Clinical Neuroendocrinology

Improving Influence of Insulin on Cognitive Functions in Humans
Werner Kern^a, Achim Peters^a, Bernd Fruehwald-Schultes^a, Eva Deininger^a, Jan Born^b, Horst L. Fehm^a

Departments of
^aInternal Medicine I and
^bClinical Neuroendocrinology, University of Lübeck, Germany

Address of Corresponding Author

Neuroendocrinology 2001;74:270-280 (DOI: 10.1159/000054694)

  Key Words

• Insulin
• Cognitive functions
• Auditory potentials
• Attention
• Mood
• Memory
• Clinical neuroendocrinology

  Abstract

Insulin receptors have been identified in limbic brain structures, but their functional relevance is still unclear. In order to characterize some of their effects, we evaluated auditory evoked brain potentials (AEP) in a vigilance task, behavioral measures of memory (recall of words) and selective attention (Stroop test) during infusion of insulin. The hormone was infused at two different rates (1.5 mU/kg × min, 'low insulin', and 15 mU/kg × min, 'high insulin'), inducing respectively serum levels of 543 ± 34 and 24,029 ± 1,595 pmol/l. This experimental design allowed to compare cognitive parameters under two conditions presenting markedly different insulin levels, but with minimal incidence on blood glucose concentrations since these were kept constant by glucose infusion. A 'no insulin treatment' group was not included in order to avoid leaving patients infused with glucose without insulin treatment. Measures were taken during a baseline phase preceding insulin infusion and every 90 min during the 360 min of insulin infusion. Compared with 'low insulin', 'high insulin' induced a slow negative potential shift in the AEP over the frontal cortex (average amplitude, high insulin: 0.27 ± 0.48 µV; low insulin: 1.87 ± 0.48 µV, p < 0.005), which was paralleled by enhanced memory performance (words recalled, high insulin: 22.04 ± 0.93; low insulin: 19.29 ± 0.92, p < 0.05). Also, during 'high insulin' subjects displayed enhanced performance on the Stroop test (p < 0.05) and expressed less difficulty in thinking than during 'low insulin' (p < 0.03). Results indicate an improving effect of insulin on cognitive function, and may provide a frame for further investigations of neurobehavioral effects of insulin in patients with lowered or enhanced brain insulin, i.e., patients with Alzheimer's disease or diabetes mellitus.

Copyright © 2001 S. Karger AG, Basel

  Author Contacts

Werner Kern
Medical University of Lübeck, Department of Internal Medicine I
Ratzeburger Allee 160, D-23538 Lübeck (Germany)
Tel. +49 451 5003 639, Fax +49 451 5003 640
E-Mail Kern@kfg.mu-luebeck.de

  Article Information

Received: Received: November 6, 2000
Accepted after revision: June 19, 2001
Number of Print Pages : 11
Number of Figures : 7, Number of Tables : 0, Number of References : 77