Diabetic nephropathy amelioration by a low-dose sitagliptin in an animal model of type 2 diabetes (Zucker diabetic fatty rat)

Alogliptin attenuates STZ-induced diabetic nephropathy in rats through the modulation of autophagy, apoptosis, and inflammation pathways: Targeting NF-κB and AMPK/mTOR pathway

AIM

Diabetic nephropathy (DN) is a type of microvascular complication that arises from diabetes mellitus and leads to further health issues. Most importantly, the prevalence of DN is steadily rising in developed countries. This research explored the therapeutic benefits of alogliptin, a dipeptidyl peptidase IV (DPP-4) inhibitor, on streptozotocin (STZ)-induced DN and its underlying mechanisms in rats.

MAIN METHODS

Ten rats were allocated to group 1, served as the normal group; and received saline. To develop diabetes, thirty rats were administered a single intraperitoneal dose of STZ (45 mg/kg). STZ-induced diabetic rats were randomly assigned to three groups: group 2 diabetic control; was given saline, groups 3 and 4 received alogliptin (10 mg/kg) and (20 mg/kg), respectively. The treatment began 8 weeks after diabetes onset and continued for four weeks. Histopathological alterations in the kidney were detected. Serum was collected to measure blood glucose levels (BGL), renal function, and lactate dehydrogenase (LDH). Tissue samples were collected to detect changes in oxidative stress (OS), inflammation, 5' adenosine monophosphate-activated protein kinase (AMPK), and the mammalian target of Rapamycin (mTOR) signaling pathways in addition to apoptotic and autophagy changes.

KEY FINDINGS

Alogliptin reduced STZ-induced histological changes in the kidney as well as OS, and inflammation. Alogliptin also ameliorated the AMPK/mTOR signaling pathways, enhanced autophagy, and reduced apoptosis.

SIGNIFICANCE

These results demonstrate that alogliptin ameliorates inflammation and OS and consequently modulates the AMPK/mTOR axis along with targeting autophagy and apoptosis, leading to the alleviation of DN.

Incretin-based therapy: a new horizon in diabetes management

Diabetes mellitus, a metabolic syndrome characterized by hyperglycemia and insulin dysfunction, often leads to serious complications such as neuropathy, nephropathy, retinopathy, and cardiovascular disease. Incretins, gut peptide hormones released post-nutrient intake, have shown promising therapeutic effects on these complications due to their wide-ranging biological impacts on various body systems. This review focuses on the role of incretin-based therapies, particularly Glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors, in managing diabetes and its complications. We also discuss the potential of novel agents like semaglutide, a recently approved oral compound, and dual/triple agonists targeting GLP-1/GIP, GLP-1/glucagon, and GLP-1/GIP/glucagon receptors, which are currently under investigation. The review aims to provide a comprehensive understanding of the beneficial impacts of natural incretins and the therapeutic potential of incretin-based therapies in diabetes management.

The DPP-4 inhibitor sitagliptin improves glycaemic control and early-stage diabetic nephropathy in adolescents with type 1 diabetes using the MiniMed 780G advanced hybrid closed-loop system: a randomised controlled trial

AIMS/HYPOTHESIS

Dipeptidyl peptidase-4 (DPP-4) inhibition has beneficial effects on various metabolic indicators in diabetes. Stromal cell-derived factor-1 (SDF-1) is expressed in diverse organs including the kidneys and is cleaved and inactivated by DPP-4 enzyme. The aim of this study was to conduct a randomised controlled trial to assess the effect of sitagliptin on diabetic nephropathy when used as an add-on therapy to the advanced hybrid closed-loop (AHCL) system in adolescents with type 1 diabetes and nephropathy.

METHODS

This open-label, parallel-group, randomised controlled trial took place at the Pediatric Diabetes Clinic, Ain Shams University, Egypt. Forty-six adolescents aged 14.13 ± 2.43 years on the MiniMed 780G system for at least 6 months before study, with HbA1c ≤69 mmol/mol (8.5%) and diabetic nephropathy in the form of microalbuminuria, were randomly assigned to two groups (n=23 for each) based on a computer-generated randomisation sequence. The intervention group received oral sitagliptin 50 mg for 3 months. The other group used AHCL only and served as a control group. The primary outcome measure was the change in urinary albumin/creatinine ratio (UACR) after 3 months of administration of sitagliptin. The key secondary outcome measure was the change from baseline in SDF-1 levels after treatment.

RESULTS

Data for all participants were analysed. No significant difference was found between the groups as regards baseline clinical and laboratory characteristics as well as AHCL system settings (p>0.05). Serum SDF-1 levels were higher in all individuals with type 1 diabetes vs healthy control individuals (p<0.001). After 3 months, sitagliptin resulted in a significant decrease of SDF-1 levels from 3.58 ± 0.73 to 1.99 ± 0.76 ng/ml (p<0.001), together with improvement of UACR from 7.27 ± 2.41 to 1.32 ± 0.31 mg/mmol (p<0.001). In addition, sitagliptin reduced postprandial glucose, sensor glucose, coefficient of variation and total daily dose of insulin, while time in range 3.9-10.0 mmol/l (70-180 mg/dl) and insulin-to-carbohydrate ratio were significantly increased. Sitagliptin was safe and well-tolerated without severe hypoglycaemia or diabetic ketoacidosis.

CONCLUSIONS/INTERPRETATION

Sitagliptin as an add-on therapy to AHCL had a reno-protective effect for individuals with type 1 diabetes and diabetic nephropathy, in addition to the improvement of time in range while reducing glycaemic variability and without compromising safety.

FUNDING

This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06115460.

Analyzing Diabetes Detection and Classification: A Bibliometric Review (2000-2023)

Bibliometric analysis is a rigorous method to analyze significant quantities of bibliometric data to assess their impact on a particular field. This study used bibliometric analysis to investigate the academic research on diabetes detection and classification from 2000 to 2023. The PRISMA 2020 framework was followed to identify, filter, and select relevant papers. This study used the Web of Science database to determine relevant publications concerning diabetes detection and classification using the keywords "diabetes detection", "diabetes classification", and "diabetes detection and classification". A total of 863 publications were selected for analysis. The research applied two bibliometric techniques: performance analysis and science mapping. Various bibliometric parameters, including publication analysis, trend analysis, citation analysis, and networking analysis, were used to assess the performance of these articles. The analysis findings showed that India, China, and the United States are the top three countries with the highest number of publications and citations on diabetes detection and classification. The most frequently used keywords are machine learning, diabetic retinopathy, and deep learning. Additionally, the study identified "classification", "diagnosis", and "validation" as the prevailing topics for diabetes identification. This research contributes valuable insights into the academic landscape of diabetes detection and classification.

Effects of selenium-cadmium co-enriched Cardamine hupingshanensis on bone damage in mice

Selenium (Se) and cadmium (Cd) usually co-existed in soils, especially in areas with Se-rich soils in China. The potential health consequences for the local populations consuming foods rich in Se and Cd are unknown. Cardamine hupingshanensis (HUP) is Se and Cd hyperaccumulator plant that could be an ideal natural product to assess the protective effects of endogenous Se against endogenous Cd-caused bone damage. Male C57BL/6 mice were fed 5.22 mg/kg cadmium chloride (CdCl2) (Cd 3.2 mg/kg body weight (BW)), or HUP solutions containing Cd 3.2 mg/kg BW and Se 0.15, 0.29 or 0.50 mg/kg BW (corresponding to the HUP0, HUP1 and HUP2 groups) interventions. Se-enriched HUP1 and HUP2 significantly decreased Cd-induced femur microstructure damage and regulated serum bone osteoclastic marker levels and osteogenesis-related genes. In addition, endogenous Se significantly decreased kidney fibroblast growth factor 23 (FGF23) protein expression and serum parathyroid hormone (PTH) levels, and raised serum calcitriol (1,25(OH)2D3). Furthermore, Se also regulated gut microbiota involved in skeletal metabolism disorder. In conclusion, endogenous Se, especially with higher doses (the HUP2 group), positively affects bone formation and resorption by mitigating the damaging effects of endogenous Cd via the modulation of renal FGF23 expression, circulating 1,25(OH)2D3 and PTH and gut microbiota composition.

Protective effects of cardamom aqueous extract against tamoxifen-induced pancreatic injury in female rats

Tamoxifen (TAM) is a commonly used drug for breast cancer treatment. Although effective, TAM has deleterious effects on many organs. The toxic effects of TAM on the pancreas and the underlying mechanisms however, have not fully investigated. In the present study, we investigated the effects of TAM on the pancreatic tissue in female rats. We also examined whether cardamom aqueous extract (CAE) protects against TAM-induced pancreatic injury. TAM-intoxicated rats were injected with 45 mg/kg of TAM for 10 days, whereas rats in the CAE-treated group were administered 10 mL/kg of CAE for 20 days, starting 10 days prior to TAM administration. Treatment with TAM resulted in severe degeneration of the pancreatic acini and marked increases in the serum levels of pancreatic lipase, α-amylase, glucose, fatty acids and triglycerides along with decreased insulin serum levels. TAM led to oxidative stress as evident from a significant increase in the pancreatic levels of lipid peroxides and nitric oxide along with the depletion of reduced glutathione, glutathione peroxidase, and superoxide dismutase. Moreover, inflammation was indicated by a significant increase in tumor necrosis factor-α and interleukin-6 levels, enhanced expression of the macrophage recruitment marker; CD68 as well as up-regulated protein levels of toll-like receptor 4 and nuclear factor kappa B and increased p-p38/MAPK ratio; which are important signals in the production of inflammatory cytokines. TAM also markedly increased the pancreatic levels of caspase-3 and BAX reflecting its apoptotic effects. The CAE treatment ameliorated all the biochemical and histological changes induced by TAM. The present study revealed, for the first time, that TAM has toxic effects on the pancreatic tissue through oxidative stress, inflammation and apoptotic effects. The present study also provides evidence that CAE exerts cytoprotective effects against these deleterious effects induced by TAM in the pancreatic tissue.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-023-00198-w.

Sitagliptin ameliorates diabetic nephropathy by upregulating renal nephrin and podocin expression through modulation of adipokines levels

Diabetic nephropathy is the leading cause of end-stage renal failure, but the effectiveness of currently available strategies for preventing diabetic nephropathy remains unsatisfactory. This study was designed to evaluate the changes in adipokines levels caused by dipeptidyl peptidase-4 inhibitor sitagliptin therapy as one of the possible mechanisms of sitagliptin's amelioration of diabetic nephropathy. Twenty-four male Wistar rats weighing 180-200 g were taken and divided into three groups, that is, control, diseased, and treatment group. High-fat diet and streptozotocin-induced Type 2 diabetic rats were divided into diseased and treatment groups. The treatment group was given sitagliptin orally, 10 mg/kg per day for 6 weeks. Serum glucose, serum insulin, serum blood urea nitrogen, serum creatinine, and 24-h urinary protein levels were measured in serum and urine samples. mRNA expression levels of podocin, nephrin, and adipokines in renal tissues were determined. Results showed that sitagliptin treatment effectively reduced serum glucose, serum creatinine, serum blood urea nitrogen, and 24-h proteinuria, along with partial prevention of insulinopenia, in the treatment group as compared to the diseased group. The renal mRNA expression levels of podocin, nephrin, and adiponectin were significantly upregulated, while those of leptin and resistin were significantly downregulated in the diabetic rats receiving sitagliptin therapy compared to the non-treated diabetic rats. Based on these findings, it is suggested that sitagliptin, via mediating the modulation of adipokines levels, upregulates renal nephrin and podocin expression, which leads to the amelioration of diabetic nephropathy.

The effect of linagliptin on microalbuminuria in patients with diabetic nephropathy: a randomized, double blinded clinical trial

The aim of the present study was to investigate the effect of linagliptin on microalbuminuria in patients with diabetic nephropathy (DN). The present double-blind randomized placebo-controlled clinical trial was performed on 92 patients with DN who were divided into two groups. The intervention and control groups received linagliptin 5 mg and placebo for 24 weeks, respectively. Blood pressure, lipid profile, liver enzymes, fasting plasma glucose (FPG), and urine albumin-creatinine ratio (UACR) were assessed and recorded before, 12 weeks, and 24 weeks after the beginning of the intervention. The mean value of UACR decrease was significant over time in both groups, with higher decrease in linagliptin group, however, the differences between two groups were not, statistically significant (P > 0.05). However, the percentage of improvement in microalbuminuria (UACR < 30 mg/g) in the linagliptin group was significantly higher than that of the control group during 24 weeks of intervention (68.3% vs. 25%; P-value < 0.001). There was no statistically significant difference in the mean value of the UACR and other parameters between linagliptin treated and placebo treated patients with diabetic nephropathy. Further studies, with longer periods of follow-up are suggested to examine these patients' renal outcomes.

Oxidative stress in the pathophysiology of type 2 diabetes and related complications: Current therapeutics strategies and future perspectives

Type 2 diabetes (T2DM) is a persistent metabolic disorder rising rapidly worldwide. It is characterized by pancreatic insulin resistance and β-cell dysfunction. Hyperglycemia induced reactive oxygen species (ROS) production and oxidative stress are correlated with the pathogenesis and progression of this metabolic disease. To counteract the harmful effects of ROS, endogenous antioxidants of the body or exogenous antioxidants neutralise it and maintain bodily homeostasis. Under hyperglycemic conditions, the imbalance between the cellular antioxidant system and ROS production results in oxidative stress, which subsequently results in the development of diabetes. These ROS are produced in the endoplasmic reticulum, phagocytic cells and peroxisomes, with the mitochondrial electron transport chain (ETC) playing a pivotal role. The exacerbated ROS production can directly cause structural and functional modifications in proteins, lipids and nucleic acids. It also modulates several intracellular signaling pathways that lead to insulin resistance and impairment of β-cell function. In addition, the hyperglycemia-induced ROS production contributes to micro- and macro-vascular diabetic complications. Various in-vivo and in-vitro studies have demonstrated the anti-oxidative effects of natural products and their derived bioactive compounds. However, there is conflicting clinical evidence on the beneficial effects of these antioxidant therapies in diabetes prevention. This review article focused on the multifaceted role of oxidative stress caused by ROS overproduction in diabetes and related complications and possible antioxidative therapeutic strategies targeting ROS in this disease.

Anti-fibrotic activity of sitagliptin against concanavalin A-induced hepatic fibrosis. Role of Nrf2 activation/NF-κB inhibition

Sitagliptin is known for its anti-diabetic activity though it has other pleiotropic pharmacological actions. Its effect against concanavalin A (Con A)-induced hepatic fibrosis has not been investigated yet. Our target was to test whether sitagliptin can suppress the development of Con A-induced hepatic fibrosis and if so, what are the mechanisms involved? Con A (6 mg/kg) was injected once weekly to male Swiss albino mice for four weeks. Sitagliptin was daily administered concurrently with Con A. Results have shown the potent hepatoprotective activity of sitagliptin against Con A-induced hepatitis and fibrosis. That was evident through the amelioration of hepatotoxicity serum parameters (ALT, AST, ALP, and LDH) and the increase in the level of serum albumin in sitagliptin treated mice. Simultaneously, there was amendment of the Con A-induced hepatic lesions and repression of fibrosis in sitagliptin-treated animals. Hydroxyproline, collagen content and the immuno-expression of the fibrotic markers, TGF-β and α-SMA were depressed upon sitagliptin treatment. Sitagliptin suppressed Con A-induced oxidative stress and increased antioxidants. RT-PCR analysis showed enhancement of mRNA expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its target genes (GCLc, GCLm, NQO-1, HO-1) by sitagliptin. Furthermore, sitagliptin ameliorated the level and immuno-expression of nuclear factor kappa-B (NF-κB) alongside the immuno-expression of the inflammatory cytokine, TNF-α. Taken together, this study demonstrates the hepatoprotective activity of sitagliptin which may be in part related to enhancement of Nrf2 signaling pathway and inhibition of NF-κB which interact inflammatory response in liver. Sitagliptin might be a new candidate to suppress hepatitis-associated fibrosis.

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.

Towards Better Drug Repositioning: Targeted Immunoinflammatory Therapy for Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common and important microvascular complications of diabetes mellitus (DM). The main clinical features of DN are proteinuria and a progressive decline in renal function, which are associated with structural and functional changes in the kidney. The pathogenesis of DN is multifactorial, including genetic, metabolic, and haemodynamic factors, which can trigger a sequence of events. Controlling metabolic risks such as hyperglycaemia, hypertension, and dyslipidaemia is not enough to slow the progression of DN. Recent studies emphasized immunoinflammation as a critical pathogenic factor in the progression of DN. Therefore, targeting inflammation is considered a potential and novel treatment strategy for DN. In this review, we will briefly introduce the inflammatory process of DN and discuss the anti-inflammatory effects of antidiabetic drugs when treating DN.

A Novel Dipeptidyl Peptidase-4 Inhibitor DA-1229 Ameliorates Tubulointerstitial Fibrosis in Cyclosporine Nephrotoxicity in Mice

Cyclosporine A (CyA) is an immunosuppressive agent that induces nephrotoxicity with long-term treatment. The roles of DPP-4 and its inhibitors in cyclosporine nephrotoxicity are not fully understood. Therefore, we investigated the effects of a novel DPP-4 inhibitor, DA-1229, on the progression of renal disease in an experimental cyclosporine nephrotoxicity model. Chronic cyclosporine nephrotoxicity was induced in six-week-old male ICR mice by subcutaneous injections of CyA at a dose of 30 mg/kg for four weeks. Animals were treated with DA-1229 at a dose of 300 mg/kg per day in food for four weeks. Although DPP-4 activity did not increase in the kidneys of mice with induced cyclosporine nephrotoxicity, DA-1229 treatment significantly suppressed DPP-4 activity in both plasma and renal tissues. DPP-4 inhibition by DA-1229 led to significantly decreased albuminuria and urinary excretion of 8-isoprosatane. DPP-4 inhibition also substantially suppressed pro-inflammatory effects, profibrotic molecules, and macrophage infiltration, and led to the improvement in renal structural changes. Our results suggest that DPP-4 inhibition by DA-1229 provides renoprotective effects in an animal model of cyclosporine nephrotoxicity via antioxidant, anti-inflammatory, and anti-fibrotic mechanisms. DPP-4 inhibition may be a useful new therapeutic approach for the management of progressive renal disease in cyclosporine nephrotoxicity.

Dipeptidyl-Peptidase 4 Inhibitors did not Improve Renal Endpoints in Advanced Diabetic Kidney Disease

OBJECTIVE

The efficacy of dipeptidyl-peptidase 4 inhibitors (DPP4is) in advanced diabetic kidney disease (DKD) is unknown. We investigated whether DPP4is confer renal protective benefits in DKD patients.

METHODS

We conducted a retrospective cohort study between 2012 and 2018 in Taiwan. We only included type 2 diabetes patients with estimated glomerular filtration rate (eGFR) between 30 and 90 mL/min/1.73 m² and urine albumin to creatinine ratio between 300 and 5,000 mg/g. Patients with DPP4i prescriptions were selected as cases, while non-DPP4i users served as controls. We followed these patients until the presence of composite primary renal endpoints, which was defined by the earliest occur-rence of clinical renal outcomes.

RESULTS

A total of 522 patients were included in the analysis, comprising 273 patients with a DPP4i prescription who were selected as cases and 249 patients without DPP4i prescription who were assigned as controls. Median follow-up duration for DPP4i users and nonusers was 2.2 years and 3.4 years, respectively. At baseline, the mean glycated hemoglobin levels for DPP4i users and nonusers were 8.1% and 8.3%, respectively. Among patients with DPP4i prescriptions, there was no reduction in composite primary renal outcome, with a crude hazard ratio (HR) of 1.50 (95% confidence interval [CI], 0.95 to 2.36). Similar results were observed for the risk of persistent eGFR <15 mL/min/1.73 m², with a HR of 1.68 (95% CI, 0.90 to 3.13), doubling of serum creatinine level, with a HR of 1.05 (95% CI, 0.15 to 7.45), and end-stage renal disease, with a HR of 0.87 (95% CI, 0.14 to 5.19).

CONCLUSION

DPP4i prescription did not reduce the risk of composite renal endpoints in DKD patients.

ABBREVIATIONS

BMI = body mass index; CI = confidence interval; CVOT = cardiovascular outcomes trial; DPP4i = dipeptidyl-peptidase 4 inhibitor; DKD = diabetic kidney disease; eGFR = estimated glomerular filtration rate; ESRD = end-stage renal disease; HbA1c = glycated hemoglobin; HR = hazard ratio; SGLT2i = sodium-glucose cotransporter 2 inhibitor; T2D = type 2 diabetes; UACR = urine albumin to creatinine ratio.

Diet-induced rodent models of obesity-related metabolic disorders-A guide to a translational perspective

Diet is a critical element determining human health and diseases, and unbalanced food habits are major risk factors for the development of obesity and related metabolic disorders. Despite technological and pharmacological advances, as well as intensification of awareness campaigns, the prevalence of metabolic disorders worldwide is still increasing. Thus, novel therapeutic approaches with increased efficacy are urgently required, which often depends on cellular and molecular investigations using robust animal models. In the absence of perfect rodent models, those induced by excessive consumption of fat and sugars better replicate the key aspects that are the root causes of human metabolic diseases. However, the results obtained using these models cannot be directly compared, particularly because of the use of different dietary protocols, and animal species and strains, among other confounding factors. This review article revisits diet-induced models of obesity and related metabolic disorders, namely, metabolic syndrome, prediabetes, diabetes and nonalcoholic fatty liver disease. A critical analysis focused on the main pathophysiological features of rodent models, as opposed to the criteria defined for humans, is provided as a practical guide with a translational perspective for the establishment of animal models of obesity-related metabolic diseases.

Maternal sitagliptin treatment attenuates offspring glucose metabolism and intestinal proinflammatory cytokines IL-6 and TNF-α expression in male rats

Increasing evidence shows that maternal overnutrition may increase the risk of diabetes in offspring. We hypothesized that maternal sitagliptin intervention may improve glucose intolerance through gut targeting. Female Sprague-Dawley (SD) rats were fed a normal diet (ND) or a high-fat diet (HFD) for 4 weeks before mating. ND pregnant rats were divided into two subgroups: ND group (ND alone) and the ND-sitagliptin group (ND combined with 10 mg/kg/day sitagliptin treatment). HFD pregnant rats were randomized to one of two groups: HFD group (HFD alone) and the HFD-sitagliptin group (HFD combined with 10 mg/kg/day sitagliptin treatment) during pregnancy and lactation. Glucose metabolism was assessed in offspring at weaning. Intestinal gene expression levels were investigated. Maternal sitagliptin intervention moderated glucose intolerance and insulin resistance in male pups. Moreover, maternal sitagliptin treatment inhibited offspring disordered intestinal expression of proinflammatory markers, including interleukin-6 (Il6), ll1b, and tumor necrosis factor (Tnf), at weaning and reduced intestinal IL-6, TNF-α expression by immunohistochemical staining and serum IL-6, TNF-α levels. However, maternal sitagliptin intervention did not affect offspring serum anti-inflammatory cytokine IL-10 level. Our results are the first to show that maternal sitagliptin intervention moderated glucose metabolism in male offspring. It may be involved with moderating intestinal IL-6 and TNF-α expression in male rat offspring.

The pivotal relation between glucagon-like peptides, NFκB and inflammatory bowel disease

Glucagon-like peptides (GLPs), GLP-1 and GLP-2, are released from intestinal enteroendocrine cells (L cells) in response to ingested nutrients. GLP-1 plays a crucial role in lowering blood glucose and controlling body weight, through stimulating the islet ß cells of pancreas to secrete insulin, inhibiting gastric emptying, and reducing food ingestion. Therefore, GLP-1 receptor agonists are now used in the treatment of obese patients with type 2 diabetes mellitus (T2DM). GLP-2, on the other hand, is used as a novel therapy for short bowel syndrome (SBS) through its ability to restore intestinal homeostasis and induce epithelial proliferation. GLPs and the inhibitors of their degradation enzymes, dipeptidyl peptidase-IV (DPP-IV) inhibitors, have many anti-inflammatory actions. Many animal-based clinical trials have proved that GLP-based therapy has a pivotal role in the management of inflammatory bowel disease (IBD), possibly through regulating the transcription factor nuclear factor kappa-ligand B (NFκB). NFκB controls the production and secretion of many cytokines and chemokines encountered in the pathophysiology of IBD such as interleukin (IL-1β-IL-12, IL-13, IL-21, IL-22, IL-6) and tumour necrosis factor-alpha (TNF-α) and hence, may provide a promising therapeutic option.

Sitagliptin and tofacitinib ameliorate adjuvant induced arthritis via modulating the cross talk between JAK/STAT and TLR-4/NF-κB signaling pathways

AIMS

Rheumatoid arthritis is an autoimmune systemic disorder causing pain, swelling, stiffness, and disability in various joints. This work was designed to evaluate the effect of sitagliptin and tofacitinib on Janus kinase (JAK)/signaling transducer and activator of transcription (STAT) and toll like receptor (TLR-4)/nuclear factor kappa B (NF-κB) signaling pathways in adjuvant induced arthritis in rats.

MATERIALS AND METHODS

Severity of arthritis was evaluated and serum was analyzed for inflammatory mediators. The mRNA and protein expression level of the most important members of the two signaling pathways were determined. Lipid profile, transaminases and renal function parameters were assessed.

KEY FINDINGS

Sitagliptin and tofacitinib significantly decreased the level of inflammatory parameters, the mRNA and protein expression level of the members of JAK/STAT and TLR-4/NF-κB pathways with more prominent effect of sitagliptin on TLR-4/NF-κB pathway and more expected obvious effect of tofacitinib on JAK/STAT pathway. The combination offered additional anti-inflammatory effect by inhibiting the cross talk between these pathways as inhibition of NF-κB activation decreased the serum level of IL-6 preventing the activation of STAT-3 in tibiotarsal tissues.

SIGNIFICANCE

The combination of tofacitinib and sitagliptin normalized serum lipids and blood glucose level which could offer protection against cardiovascular diseases and caused partial reversal of serum transaminases and creatinine levels which can protect against tofacitinb's related hepato and nephrotoxicity. We could conclude that the combination of Sitagliptin with tofacitinib can offer synergistic anti-inflammatory effect and more protective action against side effects of tofacitinib.

The effect of linagliptin on renal progression in type-2 diabetes mellitus patients with chronic kidney disease: A prospective randomized controlled study

BACKGROUND

Linagliptin does not require dose adjustment in diabetes mellitus patients with chronic kidney disease (CKD). But, renal effects of linagliptin are not clear. Our aim was to examine the effect of linagliptin on renal disease progression in only insulin dependent type 2 diabetes mellitus (DM) patients with CKD.

METHODS

Stage 3-4 CKD patients were randomized into 2 groups in this prospective randomized controlled study. In the first group, linagliptin 5mg was added in addition to the background insulin therapy. In the second group, patients continued their insulin therapy. Patients were followed up at 3-month intervals for one year.

RESULTS

The study population consisted of 164 patients (90 patients in linagliptin group, 74 patients in other group) with a mean age of 67.5±8.8 years. eGFR significantly increased in linagliptin group (p=0.033), but decreased in other group (p=0.003). No significant change was observed in total insulin dose in linagliptin group (p=0.111), but in other group, total insulin dose significantly increased (p<0.001). Proteinuria levels decreased in both groups, but there was no significant change. In the multiple logistic regression analysis, male gender and proteinuria emerged as variables that showed significant association with increased risk and the use of linagliptin emerged as variable that showed significant association with decreased risk for CKD progression.

CONCLUSION

Linagliptin in DM patients with CKD was able to improve renal progression without significant effect on proteinuria and glucose control. With regard to treating diabetic nephropathy, linagliptin may offer a new therapeutic approach.

Pleiotropic effects of anti-diabetic drugs: A comprehensive review

Diabetes mellitus characterized by hyperglycaemia presents an array of comorbidities such as cardiovascular and renal failure, dyslipidemia, and cognitive impairments. Populations above the age of 60 are in an urgent need of effective therapies to deal with the complications associated with diabetes mellitus. Widely used anti-diabetic drugs have good safety profiles and multiple reports indicate their pleiotropic effects in diabetic patients or models. This review has been written with the objective of identifying the widely-marketed anti-diabetic drugs which can be efficiently repurposed for the treatment of other diseases or disorders. It is an updated, comprehensive review, describing the protective role of various classes of anti-diabetic drugs in mitigating the macro and micro vascular complications of diabetes mellitus, and differentiating these drugs on the basis of their mode of action. Notably, metformin, the anti-diabetic drug most commonly explored for cancer therapy, has also exhibited some antimicrobial effects. Unlike class specific effects, few instances of drug specific effects in managing cardiovascular complications have also been reported. A major drawback is that the pleiotropic effects of anti-diabetic drugs have been mostly investigated only in diabetic patients. Thus, for effective repurposing, more clinical trials devoted to analyse the effects of anti-diabetic drugs in patients irrespective of their diabetic condition, are required.

Renal protective effect of pinitol in experimental diabetes

Pinitol is a natural antidiabetic agent shown to prevent or ameliorate metabolic and overall vascular and neural function. In the present study we have evaluated the potential benefits of pinitol on renal function of streptozotocin (STZ)-induced diabetic rats. Both euglycemic or 8-week or 16-week diabetic rats were treated with either saline (1 ml/kg/12h; p.o) or pinitol (20 mg/kg/12h; p.o). The renal function was evaluated by using metabolic cages, renal hemodynamic and tubular parameters measurements. Histological examination and evaluation of the protein expression of renal markers such as nephrin, TGFβ and pERK were also performed. Pinitol decreased by 50% the increased urinary albumin/creatinine ratio in both 8-week and 16 week diabetic rats. In addition, the glomerular volume of 16-week rats increased by 55% and this increase was blunted by pinitol. Remarkably, pressure-natriuresis was completely blunted in both 8 and 16-week diabetic rats but this impairment was prevented by pinitol in both treatment regimens. Pinitol ameliorated renal lesions and also prevented the decrease in nephrin expression and the increase of pERK and TGFβ expression in both diabetic groups. Natriuresis due to high renal perfusion pressure increased 7-fold in control animals but was blocked in 16-week diabetic rats and remarkably pinitol partially restored pressure natriuresis (3-fold increase in sodium excretion during pressure natriuresis). Pinitol prevents and ameliorates albuminuria, glomerular expansion, impairment of pressure-natriuresis, renal structural alterations and changes of renal markers and has the potential to be tested for the prevention of diabetic kidney disease.

Crescent-Like Lesions as an Early Signature of Nephropathy in a Rat Model of Prediabetes Induced by a Hypercaloric Diet

Diabetic nephropathy (DN) is a major microvascular complication of diabetes. Obesity and hyperlipidemia, fueled by unhealthy food habits, are risk factors to glomerular filtration rate (GFR) decline and DN progression. Several studies recommend that diabetic patients should be screened early (in prediabetes) for kidney disease, in order to prevent advanced stages, for whom the current interventions are clearly inefficient. This ambition greatly depends on the existence of accurate early biomarkers and novel molecular targets, which only may arise with a more thorough knowledge of disease pathophysiology. We used a rat model of prediabetes induced by 23 weeks of high-sugar/high-fat (HSuHF) diet to characterize the phenotype of early renal dysfunction and injury. When compared with the control animals, HSuHF-treated rats displayed a metabolic phenotype compatible with obese prediabetes, displaying impaired glucose tolerance and insulin sensitivity, along with hypertriglyceridemia, and lipid peroxidation. Despite unchanged creatinine levels, the prediabetic animals presented glomerular crescent-like lesions, accompanied by increased kidney Oil-Red-O staining, triglycerides content and mRNA expression of IL-6 and iNOS. This model of HSuHF-induced prediabetes can be a useful tool to study early features of DN, namely crescent-like lesions, an early signature that deserves in-depth elucidation.

Diet-Induced Rodent Models of Diabetic Peripheral Neuropathy, Retinopathy and Nephropathy

Unhealthy dietary habits are major modifiable risk factors for the development of type 2 diabetes mellitus, a metabolic disease with increasing prevalence and serious consequences. Microvascular complications of diabetes, namely diabetic peripheral neuropathy (DPN), retinopathy (DR), and nephropathy (DN), are associated with high morbidity rates and a heavy social and economic burden. Currently, available therapeutic options to counter the evolution of diabetic microvascular complications are clearly insufficient, which strongly recommends further research. Animal models are essential tools to dissect the molecular mechanisms underlying disease progression, to unravel new therapeutic targets, as well as to evaluate the efficacy of new drugs and/or novel therapeutic approaches. However, choosing the best animal model is challenging due to the large number of factors that need to be considered. This is particularly relevant for models induced by dietary modifications, which vary markedly in terms of macronutrient composition. In this article, we revisit the rodent models of diet-induced DPN, DR, and DN, critically comparing the main features of these microvascular complications in humans and the criteria for their diagnosis with the parameters that have been used in preclinical research using rodent models, considering the possible need for factors which can accelerate or aggravate these conditions.

Toxicity of Metformin and Hypoglycemic Therapies

Metformin along with other antidiabetic medications provide benefit to patients in the treatment of type 2 diabetes mellitus, but caution is advised in certain scenarios to avoid toxicity in kidney disease. Renal dosing, monitoring of kidney function, and evaluating the risk of developing serious side effects are warranted with some agents. The available literature with regard to incidence of adverse events and toxicity of hypoglycemic therapies is reviewed.

Effect of sitagliptin on tubulointerstitial Wnt/β-catenin signalling in diabetic nephropathy

AIM

To investigate the effect of sitagliptin on Wnt/β-catenin signalling in the tubulointerstitium of diabetic nephropathy.

METHODS

Forty male Wistar rats were divided into normal control (NC), diabetic model (DM), low and high-dose sitagliptin intervention groups (ST1 and ST2, respectively). Changes in the biochemical parameters and tubulointerstitial fibrosis index were observed. The levels of protein and gene expression of different indicators were detected via immunohistochemistry and real-time polymerase chain reaction. NRK-52E cells were divided into the normal control group, mannitol control group, high glucose group (HG), high glucose plus sitagliptin intervention group (HG + ST) and high glucose plus Wnt/β-catenin inhibitor group (HG + XAV939). The relevant indicators were examined by Western blot or enzyme-linked immunosorbent assay.

RESULTS

Compared with the NC group, the blood glucose, glycosylated haemoglobin, 24 h urinary albumin, creatinine clearance and tubulointerstitial fibrosis index were significantly increased in the DM group. These parameters were decreased in the ST1 and ST2 groups compared to the DM group. Compared with the NC group, the levels of Wnt4, β-catenin, dipeptidyl peptidase-4 and α-smooth muscle actin were higher and E-cadherin was lower in the DM group. Sitagliptin treatment reversed these changes. In the high glucose-stimulated NRK-52E cells, sitagliptin and XAV939 inhibited the elevated expression of Wnt4, β-catenin, dipeptidyl peptidase-4, α-smooth muscle actin, transforming growth factor-β and fibronectin and restored E-cadherin activity.

CONCLUSION

Sitagliptin may inhibit the tubulointerstitial Wnt/β-catenin signalling pathway in diabetic nephropathy and provide renal protection by alleviatinge renal tubulointerstitial transdifferentiation and fibrosis.

Odds of Acute Kidney Injury in Patients Receiving Dipeptidyl Peptidase 4 Inhibitors: A National Cohort Study Within the Department of Veterans Affairs

Preclinical and clinical data of dipeptidyl peptidase 4 (DPP-4) inhibitors have demonstrated discordant data regarding acute kidney injury (AKI). Therefore, we aimed to evaluate the association between DPP-4 use and AKI. This cohort study utilized data from the Department of Veterans Affairs evaluating patients diagnosed with type 2 (T2) diabetes with a DPP-4 inhibitor and compared with nondiabetic and diabetic patients. The primary end point is the development of AKI, and statistical analyses were performed to examine the association. DPP-4 use is associated with a lower odds of AKI compared with diabetics (adjusted odds ratio (OR) = 0.39; 95% confidence interval (CI) = 0.32-0.48) and nondiabetics (OR = 0.64; 95% CI = 0.52-0.79). DPP-4 use in patients with T2 diabetes mellitus is associated with lower odds of AKI within 120 days compared with nondiabetic and diabetic controls when adjusting for study covariates.

The dipeptidyl peptidase 4 inhibitor sitagliptin improves oxidative stress and ameliorates glomerular lesions in a rat model of type 1 diabetes

AIMS

Oxidative stress has been linked to the development and progression of diabetic nephropathy (DN). The present study evaluated whether the dipeptidyl peptidase-4 inhibitor sitagliptin attenuates glomerular lesions and oxidative stress evoked by chronic hyperglycemia, by a mechanism independent of insulin secretion and glycemia normalization.

MAIN METHODS

A rat model of DN caused by streptozotocin injection was established and the effects of sitagliptin (5 mg/kg/day) were evaluated after two weeks of treatment.

KEY FINDINGS

Sitagliptin treatment did not change body weight, glycemic and lipid profiles. However, histopathological observation revealed that sitagliptin attenuates diabetes-induced glomerular lesions on diabetic rats. Sitagliptin also ameliorated the increase in DPP-4 content and promoted the stabilization of GLP-1 in the diabetic kidney. Furthermore, sitagliptin treatment significantly attenuated the increase of free-radical formation and the decrease of antioxidant defenses, attenuating therefore the oxidative stress in the kidneys of diabetic animals.

SIGNIFICANCE

The results suggest that sitagliptin treatment alleviates kidney oxidative stress in type 1 diabetic rats, which could play a key role in reducing the progression of DN.

Protective effect of silencing Stat1 on high glucose-induced podocytes injury via Forkhead transcription factor O1-regulated the oxidative stress response

Background

Podocyte plays an important role in maintaining the integrity and function of the glomerular filtration barrier. Various studies reported that forkhead transcription factor (Fox) O1 played a key role in anti-oxidative signaling. This study aimed to investigate the role of Stat1 in high glucose (HG) -induced podocyte injury.

Methods

Under normal glucose, hypertonic and HG stimulated podocyte conditions, cell counting kit-8 (CCK-8) assay, flow cytometry and western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were respectively carried out to determine cell viability, apoptosis, reactive oxygen species (ROS) production and related genes expressions. We then respectively used silent Stat1, simultaneous silencing Stat1 and FoxO1 and over-expression of FoxO1, to observe whether they/it could reverse the damage of podocytes induced by HG.

Results

High glucose attenuated cell survival and promoted cell apoptosis in MPC-5 cells at the same time, and it was also observed to promote the protein expression of Stat1 and the FoxO1 expression inhibition. Silencing Stat1 could reverse HG-induced podocytes injury. Specifically, siStat1 increased cell viability, inhibited cell apoptosis and attenuated ROS level in a high-glucose environment. Cleaved caspase-3 and pro-apoptosis protein Bax was significantly down-regulated, and anti-apoptosis protein Bcl-2 was up-regulated by siStat1. The antioxidant genes Catalase, MnSOD, NQO1 and HO1 were up-regulated by siStat1. We found that silencing FoxO1 reversed the protective effect of siStat1 on the HG-induced podocytes injury.

Conclusions

Silencing Stat1 could reverse the effects of high glucose-triggered low cell viability, cell apoptosis and ROS release and the functions of Stat1 might be involved in FoxO1 mediated-oxidative stress in nucleus.

DPP-4 Inhibitors as Potential Candidates for Antihypertensive Therapy: Improving Vascular Inflammation and Assisting the Action of Traditional Antihypertensive Drugs

Dipeptidyl peptidase-4 (DPP-4) is an important protease that is widely expressed on the surface of human cells and plays a key role in immune-regulation, inflammation, oxidative stress, cell adhesion, and apoptosis by targeting different substrates. DPP-4 inhibitors (DPP-4i) are commonly used as hypoglycemic agents. However, in addition to their hypoglycemic effect, DPP-4i have also shown potent activities in the cardiovascular system, particularly in the regulation of blood pressure (BP). Previous studies have shown that the regulatory actions of DPP-4i in controlling BP are complex and that the mechanisms involved include the functional activities of the nerves, kidneys, hormones, blood vessels, and insulin. Recent work has also shown that inflammation is closely associated with the elevation of BP, and that the inhibition of DPP-4 can reduce BP by regulating the function of the immune system, by reducing inflammatory reactions and by improving oxidative stress. In this review, we describe the potential anti-hypertensive effects of DPP-4i and discuss potential new anti-hypertensive therapies. Our analysis indicated that DPP-4i treatment has a mild anti-hypertensive effect as a monotherapy and causes a significant reduction in BP when used in combined treatments. However, the combination of DPP-4i with high-dose angiotensin converting enzyme inhibitors (ACEI) can lead to increased BP. We suggest that DPP-4i improves vascular endothelial function in hypertensive patients by suppressing inflammatory responses and by alleviating oxidative stress. In addition, DPP-4i can also regulate BP by activating the sympathetic nervous system, interfering with the renin angiotensin aldosterone system (RAAS), regulating Na/H2O metabolism, and attenuating insulin resistance (IR).

Effect of switching to teneligliptin from other dipeptidyl peptidase-4 inhibitors on glucose control and renoprotection in type 2 diabetes patients with diabetic kidney disease

AIMS/INTRODUCTION

The objective of the present study was to elucidate the effect of switching to teneligliptin from other dipeptidyl peptidase-4 (DPP-4) inhibitors on glucose control and renoprotection in type 2 diabetes mellitus patients with diabetic kidney disease.

MATERIALS AND METHODS

The present study was a single-arm, open-label, observational study. A total of 23 patients, who had urinary albumin/creatinine ratios (UACR) ≥30 mg/gCr in their first urine in the early morning, and received other DPP-4 inhibitors and renin-angiotensin system inhibitors, switched to teneligliptin 20 mg/day. After switching to teneligliptin for 24 weeks, we evaluated changes in glycated hemoglobin (HbA1c), fasting plasma glucose levels, plasma DPP-4 activity and UACR.

RESULTS

HbA1c, fasting plasma glucose and UACR values showed no significant change after 24 weeks compared with baseline. However, plasma DPP-4 activity was significantly reduced after 24 weeks (0.57 ± 0.26 nmol/min/mL, P = 0.012, vs baseline), compared with baseline (1.49 ± 1.73 nmol/min/mL), and there was a positive relationship between the change rate of plasma DPP-4 activity (Δ%DPP-4) for 24 weeks and the levels of plasma DPP-4 activity (r = -0.5997, P = 0.0025) and fasting plasma glucose (r = -0.4235, P = 0.0440) at baseline. Additionally, the Δ%DPP-4 for 24 weeks was significantly correlated to the change rate of UACR (r = 0.556, P = 0.0059). However, there was no relationship between Δ%DPP-4 and ΔHbA1c (amount of HbA1c change).

CONCLUSIONS

Switching to teneligliptin from other DPP-4 inhibitors for 24 weeks reduces plasma DPP-4 activity, which is associated with a reduction in albuminuria, independent of the change in glucose levels, in type 2 diabetes mellitus patients with diabetic kidney disease.

Using DPP-4 inhibitors to modulate beta cell function in type 1 diabetes and in the treatment of diabetic kidney disease

INTRODUCTION

DPP-4 inhibitors have pleomorphic effects that extend beyond the anti-hyperglycemic labeled use of the drug. DPP-4 inhibitors have demonstrated promising renal protective effects in T2DM and T1DM and protective effects against immune destruction of pancreatic beta-cells in T1DM.

AREAS COVERED

The efficacy of DPP-4 inhibitors in the treatment of diabetic kidney disease and possible adjunct with insulin in the treatment of T1DM to preserve beta-cell function. Pertinent literature was identified through Medline, PubMed and ClinicalTrials.gov (1997-November 2018) using the search terms T1DM, sitagliptin, vildagliptin, linagliptin, beta-cell function, diabetic nephropathy. Only articles are written in the English language, and clinical trials evaluating human subjects were used.

EXPERT OPINION

DPP-4 inhibitors can be used safely in patients with diabetic kidney disease and do not appear to exacerbate existing diabetic nephropathy. Linagliptin reduces albuminuria and protects renal endothelium from the deleterious effects of hyperglycemia. The effects of DPP-4 inhibitors on preserving beta-cell function in certain subtypes of T1DM [e.g. Latent Autoimmune Diabetes in Adult (LADA) and Slowly Progressive Type 1 Diabetes (SPIDDM)] are encouraging and show promise.

Therapeutic Options Targeting Oxidative Stress, Mitochondrial Dysfunction and Inflammation to Hinder the Progression of Vascular Complications of Diabetes

Type 2 diabetes mellitus is a leading cause of morbidity and mortality worldwide, given its serious associated complications. Despite constant efforts and intensive research, an effective, ubiquitous treatment still eludes the scientific community. As such, the identification of novel avenues of research is key to the potential discovery of this evasive "silver bullet." We focus on this review on the matter of diabetic injury to endothelial tissue and some of the pivotal underlying mechanisms, including hyperglycemia and hyperlipidemia evoked oxidative stress and inflammation. In this sense, we revisited the most promising therapeutic interventions (both non-pharmacological and antidiabetic drugs) targeting oxidative stress and inflammation to hinder progression of vascular complications of diabetes. This review article gives particular attention to the relevance of mitochondrial function, an often ignored and understudied organelle in the vascular endothelium. We highlight the importance of mitochondrial function and number homeostasis in diabetic conditions and discuss the work conducted to address the aforementioned issue by the use of various therapeutic strategies. We explore here the functional, biochemical and bioenergetic alterations provoked by hyperglycemia in the endothelium, from elevated oxidative stress to inflammation and cell death, as well as loss of tissue function. Furthermore, we synthetize the literature regarding the current and promising approaches into dealing with these alterations. We discuss how known agents and therapeutic behaviors (as, for example, metformin, dietary restriction or antioxidants) can restore normality to mitochondrial and endothelial function, preserving the tissue's function and averting the aforementioned complications.

Dipeptidyl Peptidase 4 Inhibition Ameliorates Chronic Kidney Disease in a Model of Salt-Dependent Hypertension

Cardiovascular diseases frequently coexist with chronic kidney disease that constitutes a major determinant of outcome in patients with heart failure. Dysfunction of both organs is related to chronic inflammation, endothelial dysfunction, oxidative stress, and fibrosis. Widespread expression of serine protease DPP4 that degrades varieties of substrates suggests its involvement in numerous physiological processes. In this study, we tested the effects of selective DPP4 inhibition on the progression of renal disease in a nondiabetic model of hypertensive heart disease using Dahl salt-sensitive rats. Chronic DPP4 inhibition positively affected renal function with a significant reduction in albuminuria and serum creatinine. DPP4 inhibition attenuated the inflammatory component by reducing the expression of NF-κB, TNFα, IL-1β, IL-6, and MCP-1. Kidney macrophages expressed GLP-1R, and DPP4 inhibition promoted macrophage polarization toward the anti-inflammatory M2 phenotype. Finally, high degrees of NADPH oxidase 4 expression and oxidation of nucleic acids, lipids, and proteins were reduced upon DPP4 inhibition. Our study provides evidence of renoprotection by DPP4 inhibition in a nondiabetic hypertension-induced model of chronic cardiorenal syndrome, indicating that DPP4 pathway remains a valid object to study in the context of chronic multiorgan diseases.

The Effects of Novel Antidiabetic Drugs on Albuminuria in Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND AND OBJECTIVE

The effects of novel antidiabetic drugs, including sodium-glucose cotransporter 2 (SGLT-2) inhibitors, glucagon-like peptide 1 (GLP-1) receptor agonists, and dipeptidyl peptidase 4 (DPP-4) inhibitors, on albuminuria in patients with type 2 diabetes mellitus (T2DM) are still controversial. Therefore, we performed a meta-analysis to evaluate the effects of novel antidiabetic drugs on albuminuria in patients with T2DM.

METHODS

We conducted a random-effects meta-analysis of randomized controlled trials (RCTs) by searching the MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials databases up to 16 August 2018. The effects of novel antidiabetic drugs on albuminuria were evaluated as percent changes from baseline to follow-up urinary albumin excretion/urinary albumin to creatinine ratio (UAE/UACR) levels in both the intervention and control groups. Data regarding percent changes were used to generate weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

In this meta-analysis, 26 RCTs involving 14,929 patients were included. Pooled analysis suggested that SGLT-2 inhibitors (WMD - 26.23%, 95% CI - 35.90 to - 16.56; p < 0.00001) and GLP-1 receptor agonists (WMD - 13.85%, 95% CI - 15.96 to - 11.74; p < 0.00001) were associated with a significant reduction in albuminuria compared with other conventional therapies or placebo. DPP-4 inhibitors (WMD - 6.19%, 95% CI - 14.03 to 1.66; p = 0.12) were not significantly associated with lower albuminuria than other conventional therapies or placebo.

CONCLUSION

This meta-analysis indicates that SGLT-2 inhibitors and GLP-1 receptor agonists were associated with a reduction in albuminuria compared with other conventional therapies or placebo, while DPP-4 inhibitors were not associated with albuminuria-reducing effects compared with other conventional therapies or placebo.

Sitagliptin-Moringa oleifera coadministration did not delay the progression nor ameliorated functional and morphological anomalies in alloxan-induced diabetic nephropathy

OBJECTIVE:

Sitagliptin (ST) and Moringa oleifera (MO) Lam (Moringaceae) are used concomitantly by diabetic patients, with no study ascertaining for potential favorable or otherwise renal implications. We investigated the effect of coadministration of ST and MO leaf extract on functional and morphological biomarkers of alloxan-induced diabetic nephropathy (DN).

MATERIALS AND METHODS:

Diabetes was induced with a single dose of 150 mg/kg of alloxan intraperitoneally. Seven groups of eight rats per group were used, with Groups I, II, and VII as normal (NS), diabetic control (DC), and postprandial controls. Groups III, IV, V, and VI were diabetic rats on ST, MO, ST and MO (SM), for 42 days with 2 weeks delayed treatment in a postprandial hyperglycemic group (PPSM), respectively. Serum urea, albumin, electrolyte levels, lipid profile, and kidney tropism were determined in addition to histological examinations.

RESULTS:

There was a significant increase (P < 0.05) in kidney tropism comparing all drug-treated groups and DC to normal rats. Significant increases in serum urea were observed (P = 0.02) in DC, MO-treated, and SM-treated rats compared to normal rats and also in serum triglyceride (P < 0.05) in MO-treated and SM-treated rats compared to controls and other drug-treated groups. A mild reduction in severity of pathologic lesions was observed (glomerulosclerosis Grade 1) in SM-treated rats compared to a marked necrosis in DC (Grade 3).

CONCLUSION:

The coadministration of ST–MO did not delay the progression of functional anomalies and renal injury nor ameliorated the lesions associated with chronic DN in Wistar rats.

Dipeptidyl peptidase-4 inhibition and renoprotection: the role of antifibrotic effects

PURPOSE OF REVIEW

This article analyzes the potential beneficial effects of dipeptidyl peptidase (DPP)-4 inhibitors on renal diseases.

RECENT FINDINGS

The pathological significance of DPP-4, either dependent or independent on catalytic activities, on renal diseases has been reported in preclinical studies. With regard to this, we have shown that damaged endothelial cells are converted to a mesenchymal cell phenotype, which is associated with the induction of DPP-4 in endothelial cells. The endothelial mesenchymal transition may contribute to kidney fibrosis; indeed, the antifibrotic effects of DPP-4 inhibitors have been reported elsewhere. However, even though such potential benefits of DPP-4 inhibitors on renal diseases were shown in preclinical studies, clinical trials have not yet revealed significant benefits in renal hard outcomes of DPP-4 inhibitors.

SUMMARY

To completely understand the beneficial effects of DPP-4 inhibitors, both the following studies are required: first, preclinical studies that analyze deeper molecular mechanisms of DPP-4 inhibition, and, second, clinical studies that investigate whether such potential beneficial effects of DPP-4 inhibitors are relevant to the patients in the clinic.

The role of dipeptidylpeptidase-4 inhibitors in management of cardiovascular disease in diabetes; focus on linagliptin

Multiple population based analyses have demonstrated a high incidence of cardiovascular disease (CVD) and cardiovascular (CV) mortality in subjects with T2DM that reduces life expectancy by as much as 15 years. Importantly, the CV system is particularly sensitive to the metabolic and immune derangements present in obese pre-diabetic and diabetic individuals; consequently, CV dysfunction is often the initial CV derangement to occur and promotes the progression to end organ/tissue damage in T2DM. Specifically, diabetic CVD can manifest as microvascular complications, such as nephropathy, retinopathy, and neuropathy, as well as, macrovascular impairments, including ischemic heart disease, peripheral vascular disease, and cerebrovascular disease. Despite some progress in prevention and treatment of CVD, mainly via blood pressure and dyslipidemia control strategies, the impact of metabolic disease on CV outcomes is still a major challenge and persists in proportion to the epidemics of obesity and diabetes. There is abundant pre-clinical and clinical evidence implicating the DPP-4-incretin axis in CVD. In this regard, linagliptin is a unique DPP-4 inhibitor with both CV and renal safety profiles. Moreover, it exerts beneficial CV effects beyond glycemic control and beyond class effects. Linagliptin is protective for both macrovascular and microvascular complications of diabetes in preclinical models, as well as clinical models. Given the role of endothelial-immune cell interactions as one of the key events in the initiation and progression of CVD, linagliptin modulates these cell–cell interactions by affecting two important pathways involving stimulation of NO signaling and potent inhibition of a key immunoregulatory molecule.

[Correlation between expressions of VEGF and TRPC6 and their roles in podocyte injury in rats with diabetic nephropathy]

OBJECTIVE

To analyze the correlation between the expressions of vascular endothelial growth factor (VEGF) and transient receptor potential canonical 6 (TRPC6) and their role in podocyte injury in rats with diabetic nephropathy.

METHODS

Forty SD rats with diabetic nephropathy induced by intraperitoneal injection of 65 mg/kg streptozotocin were randomized equally into 5 groups, including a diabetic nephropathy model group and 4 treatment groups, with 8 normal SD rats as the normal control group. In the 4 treatment groups, the rats received intraperitoneal injections with SU5416 at 5 mg/kg or 10 mg/kg twice a week or with LY294002 at 1 mg/kg or 2 mg/kg once daily for 8 weeks. Blood glucose, serum creatinine, blood urea nitrogen, and 24-h urinary protein levels of the rats were detected at different time points, and the pathologies in the renal tissue were observed using HE staining, PAS staining and immunohistochemistry. The expressions of VEGF, nephrin, and TRPC6 at mRNA and protein levels were detected using RT-PCR and Western blotting.

RESULTS

Compared with normal control rats, the diabetic rats showed significantly increased fasting blood glucose, serum creatinine, blood urea nitrogen and 24-h urinary protein levels with decreased expressions of nephrin mRNA and protein (P<0.05) and increased expressions of VEGF and TRPC6 (P<0.05). Compared with the untreated diabetic rats, the rats with SU5416 treatment showed increased 24-h urinary protein, urea nitrogen, and nephrin expression and decreased TRPC6 expression without significant changes in fasting blood glucose, serum creatinine, or VEGF expression. The rats treated with LY294002 showed decreased 24-h urinary protein and TRPC6 expression without significant changes in fasting blood glucose, serum creatinine, urea nitrogen, or expressions of nephrin and VEGF.

CONCLUSION

The regulatory effect of VEGF on TRPC6 can be blocked by inhibiting VEGFR-2 or blocking PI3K/Akt signaling pathway.

Sitagliptin ameliorates diabetic nephropathy by blocking TGF-β1/Smad signaling pathway

Diabetic nephropathy (DN) is the leading cause of end-stage failure of the kidney, but the efficacy of current strategies available for the prevention of DN remains unsatisfactory. The purpose of this study was to assess whether sitagliptin (SIT) has therapeutic potential for prevention of DN and to investigate its possible mechanism. The effects of SIT on DN were investigated in rats with type 2 diabetes mellitus (T2DM) and rat mesangial cells (MCs) induced by high glucose. T2DM rats were administered at a dose of 10 mg/kg SIT. The kidney index, 24 h urinary protein, blood urea nitrogen (BUN), serum creatinine (Cr), accumulation of glycogen and collagens were investigated by different methods. MCs were administered with SIT at doses of 0.1, 1 and 10 µmol/ml. The possible mechanism of SIT on protection of diabetic kidney injury was examined by expression of transforming growth factor-β1 (TGF-β1)/Smad pathway. The results showed that the SIT-treated diabetic rats significantly reduced diabetic kidney injury by inhibiting the kidney index and attenuating 24 h urinary protein, reducing BUN and serum creatinine, inhibiting progressive renal fibrosis and increassing extracellular matrix including collagen IV and fibronectin. Further studies showed that inhibition of renal fibrosis in SIT-treated diabetic rats and MCs were associated with rebalancing of TGF-β1/Smad pathway. Sitagliptin may be a potent agent for preventing the progression of DN through inhabiting TGF-β1/Smad-mediated renal fibrosis.

A review of dipeptidyl peptidase-4 inhibitors. Hot topics from randomized controlled trials

The first clinical study to investigate effects of dipeptidyl peptidase-4 (DPP-4) inhibition was published in 2002, and since then, numerous randomized controlled trials (RCTs) have shown that DPP-4 inhibitors are efficacious, safe and well-tolerated. This review will focus upon RCTs which have investigated DPP-4 inhibitors in patient groups which are often under-represented or excluded from typical phase 3 clinical trials. Large cardiovascular (CV) safety outcome trials in patients with established CV disease have confirmed that DPP-4 inhibitors are not associated with any additional CV risk in these already-at-high-risk individuals, while raising awareness of any uncommon adverse events, such as heart failure hospitalization seen in one of the trials. Studies in patients with kidney disease have shown DPP-4 inhibitors to be efficacious without increasing the risk of hypoglycaemia, irrespective of the degree of renal impairment, while data from the large CV trials as well as smaller RCTs have even pointed towards potential renoprotective effects such individuals. The use of DPP-4 inhibitors with insulin when therapy requires intensification may be beneficial without affecting the incidence or severity of hypoglycaemia, with these effects also being replicated in patients with chronic kidney disease, for whom other agents may not be suitable. Attention is now turning towards exploring the potential utility of DPP-4 inhibitors in other circumstances, including for in-hospital management of hyperglycaemia and in other metabolic disorders. Together, these RCTs raise the possibility that in the future, DPP-4 inhibitors may have a broader use which may extend beyond glycaemic control in the typical type 2 diabetes mellitus (T2DM) patient seen in general practice and may encompass conditions other than T2DM.

Cathepsin D plays a role in endothelial-pericyte interactions during alteration of the blood-retinal barrier in diabetic retinopathy

Inflammation plays an important role in the pathogenesis of diabetic retinopathy. We have previously demonstrated the effect of cathepsin D (CD) on the mechanical disruption of retinal endothelial cell junctions and increased vasopermeability, as well as increased levels of CD in retinas of diabetic mice. Here, we have also examined the effect of CD on endothelial-pericyte interactions, as well as the effect of dipeptidyl peptidase-4 (DPP4) inhibitor on CD in endothelial-pericyte interactions in vitro and in vivo. Cocultured cells that were treated with pro-CD demonstrated a significant decrease in the expression of platelet-derived growth factor receptor-β, a tyrosine kinase receptor that is required for pericyte cell survival; N-cadherin, the key adherens junction protein between endothelium and pericytes; and increases in the vessel destabilizing agent, angiopoietin-2. The effect was reversed in cells that were treated with DPP4 inhibitor along with pro-CD. With pro-CD treatment, there was a significant increase in the phosphorylation of the downstream signaling protein, PKC-α, and Ca²⁺/calmodulin-dependent protein kinase II in endothelial cells and pericytes, which disrupts adherens junction structure and function, and this was significantly reduced with DPP4 inhibitor treatment. Increased CD levels, vasopermeability, and alteration in junctional-related proteins were observed in the retinas of diabetic rats, which were significantly changed with DPP4 inhibitor treatment. Thus, DPP4 inhibitors may be used as potential adjuvant therapeutic agents to treat increased vascular leakage observed in patients with diabetic macular edema.-Monickaraj, F., McGuire, P., Das, A. Cathepsin D plays a role in endothelial-pericyte interactions during alteration of the blood-retinal barrier in diabetic retinopathy.

Renal outcomes with dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 inhibitors (DPP-4is) are increasingly being used in the management of type 2 diabetes (T2D). The present review summarizes the current knowledge of the effects of DPP-4is on renal outcomes by analyzing the experimental preclinical data, the effects of DPP-4is on urinary albumin-creatinine ratios (UACRs) and estimated glomerular filtration rates (eGFRs) from observational studies and clinical trials, and renal events (including kidney failure requiring renal replacement therapy) in recent large prospective cardiovascular outcome trials. Renal protection has been demonstrated in various animal models that have implicated different underlying mechanisms independent of glucose control, whereas prevention of new onset microalbuminuria and/or progression of albuminuria has been reported in some clinical studies, but with no significant effects on eGFR in most of them. The long-term clinical effects of DPP-4is on renal outcomes and the development of end-stage renal disease remain largely unknown and, thus, demand further investigations in prospective trials and long-term observational studies. In conclusion, despite promising results in animal models, data on surrogate biological markers of renal function and clinical renal outcomes remain rather scanty in patients with T2D, and mostly demonstrate the safety rather than true efficacy of DPP-4is.

Renoprotective Effects of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin: A Review in Type 2 Diabetes

Diabetic nephropathy (DN) is now the single commonest cause of end-stage renal disease (ESRD) worldwide and one of the main causes of death in diabetic patients. It is also acknowledged as an independent risk factor for cardiovascular disease (CVD). Since sitagliptin was approved, many studies have been carried out revealing its ability to not only improve metabolic control but also ameliorate dysfunction in various diabetes-targeted organs, especially the kidney, due to putative underlying cytoprotective properties, namely, its antiapoptotic, antioxidant, anti-inflammatory, and antifibrotic properties. Despite overall recommendations, many patients spend a long time well outside the recommended glycaemic range and, therefore, have an increased risk for developing micro- and macrovascular complications. Currently, it is becoming clearer that type 2 diabetes mellitus (T2DM) management must envision not only the improvement in glycaemic control but also, and particularly, the prevention of pancreatic deterioration and the evolution of complications, such as DN. This review aims to provide an overview of the current knowledge in the field of renoprotective actions of sitagliptin, namely, improvement in diabetic dysmetabolism, hemodynamic factors, renal function, diabetic kidney lesions, and cytoprotective properties.

Role of soluble and membrane-bound dipeptidyl peptidase-4 in diabetic nephropathy

Diabetic nephropathy is one of the most frequent, devastating and costly complications of diabetes. The available therapeutic approaches are limited. Dipeptidyl peptidase type 4 (DPP-4) inhibitors represent a new class of glucose-lowering drugs that might also have reno-protective properties. DPP-4 exists in two forms: a plasma membrane-bound form and a soluble form, and can exert many biological actions mainly through its peptidase activity and interaction with extracellular matrix components. The kidneys have the highest DPP-4 expression level in mammalians. DPP-4 expression and urinary activity are up-regulated in diabetic nephropathy, highlighting its role as a potential target to manage diabetic nephropathy. Preclinical animal studies and some clinical data suggest that DPP-4 inhibitors decrease the progression of diabetic nephropathy in a blood pressure- and glucose-independent manner. Many studies reported that these reno-protective effects could be due to increased half-life of DPP-4 substrates such as glucagon-like peptide-1 (GLP-1) and stromal derived factor-1 alpha (SDF-1a). However, the underlying mechanisms are far from being completely understood and clearly need further investigations.

Treatment of diabetic kidney disease: current and future targets

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease in Korea and worldwide, and is a risk factor for the development of cardiovascular complications. The conventional treatments for DKD are control of blood glucose and blood pressure levels by inhibiting the renin-angiotensin system. However, the prevalence of DKD continues to increase and additional therapies are required to prevent or ameliorate the condition. Many drugs have been, or are being, developed to target the molecular mechanisms in play in DKD. This review focuses on DVD treatment, considering current and emerging therapeutic targets and the clinical trial-based evidence.

Sitagliptin Attenuates Endothelial Dysfunction of Zucker Diabetic Fatty Rats: Implication of the Antiperoxynitrite and Autophagy

Although the contributions of sitagliptin to endothelial function in diabetes mellitus were previously reported, the potential mechanisms still remain undefined. Our research was intended to explore the underlying mechanisms of protective effects of sitagliptin treatment on endothelial dysfunction in Zucker diabetic fatty (ZDF) rats. Male lean nondiabetic Zucker rats were used as control and male obese ZDF rats were randomly divided into ZDF and ZDF + sitagliptin groups. The significant decrease in endothelium-dependent relaxation induced by acetylcholine was observed in mesenteric arteries and thoracic aorta rings of ZDF rats. The administration of sitagliptin restored the vascular function effectively. The morphology study showed severe endothelial injuries in thoracic aortas of ZDF rats, and sitagliptin treatment attenuated these changes. The increased malondialdehyde levels and decreased superoxide dismutase activities in serum of ZDF rats were reversed by sitagliptin treatment. Sitagliptin also increased the expression of endothelial nitric oxide synthase and microtubule-associated protein 1 light chain 3 (LC3) and decreased the expression of inducible nitric oxide synthase, 3-nitrotyrosine, and p62 in ZDF rats. After giving Fe (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride porphyrin pentachloride (FeTMPyP, a peroxynitrite [ONOO^-] scavenger) or sitagliptin to high-glucose (30 mmol/L, 48 hours) cultured human umbilical vein endothelial cells (HUVECs), the increased levels of Beclin-1 and lysosome-associated membrane protein type 2 were detected. Both FeTMPyP and sitagliptin also significantly increased the number of mRFP-GFP-LC3 dots per cell, suggesting that autophagic flux was increased in HUVECs. Our study indicated that sitagliptin treatment can improve the endothelium-dependent relaxation and attenuate the endothelial impairment of ZDF rats. The protective effects of sitagliptin are possibly related to antiperoxynitrite and promoting autophagy.

Novel avenues for treating diabetic nephropathy: new investigational drugs

At present, treatment of diabetic kidney disease (DKD) is still mainly based on drugs acting on glycemic and blood pressure control, as there is no validated therapy able to halt the progression of renal failure. Because of the high incidence of DKD, due to the increase of diabetes mellitus in general population, new therapeutic strategies are needed. Areas covered: We analysed ongoing and already completed clinical trials, from clinicaltrials.gov and PubMed, dealing with new therapies for DKD. Expert opinion: Among the drugs currently being explored, the most promising molecules are those that interfere with glucose-dependent pathways, in particular polyol, protein kinase, hexosamine and AGEs metabolic pathways, and impaired renal vascular regulation. One of the recent goals achieved by molecular biology is the development of monoclonal antibodies able to interfere with extracellular matrix accumulation and fibrosis. Other interesting therapies are under investigation and further studies with a greater number of patients will establish a better approach for diabetic nephropathy.