The thermogenic response induced by glucose/insulin administered intravenously was examined in 22 healthy male volunteers using indirect calorimetry in combination with the euglycaemic insulin clamp technique. Five increasing steady state levels of insulinaemia (62 μU/ml to 1132 μU/ml) were achieved by means of continuous infusions of insulin at 5 rates ranging from 0.5 mU/kg.min to 10 mU/kg.min. Euglycaemia was maintained at each insulin level by infusing glucose at different rates ranging from steady state values of 0.41 g/min to 0.77 g/min. These glucose/insulin infusions resulted in a significant net rise in resting energy expenditure from 0.33 kJ/min to 0.94 kJ/min over preinfusion baseline values for the lowest and the highest doses respectively. There was a highly significant relationship (r = 0.93, p<0.001, n = 42) between the amount of glucose infused and the net increase in energy expenditure over preinfusion baseline values. Intravenous glucose induced thermogenesis (GITiv) was calculated as incremental values of energy expenditure related to step changes in glucose infusion rates. GITiv was found to be approximately 5.5% a physiological plasma insulin levels (i.e. below 200 μU/ml) whereas at supraphysiological levels (i.e.>400 μU/ml) GITiv was increased up to 8%. It was concluded that: 1. the magnitude of the GITiv at physiological insulinaemia was similar to that found by other intestigators who have administered glucose per os; 2. the elevated thermogenesis observed at high doses of glucose/insulin infusion is consistent with recent clinical findings showing a markedly increased energy expenditure in patients supported by large quantities of intravenous glucose (TPN).
ASJC Scopus subject areas
- Nutrition and Dietetics
- Critical Care and Intensive Care Medicine