Identification of Glomerular and Plasma Apolipoprotein M as Novel Biomarkers in Glomerular Disease

Delineating the intricacies of polymorphisms, structures, functions and therapeutic applications of biological high-density lipoprotein-apolipoprotein M: A review

Apolipoprotein-M (ApoM), primarily associated with high-density lipoproteins (HDL), plays a crucial role in lipid metabolism and cardiovascular health. It facilitates the transport of lipids such as cholesterol and sphingosine-1-phosphate (S1P), contributing to reverse cholesterol transport (RCT), which removes excess cholesterol from peripheral tissues to the liver for excretion. Through its association with HDL and S1P, ApoM exerts anti-inflammatory, anti-thrombotic, and anti-apoptotic effects. The ApoM-S1P complex regulates various cellular, immunological, and physiological processes via S1P receptors, and its dysregulation is linked to metabolic and inflammatory disorders. Reduced plasma ApoM levels are associated with atherosclerosis, diabetes, and chronic systemic inflammation. ApoM levels and paraoxonase-1 activity in early pregnancy correlate with gestational hypertension risk, potentially affecting fetal vascular health. ApoM also functions as a S1P chaperone, and recent research highlights the roles of ApoM/S1P axis and the ApoA1-ApoM (A1M) complex in glucose and lipid metabolism, emphasizing its therapeutic relevance in cardiovascular diseases (CVD), cancer, and diabetes. The ApoM-Fc fusion protein exhibits promising therapeutic potential by reducing fibrosis, enhancing endothelial function, and promoting tissue regeneration. HDL-ApoM macromolecules bind bacterial endotoxins and aids in its clearance. This review explores ApoM gene organization, isoforms, point mutations, protein structure, functions and their relevance for developing novel therapeutics.

Risk stratification of metabolic disorder-associated kidney disease

During the last 20 years, the disease burden attributable to metabolic disorders increased by 49.4%. Metabolic disorders are established risk factors for both chronic kidney disease (CKD) and cardiovascular disease (CVD). A concept of cardiovascular-kidney-metabolic (CKM) syndrome has recently been proposed to underscore the pathophysiological interrelatedness of the metabolic risk factors, CKD, and CVD. Two major adverse outcomes of the metabolic disorder-associated kidney disease are cardiovascular disease and, to a less extent, kidney failure. This review aims to briefly summarize the traditional metabolic risk factors for kidney disease; to introduce the concept of CKM health; to present the methods for risk assessment for CKD progression and CVD, with focus on validated and clinically applicable prediction tools; and to discuss the key gaps in the current tools for the risk stratification. In summary, in general clinical settings, the CKM health and associated risk in patients with the metabolic disorder-associated kidney disease can be assessed by combining the CKM staging model, the CKD Prognosis Consortium equations for CKD progression, and the Predicting Risk of CVD Events (PREVENT) equations for CVD. More efficient risk prediction tools, potentially incorporating multimodal data, are needed for more accurate and early identification of individuals at high risk and better personalized management of the disease.

Sphingolipids and Chronic Kidney Disease

Sphingolipids (SLs) are bioactive signaling molecules essential for various cellular processes, including cell survival, proliferation, migration, and apoptosis. Key SLs such as ceramides, sphingosine, and their phosphorylated forms play critical roles in cellular integrity. Dysregulation of SL levels is implicated in numerous diseases, notably chronic kidney disease (CKD). This review focuses on the role of SLs in CKD, highlighting their potential as biomarkers for early detection and prognosis. SLs maintain renal function by modulating the glomerular filtration barrier, primarily through the activity of podocytes. An imbalance in SLs can lead to podocyte damage, contributing to CKD progression. SL metabolism involves complex enzyme-catalyzed pathways, with ceramide serving as a central molecule in de novo and salvage pathways. Ceramides induce apoptosis and are implicated in oxidative stress and inflammation, while sphingosine-1-phosphate (S1P) promotes cell survival and vascular health. Studies have shown that SL metabolism disorders are linked to CKD progression, diabetic kidney disease, and glomerular diseases. Targeting SL pathways could offer novel therapeutic approaches for CKD. This review synthesizes recent research on SL signaling regulation in kidney diseases, emphasizing the importance of maintaining SL balance for renal health and the potential therapeutic benefits of modulating SL pathways.

Normal and Dysregulated Sphingolipid Metabolism: Contributions to Podocyte Injury and Beyond

Podocyte health is vital for maintaining proper glomerular filtration in the kidney. Interdigitating foot processes from podocytes form slit diaphragms which regulate the filtration of molecules through size and charge selectivity. The abundance of lipid rafts, which are ordered membrane domains rich in cholesterol and sphingolipids, near the slit diaphragm highlights the importance of lipid metabolism in podocyte health. Emerging research shows the importance of sphingolipid metabolism to podocyte health through structural and signaling roles. Dysregulation in sphingolipid metabolism has been shown to cause podocyte injury and drive glomerular disease progression. In this review, we discuss the structure and metabolism of sphingolipids, as well as their role in proper podocyte function and how alterations in sphingolipid metabolism contributes to podocyte injury and drives glomerular disease progression.

The 14th International Podocyte Conference 2023: from podocyte biology to glomerular medicine

The 14th International Podocyte Conference took place in Philadelphia, Pennsylvania, USA from May 23 to 26, 2023. It commenced with an early-career researchers' meeting on May 23, providing young scientists with a platform to present and discuss their research findings. Throughout the main conference, 29 speakers across 9 sessions shared their insights on podocyte biology, glomerular medicine, novel technologic advancements, and translational approaches. Additionally, the event featured 3 keynote lectures addressing engineered chimeric antigen receptor T cell- and mRNA-based therapies and the use of biobanks for enhanced disease comprehension. Furthermore, 4 brief oral abstract sessions allowed scientists to present their findings to a broad audience. The program also included a panel discussion addressing the challenges of conducting human research within the American Black community. Remarkably, after a 5-year hiatus from in-person conferences, the 14th International Podocyte Conference successfully convened scientists from around the globe, fostering the presentation and discussion of crucial research findings, as summarized in this review. Furthermore, to ensure continuous and sustainable education, research, translation, and trial medicine related to podocyte and glomerular diseases for the benefit of patients, the International Society of Glomerular Disease was officially launched during the conference.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

Apolipoprotein M gene polymorphisms in childhood-onset type 1 diabetes in southern Brazil

Type 1 diabetes mellitus (T1DM), associated with autoimmune destruction of pancreatic β cells, is observed in children and adolescents.

OBJECTIVE

We investigated the potential association of the apolipoprotein M (APOM) polymorphisms rs707921, rs805264, rs805296, rs805297, and rs9404941 in childhood-onset T1DM (n = 144) and compared them to those in healthy (mostly Euro-Brazilian) children (n = 168).

METHODS

This project was approved by the Ethics Committee of the Federal University of Parana (CAAE 24676613.6.0000.0102). Genotyping was performed using PCR-restriction fragment length polymorphisms (rs805296 and rs9404941) and TaqMan probes (rs707921, rs805264, and rs805297).

RESULTS

All polymorphisms were in Hardy-Weinberg equilibrium. In the codominant model, no significant differences (P > 0.05) were observed in genotype and allele frequencies between healthy controls and children with T1DM. The minor allele frequencies (95% CI) for healthy subjects were rs707921 (A, 10.7%; 7-14%), rs805264 (A, 6.5%; 4-9%), rs805296 (C, 3.6%; 2-6%), rs805297 (A, 22.6%; 22-31%), and rs9404941 (C, 2.7%; 1-4%). The frequencies of the rs805297 A allele and rs805296 C allele were similar to those of other Caucasian populations; both the rs707921 and rs805264 A alleles were similar to American and Latin American populations, whereas that of the rs9404941 C allele was lower than that observed in the Caucasian and Asian populations.

CONCLUSIONS

Haplotype analysis suggests that rs805297-C, rs9404941-T, rs805296-T, rs805264-G, and rs707921-C conferred risk (OR: 4.25; 95% CI: 1.81-10.1) to childhood-onset T1DM in the Euro-Brazilian population.