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Author Report for: Deacon CF

Title: Dipeptidyl peptidase 4 inhibitors in the treatment of type 2 diabetes mellitus
Deacon CF
Ref: Nat Rev Endocrinol, 16:642, 2020 : PubMed
Abstract


ESTHER: Deacon_2020_Nat.Rev.Endocrinol_16_642
PubMedSearch: Deacon 2020 Nat.Rev.Endocrinol 16 642
PubMedID: 32929230

Abstract

Dipeptidyl peptidase 4 inhibitors (DPP4i) have been available for treating type 2 diabetes mellitus since 2006. Although they are a diverse group, DPP4i are all small, orally available molecules that interact with the catalytic site of DPP4 without disturbing any of its other known functions, including its effects on the immune system. DPP4i have no intrinsic glucose-lowering activity, so their efficacy as anti-diabetic agents is related directly to their ability to inhibit DPP4 activity and is mediated through the effects of the substrates they protect. Of these, the incretin hormone, glucagon-like peptide 1, is probably the most important. As the effects of glucagon-like peptide 1 are glucose-dependent, the risk of hypoglycaemia with DPP4i is low. Class effects, which are directly related to the mechanism of action, are common to all DPP4i; these include their overall good safety profile and tolerability, as well as their efficacy in improving glycaemic control, but also, potentially, a small increased risk of acute pancreatitis. Compound-specific effects are those related to their differing chemistries and/or pharmacokinetic profiles. These compound-specific effects could affect the way in which individual DPP4i are used therapeutically and potentially explain off-target adverse effects, such as hospitalization for heart failure, which is seen only with one DPP4i. Overall, DPP4i have a favourable therapeutic profile and are safe and effective in the majority of patients with type 2 diabetes mellitus.



        

Title: Why is it so difficult to measure glucagon-like peptide-1 in a mouse?
Windelov JA, Wewer Albrechtsen NJ, Kuhre RE, Jepsen SL, Hornburg D, Pedersen J, Jensen EP, Galsgaard KD, Winther-Sorensen M and Holst JJ <5 more author(s)> Windelov JA, Wewer Albrechtsen NJ, Kuhre RE, Jepsen SL, Hornburg D, Pedersen J, Jensen EP, Galsgaard KD, Winther-Sorensen M, Orgaard A, Deacon CF, Mann M, Kissow H, Hartmann B, Holst JJ (- 5)
Ref: Diabetologia, 60:2066, 2017 : PubMed
Abstract


ESTHER: Windelov_2017_Diabetologia_60_2066
PubMedSearch: Windelov 2017 Diabetologia 60 2066
PubMedID: 28669086

Abstract

AIMS/HYPOTHESIS: In humans, glucagon-like peptide-1 (GLP-1) is rapidly degraded by dipeptidyl peptidase-4 to a relatively stable metabolite, GLP-1(9-36)NH2, which allows measurement of GLP-1 secretion. However, little is known about the kinetics of the GLP-1 metabolite in mice. We hypothesised that the GLP-1 metabolite is rapidly degraded in this species by neutral endopeptidase(s) (NEP[s]). METHODS: We administered glucose, mixed meal or water orally to 256 mice, and took blood samples before and 2, 6, 10, 20, 30, 60 or 90 min after stimulation. To study the metabolism of the GLP-1 metabolite, i.v. GLP-1(9-36)NH2 (800 fmol) or saline (154 mmol/l NaCl) was administered to 160 mice, some of which had a prior injection of a selective NEP 24.11 +/- inhibitor (candoxatril, 5 mg/kg) or saline. Blood was collected before and 1, 2, 4 and 12 min after GLP-1/saline injection. Plasma GLP-1 levels were analysed using a customised single-site C-terminal ELISA, two different two-site ELISAs and MS. RESULTS: GLP-1 secretion profiles after oral glucose administration differed markedly when assayed by C-terminal ELISA compared with sandwich ELISAs, with the former showing a far higher peak value and AUC. In mice injected with GLP-1(9-36)NH2, immunoreactive GLP-1 plasma levels peaked at approximately 75 pmol/l at 1 min when measured with sandwich ELISAs, returning to baseline (~20 pmol/l) after 12 min, but remained elevated using the C-terminal ELISA (~90 pmol/l at 12 min). NEP 24.11 inhibition by candoxatril significantly attenuated GLP-1(9-36)NH2 degradation in vivo and in vitro. MS identified GLP-1 fragments consistent with NEP 24.11 degradation. CONCLUSIONS/INTERPRETATION: In mice, the GLP-1 metabolite is eliminated within a few minutes owing to endoproteolytic cleavage by NEP 24.11. Therefore, accurate measurement of GLP-1 secretion in mice requires assays for NEP 24.11 metabolites. Conventional sandwich ELISAs are inadequate because of endoproteolytic cleavage of the dipeptidyl peptidase-4-generated metabolite.



        

Title: Comparative review of dipeptidyl peptidase-4 inhibitors and sulphonylureas
Deacon CF, Lebovitz HE
Ref: Diabetes Obes Metab, 18:333, 2016 : PubMed
Abstract


ESTHER: Deacon_2016_Diabetes.Obes.Metab_18_333
PubMedSearch: Deacon 2016 Diabetes.Obes.Metab 18 333
PubMedID: 26597596

Abstract

Type 2 diabetes (T2DM) is a progressive disease, and pharmacotherapy with a single agent does not generally provide durable glycaemic control over the long term. Sulphonylurea (SU) drugs have a history stretching back over 60 years, and have traditionally been the mainstay choice as second-line agents to be added to metformin once glycaemic control with metformin monotherapy deteriorates; however, they are associated with undesirable side effects, including increased hypoglycaemia risk and weight gain. Dipeptidyl peptidase (DPP)-4 inhibitors are, by comparison, more recent, with the first compound being launched in 2006, but the class now globally encompasses at least 11 different compounds. DPP-4 inhibitors improve glycaemic control with similar efficacy to SUs, but do not usually provoke hypoglycaemia or weight gain, are relatively free from adverse side effects, and have recently been shown not to increase cardiovascular risk in large prospective safety trials. Because of these factors, DPP-4 inhibitors have become an established therapy for T2DM and are increasingly being positioned earlier in treatment algorithms. The present article reviews these two classes of oral antidiabetic drugs (DPP-4 inhibitors and SUs), highlighting differences and similarities between members of the same class, as well as discussing the potential advantages and disadvantages of the two drug classes. While both classes have their merits, the choice of which to use depends on the characteristics of each individual patient; however, for the majority of patients, DPP-4 inhibitors are now the preferred choice.



        

Title: Dipeptidyl peptidase-4 inhibitors in the treatment of type 2 diabetes: a comparative review
Deacon CF
Ref: Diabetes Obes Metab, 13:7, 2011 : PubMed
Abstract


ESTHER: Deacon_2011_Diabetes.Obes.Metab_13_7
PubMedSearch: Deacon 2011 Diabetes.Obes.Metab 13 7
PubMedID: 21114598

Abstract

The dipeptidyl peptidase (DPP)-4 inhibitors are a new class of antihyperglycaemic agents which were developed for the treatment of type 2 diabetes by rational drug design, based on an understanding of the underlying mechanism of action and knowledge of the structure of the target enzyme. Although they differ in terms of their chemistry, they are all small molecules which are orally available. There are some differences between them in terms of their absorption, distribution, metabolism and elimination, as well as in their potency and duration of action, but their efficacy, both in terms of inhibiting plasma DPP-4 activity and as antidiabetic agents, appears to be similar. They improve glycaemic control, reducing both fasting and postprandial glucose levels to lower HbA1c levels, without weight gain and with an apparently benign adverse event profile. At present, there seems to be little to distinguish between the different inhibitors in terms of their efficacy as antidiabetic agents and their safety. Long-term accumulated clinical experience will reveal whether compound-related characteristics lead to any clinically relevant differences.



        

Title: Secretion of glucagon-like peptide-1 (GLP-1) in type 2 diabetes: what is up, what is down?
Nauck MA, Vardarli I, Deacon CF, Holst JJ, Meier JJ
Ref: Diabetologia, 54:10, 2011 : PubMed
Abstract


ESTHER: Nauck_2011_Diabetologia_54_10
PubMedSearch: Nauck 2011 Diabetologia 54 10
PubMedID: 20871975

Abstract

The incretin hormones gastric inhibitory polypeptide and especially glucagon-like peptide (GLP) have an important physiological function in augmenting postprandial insulin secretion. Since GLP-1 may play a role in the pathophysiology and treatment of type 2 diabetes, assessment of meal-related GLP-1 secretory responses in type 2 diabetic patients vs healthy individuals is of great interest. A common view states that GLP-1 secretion in patients with type 2 diabetes is deficient and that this applies to a lesser degree in individuals with impaired glucose tolerance. Such a deficiency is the rationale for replacing endogenous incretins with GLP-1 receptor agonists or re-normalising active GLP-1 concentrations with dipeptidyl peptidase-4 inhibitors. This review summarises the literature on this topic, including a meta-analysis of published studies on GLP-1 secretion in individuals with and without diabetes after oral glucose and mixed meals. Our analysis does not support the contention of a generalised defect in nutrient-related GLP-1 secretory responses in type 2 diabetes patients. Rather, factors are identified that may determine individual incretin secretory responses and explain some of the variations in published findings of group differences in GLP-1 responses to nutrient intake.



        

Title: Inhibition of DPP-4 with Vildagliptin Improved Insulin Secretion in Response to Oral as well as Isoglycemic Intravenous Glucose without Numerically Changing the Incretin Effect in Patients with Type 2 Diabetes
Vardarli I, Nauck MA, Kothe LD, Deacon CF, Holst JJ, Schweizer A, Foley JE
Ref: J Clinical Endocrinology Metab, 96:945, 2011 : PubMed
Abstract


ESTHER: Vardarli_2011_J.Clin.Endocrinol.Metab_96_945
PubMedSearch: Vardarli 2011 J.Clin.Endocrinol.Metab 96 945
PubMedID: 21239518

Abstract

BACKGROUND AND AIMS: Dipeptidyl peptidase-4 (DPP-4) inhibitors block the degradation of glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide. The aim of the present study was to quantitatively assess the incretin effect after treatment with the DPP-4 inhibitor vildagliptin (V) or placebo (P) in patients with type 2 diabetes. MATERIALS AND METHODS: Twenty-one patients (three women, 18 men) with type 2 diabetes previously treated with metformin (mean age, 59 yr; body mass index, 28.6 kg/m(2); glycosylated hemoglobin, 7.3%) were studied in a two-period crossover design. They received 100 mg V once daily or P for 13 d in randomized order. The incretin effect was measured on d 12 (75-g oral glucose) and d 13 ("isoglycemic" iv glucose) based on insulin and C-peptide determinations and insulin secretion rates (ISR). RESULTS: V relative to P treatment significantly increased intact incretin concentrations after oral glucose and insulin secretory responses to both oral glucose and isoglycemic iv glucose (e.g. AUC(ISR oral), by 32.7%, P = 0.0006; AUC(ISR iv), by 33.1%, P = 0.01). The numerical incretin effect was not changed (IE(ISR), V vs. P, 35.7 +/- 4.9 and 34.6 +/- 4.0%, P = 0.80).
CONCLUSIONS: DPP-4 inhibition augmented insulin secretory responses both after oral glucose and during isoglycemic iv glucose infusions, with no net change in the incretin effect. Thus, slight variations in basal incretin levels may be more important than previously thought. Or, DPP-4 inhibitor-induced change in the incretin-related environment of islets may persist overnight, augmenting insulin secretory responses to iv glucose as well. Alternatively, yet unidentified mediators of DPP-4 inhibition may have caused these effects.



        

Title: The effect of DPP-4 inhibition with sitagliptin on incretin secretion and on fasting and postprandial glucose turnover in subjects with impaired fasting glucose
Bock G, Dalla Man C, Micheletto F, Basu R, Giesler PD, Laugen J, Deacon CF, Holst JJ, Toffolo G and Vella A <2 more author(s)> Bock G, Dalla Man C, Micheletto F, Basu R, Giesler PD, Laugen J, Deacon CF, Holst JJ, Toffolo G, Cobelli C, Rizza RA, Vella A (- 2)
Ref: Clinical Endocrinology (Oxf), 73:189, 2010 : PubMed
Abstract


ESTHER: Bock_2010_Clin.Endocrinol.(Oxf)_73_189
PubMedSearch: Bock 2010 Clin.Endocrinol.(Oxf) 73 189
PubMedID: 20039889

Abstract

OBJECTIVE: Low glucagon-like peptide-1 (GLP-1) concentrations have been observed in impaired fasting glucose (IFG). It is uncertain whether these abnormalities contribute directly to the pathogenesis of IFG and impaired glucose tolerance. Dipeptidyl peptidase-4 (DPP-4) inhibitors raise incretin hormone concentrations enabling an examination of their effects on glucose turnover in IFG. RESEARCH DESIGN AND METHODS: We studied 22 subjects with IFG using a double-blinded, placebo-controlled, parallel-group design. At the time of enrollment, subjects ate a standardized meal labelled with [1-(13)C]-glucose. Infused [6-(3)H] glucose enabled measurement of systemic meal appearance (MRa). Infused [6,6-(2)H(2)] glucose enabled measurement of endogenous glucose production (EGP) and glucose disappearance (Rd). Subsequently, subjects were randomized to 100 mg of sitagliptin daily or placebo. After an 8-week treatment period, the mixed meal was repeated. RESULTS: As expected, subjects with IFG who received placebo did not experience any change in glucose concentrations. Despite raising intact GLP-1 concentrations, treatment with sitagliptin did not alter either fasting or postprandial glucose, insulin or C-peptide concentrations. Postprandial EGP (18.1 +/- 0.7 vs 17.6 +/- 0.8 micromol/kg per min, P = 0.53), Rd (55.6 +/- 4.3 vs 58.9 +/- 3.3 micromol/kg per min, P = 0.47) and MRa (6639 +/- 377 vs 6581 +/- 316 micromol/kg per 6 h, P = 0.85) were unchanged. Sitagliptin was associated with decreased total GLP-1 implying decreased incretin secretion. CONCLUSIONS: DPP-4 inhibition did not alter fasting or postprandial glucose turnover in people with IFG. Low incretin concentrations are unlikely to be involved in the pathogenesis of IFG.



        

Title: Secretion and dipeptidyl peptidase-4-mediated metabolism of incretin hormones after a mixed meal or glucose ingestion in obese compared to lean, nondiabetic men
Carr RD, Larsen MO, Jelic K, Lindgren O, Vikman J, Holst JJ, Deacon CF, Ahren B
Ref: J Clinical Endocrinology Metab, 95:872, 2010 : PubMed
Abstract


ESTHER: Carr_2010_J.Clin.Endocrinol.Metab_95_872
PubMedSearch: Carr 2010 J.Clin.Endocrinol.Metab 95 872
PubMedID: 20008019

Abstract

CONTEXT: Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are cleaved by dipeptidyl peptidase-4 (DPP-4); plasma activity of DPP-4 may be increased in obesity. The impact of this increase on incretin hormone secretion and metabolism is not known. OBJECTIVE: The aim of the study was to assess incretin hormone secretion and degradation in lean and obese nondiabetic subjects. DESIGN, SETTINGS, AND PARTICIPANTS: We studied the ingestion of a mixed meal (560 kcal) or oral glucose (2 g/kg) in healthy lean (n = 12; body mass index, 20-25 kg/m(2)) or obese (n = 13; body mass index, 30-35 kg/m(2)) males at a University Clinical Research Unit. MAIN OUTCOME MEASURES: We measured the area under the curve of plasma intact (i) and total (t) GIP and GLP-1 after meal ingestion and oral glucose. RESULTS: Plasma DPP-4 activity was higher in the obese subjects (38.5 +/- 3.0 vs. 26.7 +/- 1.6 mmol/min . microl; P = 0.002). Although GIP secretion (AUC(tGIP)) was not reduced in obese subjects after meal ingestion or oral glucose, AUC(iGIP) was lower in obese subjects (8.5 +/- 0.6 vs. 12.7 +/- 0.9 nmol/liter x 300 min; P < 0.001) after meal ingestion. GLP-1 secretion (AUC(tGLP-1)) was reduced in obese subjects after both meal ingestion (7.3 +/- 0.9 vs. 10.0 +/- 0.6 nmol/liter x 300 min; P = 0.022) and oral glucose (6.6 +/- 0.8 vs. 9.6 +/- 1.1 nmol/liter x 180 min; P = 0.035). iGLP-1 was reduced in parallel to tGLP-1. CONCLUSIONS: 1) Release and degradation of the two incretin hormones show dissociated changes in obesity: GLP-1 but not GIP secretion is lower after meal ingestion and oral glucose, whereas GIP but not GLP-1 metabolism is increased after meal ingestion. 2) Increased plasma DPP-4 activity in obesity is not associated with a generalized augmented incretin hormone metabolism.



        

Title: Immunoassays for the incretin hormones GIP and GLP-1
Deacon CF, Holst JJ
Ref: Best Pract Res Clinical Endocrinology Metab, 23:425, 2009 : PubMed
Abstract


ESTHER: Deacon_2009_Best.Pract.Res.Clin.Endocrinol.Metab_23_425
PubMedSearch: Deacon 2009 Best.Pract.Res.Clin.Endocrinol.Metab 23 425
PubMedID: 19748060

Abstract

The measurement of the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), using immunologically based assays is made difficult by the fact that the processing of the precursor molecules gives rise to a number of different peptides which cross-react with antisera raised against the two hormones. For GLP-1, the picture is further complicated because of the necessity to differentiate between the intestinal and pancreatic proglucagon products. Finally, once secreted, both incretins are rapidly degraded by the enzyme dipeptidyl peptidase-4 (DPP-4) to generate metabolites which have lost their insulinotropic activities. These metabolites are the major circulating forms of the incretins, accounting for 60-80% of total immunoreactive GLP-1 and GIP in the peripheral plasma, while concentrations of the intact forms can be very low and, in some cases, barely detectable. The use of highly specific assays using well-characterised antisera and careful sample handling is therefore required for a reliable determination of incretin hormone concentrations.



        

Title: Saxagliptin: a new dipeptidyl peptidase-4 inhibitor for the treatment of type 2 diabetes
Deacon CF, Holst JJ
Ref: Adv Ther, 26:488, 2009 : PubMed
Abstract


ESTHER: Deacon_2009_Adv.Ther_26_488
PubMedSearch: Deacon 2009 Adv.Ther 26 488
PubMedID: 19444391
Inhibitor(s) related to this paper: Saxagliptin

Abstract

Saxagliptin is a potent and selective reversible inhibitor of dipeptidyl peptidase-4, which is being developed for the treatment of type 2 diabetes. It is absorbed rapidly after oral administration and has a pharmacokinetic profile compatible with once daily dosing. Saxagliptin is metabolized in vivo to form an active metabolite, and both parent drug and metabolite are excreted primarily via the kidneys. Saxagliptin reduces the degradation of the incretin hormone glucagon-like peptide-1, thereby enhancing its actions, and is associated with improved beta-cell function and suppression of glucagon secretion. Clinical trials of up to 24 weeks duration have shown that saxagliptin improves glycemic control in monotherapy and provides additional efficacy when used in combination with other oral antidiabetic agents (metformin, sulfonylurea, thiazolidinedione). Both fasting and postprandial glucose concentrations are reduce leading to clinically meaningful reductions in glycated hemoglobin, and due to the glucose-dependency of its mechanism of action, there is a low risk of hypoglycemia. Saxagliptin is reported to be well tolerated with a side-effect profile similar to placebo. It has a neutral effect on body weight and dose adjustment because of age, gender, or hepatic impairment is not necessary. Saxagliptin is being co-developed by Bristol-Myers-Squibb (New York, NY, USA) and AstraZeneca (Cheshire, UK), and is currently undergoing regulatory review.



        

Title: Measurements of islet function and glucose metabolism with the dipeptidyl peptidase 4 inhibitor vildagliptin in patients with type 2 diabetes
Azuma K, Radikova Z, Mancino J, Toledo FG, Thomas E, Kangani C, Dalla Man C, Cobelli C, Holst JJ and Kelley DE <5 more author(s)> Azuma K, Radikova Z, Mancino J, Toledo FG, Thomas E, Kangani C, Dalla Man C, Cobelli C, Holst JJ, Deacon CF, He Y, Ligueros-Saylan M, Serra D, Foley JE, Kelley DE (- 5)
Ref: J Clinical Endocrinology Metab, 93:459, 2008 : PubMed
Abstract


ESTHER: Azuma_2008_J.Clin.Endocrinol.Metab_93_459
PubMedSearch: Azuma 2008 J.Clin.Endocrinol.Metab 93 459
PubMedID: 18042650

Abstract

OBJECTIVE: Pharmacological inhibition with the dipeptidyl peptidase 4 (DPP-4) inhibitor vildagliptin prolongs the action of endogenously secreted incretin hormones leading to improved glycemic control in patients with type 2 diabetes mellitus (T2DM). We undertook a double-blinded, randomized-order, crossover study to examine the vildagliptin mechanisms of action on islet function and glucose utilization. RESEARCH DESIGN AND
METHODS: Participants with T2DM (n = 16) who had a baseline hemoglobin A(1c) of 7.1 +/- 0.2% completed a crossover study with 6 wk of treatment with vildagliptin and 6 wk with placebo. At the completion of each arm, participants had a study of postprandial metabolism and a two-step glucose clamp performed at 20 and 80 mU/min x m(2) insulin infusions.
RESULTS: Vildagliptin increased postprandial glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide by 3- and 2-fold, respectively, reduced fasting plasma glucose and postprandial plasma glucose by 1.3 +/- 0.3 mmol/liter and 1.6 +/- 0.3 mmol/liter (both P <0.01), and improved glucose responsiveness of insulin secretion by 50% (P < 0.01). Vildagliptin lowered postprandial glucagon by 16% (P <0.01). Examined by glucose clamp, insulin sensitivity and glucose clearance improved after vildagliptin (P < 0.01).
CONCLUSIONS: Vildagliptin improves islet function in T2DM and improves glucose metabolism in peripheral tissues.



        

Title: DPP-4 inhibitor therapy: new directions in the treatment of type 2 diabetes
Deacon CF, Carr RD, Holst JJ
Ref: Front Biosci, 13:1780, 2008 : PubMed
Abstract


ESTHER: Deacon_2008_Front.Biosci_13_1780
PubMedSearch: Deacon 2008 Front.Biosci 13 1780
PubMedID: 17981667

Abstract

Many patients with type 2 diabetes fail to achieve adequate glycaemic control with available treatments, even when used in combination, and eventually develop microvascular and macrovascular diabetic complications. Even intensive interventions to control glycaemia reduce macrovascular complications only minimally. There is, therefore, a need for new agents that more effectively treat the disease, as well as target its prevention, its progression, and its associated complications. One emerging area of interest is centred upon the actions of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which enhance meal-induced insulin secretion and have trophic effects on the beta-cell. GLP-1 also inhibits glucagon secretion, and suppresses food intake and appetite. Two new classes of agents have recently gained regulatory approval for therapy of type 2 diabetes; long-acting stable analogues of GLP-1, the so-called incretin mimetics, and inhibitors of dipeptidyl peptidase 4 (DPP-4, the enzyme responsible for the rapid degradation of the incretin hormones), the so-called incretin enhancers. This article focuses on DPP-4 inhibitors.



        

Title: Alogliptin, a potent and selective dipeptidyl peptidase-IV inhibitor for the treatment of type 2 diabetes
Deacon CF
Ref: Curr Opin Investig Drugs, 9:402, 2008 : PubMed
Abstract


ESTHER: Deacon_2008_Curr.Opin.Investig.Drugs_9_402
PubMedSearch: Deacon 2008 Curr.Opin.Investig.Drugs 9 402
PubMedID: 18393107

Abstract

Takeda San Diego Inc is developing alogliptin, a small-molecule, orally available dipeptidyl peptidase IV (DPP IV) inhibitor, for the potential treatment of type 2 diabetes. In January 2008, Takeda announced that an NDA for alogliptin had been submitted to the FDA.



        

Title: Glucagon-like peptide-1, glucose homeostasis and diabetes
Holst JJ, Deacon CF, Vilsboll T, Krarup T, Madsbad S
Ref: Trends Mol Med, 14:161, 2008 : PubMed
Abstract


ESTHER: Holst_2008_Trends.Mol.Med_14_161
PubMedSearch: Holst 2008 Trends.Mol.Med 14 161
PubMedID: 18353723

Abstract

Incretins, enhancers of insulin secretion, are essential for glucose tolerance, and a reduction in their function might contribute to poor beta-cell function in patients with type-2 diabetes mellitus. However, at supraphysiological doses, the incretin glucagon-like peptide-1 (GLP-1) protects pancreatic beta cells, and inhibits glucagon secretion, gastric emptying and food intake, leading to weight loss. GLP-1 mimetics, which are stable-peptide-based activators of the GLP-1 receptor, and incretin enhancers, which inhibit the incretin-degrading enzyme dipeptidyl peptidase-4, have emerged as therapies for type-2 diabetes and have recently reached the market. The pathophysiological basis the clinical use of these therapeutics is reviewed here.



        

Title: Glucagon-like peptide receptor agonists and dipeptidyl peptidase-4 inhibitors in the treatment of diabetes: a review of clinical trials
Madsbad S, Krarup T, Deacon CF, Holst JJ
Ref: Curr Opin Clin Nutr Metab Care, 11:491, 2008 : PubMed
Abstract


ESTHER: Madsbad_2008_Curr.Opin.Clin.Nutr.Metab.Care_11_491
PubMedSearch: Madsbad 2008 Curr.Opin.Clin.Nutr.Metab.Care 11 491
PubMedID: 18542012

Abstract

PURPOSE OF REVIEW: To discuss the virtues and shortcomings of the glucagon-like peptide-1 receptor agonists and the dipeptidyl peptidase-4 inhibitors in the treatment of type 2 diabetes. RECENT FINDINGS: The injectable glucagon-like peptide-1 receptor agonists exenatide significantly improves glycaemic control, with average reductions in haemoglobin A1c of about 1.0%, fasting plasma glucose of about 1.4 mmol/l, and causes a weight loss of approximately 2-3 kg after 30 weeks of treatment in patients with type 2 diabetes. The adverse effects are transient nausea and vomiting. The long-acting glucagon-like peptide-1 receptor agonists liraglutide and exenatide long-acting release reduce haemoglobin A1c by about 1.0-2.0% and have fewer gastrointestinal side-effects. The orally available dipeptidyl peptidase-4 inhibitors, that is sitagliptin and vildagliptin reduce haemoglobin A1c by 0.5-1.0%, are weight neutral and without gastrointestinal side-effects. SUMMARY: The benefits and position of the glucagon-like peptide-1 analogues and the dipeptidyl peptidase-4 inhibitors in the diabetes treatment algorithm will be clarified when we have long-term trials with hard cardiovascular endpoints and data illustrating the effects on the progression of type 2 diabetes.



        

Title: The effect of dipeptidyl peptidase-4 inhibition on gastric volume, satiation and enteroendocrine secretion in type 2 diabetes: a double-blind, placebo-controlled crossover study
Vella A, Bock G, Giesler PD, Burton DB, Serra DB, Saylan ML, Deacon CF, Foley JE, Rizza RA, Camilleri M
Ref: Clinical Endocrinology (Oxf), 69:737, 2008 : PubMed
Abstract


ESTHER: Vella_2008_Clin.Endocrinol.(Oxf)_69_737
PubMedSearch: Vella 2008 Clin.Endocrinol.(Oxf) 69 737
PubMedID: 18331607

Abstract

OBJECTIVES: The incretin hormone glucagon-like peptide-1 (GLP-1) retards gastric emptying and decreases caloric intake. It is unclear whether increased GLP-1 concentrations achieved by inhibition of the inactivating enzyme dipeptidyl peptidase-4 (DPP-4) alter gastric volumes and satiation in people with type 2 diabetes. METHODS: In a double-blind, placebo-controlled crossover design, 14 subjects with type 2 diabetes received vildagliptin (50 mg bid) or placebo for 10 days in random order separated by a 2-week washout. On day 7, fasting and postmeal gastric volumes were measured by a (99m)Tc single-photon emission computed tomography (SPECT) method. On day 8, a liquid Ensure meal was consumed at 30 ml/min, and maximum tolerated volume (MTV) and symptoms 30 min later were measured using a visual analogue scale (VAS) to assess effects on satiation. On day 10, subjects ingested water until maximum satiation was achieved. The volume ingested was recorded and symptoms similarly measured using a VAS. RESULTS: Vildagliptin raised plasma GLP-1 concentrations. However, fasting (248 +/- 21 vs. 247 +/- 19 ml, P = 0.98) and fed (746 +/- 28 vs. 772 +/- 26 ml, P = 0.54) gastric volumes did not differ when subjects received vildagliptin or placebo. Treatment with vildagliptin did not alter the MTV of Ensure (1657 +/- 308 vs. 1389 +/- 197 ml, P = 0.15) or water compared to placebo (1371 +/- 141 vs. 1172 +/- 156 ml, P = 0.23). Vildagliptin was associated with decreased peptide YY (PYY) concentrations 60 min after initiation of the meal (166 +/- 27 vs. 229 +/- 34 pmol/l, P = 0.01). CONCLUSIONS: Vildagliptin does not alter satiation or gastric volume in people with type 2 diabetes despite elevated GLP-1 concentrations. Compensatory changes in enteroendocrine secretion could account for the lack of gastrointestinal symptoms.



        

Title: The dipeptidyl peptidase IV inhibitor vildagliptin suppresses endogenous glucose production and enhances islet function after single-dose administration in type 2 diabetic patients
Balas B, Baig MR, Watson C, Dunning BE, Ligueros-Saylan M, Wang Y, He YL, Darland C, Holst JJ and DeFronzo RA <4 more author(s)> Balas B, Baig MR, Watson C, Dunning BE, Ligueros-Saylan M, Wang Y, He YL, Darland C, Holst JJ, Deacon CF, Cusi K, Mari A, Foley JE, DeFronzo RA (- 4)
Ref: J Clinical Endocrinology Metab, 92:1249, 2007 : PubMed
Abstract


ESTHER: Balas_2007_J.Clin.Endocrinol.Metab_92_1249
PubMedSearch: Balas 2007 J.Clin.Endocrinol.Metab 92 1249
PubMedID: 17244786

Abstract

AIMS/HYPOTHESIS: Vildagliptin is a selective dipeptidyl peptidase IV inhibitor that augments meal-stimulated levels of biologically active glucagon-like peptide-1. Chronic vildagliptin treatment decreases postprandial glucose levels and reduces hemoglobin A1c in type 2 diabetic patients. However, little is known about the mechanism(s) by which vildagliptin promotes reduction in plasma glucose concentration. METHODS: Sixteen patients with type 2 diabetes (age, 48+/-3 yr; body mass index, 34.4+/-1.7 kg/m2; hemoglobin A1c, 9.0+/-0.3%) participated in a randomized, double-blind, placebo-controlled trial. On separate days patients received 100 mg vildagliptin or placebo at 1730 h followed 30 min later by a meal tolerance test (MTT) performed with double tracer technique (3-(3)H-glucose iv and 1-(14)C-glucose orally). RESULTS: After vildagliptin, suppression of endogenous glucose production (EGP) during 6-h MTT was greater than with placebo (1.02+/-0.06 vs. 0.74+/-0.06 mg.kg-1.min-1; P=0.004), and insulin secretion rate increased by 21% (P=0.003) despite significant reduction in mean plasma glucose (213+/-4 vs. 230+/-4 mg/dl; P=0.006). Consequently, insulin secretion rate (area under the curve) divided by plasma glucose (area under the curve) increased by 29% (P=0.01). Suppression of plasma glucagon during MTT was 5-fold greater with vildagliptin (P<0.02). The decline in EGP was positively correlated (r=0.55; P<0.03) with the decrease in fasting plasma glucose (change=-14 mg/dl). CONCLUSIONS: During MTT, vildagliptin augments insulin secretion and inhibits glucagon release, leading to enhanced suppression of EGP. During the postprandial period, a single dose of vildagliptin reduced plasma glucose levels by enhancing suppression of EGP.



        

Title: Incretin-based treatment of type 2 diabetes: glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors
Deacon CF
Ref: Diabetes Obes Metab, 9 Suppl 1:23, 2007 : PubMed
Abstract


ESTHER: Deacon_2007_Diabetes.Obes.Metab_9 Suppl 1_23
PubMedSearch: Deacon 2007 Diabetes.Obes.Metab 9 Suppl 1 23
PubMedID: 17877544

Abstract

Incretins are gut peptides that potentiate nutrient-stimulated insulin secretion following meal ingestion. Activities of the dominant incretins, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide, include glucose-dependent stimulation of insulin secretion and, in preclinical models, improvement in islet beta-cell mass. GLP-1 additionally reduces glucagon secretion, inhibits gastric emptying and promotes satiety. Patients with type 2 diabetes mellitus (T2DM) exhibit reduced total and intact GLP-1 levels, and exogenous administration of the hormone via continuous infusion results in glucose profiles similar to those in non-diabetic subjects. Incretins are rapidly degraded by dipeptidyl peptidase-4 (DPP-4). Thus, strategies to enhance incretin activity have included development of GLP-1 receptor agonists resistant to the action of DPP-4 (e.g. exenatide and liraglutide) and DPP-4 inhibitors that act to increase concentrations of endogenous intact incretins (e.g. sitagliptin and vildagliptin). Clinical trials of these incretin-based therapies have shown them to be effective in improving glycaemic control in patients with T2DM.



        

Title: Dipeptidyl peptidase 4 inhibition with sitagliptin: a new therapy for type 2 diabetes
Deacon CF
Ref: Expert Opin Investig Drugs, 16:533, 2007 : PubMed
Abstract


ESTHER: Deacon_2007_Expert.Opin.Investig.Drugs_16_533
PubMedSearch: Deacon 2007 Expert.Opin.Investig.Drugs 16 533
PubMedID: 17371200

Abstract

Sitagliptin is a once-daily, orally active, competitive and fully reversible inhibitor of dipeptidyl peptidase 4, the enzyme that is responsible for the rapid degradation of the incretin hormone glucagon-like peptide-1. It is the first in this new class of antihyperglycaemic agents to gain regulatory approval for the treatment of Type 2 diabetes, both as a monotherapy and for use in combination with metformin or a thiazolidinedione. In clinical trials of < or = 1-year duration, sitagliptin improves glycaemic control by reducing both fasting and postprandial glucose concentrations, leading to clinically meaningful reductions in glycosylated haemoglobin levels. It is safe and well tolerated, with a side-effect profile that is similar to that of the placebo, a low incidence of hypoglycaemia and body weight neutrality. Further clinical experience with sitagliptin will reveal its long-term durability, safety and efficacy.



        

Title: Dipeptidyl peptidase IV inhibitors: a promising new therapeutic approach for the management of type 2 diabetes
Deacon CF, Holst JJ
Ref: International Journal of Biochemistryistry & Cell Biology, 38:831, 2006 : PubMed
Abstract


ESTHER: Deacon_2006_Int.J.Biochem.Cell.Biol_38_831
PubMedSearch: Deacon 2006 Int.J.Biochem.Cell.Biol 38 831
PubMedID: 16242377

Abstract

Glucagon-like peptide-1 is an insulinotropic hormone with antidiabetic potential due to its spectrum of effects, which include glucose-dependent stimulation of insulin and inhibition of glucagon secretion, tropic effects on the pancreatic beta-cells, inhibition of gastric emptying and the reduction of appetite. Glucagon-like peptide-1 is, however, extremely rapidly inactivated by the serine peptidase, dipeptidyl peptidase IV, so that the native peptide is not useful clinically. A new approach to utilise the beneficial effects of glucagon-like peptide-1 in the treatment of type 2 diabetes has been the development of orally active dipeptidyl peptidase IV inhibitors. Preclinical studies have demonstrated that this approach is effective in enhancing endogenous levels of glucagon-like peptide-1, resulting in improved glucose tolerance in glucose-intolerant and diabetic animal models. In recent studies of 3-12 months duration in patients with type 2 diabetes, dipeptidyl peptidase IV inhibitors have proved efficacious, both as monotherapy and when given in combination with metformin. Fasting and postprandial glucose concentrations were reduced, leading to reductions in glycosylated haemoglobin levels, while beta-cell function was preserved. Current information suggests dipeptidyl peptidase IV inhibitors are body weight neutral and are well tolerated. A number of dipeptidyl peptidase IV inhibitors are now in the late stages of clinical development. These have different properties, in terms of their duration of action and anticipated dosing frequency, but data from protracted dosing studies is presently not available to allow comparison of their clinical efficacy.



        

Title: Effect of single oral doses of sitagliptin, a dipeptidyl peptidase-4 inhibitor, on incretin and plasma glucose levels after an oral glucose tolerance test in patients with type 2 diabetes
Herman GA, Bergman A, Stevens C, Kotey P, Yi B, Zhao P, Dietrich B, Golor G, Schrodter A and Wagner JA <17 more author(s)> Herman GA, Bergman A, Stevens C, Kotey P, Yi B, Zhao P, Dietrich B, Golor G, Schrodter A, Keymeulen B, Lasseter KC, Kipnes MS, Snyder K, Hilliard D, Tanen M, Cilissen C, De Smet M, De Lepeleire I, Van Dyck K, Wang AQ, Zeng W, Davies MJ, Tanaka W, Holst JJ, Deacon CF, Gottesdiener KM, Wagner JA (- 17)
Ref: J Clinical Endocrinology Metab, 91:4612, 2006 : PubMed
Abstract


ESTHER: Herman_2006_J.Clin.Endocrinol.Metab_91_4612
PubMedSearch: Herman 2006 J.Clin.Endocrinol.Metab 91 4612
PubMedID: 16912128

Abstract

CONTEXT: In response to a meal, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are released and modulate glycemic control. Normally these incretins are rapidly degraded by dipeptidyl peptidase-4 (DPP-4). DPP-4 inhibitors are a novel class of oral antihyperglycemic agents in development for the treatment of type 2 diabetes. The degree of DPP-4 inhibition and the level of active incretin augmentation required for glucose lowering efficacy after an oral glucose tolerance test (OGTT) were evaluated. OBJECTIVE: The objective of the study was to examine the pharmacodynamics, pharmacokinetics, and tolerability of sitagliptin. DESIGN: This was a randomized, double-blind, placebo-controlled, three-period, single-dose crossover study. SETTING: The study was conducted at six investigational sites. PATIENTS: The study population consisted of 58 patients with type 2 diabetes who were not on antihyperglycemic agents. INTERVENTIONS: Interventions included sitagliptin 25 mg, sitagliptin 200 mg, or placebo. MAIN OUTCOME MEASURES: Measurements included plasma DPP-4 activity; post-OGTT glucose excursion; active and total incretin GIP levels; insulin, C-peptide, and glucagon concentrations; and sitagliptin pharmacokinetics.
RESULTS: Sitagliptin dose-dependently inhibited plasma DPP-4 activity over 24 h, enhanced active GLP-1 and GIP levels, increased insulin/C-peptide, decreased glucagon, and reduced glycemic excursion after OGTTs administered at 2 and 24 h after single oral 25- or 200-mg doses of sitagliptin. Sitagliptin was generally well tolerated, with no hypoglycemic events.
CONCLUSIONS: In this study in patients with type 2 diabetes, near maximal glucose-lowering efficacy of sitagliptin after single oral doses was associated with inhibition of plasma DPP-4 activity of 80% or greater, corresponding to a plasma sitagliptin concentration of 100 nm or greater, and an augmentation of active GLP-1 and GIP levels of 2-fold or higher after an OGTT.



        

Title: The glucagon-like peptide-1 metabolite GLP-1-(9-36) amide reduces postprandial glycemia independently of gastric emptying and insulin secretion in humans
Meier JJ, Gethmann A, Nauck MA, Gotze O, Schmitz F, Deacon CF, Gallwitz B, Schmidt WE, Holst JJ
Ref: American Journal of Physiology Endocrinol Metab, 290:E1118, 2006 : PubMed
Abstract


ESTHER: Meier_2006_Am.J.Physiol.Endocrinol.Metab_290_E1118
PubMedSearch: Meier 2006 Am.J.Physiol.Endocrinol.Metab 290 E1118
PubMedID: 16403774

Abstract

Glucagon-like peptide 1 (GLP-1) lowers glycemia by modulating gastric emptying and endocrine pancreatic secretion. Rapidly after its secretion, GLP-1-(7-36) amide is degraded to the metabolite GLP-1-(9-36) amide. The effects of GLP-1-(9-36) amide in humans are less well characterized. Fourteen healthy volunteers were studied with intravenous infusion of GLP-1-(7-36) amide, GLP-1-(9-36) amide, or placebo over 390 min. After 30 min, a solid test meal was served, and gastric emptying was assessed. Blood was drawn for GLP-1 (total and intact), glucose, insulin, C-peptide, and glucagon measurements. Administration of GLP-1-(7-36) amide and GLP-1-(9-36) amide significantly raised total GLP-1 plasma levels. Plasma concentrations of intact GLP-1 increased to 21 +/- 5 pmol/l during the infusion of GLP-1-(7-36) amide but remained unchanged during GLP-1-(9-36) amide infusion [5 +/- 3 pmol/l; P < 0.001 vs. GLP-1-(7-36) amide administration]. GLP-1-(7-36) amide reduced fasting and postprandial glucose concentrations (P < 0.001) and delayed gastric emptying (P < 0.001). The GLP-1 metabolite had no influence on insulin or C-peptide concentrations. Glucagon levels were lowered by GLP-1-(7-36) amide but not by GLP-1-(9-36) amide. However, the postprandial rise in glycemia was reduced significantly (by approximately 6 mg/dl) by GLP-1-(9-36) amide (P < 0.05). In contrast, gastric emptying was completely unaffected by the GLP-1 metabolite. The GLP-1 metabolite lowers postprandial glycemia independently of changes in insulin and glucagon secretion or in the rate of gastric emptying. Most likely, this is because of direct effects on glucose disposal. However, the glucose-lowering potential of GLP-1-(9-36) amide appears to be small compared with that of intact GLP-1-(7-36) amide.



        

Title: Plasma dipeptidyl peptidase-IV activity in patients with type-2 diabetes mellitus correlates positively with HbAlc levels, but is not acutely affected by food intake
Ryskjaer J, Deacon CF, Carr RD, Krarup T, Madsbad S, Holst J, Vilsboll T
Ref: European Journal of Endocrinology, 155:485, 2006 : PubMed
Abstract


ESTHER: Ryskjaer_2006_Eur.J.Endocrinol_155_485
PubMedSearch: Ryskjaer 2006 Eur.J.Endocrinol 155 485
PubMedID: 16914604

Abstract

OBJECTIVE: Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide are incretin hormones, secreted in response to meal ingestion. The incretin hormones stimulate insulin secretion and are essential for the maintenance of normal plasma glucose concentrations. Both incretin hormones are metabolized quickly by the enzyme dipeptidyl peptidase-IV (DPP-IV). It is well known that type-2 diabetic patients have an impaired incretin effect. Therefore, the aim of the present study was to investigate plasma DPP-IV activity in the fasting and the postprandial state in type-2 diabetic patients and control subjects. DESIGN: The study included two protocols. Protocol one involved 40 fasting type-2 diabetic patients (28 men); age 61 +/- 1.4 (mean +/- s.e.m.) years; body mass index (BMI) 31 +/- 0.6 kg/m(2); HbAlc 7.2 +/- 0.2%; and 20 matched control subjects (14 men) were studied. Protocol two involved eight type-2 diabetic patients (six men); age 63 +/- 1.2 years; BMI 33 +/- 0.5 kg/m(2); HbAlc 7.5 +/- 0.4%; eight matched control subjects were included.
METHODS: In protocol one, fasting values of DPP-IV activity were evaluated and in protocol two, postprandial DPP-IV activity during a standard meal test (566 kcal) was estimated.
RESULTS: Mean fasting plasma DPP-IV activity (expressed as degradation of GLP-1) was significantly higher in this patient group compared with the control subjects (67.5 +/- 1.9 vs 56.8 +/- 2.2 fmol GLP-1/h (mean +/- s.e.m.); P=0.001). In the type-2 diabetic patients, DPP-IV activity was positively correlated to FPG and HbAlc and negatively to the duration of diabetes and age of the patients. No postprandial changes were seen in plasma DPP-IV activity in any of the groups.
CONCLUSIONS: Plasma DPP-IVactivity increases in the fasting state and is positively correlated to FPG and HbAlc levels, but plasma DPP-IV activity is not altered following meal ingestion and acute changes in plasma glucose.



        

Title: The metabolite generated by dipeptidyl-peptidase 4 metabolism of glucagon-like peptide-1 has no influence on plasma glucose levels in patients with type 2 diabetes
Zander M, Madsbad S, Deacon CF, Holst JJ
Ref: Diabetologia, 49:369, 2006 : PubMed
Abstract


ESTHER: Zander_2006_Diabetologia_49_369
PubMedSearch: Zander 2006 Diabetologia 49 369
PubMedID: 16385384

Abstract

AIM/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) is metabolised by the enzyme dipeptidyl-peptidase 4 (DPP-4), generating a metabolite with potential antagonistic properties. This study was conducted to evaluate the effect of that metabolite on plasma glucose levels in patients with type 2 diabetes. MATERIALS AND
METHODS: The randomised crossover study consisted of five regimens: (1) i.v. infusion of GLP-1 (1.2 pmol kg(-1) min(-1); IV); (2 and 3) s.c. infusion of GLP-1 (2.4 and 9.6 pmol kg(-1) min(-1); LSC, HSC); (4) s.c. infusion of GLP-1 (2.4 pmol kg(-1) min(-1)) in combination with a DPP-4 inhibitor (IB); and (5) s.c. infusion of saline (154 mmol NaCl/l; SAL). Seven patients with type 2 diabetes participated in all protocols.
RESULTS: Plasma levels of intact GLP-1 increased from 7+/-1 (SAL) to 17+/-3 (LSC), 61+/-7 (IB), 62+/-5 (IV) and 94+/-10 (9.6 s.c.) pmol/l, p<0.0001. Plasma concentrations of the metabolite increased from 1+/-3 (SAL) and 2+/-6 (IB) pmol/l to 42+/-4 (LSC), 64+/-8 (IV) and 327+/-16 (HSC) pmol/l, p<0.0001. Mean plasma glucose levels at 6 h decreased from 12.4+/-1.1 (SAL) mmol/l to 10.4+/-1.1 (LSC), 8.6+/-0.6 (IB), 8.8+/-0.8 (IV) and 9.1+/-0.9 (HSC) mmol/l, p<0.0001. CONCLUSIONS/INTERPRETATION: At approximately similar concentrations of intact GLP-1 (IV, IB, HSC), but with widely ranging metabolite concentrations, the effect on plasma glucose levels was equal, indicating that the presence of the metabolite does not antagonise the glucose-lowering effect of GLP-1.



        

Title: MK-431 (Merck)
Deacon CF
Ref: Curr Opin Investig Drugs, 6:419, 2005 : PubMed
Abstract


ESTHER: Deacon_2005_Curr.Opin.Investig.Drugs_6_419
PubMedSearch: Deacon 2005 Curr.Opin.Investig.Drugs 6 419
PubMedID: 15898349

Abstract

Merck & Co is developing MK-431, the lead from a series of dipeptidyl peptidase IV inhibitors that enhance endogenous glucagon-like peptide-1 levels, for the potential treatment of type 2 diabetes. Phase III studies were initiated in the second quarter of 2004.



        

Title: Vildagliptin, a dipeptidyl peptidase-IV inhibitor, improves model-assessed beta-cell function in patients with type 2 diabetes
Mari A, Sallas WM, He YL, Watson C, Ligueros-Saylan M, Dunning BE, Deacon CF, Holst JJ, Foley JE
Ref: J Clinical Endocrinology Metab, 90:4888, 2005 : PubMed
Abstract


ESTHER: Mari_2005_J.Clin.Endocrinol.Metab_90_4888
PubMedSearch: Mari 2005 J.Clin.Endocrinol.Metab 90 4888
PubMedID: 15886245

Abstract

AIMS/HYPOTHESIS: The dipeptidyl peptidase IV inhibitor, vildagliptin, increases levels of intact glucagon-like peptide-1 (GLP-1) and improves glycemic control in patients with type 2 diabetes. Although GLP-1 is known to stimulate insulin secretion, vildagliptin does not affect plasma insulin levels in diabetic patients, suggesting that more sophisticated measures are necessary to ascertain the influence of vildagliptin on beta-cell function.
METHODS: This study examined the effects of 28-d treatment with vildagliptin (100 mg, twice daily; n = 9) vs. placebo (n = 11) on beta-cell function in diabetic patients using a mathematical model that describes the insulin secretory rate as a function of glucose levels (beta-cell dose response), the change in glucose with time (derivative component), and a potentiation factor, which is a function of time and may reflect the actions of nonglucose secretagogues and other factors.
RESULTS: Vildagliptin significantly increased the insulin secretory rate at 7 mmol/liter glucose (secretory tone), calculated from the dose response; the difference in least squares mean (deltaLSM) was 101 +/- 51 pmol.min(-1).m(-2) (P = 0.002). The slope of the beta-cell dose response, the derivative component, and the potentiation factor were not affected. Vildagliptin also significantly decreased mean prandial glucose (deltaLSM, -1.2 +/- 0.4 mmol/liter; P = 0.01) and glucagon (deltaLSM, -10.7 +/- 4.8 ng/liter; P = 0.03) levels and increased plasma levels of intact GLP-1 (deltaLSM, +10.8 +/- 1.6 pmol/liter; P < 0.0001) and gastric inhibitory polypeptide (deltaLSM, +43.4 +/- 9.4 pmol/liter; P < 0.0001) relative to placebo. CONCLUSION: Vildagliptin is an incretin degradation inhibitor that improves beta-cell function in diabetic patients by increasing the insulin secretory tone.



        

Title: Neutral endopeptidase 24.11 and dipeptidyl peptidase IV are both mediators of the degradation of glucagon-like peptide 1 in the anaesthetised pig
Plamboeck A, Holst JJ, Carr RD, Deacon CF
Ref: Diabetologia, 48:1882, 2005 : PubMed
Abstract


ESTHER: Plamboeck_2005_Diabetologia_48_1882
PubMedSearch: Plamboeck 2005 Diabetologia 48 1882
PubMedID: 16025254

Abstract

AIMS/HYPOTHESIS: The incretin hormone glucagon-like peptide 1 (GLP-1) has antihyperglycaemic effects, but its therapeutic usefulness is limited by its metabolic instability. Dipeptidyl peptidase IV (DPP-IV) is established as the primary inactivating enzyme, but the roles of other enzymes remain unclear.
METHODS: The effect of candoxatril, a selective inhibitor of neutral endopeptidase (NEP) 24.11, on GLP-1 pharmacokinetics/pharmacodynamics with or without DPP-IV inhibition was examined in anaesthetised pigs.
RESULTS: During GLP-1 infusion, candoxatril doubled C-terminal immunoreactivity, improving the pharmacokinetics (t(1/2) 2.3+/-0.1 to 8.8+/-1.2 min; metabolic clearance rate [MCR] 20.4+/-3.4 to 4.8+/-0.4 ml.kg(-1). min(-1); p<0.01), but had no effect upon intact GLP-1 (t(1/2) 1.4+/-0.1 to 1.6+/-0.1 min; MCR 47.9+/-8.0 to 38.8+/-5.0 ml.kg(-1).min(-1)). Insulin responses to intravenous glucose were unaffected by candoxatril, but glucose tolerance was improved (DeltaAUC(min 27-87) 118+/-5 to 74+/-14 min.mmol.l(-1); glucose elimination rate [k] 6.6+/-0.5 to 8.6+/-0.5%; p<0.05). When candoxatril was co-administered with valine pyrrolidide (a DPP-IV inhibitor), changes in C-terminal GLP-1 pharmacokinetics mirrored those seen when candoxatril alone was administered (t(1/2) 2.7+/-0.3 and 7.7+/-0.8 min; MCR 17.3+/-2.6 and 6.5+/-0.8 ml.kg(-1).min(-1) for valine pyrrolidide without and with candoxatril, respectively). However, intact GLP-1 pharmacokinetics were improved (t(1/2) 2.8+/-0.3 and 7.5+/-0.6 min; MCR 18.3+/-0.6 and 9.4+/-0.9 ml.kg(-1).min(-1); p<0.02), potentiating the antihyperglycaemic/insulinotropic effects of GLP-1 (glucose deltaAUC(min 27- 87) 103+/-8 to 62+/-14 min.mmol.l(-1); k 6.8+/-0.4 to 11.4+/-1.4%; insulin deltaAUC(min 27-87) 3,680+/-738 to 7,201+/-1,183 min.pmol.l(-1); p<0.05). CONCLUSIONS/INTERPRETATION: This study confirms a role for NEP-24.11 in GLP-1 metabolism in vivo, suggesting that up to 50% of GLP-1 entering the circulation may be degraded by NEP-24.11. Furthermore, combined inhibition of DPP-IV and NEP-24.11 is superior to DPP-IV inhibition alone in preserving intact GLP-1, which raises the possibility that the combination has therapeutic potential.



        

Title: Circulation and degradation of GIP and GLP-1
Deacon CF
Ref: Hormone & Metabolic Research, 36:761, 2004 : PubMed
Abstract


ESTHER: Deacon_2004_Horm.Metab.Res_36_761
PubMedSearch: Deacon 2004 Horm.Metab.Res 36 761
PubMedID: 15655705

Abstract

The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are secreted from the intestinal K- and L-cells, respectively, but are immediately subject to rapid degradation. GLP-1 is found in two active forms, amidated GLP-1 (7-36) amide and glycine-extended GLP-1 (7-37), while GIP exists as a single 42 amino acid peptide. The aminopeptidase, dipeptidyl peptidase IV (DPP IV), which is found in the endothelium of the local capillary bed within the intestinal wall, is important for the initial inactivation of both peptides, with GLP-1 being particularly readily degraded. DPP IV cleavage generates N-terminally truncated metabolites (GLP-1 (9-36) amide / (9-37) and GIP (3-42)), which are the major circulating forms. Subsequently, the peptides may be degraded by other enzymes and extracted in an organ-specific manner. However, other endogenous metabolites have not yet been identified, possibly because existing assays are unable either to recognize them or to differentiate them from the primary metabolites. Neutral endopeptidase 24.11 has been demonstrated to be able to degrade GLP-1 in vivo, but its relevance in GIP metabolism has not yet been established. Intact GLP-1 and GIP are inactivated during passage across the hepatic bed by DPP IV associated with the hepatocytes, and further degraded by the peripheral tissues, while the kidney is important for the final elimination of the metabolites.