Renoprotection Provided by Dipeptidyl Peptidase-4 Inhibitors in Combination with Angiotensin Receptor Blockers in Patients with Type 2 Diabetic Nephropathy

Sitagliptin Mitigates Diabetic Nephropathy in a Rat Model of Streptozotocin-Induced Type 2 Diabetes: Possible Role of PTP1B/JAK-STAT Pathway

Diabetic nephropathy (DN) is a microvascular complication of diabetes mellitus. This study examined the therapeutic effects of sitagliptin, a dipeptidyl peptidase inhibitor, on DN and explored the underlying mechanism. Male Wistar albino rats (n = 12) were intraperitoneally administered a single dose of streptozotocin (30 mg/kg) to induce diabetes. Streptozotocin-treated and untreated rats (n = 12) were further divided into normal control, normal sitagliptin-treated control, diabetic control, and sitagliptin-treated diabetic groups (n = 6 in each). The normal and diabetic control groups received normal saline, whereas the sitagliptin-treated control and diabetic groups received sitagliptin (100 mg/kg, p.o.). We assessed the serum levels of DN and inflammatory biomarkers. Protein tyrosine phosphatase 1 B (PTP1B), phosphorylated Janus kinase 2 (P-JAK2), and phosphorylated signal transducer activator of transcription (P-STAT3) levels in kidney tissues were assessed using Western blotting, and kidney sections were examined histologically. Sitagliptin reduced DN and inflammatory biomarkers and the expression of PTP1B, p-JAK2, and p-STAT3 (p < 0.001) and improved streptozotocin-induced histological changes in the kidney. These results demonstrate that sitagliptin ameliorates inflammation by inhibiting DPP-4 and consequently modulating the PTP1B-related JAK/STAT axis, leading to the alleviation of DN.

Metformin attenuates diabetic renal injury via the AMPK-autophagy axis

Diabetic nephropathy (DN) is a clinical condition characterized by kidney damage that is observed in patients with diabetes. DN is the main cause of end-stage renal disease (ESRD), which is the final stage of chronic kidney disease. Increasing evidence suggests that metformin, a characteristic oral hypoglycemic drug used for treating diabetes, exerts beneficial effects on various medical conditions and diseases, including cancer, cardiovascular diseases and thyroid-related disorders. However, the impact of metformin on DN remains unknown. The present study investigated whether metformin could attenuate the inflammatory response, fibrosis and increased oxidative stress observed during DN in diabetic/dyslipidemic (db/db) mice. The kidneys of the mice (12-16 weeks) were isolated for immunohistochemistry and western blotting. The results demonstrated that metformin significantly reduced the oxidative damage and fibrosis in the kidneys of db/db mice. Furthermore, metformin treatment significantly inhibited the generation of inflammatory cytokines, including TNF-α and IL-1β in db/db mice. These effects were induced by the activation of the AMP-activated protein kinase (AMPK) pathway, which was mediated by increased phosphorylation of AMPK and mammalian target of rapamycin (mTOR), resulting in autophagy and the simultaneous decrease in reactive oxygen species production, cell apoptosis and inflammatory response. These findings suggested that metformin may reduce DN damage via regulation of the AMPK-mTOR-autophagy axis and indicated that metformin may be considered as a potential target in the treatment of DN.

A Pharmacokinetic Drug Interaction Between Fimasartan and Linagliptin in Healthy Volunteers

Objective

Fimasartan, an angiotensin II type 1 receptor blocker, and linagliptin, a dipeptidyl-peptidase-4 inhibitor, are frequently coadministered to treat patients with hypertension and diabetes, respectively. This study sought to evaluate the pharmacokinetic interactions between fimasartan and linagliptin after co-administration in healthy Korean subjects.

Methods

The overall study was divided into two separate parts, with each part designed as an open-label, multiple-dose, two-period, and single-sequence study. In Part A, to investigate the effect of linagliptin on fimasartan, 25 subjects received 120 mg fimasartan alone once daily for seven days during Period I, and 120 mg fimasartan with 20 mg linagliptin for seven days during Period II. In Part B, to examine the effect of fimasartan on linagliptin, 12 subjects received only linagliptin once daily for seven days during Period I, followed by concomitant administration of fimasartan for seven days during Period II, at the same doses used in Part A. Serial blood samples were collected at scheduled intervals for up to 24 h after the last dose to determine the steady-state pharmacokinetics of both drugs.

Results

Thirty-six subjects completed the study. The geometric mean ratio and 90% confidence intervals for maximum plasma concentration at steady state (C_max,ss) and area under the concentration–time curve at steady state (AUC_τ,ss) of fimasartan with or without linagliptin were 1.2633 (0.9175–1.7396) and 1.1740 (1.0499–1.3126), respectively. The corresponding values for C_max,ss and AUC_τ,ss of linagliptin with or without fimasartan were 0.9804 (0.8480–1.1336) and 0.9950 (0.9322–1.0619), respectively. A total of eight adverse events (AEs) were reported and the incidence of AEs did not increase significantly with co-administration of the drugs.

Conclusion

Our results suggest that there are no clinically significant pharmacokinetic interactions between fimasartan and linagliptin when co-administered. Treatments were well tolerated during the study, with no serious adverse effects.

Clinical Trial Registry

http://clinicaltrials.gov, NCT03250052.

Urinary DPP4 correlates with renal dysfunction, and DPP4 inhibition protects against the reduction in megalin and podocin expression in experimental CKD

This study investigated the molecular mechanisms underlying the antiproteinuric effect of DPP4 inhibition in 5/6 renal ablation rats and tested the hypothesis that the urinary activity of DPP4 correlates with chronic kidney disease (CKD) progression. Experiments were conducted in male Wistar rats who underwent 5/6 nephrectomy (Nx) or sham operation followed by 8 wk of treatment with the DPP4 inhibitor (DPP4i) sitagliptin or vehicle. Proteinuria increased progressively in Nx rats throughout the observation period. This increase was remarkably mitigated by sitagliptin. Higher levels of proteinuria in Nx rats compared to control rats were accompanied by higher urinary excretion of retinol-binding protein 4, a marker of tubular proteinuria, as well as higher urinary levels of podocin, a marker of glomerular proteinuria. Retinol-binding protein 4 and podocin were not detected in the urine of Nx + DPP4i rats. Tubular and glomerular proteinuria was associated with the reduced expression of megalin and podocin in the renal cortex of Nx rats. Sitagliptin treatment partially prevented this decrease. Besides, the angiotensin II renal content was significantly reduced in the Nx rats that received sitagliptin compared to vehicle-treated Nx rats. Interestingly, both urinary DPP4 activity and abundance increased progressively in Nx rats. Additionally, urinary DPP4 activity correlated positively with serum creatinine levels, proteinuria, and blood pressure. Collectively, these results suggest that DPP4 inhibition ameliorated both tubular and glomerular proteinuria and prevented the reduction of megalin and podocin expression in CKD rats. Furthermore, these findings suggest that urinary DPP4 activity may serve as a biomarker of renal disease and progression.

Pathophysiologic mechanisms in diabetic kidney disease: A focus on current and future therapeutic targets

Diabetic kidney disease (DKD) is the primary cause of chronic kidney disease around the globe and is one of the main complications in patients with type 1 and 2 diabetes. The standard treatment for DKD is drugs controlling hyperglycemia and high blood pressure. Renin angiotensin aldosterone system blockade and sodium glucose cotransporter 2 (SGLT2) inhibition have yielded promising results in DKD, but many diabetic patients on such treatments nevertheless continue to develop DKD, leading to kidney failure and cardiovascular comorbidities. New therapeutic options are urgently required. We review here the promising therapeutic avenues based on insights into the mechanisms of DKD that have recently emerged, including mineralocorticoid receptor antagonists, SGLT2 inhibitors, glucagon-like peptide-1 receptor agonist, endothelin receptor A inhibition, anti-inflammatory agents, autophagy activators and epigenetic remodelling. The involvement of several molecular mechanisms in DKD pathogenesis, together with the genetic and epigenetic variability of this condition, makes it difficult to target this heterogeneous patient population with a single drug. Personalized medicine, taking into account the genetic and mechanistic variability, may therefore improve renal and cardiovascular protection in diabetic patients with DKD.