Cardiorenal Protection in Diabetic Kidney Disease

Narrative review investigating the nephroprotective mechanisms of sodium glucose cotransporter type 2 inhibitors in diabetic and nondiabetic patients with chronic kidney disease

Background and aims

Outcome trials using sodium glucose cotransporter type 2 inhibitors have consistently shown their potential to preserve kidney function in diabetic and nondiabetic patients. Several mechanisms have been introduced which may explain the nephroprotective effect of sodium glucose cotransporter type 2 inhibitors beyond lowering blood glucose. This current narrative review has the objective to describe main underlying mechanisms causing a nephroprotective effect and to show similarities as well as differences between proposed mechanisms which can be observed in patients with diabetic and nondiabetic chronic kidney disease.

Methods

We performed a narrative review of the literature on Pubmed and Embase. The research string comprised various combinations of items including "chronic kidney disease", "sodium glucose cotransporter 2 inhibitor" and "mechanisms". We searched for original research and review articles published until march, 2022. The databases were searched independently and the agreements by two authors were jointly obtained.

Results

Sodium glucose cotransporter type 2 inhibitors show systemic, hemodynamic, and metabolic effects. Systemic effects include reduction of blood pressure without compensatory activation of the sympathetic nervous system. Hemodynamic effects include restoration of tubuloglomerular feedback which may improve pathologic hyperfiltration observed in most cases with chronic kidney disease. Current literature indicates that SGLT2i may not improve cortical oxygenation and may reduce medullar oxygenation.

Conclusion

Sodium glucose cotransporter type 2 inhibitors cause nephroprotective effects by several mechanisms. However, several mediators which are involved in the underlying pathophysiology may be different between diabetic and nondiabetic patients.

SGLT2 and DPP4 inhibitors improve Alzheimer's disease-like pathology and cognitive function through distinct mechanisms in a T2D-AD mouse model

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2D) share common features, including insulin resistance. Brain insulin resistance has been implicated as a key factor in the pathogenesis of AD. Recent studies have demonstrated that anti-diabetic drugs sodium-glucose cotransporter-2 inhibitor (SGLT2-i) and dipeptidyl peptidase-4 inhibitor (DPP4-i) improve insulin sensitivity and provide neuroprotection. However, the effects of these two inhibitors on the brain metabolism and insulin resistance remain uninvestigated. We developed a T2D-AD mouse model using a high-fat diet (HFD) for 19 weeks along with a single dose of streptozotocin (100 mg/kg, intraperitoneally) at the fourth week of HFD initiation. Subsequently, the animals were treated with SGLT2-i (empagliflozin, 25 mg/kg/day orally [p.o.]) and DPP4-i (sitagliptin, 100 mg/kg/day p.o.) for 7 weeks. Subsequently, behavioral tests were performed, and the expression of insulin signaling, AD-related, and other signaling pathway proteins in the brain were examined. T2D-AD mice not only showed increased blood glucose levels and body weight but also insulin resistance. SGLT2-i and DPP4-i effectively ameliorated insulin sensitivity and reduced body weight in these mice. Furthermore, SGLT2-i and DPP4-i significantly improved hippocampal-dependent learning, memory, and cognitive functions in the T2D-AD mouse model. Interestingly, SGLT2-i and DPP4-i reduced the hyperphosphorylated tau (pTau) levels and amyloid β (Aβ) accumulation and enhanced brain insulin signaling. SGLT2-i reduced pTau accumulation through the angiotensin converting enzyme-2/angiotensin (1-7)/ mitochondrial assembly receptor axis, whereas DPP4-i reduced Aβ accumulation by increasing insulin-degrading enzyme levels. These findings suggest that SGLT2-i and DPP4-i prevent AD-like pathology and cognitive dysfunction in T2D mice potentially through affecting brain insulin signaling via different mechanisms.

Intrarenal Mechanisms of Sodium-Glucose Cotransporter-2 Inhibitors on Tubuloglomerular Feedback and Natriuresis

When sodium-glucose cotransporter-2 (SGLT2) inhibitors were first introduced a decade ago, no one expected them to have substantial effects beyond their known glucose-lowering effects, until the emergence of evidence of their robust renal and cardiovascular benefits showing that they could attenuate progression of kidney disease, irrespective of diabetes, as well as prevent the development of acute kidney injury. Still, the precise and elaborate mechanisms underlying the major organ protection of SGLT2 inhibitors remain unclear. SGLT2 inhibitors inhibit the reabsorption of sodium and glucose in the proximal tubule of the kidney and then recovers tubuloglomerular feedback, whereby SGLT2 inhibitors reduce glomerular hyperfiltration. This simple demonstration of their beneficial effects has perplexed experts in seeking more plausible and as yet undisclosed explanations for the whole effects of SGLT2 inhibitors, including metabolism reprogramming and the modulation of hypoxia, inflammation, and oxidative stress. Given that the renal benefits of SGLT2 inhibitors in patients with kidney disease but without diabetes were comparable to those seen in patients with diabetes, it may be reasonable to keep the emphasis on their hemodynamic actions. In this context, the aim of the present review is to provide a comprehensive overview of renal hemodynamics in individuals with diabetes who are treated with SGLT2 inhibitors, with a focus on natriuresis associated with the regulation of tubuloglomerular feedback and potential aquaresis. Throughout the discussion of alterations in renal sodium and water transports, particular attention will be given to the potential enhancement of adenosine and its receptors following SGLT2 inhibition.

Renal Protection of Mineralocorticoid Receptor Antagonist, Finerenone, in Diabetic Kidney Disease

Chronic kidney disease (CKD) is the most common cause of end-stage renal disease in patients with type 2 diabetes mellitus (T2DM). CKD increases the risk of cardiovascular diseases; therefore, its prevention and treatment are important. The prevention of diabetic kidney disease (DKD) can be achieved through intensive glycemic control and blood pressure management. Additionally, DKD treatment aims to reduce albuminuria and improve kidney function. In patients with T2DM, renin-angiotensin-aldosterone system inhibitors, sodium glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists can delay the progression of DKD. Hence, there is a need for novel treatments that can effectively suppress DKD progression. Finerenone is a first-in-class nonsteroidal mineralocorticoid receptor antagonist with clinically proven efficacy in improving albuminuria, estimated glomerular filtration rate, and risk of cardiovascular events in early and advanced DKD. Therefore, finerenone is a promising treatment option to delay DKD progression. This article reviews the mechanism of renal effects and major clinical outcomes of finerenone in DKD.

Finerenone: A Potential Treatment for Patients with Chronic Kidney Disease and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) affects an estimated 463 million people worldwide, equivalent to 1 in 11 adults. Moreover, the rapid growth of this disease has resulted in a high incidence of diabetic kidney disease (DKD), which, together with hypertension, is the main cause of chronic kidney disease (CKD). Hyperglycaemia, low-grade inflammation, altered lipid metabolism and hyperactivation of the renin-angiotensin-aldosterone system (RAAS) seem to be interrelated mechanisms contributing to both T2DM and microvascular complications. The introduction of drugs such as sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide 1 receptor agonists has improved the ability to slow the progression of DKD, and has also demonstrated benefits in cardiovascular disease. Beyond the effects of these novel antidiabetic drugs, a body of evidence suggests that the overactivation of the mineralocorticoid receptor also contributes to CKD progression. Moreover, new and ongoing trials have demonstrated that the selective nonsteroidal mineralocorticoid receptor antagonist (MRA) finerenone improves the risk of CKD progression and cardiovascular events in patients with CKD and T2DM and optimized RAAS blockade. We review the rationale for the development and use of MRA drugs to slow CKD progression in patients with DKD, as well as other pleiotropic effects, and highlight the warnings associated with these agents.

Sodium-Glucose Cotransporter 2 Inhibitors Mechanisms of Action: A Review

Sodium-Glucose Cotransporter 2 inhibitors (SGLT2i), or gliflozins, are a group of antidiabetic drugs that have shown improvement in renal and cardiovascular outcomes in patients with kidney disease, with and without diabetes. In this review, we will describe the different proposed mechanisms of action of SGLT2i. Gliflozins inhibit renal glucose reabsorption by blocking the SGLT2 cotransporters in the proximal tubules and causing glucosuria. This reduces glycemia and lowers HbA_1c by ~1.0%. The accompanying sodium excretion reverts the tubuloglomerular feedback and reduces intraglomerular pressure, which is central to the nephroprotective effects of SGLT2i. The caloric loss reduces weight, increases insulin sensitivity, lipid metabolism, and likely reduces lipotoxicity. Metabolism shifts toward gluconeogenesis and ketogenesis, thought to be protective for the heart and kidneys. Additionally, there is evidence of a reduction in tubular cell glucotoxicity through reduced mitochondrial dysfunction and inflammation. SGLT2i likely reduce kidney hypoxia by reducing tubular energy and oxygen demand. SGLT2i improve blood pressure through a negative sodium and water balance and possibly by inhibiting the sympathetic nervous system. These changes contribute to the improvement of cardiovascular function and are thought to be central in the cardiovascular benefits of SGLT2i. Gliflozins also reduce hepcidin levels, improving erythropoiesis and anemia. Finally, other possible mechanisms include a reduction in inflammatory markers, fibrosis, podocyte injury, and other related mechanisms. SGLT2i have shown significant and highly consistent benefits in renal and cardiovascular protection. The complexity and interconnectedness of the primary and secondary mechanisms of action make them a most interesting and exciting pharmacologic group.

Sodium-Glucose Cotransporter 2 Inhibitors, All-Cause Mortality, and Cardiovascular Outcomes in Adults with Type 2 Diabetes: A Bayesian Meta-Analysis and Meta-Regression

Background

This study aimed to assess the effectiveness of sodium‐glucose cotransporter 2 inhibitors in reducing the incidence of mortality and cardiovascular outcomes in adults with type 2 diabetes.

Methods and Results

We conducted a Bayesian meta‐analysis of randomized controlled trials comparing sodium‐glucose cotransporter 2 inhibitors with placebo. We used meta‐regression to examine the association between treatment effects and control group event rates as measures of cardiovascular baseline risk. Fifty‐three randomized controlled trials were included in our synthesis. Empagliflozin, canagliflozin, and dapagliflozin reduced the incidence of all‐cause mortality (empagliflozin: rate ratio [RR], 0.79; 95% credibility interval [CrI], 0.63–0.97; canagliflozin: RR, 0.86; 95% CrI, 0.69–1.05; dapagliflozin: RR, 0.86; 95% CrI, 0.72–1.01) and cardiovascular mortality (empagliflozin: RR, 0.78; 95% CrI, 0.61–1.00; canagliflozin: RR, 0.83; 95% CrI, 0.63–1.05; dapagliflozin: RR, 0.88; 95% CrI, 0.71–1.08), with a 90.1% to 98.7% probability for the true RR to be <1.00 for both outcomes. There was little evidence for ertugliflozin and sotagliflozin versus placebo for reducing all‐cause and cardiovascular mortality. There was no association between treatment effects for all‐cause and cardiovascular mortality and the control group event rates. There was evidence for a reduction in the incidence of heart failure for empagliflozin, canagliflozin, dapagliflozin, and ertugliflozin versus placebo (probability RR <1.00 of ≥99.3%) and weaker, albeit positive, evidence for acute myocardial infarction for the first 3 agents (probability RR <1.00 of 89.0%–95.2%). There was little evidence of any agent except canagliflozin for reducing the incidence of stroke.

Conclusions

Empagliflozin, canagliflozin, and dapagliflozin reduced the incidence of all‐cause and cardiovascular mortality versus placebo. Treatment effects of sodium‐glucose cotransporter 2 inhibitors versus placebo do not vary by baseline risk.

Nonsteroidal mineralocorticoid receptor antagonism for cardiovascular and renal disorders - New perspectives for combination therapy

During the recent 30 years, there has been a dramatic increase in knowledge about the role of aldosterone and the mineralocorticoid receptor (MR) in the pathophysiology of cardiovascular (CV) and kidney diseases. The scientific perspective on the aldosterone/MR ensemble extended from a previously renal epithelial-centered focus on sodium-potassium exchange to a broader view as systemic modulators of extracellular matrix, inflammation and fibrosis. Spironolactone was launched as the first antagonist of aldosterone 27 years before the MR was cloned. It was classified as a potassium-sparing diuretic, based on its initial clinical characterization as a diuretic and its preferred activity to compensate for the potassium loss induced by loop diuretics when used in combination. The second steroidal MR antagonist was eplerenone which was discovered at a time when the role of aldosterone and MR in cardiac fibrosis was rediscovered. The constraint of developing potentially life-threatening hyperkalaemia when used in combination with other inhibitors of the renin-angiotensin-system (RAS) in patients with reduced kidney function initiated extensive research and development activities with the goal to identify novel nonsteroidal MR antagonists with an improved benefit-risk ratio. Here we summarize major current clinical trials with MRAs in different CV and renal diseases. Addition of the nonsteroidal MRA finerenone to optimal RAS blockade recently reduced CV and kidney outcomes in two large phase III trials in patients with chronic kidney disease (CKD) and type 2 diabetes (T2D). We provide an outlook on further opportunities for combination therapy of nonsteroidal MRA finerenone with RAS inhibitors and sodium-glucose cotransporter-2 inhibitors (SGLT2i).