Thermic effect of glucose in man. Obligatory and facultative thermogenesis.

Abstract

As bstract. The contribution of the sympathetic nervous system to the thermic effect of intravenously infused glucose and insulin was studied in 10 healthy young men before and after fl-adrenergic receptor blockade with propranolol during conditions of normoglycemia (90 mg/dl) at two levels of hyperinsulinemia (-90 MU/ml and -620 jAU/ml).During steady state conditions of glucose uptake (0.515±0.046 and 0.754±0.056 g/min), significant increases were observed in energy expenditure (0.10±0.02 kcal/min, P < 0.001, and 0.21±0.02 kcal/min, P < 0.01, respectively). Similarly, glucose oxidation increased from 0.100±0.015 to 0.266±0.022 g/min (P < 0.001) at -90 ,uU/ml insulin and from 0.082±0.013 to 0.295±0.018 g/min (P < 0.001) at -620 AU/ml insulin. Concomitantly, the rate of nonoxidative glucose disposal or "glucose storage" was 0.249±0.033 and 0.459±0.048 g/min, respectively. At this time the thermic effect of infused glucose/insulin was 5.3±0.9 and 7.5±0.7%, and the energy cost of "glucose storage" was 0.50±0.16 kcal/g and 0.47±0.04 kcal/g at the two different levels of glucose uptake.After ,B-adrenergic receptor blockade with propranolol, glucose uptake, oxidation, and "storage" were unchanged in both studies, but significant decreases in energy expenditure were observed (1.41±0.06- Receivedfor publication 24 February 1984. Regression analysis of the results from both studies indicated a mean energy cost for "glucose storage" of 0.36 kcal/g (r = 0.74, P < 0.001), which fell significantly (P < 0.005) to 0.21 kcal/g (r = 0.49, P < 0.05) during ,B-adrenergic receptor blockade with propranolol. The latter is in close agreement with that calculated on theoretical grounds for the metabolic cost of glucose storage as glycogen, i.e., obligatory thermogenesis.It is concluded that f3-adrenergically mediated sympathetic nervous activity is responsible for almost the entire rise in energy expenditure in excess of the obligatory requirements for processing and storing glucose during conditions of normoglycemia and hyperinsulinemia in healthy man, and that the energy cost of "glucose storage" is not different at normal (-90 uU/ ml) and supraphysiological (-620,uU/ml) plasma insulin concentrations.

Postprandial thermogenesis and alimentary sensory stimulation in human subjects

“…In contrast, the metabolic component of the TEF, observed after tube feeding, was independent of the subject's BMI. As other authors have shown, 1,39,40 this component is related to the quantity andaor nature of the ingested nutrients and so may correspond to the obligatory component of the TEF. …”

Weight loss and changes in energy metabolism in massively obese adolescents

“…34 The obligatory component corresponds to the energy required for glucose absorption and storage. The facultative component is mediated by the sympathetic nervous system via catecholamines acting on b-adrenergic receptors.…”

Thermic effect of food and sympathetic nervous system activity in humans

“…This part of the TEF of intravenous glucose which can be suppressed by betaadrenergic antagonists has been called 'facultative thermogenesis' (Acheson et al, 1984). Activation by the sympathetic nervous system of energy-requiring processes, such as the Cori cycle (Kusaka and Ui, 1977) and the lipolysis-reesterification of free fatty acids (Wolfe et al, 1987;Breitenstein et al, 1990), is likely to be involved in this facultative portion of TEF.…”