Human Insulin in Hypoglycemia: A New Arena?

Amiel, Stephanie A.

doi:10.2337/diab.44.3.257

Cited by 6 publications

(2 citation statements)

References 31 publications

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“…The authors suggested that these differences may relate to different intracerebral in sulin concentrations subsequent to different physical properties of the insulins, implying that insulin does af fect at least some cerebral functions in man. This has clinical implications in view of suggestions that different insulin preparations may affect hypoglycemic responses differently (reviewed in Amiel, 1995). Furthermore, al though the evidence for an effect of insulin on counter regulatory responses to hypoglycemia in man is contro versial (Kerr et aI., 1991;Diamond et aI., 1991;Lui et aI., 1991;Davis et aI., 1993;Mellman et aI., 1992), a recent study using selective catheterization to elevate cerebral blood insulin levels during hypoglycemia in dogs sug gests that insulin may affect brain behavior in hypogly cemia (Davis et aI., 1995).…”

Section: Discussionmentioning

confidence: 99%

Regional Differences in Cerebral Blood Flow and Glucose Utilization in Diabetic Man: The Effect of Insulin

Cranston

Marsden

Matyka

et al. 1998

J Cereb Blood Flow Metab

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To determine the effect of insulin on regional cerebral blood flow (rCBF) and glucose metabolism (CMRglu), we performed quantitative dynamic PET scanning of labeled water (H215O) and deoxyglucose (18FDG) using two protocols in 10 diabetic men. In protocol A, to test reproducibility of the technique, insulin was infused at 1.5 mU.kg-1.min-1 twice (n = 5). In protocol B, low (0.3 mU.kg-1.min-1) and high (3 mU.kg-1.min-1) dose insulin was given on separate occasions (n = 5). Euglycemia (5 mmol/L) was maintained by glucose infusion. In protocol A, CMRglu was 6% higher during the first infusion, and catecholamines were also increased, indicating stress. Blood flow was not different. Changing free insulin levels from 20.5 +/- 4.8 to 191 +/- 44.5 mU/L (P < 0.001, low versus high dose, protocol B) did not alter total or regional CMRglu (whole brain 36.6 +/- 4.0 versus 32.8 +/- 6.2 mumol.100 g-1.min-1, P = 0.32) or CBF (41.7 +/- 5.1 and 45.6 +/- 9.7 mL.100 g-1.min-1, P = 0.4) or rCBF. In cerebellum, CMRglu was lower than in cortex and the ratio between rate constants for glucose uptake and phosphorylation (K1 and k3) was reversed. There are regional differences in cerebral metabolic capacity that may explain why cerebral cortex is more sensitive to hypoglycemia than cerebellum. Brain glucose metabolism is not sensitive to insulin concentration within the physiologic range. This suggests that intracerebral insulin receptors have a different role from those in the periphery.

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