Diabetes: Rationale for Dipeptidyl Peptidase 4 Inhibitors: A New Class of Oral Agents for the Treatment of Type 2 Diabetes Mellitus

Review of pharmaceutical and therapeutic approaches for type 2 diabetes and related disorders

One of the essential diseases that are increasing in the world is type 2 diabetes (T2D), which many people around the world live with this disease. Various studies have revealed that insulin resistance, lessened insulin production has been associated with T2D, and they also show that this disease can have a genetic origin and is associated with different genes such as KCNQ1, PPAR-γ, calpain-10, ADIPOR2, TCF7L2 that can be utilized as a therapeutic target. Different therapeutic approaches and strategies such as exercise and diet, pharmacological approaches, and utilization of nanoparticles in drug delivery and gene therapy can be effective in the treatment and control of T2D. Glucagon-like peptide 1 (GLP-1) and sodium glucose cotransporter-2 (SGLT2) have both been considered as drug classes in the treatment of T2D and T2D-related diseases such as cardiovascular disease and renal disease, and have considerable influences such as diminished cardiovascular mortality in individuals with T2D, ameliorate postprandial glycaemia, ameliorate fasting glycaemia, and diminish body weight on disease treatment and improvement process. In the present review article, we have made an attempt to explore the risk factors, Genes, and diseases associated with T2D, therapeutic approaches in T2D, the influences of drugs such as Dapagliflozin, Metformin, Acarbose, Januvia (Sitagliptin), and Ertugliflozin on T2D in clinical trials and animal model studies. Research in clinical trials has promising results that support the role of these drug approaches in T2D prophylaxis and ameliorate safety even though additional clinical research is still obligatory.

The Involvement of the Mammalian Target of Rapamycin, Protein Tyrosine Phosphatase 1b and Dipeptidase 4 Signaling Pathways in Cancer and Diabetes: A Narrative Review

BACKGROUND

The mammalian target of rapamycin (mTOR), protein tyrosine phosphatase 1b (PTP1B) and dipeptidase 4 (DPP4) signaling pathways regulate eukaryotic cell proliferation and metabolism. Previous researches described different transduction mechanisms in the progression of cancer and diabetes.

METHODOLOGY

We reviewed recent advances in the signal transduction pathways of mTOR, PTP1B and DPP4 regulation and determined the crosstalk and common pathway in diabetes and cancer.

RESULTS

We showed that according to numerous past studies, the proteins participate in the signaling networks for both diseases.

CONCLUSION

There are common pathways and specific proteins involved in diabetes and cancer. This article demonstrates and explains the potential mechanisms of association and future prospects for targeting these proteins in pharmacological studies.

Current situation analysis of diabetic home care patients

OBJECTIVE

Diabetes is one of the primary diagnoses for admission to home health care units. Although there are many studies about elderly diabetic patients, there are not many studies on home care patients with diabetes. The present study aims to analyze the current status of diabetic home care patients with their biochemical data and medications.

METHODS

This was a retrospective study, including 256 diabetic patients who were following up by the Home Health Unit of Istanbul Provincial Health Directorate Public Hospitals Services-2. In this study, we analyzed the current biochemical data of the patients with their medications.

RESULTS

In this study, 185 female (72.3%) and 71 male (27.7%) patients were recruited with the mean HbA1c of 8.25±1.77. Among these patients, 65% of them were using oral antidiabetic (OAD), and 58% were using insulin. There were 21 (8.2%) patients who were not receiving any treatment. While patients who were using only oral antidiabetic have better A1c levels (A1c: 7.73±1.45), patients who were insülin using had HbA1c levels as high as the patients who were not using any medication. This may be due to the progression of diabetes, fear of hypoglycemia or insufficient insülin use. While metformin was the most commonly used OAD, with a 38% usage rate. When compared to HbA1c levels, there was no difference between the types of insulin used (p=0.167).

CONCLUSION

As a result, it is important to plan regular visits and personalized treatment by keeping in mind the benefits to risk ratios in home-care diabetic patients.

Insights into replicative senescence of human testicular peritubular cells

There is evidence for an age-related decline in male reproductive functions, yet how the human testis may age is not understood. Human testicular peritubular cells (HTPCs) transport sperm, contribute to the spermatogonial stem cell (SSC) niche and immune surveillance, and can be isolated and studied in vitro. Consequences of replicative senescence of HTPCs were evaluated to gain partial insights into human testicular aging. To this end, early and advanced HTPC passages, in which replicative senescence was indicated by increased cell size, altered nuclear morphology, enhanced β-galactosidase activity, telomere attrition and reduced mitochondrial DNA (mtDNA), were compared. These alterations are typical for senescent cells, in general. To examine HTPC-specific changes, focused ion beam scanning electron microscopy (FIB/SEM) tomography was employed, which revealed a reduced mitochondrial network and an increased lysosome population. The results coincide with the data of a parallel proteomic analysis and indicate deranged proteostasis. The mRNA levels of typical contractility markers and growth factors, important for the SSC niche, were not significantly altered. A secretome analysis identified, however, elevated levels of macrophage migration inhibitory factor (MIF) and dipeptidyl peptidase 4 (DPP4), which may play a role in spermatogenesis. Testicular DPP4 may further represent a possible drug target.

Safety and Efficacy of DPP4 Inhibitor and Basal Insulin in Type 2 Diabetes: An Updated Review and Challenging Clinical Scenarios

The safety and efficacy of dipeptidyl peptidase-4 (DPP4) inhibitors as monotherapy or in combination with other oral antidiabetic agents or basal insulin are well established. DPP4 inhibitors stimulate glucose-dependent insulin secretion and inhibit glucagon production. As monotherapy, they reduce the hemoglobin A1c level by about 0.6-0.8%. The addition of a DPP4 inhibitor to basal insulin is an attractive option, because they lower both postprandial and fasting plasma glucose concentrations without increasing the risk of hypoglycemia or weight gain. The present review summarizes the extensive evidence on the combination therapy of DPP4 inhibitors and insulin-based regimens in patients with type 2 diabetes. We focus our discussion on challenging clinical scenarios including patients with chronic renal impairment, elderly persons and hospitalized patients. The evidence indicates that these drugs are highly effective and safe in the elderly and in the presence of mild, moderate and severe renal failure improving glycemic control with low risk of hypoglycemia. In addition, several randomized-controlled trials have shown that the use of DPP4 inhibitors in combination with basal insulin represents an alternative to the basal-bolus insulin regimen in hospitalized patients with type 2 diabetes.

Renoprotective Effects of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin: A Review in Type 2 Diabetes

Diabetic nephropathy (DN) is now the single commonest cause of end-stage renal disease (ESRD) worldwide and one of the main causes of death in diabetic patients. It is also acknowledged as an independent risk factor for cardiovascular disease (CVD). Since sitagliptin was approved, many studies have been carried out revealing its ability to not only improve metabolic control but also ameliorate dysfunction in various diabetes-targeted organs, especially the kidney, due to putative underlying cytoprotective properties, namely, its antiapoptotic, antioxidant, anti-inflammatory, and antifibrotic properties. Despite overall recommendations, many patients spend a long time well outside the recommended glycaemic range and, therefore, have an increased risk for developing micro- and macrovascular complications. Currently, it is becoming clearer that type 2 diabetes mellitus (T2DM) management must envision not only the improvement in glycaemic control but also, and particularly, the prevention of pancreatic deterioration and the evolution of complications, such as DN. This review aims to provide an overview of the current knowledge in the field of renoprotective actions of sitagliptin, namely, improvement in diabetic dysmetabolism, hemodynamic factors, renal function, diabetic kidney lesions, and cytoprotective properties.

The Effect of Sitagliptin on Lipid Metabolism of Fatty Liver Mice and Related Mechanisms

Background

In clinics, patients with type 2 diabetes complicated with non-alcoholic fatty liver disease (NAFLD) have been shown to receive significant improvements in blood glucose levels, lipid levels, and liver function after sitagliptin treatment, although the mechanism of drug action remains poorly understood. This study investigated the possible mechanism of sitagliptin on lipid metabolism of NAFLD mice.

Material/Methods

Male C57/BL6 mice were induced for NAFLD via 16 weeks of a high-fat diet, and were treated with 15 mg/kg/day sitagliptin for 16 consecutive weeks. Blood lipid levels were measured and samples were stained with hematoxylin and eosin (H&E) and oil red staining for liver pathology and lipid deposition. Serum levels of fibroblast growth factor (FGF)-9 and FGF-21 were quantified by enzyme-linked immunosorbent assay (ELISA). Peroxisome proliferator-activated receptor (PPAR)-α, and cAMP reactive element binding homolog (CREBH) were measured by Western blotting, while fatty acid synthase and carnitine palmitoyltransferase 1 (CPT1) mRNA levels were assayed by RT-PCR.

Results

Compared to the control group, the NAFLD model mice had liver fatty disease, lower serum FGF-21 and FGF-19 levels, elevated serum lipid levels, depressed PPAR-α, CREBH, and CPT1 expression, and enhanced FAS expression (p<0.05). Sitagliptin treatment depressed blood lipid levels, increased serum FGF-21 and FGF-19 levels, PPAR-α, CREBH, and CPT1 expression, and suppressed FAS expression (p<0.05).

Conclusions

Sitagliptin can protect liver tissue and modulate lipid metabolism in NAFLD mice via elevating FGF-21 and FGF-19, upregulating liver PPAR-α and CREBH levels, and mediating expression levels of key enzymes for lipid metabolism.

Differential HbA1c response in the placebo arm of DPP-4 inhibitor clinical trials conducted in China compared to other countries: a systematic review and meta-analysis

BACKGROUND

It has been observed that the efficacy of dipeptidyl peptidase-4 (DPP-4) inhibitors as compared to the placebo groups in some clinical trials conducted in China is weaker than that in trials conducted outside China, leading to the suspicion that this may be caused by differential Glycosylated Hemoglobin (HbA1c) response in the placebo arm of DPP-4 inhibitor clinical trials conducted in China compared to other countries.

METHODS

We searched published articles and other documents related to phase III placebo-control trials of DPP-4 inhibitors in Type 2 diabetes mellitus (T2DM). We included studies from different countries and compared those conducted in China to those conducted in other countries. Meta-regression analysis was used to analyze the HbA1c response in the placebo arms.

RESULTS

A total of 66 studies met the inclusion criteria and 10 were conducted within China. There were a total of 8303 participants (mean age 56, male 57 %) in placebo groups. The pooled change in HbA1c for the placebo groups of 10 trials conducted in patients with T2DM in China was 0.26 % (95 % CI [-0.36 %, -0.16 %], p-value < 0.001), compared to 0.015 % (95 % CI [-0.05 %, 0.08 %], p-value is 0.637) for 56 trials conducted outside of China. The difference of placebo effect between trials conducted in and outside China is -0.273 % (95 % CI [-0.42 %, -0.13 %], p-value is less than 0.001) while after excluding trials conducted in Japan, the difference is -0.203 % (95 % CI [-0.35 %, -0.06 %], p-value is 0.005). They are both statistically significant.

CONCLUSIONS

The meta-analysis in the article demonstrates that there is statistically significant difference in the HbA1c response in the placebo arm of DPP-4 inhibitor clinical trials conducted in China compared to other countries. This differential HbA1c response in the placebo arm should be taken into consideration by both experimenters and medical decision makers when future DPP-4 studies are conducted in China.

Population pharmacodynamic analysis of hemoglobin A1c-lowering effects by adding treatment of DPP-4 inhibitors (sitagliptin) in type 2 diabetes mellitus patients based on electronic medical records

AIM

To develop a population pharmacodynamic (PPD) model describing the time course for the hemoglobin A1c (HbA1c)-lowering effects of adding treatment of DPP-4 inhibitors and to assess the efficacy of combination therapy in type 2 diabetes mellitus patients based on electronic medical records.

METHODS

Information on patients was collected retrospectively from electronic medical records. Of the 4 DPP-4 inhibitors used, we focused on sitagliptin as it had the best time-response relationships. A physiological indirect response model was developed to describe changes in HbA1c levels.

RESULTS

An indirect response model, based on the 1300 HbA1c levels of 160 patients, described the time course for the HbA1c-lowering effects of adding sitagliptin. The combination with pioglitazone decreased the HbA1c synthesis rate by 7.74% relative to without pioglitazone. Bayesian forecasting based on the final PDD model using the first two HbA1c observations, before and within 30days after the addition of sitagliptin, gave a precise prediction of HbA1c-lowering effects individually.

CONCLUSIONS

Our PPD model quantitatively described the beneficial effects of combination therapy with pioglitazone and sitagliptin. The proposal methodology is also expected to be applicable to other medicines based on electronic medical records in clinical practice.

Sitagliptin: a review of its use in patients with type 2 diabetes mellitus

Sitagliptin (Januvia(®), Xelevia™, Glactiv(®), Tesavel(®)) is an orally administered, potent and highly selective inhibitor of dipeptidyl peptidase-4 (DPP-4) and was the first agent of its class to be approved for use in the management of adults with type 2 diabetes. Numerous randomized placebo- or active comparator-controlled trials have demonstrated the efficacy of sitagliptin in terms of improving glycaemic control in patients with type 2 diabetes, including its use as monotherapy, initial combination therapy (usually with fixed-dose combinations of sitagliptin/metformin), or add-on therapy to metformin or to other antihyperglycaemic drugs, with or without metformin. The primary endpoint of the clinical trials was the reduction from baseline in glycosylated haemoglobin (HbA1c), although sitagliptin also showed beneficial effects for other endpoints, such as the proportion of patients who achieved target HbA1c, and reductions from baseline in fasting plasma glucose (FPG) levels and 2-h postprandial glucose (PPG) levels. Sitagliptin was generally well tolerated in clinical trials, had a low risk of hypoglycaemia (although this depends on background therapy) and had a neutral effect on body weight. Despite concerns regarding a possible increased risk of rare pancreatic adverse events (e.g. pancreatitis) with glucagon-like peptide-1 (GLP-1)-based therapies, such as GLP-1 receptor agonists and DPP-4 inhibitors, no causal association has been found; regulators in Europe recently conducted a review of available data, concluding that there is little evidence that these drugs could cause pancreatic inflammation or pancreatic cancer. A similar review is planned in the USA and postmarketing surveillance will continue. Thus, oral sitagliptin is an effective and generally well tolerated treatment option for the management of patients with type 2 diabetes.

Treating the elderly diabetic patient: special considerations

The prevalence of diabetes is rising in the >65 year-old group. The challenge of defining the goals of therapy arises from the heterogeneity of the aging process and the sparse clinical data in this patient population. In light of these challenges, the clinician should be aware of the pitfalls of caring for the older diabetic patient and prioritize an individualized treatment plan to ensure an optimal glycemic control, without placing the patient at unnecessary risk. We present a review of the current guidelines and literature that deal specifically with the treatment of the older diabetic patient in order to establish the principles of treatment in this age group and help the clinician make decisions regarding the care of these patients.

Tolerability of dipeptidyl peptidase-4 inhibitors: a review

BACKGROUND

Oral glucose-lowering agents are used to treat patients with type 2 diabetes mellitus (T2DM). Most patients require multiple agents to maintain glycemic targets. Dipeptidyl peptidase-4 (DPP-4) inhibitors are administered as monotherapy and in combination therapy for the treatment of T2DM.

OBJECTIVE

The aim of this article was to provide a thorough review of published tolerability data on 5 DPP-4 inhibitors.

METHODS

PubMed and Web of Science were searched for English-language clinical trials published from January 2000 to June 2001, using the following key words: dipeptidyl peptidase-4 inhibitor, vildagliptin, alogliptin, sitagliptin, saxagliptin, linagliptin, safety, tolerability, efficacy, effect, AE, and adverse effect. Studies were considered for inclusion if they were randomized, double-blind trials performed in patients ≥18 years of age with T2DM and with a hemoglobin A(1c) of ≥6.5%; included ≥1 arm that received monotherapy with DPP-4; and reported adverse events (AEs). Studies in patients with a history of type 1 or secondary forms of diabetes, significant diabetic complications or cardiovascular disease within the 6 months before the start of the study, hepatic disease or abnormalities, and/or renal abnormalities were excluded.

RESULTS

A total of 45 clinical trials, 5 pharmacokinetic studies, and 28 meta-analyses or reviews were included. The duration of studies ranged from 7 days to 104 weeks. The most commonly reported AEs were nasopharyngitis, upper respiratory infections, all-cause infections, headache, gastrointestinal symptoms, and musculoskeletal pain. Based on the findings from the studies, the DPP-4 inhibitors had minimal impact on weight and were not associated with an increased risk for hypoglycemia relative to placebo. Rates of nasopharyngitis were higher with the DDP-4 inhibitors than with placebo. Pancreatitis was reported at lower rates with the DPP-4 inhibitors compared with other oral antihyperglycemic agents. Cardiovascular events were limited, and postmarketing studies are ongoing.

CONCLUSIONS

The tolerability of DPP-4 inhibitors is supported by published clinical trials. The rates of weight gain, gastrointestinal AEs, and hypoglycemia were minimal with the DPP-4 inhibitors studied.

The DPP-4 inhibitor linagliptin does not prolong the QT interval at therapeutic and supratherapeutic doses

AIM

To evaluate the potential effects of therapeutic and supratherapeutic doses of linagliptin (BI 1356) on the QT/QT(c) interval in healthy subjects.

METHODS

The study was a randomized, double-blind, placebo-controlled, four-period crossover study using single oral doses of linagliptin (5 mg and 100 mg), moxifloxacin (400 mg) and placebo. Electrocardiogram (ECG) profiles using triplicates of 12-lead 10-s ECGs were digitally recorded pre-dose and after drug administration. The mean change from baseline (MCfB) of the individually heart rate corrected QT interval (QT(c) I) between 1 and 4 h postdrug administration was the primary end point. Blood samples to measure plasma concentrations of linagliptin and its main metabolite were also obtained.

RESULTS

Forty-four Caucasian subjects (26 male) entered the study and 43 subjects completed the study as planned in the protocol. Linagliptin was not associated with an increase in the baseline-adjusted mean QT(c) I, at any time point. The placebo-corrected MCfB of QT(c) I was -1.1 (90% CI -2.7, 0.5) ms and -2.5 (-4.1, -0.9) ms for linagliptin 5 mg and 100 mg, respectively, thus within the non-inferiority margin of 10 ms according to ICH E14. Linagliptin was well tolerated; the assessment of ECGs and other safety parameters gave no clinically relevant findings at either dose tested. Maximum plasma concentrations after administration of 100-mg linagliptin were ∼24-fold higher than those observed previously for chronic treatment with the therapeutic 5-mg dose. Assay sensitivity was confirmed by a placebo-corrected MCfB of QT(c) I with moxifloxacin of 6.9 (90% CI 5.4, 8.5) ms.

CONCLUSIONS

Therapeutic and significantly supratherapeutic exposure to linagliptin is not associated with QT interval prolongation.

Medical information about diabetes--how to keep up to date

Diabet. Med. 27, 1335-1340 (2010) ABSTRACT: There is a vast amount of new medical information published on diabetes each year; the number of systematic reviews on diabetes is also increasing rapidly. It is therefore difficult for clinicians keep up to date with the new evidence. It is suggested that reading the full National Institute for Clinical Excellence (NICE) guidelines on diabetes will bring you up to date with information as at the date of the evidence cut-off, which is usually approximately 1 year before publication. Also regularly visiting 'NHS Evidence--diabetes', an online resource that offers a foraging service, surveying the literature and alerting clinicians to all the new important and useful information, enables the busy clinician to manage information overload and help keep up to date.

Linagliptin (BI 1356), a potent and selective DPP-4 inhibitor, is safe and efficacious in combination with metformin in patients with inadequately controlled Type 2 diabetes

AIMS

The efficacy and safety of the dipeptidyl peptidase-4 inhibitor, linagliptin, added to ongoing metformin therapy, were assessed in patients with Type 2 diabetes who had inadequate glycaemic control (HbA(1c) ≥ 7.5 to ≤ 10%; ≥ 58.5 to ≤ 85.8 mmol/mol) with metformin alone.

METHODS

Patients (n=333) were randomized to receive double-blind linagliptin (1, 5 or 10 mg once daily) or placebo or open-label glimepiride (1-3 mg once daily). The primary outcome measure was the change from baseline in HbA(1c) at week 12 in patients receiving combination therapy compared with metformin alone.

RESULTS

Twelve weeks of treatment resulted in a mean (sem) placebo-corrected lowering in HbA(1c) levels of 0.40% (± 0.14); 4.4 mmol/mol (± 1.5) for 1 mg linagliptin, 0.73% (± 0.14); 8.0 mmol/mol (± 1.5) for 5 mg, and 0.67% (± 0.14); 7.3 mmol/mol (± 1.5) for 10 mg. Differences between linagliptin and placebo were statistically significant for all doses (1 mg, P = 0.01; 5 mg and 10 mg, P < 0.0001). The change in mean (sem) placebo-corrected HbA(1c) from baseline was -0.90% (± 0.13); -9.8 mmol/mol (± 1.4) for glimepiride. Adjusted and placebo-corrected mean changes in fasting plasma glucose were -1.1 mmol/l for linagliptin 1 mg (P = 0.002), -1.9 mmol/l for 5 mg and -1.6 mmol/l for 10 mg (both P < 0.0001). One hundred and six (43.1%) patients reported adverse events; the incidence was similar across all five groups. There were no hypoglycaemic events for linagliptin or placebo, whereas three patients (5%) receiving glimepiride experienced hypoglycaemia.

CONCLUSIONS

The addition of linagliptin to ongoing metformin treatment in patients with Type 2 diabetes was well tolerated and resulted in significant and clinically relevant improvements in glycaemic control, with 5 mg linagliptin being the most effective dose.

Sitagliptin: a review of its use in the management of type 2 diabetes mellitus

Sitagliptin (Januvia, Glactiv(R), Tesavel(R)) is a dipeptidyl peptidase-4 inhibitor indicated for the treatment of type 2 diabetes mellitus. Oral sitagliptin as monotherapy or combination therapy was generally well tolerated and improved glycaemic control in well designed clinical trials in patients with type 2 diabetes. Glycosylated haemoglobin (HbA(1c)) levels were significantly reduced with sitagliptin monotherapy relative to voglibose monotherapy or placebo, and with sitagliptin as initial combination therapy with metformin or pioglitazone relative to monotherapy with these agents or placebo. Moreover, sitagliptin monotherapy was noninferior to metformin monotherapy in terms of the reduction in HbA(1c) levels. Significant reductions in HbA(1c) levels, relative to background therapy, were also observed with sitagliptin add-on therapy to ongoing treatment with thiazolidinediones, sulfonylureas or insulin with or without metformin, or metformin alone. In terms of the reduction in HbA(1c) levels as add-on treatment to metformin, sitagliptin was noninferior to glipizide and generally did not differ from rosiglitazone, and as add-on treatment to pioglitazone, it did not differ significantly from metformin. Sitagliptin had a low risk of hypoglycaemia (except when used in combination with agents that may be associated with hypoglycaemia, such as sulfonylureas or insulin) and was generally weight-neutral. Although additional comparative data and longer-term studies with glycaemic and clinical outcomes are required to definitively position sitagliptin relative to other antihyperglycaemic agents, current evidence suggests that it is a useful treatment option for patients with type 2 diabetes, with potential advantages including oral administration, a generally weight-neutral effect and a low risk of hypoglycaemia.

Xenin-25 potentiates glucose-dependent insulinotropic polypeptide action via a novel cholinergic relay mechanism

The intestinal peptides GLP-1 and GIP potentiate glucose-mediated insulin release. Agents that increase GLP-1 action are effective therapies in type 2 diabetes mellitus (T2DM). However, GIP action is blunted in T2DM, and GIP-based therapies have not been developed. Thus, it is important to increase our understanding of the mechanisms of GIP action. We developed mice lacking GIP-producing K cells. Like humans with T2DM, "GIP/DT" animals exhibited a normal insulin secretory response to exogenous GLP-1 but a blunted response to GIP. Pharmacologic doses of xenin-25, another peptide produced by K cells, restored the GIP-mediated insulin secretory response and reduced hyperglycemia in GIP/DT mice. Xenin-25 alone had no effect. Studies with islets, insulin-producing cell lines, and perfused pancreata indicated xenin-25 does not enhance GIP-mediated insulin release by acting directly on the beta-cell. The in vivo effects of xenin-25 to potentiate insulin release were inhibited by atropine sulfate and atropine methyl bromide but not by hexamethonium. Consistent with this, carbachol potentiated GIP-mediated insulin release from in situ perfused pancreata of GIP/DT mice. In vivo, xenin-25 did not activate c-fos expression in the hind brain or paraventricular nucleus of the hypothalamus indicating that central nervous system activation is not required. These data suggest that xenin-25 potentiates GIP-mediated insulin release by activating non-ganglionic cholinergic neurons that innervate the islets, presumably part of an enteric-neuronal-pancreatic pathway. Xenin-25, or molecules that increase acetylcholine receptor signaling in beta-cells, may represent a novel approach to overcome GIP resistance and therefore treat humans with T2DM.

Pharmacologic management of the older patient with type 2 diabetes mellitus

BACKGROUND

Pharmacologic options for the treatment of elderly patients with type 2 diabetes mellitus (T2DM) are the same as in younger adults; however, treatment considerations differ in the elderly due to changes in renal and hepatic function, life expectancy, and various other clinical and practical considerations.

OBJECTIVE

This article discusses geriatric considerations in the pharmacologic management of T2DM and reviews the potential clinical advantages and disadvantages of pharmacologic agents currently available for the treatment of T2DM, including oral and injectable medications.

METHODS

A search of MEDLINE was conducted for articles published in English between January 1966 and September 2009 using the terms type 2 diabetes mellitus, elderly, geriatric, treatment, insulin, metformin, sulfonylurea, thiazolidinedione, alpha-glucosidase inhibitor, meglitinide, DPP-4 inhibitor, colesevelam, exenatide, and pramlintide. Meta-analyses, randomized controlled trials of pharmacologic treatment, and evidence-based reviews and/or expert opinions regarding the treatment of T2DM in the elderly were selected for review.

RESULTS

In overweight patients, metformin has been associated with reductions in risk for all-cause mortality and stroke compared with insulin and sulfonylureas. Older patients who are frail, anorexic, or underweight and those with congestive heart failure (CHF), renal or hepatic insufficiency, or dehydration may not be appropriate candidates for metformin therapy. The substantial risk of hypoglycemia with insulin secretagogues is increased by 36% in the elderly compared with younger adults; however, this risk is counterbalanced by the extensive clinical experience with these agents in the geriatric population. Thiazolidinediones should generally be avoided in patients with CHF and are absolutely contraindicated in patients with class II-IV heart failure. They have been associated with peripheral edema, as well as with decreases in bone mineral density in women. There is limited information on the use of dipeptidyl peptidase-4 inhibitors in the elderly, although dose adjustment is required in patients with renal compromise. In practice, substantial gastrointestinal adverse effects limit the use of alpha-glucosidase inhibitors in older patients. Colesevelam is associated with numerous drug interactions and can cause new or worsening constipation. There are limited data on the use of exenatide in the elderly. It may be beneficial in older patients with limited mobility who could benefit from weight loss, whereas it may not be a good option for frail, underweight adults. Use of exenatide is not recommended in patients with a creatinine clearance <30 mL/min. Given the increased monitoring required to avoid hypoglycemic events with pramlintide, this agent should be used with caution in older adults, particularly the frail elderly. Most patients with T2DM eventually require insulin; however, due to the risk of hypoglycemia and related morbidity, careful use of insulin is warranted in the geriatric population.

CONCLUSIONS

Overall, there is a scarcity of data regarding the use of pharmacologic agents in older adults with T2DM, and clinical guidance is largely based on data obtained from younger populations. The selection of appropriate drug regimens for these patients remains challenging.

The incretin system and cardiometabolic disease

Rates of type 2 diabetes, obesity and their associated detrimental cardiovascular effects are rapidly increasing. Despite the availability of several treatment options for type 2 diabetes and the use of intensive regimens combining several antidiabetic drugs, less than one-half of all patients reach a target glycosylated hemoglobin level of less than 7%. Disease progression due to ongoing deterioration of pancreatic islet cell health and beta-cell function is likely responsible. Therefore, there is a need to identify new pharmacological compounds that may not only treat hyperglycemia, but may also correct impaired glucose homeostasis and preserve endogenous beta-cell function. Identification and characterization of the incretin system and its effect on glucose homeostasis have resulted in the development of new antidiabetic agents that target these concerns. The current review examines the incretin effect and the pharmacological agents that have been developed based on the understanding of this physiological system. The influence of incretins on the cardiovascular system beyond the proatherogenic effect of type 2 diabetes will also be discussed.

Saxagliptin

Saxagliptin and its active metabolite M2 are dipeptidyl peptidase-4 inhibitors that improve glycaemic control by preventing the inactivation of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide. This increases GLP-1 levels, stimulates insulin secretion and reduces postprandial glucagon and glucose levels. In well designed, 24-week trials in treatment-naive patients with type 2 diabetes mellitus, monotherapy with oral saxagliptin 2.5 or 5 mg once daily significantly improved glycaemic control, as measured by mean glycosylated haemoglobin (HbA(1c)) levels, relative to placebo. In large, well designed, 24-week trials, combination therapy with saxagliptin 5 mg once daily plus metformin significantly improved HbA(1c) levels relative to single-agent saxagliptin or metformin in treatment-naive patients; in treatment-experienced patients with inadequate glycaemic control, the addition of saxagliptin 2.5 or 5 mg once daily to metformin, glyburide or a thiazolidinedione, significantly improved HbA(1c) levels relative to continued use of existing monotherapy. Saxagliptin as monotherapy or in combination with other oral antihyperglycaemics was generally well tolerated, with most adverse events being of mild to moderate severity. In clinical trials, the incidence of hypoglycaemic events in patients receiving saxagliptin was generally similar to that in patients receiving placebo or other oral antihyperglycaemic agents. Saxagliptin therapy was not associated with an increased risk of cardiovascular events according to pooled data from eight clinical trials. Saxagliptin generally had a weight-neutral effect.

Prospective controlled study of effect of laparoscopic sleeve gastrectomy on small bowel transit time and gastric emptying half-time in morbidly obese patients with type 2 diabetes mellitus

BACKGROUND

Published data on sleeve gastrectomy (SG) have indicated better remission of type 2 diabetes mellitus (T2DM) and improvement in satiety compared with other restrictive procedures. Mechanisms in addition to rapid, extensive weight loss are responsible for the restoration of the euglycemic state. To prospectively evaluate the role of laparoscopic SG on gastric emptying half-time and small bowel transit time (SBTT) and effect of these on weight loss, satiety, and improvement in T2DM.

METHODS

A total of 67 subjects were studied. Of these 67 subjects, 24 were lean controls (body mass index 22.2 +/- 2.84 kg/m(2)), 20 were severely and morbidly obese patients with T2DM who had not undergone SG (body mass index 37.73 +/- 5.35 kg/m(2)), and 23 were severely and morbidly obese patients with T2DM after SG (body mass index 40.71 +/- 6.59 kg/m(2)). All 67 patients were evaluated for gastric emptying half-time and SBTT using scintigraphic imaging. Imaging was performed every 15 minutes up to the ileocecal region. The Three-Factor Eating Questionnaire was administered simultaneously. Fasting blood sugar, postprandial blood sugar, and glycated hemoglobin were assessed. Nonparametric analysis of variance and the Mann-Whitney U test were applied.

RESULTS

The mean SBTT was significantly lower (P <.05) in the post-SG group (199 +/- 65.7 minutes) than in the non-SG group (281.5 +/- 46.2 minutes) or control group (298.1 +/- 9.2 minutes). The gastric emptying half-time values were also significantly shorter (P <.05) in the post-SG (52.8 +/- 13.5 minutes) than in the non-SG (73.7 +/- 29.0 minutes) and control (72.8 +/- 29.6 minutes) groups. The glycated hemoglobin, fasting blood sugar, and postprandial sugar were all significantly lower after SG. The Three-Factor Eating Questionnaire findings revealed significantly earlier satiety (29.0 +/- 7.2) for the post-SG patients (P <.05) compared with the non-SG (45.8 +/- 9.0) and control (37.9 +/- 6.2) subjects.

CONCLUSION

A decreased gastric emptying half-time and SBTT after SG can possibly contribute to better glucose homeostasis in patients with T2DM.

Evaluation of the potential for steady-state pharmacokinetic and pharmacodynamic interactions between the DPP-4 inhibitor linagliptin and metformin in healthy subjects

OBJECTIVE

Linagliptin (BI 1356) is a novel, orally available inhibitor of dipeptidyl peptidase-4 (DPP-4). Linagliptin improves glycaemic control in type 2 diabetic patients by increasing the half-life of the incretin hormone glucagon-like peptide-1 (GLP-1). Linagliptin is expected to be used as monotherapy or in combination with other antihyperglycaemic agents. This study was conducted to investigate potential pharmacokinetic or pharmacodynamic interactions between linagliptin and metformin.

METHODS

This randomised, monocentric, open-label, two-way crossover design study was conducted in 16 healthy male subjects. Linagliptin (10 mg/day) and metformin (850 mg three times daily) were each administered alone and concomitantly. The steady-state pharmacokinetics of linagliptin and metformin and the inhibition of DPP-4 activity were determined at the end of each dosing period.

RESULTS

Co-administration of linagliptin had no apparent effect on metformin exposure (metformin AUC(tau,ss); geometric mean ratio [GMR] co-administration:individual administration was 1.01; 90% confidence interval [CI] was 0.89-1.14). Effects on maximum concentration (C(max,ss)) were small (GMR: 0.89; 90% CI: 0.78-1.00). Co-administration of metformin did not significantly affect C(max,ss) of linagliptin (GMR: 1.03; 90% CI: 0.86-1.24), but increased AUC(tau)(,ss) by 20% (GMR: 1.20; 90% CI: 1.07-1.34). Metformin alone had no effect on DPP-4 activity, and the inhibition of DPP-4 caused by linagliptin was not affected by concomitant administration of metformin. Tolerability was good whether linagliptin and metformin were administered alone or concomitantly. No serious adverse events occurred and the frequency of adverse events was low; 7 events in 6 subjects. The most frequent events were related to the gastrointestinal tract, as expected with metformin. Importantly, no subjects experienced signs or symptoms relating to episodes of hypoglycaemia.

CONCLUSION

In this small, multiple dose study carried out in healthy subjects, co-administration of linagliptin with metformin did not have a clinically relevant effect on the pharmacokinetics or pharmacodynamics of either agent. This study suggests linagliptin and metformin can safely be administered concomitantly in type 2 diabetes patients without dose adjustment; larger, longer-term clinical trials in diabetic patients are underway.

Use of serum c-peptide level to simplify diabetes treatment regimens in older adults

BACKGROUND

Diabetes management in older adults is challenging. Poor glycemic control and high risk of hypoglycemia are common in older patients on a complicated insulin regimen. Newer oral hypoglycemic agents have provided an opportunity to simplify regimens in patients with type-2 diabetes on insulin. Serum c-peptide is a test to assess endogenous production of insulin. We analyze the use of serum c-peptide level in simplifying diabetes regimen by decreasing or stopping insulin injection and adding oral hypoglycemic agents in older adults.

METHODS

One hundred patients aged over 65 years with either poor glycemic control or difficulty coping with insulin regimen seen at a geriatric diabetes clinic were analyzed for this study. The data on serum c-peptide levels and A1c, along with demographic information, were obtained from medical charts.

RESULTS

Sixty-five of 100 patients (aged 79+/-14 years, duration of diabetes 21+/-13 years) had detectable serum c-peptide levels. Forty-six of 65 patients were available for simplification of regimen. Eleven of 46 patients had other co-morbidities preventing use of oral hypoglycemic agents. In 35/65 patients, simplification was completed successfully. Nineteen of 35 patients were converted to all-oral regimens (off insulin), while 16/35 had simplification of regimen by addition of oral hypoglycemic agents and lowering the number of insulin injections from an average of 2.7 to 1.5 injections/day (P=.001). Glycemic control improved significantly in patients with a simplified regimen (8.0%+/-1.5% vs 7.4%+/-1.5%; P<.002), and patients reported fewer hypoglycemia episodes.

CONCLUSIONS

Serum c-peptide level can be used to simplify insulin regimen in older adults with diabetes.

Novel Approaches to the Treatment of Type 2 Diabetes

The emergence of the glucoregulatory hormone, glucagon-like peptide-1, has expanded our understanding of glucose homeostasis. The glucoregulatory actions of glucagon-like peptide-1 include enhancement of glucose-dependent insulin secretion, suppression of inappropriately elevated glucagon secretion, slowing of gastric emptying, and reduction of food intake. Two approaches have been developed to potentiate the effects of glucagon-like peptide-1 in those with type 2 diabetes. The glucagon-like peptide-1 analogs, such as exenatide, and dipeptidyl peptidase-IV inhibitors, such as sitagliptin, are currently available whereas others are in the final stages of development. These agents effectively reduce hemoglobin A1c while providing the other benefits associated with increased glucagon-like peptide-1. They also offer the potential to preserve the β-cell function. The effects on cardiovascular disease, if any, are unknown. Based on the current evidence, these agents represent viable second-and third-line options in the management of type 2 diabetes.

Third-line agent selection for patients with type 2 diabetes mellitus uncontrolled with sulfonylureas and metformin

Patients with type 2 diabetes mellitus often begin treatment by taking oral agents, usually metformin or a sulfonylurea, and then progress to the combination of these two agents. Most patients often require three or more agents or a change to an insulin regimen. However, no guidelines are available to aid the clinician in the decision-making process for selecting the third agent. Many options are available for additional therapy, including thiazolidinediones, intermediate- and long-acting insulins, exenatide, and dipeptidyl peptidase-4 inhibitors. Although the American Diabetes Association recommends metformin as first-line therapy, it does not give exact specifications for second- and third-line agents but only summarizes clinical data and options about each therapeutic drug class. Guidelines from the American College of Endocrinology and American Association of Clinical Endocrinologists recommend several options depending on the patient's hemoglobin A(1c) level. Therefore, a standard of care cannot be provided; rather, clinicians must evaluate each patient to ascertain that patient's optimum therapy. In doing so, clinicians need to be familiar with the efficacy, safety, and cost of each agent.

Dipeptidyl peptidase-4 (DPP-4) inhibitors for type 2 diabetes mellitus

BACKGROUND

In type 2 diabetes mellitus there is a progressive loss of beta-cell function. One new approach yielding promising results is the use of the orally active dipeptidyl peptidase-4 (DPP-4) inhibitors like sitagliptin and vildagliptin.

OBJECTIVES

To assess the effects of dipeptidyl peptidase-4 (DPP-4) inhibitors for type 2 diabetes mellitus.

SEARCH STRATEGY

Studies were obtained from computerised searches of MEDLINE, EMBASE and The Cochrane Library.

SELECTION CRITERIA

Studies were included if they were randomised controlled trials in adult people with type 2 diabetes mellitus and had a trial duration of at least 12 weeks.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed risk of bias and extracted data. Pooling of studies was performed by means of fixed-effect meta-analysis.

MAIN RESULTS

Twenty-five studies of good quality were identified, 11 trials evaluated sitagliptin and 14 trials vildagliptin treatment. Altogether, 6743 patients were randomised in sitagliptin and 6121 patients in vildagliptin studies, respectively. Sitagliptin and vildagliptin studies ranged from 12 to 52 weeks duration. No data were published on mortality, diabetic complications, costs of treatment and health-related quality of life. Sitagliptin and vildagliptin therapy in comparison with placebo resulted in an HbA1c reduction of approximately 0.7% and 0.6%, respectively. Data on comparisons with active comparators were limited but indicated no improved metabolic control following DPP-4 intervention in contrast to other hypoglycaemic agents. Sitagliptin and vildagliptin therapy did not result in weight gain but weight loss was more pronounced following placebo interventions. No definite conclusions could be drawn from published data on sitagliptin and vildagliptin effects on measurements of beta-cell function. Overall, sitagliptin and vildagliptin were well tolerated, no severe hypoglycaemia was reported in patients taking sitagliptin or vildagliptin. All-cause infections increased significantly after sitagliptin treatment but did not reach statistical significance following vildagliptin therapy. All published randomised controlled trials of at least 12 weeks treatment with sitagliptin and vildagliptin only reported routine laboratory safety measurements

AUTHORS' CONCLUSIONS

DPP-4 inhibitors have some theoretical advantages over existing therapies with oral antidiabetic compounds but should currently be restricted to individual patients. Long-term data especially on cardiovascular outcomes and safety are urgently needed before widespread use of these new agents. More information on the benefit-risk ratio of DPP-4 inhibitor treatment is necessary especially analysing adverse effects on parameters of immune function. Also, long-term data are needed investigating patient-oriented parameters like health-related quality of life, diabetic complications and all-cause mortality.