Low-dose lixisenatide protects against early-onset nephropathy induced in diabetic rats

Oxidative Stress: A Culprit in the Progression of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the principal culprit behind chronic kidney disease (CKD), ultimately developing end-stage renal disease (ESRD) and necessitating costly dialysis or kidney transplantation. The limited therapeutic efficiency among individuals with DKD is a result of our finite understanding of its pathogenesis. DKD is the result of complex interactions between various factors. Oxidative stress is a fundamental factor that can establish a link between hyperglycemia and the vascular complications frequently encountered in diabetes, particularly DKD. It is crucial to recognize the essential and integral role of oxidative stress in the development of diabetic vascular complications, particularly DKD. Hyperglycemia is the primary culprit that can trigger an upsurge in the production of reactive oxygen species (ROS), ultimately sparking oxidative stress. The main endogenous sources of ROS include mitochondrial ROS production, NADPH oxidases (Nox), uncoupled endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), cytochrome P450 (CYP450), and lipoxygenase. Under persistent high glucose levels, immune cells, the complement system, advanced glycation end products (AGEs), protein kinase C (PKC), polyol pathway, and the hexosamine pathway are activated. Consequently, the oxidant-antioxidant balance within the body is disrupted, which triggers a series of reactions in various downstream pathways, including phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), transforming growth factor beta/p38-mitogen-activated protein kinase (TGF-β/p38-MAPK), nuclear factor kappa B (NF-κB), adenosine monophosphate-activated protein kinase (AMPK), and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. The disease might persist even if strict glucose control is achieved, which can be attributed to epigenetic modifications. The treatment of DKD remains an unresolved issue. Therefore, reducing ROS is an intriguing therapeutic target. The clinical trials have shown that bardoxolone methyl, a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, blood glucose-lowering drugs, such as sodium-glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists can effectively slow down the progression of DKD by reducing oxidative stress. Other antioxidants, including vitamins, lipoic acid, Nox inhibitors, epigenetic regulators, and complement inhibitors, present a promising therapeutic option for the treatment of DKD. In this review, we conduct a thorough assessment of both preclinical studies and current findings from clinical studies that focus on targeted interventions aimed at manipulating these pathways. We aim to provide a comprehensive overview of the current state of research in this area and identify key areas for future exploration.

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.

Role of GLP-1 Receptor Agonist in Diabetic Cardio-renal Disorder: Recent Updates of Clinical and Pre-clinical Evidence

Cardiovascular complications and renal disease is the growing cause of mortality in patients with diabetes. The subversive complications of diabetes such as hyperglycemia, hyperlipidemia and insulin resistance lead to an increase in the risk of myocardial infarction (MI), stroke, heart failure (HF) as well as chronic kidney disease (CKD). Among the commercially available anti-hyperglycemic agents, incretin-based medications appear to be safe and effective in the treatment of type 2 diabetes mellitus (T2DM) and associated cardiovascular and renal disease. Glucagon-like peptide 1 receptor agonists (GLP-1RAs) have been shown to be fruitful in reducing HbA1c, blood glucose, lipid profile, and body weight in diabetic patients. Several preclinical and clinical studies revealed the safety, efficacy, and preventive advantages of GLP-1RAs against diabetes- induced cardiovascular and kidney disease. Data from cardio-renal outcome trials had highlighted that GLP-1RAs protected people with established CKD from significant cardiovascular disease, lowered the likelihood of hospitalization for heart failure (HHF), and lowered all-cause mortality. They also had a positive effect on people with end-stage renal disease (ESRD) and CKD. Beside clinical outcomes, GLP-1RAs reduced oxidative stress, inflammation, fibrosis, and improved lipid profile pre-clinically in diabetic models of cardiomyopathy and nephropathy that demonstrated the cardio-protective and reno-protective effect of GLP-1RAs. In this review, we have focused on the recent clinical and preclinical outcomes of GLP-1RAs as cardio-protective and reno-protective agents as GLP-1RAs medications have been demonstrated to be more effective in treating T2DM and diabetes-induced cardiovascular and renal disease than currently available treatments in clinics, without inducing hypoglycemia or weight gain.

Experimental Models to Study Diabetes Mellitus and Its Complications: Limitations and New Opportunities

Preclinical biomedical models are a fundamental tool to improve the knowledge and management of diseases, particularly in diabetes mellitus (DM) since, currently, the pathophysiological and molecular mechanisms involved in its development are not fully clarified, and there is no treatment to cure DM. This review will focus on the features, advantages and limitations of some of the most used DM models in rats, such as the spontaneous models: Bio-Breeding Diabetes-Prone (BB-DP) and LEW.1AR1-iddm, as representative models of type 1 DM (DM-1); the Zucker diabetic fatty (ZDF) and Goto-kakizaki (GK) rats, as representative models of type 2 DM (DM-2); and other models induced by surgical, dietary and pharmacological-alloxan and streptozotocin-procedures. Given the variety of DM models in rats, as well as the non-uniformity in the protocols and the absence of all the manifestation of the long-term multifactorial complications of DM in humans, the researchers must choose the one that best suits the final objectives of the study. These circumstances, added to the fact that most of the experimental research in the literature is focused on the study of the early phase of DM, makes it necessary to develop long-term studies closer to DM in humans. In this review, a recently published rat DM model induced by streptozotocin injection with chronic exogenous administration of insulin to reduce hyperglycaemia has also been included in an attempt to mimic the chronic phase of DM in humans.

Oxidative stress as a culprit in diabetic kidney disease

Diabetic kidney disease (DKD) has become the leading cause of end-stage renal disease (ESRD), and the prevalence of DKD has increased worldwide during recent years. DKD is associated with poor therapeutic outcomes in most patients, but there is limited understanding of its pathogenesis. This review suggests that oxidative stress interacts with many other factors in causing DKD. Highly active mitochondria and NAD(P)H oxidase are major sources of oxidants, and they significantly affect the risk for DKD. Oxidative stress and inflammation may be considered reciprocal causes of DKD, in that each is a cause and an effect of DKD. Reactive oxygen species (ROS) can act as second messengers in various signaling pathways and as regulators of metabolism, activation, proliferation, differentiation, and apoptosis of immune cells. Epigenetic modifications, such as DNA methylation, histone modifications, and non-coding RNAs can modulate oxidative stress. The development of new technologies and identification of new epigenetic mechanisms may provide novel opportunities for the diagnosis and treatment of DKD. Clinical trials demonstrated that novel therapies which reduce oxidative stress can slow the progression of DKD. These therapies include the NRF2 activator bardoxolone methyl, new blood glucose-lowering drugs such as sodium-glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists. Future studies should focus on improving early diagnosis and the development of more effective combination treatments for this multifactorial disease.

Advances in the management of diabetic kidney disease: beyond sodium-glucose co-transporter 2 inhibitors

Progress in the treatment of diabetic kidney disease (DKD) has been modest since the early trials on renin-angiotensin-aldosterone system inhibitors (RAASis). Although sodium-glucose co-transporter 2 inhibitors (SGLT2is) have revolutionized the management of DKD by lowering proteinuria and protecting organs, other novel treatment approaches with good evidence and efficacy that can be used in conjunction with a RAASi or SGLT2i in managing DKD have emerged in the past few years. This review discusses the evidence for glucagon-like peptide-1 receptor agonist, selective mineralocorticoid receptor antagonist, and selective endothelin A receptor antagonist, emerging treatment options for DKD beyond SGLT2 inhibition.

The anti-inflammatory and immunological properties of GLP-1 Receptor Agonists

In the last few years, a great interest has emerged in investigating the pleiotropic effects of Glucagon Like Peptide-1 Receptor Agonists (GLP-1RAs). While GLP-1RAs ability to lower plasma glucose and to induce weight loss has allowed them to be approved for the treatment of diabetes and obesity, consistent evidences from in vitro studies and preclinical models suggested that GLP-1RAs have anti-inflammatory properties and that may modulate the immune-system. Notably, such anti-inflammatory effects target different pathways in different tissues, underling the broad spectrum of GLP-1RAs actions. This review examines some of the currently proposed molecular mechanisms of GLP-1RAs actions and explores their potential benefits in reducing inflammatory responses, which may well suggest a future therapeutic use of GLP-1RAs in new indications.

Moutan Cortex polysaccharide ameliorates diabetic kidney disease via modulating gut microbiota dynamically in rats

Growing evidence suggests that polysaccharides from traditional Chinese medicine positively affect diabetic kidney disease (DKD) mainly through modulating gut microbiota. Previously, we demonstrated that supplementation with the polysaccharide from Moutan Cortex (MC-Pa) alleviated DKD in rats. The study intends to investigate the dynamic modulation of MC-Pa on DKD from the gut microbiota perspective. The DKD rat model was induced by a high-fat and high-sugar diet combined with streptozotocin (STZ). The rats were then supplemented with MC-Pa (80 and 160 mg/kg BW) for 12 weeks. The results showed that MC-Pa administration relieved hyperglycemia and renal injury in DKD rats. MC-Pa also reconstructed gut microbiota, improved intestinal barrier function, reduced serum proinflammatory mediators, and elevated the short-chain fatty acid (SCFAs) contents. In addition, the dynamics of Lactobacillus and Muribaculaceae_unclassified were in a dose- and time-dependent manner. Spearman correlation analysis found that a cluster of gut microbiota phyla and genera were significantly associated with DKD-related indicators. These results demonstrated that MC-Pa positively affected DKD rats by modulating gut microbiota dynamically and had potential as a prebiotic.

Inflammation and Oxidative Stress in Diabetic Kidney Disease: The Targets for SGLT2 Inhibitors and GLP-1 Receptor Agonists

The incidence of type 2 diabetes (T2D) has been increasing worldwide, and diabetic kidney disease (DKD) remains one of the leading long-term complications of T2D. Several lines of evidence indicate that glucose-lowering agents prevent the onset and progression of DKD in its early stages but are of limited efficacy in later stages of DKD. However, sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor (GLP-1R) agonists were shown to exert nephroprotective effects in patients with established DKD, i.e., those who had a reduced glomerular filtration rate. These effects cannot be solely attributed to the improved metabolic control of diabetes. In our review, we attempted to discuss the interactions of both groups of agents with inflammation and oxidative stress—the key pathways contributing to organ damage in the course of diabetes. SGLT2i and GLP-1R agonists attenuate inflammation and oxidative stress in experimental in vitro and in vivo models of DKD in several ways. In addition, we have described experiments showing the same protective mechanisms as found in DKD in non-diabetic kidney injury models as well as in some tissues and organs other than the kidney. The interaction between both drug groups, inflammation and oxidative stress appears to have a universal mechanism of organ protection in diabetes and other diseases.

Comparative effects of incretin-based therapy on early-onset diabetic nephropathy in rats: Role of TNF-α, TGF-β and c-caspase-3

AIMS

Diabetic nephropathy, a major threat to diabetic patients, is considered as the main reason for end-stage renal disease. Fortunately, incretin-based therapy has been aroused as considerable source to attenuate diabetic renal damage. This study aimed to investigate whether superior protective effects on the progression of diabetic kidney are exerted by glucagon-like peptide-1 analog, exenatide, or dipeptidyl peptidase-4 inhibitor, sitagliptin.

MATERIALS AND METHODS

Male Wistar rats were fed high-fat diet for 2 weeks followed by injection of low dose streptozotocin to induce type 2 diabetes mellitus. Four weeks after induction of diabetes, diabetic rats were administered vehicle, exenatide (5 μg/kg/day, SC) or sitagliptin (10 mg/kg/day, orally) for 4 weeks.

KEY FINDINGS

Different incretin mimetic agents improved renal function as evident by significant decreases in serum creatinine and urea levels with decline in urinary microalbuminuria and marked improvement in histological alterations. Both treated diabetic rats also exhibited a significant improvement in metabolic intolerance with more pronounced effect of exenatide on glucose regulation. Ameliorated renal oxidative stress alongside significant downregulation in transforming growth factor-beta, tumor necrosis factor-alpha and cleaved-caspase-3 protein expressions in renal tissues were recorded in treated diabetic rats.

SIGNIFICANCE

Administration of either exenatide or sitagliptin showed ameliorative effects on early diabetic nephropathy without notable differences between their renal protective effects. However, further clinical studies are still required to ensure their comparative promising effects on the management of renal complication of diabetes.