Signe Harring Østoft, Jonatan Ising Bagger, Torben Hansen, Bolette Hartmann, Oluf Pedersen, Jens Juul Holst, Filip Krag Knop and Tina Vilsbøll
The role of the incretin hormones in the pathophysiology of maturity onset diabetes of the young (MODY) is unclear.
We studied the postprandial plasma responses of glucagon, incretin hormones (glucagon-like peptide 1 (GLP1) and glucose-dependent insulinotropic polypeptide (GIP)) and dipeptidyl-peptidase 4 (DPP4) enzymatic activity in patients with glucokinase (GCK) diabetes (MODY2) and hepatocyte nuclear factor 1α (HNF1A) diabetes (MODY3) as well as in matched healthy individuals (CTRLs).
Subjects and methods
Ten patients with MODY2 (mean age±s.e.m. 43±5 years; BMI 24±2 kg/m2; fasting plasma glucose (FPG) 7.1±0.3 mmol/l: HbA1c 6.6±0.2%), ten patients with MODY3 (age 31±3 years; BMI 24±1 kg/m2; FPG 8.9±0.8 mmol/l; HbA1c 7.0±0.3%) and ten CTRLs (age 40±5 years; BMI 24±1 kg/m2; FPG 5.1±0.1 mmol/l; HbA1c 5.3±0.1%) were examined with a liquid test meal.
All of the groups exhibited similar baseline values of glucagon (MODY2: 7±1 pmol/l; MODY3: 6±1 pmol/l; CTRLs: 8±2 pmol/l, P=0.787), but patients with MODY3 exhibited postprandial hyperglucagonaemia (area under the curve (AUC) 838±108 min×pmol/l) as compared to CTRLs (182±176 min×pmol/l, P=0.005) and tended to have a greater response than did patients with MODY2 (410±154 min×pmol/l, P=0.063). Similar peak concentrations and AUCs for plasma GIP and plasma GLP1 were observed across the groups. Increased fasting DPP4 activity was seen in patients with MODY3 (17.7±1.2 mU/ml) vs CTRLs (13.6±0.8 mU/ml, P=0.011), but the amount of activity was similar to that in patients with MODY2 (15.0±0.7 mU/ml, P=0.133).
The pathophysiology of MODY3 includes exaggerated postprandial glucagon responses and increased fasting DPP4 enzymatic activity but normal postprandial incretin responses both in patients with MODY2 and in patients with MODY3.
Astrid Plamboeck, Simon Veedfald, Carolyn F Deacon, Bolette Hartmann, André Wettergren, Lars B Svendsen, Søren Meisner, Claus Hovendal, Filip K Knop, Tina Vilsbøll and Jens J Holst
Glucagon-like peptide 1 (GLP1) is rapidly inactivated by dipeptidyl peptidase 4 (DPP4), but may interact with vagal neurons at its site of secretion. We investigated the role of vagal innervation for handling of oral and i.v. glucose.
Design and methods
Truncally vagotomised subjects (n=16) and matched controls (n=10) underwent 50 g-oral glucose tolerance test (OGTT)±vildagliptin, a DPP4 inhibitor (DPP4i) and isoglycaemic i.v. glucose infusion (IIGI), copying the OGTT without DPP4i.
Isoglycaemia was obtained with 25±2 g glucose in vagotomised subjects and 18±2 g in controls (P<0.03); thus, gastrointestinal-mediated glucose disposal (GIGD) – a measure of glucose handling (100%×(glucoseOGTT−glucoseIIGI/glucoseOGTT)) – was reduced in the vagotomised compared with the control group. Peak intact GLP1 concentrations were higher in the vagotomised group. Gastric emptying was faster in vagotomised subjects after OGTT and was unaffected by DPP4i. The early glucose-dependent insulinotropic polypeptide response was higher in vagotomised subjects. Despite this, the incretin effect was equal in both groups. DPP4i enhanced insulin secretion in controls, but had no effect in the vagotomised subjects. Controls suppressed glucagon concentrations similarly, irrespective of the route of glucose administration, whereas vagotomised subjects showed suppression only during IIGI and exhibited hyperglucagonaemia following OGTT. DPP4i further suppressed glucagon secretion in controls and tended to normalise glucagon responses in vagotomised subjects.
GIGD is diminished, but the incretin effect is unaffected in vagotomised subjects despite higher GLP1 levels. This, together with the small effect of DPP4i, is compatible with the notion that part of the physiological effects of GLP1 involves vagal transmission.
Monika J Bak, Nicolai Wewer Albrechtsen, Jens Pedersen, Bolette Hartmann, Mikkel Christensen, Tina Vilsbøll, Filip K Knop, Carolyn F Deacon, Lars O Dragsted and Jens J Holst
To determine the specificity and sensitivity of assays carried out using commercially available kits for glucagon and/or oxyntomodulin measurements.
Ten different assay kits used for the measurement of either glucagon or oxyntomodulin concentrations were obtained. Solutions of synthetic glucagon (proglucagon (PG) residues 33–61), oxyntomodulin (PG residues 33–69) and glicentin (PG residues 1–69) were prepared and peptide concentrations were verified by quantitative amino acid analysis and a processing-independent in-house RIA. Peptides were added to the matrix (assay buffer) supplied with the kits (concentration range: 1.25–300 pmol/l) and to human plasma and recoveries were determined. Assays yielding meaningful results were analysed for precision and sensitivity by repeated analysis and ability to discriminate low concentrations.
Results and conclusion
Three assays were specific for glucagon (carried out using the Millipore (Billerica, MA, USA), Bio-Rad (Sundbyberg, Sweden), and ALPCO (Salem, NH, USA) and Yanaihara Institute (Shizuoka, Japan) kits), but none was specific for oxyntomodulin. The assay carried out using the Phoenix (Burlingame, CA, USA) glucagon kit measured the concentrations of all three peptides (total glucagon) equally. Sensitivity and precision were generally poor; the assay carried out using the Millipore RIA kit performed best with a sensitivity around 10 pmol/l. Assays carried out using the BlueGene (Shanghai, China), USCN LIFE (Wuhan, China) (oxyntomodulin and glucagon), MyBioSource (San Diego, CA, USA) and Phoenix oxyntomodulin kits yielded inconsistent results.
Katrine Hygum, Jakob Starup-Linde, Torben Harsløf, Niklas Rye Jørgensen, Bolette Hartmann, Jens Juul Holst and Bente L Langdahl
Bone turnover has a diurnal variation influenced by food intake, incretin hormones, the sympathetic nervous system and osteocyte function. The aim of the study was to compare diurnal variation in bone turnover in patients with diabetes and controls.
A clinical 24-h study with patients with type 1 diabetes (n = 5), patients with type 2 diabetes (n = 5) and controls (n = 5).
Inclusion criterion: age >50 years. Exclusion criteria: diseases/medication that affect bone metabolism or recent use of incretin-based drugs. We drew blood samples hourly during the day and every 3 h during the night. We served an identical diet on all study days. We used repeated-measures one-way ANOVA to compare the levels of the investigated markers, and we quantified the effect of time by comparing group mean standard deviations.
The bone formation marker procollagen type 1 N-terminal propeptide showed a significant interaction between time and group (P = 0.01), and the mean standard deviation was lower in patients with type 2 diabetes compared with controls (P = 0.04) and patients with type 1 diabetes (P = 0.02). Other markers of bone formation and resorption showed significant effect of time. Levels of glucagon-like peptide-2, glucose-dependent insulinotropic peptide and sclerostin only showed significant effect of time (all P values 0.01), but levels of sclerostin tended to being highest in type 2 diabetes and lowest in controls.
The diurnal variation in bone formation is attenuated in patients with type 2 diabetes. This is not explained by changes in incretin hormone levels, but possibly mediated by sclerostin.