Glucose response following infusion

Fig. 7. Systemic (a) human insulin concentration and (b) glucose response following infusion of human insulin from external pump, 5 months postimplantation (Dziubla et ai, 2002).

Over the past several years we have applied stable isotopic tracers to a vetriety of metabolic and nutritional problems in human subjects. This chapter will focus on examples of our studies of glucose metabolism. The general principle and vaUdatLon of the tracer techniques we have used will be presented first, followed by a review of some of our work examining the response to infused glucose. In these studies we used stable isotopes because of the... 

The initial suppression of insulin response is probably mediated through increased epinephrine and sympathetic activity in view of the observation that an infusion of epinephrine can suppress insulin release following a glucose infusion in normal subjects (P2). This effect can be blocked by phentolamine. 

All were successfully treated with hyperinsulinemia/ euglycemia therapy. The authors described the mechanism of action of this form of therapy, which is mainly related to improvement in cardiac contractility and peripheral vascular resistance and reversal of acidosis. They proposed indications and dosing for this therapy consisting in most cases of intravenous glucose with an intravenous bolus dose of insulin 1 U/kg followed by an infusion of 0.5-1 U/kg/hour until the systolic blood pressure is over 100 mm/Hg and the heart rate over 50/minute. Hyperinsulinemia/euglycemia therapy is currently reserved as an adjunct to conventional therapy and is recommended only after an inadequate response to fluid resuscitation, high-dose calcium salts, and pressor agents. 

The mam indication for the intravenous glucose tolerance test is in clinical research to evaluate the first-phase insulin response to glucose (see Figure 25-13). The test is performed as described earlier, but samples are drawn as follows Two baseline samples 5 minutes apart (the latter immediately before infusion) and samples 1, 3, 5, and 10 minutes after the end of the glucose infusion. The first-phase insulin release is usually measured by the sum of the insuhn concentrations 1 and 3 minutes after the glucose bolus. Alternatively, the 0 to 10-minute incremental insulin area may be used. Like the OGTT, the intravenous glucose tolerance test has poor reproducibility. 

So far, several investigators (Samols et al., 1965 Porte et al., 1965 Karam et al., 1965 Crockford et al., 1966) noticed that the Intravenous injection of glucagon was followed by a rapid significant rise of plamaa insulin and that this response was enhanced by simultaneous infusion of glucose,... 

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