Water Conservation Overrides Osmotic Diuresis During SGLT2 Inhibition in Patients With Heart Failure

BACKGROUND

Sodium-glucose cotransporter 2 inhibitors are believed to improve cardiac outcomes due to their osmotic diuretic potential.

OBJECTIVES

The goal of this study was to test the hypothesis that vasopressin-driven urine concentration overrides the osmotic diuretic effect of glucosuria induced by dapagliflozin treatment.

METHODS

DAPA-Shuttle1 (Hepato-renal Regulation of Water Conservation in Heart Failure Patients With SGLT-2 Inhibitor Treatment) was a single-center, double-blind, randomized, placebo-controlled trial, in which patients with chronic heart failure NYHA functional classes I/II and reduced ejection fraction were randomly assigned to receive dapagliflozin 10 mg daily or placebo (1:1) for 4 weeks. The primary endpoint was change from baseline in urine osmolyte concentration. Secondary endpoints included changes in copeptin levels and solute free water clearance.

RESULTS

Thirty-three randomized, sodium-glucose cotransporter 2 inhibitor-naïve participants completed the study, 29 of whom (placebo: n = 14; dapagliflozin: n = 15) provided accurate 24-hour urine collections (mean age 59 ± 14 years; left ventricular ejection fraction 31% ± 9%). Dapagliflozin treatment led to an isolated increase in urine glucose excretion by 3.3 mmol/kg/d (95% CI: 2.51-4.04; P < 0.0001) within 48 hours (early) which persisted after 4 weeks (late; 2.7 mmol/kg/d [95% CI: 1.98-3.51]; P < 0.0001). Dapagliflozin treatment increased serum copeptin early (5.5 pmol/L [95% CI: 0.45-10.5]; P < 0.05) and late (7.8 pmol/L [95% CI: 2.77-12.81]; P < 0.01), leading to proportional reductions in free water clearance (early: -9.1 mL/kg/d [95% CI: -14 to -4.12; P < 0.001]; late: -11.0 mL/kg/d [95% CI: -15.94 to -6.07; P < 0.0001]) and elevated urine concentrations (late: 134 mmol/L [95% CI: 39.28-229.12]; P < 0.01). Therefore, urine volume did not significantly increase with dapagliflozin (mean difference early: 2.8 mL/kg/d [95% CI: -1.97 to 7.48; P = 0.25]; mean difference late: 0.9 mL/kg/d [95% CI: -3.83 to 5.62]; P = 0.70).

CONCLUSIONS

Physiological-adaptive water conservation eliminated the expected osmotic diuretic potential of dapagliflozin and thereby prevented a glucose-driven increase in urine volume of approximately 10 mL/kg/d · 75 kg = 750 mL/kg/d. (Hepato-renal Regulation of Water Conservation in Heart Failure Patients With SGLT-2 Inhibitor Treatment [DAPA-Shuttle1]; NCT04080518).

Mfsd2a-mediated lysolipid transport is important for renal recovery after acute kidney injury

Acute kidney injury (AKI) is a global public health concern with high mortality and morbidity. In ischemic-reperfusion injury (IRI), a main cause of AKI, the brush border membrane of S3 proximal tubules (PT) is lost to the tubular lumen. How injured tubules reconstitute lost membrane lipids during renal recovery is not known. Here, we identified Mfsd2a, a sodium-dependent lysophosphatidylcholine (LPC) transporter, to be expressed specifically in the basolateral membrane of S3 PT. Using an in vivo activity probe for Mfsd2a, transport activity was found to be specific to the S3 PT. Mice with haploinsufficiency of Mfsd2a exhibited delayed recovery of renal function after acute IRI, with depressed urine osmolality and elevated levels of histological markers of damage, fibrosis, and inflammation, findings corroborated by transcriptomic analysis. Lipidomics revealed a deficiency in docosahexaenoic acid (DHA) containing phospholipids in Mfsd2a haploinsufficiency. Treatment of Mfsd2a haploinsufficient mice with LPC-DHA improved renal function and reduced markers of injury, fibrosis, and inflammation. Additionally, LPC-DHA treatment restored S3 brush border membrane architecture and normalized DHA-containing phospholipid content. These findings indicate that Mfsd2a-mediated transport of LPC-DHA is limiting for renal recovery after AKI and suggest that LPC-DHA could be a promising dietary supplement for improving recovery following AKI.

Association of Antihypertensive Effects of Esaxerenone with the Internal Sodium Balance in Dahl Salt-Sensitive Hypertensive Rats

Background: The nonsteroidal mineralocorticoid receptor blocker esaxerenone is effective in reducing blood pressure (BP). Objective: In this study, we investigated esaxerenone-driven sodium homeostasis and its association with changes in BP in Dahl salt-sensitive (DSS) hypertensive rats. Methods: In the different experimental setups, we evaluated BP by a radiotelemetry system, and sodium homeostasis was determined by an approach of sodium intake (food intake) and excretion (urinary excretion) in DSS rats with a low-salt diet (0.3% NaCl), high-salt diet (HSD, 8% NaCl), HSD plus 0.001% esaxerenone (w/w), and HSD plus 0.05% furosemide. Results: HSD-fed DSS rats showed a dramatic increase in BP with a non-dipper pattern, while esaxerenone treatment, but not furosemide, significantly reduced BP with a dipper pattern. The cumulative sodium excretion in the active period was significantly elevated in esaxerenone- and furosemide-treated rats compared with their HSD-fed counterparts. Sodium content in the skin, skinned carcass, and total body tended to be lower in esaxerenone-treated rats than in their HSD-fed counterparts, while these values were unchanged in furosemide-treated rats. Consistently, sodium balance tended to be reduced in esaxerenone-treated rats during the active period. Histological evaluation showed that esaxerenone, but not furosemide, treatment attenuated glomerulosclerosis, tubulointerstitial fibrosis, and urinary protein excretion induced by high salt loading. Conclusions: Collectively, these findings suggest that an esaxerenone treatment-induced reduction in BP and renoprotection are associated with body sodium homeostasis in salt-loaded DSS rats.

Effects of molidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, on sodium dynamics in hypertensive subtotally nephrectomized rats

Hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitors were developed for treatment of renal anemia. Patients applicable for HIF-PHD inhibitor treatment experience complications such as chronic kidney disease, whereby water and electrolyte homeostasis is disrupted. The effects of hypoxia-inducible factor stabilization on salt accumulation in the setting of reduced renal function remain unclear. In the present study, we investigated the effect of a HIF-PHD inhibitor, molidustat, on salt distribution and excretion in rats with subtotal nephrectomy-induced chronic kidney disease. Male Wistar rats were subjected to 5/6 nephrectomy. After confirming blood pressure elevation (>150 mmHg, at 4 weeks after surgery), rats were treated with molidustat. After 1 week of treatment, molidustat did not significantly improve blood cell volume or blood pressure. Distribution of sodium, potassium, and water in skin, carcass, and bone samples was not affected by molidustat. Furthermore, molidustat had no significant effect on urinary sodium excretion or concentration in response to acute oral salt loading (1 g/kg). In conclusion, molidustat did not affect distribution or excretion of salt in rats subjected to a model of nephron loss.

Adaptive physiological water conservation explains hypertension and muscle catabolism in experimental chronic renal failure

Aim

We have reported earlier that a high salt intake triggered an aestivation‐like natriuretic‐ureotelic body water conservation response that lowered muscle mass and increased blood pressure. Here, we tested the hypothesis that a similar adaptive water conservation response occurs in experimental chronic renal failure.

Methods

In four subsequent experiments in Sprague Dawley rats, we used surgical 5/6 renal mass reduction (5/6 Nx) to induce chronic renal failure. We studied solute and water excretion in 24‐hour metabolic cage experiments, chronic blood pressure by radiotelemetry, chronic metabolic adjustment in liver and skeletal muscle by metabolomics and selected enzyme activity measurements, body Na⁺, K⁺ and water by dry ashing, and acute transepidermal water loss in conjunction with skin blood flow and intra‐arterial blood pressure.

Results

5/6 Nx rats were polyuric, because their kidneys could not sufficiently concentrate the urine. Physiological adaptation to this renal water loss included mobilization of nitrogen and energy from muscle for organic osmolyte production, elevated norepinephrine and copeptin levels with reduced skin blood flow, which by means of compensation reduced their transepidermal water loss. This complex physiologic‐metabolic adjustment across multiple organs allowed the rats to stabilize their body water content despite persisting renal water loss, albeit at the expense of hypertension and catabolic mobilization of muscle protein.

Conclusion

Physiological adaptation to body water loss, termed aestivation, is an evolutionary conserved survival strategy and an under‐studied research area in medical physiology, which besides hypertension and muscle mass loss in chronic renal failure may explain many otherwise unexplainable phenomena in medicine.

Effects of post-renal anemia treatment with the HIF-PHD inhibitor molidustat on adenine-induced renal anemia and kidney disease in mice

The kidneys are the major organs for erythropoietin (EPO) production in adults, and thus, kidney damage results in reduced EPO levels and anemia. Inhibitors of Hypoxia-inducible factor-prolyl hydroxylase domain-containing protein (HIF-PHD) are awaited as new therapeutic options for renal anemia. It can be predicted that most patients who receive HIF-PHD inhibitors have renal dysfunction as a cause of anemia. Therefore, in the present study, we investigated the effects of the HIF-PHD inhibitor molidustat on anemia and renal dysfunction when initiated after the onset of renal anemia. Male C57BL/6J mice received adenine orally to induce nephropathy. After the onset of nephropathy, the mice were treated with either vehicle or molidustat. After 4 weeks of administration, vehicle-treated mice displayed significant anemia, and molidustat ameliorated this anemia. Vehicle-treated mice exhibited reduced creatinine clearance and body weight, increased blood urea nitrogen levels, histopathological changes, immune cell infiltration, and dehydration. Molidustat reversed immune cell infiltration, dehydration, and renal fibrosis without improving renal functional parameters. In conclusion, molidustat treatment initiated after the onset of nephropathy and renal anemia reversed anemia in mice. Molidustat improved some parameters of renal abnormality, but it did not restore renal function.

Renal sympathetic nerve activity regulates cardiovascular energy expenditure in rats fed high salt

We recently reported that a 4% high-salt diet + saline for drinking (HS + saline) leads to a catabolic state, reduced heart rate, and suppression of cardiovascular energy expenditure in mice. We suggested that HS + saline reduces heart rate via the suppression of the sympathetic nervous system to compensate for the high salt intake-induced catabolic state. To test this hypothesis, we directly measured renal sympathetic nerve activity (RSNA) in conscious Sprague-Dawley (SD) rats using a radiotelemetry system. We confirmed that HS + saline induced a catabolic state. HS + saline decreased heart rate, while also reducing RSNA in SD rats. In contrast, Dahl salt-sensitive (DSS) rats exhibited no change in heart rate and increased RSNA during high salt intake. Renal denervation significantly decreased heart rate and attenuated the catabolic state independent of blood pressure in DSS rats fed HS + saline, suggesting that salt-sensitive animals were unable to decrease cardiovascular energy consumption due to abnormal renal sympathetic nerve activation during high salt intake. These findings support the hypothesis that RSNA mediates heart rate during high salt intake in SD rats. However, the insensitivity of heart rate and enhanced RSNA observed in DSS rats may be additional critical diagnostic factors for salt-sensitive hypertension. Renal denervation may benefit salt-sensitive hypertension by reducing its effects on catabolism and cardiovascular energy expenditure.

Abstract P169: Renal Denervation Attenuates a Catabolic State in Mice Fed High Salt

Introduction: We recently reported that kidneys accumulate urea as an alternative osmolyte in the renal medulla to concentrate sodium into the urine during high salt intake. This urea-driven water conservation process is coupled with the energy-intensive nature of hepatic urea production, which leads to a catabolic state in mice fed high salt. In this study, we examined the effects of renal denervation on the salt-driven catabolic state since previous studies found that the renal sympathetic nervous system regulates urinary sodium excretion and energy metabolism of some organs such as liver and muscle.

Methods: Sham-operated (sham) or renal denervated (RDX) male C57/B6J mice were fed on 0.3% NaCl diet with tap water (NS) or 4% NaCl high salt diet + 0.9% NaCl water to drink (HS) for 4 consecutive weeks (ad libitum), followed by 2 weeks of pair-feeding to match energy intake in all groups. We measured daily food intake and body weight, 24 hours urinary sodium excretion, body sodium content, and activity of liver arginase, a urea producing enzyme.

Results: NS + sham and HS + sham mice showed similar body weight gain (NS + sham: +3.6 ± 0.2, HS + sham: +3.4 ± 0.2 g) during ad libitum feeding although HS significantly increased food intake (NS + sham: 3.1 ± 0.04, HS + sham: 3.3 ± 0.04 g/day). After the pair-feeding, HS mice significantly decreased their body weight (NS + sham: +0.9 ± 0.07, HS + sham: -0.6 ± 0.05 g) and increased liver arginase activity (NS + sham: 3792 ± 322, HS + sham: 5412 ± 499 units/L/tissue), confirming the high salt-induced catabolic hepatic urea production. On the other hand, HS did not increase food intake (NS + RDX: 3.2 ± 0.1, HS + RDX: 3.1 ± 0.01 g/day) and liver arginase activity (NS + RDX: 3599 ± 316, HS + RDX: 3363 ± 369 units/L/tissue) in RDX group. In addition, HS + RDX mice did not show pair feeding-induced body weight loss (NS + RDX: +0.6 ± 0.3, HS + RDX: +0.3 ± 0.3 g). HS + RDX mice did not alter 24 hours urinary sodium excretion (HS + sham: 135 ± 6.3, HS + RDX: 142 ± 13 mmol/d/kg) and body sodium content (HS + sham: 0.15 ± 0.003, HS + RDX: 0.15 ± 0.006 mmol/d/kg) compared with HS + sham mice.

Conclusion: These findings suggest that renal denervation attenuates the HS-induced body weight loss and catabolic urea production independently of urinary sodium excretion.

The characteristics of captopril challenge test-positive patients using various criteria

Introduction:

The captopril challenge test (CCT) is the major confirmatory test for primary aldosteronism (PA), and frequently carried out because of its convenience. However, it presents false-negative results with a certain probability, and as there are many criteria for CCT, it is not concluded yet which criteria to use.

Materials and methods:

A total of 71 PA patients were evaluated. We compared CCT-positive and CCT-negative patients in the following three criteria: plasma aldosterone/renin ratio (ARR) >200 after the CCT (criterion 1); plasma aldosterone concentration (PAC) >120 pg/ml after the CCT (criterion 2); and PAC suppression <30% of PAC before CCT (criterion 3).

Results:

The positive rate was 70.4%, 64.8% and 54.9% for criterion 1, criterion 2 and criterion 3, respectively. With criterion 1, the baseline plasma renin activity was lower, thus baseline ARR was higher in CCT-positive patients. With criterion 2, PAC was higher and estimated sodium intake and K were lower in CCT-positive patients. With criterion 3, K and PAC were lower in CCT-positive patients. Although it was not significant, in the patients with high sodium intake, the positive rate of criterion 1 was higher than that of the other criteria.

Conclusions:

ARR>200 is the valuable criterion for the diagnosis of PA.

Azilsartan causes natriuresis due to its sympatholytic action in kidney disease

The sympathoinhibitory mechanism of azilsartan was investigated in an adenine-induced chronic renal failure model. Azilsartan exerted an antihypertensive effect, though BP elevation induced by adenine was marginal. The creatinine value was significantly lower in the azilsartan group (AZ) than in the vehicle group (VEH); furthermore, proteinuria was suppressed, and sodium excretion was augmented in the AZ group. The low frequency (LF) of systolic BP was suppressed (VEH: 4.07 ± 2.67 mmHg² vs. AZ: 3.32 ± 1.93 mmHg² P < 0.001), and the spontaneous baroreflex gain (sBRG) was augmented (VEH: 1.04 ± 0.62ms/mmHg vs. AZ: 1.38 ± 0.69 ms/mmHg, P < 0.001) in AZ. There were no significant differences in ACE1 and ACE2 expression between the groups, which indicated that the action of azilsartan on these components of the intrarenal renin-angiotensin-aldosterone system was comparatively small. Although NHE3, NKCC, and ENaC expression was similar between the groups, NaCl cotransporter (NCC) expression was markedly suppressed by azilsartan (P < 0.05). Thus, in a mild chronic kidney disease (CKD) model with slight BP elevation, the sympatholytic effect of ARB might be expected, and azilsartan might exert its natriuretic effect by NCC suppression achieved by sympathoinhibitory activity.

Abstract P220: High Salt Intake Induces Catabolism Accompanied by Hepatic Urea Osmolyte Production and Decreases Renal Sympathetic Nerve Activity

Introduction: We have recently reported that high salt intake induces the energy-intensive nature of hepatic urea osmolyte production that accompanied the decrease in heart rate (HR). These findings suggest that high salt intake decreases sympathetic nerve activity to reduce cardiovascular energy expenditure for the hepatic urea production. Therefore, we examined the effects of high salt intake on renal sympathetic nerve activity (RSNA) by using a radiotelemetry system in rats.

Methods: We inserted the radiotelemetry system into male Sprague Dawley (SD) rats for recording RSNA and HR. After 2 weeks recovery, we fed the rats 0.3% NaCl diet (NS) with tap water to drink (NS + tap), 4% NaCl diet with tap water (HS + tap), and 4% NaCl diet with saline (HS + saline) for 4 days in this order, and kept monitoring their HR and RSNA. In the separate experiment, we also fed male SD rats NS + tap or HS + saline for 6 consecutive weeks to confirm a catabolic state in HS + saline rats.

Results: Rats exhibited marked reductions in RSNA and HR during HS + saline phase compared with other phases. HS + saline rats significantly decreased body weight (369±35 g) compared with NS + tap rats (405±48 g) despite of the similar daily food intake (18.5±1.3 vs. 19.2±1.6 g/day). And HS + saline rats increased liver arginase, a urea producing enzyme, activity (1561±121 units/L/mg) compared with NS + tap rats (1337±131 units/L/mg) at 6 weeks after the feeding.

Conclusion: High salt intake decreased RSNA accompanied by the catabolic urea production in rats. These findings suggest that the sympathetic nervous system is one of the key regulators to reduce cardiovascular energy expenditure, which could support the energy-intensive nature of hepatic urea production in high salt-fed rats.

Effectiveness of a fixed combination formula of ombitasvir/paritaprevir/ritonavir for hepatitis C virus infection in patients on maintenance haemodialysis

A fixed-dose formula that combines Ombitasvir (OBV), Paritaprevir (PTV) and Ritonavir (RTV) has been launched into the field of anti-HCV therapy in Japan for patients infected with HCV genotypes 1 and 2 in 2015. However, little is yet known as to the efficacy and safety of this novel therapy in patients on maintenance haemodialysis (HD). The present report describes a preliminary experience in 10 patients (five males and five females) who underwent maintenance HD. All of them had HCV genotype 1b, without having the resistance-associated variants at Y93 or L31 in the nonstructural proteins 5A (NS5A) region. After the treatment, eight patients successfully achieved virus eradication and sustained a virological response at 12 weeks (SVR12). In addition, mac-2 binding protein glycosylation isomer (M2BPGi), a biomarker for liver fibrosis, was reduced after the therapy. Two patients withdrew from the therapy due to the development of erythema multiforme and a strong drowsiness, respectively. These results suggest that triple therapy combining OBV, PTV and RTV is effective in achieving SVR12 in most of the HCV-infected patients on HD. In addition, this combination therapy contributed to retard the progression of liver fibrosis. However, we suggest that further trial will be required to establish its clinical efficacy and safety.

Metastatic lymph nodes in urogenital cancers: contribution of imaging findings

The presence of nodal metastasis in patients with urogenital malignancies is an important factor for prognosis, and radiologic identification of enlarged nodes greatly affects treatment choices. Radiologic evaluation for nodal metastases is usually performed with computed tomography, but magnetic resonance imaging is also useful in evaluating primary and nodal metastases in pelvic tumors. On these cross-sectional modalities, nodal metastases are usually suspected according to location and size criteria. Although there has been no general consensus on the criteria, a short axis diameter of 8 to 10 mm is generally applied. However, radiologic evaluation does not always provide sufficient accuracy for nodal staging because of an inability to diagnose smaller metastatic lymph nodes. The clinical significance of a radiologic recognition of enlarged nodes also differs by cancer type in relation to differences in staging systems and treatment. The presence of regional lymphadenopathy in patients with renal cell carcinoma often alters surgical methods, whereas the presence of regional lymphadenopathy is an indication of systemic chemotherapy in patients with cancers of the urinary tract, prostate, and testicles. In this report, preferential sites and staging of nodal metastasis and contributions of radiologic imaging are reviewed for each urogenital cancer.

Pathogenicity of Rhodococcus equi strains possessing virulence-associated 15- to 17-kDa and 20-kDa antigens: experimental and natural cases in pigs

The pathogenic role of Rhodococcus equi in pigs remains controversial. Small numbers of pigs were inoculated intravenously (i.v.), or intramuscularly (i.m.) around the mouth, with a virulent, an intermediately virulent, or an avirulent strain of R. equi and killed 14 days later. None showed clinical signs other than transient fever and weight loss. The virulent and intermediately virulent strains were recovered in culture from various organs and lymph nodes of pigs inoculated i.v., but only from the mandibular lymph nodes of pigs inoculated i.m. The avirulent strain was not recovered from any site. None of the pigs developed macroscopically visible lesions, but they showed reactive hyperplasia of the mandibular lymph nodes. The latter contained scattered phagocytic cells, which were labelled immunohistochemically for virulence-associated antigens (15- to 17-kDa antigens or 20-kDa antigen). Intermediately virulent and virulent strains of R. equi were isolated from mandibular lymph nodes of 5.5% of apparently healthy abattoir pigs (n = 1615). Virulence-associated antigens were detected in phagocytic cells of culture-positive nodes, but the latter showed no lesions other than reactive lymphoid hyperplasia. The results would seem to question the pathogenic role of R. equi in pigs, and it is speculated that the organism survives in the lymph nodes without causing pathognomonic lesions.

Immunohistochemical detection of virulence-associated antigens of Rhodococcus equi in pulmonary lesions of foals

Rhodococcus equi was isolated from the lungs of six foals with bronchopneumonia. All isolates expressed 15-17-kd antigens by immunoblot analysis and contained a virulence-associated plasmid of 85 or 90 kb. Immunohistochemically, R. equi from all pulmonary lesions showed the expression of 15-17-kd antigens mainly in the phagocytic cells. The specific monoclonal antibody to 15-17-kd antigens of R. equi (MAb 10G5) may be an aid in the diagnosis of R. equi-induced pneumonia.