Adiponectin Reduces Glomerular Endothelial Glycocalyx Disruption and Restores Glomerular Barrier Function in a Mouse Model of Type 2 Diabetes

Adiponectin has vascular anti-inflammatory and protective effects. Although adiponectin protects against the development of albuminuria, historically, the focus has been on podocyte protection within the glomerular filtration barrier (GFB). The first barrier to albumin in the GFB is the endothelial glycocalyx (eGlx), a surface gel-like barrier covering glomerular endothelial cells (GEnCs). In diabetes, eGlx dysfunction occurs before podocyte damage; hence, we hypothesized that adiponectin could protect from eGlx damage to prevent early vascular damage in diabetic kidney disease (DKD). Globular adiponectin (gAd) activated AMPK signaling in human GEnCs through AdipoR1. It significantly reduced eGlx shedding and the tumor necrosis factor-α (TNF-α)-mediated increase in syndecan-4 (SDC4) and MMP2 mRNA expression in GEnCs in vitro. It protected against increased TNF-α mRNA expression in glomeruli isolated from db/db mice and against expression of genes associated with glycocalyx shedding (namely, SDC4, MMP2, and MMP9). In addition, gAd protected against increased glomerular albumin permeability (Ps'alb) in glomeruli isolated from db/db mice when administered intraperitoneally and when applied directly to glomeruli (ex vivo). Ps'alb was inversely correlated with eGlx depth in vivo. In summary, adiponectin restored eGlx depth, which was correlated with improved glomerular barrier function, in diabetes.

ARTICLE HIGHLIGHTS

Heparanase inhibition as a systemic approach to protect the endothelial glycocalyx and prevent microvascular complications in diabetes

BACKGROUND

Diabetes mellitus is a chronic disease which is detrimental to cardiovascular health, often leading to secondary microvascular complications, with huge global health implications. Therapeutic interventions that can be applied to multiple vascular beds are urgently needed. Diabetic retinopathy (DR) and diabetic kidney disease (DKD) are characterised by early microvascular permeability changes which, if left untreated, lead to visual impairment and renal failure, respectively. The heparan sulphate cleaving enzyme, heparanase, has previously been shown to contribute to diabetic microvascular complications, but the common underlying mechanism which results in microvascular dysfunction in conditions such as DR and DKD has not been determined.

METHODS

In this study, two mouse models of heparan sulphate depletion (enzymatic removal and genetic ablation by endothelial specific Exotosin-1 knock down) were utilized to investigate the impact of endothelial cell surface (i.e., endothelial glycocalyx) heparan sulphate loss on microvascular barrier function. Endothelial glycocalyx changes were measured using fluorescence microscopy or transmission electron microscopy. To measure the impact on barrier function, we used sodium fluorescein angiography in the eye and a glomerular albumin permeability assay in the kidney. A type 2 diabetic (T2D, db/db) mouse model was used to determine the therapeutic potential of preventing heparan sulphate damage using treatment with a novel heparanase inhibitor, OVZ/HS-1638. Endothelial glycocalyx changes were measured as above, and microvascular barrier function assessed by albumin extravasation in the eye and a glomerular permeability assay in the kidney.

RESULTS

In both models of heparan sulphate depletion, endothelial glycocalyx depth was reduced and retinal solute flux and glomerular albumin permeability was increased. T2D mice treated with OVZ/HS-1638 had improved endothelial glycocalyx measurements compared to vehicle treated T2D mice and were simultaneously protected from microvascular permeability changes associated with DR and DKD.

CONCLUSION

We demonstrate that endothelial glycocalyx heparan sulphate plays a common mechanistic role in microvascular barrier function in the eye and kidney. Protecting the endothelial glycocalyx damage in diabetes, using the novel heparanase inhibitor OVZ/HS-1638, effectively prevents microvascular permeability changes associated with DR and DKD, demonstrating a novel systemic approach to address diabetic microvascular complications.

Endothelial glycocalyx is damaged in diabetic cardiomyopathy: angiopoietin 1 restores glycocalyx and improves diastolic function in mice

AIMS/HYPOTHESIS

Diabetic cardiomyopathy (DCM) is a serious and under-recognised complication of diabetes. The first sign is diastolic dysfunction, which progresses to heart failure. The pathophysiology of DCM is incompletely understood but microcirculatory changes are important. Endothelial glycocalyx (eGlx) plays multiple vital roles in the microcirculation, including in the regulation of vascular permeability, and is compromised in diabetes but has not previously been studied in the coronary microcirculation in diabetes. We hypothesised that eGlx damage in the coronary microcirculation contributes to increased microvascular permeability and hence to cardiac dysfunction.

METHODS

We investigated eGlx damage and cardiomyopathy in mouse models of type 1 (streptozotocin-induced) and type 2 (db/db) diabetes. Cardiac dysfunction was determined by echocardiography. We obtained eGlx depth and coverage by transmission electron microscopy (TEM) on mouse hearts perfusion-fixed with glutaraldehyde and Alcian Blue. Perivascular oedema was assessed from TEM images by measuring the perivascular space area. Lectin-based fluorescence was developed to study eGlx in paraformaldehyde-fixed mouse and human tissues. The eGlx of human conditionally immortalised coronary microvascular endothelial cells (CMVECs) in culture was removed with eGlx-degrading enzymes before measurement of protein passage across the cell monolayer. The mechanism of eGlx damage in the diabetic heart was investigated by quantitative reverse transcription-PCR array and matrix metalloproteinase (MMP) activity assay. To directly demonstrate that eGlx damage disturbs cardiac function, isolated rat hearts were treated with enzymes in a Langendorff preparation. Angiopoietin 1 (Ang1) is known to restore eGlx and so was used to investigate whether eGlx restoration reverses diastolic dysfunction in mice with type 1 diabetes.

RESULTS

In a mouse model of type 1 diabetes, diastolic dysfunction (confirmed by echocardiography) was associated with loss of eGlx from CMVECs and the development of perivascular oedema, suggesting increased microvascular permeability. We confirmed in vitro that eGlx removal increases CMVEC monolayer permeability. We identified increased MMP activity as a potential mechanism of eGlx damage and we observed loss of syndecan 4 consistent with MMP activity. In a mouse model of type 2 diabetes we found a similar loss of eGlx preceding the development of diastolic dysfunction. We used isolated rat hearts to demonstrate that eGlx damage (induced by enzymes) is sufficient to disturb cardiac function. Ang1 restored eGlx and this was associated with reduced perivascular oedema and amelioration of the diastolic dysfunction seen in mice with type 1 diabetes.

CONCLUSIONS/INTERPRETATION

The association of CMVEC glycocalyx damage with diastolic dysfunction in two diabetes models suggests that it may play a pathophysiological role and the enzyme studies confirm that eGlx damage is sufficient to impair cardiac function. Ang1 rapidly restores the CMVEC glycocalyx and improves diastolic function. Our work identifies CMVEC glycocalyx damage as a potential contributor to the development of DCM and therefore as a therapeutic target.

Stability of Amoxicillin and Clavulanic Acid in Separate Containers for Administration via a Y-Site

Rationale

With the discovery of new antibiotics diminishing, optimising the administration of existing antibiotics such as amoxicillin-clavulanic acid has become a necessity. At present, the optimal approach for enhancing the effectiveness of time-dependent antibiotics involves extending the time at which antibiotic concentrations are maintained above the minimal inhibitory concentration by prolonging the infusion time. This pharmacodynamic rationale cannot be applied to co-amoxiclav because of poor stability at room temperature. The aim of this study was to establish the shelf-life of amoxicillin and clavulanic acid prepared in separate containers to determine the feasibility of 24-hr continuous infusion therapy.

Methods

A previously developed and validated stability-indicating HPLC method was used to establish the shelf-life of reconstituted amoxicillin and clavulanic acid when prepared in separate containers. Stability at clinical concentration was evaluated at three temperatures. To establish whether there were significant differences at the level of both active ingredients and temperature, results were analysed using analysis of covariance (ANCOVA) to assess differences between the attained slopes of regression.

Results

Data obtained indicated amoxicillin and clavulanic acid stability superior to that previously proposed making it suitable for continuous infusion therapy. Analysis of regression slopes via ANCOVA showed that temperature significantly affected amoxicillin and clavulanic acid stability. Amoxicillin retained 90% of its initial concentration for 80.3 hrs when stored at 4°C, 24.8 hrs at 25°C and 9 hrs when incubated at 37°C. Clavulanic acid retained 90% of its initial concentration for 152 hrs when stored at 4°C, 26 hrs at 25°C and 6.4 hrs when incubated at 37°C.

Conclusion

Amoxicillin and clavulanic acid are suitable for administration via continuous infusion when prepared, stored, and administered in separate containers. Results obtained from this study aid in ameliorating current dosing regimens to optimise antibiotic efficacy; however, more in-depth amoxicillin and clavulanic acid y-site compatibility studies are warranted.

Differential antibiotic dosing in critical care: survey on nurses' knowledge, perceptions and experience

Background

With the discovery of new antibiotics diminishing, optimizing the administration of existing antibiotics has become a necessity. Critical care nurses play a crucial role in combating antimicrobial resistance and are involved in preparing and administering antibiotics as well as monitoring their effects on patients. A dosing strategy proposed to reduce the development of ever-evolving antimicrobial resistance involves differential dosing regimens such as prolonged/continuous infusions.

Objectives

To assess critical care nurses’ knowledge, perceptions, comfort and experience in relation to prolonged/continuous infusion antibiotics.

Methods

A descriptive cross-sectional study was conducted using an investigator-developed, self-administered survey consisting of open- and closed-ended questions. Obtained data were computed using SPSS. Descriptive and inferential statistics were used to analyse the data.

Results

Fifty-two critical care nurses participated in the survey. Data revealed that nurses have adequate levels of knowledge and comfort relating to the use of prolonged/continuous infusion antibiotics along with the ability to communicate effectively on the topic. Results indicate there is a need for further learning, especially in terms of multiplicity of methods for preparing and administering prolonged/continuous infusions and dose calculations. Overall, results are promising as nurses support the wider implementation of prolonged/continuous infusion treatment regimens in critical care.

Conclusion

Although critical care nurses had a good understanding surrounding the use of prolonged/continuous infusion antibiotics, there is a need for further learning beyond information gained from nursing education courses. Findings from this study indicate that nurses are supportive of prolonged/continuous infusion antibiotics. However, further research is needed to determine the most effective mode of antibiotic administration.

Comparing clinical outcomes of piperacillin-tazobactam administration and dosage strategies in critically ill adult patients: a systematic review and meta-analysis

Background

Recently, continuous administration of piperacillin-tazobactam has been proposed as a valuable alternative to traditional intermittent administration especially in critically ill patients. However, antibiotic dosing remains a challenge for clinicians as antibiotic dosing regimens are usually determined in non-critically ill hospitalized adult patients. The aim was to conduct a systematic review to identify and highlight studies comparing clinical outcomes of piperacillin tazobactam dosing regimens, continuous/prolonged infusion vs intermittent infusion in critically ill patients. Meta-analyses were performed to assess the overall effect of dosing regimen on clinical efficacy.

Methods

Studies were identified systematically through searches of PubMed and Science Direct, in compliance with PRISMA guidelines. Following the systematic literature review, meta-analyses were performed using Review Manager.

Results

Twenty-three studies were included in the analysis involving 3828 critically ill adult participants in total (continuous/prolonged infusion = 2197 and intermittent infusion = 1631) from geographically diverse regions. Continuous/prolonged resulted in significantly: higher clinical cure rates (Odds Ratio 1.56, 95% Confidence Interval 1.28–1.90, P = 0 .0001), lower mortality rates (Odds Ratio 0.68, 95% Confidence Interval 0.55–0.84, P = 0 .0003), higher microbiological success rates (Odds Ratio 1.52, 95% Confidence Interval 1.10–2.11, P = 0.01) and decreasing the length of hospital stay (Mean Difference − 1.27, 95% Confidence Interval − 2.45—0.08, P = 0.04) in critically ill patients.

Conclusion

Results from this study show that there is a significant level of evidence that clinical outcome in critically ill patients is improved in patients receiving piperacillin-tazobactam via continuous/prolonged infusion. However, more rigorous scientific studies in critically ill patients are warranted to reach a sufficient level of evidence and promote further implementation of C/PI as a dosing strategy.

Blocking matrix metalloproteinase-mediated syndecan-4 shedding restores the endothelial glycocalyx and glomerular filtration barrier function in early diabetic kidney disease

The endothelial glycocalyx is a key component of the glomerular filtration barrier. We have shown that matrix metalloproteinase (MMP)-mediated syndecan 4 shedding is a mechanism of glomerular endothelial glycocalyx damage in vitro, resulting in increased albumin permeability. Here we sought to determine whether this mechanism is important in early diabetic kidney disease, by studying streptozotocin-induced type 1 diabetes in DBA2/J mice. Diabetic mice were albuminuric, had increased glomerular albumin permeability and endothelial glycocalyx damage. Syndecan 4 mRNA expression was found to be upregulated in isolated glomeruli and in flow cytometry-sorted glomerular endothelial cells. In contrast, glomerular endothelial luminal surface syndecan 4 and Marasmium oreades agglutinin lectin labelling measurements were reduced in the diabetic mice. Similarly, syndecan 4 protein expression was significantly decreased in isolated glomeruli but increased in plasma and urine, suggesting syndecan 4 shedding. Mmp-2, 9 and 14 mRNA expression were upregulated in isolated glomeruli, suggesting a possible mechanism of glycocalyx damage and albuminuria. We therefore characterised in detail the activity of MMP-2 and 9 and found significant increases in kidney cortex, plasma and urine. Treatment with MMP-2/9 inhibitor I for 21 days, started six weeks after diabetes induction, restored endothelial glycocalyx depth and coverage and attenuated diabetes-induced albuminuria and reduced glomerular albumin permeability. MMP inhibitor treatment significantly attenuated glomerular endothelial and plasma syndecan 4 shedding and inhibited plasma MMP activity. Thus, our studies confirm the importance of MMPs in endothelial glycocalyx damage and albuminuria in early diabetes and demonstrate that this pathway is amenable to therapeutic intervention. Hence, treatments targeted at glycocalyx protection by MMP inhibition may be of benefit in diabetic kidney disease.

Suitability of Amoxicillin-Clavulanic Acid for Administration via Prolonged Infusion

Rationale

Previously, we have been able to outpace bacterial mutation by replacing increasingly ineffective antibiotics with new agents. However, with the discovery of new antibiotics diminishing, optimising the administration of existing broad-spectrum antibiotics such as co-amoxiclav has become a necessity.

Methods

A stability indicating HPLC method was developed and validated in compliance with International Council for Harmonisation (ICH) guidelines. Stability of co-amoxiclav at clinical concentration was evaluated at three temperatures (4°C, ambient (23-25°C) and 37°C) in three diluents (water for injection (WFI), 0.9% w/v NaCl and Ringer's solution). To establish whether there were significant differences at the level of both diluent and temperature, results were analysed using analysis of covariance (ANCOVA) to assess differences between the attained slopes of regression.

Results

Data obtained indicated co-amoxiclav stability superior to that previously proposed making it suitable for extended infusion therapy. The degradation of amoxicillin appeared to follow a linear trend, with the rate of degradation elevated at higher temperatures, demonstrated by the magnitude of the regression slopes in these conditions. Analysis of regression slopes via ANCOVA demonstrated that diluent and temperature both significantly affected co-amoxiclav stability. Amoxicillin retained 90% of its initial concentration for 7.8 to 10 hrs when stored at 4°C, 5.9 to 8.8 hrs at ambient and 3.5 to 4.5 hrs when incubated at 37°C.

Conclusion

Co-amoxiclav is suitable for administration via prolonged infusion. Findings from this study aid in ameliorating current dosing regimens to optimise antibiotic efficacy. Other valuable applications conferred from these findings include the ability to pre-prepare solutions for use in bolus administration, minimising preparation time and workload.

Stability of Meropenem After Reconstitution for Administration by Prolonged Infusion

Objective: Meropenem is a parenteral carbapenem antibiotic which has a broad spectrum of activity against aerobes and anaerobes. Meropenem's bactericidal activity is determined by the time during which meropenem concentration remains above the minimal inhibition concentration (MIC) during the dosing interval. Thus, prolonged infusion is the optimal way to maximize the time-dependant activity. However, studies to date have shown that carbapenems and in particular, meropenem, are relatively unstable in solution. The aims of this study were therefore (1) to establish the effects of temperature on the concentration of a generic brand reconstituted meropenem solution and (2) to determine whether 24-hour continuous infusion is possible without concentrations dropping below the recommended 90%. Method: Preliminary examination was carried out by the means of nuclear magnetic resonance (NMR) spectroscopy. Meropenem was subsequently assayed using high-performance liquid chromatography (HPLC). The method was developed and validated in compliance with International Council for Harmonisation (ICH) guidelines. Meropenem's stability was examined at two temperatures 22°C and 33°C to mimic average and high temperature in hospital wards. Solutions were prepared aseptically at the clinically relevant concentration. Results: NMR results obtained showed an increase in open ring methyl groups peak intensity, indicating that meropenem begins to degrade upon dissolution (d=1.05 and 1.25). Results obtained from quantitative HPLC confirm that meropenem concentrations dropped to 90% of initial concentration at 7.4 hours and 5.7 hours at 22°C and 33°C, respectively. Conclusion: Although results obtained indicate that meropenem should not be continuously infused over 24 hours, it is possible that meropenem could be continuously infused for at least 7 hours if temperature does not exceed 22°C and for 5 hours if temperature does not exceed 33°C.

To what degree does adenotonsillectomy affect neurocognitive performance in children with obstructive sleep apnea hypopnea syndrome due to adenotonsillar enlargement?

BACKGROUND

Obstructive sleep apnea/hypopnea syndrome (OSAHS) is a common childhood problem; complications include possibly reduced neurocognitive performance. Treatment of OSAHS is usually by adenotonsillectomy, but whether surgery relieves both sleep disturbances and associated behavioral problems to the same degree or not is a reasonable question.

OBJECTIVE

To correlate the degree of OSAHS due to adenotonsillar hypertrophy to the preoperative level of the intelligence quotient (IQ) of children, and to assess the degree of postoperative change, if any, in IQ.

PATIENTS AND METHODS

The IQ of 84 children suffering from OSAHS due to adenotonsillar hypertrophy was assessed preoperatively and after adenotonsillectomy. The results were compared to a matched control group.

RESULTS

The IQ was reduced in children with OSAHS; the degree of the reduction was correlated to the degree of apnea. The comparison of the pre- and postoperative values of the study group showed a significant improvement in IQ postoperatively, with postoperative values matching the control group.

CONCLUSION

The IQ of children with OSAHS, as an indicator of neurocognitive function, is reduced, and this reduction can be correlated to the degree of obstruction; but the reduction is reversible and can be reduced even a short period after having experienced relief from the obstruction.