Chronic kidney disease in type 1 diabetes: translation of novel type 2 diabetes therapeutics to individuals with type 1 diabetes

Current management of chronic kidney disease (CKD) in type 1 diabetes centres on glycaemic control, renin-angiotensin system inhibition and optimisation of risk factors including blood pressure, lipids and body weight. While these therapeutic approaches have significantly improved outcomes among people with type 1 diabetes and CKD, this population remains at substantial elevated risk for adverse kidney and cardiovascular events, with limited improvements over the last few decades. The significant burden of CKD and CVD in type 1 diabetes populations highlights the need to identify novel therapies with the potential for heart and kidney protection. Over the last decade, sodium-glucose cotransporter-2 inhibitors, glucagon-like peptide 1 receptor agonists and non-steroidal mineralocorticoid receptor antagonists have emerged as potent kidney-protective and/or cardioprotective agents in type 2 diabetes. The consistent, substantial kidney and cardiovascular benefits of these agents has led to their incorporation into professional guidelines as foundational care for type 2 diabetes. Furthermore, introduction of these agents into clinical practice has been accompanied by a shift in the focus of diabetes care from a 'glucose-centric' to a 'cardiorenal risk-centric' approach. In this review, we evaluate the potential translation of novel type 2 diabetes therapeutics to individuals with type 1 diabetes with the lens of preventing the development and progression of CKD.

Aldosterone antagonists in addition to renin angiotensin system antagonists for preventing the progression of chronic kidney disease

BACKGROUND

Treatment with angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) is used to reduce proteinuria and retard the progression of chronic kidney disease (CKD). However, resolution of proteinuria may be incomplete with these therapies and the addition of an aldosterone antagonist may be added to further prevent progression of CKD. This is an update of a Cochrane review first published in 2009 and updated in 2014.

OBJECTIVES

To evaluate the effects of aldosterone antagonists (selective (eplerenone), non-selective (spironolactone or canrenone), or non-steroidal mineralocorticoid antagonists (finerenone)) in adults who have CKD with proteinuria (nephrotic and non-nephrotic range) on: patient-centred endpoints including kidney failure (previously know as end-stage kidney disease (ESKD)), major cardiovascular events, and death (any cause); kidney function (proteinuria, estimated glomerular filtration rate (eGFR), and doubling of serum creatinine); blood pressure; and adverse events (including hyperkalaemia, acute kidney injury, and gynaecomastia).

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 13 January 2020 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that compared aldosterone antagonists in combination with ACEi or ARB (or both) to other anti-hypertensive strategies or placebo in participants with proteinuric CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Data were summarised using random effects meta-analysis. We expressed summary treatment estimates as a risk ratio (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes, or standardised mean difference (SMD) when different scales were used together with their 95% confidence interval (CI). Risk of bias were assessed using the Cochrane tool. Evidence certainty was evaluated using GRADE.

MAIN RESULTS

Forty-four studies (5745 participants) were included. Risk of bias in the evaluated methodological domains were unclear or high risk in most studies. Adequate random sequence generation was present in 12 studies, allocation concealment in five studies, blinding of participant and investigators in 18 studies, blinding of outcome assessment in 15 studies, and complete outcome reporting in 24 studies. All studies comparing aldosterone antagonists to placebo or standard care were used in addition to an ACEi or ARB (or both). None of the studies were powered to detect differences in patient-level outcomes including kidney failure, major cardiovascular events or death. Aldosterone antagonists had uncertain effects on kidney failure (2 studies, 84 participants: RR 3.00, 95% CI 0.33 to 27.65, I² = 0%; very low certainty evidence), death (3 studies, 421 participants: RR 0.58, 95% CI 0.10 to 3.50, I² = 0%; low certainty evidence), and cardiovascular events (3 studies, 1067 participants: RR 0.95, 95% CI 0.26 to 3.56; I² = 42%; low certainty evidence) compared to placebo or standard care. Aldosterone antagonists may reduce protein excretion (14 studies, 1193 participants: SMD -0.51, 95% CI -0.82 to -0.20, I² = 82%; very low certainty evidence), eGFR (13 studies, 1165 participants, MD -3.00 mL/min/1.73 m², 95% CI -5.51 to -0.49, I² = 0%, low certainty evidence) and systolic blood pressure (14 studies, 911 participants: MD -4.98 mmHg, 95% CI -8.22 to -1.75, I² = 87%; very low certainty evidence) compared to placebo or standard care. Aldosterone antagonists probably increase the risk of hyperkalaemia (17 studies, 3001 participants: RR 2.17, 95% CI 1.47 to 3.22, I² = 0%; moderate certainty evidence), acute kidney injury (5 studies, 1446 participants: RR 2.04, 95% CI 1.05 to 3.97, I² = 0%; moderate certainty evidence), and gynaecomastia (4 studies, 281 participants: RR 5.14, 95% CI 1.14 to 23.23, I² = 0%; moderate certainty evidence) compared to placebo or standard care. Non-selective aldosterone antagonists plus ACEi or ARB had uncertain effects on protein excretion (2 studies, 139 participants: SMD -1.59, 95% CI -3.80 to 0.62, I² = 93%; very low certainty evidence) but may increase serum potassium (2 studies, 121 participants: MD 0.31 mEq/L, 95% CI 0.17 to 0.45, I² = 0%; low certainty evidence) compared to diuretics plus ACEi or ARB. Selective aldosterone antagonists may increase the risk of hyperkalaemia (2 studies, 500 participants: RR 1.62, 95% CI 0.66 to 3.95, I² = 0%; low certainty evidence) compared ACEi or ARB (or both). There were insufficient studies to perform meta-analyses for the comparison between non-selective aldosterone antagonists and calcium channel blockers, selective aldosterone antagonists plus ACEi or ARB (or both) and nitrate plus ACEi or ARB (or both), and non-steroidal mineralocorticoid antagonists and selective aldosterone antagonists.

AUTHORS' CONCLUSIONS

The effects of aldosterone antagonists when added to ACEi or ARB (or both) on the risks of death, major cardiovascular events, and kidney failure in people with proteinuric CKD are uncertain. Aldosterone antagonists may reduce proteinuria, eGFR, and systolic blood pressure in adults who have mild to moderate CKD but may increase the risk of hyperkalaemia, acute kidney injury and gynaecomastia when added to ACEi and/or ARB.

Purinoceptors, renal microvascular function and hypertension

Proper renal blood flow (RBF) and glomerular filtration rate (GFR) are critical for maintaining normal blood pressure, kidney function and water and electrolyte homeostasis. The renal microvasculature expresses a multitude of receptors mediating vasodilation and vasoconstriction, which can influence glomerular blood flow and capillary pressure. Despite this, RBF and GFR remain quite stable when arterial pressure fluctuates because of the autoregulatory mechanism. ATP and adenosine participate in autoregulatory control of RBF and GFR via activation of two different purinoceptor families (P1 and P2). Purinoceptors are widely expressed in renal microvasculature and tubules. Emerging data show altered purinoceptor signaling in hypertension-associated kidney injury, diabetic nephropathy, sepsis, ischemia-reperfusion induced acute kidney injury and polycystic kidney disease. In this brief review, we highlight recent studies and new insights on purinoceptors regulating renal microvascular function and renal hemodynamics. We also address the mechanisms underlying renal microvascular injury and impaired renal autoregulation, focusing on purinoceptor signaling and hypertension-induced renal microvascular dysfunction. Interested readers are directed to several excellent and comprehensive reviews that recently covered the topics of renal autoregulation, and nucleotides in kidney function under physiological and pathophysiological conditions (Inscho 2009, Navar et al. 2008, Carlstrom et al. 2015, Vallon et al. 2020).

Activation and Inhibition of Sodium-Hydrogen Exchanger Is a Mechanism That Links the Pathophysiology and Treatment of Diabetes Mellitus With That of Heart Failure

The mechanisms underlying the progression of diabetes mellitus and heart failure are closely intertwined, such that worsening of one condition is frequently accompanied by worsening of the other; the degree of clinical acceleration is marked when the 2 coexist. Activation of the sodium-hydrogen exchanger in the heart and vasculature (NHE1 isoform) and the kidneys (NHE3 isoform) may serve as a common mechanism that links both disorders and may underlie their interplay. Insulin insensitivity and adipokine abnormalities (the hallmarks of type 2 diabetes mellitus) are characteristic features of heart failure; conversely, neurohormonal systems activated in heart failure (norepinephrine, angiotensin II, aldosterone, and neprilysin) impair insulin sensitivity and contribute to microvascular disease in diabetes mellitus. Each of these neurohormonal derangements may act through increased activity of both NHE1 and NHE3. Drugs used to treat diabetes mellitus may favorably affect the pathophysiological mechanisms of heart failure by inhibiting either or both NHE isoforms, and drugs used to treat heart failure may have beneficial effects on glucose tolerance and the complications of diabetes mellitus by interfering with the actions of NHE1 and NHE3. The efficacy of NHE inhibitors on the risk of cardiovascular events may be enhanced when heart failure and glucose intolerance coexist and may be attenuated when drugs with NHE inhibitory actions are given concomitantly. Therefore, the sodium-hydrogen exchanger may play a central role in the interplay of diabetes mellitus and heart failure, contribute to the physiological and clinical progression of both diseases, and explain certain drug-drug and drug-disease interactions that have been reported in large-scale randomized clinical trials.

Renal autoregulation in health and disease

Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.

Aldosterone antagonists for preventing the progression of chronic kidney disease

BACKGROUND

Treatment with angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) is increasingly used to reduce proteinuria and retard the progression of chronic kidney disease (CKD). However, resolution of proteinuria may be incomplete with these therapies and the addition of an aldosterone antagonist may be added to further prevent progression of CKD. This is an update of a review first published in 2009.

OBJECTIVES

To evaluate the effect of aldosterone antagonists (both selective (eplerenone) and non-selective (spironolactone)) alone or in combination with ACEi or ARB in adults who have CKD with proteinuria (nephrotic and non-nephrotic range) on: patient-centred endpoints including major cardiovascular events, hospitalisation and all-cause mortality; kidney function (proteinuria, glomerular filtration rate (GFR), serum creatinine, and need for renal replacement therapy; and adverse events (including gynaecomastia and hyperkalaemia).

SEARCH METHODS

For this update, we searched the Cochrane Renal Group's Specialised Register to 30 January 2013 using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that compared aldosterone antagonists alone or in combination with ACEi or ARB (or both) with other anti-hypertensive strategies or placebo.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Data were summarised using random effects meta-analysis. We tested for heterogeneity in estimated treatment effects using the Cochran Q test and I² statistic. We expressed summary treatment estimates as a risk ratio (RR) for dichotomous outcomes together with their 95% confidence intervals (CI) and mean difference (MD) for continuous outcomes, or standardised mean difference (SMD) when different scales were used.

MAIN RESULTS

We identified 27 studies (1549 participants) that were eligible for inclusion. These studies provided no data relating to aldosterone antagonists in addition to ACEi or ARB (or both) on patient-level outcomes including major cardiovascular events and mortality and progression to end-stage kidney disease (ESKD) requiring dialysis or transplantation.Compared with ACEi or ARB (or both), non-selective aldosterone antagonists (spironolactone) combined with ACEi or ARB (or both) significantly reduced 24-hour protein excretion (11 studies, 596 participants): SMD -0.61, 95% CI -1.08 to -0.13). There was a significant reduction in both systolic and diastolic blood pressure (BP) at the end of treatment with additional non-selective aldosterone antagonist therapy (systolic BP (10 studies, 556 participants): MD -3.44 mm Hg, 95% CI -5.05 to -1.83) (diastolic BP (9 studies, 520 participants): MD -1.73 mm Hg, 95% CI -2.83 to -0.62).However, we found that aldosterone antagonist treatment had imprecise effects at the end of treatment on GFR (9 studies, 528 participants; MD -2.55 mL/min/1.73 m², 95% CI -5.67 to 0.51), doubled the risk of hyperkalaemia (11 studies, 632 patients): RR 2.00, 95% CI 1.25 to 3.20; number needed to treat for an additional harmful outcome (NNTH): 7.2, 95% CI 3.4 to ∞) and increased the risk of gynaecomastia compared to ACEi or ARB (or both) (4 studies, 281 patients): RR 5.14, 95% CI 1.14 to 23.23; NNTH: 14.1, 95% CI 8.7 to 37.3).Most studies enrolled few patients (range 12 to 268) and were powered to observe differences in surrogate end points rather than patient-focused outcomes. Nine studies had a cross-over design and the majority of studies did not adequately report study methods to assess methods and study quality.

AUTHORS' CONCLUSIONS

Aldosterone antagonists reduced proteinuria and blood pressure in adults who had mild to moderate CKD and were treated with ACEi or ARB (or both), but increase hyperkalaemia and gynaecomastia. Whether adding aldosterone antagonists to ACEi or ARB (or both) reduced the risk of major cardiovascular events or ESKD in this population is unknown.

Effect of eplerenone, a selective aldosterone blocker, on the development of diabetic nephropathy in type 2 diabetic rats

BACKGROUND

Aldosterone antagonists are reported to have beneficial effects on diabetic nephropathy by effective blocking of the renin-angiotensin-aldosterone system. We investigated the renoprotective effect of the selective aldosterone receptor blocker eplerenone, the angiotensin converting enzyme inhibitor lisinopril, and combined eplerenone and lisinopril treatment in type 2 diabetic rats.

METHODS

ANIMALS WERE DIVIDED INTO SIX GROUPS AS FOLLOWS: Otsuka Long-Evans Tokushima Fatty (OLETF) rat control, OLETF rats treated with a low dose of eplerenone (50 mg/kg/day), OLETF rats treated with a high dose of eplerenone (200 mg/kg/day), OLETF rats treated with lisinopril (10 mg/kg/day), OLETF rats treated with a combination of both drugs (eplerenone 200 mg/kg/day and lisinopril 10 mg/kg/day), and obese non-diabetic Long-Evans Tokushima Otsuka rats for 26 weeks.

RESULTS

Urinary albumin excretion was significantly lower in the lisinopril group, but not in the eplerenone group. Urinary albumin excretion was decreased in the combination group than in the lisinopril group. Glomerulosclerosis and renal expression of type I and type IV collagen, plasminogen activator inhibitor-1, transforming growth factor-β1, connective tissue growth factor, and fibronectin mRNA were markedly decreased in the lisinopril, eplerenone, and combination groups.

CONCLUSION

Eplerenone and lisinopril combination showed additional benefits on type 2 diabetic nephropathy compared to monotherapy of each drug.

The renal vascular response to diabetes

PURPOSE OF REVIEW

Diabetes mellitus is the primary cause of end-stage renal disease, yet the mechanisms underlying diabetic nephropathy remain ill-defined. The widely accepted opinion holds that events occurring early during the course of diabetes engender the eventual decline in renal function. This review will summarize recent advances (published January 2008 through June 2009) regarding the renal vascular and glomerular functional changes that occur during the early stage of diabetes.

RECENT FINDINGS

Reduced C-peptide levels and increased cyclooxygenase-2 activity both seem to promote diabetic hyperfiltration, presumably via effects on afferent arteriolar tone. In addition, exaggerated tonic influences of K+ channels on afferent arteriolar function likely act in concert with impaired Ca2+ influx responses to changes in membrane potential to promote vasodilation. Mechanisms underlying these changes remain largely speculative. Diabetes may also alter autoregulation of renal blood flow and glomerular filtration rate, as well as provoke afferent arteriolar dilation secondary to alterations in proximal tubular reabsorption; however, conflicting evidence continues to flood the literature concerning these events.

SUMMARY

New evidence has expanded our appreciation of the complexity of events that promote preglomerular vasodilation during the early stage of diabetes; however, it seems that the more we know, the less we understand.