High tissue-sodium associates with systemic inflammation and insulin resistance in obese individuals.

BACKGROUND AND AIMS: High sodium intake is associated with obesity and insulin resistance, and high extracellular sodium content may induce systemic inflammation, leading to cardiovascular disease. In this study, we aim to investigate whether high tissue sodium accumulation relates with obesity-related insulin resistance and whether the pro-inflammatory effects of excess tissue sodium accumulation may contribute to such association. METHODS AND RESULTS: In a cross-sectional study of 30 obese and 53 non-obese subjects, we measured insulin sensitivity determined as glucose disposal rate (GDR) using hyperinsulinemic euglycemic clamp, and tissue sodium content using 23Na magnetic resonance imaging. Median age was 48 years, 68% were female and 41% were African American. Median (interquartile range) BMI was 33 (31.5, 36.3) and 25 (23.5, 27.2) kg/m2 in the obese and non-obese individuals, respectively. In obese individuals, insulin sensitivity negatively correlated with muscle (r = -0.45, p = 0.01) and skin sodium (r = -0.46, p = 0.01). In interaction analysis among obese individuals, tissue sodium had a greater effect on insulin sensitivity at higher levels of high-sensitivity C-reactive protein (p-interaction = 0.03 and 0.01 for muscle and skin Na+, respectively) and interleukin-6 (p-interaction = 0.024 and 0.003 for muscle and skin Na+, respectively). In interaction analysis of the entire cohort, the association between muscle sodium and insulin sensitivity was stronger with increasing levels of serum leptin (p-interaction = 0.01). CONCLUSIONS: Higher muscle and skin sodium are associated with insulin resistance in obese patients. Whether high tissue sodium accumulation has a mechanistic role in the development of obesity-related insulin resistance through systemic inflammation and leptin dysregulation remains to be examined in future studies. CLINICALTRIALS: gov registration: NCT02236520.

Effect of cardiopulmonary bypass on plasma and erythrocytes oxylipins.

BACKGROUND: Oxylipins, the oxidative metabolites of polyunsaturated fatty acids (PUFAs), serve as key mediators of oxidative stress, inflammatory responses, and vasoactive reactions in vivo. Our previous work has established that hemodialysis affects both long chain fatty acids (LCFAs) and oxylipins in plasma and erythrocytes to varying degrees, which may be responsible for excess cardiovascular complications in end-stage renal disease. In this study, we aimed to determine changes in blood oxylipins during cardiopulmonary bypass (CPB) in patients undergoing cardiac surgery to identify novel biomarkers and potential metabolites of CPB-related complications. We tested the hypothesis that CPB would differentially affect plasma oxylipins and erythrocytes oxylipins. METHODS: We conducted a prospective observational study of 12 patients undergoing elective cardiac surgery with expected CPB procedure. We collected venous and arterial blood samples before CPB, 15 and 45 min after the start of CPB, and 60 min after the end of CPB, respectively. Oxylipins profiling in plasma and erythrocytes was achieved using targeted HPLC-MS mass spectrometry. RESULTS: Our results revealed that most venous plasma diols and hydroxy- oxylipins decreased after CPB initiation, with a continuous decline until the termination of CPB. Nevertheless, no statistically significant alterations were detected in erythrocytes oxylipins at all time points. CONCLUSIONS: CPB decreases numerous diols and hydroxy oxylipins in blood plasma, whereas no changes in erythrocytes oxylipins are observed during this procedure in patients undergoing cardiac surgery. As lipid mediators primarily responsive to CPB, plasma diols and hydroxy oxylipins may serve as potential key biomarkers for CPB-related complications.

Reorganization of inter-chromosomal interactions in the 2q37-deletion syndrome.

Chromosomes occupy distinct interphase territories in the three-dimensional nucleus. However, how these chromosome territories are arranged relative to one another is poorly understood. Here, we investigated the inter-chromosomal interactions between chromosomes 2q, 12, and 17 in human mesenchymal stem cells (MSCs) and MSC-derived cell types by DNA-FISH We compared our findings in normal karyotypes with a three-generation family harboring a 2q37-deletion syndrome, featuring a heterozygous partial deletion of histone deacetylase 4 (HDAC4) on chr2q37. In normal karyotypes, we detected stable, recurring arrangements and interactions between the three chromosomal territories with a tissue-specific interaction bias at certain loci. These inter-chromosomal interactions were confirmed by Hi-C. Interestingly, the disease-related HDAC4 deletion resulted in displaced inter-chromosomal arrangements and altered interactions between the deletion-affected chromosome 2 and chromosome 12 and/or 17 in 2q37-deletion syndrome patients. Our findings provide evidence for a direct link between a structural chromosomal aberration and altered interphase architecture that results in a nuclear configuration, supporting a possible molecular pathogenesis.

The Transcription Factor EB (TFEB) Sensitizes the Heart to Chronic Pressure Overload.

The transcription factor EB (TFEB) promotes protein degradation by the autophagy and lysosomal pathway (ALP) and overexpression of TFEB was suggested for the treatment of ALP-related diseases that often affect the heart. However, TFEB-mediated ALP induction may perturb cardiac stress response. We used adeno-associated viral vectors type 9 (AAV9) to overexpress TFEB (AAV9-Tfeb) or Luciferase-control (AAV9-Luc) in cardiomyocytes of 12-week-old male mice. Mice were subjected to transverse aortic constriction (TAC, 27G; AAV9-Luc: n = 9; AAV9-Tfeb: n = 14) or sham (AAV9-Luc: n = 9; AAV9-Tfeb: n = 9) surgery for 28 days. Heart morphology, echocardiography, gene expression, and protein levels were monitored. AAV9-Tfeb had no effect on cardiac structure and function in sham animals. TAC resulted in compensated left ventricular hypertrophy in AAV9-Luc mice. AAV9-Tfeb TAC mice showed a reduced LV ejection fraction and increased left ventricular diameters. Morphological, histological, and real-time PCR analyses showed increased heart weights, exaggerated fibrosis, and higher expression of stress markers and remodeling genes in AAV9-Tfeb TAC compared to AAV9-Luc TAC. RNA-sequencing, real-time PCR and Western Blot revealed a stronger ALP activation in the hearts of AAV9-Tfeb TAC mice. Cardiomyocyte-specific TFEB-overexpression promoted ALP gene expression during TAC, which was associated with heart failure. Treatment of ALP-related diseases by overexpression of TFEB warrants careful consideration.

HIV-1 Gag release from yeast reveals ESCRT interaction with the Gag N-terminal protein region.

The HIV-1 protein Gag assembles at the plasma membrane and drives virion budding, assisted by the cellular endosomal complex required for transport (ESCRT) proteins. Two ESCRT proteins, TSG101 and ALIX, bind to the Gag C-terminal p6 peptide. TSG101 binding is important for efficient HIV-1 release, but how ESCRTs contribute to the budding process and how their activity is coordinated with Gag assembly is poorly understood. Yeast, allowing genetic manipulation that is not easily available in human cells, has been used to characterize the cellular ESCRT function. Previous work reported Gag budding from yeast spheroplasts, but Gag release was ESCRT-independent. We developed a yeast model for ESCRT-dependent Gag release. We combined yeast genetics and Gag mutational analysis with Gag-ESCRT binding studies and the characterization of Gag-plasma membrane binding and Gag release. With our system, we identified a previously unknown interaction between ESCRT proteins and the Gag N-terminal protein region. Mutations in the Gag-plasma membrane-binding matrix domain that reduced Gag-ESCRT binding increased Gag-plasma membrane binding and Gag release. ESCRT knockout mutants showed that the release enhancement was an ESCRT-dependent effect. Similarly, matrix mutation enhanced Gag release from human HEK293 cells. Release enhancement partly depended on ALIX binding to p6, although binding site mutation did not impair WT Gag release. Accordingly, the relative affinity for matrix compared with p6 in GST-pulldown experiments was higher for ALIX than for TSG101. We suggest that a transient matrix-ESCRT interaction is replaced when Gag binds to the plasma membrane. This step may activate ESCRT proteins and thereby coordinate ESCRT function with virion assembly.

Phosphodiesterase 3A and Arterial Hypertension.

BACKGROUND: High blood pressure is the primary risk factor for cardiovascular death worldwide. Autosomal dominant hypertension with brachydactyly clinically resembles salt-resistant essential hypertension and causes death by stroke before 50 years of age. We recently implicated the gene encoding phosphodiesterase 3A (PDE3A); however, in vivo modeling of the genetic defect and thus showing an involvement of mutant PDE3A is lacking. METHODS: We used genetic mapping, sequencing, transgenic technology, CRISPR-Cas9 gene editing, immunoblotting, and fluorescence resonance energy transfer. We identified new patients, performed extensive animal phenotyping, and explored new signaling pathways. RESULTS: We describe a novel mutation within a 15 base pair (bp) region of the PDE3A gene and define this segment as a mutational hotspot in hypertension with brachydactyly. The mutations cause an increase in enzyme activity. A CRISPR/Cas9-generated rat model, with a 9-bp deletion within the hotspot analogous to a human deletion, recapitulates hypertension with brachydactyly. In mice, mutant transgenic PDE3A overexpression in smooth muscle cells confirmed that mutant PDE3A causes hypertension. The mutant PDE3A enzymes display consistent changes in their phosphorylation and an increased interaction with the 14-3-3θ adaptor protein. This aberrant signaling is associated with an increase in vascular smooth muscle cell proliferation and changes in vessel morphology and function. CONCLUSIONS: The mutated PDE3A gene drives mechanisms that increase peripheral vascular resistance causing hypertension. We present 2 new animal models that will serve to elucidate the underlying mechanisms further. Our findings could facilitate the search for new antihypertensive treatments.

Salt and cardiovascular disease: insufficient evidence to recommend low sodium intake.

Several blood pressure guidelines recommend low sodium intake (<2.3 g/day, 100 mmol, 5.8 g/day of salt) for the entire population, on the premise that reductions in sodium intake, irrespective of the levels, will lower blood pressure, and, in turn, reduce cardiovascular disease occurrence. These guidelines have been developed without effective interventions to achieve sustained low sodium intake in free-living individuals, without a feasible method to estimate sodium intake reliably in individuals, and without high-quality evidence that low sodium intake reduces cardiovascular events (compared with moderate intake). In this review, we examine whether the recommendation for low sodium intake, reached by current guideline panels, is supported by robust evidence. Our review provides a counterpoint to the current recommendation for low sodium intake and suggests that a specific low sodium intake target (e.g. <2.3 g/day) for individuals may be unfeasible, of uncertain effect on other dietary factors and of unproven effectiveness in reducing cardiovascular disease. We contend that current evidence, despite methodological limitations, suggests that most of the world's population consume a moderate range of dietary sodium (2.3-4.6g/day; 1-2 teaspoons of salt) that is not associated with increased cardiovascular risk, and that the risk of cardiovascular disease increases when sodium intakes exceed 5 g/day. While current evidence has limitations, and there are differences of opinion in interpretation of existing evidence, it is reasonable, based upon observational studies, to suggest a population-level mean target of <5 g/day in populations with mean sodium intake of >5 g/day, while awaiting the results of large randomized controlled trials of sodium reduction on incidence of cardiovascular events and mortality.

Early antihypertensive treatment and ischemia-induced acute kidney injury.

Acute kidney injury (AKI) frequently complicates major surgery and can be associated with hypertension and progress to chronic kidney disease, but reports on blood pressure normalization in AKI are conflicting. In the present study, we investigated the effects of an angiotensin-converting enzyme inhibitor, enalapril, and a soluble epoxide hydrolase inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl)urea (TPPU), on renal inflammation, fibrosis, and glomerulosclerosis in a mouse model of ischemia-reperfusion injury (IRI)-induced AKI. Male CD1 mice underwent unilateral IRI for 35 min. Blood pressure was measured by tail cuff, and mesangial matrix expansion was quantified on methenamine silver-stained sections. Renal perfusion was assessed by functional MRI in vehicle- and TPPU-treated mice. Immunohistochemistry was performed to study the severity of AKI and inflammation. Leukocyte subsets were analyzed by flow cytometry, and proinflammatory cytokines were analyzed by quantitative PCR. Plasma and tissue levels of TPPU and lipid mediators were analyzed by liquid chromatography mass spectrometry. IRI resulted in a blood pressure increase of 20 mmHg in the vehicle-treated group. TPPU and enalapril normalized blood pressure and reduced mesangial matrix expansion. However, inflammation and progressive renal fibrosis were severe in all groups. TPPU further reduced renal perfusion on days 1 and 14. In conclusion, early antihypertensive treatment worsened renal outcome after AKI by further reducing renal perfusion despite reduced glomerulosclerosis.

Hypoxia and exercise interactions on skeletal muscle insulin sensitivity in obese subjects with metabolic syndrome: results of a randomized controlled trial.

BACKGROUND: Physical activity improves insulin sensitivity in obesity. Hypoxia training is claimed to augment this effect. We tested the hypothesis that normobaric hypoxia training would improve insulin sensitivity in obese patients with metabolic syndrome. METHODS: In a randomized controlled trial, 23 obese men with metabolic syndrome who were not informed of the FiO2 conditions underwent a 6-week physical exercise intervention under ambient (n = 11; FiO2 21%) conditions or hypoxia (n = 12; FiO2 15%) using a normobaric hypoxic chamber. Three 60-min sessions of interval training were performed each week at 60% of individual V̇O2max. Assessment of myocellular insulin sensitivity by euglycemic hyperinsulinemic clamp was performed in 21 of these subjects before and after 6 weeks of training. Comprehensive phenotyping also included biopsies of subcutaneous adipose tissues. RESULTS: The intermittent moderate physical exercise protocol did not substantially change the myocellular insulin sensitivity within 6 weeks under normoxic conditions (ISIClamp: 0.035 (IQR 0.016-0.075) vs. 0.037 (IQR 0.026-0.056) mg* kg-1 *min-1/(mU* l-1); p = 0.767). In contrast, ISIClamp improved during hypoxia training (0.028 (IQR 0.018-0.035) vs. 0.038 (IQR 0.024-0.060) mg * kg-1 *min-1/(mU *l-1); p < 0.05). Between group comparison of ISIClamp change revealed a small difference between groups (Cohen's d = 0.26). Within the hypoxic group, improvement of ISIClamp during training was associated with individual increase of circulating vascular endothelial growth factor (VEGF) levels (r = 0.678, p = 0.015), even if mean VEGF levels were not modified by any training condition. Atrial natriuretic peptide (ANP) system components were not associated with increased ISIClamp during hypoxic training. CONCLUSIONS: Physical training under hypoxic conditions could partially augment the favorable effects of exercise alone on myocellular insulin sensitivity in obese men with metabolic syndrome. Concomitant changes in VEGF might represent an underlying pathophysiological mechanism.

Molecular genetics of human hypertension.

PURPOSE OF REVIEW: Genetic variance on blood pressure was shown about 100 years ago; a Mendelian inheritance was initially presumed. Platt and Pickering conducted a lively debate, whether blood pressure was inherited in a Mendelian fashion or whether the condition was polygenic. Genetic-hypertension research has appropriately followed both pathways. RECENT FINDINGS: Genome-wide association studies, Pickering model, have identified more than 500 blood-pressure loci, the targets of which are waiting to be evaluated. Then, come the 'dark-horses' of hypertension, namely 'secondary' causes. These conditions have been remarkably elucidative including pheochromocytoma, primary aldosteronism, Cushing's syndrome, and even renovascular hypertension. All these conditions feature genetic causes. Finally, arrive the Platt followers. A plethora of Mendelian conditions located within the kidney are established. These syndromes involve increased sodium (as chloride) absorption in the distal nephron. Finally, nonsalt-dependent Mendelian forms involving the vascular directly have been described. Mechanistically, Mendelian forms have large effects on blood pressure and offer effective treatment targets. SUMMARY: Which genetic models will bring us improved therapies? Ongoing studies will answer that question. It behooves the clinician to follow this dynamic area of research.

Tissue sodium stores in peritoneal dialysis and hemodialysis patients determined by 23-sodium magnetic resonance imaging.

BACKGROUND: Tissue sodium content in patients on maintenance hemodialysis (MHD) and peritoneal dialysis (PD) were previously explored using 23Sodium magnetic resonance imaging (23NaMRI). Larger studies would provide a better understanding of sodium stores in patients on dialysis as well as the factors influencing this sodium accumulation. METHODS: In this cross-sectional study, we quantified the calf muscle and skin sodium content in 162 subjects (10 PD, 33 MHD patients, and 119 controls) using 23NaMRI. Plasma levels of interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) were measured to assess systemic inflammation. Sixty-four subjects had repeat 23NaMRI scans that were analyzed to assess the repeatability of the 23NaMRI measurements. RESULTS: Patients on MHD and PD exhibited significantly higher muscle and skin sodium accumulation compared to controls. African American patients on dialysis exhibited greater muscle and skin sodium content compared to non-African Americans. Multivariable analysis showed that older age was associated with both higher muscle and skin sodium. Male sex was also associated with increased skin sodium deposition. Greater ultrafiltration was associated with lower skin sodium in patients on PD (Spearman's rho=-0.68, P = 0.035). Higher plasma IL-6 and hsCRP levels correlated with increased muscle and skin sodium content in the overall study population. Patients with higher baseline tissue sodium content exhibited greater variability in tissue sodium stores on repeat measurements. CONCLUSIONS: Our findings highlight greater muscle and skin sodium content in dialysis patients compared to controls without kidney disease. Tissue sodium deposition and systemic inflammation seen in dialysis patients might influence one another bidirectionally.

Disturbed Placental Imprinting in Preeclampsia Leads to Altered Expression of DLX5, a Human-Specific Early Trophoblast Marker.

BACKGROUND: Preeclampsia is a complex and common human-specific pregnancy syndrome associated with placental pathology. The human specificity provides both intellectual and methodological challenges, lacking a robust model system. Given the role of imprinted genes in human placentation and the vulnerability of imprinted genes to loss of imprinting changes, there has been extensive speculation, but no robust evidence, that imprinted genes are involved in preeclampsia. Our study aims to investigate whether disturbed imprinting contributes to preeclampsia. METHODS: We first aimed to confirm that preeclampsia is a disease of the placenta by generating and analyzing genome-wide molecular data on well-characterized patient material. We performed high-throughput transcriptome analyses of multiple placenta samples from healthy controls and patients with preeclampsia. Next, we identified differentially expressed genes in preeclamptic placentas and intersected them with the list of human imprinted genes. We used bioinformatics/statistical analyses to confirm association between imprinting and preeclampsia and to predict biological processes affected in preeclampsia. Validation included epigenetic and cellular assays. In terms of human specificity, we established an in vitro invasion-differentiation trophoblast model. Our comparative phylogenetic analysis involved single-cell transcriptome data of human, macaque, and mouse preimplantation embryogenesis. RESULTS: We found disturbed placental imprinting in preeclampsia and revealed potential candidates, including GATA3 and DLX5, with poorly explored imprinted status and no prior association with preeclampsia. As a result of loss of imprinting, DLX5 was upregulated in 69% of preeclamptic placentas. Levels of DLX5 correlated with classic preeclampsia markers. DLX5 is expressed in human but not in murine trophoblast. The DLX5high phenotype resulted in reduced proliferation, increased metabolism, and endoplasmic reticulum stress-response activation in trophoblasts in vitro. The transcriptional profile of such cells mimics the transcriptome of preeclamptic placentas. Pan-mammalian comparative analysis identified DLX5 as part of the human-specific regulatory network of trophoblast differentiation. CONCLUSIONS: Our analysis provides evidence of a true association among disturbed imprinting, gene expression, and preeclampsia. As a result of disturbed imprinting, the upregulated DLX5 affects trophoblast proliferation. Our in vitro model might fill a vital niche in preeclampsia research. Human-specific regulatory circuitry of DLX5 might help explain certain aspects of preeclampsia.

Pendred, pendrin, pseudohypoaldosteronism type II, and renal tubular acidosis.

The sodium chloride cotransporter is regulated by the with-no-lysine kinases 1 and 4. Mutations in these genes are responsible for Mendelian hypertension, increased sodium chloride cotransporter activity, metabolic acidosis, and hyperkalemia. Explaining metabolic acidosis and hyperkalemia has been difficult. We now learn that the versatile bicarbonate-chloride exchanger, pendrin, is important in the process. As a result, we are confronted with still another mechanism causing renal tubular acidosis.

Elevated tissue sodium deposition in patients with type 2 diabetes on hemodialysis detected by 23Na magnetic resonance imaging.

Long-term elevated blood sugar levels result in tissue matrix compositional changes in patients with diabetes mellitus type 2 (T2DM). We hypothesized that hemodialysis patients with T2DM might accumulate more tissue sodium than control hemodialysis patients. To test this, 23Na magnetic resonance imaging (23Na MRI) was used to estimate sodium in skin and muscle tissue in hemodialysis patients with or without T2DM. Muscle fat content was estimated by 1H MRI and tissue sodium content by 23Na MRI pre- and post-hemodialysis in ten hemodialysis patients with T2DM and in 30 matched control hemodialysis patients. We also assessed body fluid distribution with the Body Composition Monitor. 1H MRI indicated a tendency to higher muscle fat content in hemodialysis patients with T2DM compared to non-diabetic hemodialysis patients. 23Na MRI indicated increased sodium content in muscle and skin tissue of hemodialysis patients with T2DM compared to control hemodialysis patients. Multi-frequency bioimpedance was used to estimate extracellular water (ECW), and excess ECW in T2DM hemodialysis patients correlated with HbA1c levels. Sodium mobilization during hemodialysis lowered muscle sodium content post-dialysis to a greater degree in T2DM hemodialysis patients than in control hemodialysis patients. Thus, our findings provide evidence that increased sodium accumulation occurs in hemodialysis patients with T2DM and that impaired serum glucose metabolism is associated with disturbances in tissue sodium and water content.

CD74-Downregulation of Placental Macrophage-Trophoblastic Interactions in Preeclampsia.

RATIONALE: We hypothesized that cluster of differentiation 74 (CD74) downregulation on placental macrophages, leading to altered macrophage-trophoblast interaction, is involved in preeclampsia. OBJECTIVE: Preeclamptic pregnancies feature hypertension, proteinuria, and placental anomalies. Feto-placental macrophages regulate villous trophoblast differentiation during placental development. Disturbance of this well-balanced regulation can lead to pathological pregnancies. METHODS AND RESULTS: We performed whole-genome expression analysis of placental tissue. CD74 was one of the most downregulated genes in placentas from preeclamptic women. By reverse transcriptase-polymerase chain reaction, we confirmed this finding in early-onset (<34 gestational week, n=26) and late-onset (≥34 gestational week, n=24) samples from preeclamptic women, compared with healthy pregnant controls (n=28). CD74 protein levels were analyzed by Western blot and flow cytometry. We identified placental macrophages to express CD74 by immunofluorescence, flow cytometry, and RT-PCR. CD74-positive macrophages were significantly reduced in preeclamptic placentas compared with controls. CD74-silenced macrophages showed that the adhesion molecules ALCAM, ICAM4, and Syndecan-2, as well as macrophage adhesion to trophoblasts were diminished. Naive and activated macrophages lacking CD74 showed a shift toward a proinflammatory signature with an increased secretion of tumor necrosis factor-α, chemokine (C-C motif) ligand 5, and monocyte chemotactic protein-1, when cocultured with trophoblasts compared with control macrophages. Trophoblasts stimulated by these factors express more CYP2J2, sFlt1, TNFα, and IL-8. CD74-knockout mice showed disturbed placental morphology, reduced junctional zone, smaller placentas, and impaired spiral artery remodeling with fetal growth restriction. CONCLUSIONS: CD74 downregulation in placental macrophages is present in preeclampsia. CD74 downregulation leads to altered macrophage activation toward a proinflammatory signature and a disturbed crosstalk with trophoblasts.

The technical report on sodium intake and cardiovascular disease in low- and middle-income countries by the joint working group of the World Heart Federation, the European Society of Hypertension and the European Public Health Association.

Ingestion of sodium is essential to health, but excess sodium intake is a risk factor for hypertension and cardiovascular disease. Defining an optimal range of sodium intake in populations has been challenging and controversial. Clinical trials evaluating the effect of sodium reduction on blood pressure have shown blood pressure lowering effects down to sodium intake of less than 1.5 g/day. Findings from these blood pressure trials form the basis for current guideline recommendations to reduce sodium intake to less than 2.3 g/day. However, these clinical trials employed interventions that are not feasible for population-wide implementation (i.e. feeding studies or intensive behavioural interventions), particularly in low and middle-income countries. Prospective cohort studies have identified the optimal range of sodium intake to reside in the moderate range (3-5 g/day), where the risk of cardiovascular disease and death is lowest. Therefore, there is consistent evidence from clinical trials and observational studies to support reducing sodium intake to less than 5 g/day in populations, but inconsistent evidence for further reductions below a moderate intake range (3-5 g/day). Unfortunately, there are no large randomized controlled trials comparing low sodium intake (< 3 g/day) to moderate sodium intake (3-5 g/day) in general populations to determine the net clinical effects of low sodium intake. Until such trials are completed, it is likely that controversy about optimal sodium intake range will continue. This working group calls for the completion of large definitive clinical trials to clarify the range of sodium intake for optimal cardiovascular health within the moderate to low intake range. We support interventions to reduce sodium intake in populations who consume high sodium intake (> 5 g/day), which should be embedded within an overall healthy dietary pattern.

Speculations on salt and the genesis of arterial hypertension.

Blood pressure salt sensitivity and salt resistance are mechanistically imperfectly explained. A prescient systems medicine approach by Guyton and colleagues-more than 50 years ago-suggested how salt intake might influence blood pressure. They proposed that a high-salt diet engenders sodium accumulation, volume expansion, cardiac output adjustments, and then autoregulation for flow maintenance. The autoregulation in all vascular beds increases systemic vascular resistance, causing the kidneys to excrete more salt and water, thus reducing systems to normal and minimizing any changes in blood pressure. This schema, which is remarkably all encompassing, included all regulatory mechanisms Guyton could identify at the time. Guyton introduced the idea that the kidney is central, particularly concerning the regulation of renal pressure natriuresis. Numerous criticisms have been subsequently raised, particularly recently. Kurtz and colleagues argue that the ability of individuals to respond with an appropriate vasodilatory response to increased salt intake is pivotal. Data exist to address that issue. Salt-resistant hypertensive models provide additional information. We identified a mendelian form of hypertension not related to sodium reabsorption in the distal nephron. The hypertension develops because of increased systemic vascular resistance. In addition, we rediscovered a third salt-storage glycose-aminoglycan-related compartment, largely in the skin. This compartment operates independently of renal function, and when perturbed, is associated with salt sensitivity. More recently, we found novel molecular mechanisms demonstrating how large salt quantities are excreted by the kidneys with minimal water losses. We introduce novel interpretations as to how the kidneys excrete salt when the intake is high. The findings could have relevance as to how blood pressure may be regulated at varying salt intakes. Our purposes are to provide the readership with a banquet of thoughts to digest, to pursue Guyton's ideas, and to adjust them accordingly.