Effects of linagliptin on human immortalized podocytes: a cellular system to study dipeptidyl-peptidase 4 inhibition

Comparison of effects of Empagliflozin and Linagliptin on renal function and glycaemic control: a double-blind, randomized clinical trial

Background

This study aimed to compare the effects of Linagliptin and Empagliflozin on renal function and glycaemic control in patients with type 2 diabetes mellitus (DM).

Method

We conducted a randomized, double-blind, parallel trial on patients aged 30 to 80 years with type 2 DM and HbA1c ≤ 9%, regardless of background medical therapy, to compare the effects of Empagliflozin and Linagliptin on albuminuria, FBS, HbA1c, and eGFR. Participants were given the mentioned drugs for 12 weeks. Statistical analysis was performed using appropriate tests in IBM™SPSS® statistics software for windows version 24.

Results

In total, 60 patients participated in the study, thirty patients in each group. The mean age of participants was 56.8 (SD = 8.15) in the Empagliflozin group and 60.9 (SD = 7.22) in the Linagliptin group. Before the intervention, FBS, HbA1C, and albuminuria values were significantly higher in the Empagliflozin group than those in the Linagliptin group (P < 0.05), but there was no significant difference between groups regarding eGFR (P = 0.271). Changes in the FBS, HbA1C, and eGFR were not significantly different between groups (P > 0.05), but there was more decrease in albuminuria in the Empagliflozin group compared to the Linagliptin group (P = 0.001, Cohen’s d = 0.98).

Conclusions

Regardless of baseline albuminuria, eGFR, or HbA1c, Empagliflozin 10 mg daily significantly reduced albuminuria at 12 weeks compared to Linagliptin 5 mg daily in patients with type 2 diabetes.

Trial registration

Iranian Registry of Clinical Trials, IRCT20200722048176N1. Registered 3 August 2020.

Inhibition of Podocytes DPP4 Activity Is a Potential Mechanism of Lobeliae Chinensis Herba in Treating Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease and has become a serious public health problem worldwide. Dipeptidyl peptidase-4 (DPP4) inhibitors, an emerging drug for the treatment of diabetes, have been found to have renoprotective effects in addition to glucose-lowering effects and therefore have the potential to be a treatment modality for DKD. Lobeliae Chinensis Herba (LCH), a traditional Chinese herb widely used in the treatment of diabetes, has recently been found to have a hypoglycaemic mechanism related to the inhibition of DPP4. Firstly, analysis of single-cell sequencing data from mouse kidneys in the National Center for Biotechnology Information (NCBI) database revealed that DPP4 was specifically upregulated in DKD podocytes and was associated with podocyte proliferation. Subsequently, the network pharmacology approach was applied to the screening of compounds. Twelve LCH active ingredients targeting DPP4 were extracted from the Traditional Chinese Medicine System Pharmacology (TCMSP) database. In addition, these 12 compounds and DPP4 were molecularly docked to predict the probability of them affecting DPP4 activity. In vitro, Quercetin, Methyl rosmarinate, Kaempferol, Diosmetin and Acacetin were demonstrated to retard podocyte proliferation by inhibiting DPP4 activity and were the top five compounds predicted by molecular docking to be the most likely to affect DPP4 activity. The half maximal inhibitory concentration (IC₅₀) of the five compounds for DPP4 activity were as follows. Acacetin Log IC₅₀ = −8.349, 95%CI (−9.266, −7.265), Diosmtrin Log IC₅₀ = −8.419, 95%CI (−8.889, −7.950), Log IC₅₀ = −8.349, 95%CI (−9.266, −7.265), Methyl rosmarinate Log IC₅₀ = −8.415, 95%CI (−8.751, −8.085), Kaempferol Log IC₅₀ = −8.297, 95%CI (−9.001, −7.615), Quercetin Log IC₅₀ = −8.864, 95%CI (−9.107, −8.615). Finally, Quercetin, Methyl rosmarinate, Kaempferol, Diosmetin and Acacetin qualified for pharmacokinetic and drug similarity screening and have the potential to be the most promising oral agents for the treatment of DKD.

GPR21 Inhibition Increases Glucose-Uptake in HepG2 Cells

GPR21 is a constitutively active, orphan, G-protein-coupled receptor, with in vivo studies suggesting its involvement in the modulation of insulin sensitivity. However, its precise contribution is not fully understood. As the liver is both a major target of insulin signalling and critically involved in glucose metabolism, the aim of this study was to examine the role of GPR21 in the regulation of glucose uptake and production in human hepatocytes. In particular, HepG2 cells, which express GPR21, were adopted as cellular models. Compared with untreated cells, a significant increase in glucose uptake was measured in cells treated with siRNA to downregulate GPR21 expression or with the GPR21-inverse agonist, GRA2. Consistently, a significantly higher membrane translocation of GLUT-2 was measured under these conditions. These effects were accompanied by an increased ratio of phAKT^(Ser473)/tot-AKT and phGSK-3β^(Ser9)/tot-GSK-3β, thus indicating a marked activation of the insulin signalling pathway. Moreover, a significant reduction in ERK activation was observed with GPR21 inhibition. Collectively, these results indicate that GPR21 mediates the negative effects on glucose uptake by the liver cells. In addition, they suggest that the pharmacological inhibition of GPR21 could be a novel strategy to improve glucose homeostasis and counteract hepatic insulin resistance.

The dipeptidyl peptidase 4 inhibitor linagliptin ameliorates renal injury and accelerated resolution in a rat model of crescentic nephritis

BACKGROUND AND PURPOSE

Dipeptidyl peptidase 4 (DPP-4) inhibitors are a class of oral glucose-lowering drugs used in the treatment of type 2 diabetes. In a pilot study using human kidney biopsies, we observed high DPP-4 expression in early crescent formation. This glomerular lesion occurs in different kidney diseases and is a hallmark in the pathogenesis of renal dysfunction. Therefore, we investigated the potential involvement of DPP-4 in the pathogenesis of nephritis induced by anti-glomerular basement membrane (GBM) antibody in rats.

EXPERIMENTAL APPROACH

Linagliptin and vehicle were used to treat anti-GBM nephritis in a 2- and 8-week regimen, that is either preventive or therapeutic (treatment started 7 days or 4 weeks after disease induction). Kidney function, morphologic changes, inflammation and fibrosis were monitored.

KEY RESULTS

In the long-term experiment, linagliptin preventive treatment in anti-GBM nephritic rats significantly reduced the number of crescents, glomerulosclerosis, tubular injury and renal fibrosis, compared with those in untreated nephritic rats. Both linagliptin regimes significantly lowered the number of Pax8+ cells on the glomerular tuft in anti-GBM nephritis, indicating accelerated resolution of the cellular crescents. The linagliptin treatment did not change the podocyte stress in both therapeutic groups. Therapeutic intervention with linagliptin resulted in weaker amelioration of renal disease on Week 8 than did preventive intervention.

CONCLUSION AND IMPLICATIONS

DPP-4 inhibition with linagliptin ameliorates renal injury in a rat model of anti-GBM, indicating that linagliptin not only is a secure therapy in diabetes but also can improve resolution of glomerular injury and healing in non-diabetic renal disease.

Protective effects of DPP-4 inhibitor on podocyte injury in glomerular diseases

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) is a serine protease that inhibits the degradation of glucagon-like peptide 1. DPP-4 inhibitors are used worldwide to treat type 2 diabetes mellitus and were recently shown to have pleiotropic effects such as anti-oxidant, anti-inflammatory, and anti-fibrotic actions. DPP-4 inhibitors improve albuminuria and renal injury including glomerular damage independent of its hypoglycemic effect. Although DPP-4 is mainly expressed in the kidney, the physiological function of DPP-4 remains unclear.

METHODS

The localization of renal DPP-4 activity was determined in human renal biopsy specimens with glycyl-1-prolyl-4-methoxy-2-naphthylamide and the effects of a DPP-4 inhibitor were examined in human cultured podocyte.

RESULTS

DPP-4 activity under normal conditions was observed in some Bowman's capsular epithelial cells and proximal tubules, but not in the glomerulus. DPP-4 activity was observed in crescent formation in anti-neutrophil myeloperoxidase cytoplasmic antigen antibody nephritis, nodular lesions in diabetic nephropathy, and some podocytes in focal segmental glomerulosclerosis. Notably, the DPP-4 inhibitor saxagliptin suppressed DPP-4 activity in podocytes and the proximal tubules. To assess the effect of DPP-4 inhibitor on podocytes, human cultured podocytes were injured by Adriamycin, which increased DPP-4 activity; this activity was dose-dependently suppressed by saxagliptin. Treatment with saxagliptin maintained the structure of synaptopodin and RhoA. Saxagliptin also improved the detachment of podocytes.

CONCLUSIONS

DPP-4 activity induces degradation of synaptopodin and reduction of RhoA, resulting in destruction of the podocyte cytoskeleton. Saxagliptin may have pleiotropic effects to prevent podocyte injury.

Reno-protective effect of linagliptin against gentamycin nephrotoxicity in rats

BACKGROUND

Recent studies demonstrated the reno-protective effects of two dipeptidyl peptidase-4 (DPP-4) inhibitors, saxagliptin and sitagliptin, against gentamycin-induced renal injury. However, none of these studies investigated whether renal DPP-4 contributes to the pathogenesis of this nephrotoxicity or not. This prompted us to test this hypothesis and to assess, for the first time, the potential reno-protective effect of linagliptin and whether this action is related or not to DPP-4 inhibition. Lingliptin was chosen since it is mainly excreted through a non-renal pathway and can therefore be used safely in individuals with renal injury.

METHODS

Male Sprague-Dawley rats were administered gentamycin (100 mg/kg/day, ip for 10 days) alone or combined with linagliptin (3 mg/kg/day, orally for 14 days). Gentamycin was administered once daily during the last ten days of the linagliptin treatment.

RESULTS

Linagliptin administration ameliorated gentamycin-induced renal injury and restored renal functional, oxidative, inflammatory, apoptotic and histopathological changes. Furthermore, the current study highlighted the role of increased plasma and renal DPP-4 in the pathogenesis of gentamycin renal insults and showed that the potential reno-protective effect of linagliptin is partly, mediated via inhibition of DPP-4, in addition to other antioxidant, anti-inflammatory and anti-apoptotic actions.

CONCLUSION

Linagliptin may serve as a beneficial adjutant to reduce gentamycin-induced renal injury.

Effects of linagliptin on human immortalized podocytes: a cellular system to study dipeptidyl-peptidase 4 inhibition

BACKGROUND AND PURPOSE

Dipeptidyl-peptidase 4 (DPP4) is expressed by resident renal cells, including glomerular cells. DPP4 inhibitors (gliptins) exert albuminuria lowering effects, but the role of renal DPP4 as a pharmacological target has not been elucidated. To better understand the actions of gliptins, the effects of linagliptin on the behaviour of immortalized human podocytes and mesangial cells were evaluated.

EXPERIMENTAL APPROACH

The expression of DPP4 was measured at both the mRNA and protein levels. The effects of linagliptin on DPP4 activity, cell growth and cell cycle progression were determined. The contribution of the stromal cell-derived factor-1- CXCR4/CXCR7 signalling pathways was evaluated by studying the effects of AMD3100 (a CXCR4 antagonist and CXCR7 agonist) alone and in combination with linagliptin. The contribution of ERK1/2 activation was analysed by studying the effects of the MAPK kinase 1/2 inhibitor AZD6244.

KEY RESULTS

DPP4 was highly expressed in podocytes. The activity of DPP4 and podocyte growth were reduced by linagliptin. The effects of sitagliptin on podocyte growth were similar to those of linagliptin, were associated with inhibition of cell proliferation and mimicked by AMD3100. Moreover, linagliptin and AMD3100 were found to have a synergistic interaction, whereas no interaction was seen between linagliptin and AZD6244.

CONCLUSIONS AND IMPLICATIONS

Our cultures of human glomerular cells represent a reliable system for investigating the actions of gliptins. Moreover, DPP4 contributes to the regulation of podocyte behaviour. Inhibition of DPP4 in podocytes could underlie the effects of linagliptin on glomerular cells.