title: The effect of insulin infusion on the metabolites in cerebral tissues assessed with proton magnetic resonance spectroscopy in young healthy subjects with high and low insulin sensitivity.
abstract: OBJECTIVE
  Insulin may play important roles in brain metabolism. Proton magnetic resonance spectroscopy ((1)H-MRS) of the central nervous system gives information on neuronal viability, cellular energy, and membrane status. To elucidate the specific role of insulin action in the brain, we estimated neurometabolites with (1)H-MRS and assessed their regulation by insulin infusion and their relationship with insulin sensitivity.
  
  
  METHODS
  We studied 16 healthy young men. (1)H-MRS was performed at baseline and after 240 min of euglycemic-hyperinsulinemic clamp. Voxels were positioned in the left frontal lobe, left temporal lobe, and left thalamus. The ratios of N-acetylaspartate (NAA), choline-containing compounds (Cho), myo-inositol, and glutamate/glutamine/γ-aminobutyric acid complex (Glx) to creatine (Cr) and nonsuppressed water signal were determined. The participants were divided into subgroups of high (high IS) and low (low IS) insulin sensitivity.
  
  
  RESULTS
  Baseline neurometabolic substrates were not different between the groups. Insulin infusion resulted in an increase in frontal NAA/Cr and NAA/H2O and frontal and temporal Glx/Cr and Glx/H2O and a decrease in frontal Cho/Cr and temporal Cho/H2O and myo-inositol/H2O (all P < 0.05, except temporal Glx/H2O, P = 0.054, NS) in the high-IS, but not in the low-IS, group. Insulin sensitivity correlated positively with frontal NAA/Cr and NAA/H2O and temporal Glx/H2O and negatively with temporal myo-inositol/Cr and myo-inositol/H2O assessed during the second (1)H-MRS (all P < 0.05).
  
  
  CONCLUSIONS
  Insulin might influence cerebral metabolites, and this action is impaired in subjects with low whole-body insulin sensitivity. Thus, our results provide a potential link between insulin resistance and altered metabolism of the central nervous system.
authors.affiliation: Department of Endocrinology, Diabetology, and Internal Medicine, Medical University of Białystok, Białystok, Poland. monika3101@wp.pl
authors.forename: Monika
authors.initials: M
authors.lastname: Karczewska-Kupczewska
authors.forename: Eugeniusz
authors.initials: E
authors.lastname: Tarasów
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Nikolajuk
authors.forename: Magdalena
authors.initials: M
authors.lastname: Stefanowicz
authors.forename: Natalia
authors.initials: N
authors.lastname: Matulewicz
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Otziomek
authors.forename: Maria
authors.initials: M
authors.lastname: Górska
authors.forename: Marek
authors.initials: M
authors.lastname: Straczkowski
authors.forename: Irina
authors.initials: I
authors.lastname: Kowalska
mesh_terms: D000328:Adult; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007332:Insulin Infusion Systems; D007333:Insulin Resistance / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D055815:Young Adult
chemical_list: D007328:Insulin