Mechanisms mediating the diuretic and natriuretic actions of the incretin hormone glucagon-like peptide-1

The Regulation of Metabolic Homeostasis by Incretins and the Metabolic Hormones Produced by Pancreatic Islets

In healthy humans, the complex biochemical interplay between organs maintains metabolic homeostasis and pathological alterations in this process result in impaired metabolic homeostasis, causing metabolic diseases such as diabetes and obesity, which are major global healthcare burdens. The great advancements made during the last century in understanding both metabolic disease phenotypes and the regulation of metabolic homeostasis in healthy individuals have yielded new therapeutic options for diseases like type 2 diabetes (T2D). However, it is unlikely that highly desirable more efficacious treatments will be developed for metabolic disorders until the complex systemic regulation of metabolic homeostasis becomes more intricately understood. Hormones produced by pancreatic islet beta-cells (insulin) and alpha-cells (glucagon) are pivotal for maintaining metabolic homeostasis; the activity of insulin and glucagon are reciprocally correlated to achieve strict control of glucose levels (normoglycaemia). Metabolic hormones produced by other pancreatic islet cells and incretins produced by the gut are also crucial for maintaining metabolic homeostasis. Recent studies highlighted the incomplete understanding of metabolic hormonal synergism and, therefore, further elucidation of this will likely lead to more efficacious treatments for diseases such as T2D. The objective of this review is to summarise the systemic actions of the incretins and the metabolic hormones produced by the pancreatic islets and their interactions with their respective receptors.

Emerging therapeutic landscape: Incretin agonists in chronic kidney disease management

The increasing incidence of chronic kidney disease (CKD) poses a significant public health concern, prompting heightened attention to its treatment. Incretins, including glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide, are intestinal peptides released after nutrient intake, known for their hypoglycemic effects in diabetes management. Recent advancements highlight the promising outcomes of GLP-1 receptor agonists in reducing CKD risk factors and improving renal outcomes. The multifaceted functions of GLP-1, such as its anti-obesity, anti-hypertensive, anti-hyperglycemic, anti-lipid, anti-inflammatory, and endothelial function protective properties, contribute to its potential as a therapeutic agent for CKD. Although experiments suggest the potential benefits of incretin in CKD, a comprehensive understanding of its specific mechanisms is still lacking. This review aims to provide a detailed examination of current evidence and potential future directions, emphasizing the promising yet evolving landscape of incretin agonists in the context of CKD.

Incretin and glucagon receptor polypharmacology in chronic kidney disease

Chronic kidney disease is a debilitating condition associated with significant morbidity and mortality. In recent years, the kidney effects of incretin-based therapies, particularly glucagon-like peptide-1 receptor agonists (GLP-1RAs), have garnered substantial interest in the management of type 2 diabetes and obesity. This review delves into the intricate interactions between the kidney, GLP-1RAs, and glucagon, shedding light on their mechanisms of action and potential kidney benefits. Both GLP-1 and glucagon, known for their opposing roles in regulating glucose homeostasis, improve systemic risk factors affecting the kidney, including adiposity, inflammation, oxidative stress, and endothelial function. Additionally, these hormones and their pharmaceutical mimetics may have a direct impact on the kidney. Clinical studies have provided evidence that incretins, including those incorporating glucagon receptor agonism, are likely to exhibit improved kidney outcomes. Although further research is necessary, receptor polypharmacology holds promise for preserving kidney function through eliciting vasodilatory effects, influencing volume and electrolyte handling, and improving systemic risk factors.

Comparative effects of incretin-based therapy on doxorubicin-induced nephrotoxicity in rats: the role of SIRT1/Nrf2/NF-κB/TNF-α signaling pathways

Introduction: Nephrotoxicity represents a major complication of using doxorubicin (DOX) in the management of several types of cancers. Increased oxidative stress and the activation of inflammatory mediators play outstanding roles in the development of DOX-induced kidney damage. This study aimed to investigate whether the two pathways of incretin-based therapy, glucagon-like peptide-1 receptor agonist (presented as semaglutide, SEM) and dipeptidyl peptidase-4 inhibitor (presented as alogliptin, ALO), differentially protect against DOX-induced nephrotoxicity in rats and to clarify the underlying molecular mechanisms. Methods: Adult male rats were divided into six groups: control (received the vehicle), DOX (20 mg/kg, single I.P. on day 8), DOX + ALO (20 mg/kg/day, P.O. for 10 days), DOX + SEM (12 μg/kg/day, S.C. for 10 days), ALO-alone, and SEM-alone groups. At the end of the study, the animals were sacrificed and their kidney functions, oxidative stress, and inflammatory markers were assessed. Kidney sections were also subjected to histopathological examinations. Results: The co-treatment with either ALO or SEM manifested an improvement in the kidney functions, as evidenced by lower serum concentrations of creatinine, urea, and cystatin C compared to the DOX group. Lower levels of MDA, higher levels of GSH, and increased SOD activity were observed in either ALO- or SEM-treated groups than those observed in the DOX group. DOX administration resulted in decreased renal expressions of sirtuin 1 (SIRT1) and Nrf2 with increased NF-κB and TNF-α expressions, and these effects were ameliorated by treatment with either ALO or SEM. Discussion: Co-treatment with either ALO or SEM showed a renoprotective effect that was mediated by their antioxidant and anti-inflammatory effects via the SIRT1/Nrf2/NF-κB/TNF-α pathway. The fact that both pathways of the incretin-based therapy demonstrate an equally positive effect in alleviating DOX-induced renal damage is equally noteworthy.

Effects of Dipeptidyl Peptidase-4 Inhibitor and Angiotensin-Converting Enzyme Inhibitor on Experimental Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease in the United States and worldwide. Proteinuria is a major marker of the severity of injury. Dipeptidyl peptidase-4 inhibitor (DPP-4I) increases incretin-related insulin production and is, therefore, used to treat diabetes. We investigated whether DPP4I could have direct effect on kidney independent of its hypoglycemic activity. We, therefore, tested the effects of DPP4I with or without angiotensin-converting enzyme inhibitor (ACEI) on the progression of diabetic nephropathy and albuminuria in a murine model of DKD. eNOS-/-db/db mice were randomized to the following groups at age 10 weeks and treated until sacrifice: baseline (sacrificed at week 10), untreated control, ACEI, DPP4I, and combination of DPP4I and ACEI (Combo, sacrificed at week 18). Systemic parameters and urine albumin-creatinine ratio were assessed at baseline, weeks 14, and 18. Kidney morphology, glomerular filtration rate (GFR), WT-1, a marker for differentiated podocytes, podoplanin, a marker of foot process integrity, glomerular collagen IV, and alpha-smooth muscle actin were assessed at the end of the study. All mice had hyperglycemia and proteinuria at study entry at week 10. Untreated control mice had increased albuminuria, progression of glomerular injury, and reduced GFR at week 18 compared with baseline. DPP4I alone reduced blood glucose and kidney DPP-4 activity but failed to protect against kidney injury compared with untreated control. ACEI alone and combination groups showed significantly reduced albuminuria and glomerular injury, and maintained GFR and WT-1+ cells. Only the combination group had significantly less glomerular collagen IV deposition and more podoplanin preservation than the untreated control. DPP-4I alone does not decrease the progression of kidney injury in the eNOS-/-db/db mouse model, suggesting that targeting only hyperglycemia is not an optimal treatment strategy for DKD. Combined DPP-4I with ACEI added more benefit to reducing the glomerular matrix.

Incretin Therapies for Patients with Type 2 Diabetes and Chronic Kidney Disease

Since the early 2000s, an influx of novel glucose-lowering agents has changed the therapeutic landscape for treatment of diabetes and diabetes-related complications. Glucagon-like peptide-1 (GLP-1) receptor agonists represent an important therapeutic class for the management of type 2 diabetes (T2D), demonstrating benefits beyond glycemic control, including lowering of blood pressure and body weight, and importantly, decreased risk of development of new or worsening chronic kidney disease (CKD) and reduced rates of atherosclerotic cardiovascular events. Plausible non-glycemic mechanisms that benefit the heart and kidneys with GLP-1 receptor agonists include anti-inflammatory and antioxidant effects. Further supporting their use in CKD, the glycemic benefits of GLP-1 receptor agonists are preserved in moderate-to-severe CKD. Considering current evidence, major guideline-forming organizations recommend the use of GLP-1 receptor agonists in cases of T2D and CKD, especially in those with obesity and/or in those with high cardiovascular risk or established heart disease. Evidence continues to build that supports benefits to the heart and kidneys of the dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) receptor agonist tirzepatide. Ongoing outcome and mechanistic studies will continue to inform our understanding of the role of GLP-1 and dual GLP-1/GIP receptor agonists in diverse patient populations with kidney disease.

GLP1 Receptor Agonists-Effects beyond Obesity and Diabetes

Glucagon-like peptide-1 receptor agonists (GLP1RA) have been transformative for patients and clinicians in treating type-2 diabetes and obesity. Drugs of this class, the bioavailability of which is continuously improving, enable weight loss and control blood glucose with minimal unwanted side effects. Since adopting GLP1RA for treating metabolic diseases, animal and clinical studies have revealed their beneficial effects on several other pathologies, including cardiovascular diseases, neurodegeneration, kidney disease, and cancer. A notable commonality between these diseases is their association with older age. Clinical trials and preclinical data suggest that GLP1RA may improve outcomes in these aging-related diseases. Some of the benefits of GLP1RA may be indirect due to their effects on obesity and glucose metabolism. However, there is building evidence that GLP1RA may also act directly on multiple organs implicated in aging-related pathology. This review aims to compile the studies reporting the effects of GLP1RA on aging-related diseases and discuss potential underlying mechanisms.

Chronic kidney outcomes associated with GLP-1 receptor agonists versus long-acting insulins among type 2 diabetes patients requiring intensive glycemic control: a nationwide cohort study

BACKGROUND

Effectiveness of glucagon-like peptide-1 receptor agonists (GLP-1RAs) versus long-acting insulins (LAIs) on preventing progressive chronic kidney outcomes is uncertain for type 2 diabetes (T2D) patients requiring intensive glycemic control. This study aimed to evaluate comparative effectiveness of GLP-1RA versus LAI therapies on progressive chronic kidney outcomes among patients having poor glycemic control and requiring these injectable glucose-lowering agents (GLAs).

METHODS

7279 propensity-score-matched pairs of newly stable GLP-1RA and LAI users in 2013-2018 were identified from Taiwan's National Health Insurance Research Database and followed until death or 12/31/2019 (intention-to-treat). Subdistributional hazard model was utilized to assess the comparative effectiveness on a composite renal outcome (i.e., renal insufficiency [eGFR < 15 mL/min/1.73 m2], dialysis-dependent end-stage renal disease [ESRD], or renal death) and its individual components. Sensitivity analyses with the as-treated scenario, PS weighting, high-dimensional PS techniques, using cardiovascular diseases (CVDs) as positive control outcomes, and interaction testing were performed.

RESULTS

In primary analyses, subdistribution hazard ratios (95% CIs) for initiating GLP-1RAs versus LAIs for the composite renal outcome, renal insufficiency, dialysis-dependent ESRD, and renal death were 0.39 (0.30-0.51), 0.43 (0.32-0.57), 0.29 (0.20-0.43), and 0.28 (0.15-0.51), respectively. Sensitivity analysis results were consistent with the primary findings. CVD history and the medication possession ratio of prior oral GLAs possessed modification effects on GLP-1RA-associated kidney outcomes.

CONCLUSION

Using GLP-1RAs versus LAIs was associated with kidney benefits in T2D patients requiring intensive glycemic control and potentially at high risk of kidney progression. GLP-1RAs should be prioritized to patients with CVDs or adherence to prior oral GLAs to maximize kidney benefits.

Incretins and cardiovascular disease: to the heart of type 2 diabetes?

Major cardiovascular outcome trials and real-life observations have proven that glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs), regardless of structural GLP-1 homology, exert clinically relevant cardiovascular protection. GLP-1RAs provide cardioprotective benefits through glycaemic and non-glycaemic effects, including improved insulin secretion and action, body-weight loss, blood-pressure lowering and improved lipid profile, as well as via direct effects on the heart and vasculature. These actions are likely combined with anti-inflammatory and antioxidant properties that translate into robust and consistent reductions in atherothrombotic events, particularly in people with type 2 diabetes and established atherosclerotic CVD. GLP-1RAs may also have an impact on obesity and chronic kidney disease, conditions for which cardiovascular risk-reducing options are limited. The available evidence has prompted professional and medical societies to recommend GLP-1RAs for mitigation of the cardiovascular risk in people with type 2 diabetes. This review summarises the clinical evidence for cardiovascular protection with use of GLP-1RAs and the main mechanisms underlying this effect. Moreover, it looks into how the availability of upcoming dual and triple incretin receptor agonists might expand the possibility for cardiovascular protection in people with type 2 diabetes.

Sodium-glucose cotransporter-2 inhibitors in heart failure: Potential decongestive mechanisms and current clinical studies

Congestion is a key pathophysiological feature of heart failure (HF) syndrome that drives most of the clinical manifestations of acute HF and is related with poor quality of life and outcomes. Therefore, safe and effective decongestion is an important therapeutic target in the management of acute HF and despite the use of guideline-recommended loop diuretics, adequate decongestion is not always achieved in patients with acute HF. Recently, sodium-glucose cotransporter-2 (SGLT-2) inhibitors have been shown to provide clinical benefits across a broad spectrum of patients with HF, including consistent reduction in the risk of acute HF episodes. While the exact mechanisms underlying these benefits remain a matter of debate, a growing body of evidence suggests that effective decongestion may be partly responsible, especially in the setting of acute HF. In this review, we discuss the potential decongestive mechanisms of SGLT-2 inhibitors, such as osmotic diuresis, natriuresis, preservation of glomerular filtration and facilitation of interstitial drainage, which can collectively translate into effective and safe decongestion. Furthermore, we provide a comprehensive review of up-to-date clinical data of SGLT-2 inhibitor use in the acute HF population.

Tubular injury in diabetic kidney disease: molecular mechanisms and potential therapeutic perspectives

Diabetic kidney disease (DKD) is a chronic complication of diabetes and the leading cause of end-stage renal disease (ESRD) worldwide. Currently, there are limited therapeutic drugs available for DKD. While previous research has primarily focused on glomerular injury, recent studies have increasingly emphasized the role of renal tubular injury in the pathogenesis of DKD. Various factors, including hyperglycemia, lipid accumulation, oxidative stress, hypoxia, RAAS, ER stress, inflammation, EMT and programmed cell death, have been shown to induce renal tubular injury and contribute to the progression of DKD. Additionally, traditional hypoglycemic drugs, anti-inflammation therapies, anti-senescence therapies, mineralocorticoid receptor antagonists, and stem cell therapies have demonstrated their potential to alleviate renal tubular injury in DKD. This review will provide insights into the latest research on the mechanisms and treatments of renal tubular injury in DKD.

Mechanisms and clinical applications of incretin therapies for diabetes and chronic kidney disease

PURPOSE OF REVIEW

Diabetic kidney disease (DKD) is the leading cause of kidney failure worldwide. Development of DKD increases risks for cardiovascular events and death. Glucagon-like peptide-1 (GLP-1) receptor agonist have demonstrated improved cardiovascular and kidney outcomes in large-scale clinical trials.

RECENT FINDING

GLP-1 and dual GLP-1/glucose-depending insulinotropic polypeptide (GIP) receptor agonists have robust glucose-lowering efficacy with low risk of hypoglycemia even in advanced stages of DKD. Initially approved as antihyperglycemic therapies, these agents also reduce blood pressure and body weight. Cardiovascular outcome and glycemic lowering trials have reported decreased risks of development and progression of DKD and atherosclerotic cardiovascular events for GLP-1 receptor agonists. Kidney and cardiovascular protection is mediated partly, but not entirely, by lowering of glycemia, body weight, and blood pressure. Experimental data have identified modulation of the innate immune response as a biologically plausible mechanism underpinning kidney and cardiovascular effects.

SUMMARY

An influx of incretin-based therapies has changed the landscape of DKD treatment. GLP-1 receptor agonist use is endorsed by all major guideline forming organizations. Ongoing clinical trials and mechanistic studies with GLP-1 and dual GLP-1/GIP receptor agonists will further define the roles and pathways for these agents in the treatment of DKD.

Osmoadaptive GLP-1R signalling in hypothalamic neurones inhibits antidiuretic hormone synthesis and release

OBJECTIVES

The excessive release of the antidiuretic hormone vasopressin is implicated in many diseases including cardiovascular disease, diabetes, obesity, and metabolic syndrome. Once thought to be elevated as a consequence of diseases, data now supports a more causative role. We have previously identified CREB3L1 as a transcription factor that co-ordinates vasopressin synthesis and release in the hypothalamus. The objective here was to identify mechanisms orchestrated by CREB3L1 that co-ordinate vasopressin release.

METHODS

We mined Creb3l1 knockdown SON RNA-seq data to identify downstream target genes. We proceeded to investigate the expression of these genes and associated pathways in the supraoptic nucleus of the hypothalamus in response to physiological and pharmacological stimulation. We used viruses to selectively knockdown gene expression in the supraoptic nucleus and assessed physiological and metabolic parameters. We adopted a phosphoproteomics strategy to investigate mechanisms that facilitate hormone release by the pituitary gland.

RESULTS

We discovered glucagon like peptide 1 receptor (Glp1r) as a downstream target gene and found increased expression in stimulated vasopressin neurones. Selective knockdown of supraoptic nucleus Glp1rs resulted in decreased food intake and body weight. Treatment with GLP-1R agonist liraglutide decreased vasopressin synthesis and release. Quantitative phosphoproteomics of the pituitary neurointermediate lobe revealed that liraglutide initiates hyperphosphorylation of presynapse active zone proteins that control vasopressin exocytosis.

CONCLUSION

In summary, we show that GLP-1R signalling inhibits the vasopressin system. Our data advises that hydration status may influence the pharmacodynamics of GLP-1R agonists so should be considered in current therapeutic strategies.

The blood pressure lowering effects of glucagon-like peptide-1 receptor agonists: A mini-review of the potential mechanisms

The incretin hormone glucagon-like peptide 1 (GLP-1) is a key component of the signaling mechanisms promoting glucose homeostasis. Clinical and experimental studies demonstrated that GLP-1 receptor agonists, including GLP-1 itself, have favorable effects on blood pressure and reduce the risk of major cardiovascular events, independently of their effect on glycemic control. GLP-1 receptors are present in the hypothalamus and brainstem, the carotid body, the vasculature, and the kidneys. These organs are involved in blood pressure regulation, have their function altered in hypertension, and are positively benefited by the treatment with GLP-1 receptor agonists. Here, we discuss the potential mechanisms whereby activation of GLP-1R signaling exerts blood pressure-lowering effects beyond glycemic control.

Links between Metabolic Syndrome and Hypertension: The Relationship with the Current Antidiabetic Drugs

Hypertension poses a significant burden in the general population, being responsible for increasing cardiovascular morbidity and mortality, leading to adverse outcomes. Moreover, the association of hypertension with dyslipidaemia, obesity, and insulin resistance, also known as metabolic syndrome, further increases the overall cardiovascular risk of an individual. The complex pathophysiological overlap between the components of the metabolic syndrome may in part explain how novel antidiabetic drugs express pleiotropic effects. Taking into consideration that a significant proportion of patients do not achieve target blood pressure values or glucose levels, more efforts need to be undertaken to increase awareness among patients and physicians. Novel drugs, such as incretin-based therapies and renal glucose reuptake inhibitors, show promising results in decreasing cardiovascular events in patients with metabolic syndrome. The effects of sodium-glucose co-transporter-2 inhibitors are expressed at different levels, including renoprotection through glucosuria, natriuresis and decreased intraglomerular pressure, metabolic effects such as enhanced insulin sensitivity, cardiac protection through decreased myocardial oxidative stress and, to a lesser extent, decreased blood pressure values. These pleiotropic effects are also observed after treatment with glucagon-like peptide-1 receptor agonists, positively influencing the cardiovascular outcomes of patients with metabolic syndrome. The initial combination of the two classes may be the best choice in patients with type 2 diabetes mellitus and multiple cardiovascular risk factors because of their complementary mechanisms of action. In addition, the novel mineralocorticoid receptor antagonists show significant cardio-renal benefits, as well as anti-inflammatory and anti-fibrotic effects. Overall, the key to better control of hypertension in patients with metabolic syndrome is to consider targeting multiple pathogenic mechanisms, using a combination of the different therapeutic agents, as well as drastic lifestyle changes. This article will briefly summarize the association of hypertension with metabolic syndrome, as well as take into account the influence of antidiabetic drugs on blood pressure control.

Repurposing of Drugs for Cardiometabolic Disorders: An Out and Out Cumulation

Cardiometabolic disorders (CMD) is a constellation of metabolic predisposing factors for atherosclerosis such as insulin resistance (IR) or diabetes mellitus (DM), systemic hypertension, central obesity, and dyslipidemia. Cardiometabolic diseases (CMDs) continue to be the leading cause of mortality in both developed and developing nations, accounting for over 32% of all fatalities globally each year. Furthermore, dyslipidemia, angina, arrhythmia, heart failure, myocardial infarction (MI), and diabetes mellitus are the major causes of death, accounting for an estimated 19 million deaths in 2012. CVDs will kill more than 23 million individuals each year by 2030. Nonetheless, new drug development (NDD) in CMDs has been increasingly difficult in recent decades due to increased costs and a lower success rate. Drug repositioning in CMDs looks promising in this scenario for launching current medicines for new therapeutic indications. Repositioning is an ancient method that dates back to the 1960s and is mostly based on coincidental findings during medication trials. One significant advantage of repositioning is that the drug's safety profile is well known, lowering the odds of failure owing to undesirable toxic effects. Furthermore, repositioning takes less time and money than NDD. Given these facts, pharmaceutical corporations are becoming more interested in medication repositioning. In this follow-up, we discussed the notion of repositioning and provided some examples of repositioned medications in cardiometabolic disorders.

Therapeutic mechanism and clinical application of Chinese herbal medicine against diabetic kidney disease

Diabetic kidney disease (DKD) is the major complications of type 1 and 2 diabetes, and is the predominant cause of chronic kidney disease and end-stage renal disease. The treatment of DKD normally consists of controlling blood glucose and improving kidney function. The blockade of renin-angiotensin-aldosterone system and the inhibition of sodium glucose cotransporter 2 (SGLT2) have become the first-line therapy of DKD, but such treatments have been difficult to effectively block continuous kidney function decline, eventually resulting in kidney failure and cardiovascular comorbidities. The complex mechanism of DKD highlights the importance of multiple therapeutic targets in treatment. Chinese herbal medicine (active compound, extract and formula) synergistically improves metabolism regulation, suppresses oxidative stress and inflammation, inhibits mitochondrial dysfunction, and regulates gut microbiota and related metabolism via modulating GLP-receptor, SGLT2, Sirt1/AMPK, AGE/RAGE, NF-κB, Nrf2, NLRP3, PGC-1α, and PINK1/Parkin pathways. Clinical trials prove the reliable evidences for Chinese herbal medicine against DKD, but more efforts are still needed to ensure the efficacy and safety of Chinese herbal medicine. Additionally, the ideal combined therapy of Chinese herbal medicine and conventional medicine normally yields more favorable benefits on DKD treatment, laying the foundation for novel strategies to treat DKD.

Effects of tirzepatide versus insulin glargine on kidney outcomes in type 2 diabetes in the SURPASS-4 trial: post-hoc analysis of an open-label, randomised, phase 3 trial

BACKGROUND

In the SURPASS-4 trial, the dual GIP and GLP-1 receptor agonist tirzepatide reduced HbA_1c concentrations, bodyweight, and blood pressure more than titrated daily insulin glargine in people with type 2 diabetes inadequately controlled on oral diabetes treatments and with high cardiovascular risk. We aimed to compare the effects of tirzepatide and insulin glargine on kidney parameters and outcomes in people with type 2 diabetes.

METHODS

We did a post-hoc analysis of data from SURPASS-4, a randomised, open-label, parallel-group, phase 3 study at 187 sites (including private practice, research institutes, and hospitals) in 14 countries. Eligible participants were adults (age ≥18 years), with type 2 diabetes treated with any combination of metformin, sulfonylurea, or SGLT2 inhibitor, and with baseline HbA_1c of 7·5-10·5% (58-91 mmol/mol), BMI of 25 kg/m² or greater, and established cardiovascular disease or a high risk of cardiovascular events. Randomisation via an interactive web-response system was 1:1:1:3 to a once-weekly subcutaneous injection of tirzepatide (5 mg, 10 mg, or 15 mg) or a once-daily subcutaneous injection of titrated insulin glargine (100 U/mL). The study included up to 104 weeks of treatment, with a median treatment duration of 85 weeks. We compared the rates of estimated glomerular filtration rate (eGFR) decline and the urine albumin-creatinine ratio (UACR) between the combined tirzepatide groups and the insulin glargine group in the modified intention-to-treat population. The kidney composite outcome was time to first occurrence of eGFR decline of at least 40% from baseline, end-stage kidney disease, death owing to kidney failure, or new-onset macroalbuminuria. This study is registered with ClinicalTrials.gov, NCT03730662.

FINDINGS

Between Nov 20, 2018, and Dec 30, 2019, we screened 3045 people, of whom 1043 (34%) were ineligible, and 2002 (66%) were randomly assigned to a study drug (997 to tirzepatide and 1005 to insulin glargine). 1995 (>99%) of 2002 received at least one dose of tirzepatide (n=995) or insulin glargine (n=1000). At baseline, participants had a mean eGFR of 81·3 (SD 21·11) mL/min per 1·73 m² and a median UACR of 15·0 mg/g (IQR 5·0-55·8). The mean rate of eGFR decline was -1·4 (SE 0·2) mL/min per 1·73 m² per year in the combined tirzepatide groups and -3·6 (0·2) mL/min per 1·73 m² per year in the insulin group (between-group difference 2·2 [95% CI 1·6 to 2·8]). Compared with insulin glargine, the reduction in the annual rate of eGFR decline induced by tirzepatide was more pronounced in participants with eGFR less than 60 mL/min per 1·73 m² than in those with eGFR 60 mL/min per 1·73 m² or higher (between-group difference 3·7 [95% CI 2·4 to 5·1]). UACR increased from baseline to follow-up with insulin glargine (36·9% [95% CI 26·0 to 48·7]) but not with tirzepatide (-6·8% [-14·1 to 1·1]; between-group difference -31·9% [-37·7 to -25·7]). Participants who received tirzepatide showed a significantly lower occurrence of the composite kidney endpoint compared with those who received insulin glargine (hazard ratio 0·58 [95% CI 0·43 to 0·80]).

INTERPRETATION

Our analysis suggests that in people with type 2 diabetes and high cardiovascular risk, tirzepatide slowed the rate of eGFR decline and reduced UACR in clinically meaningful ways compared with insulin glargine.

FUNDING

Eli Lilly and Company.

Unraveling the interplay between dipeptidyl peptidase 4 and the renin-angiotensin system in heart failure

AIMS

Emerging evidence suggests the existence of a crosstalk between dipeptidyl peptidase 4 (DPP4) and the renin-angiotensin system (RAS). Therefore, combined inhibition of DPP4 and RAS may produce similar pharmacological effects rather than being additive. This study tested the hypothesis that combining an inhibitor of DPP4 with an angiotensin II (Ang II) receptor blocker does not provide additional cardioprotection compared to monotherapy in heart failure (HF) rats.

MAIN METHODS

Male Wistar rats were subjected to left ventricle (LV) radiofrequency ablation or sham operation. Six weeks after surgery, radiofrequency-ablated rats who developed HF were assigned into four groups and received vehicle (water), vildagliptin, valsartan, or both drugs, for four weeks by oral gavage.

KEY FINDINGS

Vildagliptin and valsartan in monotherapy reduced LV hypertrophy, alleviated cardiac interstitial fibrosis, and improved systolic and diastolic function in HF rats, with no additional effect of combination treatment. HF rats displayed higher cardiac and serum DPP4 activity and abundance than sham. Surprisingly, not only vildagliptin but also valsartan in monotherapy downregulated the catalytic function and expression levels of systemic and cardiac DPP4. Moreover, vildagliptin and valsartan alone or in combination comparably upregulate the components of the cardiac ACE2/Ang-(1-7)/MasR while downregulating the ACE/Ang II/AT1R axis.

SIGNIFICANCE

Vildagliptin or valsartan alone is as effective as combined to treat cardiac dysfunction and remodeling in experimental HF. DPP4 inhibition downregulates classic RAS components, and pharmacological RAS blockade downregulates DPP4 in the heart and serum of HF rats. This interplay between DPP4 and RAS may affect HF progression and pharmacotherapy.

Effect of glucagon-like peptide 1 receptor agonists on albuminuria in adult patients with type 2 diabetes mellitus: A systematic review and meta-analysis

AIMS

To determine the effect of glucagon-like peptide 1 receptor agonists (GLP-1RAs) on albuminuria in adult patients with type 2 diabetes mellitus (T2DM).

METHODS

Medline Ovid, Scopus, Web of Science, EMCARE and CINAHL databases from database inception until 27 January 2022. Studies were eligible for inclusion if they were randomized controlled trials that involved treatment with a GLP-1RA in adult patients with T2DM and assessed the effect on albuminuria in each treatment arm. Data extraction was conducted independently by three individual reviewers. The PRISMA guidelines were followed regarding data extraction and quality assessment. Data were pooled using a random effects inverse variance model and all analysis was carried out with RevMan 5.4 software. The Jadad scoring tool was employed to assess the quality of evidence and risk of bias in the randomized controlled trials.

RESULTS

The initial search revealed 2419 articles, of which 19 were included in this study. An additional three articles were identified from hand-searching references of included reviews. Therefore, in total, 22 articles comprising 39 714 patients were included. Meta-analysis suggested that use of GLP1-RAs was associated with a reduction in albuminuria in patients with T2DM (weighted mean difference -16.14%, 95% CI -18.42 to -13.86%; p < .0001) compared with controls.

CONCLUSIONS

This meta-analysis indicates that GLP-1RAs are associated with a significant reduction in albuminuria in adult patients with T2DM when compared with placebo.

Effect of once-weekly dulaglutide on renal function in patients with chronic kidney disease

Background

Dulaglutide is associated with improved cardiovascular and kidney outcomes and can be a good therapeutic option for patients with type 2 diabetes with chronic kidney disease (CKD). In this study, the effects of dulaglutide on glucose-lowering efficacy and changes in renal function were analyzed.

Methods

This retrospective study involved 197 patients with type 2 diabetes with mild-to-severe CKD treated with dulaglutide for at least 3 months between January 2017 and December 2020 at two tertiary hospitals in Korea. Changes in the creatinine-based estimated glomerular filtration rate (eGFR) and HbA1c were compared before and after the use of dulaglutide in each patient.

Results

The number of patients and mean eGFR (mL/min/1.73 m²) in CKD 2, 3a, 3b, and 4 were 94 (75.0 ± 8.5), 46 (54.8 ± 6.3), 31 (38.8 ± 4.4), and 26 (22.5 ± 5.4), respectively. Mean HbA1c level and body mass index (BMI) at the initiation of dulaglutide were 8.9% ± 1.4% and 29.1 ± 3.6 kg/m², the median duration of the use of dulaglutide was 16 months. The use of dulaglutide was associated with a mean decrease in HbA1c by 0.9% ± 1.5% and the glucose-lowering efficacy was similar across all stages of CKD. Also, it was associated with a reduced decline in the eGFR; the mean eGFR change after the use of dulaglutide was –0.76 mL/min/1.73 m² per year, whereas it was –2.41 mL/min/1.73 m² before use (paired t-test, P = 0.003). The difference was more pronounced in patients with an eGFR < 60 mL/min/1.73 m². Subgroup analysis showed that the renal protective effect was better in patients with proteinuria, age ≤ 65 years, and HbA1c < 9.0%, but showed no association with BMI.

Conclusions

The use of dulaglutide provided adequate glycemic control irrespective of CKD stage and was associated with a reduced decline in the eGFR in the CKD population.

GLP-1 receptor agonists in diabetic kidney disease: current evidence and future directions

With the emergence of various classes of blood glucose-lowering agents, choosing the appropriate drug for each patient is emphasized in diabetes management. Among incretin-based drugs, glucagon-like peptide 1 (GLP-1) receptor agonists are a promising therapeutic option for patients with diabetic kidney disease (DKD). Several cardiovascular outcome trials have demonstrated that GLP-1 receptor agonists have beneficial effects on cardiorenal outcomes beyond their blood glucose-lowering effects in patients with type 2 diabetes mellitus (T2DM). The renal protective effects of GLP-1 receptor agonists likely result from their direct actions on the kidney, in addition to their indirect actions that improve conventional risk factors for DKD, such as reducing blood glucose levels, blood pressure, and body weight. Inhibition of oxidative stress and inflammation and induction of natriuresis are major renoprotective mechanisms of GLP-1 analogues. Early evidence from the development of dual and triple combination agents suggests that GLP-1 receptor agonists will probably become popular treatment options for patients with T2DM.

Lipidomic Analysis Reveals the Protection Mechanism of GLP-1 Analogue Dulaglutide on High-Fat Diet-Induced Chronic Kidney Disease in Mice

Many clinical studies have suggested that glucagon-like peptide-1 receptor agonists (GLP-1RAs) have renoprotective properties by ameliorating albuminuria and increasing glomerular filtration rate in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) by lowering ectopic lipid accumulation in the kidney. However, the mechanism of GLP-1RAs was hitherto unknown. Here, we conducted an unbiased lipidomic analysis using ultra-high-performance liquid chromatography/electrospray ionization-quadrupole time-of-flight mass spectrometry (UHPLC/ESI-Q-TOF-MS) and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to reveal the changes of lipid composition and distribution in the kidneys of high-fat diet-fed mice after treatment with a long-acting GLP-1RA dulaglutide for 4 weeks. Treatment of dulaglutide dramatically improved hyperglycemia and albuminuria, but there was no substantial improvement in dyslipidemia and ectopic lipid accumulation in the kidney as compared with controls. Intriguingly, treatment of dulaglutide increases the level of an essential phospholipid constituent of inner mitochondrial membrane cardiolipin at the cortex region of the kidneys by inducing the expression of key cardiolipin biosynthesis enzymes. Previous studies demonstrated that lowered renal cardiolipin level impairs kidney function via mitochondrial damage. Our untargeted lipidomic analysis presents evidence for a new mechanism of how GLP-1RAs stimulate mitochondrial bioenergetics via increasing cardiolipin level and provides new insights into the therapeutic potential of GLP-1RAs in mitochondrial-related diseases.

Glucagon-Like Peptide-1 Receptor Agonist Use in People Living with Type 2 Diabetes Mellitus and Chronic Kidney Disease: A Narrative Review of the Key Evidence with Practical Considerations

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are incretin-mimetic agents that are effective adjuncts in the treatment of diabetes. This class of medications is also associated with promoting weight loss and a low risk of hypoglycemia, and some have been shown to be associated with a significant reduction of major cardiovascular events. Mounting evidence suggests that GLP-1 RAs have benefits beyond reducing blood glucose that include improving kidney function in people living with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD), a common microvascular complication of T2DM. Several large clinical studies, the majority of which are cardiovascular outcome trials, indicate that GLP-1 RA therapy is safe and tolerable for people living with T2DM and compromised renal function, and also suggest that GLP-1 RAs may have renoprotective properties. Although evidence from clinical trials has shown GLP-1 RAs to be safe and efficacious in people living with T2DM and renal impairment, their use is uncommon in this patient population. With continuing developments in the field of GLP-1 RA therapy, it is important for physicians to understand the benefits and practical use of GLP-1 RAs, as well as the clinical evidence, in order to achieve positive patient outcomes. Here, we review evidence on GLP-1 RA use in people living with T2DM and CKD and summarize renal outcomes from clinical studies. We provide practical considerations for GLP-1 RA use to provide an added benefit to guide treatment in this high-risk patient population.

Glucagon-Like Peptide-1 Receptor Agonists and Dual Glucose-Dependent Insulinotropic Polypeptide/Glucagon-Like Peptide-1 Receptor Agonists in the Treatment of Obesity/Metabolic Syndrome, Prediabetes/Diabetes and Non-Alcoholic Fatty Liver Disease-Current Evidence

The obesity pandemic is accompanied by increased risk of developing metabolic syndrome (MetS) and related conditions: non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH), type 2 diabetes mellitus (T2DM) and cardiovascular (CV) disease (CVD). Lifestyle, as well as an imbalance of energy intake/expenditure, genetic predisposition, and epigenetics could lead to a dysmetabolic milieu, which is the cornerstone for the development of cardiometabolic complications. Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) and dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 RAs promote positive effects on most components of the "cardiometabolic continuum" and consequently help reduce the need for polypharmacy. In this review, we highlight the main pathophysiological mechanisms and risk factors (RFs), that could be controlled by GLP-1 and dual GIP/GLP-1 RAs independently or through synergism or differences in their mode of action. We also address the evidence on the use of GLP-1 and dual GIP/GLP-1 RAs in the treatment of obesity, MetS and its related conditions (prediabetes, T2DM and NAFLD/NASH). In conclusion, GLP-1 RAs have already been established for the treatment of T2DM, obesity and cardioprotection in T2DM patients, while dual GIP/GLP-1 RAs appear to have the potential to possibly surpass them for the same indications. However, their use in the prevention of T2DM and the treatment of complex cardiometabolic metabolic diseases, such as NAFLD/NASH or other metabolic disorders, would benefit from more evidence and a thorough clinical patient-centered approach. There is a need to identify those patients in whom the metabolic component predominates, and whether the benefits outweigh any potential harm.

OUP accepted manuscript

Background

Methods

Results

Conclusions

GLP-1 receptor agonist versus DPP-4 inhibitor and kidney and cardiovascular outcomes in clinical practice in type-2 diabetes

Whether glucagon-like peptide-1 receptor agonists (GLP1-RA) reduce detrimental kidney outcomes is uncertain. In secondary analyses, trials have shown consistent reductions in macroalbuminuria, but inconclusive results about kidney function decline. To help clarify this, we conducted a cohort study to compare kidney and cardiovascular outcomes in individuals who started GLP1-RA or dipeptidyl peptidase-4 inhibitors (DPP4i) (reduces degradation of endogenous GLP1). The primary outcome was a composite of sustained doubling of creatinine, kidney failure or kidney death. The secondary outcomes were three-point major adverse cardiovascular events (MACE) and its individual components. Propensity score weighted Cox regression was used to balance 53 confounders. A total of 19,766 individuals were included, of whom 5,699 initiated GLP1-RA, and were followed for a median 2.9 years. Mean age was 63 years, 26.2% had atherosclerotic cardiovascular disease and 16.0% had an estimated glomerular filtration rate (eGFR) under 60 ml/min/1.73m². The adjusted hazard ratio for GLP1-RA vs. DPP4i was 0.72 (95% confidence interval 0.53-0.98) for the composite kidney outcome and 0.85 (0.73-0.99) for MACE, with absolute five-year risk reductions of 0.8% (0.1%-1.5%) and 1.6% (0.2%-2.9%), respectively. Hazard ratios were 0.79 (0.60-1.05) for cardiovascular death, 0.86 (0.68-1.09) for myocardial infarction and 0.74 (0.59-0.93) for stroke. Results were consistent within subgroups, including age, sex, eGFR and baseline metformin use. Thus, in our analysis of patients from routine clinical practice, the use of GLP1-RA was associated with a lower risk of kidney outcomes compared with DPP4i. Reductions in both kidney outcomes and MACE were similar in magnitude to those reported in large cardiovascular outcome trials.

Role of Renal Sympathetic Nerves in GLP-1 (Glucagon-Like Peptide-1) Receptor Agonist Exendin-4-Mediated Diuresis and Natriuresis in Diet-Induced Obese Rats

Background

The gut‐derived hormone GLP‐1 (glucagon‐like peptide‐1) exerts beneficial effects against established risk factors for chronic kidney disease. GLP‐1 influences renal function by stimulating diuresis and natriuresis and thus lowering arterial blood pressure. The role of the sympathetic nervous system has been implicated as an important link between obesity with elevated arterial pressure and chronic kidney disease. The primary aim of this study was to determine the contribution of renal sympathetic nerves on intrapelvic GLP‐1‐mediated diuresis and natriuresis in high‐fat diet (HFD)‐induced obese rats.

Methods and Results

Obesity was induced in rats by HFD for 12 weeks, followed by either surgical bilateral renal denervation or chronic subcutaneous endopeptidase neprilysin inhibition by sacubitril for a week. Diuretic and natriuretic responses to intrapelvic administration of the GLP‐1R (GLP‐1 receptor) agonist exendin‐4 were monitored in anesthetized control and HFD rats. Renal GLP‐1R expression and neprilysin expression and activity were measured. The effects of norepinephrine on the expression of GLP‐1R and neprilysin in kidney epithelial LLC‐PK1 cells were also examined. We found that diuretic and natriuretic responses to exendin‐4 were significantly reduced in the HFD obese rats compared with the control rats (cumulative urine flow at 40 minutes, 387±32 versus 650±65 µL/gkw; cumulative sodium excretion at 40 minutes, 42±5 versus 75±10 µEq/gkw, P<0.05). These responses in the HFD rats were restored after ablation of renal nerves (cumulative urine flow at 40 minutes, 625±62 versus 387±32 µL/gkw; cumulative sodium excretion at 40 minutes, 70±9 versus 42±5 µEq/gkw, P<0.05). Renal denervation induced significant reductions in arterial pressure and heart rate responses to intrapelvic GLP‐1 in the HFD rats. Renal denervation also significantly increased the GLP‐1R expression and reduced neprilysin expression and activity in renal tissues from the HFD rats. Chronic subcutaneous neprilysin inhibition by sacubitril increased GLP‐1–induced diuretic and natriuretic effects in the HFD rats. Finally, exposure of the renal epithelial cells to norepinephrine in vitro led to downregulation of GLP‐1R expression but upregulation of neprilysin expression and activity.

Conclusions

These results suggest that renal sympathetic nerve activation contributes to the blunted diuretic and natriuretic effects of GLP‐1 in HFD obese rats. This study provides significant novel insight into the potential renal nerve–neprilysin–GLP‐1 pathway involved in renal dysfunction during obesity that leads to hypertension.

The Role of Gasotransmitters in Gut Peptide Actions

Although gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) receive a bad connotation; in low concentrations these play a major governing role in local and systemic blood flow, stomach acid release, smooth muscles relaxations, anti-inflammatory behavior, protective effect and more. Many of these physiological processes are upstream regulated by gut peptides, for instance gastrin, cholecystokinin, secretin, motilin, ghrelin, glucagon-like peptide 1 and 2. The relationship between gasotransmitters and gut hormones is poorly understood. In this review, we discuss the role of NO, CO and H₂S on gut peptide release and functioning, and whether manipulation by gasotransmitter substrates or specific blockers leads to physiological alterations.

Hypothalamic GPCR Signaling Pathways in Cardiometabolic Control

Obesity is commonly associated with sympathetic overdrive, which is one of the major risk factors for the development of cardiovascular diseases, such as hypertension and heart failure. Over the past few decades, there has been a growing understanding of molecular mechanisms underlying obesity development with central origin; however, the relative contribution of these molecular changes to the regulation of cardiovascular function remains vague. A variety of G-protein coupled receptors (GPCRs) and their downstream signaling pathways activated in distinct hypothalamic neurons by different metabolic hormones, neuropeptides and monoamine neurotransmitters are crucial not only for the regulation of appetite and metabolic homeostasis but also for the sympathetic control of cardiovascular function. In this review, we will highlight the main GPCRs and associated hypothalamic nuclei that are important for both metabolic homeostasis and cardiovascular function. The potential downstream molecular mediators of these GPCRs will also be discussed.

Cardiorenal Protection in Diabetic Kidney Disease

Over the last 5 years there have been many new developments in the management of diabetic kidney disease. Glucagon-like peptide-1 receptor agonists (GLP-1 RA) and sodium-glucose cotransporter-2 (SGLT2) inhibitors were initially used for glycemic control, but more recent studies have now shown that their benefits extend to cardiovascular and kidney outcomes. The recent addition of data on the novel mineralocorticoid receptor antagonist (MRA) gives us another approach to further decrease the residual risk of diabetic kidney disease progression. In this review we describe the mechanism of action, key studies, and possible adverse effects related to these three classes of medications. The management of type 2 diabetes now includes an increasing number of medications for the management of comorbidities in a patient population at significant risk of cardiovascular disease and progression of chronic kidney disease. It is from this perspective that we seek to outline the rationale for the sequential and/or combined use of SGLT2 inhibitors, GLP-1 RA and MRAs in patients with type 2 diabetes for heart and kidney protection.

Incretin drugs in diabetic kidney disease: biological mechanisms and clinical evidence

As the prevalence of diabetes continues to climb, the number of individuals living with diabetic complications will reach an unprecedented magnitude. The emergence of new glucose-lowering agents - sodium-glucose cotransporter 2 inhibitors and incretin therapies - has markedly changed the treatment landscape of type 2 diabetes mellitus. In addition to effectively lowering glucose, incretin drugs, which include glucagon-like peptide 1 receptor (GLP1R) agonists and dipeptidyl peptidase 4 (DPP4) inhibitors, can also reduce blood pressure, body weight, the risk of developing or worsening chronic kidney disease and/or atherosclerotic cardiovascular events, and the risk of death. Although kidney disease events have thus far been secondary outcomes in clinical trials, an ongoing phase III trial in patients with diabetic kidney disease will test the effect of a GLP1R agonist on a primary kidney disease outcome. Experimental data have identified the modulation of innate immunity and inflammation as plausible biological mechanisms underpinning the kidney-protective effects of incretin-based agents. These drugs block the mechanisms involved in the pathogenesis of kidney damage, including the activation of resident mononuclear phagocytes, tissue infiltration by non-resident inflammatory cells, and the production of pro-inflammatory cytokines and adhesion molecules. GLP1R agonists and DPP4 inhibitors might also attenuate oxidative stress, fibrosis and cellular apoptosis in the kidney.

Circulating GLP-1 Levels as a Potential Indicator of Metabolic Syndrome Risk in Adult Women

Glucagon-like peptide-1 (GLP-1), an incretin hormone, plays an important role in regulating glucose homeostasis. In this study, the applicability of circulating GLP-1 levels as an early indicator of metabolic syndrome (MetS) risk was examined. Women without diagnosed diseases were grouped according to their number of MetS risk factors (MetS RFs) (no RFs as Super-healthy, n = 61; one or two RFs as MetS risk carriers, n = 60; 3 ≤ RFs as MetS, n = 19). The circulating GLP-1 levels and homeostasis model assessment insulin resistance (HOMA-IR) scores were significantly higher in the MetS group than in the other two groups. The GLP-1 levels correlated positively with adiposity, HOMA-IR, blood pressure, and high sensitivity C-reactive protein (hs-CRP), but not with fasting glucose and lipid profiles, whose significances were maintained after adjustments for age, smoking and drinking habits, menopausal status, and total calorie intake. The GLP-1 levels also increased proportionally with the number of MetS RFs. In the MetS group, the GLP-1 levels were much higher in individuals with obesity (body mass index ≥ 25 kg/m²). In conclusion, the circulating GLP-1 level may be applicable as a potential early indicator of MetS risk in women without diagnosed diseases. Further study with a large population is needed to confirm the conclusion.

Mitochondrion-driven nephroprotective mechanisms of novel glucose lowering medications

Therapy for diabetic kidney disease (DKD) is undergoing a revolution with the realization that some glucose-lowering drugs have nephroprotective actions that may be intrinsic to the drugs and not dependent on the impact on diabetes control, as demonstrated with the sodium glucose co-transporter-2 (SGLT-2) inhibitors. Mitochondria are a critical factor required for the maintenance of kidney function, given its high energy demanding profile, with extensive use of adenosine triphosphate (ATP). Consequently, deficiency of the master regulator of mitochondrial biogenesis peroxisome proliferator-activated receptor gamma coactivator 1α predisposes to kidney disease. Perhaps as a result of key role of mitochondria in fundamental cellular functions, mitochondrial dysfunction may play a role in the pathogenesis of common conditions such as DKD. Finding pharmacological agents to influence this pathway could therefore lead to early implementation of therapy. Importantly, glucose-lowering drugs such as glucagon-like peptide-1 receptor activators and SGLT2 inhibitors have kidney and/or cardioprotective actions in patients with diabetes. Accumulating evidence from preclinical studies has suggested a protective effect of these drugs that is in part mediated by normalizing mitochondrial function. We now critically review this evidence and discuss studies needed to confirm mitochondrial protective benefits across a range of clinical studies.

Using a Reporter Mouse to Map Known and Novel Sites of GLP-1 Receptor Expression in Peripheral Tissues of Male Mice

Glucagon-like peptide-1 receptor (GLP-1R) activation is used in the treatment of diabetes and obesity; however, GLP-1 induces many other physiological effects with unclear mechanisms of action. To identify the cellular targets of GLP-1 and GLP-1 analogues, we generated a Glp1r.tdTomato reporter mouse expressing the reporter protein, tdTomato, in Glp1r-expressing cells. The reporter signal is expressed in all cells where GLP-1R promoter was ever active. To complement this, we histologically mapped tdTomato-fluorescence, and performed Glp-1r mRNA in situ hybridization and GLP-1R immunohistochemistry on the same tissues. In male mice, we found tdTomato signal in mucus neck, chief, and parietal cells of the stomach; Brunner's glands; small intestinal enteroendocrine cells and intraepithelial lymphocytes; and myenteric plexus nerve fibers throughout the gastrointestinal tract. Pancreatic acinar-, β-, and δ cells, but rarely α cells, were tdTomato-positive, as were renal arteriolar smooth muscle cells; endothelial cells of the liver, portal vein, and endocardium; aortal tunica media; and lung type 1 and type 2 pneumocytes. Some thyroid follicular and parafollicular cells displayed tdTomato expression, as did tracheal cartilage chondrocytes, skin fibroblasts, and sublingual gland mucus cells. In conclusion, our reporter mouse is a powerful tool for mapping known and novel sites of GLP-1R expression in the mouse, thus enhancing our understanding of the many target cells and effects of GLP-1 and GLP-1R agonists.

Changes in the renal function after acute mercuric chloride exposure in the rat are associated with renal vascular endothelial dysfunction and proximal tubule NHE3 inhibition

Mercury is an environmental pollutant and a threat to human health. Mercuric chloride (HgCl₂)-induced acute renal failure has been described by several reports, but the mechanisms of renal dysfunction remain elusive. This study tested the hypothesis that HgCl₂ directly impairs renal vascular reactivity. Additionally, due to the mercury toxicity on the proximal tubule, we investigated whether the HgCl₂-induced natriuresis is accompanied by inhibition of Na⁺/H⁺ exchanger isoform-3 (NHE3). We found that 90-min HgCl₂ infusion (6.5 μg/kg i.v.) remarkably increased urinary output, reduced GFR and renal blood flow, and increased vascular resistance in rats. "In vitro" experiments of HgCl₂ infusion in isolated renal vascular bed demonstrated an elevation of perfusion pressure in a concentration- and time-dependent manner, associated with changes on the endothelium-dependent vasodilatation and the flow-pressure relationship. Moreover, by employing "in vivo" stationary microperfusion of the proximal tubule, we found that HgCl₂ inhibits NHE3 activity and increases the phosphorylation of NHE3 at serine 552 in the renal cortex, in line with the HgCl₂-induced diuresis. Changes in renal proximal tubular function induced by HgCl₂ were parallel to increased urinary markers of proximal tubular injury. Besides, atomic spectrometry showed that mercury accumulated in the renal cortex. We conclude that acute HgCl₂ exposure causes renal vasoconstriction that is associated with reduced endothelial vasodilator agonist- and flow-mediated responses and inhibition of NHE3-mediated sodium reabsorption. Thus, our data suggest that HgCl₂-induced acute renal failure may be attributable at least in part by its direct effects on renal hemodynamics and NHE3 activity.

Effects of SGLT2 Inhibitors and GLP-1 Receptor Agonists on Renin-Angiotensin-Aldosterone System

Sodium-glucose cotransporters inhibitors (SGLT2-i) and GLP-1 receptor agonists (GLP1-RA) are glucose-lowering drugs that are proved to reduce the cardiovascular (CV) risk in type 2 diabetes mellitus (T2DM). In this process, the renin-angiotensin-aldosterone system (RAAS) is assumed to play a role. The inhibition of SGLT2 improves hyperglycemia hampering urinary reabsorption of glucose and inducing glycosuria. This "hybrid" diuretic effect, which couples natriuresis with osmotic diuresis, potentially leads to systemic RAAS activation. However, the association between SGLT2-i and systemic RAAS activation is not straightforward. Available data indicate that SGLT2-i cause plasma renin activity (PRA) increase in the early phase of treatment, while PRA and aldosterone levels remain unchanged in chronic treated patients. Furthermore, emerging studies provide evidence that SGLT2-i might have an interfering effect on aldosterone/renin ratio (ARR) in patients with T2DM, due to their diuretic and sympathoinhibition effects. The cardio- and reno-protective effects of GLP-1-RA are at least in part related to the interaction with RAAS. In particular, GLP1-RA counteract the action of angiotensin II (ANG II) inhibiting its synthesis, increasing the inactivation of its circulating form and contrasting its action on target tissue like glomerular endothelial cells and cardiomyocytes. Furthermore, GLP1-RA stimulate natriuresis inhibiting Na+/H+ exchanger NHE-3, which is conversely activated by ANG II. Moreover, GLP1 infusion acutely reduces circulating aldosterone, but this effect does not seem to be chronically maintained in patients treated with GLP1-RA. In conclusion, both SGLT2-i and GLP1-RA seem to have several effects on RAAS, though additional studies are needed to clarify this relationship.

Management of post-transplant diabetes: immunosuppression, early prevention, and novel antidiabetics

Post‐transplant diabetes mellitus (PTDM) shows a relationship with risk factors including obesity and tacrolimus‐based immunosuppression, which decreases pancreatic insulin secretion. Several of the sodium–glucose‐linked transporter 2 inhibitors (SGLT2is) and glucagon‐like peptide 1 receptor agonists (GLP1‐RAs) dramatically improve outcomes of individuals with type 2 diabetes with and without chronic kidney disease, which is, as heart failure and atherosclerotic cardiovascular disease, differentially affected by both drug classes (presumably). Here, we discuss SGLT2is and GLP1‐RAs in context with other PTDM management strategies, including modification of immunosuppression, active lifestyle intervention, and early postoperative insulin administration. We also review recent studies with SGLT2is in PTDM, reporting their safety and antihyperglycemic efficacy, which is moderate to low, depending on kidney function. Finally, we reference retrospective case reports with GLP1‐RAs that have not brought forth major concerns, likely indicating that GLP1‐RAs are ideal for PTDM patients suffering from obesity. Although our article encompasses PTDM after solid organ transplantation in general, data from kidney transplant recipients constitute the largest proportion. The PTDM research community still requires data that treating and preventing PTDM will improve clinical conditions beyond hyperglycemia. We therefore suggest that it is time to collaborate, in testing novel antidiabetics among patients of all transplant disciplines.

Impact of glucagon like peptide-1 receptor agonist and sodium glucose cotransporter 2 inhibitors on type 2 diabetes patients with renal impairment

INTRODUCTION

Diabetes mellitus is a progressive disease with cardiovascular complications. We evaluated the impact of a glucagon like peptide-1 (GLP-1) receptor agonist and sodium glucose cotransporter 2 (SGLT-2) inhibitors dapagliflozin and empagliflozin on renal and cardiac function in type 2 diabetes patients with renal impairment.

MATERIALS AND METHODS

A total of 156 patients referred with suboptimal glycemic control were assigned to Group G (GLP-1): n = 72 or Group S (SGLT-2 inhibitor)-dapagliflozin (n = 52) or empagliflozin (n = 32). Renal function was assessed every 3 months for 36 months. Cardiovascular parameters were evaluated every 12 months for 36 months.

RESULTS

Compared with baseline, HbA1c and systolic blood pressure significantly decreased in both groups (p < 0.05). The estimated glomerular filtration rate decreased, but without significance. Albuminuria decreased significantly in both groups and then subsequently increased after 30 months in Group S. Diastolic cardiac function, assessed by E/e' or left atrial volume index, decreased only in Group G at 36 months.

CONCLUSIONS

The GLP-1 receptor agonist and SGLT-2 inhibitors were effective for glycemic and blood pressure control and for maintaining renal function. The GLP-1 receptor agonist improved diastolic function at 36 months.

DPP-4 Inhibitors: Renoprotective Potential and Pharmacokinetics in Type 2 Diabetes Mellitus Patients with Renal Impairment

The continuously increasing incidence of diabetes worldwide has attracted the attention of the scientific community and driven the development of a novel class of antidiabetic drugs that can be safely and effectively used in diabetic patients. Of particular interest in this context are complications associated with diabetes, such as renal impairment, which is the main cause of high cardiovascular morbidity and mortality in diabetic patients. Intensive control of glucose levels and other risk factors associated with diabetes and metabolic syndrome provides the foundations for both preventing and treating diabetic nephropathy. Dipeptidyl peptidase-4 (DPP-4) inhibitors represent a highly promising novel class of oral agents used in the treatment of type 2 diabetes mellitus that may be successfully combined with currently available antidiabetic therapeutics in order to achieve blood glucose goals. Beyond glycemic control, emerging evidence suggests that DPP-4 inhibitors may have desirable off-target effects, including renoprotection. All type 2 diabetes mellitus patients with impaired renal function require dose adjustment of any DPP-4 inhibitor administered except for linagliptin, for which renal excretion is a minor elimination pathway. Thus, linagliptin is the drug most frequently chosen to treat type 2 diabetes mellitus patients with renal failure.

A role for tubular Na+/H+ exchanger NHE3 in the natriuretic effect of the SGLT2 inhibitor empagliflozin

Inhibitors of proximal tubular Na⁺-glucose cotransporter 2 (SGLT2) are natriuretic, and they lower blood pressure. There are reports that the activities of SGLT2 and Na⁺-H⁺ exchanger 3 (NHE3) are coordinated. If so, then part of the natriuretic response to an SGLT2 inhibitor is mediated by suppressing NHE3. To examine this further, we compared the effects of an SGLT2 inhibitor, empagliflozin, on urine composition and systolic blood pressure (SBP) in nondiabetic mice with tubule-specific NHE3 knockdown (NHE3-ko) and wild-type (WT) littermates. A single dose of empagliflozin, titrated to cause minimal glucosuria, increased urinary excretion of Na⁺ and bicarbonate and raised urine pH in WT mice but not in NHE3-ko mice. Chronic empagliflozin treatment tended to lower SBP despite higher renal renin mRNA expression and lowered the ratio of SBP to renin mRNA, indicating volume loss. This effect of empagliflozin depended on tubular NHE3. In diabetic Akita mice, chronic empagliflozin enhanced phosphorylation of NHE3 (S552/S605), changes previously linked to lesser NHE3-mediated reabsorption. Chronic empagliflozin also increased expression of genes involved with renal gluconeogenesis, bicarbonate regeneration, and ammonium formation. While this could reflect compensatory responses to acidification of proximal tubular cells resulting from reduced NHE3 activity, these effects were at least in part independent of tubular NHE3 and potentially indicated metabolic adaptations to urinary glucose loss. Moreover, empagliflozin increased luminal α-ketoglutarate, which may serve to stimulate compensatory distal NaCl reabsorption, while cogenerated and excreted ammonium balances urine losses of this "potential bicarbonate." The data implicate NHE3 as a determinant of the natriuretic effect of empagliflozin.

Liraglutide Improves the Kidney Function in a Murine Model of Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is a global health burden, and the current treatment options only slow down the disease progression. GLP-1 receptor agonists (GLP-1 RA) have shown a renal protective effect in models of CKD; however, the mechanism behind the beneficial effect is not understood. In this study, we investigate the effect of the GLP-1 RA liraglutide in the nephrotoxic serum nephritis (NTN) CKD model. Moreover, we compare the gene expression pattern of liraglutide-treated mice to the gene expression pattern of mice treated with the angiotensin converting enzyme inhibitor, enalapril.

METHODS

The effect of liraglutide was tested in the NTN model by evaluating the glomerular filtration rate (GFR), albuminuria, mesangial expansion, renal fibrosis, and renal inflammation. Furthermore, the regulation of selected genes involved in CKD and in glomerular, cortical tubulointerstitial, and whole kidney structures was analyzed using a gene expression array on samples following laser capture microdissection.

RESULTS

Treatment with liraglutide improved CKD hallmarks including GFR, albuminuria, mesangial expansion, renal inflammation, and renal fibrosis. The gene expression revealed that both liraglutide and enalapril reversed the regulation of several fibrosis and inflammation associated genes, which are also regulated in human CKD patients. Furthermore, liraglutide and enalapril both regulated genes in the kidney involved in blood pressure control.

CONCLUSIONS

Treatment with liraglutide improved the kidney function and diminished renal lesions in NTN-induced mice. Both liraglutide and enalapril reversed the regulation of genes involved in CKD and regulated genes involved in blood pressure control.

Endogenous Activation of Glucagon-Like Peptide-1 Receptor Contributes to Blood Pressure Control: Role of Proximal Tubule Na+/H+ Exchanger Isoform 3, Renal Angiotensin II, and Insulin Sensitivity

The pharmacological administration of GLP-1R (glucagon-like peptide-1 receptor) agonists reduces blood pressure (BP) in type 2 diabetes mellitus and nondiabetic patients. This study tested the hypothesis that endogenous GLP-1R signaling influences the regulation of BP. To this end, SHRs (spontaneously hypertensive rats) and Wistar rats were treated with the GLP-1R antagonist Ex9 (exendin-9) or vehicle for 4 weeks. Rats receiving the GLP-1R agonist Ex4 (exenatide) were used as an additional control. We found that blockade of baseline GLP-1R signaling by Ex9 increased systolic BP in both SHR and Wistar rats, compared with vehicle-treated animals, while Ex4 only reduced systolic BP in SHR. Higher systolic BP induced by Ex9 was accompanied by reduced lithium clearance and lower levels of NHE3 (Na⁺/H⁺ exchanger isoform 3) phosphorylation at the serine 552, indicative of increased proximal tubule sodium reabsorption. Additionally, urinary AGT (angiotensinogen) and renal cortical concentration of Ang II (angiotensin II) were enhanced by Ex9. Conversely, Ex4 decreased both urinary AGT and cortical Ang II but exclusively in SHRs. Moreover, both SHR and Wistar rats treated with Ex9 displayed hyperinsulinemia as compared with vehicle-treated rats, whereas Ex4 reduced fasting insulin concentration in SHR. Collectively, these results suggest that endogenous GLP-1R signaling exerts a physiologically relevant effect on BP control, which may be attributable, in part, to its tonic actions on the proximal tubule NHE3-mediated sodium reabsorption, intrarenal renin-angiotensin system, and insulin sensitivity. The possible role of impaired GLP-1R signaling in the pathogenesis of hypertension warrants further investigation.

Blood pressure control in type 2 diabetes mellitus with arterial hypertension. The important ancillary role of SGLT2-inhibitors and GLP1-receptor agonists

Type 2 diabetes mellitus and arterial hypertension are major cardiovascular risks factors which shares metabolic and haemodynamic abnormalities as well as pathophysiological mechanisms. The simultaneous presence of diabetes and arterial hypertension increases the risk of left ventricular hypertrophy, congestive heart failure, and stroke, as compared to either condition alone. A number of guidelines recommend lifestyle measures such as salt restriction, weight reduction and ideal body weight mainteinance, regular physical activity and smoking cessation, together with moderation of alcohol consumption and high intake of vegetables and fruits, as the basis for reduction of blood pressure and prevention of CV diseases. Despite the availability of multiple drugs effective for hypertension, BP targets are reached in only 50 % of patients, with even fewer individuals with T2DM-achieving goals. It is established that new emerging classes of type 2 diabetes mellitus treatment, SGLT2 inhibitors and GLP1-receptor agonists, are efficacious on glucose control, and safe in reducing HbA1c significantly, without increasing hypoglycemic episodes. Furthermore, in recent years, many CVOT trials have demonstrated, using GLP1-RA or SGLT2-inihibitors compared to placebo (in combination with the usual diabetes medications) important benefits on reducing MACE (cardio-cerebral vascular events) in the diabetic population. In this hypothesis-driven review, we have examined the anti-hypertensive effects of these novel molecules of the two different classes, in the diabetic population, and suggest that they could have an interesting ancillary role in controlling blood pressure in type 2 diabetic patients.

GLP-1 Receptor Agonists in Diabetic Kidney Disease: From Clinical Outcomes to Mechanisms

Diabetic Kidney Disease (DKD) is the leading cause of end stage renal disease (ESRD) worldwide. Glucagon-like peptide 1 receptor agonists (GLP-1RAs) are now widely used in the treatment of patients with type 2 diabetes (T2D). A series of clinical and experimental studies demonstrated that GLP-1RAs have beneficial effects on DKD, independent of their glucose-lowering abilities, which are mediated by natriuresis, anti-inflammatory and anti-oxidative stress properties. Furthermore, GLP-1RAs have been shown to suppress renal fibrosis. Recent clinical trials have demonstrated that GLP-1RAs have beneficial effects on renal outcomes, especially in patients with T2D who are at high risk for CVD. These findings suggest that GLP-1RAs hold great promise in preventing the onset and progression of DKD. However, GLP-1RAs have only been shown to reduce albuminuria, and their ability to reduce progression to ESRD remains to be elucidated. In this review article, we highlight the current understanding of the clinical efficacy and the mechanisms underlying the effects of GLP-1RAs in DKD.

Comprehensive Efficacy of the Dipeptidyl Peptidase 4 Inhibitor Alogliptin in Practical Clinical Settings: A Prospective Multi-Center Interventional Observational Study

Background

This study aimed to verify the safety and efficacy, including glycemic control, of the selective dipeptidyl peptidase 4 inhibitor alogliptin in patients with type 2 diabetes.

Methods

This study used a multi-center, open-label, prospective observational design. Type 2 diabetes patients who were undergoing dietary therapy and/or exercise therapy alone without sufficient glycemic control (hemoglobin A1c (HbA1c) ≥ 6.5% and < 10%) were administered alogliptin (25 mg/day). The long-term effects (6 and 12 months) on blood glucose, blood pressure, heart rate, body weight and lipids were assessed.

Results

A final 50 patients were included with a high prevalence of hypertension (77%) and dyslipidemia (72%), and a mean duration of diabetes of 4.5 years. Pre-treatment HbA1c was 7.5% and was significantly decreased at 6 and 12 months (6M: 6.4%, 12M: 6.2%; P < 0.02 vs. 0M, respectively). Body weight, blood pressure and low-density lipoprotein cholesterol were significantly decreased by 6 months and maintained at 12 months. Triglycerides showed a significant decrease at 12 months. No significant differences were observed in HbA1c decrease for different grade of age, duration of diabetes, body mass index and renal function. The degree of decrease in HbA1c was most strongly correlated with pre-treatment HbA1c. Adverse events were noted in three patients, with no serious outcomes.

Conclusion

The blood glucose-lowering effect and safety of alogliptin were demonstrated regardless of baseline HbA1c, although its effect appeared stronger with higher pre-treatment HbA1c values. Additionally, alogliptin appears useful for managing atherosclerotic risk factors such as body weight and blood pressure.

Incretin-based therapies and renin-angiotensin system: Looking for new therapeutic potentials in the diabetic milieu

Incretin-based therapies include pharmacologic agents such as glucagon like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors which exert potent anti-hyperglycemic effects in the diabetic milieu. They are also shown to have extra-pancreatic effects. Renin-angiotensin system is part of the endocrine system which is widely distributed in the body and is closely involved in water and electrolyte homeostasis as well as renal and cardiovascular functions. Hence the renin-angiotensin system is the main target for treating patients with various renal and cardiovascular disorders. There is growing evidence that incretins have modulatory effects on renin-angiotensin system activity; thereby, can be promising therapeutic agents for the management of renal and cardiovascular disorders. But the exact molecular interactions between incretins and renin-angiotensin system are not clearly understood. In this current study, we have reviewed the possible molecular mechanisms by which incretins modulate renin-angiotensin system activity.

GLP-1-induced renal vasodilation in rodents depends exclusively on the known GLP-1 receptor and is lost in prehypertensive rats

Glucagon-like peptide-1 (GLP-1) is an incretin hormone known to stimulate postprandial insulin release. However, GLP-1 also exerts extrapancreatic effects, including renal effects. Some of these renal effects are attenuated in hypertensive rats, where renal expression of GLP-1 receptors is reduced. Here, we assessed the expression and vascular function of GLP-1 receptors in kidneys from young prehypertensive rats. We also examined GLP-1-induced vasodilation in the renal vasculature in wild-type (WT) and GLP-1 receptor knockout mice using wire and pressure myography and the isolated perfused juxtamedullary nephron preparation. We investigated whether GLP-1 and the metabolite GLP-1(9-36)amide had renal vascular effects independent of the known GLP-1 receptor. We hypothesized that hypertension decreased expression of renal GLP-1 receptors. We also hypothesized that GLP-1-induced renal vasodilatation depended on expression of the known GLP-1 receptor. In contrast to normotensive rats, no immunohistochemical staining or vasodilatory function of GLP-1 receptors was found in kidneys from prehypertensive rats. In WT mice, GLP-1 induced renal vasodilation and reduced the renal autoregulatory response. The GLP-1 receptor antagonist exendin 9-39 inhibited relaxation, and GLP-1(9-36)amide had no vasodilatory effect. In GLP-1 receptor knockout mice, no relaxation induced by GLP-1 or GLP-1(9-36)amide was found, the autoregulatory response in afferent arterioles was normal, and no GLP-1-induced reduction of autoregulation was found. We conclude that in prehypertensive kidneys, expression and function of GLP-1 receptors is lost. The renal vasodilatory effect of GLP-1 is mediated exclusively by the known GLP-1 receptor. GLP-1(9-36)amide has no renal vasodilatory effect. GLP-1 attenuates renal autoregulation by reducing the myogenic response.