Alpha1-Antitrypsin in Urinary Extracellular Vesicles: A Potential Biomarker of Diabetic Kidney Disease Prior to Microalbuminuria

Extracellular vesicles: Illuminating renal pathophysiology and therapeutic frontiers

Extracellular vesicles (EVs) are minute sacs released by cells into the extracellular milieu, harboring an array of biomolecules including proteins, nucleic acids, and lipids. Notably, a large number of studies have demonstrated the important involvement of EVs in both physiological and pathological aspects of renal function. EVs can facilitate communication between different renal cells, but it is important to recognize their dual role: they can either transmit beneficial information or lead to renal damage and worsening of existing conditions. The composition of EVs in the context of the kidneys offers valuable insights into the intricate mechanisms underlying specific renal functions or disease states. In addition, mesenchymal stem cell-derived EVs have the potential to alleviate acute and chronic kidney diseases. More importantly, the innate nanoparticle properties of EVs, coupled with their engineering potential, make them effective tools for drug delivery and therapeutic intervention. In this review, we focus on the intricate biological functions of EVs in the kidney. In addition, we explore the emerging role of EVs as diagnostic tools and innovative therapeutic agents in a range of renal diseases.

Proteomic insights into the pathophysiology of hypertension-associated albuminuria: Pilot study in a South African cohort

BACKGROUND

Hypertension is an important public health priority with a high prevalence in Africa. It is also an independent risk factor for kidney outcomes. We aimed to identify potential proteins and pathways involved in hypertension-associated albuminuria by assessing urinary proteomic profiles in black South African participants with combined hypertension and albuminuria compared to those who have neither condition.

METHODS

The study included 24 South African cases with both hypertension and albuminuria and 49 control participants who had neither condition. Protein was extracted from urine samples and analysed using ultra-high-performance liquid chromatography coupled with mass spectrometry. Data were generated using data-independent acquisition (DIA) and processed using Spectronaut™ 15. Statistical and functional data annotation were performed on Perseus and Cytoscape to identify and annotate differentially abundant proteins. Machine learning was applied to the dataset using the OmicLearn platform.

RESULTS

Overall, a mean of 1,225 and 915 proteins were quantified in the control and case groups, respectively. Three hundred and thirty-two differentially abundant proteins were constructed into a network. Pathways associated with these differentially abundant proteins included the immune system (q-value [false discovery rate] = 1.4 × 10- 45), innate immune system (q = 1.1 × 10- 32), extracellular matrix (ECM) organisation (q = 0.03) and activation of matrix metalloproteinases (q = 0.04). Proteins with high disease scores (76-100% confidence) for both hypertension and chronic kidney disease included angiotensinogen (AGT), albumin (ALB), apolipoprotein L1 (APOL1), and uromodulin (UMOD). A machine learning approach was able to identify a set of 20 proteins, differentiating between cases and controls.

CONCLUSIONS

The urinary proteomic data combined with the machine learning approach was able to classify disease status and identify proteins and pathways associated with hypertension-associated albuminuria.

Role of MCP-1 as an inflammatory biomarker in nephropathy

The Monocyte chemoattractant protein-1 (MCP-1), also referred to as chemokine ligand 2 (CCL2), belongs to the extensive chemokine family and serves as a crucial mediator of innate immunity and tissue inflammation. It has a notable impact on inflammatory conditions affecting the kidneys. Upon binding to its receptor, MCP-1 can induce lymphocytes and NK cells' homing, migration, activation, differentiation, and development while promoting monocytes' and macrophages' infiltration, thereby facilitating kidney disease-related inflammation. As a biomarker for kidney disease, MCP-1 has made notable advancements in primary kidney diseases such as crescentic glomerulonephritis, chronic glomerulonephritis, primary glomerulopathy, idiopathic proteinuria glomerulopathy, acute kidney injury; secondary kidney diseases like diabetic nephropathy and lupus nephritis; hereditary kidney diseases including autosomal dominant polycystic kidney disease and sickle cell kidney disease. MCP-1 not only predicts the occurrence, progression, prognosis of the disease but is also closely associated with the severity and stage of nephropathy. When renal tissue is stimulated or experiences significant damage, the expression of MCP-1 increases, demonstrating a direct correlation with the severity of renal injury.

Research progress on extracellular vesicles in the renal tubular injury of diabetic kidney disease

Diabetic kidney disease (DKD) is a severe microvascular complication of diabetes and is a chronic progressive condition. It is also a common cause of end-stage renal disease (ESRD), which is characterized by proteinuria or a progressive decline in the glomerular filtration rate. Due to their dependence on high-energy and aerobic metabolism, renal tubules are more susceptible to the metabolic disturbances associated with DKD, leading to inflammation and fibrosis. Consequently, tubular injury has become a recent research focus, and significant advancements have been made in studying the role of extracellular vesicles in DKD-associated tubular injury. This review aimed to elucidate the mechanisms and potential applications of different types of extracellular vesicles in tubular injury in DKD to provide new insights for the prevention and treatment of DKD.

Urinary Proteome Differences in Patients with Type 2 Diabetes Pre and Post Liraglutide Treatment

Diabetes mellitus is a chronic multisystem disease with a high global prevalence. The glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide is known to lower glucose levels and reduce weight. However, the mechanisms underlying the benefits of liraglutide treatment in patients with type 2 diabetes mellitus (T2DM) remain unclear. Twelve male patients with T2DM (pre and post liraglutide treatment) and HbA1c between 8% and 11% were recruited. In the present study, a two-dimensional difference gel electrophoresis (2D-DIGE) matrix-assisted laser desorption/ionization-time of flight (MALDI TOF) mass spectrometric approach combined with bioinformatics and network pathway analysis was used to explore the urine proteomic profile. The mean age of the patients was 52.4 ± 7.5 years. After treatment with liraglutide, a statistically significant change (p < 0.006) was observed in HbA1c with no significant changes in body weight or markers of dyslipidemia. Two-dimensional difference gel electrophoresis identified significant changes (≥1.5-fold change, ANOVA, p ≤ 0.05) in 32 proteins (4 down- and 28 upregulated) in liraglutide post treatment compared to the pre-treatment state. Albumin, serotransferrin, metallothionein-2 (MT-2), and keratins K1 and K10 were found to be upregulated after liraglutide treatment. The patients showed significant improvement in glycemic control after the 12-week treatment with liraglutide. The renoprotective effect of liraglutide may be linked to the increased urinary abundance of MT-2 and the decreased abundance of zinc alpha 2-glycoprotein (ZAG) and Alpha-1 antitrypsin (α1-AT). More studies are needed to elucidate the molecular mechanisms behind the renoprotective effects of liraglutide.

Novel insights into the relationship between α-1 anti-trypsin with the pathological development of cardio-metabolic disorders

According to the previous studies, chronic low-grade systemic inflammatory response has been shown to be significantly associated with the pathological development of cardio-metabolic disorder diseases, including atherosclerosis, type 2 diabetes mellitus, and non-alcoholic fatty liver disease (NAFLD). On the other hand, auto-immunity process could also facilitate the pathogenesis of type 1 diabetes mellitus importantly. Concerning on this notion, the anti-inflammatory therapeutic strategy is demonstrated to embrace an essential function in those cardio-metabolic disorders in clinical practice. The α-1 anti-trypsin, also named Serpin-A1 and as an acute phase endogenous protein, has been verified to have several modulatory effects such as anti-inflammatory response, anti-apoptosis, and immunomodulatory functions. In addition, it is also used for therapeutic strategy of a rare genetic disease caused by the deficiency of α-1 anti-trypsin. Recent emerging evidence has indicated that the serum concentrations of α-1 anti-trypsin levels and its biological activity are significantly changed in those inflammatory and immune related cardio-metabolic disorder diseases. Nevertheless, the underlying mechanism is still not elucidated. In the current review, the basic experiments and clinical trials which provided the evidence revealing the potential therapeutic function of the α-1 anti-trypsin in cardio-metabolic disorder diseases were well-summarized. Furthermore, the results which indicated that the α-1 anti-trypsin presented the possibility as a novel serum biomarker in humans to predict those cardio-metabolic disorder diseases were also elucidated.

Alpha-1 antitrypsin: A novel biomarker and potential therapeutic approach for metabolic diseases

It is well recognized that chronic low-grade systemic inflammation and autoimmunity contribute to the pathogenesis of metabolic syndrome, its associated diseases (e.g. type 2 diabetes, non-alcoholic fatty liver disease) and type 1 diabetes, respectively. Consequently, anti-inflammatory agents might play a role in managing these immune associated metabolic diseases. Alpha-1 antitrypsin (AAT), an endogenous acute phase protein being used for treatment of AAT deficiency (a rare genetic disease), has multiple functions including anti-inflammatory, immunomodulatory, anti-apoptosis and cytoprotective effects. In this review, we summarized basic and clinical studies that reported potential therapeutic role of AAT in metabolic syndrome associated diseases and type 1 diabetes. Studies that demonstrated AAT had the possibility to be used as a novel biomarker to predict these immune associated metabolic diseases were also included.

Early renal and vascular damage within the normoalbuminuria condition

OBJECTIVE

A continuous association between albuminuria and cardiorenal risk exists further below moderately increased albuminuria ranges. If only based in albumin to creatinine ratio (ACR) higher than 30 mg/g, a significant percentage of individuals may be out of the scope for therapeutic management. Despite epidemiological outcomes, the identification of biochemical changes linked to early albuminuria is underexplored, and normoalbuminuric individuals are usually considered at no risk in clinical practice. Here, we aimed to identify early molecular alterations behind albuminuria development.

METHODS

Hypertensive patients under renin-angiotensin system (RAS) suppression were classified as control, (ACR < 10 mg/g) or high-normal (ACR = 10-30 mg/g). Urinary protein alterations were quantified and confirmed by untargeted and targeted mass spectrometry. Coordinated protein responses with biological significance in albuminuria development were investigated. Immunohistochemistry assays were performed in human kidney and arterial tissue to in situ evaluate the associated damage.

RESULTS

A total of 2663 identified proteins reflect inflammation, immune response, ion transport and lipids metabolism (P value ≤ 0.01). A1AT, VTDB and KNG1 varied in high-normal individuals (P value < 0.05), correlated with ACR and associated with the high-normal condition (odds ratio of 20.76, 6.00 and 7.04 were found, respectively (P value < 0.001)). After 12 months, protein variations persist and aggravate in progressors to moderately increased albuminuria. At tissue level, differential protein expression was found in kidney from individuals with moderately increased albuminuria and atherosclerotic aortas for the three proteins, confirming their capacity to reflect subclinical organ damage.

CONCLUSION

Early renal and vascular damage is molecularly evidenced within the normoalbuminuria condition.

Urinary Extracellular Vesicles for Diabetic Kidney Disease Diagnosis

Diabetic kidney disease (DKD) is the leading cause of end stage renal disease (ESRD) in developed countries, affecting more than 40% of diabetes mellitus (DM) patients. DKD pathogenesis is multifactorial leading to a clinical presentation characterized by proteinuria, hypertension, and a gradual reduction in kidney function, accompanied by a high incidence of cardiovascular (CV) events and mortality. Unlike other diabetes-related complications, DKD prevalence has failed to decline over the past 30 years, becoming a growing socioeconomic burden. Treatments controlling glucose levels, albuminuria and blood pressure may slow down DKD evolution and reduce CV events, but are not able to completely halt its progression. Moreover, one in five patients with diabetes develop DKD in the absence of albuminuria, and in others nephropathy goes unrecognized at the time of diagnosis, urging to find novel noninvasive and more precise early diagnosis and prognosis biomarkers and therapeutic targets for these patient subgroups. Extracellular vesicles (EVs), especially urinary (u)EVs, have emerged as an alternative for this purpose, as changes in their numbers and composition have been reported in clinical conditions involving DM and renal diseases. In this review, we will summarize the current knowledge on the role of (u)EVs in DKD.