in salt-sensitive hypertensive subjects. Indeed, the presence of three or more GRK4 variants impairs the natriuretic response to dopaminergic stimulation in humans. In genetically hypertensive rats, renal inhibition of GRK4 expression ameliorates the hypertension. In mice, overexpression of GRK4 variants causes hypertension either with or without salt sensitivity according to the variant. GRK4 gene variants, by preventing the natriuretic function of the dopaminergic system and by allowing the antinatriuretic factors (e.g., angiotensin II type 1 receptor) to predominate, may be responsible for salt sensitivity. Subclasses of hypertension may occur because of additional perturbations caused by variants of other genes, the quantitative interaction of which may vary depending upon the genetic background.

Modulation of learning and memory in Dahl rats by dietary salt restriction

The Dahl rat represents a robust animal model of salt-sensitive hypertension, with Dahl S rats being salt sensitive and Dahl R rats (the Dahl S counterparts) being salt resistant for the development of hypertension. Here we evaluate the effect of reduced dietary salt intake on learning and memory in the Dahl rat model. Salt restriction produced a significant impairment in social transmission of food preference and social recognition memory in Dahl S rats without affecting spatial learning. In contrast, social transmission of food preference and social recognition memory remained unaffected in Dahl R rats, whereas navigation performance was significantly improved. This effect on learning and memory was not generalized because sodium restriction did not influence object recognition memory in either Dahl S or Dahl R rats. The significant decrement in select cognitive functions in Dahl S rats produced by salt restriction are in sharp contrast to the well known positive effect of dietary salt restriction in alleviating high blood pressure and associated target organ complications, suggesting that caution must be exercised when weighing the benefits of salt restriction in improving cardiovascular health in salt-sensitive hypertension against the potential undesirable effects of reduced cognitive function.

An evolutionary explanation of the plasticity of salt preferences: prophylaxis against sudden dehydration

Salt preferences, which vary widely across individuals, are a function of past exposure to both levels of dietary salt and dehydration. From an evolutionary perspective, such plasticity is puzzling, as the health costs of high salt intake, combined with the increased time and energy needed to obtain large quantities of salt under ancestral conditions, suggest that natural selection should have eliminated the plasticity in preferences that can produce such behavior. This puzzle is resolved once it is recognized that high salt intake may provide protection against sudden dehydration, a benefit that outweighs the costs associated with this pattern. It is proposed that an adaptive mechanism calibrates salt preferences as a function of the risk of dehydration as indexed by past dehydration events and maternal salt intake.