Biological actions of the incretins GIP and GLP-1 and therapeutic perspectives in patients with type 2 diabetes

Effects of dipeptidyl peptidase-4 inhibition in an animal model of experimental asthma: a matter of dose, route, and time

The CD26-associated enzymatic activity of dipeptidyl peptidase-4 (DPP4) as well as the recruitment of CD26(+) T cells increase under allergic airway inflammation. Furthermore, genetic deficiency of CD26/DPP4 exerts protective effects in experimental asthma. Therefore, CD26/DPP4 might represent a novel therapeutic target in asthma. To study the effects of pharmacological inhibition of DPP4 on allergic airway inflammation the DPP4-inhibitor isoleucine thiazolidide was tested using different doses at different time points (at sensitization, immediately before and simultaneously with the allergen challenge, as well as continuously via drinking water), and different routes (intraperitoneal, oral, and by inhalation). Allergic-like airway inflammation was induced in Fischer 344 rats (Charles River) sensitized against ovalbumin (OVA) using OVA aerosols. Intraperitoneal application of the DPP4 inhibitor showed effects neither at sensitization nor at challenge, whereas a continuous application via drinking water using high doses of the inhibitor led to an aggravation of the histomorphological signs of airway inflammation. In contrast, aerosolization of the DPP4 inhibitor simultaneously with the allergen significantly reduced airway hyperresponsiveness and ameliorated histopathological signs compared to controls. In addition, this treatment resulted in increased mRNA levels of surfactant proteins, suggesting an involvement of DPP4 inhibitors in surfactant metabolism in OVA-challenged rats. Continuous systemic inhibition of DPP4 via the oral route aggravates allergic airway inflammation. In contrast, topical inhibition of DPP4 exerts potential protective effects, and further research in humans is needed.

Review article: the role of gastrointestinal hormones in the treatment of delayed gastric emptying in critically ill patients

BACKGROUND

Delayed gastric emptying limits the administration of enteral nutrition, leading to malnutrition, which is associated with higher mortality and morbidity. Currently available prokinetics have limitations in terms of sustained efficacy and side effects.

AIM

To summarise the mechanisms of action and to discuss the possible utility of gastrointestinal hormones to prevent or treat delayed gastric emptying in critically ill patients.

METHODS

We searched PubMed for articles discussing 'delayed gastric emptying', 'enteral nutrition', 'treatment', 'gastrointestinal hormones', 'prokinetic', 'agonist', 'antagonist' and 'critically ill patients'.

RESULTS

Motilin and ghrelin receptor agonists initiate the migrating motor complex in the stomach, which accelerates gastric emptying. Cholecystokinin, glucagon-like peptide-1 and peptide YY have an inhibiting effect on gastric emptying; therefore, antagonising these gastrointestinal hormones may have therapeutic potential. Other gastrointestinal hormones appear less promising.

CONCLUSIONS

Manipulation of endogenous secretion, physiological replacement and administration of gastrointestinal hormones in pharmacological doses is likely to have therapeutic potential in the treatment of delayed gastric emptying. Future challenges in this field will include the search for candidates with improved selectivity and favourable kinetic properties.

Berry and Citrus Phenolic Compounds Inhibit Dipeptidyl Peptidase IV: Implications in Diabetes Management

Beneficial health effects of fruits and vegetables in the diet have been attributed to their high flavonoid content. Dipeptidyl peptidase IV (DPP-IV) is a serine aminopeptidase that is a novel target for type 2 diabetes therapy due to its incretin hormone regulatory effects. In this study, well-characterized anthocyanins (ANC) isolated from berry wine blends and twenty-seven other phenolic compounds commonly present in citrus, berry, grape, and soybean, were individually investigated for their inhibitory effects on DPP-IV by using a luminescence assay and computational modeling. ANC from blueberry-blackberry wine blends strongly inhibited DPP-IV activity (IC₅₀, 0.07 ± 0.02 to >300 μM). Of the twenty-seven phenolics tested, the most potent DPP-IV inhibitors were resveratrol (IC₅₀, 0.6 ± 0.4 nM), luteolin (0.12 ± 0.01 μM), apigenin (0.14 ± 0.02 μM), and flavone (0.17 ± 0.01 μM), with IC₅₀ values lower than diprotin A (4.21 ± 2.01 μM), a reference standard inhibitory compound. Analyses of computational modeling showed that resveratrol and flavone were competitive inhibitors which could dock directly into all three active sites of DPP-IV, while luteolin and apigenin docked in a noncompetitive manner. Hydrogen bonding was the main binding mode of all tested phenolic compounds with DPP-IV. These results indicate that flavonoids, particularly luteolin, apigenin, and flavone, and the stilbenoid resveratrol can act as naturally occurring DPP-IV inhibitors.

The effect of duodenojejunal bypass for type 2 diabetes mellitus patients below body mass index 25 kg/m(2): one year follow-up

Purpose

The goals of this study are to evaluate the effect of duodenojejunal bypass (DJB) for type 2 diabetes mellitus (T2DM) patients below body mass index (BMI) 25 kg/m² in one year follow-up, and to compare the results of 1 week which we have reported in 2011.

Methods

In this prospective observational study, there were 31 type 2 diabetic patients who underwent DJB at Inha University Hospital from July 2009 to January 2011. We did laboratories such as 75-g oral glucose tolerance test (OGTT), insulin level and hemoglobin A1c (HbA1c), etc. and compared their changes of preoperative, a week, 3 months, and 12 months.

Results

Mean BMI was 23.1 ± 1.3 kg/m², mean duration of T2DM was 8.3 ± 4.7 and mean age was 46.6 ± 7.7 years. There were a significant decrease of 75-g OGTT levels and increase of insulin secretion after 3 months. 13.3% showed diabetic remission (HbA1c < 6.0, medication cessation) and 26.7% showed diabetic improvement. The rates of remission and improvement much declined comparing with that of postoperative 1 week although those were determined by fasting and postprandial 2 hour level of glucose.

Conclusion

This is the first study of metabolic surgery in Korean diabetes patients in the healthy weight range. DJB exerted positive influences on insulin resistance as well as beta cell function. Early effects on T2DM after DJB could be estimated as one of good modalities, although the effectiveness seems to be unacceptable. Further studies are mandatory for evaluation of the effectiveness of metabolic surgery and finding prognostic factors.

Latent autoimmune diabetes in the adults (LADA) in Asia: from pathogenesis and epidemiology to therapy

Diabetes mellitus is a metabolic disorder resulting from a defect in insulin secretion, insulin action or both. An effect of this process is chronic hyperglycaemia with disorder of carbohydrate, fat and protein metabolism and with long-term complications of diabetes including retinopathy, nephropathy and neuropathy. Latent autoimmune diabetes in adults (LADA) is a type of autoimmune diabetes that resembles Type 1 diabetes (T1D), however, it shows a later onset and slower progression towards insulin necessity. Epidemiological studies suggest that LADA may account for 2-12% of all cases of diabetes in adult population. The epidemiology and phenotypic characteristics of LADA may vary between Caucasian and Asian diabetic patients as lifestyle, food habits and body mass index differ between these two populations. Data on LADA from population-based studies in Asia are sparse and only few studies have looked at it. A number of attractive therapeutic interventions may be envisaged for prevention of beta-cell loss in LADA, including hypoglycaemic and immunomodulatory agents. Because the autoimmune process in LADA seems to be slower than in childhood T1D, there is a wider window of opportunities for intervention. In deciding the best therapeutic approach, features of LADA should guide therapy including presence of other comorbidities that may influence the therapeutic choice.

New strategy for the treatment of type 2 diabetes mellitus with incretin-based therapy

Incretin-based therapy was first made available for the treatment of type 2 diabetes mellitus (T2DM) in the US in 2006 and in Japan in 2009. Four DPP-4 inhibitors and two GLP-1 analog/receptor agonists are currently available. The effects of incretin-based therapy are assumed to be exerted mainly through the hormonal and neuronal actions of one of the incretins, GLP-1, which is secreted from L cells localized in the small intestine. The benefits of this therapy over conventional sulfonylureas or insulin injections, such as fewer hypoglycemic events and reduced body weight gain, derive from the glucose-dependent insulinotropic effect. The protective effects of this therapy on vulnerable pancreatic β-cells and against micro/macroangiopathy in T2DM are also most welcome. Indications and/or contraindications for incretin-based therapy should be clarified by prospectively studying the experiences of Japanese T2DM patients undergoing this therapy in the clinical setting.

Evaluation of insulin expression and secretion in genetically engineered gut K and L-cells

Background

Gene therapy could provide an effective treatment of diabetes. Previous studies have investigated the potential for several cell and tissue types to produce mature and active insulin. Gut K and L-cells could be potential candidate hosts for gene therapy because of their special features.

Results

In this study, we isolated gut K and L-cells to compare the potential of both cell types to produce insulin when exposed to similar conditions. The isolated pure K and L-cells were transfected with recombinant plasmids encoding insulin and with specific promoters for K or L-cells. Insulin expression was studied in response to glucose or meat hydrolysate. We found that glucose and meat hydrolysate efficiently induced insulin secretion from K and L-cells. However, the effects of meat hydrolysate on insulin secretion were more potent in both cells compared with glucose. Results of enzyme-linked immunosorbent assays showed that L-cells secreted more insulin compared with K-cells regardless of the stimulator, although this difference was not statistically significant.

Conclusion

The responses of K and L-cells to stimulation with glucose or meat hydrolysate were generally comparable. Therefore, both K and L-cells show similar potential to be used as surrogate cells for insulin gene expression in vitro. The potential use of these cells for diabetic gene therapy warrants further investigation.

Early results of Roux-en-Y gastric by-pass on regulation of diabetes type 2 in patients with BMI above and below 35 kg/m2

The idea of surgical treatment of type 2 diabetes was established in the U.S. and was based on observation of patients after bariatric operations. Performed in cases of morbid obesity exclusion of the duodenum and anastomose the stomach with the central part of the intestines cause shortened absorbtion of nutrients, what showed a beneficial effect on weight loss, resolution of comorbidities and reduce the risk of developing cardiovascular diseases and cancer. Analysis of the results of surgical treatment of obese patients with type 2 diabetes confirmed the usefulness of surgical methods.The aim of the study was to evaluate the impact of Roux-en-Y gastric by-pass (RYGB) on diabetes in patients with BMI below and above 35 kg/m2.

MATERIAL AND METHODS

The study comprised 66 patients with DM2, who underwent Roux-en-Y gastric bypass due to morbid obesity (BMI above 35 kg/m2) and three patients with DM2 and BMI below 35 kg/m2. In patients with DM2 and BMI < 35 kg/m2 criteria for inclusion in the operational treatment were: DM2 difficult to be regulated pharmacologically lasting less than 10 years and BMI at the qualification about 35 kg/m2. Indications have been determined on the basis of three consecutive measurements of HbA1c values above 7%, and measurements of blood glucose (frequent fluctuations in blood glucose levels on the value of hypoglycemia to hyperglycemia).

RESULTS

The criteria for diagnosing resolution of DM2 included the level of HbA1c < 6% and glucose fasting level below 100 mg/ dl. In a group of 66 patients with DM2 and obesity, regression of DM2 was observed in 48 patients (73%) as early as during the hospitalization. In 11 patients (16.7%) glycaemia and HBA1c were stabilized within 8 weeks after surgery. In 7 (10.6%) cases of patients with difficult to control DM2, there was still need for antidiabetic medication, but glycemic control was much more effective. After one year remission was observed in 89% of patients. In all three patients with DM2 and BMI < 35 kg/m2 total glycemic resolution of DM2 was observed during hospitalization. In this group there has been no postoperative complications. In the group of 66 obese patients with DM2 postoperative complications were found in 7 cases, they were related to infection and prolonged healing of surgical wound. One patient had an intraabdominal abscess located in the left subphrenic region, it was punctured under ultrasound guidance.

CONCLUSIONS

The ultimate evaluation of this method demands several years of meticulous clinical studies. Despite of that, considering high cost of life-long conservative therapy of DM2 and its complications, severe impact on quality of life and serious consequences of the disease, the surgical metabolic intervention may become the most resonable solution in many cases.

Different incretin responses after pancreatoduodenectomy and distal pancreatectomy

OBJECTIVES

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are known as incretins to stimulate insulin secretion. The aims of this study were to investigate the postoperative β-cell function and hormonal responses of GLP-1 and GIP after pancreatoduodenectomy (PD) and distal pancreatectomy (DP).

METHODS

Oral glucose tolerance tests were performed in 34 patients (20 PD and 14 DP) before and 1 month after operation. The changes in the serum glucose and insulin concentrations, homeostasis model assessment of insulin resistance, and pancreatic β-cell function (BCF) were analyzed. GLP-1 and GIP were also measured.

RESULTS

There was no patient with postoperative deterioration of glucose tolerance after PD, whereas impairment of glucose metabolism was observed after DP. Homeostasis model assessment of insulin resistance decreased after PD, whereas those after DP showed no change. The postoperative BCF were lower than preoperative values in both groups. GLP-1 increased after DP but not after PD, whereas GIP decreased after PD but not after DP.

CONCLUSIONS

The changes in glucose metabolism and incretin responses were different between PD and DP. The increased level of GLP-1 after DP might reflect the relatively insufficient BCF; and thus, perioperative administration of GLP-1 might improve the diabetic condition after DP.

Pharmacokinetics of recombinant bifunctional fusion proteins

INTRODUCTION

The development of biotechnology has enabled the creation of various recombinant fusion proteins as a new class of biotherapeutics. The uniqueness of fusion proteins lies in their ability to fuse two or more protein domains, providing vast opportunities to generate novel combinations of functions. Pharmacokinetic (PK) studies, which are critical components in preclinical and clinical drug development, have not been fully explored for fusion proteins. The lack of general PK models and study guidelines has become a bottleneck for translation of fusion proteins from basic research to the clinic.

AREAS COVERED

This article reviews the current status of PK studies for fusion proteins, covering the processes that affect PK. According to their PK properties, a classification of fusion proteins is suggested along with examples from the clinic or under development. Current limitations and future perspectives for PK of fusion proteins are also discussed.

EXPERT OPINION

A PK model for bifunctional fusion proteins is presented to highlight the importance of mechanistic studies for a thorough understanding of the PK properties of fusion proteins. The model suggests investigating the receptor binding and subsequent intracellular disposition of individual domains, which can have dramatic impact on the PK of fusion proteins.

The acute impact of ingestion of sourdough and whole-grain breads on blood glucose, insulin, and incretins in overweight and obese men

Consumption of whole-grain and sourdough breads is associated with improved glucose homeostasis. We examined the impact of commercial breads on biomarkers of glucose homeostasis in subjects at risk for glucose intolerance. In a randomized, crossover study, overweight or obese males ingested 11-grain, sprouted-grain, 12-grain, sourdough, or white bread on different occasions, matched for available carbohydrate (50 g) in part 1 (n = 12) and bread mass (107 g) in part 2 (n = 11), and blood glucose, insulin and glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were determined for 3 h. In part 1, glucose response for sprouted-grain was lower than 11-grain, sourdough, and white breads. Insulin area under the curve (AUC) for sourdough and white was lower than 11-grain and sprouted-grain breads. GLP-1 response to sourdough was lower than all breads. In part 2, glucose and insulin AUC for sourdough was greater than 11-grain, sprouted-grain, and 12-grain breads. Sprouted-grain bread improved glycemia by lowering glucose response and increasing GLP-1 response. In overweight and obese men, the glycemic response to sprouted grain bread was reduced in both parts 1 and 2 while the other whole-grain test breads did not improve metabolic responses in the acute postprandial state.

Impact of Roux-en-Y gastric bypass on regulation of diabetes type 2 in morbidly obese patients

Background

The idea of surgery as treatment for type 2 diabetes mellitus (T2DM) was established in the US and was based on observation of patients after bariatric surgery. Resolution of T2DM is observed within a few weeks after surgery, in some cases even during hospitalization. The aim of this study was to evaluate the impact of Roux-en-Y gastric bypass (RYGB) on diabetes in morbidly obese patients.

Methods

We present 73 patients with T2DM who underwent laparoscopic RYGB (LRYGB) to treat morbid obesity. In the group of 73 obese patients (mean BMI = 42.3), there were 41 females and 32 males.

Results

Regression of T2DM was observed in 51 patients (69.8%) while hospitalized. In addition, 14 patients’ (19.1%) glycemia and HBA1c stabilized within 12 weeks after surgery (total regression rate of 88.9%).

Conclusion

The ultimate evaluation of this method of treating T2DM is still lacking and requires several years of meticulous clinical studies. Despite that, considering the high cost of life-long conservative therapy of T2DM and its complications and the severe impact T2DM has on quality of life, surgical metabolic intervention may become the most reasonable solution in many cases.

Alogliptin benzoate for the treatment of type 2 diabetes

INTRODUCTION

Alogliptin is a highly selective inhibitor of the enzyme dipeptidyl peptidase-4 (DPP-4). It is one of several agents of this class now available for treatment of type 2 diabetes.

AREAS COVERED

This review is based upon a PubMed search and personal experience with alogliptin. The pharmacokinetics and pharmacodynamics of alogliptin are reviewed. The glucose-lowering effect of this agent is discussed as monotherapy and in combination with metformin, sulfonylurea, piogilitazone and insulin. The potential adverse effects of alogliptin are summarized. Alogliptin is compared with the other available DPP-4 inhibitors.

EXPERT OPINION

Alogliptin is an additional choice in the group of DPP-4 inhibitors. As a group, these agents have a relatively modest glucose-lowering effect, inferior to that of metformin, sulfonylureas, and insulin. They do not have the benefit of weight loss offered by the glucagon-like polypeptide (GLP)-1 agonists. The primary use of DPP-4 inhibitors is in combination with other hypoglycemic agents, mainly metformin. Their principal advantage is a low incidence of hypoglycemia, making these agents desirable in patients such as the elderly and those with cardiac disease. A greater use of alogliptin and other DPP-4 inhibitors will occur if long-term studies show reduced cardiac events or long-term retention of insulin secretory capacity. The Examine Trial, a large study of alogliptin in coronary disease patients, is now underway and could provide important supportive data.

Short-term and mid-term control of type 2 diabetes mellitus by laparoscopic sleeve gastrectomy with ileal interposition

BACKGROUND

Standard surgical procedures used for the treatment of morbid obesity constitute optional treatments for type 2 diabetes mellitus (T2DM). The aim of the present study was to evaluate the short- and mid-term effects of laparoscopic sleeve gastrectomy (SG) with ileal interposition (II) in T2DM patients (n = 30).

METHODS

The variables investigated were the feasibility of the procedure, remission/alleviation of the disease, morbidity, mortality, and weight loss. Patients were followed during a period of 6-18 months after surgery.

RESULTS

The average time required for the surgical procedure was 181.47 ± 53.23 min, and the mean duration of postoperative hospital stay was 3.17 ± 0.79 days. There were no intraoperative complications, and none of the patients required conversion to open surgery. Postoperatively, all patients experienced a significant weight loss: i.e., the mean body mass index (BMI) values prior to and following surgery were significantly different (P = 0.0001). Postoperative levels of glycosylated hemoglobin, fasting glucose, and fructosamine were significantly reduced (P = 0.0001, 0.0001, and 0.0004, respectively) from those detected prior to surgery. Remission of T2DM was observed in 80% of the patients over the follow-up period, and these subjects no longer required treatment with hypoglycemic drugs or diet. The remaining 20% of patients presented significant improvement in their condition but needed an oral hypoglycemic medication.

CONCLUSIONS

Adequate glycemic control, adjustable weight loss, and absence of nutritional deficiencies were the main benefits offered by the surgical intervention. The results indicate that SG/II treatment could be a promising alternative for patients with T2DM.

Effects of chronic administration of alogliptin on the development of diabetes and β-cell function in high fat diet/streptozotocin diabetic mice

AIM

Alogliptin is a potent and highly selective dipeptidyl peptidase-4 (DPP-4) inhibitor. The aim of this study was to determine its effects on glucose control and pancreas islet function and to identify the underlying molecular mechanisms after chronic administration, in a non-genetic mouse model of type 2 diabetes.

METHODS

Alogliptin (5, 15 and 45 mg/kg) was orally administered to high fat diet/streptozotocin (HFD/STZ) diabetic mice daily for 10 weeks. Postprandial and 6-h fasting blood glucose levels, blood A1C level, oral glucose tolerance and pancreas insulin content were measured during or after the treatment period. Alogliptin plasma concentration was determined by an LC/MS/MS method. Islet morphology and architectural changes were evaluated with immunohistochemical analysis. Islet endocrine secretion ability was assessed by measuring insulin release from isolated islets which were challenged with 16 mM glucose and 30 mM potassium chloride, respectively. Gene expression profiles of the pancreas were analysed using the mouse diabetes RT(2) Profiler PCR array which contains 84 genes related to the onset, development and progression of diabetes.

RESULTS

Alogliptin showed dose-dependent reduction of postprandial and fasting blood glucose levels and blood A1C levels. Glucose clearance ability and pancreas insulin content were both increased. Alogliptin significantly restored the β-cell mass and islet morphology, thus preserving islet function of insulin secretion. Expression of 10 genes including Ins1 was significantly changed in the pancreas of diabetic mice. Chronic alogliptin treatment completely or partially reversed the abnormalities in gene expression.

CONCLUSIONS

Chronic treatment of alogliptin improved glucose control and facilitated restoration of islet architecture and function in HFD/STZ diabetic mice. The gene expression profiles suggest that the underlying molecular mechanisms of β-cell protection by alogliptin may involve alleviating endoplasmic reticulum burden and mitochondria oxidative stress, increasing β-cell differentiation and proliferation, enhancing islet architecture remodelling and preserving islet function.

Multiple-dose pharmacokinetics and pharmacodynamics of sergliflozin etabonate, a novel inhibitor of glucose reabsorption, in healthy overweight and obese subjects: a randomized double-blind study

Sergliflozin, the active entity of sergliflozin etabonate, is a selective inhibitor of the sodium-dependent glucose cotransporter-2 in the renal tubule. The pharmacokinetics and pharmacodynamics of sergliflozin were examined during administration of sergliflozin etabonate (500 or 1000 mg) or placebo 3 times daily (tid) for 14 days in healthy overweight or obese human volunteers (n = 18). At the doses tested, sergliflozin showed less than dose-proportional pharmacokinetic characteristics. Mean half-life of the active entity was approximately 2 hours; there was no evidence of drug accumulation. Sergliflozin etabonate produced rapid and sustained suppression of renal glucose reabsorption, resulting in a dose-related glucosuria, and a transient increase in urinary electrolyte and fluid loss; plasma glucose, insulin, and electrolyte levels were unchanged. Sergliflozin etabonate produced a rapid, dose-related reduction in body weight (mean changes of -0.09, -1.55, and -1.74 kg from baseline to day 15 with placebo, sergliflozin etabonate 500 mg, and sergliflozin etabonate 1000 mg, respectively), apparently through increased urinary calorie loss rather than through osmotic diuresis. Sergliflozin etabonate 500 or 1000 mg tid was generally well tolerated; no clinically significant adverse events were identified. Renal function (creatinine clearance) was not affected by sergliflozin etabonate, although urinary microalbumin, N-acetyl-beta-D-glucosaminidase, and beta(2)-microglobulin levels tended to increase.

Genetic influences on the insulin response of the beta cell to different secretagogues

AIMS/HYPOTHESIS

The aim of the present study was to estimate the heritability of the beta cell insulin response to glucose and to glucose combined with glucagon-like peptide-1 (GLP-1) or with GLP-1 plus arginine.

METHODS

This was a twin-family study that included 54 families from the Netherlands Twin Register. The participants were healthy twin pairs and their siblings of the same sex, aged 20 to 50 years. Insulin response of the beta cell was assessed by a modified hyperglycaemic clamp with additional GLP-1 and arginine. Insulin sensitivity index (ISI) was assessed by the euglycaemic-hyperinsulinaemic clamp. Multivariate structural equation modelling was used to obtain heritabilities and the genetic factors underlying individual differences in BMI, ISI and secretory responses of the beta cell.

RESULTS

The heritability of insulin levels in response to glucose was 52% and 77% for the first and second phase, respectively, 53% in response to glucose + GLP-1 and 80% in response to an additional arginine bolus. Insulin responses to the administration of glucose, glucose + GLP-1 and glucose + GLP-1 + arginine were highly correlated (0.62< r <0.79). Heritability of BMI and ISI was 74% and 60% respectively. The genetic factors that influenced BMI and ISI explained about half of the heritability of insulin levels in response to the three secretagogues. The other half was due to genetic factors specific to the beta cell.

CONCLUSIONS/INTERPRETATION

In healthy adults, genetic factors explain most of the individual differences in the secretory capacity of the beta cell. These genetic influences are partly independent from the genes that influence BMI and ISI.

Effect of the urotensin-II receptor antagonist palosuran on secretion of and sensitivity to insulin in patients with Type 2 diabetes mellitus

AIMS

To investigate the effects of palosuran, a nonpeptidic, potent and selective antagonist of the urotensin-II receptor, on insulin and glucose regulation in 20 diet-treated patients with Type 2 diabetes mellitus in a double-blind, placebo-controlled, randomized, crossover, proof-of-concept study.

METHODS

After 4 weeks' oral treatment with 125 mg palosuran or placebo b.i.d.,effects on insulin secretion and sensitivity and blood glucose levels were assessed by means of a hyperglycaemic glucose clamp, meal tolerance test, homeostasis model assessment-insulin resistance score, and daily self-monitoring of blood glucose. Plasma concentrations of palosuran were determined for 12 h on the last day of intake.

RESULTS

Palosuran did not affect second-phase insulin response (primary end-point) during the hyperglycaemic glucose clamp in comparison with placebo [paired difference of -1.8 microU ml(-1), 95% confidence interval (CI) -7.8, 4.2]. Likewise, no effects of palosuran were detected on the first-phase insulin response, or on insulin secretion and blood glucose levels during the meal tolerance test or on homeostasis model assessment-insulin resistance score. No clinically significant effects on daily blood glucose profiles were observed during the study. Geometric mean C(max) and AUC(tau) (95% CI) and median t(max) (range) in this patient population were 180 ng ml(-1) (125, 260), 581 ng.h ml(-1) (422, 800) and 3.0 h (0.67, 4.3), respectively.

CONCLUSIONS

The results of this study indicate that antagonism of the urotensin-II system does not influence insulin secretion or sensitivity or daily blood glucose levels in diet-treated patients with Type 2 diabetes.

Emerging concepts in the pathophysiology of type 2 diabetes mellitus

Type 2 diabetes mellitus is a multifactorial metabolic disorder. It is characterized by chronic hyperglycemia, insulin resistance, and a relative insulin secretion defect. The prevalence of type 2 diabetes mellitus has risen worldwide in large part because of an increase in obesity and sedentary lifestyles. The underlying pathophysiology and complications of type 2 diabetes mellitus are still being elucidated. Recent advances in diabetes research have helped us to gain a better understanding about insulin resistance and insulin secretion defects. The evolving understanding about the influence of the incretin effect, insulin signal transduction, adipose tissue, intra-islet cell communication, and inflammation is changing the way in which we view type 2 diabetes mellitus. This new understanding will eventually provide us with new treatment approaches to help patients who have type 2 diabetes mellitus. This article gives a review of the current and emerging concepts of the pathophysiology of type 2 diabetes mellitus.

Improvement of glucose metabolism after a pancreatoduodenectomy

OBJECTIVES

The aim of this study was to investigate the mechanisms of the change in glucose metabolism after a pancreatoduodenectomy (PD).

METHODS

Oral glucose tolerance tests were performed in 17 patients before and 1 month after a PD. The changes in plasma glucose and insulin concentrations, homeostasis model of insulin resistance, and insulinogenic index (beta-cell function) were analyzed. Two additional factors, gastric emptying function and plasma glucagon-like peptide-1 (GLP-1) concentration, that possibly affect perioperative glucose metabolism were also assessed.

RESULTS

The plasma glucose and insulin concentrations were significantly lower after the operation, especially in preoperative diabetic patients. beta-Cell function did not change after the operation. On the other hand, insulin resistance became normal 1 month after the operation. The value of gastric emptying function after the operation was not statistically different in comparison with that before the operation. Postoperative plasma GLP-1 concentration was significantly higher than the preoperative value.

CONCLUSIONS

beta-Cell function is maintained after a PD, whereas the improvement of insulin resistance may cause a short-term transient improvement of the glucose metabolism after the operation. The significance of increased postoperative GLP-1 concentration remains an unsolved issue.

DPP4 inhibitors: from sitagliptin monotherapy to the new alogliptin-pioglitazone combination therapy

Diabetes mellitus (DM) is currently considered to be an epidemic disease. A safe and effective treatment has long been sought by scientists. Incretin mimetics and dipeptidyl peptidase-4 (DPP4) inhibitors represent a new class of agents that have recently been included as antidiabetic drugs. Although only a limited number of studies exist regarding the treatment of DM based on the incretin effect, DPP4 inhibitors have so far proved to be safe and effective, both when administered alone or in combination with other antidiabetic medication. This review focuses on incretin-effect physiology, as well as the DPP4 inhibitors, from sitagliptin to the new alogliptin-pioglitazone combination agent, given as monotherapy and in combination with other antidiabetic agents.

Acute administration of GPR40 receptor agonist potentiates glucose-stimulated insulin secretion in vivo in the rat

Recently, several in vitro studies have shown that GPR40 receptor activation by free fatty acids (FFAs) results in glucose-dependent insulin secretion. However, whether GPR40 receptor activation results in glucose-dependent insulin secretion in vivo in rats is not known. Therefore, we evaluated the effect of synthetic GPR40 receptor agonist (compound 1) on glucose tolerance test (GTT) in fed, fasted, and insulin-resistant rats. In oral GTT, intraperitoneal GTT, and intravenous GTT, GPR40 receptor agonist improved glucose tolerance, which was associated with increase in plasma insulin level. Interestingly, in GTTs, the rise in insulin levels in agonist-treated group was directly proportional to the rate of rise and peak levels of glucose in control group. Although glibenclamide, a widely used insulin secretagogue, improved glucose tolerance in all GTTs, it did not display insulin release in intraperitoneal GTT or intravenous GTT. In the absence of glucose load, GPR40 receptor agonist did not significantly change the plasma insulin concentration, but did decrease the plasma glucose concentration. Fasted rats exhibited impaired glucose-stimulated insulin secretion (GSIS) as compared with fed rats. Compound 1 potentiated GSIS in fasted state but failed to do so in fed state. Suspecting differential pharmacokinetics, a detailed pharmacokinetic evaluation was performed, which revealed the low plasma concentration of compound 1 in fed state. Consequently, we examined the absorption profile of compound 1 at higher doses in fed state; and at a dose at which its absorption was comparable with that in fasted state, we observed significant potentiation of GSIS. Chronic high-fructose (60%) diet feeding resulted in impaired glucose tolerance, which was improved by GPR40 receptor agonist. Therefore, our results demonstrate for the first time that acute GPR40 receptor activation leads to potentiation of GSIS in vivo and improves glucose tolerance even in insulin-resistant condition in rats. Taken together, these results suggest that GPR40 receptor agonists could be potential therapeutic alternatives to sulfonylureas.

New treatments in type 2 diabetes: a focus on the incretin-based therapies

The demonstration that the incretin hormone glucagon-like peptide 1 can improve glycaemic control in patients with type 2 diabetes has led to the rapid development during the last decade of promising new classes of agent for the management of type 2 diabetes. These agents possess a range of physiological effects that are associated with improved glycaemic control in diabetes including stimulation of glucose-dependent insulin secretion, suppression of glucagon secretion, slowing of gastric emptying, and reduction of food intake. In addition, preclinical studies suggest that incretin-based therapies may improve beta-cell function via enhancement of beta-cell mass and induction of genes important for differentiated beta-cell function. Exenatide, and the dipeptidyl peptidase-4 inhibitors, sitagliptin and vildagliptin are already approved, and liraglutide is currently completing Phase 3 trials. As these agents and standard oral therapies for type 2 diabetes lower glucose levels through different, but potentially complementary mechanisms, their use in combination should provide effective, potentially additive, glycaemic control. The incretin-based therapies also offer other advantages such as weight loss with exenatide and liraglutide, a reduced risk of hypoglycaemia, and as suggested by preclinical studies, a potential beta-cell preserving effect. Long-term outcome and safety data are not available for these agents, but they appear generally well-tolerated in comparison with existing therapies for type 2 diabetes. The multiple underlying glucose-lowering actions of the incretin-based therapies, as well as a lack of weight gain or even weight loss, make these important new additions to available antidiabetic agents expanding the treatment options available for patients.

Glucagon-like peptide-1 and-2 levels in children with diabetic ketoacidosis

OBJECTIVE

The aim of this study was to investigate whether insulin deficiency and increased catabolism may have a role in the regulation of plasma glucagon-like peptide (GLP)-1 and GLP-2 levels in children with diabetic ketoacidosis (DKA) and whether insulin treatment may affect the levels of these polypeptides.

METHODS

Plasma GLP-1 and -2 levels were measured in 24 patients with DKA aged 8 to 14 years before insulin infusion (time 0), when ketonemia and acidosis disappeared (time 1), and when weight gain started (time 2). Eighteen healthy children aged 8 to 14 years constituted the control group.

RESULTS

At time 0, mean plasma GLP-1 and GLP-2 levels were significantly elevated in the patients compared with the control group (p<0.05 and p<0.01, respectively). At time 1 when ketonemia and acidosis disappeared, GLP-1 and GLP-2 levels decreased significantly from the initial levels (p<0.05 and p<0.01, respectively). At this time, while GLP-1 level was not different from that of the controls, GLP-2 level was higher than that of the controls (p<0.05). GLP-1 and-2 levels did not show any significant differences between the patients and controls when weight gain started (time 2).

CONCLUSION

Our results show that DKA is associated with increased plasma GLP-1 and -2 concentrations. Effective fluid and insulin treatment resulted in a significant decrease in plasma GLP-1 and -2 levels. This may be due to the negative feedback effect of insulin on the production of these polypeptides.

The correlation between intestinal gonadotropin-releasing hormone (GnRH) and proglucagon in hyperlipidemic rats and Goto-Kakizaki (GK) rats

Our experiment investigated the mRNA expression of intestinal gonadotropin-releasing hormone (GnRH), proglucagon (PG), and glucagon-like peptide 1 receptor (GLP-1R) in the jejunum, ileum, and colon of rats fed with high-fat diet and Goto-Kakizaki (GK) rats and revealed the physiological role of intestinal GnRH. We found that the GnRH and PG mRNA levels in high-cholesterol (HCh) diet were higher than in the control. However, the GnRH receptor (GnRHR) and GLP-1R mRNA levels did not differ significantly between HCh and control. The GnRH, PG, and GLP-1R mRNA levels in GK rats were lower, respectively, than those in control rats, while the GnRHR levels did not differ significantly between GK rats and control rats. There were no difference in GnRH, PG, GnRHR, and GLP-1R mRNA levels in the ileum and colon tissue between HCh and control rats. The GnRH mRNA levels of GK rats were lower than those in control rats; however, the PG, GLP-1R, and GnRHR levels did not differ significantly between GK and control rats. The GLP-1R mRNA levels of GK rats were lower than those in control rats. The GnRH mRNA expression showed positive correlation with PG mRNA expression in different intestinal sections. The GnRH level in the jejunum showed a significant effect on blood glucose level, while the PG level in the jejunum showed a significant effect on insulin level. This may imply that, compared with the ileum and colon, the jejunum had greater impact on glucose metabolism; furthermore, GnRH might interact with intestinal GLP-1 and GLP-2 through the paracrine and autocrine ways and then regulate glucose metabolism and insulin secretion.

Hormonal evaluation following laparoscopic treatment of type 2 diabetes mellitus patients with BMI 20-34

BACKGROUND

A group of patients with type 2 diabetes mellitus (T2DM) and body mass index (BMI) 20-34 kg/m(2) were submitted to laparoscopic interposition of a segment of ileum into the proximal jejunum or into the proximal duodenum associated to a sleeve gastrectomy. The objective of this study is to evaluate the hormonal changes in the pre- and postoperative period.

MATERIALS AND METHODS

Hormonal evaluation was done in 58 patients operated between April 2005 and July 2006. Mean age was 51.4 years (40-66 years). Mean BMI was 28.2 (20-34.8) kg/m(2). All patients had had the diagnosis of T2DM for at least 3 years. Mean duration of T2DM was 9.6 years (3-22 years). Two techniques were performed, consisting of different combinations of ileal interposition (II) associated to a sleeve gastrectomy (SG). The following hormones were assayed in the pre- and postoperative period (mean 16 months) at the baseline and following specific food stimulation (30, 60, 120 min): glucogen-like protein 1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), insulin, glucagon, C-peptide, amylin, cholecystokinin (CCK), pancreatic polypeptide (PPP), somatostatin, peptide YY (PYY), ghrelin, adiponectin, resistin, leptin, and interleukin-6 (IL-6).

RESULTS

Thirty patients had II associated to sleeve gastrectomy (II-SG) and 28 had II with diverted sleeve gastrectomy (II-DSG). GLP1 exhibited an important rise following the two operations, especially after II-DSG (p < 0.001). GIP also exhibited an important rise, with both II-SG and II-DSG being equally effective (p < 0.001). Insulin and amylin showed a significant rise at 30 min. Glucagon decreased slightly. CCK measurements were very low after II-DSG. PPP was also slightly altered by the II-DSG. PYY showed an important increase with both operations (p < 0.001). Ghrelin showed a significant decrease following the two operations (p < 0.001). Somatostatin and IL-6 were not affected (p = 0.632). Both leptin and resistin blood levels decreased. Adiponectin showed a slight increase. Mean postoperative follow-up was 19.2 months. Both II-SG and II-DSG were effective in achieving adequate glycemic control (91.2%).

CONCLUSIONS

There was a significant hormonal change following laparoscopic ileal interposition. These alterations may explain the promising good results associated to these operations for the treatment of T2DM in the nonmorbidly obese population.

Usefulness of colon targeted DHA and EPA as novel diabetes medications that promote intrinsic GLP-1 secretion

Glucagon-like peptide-1 (GLP-1) is a gut-derived peptide secreted from intestinal L-cells and now considered as an ideal diabetic medicine. Recently, it was reported that the unsaturated fatty acid alpha-linoleic acid promotes the secretion of GLP-1 via a G protein-coupled receptor, GPR120. However, the effects of long-chain polyunsaturated fatty acids on the secretion of GLP-1 have not been examined in vivo. The aim of this study was to evaluate the effects of the long-chain polyunsaturated fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on blood glucose levels, plasma insulin, and GLP-1 concentrations. In addition, site-specific differences in these effects were determined using several intestinal segments: stomach, jejunum, and colon. After an intraperitoneal glucose administration (1.5 mg/g weight), each mouse was administered vehicle or an alpha-linoleic acid, DHA, EPA or EPA ester (EPA-E) solution to each intestinal segment. After an intraperitoneal glucose challenge, marked endogenous GLP-1 secretion, substantial insulin release and subsequent glucose reductions were observed in the intracolonic DHA and EPA treatment groups. In contrast, DHA and EPA did not increase GLP-1 secretion when given in the other segments. These data suggested that the colon-specific delivery of DHA, EPA, and possibly EPA-E would be a novel antidiabetic treatment by the stimulation of intrinsic GLP-1 secretion.

Impact of therapeutic advances on hypoglycaemia in type 2 diabetes

Patients with type 2 diabetes experience hypoglycaemia less frequently than those with type 1 diabetes. Some protection against hypoglycaemia is afforded by the relatively intact glucose counter-regulatory pathways that characterize the pathophysiology of early type 2 diabetes. To some extent, this protection explains why hypoglycaemic episodes in intensively treated individuals with type 2 diabetes, when they occur, are rarely severe. As diabetes progresses and therapy intensifies to achieve recommended glycaemic goals, hypoglycaemia frequency and severity increase. Thus, when it comes to instituting intensive therapy, fear of hypoglycaemia may contribute to health-care providers' 'clinical inertia'. Because maintaining glycaemic control is so important to both public and individual health, many new therapies and technologies have been developed. This manuscript reviews and considers whether these advancements in therapy make glycaemic goals easier to achieve by minimizing hypoglycaemia. Putting the hypoglycaemia experienced by type 2 diabetes patients into appropriate clinical perspective, the impact of recent progress made in pharmacotherapy, drug delivery systems, and BG monitoring on hypoglycaemia incidence is largely positive. The extent to which this progress can effect improvement over traditional therapies will, however, depend upon patient (and provider) education, motivation and behaviour change.

Enteroendocrine cells: a site of 'taste' in gastrointestinal chemosensing

PURPOSE OF REVIEW

This review discusses the role of enteroendocrine cells of the gastrointestinal tract as chemoreceptors that sense lumen contents and induce changes in gastrointestinal function and food intake through the release of signaling substances acting on a variety of targets locally or at a distance.

RECENT FINDINGS

Recent evidence supports the concept that chemosensing in the gut involves G protein-coupled receptors and effectors that are known to mediate gustatory signals in the oral cavity. These include sweet-taste and bitter-taste receptors, and their associated G proteins, which are expressed in the gastrointestinal mucosa, including selected populations of enteroendocrine cells. In addition, taste receptor agonists elicit a secretory response in enteroendocrine cells in vitro and in animals in vivo, and induce neuronal activation.

SUMMARY

Taste-signaling molecules expressed in the gastrointestinal mucosa might participate in the functional detection of nutrients and harmful substances in the lumen and prepare the gut to absorb them or initiate a protective response. They might also participate in the control of food intake through the activation of gut-brain neural pathways. These findings provide a new dimension to unraveling the regulatory circuits initiated by luminal contents of the gastrointestinal tract.

Freeze drying of peptide drugs self-associated with long-circulating, biocompatible and biodegradable sterically stabilized phospholipid nanomicelles

The purpose of this study was to determine optimal lipid concentration range for lyophilization of sterically stabilized phospholipid nanomicelles (SSM) and the freeze drying feasibility of self-associated therapeutic peptide-SSM assemblies. SSM at 5-20 mM 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy-poly(ethylene glycol 2000) (DSPE-PEG(2000)) were analyzed for particle size and viscosity before and after freeze drying which showed no significant changes (p>0.05). However, a steep increase in viscosity was seen for SSM above 15 mM phospholipid implying micelle-micelle interaction. Greater shrinkage of lyophilized cakes was observed below 10 mM phospholipid while they were more fibrous above 15 mM. Therefore, 10-15 mM DSPE-PEG(2000) was chosen as the optimal phospholipid concentration for lyophilized SSM. When vasoactive intestinal peptide (VIP), glucagon-like peptide 1 (GLP-1) or gastric inhibitory peptide (GIP) (each, 67 microM) was added to SSM (10mM), formulations showed no significant change in particle size, peptide fluorescence and peptide alpha-helicity before and after lyophilization. In conclusion, we found that peptide drug-SSM interactions are conserved during lyophilization.

Taste receptor signaling in the mammalian gut

Molecular sensing by gastrointestinal (GI) cells plays a crucial role in the control of multiple fundamental functions including digestion, regulation of caloric intake, pancreatic insulin secretion, and metabolism, as well as protection from ingested harmful drugs and toxins. These processes are likely to be mediated by the initiation of humoral and/or neural pathways through the activation of endocrine cells. However, the initial recognition events and mechanism(s) involved are still largely unknown. This article reviews the current evidence that the chemosensory machinery discovered in specialized neuroepithelial taste receptor cells of the lingual epithelium is operational in enteroendocrine open GI cells that sense the chemical composition of the luminal contents of the gut.

Is Glucagon-like peptide-1, an agent treating diabetes, a new hope for Alzheimer's disease?

Glucagon-like peptide-1 (GLP-1) has been endorsed as a promising and attractive agent in the treatment of type 2 diabetes mellitus (T2DM). Both Alzheimer's disease (AD) and T2DM share some common pathophysiologic hallmarks, such as amyloid beta (Abeta), phosphoralation of tau protein, and glycogen synthase kinase-3. GLP-1 possesses neurotropic properties and can reduce amyloid protein levels in the brain. Based on extensive studies during the past decades, the understanding on AD leads us to believe that the primary targets in AD are the Abeta and tau protein. Combine these findings, GLP-1 is probably a promising agent in the therapy of AD. This review was focused on the biochemistry and physiology of GLP-1, communities between T2DM and AD, new progresses of GLP-1 in treating T2MD and improving some pathologic hallmarks of AD.

Modeling assisted rational design of novel, potent, and selective pyrrolopyrimidine DPP-4 inhibitors

Molecular modeling was used to improve potency of the cyclohexylamine series. In addition, a 3-D QSAR method was used to gain insight for reducing off-target DPP-8/9 activities. Compounds 3, 4, and 5 were synthesized and found to be potent DPP-4 inhibitors, in particular 4 and 5 are designed to be highly selective against off-target DASH enzymes while maintaining potency on DPP-4.