Serum uric acid and acute kidney injury: A mini review

Uric acid and inflammation in kidney disease

Asymptomatic hyperuricemia is frequently observed in patients with kidney disease. Although a substantial number of epidemiologic studies have suggested that an elevated uric acid level plays a causative role in the development and progression of kidney disease, whether hyperuricemia is simply a result of decreased renal excretion of uric acid or is a contributor to kidney disease remains a matter of debate. Over the last two decades, multiple experimental studies have expanded the knowledge of the biological effects of uric acid beyond its role in gout. In particular, uric acid induces immune system activation and alters the characteristics of resident kidney cells, such as tubular epithelial cells, endothelial cells, and vascular smooth muscle cells, toward a proinflammatory and profibrotic state. These findings have led to an increased awareness of uric acid as a potential and modifiable risk factor in kidney disease. Here, we discuss the effects of uric acid on the immune system and subsequently review the effects of uric acid on the kidneys mainly in the context of inflammation.

Serum osmolarity as a potential predictor for contrast-induced nephropathy following elective coronary angiography

BACKGROUND AND OBJECTIVES

Contrast-induced nephropathy (CIN) is a relatively common complication following primary coronary angiography (CAG) or percutaneous coronary intervention (PCI), especially in at-risk patients. The goal of this study is to evaluate the role of pre-procedural serum osmolarity as a risk factor for CIN in patients undergoing elective CAG for stable coronary artery disease (CAD).

MATERIALS AND METHODS

A total of 356 stable CAD patients scheduled to undergo CAG or PCI were included in this two-center study. Serum osmolarity was calculated on admission. CIN was defined according to the KDIGO criteria.

RESULTS

There were 45 (12.6%) patients who developed CIN 48-72 h after CAG or PCI. CIN patients had a higher prevalence of diabetes (51.1% in those with CIN vs 24.4% in those without CIN, p < 0.001), higher serum glucose (129 mg/dL in those with CIN vs 108 mg/dL in those without CIN, p < 0.001), blood urea nitrogen (22.4 mg/dL in those with CIN vs 19.0 mg/dL in those without CIN, p = 0.01) and serum osmolarity (294.2 mOsm in those with CIN vs 290.1 mOsm in those without CIN, p < 0.001) levels, had received a higher dose of contrast (250 mL in those with CIN vs 200 mL in those without CIN, p = 0.03) but had lower hemoglobin (12.9 g/dL in those with CIN vs 13.6 g/dL in those without CIN, p = 0.04) level. In multivariate analysis, serum osmolarity [odds ratio (OR) 1.11; 95% confidence interval (CI) 1.04-1.18 for each mOsm/L increase; p = 0.001], diabetes (OR 2.43, 95% CI 1.26-4.71; p = 0.01), C-reactive protein (OR 1.04, 95% CI 1.01-1.08 for each mg/dL increase; p = 0.02) and contrast volume (OR 34.66, 95% CI 1.25-962.22 for each L increase; p = 0.04) remained as independent predictors of CIN. Serum sodium, glucose and blood urea nitrogen contributed to the excess serum osmolarity of CIN patients.

CONCLUSION

Serum osmolarity is a cheap and widely available marker that can reliably predict CIN after CAG or PCI. Future research should focus on determining a clinically optimal cutoff for serum osmolarity that would warrant preventive interventions. Furthermore, later research may investigate the role of serum osmolarity not only as a risk factor but also as a pathogenetic mechanism underlying CIN.

Asymptomatic hyperuricaemia: a silent activator of the innate immune system

Asymptomatic hyperuricaemia affects ~20% of the general population in the USA, with variable rates in other countries. Historically, asymptomatic hyperuricaemia was considered a benign laboratory finding with little clinical importance in the absence of gout or kidney stones. Yet, increasing evidence suggests that asymptomatic hyperuricaemia can predict the development of hypertension, obesity, diabetes mellitus and chronic kidney disease and might contribute to disease by stimulating inflammation. Although urate has been classically viewed as an antioxidant with beneficial effects, new data suggest that both crystalline and soluble urate activate various pro-inflammatory pathways. This Review summarizes what is known about the role of urate in the inflammatory response. Further research is needed to define the role of asymptomatic hyperuricaemia in these pro-inflammatory pathways.

Evaluation of the Effects of Agro Pesticides Use on Liver and Kidney Function in Farmers from Buea, Cameroon

Agro pesticides are increasingly used worldwide to increase crop production. However, health hazards resulting from human exposure to these chemicals, especially from agricultural areas of developing countries have been a growing concern. The objective of this study was to evaluate the impact of occupational exposure to agro pesticides on the health of farmers in the Buea subdivision, which is one of the major agrarian areas in Cameroon. The study was transversal and involved 90 participants including 58 farmers using pesticides and a reference population of 32 men not involved in occupational use of agro pesticides. The participants were interviewed on agro pesticide use and their health status. Thereafter, blood samples were collected from the participants and used for the assessment of biochemical markers of the liver (alanine aminotransferase and aspartate aminotransferase) and the kidney (creatinine and uric acid) function. Results revealed that farmers frequently used insecticides, fungicides, and herbicides in their farming activities. Farmers reported several acute health symptoms related to pesticides use with the common ones being skin rash, eye irritation, and face burn. When compared to the reference population, the farmers showed significantly elevated (p < 0.01) alanine aminotransferase activity. However, other parameters investigated were not affected significantly. These results suggested that farmers were exposed to 3 different classes of agro pesticides, which induced eye and skin affections. Pesticides exposure resulted in alterations of the liver function hence the increased serum alanine aminotransferase activity. Therefore, there is a need to sensitize the farmers on toxicity and liver alteration potential of agro pesticides and the importance of appropriate protective equipment that may minimize exposure.

No Cytotoxic and Inflammatory Effects of Empagliflozin and Dapagliflozin on Primary Renal Proximal Tubular Epithelial Cells under Diabetic Conditions In Vitro

Gliflozins are inhibitors of the renal proximal tubular sodium-glucose co-transporter-2 (SGLT-2), that inhibit reabsorption of urinary glucose and they are able to reduce hyperglycemia in patients with type 2 diabetes. A renoprotective function of gliflozins has been proven in diabetic nephropathy, but harmful side effects on the kidney have also been described. In the current project, primary highly purified human renal proximal tubular epithelial cells (PTCs) have been shown to express functional SGLT-2, and were used as an in vitro model to study possible cellular damage induced by two therapeutically used gliflozins: empagliflozin and dapagliflozin. Cell viability, proliferation, and cytotoxicity assays revealed that neither empagliflozin nor dapagliflozin induce effects in PTCs cultured in a hyperglycemic environment, or in co-medication with ramipril or hydro-chloro-thiazide. Oxidative stress was significantly lowered by dapagliflozin but not by empagliflozin. No effect of either inhibitor could be detected on mRNA and protein expression of the pro-inflammatory cytokine interleukin-6 and the renal injury markers KIM-1 and NGAL. In conclusion, empa- and dapagliflozin in therapeutic concentrations were shown to induce no direct cell injury in cultured primary renal PTCs in hyperglycemic conditions.

The Effect of Urine pH and Urinary Uric Acid Levels on the Development of Contrast Nephropathy

BACKGROUND

Hyperuricemia may cause acute kidney injury by activating inflammatory, pro-oxidative and vasoconstrictive pathways. In addition, radiocontrast causes an acute uricosuria, potentially leading to crystal formation. We therefore aimed to investigate the effect of urine acidity and urine uric acid level on the development of contrast-induced nephropathy (CIN) in patients undergoing elective coronary angiography.

METHODS

We enrolled 175 patients who underwent elective coronary angiography. CIN was defined as a >25% increase in the serum creatinine levels relative to basal values 48-72 h after contrast use. Prior to coronary angiography and 48-72 h later, serum uric acid, urea, creatinine, bicarbonate levels, and spot uric acid to creatinine ratio (UACR) were measured.

RESULTS

Of the 175 subjects included, 29 (16.6%) developed CIN. Those who developed CIN had a higher prevalence of diabetes, higher UACR (0.60 vs. 0.44, p = 0.014), higher contrast volume, and lower serum sodium level. With univariate analysis of a logistic regression model, the risk of CIN was found to be associated with diabetes (p = 0.0016, OR = 3.8 [95% CI: 1.7-8.7]), urine UACR (p = 0.0027, OR = 9.6 [95% CI: 2.2-42.2]), serum sodium (p = 0.0079, OR = 0.8 [95% CI: 0.77-0.96]), and contrast volume (p = 0.0385, OR = 1.8 [95% CI: 1.03-3.09]). In a multiple logistic regression model with stepwise method of selection, diabetes (p = 0.0120, OR = 3.2 [95% CI: 1.3-8.1]) and UACR (p = 0.0163, OR = 6.9 [95% CI: 1.4-33.4]) were the 2 risk factors finally identified.

CONCLUSIONS

We have demonstrated that higher urine UACR is associated with the development of CIN in patients undergoing elective coronary angiography.

Elevation in serum uric acid levels predicts favourable response to erlotinib treatment in patients with metastatic non-small-cell lung cancer

WHAT IS KNOWN AND OBJECTIVE

Erlotinib is a small molecule tyrosine kinase inhibitor which blocks the activation of epidermal growth factor receptor (EGFR), a transmembrane receptor that is upregulated in many cancer types. Inhibition of angiogenesis with consequent impairments in intratumoral microcirculation is one of the mechanisms through which EGFR inhibition halts the progression of cancer. A consequence of impaired microcirculation is intratumoral hypoxia, which results in increases in serum uric acid levels. The goal of this study was to investigate the relationship between serum uric acid levels and response to erlotinib in metastatic non-small-cell lung cancer (NSCLC).

METHODS

A total of 56 patients with metastatic non-small-cell lung cancer who received erlotinib for a duration of at least 3 months were included in this retrospective cohort study. Demographic characteristics, progression status, baseline serum uric levels and 3-month serum uric acid levels were recorded and analysed.

RESULTS AND DISCUSSION

Of the study population, 21 (37.5%) were female and 35 (62.5%) were male patients. No significant difference in above demographic characteristics was observed among exitus, survivor with progression and survivor without progression groups. Patients who responded favourably to erlotinib with no progression of their disease had significantly increased uric acid levels at 3-month follow-up (P = .01). Such a correlation was not observed if the patient was exitus (P = .47) or had progressed on erlotinib therapy (P = .19).

WHAT IS NEW AND CONCLUSION

In conclusion, this study is the first to demonstrate significant increases in serum uric acid levels in patients with metastatic NSCLC who responded favourably to erlotinib and had no progression under erlotinib therapy. Further studies are required to confirm and characterize serum uric acid as a novel biomarker in predicting the outcome in those with metastatic NSCLC.

Febuxostat is superior to allopurinol in delaying the progression of renal impairment in patients with chronic kidney disease and hyperuricemia

PURPOSE

This study aimed to compare efficacy of renal-protective function between febuxostat and allopurinol in patients with chronic kidney disease (CKD) and hyperuricemia (HUA).

METHODS

Totally 152 CKD stage 2-3 patients complicated with HUA were recruited. According to their uric acid-lowering therapy, there were 67 patients included in febuxostat group and 85 in allopurinol group, respectively. Estimated glomerular filtration rate (eGFR), serum creatinine (Scr), 24-h proteinuria, serum uric acid (SUA) were measured at M0, M1, M3 and M6 after the treatment. Primary outcome was proportion of patients showing ≥ 10% decline in eGFR from baseline at M6.

RESULTS

The eGFR at M6 was numerically higher at M6 and eGFR change (M6-M0) was increased in febuxostat group compared with allopurinol group. Most importantly, the proportion of patients showing a ≥ 10% decline in eGFR from baseline at M6 was reduced in febuxostat group compared with allopurinol group. Multivariate logistic regression analyses further validated that febuxostat vs. allopurinol was an independent predictor for reduced risk of eGFR decline ≥ 10% from baseline. Besides, SUA change (M6-M0) was decreased, but Scr change (M6-M0) and 24-h proteinuria change (M6-M0) were similar in febuxostat group compared with allopurinol group.

CONCLUSIONS

Febuxostat presents a superior effect in delaying renal impairment progression compared with allopurinol in CKD patients complicated with HUA.

Simultaneous Monitoring of Febuxostat and Uric Acid in Human Serum Samples Using the Direct Square-Wave Voltammetric Method

Background:

High uric acid serum level, hyperuricemia, is now associated with many diseases such as gout, chronic kidney disease, hypertension, coronary artery disease and diabetes. Febuxostat is a novel selective xanthine oxidase inhibitor approved for the treatment of hyperuricemia.

Objective:

The aim of this study was to develop a first analytical method for the simultaneous determination of febuxostat and uric acid.

Methods:

An unmodified boron-doped diamond electrode provided concurrent quantitation of drug at low levels and uric acid, which has clinical significance in the diagnosis and therapy of hyperuricemia, at relatively high concentrations. The direct square-wave voltammetric method was applied to the analysis of both analytes in human serum samples.

Results:

Under the optimized conditions, the linear response of peak current on febuxostat concentration was achieved in the range from 7.5 × 10-7 to 3 × 10-5 M, while uric acid showed two linear ranges of 5 × 10-6 - 5 × 10-5 M and 5 × 10-5 - 2 × 10-4 M. The method was successfully utilised for quantification of both analytes in human serum samples. Good recoveries were obtained without interference from common inorganic cations and anions as well as glucose, dopamine, ascorbic and folic acids at concentrations expected in physiological conditions.

Conclusion:

The great benefits of developed method are fast analysis (only 7.5 s for run), low cost and simplicity of performance.

Evaluation of heat stress and cumulative incidence of acute kidney injury in sugarcane workers in Guatemala

OBJECTIVE

Agricultural workers worldwide exposed to heat stress could be at the risk of kidney injury, which could lead to chronic kidney disease of an unknown origin (CKDu). Hydration has been promoted as a key measure to reduce kidney injury. In the presence of a hydration intervention, the incidence of acute kidney injury (AKI) was calculated in a sugarcane worker population in Guatemala and several risk factors were evaluated.

METHODS

We measured kidney function at the beginning and end of the work shift at three time points in 517 sugarcane workers. We defined AKI as an increase in serum creatinine of 26.5 µmol/L or 50% or more from the pre-shift value. Associations between AKI and risk factors were examined, including interactions with hydration status.

RESULTS

The prevalence of dehydration post-shift (> 1.020 specific gravity) was 11% in February, 9% in March, and 6% in April. Cumulative incidence of AKI was 53% in February, 54% in March, and 51% in April. AKI was associated with increasing post-shift specific gravity, a dehydration marker, (OR 1.24, 95% CI 1.02-1.52) and with lower electrolyte solution intake (OR 0.94, 95% CI 0.89-0.99).

CONCLUSIONS

Dehydration and insufficient electrolyte consumption are risk factors for AKI. However even well-hydrated sugarcane workers routinely experience AKI. While hydration is important and protective, there is a need to understand other contributors to risk of AKI and identify prevention strategies with these workers.

New Insights into the Roles of Monocytes/Macrophages in Cardiovascular Calcification Associated with Chronic Kidney Disease

Cardiovascular disease (CVD) is an important cause of death in patients with chronic kidney disease (CKD), and cardiovascular calcification (CVC) is one of the strongest predictors of CVD in this population. Cardiovascular calcification results from complex cellular interactions involving the endothelium, vascular/valvular cells (i.e., vascular smooth muscle cells, valvular interstitial cells and resident fibroblasts), and monocyte-derived macrophages. Indeed, the production of pro-inflammatory cytokines and oxidative stress by monocyte-derived macrophages is responsible for the osteogenic transformation and mineralization of vascular/valvular cells. However, monocytes/macrophages show the ability to modify their phenotype, and consequently their functions, when facing environmental modifications. This plasticity complicates efforts to understand the pathogenesis of CVC-particularly in a CKD setting, where both uraemic toxins and CKD treatment may affect monocyte/macrophage functions and thereby influence CVC. Here, we review (i) the mechanisms by which each monocyte/macrophage subset either promotes or prevents CVC, and (ii) how both uraemic toxins and CKD therapies might affect these monocyte/macrophage functions.

SGLT2 Inhibitors: Nephroprotective Efficacy and Side Effects

The burden of diabetic kidney disease (DKD) has increased worldwide in the last two decades. Besides the growth of diabetic population, the main contributors to this phenomenon are the absence of novel nephroprotective drugs and the limited efficacy of those currently available, that is, the inhibitors of renin-angiotensin system. Nephroprotection in DKD therefore remains a major unmet need. Three recent trials testing effectiveness of sodium-glucose cotransporter 2 inhibitors (SGLT2-i) have produced great expectations on this therapy by consistently evidencing positive effects on hyperglycemia control, and more importantly, on the cardiovascular outcome of type 2 diabetes mellitus. Notably, these trials also disclosed nephroprotective effects when renal outcomes (glomerular filtration rate and albuminuria) were analyzed as secondary endpoints. On the other hand, the use of SGLT2-i can be potentially associated with some adverse effects. However, the balance between positive and negative effects is in favor of the former. The recent results of Canagliflozin and Renal Endpoints in Diabetes with Established Nephropathy Clinical Evaluation Study and of other trials specifically testing these drugs in the population with chronic kidney disease, either diabetic or non-diabetic, do contribute to further improving our knowledge of these antihyperglycemic drugs. Here, we review the current state of the art of SGLT2-i by addressing all aspects of therapy, from the pathophysiological basis to clinical effectiveness.

Association between previous schistosome infection and incident hyperuricemia: A prospective cohort study in China

Background

More than 11 million people were estimated to be infected by Schistosoma japonicum in China before the 1950s. However, seldom studies have been conducted to evaluate the longitudinal effects of previous schistosome infection (PSI). We aimed to investigate the association between PSI and hyperuricemia in China.

Methods

From February 2013 to October 2013, 3,517 Chinese subjects (908 persons with PSI and 2,609 persons without PSI) were recruited from a prospective cohort study of “135”. After two years, 113 and 462 participants had developed hyperuricemia in the persons with and without PSI, respectively. Multivariable logistic models were used to estimate Relative Ratios (RR) and 95% confidence intervals (CIs) for hyperuricemia.

Results

The PSI participants had a decreased risk of hyperuricemia compared with those without PSI [adjusted RR (95%CI): 0.73 (0.55, 0.97)]. Within the PSI group, higher level of fasting plasma glucose was significantly associated with the reduced incidence of hyperuricemia in PSI population (RR: 0.40, 95% CI: 0.26–0.63). For females, hypertension, increased levels of serum creatinine and triglycerides were the risk factors for incident hyperuricemia in the PSI group.

Conclusions

Our results suggest that PSI is significantly associated with the lower incidence of hyperuricemia. Moreover, elevated fasting plasma glucose might prevent the onset of hyperuricemia in PSI population.

Uric Acid and Acute Kidney Injury in the Critically Ill

Rationale & Objective

Uric acid is excreted by the kidney and accumulates in acute kidney injury (AKI). Whether higher plasma uric acid level predisposes to AKI or its complications is not known.

Study Design

Prospective observational cohort study.

Setting & Participants

2 independent cohorts of critically ill patients: (1) 208 patients without AKI admitted to the intensive care unit (ICU) at Brigham & Women's Hospital between October 2008 and December 2016; and (2) 250 participants with AKI requiring renal replacement therapy (RRT) who had not yet initiated RRT enrolled in the Acute Renal Failure Trial Network (ATN) Study.

Exposure

Plasma uric acid level upon ICU admission and before RRT initiation in the ICU and ATN Study cohorts, respectively.

Outcomes

Incident AKI and 60-day mortality in the ICU and ATN Study cohorts, respectively.

Analytical Approach

Logistic regression models were used to test the association of plasma uric acid level with incident AKI and 60-day mortality.

Results

In the ICU cohort, median plasma uric acid level was 4.7 (interquartile range [IQR], 3.6-6.4) mg/dL, and 40 patients (19.2%) developed AKI. Higher plasma uric acid levels associated with incident AKI, but this association was confounded by serum creatinine level and was not significant after multivariable adjustment (adjusted OR per doubling of uric acid, 1.50; 95% CI, 0.80-2.81). In the ATN Study cohort, median plasma uric acid level was 11.1 (IQR, 8.6-14.2) mg/dL, and 125 participants (50.0%) died within 60 days. There was no statistically significant association between plasma uric acid levels and 60-day mortality in either unadjusted models or after multivariable adjustment for demographic, severity-of-illness, and kidney-specific covariates (adjusted OR per doubling of uric acid, 1.15; 95% CI, 0.71-1.86).

Limitations

Heterogeneity of ICU patients.

Conclusions

Plasma uric acid levels upon ICU admission or before RRT initiation are not independently associated with adverse clinical outcomes in critically ill patients.

Acute kidney injury in childhood-onset nephrotic syndrome: Incidence and risk factors in hospitalized patients

Background

Nephrotic syndrome (NS) is the most common glomerulopathy in children. Acute kidney injury (AKI) is a common complication of NS, caused by severe intravascular volume depletion, acute tubular necrosis, interstitial nephritis, or progression of NS. However, the incidence and risk factors of childhood-onset NS in Korea are unclear. Therefore, we studied the incidence, causes, and risk factors of AKI in hospitalized Korean patients with childhood-onset NS.

Methods

We conducted a retrospective review of patients with childhood-onset NS who were admitted to our center from January 2015 to July 2017. Patients with decreased renal function or hereditary/secondary NS, as well as those admitted for management of other conditions unrelated to NS, were excluded.

Results

During the study period, 65 patients with idiopathic, childhood-onset NS were hospitalized 90 times for management of NS or its complications. Of these 90 cases, 29 met the Kidney Disease Improving Global Outcomes criteria for AKI (32.2%). They developed AKI in association with infection (n = 12), NS aggravation (n = 11), dehydration (n = 3), and intravenous methylprednisolone administration (n = 3). Age ≥ 9 years at admission and combined use of cyclosporine and renin-angiotensin system inhibitors were risk factors for AKI.

Conclusion

AKI occurred in one-third of the total hospitalizations related to childhood-onset NS, owing to infection, aggravation of NS, dehydration, and possibly high-dose methylprednisolone treatment. Age at admission and use of nephrotoxic agents were associated with AKI. As the AKI incidence is high, AKI should be considered during management of high-risk patients.

Blockade of enhancer of zeste homolog 2 alleviates renal injury associated with hyperuricemia

Hyperuricemia has been identified as an independent risk factor for chronic kidney disease (CKD) and is associated with the progression of kidney diseases. It remains unknown whether enhancer of zeste homolog 2 (EZH2), a histone H3 lysine 27 methyltransferase, can regulate metabolism of serum uric acid and progression of renal injury induced by hyperuricemia. In this study, we demonstrated that blockade of EZH2 with 3-DZNeP, a selective EZH2 inhibitor, or silencing of EZH2 with siRNA inhibited uric acid-induced renal fibroblast activation and phosphorylation of Smad3, epidermal growth factor receptor (EGFR), and extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in cultured renal fibroblasts. Inhibition of EZH2 also suppressed proliferation of renal fibroblasts and epithelial-mesenchymal transition of tubular cells. In a mouse model of renal injury induced by hyperuricemia, EZH2 and trimethylation of histone H3 at lysine27 expression levels were enhanced, which was coincident with renal damage and increased expression of lipocalin-2 and cleaved caspase-3. Inhibition of EZH2 with 3-DZNeP blocked all these responses. Furthermore, 3-DZNeP treatment decreased the level of serum uric acid and xanthine oxidase activity, alleviated renal interstitial fibrosis, inhibited activation of transforming growth factor-β/Smad3, EGFR/ERK1/2, and nuclear factor-κB signaling pathways, as well as reduced expression of multiple chemokines/cytokines. Collectively, EZH2 inhibition can reduce the level of serum uric acid and alleviate renal injury and fibrosis through a mechanism associated with inhibition of multiple signaling pathways. Targeting EZH2 may be a novel strategy for the treatment of hyperuricemia-induced CKD.

SGLT2 inhibitors and the kidney: Effects and mechanisms

AIMS

Numerous clinical trials have shown that sodium glucose cotransporter 2 (SGLT2) inhibitors exert a favorable effect on the indices of renal function (albuminuria, glomerular filtration rate decline over time) and the incidence of hard renal endpoints such as renal death or time to initiation of renal replacement therapy.

MATERIALS AND METHODS

In this review, we describe in detail the evidence regarding the nephroprotective mechanisms of SGLT2 inhibitors and describe the risk factors that may predispose to the development of acute kidney injury in patients receiving these drugs.

RESULTS

Although the impact of these drugs on renal hemodynamics seems to represent the most important renoprotective mechanism of action, many other effects of these compounds, including beneficial effects on metabolism and blood pressure, have been proposed to contribute to the observed clinical benefit.

CONCLUSIONS

SGLT2 inhibitors clearly act beneficially in terms of kidney function with many proposed mechanisms.

Can SGLT2 Inhibitors Cause Acute Renal Failure? Plausible Role for Altered Glomerular Hemodynamics and Medullary Hypoxia

Sodium-glucose co-transporter-2 inhibitors (SGLT2i) provide outstanding long-term cardiovascular and renal protection in high-risk patients with type 2 diabetes mellitus. Yet, despite encouraging renal safety outcomes reported in the EMPA-REG study, scattered reports suggest that there might be a risk for acute kidney injury (AKI), which may occasionally be fatal or might require renal replacement therapy. Reduced trans-glomerular pressure with a modest decline in kidney function, an inherent characteristic of SGLT2i therapy, conceivably forms the basis for the long-term renal protection, resembling agents that block the renin-angiotensin-aldosterone (RAAS) axis. Yet, a major decline in kidney function occasionally occurs, often associated with an acute illness or with specific co-administered medications. SGLT2i may lead to AKI by (a) effective volume depletion, due to excessive diuresis, particularly in hemodynamically unstable and volume-depleted patients; (b) excessive decline in trans-glomerular pressure, specifically in patients on RAAS blockade; and (c) induction of renal medullary hypoxic injury, related to enhanced distal tubular transport, especially with concomitant use of agents impairing medullary oxygenation, such as non-steroidal anti-inflammatory drugs and radiocontrast agents. The risk of developing renal impairment with SGLT2i and the role of these suggested mechanisms are yet to be defined, as there are conflicting data and inconsistent reporting with the various agents currently in use.

Increase of endocan, a new marker for inflammation and endothelial dysfunction, in acute kidney injury

OBJECTIVE:

In this study, the clinical relevance of the levels of serum endocan and 25-hydroxyvitamin D [25(OH)D] was investigated in patients with acute kidney injury (AKI). Endocan or the endothelial cell-specific molecule 1 is a soluble proteoglycan secreted by vascular endothelial cells. It plays a significant role in immunity, inflammation, and endothelial function.

METHODS:

A total of 39 patients with AKI (19 females, 20 males) and 38 healthy individuals (18 females, 20 males) were included in the study. The levels of serum endocan, vitamin D, and other biochemical parameters were compared between the two groups.

RESULTS:

In the AKI group, the values of serum creatinine, endocan, parathormone, phosphorus, and uric acid were found to be higher, and the total protein, albumin, and calcium levels were lower compared to the control group. There was no difference between the two groups in terms of the serum vitamin D, magnesium, alkaline phosphatase, and gamma-glutamyl transferase.

CONCLUSION:

In patients with AKI, an increased endocan level is a significant marker of inflammation and endothelial injury. In addition, these patients experience vitamin D deficiency.

The Role of Uric Acid in Preeclampsia: Is Uric Acid a Causative Factor or a Sign of Preeclampsia?

PURPOSE OF REVIEW

Because of the significant discrepancies on this topic, this review will focus on the role of uric acid in PE, uric acid as a predictor of preeclampsia and fetal growth retardation. We considered eligible review and original articles relevant to the research question.

RECENT FINDINGS

Hypertensive disorders of pregnancy such as preeclampsia (PE) are a major cause of both maternal and fetal morbidity and mortality worldwide. Uric acid has been reported as a key factor contributing to the pathogenesis of PE. Some studies have indicated that serum uric acid levels increase with the severity of PE, while several studies have shown contradictory results. Some studies suggested high uric acid levels lead to PE, while others state that PE causes an increase in uric acid levels. Despite the strong association of uric acid in the pathogenesis of preeclampsia, current data is still contradictory hence genetic and high-end laboratory investigations may clarify this enigma.

Effects of vitamin B12, folate, uric acid, and serum biomarkers of inflammation on bone mineral density in postmenopausal women

Introduction

Despite the accumulating evidence suggesting a possible relationship between femur and lumbar bone mineral density (BMD) and serum uric acid (UA), it is unclear whether alterations in UA levels reflect any underlying subclinical inflammatory conditions in postmenopausal osteoporosis. In addition, the mechanistic link between osteoporosis and dietary factors including vitamin B₁₂ and folate in postmenopausal women is still obscure. The aim of the present study is to investigate the association between serum vitamin B₁₂, folate, UA, and subclinical inflammatory markers and BMD measurements in postmenopausal women.

Material and methods

One hundred and eighty-four postmenopausal women were recruited for the present study. Clinical data, as well as serum vitamin B₁₂, folate, UA, conventional inflammatory markers, and other related biochemical markers, were assessed for each subject. Bone mineral density measurements of proximal femur and lumbar spine were taken using dual-energy X-ray absorptiometry. Correlation analysis was performed between serum vitamin B₁₂, folate, UA and other biochemical and metabolic parameters.

Results

Although no association was found between serum inflammatory markers, vitamin B₁₂ and folate levels with femur neck and lumbar spine BMD measurements, elevated UA levels were observed in subjects with normal BMD values. Higher BMD values were obtained in higher UA tertiles. UA (p < 0.001) and BMI (p = 0.003) were found to be correlated with femur neck BMD measurements.

Conclusions

The femoral and lumbar BMD measurements were associated with serum UA levels. Higher serum UA levels were found to have a protective effect on postmenopausal osteoporosis irrespective of inflammation and dietary factors.

Role of febuxostat in retarding progression of diabetic kidney disease with asymptomatic hyperuricemia: A 6-months open-label, randomized controlled trial

Introduction: Hyperuricemia is associated with chronic kidney disease (CKD) progression and poor cardiovascular outcomes. We studied the effect of febuxostat on estimated glomerular filtration rate (eGFR), proteinuria and monitored the safety profile of the medication.

Material and Methods: This is a prospective open-label, randomized study in CKD stage 3 and 4 patients with diabetic nephropathy and asymptomatic hyperuricemia. Patients were randomized into febuxostat 40 mg daily and no treatment group using block randomization method and were followed up for 6 months. Their usual care for diabetes mellitus, hypertension and dyslipidemia were continued in the study. Blood and urine investigations were monitored at baseline, 3 months and 6 months.

Results: The eGFR in febuxostat group was stabilized at 6 months with no significant reduction [26.2 (IQR 14.30) at baseline to 26.3 (IQR 15.2) ml/min/1.73 m²]. Whereas, there was a significant reduction of the eGFR in no treatment group from 28.2 (IQR 17.9) to 27.6 (IQR 19.3) ml/min/1.73 m² (p value < 0.01). We found the HbA1c (glycosylated hemoglobin) was significantly increased in febuxostat group from 7.2 ± 0.5 % at baseline to 7.6 ± 1.4 at 6 months (p value 0.04) but no significant change of HbA1c in the no treatment group. Proteinuria level was unchanged in both groups. The commonest adverse event was joint pain.

Conclusions: Febuxostat was able to preserve eGFR in CKD patients with diabetic nephropathy and this effect was beyond glycemic control. Increment of HbA1c level in febuxostat group needs further larger trials.

Impact of non-adherence on the safety and efficacy of uric acid-lowering therapies in the treatment of gout

AIMS

Dual-urate-lowering therapy (ULT) with xanthine oxidase inhibitor and uricosuric medications is a treatment option for severe gout. Uricosuric agents can cause hyperuricosuria, a risk factor for nephrolithiasis and acute uric acid nephropathy. The aims of the present study were to simulate the relationship between suboptimal drug adherence and efficacy, and to quantify the risk of hyperuricosuria in gout patients receiving mono- and dual-ULTs.

METHODS

The impact of poor medication adherence was studied using two-compartment pharmacokinetic (PK) models based on published evidence, and a semi-mechanistic four-compartment pharmacodynamic (PD) model. The PKPD model was used to simulate mono and dual-ULT in gout patients with either under-excretion (lowered clearance) or overproduction of uric acid, with suboptimal adherence modelled as either a single drug holiday of increasing duration or doses taken at random.

RESULTS

Simulation results showed a surge in urinary uric acid occurring when dosing is restarted following missed doses. For under-excreters taking a 20-day drug holiday, the addition of 200 mg (or 400 mg) lesinurad to 80 mg febuxostat increased the percentage of patients experiencing hyperuricosuria from 0% to 1.4% (or 3.1%). In overproducers, restarting ULTs following drug holidays of more than 5 days leads to over 60% of patients experiencing hyperuricosuria.

CONCLUSIONS

Suboptimal medication adherence may compromise the safety and efficacy of mono- and dual-ULTs, especially in patients with gout resulting from an overproduction of uric acid. Clinicians and pharmacists should consider counselling patients with respect to the risks associated with partial adherence, and offer interventions to improve adherence or tailor treatments, where appropriate.

Harnessing basic and clinic tools to evaluate SGLT2 inhibitor nephrotoxicity

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are a new class of medications that target the transporter that reabsorbs ~90% of glucose in the S1 segment of the proximal convoluted tubule. As a result, SGLT2 inhibition increases urinary glucose excretion, effectively lowering plasma glucose levels. In addition to reducing hemoglobin A1c levels, these drugs also lower body weight, blood pressure, and uric acid levels in Type 2 diabetes mellitus (T2DM) patients. Importantly, empagliflozin has been observed to slow progression of kidney disease and reduce dialysis requirements in T2DM patients. However, the Food and Drug Administration (FDA) Adverse Events Reporting System (FAERS) has collected over 100 cases of acute kidney injury (AKI) for canagloflozin and dapagliflozin since their approval. Of the 101 patients, 96 required hospitalization, 22 required intensive care unit admission, and 15 underwent hemodialysis. The FDA now requires that AKI be listed as a potential side effect of the SGLT2 inhibitors along with cautious prescription of these drugs with other medications, such as renin-angiotensin-system antagonists, diuretics, and NSAIDs. It is unclear, however, whether this FAERS reported “AKI” actually represents structural kidney injury, as randomized, controlled trials of these drugs do not describe AKI as an adverse event despite coprescription with RAS blockers and diuretics. As a result of this FDA warning, diabetic patients with early-stage CKD may not be prescribed an SGLT2 inhibitor for fear of AKI. Thus, it is imperative to ascertain whether the reported AKI represents true structural kidney injury or a functional decline in glomerular filtration rate. We propose using readily available clinical tools with experimental biomarkers of kidney injury and kidney-on-a-chip technology to resolve this question and provide solid evidence about the AKI risk of these drugs for healthcare providers.