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. 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 [FE_Na: low 0.39% (0.30–0.47) vs. high 0.81% (0.73–0.98), P < 0.001; FE_water: low 1.13% (0.73–1.72) vs. high 0.89% (0.69–1.12), P = 0.015]. Despite higher FE_Na, 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. 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.

Peritonitis and exit site infections are the major complications of peritoneal dialysis (PD). Erythrocytes (red blood cells—RBCs) are extremely sensitive cells and are important health indicators. RBCs undergo programmed cell death, known as eryptosis. Recently, some reports demonstrated enhanced percentage of eryptosis in PD patients compared to healthy subjects. Unfortunately, little is known about pathogenesis of eryptosis in PD patients in stable conditions and during peritonitis, the major complications of PD. The aim of this study was to describe eryptosis level in PD patients and evaluate this parameter in PD patients with peritonitis. We enrolled 46 PD patients without any history of systemic inflammation and peritonitis in the last 3 months, as PD patients in stable conditions, 31 PD patients with acute episode of peritonitis and 17 healthy subjects (CTR). For patients with peritonitis, we collected blood sample at the first day of peritonitis. We divided PD stable patients in two groups according to the presence of residual diuresis. We considered 24 h urine volume of 500 mL or less negligible in term of residual renal function. Phosphatidylserine exposure at RBC surface, reflecting eryptosis, was estimated using flow cytometric analyses. CRP and pro-inflammatory cytokines levels (IL-1β and IL-6) were measured in plasma of all subjects at recruiting time. Furthermore, we evaluated the in vitro induction of eryptosis doing to IL-6 and IL-1β exposure at different concentrations IL-6: 2000–1000–500–250–125–62.5–31.25–0 ng/µl and IL-1β: 1000–500–250–125–62.5–31.25–15.63–0 ng/µl) and timepoints (4–8–24 h). Eryptosis was significantly higher in PD patients than in CTR (P < 0.001). Eryptosis levels did not differ significantly between PD patients with and without diabetes, with and without hypertension, with and without cardiovascular disease. Eryptosis showed no significant differences between patients treated with continuous ambulatory peritoneal dialysis/ambulatory peritoneal dialysis, with Kt/Vurea value ≤1.7 and >1.7. Twenty-three of 46 patients had a residual diuresis: the median daily urine volume was 1000 mL (IQR 662.5–1450) and the median rGFR was 2.95 mL/min (IQR 1.95–4.6). Eryptosis showed significantly lower levels in PD patients with residual diuresis than in patients without (3.7%, 2.6–5.6 versus 5%, 3.1–16; P = 0.03). Furthermore, a significant negative correlations between percentage of eryptosis and rGFR (Spearman's rho = −0.51, P = 0.01) and diuresis volume (Spearman's rho = −0.43, P = 0.05) were found. Eryptosis resulted significantly higher in PD patients with peritonitis (9.6; IQR 4.2–16.7), compared to stable patients without peritonitis (2.7; IQR 1.6–3.9; P < 0.0001). The median eryptosis did not differ in patients with relapsing episode of peritonitis (P = 0.32) and in patients with refractory peritonitis (P = 0.64). The median values of all inflammatory markers resulted significantly higher in PD patients with peritonitis compared to PD patients without (P < 0.0001). Significant positive correlations were observed between the percentage of eryptosis and all inflammatory markers. For in vitro study, cytofluorimetric analysis of eryptosis highlighted significantly higher cell death rates in RBCs incubated with higher concentrations of both cytokines compared with other concentrations and untreated cells (P < 0.05). On the basis of these results, we hypothesized that in PD patients, an increase in eryptosis levels may result from the progressive residual diuresis loss, probably due to a decreased uremic toxins clearance. These data confirm the important role of maintaining residual diuresis and rGFR in PD patients. Furthermore, in the PD population with peritonitis, we highlighted, in vivo and in vitro, a potential connection between eryptosis and the inflammatory state of peritoneal membrane damage. In this context, eryptpossi should be an additional tool to confirm the diagnosis of peritonitis and to monitor the state of peritoneal membrane.