The glycocalyx, a novel key in understanding of mechanism of diabetic nephropathy: a commentary

Unraveling the Mechanisms of Magnesium Supplementation in Alleviating Chronic Kidney Disease Complications and Progression: Balancing Risks and Benefits

Chronic kidney disease (CKD) is a major cause of death and disability worldwide. It is usually diagnosed at early levels because of its slow progression. Treatment should consider CKD complications (such as electrolyte level imbalance, vascular calcification, and bone mineral disorders), as well as the development of CKD itself. Large-scale studies have shown that current treatment guidelines are nearly ineffective and fail to achieve treatment goals. Guidelines have not paid as much attention to magnesium (Mg) as the other electrolytes, while Mg has a significant role in the treatment goals of CKD. Hypomagnesemia is the only electrolyte imbalance that is equally prevalent in all stages of CKD. A lower plasma Mg level in each stage of CKD is associated with a higher risk of CKD progression and cardiac events. Magnesium exerts its effects both directly and via other ions. Mg supplementation increases insulin sensitivity while reducing proteinuria and inflammation. It lowers blood pressure and inhibits vascular calcification primarily because of its effects on calcium and phosphate, respectively. Vitamin D supplementation for low-active vitamin D in CKD patients increases vascular calcification and cardiac events, but magnesium supplementation enhances vitamin D levels and activity without increasing the risk of cardiac events. However, careful attention is required due to the potential threats of hypermagnesemia, particularly in advanced CKD stages. Starting magnesium supplementation early in patients' treatment plans will result in fewer side effects and more advantages. More original research is needed to determine its optimal dose and serum levels.

The therapeutic effects of marine sulfated polysaccharides on diabetic nephropathy

Marine sulfated polysaccharide (MSP) is a natural high molecular polysaccharide containing sulfate groups, which widely exists in various marine organisms. The sources determine structural variabilities of MSPs which have high security and wide biological activities, such as anticoagulation, antitumor, antivirus, immune regulation, regulation of glucose and lipid metabolism, antioxidant, etc. Due to the structural similarities between MSP and endogenous heparan sulfate, a majority of studies have shown that MSP can be used to treat diabetic nephropathy (DN) in vivo and in vitro. In this paper, we reviewed the anti-DN activities, the dominant mechanisms and structure-activity relationship of MSPs in order to provide the overall scene of MSPs as a modality of treating DN.

Succinate metabolism and membrane reorganization drives the endotheliopathy and coagulopathy of traumatic hemorrhage

Acute hemorrhage commonly leads to coagulopathy and organ dysfunction or failure. Recent evidence suggests that damage to the endothelial glycocalyx contributes to these adverse outcomes. The physiological events mediating acute glycocalyx shedding are undefined, however. Here, we show that succinate accumulation within endothelial cells drives glycocalyx degradation through a membrane reorganization-mediated mechanism. We investigated this mechanism in a cultured endothelial cell hypoxia-reoxygenation model, in a rat model of hemorrhage, and in trauma patient plasma samples. We found that succinate metabolism by succinate dehydrogenase mediates glycocalyx damage through lipid oxidation and phospholipase A2-mediated membrane reorganization, promoting the interaction of matrix metalloproteinase 24 (MMP24) and MMP25 with glycocalyx constituents. In a rat hemorrhage model, inhibiting succinate metabolism or membrane reorganization prevented glycocalyx damage and coagulopathy. In patients with trauma, succinate levels were associated with glycocalyx damage and the development of coagulopathy, and the interaction of MMP24 and syndecan-1 was elevated compared to healthy controls.

Early diabetic kidney disease: Focus on the glycocalyx

The incidence of diabetic kidney disease (DKD) is sharply increasing worldwide. Microalbuminuria is the primary clinical marker used to identify DKD, and its initiating step in diabetes is glomerular endothelial cell dysfunction, particularly glycocalyx impairment. The glycocalyx found on the surface of glomerular endothelial cells, is a dynamic hydrated layer structure composed of pro-teoglycans, glycoproteins, and some adsorbed soluble components. It reinforces the negative charge barrier, transduces the shear stress, and mediates the interaction of blood corpuscles and podocytes with endothelial cells. In the high-glucose environment of diabetes, excessive reactive oxygen species and proinflammatory cytokines can damage the endothelial glycocalyx (EG) both directly and indirectly, which induces the production of microalbuminuria. Further research is required to elucidate the role of the podocyte glycocalyx, which may, together with endothelial cells, form a line of defense against albumin filtration. Interestingly, recent research has confirmed that the negative charge barrier function of the glycocalyx found in the glomerular basement membrane and its repulsion effect on albumin is limited. Therefore, to improve the early diagnosis and treatment of DKD, the potential mechanisms of EG degradation must be analyzed and more responsive and controllable targets must be explored. The content of this review will provide insights for future research.

ABCA1 deficiency-mediated glomerular cholesterol accumulation exacerbates glomerular endothelial injury and dysfunction in diabetic kidney disease

BACKGROUND

Hyperglycemia and dyslipidemia are two major characteristics of diabetes. In this study, the effects of glomerular cholesterol accumulation primarily due to ABCA1 deficiency on glomerular endothelial injury in diabetic kidney disease (DKD) and the possible mechanisms were investigated.

METHODS

The effects of ABCA1 deficiency on glomerular lipid deposition and kidney injury were examined in a type 2 diabetic mouse model with ABCA1 deficiency in glomerular endothelial cells (DM-ABCA1-/- mice) and human renal glomerular endothelial cells (HRGECs) cultured in high glucose and high cholesterol conditions, which simulated type 2 diabetes in vitro.

RESULTS

ABCA1 deficiency in glomerular endothelial cells exacerbated renal lipid deposition and kidney injuries in type 2 diabetic mice and manifested as increased creatinine levels, more severe proteinuria, mesangial matrix expansion and fusion of foot processes, and more pronounced renal inflammatory injury and cell death. In HRGECs cultured under high glucose and high cholesterol conditions, ABCA1 deficiency increased the deposition of cellular cholesterol, contributed to inflammation and apoptosis, damaged the endothelial glycocalyx barrier, and induced endoplasmic reticulum stress (ERS). Conversely, ABCA1 overexpression enhancing cholesterol efflux or inhibition of ERS in vitro, significantly protected against glomerular endothelial injury stimulated by high glucose and high cholesterol.

CONCLUSIONS

These findings establish a pathogenic role of ABCA1 deficiency in glomerular endothelium injury and dysfunction and imply that ABCA1 may represent a potential effective therapeutic target for early diabetic kidney disease.