Glucose-dependent insulinotropic polypeptide induces lipolysis during stable basal insulin substitution and hyperglycaemia in men with type 1 diabetes: A randomized, double-blind, placebo-controlled, crossover clinical trial.

Glucose-dependent insulinotropic polypeptide (GIP) plays an important role in the glucose and lipid metabolism. We investigated the effects of exogenous GIP on lipid metabolism during time of stable insulin levels. Ten male patients with type 1 diabetes without endogenous insulin secretion (C-peptide-negative, mean [±SD] age 26 ± 4years, body mass index 24 [±2] kg/m2 , glycated haemoglobin 56 [±8] mmol/mol or 7.3 [±0.8]%) were studied in a randomized, double-blind, placebo-controlled, crossover study with continuous intravenous infusions of GIP (4 pmol/kg/min) or placebo (saline), during two separate 90-minute hyperglycaemic (12 mmol/L) clamps with basal insulin substitution (0.1-0.2 mU/kg/min). Plasma glycerol concentrations increased from baseline during GIP infusion and decreased during placebo infusion (baseline-subtracted area under the curve [bsAUC] 703 ± 407 vs. -262 ± 240 µmol/L × min, respectively; P < 0.001). Free fatty acids (FFAs) increased during GIP infusions (bsAUC 5505 ± 2170 µEq/L × min) and remained unchanged during placebo infusion (bsAUC -74 ± 2363 µEq/L × min), resulting in a significant difference between GIP and placebo infusions (P < 0.001). Plasma concentrations of glucose, insulin, glucagon-like peptide-1 and glucagon were similar during GIP and placebo infusions. GIP increased plasma glycerol and FFAs in patients with type 1 diabetes during hyperglycaemia and stable basal insulin levels. This supports a direct lipolytic effect of GIP at high glucose and low levels of plasma insulin.

The effect of 6-day subcutaneous glucose-dependent insulinotropic polypeptide infusion on time in glycaemic range in patients with type 1 diabetes: a randomised, double-blind, placebo-controlled crossover trial.

AIMS/HYPOTHESIS: Type 1 diabetes is characterised by reduced glucagon response to hypoglycaemia, increasing the risk of insulin treatment-associated hypoglycaemia known to hamper glycaemic control. We previously reported a glucagonotropic effect of exogenous glucose-dependent insulinotropic polypeptide (GIP) during insulin-induced hypoglycaemia in individuals with type 1 diabetes. Here we investigate the effect of a 6-day s.c. GIP infusion on time in glycaemic range as assessed by continuous glucose monitoring (CGM) in individuals with type 1 diabetes. METHODS: In a randomised, placebo-controlled, double-blind crossover study, time in glycaemic range (assessed by double-blinded CGM) was evaluated in 20 men with type 1 diabetes (18-75 years, stable insulin treatment ≥3 months, diabetes duration 2-15 years, fasting plasma C-peptide below 200 pmol/l, BMI 20-27 kg/m2, HbA1c <69 mmol/mol [8.5%]) during two × 6 days of continuous s.c. GIP (6 pmol kg-1 min-1) and placebo (saline [154 mmol/l NaCl]) infusion, respectively, with an interposed 7-day washout period. The primary outcome was glycaemic time below range, time in range and time above range. RESULTS: There were no significant differences in time below range (<3.9 mmol/l, p = 0.53) or above range (>10 mmol/l, p = 0.32) during night-time or daytime, in mean glucose, or in hypoglycaemic events as assessed by CGM. GIP altered neither self-reported hypoglycaemia nor safety measures. Compared with placebo, GIP significantly increased time in tight range (3.9-7.8 mmol/l) during daytime (06:00-23:59 hours) by [mean ± SEM] 11.2 ± 5.1% [95% CI 0.41, 21.9] (p = 0.02). CONCLUSIONS/INTERPRETATION: Six-day s.c. GIP infusion in men with type 1 diabetes did not procure convincing effect on overall time in range, but increased time in tight glycaemic range during daytime by ~2 h per day. TRIAL REGISTRATION: ClinicalTrials.gov NCT03734718. FUNDING: The study was funded by grants from The Leona M. and Harry B. Helmsley Charitable Trust and Aase og Ejnar Danielsens Fond.

Identification and Metabolic Profiling of a Novel Human Gut-derived LEAP2 Fragment.

CONTEXT: The mechanisms underlying Roux-en-Y gastric bypass (RYGB) surgery-induced weight loss and the immediate postoperative beneficial metabolic effects associated with the operation remain uncertain. Enteroendocrine cell (EEC) secretory function has been proposed as a key factor in the marked metabolic benefits from RYGB surgery. OBJECTIVE: To identify novel gut-derived peptides with therapeutic potential in obesity and/or diabetes by profiling EEC-specific molecular changes in obese patients following RYGB-induced weight loss. SUBJECTS AND METHODS: Genome-wide expression analysis was performed in isolated human small intestinal EECs obtained from 20 gut-biopsied obese subjects before and after RYGB. Targets of interest were profiled for preclinical and clinical metabolic effects. RESULTS: Roux-en-Y gastric bypass consistently increased expression levels of the inverse ghrelin receptor agonist, liver-expressed antimicrobial peptide 2 (LEAP2). A secreted endogenous LEAP2 fragment (LEAP238-47) demonstrated robust insulinotropic properties, stimulating insulin release in human pancreatic islets comparable to the gut hormone glucagon-like peptide-1. LEAP238-47 showed reciprocal effects on growth hormone secretagogue receptor (GHSR) activity, suggesting that the insulinotropic action of the peptide may be directly linked to attenuation of tonic GHSR activity. The fragment was infused in healthy human individuals (n = 10), but no glucoregulatory effect was observed in the chosen dose as compared to placebo. CONCLUSIONS: Small intestinal LEAP2 expression was upregulated after RYGB. The corresponding circulating LEAP238-47 fragment demonstrated strong insulinotropic action in vitro but failed to elicit glucoregulatory effects in healthy human subjects.