Salt in health and disease--a delicate balance

Renal effects and safety between Asian and non-Asian chronic kidney disease and type 2 diabetes treated with nonsteroidal mineralocorticoid antagonists

BACKGROUND

Asians bear a heavier burden of chronic kidney disease (CKD), a common comorbidity of type 2 diabetes mellitus (T2DM), than non-Asians. Nonsteroidal mineralocorticoid receptor antagonists (MRAs) have garnered attention for their potential advantages in renal outcomes. Nevertheless, the impact on diverse ethnic groups remains unknown.

METHODS

The PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang database, and clinical trial registries were searched through August 2023 with the following keywords: nonsteroidal MRAs (finerenone, apararenone, esaxerenone, AZD9977, KBP-5074), CKD, T2DM, and randomized controlled trial (RCT). A random effects model was used to calculate overall effect sizes.

RESULTS

Seven RCTs with 14 997 participants were enrolled. Nonsteroidal MRAs reduced urinary albumin to creatinine ratio (UACR) significantly more in Asians than non-Asians: (weighted mean difference [WMD], -0.59, 95% CI, -0.73 to -0.45, p < .01) vs (WMD, -0.29, 95% CI, -0.32 to -0.27, p < .01), respectively. The average decline of estimated glomerular filtration rate (eGFR) was similar in Asians and non-Asians (p > .05). Regarding systolic blood pressure (SBP), nonsteroidal MRAs had a better antihypertension performance in Asians (WMD, -5.12, 95% CI, -5.84 to -4.41, p < .01) compared to non-Asians (WMD, -3.64, 95% CI, -4.38 to -2.89, p < .01). A higher incidence of hyperkalemia and eGFR decrease ≥30% was found in Asians than non-Asians (p < .01).

CONCLUSIONS

Nonsteroidal MRAs exhibited significant renal benefits by decreasing UACR and lowering SBP in Asian than that of non-Asian patients with CKD and T2DM, without increase of adverse events except hyperkalemia and eGFR decrease ≥30%.

Sodium and water dynamics in the progression of chronic kidney disease: mechanisms and clinical significance

AIM

Lifestyle modifications can postpone the progression of chronic kidney disease toward its terminal stage. This mini-review aims to explore the impact of salt and water intake on the progression of chronic kidney disease (CKD) and provide insights into the optimal consumption levels to preserve the glomerular filtration rate.

METHODS

We reviewed relevant literature to examine the association between salt and water consumption and CKD progression. Our analysis includes discussions on the pathophysiology, findings from clinical trials, and recommended intake guidelines.

RESULTS

Sodium intake, often linked to cardiovascular risk and CKD progression, has shown a complex J-shaped association in some studies, leading to uncertainty about the ideal salt intake level. Sodium and fluid retention are key factors contributing to hypertension, a well-established risk factor for CKD progression. Low-sodium diets have demonstrated promise in reducing blood pressure and enhancing the effects of renin-angiotensin-aldosterone system inhibitors in non-dialysis CKD patients. However, a debate persists regarding the independent effect of salt restriction on CKD progression. Despite medical recommendations, salt consumption remains high among CKD patients. Additionally, the role of water consumption in CKD remains controversial despite its established benefits for CKD prevention in the general population.

CONCLUSION

Lifestyle modifications involving salt and water intake can influence the progression of CKD. While low-sodium diets have shown potential for mitigating hypertension and proteinuria in non-dialysis CKD patients, their independent impact on CKD progression warrants further investigation. The role of water consumption in CKD remains uncertain, and there is a need for additional research in this area. Clinicians should consider individualized dietary recommendations for CKD patients to help preserve the glomerular filtration rate and improve overall outcomes.

Low-Salt Diet Regulates the Metabolic and Signal Transduction Genomic Fabrics, and Remodels the Cardiac Normal and Chronic Pathological Pathways

Low-salt diet (LSD) is a constant recommendation to hypertensive patients, but the genomic mechanisms through which it improves cardiac pathophysiology are still not fully understood. Our publicly accessible transcriptomic dataset of the left ventricle myocardium of adult male mice subjected to prolonged LSD or normal diet was analyzed from the perspective of the Genomic Fabric Paradigm. We found that LSD shifted the metabolic priorities by increasing the transcription control for fatty acids biosynthesis while decreasing it for steroid hormone biosynthesis. Moreover, LSD remodeled pathways responsible for cardiac muscle contraction (CMC), chronic Chagas (CHA), diabetic (DIA), dilated (DIL), and hypertrophic (HCM) cardiomyopathies, and their interplays with the glycolysis/glucogenesis (GLY), oxidative phosphorylation (OXP), and adrenergic signaling in cardiomyocytes (ASC). For instance, the statistically (p < 0.05) significant coupling between GLY and ASC was reduced by LSD from 13.82% to 2.91% (i.e., -4.75×), and that of ASC with HCM from 10.50% to 2.83% (-3.71×). The substantial up-regulation of the CMC, ASC, and OXP genes, and the significant weakening of the synchronization of the expression of the HCM, CHA, DIA, and DIL genes within their respective fabrics justify the benefits of the LSD recommendation.

Salt: a narrative review and local policy initiatives in Israel

High salt intake is a well-known risk factor for cardiovascular disease (CVD). Some recent prospective studies have challenged the salt-CVD link. We conducted a narrative review based on a systematic search and provided a national policy update. We reviewed 14 observational prospective studies in healthy adults, reporting the association between sodium intake and excretion or reduction and CVD incidence. Validated by cohort studies, recommended sodium consumption levels (< 1.5-2 gram per day) are still relevant for the prevention of CVD in adults. We discussed the findings and policy initiatives implemented in Israel. Such initiatives included voluntary and mandatory food labeling, and culturally tailored educational programs. The Ministry of Health in Israel initiated a salt reduction policy in recent years-aimed for the future of the industry as well as the population.

Recent Advances in Understanding Peripheral and Gut Immune Cell-Mediated Salt-Sensitive Hypertension and Nephropathy

Hypertension is the primary modifiable risk factor for cardiovascular, renal, and cerebrovascular diseases and is considered the main contributing factor to morbidity and mortality worldwide. Approximately 50% of hypertensive and 25% of normotensive people exhibit salt sensitivity of blood pressure, which is an independent risk factor for cardiovascular disease. Human and animal studies demonstrate that the immune system plays an important role in the etiology and pathogenesis of salt sensitivity of blood pressure, kidney damage, and vascular diseases. Antigen-presenting and adaptive immune cells are implicated in salt-sensitive hypertension and salt-induced renal and vascular injury. Elevated sodium activates antigen-presenting cells to release proinflammatory cytokines including IL (interleukin) 6, tumor necrosis factor-α, IL-1β, and accumulate isolevuglandin-protein adducts. In turn, these activate T cells release prohypertensive cytokines including IL-17A. Moreover, high-salt intake is associated with gut dysbiosis, leading to inflammation, oxidative stress, and blood pressure elevation but the mechanistic contribution to salt-sensitivity of blood pressure is not clearly understood. Here, we discuss recent advances in research investigating the cause, potential biomarkers, and therapeutic targets for salt-sensitive hypertension as they pertain to the gut microbiome, immunity, and inflammation.

Histone Modifications and Their Contributions to Hypertension

Essential hypertension, a multifaceted disorder, is a worldwide health problem. A complex network of genetic, epigenetic, physiological, and environmental components regulates blood pressure (BP), and any dysregulation of this network may result in hypertension. Growing evidence suggests a role for epigenetic factors in BP regulation. Any alterations in the expression or functions of these epigenetic regulators may dysregulate various determinants of BP, thereby promoting the development of hypertension. Histone posttranslational modifications are critical epigenetic regulators that have been implicated in hypertension. Several studies have demonstrated a clear association between the increased expression of some histone-modifying enzymes, especially HDACs (histone deacetylases), and hypertension. In addition, treatment with HDAC inhibitors lowers BP in hypertensive animal models, providing an excellent opportunity to design new drugs to treat hypertension. In this review, we discuss the potential contribution of different histone modifications to the regulation of BP.

Association between the salinity level with miscarriage and unintended pregnancy in Bangladesh: Impact of salinity level on miscarriage and unintended pregnancy in Bangladesh

Miscarriage is a significant public health concern worldwide, particularly in developing nations like Bangladesh. Moreover, people in coastal areas are more affected by miscarriage as compared to other areas. Increasing sea levels and salinity is the main reason for this discrepancy. This study aimed to investigate the association between different salinity levels (S1, S2, S3, S4, and S5) and miscarriage and unintended pregnancy. The outcome variables are pregnancy-related outcomes (miscarriage, unintended pregnancy), and the independent variables are different salinity levels. A frequency table and correlation analysis were done to find the descriptive scenarios of miscarriage, unintended pregnancy, and salinity levels. We found 621 miscarriage patients and 2271 unintended pregnant patients in our study. Furthermore, the Poisson regression model was used to observe the incidence of miscarriage and unintended pregnancy for different salinity levels. A higher amount of miscarriage and unintended pregnancy rate was found in Dhaka and Khulna, while these rates were lower in Barisal and Chittagong. However, the salinity levels were highest in Barisal and Khulna. Both miscarriage and unintended pregnancy are highly and negatively correlated with salinity levels. The Poisson regression model shows that the salinity levels s1-s5 are strongly associated with miscarriage. Lower and moderate levels of salinity are strongly associated with miscarriage than higher levels of salinity. Again, the average number of miscarriages decreases with the salinity levels. Likewise, unintended pregnancy was also negatively associated with salinity levels. However, it only reported a significant association with lower and moderate salinity levels, and higher salinity levels did not affect unintended pregnancy. Taking initiatives for raising awareness from government and non-government organizations, setting up deep tube water pumps extensively, and properly treating coastal areas women during pregnancy would be the ideal next step to reduce the miscarriage and unintended pregnancy rate in coastal zones in Bangladesh.

The underlying mechanisms of DNA methylation in high salt memory in hypertensive vascular disease

This study demonstrates the effect and DNA methylation-related mechanisms of a high-salt diet and salt memory-induced hypertension and vasculopathy. Thirty Sprague Dawley rats were randomly divided into a control (CON) group (n = 6) and a modeling group (n = 24). A 12% NaCl solution (1 mL/100 g) was intragastrically administered for 60 consecutive days for modeling. An increase in blood pressure up to 140 mmHg was considered successful modeling. Twelve of fifteen successfully modeled rats were randomly selected and divided into a High Salt Diet (HSD) group and a High Salt Memory (HSM) group (n = 6). Rats in HSD group were intragastrically administered a 12% NaCl solution, while rats in HSM group were administered a 3% NaCl solution twice a day for 30 days. At the end of the intervention, blood pressure and the serum levels of ET-1, NO, TNF-α and IL-1β were measured. RRBS-heavy sulfite sequencing technology was selected for DNA methylation analysis. The systolic blood pressure of rats in the HSD group and HSM group was significantly higher than that in the CON group. Compared with those in the CON group, the serum levels of ET-1 in the HSM group and the serum levels of NO in the HSD group and HSM group were significantly increased. The methylation level of the CON group was lower than that of the HSD group and the HSM group, and there was no significant difference between the HSD group and the HSM group. The methylation level of Myoz3 was downregulated in the HSD group and HSM group. The methylation level of Fgd3 were upregulated in HSD group and downregulated in the HSM group. The methylation levels of AC095693.1, Adamts3, PDGFA and PDGFRα were downregulated in the HSD group and upregulated in the HSM group. According to the GO database, the differentially methylated genes were significantly enriched in the coordination of cell function, genetic development, and RNA transcription. There were three main metabolic pathways that were enriched in the differentially expressed genes between the groups: the PI3K-Akt signaling pathway, MAPK signaling pathway, and Hippo signaling pathway. Excessive salt intake may cause hypertension and vascular damage, and this damage may continue after the reduction of salt intake. Therefore, salt memory phenomenon exists, and this memory effect may be correlated with the levels of DNA methylation.

Interaction of Dietary Sodium-to-potassium Ratio and Dinner Energy Ratio on Prevalence of Hypertension in Inner Mongolia, China

BACKGROUND

Hypertension is one of the most common chronic diseases, and dietary factors play an important role in hypertension. We examined the interaction of dietary sodium-to-potassium (Na/K) ratio and dinner energy ratio on hypertension.

METHODS

We conducted this study using data from the cross-sectional National Survey for Nutrition and Adult Chronic Disease in 2015 in Inner Mongolia, China. Dietary data were collected using 24-hour diet records with food weights across 3 consecutive days. Logistic regression was used to determine the interaction of dinner energy ratio and dietary Na/K ratio on hypertension.

RESULTS

A total of 1,861 participants were included in this study, and 914 individuals were hypertensive (49.1%). Dinner energy ratio and high dietary Na/K ratio were independently related to high prevalence of hypertension. A formal test showed that dinner energy ratio interacted significantly with dietary Na/K ratio on hypertension (P < 0.001), with an adjusted odds ratio (OR) of 1.119 (95% confidence interval [CI], 1.040-1.203). Participants whose dinner energy ratio greater than 39.1% and dietary Na/K ratio of 3.625-6.053 had the highest OR of hypertension prevalence, with an adjusted OR of 2.984 (95% CI, 1.758-5.066), compared with participants with dinner energy ratio of 30.2-39.1%, and dietary Na/K ratio less than 2.348.

CONCLUSION

Our study highlighted the interactive effect of dinner energy ratio and dietary Na/K ratio on hypertension among adults in Inner Mongolia. We advocated a balanced diet (dinner energy ratio not small or large) and a low dietary Na/K ratio for reducing the prevalence of hypertension.

High-Salt-Diet (HSD) aggravates the progression of Inflammatory Bowel Disease (IBD) via regulating epithelial necroptosis

Due to its unclear etiology, there is no specific medicine to cure the recurrent and incurable inflammatory bowel disease (IBD). Unhealthy dietary habits unconsciously contributed to the progression of IBD, for example a High-Salt-Diet (HSD) is the most neglected and frequently adopted habit. However, the molecular mechanism of how HSD aggravates the progression of IBD has yet to remain uncovered. Herein, we focus on the hypothesis that necroptosis pathway may be involved in the process of IBD exacerbated by HSD. To this end, different gene expression (DEGs) profiles of human epithelia under hypertonic culture conditions were applied to screen candidate pathways. What's more, gene expression manipulation, immune microenvironment detection, RIPK3/MLKL gene knockout (KO), and wild-type (WT) mice were carried out to research the promotion of IBD progression under treatments of high salt intake. Based on our present results, gene expression profiles in human normal colon epithelia cell NCM460 were significantly changed under salt- or sucrose-induced hypertonic culture conditions. RIPK3 was significantly up-regulated under both conditions. Furthermore, mice colon epithelia cell CT26 growth was inhibited in a time- and dose-dependent manner by extra NaCl incubation. Autophagy, and Necroptosis pathways were activated and enhanced by LPS pretreatment. HSD significantly exacerbated DSS-induced IBD symptoms in vivo in a dose-dependent manner. Moreover, RIPK3-/- and MLKL-/- mice presented severe IBD symptoms in vivo. Overall, the results demonstrated that HSD aggravated the IBD progression via necroptosis activation, providing novel strategies and promising targets for the clinical treatment of IBD.

Epigenetics of the blood pressure reactivity to salt: Is the salt sensitive phenotype correctable?

Salt sensitivity defines a state characterized by a highly reactive blood pressure to changes in salt intake. The salt-sensitive phenotype is strongly associated with hypertension, visceral adiposity/metabolic syndrome, and ageing. Obesity accounts for around 70% of hypertension in young adults, and 30% to 50% of adult hypertensives carry the salt-sensitive phenotype. It is estimated that the salt-sensitive phenotype is responsible for high blood pressure in over 600 million adults. But is the salt-sensitive phenotype correctable? Interventional, controlled, clinical trials in obese adolescents and young obese adults, demonstrated that weight-reducing lifestyle modifications revert the salt-sensitive to the salt-resistant phenotype, and restored the faulty production of nitric oxide. Correction of the salt-sensitive phenotype lowers the blood pressure by reducing its reactivity to dietary salt. In a random sample of obese adults subjected to lifestyle modifications, those who were salt-resistant at baseline, were also normotensive and failed to further lower their blood pressure despite a 12% drop in body weight. The salt-resistant phenotype protects the metabolically healthy obese from hypertension, even if their salt consumption is comparable to that of salt-sensitive obese. In summary, at early stages, the elevated blood pressure of obesity, is determined by epigenetic changes leading to a state of salt-sensitivity.

Transient high salt intake causes epigenetic changes and leads to persistent inflammatory activation to produce "salt memory"

Transient high salt intake causes a sustained increase in blood pressure (BP) even after returning to a normal-salt diet, a phenomenon known as "salt memory." However, the molecular mechanisms of this phenomenon remain to be elucidated. Dahl salt-sensitive (SS) rats were fed a high-salt (8% NaCl) or high-salt diet and treated with drugs for 8 to 16 weeks and then returned to a normal-salt diet for 3 months. This study investigated the molecular mechanisms of salt memory and its mediation of SS hypertension and renal damage. We show that transient high salt intake caused persistent elevation of BP and exacerbation of kidney damage in Dahl SS rats even after returning to a normal-salt diet. Both epigenetic changes and inflammatory activation also persisted after resumption of a normal diet. Arterial BP, renal injury and the inflammatory response returned to normal levels in rats administered mycophenolate mofetil (MMF) during the 8-week period of high salt intake, resulting in the disappearance of salt memory. However, the vasodilator hydralazine did not ameliorate kidney damage or inflammatory activation, although it decreased BP to control levels. Transient high salt intake increased histone 3 lysine 4 monomethylation (H3K4me1) levels at the nuclear factor κB (NF-κB) subunit p65 promoter in SS rats, promoting p65 gene transcription and NF-κB activation and further leading to a series of inflammatory responses. Our findings demonstrate that transient high salt-induced epigenetic changes and persistent inflammatory activation play important roles in salt memory and its mediation of SS hypertension and renal damage.

Brown-Norway chromosome 1 mitigates the upregulation of proinflammatory pathways in mTAL cells and subsequent age-related CKD in Dahl SS/JrHsdMcwi rats

Chronic kidney disease (CKD) has a strong genetic component; however, the underlying pathways are not well understood. Dahl salt-sensitive (SS)/Jr rats spontaneously develop CKD with age and are used to investigate the genetic determinants of CKD. However, there are currently several genetically diverse Dahl SS rats maintained at various institutions and the extent to which some exhibit age-related CKD is unclear. We assessed glomerulosclerosis (GS) and tubulointerstitial fibrosis (TIF) in 3- and 6-mo-old male and female SS/JrHsdMcwi, BN/NHsd/Mcwi [Brown-Norway (BN)], and consomic SS-Chr 1BN/Mcwi (SS.BN1) rats, in which chromosome 1 from the BN rat was introgressed into the genome of the SS/JrHsdMcwi rat. Rats were fed a 0.4% NaCl diet. GS (31 ± 3% vs. 7 ± 1%) and TIF (2.3 ± 0.2 vs. 0.5 ± 0.1) were significantly greater in 6-mo-old compared with 3-mo-old SS/JrHsdMcwi rats, and CKD was exacerbated in males. GS was minimal in 6- and 3-mo-old BN (3.9 ± 0.6% vs. 1.2 ± 0.4%) and SS.BN1 (2.4 ± 0.5% vs. 1.0 ± 0.3%) rats, and neither exhibited TIF. In SS/JrHsdMcwi and SS.BN1 rats, mean arterial blood pressure was significantly greater in 6-mo-old compared with 3-mo-old SS/JrHsdMcwi (162 ± 4 vs. 131 ± 2 mmHg) but not SS.BN1 (115 ± 2 vs. 116 ± 1 mmHg) rats. In 6-mo-old SS/JrHsdMcwi rats, blood pressure was significantly greater in females. RNA-sequencing analysis revealed that inflammatory pathways were upregulated in isolated medullary thick ascending tubules in 7-wk-old SS/JrHsdMcwi rats, before the development of tubule pathology, compared with SS.BN1 rats. In summary, SS/JrHsdMcwi rats exhibit robust age-related progression of medullary thick ascending limb abnormalities, CKD, and hypertension, and gene(s) on chromosome 1 have a major pathogenic role in such changes.NEW & NOTEWORTHY This study shows that the robust age-related progression of kidney disease in Dahl SS/JrHsdMcw rats maintained on a normal-salt diet is abolished in consomic SS.BN1 rats. Evidence that medullary thick ascending limb segments of SS/JrHsdMcw rats are structurally abnormal and enriched in proinflammatory pathways before the development of protein casts provides new insights into the pathogenesis of kidney disease in this model.

The association of dietary glutamine supplementation with the development of high salt-induced hypertension in rats

Glutamine supplementation has been reported to affect blood pressure (BP). However, its role in the progression of hypertension induced by high salt diet (HSD) has not been elucidated. Male normotensive Wistar rats were exposed to high salt diet and treated with different doses of glutamine supplementation. Rats aged 6 weeks were assigned to five groups: (1) Normal-salt diet (0.3% NaCl, NSD); (2) High-salt diet (8% NaCl, HSD); (3) High-salt + low-dose diet (8% NaCl, 0.5 g of L-glutamine/kg body weight, HSLGD); (4) High-salt + middle-dose diet (8% NaCl, 1.5 g of L-glutamine/kg body weight, HSMGD); and (5) High-salt + high-dose diet (8% NaCl, 2.5 g of L-glutamine/kg body weight, HSHGD). After supplementing different doses of glutamine to male Wistar 6-week-old rats fed with HSD for 7 weeks, we found no difference in body weight among groups. Importantly, we showed that dietary L-glutamine supplementation could prevent the development of hypertension in a dose-dependent manner [dramatically lowering systolic blood pressure (SBP) and slightly reducing diastolic blood pressure (DBP) of hypertensive rats, while the differences of DBP between groups did not reach statistical significance]. Our data further elucidated that dietary glutamine supplementation mildly alleviated the degree of left ventricular hypertrophy, including interventricular septal thickness (IVST) and left ventricular posterior wall thickness (LVPWT) in hypertensive rats. Together, our results offer evidence that the dietary uptake of glutamine may be associated with attenuating the development of high salt-induced hypertension and slightly alleviating the degree of left ventricular hypertrophy in hypertensive rats. Therefore, glutamine supplementation may act as a prospective dietary intervention for the treatment of hypertension.

Broad-acting therapeutic effects of miR-29b-chitosan on hypertension and diabetic complications

MicroRNA miR-29 promotes endothelial function in human arterioles in part by targeting LYPLA1 and increasing nitric oxide production. In addition, miR-29 is a master inhibitor of extracellular matrix gene expression, which may attenuate fibrosis but could also weaken tissue structure. The goal of this study was to test whether miR-29 could be developed as an effective, broad-acting, and safe therapeutic. Substantial accumulation of miR-29b and effective knockdown of Lypla1 in several mouse tissues were achieved using a chitosan-packaged, chemically modified miR-29b mimic (miR-29b-CH-NP) injected systemically at 200 μg/kg body weight. miR-29b-CH-NP, injected once every 3 days, significantly attenuated angiotensin II-induced hypertension. In db/db mice, miR-29b-CH-NP treatment for 12 weeks decreased cardiac and renal fibrosis and urinary albuminuria. In uninephrectomized db/db mice, miR-29b-CH-NP treatment for 20 weeks significantly improved myocardial performance index and attenuated proteinuria. miR-29b-CH-NP did not worsen abdominal aortic aneurysm in ApoE knockout mice treated with angiotensin II. miR-29b-CH-NP caused aortic root fibrotic cap thinning in ApoE knockout mice fed a high-cholesterol and high-fat diet but did not worsen the necrotic zone or mortality. In conclusion, systemic delivery of low-dose miR-29b-CH-NP is an effective therapeutic for several forms of cardiovascular and renal disease in mice.

Excessive Sodium Intake Leads to Cardiovascular Disease by Promoting Sex-Specific Dysfunction of Murine Heart

Background

Globally, a high-salt diet (HSD) has become a threat to human health as it can lead to a high risk of cardiac damage. Although some studies investigating HSD have been carried out, the majority has been conducted in males, and there are few female-specific studies, thereby ignoring any effects of sex-specific damage on the heart. In this study, we determined how HSD induces different pathways of cardiovascular diseases through sex-specific effects on cardiac damage in mice.

Methods

An HSD murine model of male and female C57BL/6J mice was fed with sodium-rich chow (4% NaCl). After 8 weeks, cardiac tissues were collected, and the whole gene transcriptome of the hearts of male and female mice was characterized and analyzed using high-throughput RNA sequencing. Immunohistochemistry staining was used to further assess the harmful effects of HSD on protein expression of genes associated with immunity, fibrosis, and apoptosis in male and female mice.

Results

HSD drastically altered the cardiac transcriptome compared to that of the normal heart in both male and female mice and had a sex-specific effect on the cardiac composition in the transcriptome. HSD produced various differentially expressed genes and affected different KEGG pathways of the transcriptome in male and female mice. Furthermore, we found that HSD induced different pathways of cardiovascular disease in the male mice and female mice. The pathway of hypertrophic cardiomyopathy is significantly enriched in HSD-treated male mice, while the pathway of dilated cardiomyopathy is significantly enriched in HSD-treated female mice. Finally, metabolism, immunity, fibrosis, and apoptosis in the mouse heart showed sex-specific changes predicting cardiac damage.

Conclusion

Our results demonstrate that HSD adversely impacts cardiac structure and function by affecting the metabolism, immunity, fibrosis, and apoptosis in the murine heart and induces the mouse to suffer from sex-specific cardiovascular disease. This study provides a new perspective and basis for the differences in the pharmacology and interventional treatment of sex-specific cardiovascular diseases induced by HSD in men and women.

Urinary sodium, iodine, and volume in relation to metabolic syndrome in Mesoamerican children and their parents

BACKGROUND AND AIMS

The roles of sodium or iodine intake on the metabolic syndrome (MetS) etiology remain controversial. We evaluated the associations of 24 h urinary sodium and iodine with MetS among Mesoamerican children and their adult parents.

METHODS AND RESULTS

We conducted a cross-sectional study among 217 school-age children and 478 parents from 9 Mesoamerican cities. Exposures were high 24 h urinary sodium excretion and concentration (>2000 mg/d or mg/L, respectively) and high 24 h urinary iodine excretion and concentration (≥300 μg/d or μg/L, respectively). In children, the outcome was a standardized metabolic score from five criteria analogous to the Adult Treatment Panel (ATP) III criteria. In adults, MetS was defined according to the ATP III criteria. We estimated adjusted mean differences in the metabolic risk score and adjusted prevalence ratios of MetS between exposure categories using multivariable regression. In children, high sodium concentration was associated with a 0.10 units (43% of a SD) higher score (P = 0.001) and high iodine concentration was related to a 0.09 units (39% of a SD) higher score (P = 0.009). Unexpectedly, high 24 h urinary volume was associated with a lower metabolic score. In adults, high 24 h sodium excretion was related to hypertension and high iodine concentration was related to increased MetS prevalence.

CONCLUSION

High sodium and iodine concentrations, but not 24 h iodine excretion, are significantly associated with MetS in children, whereas high 24 h urinary volume is related to a decreased metabolic score. In adults, high iodine concentration tends to be related to increased MetS prevalence, but not 24 h iodine excretion.

The effect of sodium restriction on iodine prophylaxis: a review

PURPOSE

Sodium is essential to life. However, its dietary excess is detrimental to the cardiovascular system, and sodium restriction is a crucial step in cardiovascular prevention. Iodine deficiency has been fought worldwide for decades, and substantial success has been achieved introducing the use of iodine-enriched salt. Nevertheless, areas of iodine deficiency persist around the world, both in developing and industrialized countries, and a major concern affecting dietary sodium reduction programs is represented by a possible iodine intake deficiency. There are substantial differences in the source of alimentary iodine among countries, such as iodized salt added, household tap water, seafood, or salt employed in packaged food. It is clear that a sodium-restricted diet can induce differences in terms of iodine intake, depending on the country considered. Moreover, iodine status has undergone relevant changes in many countries in the last years.

METHODS

Systematic review of literature evidence about the possible effects of sodium restriction on population iodine status.

RESULTS

To date, the available results are conflicting, depending on country, salt iodization policy, as well as time frame of data collection. However, to ensure an optimal iodine supply by salt fortification, without exceeding the current recommendation by World Health Organization for salt intake, seems to be an achievable goal.

CONCLUSION

A balanced approach may be obtained by an adequate iodine concentration in fortified salt and by promoting the availability of iodized salt for household consumption and food industry use. In this scenario, updated prospective studies are strongly needed.

Btg2 mutation induces renal injury and impairs blood pressure control in female rats

Hypertension (HTN) is a complex disease influenced by heritable genetic elements and environmental interactions. Dietary salt is among the most influential modifiable factors contributing to increased blood pressure (BP). It is well established that men and women develop BP impairment in different patterns and a recent emphasis has been placed on identifying mechanisms leading to the differences observed between the sexes in HTN development. The current work reported here builds on an extensive genetic mapping experiment which sought to identify genetic determinants of salt sensitive (SS) HTN using the Dahl SS rat. BTG anti-proliferation factor 2 (Btg2) was previously identified by our group as a candidate gene contributing to SS HTN in female rats. In the current study, Btg2 was mutated using TALEN targeted gene disruption on the SSBN congenic rat background. The Btg2 mutated rats exhibited impaired BP and proteinuria responses to a high salt diet compared to wild type rats. Differences in body weight, mutant pup viability, skeletal morphology, and adult nephron density suggest a potential role for Btg2 in developmental signaling pathways. Subsequent cell cycle gene expression assessment provides several additional signaling pathways that Btg2 may function through during salt handling in the kidney. The expression analysis also identified several potential upstream targets that can be explored to further isolate therapeutic approaches for SS HTN.

Mechanism-based strategies to prevent salt sensitivity and salt-induced hypertension

High-salt diets are a major cause of hypertension and cardiovascular (CV) disease. Many governments are interested in using food salt reduction programs to reduce the risk for salt-induced increases in blood pressure and CV events. It is assumed that reducing the salt concentration of processed foods will substantially reduce mean salt intake in the general population. However, contrary to expectations, reducing the sodium density of nearly all foods consumed in England by 21% had little or no effect on salt intake in the general population. This may be due to the fact that in England, as in other countries including the U.S.A., mean salt intake is already close to the lower normal physiologic limit for mean salt intake of free-living populations. Thus, mechanism-based strategies for preventing salt-induced increases in blood pressure that do not solely depend on reducing salt intake merit attention. It is now recognized that the initiation of salt-induced increases in blood pressure often involves a combination of normal increases in sodium balance, blood volume and cardiac output together with abnormal vascular resistance responses to increased salt intake. Therefore, preventing either the normal increases in sodium balance and cardiac output, or the abnormal vascular resistance responses to salt, can prevent salt-induced increases in blood pressure. Suboptimal nutrient intake is a common cause of the hemodynamic disturbances mediating salt-induced hypertension. Accordingly, efforts to identify and correct the nutrient deficiencies that promote salt sensitivity hold promise for decreasing population risk of salt-induced hypertension without requiring reductions in salt intake.

Sodium Accumulation and Blood Capillary Rarefaction in the Skin Predispose Spontaneously Hypertensive Rats to Salt Sensitive Hypertension

Recent studies in humans and rats suggested that increased Na⁺ storage in the skin without parallel water retention may predispose to salt-sensitive hypertension. In the current studies, we compared tissue Na⁺ storage in salt sensitive spontaneously hypertensive rats (SHR) versus salt resistant normotensive Brown Norway (BN-Lx) rats. After salt loading (10 days drinking 1% NaCl solution), the SHR showed significant parallel increase in Na⁺-to-water as well as (Na⁺+K⁺)-to-water ratios suggesting increased storage of osmotically inactive Na⁺ in the skin while no significant changes in skin electrolyte concentrations were observed in BN-Lx rats. SHR rats after salt treatment exhibited a nonsignificant decrease in skin blood capillary number (rarefaction) while BN-Lx rats showed significantly increased skin blood capillary density. Analysis of dermal gene expression profiles in BN-Lx rats after salt treatment showed significant up-regulation of genes involved in angiogenesis and proliferation of endothelial cells contrary to the SHR. Since the skin harbors most of the body’s resistance vessels it is possible that blood capillary rarefaction may lead to increased peripheral resistance and salt sensitivity in the SHR.

Salt-Induced Hepatic Inflammatory Memory Contributes to Cardiovascular Damage Through Epigenetic Modulation of SIRT3

BACKGROUND

High salt intake is the leading dietary risk factor for cardiovascular diseases. Although clinical evidence suggests that high salt intake is associated with nonalcoholic fatty liver disease, which is an independent risk factor for cardiovascular diseases, it remains elusive whether salt-induced hepatic damage leads to the development of cardiovascular diseases.

METHODS

Mice were fed with normal or high-salt diet for 8 weeks to determine the effect of salt loading on liver histological changes and blood pressure, and salt withdrawal and metformin treatment were also conducted on some high-salt diet-fed mice. Adeno-associated virus 8, global knockout, or tissue-specific knockout mice were used to manipulate the expression of some target genes in vivo, including SIRT3 (sirtuin 3), NRF2 (NF-E2-related factor 2), and AMPK (AMP-activated protein kinase).

RESULTS

Mice fed with a high-salt diet displayed obvious hepatic steatosis and inflammation, accompanied with hypertension and cardiac dysfunction. All these pathological changes persisted after salt withdrawal, displaying a memory phenomenon. Gene expression analysis and phenotypes of SIRT3 knockout mice revealed that reduced expression of SIRT3 was a chief culprit responsible for the persistent inflammation in the liver, and recovering SIRT3 expression in the liver effectively inhibits the sustained hepatic inflammation and cardiovascular damage. Mechanistical studies reveal that high salt increases acetylated histone 3 lysine 27 (H3K27ac) on SIRT3 promoter in hepatocytes, thus inhibiting the binding of NRF2, and results in the sustained inhibition of SIRT3 expression. Treatment with metformin activated AMPK, which inhibited salt-induced hepatic inflammatory memory and cardiovascular damage by lowering the H3K27ac level on SIRT3 promoter, and increased NRF2 binding ability to activate SIRT3 expression.

CONCLUSIONS

This study demonstrates that SIRT3 inhibition caused by histone modification is the key factor for the persistent hepatic steatosis and inflammation that contributes to cardiovascular damage under high salt loading. Avoidance of excessive salt intake and active intervention of epigenetic modification may help to stave off the persistent inflammatory status that underlies high-salt-induced cardiovascular damage in clinical practice.

High salt activates p97 to reduce host antiviral immunity by restricting Viperin induction

High-salt diets have recently been implicated in hypertension, cardiovascular disease, and autoimmune disease. However, whether and how dietary salt affects host antiviral response remain elusive. Here, we report that high salt induces an instant reduction in host antiviral immunity, although this effect is compromised during a long-term high-salt diet. Further studies reveal that high salt stimulates the acetylation at Lys663 of p97, which promotes the recruitment of ubiquitinated proteins for proteasome-dependent degradation. p97-mediated degradation of the deubiquitinase USP33 results in a deficiency of Viperin protein expression during viral infection, which substantially attenuates host antiviral ability. Importantly, switching to a low-salt diet during viral infection significantly enhances Viperin expression and improves host antiviral ability. These findings uncover dietary salt-induced regulation of ubiquitinated cellular proteins and host antiviral immunity, and could offer insight into the daily consumption of salt-containing diets during virus epidemics.

OUP accepted manuscript

Aims

Previous studies have found high sodium intake to be associated with increased risks of cardiovascular disease (CVD) and all-cause mortality among individuals with hypertension; findings on the effect of intake among individuals without hypertension have been equivocal. We aimed to compare the risks of incident CVD and all-cause mortality among initiators of sodium-containing acetaminophen with the risk of initiators of non-sodium-containing formulations of the same drug according to the history of hypertension.

Methods and results

Using The Health Improvement Network, we conducted two cohort studies among individuals with and without hypertension. We examined the relation of sodium-containing acetaminophen to the risk of each outcome during 1-year follow-up using marginal structural models with an inverse probability weighting to adjust for time-varying confounders. The outcomes were incident CVD (myocardial infarction, stroke, and heart failure) and all-cause mortality. Among individuals with hypertension (mean age: 73.4 years), 122 CVDs occurred among 4532 initiators of sodium-containing acetaminophen (1-year risk: 5.6%) and 3051 among 146 866 non-sodium-containing acetaminophen initiators (1-year risk: 4.6%). The average weighted hazard ratio (HR) was 1.59 [95% confidence interval (CI) 1.32–1.92]. Among individuals without hypertension (mean age: 71.0 years), 105 CVDs occurred among 5351 initiators of sodium-containing acetaminophen (1-year risk: 4.4%) and 2079 among 141 948 non-sodium-containing acetaminophen initiators (1-year risk: 3.7%), with an average weighted HR of 1.45 (95% CI 1.18–1.79). Results of specific CVD outcomes and all-cause mortality were similar.

Conclusion

The initiation of sodium-containing acetaminophen was associated with increased risks of CVD and all-cause mortality among individuals with or without hypertension. Our findings suggest that individuals should avoid unnecessary excessive sodium intake through sodium-containing acetaminophen use.

A Review on Sarcocornia Species: Ethnopharmacology, Nutritional Properties, Phytochemistry, Biological Activities and Propagation

Sarcocornia A. J. Scott is a halophytic edible succulent plant belonging to the Amaranthaceae family. To date, the genus includes 28 species distributed worldwide in saline environments, usually salt marshes. Sarcocornia (Scott) is similar to Salicornia (L.), which has a recognized commercial value in morphological and taxonomical traits. Species of both genera are commonly named samphire or glassworts in Europe, and their fleshy shoots are commercialized under their traditional names. Due to their nutritional, organoleptic and medicinal properties, Sarcocornia species have a high economic potential in various biotechnology sectors. Being highly tolerant to salt, they can be cultivated in saline conditions, and dissimilar to Salicornia, they are perennial, i.e., they can be harvested year-round. Therefore, Sarcocornia species are considered promising gourmet vegetables to be explored in the context of climate change, soil and water salinization and eco-sustainability. We hereby put together and reviewed the most relevant information on Sarcocornia taxonomy, morphology, nutritional and pharmacological properties, uses in ethnomedicine, potential applications in biotechnology, and propagation strategies.

Salt-Sensitive Hypertension of the Renal Tubular Cell-Specific NFAT5 (Nuclear Factor of Activated T-Cells 5) Knockout Mice

[Figure: see text].

Chronic Kidney Disease: Role of Diet for a Reduction in the Severity of the Disease

Chronic kidney disease affects ~37 million adults in the US, and it is often undiagnosed due to a lack of apparent symptoms in early stages. Chronic kidney disease (CKD) interferes with the body's physiological and biological mechanisms, such as fluid electrolyte and pH balance, blood pressure regulation, excretion of toxins and waste, vitamin D metabolism, and hormonal regulation. Many CKD patients are at risk of hyperkalemia, hyperphosphatemia, chronic metabolic acidosis, bone deterioration, blood pressure abnormalities, and edema. These risks may be minimized, and the disease's progression may be slowed through careful monitoring of protein, phosphorus, potassium, sodium, and calcium, relieving symptoms experienced by CKD patients. In this review, the current Kidney Disease Outcomes Quality Initiative (KDOQI) recommendations are highlighted, reflecting the 2020 update, including explanations for the pathophysiology behind the recommendations. The Dietary Approaches to Stop Hypertension, the Mediterranean diet, and the whole foods plant-based diet are currently being examined for their potential role in delaying CKD progression. Biological explanations for why the whole foods plant-based diet may benefit CKD patients compared to diets that include animal products are examined. Strong evidence continues to support the importance of diet meeting the daily requirement in the prevention and progression of kidney disease, and medical nutrition therapy with a registered dietitian is a critical aspect in medical intervention for CKD.

High salt diet-induced proximal tubular phenotypic changes and sodium-glucose cotransporter-2 expression are coordinated by cold shock Y-box binding protein-1

High salt diet (HSD) is a hallmark of blood pressure elevations, weight gain and diabetes onset in the metabolic syndrome. In kidney, compensatory mechanisms are activated to balance salt turnover and maintain homeostasis. Data on the long-term effects of HSD with respect to tubular cell functions and kidney architecture that exclude confounding indirect blood pressure effects are scarce. Additionally we focus on cold shock Y-box binding protein-1 as a tubular cell protective factor. A HSD model (4% NaCl in chow; 1% NaCl in water) was compared to normal salt diet (NSD, standard chow) over 16 months using wild type mice and an inducible conditional whole body knockout for cold shock Y-box binding protein-1 (BL6J/N, Ybx1). HSD induced no difference in blood pressure over 16 months, comparing NSD/HSD and Ybx1 wild type/knockout. Nevertheless, marked phenotypic changes were detected. Glucosuria and subnephrotic albuminuria ensued in wild type animals under HSD, which subsided in Ybx1-deficient animals. At the same time megalin receptors were upregulated. The sodium-glucose cotransporter-2 (SGLT2) was completely downregulated in wild type HSD animals that developed glucosuria. In Ybx1 knockouts, expression of AQP1 and SGLT2 was maintained under HSD; proximal tubular widening and glomerular tubularization developed. Concurrently, amino aciduria of neutral and hydrophobic amino acids was seen. In vitro translation confirmed that YB-1 translationally represses Sglt2 transcripts. Our data reveal profound effects of HSD primarily within glomeruli and proximal tubular segments. YB-1 is regulated by HSD and orchestrates HSD-dependent changes; notably, sets reabsorption thresholds for amino acids, proteins and glucose.

Association of Sodium with Obstructive Sleep Apnea. The ELSA-Brasil Study

Rationale: Excessive sodium may have a role in the pathogenesis of obstructive sleep apnea (OSA) for patients with hypervolemic conditions, but it is unclear whether this is valid for all patients with OSA, including those with no significant comorbidities.Objectives: To test the association of urinary sodium and OSA in a large sample of participants from the ELSA-Brasil (Estudo Longitudinal de Saúde do Adulto-Brasil) Study. In addition, we stratified the analysis participants according to the presence of hypertension.Methods: In this cross-sectional study, OSA was defined by an apnea-hypopnea index ≥15 events/h. A validated 12-hour urine collection as representative of the 24-hour period was obtained from all participants to measure sodium excretion. We performed a logistic regression analysis to test the association of urinary sodium excretion with OSA (dependent variable) adjusting for age, sex, race and income, glomerular filtration rate, diabetes, physical activity, and antihypertensive classes related to sodium excretion. To address potential residual factors that may influence sodium excretion, we performed additional analysis replacing sodium excretion for salt intake (food frequency questionnaire) using the same models.Results: We studied 1,946 participants (age 49 ± 8 yr; 43.4% men). A third of them had OSA. Compared with those with no OSA, participants with OSA presented with higher sodium excretion (1.66 [1.19-2.29] vs. 1.99 [1.44-2.69] g/12 h; P < 0.001). After adjustments for confounding factors, we found no overall significant associations of sodium excretion with OSA (odds ratio [OR], 1.09; 95% confidence interval [CI], 0.97-1.23; P = 0.150). Regardless of the OSA status, the sodium excretion was higher in hypertensive than in normotensive participants (1.93 [1.35-2.64] vs. 1.71 [1.22-2.37] g/12 h). An independent association of sodium excretion with OSA was observed in patients with hypertension only (OR, 1.326; 95% CI, 1.067-1.648; P = 0.011), but the interaction of urinary sodium with hypertension was not significant (P = 0.37). The analysis of salt intake revealed consistent findings.Conclusions: The potential role of sodium in the pathogenesis of OSA seems to be modest and limited for those with higher salt intake and, consequently, higher fluid retention such as observed in patients with hypertension.

24-h Potassium Excretion Is Associated with Components of the Metabolic Syndrome: Results from a National Survey Based on Urine Collection in Adults

A balanced diet and weight loss are the first lines of treatment for the prevention of metabolic syndrome (MS). Dietary strategies may include changing the composition of macronutrients, adopting a particular dietary pattern as a Mediterranean diet. However, the role of micronutrients, particularly potassium, in the propensity for or treatment of the syndrome is unclear. The study aimed to examine the relationship between the presence of the MS and its risk factors and the 24-h potassium excretion as the most valid proxy for dietary intake. The analyses were performed as part of the national survey estimating sodium and other electrolytes excretion conducted between 2014-2016 in Israel. The survey included urine collection, anthropometric and blood pressure measurements, and a comprehensive medical questionnaire that included details on the intake of medications that may affect electrolyte secretion. A model was constructed to evaluate the probability for the MS. MS score and its probability were examined in relation to potassium excretion at different levels and in stratification to sex. A total of 581 participants were included in the analysis. The mean potassium excretion was 2818 ± 1417 mg. The prevalence of the MS was 18.5% among participants with above-average potassium excretion and about 10.4% among participants with lower-than-average excretion (p = 0.007). A dose-response relationship was observed between MS score and potassium: the higher the score, the lower was the excretion of potassium. Potassium excretion, rather than sodium excretion, correlated with all components of the MS and even predicted MS independently from other variables. This is the first study based on a national survey showing that potassium consumption, as represented by daily excretion in urine, is inversely related to the presence of MS components after adjustment for several leading variables and careful exclusion of participants taking drugs which may interfere in potassium excretion.

Sodium intake assessed by 24-h urine excretion and its relationship with anthropometric measurements in Malaysian adults

BACKGROUND

Sodium intake is associated with anthropometric measurement including weight, waist circumference (WC), and body mass index (BMI). Higher intake of sodium is usually linked to higher risk of obesity among adults globally, especially in developing countries. This study aims to explore the probable relationship between sodium intake by 24-h urine excretion assessment and anthropometric measurement of adults in Malaysia.

METHODS

A cross-sectional study was conducted from October 2017 to March 2018 using a multi-stage stratified sampling method among Malaysian adults aged 18 years old and above. Sodium intake was determined by 24-h urinary sodium excretion, estimated from the respondents' 24-h urinary sample. Height was obtained based on standard protocol. Weight and WC were measured twice using validated anthropometric equipment and BMI was calculated according to World Health Organization (WHO) 1998 classification. Descriptive analysis was done to describe socio-demographic characteristics. A simple linear regression and multiple linear regression tests were done to assess the relationship of 24-h urinary excretion and anthropometric measurement. All statistical analysis was done using SPSS version 22.0.

RESULTS

Of 1047 interviewed respondents, 798 respondents had done the 24-h urine collection (76.0% response rate). Majority was between 40 and 59 years old (43.5%) and married (77.7%). Simple linear regression showed a significant positive linear association between 24-h urinary excretion and household income, WC, and obese group. In the multivariate analysis, it was indicated that, an increase of 1 unit of BMI will significantly increase the sodium intake by 129.20 mg/dl and an increase of 1 cm of WC will significantly increase the sodium intake by 376.45 mg/dl.

CONCLUSION

Our study showed a positive significant relationship between sodium intake estimated by 24-h urinary sodium excretion and BMI of Malaysian adults. More research is suggested on how sodium control can potentially contribute to obesity prevention.

Impact of dietary intake of sodium and potassium on short-term blood pressure variability

BACKGROUND

Dietary Approaches to Stop Hypertension (DASH)-Sodium trial showed that dietary sodium and potassium affect blood pressure (BP). We aimed to investigate whether dietary sodium and potassium affect short-term BP variability (BPV) in addition to BP.

METHODS

A total of 343 participants from the DASH-Sodium trial (age 48.4 ± 9.7, 42.5% men) and 323 individuals from the Jackson Heart Study (JHS) (age 56.7 ± 11.2, 30.7% men) with satisfactory ambulatory BP monitoring records and 24-h urine collection were included. Average real variability (ARV) was calculated as a measure of short-term BPV.

RESULTS

By estimating dietary intake from urinary excretion, we observed that higher urinary sodium-to-potassium ratio was significantly associated with higher diastolic ARV in both studies. Among the DASH-Sodium trial, potassium-rich DASH diet alone had insignificant effect on both systolic (-0.1 ± 1.7 mmHg, P = 0.343) or diastolic ARV (-0.2 ± 1.5 mmHg, P = 0.164), whereas combined DASH diet and low sodium intake significantly reduced both systolic (8.5 ± 1.6 vs. 8.9 ± 1.7 mmHg, P = 0.032) and diastolic ARV (7.5 ± 1.5 vs. 7.8 ± 1.6 mmHg, P = 0.025) as compared with control diet and high sodium intake. As the reduction of systolic ARV was majorly derived from the change of mean SBP, diastolic ARV was significantly determined by urinary sodium-to-potassium ratio (β coefficient ± standard error: 0.012 ± 0.004; P = 0.006) after adjusting for age, sex, smoking, mean DBP, BMI, and race.

CONCLUSION

Dietary sodium and potassium can jointly modulate short-term BPV in addition to BP. Combined DASH diet and low sodium intake may reduce systolic and diastolic ARV via different mechanisms.

Regulatory control of the Na-Cl co-transporter NCC and its therapeutic potential for hypertension

Hypertension is the largest risk factor for cardiovascular disease, the leading cause of mortality worldwide. As blood pressure regulation is influenced by multiple physiological systems, hypertension cannot be attributed to a single identifiable etiology. Three decades of research into Mendelian forms of hypertension implicated alterations in the renal tubular sodium handling, particularly the distal convoluted tubule (DCT)-native, thiazide-sensitive Na-Cl cotransporter (NCC). Altered functions of the NCC have shown to have profound effects on blood pressure regulation as illustrated by the over activation and inactivation of the NCC in Gordon's and Gitelman syndromes respectively. Substantial progress has uncovered multiple factors that affect the expression and activity of the NCC. In particular, NCC activity is controlled by phosphorylation/dephosphorylation, and NCC expression is facilitated by glycosylation and negatively regulated by ubiquitination. Studies have even found parvalbumin to be an unexpected regulator of the NCC. In recent years, there have been considerable advances in our understanding of NCC control mechanisms, particularly via the pathway containing the with-no-lysine [K] (WNK) and its downstream target kinases, SPS/Ste20-related proline-alanine-rich kinase (SPAK) and oxidative stress responsive 1 (OSR1), which has led to the discovery of novel inhibitory molecules. This review summarizes the currently reported regulatory mechanisms of the NCC and discusses their potential as therapeutic targets for treating hypertension.

High sodium intake, glomerular hyperfiltration, and protein catabolism in patients with essential hypertension

AIMS

A blood pressure (BP)-independent metabolic shift towards a catabolic state upon high sodium (Na+) diet, ultimately favouring body fluid preservation, has recently been described in pre-clinical controlled settings. We sought to investigate the real-life impact of high Na+ intake on measures of renal Na+/water handling and metabolic signatures, as surrogates for cardiovascular risk, in hypertensive patients.

METHODS AND RESULTS

We analysed clinical and biochemical data from 766 consecutive patients with essential hypertension, collected at the time of screening for secondary causes. The systematic screening protocol included 24 h urine (24 h-u-) collection on usual diet and avoidance of renin-angiotensin-aldosterone system-confounding medications. Urinary 24 h-Na+ excretion, used to define classes of Na+ intake (low ≤2.3 g/day; medium 2.3-5 g/day; high >5 g/day), was an independent predictor of glomerular filtration rate after correction for age, sex, BP, BMI, aldosterone, and potassium excretion [P = 0.001; low: 94.1 (69.9-118.8) vs. high: 127.5 (108.3-147.8) mL/min/1.73 m2]. Renal Na+ and water handling diverged, with higher fractional excretion of Na+ and lower fractional excretion of water in those with evidence of high Na+ intake [FENa: low 0.39% (0.30-0.47) vs. high 0.81% (0.73-0.98), P < 0.001; FEwater: low 1.13% (0.73-1.72) vs. high 0.89% (0.69-1.12), P = 0.015]. Despite higher FENa, these patients showed higher absolute 24 h Na+ reabsorption and higher associated tubular energy expenditure, estimated by tubular Na+/ATP stoichiometry, accordingly [Δhigh-low = 18 (12-24) kcal/day, P < 0.001]. At non-targeted liquid chromatography/mass spectrometry plasma metabolomics in an unselected subcohort (n = 67), metabolites which were more abundant in high versus low Na+ intake (P < 0.05) mostly entailed intermediates or end products of protein catabolism/urea cycle.

CONCLUSION

When exposed to high Na+ intake, kidneys dissociate Na+ and water handling. In hypertensive patients, this comes at the cost of higher glomerular filtration rate, increased tubular energy expenditure, and protein catabolism from endogenous (muscle) or excess exogenous (dietary) sources. Glomerular hyperfiltration and the metabolic shift may have broad implications on global cardiovascular risk independent of BP.

NFAT5 Is Involved in GRP-Enhanced Secretion of GLP-1 by Sodium

Gastrin, secreted by G-cells, and glucagon-like peptide-1 (GLP-1), secreted by L-cells, may participate in the regulation of sodium balance. We studied the effect of sodium in mice in vivo and mouse ileum and human L-cells, on GLP-1 secretion, and the role of NFAT5 and gastrin-releasing peptide receptor (GRPR) in this process. A high-sodium diet increases serum GLP-1 levels in mice. Increasing sodium concentration stimulates GLP-1 secretion from mouse ileum and L-cells. GRP enhances the high sodium-induced increase in GLP-1 secretion. High sodium increases cellular GLP-1 expression, while low and high sodium concentrations increase NFAT5 and GRPR expression. Silencing NFAT5 in L-cells abrogates the stimulatory effect of GRP on the high sodium-induced GLP-1 secretion and protein expression, and the sodium-induced increase in GRPR expression. GLP-1 and gastrin decrease the expression of Na⁺-K⁺/ATPase and increase the phosphorylation of sodium/hydrogen exchanger type 3 (NHE3) in human renal proximal tubule cells (hRPTCs). This study gives a new perspective on the mechanisms of GLP-1 secretion, especially that engendered by ingested sodium, and the ability of GLP-1, with gastrin, to decrease Na⁺-K⁺/ATPase expression and NHE3 function in hRPTCs. These results may contribute to the better utilization of current and future GLP-1-based drugs in the treatment of hypertension.

No evidence of racial disparities in blood pressure salt sensitivity when potassium intake exceeds levels recommended in the US dietary guidelines

On average, black individuals are widely believed to be more sensitive than white individuals to blood pressure (BP) effects of changes in salt intake. However, few studies have directly compared the BP effects of changing salt intake in black versus white individuals. In this narrative review, we analyze those studies and note that when potassium intake substantially exceeds the recently recommended US dietary goal of 87 mmol/day, black adults do not appear more sensitive than white adults to BP effects of short-term or long-term increases in salt intake (from an intake ≤50 mmol/day up to 150 mmol/day or more). However, with lower potassium intakes, racial differences in salt sensitivity are observed. Mechanistic studies suggest that racial differences in salt sensitivity are related to differences in vascular resistance responses to changes in salt intake mediated by vasodilator and vasoconstrictor pathways. With respect to cause and prevention of racial disparities in salt sensitivity, it is noteworthy that 1) on average, black individuals consume less potassium than white individuals and 2) consuming supplemental potassium bicarbonate, or potassium rich foods can prevent racial disparities in salt sensitivity. However, the new US dietary guidelines reduced the dietary potassium goal well below the amount associated with preventing racial disparities in salt sensitivity. These observations should motivate research on the impact of the new dietary potassium guidelines on racial disparities in salt sensitivity, the risks and benefits of potassium-containing salt substitutes or supplements, and methods for increasing consumption of foods rich in nutrients that protect against salt-induced hypertension.

Transfer RNA Fragments in the Kidney in Hypertension

[Figure: see text].

Amplification of Salt-Sensitive Hypertension and Kidney Damage by Immune Mechanisms

Humans with salt-sensitive (SS) hypertension demonstrate increased morbidity, increased mortality, and renal end-organ damage when compared with normotensive subjects or those with salt-resistant hypertension. Increasing evidence indicates that immune mechanisms play an important role in the full development of SS hypertension and associated renal damage. Recent experimental advances and studies in animal models have permitted a greater understanding of the mechanisms of activation and action of immunity in this disease process. Evidence favors a role of both innate and adaptive immune mechanisms that are triggered by initial, immune-independent alterations in blood pressure, sympathetic activity, or tissue damage. Activation of immunity, which can be enhanced by a high-salt intake or by alterations in other components of the diet, leads to the release of cytokines, free radicals, or other factors that amplify renal damage and hypertension and mediate malignant disease.

Renal metabolism and hypertension

Hypertension is a leading risk factor for disease burden worldwide. The kidneys, which have a high specific metabolic rate, play an essential role in the long-term regulation of arterial blood pressure. In this review, we discuss the emerging role of renal metabolism in the development of hypertension. Renal energy and substrate metabolism is characterized by several important and, in some cases, unique features. Recent advances suggest that alterations of renal metabolism may result from genetic abnormalities or serve initially as a physiological response to environmental stressors to support tubular transport, which may ultimately affect regulatory pathways and lead to unfavorable cellular and pathophysiological consequences that contribute to the development of hypertension.

Salt Consumption and Myocardial Infarction: Is Limited Salt Intake Beneficial?

Introduction: Sodium is an essential mineral that plays a crucial role in the maintenance of normal cellular homeostasis, regulation of fluid and electrolytes, and blood pressure (BP). Due to the presence of sodium in a variety of regularly consumed food products, the deficiency of sodium is extremely unlikely. On the other hand, excess intake of dietary sodium is observed in many populations as it is generally used in most food products. Existing guidelines recommend lowering salt consumption for better cardiovascular health; these dietary sodium intake recommendations are not reassuring as the evolving studies show evidence that there is a higher risk of cardiovascular disease (CVD) with low sodium consumption. The aim of this study was to identify the association between salt consumption and myocardial infarction (MI).

Methods: The National Health and Nutrition Examination Survey (NHANES) data between 2017- 2018 was analyzed to examine the association between sodium intake (use in daily meal preparation) and reported history of MI. Logistic regression was used to assess for significant differences between the groups and calculated odds ratios while adjusting for confounders.

Results: A total of 4626 participants were included in the study, with a mean age of 66 ± 11 years in those with a history of MI (n = 212). Amongst these participants, those with salt consumption "Occasionally used" or "Very often used" were less likely to have suffered from MI than those who "Never used" salt in meal preparation. Multivariable logistic regression was performed to control for confounders. “Occasionally used” compared to “Never used” odds ratio was 0.5227 (95% confidence interval (CI); 0.3053-0.9009 p = 0.0184) and “Very often used” compared to “Never used” odds ratio was 0.5033 (95% CI; 0.2892-0.8799 p = 0.0152).

Conclusion: After adjusting for confounders, the participants that used salt more liberally during meal preparation were less likely to have MI than those who minimally or never used salt in meal preparation.

Trajectory of extracellular fluid volume over time and subsequent risks of end-stage kidney disease and mortality in chronic kidney disease: a prospective cohort study

BACKGROUND

Extracellular fluid volume (ECF) is independently associated with chronic kidney disease (CKD) progression and mortality in patients with CKD, but the prognostic value of the trajectory of ECF over time beyond that of baseline value is unknown.

OBJECTIVES

To characterize ECF trajectory and evaluate its association with the risks of end-stage kidney disease (ESKD) and mortality.

METHODS

From the prospective tricentric NephroTest cohort, we included 1588 patients with baseline measured glomerular filtration rate (mGFR) ≥15 mL min^-1 /1.73 m² and ECF measurement. ECF and GFR were measured repeatedly using the distribution volume and clearance of ⁵¹ Cr-EDTA, respectively. ESKD and mortality were traced through record linkage with the national registries. Adjusted shared random-effect joint models were used to analyse the association between the trajectory of ECF over time and the two competing outcomes.

RESULTS

Patients were mean age 58.7 years, 66.7% men, mean mGFR of 43.6 ± 18.6 mL min^-1 /1.73 m² and mean ECF of 16.1 ± 3.6 L. Over a median follow-up of 5.3 [IQR: 3.0;7.4] years, ECF increased by 136 [95%CI 106;167] mL per year on average, whilst diuretic prescription and 24-hour urinary sodium excretion remained stable. ESKD occurred in 324 (20.4%) patients, and 185 (11.6%) patients died before ESKD. A higher current value of ECF was associated with increased hazards of ESKD (adjusted hazard ratio [aHR]: 1.12 [95%CI 1.06;1.18]; P < 0.001 per 1 L increase in ECF), and death before ESKD (aHR: 1.10 [95%CI 1.04;1.17]; P = 0.002).

CONCLUSIONS

The current value of ECF was associated with the risks of ESKD and mortality, independent of multiple potential confounders, including kidney function decline. This highlights the need for a close monitoring and adjustment of treatment to avoid fluid overload in CKD patients.

Intake of Natural Compounds and Circulating microRNA Expression Levels: Their Relationship Investigated in Healthy Subjects With Different Dietary Habits

Diet has a strong influence on many physiological processes, which in turn have important implications on a variety of pathological conditions. In this respect, microRNAs (miRNAs), a class of small non-coding RNAs playing a relevant epigenetic role in controlling gene expression, may represent mediators between the dietary intake and the healthy status. Despite great advances in the field of nutri-epigenomics, it remains unclear how miRNA expression is modulated by the diet and, specifically, the intake of specific nutrients. We investigated the whole circulating miRNome by small RNA-sequencing performed on plasma samples of 120 healthy volunteers with different dietary habits (vegans, vegetarians, and omnivores). Dietary intakes of specific nutrients were estimated for each subject from the information reported in the food-frequency questionnaire previously validated in the EPIC study. We focused hereby on the intake of 23 natural compounds (NCs) of the classes of lipids, micro-elements, and vitamins. We identified 78 significant correlations (rho > 0.300, p-value < 0.05) among the estimated daily intake of 13 NCs and the expression levels of 58 plasma miRNAs. Overall, vitamin D, sodium, and vitamin E correlated with the largest number of miRNAs. All the identified correlations were consistent among the three dietary groups and 22 of them were confirmed as significant (p-value < 0.05) by age-, gender-, and body-mass index-adjusted Generalized Linear regression Model analysis. miR-23a-3p expression levels were related with different NCs including a significant positive correlation with sodium (rho = 0.377) and significant negative correlations with lipid-related NCs and vitamin E. Conversely, the estimated intake of vitamin D was negatively correlated with the expression of the highest number of circulating miRNAs, particularly miR-1277-5p (rho = −0.393) and miR-144-3p (rho = −0.393). Functional analysis of the targets of sodium intake-correlated miRNAs highlighted terms related to cardiac development. A similar approach on targets of those miRNAs correlated with vitamin D intake showed an enrichment in genes involved in hormone metabolisms, while the response to chronic inflammation was among the top enriched processes involving targets of miRNAs negatively related with vitamin E intake. Our findings show that nutrients through the habitual diet influence circulating miRNA profiles and highlight that this aspect must be considered in the nutri-epigenomic research.

Angiotensin II increases activity of the ClC-K2 Cl- channel in collecting duct intercalated cells by stimulating production of reactive oxygen species

The renal collecting duct plays a critical role in setting urinary volume and composition, with principal cells transporting Na+ and K+ and intercalated cells mediating Cl- reabsorption. Published evidence implies Angiotensin II (Ang II) is a potent regulator of the collecting duct apical transport systems in response to systemic volume depletion. However, virtually nothing is known about Ang II actions on the basolateral conductance of principal and intercalated cells. Here, we combined macroscopic and single channel patch clamp recordings from freshly isolated mouse collecting ducts with biochemical and fluorescence methods to demonstrate an acute stimulation of the basolateral Cl- conductance and specifically the ClC-K2 Cl- channel by nanomolar Ang II concentrations in intercalated cells. In contrast, Ang II did not exhibit measurable effects on the basolateral conductance and on Kir4.1/5.1 potassium channel activity in principal cells. Although both Ang II receptors AT1 and AT2 are expressed in collecting duct cells, we show that AT1 receptors were essential for stimulatory actions of Ang II on ClC-K2. Moreover, AT1R-/- mice had decreased renal ClC-K2 expression. We further demonstrated that activation of NADPH oxidases is the major signaling pathway downstream of Ang II-AT1R that leads to stimulation of ClC-K2. Treatment of freshly isolated collecting ducts with Ang II led to production of reactive oxygen species on the same timescale as single channel ClC-K2 activation. Overall, we propose that Ang II-dependent regulation of ClC-K2 in intercalated cells is instrumental for stimulation of Cl- reabsorption by the collecting duct, particularly during hypovolemic states.

Excessive maternal salt intake gives rise to vasopressin-dependent salt sensitivity of blood pressure in male offspring

Salt sensitivity of blood pressure (SSBP) is a trait carrying strong prognostic implications for various cardiovascular diseases. To test the hypothesis that excessive maternal salt intake causes SSBP in offspring through a mechanism dependent upon arginine-vasopressin (AVP), we performed a series of experiments using offspring of the rat dams salt-loaded during pregnancy and lactation with 1.5% saline drink ("experimental offspring") and those with normal perinatal salt exposure ("control offspring"). Salt challenge, given at 7-8 weeks of age with either 2% saline drink (3 days) or 8% NaCl-containing chow (4 weeks), had little or no effect on systolic blood pressure (SBP) in female offspring, whereas the salt challenge significantly raised SBP in male offspring, with the magnitude of increase being greater in experimental, than control, rats. Furthermore, the salt challenge not only raised plasma AVP level more and caused greater depressor responses to V1a and V2 AVP receptor antagonists to occur in experimental, than control, males, but it also made GABA excitatory in a significant proportion of magnocellular AVP neurons of experimental males by depolarizing GABA equilibrium potential. The effect of the maternal salt loading on the salt challenge-elicited SBP response in male offspring was precluded by maternal conivaptan treatment (non-selective AVP receptor antagonist) during the salt-loading period, whereas it was mimicked by neonatal AVP treatment. These results suggest that the excessive maternal salt intake brings about SSBP in male offspring, both the programming and the expression of which depend on increased AVP secretion that may partly result from excitatory GABAergic action.

Impact of Gut Microbiome on Hypertensive Patients With Low-Salt Intake: Shika Study Results

Salt intake is one of the most important environmental factors impacting hypertension onset. Meanwhile, the potential roles of the gut microbiome (GM) in altering the health status of hosts have drawn considerable attention. Here, we aimed to perform an observational study to investigate the impact of intestinal bacterial flora in hypertensive patients with low-salt or high-salt intake. A total of 239 participants were enrolled, and their gut microbiomes, clinical and demographic details, as well as physiological parameters pertaining to the renin-angiotensin-aldosterone system and inflammatory cytokine profiles, were examined. The participants were classified into four groups based on the presence of different enterotype bacteria, as determined via cluster analysis, and salt intake: low salt/GM enterotype 1, low salt/GM enterotype 2, high salt/GM enterotype 1, and high salt/GM enterotype 2. Results show that the prevalence of hypertension was significantly lower in the low-salt/GM enterotype 2 group (27%) compared to the low salt/GM enterotype 1 group (47%; p = 0.04). Alternatively, no significant differences were observed in hypertension prevalence between the two high-salt intake groups (GM enterotype 1 = 50%, GM enterotype 2 = 47%; p = 0.83). Furthermore, The low-salt/GM enterotype 2 was higher in the relative abundances of Blautia, Bifidobacterium, Escherichia-Shigella, Lachnoclostridium, and Clostridium sensu stricto than the low-salt/GM enterotype 1. differed significantly between the GM enterotypes. These results suggested that consumption of a low-salt diet was ineffective in regulating hypertension in individuals with a specific gut bacteria composition. Our findings support the restoration of GM homeostasis as a new strategy for controlling blood pressure and preventing the development of hypertension.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

High salt diet elevates the mean arterial pressure of SLC14α1 gene depletion mice

AIMS

Urea transporter B (UTB) is encoded by the SLC14α1 gene, and exerts its activity in the choroid plexus (CP) by regulating [Na+] in the cerebrospinal fluid (CSF) and maintaining normal blood pressure in mice fed on high salt diet. The aim of this study is to investigate the effect of high salt diet on the mean arterial pressure (MAP) in SLC14α1 depletion mice and its possible molecular mechanism.

MAIN METHODS

Adult male mice were divided into four groups: 1) UTB+/+(wild type) mice + normal salt diet (0.3% NaCl, NS); 2) UTB+/+ mice + high salt diet (8% NaCl, HS); 3) UTB-/- (SLC14α1 knockout) mice + NS; 4) UTB-/- mice + HS, each group consisted of 6 mice. The MAP of mice was measured by non-invasive detection method after HS diet for 4 weeks, followed by euthanization for brain and blood collection.

KEY FINDINGS

HS significantly elevated the MAP and CSF [Na+] in UTB-/- mice in comparison with wild type mice; however, NS didn't alter the MAP and CSF [Na+] in either wild type mice or UTB-/- mice. HS also induced the expression of ENaC-α and α1-Na+-K+-ATPase in UTB-/- mice as confirmed by RT-PCR and Western blot.

SIGNIFICANCE

These results suggest that the depletion of SLC14α1 gene in mice may contribute to the HS-induced abnormality of sodium transportation in the CSF, and lead to the elevation of MAP, which eventually promote the development of salt-sensitive hypertension.