The brain response to peripheral insulin declines with age: A contribution of the blood-brain barrier?
    
    
        
    
    
        
        PLoS ONE 10:e0126804 (2015)
    
    
    
		
		
			
				OBJECTIVES: It is a matter of debate whether impaired insulin action originates from a defect at the neural level or impaired transport of the hormone into the brain. In this study, we aimed to investigate the effect of aging on insulin concentrations in the periphery and the central nervous system as well as its impact on insulin-dependent brain activity. METHODS: Insulin, glucose and albumin concentrations were determined in 160 paired human serum and cerebrospinal fluid (CSF) samples. Additionally, insulin was applied in young and aged mice by subcutaneous injection or intracerebroventricularly to circumvent the blood-brain barrier. Insulin action and cortical activity were assessed by Western blotting and electrocorticography radiotelemetric measurements. RESULTS: In humans, CSF glucose and insulin concentrations were tightly correlated with the respective serum/plasma concentrations. The CSF/serum ratio for insulin was reduced in older subjects while the CSF/serum ratio for albumin increased with age like for most other proteins. Western blot analysis in murine whole brain lysates revealed impaired phosphorylation of AKT (P-AKT) in aged mice following peripheral insulin stimulation whereas P-AKT was comparable to levels in young mice after intracerebroventricular insulin application. As readout for insulin action in the brain, insulin-mediated cortical brain activity instantly increased in young mice subcutaneously injected with insulin but was significantly reduced and delayed in aged mice during the treatment period. When insulin was applied intracerebroventricularly into aged animals, brain activity was readily improved. CONCLUSIONS: This study discloses age-dependent changes in insulin CSF/serum ratios in humans. In the elderly, cerebral insulin resistance might be partially attributed to an impaired transport of insulin into the central nervous system.
			
			
				
			
		 
		
			
				
					
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        Artikel: Journalartikel
    
 
    
        Dokumenttyp
        Wissenschaftlicher Artikel
    
 
    
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        Schlagwörter
        Central-nervous-system; Cerebrospinal-fluid; Alzheimers-disease; Endothelial-cells; Temporal-lobe; In-vivo; Transport; Humans; Resistance; Obesity
    
 
    
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        Sprache
        englisch
    
 
    
        Veröffentlichungsjahr
        2015
    
 
    
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        HGF-Berichtsjahr
        2015
    
 
    
    
        ISSN (print) / ISBN
        1932-6203
    
 
    
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	    Band: 10,  
	    Heft: 5,  
	    Seiten: ,  
	    Artikelnummer: e0126804 
	    Supplement: ,  
	
    
 
  
        
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            Verlag
            Public Library of Science (PLoS)
        
 
        
            Verlagsort
            Lawrence, Kan.
        
 
	
        
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        Peer reviewed
    
 
     
    
        POF Topic(s)
        90000 - German Center for Diabetes Research
    
 
    
        Forschungsfeld(er)
        Helmholtz Diabetes Center
    
 
    
        PSP-Element(e)
        G-502400-002
G-502400-001
G-502490-001
    
 
    
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        Erfassungsdatum
        2015-05-14