C. Ørskov

Normalization of fasting hyperglycaemia by exogenous glucagon-like peptide 1 (7-36 amide) in type 2 (non-insulin-dependent) diabetic patients.

SummaryGlucagon-like peptide 1 (GLP-1) (7-36 amide) is a physiological incretin hormone that is released after nutrient intake from the lower gut and stimulates insulin secretion at elevated plasma glucose concentrations. Previous work has shown that even in Type 2 (non-insulin-dependent) diabetic patients GLP-1 (7-36 amide) retains much of its insulinotropic action. However, it is not known whether the magnitude of this response is sufficient to normalize plasma glucose in Type 2 diabetic patients with poor metabolic control. Therefore, in 10 Type 2 diabetic patients with unsatisfactory metabolic control (HbAlc 11.6±1.7%) on diet and sulphonylurea therapy (in some patients supplemented by metformin or acarbose), 1.2 pmol ×kg−1×min−1 GLP-1 (7-36 amide) or placebo was infused intravenously in the fasting state (plasma glucose 13.1±0.6 mmol/l). In all patients, insulin (by 17.4±4.7 nmol ×1−1×min; p=0.0157) and C-peptide (by 228.0±39.1 nmol×1−1×min; p=0.0019) increased significantly over basal levels, glucagon was reduced (by -1418±308 pmol ×1−1×min) and plasma glucose reached normal fasting concentrations (4.9±0.3 mmol/l) within 4 h of GLP-1 (7-36 amide) administration, but not with placebo. When normal fasting plasma glucose concentrations were reached insulin returned towards basal levels and plasma glucose concentrations remained stable despite the ongoing infusion of GLP-1 (7-36 amide). Therefore, exogenous GLP-1 (7-36 amide) is an effective means of normalizing fasting plasma glucose concentrations in poorly-controlled Type 2 diabetic patients. The glucose-dependence of insulinotropic actions of GLP-1 (7-36 amide) appears to be retained in such patients.

GLP-1 (Glucagon-like Peptide 1) and Truncated GLP-1, Fragments of Human Proglucagon, Inhibit Gastric Acid Secretion in Humans

Glucagon-like peptide 1 amide (GLP-1 amide), a predicted product of the glucagon gene (proglucagon 72-107-amide), and truncated GLP-1 (proglucagon 78-107-amide), recently isolated from porcine small intestine, were infused in doses of 100 and 400 ng/kg/hr and 12.5 and 50 ng/kg/hr, respectively, into eight volunteers to study pharmacokinetics and effects on pentagastrin- stimulated gastric acid secretion (plateau stimulation with pentagastrin at D50:100ng/kg/hr). The concentration of GLP-1 in plasma increased from 64±12 to 189±23 and 631±76 pmol/liter, respectively. The concentration of truncated GLP increased from approximately 7 pmol/liter to 28±3 pmol/liter during the high rate of infusion. A similar increase was seen in response to a mixed meal in eight normal volunteers. The metabolic clearance rate (MCR) of GLP-1 was 2.2±0.3 and 2.6±0.3 ml/kg/min, respectively, and the half- life in plasma was 17±2 min. The MCR of truncated GLP-1 was 13±2.8 ml/kg/min and the half- life 11.4±2.1 min. GLP-1 reduced the pentagastrin- stimulated acid secretion 16±9% during the low-rate infusion and 23±12% during the high rate (P<0.05). Truncated GLP-1 caused a 36±3% inhibition during the high infusion rate. Thus truncated GLP-1, a naturally occurring peptide, is a potent inhibitor of acid secretion in man and more so than GLP-1.

MHC Class II-Associated Invariant Chain Linkage of Antigen Dramatically Improves Cell-Mediated Immunity Induced by Adenovirus Vaccines

The ideal vaccine induces a potent protective immune response, which should be rapidly induced, long-standing, and of broad specificity. Recombinant adenoviral vectors induce potent Ab and CD8+ T cell responses against transgenic Ags within weeks of administration, and they are among the most potent and versatile Ag delivery vehicles available. However, the impact of chronic infections like HIV and hepatitis C virus underscore the need for further improvements. In this study, we show that the protective immune response to an adenovirus-encoded vaccine Ag can be accelerated, enhanced, broadened, and prolonged by tethering of the rAg to the MHC class II-associated invariant chain (Ii). Thus, adenovirus-vectored vaccines expressing lymphocytic choriomeningitis virus (LCMV)-derived glycoprotein linked to Ii increased the CD4+ and CD8+ T cell stimulatory capacity in vitro and in vivo. Furthermore, mice vaccinated with a single dose of adenovirus-expressing LCMV-derived glycoprotein linked to Ii were protected against lethal virus-induced choriomeningitis, lethal challenge with strains mutated in immunodominant T cell epitopes, and systemic infection with a highly invasive strain. In therapeutic tumor vaccination, the vaccine was as efficient as live LCMV. In comparison, animals vaccinated with a conventional adenovirus vaccine expressing unmodified glycoprotein were protected against systemic infection, but only temporarily against lethal choriomeningitis, and this vaccine was less efficient in tumor therapy.

Co-localisation of the Kir6.2/SUR1 channel complex with glucagon-like peptide-1 and glucose-dependent insulinotrophic polypeptide expression in human ileal cells and implications for glycaemic control in new onset type 1 diabetes

OBJECTIVEnThe ATP-dependent K+-channel (K(ATP)) is critical for glucose sensing and normal glucagon and insulin secretion from pancreatic endocrine alpha- and beta-cells. Gastrointestinal endocrine L- and K-cells are also glucose-sensing cells secreting glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotrophic polypeptide (GIP) respectively. The aims of this study were to 1) investigate the expression and co-localisation of the K(ATP) channel subunits, Kir6.2 and SUR1, in human L- and K-cells and 2) investigate if a common hyperactive variant of the Kir6.2 subunit, Glu23Lys, exerts a functional impact on glucose-sensing tissues in vivo that may affect the overall glycaemic control in children with new-onset type 1 diabetes.nnnDESIGN AND METHODSnWestern blot and immunohistochemical analyses were performed for expression and co-localisation studies. Meal-stimulated C-peptide test was carried out in 257 children at 1, 6 and 12 months after diagnosis. Genotyping for the Glu23Lys variant was by PCR-restriction fragment length polymorphism.nnnRESULTSnKir6.2 and SUR1 co-localise with GLP-1 in L-cells and with GIP in K-cells in human ileum tissue. Children with type 1 diabetes carrying the hyperactive Glu23Lys variant had higher HbA1C at diagnosis (coefficient = 0.61%, P = 0.02) and 1 month after initial insulin therapy (coefficient = 0.30%, P = 0.05), but later disappeared. However, when adjusting HbA1C for the given dose of exogenous insulin, the dose-adjusted HbA1C remained higher throughout the 12 month study period (coefficient = 0.42%, P = 0.03).nnnCONCLUSIONSnKir6.2 and SUR1 co-localise in the gastrointestinal endocrine L- and K-cells. The hyperactive Glu23Lys variant of the K(ATP) channel subunit Kir6.2 may cause defective glucose sensing in several tissues and impaired glycaemic control in children with type 1 diabetes.

Carboxypeptidase-B-like processing of the C-terminus of glucagon-like peptide-2 in pig and human small intestine

We developed specific, C‐terminal radioimmunoassays for three proglucagon (PG) fragments: PG 151–158, PG 151–160 and PG 126–159 (glucagon‐like peptide‐2 (GLP‐2)) in order to determine the exact C‐terminal sequence of the newly isolated GLP‐2 in man and pig. The antigens and the antisera showed no mutual cross‐reactivity. By gel filtration of extracts of pig and human small intestine, the immunoreactivity eluting at the position of GLP‐2 was identified by the radioimmunoassays for glucagon‐like peptide‐2 (PG 126–159) and for PG 151–158, whereas the assay for PG 151–160 was completely negative. We conclude that the C‐terminal amino acid residue of pig and human ileal GLP‐2 is PG 158. Thus the basic residues, PG 159 and 160 are removed during its processing in the small intestine.

Postprandial Release of Glucagon-Like Peptide-1, Pancreatic Glucagon, and Insulin after Esophageal Resection

Postprandial concentrations of glucose and the immunoreactivity of insulin, glucagon-like peptide-1 (GLP-1), and pancreatic glucagon were measured in 10 patients who had undergone esophageal resection (ER) and replacement by the stomach. Emptying of the esophageal substitute was assessed by scintigraphy using a 99Tc-labeled solid test meal. The data were compared with measurements performed in 14 controls, in 7 of whom gastric emptying was measured. The gastric emptying half time was 6.8 +/- 6.2 min (median 144 s) in ER cases, significantly shorter than in controls: 70 +/- 29 min (median 51 min). The early integrated (first 30 min) and total integrated insulin and GLP-1 concentrations were significantly higher than in controls. In 3 of 10 esophagectomy patients the blood glucose concentration fell below 3.8 mmol/l postprandially. High GLP-1 concentrations in the first 30 min were associated with low serum glucose during the 2nd h postprandially when all the hypoglycemic episodes occurred. It is concluded that rapid emptying of the esophageal substitute induces the exaggerated GLP-1 response, which is a main factor for reactive hypoglycemia.