High plasma levels of pro-NT are associated with increased colon cancer risk.

Emerging data supports a potential role of neurotensin (NT) in the development of obesity, obesity-associated comorbidities, and certain cancers. The association of NT with colon cancer risk has not been explicitly explored. We determined plasma levels of pro-NT, a stable NT precursor fragment, in 223 incident colon cancer patients and 223 age-, gender-, BMI-matched population controls participating in a population-based case-control study of colon cancer. On average, the cases have significantly higher levels of pro-NT than the controls (median = 205.6 pmol/L vs 183.1 pmol/L, respectively; P = 0.02). Multivariate logistic regression models, adjusted for age, gender, BMI, family history of colorectal cancer, smoking, diabetes mellitus, alcohol, and non-steroidal anti-inflammatory drugs use, show statistically significant risk associations: for continuous measure of pro-NT, the OR estimate was 1.30 (95% CI =1.03-1.64; P = 0.026) for each increment of 175 pmol/L; for dichotomized measure of pro-NT, the OR estimate was 1.75 (95% CI = 1.12-2.74; P = 0.025) for those in the top quartile comparing to the other participants. Our results support circulating levels of pro-NT as a novel risk biomarker for colon cancer.

Drinking to death: Hyponatraemia induced by synthetic phenethylamines.

Synthetic phenethylamines are widely abused drugs, comprising new psychoactive substances such as synthetic cathinones, but also well-known amphetamines such as methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy). Cathinones and amphetamines share many toxicodynamic mechanisms. One of their potentially life-threatening consequences, particularly of MDMA, is serotonin-mediated hyponatraemia. Herein, we review the state of the art on phenethylamine-induced hyponatremia; discuss the mechanisms involved; and present the preventive and therapeutic measures. Hyponatraemia mediated by phenethylamines results from increased secretion of antidiuretic hormone (ADH) and consequent kidney water reabsorption, additionally involving diaphoresis and polydipsia. Data for MDMA suggest that acute hyponatraemia elicited by cathinones may also be a consequence of metabolic activation. The literature often reveals hyponatraemia-associated complications such as cerebral oedema, cerebellar tonsillar herniation and coma that may evolve to a fatal outcome, particularly in women. Ready availability of fluids and the recommendation to drink copiously at the rave scene to counteract hyperthermia, often precipitate water intoxication. Users should be advised about the importance of controlling fluid intake while using phenethylamines. At early signs of adverse effects, medical assistance should be promptly sought. Severe hyponatraemia (<130 mmol sodium/L plasma) may be corrected with hypertonic saline or suppression of fluid intake. Also, clinicians should be made aware of the hyponatraemic potential of these drugs and encouraged to report future cases of toxicity to increase knowledge on this potentially lethal outcome.

Functional Characterization of Human ProNGF and NGF Mutants: Identification of NGF P61SR100E as a "Painless" Lead Investigational Candidate for Therapeutic Applications.

BACKGROUND: Nerve Growth Factor (NGF) holds a great therapeutic promise for Alzheimer's disease, diabetic neuropathies, ophthalmic diseases, dermatological ulcers. However, the necessity for systemic delivery has hampered the clinical applications of NGF due to its potent pro-nociceptive action. A "painless" human NGF (hNGF R100E) mutant has been engineered. It has equal neurotrophic potency to hNGF but a lower nociceptive activity. We previously described and characterized the neurotrophic and nociceptive properties also of the hNGF P61S and P61SR100E mutants, selectively detectable against wild type hNGF. However, the reduced pain-sensitizing potency of the "painless" hNGF mutants has not been quantified. OBJECTIVES AND RESULTS: Aiming at the therapeutic application of the "painless" hNGF mutants, we report on the comparative functional characterization of the precursor and mature forms of the mutants hNGF R100E and hNGF P61SR100E as therapeutic candidates, also in comparison to wild type hNGF and to hNGF P61S. The mutants were assessed by a number of biochemical, biophysical methods and assayed by cellular assays. Moreover, a highly sensitive ELISA for the detection of the P61S-tagged mutants in biological samples has been developed. Finally, we explored the pro-nociceptive effects elicited by hNGF mutants in vivo, demonstrating an expanded therapeutic window with a ten-fold increase in potency. CONCLUSIONS: This structure-activity relationship study has led to validate the concept of developing painless NGF as a therapeutic, targeting the NGF receptor system and supporting the choice of hNGF P61S R100E as the best candidate to advance in clinical development. Moreover, this study contributes to the identification of the molecular determinants modulating the properties of the hNGF "painless" mutants.

Hepatitis B Virus Revaccination With Standard Versus Pre-S Vaccine in Previously Immunized Patients With Celiac Disease.

OBJECTIVE: Previous studies have suggested that hepatitis B virus (HBV) vaccines may be less immunogenic in individuals with celiac disease (CD). A pre-S vaccine (Sci-B-Vac) has demonstrated superior immunogenicity compared with standard HBV vaccines in several diseases. We compared the short-term immunogenicity of a pre-S vaccine with a HBV vaccine (Engerix B) for repeat vaccination of seronegative, previously immunized patients with CD. METHODS: Participants were 1 to 18-year-old children with CD who despite standard HBV vaccines in infancy had nonprotective hepatitis B surface antibody (HBs-Ab) concentrations (≤10 mIU/mL). Patients were randomized to receive either Engerix B or pre-S vaccine. HBs-Ab concentrations were measured 1 month after the first dose. For those who had not responded after 1 dose, measurement was repeated after the third dose. RESULTS: Children (n = 82) were analyzed (42 pre-S vaccine and 40 Engerix B). Baseline characteristics were similar for both groups, including gluten-free diet status. Both arms showed high response rates following the first injection: 41 (98%) versus 35 (87%) for pre-S vaccine and Engerix B recipients, respectively (P = 0.08). All other patients responded when measured after dose 3. HBs-Ab concentrations (mIU/mL) were higher in the pre-S vaccine group (median 925, interquartile range [IQR] 424-1000) than the Engerix B group (median 363, IQR 106-996, P = 0.005). Twenty (48%) of the pre-S vaccine recipients were "high responders" (>1000 mIU/mL) versus 10 (25%) in Engerix B recipients (P = 0.008). CONCLUSIONS: Both vaccines elicited adequate booster responses in most previously vaccinated patients with CD with nonprotective HBs-Ab concentrations. Pre-S vaccine administration resulted in higher Hbs-Ab concentrations. Our data suggest that a single dose of either vaccine is sufficient to raise titers to protective levels in most patients with CD.

Plasma B-type natriuretic peptide (BNP) in acute Puumala hantavirus infection.

BACKGROUND: Nephropathia epidemica (NE) is a haemorrhagic fever with renal syndrome (HFRS) caused by Puumala hantavirus (PUUV). Acute infection causes transient kidney injury, permeability disorder, and fluid retention, for example. METHODS: B-type natriuretic peptide (BNP) and N-terminal peptide (NT-proBNP) during NE were investigated; disease severity and development of clinical symptoms were considered. RESULTS: Mean concentrations were 80.2 pg/mL and 55.2 pg/mL for BNP, and 2362.5 pg/mL and 1057.0 pg/mL for NT-proBNP in males and females, respectively. Hospitalization was 6.3 versus 5.2 days (P = 0.01) and 5.9 versus 4.4 days (P = 0.01) for patients with elevated BNP (> 100 pg/mL) or NT-proBNP (> 300 pg/mL), respectively, compared to those with normal peptide concentrations. Weight change during hospitalization was -2.8 or -0.3 kg (P <0.05) in patients with elevated or normal BNP, respectively. Heart rate (r = -0.46, P = 0.001 and r = -0.37, P = 0.01), creatinine clearance (r = -0.46, P = 0.001 and r = -0.56, P = 0.000), blood haemoglobin concentration (r = -0.55, P = 0.000 and r = -0.52, P = 0.000), and C-reactive protein (r = -0.47, P = 0.001 and r = -0.36, P = 0.01) measured when the peptide samples were collected correlated with BNP and NT-proBNP, respectively. In addition, anterior chamber depth of eye and plasma BNP (r = -0.39, P < 0.05) displayed a correlation. CONCLUSIONS: BNP and NT-proBNP levels are associated with severity of several clinical features of acute NE.

Guidance of antibiotic therapy with procalcitonin in lower respiratory tract infections: insights into the ProHOSP study.

In the recently published ProHOSP trial, we investigated the safety and external validity of procalcitonin (PCT) guidance for antibiotic therapy in patients with different severities of lower respiratory tract infections, mainly pneumonia. In this addendum, we aim to extend the initial report by reinforcing the rational of the PCT algorithm and by presenting more detailed data on antibiotic therapy in different severities of infection. In milder, mostly viral respiratory infections (i.e. acute or chronic bronchitis) initial prescription of antibiotics was markedly reduced by PCT guidance because PCT remained low in most patients. In pneumonia, PCT showed a severity-dependent increase and highest levels in patients with positive blood cultures. Thus, the main effect in pneumonia was a severity- and bacteremia-adapted reduction of the duration of antibiotic courses. In lower respiratory tract infections, PCT guidance had a differential effect on antibiotic exposure depending on the underlying type and severity of respiratory tract infection.

Sudden death: do cytokines and prothrombotic peptides contribute to the occurrence of ventricular fibrillation during acute myocardial infarction?

AIMS: Sudden cardiac death (SCD) is frequently caused by ventricular fibrillation (VF) occurring in the course of acute myocardial infarction (AMI). It has not been investigated yet, to what extent markers of coagulation activation and inflammation differ between patients with and without VF in the acute phase of AMI.

Effectiveness of a procalcitonin algorithm to guide antibiotic therapy in respiratory tract infections outside of study conditions: a post-study survey.

All published evidence on procalcitonin (PCT)-guided antibiotic therapy was obtained in trials where physicians knew that they were being monitored, possibly resulting in higher adherence to the PCT algorithm. This study investigates the effectiveness of PCT guidance in an observational quality control survey. We monitored antibiotic therapy and algorithm adherence in consecutive patients with respiratory tract infections admitted to the Kantonsspital Aarau, Switzerland, between May 2008 and February 2009. The results were compared to the site-specific results of the former ProHOSP study. Overall and more pronounced for patients with community-acquired pneumonia, the median duration of antibiotic treatment in this survey was shorter than the ProHOSP control patients (6 vs. 7 days, P = 0.048 and 7 vs. 9 days, P < 0.001). In 72.5% of patients, antibiotics were administered according to the prespecified PCT algorithm. No significant differences concerning adverse medical outcome could be detected. This study mirrors the use of PCT-guided antibiotic therapy in clinical practice, outside of trial conditions. If algorithm adherence is reinforced, antibiotic exposure can be markedly reduced with subsequent reduction of antibiotic-associated side effects and antibiotic resistance. The integration of the PCT algorithm into daily practice requires ongoing reinforcement and involves a learning process of the prescribing physicians.

Glucagon-like peptide 1 and its derivatives in the treatment of diabetes.

Glucagon-like peptide 1 (GLP-1) was discovered as an insulinotropic gut hormone, suggesting a physiological role as an incretin hormone, i.e., being responsible, in part, for the higher insulin secretory response after oral as compared to intravenous glucose administration. This difference, the incretin effect, is partially lost in patients with Type 2 diabetes. The actions of GLP-1 include (a) a stimulation of insulin secretion in a glucose-dependent manner, (b) a suppression of glucagon, (c) a reduction in appetite and food intake, (d) a deceleration of gastric emptying, (e) a stimulation of beta-cell neogenesis, growth and differentiation in animal and tissue culture experiments, and (f) an in vitro inhibition of beta-cell apoptosis induced by different toxins. Intravenous GLP-1 can normalize and subcutaneous GLP-1 can significantly lower plasma glucose in the majority of patients with Type 2 diabetes. GLP-1 itself, however, is inactivated rapidly in vivo and thus does not appear to be useful as a therapeutic agent in the long-term treatment of Type 2 diabetes. Other agents acting on GLP-1 receptors have been found (like exendin-4) or developed as GLP-1 derivatives (like liraglutide or GLP-1/CJC-1131). Clinical trials with exenatide (two injections per day) and liraglutide (one injection per day) have shown reductions in glucose concentrations and HbA1c by more than 1%, associated with moderate weight loss (2-3 kg), but also some nausea and, rarely, vomiting. It is hoped that this new class of drugs interacting with the GLP-1 or other incretin receptors, the so-called "incretin mimetics", will broaden our armamentarium of antidiabetic medications in the nearest future.

Incretin mimetics as emerging treatments for type 2 diabetes.

OBJECTIVE: To review the physiology, pharmacology, and clinical efficacy of glucagon-like peptide (GLP-1) and the incretin mimetics exenatide and liraglutide in clinical studies. DATA SOURCES: Primary literature obtained via MEDLINE (1966-April 2004) and International Pharmaceutical Abstracts (1970-April 2004) searches; abstracts obtained from meeting sources and manufacturers. STUDY SELECTION AND DATA EXTRACTION: All English-language studies and abstracts evaluating GLP-1, exenatide, and liraglutide in the treatment of patients with type 2 diabetes were reviewed. Data from animal studies were also included if human data were not available. Primary and review articles related to the physiology, development, and evaluation of GLP-1s were reviewed. DATA SYNTHESIS: GLP-1, exenatide (exendin-4, AC2993), and liraglutide (NN2211) are incretin mimetics that have been shown in human studies to be an effective treatment to improve glycemic control in patients with type 2 diabetes. Mechanisms by which these compounds improve glycemic control include enhancing glucose-dependent pancreatic secretion of insulin in response to nutrient intake, inhibiting glucagon secretion, delaying gastric emptying, and promoting early satiety. GLP-1 has been shown to promote pancreatic progenitor cell differentiation and improve beta-cell function and lifespan. Reported adverse effects of exenatide and liraglutide include nausea, vomiting, and transient headache, as well as increased risk of hypoglycemia when used with sulfonylureas. CONCLUSIONS: Clinical studies show that GLP-1, exenatide, and liraglutide improve glycemic control for patients with type 2 diabetes through unique mechanisms not available with current pharmaceutical products. Ongoing Phase III studies will help to further position these compounds as treatment options for patients with type 2 diabetes.

Unique characteristics of the geriatric diabetic population and the role for therapeutic strategies that enhance glucagon-like peptide-1 activity.

PURPOSE OF REVIEW: Care for elderly diabetic patients poses a unique clinical challenge. This review highlights distinct aspects of the pathophysiology and the risks for secondary complications in the geriatric diabetic population. Based on these considerations, we discuss emerging therapeutic options based on the actions of the incretin hormone glucagon-like peptide (GLP)-1, which may be ideal for achieving glycemic control in the elderly diabetic patient. RECENT FINDINGS: Aging is associated with diminished capacity of pancreatic beta-cells to respond to glucose. This functional decline in beta-cell insulin secretion is a major contributor to the development of diabetes in the older patient. In addition, elderly diabetics suffer from a broader range of diabetic complications than do younger diabetics, warranting aggressive glycemic control. GLP-1 is known to improve beta-cell insulin secretion, increase beta-cell mass, and suppress glucagon secretion. Recent studies investigating improved GLP-1 activity have yielded promising results, with improved glycemic control in elderly patients with type 2 diabetes and without significant risk for hypoglycemia. SUMMARY: Elderly diabetics are a growing subset of the type 2 diabetic population with unique pathophysiologic characteristics and diabetic risk profiles. Therapeutic strategies that incorporate enhancement of GLP-1 action on beta-cells to improve beta-cell insulin secretion and glycemic control may be ideal for this distinct population and should be validated with further long-term clinical studies.

Heat denaturation affects the ProDer p 1 IgE reactivity and downregulates the development of the specific allergic response.

BACKGROUND: Modified allergens with reduced IgE-binding activity represent an elegant approach to circumvent the risk of anaphylactic reactions in allergen-specific immunotherapy. OBJECTIVE: The current work investigated the effect of heat denaturation on the allergenic properties of recombinant ProDer p 1, a precursor form of the major house dust mite allergen Der p 1. METHODS: The IgE reactivity was estimated by direct and competition ELISA. The immunogenicity of heat-denatured ProDer p 1 was evaluated in naive and Der p 1-allergic mice. RESULTS: Heat denaturation in reducing conditions drastically reduced the in vitro ProDer p 1 IgE reactivity toward human allergic sera. In naive mice, heat-denatured ProDer p 1 generated mixed T(H)1-T(H)2 responses characterized by the absence of specific IgE with concomitant rise in specific IgG2a titers and the presence of IL-5 and IFN-gamma in splenocyte cultures. In contrast, natural Der p 1 or native ProDer p 1 induced typical strict T(H)2-biased allergic responses with strong IgG1 and IgE titers, whereas spleen cells exhibited only high IL-5 secretion. Moreover, native or heat-denatured ProDer p 1 vaccinations prevented airway eosinophil infiltrations after challenge. Although native or heat-treated ProDer p 1 adjuvanted with SBAS1b induced mixed T(H)1-T(H)2 responses in allergic mice, heat-denatured ProDer p 1, compared with native ProDer p 1, proved to be more effective in redirecting the T(H)2-allergic response toward T(H)1. CONCLUSION: Taken together, our results suggest that variants of Der p 1 with reduced IgE-binding reactivity could represent hypoallergenic molecules suitable for allergen-specific immunotherapy.

Effects of glucagon-like peptide-1 on endothelial function in type 2 diabetes patients with stable coronary artery disease.

GLP-1 stimulates insulin secretion, suppresses glucagon secretion, delays gastric emptying, and inhibits small bowel motility, all actions contributing to the anti-diabetogenic peptide effect. Endothelial dysfunction is strongly associated with insulin resistance and type 2 diabetes mellitus and may cause the angiopathy typifying this debilitating disease. Therefore, interventions affecting both endothelial dysfunction and insulin resistance may prove useful in improving survival in type 2 diabetes patients. We investigated GLP-1's effect on endothelial function and insulin sensitivity (S(I)) in two groups: 1) 12 type 2 diabetes patients with stable coronary artery disease and 2) 10 healthy subjects with normal endothelial function and S(I). Subjects underwent infusion of recombinant GLP-1 or saline in a random crossover study. Endothelial function was measured by postischemic FMD of brachial artery, using ultrasonography. S(I) [in (10(-4) dl.kg(-1).min(-1))/(muU/ml)] was measured by hyperinsulinemic isoglycemic clamp technique. In type 2 diabetic subjects, GLP-1 infusion significantly increased relative changes in brachial artery diameter from baseline FMD(%) (3.1 +/- 0.6 vs. 6.6 +/- 1.0%, P < 0.05), with no significant effects on S(I) (4.5 +/- 0.8 vs. 5.2 +/- 0.9, P = NS). In healthy subjects, GLP-1 infusion affected neither FMD(%) (11.9 +/- 0.9 vs. 10.3 +/- 1.0%, P = NS) nor S(I) (14.8 +/- 1.8 vs. 11.6 +/- 2.0, P = NS). We conclude that GLP-1 improves endothelial dysfunction but not insulin resistance in type 2 diabetic patients with coronary heart disease. This beneficial vascular effect of GLP-1 adds yet another salutary property of the peptide useful in diabetes treatment.

Prandial subcutaneous injections of glucagon-like peptide-1 cause weight loss in obese human subjects.

Recombinant glucagon-like peptide-1 (7-36)amide (rGLP-1) was recently shown to cause significant weight loss in type 2 diabetics when administered for 6 weeks as a continuous subcutaneous infusion. The mechanisms responsible for the weight loss are not clarified. In the present study, rGLP-1 was given for 5 d by prandial subcutaneous injections (PSI) (76 nmol 30 min before meals, four times daily; a total of 302.4 nmol/24 h) or by continuous subcutaneous infusion (CSI) (12.7 nmol/h; a total of 304.8 nmol/24 h). This was performed in nineteen healthy obese subjects (mean age 44.2 (sem 2.5) years; BMI 39.0 (sem 1.2) kg/m(2)) in a prospective randomised, double-blind, placebo-controlled, cross-over study. Compared with the placebo, rGLP-1 administered as PSI and by CSI generated a 15 % reduction in mean food intake per meal (P=0.02) after 5 d treatment. A weight loss of 0.55 (sem 0.2) kg (P<0.05) was registered after 5 d with PSI of rGLP-1. Gastric emptying rate was reduced during both PSI (P<0.001) and CSI (P<0.05) treatment, but more rapidly and to a greater extent with PSI of rGLP-1. To conclude, a 5 d treatment of rGLP-1 at high doses by PSI, but not CSI, promptly slowed gastric emptying as a probable mechanism of action of increased satiety, decreased hunger and, hence, reduced food intake with an ensuing weight loss.

Effects of 3 months of continuous subcutaneous administration of glucagon-like peptide 1 in elderly patients with type 2 diabetes.

OBJECTIVE: Glucagon-like peptide 1 (GLP-1) is an insulinotropic gut hormone that, when given exogenously, may be a useful agent in the treatment of type 2 diabetes. We conducted a 3-month trial to determine the efficacy and safety of GLP-1 in elderly diabetic patients. RESEARCH DESIGN AND METHODS: A total of 16 patients with type 2 diabetes who were being treated with oral hypoglycemic agents were enrolled. Eight patients (aged 75 +/- 2 years, BMI 27 +/- 1 kg/m(2)) remained on usual glucose-lowering therapy and eight patients (aged 73 +/- 1 years, BMI 27 +/- 1 kg/m(2)), after discontinuing hypoglycemic medications, received GLP-1 delivered by continuous subcutaneous infusion for 12 weeks. The maximum dose was 120 pmol x kg(-1). h(-1). Patients recorded their capillary blood glucose (CBG) levels (four times per day, 3 days per week) and whenever they perceived hypoglycemic symptoms. The primary end points were HbA(1c) and CBG determinations. Additionally, changes in beta-cell sensitivity to glucose, peripheral tissue sensitivity to insulin, and changes in plasma ghrelin levels were examined. RESULTS: HbA(1c) levels (7.1%) and body weight were equally maintained in both groups. The usual treatment group had a total of 87 CBG measurements of

[Advances in safety studies of soil Bt toxin proteins released from transgenic Bt crops].

Commercialized transgenic Bt (Bacillus thuringiensis) crops are permitted for field growth in a large scale, which leads to significant issues of ecological risk assessment in soil ecosystem. In this paper, some general safety problems involving in the soil Bt active toxins released from insect-resistant transgenic Bt crops in the forms of plant residues, root exudates and pollens were reviewed, including their adsorption by soil active-particles, their insecticidal activity, persistence, and biodegradation by soil microbes, and their effects on soil organisms.

New vaccination strategies for low- and non-responders to hepatitis B vaccine.

The currently available recombinant hepatitis B vaccines are safe, efficacious and immunogenic. Nevertheless, a high rate of low- and nonresponsiveness to the current vaccine poses a problem since this group remains susceptible to infection with hepatitis B virus. Efforts are underway to develop new vaccines and strategies to enhance seroprotection rates. One possibility under investigation is the low-dose intradermal administration of vaccine since the immune system is well represented in both the epidermis and the dermis. Despite encouraging results concerning the immunogenicity in previous non-responders, the main difficulty is the technique of administration and unacceptable local adverse effects. Promising data have emerged from clinical trials evaluating the immunogenicity of new recombinant vaccines containing the complete pre-S1 and pre-S2 regions of HbsAg and, more recently, of novel adjuvanted hepatitis B vaccines. Future approaches include DNA vaccination and expression of HbsAg determinants in live recombinant vectors.

Glucagon-like peptide-1 infusion must be maintained for 24 h/day to obtain acceptable glycemia in type 2 diabetic patients who are poorly controlled on sulphonylurea treatment.

OBJECTIVE: To assess the efficacy and safety of glucagon-like peptide-1 (GLP-1) on the plasma glucose level when given as a continuous infusion for either 16 or 24 h per day to type 2 diabetic patients who were poorly controlled on sulfonylurea treatment. RESEARCH DESIGN AND METHODS: This single-center, randomized, parallel, double-blind, placebo-controlled trial was conducted in 40 hospitalized patients who were randomized to receive infusions of either placebo or GLP-1 4 or 8 ng. kg(-1). min(-1) for either 16 or 24 h per day for 7 days. At predetermined intervals, 24-h profiles of glucose, glucagon, and insulin were measured. Adverse events and clinical chemistry and hematology were recorded. RESULTS: For all active treatment groups, the change in average glucose (area under the curve [AUC] for day 7 minus AUC for day 0 divided by 24 h) was statistically significantly different from placebo (P < or = 0.001). The GLP-1 8 ng. kg(-1). min(-1) dose given for 24 h was more efficacious than any of the other doses (P < or = 0.05). Nocturnal and fasting plasma glucose levels at day 7 were greater in the 16-h groups compared with the 24-h groups (P < or = 0.05). Insulin AUC did not show any treatment effect for any of the treatment groups when change was assessed from day 0 to day 7. However, for the 16-h groups, the pattern of the insulin profiles changed; the insulin profiles were considerably higher during the initial 3-4 h after restart of the GLP-1 infusion on day 7, although there was a tendency for insulin levels to decrease during the afternoon and evening. Glucagon AUC decreased significantly for all active treatment groups compared with placebo. GLP-1 was generally well tolerated. CONCLUSIONS: This study demonstrated that GLP-1 should be given continuously to obtain the most optimal glycemic control. Because of the short plasma half-life of native GLP-1, long-acting derivatives should be developed to make GLP-1 treatment clinically relevant.

A novel hyperglycaemic clamp for characterization of islet function in humans: assessment of three different secretagogues, maximal insulin response and reproducibility.

BACKGROUND: Characterization of beta-cell function in humans is essential for identifying genetic defects involved in abnormal insulin secretion and the pathogenesis of type 2 diabetes. MATERIALS AND METHODS: We designed a novel test assessing plasma insulin and C-peptide in response to 3 different secretagogues. Seven lean, healthy volunteers twice underwent a 200 min hyperglycaemic clamp (10 mmol L-1) with administration of GLP-1 (1.5 pmol. kg-1. min-1) starting at 120 min and an arginine bolus at 180 min. We determined glucose-induced first and second-phase insulin secretion, GLP-1-stimulated insulin secretion, arginine-stimulated insulin response (increase above prestimulus, DeltaIarg) and the maximal, i. e. highest absolute, insulin concentration (Imax). Insulin sensitivity was assessed during second-phase hyperglycaemia. On a third occasion 6 subjects additionally received an arginine bolus at > 25 mM blood glucose, a test hitherto claimed to provoke maximal insulin secretion. RESULTS: Insulin levels increased from 46 +/- 11 pM to 566 +/- 202 pM at 120 min, to 5104 +/- 1179 pM at 180 min and to maximally 8361 +/- 1368 pM after arginine (all P < 0.001). The within subject coefficients of variation of the different secretion parameters ranged from 10 +/- 3% to 16 +/- 6%. Except for second-phase which failed to correlate significantly with DeltaIarg (r = 0.52, P = 0.23) and Imax (r = 0.75, P = 0.053) all phases of insulin secretion correlated with one another. The insulin concentration after the arginine bolus at > 25 mM glucose (n = 6) was 2773 +/- 855 pM vs. 7562 +/- 1168 pM for Imax (P = 0.003). CONCLUSION: This novel insulin secretion test elicits a distinct pattern of plasma insulin concentrations in response to the secretagogues glucose, GLP-1 and arginine and is highly reproducible and can be used for differential characterization of islet function.