Geltrude Mingrone1,2,3,4, Simona Panunzi5, Andrea De Gaetano5, Sofie Ahlin6, Valerio Spuntarelli7,8, Isabel Bondia-Pons9, Chiara Barbieri10, Esmeralda Capristo7,8, Amalia Gastaldelli10, John J Nolan9,11. 1. Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. geltrude.mingrone@kcl.ac.uk. 2. Università Cattolica del Sacro Cuore, Rome, Italy. geltrude.mingrone@kcl.ac.uk. 3. Division of Diabetes & Nutritional Sciences, Faculty of Life Sciences & Medicine, King's College London, Denmark Hill Campus, 125 Coldharbour Road, London, SE5 9NU, UK. geltrude.mingrone@kcl.ac.uk. 4. Steno Diabetes Center, Gentofte, Denmark. geltrude.mingrone@kcl.ac.uk. 5. CNR-IASI BioMatLab, Consiglio Nazionale delle Ricerche, Istituto di Analisi dei Sistemi ed Informatica, Laboratorio di Biomatematica (Italian National Research Council, Institute for System Analysis and Computer Science, Biomathematics Laboratory), Rome, Italy. 6. Department of Molecular and Clinical Medicine, Institute of Medicine, the Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden. 7. Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy. 8. Università Cattolica del Sacro Cuore, Rome, Italy. 9. Steno Diabetes Center, Gentofte, Denmark. 10. Cardiometabolic Risk Laboratory, Institute of Clinical Physiology, CNR, Pisa, Italy. 11. School of Medicine, Trinity College Dublin, Dublin, Ireland.
Abstract
AIMS/HYPOTHESIS: The small intestine plays an important role in hepatic and whole-body insulin sensitivity, as shown by bariatric surgery. Our goal was to study whether routes and dose of glucose administration have an acute impact on insulin sensitivity. The primary endpoint of this proof-of-concept study was the difference in insulin-mediated metabolic clearance rate (MCR/I) of glucose between the oral and intravenous routes of glucose administration. Secondary endpoints were differences in insulin effect on proteolysis, ketogenesis, lipolysis and glucagon levels. METHODS: In this parallel cohort study, we administered multiple oral glucose loads to 23 participants (aged between 18 and 65 years) with morbid obesity and with normal or impaired glucose tolerance or type 2 diabetes. In a different session, we administered isoglycaemic intravenous glucose infusions (IGIVI) to match the plasma glucose levels observed during the oral challenges. Glucose rate of appearance (Ra) and disappearance (Rd) and endogenous glucose production (EGP) were calculated by infusing [6,6-2H2]glucose with or without oral [U-13C6]glucose. Plasma small polar metabolites were measured by gas chromatography and time-of-flight mass spectrometry. Lipids were measured by ultra-HPLC and quadrupole mass spectrometry. Glucagon-like peptide-1, insulin, C-peptide and glucagon were also measured. Participants, caregivers, people doing measurements or examinations, and people assessing the outcomes were unblinded to group assignment. RESULTS: Glucose MCR/I was significantly higher during IGIVI than during oral glucose administration, independently of glycaemic status (12 ± 6 for IGIVI vs 7.4 ± 3 ml min-1 kg-1 per nmol/l for oral, p< 0.001 from paired t test). Insulin secretion was higher during oral administration than during IGIVI (p< 0.001). The disposition index was significantly lower during the oral procedure: 4260 ± 1820 vs 5000 ± 2360 (ml min-1 kg-1 (nmol/l)-1 pmol/min; p = 0.005). Insulin clearance was significantly higher when glucose was infused rather than ingested (2.53 ± 0.82 vs 2.16 ± 0.49 l/min in intravenous and oral procedure, respectively, p = 0.006). The efficacy of insulin in inhibiting lipolysis and proteolysis was decreased after oral glucose loads. A heat map diagram showed a different pattern for the metabolites between the two routes of glucose administration. CONCLUSIONS/ INTERPRETATION: Our study shows that insulin sensitivity depends on the route of glucose administration, the oral route leading to increased insulin secretion and compensatory insulin resistance compared with the intravenous route. The efficacy of insulin in blocking lipolysis and protein breakdown is lower after oral glucose loads vs the intravenous route. Our findings suggest that, while the glucose-mediated incretin release is followed by an increase in insulin release, the effect of the released insulin is limited by an increase in insulin resistance. TRIAL REGISTRATION: ClinicalTrials.gov NCT03223129. Graphical abstract.
AIMS/HYPOTHESIS: The small intestine plays an important role in hepatic and whole-body insulin sensitivity, as shown by bariatric surgery. Our goal was to study whether routes and dose of glucose administration have an acute impact on insulin sensitivity. The primary endpoint of this proof-of-concept study was the difference in insulin-mediated metabolic clearance rate (MCR/I) of glucose between the oral and intravenous routes of glucose administration. Secondary endpoints were differences in insulin effect on proteolysis, ketogenesis, lipolysis and glucagon levels. METHODS: In this parallel cohort study, we administered multiple oral glucose loads to 23 participants (aged between 18 and 65 years) with morbid obesity and with normal or impaired glucose tolerance or type 2 diabetes. In a different session, we administered isoglycaemic intravenous glucose infusions (IGIVI) to match the plasma glucose levels observed during the oral challenges. Glucose rate of appearance (Ra) and disappearance (Rd) and endogenous glucose production (EGP) were calculated by infusing [6,6-2H2]glucose with or without oral [U-13C6]glucose. Plasma small polar metabolites were measured by gas chromatography and time-of-flight mass spectrometry. Lipids were measured by ultra-HPLC and quadrupole mass spectrometry. Glucagon-like peptide-1, insulin, C-peptide and glucagon were also measured. Participants, caregivers, people doing measurements or examinations, and people assessing the outcomes were unblinded to group assignment. RESULTS:GlucoseMCR/I was significantly higher during IGIVI than during oral glucose administration, independently of glycaemic status (12 ± 6 for IGIVI vs 7.4 ± 3 ml min-1 kg-1 per nmol/l for oral, p< 0.001 from paired t test). Insulin secretion was higher during oral administration than during IGIVI (p< 0.001). The disposition index was significantly lower during the oral procedure: 4260 ± 1820 vs 5000 ± 2360 (ml min-1 kg-1 (nmol/l)-1 pmol/min; p = 0.005). Insulin clearance was significantly higher when glucose was infused rather than ingested (2.53 ± 0.82 vs 2.16 ± 0.49 l/min in intravenous and oral procedure, respectively, p = 0.006). The efficacy of insulin in inhibiting lipolysis and proteolysis was decreased after oral glucose loads. A heat map diagram showed a different pattern for the metabolites between the two routes of glucose administration. CONCLUSIONS/ INTERPRETATION: Our study shows that insulin sensitivity depends on the route of glucose administration, the oral route leading to increased insulin secretion and compensatory insulin resistance compared with the intravenous route. The efficacy of insulin in blocking lipolysis and protein breakdown is lower after oral glucose loads vs the intravenous route. Our findings suggest that, while the glucose-mediated incretin release is followed by an increase in insulin release, the effect of the released insulin is limited by an increase in insulin resistance. TRIAL REGISTRATION: ClinicalTrials.gov NCT03223129. Graphical abstract.
Authors: Elvis A Carnero; Christopher P Bock; Giovanna Distefano; Karen D Corbin; Natalie A Stephens; Richard E Pratley; Steven R Smith; Bret H Goodpaster; Lauren M Sparks Journal: Diabetologia Date: 2021-08-17 Impact factor: 10.122