Plants Fagonia cretica L. and Hedera nepalensis K. Koch contain natural compounds with potent dipeptidyl peptidase-4 (DPP-4) inhibitory activity

Ethnopharmacological relevance
The two plants investigated here (Fagonia cretica L. and Hedera nepalensis K. Koch) have been previously reported as natural folk medicines for the treatment of diabetes but until now no scientific investigation of potential anti-diabetic effects has been reported. 

Materials and methods
In vitro inhibitory effect of the two tested plants and their five isolated compounds on the dipeptidyl peptidase 4 (DPP-4) was studied for the assessment of anti-diabetic activity. 

Results
A crude extract of Fagonia cretica possessed good inhibitory activity (IC₅₀value: 38.1 μg/ml) which was also present in its n-hexane (FCN), ethyl acetate (FCE) or aqueous (FCA) fractions. A crude extract of Hedera nepalensis (HNC) possessed even higher inhibitory activity (IC₅₀value: 17.2 μg/ml) and this activity was largely retained when further fractionated in either ethyl acetate (HNE; IC₅₀: 34.4 μg/ml) or n-hexane (HNN; 34.2 μg/ml). Bioactivity guided isolation led to the identification of four known compounds (isolated for the first time) from Fagonia cretica: quinovic acid (1), quinovic acid-3β-O-β-d-glycopyranoside (2), quinovic acid-3β-O-β-d-glucopyranosyl-(28→1)-β-d-glucopyranosyl ester (3), and stigmasterol (4) all of which inhibited DPP-4 activity (IC₅₀: 30.7, 57.9, 23.5 and >100 μM, respectively). The fifth DPP-4 inhibitor, the triterpenoid lupeol (5) was identified in Hedera nepalensis (IC₅₀: 31.6 μM). 

Conclusion
The experimental study revealed that Fagonia cretica and Hedera nepalensis contain compounds with significant DPP-4 inhibitory activity which should be further investigated for their anti-diabetic potential.

Lactobacilli possess inhibitory activity against dipeptidyl peptidase-4 (DPP-4)

Dipeptidyl peptidase 4 (DPP-4) enzymatically inactivates incretin hormones, and DPP-4 inhibitor drugs are clinically approved therapies for type 2 diabetes. The primary substrates of DPP-4 are produced in the intestinal lining and we therefore investigated whether lactobacilli colonizing the gut can inhibit this enzyme. Fifteen Lactobacillus strains (Lb 1-15) from human infant faecal samples were isolated, identified, extracted and screened for inhibitory activity against DPP-4. Activity was compared against Lactobacillus reference strains (Ref 1-7), a Gram positive control (Ctrl 1) and two Gram negative controls (Ctrl 2-3). A range of DPP-4 inhibitory activity was observed (10-32%; P<0.05-0.001). Strains of L. fabifermentans (25%), L. plantarum (12-24%) and L. fermentum (14%) had significant inhibitory activity. However, we also noted that E. coli (Ctrl 2) and S. Typhimurium (Ctrl 3) had the greatest inhibitory activity (30-32%). Contrastingly, some isolates (Lb 12-15) and reference cultures (Ref 1-4) instead of inhibiting DPP-4 actually enhanced it, perhaps indicating the presence of X-prolyl-dipeptidyl-amino-peptidase (PepX). This provides a future rationale for using probiotic bacteria or their components for management of type 2 diabetes via DPP-4 inhibition.

An update on the clinical pharmacology of the dipeptidyl peptidase 4 inhibitor alogliptin used for the treatment of type 2 diabetes mellitus.

Alogliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor that is a class of relatively new oral hypoglycaemic drugs used in patients with type 2 diabetes (T2DM), can be used as monotherapy or in combination with other anti-diabetic agents, including metformin, pioglitazone, sulfonylureas and insulin with a considerable therapeutic effect. Alogliptin exhibits favorable pharmacokinetic and pharmacodynamic profiles in humans. Alogliptin is mainly metabolized by cytochrome P450 (CYP2D6) and CYP3A4. Dose reduction is recommended for patients with moderate or worse renal impairment. Side effects of alogliptin include nasopharyngitis, upper-respiratory tract infections and headache. Hypoglycaemia is seen in about 1.5% of the T2DM patients. Rare but severe adverse reactions such as acute pancreatitis, serious hypersensitivity including anaphylaxis, angioedema and severe cutaneous reactions such as Stevens-Johnson syndrome have been reported from post-marketing monitoring. Pharmacokinetic interactions have not been observed between alogliptin and other drugs including glyburide, metformin, pioglitazone, insulin and warfarin. The present review aimed to update the clinical information on pharmacodynamics, pharmacokinetics, adverse effects and drug interactions, and to discuss the future directions of alogliptin.

The place of DPP-4 inhibitors in the treatment algorithm of diabetes type 2 : a systematic review of cost-effectiveness studies

Tese de mestrado, Epidemiologia, Universidade de Lisboa, Faculdade de Medicina, 2015

Fixed-dose combination therapy for type 2 diabetes: sitagliptin plus pioglitazone

Importance of the field: Type 2 diabetes is typically associated with insulin resistance and dysfunction of insulin-secreting pancreatic beta-cells. Addressing these defects often requires therapy with a combination of differently acting antidiabetic agents. A potential novel combination in development brings together the dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin with the thiazolidinedione pioglitazone into a fixed-dose single-tablet combination. The former component acts mainly to increase prandial insulin secretion; the latter improves insulin sensitivity.

Patient-reported outcomes in trials of incretin-based therapies in patients with type 2 diabetes mellitus

Incretin-based therapies have a glucose-dependent mode of action that results in excellent glucose-lowering efficacy with very low risk of hypoglycaemia, and weight neutrality [dipeptidyl peptidase-4 (DPP-4) inhibitors] or weight loss [glucagon-like peptide-1 (GLP-1) receptor agonists], in people with type 2 diabetes mellitus (T2DM). Patient-reported outcomes (PROs) complement physician evaluations of efficacy and tolerability and offer insights into the subjective experience of using modern diabetes treatments. We conducted a systematic search of clinical trials of the GLP-1 receptor agonists liraglutide, exenatide and long-acting exenatide, one of which included the oral DPP-4 inhibitor sitagliptin as a comparator. No other PRO data for DPP-4 inhibitors were identified. This review summarizes PRO data from eight clinical trials, the majority of which used the Diabetes Treatment Satisfaction Questionnaire (DTSQ) and/or Impact of Weight on Quality of Life-Lite (IWQOL-Lite) to evaluate patient experience. People with T2DM were highly satisfied with modern incretin-based therapies compared with traditional therapies. Treatment satisfaction (including perceptions of convenience and flexibility) was high and generally higher with GLP-1 agonists in association with their greater glucose-lowering efficacy and tendency to facilitate weight loss. Weight-related quality of life (QoL) also improved in people using incretin therapies. The glycaemic improvements achieved with GLP-1 receptor agonists, coupled with the low incidence of hypoglycaemia and ability to cause weight loss, seemed to offset potential concern about injections. It is plausible that superior patient-reported benefits found in clinical trials may translate into improved, clinically meaningful, long-term outcomes through increased treatment acceptability. Long-term, prospective data are needed to ascertain whether this is the case in practice.

One year of sitagliptin treatment protects against islet amyloid-associated β-cell loss and does not induce pancreatitis or pancreatic neoplasia in mice

The dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin is an attractive therapy for diabetes, as it increases insulin release and may preserve β-cell mass. However, sitagliptin also increases β-cell release of human islet amyloid polypeptide (hIAPP), the peptide component of islet amyloid, which is cosecreted with insulin. Thus, sitagliptin treatment may promote islet amyloid formation and its associated β-cell toxicity. Conversely, metformin treatment decreases islet amyloid formation by decreasing β-cell secretory demand and could therefore offset sitagliptin's potential proamyloidogenic effects. Sitagliptin treatment has also been reported to be detrimental to the exocrine pancreas. We investigated whether long-term sitagliptin treatment, alone or with metformin, increased islet amyloid deposition and β-cell toxicity and induced pancreatic ductal proliferation, pancreatitis, and/or pancreatic metaplasia/neoplasia. hIAPP transgenic and nontransgenic littermates were followed for 1 yr on no treatment, sitagliptin, metformin, or the combination. Islet amyloid deposition, β-cell mass, insulin release, and measures of exocrine pancreas pathology were determined. Relative to untreated mice, sitagliptin treatment did not increase amyloid deposition, despite increasing hIAPP release, and prevented amyloid-induced β-cell loss. Metformin treatment alone or with sitagliptin decreased islet amyloid deposition to a similar extent vs untreated mice. Ductal proliferation was not altered among treatment groups, and no evidence of pancreatitis, ductal metaplasia, or neoplasia were observed. Therefore, long-term sitagliptin treatment stimulates β-cell secretion without increasing amyloid formation and protects against amyloid-induced β-cell loss. This suggests a novel effect of sitagliptin to protect the β-cell in type 2 diabetes that appears to occur without adverse effects on the exocrine pancreas.

Efeitos da Exenatida e da Sitagliptina durante a indução da periodontite em ratos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Exenatide and sitagliptin decrease interleukin 1β, matrix metalloproteinase 9, and nitric oxide synthase 2 gene expression but does not reduce alveolar bone loss in rats with periodontitis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fixed-dose combination therapy for type 2 diabetes:sitagliptin plus pioglitazone

Type 2 diabetes is typically associated with insulin resistance and dysfunction of insulin-secreting pancreatic beta-cells. Addressing these defects often requires therapy with a combination of differently acting antidiabetic agents. A potential novel combination in development brings together the dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin with the thiazolidinedione pioglitazone into a fixed-dose single-tablet combination. The former component acts mainly to increase prandial insulin secretion; the latter improves insulin sensitivity.

Alogliptin after acute coronary syndrome in patients with type 2 diabetes

Background - To assess potentially elevated cardiovascular risk related to new antihyperglycemic drugs in patients with type 2 diabetes, regulatory agencies require a comprehensive evaluation of the cardiovascular safety profile of new antidiabetic therapies. We assessed cardiovascular outcomes with alogliptin, a new inhibitor of dipeptidyl peptidase 4 (DPP-4), as compared with placebo in patients with type 2 diabetes who had had a recent acute coronary syndrome. Methods - We randomly assigned patients with type 2 diabetes and either an acute myocardial infarction or unstable angina requiring hospitalization within the previous 15 to 90 days to receive alogliptin or placebo in addition to existing antihyperglycemic and cardiovascular drug therapy. The study design was a double-blind, noninferiority trial with a prespecified noninferiority margin of 1.3 for the hazard ratio for the primary end point of a composite of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. Results - A total of 5380 patients underwent randomization and were followed for up to 40 months (median, 18 months). A primary end-point event occurred in 305 patients assigned to alogliptin (11.3%) and in 316 patients assigned to placebo (11.8%) (hazard ratio, 0.96; upper boundary of the one-sided repeated confidence interval, 1.16; P<0.001 for noninferiority). Glycated hemoglobin levels were significantly lower with alogliptin than with placebo (mean difference, -0.36 percentage points; P<0.001). Incidences of hypoglycemia, cancer, pancreatitis, and initiation of dialysis were similar with alogliptin and placebo. Conclusions - Among patients with type 2 diabetes who had had a recent acute coronary syndrome, the rates of major adverse cardiovascular events were not increased with the DPP-4 inhibitor alogliptin as compared with placebo. (Funded by Takeda Development Center Americas; EXAMINE ClinicalTrials.gov number, NCT00968708.)

Clinical pharmacology of dipeptidyl peptidase 4 inhibitors indicated for the treatment of type 2 diabetes mellitus

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a class of oral antidiabetic drugs that improve glycaemic control without causing weight gain or increasing hypoglycaemic risk in patients with type 2 diabetes mellitus (T2DM). The eight available DPP-4 inhibitors, including alogliptin, anagliptin, gemigliptin, linagliptin, saxagliptin, sitagliptin, teneligliptin, and vildagliptin, are small molecules used orally with identical mechanism of action and similar safety profiles in patients with T2DM. DPP-4 inhibitors may be used as monotherapy or in double or triple combination with other oral glucose-lowering agents such as metformin, thiazolidinediones, or sulfonylureas. Although DPP-4 inhibitors have the same mode of action, they differ by some important pharmacokinetic and pharmacodynamic properties that may be clinically relevant in some patients. The main differences between the eight gliptins include: potency, target selectivity, oral bioavailability, elimination half-life, binding to plasma proteins, metabolic pathways, formation of active metabolite(s), main excretion routes, dosage adjustment for renal and liver insufficiency, and potential drug-drug interactions. The off-target inhibition of selective DPP-4 inhibitors is responsible for multiorgan toxicities such as immune dysfunction, impaired healing, and skin reactions. As a drug class, the DPP-4 inhibitors have become accepted in clinical practice due to their excellent tolerability profile, with a low risk of hypoglycaemia, a neutral effect on body weight, and once-daily dosing. It is unknown if DPP-4 inhibitors can prevent disease progression. More clinical studies are needed to validate the optimal regimens of DPP-4 inhibitors for the management of T2DM when their potential toxicities are closely monitored.