Characteristics of norepinephrine stimulated thermogenesis in undernourished subjects.

ABSTRACT

Thermoregulatory thermogenesis was evaluated in chronically undernourished subjects as well as normally nourished controls by 60 min infusions of norepinephrine at a calculated dose of 0·15 μg/kg fat free mass/min. There was a significant (P<0·05) reduction in the thermogenic response to norepinephrine in the undernourished labourers. When the characteristics of response were evaluated, the baseline and peak responses were comparable in both groups. However, the steepness of the response was greater (P<0·05) in the undernourished subjects. The time to register a threshold response of 5 ml per min increase in oxygen consumption over the baseline after the start of infusion was longer in undernourished (about 20 min) as compared to the controls (about 10 min). It appears that, while the undernourished subjects have a reduced thermogenic component in their energy output, their peak capacity or potential for regulatory thermogenesis is the same as that in control subjects, since their thermogenic response has a greater slope. It is possible that chronically undernourished subjects may have a suppressed response over shorter periods of stimulation (less than 20 min), that is, before steady state thermogenic responses are achieved.