Salt Intake Research Articles

PERSISTENT EFFECT OF SALT REDUCTION IN SCHOOLCHILDREN AND THEIR FAMILIES: ONE-YEAR FOLLOW-UP AFTER A RANDOMISED CONTROLLED TRIAL

Objective: A previous 12-month randomised controlled trial (RCT) demonstrated the effectiveness of an application-based education program, conducted through schoolchildren, in reducing the salt intake and systolic blood pressure of their adult family members. This study aimed to assess whether the effect at 12 months persisted at 24 months. Design and method: As a follow-up survey of a cluster RCT with 54 schools randomly assigned to either the intervention or control group, all participants who completed the baseline survey were contacted again at 24 months, following a 12-month non-intervention period after the RCT. The primary outcome was the difference in salt intake change between the intervention and control groups at 24 months versus baseline and 12-month follow-up, measured by the mean two consecutive 24-hour urinary sodium excretions. The secondary outcome was the difference in blood pressure change. Results: At 24 months, 542 children and 974 adults were followed up, accounting for 91.6% and 82.3% of the participants, respectively. The mean salt intake in adults at baseline, 12 months and 24 months was 10.0 g/day (standard deviation 3.5), 8.9 g/day (standard deviation 3.2) and 9.4 g/day (standard deviation 3.5) in the intervention group and 10.0 g/day (standard deviation 3.6), 9.8 g/day (standard deviation 3.9) and 9.8 g/day (standard deviation 3.9) in the control group. The mean difference in salt intake change in adults between the intervention and control groups after adjusting for confounding factors is -0.38 g/day at 24 months versus baseline (95% confidence interval -0.81 to 0.05, P=0.086), and 0.45 g/day at 24 months versus 12 months (95% confidence interval 0.01 to 0.85, P=0.046). The mean difference in systolic blood pressure change after adjusting for confounding factors is -2.19 mm Hg (95% confidence interval -3.63 to -0.76, P=0.003) at 24 months versus baseline and -0.40 mm Hg (95% confidence interval -1.86 to 1.07, P=0.596) at 24 months versus 12 months. Conclusions: The effect of the education program on adults’ salt intake faded, but the systolic blood pressure lowering effect remained 12 months after the RCT. Continuous salt reduction education is recommended to maintain the effect.

Association between adding salt in food and dementia in European descent: A mendelian randomization study.

High salt intake has been proposed as a risk factor for dementia. However, causal relationship between salt intake and dementia remains uncertain. The aim of this study was to employ a mendelian randomization (MR) design to investigate the causal impact of salt intake on the risk of dementia. Genome-wide association study (GWAS) data of exposures and outcomes (any dementia, cognitive performance, different types of dementia, Alzheimer's disease [AD], and Parkinson's disease) were obtained from the IEU database. MR estimates were generated though inverse-variance weighted model. MR-Egger, weighted median, and MR-Pleiotropy Residual Sum and Outlier (MR-PRESSO) method also used in our study. Sensitivity analyses included Cochran's Q test, MR-Egger intercept, MR-PRESSO global test and outlier test, leave-one-out analysis, and funnel plot assessment. Our MR analysis provided evidence of a causal association between high salt added to food and dementia (odds ratio [OR]=1.73, 95% confidence interval [CI]: 1.21-2.49, and p=.003), dementia in AD (OR=2.10, 95% CI: 1.15-3.83, and p=.015), and undefined dementia (OR=2.61, 95% CI: 1.26-5.39, and p=.009). Higher salt added was also associated with increased risk of AD (OR=1.80, 95% CI: 1.12-2.87, and p=.014) and lower cognitive performance (β=-.133, 95% CI: -.229 to -.038, and p=.006). This study provides evidence suggesting that high salt intake is causally associated with an increased risk of developing dementia, including AD and undefined dementia, highlighting the potential importance of reducing salt consumption as a preventive measure.

Profound Sex Differences in the Kidney Expression of Mitochondria-Related Genes in Endothelin-1 Receptor B (ETB) Deficient Rats Fed a High Salt Diet

Elevated levels of endothelin-1 (ET-1), overactivation of the ETA receptor and oxidative stress are critical in the development of hypertensive kidney disease. Females are more resistant than males to kidney damage; however, it is unclear if overactivation of the ETA receptor disrupts mitochondrial homeostasis similarly in both sexes. With these studies we aimed to determine if overactivation of the ET-1/ETA axis has a differential effect on mitochondrial homeostasis in the male and female kidney during high salt consumption. Male and female ETB deficient (ETB def) and transgenic (TG) control rats were placed on a high salt diet (4.0% NaCl) for 3 weeks. Kidneys were collected and the expression of 84 mitochondria-related genes in renal cortex and outer medulla was assessed with qRT-PCR arrays. In response to high salt, male ETB def rats displayed cortical overexpression of 13 genes when compared to male TG controls, while only 7 genes were upregulated in cortex of female ETB def rats compared to female TG controls. Genes upregulated in male ETB def rats are involved in apoptosis, mitochondrial biogenesis and transport, energy metabolism and ROS handling (selected genes, male ETB def vs. TG controls, n=3/group: Ucp1 (19-fold increase, p=0.03), Bnip3 and Scl25a21 (6-fold, p=0.003 and p=0.004, respectively), and Mfn1 (5-fold, p=0.03). Genes upregulated in females are involved in apoptosis, ROS handling and mitochondrial transport (selected examples, female ETB def vs. TG control, n=3/group: 2-fold increase in Sod1 (p=0.03), Akt1 (p=0.003) and Grpel1 (p=0.019). No common genes were changed between the sexes. When comparisons were made in the outer medulla, we found that deficiency of the ETB receptor in males resulted in a ≥30% reduction in the expression of 29 genes involved in apoptosis, mitochondrial biogenesis and transport, energy metabolism, ROS handling and other mitochondrial functions (p<0.05). On the other hand, the expression of 8 genes involved in mitochondrial transport and apoptosis was reduced by ≥80% in the female ETB def rat outer medulla vs. TG controls, while 3 genes involved in mitochondrial transport and energy metabolism had a 2-fold overexpression (p<0.05). Altogether, our results demonstrate that salt-sensitive hypertension affects mitochondrial homeostasis differentially in distinct regions of the kidney, and that the male and female kidney respond to salt in a disparate manner: with overactivation of the ET-1/ETA axis resulting in greater dysregulation of mitochondria-related genes in the male versus the female kidney during a high salt diet. Funded by UAB-UCSD O’Brien Center Summer Research Pathway for Students P30 DK079337 and KURE R25 DK115353 to BSM, NIGMS UAB CORD BBRT to GJC, and NIH K01HL145324 and Sapphire North America Return to Science Research grant to CDM. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

ARE ADOLESCENTS CONSUMING MORE SALT THAN RECOMMENDED?

Objective: To study and compare the amount and pattern of sodium (Na) consumption in urban and rural school-going adolescents in Western India and identify high risk groups for conducting awareness programs. Design and method: 1850 subjects (urban- 935; rural- 915; Males-1012, Females -838) aged 14 - 17 years were recruited with prior permission from 5 schools in and around Mumbai. Data pertaining to demography, anthropometry and eating habits was collected. A self-administered semi-quantitative Food Frequency Questionnaire was used to record consumption pattern of 22 high salt containing food items, divided into 5 categories (bakery, fried, packed, preserved and fast foods). Each participant‘s sodium consumption from these food items was calculated. Additional sodium consumption from regular meals was excluded. Data was analyzed using standard growth charts and MS Excel. Results: Only 13% of subjects added table salt. 67% and 81% brought homemade food for snacks and lunch respectively. Median Sodium consumption of the study population was 573 mg/day (∼ 1.5 g salt) (Q1-Q3:254 - 851 mg/day). There was no statistically significant difference (p> 0.05) in the Median Na consumption of girls (454 mg/day) and boys (489 mg/day). Daily Median Na consumption was not significantly different (p < 0.05) in urban students (624 mg/day) as compared to rural (592 mg/day). Bakery and fried foods together comprised 51% of sodium consumption among the rural population, whereas all five food categories had almost equal representation in the urban population. 54% subjects’ BMI (34% urban, 20% rural) was above the normal range. Higher BMI values correlated significantly with higher daily Na consumption (p =0.001, Mann-Whitney test). Conclusions: The salt intake over and above the usual dietary salt consumption was high (∼ 2 g per day for urban and ∼1.8 g/day for rural adolescents). Nearly half the study population was found to be either overweight or obese. This double whammy has a singular potential for producing future hypertensives. Thus, targeted awareness and counselling programs for salt reduction in adolescents is the urgent need of the hour.

Sodium-glucose exchanger 2 inhibitor canagliflozin promotes mitochondrial metabolism and alleviates salt-induced cardiac hypertrophy via preserving SIRT3 expression

IntroductionExcess salt intake is not only an independent risk factor for heart failure, but also one of the most important dietary factors associated with cardiovascular disease worldwide. Metabolic reprogramming in cardiomyocytes is an early event provoking cardiac hypertrophy that leads to subsequent cardiovascular events upon high salt loading. Although SGLT2 inhibitors, such as canagliflozin, displayed impressive cardiovascular health benefits, whether SGLT2 inhibitors protect against cardiac hypertrophy-related metabolic reprogramming upon salt loading remain elusive. ObjectivesTo investigate whether canagliflozin can improve salt-induced cardiac hypertrophy and the underlying mechanisms. MethodsDahl salt-sensitive rats developed cardiac hypertrophy by feeding them an 8% high-salt diet, and some rats were treated with canagliflozin. Cardiac function and structure as well as mitochondrial function were examined. Cardiac proteomics, targeted metabolomics and SIRT3 cardiac-specific knockout mice were used to uncover the underlying mechanisms. ResultsIn Dahl salt-sensitive rats, canagliflozin showed a potent therapeutic effect on salt-induced cardiac hypertrophy, accompanied by lowered glucose uptake, reduced accumulation of glycolytic end-products and improved cardiac mitochondrial function, which was associated with the recovery of cardiac expression of SIRT3, a key mitochondrial metabolic regulator. Cardiac-specific knockout of SIRT3 not only exacerbated salt-induced cardiac hypertrophy but also abolished the therapeutic effect of canagliflozin. Mechanistically, high salt intake repressed cardiac SIRT3 expression through a calcium-dependent epigenetic modifications, which could be blocked by canagliflozin by inhibiting SGLT1-mediated calcium uptake. SIRT3 improved myocardial metabolic reprogramming by deacetylating MPC1 in cardiomyocytes exposed to pro-hypertrophic stimuli. Similar to canagliflozin, the SIRT3 activator honokiol also exerted therapeutic effects on cardiac hypertrophy. ConclusionCardiac mitochondrial dysfunction caused by SIRT3 repression is a critical promotional determinant of metabolic pattern switching underlying salt-induced cardiac hypertrophy. Improving SIRT3-mediated mitochondrial function by SGLT2 inhibitors-mediated calcium handling would represent a therapeutic strategy against salt-related cardiovascular events.

Sex differences in the regulation of salt appetite in Spontaneously Hypertensive Rats after loss of interoceptive input from the kidney

The average American consumes 3,400 mg/day of sodium, 1000mg over the American Heart Association’s recommended maximum daily allowance. Excessive salt intake accelerates the progression of many diseases including hypertension, congestive heart failure, and chronic kidney disease. Reducing sodium intake has beneficial effects on a population level and in at risk patients. In previous studies we have shown that afferent renal nerves are involved in the regulation of sodium intake in DOCA hypertensive rats. Like DOCA hypertensive rats, Spontaneously Hypertensive rats (SHR) are a model with increased salt appetite. Here, we tested the hypothesis that afferent renal nerves regulate sodium intake in SHR. Secondarily, it is well documented that estrogens modulate salt intake. To examine the effect of sex on sodium intake we compared salt-appetite between male and female SHR. Bilateral afferent renal denervation (ARDN) was performed using the periaxonal application of 33mM capsaicin. In sham rats the renal arteries were isolated but not treated. Mean arterial blood pressure (MAP) was assessed using radiotelemetry, with the catheter implanted in the femoral artery. Four groups of rats were studied: male SHR-sham (n=9), female SHR-sham (n=3), male SHR+ARDN (n=8) and female SHR+ARDN (n=4). All rats were given ad libitum access to two bottles, one containing dH2O and the other containing 1.8% NaCl. The bottle position was rotated, and fluid intake was recorded daily for 21-days. ARDN caused a significant reduction in 1.8% intake in female but not male SHR rats (p=0.02, female SHR-sham v female SHR-ARDN, p>0.99 male SHR v male SHR-ARDN). This effect was specific for saline intake, water intake was not altered by ARDN in the female SHR (p=0.3). The female SHR drank more saline than male SHR when normalized to body weight (p=0.04 female SHR-sham v male SHR-sham). MAP was not reduced by ARDN in the male SHR (p=0.39), and ongoing studies are examining MAP in response to ARDN in female SHR. The data presented demonstrate for the first time that ARDN decreases salt appetite in female but not male SHR. We also found that baseline saline intake was higher in female SHR than male SHR. In future studies we will examine the renal mechanisms underlying these sex differences. Together, these data suggest that reduced sodium intake may offer an additional therapeutic benefit of renal denervation in female patients with hypertension and cardiovascular disease. LE is funded by R01HL152166; ACV is funded by FAPESP. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Global Deletion of DPP4 Prevents the Development of Salt-sensitive Hypertension in Obese Mice via Regulation of Sodium and Water Excretion

Salt-sensitivity of hypertension (HTN) occurs in up to 50% of hypertensive patients and is more common in the older population, Blacks and the obesity/diabetes/hypertension subsets. The renin-angiotensin aldosterone system (RAAS), in particular Angiotensin II (Ang II) and aldosterone known to regulate the Na+/H+ exchanger isoform 3 (NHE3) and ENaC respectively, is thought to be activated in the obesity/diabetes/hypertension subsets and thereby plays an important role in salt-sensitive HTN. RAAS blockade is an acceptable treatment for salt-sensitive HTN along with the use of diuretics. However, not every patient can tolerate RAAS blockade. Recently, dipeptidyl peptidase 4 (DPP4) has been shown to bind to NHE3, colocalizes to the microvillar fractions with active NHE3 and DPP4 inhibition reduces sodium uptake into proximal tubule cells and isolated rat proximal tubules. In addition, DPP4 may act on more distal transporters. Furthermore, data from our lab has revealed that DPP4 knockout (DPP4KO) mice have a lower sodium balance both under conditions of high salt (1.23%) and low salt (0.02%) ingestion suggesting that DPP4 regulates sodium transport and/or balance under physiological conditions. However, whether DPP4 has any effects on salt-sensitive HTN and the underlying mechanisms remain unknown. Therefore, we hypothesized that the absence of DPP4 could mitigate the development of salt-sensitive HTN in an obesity model, by improving the natriuretic and diuretic response mediated by NHE3 and/or distal mechanisms. To this end, 6-8wk old DPP4KO and C57Bl/6 littermate wild-type (WT) mice were fed a control (CD) or Western diet (WD, high in refined fats and sugars) to induce obesity. Circulating (175%) and kidney (125%) DPP4 activity were both elevated in the obese WT mice compared to the CD-fed WT mice (100%) and DPP4KO mice had minimal DPP4 activity as expected. The lack of DPP4 prevented the increase in systolic blood pressure (~15 mmHg) in the obese animals, and the absence of the development of cardiac hypertrophy in this group corroborated the pressure effect. The development of salt-sensitive HTN in the obese WT mice was associated with a lower natriuretic and diuretic response assessed by the salt overload experiment, suggesting higher tubular reabsorption of sodium and water by the nephrons. In turn, the lack of DPP4 prevented the lowering of natriuretic and diuretic response in obese mice, indicating that the beneficial effect of the absence of DPP4 on the development of salt-sensitive HTN is closely related to effects on renal tubule transport. Importantly, a high salt diet increased sodium balance and blood pressure in the obese WT mice and DPP4 deletion mitigated this increase. Furthermore, on low salt diet, the absence of DPP4 led to “salt wasting” in the obese mice similar to the CD-fed mice. Surprisingly, gene and protein expression measurements showed involvement of distal tubule sodium transporters and aquaporins and not NHE3. In contrast, assessment of the DPP4 interactome in obese mice showed binding to Myosin 6 and APN, which may regulate proximal tubule transporters and hypertension. Transdermal measurements showed no changes in the glomerular filtration rate. In conclusion, deletion of DPP4 protects against the development of salt-sensitive hypertension in obese mice by improving the natriuretic and diuretic response likely via regulation of sodium and water transporters. FAPESP, Brazil NIH K08DK115886, USA. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PRIMARY CARE PHYSICIAN'S APPROACH TOWARDS LIFESTYLE CHANGES IN HYPERTENSIVE PATIENTS

Objective: The role of lifestyle and diet changes in hypertension management is very well known. Economic constraints, additional benefits, and few or almost no side effects have made it an attractive option for hypertension control. However, it is still not widely used in primary care. This study was conducted to assess the knowledge and approach of primary care physician (PCP) towards the D.A.S.H (Dietary approaches to stop hypertension) in Tunisia. Design and method: We surveyed 132 PCPs among the 148 PCPs. We used a questionnaire on Google forms, with 16 questions assessing practices regarding the D.A.S.H, its use and source of information about it. Results: The participants had a mean duration of practice of 9.2 years (+/-3.4SD). They all receive hypertensive patients daily with an average of 6.12 (+/-2.7SD). Most of the PCPs (60.7%, n=80) recommend the lifestyle changes. However only 82.5% (n=65) of them based their recommendations on guidelines. The D.A.S.H is used by 60% (n=48), these participants knew the D.A.S.H diet through internet. Weight loss, low salt intake, daily physical activity and stop smoking were recommended by most of the PCPs. For the low salt intake, few (35%, n=28) precised that it includes sauces and cold cuts. Limiting foods that are high in saturated fat, such as fatty meats, full-fat dairy products, and tropical oils such as coconut and sugar-sweetened beverages and sweets was recommended by only 12 PCPs. Most (74%) said that lifestyle changes can alone, if well conducted, help to lower the blood pressure. Ninety percent (90%) said that they are more effective with the medication, and it could help lowering the number and the doses of the drug used. All the PCPS(n=132) said that their informations about the DASH diet and others heart-healthy diets are incomplete which may lead to the failure of the lifestyle changes. Conclusions: PCPs’ knowledge and management of lifestyle in hypertensive patients is poor in Tunisia. Our data point to a need for continually updating about the non-pharmacological treatment of hypertension

Dynamic Shift Towards Increased O2 Consumption and Reduced Lactate Uptake During Acute Volume Expansion in Sprague Dawley (SD) Rats

Rationale: In a recent study (PMID: 37575482), we established a method to assess alterations in O2 and substance metabolism in the kidneys in conscious free moving rat. This involved the repeated collection of renal arteriovenous blood and urine, alongside continuous measurements (24/7) of renal blood flow (RBF) and blood pressure (BP). Our previous studies demonstrated that in SD rats, there is an augmentation in RBF and GFR following chronic salt loading. Additionally, total renal O2 consumption (VO2) increases while there is a decrease in the net consumption of lactate with a tendency for its increased production. We hypothesize that these changes are not exclusive to the chronic phase of salt-loading but can also manifest during rapid increases of RBF and GFR. The primary aim of this study was to establish an experimental model reflecting these dynamics. Methods: SD rat (male, 10 wk age fed 0.4 NaCl (LS) diet, n=8) were studied. The jugular vein and femoral vein and artery were catheterized together with the renal vein. FITC-inulin (2 mg/mL) dissolved in 2%BSA saline was infused at 1.0 mL/100 g body wt/h from jugular vein. RBF was measured with an ultrasonic flow probe (Transonic, Inc) on the left renal artery and BP was measured through an arterial catheter. Whole blood, collected from donor rats, was diluted by 20% with saline, and a 6 mL volume expansion was performed with this solution over 1 hour. Blood was collected from both the renal venous and arterial catheters and urine from a ureteral catheter before and after volume expansion. O2 content was measured by radiometer and plasma lactate measured with a high sensitivity L-lactate fluorescent assay kit (ab169557, abcam). The same experiment was performed without volume expansion (i.e., sham study). O2 and lactate delivery and consumption were calculated as follows: Delivery = arterial content (A) x RBF; Consumption = (A − renal venous content (RV)) x RBF; Extraction = (A-RV) / A. Results: BP increased from 101 ± 3 to 111 ± 4 mmHg (p<0.05), RBF increased from 5.4 ± 0.5 to 7.9 to 0.6 mL/min/g kidney weight (gkw) (p<0.05) by volume expansion. GFR increased from 0.94 ± 0.06 to 1.19 ± 0.08 mL/min/gkw (p<0.05). O2 delivery increased from 1.06 ± 0.09 to 1.61 ± 0.12 mL/min/gkw (p<0.05). O2 consumption (VO2) increased from 0.06 ± 0.01 to 0.08 ± 0.01 mL/min/gkw (p<0.05). The O2 extraction ratio remained unchanged. Both lactate consumption (0.94 ± 0.11 to 0.47 ± 0.11 mM/gkw, p<0.05) and extraction ratio (0.18 ± 0.01 to 0.11 ± 0.02, p<0.05) were reduced by volume expansion. Conclusion: The increase of O2 consumption and reduction of lactate consumption with acute volume expansion model appear to be similar to those that we observed when SD rats were subjected to a chronic step increase of salt intake (from 0.4 to 4.0% NaCl). In contrast, however, an increase in O2 extraction was not observed with acute volume expansion as was the case with a high salt diet in which our studies have indicated that a prolonged tubular reabsorptive workload leads to enhanced oxidative stress with an uncoupling of oxidative phosphorylation. R01 HL151587, AHA 23POST1008714. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

COMPARISON OF OFFICE-BASED BLOOD PRESSURE TO DAYTIME CUFFLESS BLOOD PRESSURE IN A POPULATION-BASED STUDY

Objective: The latest ESH 2023 guidelines still recommend the use of office blood pressure (BP) measurement for the diagnosis and the follow-up of arterial hypertension. Although cuffless (BP) devices are attractive for patients due their practicality and easy to use, they are not yet recommended by international guidelines. The aim of this project was to test the diagnostic performance of a cuffless device in the adult Swiss population. Design and method: This was a multicentric sub-study nested within a nationwide population-based survey on dietary salt intake in Switzerland. Blood pressure was measured 5 times with a validated oscillometric device (Omron HEM-907) on two separate visits according to a standardized protocol. Cuffless blood pressure using the Aktiia® bracelet was measured intermittently over 24 hours in between visits. The device was calibrated on the first visit using an independent oscillometric device. The average of the last four office BP at each visit was compared to the daytime average BP from the cuffless device with a Bland-Altman plot. Results: Of the 863 individuals included in the study, 511 (46% women, age: 48.6±15.8 years) had their BP taken with both devices. The median number of BP measurements with the cuffless device was 46(IQR 28-90)). Bland and Altman analysis revealed a difference of 0.015 (CI -0.734 to 0.763) in systolic BP and of 0.380 (CI -0.216 to 0.975) in diastolic BP (Figure 1). The agreement for the diagnosis of hypertension was 92.4% with a kappa of 0.61±0.04 for systolic BP and 94.7% with a kappa of 0.50±0.04. Conclusions: In this adult population-based study, the accuracy and the diagnostic performance of a cuffless device were promising. The differences may be secondary to either accuracy or to white coat/masked effect reflecting the different environments of BP measures.

POLYCYSTIC OVARY SYNDROME (PCOS) AND ITS TREATMENT AS CAUSE OF SECONDARY ALDOSTERONISM: A DOG CHASING ITS TAIL

Objective: Polycystic Ovary Syndrome (PCOS) is a complex endocrine-metabolic disorder affecting about 7% of childbearing women. PCOS is characterized by anovulation, hyperandrogenism, insulin resistance and it is associated with an increased cardiovascular risk. PCOS patients may exhibit high blood pressure and signs of hydro-saline retention. Therefore, clinicians would be interested in performing hormonal screening for secondary hypertension. Design and method: We perform the aldosterone/direct renin concentration ratio as a screening test for primary aldosteronism (PA). The test was proceed after serum potassium correction and previous a wash-out period of interfering medications. The recumbent saline suppression test was performed with infusion of 2L NaCl 0.9% in 4 hours under standardized salt intake (9gr/24h). Aldosterone and direct renin were determined by chemiluminescent immunoassay technology (DiaSorin®). Results: A 33yrs old woman attended our renal outpatient clinic because of recurrent episodes of generalized swelling, diuresis contraction and fluid retention. The patient, known for PCOS, was treated with combined oral contraceptives and loop diuretics. She had no history of hypertension, but she repeatedly displayed very high aldosterone values. Clinical examination was unremarkable, in-office and home blood pressure values were normal. Laboratory data showed normal renal function and the absence of acid-base disorders; serum potassium was at lower limit of normal. A CT-scan showed normal adrenal glands. We performed a recumbent saline suppression test, previous a wash-out period of oral contraceptives (> 6 weeks) and loop diuretics (> 2 weeks). The results listed below are consistent with a baseline hyperaldosteronism with normal aldosterone adrenal response to volume expansion, excluding PA. Several years before, the same results were presented, without suspension of the oral contraceptives. Conclusions: In patients with PCOS the increased adrenal production of aldosterone is usually secondary and independent from the renin-aldosterone axis (direct stimulation of adrenal zona glomerulosa via testosterone). Other iatrogenic factors may affect the renin-aldosterone values, such us the use of oral contraceptives and diuretics. Therefore, a confirmatory test performed under standardized conditions is often required, in order to exclude primary versus secondary forms of hyperaldosteronism.

Peripheral Blood Mononuclear Cells from Patients with Systemic Lupus Erythematosus Induce Salt Sensitivity of Blood Pressure in Humanized Mice

Salt sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular disease (CVD), even in normotensive people. Systemic lupus erythematosus (SLE) is also a risk factor for CVD and hypertension. SLE and CVD are on the rise, and it is not known if this is attributable to the increased dietary salt in the modern diet and SSBP. Isolevuglandins (IsoLGs) adduct self-proteins forming neoantigens in antigen presenting cells (APC) to activate T cells and produce cytokines that promote sodium retention, kidney damage, salt sensitivity of blood pressure, and SLE. We hypothesized that high salt intake increases both blood pressure and the proinflammatory milieu in mice humanized with the immune cells of patients with SLE. We humanized female NSG/MHCI/MHCII−/− immunodeficient mice with peripheral blood mononuclear cells (PBMCs) isolated from patients with SLE (n=5) and controls without autoimmune disease (n=4). The blood pressure was measured with radiotelemetry, immune phenotyping was performed with flow cytometry, and vascular reactivity was assessed in mesenteric arteries using wire myography after two weeks of a 4% high salt diet. High salt treatment significantly increased systolic blood pressure in lupus mice compared to the controls (135.5 vs. 123.8 mmHg, p=0.014). APC infiltration (macrophages, monocytes, dendritic cells), their activation (CD86) and proinflammatory markers (IL-23 p19, TNF-alpha), and oxidative stress (Isolevuglandins, Nox2) were significantly higher in the kidneys of lupus mice. Moreover, the signaling molecule p-STAT3 was significantly higher in myeloid cells in the kidneys of lupus mice. The classical monocyte and proinflammatory markers were significantly elevated in the spleen lymphocytes, and proinflammatory markers were increased in the kidney, spleen, and aorta in lupus mice. These mice exhibited vascular dysfunction (p<0.05), suggesting reduced vascular compliance. We measured urine albumin and found that lupus mice tended to excrete more albumin than the controls (17.24 vs. 25.89 μg/ml p=0.142), suggesting greater kidney injury. In conclusion, our findings suggest that immune cells from patients with SLE, in response to high salt intake, increase blood pressure and the proinflammatory milieu in the kidney, aorta, and spleen; impair vascular compliance; and worsen albuminuria in immunodeficient mice. 1R01HL144941-01A1 1R03HL155041 23CDA1053072. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

High Salt Diet Regulates Intrarenal Sex Steroid Biosynthesis Pathway in a Sex-Specific Manner

Hypertension is more prevalent in men than age-matched pre-menopausal women. Sodium (Na+) homeostasis plays a major role in the control of blood pressure. Renal medullary estrogenic signaling promotes Na+ excretion in female, but not male Sprague Dawley (SD) rats implicating estrogen as a potential female-specific natriuretic factor. Recently we showed that the components of estrogen biosynthesis pathway are expressed in rat kidney suggesting the kidneys can produce estrogen locally to invoke this natriuretic response. It is unknown how dietary Na+ impacts biosynthesis of sex hormones. We hypothesize that a high salt (HS) diet enhances intrarenal estrogen biosynthesis pathway, and this enhancement is more pronounced in females compared to males. To test this hypothesis, we harvested the renal cortex from 14 week old male and female SD rats maintained on either a normal salt (NS 0.3% NaCl) or HS (4% NaCl) diet for 5 days. Given that cholesterol is the main precursor of steroid hormones, we measured the mRNA expression of HMG-CoA reductase (HMGCR), the key enzyme for cholesterol synthesis; and the steroidogenic acute regulatory protein (StAR), which transports cholesterol into the mitochondria for steroid commitment. We also assessed the mRNA expression of steroid 5α reductase (SRD5A), which converts testosterone to the non-aromatizable androgen, dihydrotestosterone. Further, we assessed aromatase, the key enzyme in estrogen biosynthesis, via immunohistochemistry. We found that renal HMGCR was more abundant in female compared to male rats maintained on a NS diet (P=0.0467). Increasing dietary salt intake upregulated renal HMGCR expression in male (P=0.0020), but not female rats (NS male; 100.0 ± 26.8 vs. NS female; 235.3 ± 23.2 vs. HS male 294.6 ± 42.0 vs HS female 314.6 ± 21.0 relative expression % NS male n=6-7/group). On a NS diet, renal StAR was more abundant in female compared to male rats (NS male; 100.0 ± 25.3 vs. NS female; 217.2 ± 36.5 relative expression % NS male P=0.0255 n=5-7/group). Increasing dietary salt did not alter expression of StAR in either sex. Similarly, renal SRD5A expression was higher in female compared to male (P=0.0141) rats. In addition, a HS diet increased the expression of SRD5A in female rats (0.0093) and tended to increase SRD5A expression in male (P=0.0849) rats (NS male; 100.0 ± 11.6 vs. NS female; 297.8 ± 37.7 vs. HS male 243.0 ± 39.2 vs HS female 498.8 ± 44.8 relative expression % NS male n=6-7/group). We also revealed that aromatase was expressed at a comparable level in male and female renal cortex, regardless of the diet (NS male; 2.4 ± 0.3 vs. NS female; 2.6 ± 0.3 vs. HS male 2.8 ± 0.3 vs HS female 1.9 ± 0.1 Average intensity x area mM2 n=6-9/group). Together, this data suggests that (i) the female kidney may be more primed for steroid biosynthesis and (ii) there is a sex-specific upregulation of the intrarenal sex steroid biosynthesis pathway in response to increasing dietary salt intake. Additional work is required to investigate the potential role of the kidney in androgen and estrogen production. A better understanding of this steroidogenic pathway could reveal novel sex-specific therapeutics for hypertension. T32DK007569-34 Carl Gottschalk Grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Kidney resident memory CD8 T cells mediate recurrence of salt-sensitive hypertension

One of the significant challenges in treating hypertension is insuffcient blood pressure (BP) control and recurring high BP due to high salt intake or cessation of medication. We previously reported that CD8 T cells contribute to the pathogenesis of salt-sensitive hypertension. Notably, while antihypertensive therapy temporarily lowered BP in hypertensive mice, it failed to disrupt T cell residency in the kidneys, and high BP recurred after stopping treatment. Building on these findings, we hypothesize that the establishment of long-living resident memory CD8Ts (CD8Trms) in the kidney is essential in the progression and recurrence of salt-sensitive hypertension. To test this hypothesis, we employed both wild-type (WT) mice and mice with T-cell-specific KO of TGFβRII (Tsp-TGFβRKO), which prevents the formation of resident memory T cells (Trms). Our mouse models of hypertension include the classic DOCA + salt (DOCA) model and an Angiotensin II (Ang II) model simulating the recurrence of hypertension induced by salt memory. In this salt-memory model, the initial BP elevation was induced by a one-week infusion of Ang II. Following recovery and the normalization of blood pressure after removal of Ang II, the mice were subjected to a chronic high salt intake to rechallenge their blood pressure. Throughout the experiments, we continuously recorded blood pressure using radiotelemetry. We isolated and extensively examined T cells from the spleen (representing circulating T cells) and the kidney (Trms) using multicolor flow cytometry. As expected, DOCA treatment induced salt-sensitive hypertension in WT mice, accompanied by a significant expansion of the CD8Trm population within their kidneys. Intriguingly, this population of CD8Trms was notably diminished in the kidneys of DOCA-treated Tsp-TGFβRKO mice. Importantly, mice lacking CD8Trms in their kidneys exhibited attenuated BP elevation upon DOCA treatment. Additionally, in the Ang II-induced salt-memory model, WT mice demonstrated recurring hypertension as they quickly developed hypertension not only during Ang II infusion but also when faced with the high-salt challenge after the resting period. Testing the capability of retaining salt memory in mice unable to develop Trm, we repeated this model in the Tsp-TGFβRII KO mice. Initially, no significant difference was observed in the initial development of hypertension with Ang II or the return to baseline blood pressure during the resting period in Tsp-TGFβRII KO mice compared to WT. However, when challenged with high salt after a resting period, the Tsp-TGFβRII KO mice remained normotensive, while their WT counterparts quickly redeveloped hypertension. Isolation of T cells from the kidney at the end of the model confirmed significant CD8Trm population development in the WT mice, which was absent in the Tsp-TGFβRII KO mice. In summary, our study revealed a critical role of kidney CD8Trms in contributing to salt-sensitive hypertension and conferring the ‘salt memory’ that mediates its recurrence. The key molecules that participate in establishing the kidney CD8Trms represent potential therapeutic targets for developing new medications to manage the progression of hypertension and mitigate its persisting effects. T32 T-SPaT GM150536 (Deck), NIH R01-HL146713 (Mu), AHA 23TPA10764467 (Mu). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sex Differences in Blood Pressure Response to Dietary Salt in Aged Rats

Background: The impact of dietary salt intake on blood pressure (BP) and its variability is critical for understanding cardiovascular risks, yet there is a scarcity of data exploring these effects across different sexes, particularly in the context of aging. Methods: This study examined the effects of varying salt diets on BP among aged female and male Sprague-Dawley rats (22-24 months). Subjects were administered either a control (0.4% NaCl), low (0.1% NaCl), or moderate-high (1% NaCl) salt diet for 12 weeks. BP levels and variability were measured at baseline, 2, 4, 8, and 12 weeks after dietary onset. Results: Preliminary findings revealed that, from the eighth week following dietary initiation, aged male rats exhibited a pronounced elevation in systolic BP when exposed to all types of diets, in contrast to aged female rats consuming low-salt diets. Additionally, aged male rats presented with a marked rise in diastolic BP upon consumption of both control and high-salt diets relative to female rats across all diets from the eighth week onward. Although systolic BP variability did not differ significantly between sexes, there were marked sex-specific differences in diastolic BP variability. Conclusions: The study identified sex-specific responses in BP and its variability to dietary salt intake in aged rats, with male rats showing heightened sensitivity. These findings underscore the importance of considering sex as a biological variable in dietary and cardiovascular health research. This research was funded by the START-UP FUNDING OF HANGZHOU NORMAL UNIVERSITY, grant number 4255C50221204123 (Dr. Fen Sun). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Immune Metabolic Reprogramming by Excess Dietary Salt in Salt Sensitive Hypertension via CXCL8

Salt sensitivity of blood pressure (SSBP) is when blood pressure changes parallel to salt loading/ depletion and is an independent risk factor for cardiovascular disease. Despite its importance, there is no feasible diagnosis, which limits investigational studies to identify therapeutic targets. We have found that immune cells mediate SSBP via Epithelial Sodium Channel (ENaC). CXCL8/(IL-8), a known chemoattractant plays a well-known role in glycolysis. We hypothesize that CXCL8 mediates immune metabolic reprogramming of immune cells to glycolysis via ENaC. To test this hypothesis, we performed bulk and single cell RNA sequencing in human monocytes from individuals from a modified Weinberger inpatient salt loading/ depletion protocol. The participants were instructed to refrain from taking their blood pressure medication for 2 weeks prior to the salt loading/depletion protocol. Blood and urine samples were collected, as well as ambulatory blood pressure recording. We found that changes in immune cell activation via isolevuglandin (IsoLG) protein-adducts mirror changes in salt balance and blood pressure in salt sensitive but not salt resistant individuals. We confirmed that these in vivo changes can be recapitulated in vitro. In addition, we found that salt-loading both in vivo and in vitro increases antigen presenting cell production of IL-8, which was reversed after salt depletion in salt sensitive, but not salt resistant people. ENaC inhibition by amiloride prevented the high salt-induced production of IL-8. Moreover, high salt induced blood pressure changes of expression of CXCL8 (p = 0.01553, r = 0.8067) were significant along with varying expression of glycolytic genes, including hexokinase 1(HK1)(p = 0.04190, r = -0.7249), phosphofructokinase (PFKP)(p = 0.05932, r = 0.6879) and galactose mutarotase (GALM) (p = 0.04176, r = 0.5138). Seahorse analysis revealed increased extracellular acidification rate (ECAR) in high salt conditioned monocytes, which was associated with mitochondrial dysfunction. Our results suggest that high salt intake reprograms antigen presenting cell metabolism to glycolysis via IL-8 signaling. Furthermore, targeting IL-8 and mitochondrial switching to glycolysis may not only provide novel therapeutic approaches, but also important biomarkers for diagnosis of salt sensitivity of blood pressure. 1R03HL155041-01 (Kirabo, PI), 1R01HL144941-01A1 (Kirabo, PI), 5R01HL147818-22 (Kleyman & Kirabo), 1R01HL157584-01 (Shibao, Kirabo — MPI), R01DK135764 (Kon, Shelton, Kirabo — MPI), R21TW012635 (Kirabo, Masenga — MPI), Meharry Medical College: School of Graduate Studies T32AI007281, T32GM14492, andT32HL00773. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

INCREASED INTAKE OF TABLE SALT AS A RISK FACTOR FOR THE DEVELOPMENT OF ARTERIAL HYPERTENSION

Objective: to study association of high table salt intake with hypertension among hypertensive patients of Aral Sea region of Uzbekistan. Design and method: The results of screening of the population over 40 years of age (total 2430 respondents) in family clinics of the region were analyzed, according to the modified (for the region of Central Asia and Transcaucasia) PEN WHO protocol. From the total number of respondents, individuals with high blood pressure (BP) 140/90 mm Hg or more were selected. Taking into account the Aral Sea region, characterized by an unfavorable climate and salinity of soil and water, all subjects were tested according to the method of R. Henkin to determine the threshold of taste sensitivity to table salt. Results: The 2019 STEPS Uzbekistan study shows that more than a third (36.6%) of residents always or often add or directly during meals and more than a third (36.2%) always or often eat processed foods high in salt. Hypertensive patients in the Aral region were characterized by a pronounced prevalence of a high threshold of taste sensitivity to table salt: in the general group - 85.6%, women 83.7%, men 88.7%, which on average required more than 0.32% NaCl concentration to assess the threshold. At the same time, there was a noticeable direct correlation between hemodynamic parameters – systolic and diastolic BP, mean BP and NaCl concentration in the test for determining the taste sensitivity to table salt threshold (r = 0.646; r = 0.610; r = 0.645, respectively). A survey on proper nutrition, according to the PEN protocol, also showed that 68% of those surveyed added salt to their food and/or consumed saltiness in their diet, with a slight difference between women and men: women 61.2%, men 72.6%, which is significantly more similar indicators identified. Conclusions: As our results showed, among patients with hypertension in the Aral region, high consumption of table salt prevails, which is confirmed by a high threshold of taste sensitivity to NaCl. A correlation was revealed between a high threshold of taste sensitivity to table salt and blood pressure in hypertensive patients.

ACUTE EFFECTS OF SODIUM CHLORIDE OR ITS SUBSTITUTE POTASSIUM CHLORIDE ON VASCULAR FUNCTION IN HEALTHY VOLUNTEERS

Objective: High blood pressure, one of the most important risk factors for cardiovascular mortality, leads to vascular dysfunction and subsequently to arteriosclerosis, stroke, kidney and heart failure. High salt intake and low potassium intake are associated with high blood pressure and an increased risk of cardiovascular disease and mortality. Partial replacement of sodium with potassium led to a lower risk of cardiovascular events and death in a long-term follow-up study. However, the exact mechanism remains unclear. Our aim was to investigate the acute effects of sodium or potassium intake on vascular health to unravel the underlying mechanisms leading to vascular adaptations. Design and method: Six male and nine female healthy individuals (mean age 31 years) were randomized to either 9g of sodium chloride (high salt group), 6g of sodium chloride (regular salt group) or 6 g of sodium chloride plus 3g of potassium chloride group (substitution group). Individuals received a salty soup with the corresponding sodium or potassium load. Blood analyses, blood pressure, body composition and macro- as well as microvascular measurements were performed before as well as four (t4) and 24 hours (t24) after soup intake. To investigate macrovascular health, carotid-to-femoral pulse wave velocity was analyzed. Microvascular health was measured by investigating retinal vessel diameters. Results: The high (139±2mmol/l vs. 143±2mmol/l p=0,003) and regular salt group (140±2mmol/l vs. 141±0,6 mmol/l p=0,029) showed both higher serum sodium concentrations at t4 compared to baseline. These higher values were normalized at t24. The serum sodium concentration of the substitution group showed no statistically significant difference between timepoints. The substitution group showed improved microvascular health, quantified by higher arteriolar-to-venular diameter ratio from baseline to t4 (0,86±0,09 vs. 0,89±0,08 p=0,005). These improvements were regressive at t24 (0,88±0,09). No statistically significant changes were found on pulse wave velocity. The high and regular salt group showed no statistically significant differences at any timepoint on micro- or macrovascular health parameters. Conclusions: Replacement of sodium by potassium seems to improve microvascular function directly after potassium intake. These results might explain the long-term beneficial effects of potassium on cardiovascular outcomes.

Synergistic effect of combining umami substances enhances perceived saltiness

Umami substances have the potential to enhance the perception of saltiness and thus reduce sodium intake. Two sensory evaluation experiments were conducted, involving participants tasting salt solutions, and solutions with added umami substances at equal sodium concentrations. Umami substances included sodium glutamate (MSG), disodium inosinate (IMP), and the combination of them which has a synergistic effect and is a closer match to commonly-consumed foods. In Experiment 1, using the two-alternative forced-choice (2-AFC) method by 330 consumers, paired comparisons were conducted at three different sodium concentrations. The combination of MSG and IMP enhanced the perception of saltiness (p < .001 in the difference test), whereas presenting either umami substance in isolation failed to do so (p > .05 in the similarity test). Significant order effects occurred in paired comparisons. In Experiment 2, a two-sip time-intensity (TI) analysis with trained panellists verified these results and found that tasting MSG and IMP either simultaneously or successively enhanced saltiness perception at equal sodium concentrations. These findings indicate that the synergistic effect of umami substances may be the cause of saltiness enhancement, and represents a potential strategy for sodium reduction while satisfying the consumer demand for saltiness perception. Considering the application in food processing and in food pairing, umami substances can potentially be used to help to reduce salt intake in food consumption.

ASSESSMENT AND MANAGEMENT OF PATIENTS WITH OBESITY AND HYPERTENSION IN EUROPEAN SOCIETY OF HYPERTENSION EXCELLENCE CENTRES. A SURVEY FROM THE ESH WORKING GROUP ON DIABETES AND META

Objective: Healthcare providers are faced with an increasing number of patients with obesity and arterial hypertension. Preventing obesity-associated hypertension and appropriately managing patients with established disease are both important. Hence, the aim of our study was to evaluate the clinical care of patients with obesity and hypertension among ESH Excellence Centres (ECs). Design and method: We conducted a cross-sectional, worldwide 30-item survey through e-mails. Results: In total, 70 representatives of ECs participated (78% men) with 66% of them practicing medicine for more than 30 years and working in well-equipped clinics. Most were internists (41%) and cardiologists (37%) and 73% reported training on the management of obese patients with hypertension. A majority weigh their patients (77%) and evaluate patients for sleep disorders (93%). However, only 47% spend more than 5 min to advise for lifestyle modification in general, 59% for weight loss, 56% for salt intake and 64% for exercise. Finally, a minority of participants ask patients if they like their body (6%) or about previous attempts to lose weight (28%), evaluate 24h urinary sodium excretion rate (22%) and provide written (15%) or personalized (10%) dietary advices. If the patient suffers also from type 2 diabetes mellitus, 66% switch treatment to GLP1 receptor agonists and 60% to SGLT2 inhibitors. Conclusions: Most clinicians in ESH ECs are well educated regarding obesity-associated hypertension, and clinics are sufficiently equipped to manage these patients, as well. However, several deficits were reported regarding efforts to address and implement obesity specific aspects and interventions to improve care in patients with obesity and hypertension.