Metabolic Acidosis in Chronic Kidney Disease: Pathogenesis, Clinical Consequences, and Treatment

Coordination between glycogen metabolism and pH regulation in stingray gill cells

Elasmobranchs (shark, rays and relatives) have specialized epithelial cells in their gills that maintain blood pH homeostasis that are functionally analogous to distal tubule cells in the mammalian kidney. The gill cells are either enriched with the Na+/K+-ATPase (NKA) and responsible for acid secretion or enriched for the vacuolar-type V-H+-ATPase (VHA) and responsible for base secretion; both cell types are enriched in mitochondria and glycogen stores that support their high metabolic rates. In this study, we isolated and cultured stingray gill cells and found that the subcellular localization of glycogen coincides with that of NKA and VHA. Under control conditions, glycogen and NKA were located at the cell membrane of acid-secreting cells while glycogen and VHA were in the cytoplasm of the base-secreting cells. During an alkalosis, NKA and glycogen localization in the acid-secreting cells remained unchanged; however, both VHA and glycogen localized to the cell membrane of base-secreting cells. Interestingly, this process was prevented by pharmacological inhibition of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC). This suggests a novel mechanism coupling glycogen metabolism with acid-base regulation that sustains ATPase function during sudden periods of increased energy demand. Since VHA, sAC, and glycogen are evolutionarily widespread, this mechanism may apply broadly to other organisms and systems including mammalian kidney cells.

Veverimer, a Nonabsorbed Gastrointestinal Tract HCl Binder, Decreases Renal Ammoniagenesis and Mitigates Nephrotoxic Serum Nephritis

Key Points

Background

Increased tubular ammoniagenesis is an adaptive response to progressive kidney disease, facilitating net acid excretion. However, excess ammonia production can also exacerbate kidney disease progression, in part, by activating the alternative complement cascade. Oral Na bicarbonate therapy can decrease the systemic H+ burden, limiting ammonia production. However, poor compliance limits bicarbonate's efficacy. Veverimer is an oral, Na+-free, nonabsorbed polymer that binds H+ within the gastrointestinal (GI) tract. This stimulates GI carbonic anhydrase-mediated bicarbonate production and systemic bicarbonate uptake. Hence, the goals of this study were to test whether GI HCl binding decreases renal tubular ammoniagenesis, to assess whether complement activation decreases, and to determine whether these changes can mitigate nephrotoxic serum (NTS) nephritis, in which complement activation may play a role.

Methods

A normal diet± veverimer (4.5% w/w) was fed to normal mice for approximately 1 week. Veverimer's effect on plasma bicarbonate; blood/urinary pH; urinary ammonia excretion; and tubular H+ transporter, NHE3, density was assessed. Additional mice were fed the normal or veverimer diet after NTS injection. Urine protein, albumin, ammonia, C5b-9 excretion, and plasma C3a levels were measured 1 week and/or 2 weeks after NTS injection. Renal histologic changes (hematoxylin and eosin stain; C5b-9, CD45 immunohistochemistry), and selected injury mediators/biomarkers (NGAL, IL-6, MCP-1, TGFβ1, and endothelin-1 mRNAs) were also assessed.

Results

Veverimer increased plasma bicarbonate/urinary pH, reduced urinary ammonia, and decreased NHE3 in normal mice. Veverimer also reduced NTS-induced proteinuria/albuminuria, urinary ammonia, and C5b-9 excretion (by approximately 60%, 75%, and 50%, respectively). Significant reductions in NTS-induced glomerular/tubulointerstitial injury, inflammatory/profibrotic gene expression, renal C5b-9 deposition, and suppressed plasma C3a levels were observed. Oral bicarbonate also conferred protection, implicating bicarbonate's role in veverimer's beneficial effect.

Conclusions

Veverimer-mediated bicarbonate generation can suppress renal ammoniagenesis and complement activation. These findings suggest a potential benefit of veverimer/bicarbonate therapy in selected complement-mediated kidney diseases.

Realistic Albumin Concentrations in Virtual Subjects Across A Spectrum of Renal Function to Account for Variability in Protein Binding Within PBPK Models

Use of physiologically-based pharmacokinetic (PBPK) modelling for extrapolation to organ impairment populations requires successful prediction for physiological changes. For drugs bound to human serum albumin (HSA), prediction of albumin concentrations is crucial to predict population differences in fraction unbound in plasma (fu). In this study, a multi-variable model was developed for prediction of HSA concentrations in renal impairment, using easily accessible variables (BMI, eGFR, age, sex, race and ethnicity) as predictors. An increase of eGFR from 15 to 90 mL/min/1.73m2 was predicted to elevate HSA concentration by 0.30-0.32 g/dL regardless of subjects' characteristics. Data from obese patients undergoing mini-gastric bypass surgery was used for external validation (observed BMI from 44.5 to 27.3 kg/m2, leading to predicted HSA concentration change of 0.3 versus 0.1-0.3 g/dL), highlighting the model's potential to enhance PBPK simulations for a broader population. Application of the new albumin model for predicting fu in renal impairment was evaluated with the single binding protein model. Consideration of inter-individual variability predicted by the albumin model could explain some variability in the observed fu data between different drugs and studies (54% observed records within 2.5th-97.5th percentile range of prediction). However, overall underprediction of fold-change in fu between healthy and severe renal impairment (45% observed data exceeded 97.5th percentile of prediction) was noted. Although accounting for changes in binding affinity in predictive models of fu remains a challenge, the newly developed albumin model can support generation of realistic virtual subjects to support PBPK predictions of plasma protein binding.

Critical Review of the Benefit from Early Pharmacological and Dietary Support for Patients with Moderate-to-Severe (Non-Terminal) Chronic Kidney Disease

Moderate-to-severe chronic kidney disease (CKD) is a public health problem affecting hundreds of millions of people around the world. Started early, nephroprotection measures are able to prevent the degradation of renal function and are a major issue in CKD management. This approach consists of a combination of pharmacological and non-pharmacological treatments aimed at slowing down the decline in renal filtration capacity and improving patient well-being. Drugs such as angiotensin-converting enzyme inhibitors, angiotensin II receptor antagonists, and sodium-glucose cotransport type 2 inhibitors play a crucial role in reducing intraglomerular pressure and renal inflammation. Their beneficial effects are potentiated when they are combined with non-pharmacological approaches, such as salt and protein restriction. This present review provides a critical overview of the current pharmacological and nutritional therapies that may slow down the progression of CKD. Recently, many pharmacological treatments have opened up new perspectives for managing this condition. Nevertheless, prevention remains the cornerstone of effective disease management. Actually, very few studies include both pharmacists and dietitians in their interdisciplinary team mainly represented by nephrologists, nurses, and social workers. However, their specific collaboration may significantly improve the knowledge and skills to help patients in their own CKD management. Future research is required to assess the benefit of collaboration in supporting patients with moderate-to-severe CKD before any concern of renal replacement therapy (RRT).

Hyperkalemia management: a multidisciplinary expert panel's perspective on the role of new potassium binders

Hyperkalemia is a potentially life-threatening condition frequently encountered in clinical practice, particularly among patients with chronic kidney disease, heart failure, diabetes, and hypertension and those undergoing treatment with renin-angiotensin-aldosterone system inhibitors (RAASi). The management of chronic and acute hyperkalemia is complex and requires timely intervention to prevent severe complications such as cardiac arrhythmias and sudden death. Traditional therapeutic approaches to chronic hyperkalemia, including dietary potassium restriction, use of diuretics, and administration of cation-exchange resins like sodium polystyrene sulfonate, often suffer from limitations like gastrointestinal side effects, variable efficacy, delayed onset of action, and RAASi treatment discontinuation. In recent years, the development of new potassium binders, specifically patiromer and sodium zirconium cyclosilicate (SZC), has revolutionized the management of hyperkalemia. Patiromer, a non-absorbed polymer, binds potassium in the gastrointestinal tract in exchange for calcium, thus facilitating its excretion. SZC operates by exchanging sodium and hydrogen ions for potassium, leading to efficient potassium removal. Both agents have demonstrated rapid and sustained reductions in serum potassium levels, coupled with favorable safety and tolerability profiles, in multiple clinical trials. This review article, authored by a multidisciplinary group of Portuguese experts in hyperkalemia management, provides an in-depth analysis of the efficacy and safety of current therapeutic strategies and highlights the clinical potential of new potassium binders. The introduction of patiromer and SZC offers significant advantages over traditional therapies, providing effective and better-tolerated options for patients. The review highlights the role of these novel agents in contemporary hyperkalemia management and calls for ongoing research to further refine treatment protocols and improve patient outcomes.

Cultivating Innovative, Pragmatic, Randomized Controlled Registry Trials Embedded in Hemodialysis Care: Conference Proceeding From Gardener's Grove 2023

Purpose of the Conference

Hemodialysis is a life-sustaining treatment for patients with end-stage kidney disease. However, patients on dialysis continue to face poor quality of life and short life expectancies. Despite this, the nephrology community conducts the fewest randomized controlled trials of any medical discipline, relying instead on expert opinion to guide many aspects of hemodialysis care. There is a need to conduct high-quality pragmatic randomized controlled trials in hemodialysis to drive evidence-based practice. To this end, the Innovative Clinical Trials in Hemodialysis Centers initiative, with the support of the Canadian Institutes of Health Research and its Strategy for Patient-Oriented Research, funded the development of 6 pragmatic trial protocols. Gardener's Grove 2023 created a space to support the development of these trials and increase awareness and knowledge of past, ongoing, and future innovative, pragmatic, randomized controlled registry trials embedded in routine hemodialysis care. This report summarizes the proceedings of this conference.

Sources of information

The conference included 6 panel presentations, each featuring an overview of a new pragmatic trial followed by expert panel feedback from patient partners, nephrologists, researchers, and health care providers. The conference also included 10 educational sessions led by clinicians and researchers with experience in the fields of kidney medicine and clinical trials.

Methods

Gardener's Grove 2023 was a 4-day virtual conference held in March of 2023. Recordings of all the conference presentations were later published on the Gardener's Grove website and are summarized in the Supplemental Appendix of this report.

Key Findings

The conference brought together 118 Canadian and international researchers, patients, and health care providers to collaborate on 6 pragmatic trials intended to test interventions to improve hemodialysis care. The proposed trials included (1) PREventing FracturEs in REnal Disease (PREFERRED), (2) DIALysis with EXpanded solute removal (DIALEX), (3) Sodium fOr diaLysis oUTcome rEduction (SOLUTE), (4) Finding the right blood pressure target for patients on dialysis, (5) DIuretic Use in patients with Residual renal function on hemodialysis (DIURESED), and (6) Lower vs higher dialysate bicarbonate concentration in patients receiving hemodialysis (Dial-Bicarb). All of these interventions were widely supported and received valuable feedback from panelists and conference attendees. The education sessions focused on various design and execution elements of pragmatic, randomized controlled registry trials embedded in routine care.

Limitations

The conference could have been improved by streamlining session topics and pacing, allowing additional time for discussions, strengthening online network opportunities, and improving survey response rates. A follow-up conference is planned to take place in a few years, and the coordinators will aim to implement these changes.

Implications

Gardener's Grove 2023 successfully created a space for patients, researchers, and health care providers to support the development of 6 new pragmatic trials in hemodialysis care. Since Gardener's Grove 2023, several of these trials have secured CIHR funding, obtained ethics approval, and are actively preparing to launch their interventions.

Management of diabetes-related hyperglycaemic emergencies in advanced chronic kidney disease: Review of the literature and recommendations

AIMS

Despite the substantial progress in the management of diabetes mellitus (DM), chronic kidney disease (CKD) remains one of the most common complications. Although uncommon, diabetic emergencies [diabetic ketoacidosis (DKA), hyperosmolar hyperglycaemic state (HHS)] can still occur in stage 4 and 5 CKD, at times with less typical clinical manifestations due to the altered pathophysiology, presence of chronic metabolic acidosis and effect of haemodialysis on glycaemic control and metabolic parameters. The purpose of this article is to review the current literature and provide recommendations for the diagnosis and treatment of DKA, euglycaemic DKA and HHS in people with advanced CKD.

METHODS AND RESULTS

Guidance on the management of diabetes-related emergencies mainly focuses on individuals with preserved renal function or early-stage CKD. Existing literature is limited, and recommendations are based on expert opinions and case reports. Given the clinical need for amended guidelines for this population, we are proposing a management algorithm for DKA and HHS based on clinical and metabolic parameters.

CONCLUSIONS

In this review article, we propose treatment algorithms for diabetes-related hyperglycaemic emergencies in people with advanced CKD. Further research is needed to validate our proposed algorithms.

The effect of renal function on the clinical outcomes and management of patients hospitalized with hyperglycemic crises

Background

The global prevalence of diabetes has been rising rapidly in recent years, leading to an increase in patients experiencing hyperglycemic crises like diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS). Patients with impaired renal function experience a delay in insulin clearance, complicating the adjustment of insulin dosing and elevating hypoglycemia risk. Accordingly, this study aims to evaluate the impact of renal function on the safety and efficacy of insulin use in patients with isolated DKA or combined DKA/HHS.

Methods

A retrospective observational study was conducted at King Abdulaziz Medical City, Saudi Arabia, from January 2016 to December 2021. Eligible patients were ≥18 years, had a confirmed diagnosis of isolated DKA or combined DKA/HHS, presented with an anion gap (AG) of ≥ 16 mmol/L, and received insulin either via continuous infusion or as bolus doses. Patients were categorized into normal kidney function and patients with chronic kidney disease (CKD). The primary outcome was to determine the difference in time to close the AG between the two groups. Statistical analyses were performed using SAS® software.

Results

Out of 319 screened patients, 183 patients met the inclusion criteria. The patients were divided into normal kidney function (43.2%) and CKD (56.8%) groups. The average eGFR for patients with normal kidney function was 93.7 ± 32.5 mL/min/1.73m2 compared to 33.4 ± 14.3 mL/min/1.73m2 for patients with CKD. The time to close AG was similar between patients in the normal kidney function and CKD groups (22.6 ± 16.0 hours vs. 24.5 ± 17.5 hours, p=0.4475). However, the patients' length of stay in hospital (3.4 ± 2.5 days vs. 5.2 ± 4.0 days; p=0.0004) and ICU (2.5 ± 1.8 days vs. 4.0 ± 2.8 days; p=0.0453) were both significantly longer for patients with CKD. Hypoglycemic events were low in our study with only four documented cases among patients with CKD.

Conclusion

This study provides insights into DKA management and outcomes in patients with normal and impaired renal function. The time required to close AG was comparable between the two groups. Larger, multi-center studies are needed to validate these findings and explore additional factors that may impact the management of DKA in patients with CKD.

Ameliorating role of co-administration of granulocyte colony stimulating factor and sodium bicarbonate on the skeletal muscle of a rat model of chronic kidney disease (A histological and immunohistochemical study)

Over half million individuals suffer from chronic kidney disease (CKD) worldwide. In addition to raising the possibility of cardiovascular diseases, skeletal myopathy remains a challenging complication that is highly correlated with mortality and a lower quality of life. Granulocyte-colony stimulating factor (G-CSF) is an active cytokine for mobilization of immunological and hematopoietic stem cells that can replace exogenous stem cell infusions. So, it is seen as a less expensive and noninvasive tool for regenerative medicine. Sixty three rats were divided into 4 groups: I control, II CKD induced, IIIa, IIIb treated and IV recovery groups. After induction of CKD in all rats, group II were sacrificed after 4 weeks. Rats of group IIIa received NaHCO3. Group IIIb rats were injected subcutaneously by G-CSF as 100 µg/kg/day for 5 successive days in addition to NaHCO3 as group IIIa. Group IV rats were housed for 4 weeks without treatment. Serum urea, creatinine, tissue MDA& TNF-α were assessed. Renal and gastrocnemius muscle sections were evaluated for histological structure, CD34 and myogenin immune expression, morphometric and statistical analyses. The CKD group revealed a significant increase in MDA and TNF-α. Furthermore, features of renal injury, muscle degenerative changes, increased collagen and decreased CD34 and myogenin expression were observed. Alterations were partially attenuated by NaHCO3, while GCSF remarkably improved most parameters. The current results indicated that co-administration of GCSF and NaHCO3 could ameliorate CKD myopathy via attenuating oxidative stress, immunomodulation, pro-angiogenic ability, myocyte regeneration. In addition to the reduction of mitochondrial stress and maintenance of cellular homeostasis.

Oral alkalinizing supplementation suppressed intrarenal reactive oxidative stress in mild-stage chronic kidney disease: a randomized cohort study

BACKGROUND

The beneficial effects of oral supplements with alkalinizing agents in patients with chronic kidney disease (CKD) have been limited to the severe stages. We investigated whether two types of supplements, sodium bicarbonate (SB) and potassium citrate/sodium citrate (PCSC), could maintain renal function in patients with mild-stage CKD.

METHODS

This was a single-center, open-labeled, randomized cohort trial. Study participants with CKD stages G2, G3a, and G3b were enrolled between March 2013 and January 2019 and randomly assigned by stratification according to age, sex, estimated glomerular filtration rate (eGFR), and diabetes. They were followed up for 6 months (short-term study) for the primary endpoints and extended to 2 years (long-term study) for the secondary endpoints. Supplementary doses were adjusted to achieve an early morning urinary pH of 6.8-7.2. We observed renal dysfunction or new-onset cerebrovascular disease and evaluated urinary surrogate markers for renal injury.

RESULTS

Overall, 101 participants were registered and allocated to three groups: standard (n = 32), SB (n = 34), and PCSC (n = 35). Two patients in the standard group attained the primary endpoints (renal stones and overt proteinuria) but were not statistically significant. There was one patient in the standard reduced eGFR during the long-term study (p = 0.042 by ANOVA). SB increased proteinuria (p = 0.0139, baseline vs. 6 months), whereas PCSC significantly reduced proteinuria (p = 0.0061, baseline vs. 1 year, or p = 0.0186, vs. 2 years) and urinary excretion of 8-hydroxy-2'-deoxyguanosine (p = 0.0481, baseline vs. 6 months).

CONCLUSION

This study is the first to report supplementation of PCSC reduced intrarenal oxidative stress in patients with mild-stage CKD.

Safety and impact of the Mediterranean diet in patients with chronic kidney disease: a pilot randomized crossover trial

Introduction

Emerging evidence highlights the potential advantages of the Mediterranean diet (MD) in preserving kidney function and slowing chronic kidney disease (CKD) progression. However, interventional studies on the MD are scarce in East Asian populations.

Methods

This randomized crossover trial aimed to assess the safety and short-term impact of the Mediterranean Proper Optimal Balance (MEDi-POB) diet in Korean patients with stage 3-4 CKD. Kidney function was assessed using the estimated glomerular filtration rate, which was calculated using the CKD Epidemiology Collaboration equation. Fifty patients with CKD were randomly assigned to two groups, each starting with a different 4-week intervention, followed by a 4-week washout period, followed by a switch to the other 4-week intervention. During the MEDi-POB intervention, patients received home delivery of meals twice daily, 5 days a week, while the control intervention comprised a conventional diet. Forty-six patients successfully completed the entire 12-week trial. Paired t-tests were conducted to assess mean differences between the two groups. A linear mixed model was used to adjust for sequence and period.

Results

Dietary fat, fiber, and niacin intake were significantly higher following the MEDi-POB diet than following the control diet (p = 0.001 for fat, p < 0.001 for fiber, and p = 0.007 for niacin). The MEDi-POB diet also yielded slightly increased total CO2 levels (p = 0.043), indicating effective management of metabolic acidosis. Conversely, sodium and copper intake were significantly lower with the MEDi-POB diet (p = 0.032 and p = 0.037, respectively). Caloric intake increased, but body mass index slightly decreased from baseline after consuming the MEDi-POB diet. Dietary potassium intake exhibited a non-significant increase (p = 0.053), and no significant changes in serum (p = 0.883) and urine potassium levels (p = 0.087) occurred. Kidney function remained well-preserved following the MEDi-POB diet.

Conclusion

These results indicate that the MEDi-POB diet is safe even in patients with advanced CKD, as it does not adversely affect serum and urine potassium levels and helps maintain kidney function.

The Modification of Dietary Protein with Ammonium Hydroxide Enhancement Improves Longevity and Metabolic Outcomes in a Sex-Dependent Manner

(1) Background: Dietary protein is a key component of all dietary patterns. It has been demonstrated that there are subtle differences in health implications associated with the source of dietary protein consumed. This study examined dietary protein sources (DPSs) in a long-term study of diet-induced obesity ± ammonium hydroxide enhancement (AHE) and its role in improving long-term health outcomes. (2) Methods: Over 18 months, 272 C3H/HeJ mice (136 male and 136 female) were monitored on high-fat diets with varying DPSs ± AHE. Mice were monitored for weekly change in total mass, as well as 6-month assessments of lean and fat mass. At each assessment, a cohort (~8 mice per diet per sex) was censored for a cross-sectional examination of organ function. (3) Results: Longevity was improved in females fed AHE diets, regardless of DPSs. Females' measures of fat and lean mass were markedly elevated with casein protein diets compared to beef protein diets regardless of AHE. Females fed a beef protein diet + AHE demonstrated reduced fat mass and increased lean mass with aging. In males, AHE beef protein diet-fed mice showed marked improvement to longevity and increased lean mass at 6 months. (4) Conclusions: This study demonstrates that dietary protein modification by AHE attenuates the negative impacts of HF diets in both males and females in a sex-dependent manner. Furthermore, the results from this study emphasize the importance of identifying the differences in the utilization of dietary proteins in both a sex- and age-related manner and demonstrate the potential of DPS modification by AHE as a dietary intervention.

Explainable artificial intelligence in the design of selective carbonic anhydrase I-II inhibitors via molecular fingerprinting

Inhibiting the enzymes carbonic anhydrase I (CA I) and carbonic anhydrase II (CA II) presents a potential avenue for addressing nervous system ailments such as glaucoma and Alzheimer's disease. Our study explored harnessing explainable artificial intelligence (XAI) to unveil the molecular traits inherent in CA I and CA II inhibitors. The PubChem molecular fingerprints of these inhibitors, sourced from the ChEMBL database, were subjected to detailed XAI analysis. The study encompassed training 10 regression models using IC50 values, and their efficacy was gauged using metrics including R2, RMSE, and time taken. The Decision Tree Regressor algorithm emerged as the optimal performer (R2: 0.93, RMSE: 0.43, time-taken: 0.07). Furthermore, the PFI method unveiled key molecular features for CA I inhibitors, notably PubChemFP432 (C(O)N) and PubChemFP6978 (C(O)O). The SHAP analysis highlighted the significance of attributes like PubChemFP539 (C(O)NCC), PubChemFP601 (C(O)OCC), and PubChemFP432 (C(O)N) in CA I inhibitiotable n. Likewise, features for CA II inhibitors encompassed PubChemFP528(C(O)OCCN), PubChemFP791 (C(O)OCCC), PubChemFP696 (C(O)OCCCC), PubChemFP335 (C(O)NCCN), PubChemFP580 (C(O)NCCCN), and PubChemFP180 (C(O)NCCC), identified through SHAP analysis. The sulfonamide group (S), aromatic ring (A), and hydrogen bonding group (H) exert a substantial impact on CA I and CA II enzyme activities and IC50 values through the XAI approach. These insights into the CA I and CA II inhibitors are poised to guide future drug discovery efforts, serving as a beacon for innovative therapeutic interventions.

The Role of Dietary Acid Load on Progression of Estimated Glomerular Filtration Rate Among Individuals Diagnosed With Chronic Kidney Disease

OBJECTIVE

Individuals with chronic kidney disease (CKD) are at an increased risk for developing metabolic acidosis. Metabolic acidosis has been shown to worsen kidney function and exacerbate systemic inflammation. Diets high in protein foods can exacerbate metabolic acidosis as protein foods tend to be more acidic, while fruits and vegetables are more alkalotic. The main objective of this systematic review was to determine if higher consumption of fruits and vegetables in adults with CKD stages 1-5 reduces the rate of decline of estimated glomerular filtration rate.

METHODS

Searches of Cumulated Index to Nursing and Allied Health Literature (CINAHL -Elton B. Stephens Company [EBSCO]), Cochrane Library (Wiley), Dissertation & Thesis Global (ProQuest), Embase (Elsevier), Medline (OVID), PubMed (National Library of Medicine), Scopus (Elsevier), and Web of Sciences (Clarivate) identified 1,451 articles published between January 2015 and June 2023.

RESULTS

After independent review, 7 total studies were included. Six of the studies found an association between dietary acid load and progression of CKD.

CONCLUSIONS

Dietary counseling focusing on decreasing dietary acid load may be beneficial for individuals with CKD.

Association between peri-transplant acid-base parameters and graft dysfunction types in kidney transplantation

Perioperative acid-base disturbance could be informative regarding the possible slow graft function (SGF) or delayed graft function (DGF) development. There is a lack of data regarding the relationship between perioperative acid-base parameters and graft dysfunction in kidney transplant (KT) recipients. We aim to determine the incidence of graft dysfunction types and the association between them and acid-base parameters. We performed a prospective, cohort study on 54 adults, KT recipients, between 1st of January 2019 and 31st of December 2019. Graft function was defined and classified in three categories: immediate graft function (IGF) (serum creatinine < 3 mg/dL at day 5 after KT), SGF (serum creatinine ≥ 3mg/dL at day 5 or ≥ 2.5mg dL at day 7 after KT) and DGF (the need for at least one dialysis treatment in the first week after kidney transplantation). Among the 54 KT recipients, the incidence of SGF and DGF was 13% and 11.1%, respectively. SGF was significantly associated with lower intraoperative pH (7.26± 0.05 vs 7.35± 0.06, p= 0.004), preoperative and intraoperative base excess (BE) [-7.0 (-10.0 ߝ -6.0) vs -3.4 (-7.8 ߝ - 2.1) mmol/L, p= 0.04 and -10.3 (-11.0 ߝ -9.1) vs -4.0 (-6.3 ߝ - 3.0) mmol/L, p= 0.002, respectively] and serum bicarbonate (HCO3-) (16.0± 2.7 vs 19.3± 3.4 mmol/L, p= 0.01 and 14.1± 1.9 vs 18.8± 3.2 mmol/L, p= 0.002 respectively), compared to IGF. DGF was significantly associated with lower intraoperative values of pH (7.27± 0.05 vs 7.35± 0.06, p= 0.003), BE [-7.1 (-10.9 ߝ -6.1) vs -4.0 (-6.3 ߝ - 3.0) mmol/L, p= 0.02] and HCO3- (15.9± 2.4 vs 18.8± 3.2 mmol/L, p=0.02) compared to IGF. No differences were observed between SGF and DGF patients in any of the perioperative acid-base parameters. In conclusion we found that kidney graft dysfunction types are associated with perioperative acid-base parameters and perioperative metabolic acidosis could provide important information to predict SGF or DGF occurrence.

Chloride ions in health and disease

Chloride is a key anion involved in cellular physiology by regulating its homeostasis and rheostatic processes. Changes in cellular Cl- concentration result in differential regulation of cellular functions such as transcription and translation, post-translation modifications, cell cycle and proliferation, cell volume, and pH levels. In intracellular compartments, Cl- modulates the function of lysosomes, mitochondria, endosomes, phagosomes, the nucleus, and the endoplasmic reticulum. In extracellular fluid (ECF), Cl- is present in blood/plasma and interstitial fluid compartments. A reduction in Cl- levels in ECF can result in cell volume contraction. Cl- is the key physiological anion and is a principal compensatory ion for the movement of the major cations such as Na+, K+, and Ca2+. Over the past 25 years, we have increased our understanding of cellular signaling mediated by Cl-, which has helped in understanding the molecular and metabolic changes observed in pathologies with altered Cl- levels. Here, we review the concentration of Cl- in various organs and cellular compartments, ion channels responsible for its transportation, and recent information on its physiological roles.

Ammonia detection: A pathway towards potential point-of-care diagnostics

Invasive methods such as blood collection and biopsy are commonly used for testing liver and kidney function, which are painful, time-consuming, require trained personnel, and may not be easily accessible to people for their routine checkup. Early diagnosis of liver and kidney diseases can prevent severe symptoms and ensure better management of these patients. Emerging approaches such as breath and sweat analysis have shown potential as non-invasive methods for disease diagnosis. Among the many markers, ammonia is often used as a biomarker for the monitoring of liver and kidney functions. In this review we provide an insight into the production and expulsion of ammonia gas in the human body, the different diseases that could potentially use ammonia as biomarker and analytical devices such as chemiresistive gas sensors for non-invasive monitoring of this gas. The review also provides an understanding into the different materials, doping agents and substrates used to develop such multifunctional sensors. Finally, the current challenges and the possible future trends have been discussed.

The multi-faceted nature of age-associated osteoporosis

Age-associated osteoporosis (AAOP) poses a significant health burden, characterized by increased fracture risk due to declining bone mass and strength. Effective prevention and early treatment strategies are crucial to mitigate the disease burden and the associated healthcare costs. Current therapeutic approaches effectively target the individual contributing factors to AAOP. Nonetheless, the management of AAOP is complicated by the multitude of variables that affect its development. Main intrinsic and extrinsic factors contributing to AAOP risk are reviewed here, including mechanical unloading, nutrient deficiency, hormonal disbalance, disrupted metabolism, cognitive decline, inflammation and circadian disruption. Furthermore, it is discussed how these can be targeted for prevention and treatment. Although valuable as individual targets for intervention, the interconnectedness of these risk factors result in a unique etiology for every patient. Acknowledgement of the multifaceted nature of AAOP will enable the development of more effective and sustainable management strategies, based on a holistic, patient-centered approach.

NaHCO3 loading causes increased arterial pressure and kidney damage in rats with chronic kidney disease

Sodium bicarbonate (NaHCO3) is commonly utilized as a therapeutic to treat metabolic acidosis in people with chronic kidney disease (CKD). While increased dietary sodium chloride (NaCl) is known to promote volume retention and increase blood pressure, the effects of NaHCO3 loading on blood pressure and volume retention in CKD remain unclear. In the present study, we compared the effects of NaCl and NaHCO3 loading on volume retention, blood pressure, and kidney injury in both 2/3 and 5/6 nephrectomy remnant kidney rats, a well-established rodent model of CKD. We tested the hypothesis that NaCl loading promotes greater volume retention and increases in blood pressure than equimolar NaHCO3. Blood pressure was measured 24 h daily using radio telemetry. NaCl and NaHCO3 were administered in drinking water ad libitum or infused via indwelling catheters. Rats were housed in metabolic cages to determine volume retention. Our data indicate that both NaHCO3 and NaCl promote hypertension and volume retention in remnant kidney rats, with salt-sensitivity increasing with greater renal mass reduction. Importantly, while NaHCO3 intake was less pro-hypertensive than equimolar NaCl intake, NaHCO3 was not benign. NaHCO3 loading significantly elevated blood pressure and promoted volume retention in rats with CKD when compared with control rats receiving tap water. Our findings provide important insight into the effects of sodium loading with NaHCO3 in CKD and indicate that NaHCO3 loading in patients with CKD is unlikely to be benign.

The Effects of Acid on Calcium and Phosphate Metabolism

A variety of changes in mineral metabolism aiming to restore acid-base balance occur in acid loading and metabolic acidosis. Phosphate plays a key role in defense against metabolic acidosis, both as an intracellular and extracellular buffer, as well as in the renal excretion of excess acid in the form of urinary titratable acid. The skeleton acts as an extracellular buffer in states of metabolic acidosis, as the bone matrix demineralizes, leading to bone apatite dissolution and the release of phosphate, calcium, carbonate, and citrate into the circulation. The renal handling of calcium, phosphate and citrate is also affected, with resultant hypercalciuria, hyperphosphaturia and hypocitraturia.

Hyperchloremic metabolic acidosis after plasma exchange in a patient with renal transplant rejection: A case report

Therapeutic plasma exchange (TPE) is an effective treatment for several renal disorders, including renal transplant rejection. However, repeated plasma exchanges can result in various metabolic disturbances and complications. We present a 61-year old male with a medical history of type 2 diabetes, hypertension, successfully treated multiple myeloma, and a post-mortem kidney transplantation 7 months prior to presentation. The patient was hospitalized with an antibody-mediated transplant rejection for which treatment with methylprednisolone, TPE with a 40 g/L albumin solution as a replacement fluid, and intravenous immunoglobulins was initiated. After four TPE treatments, the patient developed gastrointestinal complaints and muscle weakness. Despite daily oral bicarbonate supplementation, laboratory tests revealed a hyperchloremic metabolic acidosis: bicarbonate 11.7 mmol/L, chloride 111 mmol/L, and sodium 138 mmol/L. Metabolic acidosis due to citrate accumulation was ruled out with a normal total-to-ionized calcium ratio. After treatment with intravenous bicarbonate supplementation, the symptoms disappeared. Analysis of the albumin solution showed a chloride concentration of 132 mmol/L. This is the first case that describes severe metabolic acidosis after multiple sessions of TPE with an albumin solution in a patient with impaired renal function. The hyperchloremic metabolic acidosis is the result of administration of large volumes of an albumin solution with high chloride concentrations. Special attention should be paid to the acid-base balance during TPE in patients with impaired renal function. Future research should investigate the incidence of hyperchloremic metabolic acidosis during TPE in patients with impaired renal function.

Prediction of adverse events risk in patients with comorbid post-traumatic stress disorder and alcohol use disorder using electronic medical records by deep learning models

BACKGROUND

Identifying co-occurring mental disorders and elevated risk is vital for optimization of healthcare processes. In this study, we will use DeepBiomarker2, an updated version of our deep learning model to predict the adverse events among patients with comorbid post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD), a high-risk population.

METHODS

We analyzed electronic medical records of 5565 patients from University of Pittsburgh Medical Center to predict adverse events (opioid use disorder, suicide related events, depression, and death) within 3 months at any encounter after the diagnosis of PTSD+AUD by using DeepBiomarker2. We integrated multimodal information including: lab tests, medications, co-morbidities, individual and neighborhood level social determinants of health (SDoH), psychotherapy and veteran data.

RESULTS

DeepBiomarker2 achieved an area under the receiver operator curve (AUROC) of 0.94 on the prediction of adverse events among those PTSD+AUD patients. Medications such as vilazodone, dronabinol, tenofovir, suvorexant, modafinil, and lamivudine showed potential for risk reduction. SDoH parameters such as cognitive behavioral therapy and trauma focused psychotherapy lowered risk while active veteran status, income segregation, limited access to parks and greenery, low Gini index, limited English-speaking capacity, and younger patients increased risk.

CONCLUSIONS

Our improved version of DeepBiomarker2 demonstrated its capability of predicting multiple adverse event risk with high accuracy and identifying potential risk and beneficial factors.

Management of Hyperkalemia in Patients with Chronic Kidney Disease Using Renin Angiotensin Aldosterone System Inhibitors

PURPOSE OF REVIEW

Use of renin-angiotensin-aldosterone system (RAAS) inhibiting medications is critical in the prevention of cardiovascular disease and kidney function decline in patients with chronic kidney disease (CKD); however, these agents can lead to hyperkalemia, an electrolyte disorder associated with risk of arrythmia, conduction disorders, and increased overall mortality. Discontinuation, or reduction of dose, of RAAS inhibitor therapy in hyperkalemic patients with CKD can lead to loss of kidney and cardiovascular protection afforded by these medications. Given the high prevalence of hyperkalemia among patients with CKD utilizing RAAS inhibitors, clear management principles are critical to minimize risk and maximize benefit when facing this clinical dilemma.

RECENT FINDINGS

Strategies to mitigate hyperkalemia that do not interfere with optimal RAAS inhibitor therapy should be prioritized when managing potassium elevation in patients with CKD. These strategies include discontinuing non-RAAS inhibitor medications known to cause hyperkalemia, correction of metabolic acidosis, and maximization of medication therapies that lower serum potassium, including diuretics and sodium-glucose cotransporter-2 (SGLT-2) inhibitors. Initiation of potassium exchange resins should also be considered to allow for sustained RAAS inhibitor utilization. An approach which employs multiple strategies concurrently is important to mitigate hyperkalemia and maintain long-term use of RAAS-inhibitors. Persistence of RAAS inhibitor use in patients with CKD is important to slow kidney function decline, delay onset of dialysis or the need for kidney transplant, and prevent adverse cardiovascular outcomes. When hyperkalemia develops among patients with CKD utilizing a RAAS inhibitor, a deliberate effort to reduce serum potassium levels using an approach that allows for continuation of maximally dosed RAAS inhibitor therapy is important. Patient education and engagement in the potassium management process is important for sustained success.

Prediction of Adverse Events Risk in Patients with Comorbid Post- Traumatic Stress Disorder and Alcohol Use Disorder Using Electronic Medical Records by Deep Learning Models

Background

Prediction of high-risk events in mental disorder patients is crucial. In our previous study, we developed a deep learning model: DeepBiomarker by using electronic medical records (EMR) to predict suicide related event (SRE) risk in post-traumatic stress disorder (PTSD) patients.

Methods

We applied DeepBiomarker2 through data integration of multimodal information: lab test, medication, co-morbidities, and social determinants of health. We analyzed EMRs of 5,565 patients from University of Pittsburgh Medical Center with a diagnosis of PTSD and alcohol use disorder (AUD) on risk of developing an adverse event (opioid use disorder, SREs, depression and death).

Results

DeepBiomarker2 predicted whether a PTSD + AUD patient will have a diagnosis of any adverse events (SREs, opioid use disorder, depression, death) within 3 months with area under the receiver operator curve (AUROC) of 0.94. We found piroxicam, vilazodone, dronabinol, tenofovir, suvorexant, empagliflozin, famciclovir, veramyst, amantadine, sulfasalazine, and lamivudine to have potential to reduce risk.

Conclusions

DeepBiomarker2 can predict multiple adverse event risk with high accuracy and identify potential risk and beneficial factors. Our results offer suggestions for personalized interventions in a variety of clinical and diverse populations.

Administration of alendronate exacerbates ammonium chloride-induced acidosis in mice

Bone disease is highly prevalent in patients with chronic kidney disease (CKD), leading to an increased risk of bone fractures. This is due in part to metabolic acid-induced bone dissolution. Bisphosphonates (BPPs) are a potential treatment for inhibiting bone dissolution; however, there are limited studies observing the use of BPPs on acidotic patients. We aimed to determine efficacy of BPPs on maintaining bone health and pH regulation in acid-exposed mice. Using a diet-induced murine model of metabolic acidosis, we examined bone structure, composition, and mechanics as well as blood gases for three groups: control, acidosis, and acidosis + bisphosphonates (acidosis+BPP). Acidosis was induced for 14 days and alendronate was administered every 3 days for the acidosis+BPP group. The administration of BPP had little to no effect on bone structure, mechanics, and composition of the acidosis bones. However, administration of BPP did cause the mice to develop more severe acidosis than the acidosis only group. Overall, we discovered that BPPs may exacerbate acidosis symptoms by inhibiting the release of buffering ions from bone. Therefore, we propose that BPP administration should be carefully considered for those with CKD and that alkali supplementation could help minimize acidifying effects.

The Potential Influence of Uremic Toxins on the Homeostasis of Bones and Muscles in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) often experience a high accumulation of protein-bound uremic toxins (PBUTs), specifically indoxyl sulfate (IS) and p-cresyl sulfate (pCS). In the early stages of CKD, the buildup of PBUTs inhibits bone and muscle function. As CKD progresses, elevated PBUT levels further hinder bone turnover and exacerbate muscle wasting. In the late stage of CKD, hyperparathyroidism worsens PBUT-induced muscle damage but can improve low bone turnover. PBUTs play a significant role in reducing both the quantity and quality of bone by affecting osteoblast and osteoclast lineage. IS, in particular, interferes with osteoblastogenesis by activating aryl hydrocarbon receptor (AhR) signaling, which reduces the expression of Runx2 and impedes osteoblast differentiation. High PBUT levels can also reduce calcitriol production, increase the expression of Wnt antagonists (SOST, DKK1), and decrease klotho expression, all of which contribute to low bone turnover disorders. Furthermore, PBUT accumulation leads to continuous muscle protein breakdown through the excessive production of reactive oxygen species (ROS) and inflammatory cytokines. Interactions between muscles and bones, mediated by various factors released from individual tissues, play a crucial role in the mutual modulation of bone and muscle in CKD. Exercise and nutritional therapy have the potential to yield favorable outcomes. Understanding the underlying mechanisms of bone and muscle loss in CKD can aid in developing new therapies for musculoskeletal diseases, particularly those related to bone loss and muscle wasting.

The Role of Dietary Potassium in the Cardiovascular Protective Effects of Plant-Based Diets

Dietary intervention is an essential factor in managing a multitude of chronic health conditions such as cardiovascular and chronic kidney disease. In recent decades, there has been a host of research suggesting the potential benefit of plant-based diets in mitigating the health outcomes of these conditions. Plant-based diets are rich in vegetables and fruits, while limiting processed food and animal protein sources. The underlying physiological mechanism involves the interaction of several macronutrients and micronutrients such as plant protein, carbohydrates, and dietary potassium. Specifically, plant-based foods rich in potassium provide cardiorenal protective effects to include urinary alkalization and increased sodium excretion. These diets induce adaptive physiologic responses that improve kidney and cardiovascular hemodynamics and improve overall metabolic health. A shift toward consuming plant-based diets even in subjects with cardiorenal decrements may reduce their morbidity and mortality. Nonetheless, randomized controlled trials are needed to confirm the clinical benefits of plant-based diets.

Sodium zirconium cyclosilicate and metabolic acidosis: Potential mechanisms and clinical consequences

Metabolic acidosis is frequent in chronic kidney disease (CKD) and is associated with accelerated progression of CKD, hypercatabolism, bone disease, hyperkalemia, and mortality. Clinical guidelines recommend a target serum bicarbonate ≥ 22 mmol/L, but metabolic acidosis frequently remains undiagnosed and untreated. Sodium zirconium cyclosilicate (SZC) binds potassium in the gut and is approved to treat hyperkalemia. In clinical trials with a primary endpoint of serum potassium, SZC increased serum bicarbonate, thus treating CKD-associated metabolic acidosis. The increase in serum bicarbonate was larger in patients with more severe pre-existent metabolic acidosis, was associated to decreased serum urea and was maintained for over a year of SZC therapy. SZC also decreased serum urea and increased serum bicarbonate after switching from a potassium-binding resin in normokalemic individuals. Mechanistically, these findings are consistent with SZC binding the ammonium ion (NH₄⁺) generated from urea by gut microbial urease, preventing its absorption and, thus, preventing the liver regeneration of urea and promoting the fecal excretion of H⁺. This mechanism of action may potentially result in benefits dependent on corrected metabolic acidosis (e.g., improved well-being, decreased catabolism, improved CKD mineral bone disorder, better control of serum phosphate, slower progression of CKD) and dependent on lower urea levels, such as decreased protein carbamylation. A roadmap is provided to guide research into the mechanisms and clinical consequences of the impact of SZC on serum bicarbonate and urate.

Wearable and implantable artificial kidney devices for end-stage kidney disease treatment-Current status and review

BACKGROUND

Chronic kidney disease (CKD) is a major cause of early death worldwide. By 2030, 14.5 million people will have end-stage kidney disease (ESKD, or CKD stage 5), yet only 5.4 million will receive kidney replacement therapy (KRT) due to economic, social, and political factors. Even for those who are offered KRT by various means of dialysis, the life expectancy remains far too low.

OBSERVATION

Researchers from different fields of artificial organs collaborate to overcome the challenges of creating products such as Wearable and/or Implantable Artificial Kidneys capable of providing long-term effective physiologic kidney functions such as removal of uremic toxins, electrolyte homeostasis, and fluid regulation. A focus should be to develop easily accessible, safe, and inexpensive KRT options that enable a good quality of life and will also be available for patients in less-developed regions of the world.

CONCLUSIONS

Hence, it is required to discuss some of the limits and burdens of transplantation and different techniques of dialysis, including those performed at home. Furthermore, hurdles must be considered and overcome to develop wearable and implantable artificial kidney devices that can help to improve the quality of life and life expectancy of patients with CKD.