Elevated plasma glypicans are associated with organ failure in patients with infection

Evaluation of circulating glypican 4 as a novel biomarker in disease - A comprehensive review

Glypican 4 (GPC4), a member of the cell surface heparan sulfate proteoglycan family, plays a crucial role in regulating various cell signaling and developmental processes. Its ability to be released from the cell surface into the bloodstream through shedding makes it a promising blood-based biomarker in health and disease. In this context, circulating GPC4 has been initially proposed as an insulin-sensitizing adipokine being linked with various conditions of insulin resistance. In addition, serum levels of GPC4 can indicate glycocalyx shedding and associated pathophysiological states, such as systemic inflammation. Particularly in a morbid and elderly population, increased GPC4 concentrations may reflect general organ dysfunction and an advanced state of multimorbidity, showing a strong association with the prognosis of severe conditions such as heart failure or advanced cancer. This comprehensive review is the first to summarize the existing scientific knowledge on the role of circulating GPC4 as a novel diagnostic and prognostic biomarker across different pathologic conditions. We also discuss in detail the putative underlying pathophysiological mechanisms behind these findings.

Sepsis-associated endothelial glycocalyx damage: a review of animal models, clinical evidence, and molecular mechanisms

In the mammalian cardiovascular system, endothelial glycocalyx is a gel-like layer that covers the luminal surface of endothelial cells (ECs) and plays crucial roles in vascular homeostasis, permeability and leukocyte adhesion. Degradation of this structure occurs early in sepsis and becomes accordingly dysfunctional. In severe cases, it is not self-regulated by the organism. However, the relationship between the glycocalyx and the occurrence and development of sepsis remains poorly understood. One possibility is that thinned glycocalyx promotes leukocyte recognition and adhesion, thereby facilitating the elimination of pathogens from infected areas. This may represent a protective mechanism developed by the organism during through evolutionary processes. However, if the damage persists and disrupts the dynamic balance of the microcirculation, interstitial edema or organ failure can occur. Thus, we asked the questions, what is the precise composition and structure of the glycocalyx? How is it degraded? What animal models are available to study the relationship between the glycocalyx and sepsis? What glycocalyx biomarkers are found in the blood of patients with sepsis? To determine whether sepsis can be treated by interfering with the glycocalyx, this study provides a systematic summary and discussion of the latest progress in addressing these questions.

Soluble Proteoglycans and Proteoglycan Fragments as Biomarkers of Pathological Extracellular Matrix Remodeling

Proteoglycans and their proteolytic fragments diffuse into biological fluids such as plasma, serum, urine, or synovial fluid, where they can be detected by antibodies or mass-spectrometry. Neopeptides generated by the proteolysis of proteoglycans are recognized by specific neoepitope antibodies and can act as a proxy for the activity of certain proteases. Proteoglycan and proteoglycan fragments can be potentially used as prognostic, diagnostic, or theragnostic biomarkers for several diseases characterized by dysregulated extracellular matrix remodeling such as osteoarthritis, rheumatoid arthritis, atherosclerosis, thoracic aortic aneurysms, central nervous system disorders, viral infections, and cancer. Here, we review the main mechanisms accounting for the presence of soluble proteoglycans and their fragments in biological fluids, their potential application as diagnostic, prognostic, or theragnostic biomarkers, and highlight challenges and opportunities ahead of their clinical translation.

Soluble vascular endothelial glycocalyx proteoglycans as potential therapeutic targets in inflammatory diseases

Reducing the activity of cytokines and leukocyte extravasation is an emerging therapeutic strategy to limit tissue-damaging inflammatory responses and restore immune homeostasis in inflammatory diseases. Proteoglycans embedded in the vascular endothelial glycocalyx, which regulate the activity of cytokines to restrict the inflammatory response in physiological conditions, are proteolytically cleaved in inflammatory diseases. Here we critically review the potential of proteolytically shed, soluble vascular endothelial glycocalyx proteoglycans to modulate pathological inflammatory responses. Soluble forms of the proteoglycans syndecan-1, syndecan-3 and biglycan exert beneficial anti-inflammatory effects by the removal of chemokines, suppression of proinflammatory cytokine expression and leukocyte migration, and induction of autophagy of proinflammatory M1 macrophages. By contrast, soluble versikine and decorin enhance proinflammatory responses by increasing inflammatory cytokine synthesis and leukocyte migration. Endogenous syndecan-2 and mimecan exert proinflammatory effects, syndecan-4 and perlecan mediate beneficial anti-inflammatory effects and glypican regulates Hh and Wnt signaling pathways involved in systemic inflammatory responses. Taken together, targeting the vascular endothelial glycocalyx-derived, soluble syndecan-1, syndecan-2, syndecan-3, syndecan-4, biglycan, versikine, mimecan, perlecan, glypican and decorin might be a potential therapeutic strategy to suppress overstimulated cytokine and leukocyte responses in inflammatory diseases.

Capillary leak and endothelial permeability in critically ill patients: a current overview

Capillary leak syndrome (CLS) represents a phenotype of increased fluid extravasation, resulting in intravascular hypovolemia, extravascular edema formation and ultimately hypoperfusion. While endothelial permeability is an evolutionary preserved physiological process needed to sustain life, excessive fluid leak-often caused by systemic inflammation-can have detrimental effects on patients' outcomes. This article delves into the current understanding of CLS pathophysiology, diagnosis and potential treatments. Systemic inflammation leading to a compromise of endothelial cell interactions through various signaling cues (e.g., the angiopoietin-Tie2 pathway), and shedding of the glycocalyx collectively contribute to the manifestation of CLS. Capillary permeability subsequently leads to the seepage of protein-rich fluid into the interstitial space. Recent insights into the importance of the sub-glycocalyx space and preserving lymphatic flow are highlighted for an in-depth understanding. While no established diagnostic criteria exist and CLS is frequently diagnosed by clinical characteristics only, we highlight more objective serological and (non)-invasive measurements that hint towards a CLS phenotype. While currently available treatment options are limited, we further review understanding of fluid resuscitation and experimental approaches to target endothelial permeability. Despite the improved understanding of CLS pathophysiology, efforts are needed to develop uniform diagnostic criteria, associate clinical consequences to these criteria, and delineate treatment options.

Circulating glypican-4 is a new predictor of all-cause mortality in patients with heart failure

BACKGROUND

Heart failure confers a high burden of morbidity and mortality. However, risk prediction in heart failure patients still is limited. Blood-based biomarkers hold promise to improve clinical risk assessment. Recently we have identified circulating glypican-4 (GPC4) as a significant predictor of mortality in coronary angiography patients and patients with peripheral artery disease. The impact of serum GPC4 on mortality in patients with heart failure is unknown and is addressed in this prospective cohort study.

METHODS

We prospectively recorded all-cause mortality in 288 patients with heart failure. GPC4 levels were measured using an enzyme-linked immunosorbent assay at baseline.

RESULTS

During the 24-month follow-up period, 28.1% (n = 81) of the patients died. Serum GPC4 significantly predicted all-cause mortality (hazard ratio (HR) per doublingof GPC4 = 3.57 [2.31-5.53]; P < 0.001). Subgroup analysis showed that GPC4 was significantly associated with all-cause mortality in patients with reduced ejection fraction (HR per doubling = 3.25 [1.75-6.04]; P < 0.001) as well as in those with preserved ejection fraction (HR per doubling = 3.07 [1.22-7.70]; P = 0.017). The association between serum GPC4 and all-cause mortality remained significant in multivariable Cox regression analysis correcting for traditional risk factors (P = 0.035). Results from C-statistics indicated an additional prognostic value of GPC4 relative to NT-proBNP for the prediction of two-year all-cause mortality (P = 0.030).

CONCLUSION

Circulating GPC4 independently predicts all-cause mortality in patients with heart failure.

Advances in the Physiology of Transvascular Exchange and A New Look At Rational Fluid Prescription

The Starling principle is a model that explains the transvascular distribution of fluids essentially governed by hydrostatic and oncotic forces, which dynamically allow vascular refilling according to the characteristics of the blood vessel. However, careful analysis of fluid physiology has shown that the principle, while correct, is not complete. The revised Starling principle (Michel-Weinbaum model) provides relevant information on fluid kinetics. Special emphasis has been placed on the endothelial glycocalyx, whose subendothelial area allows a restricted oncotic pressure that limits the reabsorption of fluid from the interstitial space, so that transvascular refilling occurs mainly from the lymphatic vessels. The close correlation between pathological states of the endothelium (eg: sepsis, acute inflammation, or chronic kidney disease) and the prescription of fluids forces the physician to understand the dynamics of fluids in the organism; this will allow rational fluid prescriptions. A theory that integrates the physiology of exchange and transvascular refilling is the "microconstant model", whose variables include dynamic mechanisms that can explain edematous states, management of acute resuscitation, and type of fluids for common clinical conditions. The clinical-physiological integration of the concepts will be the hinges that allow a rational and dynamic prescription of fluids.

Reduction of Endothelial Glycocalyx on Peritubular Capillaries in Chronic Kidney Disease

In chronic kidney disease (CKD), peritubular capillaries undergo anatomic and functional alterations, such as rarefaction and increased permeability. The endothelial glycocalyx (EG) is a carbohydrate-rich gel-like mesh, which covers the luminal surface of endothelial cells. It is involved in many regulatory functions of the endothelium, including vascular permeability. Herein, we investigated ultrastructural alterations of the EG in different murine CKD models. Fluorescence staining using different lectins with high affinity to components of the renal glycocalyx revealed a reduced binding to the endothelium in CKD in the animal models, and there were similar finding in human kidney specimens. Lanthanum Dysprosium Glycosamino Glycan adhesion staining technique was used to visualize the ultrastructure of the glycocalyx in transmission electron microscopy. This also enabled quantitative analyses, showing a significant reduction of the EG thickness and density. In addition, mRNA expression of proteins involved in glycocalyx biology, synthesis, and turnover (ie, syndecan 1 and glypican 1), which are main components of the glycocalyx, and exostosin 2, involved in the synthesis of the glycocalyx, were significantly up-regulated in endothelial cells isolated from murine CKD models. Visualization of glycocalyx using specific transmission electron microscopy analyses allows qualitative and quantitative analyses and revealed significant pathologic alterations in peritubular capillaries in CKD.

Plasma proteomic characterization of the development of acute kidney injury in early sepsis patients

Acute kidney injury (AKI) develops frequently in the course of patients with sepsis and strongly associates with in-hospital mortality. However, diagnosing AKI involves a considerable lag-time because it depends on assessing an increase in serum creatinine, and offers no insight in the underlying pathophysiology. Consequently, identifying a set of proteins reflecting the development of AKI may improve earlier recognition of AKI and the understanding of its pathophysiology. A targeted plasma proteomic approach was performed in early sepsis patients with and without subsequent AKI development in a matched pair design (n = 19 each). Principal component analysis identified 53 proteins associated with development of AKI, which were further analysed using Enrichr gene ontology and pathway analysis. Nine differentially expressed proteins from the targeted proteomics were increased among patients who subsequently developed AKI and correlated with principal components, namely CALCA, CALR, CA12, CLEC1A, PTK7, KIM-1, NPPC, NUCB2 and PGF. We demonstrated the biological insight in the development of AKI in early sepsis compared to non-AKI sepsis.

HYDROCORTISONE, ASCORBIC ACID, AND THIAMINE THERAPY DECREASE RENAL OXIDATIVE STRESS AND ACUTE KIDNEY INJURY IN MURINE SEPSIS

ABSTRACT

Background: Acute kidney injury (AKI) occurs frequently in septic patients and correlates with increased mortality. Because clinical studies investigating hydrocortisone, ascorbic acid, and thiamine (HAT) have demonstrated discordant results, studies were performed using mortality stratification for therapy to identify candidates for therapy and determine mechanisms of organ injury. Methods: Sepsis was induced using the cecal ligation and puncture (CLP) model of sepsis with fluid and antibiotic support. Heart rate (HR) measurements obtained 6 hours after CLP stratified mice into live predicted (P-Live) or die predicted (P-Die). Stratified mice were then randomized for treatment with HAT or vehicle given 7 hours after CLP. Physiologic measurements were taken again at 24 hours, and mice were killed to collect blood and organs. Results: The following five groups were created: (1) P-Live vehicle, (2) P-Live HAT, (3) P-Die vehicle, (4) P-Die HAT, and (5) naive mice. Comparisons were made to test the hypotheses that (1) P-Die vehicle mice will have significant deterioration compared with P-Live mice targeting the kidney and (2) HAT will correct these deleterious changes in P-Die mice. Compared with P-Live, P-Die mice had a significant decline in all measured physiologic parameters (HR, cardiac output, breath rate, and temperature), which were corrected with HAT therapy (P < 0.05 for all parameters). The P-Die mice had declines in the ascorbic acid within the blood, peritoneal lavage, and kidney homogenate compared with P-Live mice indicating consumption, and the decline was corrected with HAT. Elevated IL-6, KC, Macrophage Inflammatory Protein-2, and IL-1RA were found in P-Die mice and decreased with HAT. Markers of endothelial cell injury (glypican 1 and glypican 4) were elevated in the P-Die mice, and these values were decreased with HAT therapy. Low oxygen levels with subsequent oxidative stress (OS) in the kidney were visualized in histologic sections using hypoxyprobe and also with carbonyl proteins and 8-iso-prostaglandin F2α in kidney homogenates. The P-Die mice had significant elevations of renal OSs, which was ameliorated with HAT. Kidney injury was evident in the P-Die mice compared with P-Live mice with elevations in blood urea nitrogen and cystatin C, which were significantly reduced with HAT. There was no evidence of global hypoxia or organ injury because hepatic parameters remained normal. Conclusions: Our data show that in CLP-induced sepsis, P-Die mice have increased inflammation, OS, and kidney injury. Hydrocortisone, ascorbic acid, and thiamine therapy decreased renal OS and injury in the P-Die group when given after the onset of sepsis-induced physiologic changes.

Circulating syndecan-1 and glypican-4 predict 12-month survival in metastatic colorectal cancer patients

Cell surface syndecans and glypicans play important roles in the development and prognosis of colorectal cancer (CRC). Their soluble forms from proteoglycan shedding can be detected in blood and have been proposed as new prognostic biomarkers in several cancer entities. However, studies on circulating syndecan-1 (SDC1) and glypican-4 (GPC4) in CRC are limited. We, therefore, evaluated the impact of plasma SDC1 and GPC4 on the prognosis of metastatic (m)CRC patients. The present study included 93 patients with mCRC. The endpoints were progression-free survival (PFS) and overall survival (OS) at 12 months. SDC1 and GPC4 levels were measured in plasma using enzyme-linked immunosorbent assays. Plasma levels of SDC1 and GPC4 were significantly correlated. Significant correlations of these two markers were also found with carcinoembryonic antigen (CEA). Kaplan-Meier curve analyses indicated that PFS and OS probabilities significantly decreased with increasing levels of SDC1 and GPC4, respectively. Multivariable Cox regression analyses showed that both markers were significantly associated with PFS and OS independently from clinicopathological characteristics including CEA. Respective adjusted hazard ratios (HR) together with corresponding 95% confidence intervals for one standard deviation change of SDC1 were 1.32 [1.02-1.84] for PFS and 1.48 [1.01-2.15] for OS. Adjusted HRs [95% confidence intervals] of GPC4 were 1.42 [1.07-1.89] for PFS and 2.40 [1.51-3.81] for OS. Results from area under the receiver operating characteristic curve analyses suggest that GPC4 and SDC1 add additional prognostic values to CEA for OS. In conclusion, we showed significant associations of circulating SDC1 and GPC4 with poor survival of mCRC patients.

Markers of endothelial glycocalyx dysfunction in Clarkson disease

BACKGROUND

Clarkson disease (monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome, ISCLS) is a rare idiopathic condition marked by transient, relapsing-remitting episodes of systemic microvascular hyper-permeability, which liberates plasma fluid and macromolecules into the peripheral tissues. This pathology manifests clinically as the abrupt onset of hypotensive shock, hemoconcentration, and hypoalbuminemia.

METHODS

We analysed endothelial glycocalyx (eGCX)-related markers in plasma from patients with ISCLS during acute disease flares and convalescence by ELISA and comprehensive proteomic profiling. We evaluated eGCX-related components and gene expression in cultured endothelial cells using RNA-sequencing, real-time PCR, and fluorescence staining.

RESULTS

Serum levels of eGCX-related core components including hyaluronic acid (HA) and the core proteoglycan soluble syndecan-1 (sCD138) were elevated at baseline and during acute ISCLS flares. Serial measurements demonstrated that sCD138 levels peaked during the recovery (post-leak) phase of the illness. Proteomic analysis of matched acute and convalescent ISCLS plasma revealed increased abundance of eGCX-related proteins, including glypicans, thrombospondin-1 (TSP-1), and eGCX-degrading enzymes in acute compared to remission plasma. Abundance of endothelial cell damage markers did not differ in acute and baseline plasma. Expression of several eGCX-related genes and surface carbohydrate content in endothelial cells from patients with ISCLS did not differ significantly from that observed in healthy control cells.

CONCLUSIONS

eGCX dysfunction, but not endothelial injury, may contribute to clinical symptoms of acute ISCLS. Serum levels of of eGCX components including sCD138 may be measured during acute episodes of ISCLS to monitor clinical status and therapeutic responses.

Endothelial glycocalyx degradation during sepsis: Causes and consequences

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The endothelial glycocalyx is a ubiquitous intravascular structure essential for vascular homeostasis.

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During sepsis, the glycocalyx is degraded via the collective action of a variety of redundant sheddases, the regulation of which remains the focus of active investigation.

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Septic loss of the glycocalyx imparts both local vascular injury (leading to acute respiratory distress syndrome and acute kidney injury) as well as the systemic consequences of circulating glycosaminoglycan fragments (leading to cognitive dysfunction).

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Glycocalyx degradation during sepsis is potentially shaped by clinically-modifiable factors, suggesting opportunities for therapeutic intervention to mitigate the end-organ consequences of sepsis.

The glycocalyx is a ubiquitous structure found on endothelial cells that extends into the vascular lumen. It is enriched in proteoglycans, which are proteins attached to the glycosaminoglycans heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. In health and disease, the endothelial glycocalyx is a central regulator of vascular permeability, inflammation, coagulation, and circulatory tonicity. During sepsis, a life-threatening syndrome seen commonly in hospitalized patients, the endothelial glycocalyx is degraded, significantly contributing to its many clinical manifestations. In this review we discuss the intrinsically linked mechanisms responsible for septic endothelial glycocalyx destruction: glycosaminoglycan degradation and proteoglycan cleavage. We then examine the consequences of local endothelial glycocalyx loss to several organ systems and the systemic consequences of shed glycocalyx constituents. Last, we explore clinically relevant non-modifiable and modifiable factors that exacerbate or protect against endothelial glycocalyx shedding during sepsis.

Human glycocalyx shedding: Systematic review and critical appraisal

BACKGROUND

The number of studies measuring breakdown products of the glycocalyx in plasma has increased rapidly during the past decade. The purpose of the present systematic review was to assess the current knowledge concerning the association between plasma concentrations of glycocalyx components and structural assessment of the endothelium.

METHODS

We performed a literature review of Pubmed to determine which glycocalyx components change in a wide variety of human diseases and conditions. We also searched for evidence of a relationship between plasma concentrations and the thickness of the endothelial glycocalyx layer as obtained by imaging methods.

RESULTS

Out of 3,454 publications, we identified 228 that met our inclusion criteria. The vast majority demonstrate an increase in plasma glycocalyx products. Sepsis and trauma are most frequently studied, and comprise approximately 40 publications. They usually report 3-4-foldt increased levels of glycocalyx degradation products, most commonly of syndecan-1. Surgery shows a variable picture. Cardiac surgery and transplantations are most likely to involve elevations of glycocalyx degradation products. Structural assessment using imaging methods show thinning of the endothelial glycocalyx layer in cardiovascular conditions and during major surgery, but thinning does not always correlate with the plasma concentrations of glycocalyx products. The few structural assessments performed do not currently support that capillary permeability is increased when the plasma levels of glycocalyx fragments in plasma are increased.

CONCLUSIONS

Shedding of glycocalyx components is a ubiquitous process that occurs during both acute and chronic inflammation with no sensitivity or specificity for a specific disease or condition.

Endothelial Heparan Sulfate Proteoglycans in Sepsis: The Role of the Glycocalyx

There is increasing recognition of the importance of the endothelial glycocalyx and its in vivo manifestation, the endothelial surface layer, in vascular homeostasis. Heparan sulfate proteoglycans (HSPGs) are a major structural constituent of the endothelial glycocalyx and serve to regulate vascular permeability, microcirculatory tone, leukocyte and platelet adhesion, and hemostasis. During sepsis, endothelial HSPGs are shed through the induction of "sheddases" such as heparanase and matrix metalloproteinases, leading to loss of glycocalyx integrity and consequent vascular dysfunction. Less well recognized is that glycocalyx degradation releases HSPG fragments into the circulation, which can shape the systemic consequences of sepsis. In this review, we will discuss (1) the normal, homeostatic functions of HSPGs within the endothelial glycocalyx, (2) the pathological changes in HSPGs during sepsis and their consequences on the local vascular bed, and (3) the systemic consequences of HSPG degradation. In doing so, we will identify potential therapeutic targets to improve vascular function during sepsis as well as highlight key areas of uncertainty that require further mechanistic investigation.

How Reliable are Commercially Available Glypican4 ELISA Kits?

OBJECTIVE

Glypican4 is an interesting new adipokine, which seems to play an important role in developmental processes and is potentially associated with metabolic changes in obesity and type 2 diabetes mellitus. Currently, only a few studies examined glypican4 in human blood, mainly in adults.

DESIGN, PATIENTS AND MEASUREMENTS

The aim of our study was to investigate glypican4 serum levels in lean, overweight, and obese children and adolescents, to unravel a possible association between glypican4 serum levels and parameters of obesity and insulin resistance. In order to determine a suitable method for investigating glypican4 serum levels, we validated two commercially available human glypican4 ELISA kits, using serum and plasma samples of an obese, insulin-resistant patient, and a healthy control subject, a human recombinant glypican4 protein fragment and glypican4-overexpressing cell lysate.

RESULTS

Using ELISA kit #1 we were not able to detect values above background level, apart from standard curve values. ELISA kit #2 initially seemed suitable to measure glypican4, but further validation experiments showed non-linearity of serial dilutions, no recognition of a human recombinant glypican4 protein fragment and non-linearity in the recovery of glypican4-overexpressing cell lysate. In addition, there was a considerable decrease (approx. 68%) of measured values between two experiments, performed at different time points with aliquots of the same serum sample. Contrary to that, further experiments found sample stability not to be compromised.

CONCLUSIONS

Extensive evaluation of the performance of two commercially available ELISA kits led to the conclusion that none of them is applicable for the measurement of glypican4 in human blood samples.

Is microcirculatory assessment ready for regular use in clinical practice?

PURPOSE OF REVIEW

The present review discusses the current role of microcirculatory assessment in the hemodynamic monitoring of critically ill patients.

RECENT FINDINGS

Videomicroscopic techniques have demonstrated that microvascular perfusion is altered in critically ill patients, and especially in sepsis. These alterations are associated with organ dysfunction and poor outcome. Handheld microscopes can easily be applied on the sublingual area of critically ill patients. Among the specific limitations of these techniques, the most important is that these can mostly investigate the sublingual microcirculation. The representativity of the sublingual area may be questioned, especially as some areas may sometimes be more affected than the sublingual area. Also, evaluation of the sublingual area may be difficult in nonintubated hypoxemic patients. Alternative techniques include vasoreactivity tests using either transient occlusion or performing a thermal challenge. These techniques evaluate the maximal dilatory properties of the microcirculation but do not really evaluate the actual microvascular perfusion. Focusing on the glycocalyx may be another option, especially with biomarkers of glycocalyx degradation and shedding. Evaluation of the glycocalyx is still largely experimental, with different tools still in investigation and lack of therapeutic target. Venoarterial differences in PCO2 are inversely related with microvascular perfusion, and can thus be used as surrogate for microcirculation assessment. Several limitations prevent the regular use in clinical practice. The first is the difficult use of some of these techniques outside research teams, whereas nurse-driven measurements are probably desired. The second important limitation for daily practice use is the lack of uniformly defined endpoint. The final limitation is that therapeutic interventions affecting the microcirculation are not straightforward.

SUMMARY

Clinical and biological surrogates of microcirculatory assessment can be used at bedside. The role of microvideoscopic techniques is still hampered by the lack of clearly defined targets as well as interventions specifically targeting the microcirculation.

Apolipoprotein M/sphingosine-1-phosphate: novel effects on lipids, inflammation and kidney biology

PURPOSE OF REVIEW

In 2011, the crystal structure of apolipoprotein M (apoM) and its capacity to bind sphingosine-1-phosphate (S1P) was characterized. Since then, a variety of studies has increased our knowledge on apoM biology and functionality. From being an unknown and hardly significant player in overall metabolism, apoM has gained significant interest.

RECENT FINDINGS

Key discoveries in the last 2 years have indicated that the apoM/S1P complex has important roles in lipid metabolism (affecting triglyceride turnover), inflammation (a marker of severe sepsis and potentially providing anti-inflammatory signaling) and kidney biology (potential to protect against immunoglobulin A nephropathy).

SUMMARY

Several studies suggest a potential for apoM/S1P as biomarkers for inflammation, sepsis and nephropathy. Also, a novel chaperone is characterized and could have potential as a drug for treatment in inflammation and nephropathy.