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Diabetes. 2014 Dec;63(12):4083-8. doi: 10.2337/db14-0477. Epub 2014 Jul 15.

Central insulin administration improves whole-body insulin sensitivity via hypothalamus and parasympathetic outputs in men.

Author information

1
Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany.
2
Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany robert.wagner@med.uni-tuebingen.de.
3
Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany.
4
German Center for Diabetes Research (DZD e.V.), Neuherberg, Germany Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany.
5
Institute of Medical Psychology and Behavioral Neurobiology/fMEG Center, Eberhard Karls University Tübingen, Tübingen, Germany.
6
Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Eberhard Karls University Tübingen, Tübingen, Germany.

Abstract

Animal studies suggest that insulin action in the brain is involved in the regulation of peripheral insulin sensitivity. Whether this holds true in humans is unknown. Using intranasal application of insulin to the human brain, we studied the impacts of brain insulin action on whole-body insulin sensitivity and the mechanisms involved in this process. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic glucose clamp before and after intranasal application of insulin and placebo in randomized order in lean and obese men. After insulin spray application in lean subjects, a higher glucose infusion rate was necessary to maintain euglycemia compared with placebo. Accordingly, clamp-derived insulin sensitivity index improved after insulin spray. In obese subjects, this insulin-sensitizing effect could not be detected. Change in the high-frequency band of heart rate variability, an estimate of parasympathetic output, correlated positively with change in whole-body insulin sensitivity after intranasal insulin. Improvement in whole-body insulin sensitivity correlated with the change in hypothalamic activity as assessed by functional magnetic resonance imaging. Intranasal insulin improves peripheral insulin sensitivity in lean but not in obese men. Furthermore, brain-derived peripheral insulin sensitization is associated with hypothalamic activity and parasympathetic outputs. Thus, the findings provide novel insights into the regulation of insulin sensitivity and the pathogenesis of insulin resistance in humans.

TRIAL REGISTRATION:

ClinicalTrials.gov NCT01847456.

PMID:
25028522
DOI:
10.2337/db14-0477
[Indexed for MEDLINE]
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