Vildagliptin inhibits high fat and fetuin-A mediated DPP-4 expression, intracellular lipid accumulation and improves insulin secretory defects in pancreatic beta cells.

Dipeptidyl peptidase-4 (DPP-4), a ubiquitous proteolytic enzyme, inhibits insulin secretion from pancreatic beta cells by inactivating circulating incretin hormones GLP-1 and GIP. High circulating levels of DPP-4 is presumed to compromise insulin secretion in people with type 2 diabetes (T2D). Our group recently reported lipid induced DPP-4 expression in pancreatic beta cells, mediated by the TLR4-NFkB pathway. In the present study, we looked at the role of Vildagliptin on pancreatic DPP-4 inhibition, preservation of islet mass and restoration of insulin secretion. MIN6 mouse insulinoma cells incubated with palmitate and fetuin-A, a proinflammatory organokine associated with insulin resistance, showed activation of TLR4-NFkB pathway, which was rescued on Vildagliptin treatment. In addition, Vildagliptin, by suppressing palmitate-fetuin-A mediated DPP-4 expression in MIN6, prevented the secretion of IL-1beta and fetuin-A in the culture media. DPP-4 siRNA abrogated TLR4-NFkB pathway mediated islet cell inflammation. Vildagliptin also reduced palmitate-fetuin-A mediated intracellular lipid accumulation in MIN6 and isolated islets from high fat fed (HFD) mice as observed by Oil O Red staining with downregulation of CD36 and PPARgamma. Vildagliptin also preserved islet mass and rescued insulin secretory defect in HFD mice. Our results suggest that inhibition of DPP-4 by Vildagliptin protects pancreatic beta cells from the deleterious effects of lipid and fetuin-A, preserves insulin secretory functions and improves hyperglycemia.

Vildagliptin Treatment Ameliorates Renal Interstitial Fibrosis in a Murine Model of Unilateral Ureteral Obstruction.

Renal interstitial fibrosis in mice can be modeled using unilateral ureteral obstruction (UUO). Here, we investigated the anti-fibrotic effects of the dipeptidyl peptidase-4 inhibitor vildagliptin in this model. We found that vildagliptin given in the drinking water at 10.6 ± 1.5 mg/kg/d prevented fibrosis. Mechanistically, UUO was associated with extracellular signal-regulated kinase (ERK) phosphorylation and with the accumulation of the toxic lipid peroxidation product expression of 4-hydroxy-2-nonenal (4-HNE). Both were significantly inhibited by vildagliptin. Similarly, UUO caused reductions in heme oxygenase-1 (HO-1) mRNA in the kidney, whereas interleukin-6 (IL-6) and cyclooxygenase-1 (COX-1) mRNA were increased; these effects were also prevented by vildagliptin. Taking these data together, we propose that vildagliptin reduces renal interstitial fibrosis resulting from UUO by means of its effects on ERK phosphorylation and the amounts of 4-HNE, HO-1, IL-6 and COX-1 in the kidney.

Protective roles of thymoquinone and vildagliptin in manganese-induced nephrotoxicity in adult albino rats.

Despite being important in the body's mechanisms, excessive accumulation of manganese (Mn) can induce severe toxicity in vital organs of the body. Thymoquinone (TQ) is extracted from Nigella sativa seeds which recently gained popularity as dietary supplements and plant-based antioxidants. Vildagliptin (VLD) is a dipeptidyl peptidase IV (DPPIV) inhibitor, approved as anti-hyperglycemic agents with cardioprotective and renoprotective effects. The present study aimed to investigate the nephrotoxicity of Mn and the potential protective effects of thymoquinone and vildagliptin. Sixty-four adult male albino rats were equally divided into 8 groups: group I (control, received no medication), group II (vehicle, received normal saline), group III (TQ, 50 mg/kg/day), group IV (VLD, 10 mg/kg/day), group V (MnCl2, 50 mg/kg/day), group VI (Mn+TQ), group VII (Mn+VLD), and group VIII (Mn+TQ+VLD). Groups VI, VII, and VIII, received the same previously mentioned doses. All drugs were orally gavaged for 12 weeks. Manganese administration resulted in an elevation in the levels of serum and tissues Mn, blood glucose, serum urea, creatinine, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and reduction in insulin, kidney superoxide dismutase (SOD), glutathione (GSH), and interleukin-10. Histopathological structural renal damage was detected associated with strong positive immunoexpression of caspase-3. On the other hand, individual or combined TQ and VLD administration with Mn significantly decreased the serum and tissue levels of Mn, declined the blood glucose, inflammatory markers, oxidative stress markers, ameliorated the histopathological effects, and down-regulated the immunoexpression of caspase-3. In conclusion, TQ and VLD co-administration elicited protective effects against Mn-induced nephrotoxicity.

Similarity and dissimilarity in antinociceptive effects of dipeptidyl-peptidase 4 inhibitors, Diprotin A and vildagliptin in rat inflammatory pain models following spinal administration.

Dipeptidyl-peptidase 4 (DPP4) enzyme is involved in the degradation of many biologically active peptides including opioids. Its role in pain transmission is poorly elucidated. Recently we reported on the spinal antihyperalgesic effects of DPP4 inhibitors, Ile-Pro-Ile (Diprotin A) and vildagliptin in carrageenan-evoked acute inflammatory pain in rats. The present study investigated the effects of intrathecal (it.) diprotin A and vildagliptin in Complete Freund's Adjuvant- (CFA) and formalin induced pain in rats. The former assay can model the subchronic inflammatory pain condition and the later one reflects both acute tonic and inflammatory pain conditions. The involvement of opioid receptor (OR) subtypes, Y1-, and GLP1 receptors were also investigated. In CFA pain model it. diprotin A or vildagliptin dose-dependently inhibits hyperalgesia in ipsilateral while has no effect in contralateral paws. The peak effect was achieved 30 min following drug administration which was used for further analysis. Both compounds showed naltrexone reversible antihyperalgesia. Co-administration of OR-subtype-selective antagonists with diprotin A and vildagliptin revealed involvement of µ and δ > µ opioid receptors, respectively. Co-administered Y1 but not GLP1 receptor antagonists reversed the antihyperalgesic action of both DPP4 inhibitors. In touch-hypersensitivity both compounds were ineffective. In formalin test only diprotin A showed µ and δ OR-mediated antinociception and only in the 2nd phase. This effect was Y1 or GLP-1 receptor antagonist insensitive. In conclusion, diprotin A and vildagliptin display antinociception of different mechanisms of action in subchronic inflammatory pain. Furthermore, the spinal pain relay points of inflammatory pain of acute or subchronic conditions were more effectively affected by diprotin A than vildagliptin which needs future elucidation.

Dipeptidyl peptidase IV Inhibitory activity of Terminalia arjuna attributes to its cardioprotective effects in experimental diabetes: In silico, in vitro and in vivo analyses.

BACKGROUND: The marketed synthetic (Dipeptidyl peptidase-IV) DPP-IV Inhibitors are expensive antidiabetic drugs and have been reported to cause unacceptable adverse effects such as pancreatitis, angioedema, thyroid and pancreatic cancers. In this scenario research to develop novel DPP-IV Inhibitors from alternative sources is the need of the hour. HYPOTHESIS/PURPOSE: Terminalia arjuna, a medicinal herb with antidiabetic and cardioprotective activities may represent a natural DPP-IV Inhibitor, the DPP-IV Inhibitory activity of which may translate into demonstrable therapeutic benefits in setting of diabetes with cardiovascular co-morbidities. STUDY DESIGN: The study type used for the present study was an experimental (In vitro, In vivo and In silico) design. METHOD: The DPP-IV Inhibitory, antidiabetic and cardioprotective effects of Terminalia arjuna was evaluated in the experimental model of myocardial infarction co-existing with diabetes. To determine the active principle of Terminalia arjuna responsible for DPP-IV Inhibitory activity, the crystal structure of DPP-IV was considered as receptor which was docked against Arjunetin, Arjungenin, Arjunic acid, Arjunone, Ellagic acid, Gallic acid, Sitagliptin and Vildagliptin. The binding sites as well as affinity of various active ingredients of Terminalia arjuna for DPP- IV enzyme was elucidated using in silico studies and compared to Vildagliptin. RESULTS: Terminalia arjuna demonstrated significant DPP-IV Inhibitory, antidiabetic (significant reduction in HbA1C) and cardioprotective effects (restoration of myocardial CPK-MB) in the experimental model of myocardial infarction co-existing with diabetes. The cardioprotective efficacy correlated to its DPP-IV Inhibitory activity. The active ingredients of Terminalia arjuna (Arjunetin, Arjungenin, Arjunic Acid Arjunone, Ellagic acid and Gallic acid) demonstrated significant inhibition of DPP-IV enzyme. Arjunic acid and Arjunone prefers the active site pocket of DPP-IV enzyme. Compounds like Arjunetin and Vildagliptin prefers to bind near the interface region of the DPP-IV as their biological active forms are homodimer. Sitagliptin binds near the α/ß hydrolase domain. CONCLUSION: The DPP-IV Inhibitory activity of Terminalia arjuna was found to be comparable to Vildagliptin. The DPP-IV Inhibitory activity translated into significant cardioprotective effects in the setting of diabetes. The active ingredient of Terminalia arjuna; Arjunetin, Arjungenin, Ellagic acid and Arjunic acid showed superior DPP-IV Inhibitory activity as compared to synthetic DPP-IV inhibitors (Sitagliptin and Vildagliptin) based on results of docking studies.

Gas-Phase Rearrangement of the O-Glucuronide of Vildagliptin Forms Product-Ion Fragments Suggesting Wrongly an N-Glucuronide.

The O-glucuronide of vildagliptin, a dipeptidyl peptidase 4 inhibitor, is a major metabolite in monkeys and a minor metabolite in humans, rats, and dogs. Its product ion spectrum shows fragments that can be explained only by an N-glucuronide. Biotransformation using rat liver yielded milligram amounts of the O-glucuronide, and its structure was assigned unambiguously by nuclear magnetic resonance. The tandem mass spectra (MS/MS) of this compound was investigated in detail using MSn and accurate mass spectrometers and was identical to the animal metabolite. Thus, the MS/MS fragments suggesting an N-glucuronide had to be formed by gas-phase rearrangement. This gas-phase rearrangement can be observed on quadrupole time-of-flight and ion-trap mass instruments. The literature on gas-phase rearrangements is reviewed.

Identification of a novel metabolite of vildagliptin in humans: Cysteine targets the nitrile moiety to form a thiazoline ring.

The dipeptidyl peptidase-4 (DPP-4) inhibitor vildagliptin (VG) is used to treat type 2 diabetes. In rare cases, VG-induced liver injury has been reported. One case report suggested that immune responses were involved in the hepatotoxicity. However, the underlying mechanisms of VG-induced hepatotoxicity are uncertain. In the present study, we investigated whether VG has the potential to covalently bind to macromolecules in cells, a process that could initiate immune-mediated hepatotoxicity. For comparison, M20.7, a major metabolite of VG, and other DPP-4 inhibitors were also evaluated. We found that VG and anagliptin (ANG), which both contain a cyanopyrrolidine moiety, rapidly reacted in non-enzymatic manners on co-incubation with l-cysteine. Both VG and ANG had half-lives of 20-30 min. In contrast, incubation with GSH, rather than l-cysteine, failed to decrease the concentrations of VG or ANG. M20.7, sitagliptin, linagliptin, and alogliptin, having no cyanopyrrolidine moiety, were stable on incubation with l-cysteine or GSH. Structural analysis of the VG- and ANG-cysteine adducts, designated M407 and M487, respectively, revealed that the nitrile moieties of VG and ANG were irreversibly converted to a thiazoline acid. In conclusion, we found that VG and ANG have the potential to covalently bind to a thiol residue of l-cysteine in proteins. Such binding may lead to unpredictable immune responses in humans. l-Cysteine, rather than GSH, would likely be useful to detect the potential for covalent binding that could initiate immune-mediated hepatotoxicity.