Acute and Chronic Exposure to Linagliptin, a Selective Inhibitor of Dipeptidyl Peptidase-4 (DPP-4), Has an Effect on Dopamine, Serotonin and Noradrenaline Level in the Striatum and Hippocampus of Rats

Linagliptin is a selective dipeptidyl peptidase-4 (DPP-4) inhibitor that indirectly elevates the glucagon-like peptide-1 (GLP-1) level. The aim of the present study was to check whether linagliptin has an influence on neurotransmission in rat brain. Rats were acutely and chronically exposed to linagliptin (10 and 20 mg/kg, intraperitoneally (i.p.)). Twenty-four hours later, the striatum and hippocampus were selected for further studies. In neurochemical experiments, using high-performance liquid chromatography with electrochemical detection (HPLC-ED), the concentrations of three major neurotransmitters-dopamine, serotonin and noradrenaline-and their metabolites were measured. The analysis of mRNA expression of dopamine (D1 and D2), serotonin (5-HT-1 and 5-HT-2) and noradrenaline (α1 and α2a) receptors was also investigated using real-time quantitative reverse transcription polymerase chain reaction (RQ-PCR) in the same brain areas. Linagliptin has the ability to influence the dopaminergic system. In the striatum, the elevation of dopamine and its metabolites was observed after repeated administration of that linagliptin, and in the hippocampus, a reduction in dopamine metabolism was demonstrated. Acute linagliptin exposure increases the serotonin level in both areas, while after chronic linagliptin administration a tendency for the mRNA expression of serotoninergic receptors (5-HT1A and 5-HT2A) to increase was observed. A single instance of exposure to linagliptin significantly modified the noradrenaline level in the striatum and intensified noradrenaline turnover in the hippocampus. The recognition of the interactions in the brain between DPP-4 inhibitors and neurotransmitters and/or receptors is a crucial step for finding novel discoveries in the pharmacology of DPP-4 inhibitors and raises hope for further applications of DPP-4 inhibitors in clinical practices.

Linagliptin in combination with insulin suppresses apoptotic unfolded protein response in ovaries exposed to type 1 diabetes

Type 1 diabetes mellitus (T1DM) is one of the main causes of ovarian atresia, but its molecular effect on the ovaries is not fully understood. Accumulating evidence suggests that T1DM causes excessive endoplasmic reticulum (ER) stress and insufficient adaptive unfolded protein response that triggers proapoptotic signaling pathways in ovarian tissue. In addition, problems such as amenorrhea and infertility, which are frequently seen in women with T1DM, continue despite the intensification of insulin therapy and improvement of metabolic control. Therefore new, and adjunctive treatments for women with T1DM need to be explored. We aimed to examine how the use of linagliptin, which has blood sugar-lowering effects and high antioxidant activity, together with insulin affects the expression levels of proteins and genes that play a role in ER stress in type 1 diabetic mouse ovaries. Eighty-four Balb/C 6-week-old female mice were randomly divided into seven groups: control, vehicle, diabetes + insulin, diabetes + linagliptin, diabetes + linagliptin + insulin, diabetes + TUDCA, and diabetes + TUDCA + insulin. TUDCA (an inhibitor of ER stress) groups are positive control groups created to compare linagliptin groups in terms of ER stress. Linagliptin and TUDCA were given by oral gavage and 1U insulin was administered subcutaneously for 2 weeks. A significant decrease was observed in the MDA and NOX1 levels and the number of atretic follicles in the ovaries of the diabetes + linagliptin + insulin group compared to the diabetes + insulin group. The use of linagliptin and insulin increased the expression of pro-survival XBP1s transmembrane protein and decreased the expression of proapoptotic ATF4, pJNK1/2, cleaved caspase 12, and cleaved caspase 3 in mouse ovaries. Our study provides new therapeutic evidence that linagliptin administered in addition to insulin induces ER stress mechanism-dependent survival in ovaries with type 1 diabetes.

Identification and Structural Characterization of Degradation Products of Linagliptin by Mass Spectrometry Techniques

As part of the development and production of pharmaceuticals, the purity of Active Pharmaceutical Ingredients stands as a fundamental parameter that significantly influences the quality, safety, and efficacy of the final drug product. Impurities in Active Pharmaceutical Ingredients are various unwanted substances that can appear during the whole manufacturing process, from raw materials to the final product. These impurities can stem from multiple sources, including starting materials, intermediates, reagents, solvents, and even degradation products resulting from exposure to environmental factors such as heat, light, or moisture. Their presence can potentially compromise the therapeutic effect of the drug, introduce unexpected side effects, or even pose safety risks to patients. This study aims to conduct the forced degradation of linagliptin and subsequently attempt to identify the resulting degradants. The degradation procedures were carried out in accordance with the guidelines of the International Committee for Harmonization. The degradation profile of linagliptin was investigated under various conditions, including acid hydrolysis, alkaline hydrolysis, oxidation, heat, and light exposure, utilizing ultra-performance liquid chromatography connected to a photo array detector. Identification and characterization of the degradation products were achieved using an ultra-performance liquid chromatography coupled with a single quadrupole detector mass spectrometer and also a liquid chromatography coupled with a high-resolution mass spectrometry. The identified degradation products demonstrate that linagliptin is particularly susceptible to degradation when exposed to acid and peroxide. Whereas, no significant degradation effects were observed under alkali, thermolytic, and photolytic conditions.

Linagliptin's impact on lymphatic barrier and lymphangiogenesis in oral cancer with high glucose

OBJECTIVES

Uncertainties remain regarding the effect of elevated glucose levels on lymphatic metastasis of cancer cells. Our study elucidated the mechanisms linking high glucose to lymphangiogenesis and lymphatic barrier-related factors and investigated the protective role of linagliptin against lymphatic barrier dysfunction.

MATERIALS AND METHODS

A CAL-27-LEC co-culture system was established. Sodium fluorescein permeability assay observed lymphatic endothelial cell permeability. Western blotting and RT-qPCR detected protein and mRNA expression under different conditions, respectively. CCK-8, scratch wound healing, and transwell assays revealed cell migration and proliferation. Tube formation experiment tested capacity for endothelial tube formation. Immunohistochemical staining analyzed tissue sections from 43 oral cancer individuals with/without diabetes.

RESULTS

In high-glucose co-culture system, we observed increased lymphatic barrier permeability and decreased expression of ZO-1 and occludin, two tight-junction proteins; conversely, the expression of PAR2, a high permeability-related protein, was increased. Following linagliptin treatment, the expression levels of VEGF-C, VEGFR-3, and PAR2 decreased, while those of ZO-1 and occludin increased. Considerably higher levels of LYVE-1 expression in individuals with diabetes than in those without diabetes.

CONCLUSIONS

By ameliorating the high glucose-induced disruption of the lymphatic endothelial barrier, linagliptin may reduce lymphangiogenesis and exhibit an inhibitory effect on lymphatic metastasis in oral cancer patients with diabetes.

Development of sensitive spectrofluorometric approach based on formation of pyrrolidone derivative for determination of linagliptin through condensation reaction with ninhydrin and phenylacetaldehyde: Application to content uniformity and real plasma

The new drug linagliptin belongs to the class of dipeptidyl peptidase-4 enzyme inhibitors. Linagliptin is used to treat type 2 diabetes and is taken orally either alone or in combination with other drugs. In this instance, a new, simple, and economical technique for analyzing linagliptin was developed by the effective use of a pyrrolidone derivative. The primary amine group of linagliptin permits its condensation with ninhydrin (0.14% w/v) to produce a fluorescent product in the presence of phenylacetaldehyde (0.02% v/v). All experimental parameters were carefully examined and adjusted in order to monitor the generation of the pyrrolidone derivative at excitation and emission wavelengths of 385 and 475 nm, respectively. The calibration graph was made by plotting the intensity of the fluorescence in relation to linagliptin concentration. A significant linearity was found for values ranging from 20 to 460 ng/mL. The process's validity has been verified by a thorough assessment of the instructions provided by the International Conference on Harmonization (ICH). The results indicate excellent uniformity with a reference method, showing that there is no substantial difference in precision and accuracy. The proposed approach was utilized for determining linagliptin in real rat plasma successfully owing to its high sensitivity. Additionally, the proposed approach was evaluated using the Eco-Scale evaluation tool and showed a high degree of eco-friendliness (86/100).

[Linagliptin improves diabetic kidney disease in rats by promoting mitochondrial biogenesis through the AMPK/PGC-1α/TFAM pathway]

OBJECTIVE

To investigate whether linagliptin improves diabetic kidney disease (DKD) by promoting mitochondrial biosynthesis via activating adenosine monophosphate activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1α/mitochondrial transcription factor A (AMPK/PGC-1α/TFAM) pathway.

METHODS

With 6 male SD rats feeding normal chow as the control group, 16 SD rat models of DKD induced by intraperitoneal injection of 45 mg/kg STZ and high-fat and high-glucose feeding for 4 weeks were randomized into DKD model group and linagliptin treatment group. The rats in the latter two groups were subjected to daily intragastric administration of vehicle or 5 mg/kg linagliptin (dissolved in 5 g/L sodium carboxymethylcellulose, final concentration of 2 mg/mL) for 12 weeks with further high-fat and high-glucose feeding. After the treatments, the rats were sacrificed and blood samples from the abdominal aorta and kidney tissues were collected for testing blood glucose, liver function and lipid metabolism; HE, PAS, Masson, Sirius red staining and electron microscopy were used to observe renal tissue damage. Renal expressions of transforming growth factor β1 (TGF-β1), fibronectin (FN) and collagen I (Col I) were detected by immunohistochemistry, and the changes in membrane potential (ΔψM) and ATP enzyme content were analyzed to assess mitochondrial damage; The expressions of AMPK/PGC-1α/TFAM pathway proteins were detected using Western blotting.

RESULTS

Compared with DKD model rats, the rats receiving linagliptin treatment showed significantly decreased blood glucose level (P < 0.01) and improved proteinuria (P < 0.05) with obviously alleviated renal ultrastructural damage and fibrosis, increased ATPase content and ΔψM (P < 0.0001), and enhanced renal expressions of P-AMPK/AMPK, PGC-1α and TFAM (P < 0.05).

CONCLUSIONS

Linagliptin improves proteinuria and renal fibrosis in rat models of DKD possibly by activating the AMPK/PGC-1α/TFAM pathway to promote mitochondrial biosynthesis.

Is the combination of linagliptin and allopurinol better prophylaxis against post-contrast acute kidney injury? A multicenter prospective randomized controlled study

BACKGROUND

Patients with diabetic kidney disease (DKD) are at increased risk to develop post-contrast acute kidney injury (AKI). Diabetic patients under dipeptidyl peptidase 4 inhibitors (DPP4Is) experience a lower propensity to develop AKI. We speculated that linagliptin as a single agent or in combination with allopurinol may reduce the incidence of post-contrast AKI in stage 3-5 chronic kidney disease (CKD) patients with underlying DKD.

METHODS

Out of 951 DKD patients eligible for this study, 800 accepted to sign informed consent. They were randomly allocated to 4 equal groups that received their prophylaxis for 2 days before and after radiocontrast. The first control group received N-acetyl cysteine and saline, the 2^nd received allopurinol, the 3^rd group received linagliptin, and the 4^th received both allopurinol and linagliptin. Post-procedure follow-up for kidney functions was conducted for 2 weeks in all patients.

RESULTS

20, 19, 14, and 8 patients developed post-contrast AKI in groups 1 through 4, respectively. Neither linagliptin nor allopurinol was superior to N-acetyl cysteine and saline alone. However, the combination of the two agents provided statistically significant renal protection: post-contrast AKI in group 4 was significantly lower than in groups 1 and 2 (p < 0.02 and <0.03, respectively). None of the post-contrast AKI cases required dialysis.

CONCLUSION

Linagliptin and allopurinol in combination may offer protection against post-contrast AKI in DKD exposed to radiocontrast. Further studies are needed to support this view.

TRIAL REGISTRATION CLINICALTRIALS.GOV

NCT03470454.

Effects of pioglitazone and linagliptin on glycemic control, lipid profile and hs-CRP in metformin-treated patients with type 2 diabetes: a comparative study

OBJECTIVES

The purpose of this study was to compare the effects of pioglitazone and linagliptin on glycemic control, lipid profile and high-sensitivity C-reactive protein (hs-CRP) parameters in patients with type 2 diabetes treated with metformin.

METHODS

The present randomized clinical trial was conducted on 60 patients with type 2 diabetes treated with metformin in the age range of 30-60 years. The participants with informed consent were randomly assigned to receive pioglitazone or linagliptin. The first intervention group (n=30) received 30 mg of pioglitazone daily and the second intervention group (n=30) received 5 mg of linagliptin daily for 12 weeks. Fasting blood samples were taken from patients at the baseline and after 12 weeks to measure related variables. The current study was approved in Kashan University of Medical Sciences (with the code of ethics of IR.KAUMS.MEDNT.REC.1398.016), and the Iranian Registry of Clinical Trials (with the registration number of IRCT20170513033941N66).

RESULTS

The linagliptin administration significantly reduced serum levels of fasting blood sugar (p=0.03), blood sugar 2 h after a meal (p=0.02), glycosylated hemoglobin (p=0.02) and hs-CRP (p=0.005) after 12 weeks compared with pioglitazone. In contrast, the pioglitazone administration significantly decreased triglyceride levels (p=0.01) and increased HDL-cholesterol (p=0.002) compared to linagliptin. In addition, the administration of both linagliptin and pioglitazone drugs had no significant effect on LDL-cholesterol, total cholesterol, systolic and diastolic blood pressure, creatinine and blood urea.

CONCLUSIONS

The present study demonstrated the superiority of linagliptin over pioglitazone for glycemic control, although pioglitazone compared to linagliptin showed greater efficacy in reducing triglycerides and raising HDL-cholesterol.

Linagliptin and secoisolariciresinol diglucoside attenuate hyperlipidemia and cardiac hypertrophy induced by a high-methionine diet in rats via suppression of hyperhomocysteinemia-induced endoplasmic reticulum stress

Background: Cardiac hypertrophy (CH) is one of the contributing causes of morbidity and mortality. Hyperhomocysteinemia (HHcy) is one of the diseases which may predispose hyperlipidemia and CH. Linagliptin (Lina) and secoisolariciresinol diglucoside (SDG) are known to alleviate a variety of illnesses by reducing oxidative stress and inflammation. Aim: This study aimed to study the effect of HHcy on cardiac tissues, with a special focus on endoplasmic reticulum (ER) stress as a mainstay pathophysiological pathway. In addition, our study examined the protective effect of Lina, SDG, and their combination against HHcy-induced hyperlipidemia and CH in rats. Methods: Seventy-five male Sprague-Dawley rats were randomly divided into five groups, and for 60 days, the following regimen was administered: Group I: rats received distilled water; Group II: rats received methionine (MET) (2 g/kg/day, p.o.); groups III and IV: rats received Lina (3 mg/kg/day, p.o.) and SDG (20 mg/kg/day, p.o.), respectively, followed by MET (2 g/kg/day, p.o.); Group V: rats received Lina and SDG, followed by MET (2 g/kg/day, p.o.). Results: Pretreatment with Lina, SDG, and their combination showed a significant decrease in serum levels of HHcy and an improved lipid profile compared to the MET group. Moreover, both drugs improved cardiac injury, as evidenced by the substantial improvement in ECG parameters, morphological features of the cardiac muscle, and reduced serum levels of cardiac markers. Additionally, Lina and SDG significantly attenuated cardiac oxidative stress, inflammation, and apoptosis. Furthermore, Lina, SDG, and their combination remarkably downregulated the enhanced expression of endoplasmic reticulum (ER) stress markers, GRP78, PERK, ATF-4, CHOP, NF-κB, and SREBP1c compared to the MET-group. Conclusion: Lina and SDG showed cardioprotective effects against HHcy-induced heart hypertrophy and hyperlipidemia in rats.

Evaluation of linagliptin and insulin combined therapy on unfolded protein response in type 1 diabetic mouse heart

The aim of this study is to reveal the effects of the use of linagliptin, a DPP-4 inhibitor due to its beneficial cardiovascular effects, on endoplasmic reticulum stress (ERS) signaling, which is involved in the pathogenesis of cardiovascular complications related to type 1 diabetes. BALB/c female mice (n = 72) were divided into six groups: control, diabetes+insulin, diabetes+linagliptin, diabetes+linagliptin+insulin, diabetes+TUDCA, and diabetes+TUDCA+insulin. Immunohistochemistry and western blot method, qRT-PCR, ELISA method, and malondialdehyde (MDA) measurements were performed. Linagliptin administered to the type 1 diabetic mouse heart significantly reduced the expression levels of the total and cleaved forms of ATF6, ATF4, and p-JNK, caspase 3. Immunohistochemical and western blot analyses revealed that cleaved caspase 3 protein expression was significantly increased in the diabetes+insulin group compared to the other groups. According to ELISA findings, TUDCA was more effective in reducing NOX 1 and MDA levels than linagliptin. While linagliptin decreased the Chop mRNA level, no change was observed in the Grp78 mRNA level. Our findings showed that there was not much difference between the administration of linagliptin alone or in combination with insulin. Our study reveals that linagliptin is an effective therapeutic agent on ERS and apoptotic UPR in type 1 diabetic hearts.

Neuroprotective Impact of Linagliptin against Cadmium-Induced Cognitive Impairment and Neuropathological Aberrations: Targeting SIRT1/Nrf2 Axis, Apoptosis, and Autophagy

Cadmium is an environmental contaminant associated with marked neurotoxicity and cognitive impairment. Linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has demonstrated promising neuroprotection against cerebral ischemia and diabetic dementia. However, there has been no study of its effect on cadmium-induced cognitive deficits. In the present work, linagliptin's prospective neuroprotective effects against cadmium-evoked cognitive decline were examined in vivo in rats. The molecular pathways related to oxidative stress, apoptosis, and autophagy were investigated. Histology, immunohistochemistry, ELISA, and biochemical assays were performed on brain hippocampi after receiving linagliptin (5 mg/kg/day). The current findings revealed that cadmium-induced learning and memory impairment were improved by linagliptin as seen in the Morris water maze, Y-maze, and novel object recognition test. Moreover, linagliptin lowered hippocampal neurodegeneration as seen in histopathology. At the molecular level, linagliptin curtailed hippocampal DPP-4 and augmented GLP-1 levels, triggering dampening of the hippocampal neurotoxic signals Aβ42 and p-tau in rats. Meanwhile, it enhanced hippocampal acetylcholine and GABA and diminished the glutamate spike. The behavioral recovery was associated with dampening of the hippocampal pro-oxidant response alongside SIRT1/Nrf2/HO-1 axis stimulation. Meanwhile, linagliptin counteracted hippocampal apoptosis markers and inhibited the pro-apoptotic kinase GSK-3β. In tandem, linagliptin activated hippocampal autophagy by lowering SQSTM-1/p62 accumulation, upregulating Beclin 1, and stimulating AMPK/mTOR pathway. In conclusion, linagliptin's antioxidant, antiapoptotic, and pro-autophagic properties advocated its promising neuroprotective impact. Thus, linagliptin may serve as a management approach against cadmium-induced cognitive deficits.

The combination of linagliptin and metformin rescues bone loss in type 2 diabetic osteoporosis

To develop an approach to reduce the type 2 diabetic osteoporosis, this study investigated the protective effects of the combination of linagliptin and metformin against osteoporosis. Micro-CT and dynamic biomechanical measurements were used to determine the bone microstructure in the type 2 diabetes mellitus (T2DM) rats. MC3T3-E1 cells were cultured in high glucose environments. In addition, we used qRT-PCR and Western blotting to assess osteogenic markers and p38 and extracellular signal-regulated kinase (ERK) protein expression. The combination of linagliptin and metformin treatment significantly restored bone micro-architecture and femoral mechanical properties in the T2DM rats. In contrast, bone markers including osteocalcin, NH2-terminal propeptide of type I procollagen, COOH-terminal telopeptide of type I collagen and tartrate-resistant acid phosphatase were significantly reduced by the combination of linagliptin and metformin treatment. We used high glucose treated MC3T3-E1 cells to mimic the condition of T2DM. Linagliptin combined with metformin treatment significantly inhibited the phosphorylation of p38 and ERK induced by high glucose treatment. In conclusion, the linagliptin combined with metformin treatment improved the rats' bone mineral density, bone structure, and osteogenic markers. Both p38 and ERK phosphorylation were reduced in high glucose MC3T3-E1 cells. Our findings highlight the potential of linagliptin combined with metformin for the treatment of T2DM-related osteoporosis.

Mild Pancreatitis Induced by Linagliptin Revealed by a Medication Review

As dipeptidyl peptidase-4 inhibitors are becoming more utilized in the treatment of diabetes, it is important to recognize their side effects and become more familiar with them. As these side effects arise, physicians are more prepared to recognize and discontinue these medications. This case report describes a 34-year-old male who initially presented with a hemoglobin A1c greater than 16%. After titration of his diabetic medications, he presented with pancreatitis diagnosed by symptoms and imaging. Common causes of pancreatitis were ruled out, including biliary pathology, alcohol use, tobacco use, elevated calcium levels, and hypertriglyceridemia. The patient followed up in the clinic with persistent symptoms. A review of his medication list revealed pancreatitis as a side effect of linagliptin. After holding this medication, his symptoms improved over the course of a month.

Investigation of the effect of concurrently administered carvedilol, atorvastatin and bile salts on intestinal absorption of linagliptin

OBJECTIVES

The aim of this work was to investigate the regional difference in linagliptin intestinal membrane transport and to investigate the effects of carvedilol, atorvastatin and bile salts on intestinal absorption of linagliptin.

METHODS

The study employed an in-situ rabbit intestinal absorption technique. The membrane transport parameters of linagliptin were determined through duodenum, jejunum, ileum and colon segments. The effect of carvedilol, atorvastatin and sodium cholate was investigated by co-perfusion of each with linagliptin through jejunum and ileum.

KEY FINDINGS

The study reflected incomplete linagliptin absorption from the explored intestinal segments. The resulted rank indicated that the extent of absorption decreases as we move distally through the small intestine before increasing at the ascending colon. This behaviour suggests a role of P-glycoprotein (P-gp) efflux on reduced linagliptin intestinal absorption. Co-perfusion with carvedilol, atorvastatin or bile salts significantly enhanced linagliptin absorption. This elects P-gp efflux inhibition as one possible mechanism for enhanced linagliptin intestinal membrane transport.

CONCLUSIONS

The study confirmed the role of P-gp efflux transporters in reduced intestinal linagliptin absorption. Co-administration of linagliptin with either carvedilol or atorvastatin can modulate the oral bioavailability of linagliptin. Bile salts can be employed as a formulation excipient for enhanced oral absorption of linagliptin.

Dipeptidylpeptidase 4 promotes survival and stemness of acute myeloid leukemia stem cells

Leukemic-stem-cell-specific targeting may improve the survival of patients with acute myeloid leukemia (AML) by avoiding the ablative effects of standard regimens on normal hematopoiesis. Herein, we perform an unbiased screening of compounds targeting cell surface proteins and identify clinically used DPP4 inhibitors as strong suppressors of AML development in both murine AML models and primary human AML cells xenograft model. We find in retrovirus-induced AML mouse models that DPP4-deficient AML cell-transplanted mice exhibit delay and reversal of AML development, whereas deletion of DPP4 has no significant effect on normal hematopoiesis. DPP4 activates and sustains survival of AML stem cells that are critical for AML development in both human and animal models via binding with Src kinase and activation of nuclear factor κB (NF-κB) signaling. Thus, inhibition of DPP4 is a potential therapeutic strategy against AML development through suppression of survival and stemness of AML cells.

Safety and effectiveness of empagliflozin and linagliptin fixed-dose combination therapy in Japanese patients with type 2 diabetes: final results of a one-year post-marketing surveillance study

BACKGROUND

Fixed-dose combination (FDC) of the sodium-glucose co-transporter 2 inhibitor empagliflozin and the dipeptidyl peptidase-4 inhibitor linagliptin was approved for type 2 diabetes (T2D) treatment in Japan in 2018. We conducted a post-marketing surveillance study of empagliflozin/linagliptin FDC in routine clinical practice in Japan.

RESEARCH DESIGN AND METHODS

This one-year, prospective, multicenter, observational study investigated the safety and effectiveness of empagliflozin/linagliptin FDC in Japanese patients with T2D. The primary outcome was incidence of adverse drug reactions (ADRs).

RESULTS

Among 1146 patients, mean (SD) age was 63.8 (12.8) years and 22.08% were aged ≥75 years. Mean (SD) glycated hemoglobin (HbA1c) was 7.66% (1.21); fasting plasma glucose (FPG) was 142.90 mg/dl (43.75). ADRs were experienced by 32 (2.79%) patients (1 serious ADR); ADRs of important identified risk included urinary tract infection (7 patients [0.61%]), hypoglycemia (2 [0.17%]), ketoacidosis (0), genital infection (1 [0.09%]), and volume depletion (1 [0.09%]). Overall mean (SD) change from baseline in body weight, HbA1c, and FPG were -1.08 kg (3.21), -0.39% (1.11), and -7.90 mg/dl (39.12), respectively.

CONCLUSIONS

Empagliflozin/linagliptin FDC was effective and generally well tolerated in Japanese patients with T2D; no new safety concerns were identified.

TRIAL REGISTRATION

The trial is registered at ClinicalTrials.gov (CT.gov identifier: NCT03761797) [Figure: see text] [Figure: see text].

Incident and recurrent hypoglycaemia with linagliptin and glimepiride over a median of 6 years in the CAROLINA cardiovascular outcome trial

AIM

The CAROLINA trial established non-inferiority of linagliptin versus glimepiride for major adverse cardiovascular events in patients with relatively early type 2 diabetes at increased cardiovascular risk. In pre-specified and post-hoc analyses, we investigated treatment effects on total hypoglycaemic burden in CAROLINA.

MATERIALS AND METHODS

Patients were randomized and treated with 5 mg linagliptin (n = 3014) or 1-4 mg glimepiride (n = 3000) once daily added to standard care. Hypoglycaemia captured from investigator-reported adverse events was analysed with Poisson and negative binomial regressions for the first and total (first plus recurrent) events, respectively. The influence of insulin initiation and glycated haemoglobin (HbA1c) change on the treatment effect for hypoglycaemia was also explored.

RESULTS

Over 6.3 years median follow-up, average HbA1c over time did not differ between linagliptin versus glimepiride (weighted mean difference [95% confidence interval]: 0.00%, [-0.05, 0.05]), nor did insulin initiation (18.6% vs. 19.2% of patients, respectively), whereas body weight was lower with linagliptin (-1.54 kg, [-1.80, -1.28]). Hypoglycaemia frequency was lower with linagliptin across all hypoglycaemia categories, including severe episodes. Rate ratios (95% confidence interval) for first and total events for investigator-reported hypoglycaemia were 0.21 (0.19-0.24) and 0.12 (0.10-0.14), respectively, with 8.7 first and 60.8 total estimated events prevented/100 patient-years with linagliptin versus glimepiride. These differences occurred during night-time and daytime, and in subgroup analyses of total events. Treatment differences in hypoglycaemia were neither impacted by HbA1c changes nor insulin initiation.

CONCLUSIONS

Across the severity spectrum, linagliptin substantially reduced the hypoglycaemic burden versus glimepiride in patients with relatively early type 2 diabetes at increased cardiovascular risk.

Hiring of the Anti-Quorum Sensing Activities of Hypoglycemic Agent Linagliptin to Alleviate the Pseudomonas aeruginosa Pathogenesis

Bacteria communicate with each other using quorum sensing (QS) which works in an inducer/receptor manner. QS plays the main role in orchestrating diverse bacterial virulence factors. Pseudomonas aeruginosa is one of the most clinically important bacterial pathogens that can cause infection in almost all body tissues. Besides its efficient capability to develop resistance to different antibiotics, P. aeruginosa acquires a huge arsenal of virulence factors that are controlled mainly by QS. Challenging QS with FDA-approved drugs and natural products was proposed as a promising approach to mitigate bacterial virulence enabling the host immunity to complete the eradication of bacterial infection. The present study aims to evaluate the dipeptidase inhibitor-4 inhibitor hypoglycemic linagliptin anti-QS and anti-virulence activities against P. aeruginosa in vitro, in vivo, and in silico. The current results revealed the significant ability to diminish the production of protease and pyocyanin, motility, and biofilm formation in P. aeruginosa. Furthermore, the histopathological examination of liver and kidney tissues of mice injected with linagliptin-treated bacteria showed an obvious reduction of pathogenesis. Linagliptin downregulation to QS-encoding genes, besides the virtual ability to interact with QS receptors, indicates its anti-QS activities. In conclusion, linagliptin is a promising anti-virulence and anti-QS candidate that can be used solely or in combination with traditional antimicrobial agents in the treatment of P. aeruginosa aggressive infections.

Effects of Linagliptin and Pioglitazone on Fracture Healing in an Experimental Type 2 Diabetes Rat Model

AIM

Our study aimed to examine the effects of Linagliptin, Pioglitazone, and their combination on fracture healing in a diabetes rat femur fracture model.

MATERIAL AND METHODS

Type 2 diabetes mellitus (T2DM) induced rats were randomly divided into four groups: non-treated diabetes group (TD), Pioglitazone group (P), Linagliptin group (L), and Pioglitazone and Linagliptin group (PL). Daily oral dosage of pioglitazone (10 mg/kg/day), linagliptin (10 mg/kg/day), and their combination were administered. Femur fractures were stabilized intramedullary. At weeks 2 and 6, rats were sacrificed for evaluation radiologically, biomechanically, histopathologically, histomorphometrically, and immunohistochemically.

RESULTS

Flexural strength of the L and PL groups were significantly higher compared to the P group. The highest healing score was in the L group and lowest in the P group, while the highest inflammation score was in the P group and lowest in the L group. A cluster of differentiation (CD) CD 34 reactivity was highest in the L group and lowest in the PL group.

CONCLUSION

Linagliptin treatment significantly increased histological healing scores, callus volume, biomechanical strength, and vascularity, however, minimized the inflammatory process, which was increased by pioglitazone. The combination of linagliptin and pioglitazone restored BMD and increased biomechanical strength. Linagliptin monotherapy is rarely indicated; hence, T2DM patients with a high risk of bone fractures can be considered for combined therapy of pioglitazone and linagliptin.

Pharmacokinetics and Bioequivalence of Single-Oral-Dose Linagliptin: A Randomized, 2-Period Crossover Trial in Chinese Healthy Subjects Under Fasting and Fed Conditions

The bioequivalence of the reference and test linagliptin formulations was assessed in healthy Chinese subjects under fasting and fed conditions. The study was designed as a single-dose, randomized, open-label, 2-period crossover study with a 35-day washout period between 2 administrations. Forty-eight healthy subjects received 5 mg of test and reference linagliptin formulation orally under fasting condition. The geometric mean of the maximum observed linagliptin concentration (C_max ) for the test formulation was 4.9 ng/mL (reference, 5.0 ng/mL), the area under the plasma concentration-time curve from 0 to 72 hours (AUC_0-72 ) was 154.7 ng · h/mL (reference, 157.4 ng · h/mL). Thirty-six subjects received 5 mg of test and reference linagliptin formulation orally under fed conditions. The geometric mean of C_max for the test linagliptin formulation was 2.8 ng/mL (reference, 2.8 ng/mL), AUC_0-72 was 133.5 ng · h/mL (reference, 136.6 ng · h/mL). The 90%CIs for the test/reference ratio for C_max and AUC_0-72 met the bioequivalence criteria (80%-125%). The test and reference formulations of linagliptin were well tolerated and bioequivalent under fasting and fed conditions.

Analytical quality by design based on design space in reversed-phase-high performance liquid chromatography analysis for simultaneous estimation of metformin, linagliptin and empagliflozin

Employing the Quality by Design paradigm through this work helped conclude the method operable design region for optimizing the high performance liquid chromatography (HPLC) assay using Design of Experiments and response surface methodology to obtain a good resolution and determination of all analysed compounds and to achieve a suitable analysis time. A deep understanding of the quality target product profile, analytical target profile and risk assessment for parameters that affect the method performance led to developing an accurate, precise and cost-effective method. Quality risk management principles were applied for determining the critical method parameters affecting the simultaneous determination of metformin hydrochloride (MET), linagliptin (LIN) and empagliflozin (EMP) by reversed-phase HPLC . The ternary mixture was successfully resolved in 5 min with a linearity range of (0.1-600) µg ml^-1 for MET and (0.05-50) µg ml^-1 for LIN and EMP. The newly developed method was validated according to the International Council for Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines. Good agreement was observed with the assay results of the reported UPLC one. To evaluate the greenness of the proposed method, an analytical Eco-Scale method was used.

Acute effects of linagliptin on intact and total glucagon-like peptide-1 and gastric inhibitory polypeptide levels in insulin-dependent type 2 diabetes patients with and without moderate renal impairment

AIMS

To investigate the effect of renal impairment on incretin metabolism in patients with type 2 diabetes mellitus (T2DM) before and after treatment with the dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin.

MATERIALS AND METHODS

Long-standing T2DM patients with normal (estimated glomerular filtration rate [eGFR] >90 mL/min/1.73m² ) and impaired (eGFR <60 mL/min/1.73m² ) renal function on stable treatment with insulin were included. Before and after 8 days of treatment with 5 mg linagliptin once daily, patients underwent a 75-g oral glucose tolerance test (OGTT) and total and intact glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP), glucose, insulin, C-peptide and glucagon concentrations were measured. The primary outcome was the difference between the study groups in change of intact GLP-1 concentrations.

RESULTS

Of 115 patients screened, 29 were analysed (15 [51.7%] with and 14 [48.3%] without renal impairment). Renal function differed significantly between the groups (101 ± 11 vs. 47 ± 13 mL/min/1.73m² ; P < 0.0001), while glycaemic control was similar (glycated haemoglobin 68 ±  5 vs. 66 ± 5 mmol/mol; P = 0.45). Baseline GLP-1 and GIP levels were comparable. Glucose concentrations during the OGTT were significantly lowered by linagliptin treatment in patients with renal impairment (P = 0.017), but not in those with normal renal function (P = 0.17). Treatment with linagliptin resulted in a significant increase in intact GLP-1 and GIP levels in patients with normal (P = 0.048 and P = 0.0001, respectively) and impaired (P = 0.040 and P = 0.0011, respectively) renal function during the OGTT. However, the primary outcome (difference between the groups in change of intact GLP-1 concentrations) was not significant (P = 0.22). Overall, linagliptin was well tolerated.

CONCLUSIONS

Treatment with linagliptin increases intact incretin levels in patients with T2DM. Impaired renal function does not compromise the effects of linagliptin on active or total incretin levels as well as on glucagon secretion. Thus, treatment with linagliptin is suitable for patients with T2DM, independently of renal function.

Long-term safety and effectiveness of linagliptin by baseline body mass index in Japanese patients with type 2 diabetes: a 3-year post-marketing surveillance study

BACKGROUND

A recent 3-year post-marketing surveillance (PMS) study reaffirmed the safety and effectiveness of linagliptin in linagliptin-naïve Japanese patients with type 2 diabetes (T2D). We present further analyses from this study by body mass index (BMI).

RESEARCH DESIGN AND METHODS

Safety and effectiveness were assessed across BMI subgroups (<25, 25 to <30, and ≥30 kg/m²).

RESULTS

Data were available for 876, 566, and 201 patients in the BMI subgroups, respectively. Incidence of adverse drug reactions [ADR] with linagliptin was 11.42%, 11.31%, 10.45%, respectively. The most common ADR of special interest was hepatic disorders (n [%]: 6 [0.68], 7 [1.24] and 3 [1.49], respectively). Additional use of glucose-lowering drugs (GLDs) increased with BMI (15.0%, 19.1%, 24.4% of patients; P < 0.001). In the overall population, a sustained decrease in HbA1c was observed in all BMI subgroups. In patients receiving linagliptin with no additional GLDs, changes in HbA1c were -0.58%±0.04, -0.62%±0.04, and -0.77%±0.11.

CONCLUSIONS

In this study of linagliptin in Japanese patients with T2D, across BMI subgroups no new safety concerns were observed. The proportion of patients with additional GLD use increased with baseline BMI. Decreases in HbA1c were observed in all subgroups, including in patients with no additional GLD use.

CLINICALTRIALS.GOV

NCT01650259.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Comparison of Adverse Kidney Outcomes With Empagliflozin and Linagliptin Use in Patients With Type 2 Diabetic Patients in a Real-World Setting

Background: To compare the effects of empagliflozin and linagliptin use on kidney outcomes of type 2 diabetes mellitus (T2DM) patients in a real-world setting. Methods: The study involved a propensity score-matched cohort comprising new users of empagliflozin or linagliptin with T2DM between January 1, 2013 and December 31, 2018 from a large healthcare delivery system in Taiwan. Clinical outcomes assessed: acute kidney injury (AKI), post-AKI dialysis, and mortality. Cox proportional hazard model was used to estimate the relative risk of empagliflozin or linagliptin use; a linear mixed model was used to compare the average change in estimated glomerular filtration rate (eGFR) over time. Results: Of the 7,042 individuals, 67 of 3,521 (1.9%) in the empagliflozin group and 144 of 3,521 (4.1%) in the linagliptin group developed AKI during the 2 years follow-up. Patients in the empagliflozin group were at a 40% lower risk of developing AKI compared to those in the linagliptin group (adjusted hazard ratio [aHR], 0.60; 95% confidence interval [CI], 0.45-0.82, p = 0.001). Stratified analysis showed that empagliflozin users ≥65 years of age (aHR, 0.70; 95% CI, 0.43-1.13, p = 0.148), or with a baseline eGFR <60 ml/min/1.73 m² (aHR, 0.97; 95% CI, 0.57-1.65, p = 0.899), or with a baseline glycohemoglobin ≦7% (aHR, 1.01; 95% CI, 0.51-2.00, p =0.973) experienced attenuated benefits with respect to AKI risk. A smaller decline in eGFR was observed in empagliflozin users compared to linagliptin users regardless of AKI occurrence (adjusted β = 1.51; 95% CI, 0.30-2.72 ml/min/1.73 m², p = 0.014). Conclusion: Empagliflozin users were at a lower risk of developing AKI and exhibited a smaller eGFR decline than linagliptin users. Thus, empagliflozin may be a safer alternative to linagliptin for T2DM patients.

Endogenous GLP-1 levels play an important role in determining the efficacy of DPP-IV Inhibitors in both prediabetes and type 2 diabetes

BACKGROUND

In contrast to Western population, glucagon-like peptide-1 (GLP-1) levels are preserved in some East Asian population with type 2 diabetes (T2D), explaining why dipeptidyl peptidase-IV (DPP-IV) inhibitors are more effective in East Asians. We assessed whether differences in endogenous GLP-1 levels resulted in different treatment responses to DPP-IV inhibitors in prediabetes and T2D.

METHODS

A prospective 12-week study using linagliptin 5mg once daily in 50 subjects (28 prediabetes and 22 T2D) who were stratified into high versus low fasting GLP-1 groups. A 75-g oral glucose tolerance test (OGTT) was performed at week 0 and 12. Primary outcomes were changes in HbA1c, fasting and post-OGTT glucose after 12 weeks. Secondary outcomes included changes in insulin resistance and beta cell function indices.

RESULTS

There was a greater HbA1c reduction in subjects with high GLP-1 compared to low GLP-1 levels in both the prediabetes and T2D populations [least-squares mean (LS-mean) change of -0.33% vs. -0.11% and -1.48% vs. -0.90% respectively)]. Linagliptin significantly reduced glucose excursion by 18% in high GLP-1 compared with 8% in low GLP-1 prediabetes groups. The reduction in glucose excursion was greater in high GLP-1 compared to low GLP-1 T2D by 30% and 21% respectively. There were significant LS-mean between-group differences in fasting glucose (-0.95 mmol/L), 2-hour glucose post-OGTT (-2.4 mmol/L) in the high GLP-1 T2D group. Improvement in insulin resistance indices were seen in the high GLP-1 T2D group while high GLP-1 prediabetes group demonstrated improvement in beta cell function indices. No incidence of hypoglycemia was reported.

CONCLUSIONS

Linagliptin resulted in a greater HbA1c reduction in the high GLP-1 prediabetes and T2D compared to low GLP-1 groups. Endogenous GLP-1 level play an important role in determining the efficacy of DPP-IV inhibitors irrespective of the abnormal glucose tolerance states.

Postprandial renal haemodynamic effects of the dipeptidyl peptidase-4 inhibitor linagliptin versus the sulphonylurea glimepiride in adults with type 2 diabetes (RENALIS): A predefined substudy of a randomized, double-blind trial

AIM

To determine the effect of the dipeptidyl peptidase-4 inhibitor linagliptin on postprandial glomerular hyperfiltration compared with the sulphonylurea glimepiride in adults with type 2 diabetes (T2D).

MATERIALS AND METHODS

In this predefined substudy within a randomized, double-blind, parallel-group, intervention trial, overweight people with T2D without renal impairment were treated with once-daily linagliptin 5 mg (N = 10) or glimepiride 1 mg (N = 13) as an add-on to metformin for 8 weeks. After a standardized liquid protein-rich meal, the glomerular filtration rate (GFR) and effective renal plasma flow were determined by inulin and para-aminohippuric acid clearance, respectively, based on timed urine sampling. Intrarenal haemodynamics were estimated using the Gomez equations. Glucoregulatory/vasoactive hormones, urinary pH and fractional excretions (FE) of sodium, potassium and urea were measured.

RESULTS

Compared with glimepiride, linagliptin increased the postprandial filtration fraction (FF; mean difference 2.1%-point; P = .016) and estimated glomerular hydraulic pressure (mean difference 3.0 mmHg; P = .050), and tended to increase GFR (P = .08) and estimated efferent renal arteriolar resistance (R_E ; P = .08) from baseline to week 8. No differences in FE were noted. Glimepiride reduced HbA1c more than linagliptin (mean difference -0.40%; P = .004), without between-group differences in time-averaged postprandial glucose levels. In the linagliptin group, change in FF correlated with change in mean arterial pressure (R = 0.807; P = .009) and time-averaged mean glucagon (R = 0.782; P = .008), but not with changes in glucose, insulin, intact glucagon-like peptide-1, renin or FE_Na . Change in glucagon was associated with change in R_E (R = 0.830; P = .003).

CONCLUSIONS

In contrast to our hypothesis, compared with glimepiride, linagliptin does not reduce postprandial hyperfiltration, yet appears to increase FF after meal ingestion by increasing blood pressure or R_E .

Linagliptin in Combination With Metformin Ameliorates Diabetic Osteoporosis Through Modulating BMP-2 and Sclerostin in the High-Fat Diet Fed C57BL/6 Mice

BACKGROUND

Diabetic osteoporosis is a poorly managed serious skeletal complication, characterized by high fracture risk, increased bone resorption, reduced bone formation, and disrupted bone architecture. There is a need to investigate drugs that can improve bone health along with managing glycemic control. DPP-4 inhibitors and metformin have proven benefits in improving bone health. Here, we investigated the effects of linagliptin, a DPP inhibitor, and metformin alone and in combination to treat diabetic osteoporosis in high-fat-fed mice.

METHODS

C57BL/6 mice were kept on the high-fat diet (HFD) for 22 weeks to induce diabetic osteoporosis. Linagliptin (10mg/Kg), metformin (150mg/Kg), and their combination were orally administered to the diabetic mice from the 18^th-22^nd week. Femur and tibial bone microarchitecture together with bone mineral density (BMD) were evaluated using µCT and histopathological changes were assessed. Further, bone turnover biomarkers namely bone morphogenetic protein-2 (BMP-2), sclerostin, tartrate-resistant acid phosphatase (TRAP), osteocalcin, alkaline phosphatase (ALP), calcium, and pro-inflammatory cytokines were assessed. Additionally, metabolic parameters including body weight, fasting blood glucose (FBG), glucose & insulin tolerance, lipids profile, and leptin were measured.

RESULTS

HFD feeding resulted in impaired bone microarchitecture, reduced BMD, distorted bone histology, and altered bone turnover biomarkers as indicated by the significant reduction in bone ALP, BMP-2, osteocalcin, and an increase in sclerostin, TRAP, and serum calcium. Interestingly, treatment with linagliptin and its combination with metformin significantly reverted the impaired bone architecture, BMD, and positively modulated bone turnover biomarkers, while metformin alone did not exhibit any significant improvement. Further, HFD induced diabetes and metabolic abnormalities (including an increase in body weight, FBG, impaired glucose and insulin tolerance, leptin, triglycerides, cholesterol), and pro-inflammatory cytokines (TNF-alpha and IL-1β) were successfully reversed by treatment with linagliptin, metformin, and their combination.

CONCLUSION

Linagliptin and its combination with metformin successfully ameliorated diabetic osteoporosis in HFD-fed mice possibly through modulation of BMP-2 and sclerostin. The study provides the first evidence for the possible use of linagliptin and metformin combination for managing diabetic osteoporosis.

Neuroprotective effects of linagliptin in a rotenone-induced rat model of Parkinson's disease

The present study investigates the antiParkinsonian activity of dipeptidyl peptidase-4 (DPP-IV) inhibitor, linagliptin. The experimental Parkinson's disease (PD) was induced by administration of rotenone at a dose of 1.5 mg/kg at alternate day subcutaneously for 21 days. Standard drug (levodopa-200 mg/kg and carbidopa-50 mg/kg) and treatment drug (linagliptin-5 mg/kg, 10 mg/kg, and 20mg/kg) were administered orally daily 1 h before rotenone administration. In a rat rotenone model, linagliptin improved muscle coordination, motor performance, and corrected akinesia. Pretreatment with linagliptin showed significant higher levels of superoxide dismutase, catalase, and glutathione in brain homogenate of animals. Linagliptin significantly elevated the levels of striatal DA and active glucagon-like peptide 1 in brain homogenate of animals. Furthermore, linagliptin amended alterations induced by rotenone in the thiobarbituric acid reactive substances and inflammatory marker such as tumor necrosis factor-α level. The results of the present study indicate the neuroprotective potential of linagliptin for the management of PD might be due to remarkable improvement in motor functions, antioxidant, anti-inflammatory, anti-apoptotic, and neuroprotective mechanisms.

Safety and tolerability of linagliptin in Asians with type 2 diabetes: a pooled analysis of 4457 patients from 21 randomized, double-blind, placebo-controlled clinical trials

BACKGROUND

Safety and tolerability of glucose-lowering drugs is a key consideration for use in type 2 diabetes (T2D). We evaluated the safety and tolerability of the dipeptidyl peptidase-4 inhibitor linagliptin in Asian patients with T2D.

RESEARCH DESIGN AND METHODS

This was a post-hoc, descriptive pooled analysis of 21 randomized, double-blind, placebo-controlled clinical trials of linagliptin in T2D patients lasting ≤52 weeks. We evaluated adverse events (AEs) and laboratory parameters in Asian participants living in Asia, both overall and in the East Asian subgroup.

RESULTS

This analysis included 4457 Asian patients overall (2712 receiving linagliptin; 1745 receiving placebo) and 3057 (68.6%) East Asians. AEs were reported in 1510 (55.7%) Asian patients receiving linagliptin and 1032 (59.1%) receiving placebo but were considered drug-related in only 13.0% of each group. Serious AEs occurred in 109 (4.0%) linagliptin patients and 90 (5.2%) placebo patients. The most common AEs were nasopharyngitis (6.4% linagliptin, 7.3% placebo), upper respiratory tract infection (5.7% linagliptin, 6.5% placebo), and hypoglycemia (7.3% linagliptin, 6.3% placebo). One linagliptin patient had pancreatitis; none had bullous pemphigoid. No clinically relevant mean changes in laboratory parameters occurred. These findings were consistent in East Asians.

CONCLUSIONS

Linagliptin is well tolerated in Asian T2D patients, including East Asians, with low risk for AEs.

Electrochemical Detection of Linagliptin and its Interaction with DNA

Objectives

Linagliptin (Lin) is a drug used in treatment of type 2 diabetes mellitus. In this study, the electrochemical detection of Lin and its interaction with DNA was analyzed for the first time using voltammetric methods by measuring the oxidation currents of the adenine bases of DNA before and after the interaction. In addition, the electrochemical properties of the Lin were studied.

Materials and Methods

The interaction between Lin and DNA was evaluated using differential pulse voltammetry. A three-electrode system comprising of a pencil graphite electrode as the working electrode, reference electrode (Ag/AgCl), and platinum wire as the auxiliary electrode was used in the electrochemical studies. Experimental conditions, such as the concentration, pH of the supporting electrolyte, and immobilization time were optimized to obtain maximum analytical signals.

Results

The adenine bases of DNA were evaluated as an analytical signal obtained at approximately +1.2 V vs. Ag/AgCl. After the Lin-DNA interaction, the oxidation currents of adenine decreased as proof of interaction. No reports have been published on Lin interacting with DNA. Based on our results, a diffusion-controlled irreversible redox process involving independent oxidation was revealed for Lin. Under optimum conditions, the detection limit was 6.7 µg/mL for DNA and 21.5 µg/mL for Lin. Based on the observations, Lin has a toxic effect on DNA.

Conclusion

We successfully demonstrated that Lin interacts with DNA, and its influence on DNA could play a vital role in the medical effect of the drug.

Linagliptin Protects against Endotoxin-Induced Acute Kidney Injury in Rats by Decreasing Inflammatory Cytokines and Reactive Oxygen Species

Septic shock can increase pro-inflammatory cytokines, reactive oxygen species (ROS), and multiple organ dysfunction syndrome (MODs) and even lead to death. Dipeptidyl peptidase-4 (DPP-4) inhibitors have been proven to exert potential antioxidant and anti-inflammatory effects. We investigated the effects of linagliptin on endotoxic shock and acute kidney injury (AKI) in animal and cell models. In the cell model, linagliptin attenuated ROS by activating the AMP-activated protein kinase (AMPK) pathway, restoring nuclear-factor-erythroid-2-related factor (Nrf2) and heme oxygenase 1 (HO-1) protein, and decreasing pro-inflammatory cytokines (tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β)). In the animal model, 14-week-old conscious Wistar–Kyoto rats were randomly divided into three groups (n = 8 in each group). Endotoxin shock with MODs was induced by the intravenous injection of Klebsiella pneumoniae lipopolysaccharide (LPS, 20 mg/kg). Linagliptin improved animal survival without affecting hemodynamic profiles. In the histopathology and immunohistochemistry examinations of the rat kidneys, linagliptin (10 mg/kg) suppressed nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and inducible nitric oxide synthase (iNOS), decreased injury scores, and preserved E-cadherin expression from LPS damage. In conclusion, linagliptin ameliorated endotoxin-shock-induced AKI by reducing ROS via AMPK pathway activation and suppressing the release of TNF-α and IL-1β in conscious rats.

Plasma Nitrate Levels Are Related to Metabolic Syndrome and Are Not Altered by Treatment with DPP-4 Inhibitor Linagliptin: A Randomised, Placebo-Controlled Trial in Patients with Early Type 2 Diabetes Mellitus

The depletion of nitrate and nitrite, stable nitric oxide (NO) end-products, promotes adipose tissue dysfunction and insulin resistance (IR). Dipeptidyl peptidase-4 (DPP-4) inhibitors have the potentially beneficial side effect of increasing NO availability. In this study, nitrate and nitrite levels and the effects of DPP-4 inhibitor linagliptin were investigated in relation to metabolic syndrome (MetS) markers. Treatment-naive patients with early type 2 diabetes mellitus (T2DM) (n = 40, median age 63 IQR (55–67) years, 63% male, mean HbA1c 45 ± 4.4 mmol/mol) were randomized (1:1) to linagliptin (5 mg/day) or placebo. MetS-related markers (body mass index (BMI), triglycerides, HOMA-IR, gamma-glutamyltransferase (GGT), C-reactive protein (CRP), and adiponectin), plasma levels of nitrate, nitrite, total free thiols (TFT) and vegetable intake were estimated at baseline and after 4 and 26 weeks of treatment. Plasma nitrate, but not nitrite, correlated positively with vegetable intake (r = 0.38, p = 0.018) and was inversely associated with HOMA-IR (r = −0.44, p = 0.006), BMI (r = −0.35, p = 0.028), GGT (r = −0.37, p = 0.019) and CRP (r = −0.34, p = 0.034). The relationship between nitrate and HOMA-IR remained significant after adjusting for BMI, CRP, vegetable intake and GGT. With stable vegetable intake, nitrate and nitrite, TFT, adipokines and CRP did not change after 26 weeks of linagliptin treatment. While plasma nitrate is inversely associated with MetS, linagliptin treatment does not significantly influence nitrate and nitrite concentrations, oxidative stress, adipose tissue function and systemic inflammation.

No Significant Changes of Glycemic Control and Renal Function in Patients with Advanced-Stage Diabetic Kidney Disease by Switching from Linagliptin to Teneligliptin

Purpose

We compared the efficacy of teneligliptin versus linagliptin for glycemic control and renoprotection in patients with advanced-stage diabetic kidney disease.

Patients and Methods

Changes in the glycated hemoglobin (HbA1c), fasting blood glucose concentration, urine albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR) during a 12-month period were retrospectively analyzed after switching from linagliptin to teneligliptin in 13 patients with advanced-stage diabetic kidney disease (teneligliptin group). Thirteen propensity score-matched patients who were treated with linagliptin alone served as controls (linagliptin group).

Results

The HbA1c, fasting blood glucose concentration, and UACR did not change during the 12-month study period in either group. The annual change rate in the eGFR did not differ between before and after baseline in either group.

Conclusion

Switching from linagliptin to teneligliptin may not improve glycemic control, reduce urinary protein excretion, or ameliorate the rate of renal function decline in patients with advanced-stage diabetic kidney disease. These results suggest that teneligliptin may not be more advantageous for glycemic control and renoprotection compared with linagliptin in patients with advanced-stage diabetic kidney disease.

Urinary dipeptidyl peptidase-4 protein is increased by linagliptin and is a potential predictive marker of urine albumin-to-creatinine ratio reduction in patients with type 2 diabetes

Results of a post hoc analysis of urinary dipeptidyl peptidase-4 (DPP-4) protein as a predictor of urine albumin-to-creatinine ratio (UACR) response to linagliptin treatment based on MARLINA-T2D trial data are described. MARLINA was a 24-week, phase 3b, multinational, placebo-controlled clinical trial, in which patients with type 2 diabetes (T2D), HbA1c 6.5%-10.0% and UACR 30-3000 mg/g (n = 360) were treated with linagliptin or placebo. After 24 weeks of treatment, linagliptin significantly inhibited urinary DPP-4 activity and increased urinary DPP-4 protein. Furthermore, medium urinary DPP-4 protein levels (between 5.5 and 7.5 natural logarithmic [ln] μg/g creatinine) at baseline allowed for prediction of improved UACR in linagliptin-treated individuals. In patients with lower or higher levels of urinary DPP-4 protein at baseline, no association between linagliptin treatment and improved UACR was present. This might suggest a varying degree of importance of DPP-4 as a pathophysiological factor in T2D-associated kidney disease. In summary, urinary DPP-4 might be a useful predictive biomarker for UACR improvement by linagliptin.

Application of experimental design in HPLC method optimization and robustness for the simultaneous determination of canagliflozin, empagliflozin, linagliptin, and metformin in tablet

Gliflozins and gliptins represent two different pharmacological drug classes that exert different and potentially complementary glucose-lowering effect in patients with type II diabetes mellitus. A novel, selective, and sensitive HPLC method was developed for the determination of canagliflozin, empaglifozin, linagliptin, and metformin in pure form, in laboratory prepared mixtures, and in pharmaceutical dosage form. Experimental design optimization was applied by using Plackett-Burman and face-centered composite designs to achieve the best resolution with minimum experimental trials. Three significant variables affecting optimization, namely buffer pH, percentage of methanol, and percentage of acetonitrile, were studied. Chromatographic separation was achieved using an Agilent Eclipse C₈ column, and column temperature was kept at 45°C. The mobile phase was composed of dipotassium hydrogen phosphate buffer (0.05 M, adjusted to pH 6 using o-phosphoric acid):acetonitrile:methanol (50:25:25, v/v/v) at a flow rate of 1.5 mL/min. Sharp and well-resolved peaks of the cited drugs were obtained. The method was fully validated in terms of linearity, accuracy, precision, selectivity and robustness in agreement with the International Council of Harmonization (ICH) guidelines Q2 (R1). Satisfactory results were obtained by the analysis of tablets through applying the developed method. Therefore, it could be performed for the analysis of the cited drugs in quality control laboratories.

Safety and effectiveness of linagliptin in Korean patients with type 2 diabetes: A postmarketing surveillance study

We designed a postmarketing surveillance study of linagliptin for patients with type 2 diabetes (T2D) in Korea. This prospective, observational, multicentre study investigated the safety and glycaemic effectiveness of linagliptin as monotherapy or combination therapy with other antidiabetic drugs in routine clinical practice. Endpoints were the incidence of adverse drug reactions (ADRs) and the change in HbA1c. Overall, 3119 and 2171 patients were included in the safety and effectiveness analysis sets, respectively. A total of 56 patients (1.8%) experienced ADRs. The most common ADR was gastrointestinal disorders (0.7%), followed by metabolism and nutrition disorders (0.5%). ADRs of special interest, including pancreatic diseases, cardiac diseases and hypoglycaemia, occurred in 12 patients, 11 of whom had hypoglycaemia, while one had a skin lesion. Mean HbA1c change during the study period was -0.8%. Lower body mass index, shorter diabetes duration and higher baseline HbA1c were independently associated with a better effectiveness, while the presence of diabetic complications, dyslipidaemia and the use of sulphonylureas were associated with a poor response. In conclusion, linagliptin showed an excellent safety profile and glycaemic effectiveness in Korean patients with T2D.

[Neuroprotective effects of linagliptin on ischemia/reperfusion in mice]

Objective: To evaluate the neuroprotective effects of linagliptin, a dipeptidyl peptidase-4(DPP-4) inhibitor, on cerebral ischemia/reperfusion(I/R) injury in mice. Methods: BALB/c mice were randomly divided into Sham group, I/R group and linagliptin (2.5, 5 and 10 mg/kg) +I/R group, 8 mice in each group. The mice in the linagliptin group were administrated by gavage 3 weeks before I/R. I/R injury model was induced by MCAO, neurological deficit scores(n=8) and infarct volume(n=4) were assessed 24 h following reperfusion. Forty-eight hours following reperfusion, mice were euthanized, the contents of glutathione (GSH), malondialdehyde (MDA), phosphoinositide 3 kinase (PI3K), phosphoprotein kinase B (p-Akt) and rapamycin target protein (mTOR) in brain tissue were measured (n=4). Results: Compared with the I/R group, the neurological deficit score and infarct volume were significantly decreased in the linagliptin pretreatment group after 24 h reperfusion (P＜0.05); the MDA content in the brain was significantly decreased (P＜0.05), while the GSH, PI3K, p-Akt and mTOR levels were significantly increased (P＜0.05). Conclusion: This study proves that linagliptin exerted a neuroprotective effect in I/R mice, which may be mediated by activation of the PI3K/AKT/mTOR pathway.

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.

Acute Pancreatitis Induced by Linagliptin: A Rare but Dangerous Side Effect

Diabetes mellitus type 2 (DMT2) is a highly prevalent disease both in the United States and worldwide. Multiple treatment options are currently available, and several new groups of medications have been introduced over the last couple of decades. One of these groups is dipeptidyl peptidase-4 (DPP-4) inhibitors. These medications have side effects, some of which are severe and potentially life-threatening; however, some of their side effects have been underreported since they are relatively new. When prescribing these medications, it is essential to be cautious, especially with patients at an increased risk of developing an adverse effect. We present the case of a 57-year-old male who developed DPP-4 inhibitor-induced acute pancreatitis after the initiation of linagliptin. The patient did not have any apparent risk factors for pancreatitis as he did not drink alcohol or smoke cigarettes, his lipid panel was within normal limits, and he had a cholecystectomy five years prior. His linagliptin was held in the hospital and discontinued post-discharge, which led to the resolution of his symptoms.

Metformin dose increase versus added linagliptin in non-alcoholic fatty liver disease and type 2 diabetes: An analysis of the J-LINK study

We validated the effect of linagliptin, an oral dipeptidyl peptidase-4 inhibitor, on nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). A total of 50 patients with NAFLD and T2DM treated with metformin were randomized (1:1) to metformin plus add-on linagliptin (linagliptin group) or to an increased dose of metformin (metformin group) for 52 weeks. The primary endpoint was change in hepatic steatosis from baseline to week 52 as quantified by unenhanced computed tomography imaging. Secondary endpoints included changes in the levels of anthropometric, biochemical and adipokinetic markers. The linagliptin group showed no statistically significant reduction in hepatic steatosis as compared to the metformin group (P = 0.97), although changes in hepatic steatosis were significantly correlated with decreased liver enzymes in both groups. Body weight was significantly reduced in the metformin group but not in the linagliptin group (P = 0.002). Serum leptin levels were significantly increased in the linagliptin group compared to the metformin group (P = 0.003), and were correlated with the changes body weight in whole samples. Adverse events were not different between the two groups (P = 0.78). Add-on linagliptin demonstrated a safe profile but was not superior to increased metformin in reducing hepatic steatosis.

Determination of linagliptin and empagliflozin by UPLC and HPTLC techniques aided by lean six sigma approach

Two chromatographic techniques were developed and validated for simultaneous determination of the newly co-formulated antidiabetic combination linagliptin and empagliflozin in their pure form and film-coated tables. The first technique was UPLC; the separation and resolution of both analytes were achieved using a Zorbax eclipse plus C₁₈ column applying an isocratic elution based on phosphate buffer pH 4-acetonitrile (65:35, v/v) as a running mobile phase at flow rate 1.5 ml/min and the effluent was monitored at 220 nm. Augmentation of Lean Six Sigma with UPLC and HPTLC methods had a major impact on the development of robust specifications to ensure that the quality at six sigma level has a high level of statistical confidence and target performance. On the chromatogram, empagliflozin and linagliptin appeared at retention times of 1.417 and 2.453 min, respectively. The second technique was HPTLC; both analytes were fairly well resolved and separated using a developing mobile phase composed of ethyl acetate-chloroform-acetonitrile (55:25:20 by volume). The values of retention factor (R_F ) were 0.29 and 0.53 for linagliptin and empagliflozin, respectively. All variables were investigated to adjust the whole conditions.

Action of Dipeptidyl Peptidase-4 Inhibitors on SARS-CoV-2 Main Protease

In a recent publication, Eleftheriou et al. proposed that inhibitors of dipeptidyl peptidase‐4 (DPP‐4) are functional inhibitors of the main protease (M^pro) of SARS‐CoV‐2. Their predictions prompted the authors to suggest linagliptin, a DPP‐4 inhibitor and approved anti‐diabetes drug, as a repurposed drug candidate against the ongoing COVID‐19 pandemic. We used an enzymatic assay measuring the inhibition of M^pro catalytic activity in the presence of four different commercially available gliptins (linagliptin, sitagliptin, alogliptin and saxagliptin) and several structural analogues of linagliptin to study the binding of DPP‐4 inhibitors to M^pro and their functional activity. We show here that DPP‐4 inhibitors like linagliptin, other gliptins and structural analogues are inactive against M^pro.

Cardiovascular outcomes and safety with linagliptin, a dipeptidyl peptidase-4 inhibitor, compared with the sulphonylurea glimepiride in older people with type 2 diabetes: A subgroup analysis of the randomized CAROLINA trial

AIM

To compare the cardiovascular (CV) safety of linagliptin with glimepiride in older and younger participants in the CAROLINA trial in both prespecified and post hoc analyses.

MATERIALS AND METHODS

People aged 40 to 85 years with relatively early type 2 diabetes, inadequate glycaemic control and elevated CV risk were randomly assigned to linagliptin 5 mg or glimepiride 1 to 4 mg. The primary endpoint was time to first occurrence of three-point major adverse CV events (MACE: CV death, non-fatal myocardial infarction, or non-fatal stroke). We evaluated clinical and safety outcomes across age groups.

RESULTS

Of 6033 participants, 50.7% were aged <65 years, 35.3% were aged 65 to 74 years, and 14.0% were aged ≥75 years. During the 6.3-year median follow-up, CV/mortality outcomes did not differ between linagliptin and glimepiride overall (hazard ratio [HR] for three-point MACE 0.98, 95.47% confidence interval [CI] 0.84, 1.14) or across age groups (interaction P >0.05). Between treatment groups, reductions in glycated haemoglobin were comparable across age groups but moderate-to-severe hypoglycaemia was markedly reduced with linagliptin (HR 0.18, 95% CI 0.15, 0.21) with no differences among age groups (P = 0.23). Mean weight was -1.54 kg (95% CI -1.80, -1.28) lower for linagliptin versus glimepiride. Adverse events increased with age, but were generally balanced between treatment groups. Significantly fewer falls or fractures occurred with linagliptin.

CONCLUSIONS

Linagliptin and glimepiride were comparable for CV/mortality outcomes across age groups. Linagliptin had significantly lower risk of hypoglycaemia and falls or fractures than glimepiride, including in "older-old" individuals for whom these are particularly important treatment considerations.

Efficacy and safety of linagliptin as add-on therapy to insulin in Chinese patients with type 2 diabetes mellitus: A randomized, double-blind, placebo-controlled trial

This 24-week, double-blind, placebo-controlled, phase III trial evaluated the efficacy and safety of linagliptin in 206 Chinese patients with inadequately controlled (glycated haemoglobin [HbA1c] 7.5%-10.0%) type 2 diabetes mellitus (T2DM) receiving insulin (basal or premixed) ± metformin. Patients were randomized (1:1) to receive linagliptin 5 mg/d or placebo. The decrease from baseline in HbA1c (primary endpoint) was greater with linagliptin than with placebo (-0.61% vs. -0.20%, adjusted mean difference -0.40%; P = 0.0016). Linagliptin demonstrated significantly greater improvement in 2-hour postprandial glucose (-1.77 mmol/L [-31.95 mg/dL]; P < 0.001), and a numerical reduction in fasting plasma glucose (-0.34 mmol/L [-6.2 mg/dL]; P = 0.2241) versus placebo. Proportionally more patients on linagliptin achieved a HbA1c reduction of ≥0.5% versus those on placebo (odds ratio 2.293, P < 0.01). Adverse events in both groups were similar, with no new safety findings or clinically relevant changes in body weight. Among investigator-defined hypoglycaemic events (linagliptin: 17.3%; placebo: 12.7%; odds ratio 1.48, P = 0.337), none were severe. In Chinese patients with T2DM, linagliptin add-on to insulin improved glycaemic control and was well tolerated, without increased risk of hypoglycaemia or weight gain.