Treatment Effect of the SGLT2 Inhibitor Empagliflozin on Chronic Syndrome of Inappropriate Antidiuresis: Results of a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

Dapagliflozin attenuates AKI to CKD transition in diabetes by activating SIRT3/PGC1-α signaling and alleviating aberrant metabolic reprogramming

BACKGROUND

Patients with diabetes are prone to acute kidney injury (AKI) with a high mortality rate, poor prognosis, and a higher risk of progression to chronic kidney disease than non-diabetic patients.

METHODS

Streptozotocin (STZ)-treated type 1 and db/db type 2 diabetes model were established, AKI model was induced in mice by ischemia-reperfusion injury(IRI). Mouse proximal tubular cell cells were subjected to high glucose and hypoxia-reoxygenation in vitro. Transcriptional RNA sequencing was performed for clustering analysis and target gene screening. Renal structural damage was determined by histological staining, whereas creatinine and urea nitrogen levels were used to measure renal function.

RESULTS

Deteriorated renal function and renal tissue damage were observed in AKI mice with diabetic background. RNA sequencing showed a decrease in fatty acid oxidation (FAO) pathway and an increase in abnormal glycolysis. Treatment with Dapa, Sitagliptin(a DPP-4 inhibitor)and insulin reduced blood glucose levels in mice, and improved renal function. However, Dapa had a superior therapeutic effect and alleviated aberrant FAO and glycosis. Dapa reduced cellular death in cultured cells under high glucose hypoxia-reoxygenation conditions, alleviated FAO dysfunction, and reduced abnormal glycolysis. RNA sequencing showed that SIRT3 expression was reduced in diabetic IRI, which was largely restored by Dapa intervention. 3-TYP, a SIRT3 inhibitor, reversed the renal protective effects of Dapa and mediated abnormal FAO and glycolysis in mice and tubular cells.

CONCLUSION

Our study provides experimental evidence for the use of Dapa as a means to reduce diabetic AKI by ameliorating metabolic reprogramming in renal tubular cells.

Hyponatraemia-treatment standard 2024

Hyponatraemia is the most common electrolyte disorder in hospital patients associated with increased morbidity, mortality, hospital stay and financial burden. The speed of a correction with 3% sodium chloride as a 100- to 150-ml intravenous bolus or continuous infusion depends on the severity and persistence of the symptoms and needs frequent biochemical monitoring. The rapid intermittent administration of hypertonic saline is preferred for treatment of symptomatic hyponatraemia. In asymptomatic mild hyponatraemia, an adequate solute intake with an initial fluid restriction (FR) of 500 ml/day adjusted according to the serum sodium (sNa) levels is preferred. Almost half of the syndrome of inappropriate antidiuretic hormone (SIADH) patients do not respond to FR as first-line therapy. At present, urea and tolvaptan are considered the most effective second-line therapies in SIADH. However, the evidence for guidance on the choice of second-line therapy of hypotonic hyponatraemia is lacking. Oral urea is considered to be a very effective and safe treatment. Mild and asymptomatic hyponatraemia is treated with adequate solute intake (salt and protein) and initial FR with adjustments based on sNa levels. Specific treatment with vaptans may be considered in either euvolaemic or hypervolaemic patients with high ADH activity. In order to ensure optimal patient outcome, close monitoring and readiness for administration of either hypotonic fluids or desmopressin may be crucial in the decision-making process for specific treatment and eventual overcorrection consequences. According to the guidelines, gradual correction and clinical evaluation is preferable over rapid normalization of sNa towards the laboratory reference ranges.

Extraventricular Neurocytoma of the Sellar Region Presenting With Syndrome of Inappropriate Antidiuresis

Neurocytomas are neuronal tumors that are usually intraventricular. Rare cases can arise from extraventricular sites. To our knowledge, only 29 cases of extraventricular neurocytoma of the sellar region (EVNSR) have been reported in the literature. We describe a case of a 39-year-old woman who presented with a one-month history of refractory headache, nausea and vomiting. Magnetic resonance imaging (MRI) showed a 5.1 × 3.1 × 2.2 cm sellar and suprasellar mass, suggestive of a pituitary adenoma (PA). She had hyponatremia, obstructive hydrocephalus, and panhypopituitarism at presentation (hypogonadism, adrenal insufficiency). After glucocorticoid replacement therapy and ventriculoperitoneal shunt, the vomiting and headache resolved, but she remained with nausea and hyponatremia. She was submitted to surgery, and histopathological analysis revealed a neurocytoma with positive immunostaining for arginine vasopressin. Syndrome of inappropriate antidiuresis (SIAD) was diagnosed but did not resolve after surgery due to residual tumor, despite fluid restriction and saline replacement. SIAD later resolved with empagliflozin. In conclusion, EVNSR is extremely rare and can be misdiagnosed as PA on MRI. In the context of SIAD and extraventricular neurocytoma, a secreting arginine vasopressin tumor must be considered. SIAD can be challenging to treat, with excision of the EVNSR the treatment choice and, alternatively, empagliflozin associated with fluid restriction.

Update on the clinical applications of SGLTis: Insight to benefits beyond hypoglycemic and cardiorenal protection

Sodium glucose cotransporter inhibitor (SGLTi) drugs have been widely used in clinical practice. In addition to their benefits in hyperglycemia, heart failure (HF), and kidney disease, their effects on obesity, metabolic dysfunction-associated steatotic liver disease (MASLD, formerly named nonalcoholic fatty liver disease [NAFLD]), polycystic ovarian syndrome (PCOS), abnormal lipid metabolism, hyperuricemia, obstructive sleep apnea syndrome (OSAS), anemia, and syndrome of inappropriate antidiuresis (SIAD, formerly named syndrome of inappropriate antidiuretic hormone [SIADH]) have been explored. In this review, we searched the data of clinical randomized controlled trials (RCTs) and meta-analyses of SGLTis in patients with diabetes from the PubMed library between January 1, 2020, and February 1, 2024. According to our review, certain SGLTis exhibit relatively superior clinical safety and effectiveness for treating the abovementioned diseases. Proper utilization of SGLTis in these patients can provide additional medication options for patients with different disease scenarios. However, studies of SGLTis in these diseases are relatively rare, with shortcomings such as small sample sizes and short intervention periods. Therefore, further large-scale, long-term, well-designed studies are needed to clarify the findings.

SGLT2 inhibition, circulating proteins, and insomnia: A mendelian randomization study

BACKGROUND

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) initially emerged as oral antidiabetic medication but were subsequently discovered to exhibit pleiotropic actions. Insomnia is a prevalent and debilitating sleep disorder. To date, the causality between SGLT2 inhibitors and insomnia remains unclear. This study aims to evaluate the causality between SGLT2 inhibitors and insomnia and identify potential plasma protein mediators.

METHODS

Using a two-sample Mendelian Randomization (MR) analysis, we estimated the causality of SGLT2 inhibition on insomnia and sleep duration. Additionally, employing a two-step and proteome-wide MR analysis, we evaluated the causal link of SGLT2 inhibition on 4907 circulating proteins and the causality of SGLT2 inhibition-driven plasma proteins on insomnia. We applied a false discovery rate (FDR) correction for multiple comparisons. Furthermore, mediation analyses were used to identify plasma proteins that mediate the effects of SGLT2 inhibition on insomnia.

RESULTS

SGLT2 inhibition was negatively correlated with insomnia (odds ratio [OR] = 0.791, 95 % confidence interval [CI] [0.715, 0.876], P = 5.579*10^-6) and positively correlated with sleep duration (β = 0.186, 95 % CI [0.059, 0.314], P = 0.004). Among the 4907 circulating proteins, diadenosine tetraphosphatase (Ap4A) was identified as being linked to both SGLT2 inhibition and insomnia. Mediation analysis indicated that the effect of SGLT2 inhibition on insomnia partially operates through Ap4A (β = -0.018, 95 % CI [-0.036, -0.005], P = 0.023), with a mediation proportion of 7.7 %.

CONCLUSION

The study indicated a causality between SGLT2 inhibition and insomnia, with plasma Ap4A potentially serving as a mediator.

Apelin and Copeptin Levels in Patients With Chronic SIAD Treated With Empagliflozin

Background

Empagliflozin increases sodium levels in patients with a chronic syndrome of inappropriate antidiuresis (SIAD), and dapagliflozin increases apelin levels in patients with diabetes mellitus. Exogenous apelin increases sodium levels in rats with SIAD. We aimed to investigate whether an increase in plasma apelin concentration may contribute to the efficacy of empagliflozin in SIAD.

Methods

Post hoc secondary analysis of a double-blind, crossover, placebo-controlled trial performed from December 2017 to August 2021 at the University Hospital Basel, Switzerland, investigating the effect of 4-week treatment with empagliflozin 25 mg/day as compared to placebo in 14 outpatients with chronic SIAD (NCT03202667). The objective was to investigate the effect of empagliflozin on plasma apelin and copeptin concentrations and their ratio.

Results

Fourteen patients, 50% female, with a median [interquartile range] age of 72 years [65-77] were analyzed. Median apelin concentration was 956 pmol/L [853, 1038] at baseline. Median [interquartile range] apelin relative changes were +11% [0.7, 21] and +8% [-5, 25] (P = .672) at the end of the placebo and empagliflozin phases, respectively. Median copeptin concentration was 2.6 [2.2, 4.5] pmol/L at baseline and had a relative change of +5 [-2. 11]% and +25% [10, 28] (P = .047) over the placebo and empagliflozin phases, respectively.

Conclusion

Empagliflozin did not lead to significant changes in apelin or the apelin/copeptin ratio in patients with chronic SIAD but led to an increase in copeptin. This suggests that the efficacy of empagliflozin in SIAD is independent of apelin and is not blunted by the adaptative increase in copeptin.

Exploring nontraditional cardiorenal advantages of SGLT-2 inhibitors and GLP-1 receptor agonists

This commentary provides an analysis of the study by Fu et al. in Kidney International, which employs 3 administrative databases to investigate the hyperkalemia protective effects of sodium-glucose cotransporter-2 inhibitors, glucagon-like peptide-1 receptor agonists, and dipeptidyl peptidase-4 inhibitors. It emphasizes the methodological approach, notably the use of a fixed-effect model to aggregate pairwise comparisons from 3 data sets. In addition, we explored the broader cardiorenal and potential nonrenal benefits of these drug classes, underscoring the imperative for continued research in this domain.

Efficacy of empagliflozin as adjunctive therapy to citalopram in major depressive disorder: a randomized double-blind, placebo-controlled clinical trial

BACKGROUND

Major depressive disorder is one of the most common psychiatric disorders, which is associated with a high disease burden. Current treatments using antidepressants have limitations, so using medication with neuromodulating and anti-inflammatory properties alongside them could be helpful. In a clinical trial, we studied the effectiveness of empagliflozin, a blood sugar-lowering drug, as an adjunctive therapy to reduce the severity of depression symptoms.

METHODS

A number of outpatients with moderate to severe depression (Hamilton Depression Rating Scale (HDRS) > = 17) who were not under related medication or had not taken medication for at least the last two months, had an age range of 18-60 years and had written informed consent to enter the study (N = 90) were randomly divided into two groups receiving placebo or empagliflozin (10 mg daily) combined with citalopram (40 mg daily) based on permuted block randomization method in an 8-week randomized, double-blind, placebo-controlled clinical trial. They were evaluated using the HDRS in weeks 0, 4, and 8.

RESULTS

HDRS scores were equal to 28.42(± 3.83), 20.20(± 3.82), and 13.42(± 3.42) in the placebo group during weeks 0,4, and 8, respectively. These scores were 27.36(± 3.77), 13.76(± 1.40), and 7.00(± 1.13), respectively, for the group treated with empagliflozin. Compared to the control group, patients treated with empagliflozin using repeated-measures ANOVA showed greater improvement in reducing the severity of depression symptoms over time (p value = 0.0001).

CONCLUSIONS

Considering the promising findings in this clinical trial, further study of empagliflozin as adjunctive therapy in MDD with larger sample sizes and longer follow-ups is recommended.

[Dysnatremias - concepts and clinical work-up]

Osmotic gradients over cell membranes lead to water movement into or out of cells. An intact osmoregulation prevents osmotic gradients, thereby protecting cells from swelling or shrinking. Na+ is the major cation in the extracellular fluid (ECF) and the major determinant of the osmolarity in the ECF, including plasma. Therefore, the plasma-Na+ concentration needs to be tightly regulated. An excess of electrolyte-free water decreases the concentration of osmolytes leading to hyponatremia. In contrast, a free water deficit increases the osmolyte concentration leading to hypernatremia. Pathophysiology-oriented approaches to dysnatremic patients help both clinicians and patients. Therapeutic interventions depend on the differentiation between acute and chronic, asymptomatic, and symptomatic dysnatremia, and on the patient's extracellular volume status. The therapeutic armamentarium for hyponatremia consists of water restriction, hypertonic infusions, urea, V2 receptor-blockers, and sodium-glucose cotransporter 2 (SGLT2) inhibitors. Patients with hypernatremia are treated with electrolyte-free water or hypotonic sodium-containing solutions depending on their volume status. Basic concepts in the management of dysnatremic patients are discussed.

Dapagliflozin induced hypernatremia via osmotic diuresis: a case report

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have been widely used. They inhibit proximal tubular glucose reabsorption, resulting in glycosuria. Herein, we report the case of a 65-year-old woman who presented with hypernatremia during the perioperative period of a subarachnoid hemorrhage. The patient continued to take dapagliflozin postoperatively and subsequently developed severe hypernatremia. Based on the urinalysis findings, we diagnosed osmotic diuresis due to glycosuria as contributing to hypernatremia. Hypernatremia improved with the discontinuation of dapagliflozin and the administration of a hypotonic infusion. In the perioperative period, physicians should discontinue SGLT2 inhibitors owing to concerns about the development of hypernatremia.

[Consensus recommendations on the diagnosis and treatment of hyponatremia from the Austrian Society for Nephrology 2024]

Hyponatremia is a disorder of water homeostasis. Water balance is maintained by the collaboration of renal function and cerebral structures, which regulate thirst mechanisms and secretion of the antidiuretic hormone. Measurement of serum-osmolality, urine osmolality and urine-sodium concentration help to diagnose the different reasons for hyponatremia. Hyponatremia induces cerebral edema and might lead to severe neurological symptoms, which need acute therapy. Also, mild forms of hyponatremia should be treated causally, or at least symptomatically. An inadequate fast increase of the serum sodium level should be avoided, because it raises the risk of cerebral osmotic demyelination. Basic pathophysiological knowledge is necessary to identify the different reasons for hyponatremia which need different therapeutic procedures.

Case report: Twice-daily tolvaptan dosing regimen in a challenging case of hyponatremia due to SIAD

Background

Syndrome of inappropriate antidiuresis (SIAD) is one of the most frequent causes of euvolemic hyponatremia (serum sodium levels < 135 mEq/L) and it represents more than 35% of hyponatremia cases in hospitalized patients. It is characterized by an inappropriate vasopressin (AVP)/antidiuretic hormone (ADH) secretion, which occurs independently from effective serum osmolality or circulating volume, leading to water retention via its action on type 2 vasopressin receptor in the distal renal tubules. Corpus callosum agenesis (CCA) is one of the most common congenital brain defects, which can be associated to alterations in serum sodium levels. This report presents a rare case of chronic hyponatremia associated with SIAD in a woman with CCA, whose correction of serum sodium levels only occurred following twice-daily tolvaptan administration.

Case presentation

A 30-year-old female was admitted to our hospital for non-acute hyponatremia with dizziness, headache, distal tremors, and concentration deficits. She had profound hyponatremia (Na 121 mmol/L) with measured plasma hypo-osmolality (259 mOsm/Kg) and urinary osmolality greater than 100 mOsm/Kg (517 mOsm/Kg). She presented clinically as normovolemic. After the exclusion of other causes of normovolemic hyponatremia, such as hypothyroidism and adrenal insufficiency, a diagnosis of SIAD was established. We have ruled out paraneoplastic, inflammatory, and infectious causes, as well as ischemic events. Her medical history showed a CCA and frontal teratoma. We administered tolvaptan initially at a low dosage (15 mg once a day) with persistence of hyponatremia. Therefore, the dosage was first doubled (30 mg once a day) and then increased to 45 mg once a day with an initial improvement in serum sodium levels, although not long-lasting. We therefore tried dividing the 45 mg tolvaptan administration into two doses of 30 mg and 15 mg respectively, using an off-label treatment schedule, thus achieving long-lasting serum sodium levels in the low-normal range associated with a general clinical improvement.

Conclusions

This report underlines the importance of the correct diagnosis, management and treatment of SIAD, as well as the need for further studies about the pharmacokinetics and pharmacodynamics of vasopressin receptor antagonists.

Classifying Hypotonic Hyponatremia by Projected Treatment Effects - A Quantitative 3-Dimensional Framework

Introduction

The diagnostic algorithms currently used for hypotonic hyponatremia focus primarily on impaired urinary dilution and often neglect the influence of free water intake and solute excretion. We hypothesized that, in each case of hypotonic hyponatremia different pathophysiological mechanisms play a role simultaneously.

Methods

Using clinical data of the previous observational Co-Med study, we defined each case of hypotonic hyponatremia concurrently in 3 dimensions as follows: (i) high net free water intake (HNFWI), (ii) impaired dilution of the urine (IDU), and (iii) low nonelectrolyte solute excretion (LNESE). For each dimension, a "standard delta sodium" (sdna) was calculated reflecting the expected difference to the serum sodium concentration, that would result from changing a dimension to a specific and equivalent target level.

Results

Results from 279 patients were used for this analysis. With target levels of free water intake and urine osmolality at the fifth percentile, and nonelectrolyte solute excretion at the 95th percentile, median (interquartile range) sdna values were 7.1 (4.8-10.2) for HNFWI, 11.8 (7.0-18.6) for IDU and 2.6 (1.6-4.2) mmol/l per 24 hours for LNESE. Sdna results in individual patients were highest with IDU in 68.5%, HNFWI in 30.8% and 0.7% with LNESE. At an sdna-level of at least 4mmol/l per 24 hours, the prevalence of HNFWI was 78.9%, IDU 87.1%, and LNESE 26.5%. 77.5% of patients had 2 or all 3 mechanisms present. Hyponatremia was mostly multifactorial in subgroups according to classic categories of hyponatremia and typical comorbidities as well.

Conclusion

Hypotonic hyponatremia can be quantitatively defined by 3 dimensions. Most cases should be considered multifactorial.

An Increase in Plasma Sodium Levels Is Associated With an Increase in Osteoblast Function in Chronic SIAD

CONTEXT

Hyponatremia is associated with increased risk for osteoporosis. Preclinical studies in untreated hyponatremia suggest osteoclast upregulation, whereas a clinical study showed improved osteoblast function after hyponatremia normalization in hospitalized patients with syndrome of inappropriate antidiuresis (SIAD).

OBJECTIVE

This work aimed to investigate the effect of an increase in sodium on bone turnover, that is, the ratio of the osteoblast marker procollagen type 1 N-terminal propeptide (P1NP) to the osteoclast marker cross-linked C-terminal telopeptide of type 1 collagen (CTX), in outpatients with chronic SIAD.

METHODS

A predefined secondary analysis was conducted of the 2-month double-blind, crossover, placebo-controlled SANDx Trial (NCT03202667) performed from December 2017 to August 2021. Participants included 11 outpatients with chronic SIAD: 6 women, median age 73 years, who received a 4-week treatment with 25-mg empagliflozin or placebo. Main outcome measures included the relationship between the change in bone formation index (BFI), defined as P1NP/CTX, and the change in plasma sodium levels.

RESULTS

Changes in sodium were positively correlated with changes in BFI and P1NP (BFI: ρ=.55; P < .001; P1NP: ρ=.45; P = .004) but not with CTX (P = .184) and osteocalcin (P = .149). A sodium increase of 1 mmol/l was associated with an increase of 5.21 in BFI (95% CI, 1.41-9.00; P = .013) and with an increase of 1.48 µg/l in P1NP (95% CI, .26-2.62; P = .03). The effect of sodium change on bone markers was independent of the study medication empagliflozin.

CONCLUSION

An increase in plasma sodium levels in outpatients with chronic hyponatremia due to SIAD, even when mild, was associated with an increase in bone formation index (P1NP/CTX) triggered by an increase in P1NP, a surrogate marker of osteoblast function.

Association of hyponatremia with bone mineral density and fractures: a narrative review

Recent studies suggest a possible association of hyponatremia with osteoporosis, falls and bone fractures. The objectives of this narrative review were to further explore this association and the related pathophysiological mechanisms and to suggest a practical approach to patients with osteoporosis or chronic hyponatremia in clinical practice. We conducted an extensive PubMed search until October 2022 with the combination of the following keywords: 'hyponatremia' or 'sodium' or 'SIADH' and 'fractures' or 'bone' or 'osteoporosis', as MeSH Terms. Review of numerous observational studies confirms a significant independent association of, even mild, hyponatremia with two- to three-fold increase in the occurrence of bone fractures. Hyponatremia is a risk factor for osteoporosis with a predilection to affect the hip, while the magnitude of association depends on the severity and chronicity of hyponatremia. Chronic hyponatremia also increases the risk for falls by inducing gait instability and neurocognitive deficits. Besides the detrimental impact of hyponatremia on bone mineral density and risk of falls, it also induces changes in bone quality. Emerging evidence suggests that acute hyponatremia shifts bone turnover dynamics towards less bone formation, while hyponatremia correction increases bone formation. The key unanswered question whether treatment of hyponatremia could improve osteoporosis and lower fracture risk highlights the need for prospective studies, evaluating the impact of sodium normalization on bone metabolism and occurrence of fractures. Recommendations for clinical approach should include measurement of serum sodium in all individuals with fracture or osteoporosis. Also, hyponatremia, as an independent risk factor for fracture, should be taken into consideration when estimating the likelihood for future fragility fracture and in clinical decision-making about pharmacological therapy of osteoporosis. Until it is proven that normalization of sodium can lower fracture occurrence, correcting hyponatremia cannot be universally recommended on this basis, but should be decided on a case-by-case basis.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Effect of protein supplementation on plasma sodium levels in the syndrome of inappropriate antidiuresis: a monocentric, open-label, proof-of-concept study-the TREASURE study

IMPORTANCE

The syndrome of inappropriate antidiuresis (SIAD) can be treated with oral urea; however, compliance is impaired by its poor palatability.

OBJECTIVE

To investigate whether dietary proteins could increase plasma sodium levels through urea-induced osmotic diuresis.

DESIGN

An open-label, proof-of-concept trial.

SETTING

University Hospital of Basel, Switzerland, between October 2021 and February 2023.

PARTICIPANTS

Outpatients with chronic SIAD.

INTERVENTIONS OR EXPOSURES

Ninety grams of protein daily for 7 days in the form of protein powder, followed by 30 g of oral urea daily for 7 days after a wash-out period of ≥1 week.

MAIN OUTCOMES AND MEASURES

The increase in sodium levels from baseline to the end of the 7-day protein supplementation.

RESULTS

Seventeen patients were included. After 7 days of 90 g daily protein supplementation (n = 17), plasma sodium levels increased from 131 (129-133) to 133 (132-137), that is, by a median of 3 mmol L-1 (0-5) (P = .01). Plasma urea levels increased by 3 mmol L-1 (1.7-4.9) (P < .01), and urine urea to creatinine ratio increased by 21.2 mmol mmol-1 (6.2-29.1) (P < .01). After 7 days of 30 g oral urea (n = 10), plasma sodium levels increased from 132 (130-133) to 134 (131-136), that is, by a median of 2 mmol L-1 (1-3) (P = .06). Plasma urea levels increased by 5.8 mmol L-1 (2.7-9.2) (P < .01), and urine urea to creatinine ratio increased by 31.0 mmol mmol-1 (18.7-45.1) (P < .01).

CONCLUSIONS AND RELEVANCE

Our findings suggest that protein powder increases plasma sodium levels in patients with chronic SIAD through protein-induced ureagenesis and osmotic diuresis. The effects are comparable with oral urea.

Intrarenal Mechanisms of Sodium-Glucose Cotransporter-2 Inhibitors on Tubuloglomerular Feedback and Natriuresis

When sodium-glucose cotransporter-2 (SGLT2) inhibitors were first introduced a decade ago, no one expected them to have substantial effects beyond their known glucose-lowering effects, until the emergence of evidence of their robust renal and cardiovascular benefits showing that they could attenuate progression of kidney disease, irrespective of diabetes, as well as prevent the development of acute kidney injury. Still, the precise and elaborate mechanisms underlying the major organ protection of SGLT2 inhibitors remain unclear. SGLT2 inhibitors inhibit the reabsorption of sodium and glucose in the proximal tubule of the kidney and then recovers tubuloglomerular feedback, whereby SGLT2 inhibitors reduce glomerular hyperfiltration. This simple demonstration of their beneficial effects has perplexed experts in seeking more plausible and as yet undisclosed explanations for the whole effects of SGLT2 inhibitors, including metabolism reprogramming and the modulation of hypoxia, inflammation, and oxidative stress. Given that the renal benefits of SGLT2 inhibitors in patients with kidney disease but without diabetes were comparable to those seen in patients with diabetes, it may be reasonable to keep the emphasis on their hemodynamic actions. In this context, the aim of the present review is to provide a comprehensive overview of renal hemodynamics in individuals with diabetes who are treated with SGLT2 inhibitors, with a focus on natriuresis associated with the regulation of tubuloglomerular feedback and potential aquaresis. Throughout the discussion of alterations in renal sodium and water transports, particular attention will be given to the potential enhancement of adenosine and its receptors following SGLT2 inhibition.

Tolvaptan for the treatment of the syndrome of inappropriate antidiuresis (SIAD)

The syndrome of inappropriate antidiuresis (SIAD), the commonest cause of hyponatraemia, is associated with significant morbidity and mortality. Tolvaptan, an oral vasopressin V2-receptor antagonist, leads through aquaresis to an increase in serum sodium concentration and is the only medication licenced in Europe for the treatment of euvolaemic hyponatraemia. Randomised controlled trials have shown that tolvaptan is highly efficacious in correcting SIAD-related hyponatraemia. Real-world data have confirmed the marked efficacy of tolvaptan, but they have also reported a high risk of overly rapid sodium increase in patients with a very low baseline serum sodium. The lower the baseline serum sodium, the higher the tolvaptan-induced correction rate occurs. Therefore, a lower starting tolvaptan dose of 7.5 mg has been evaluated in small cohort studies, demonstrating its efficacy, but it still remains unclear as to whether it can reduce the risk of overcorrection. Most international guidelines, except for the European ones, recommend tolvaptan as second-line treatment for SIAD after fluid restriction. However, the risk of unduly rapid sodium correction in combination with its high cost have limited its routine use. Prospective controlled studies are warranted to evaluate whether tolvaptan-related sodium increase can improve patient-related clinical outcomes, such as mortality and length of hospital stay in the acute setting or neurocognitive symptoms and quality of life in the chronic setting. In addition, the potential role of a low tolvaptan starting dose needs to be further explored. Until then, tolvaptan should mainly be used as second-line treatment for SIAD, especially when there is a clinical need for prompt restoration of normonatraemia. Tolvaptan should be used with specialist input according to a structured clinical pathway, including rigorous monitoring of electrolyte and fluid balance and, if needed, implementation of appropriate measures to prevent, or when necessary reverse, overly rapid hyponatraemia correction.

A profile of SGLT-2 inhibitors in hyponatremia: The evidence to date

Hyponatremia is the most common electrolyte disorder in clinical practice, which may lead to life-threatening complications. Several lines of evidence suggest that hyponatremia is associated not only with significant increases in length of stay, cost, and financial burden, but also with increased morbidity and mortality. Hyponatremia is also considered to be a negative prognostic factor in patients with heart failure and cancer. Although multiple therapeutic methods are available for treating hyponatremia, most have some limitations, such as poor compliance, rapid correction of serum Na⁺, other negative side effects and high cost. Given these limitations, identifying novel therapies for hyponatremia is essential. Recent clinical studies have shown that SGLT-2 inhibitors (SGLT 2i) significantly increased serum Na⁺ levels and were well tolerated by patients who underwent this treatment. Therefore, oral administration of SGLT 2i appears to be an effective treatment for hyponatremia. This article will briefly review the etiology of hyponatremia and integrated control of sodium within the kidney, current therapies for hyponatremia, potential mechanisms and efficacy of SGLT 2i for hyponatremia, and the benefits in cardiovascular, cancer, and kidney disease by regulating sodium and water balance.

Prevalence of Admission Hyponatremia in Patients With Diabetes Treated With and Without an SGLT2 inhibitor

Context

Hyponatremia often reflects a free water excess. Sodium/glucose cotransporter 2 (SGLT2) inhibitors increase free water excretion through glucose-induced osmotic diuresis. In 2 randomized double-blind, placebo-controlled trials in patients with the syndrome of inappropriate antidiuresis (SIAD), we showed that empagliflozin increased plasma sodium concentration more effectively than placebo.

Objective

We hypothesized that long-term therapy with SGLT2 inhibitors might reduce the prevalence of hyponatremia on hospital admission.

Methods

In this retrospective analysis, we extracted data from adult patients with type 2 diabetes (T2DM) hospitalized at the University Hospital Basel between 2015 and 2020. Patients with an SGLT2 inhibitor on admission were matched 1:1 according to age, gender, diagnosis of heart failure, and principal diagnosis to patients without an SGLT2 inhibitor on admission. The primary outcome was the prevalence of hyponatremia (plasma sodium concentration corrected for glycemia <135 mmol/L) on admission.

Results

We analyzed 821 patients with T2DM treated with and 821 patients with T2DM without an SGLT2 inhibitor on admission. Hyponatremia prevalence on admission was 9.9% in the treated group, and 8.9% in the matched control group (P = .554), in other words, the risk for hyponatremia did not differ (multivariable adjusted odds ratio 1.08, 95% CI 0.72-1.44, P = .666). There was no difference in the median (interquartile range) plasma sodium concentration between the groups (treated 140 mmol/L [138-142], controls 140 mmol/L [138-142]; P = .1017).

Conclusion

Based on these retrospective findings, treatment with SGLT2 inhibitors does not prevent hyponatremia. However, prospective randomized data suggest their efficacy at a higher dosage in overt SIAD.

Long-term efficacy of empagliflozin as an add-on treatment for chronic SIAD: a case report and literature review

BACKGROUND

SLGT-2 inhibitors have recently been investigated as a promising therapy for syndrome of inappropriate antidiuresis (SIAD). However, to our knowledge, no report has been published about their use for this indication in the long term.

CASE PRESENTATION

We report the case of a 68-year-old male with type 2 diabetes and chronic SIAD, in whom serum sodium levels were not adequately controlled by urea monotherapy. Other treatment options were not viable due to inefficacy or adverse effects. The initiation of empagliflozin, in addition to urea, led to the full normalization of serum sodium. Reduction and subsequent discontinuation of urea were attempted upon patient request, but this resulted in a relapse of hyponatremia. Nevertheless, stable normonatremia was again achieved and maintained for more than 6 months after re-establishing a combination therapy with empagliflozin and urea.

CONCLUSIONS

SGLT2 inhibitors might represent an effective treatment for SIAD, even in the long term. Specific clinical trials are needed to confirm this result.