The role of incretin-based therapies in prediabetes: a review

A bibliometric analysis of the 100 most-influential papers in the field of anti-diabetic drugs

Aim: We analyzed the 100 most-cited articles on all anti-diabetic drugs. A comprehensive literature review found no bibliometrics on this. Methods: Two researchers independently extracted articles from Scopus and ranked them by citation count as the 'top 100 most-cited'. Results: The median number of citations is 1385.5. Most articles are from the USA (n = 59). Insulin has the most papers (n = 24). Majority (n = 76) were privately funded and contained at least one conflict of interest (n = 66). The New England Journal of Medicine has the most publications (n = 44). Male authors made majority of both first and last authorship positions. Conclusion: This study aims to aid in directing future research and in reducing biases.

Postprandial Reactive Hypoglycemia

Reactive hypoglycemia (RH) is the condition of postprandially hypoglycemia occurring 2-5 hours after food intake. RH is clinically seen in three different forms as follows: idiopathic RH (at 180 min), alimentary (within 120 min), and late RH (at 240–300 min). When the first-phase insulin response decreases, firstly, blood glucose starts to rise after the meal. This leads to late but excessive secretion of the second-phase insulin secretion. Thus, late reactive hypoglycemia occurs. Elevated insulin levels also cause down-regulation of the insulin post-receptor on the muscle and fat cells, thus decreasing insulin sensitivity. The cause of the increase in insulin sensitivity in IRH at 3 h is not completely clear. However, there is a decrease in insulin sensitivity in late reactive hypoglycaemia at 4 or 5 hours. Thus, patients with hypoglycemia at 4 or 5 h who have a family history of diabetes and obesity may be more susceptible to diabetes than patients with hypoglycemia at 3 h. We believe that some cases with normal glucose tolerance in OGTT should be considered as prediabetes at <55 or 60 mg/dl after 4-5 hours after OGTT. Metformin and AGI therapy may be recommended if there is late RH with IFG. Also Metformin, AGİ, TZD, DPP-IVInhibitors, GLP1RA therapy may be recommended if there is late RH with IGT. As a result, postprandial RH (<55 or 60 mg/dl), especially after 4 hours may predict diabetes. Therefore, people with RH along with weight gain and with diabetes history in the family will benefit from a lifestyle modification as well as the appropriate antidiabetic approach in the prevention of diabetes.

Modulatory effect of empagliflozin on cellular parameters of endocrine pancreas in experimental pre-diabetes

The effect of empagliflozin (EMPA), a sodium-glucose cotransporter 2 inhibitor (SGLT2i), on the structure of endocrine pancreas in pre-diabetes (Pre-DM) is not yet elucidated. In the current study the relatively enlarged islets of Langerhans seen in the Pre-DM group was restored to control size by administration of EMPA. In addition the disbalance in the percentage of β-cells and α-cells in islets of the Pre-DM was corrected in the Pre-DM + EMPA group with reversal of the significantly increased islet mass, β-cell mass and neogenesis. Administrating EMPA in Pre-DM decreased level of caspase-3, increased that of Bcl-2 to control level and reduced the significantly increased inflammatory cytokines to levels approximated to those of the control group. In Pre-DM + EMPA group, EMPA had efficiently restored the significantly impaired glucose hemostasis to levels nearly similar to those of the control animals. This may indicate that the modulatory effect of EMPA on cells of the islets in Pre-DM is associated with a local pleotropic effect on inflammatory cytokines.

Incretin - based therapy in diabetes mellitus: present scenario and expanding horizons

Let us hope that best is yet to come which is likely to bring us nearer to achieving our cherished goal of finding a cure of diabetes. I would like to sum up with an optimistic note by quoting Cristopher Reeve “So many of our dreams at first seem impossible, then they seem improbable, and then when we summon the will, they soon become inevitable ‘’.

Mechanisms for the cardiovascular effects of glucagon-like peptide-1

Over the past three decades, at least 10 hormones secreted by the enteroendocrine cells have been discovered, which directly affect the cardiovascular system through their innate receptors expressed in the heart and blood vessels or through a neural mechanism. Glucagon-like peptide-1 (GLP-1), an important incretin, is perhaps best studied of these gut-derived hormones with important cardiovascular effects. In this review, I have discussed the mechanism of GLP-1 release from the enteroendocrine L-cells and its physiological effects on the cardiovascular system. Current evidence suggests that GLP-1 has positive inotropic and chronotropic effects on the heart and may be important in preserving left ventricular structure and function by direct and indirect mechanisms. The direct effects of GLP-1 in the heart may be mediated through GLP-1R expressed in atria as well as arteries and arterioles in the left ventricle and mainly involve in the activation of multiple pro-survival kinases and enhanced energy utilization. There is also good evidence to support the involvement of a second, yet to be identified, GLP-1 receptor. Further, GLP-1(9-36)amide, which was previously thought to be the inactive metabolite of the active GLP-1(7-36)amide, may also have direct cardioprotective effects. GLP-1's action on GLP-1R expressed in the central nervous system, kidney, vasculature and the pancreas may indirectly contribute to its cardioprotective effects.

New perspectives on exploitation of incretin peptides for the treatment of diabetes and related disorders

The applicability of stable gut hormones for the treatment of obesity-related diabetes is now undisputable. This is based predominantly on prominent and sustained glucose-lowering actions, plus evidence that these peptides can augment insulin secretion and pancreatic islet function over time. This review highlights the therapeutic potential of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), oxyntomodulin (OXM) and cholecystokinin (CCK) for obesity-related diabetes. Stable GLP-1 mimetics have already been successfully adopted into the diabetic clinic, whereas GIP, CCK and OXM molecules offer promise as potential new classes of antidiabetic drugs. Moreover, recent studies have shown improved therapeutic effects following simultaneous modulation of multiple receptor signalling pathways by combination therapy or use of dual/triple agonist peptides. However, timing and composition of injections may be important to permit interludes of beta-cell rest. The review also addresses the possible perils of incretin based drugs for treatment of prediabetes. Finally, the unanticipated utility of stable gut peptides as effective treatments for complications of diabetes, bone disorders, cognitive impairment and cardiovascular dysfunction is considered.

Glucose-dependent insulinotropic polypeptide directly induces glucose transport in rat skeletal muscle

Several gastrointestinal proteins have been identified to have insulinotropic effects, including glucose-dependent insulinotropic polypeptide (GIP); however, the direct effects of incretins on skeletal muscle glucose transport remain largely unknown. Therefore, the purpose of the current study was to examine the role of GIP on skeletal muscle glucose transport and insulin signaling in rats. Relative to a glucose challenge, a mixed glucose+lipid oral challenge increased circulating GIP concentrations, skeletal muscle Akt phosphorylation, and improved glucose clearance by ∼35% (P < 0.05). These responses occurred without alterations in serum insulin concentrations. In an incubated soleus muscle preparation, GIP directly stimulated glucose transport and increased GLUT4 accumulation on the plasma membrane in the absence of insulin. Moreover, the ability of GIP to stimulate glucose transport was mitigated by the addition of the PI 3-kinase (PI3K) inhibitor wortmannin, suggesting that signaling through PI3K is required for these responses. We also provide evidence that the combined stimulatory effects of GIP and insulin on soleus muscle glucose transport are additive. However, the specific GIP receptor antagonist (Pro(3))GIP did not attenuate GIP-stimulated glucose transport, suggesting that GIP is not signaling through its classical receptor. Together, the current data provide evidence that GIP regulates skeletal muscle glucose transport; however, the exact signaling mechanism(s) remain unknown.

The Place of Dipeptidyl Peptidase-4 Inhibitors in Type 2 Diabetes Therapeutics: A "Me Too" or "the Special One" Antidiabetic Class?

Incretin-based therapies, the most recent therapeutic options for type 2 diabetes mellitus (T2DM) management, can modify various elements of the disease, including hypersecretion of glucagon, abnormal gastric emptying, postprandial hyperglycaemia, and, possibly, pancreatic β cell dysfunction. Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) increase glucagon-like peptide-1 (GLP-1) availability and correct the "incretin defect" seen in T2DM patients. Clinical studies have shown good glycaemic control with minimal risk of hypoglycaemia or any other adverse effects, despite the reports of pancreatitis, whose association remains to be proved. Recent studies have been focusing on the putative ability of DPP-4 inhibitors to preserve pancreas function, in particular due to the inhibition of apoptotic pathways and stimulation of β cell proliferation. In addition, other cytoprotective effects on other organs/tissues that are involved in serious T2DM complications, including the heart, kidney, and retina, have been increasingly reported. This review outlines the therapeutic potential of DPP-4 inhibitors for the treatment of T2DM, focusing on their main features, clinical applications, and risks, and discusses the major challenges for the future, in particular the possibility of becoming the preferred therapy for T2DM due to their ability to modify the natural history of the disease and ameliorate nephropathy, retinopathy, and cardiovascular complications.

Real-life safety and efficacy of vildagliptin as add-on to metformin in patients with type 2 diabetes in Turkey--GALATA study

OBJECTIVE

To evaluate tolerability/safety and the efficacy of the combination of vildagliptin plus metformin in a real-life population of patients with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

This multicenter, single-arm, 6 month, observational, prospective cohort study was conducted at 39 centers across Turkey. T2DM patients on vildagliptin and metformin for ≤4 weeks were enrolled regardless of their previous antidiabetic therapy.

MAIN OUTCOME MEASURES

Efficacy was evaluated by measuring hemoglobin A1c (HbA1c) levels. Tolerability/safety parameters evaluated included hypoglycemic events, gastrointestinal events, peripheral edema and weight gain.

RESULTS

This study enrolled 665 patients with a mean ± standard deviation (SD) age of 55.1 ± 10.2 years and female predominance (n = 394, 59.2%). Safety was assessed in all enrolled patients. Hypoglycemia was reported in 10 (1.5%) patients (95% confidence interval = 0.8-2.7%). Efficacy was assessed in 289 (43.5%) patients treated for 6 ± 1 months; these patients showed a mean decrease in HbA1c of 0.8% from baseline value of 7.8% (p < 0.001). The percentages of patients who achieved HbA1c targets of ≤6.5% and ≤7.0% were significantly increased, from 10.7% to 33.6% and from 22.1% to 52.6%, respectively (p < 0.001 each). The decrease in HbA1c was independent of baseline HbA1c (≤8% vs. 8-10% vs. ≥10%), age (≤65 vs. >65 years) and body mass index (<30 vs. ≥30 kg/m(2)) (p < 0.001 each). In total, 136 adverse events (AEs) were observed in 71 (10.7%) patients; 10 (1.5%) patients experienced hypoglycemia and gastrointestinal AEs were most commonly reported (n = 29, 4.4%).

CONCLUSIONS

In a 'real-life' setting, the vildagliptin and metformin combination was associated with significant improvements in reaching target HbA1c levels, even in elderly and obese patients with T2DM. Moreover, vildagliptin and metformin demonstrated a good overall tolerability/safety profile.