Inter-organ Communication Pathway Manifested by Non-physiological Stress to the Kidney in Type II Diabetic Patients -Why Are Diabetic Patients Prone to Develop Heart Failure?

A Role of Sodium-Glucose Co-Transporter 2 in Cardiorenal Anemia Iron Deficiency Syndrome

Heart failure, renal dysfunction, anemia, and iron deficiency affect each other and form a vicious cycle, a condition referred to as cardiorenal anemia iron deficiency syndrome. The presence of diabetes further accelerates this vicious cycle. Surprisingly, simply inhibiting sodium-glucose co-transporter 2 (SGLT2), which is expressed almost exclusively in the proximal tubular epithelial cells of the kidney, not only increases glucose excretion into the urine and effectively controls blood glucose levels in diabetes but can also correct the vicious cycle of cardiorenal anemia iron deficiency syndrome. This review describes how SGLT2 is involved in energy metabolism regulation, hemodynamics (i.e., circulating blood volume and sympathetic nervous system activity), erythropoiesis, iron bioavailability, and inflammatory set points in diabetes, heart failure, and renal dysfunction.

Current Challenges and Future Perspectives of Renal Tubular Dysfunction in Diabetic Kidney Disease

Over decades, substantial progress has been achieved in understanding the pathogenesis of proteinuria in diabetic kidney disease (DKD), biomarkers for DKD screening, diagnosis, and prognosis, as well as novel hypoglycemia agents in clinical trials, thereby rendering more attention focused on the role of renal tubules in DKD. Previous studies have demonstrated that morphological and functional changes in renal tubules are highly involved in the occurrence and development of DKD. Novel tubular biomarkers have shown some clinical importance. However, there are many challenges to transition into personalized diagnosis and guidance for individual therapy in clinical practice. Large-scale clinical trials suggested the clinical relevance of increased proximal reabsorption and hyperfiltration by sodium-glucose cotransporter-2 (SGLT2) to improve renal outcomes in patients with diabetes, further promoting the emergence of renal tubulocentric research. Therefore, this review summarized the recent progress in the pathophysiology associated with involved mechanisms of renal tubules, potential tubular biomarkers with clinical application, and renal tubular factors in DKD management. The mechanism of kidney protection and impressive results from clinical trials of SGLT2 inhibitors were summarized and discussed, offering a comprehensive update on therapeutic strategies targeting renal tubules.

Daily inhalation of hydrogen gas has a blood pressure-lowering effect in a rat model of hypertension

A recent clinical study demonstrated that haemodialysis with a dialysate containing hydrogen (H₂) improves blood pressure control in end-stage kidney disease. Herein, we examined whether H₂ has a salutary effect on hypertension in animal models. We subjected 5/6 nephrectomised rats to inhalation of either H₂ (1.3% H₂ + 21% O₂ + 77.7% N₂) or control (21% O₂ + 79% N₂) gas mixture for 1 h per day. H₂ significantly suppressed increases in blood pressure after 5/6 nephrectomy. The anti-hypertensive effect of H₂ was also confirmed in rats in a stable hypertensive state 3 weeks after nephrectomy. To examine the detailed effects of H₂ on hypertension, we used an implanted telemetry system to continuously monitor blood pressure. H₂ exerted an anti-hypertensive effect not only during daytime rest, but also during night-time activities. Spectral analysis of blood pressure variability revealed that H₂ improved autonomic imbalance, namely by suppressing the overly active sympathetic nervous system and augmenting parasympathetic nervous system activity; these effects co-occurred with the blood pressure-lowering effect. In conclusion, 1-h daily exposure to H₂ exerts an anti-hypertensive effect in an animal model of hypertension.

Molecular Mechanisms of SGLT2 Inhibitor on Cardiorenal Protection

The development of sodium-glucose transporter 2 inhibitor (SGLT2i) broadens the therapeutic strategies in treating diabetes mellitus. By inhibiting sodium and glucose reabsorption from the proximal tubules, the improvement in insulin resistance and natriuresis improved the cardiovascular mortality in diabetes mellitus (DM) patients. It has been known that SGLT2i also provided renoprotection by lowering the intraglomerular hypertension by modulating the pre- and post- glomerular vascular tone. The application of SGLT2i also provided metabolic and hemodynamic benefits in molecular aspects. The recent DAPA-CKD trial and EMPEROR-Reduced trial provided clinical evidence of renal and cardiac protection, even in non-DM patients. Therefore, the aim of the review is to clarify the hemodynamic and metabolic modulation of SGLT2i from the molecular mechanism.

Sodium glucose cotransporter (SGLT)-2 inhibitors alleviate the renal stress responsible for sympathetic activation

This review focuses on the pathogenic role of sodium glucose cotransporter (SGLT)-2 in the development of renal dysfunction and heart failure in patients with diabetes, by emphasizing the concept of reno-cardiac syndrome (kidney injury worsens cardiac condition) and by substantiating the deleterious effect of sympathetic overdrive in this context. Furthermore, the review proposes a mechanistic hypothesis to explain the benefits of SGLT2 inhibitors, specifically that SGLT-2 inhibitors reduce sympathetic activation at the renal level. To illustrate this point, several examples from both animal experiments and clinical observations are introduced. The bidirectional interaction of the heart and kidney were deeply implicated as an exacerbator of heart failure and renal failure without diabetes. Renal cortical ischemia and abnormal glucose metabolism of tubular epithelial cells are likely to exist as common pathologies in nondiabetic heart failure patients. It is no wonder why SGLT-2 inhibitors are specifically being studied even in the absence of diabetes, both for heart failure and also for renal failure.

A Paradigm Shift in the Treatment of Type 2 Diabetes and Heart Failure

Despite good control of all risk factors for myocardial infarction, including blood glucose, blood pressure, lipids, and smoking, the probability of heart failure is significantly higher in diabetic patients than in healthy individuals. This observational study shows that the current treatment guidelines, which focus on the prevention of myocardial infarction, are insufficient in preventing heart failure development. Now, understanding the mechanisms of heart failure in diabetic patients and developing treatment guidelines based on these mechanisms are urgently needed. Instead of narrowly viewing that heart failure is caused by poor cardiac function, we need to take a bird's-eye view that heart failure is caused by a shift in the hemodynamic set point (blood pressure, heart rate, circulating blood volume, and autonomic balance) toward overloading the heart due to the persistent drive of the pathological kidney-brain-heart coupling. Clinical evidence, which shows that sodium-glucose-coupled transporter [Na⁺/glucose co-transporter (SGLT)-2] inhibitors slowed the progression of chronic kidney disease (CKD) and reduced heart failure hospitalizations and deaths, underscores the importance of the renocardiac syndrome in heart failure development in diabetic patients.