title: Changes in differential functional magnetic resonance signals in the rodent brain elicited by mixed-nutrient or protein-enriched meals.
abstract: OBJECTIVE
  The hypothalamus and brain stem have important roles in regulating food intake; the roles of other nonhomeostatic centers in detecting nutrient content of ingested food have been poorly characterized. We used blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) to map brain regions that are responsive to intragastric infusion of isocaloric amounts of a mixed nutrient or protein, and assessed the role of blood glucose in the observed BOLD signal changes.
  
  
  METHODS
  Brain images were acquired, using a 9.4 T MRI system, from anesthetized rats during intragastric infusion of saline (n = 7), or 12 kcal of a mixed nutrient (n = 13) or protein (n = 6). Nutrient-induced changes in blood parameters and the effects of intravenous infusion of saline or glucose (n = 5/treatment) on BOLD fMRI signal changes were also evaluated. Intragastric nutrient infusion reduced the BOLD fMRI signal intensity in homeostatic (hypothalamus, nucleus tractus solitarius) and nonhomeostatic (thalamus, hippocampus, caudate putamen, cerebral cortex, cerebellum) centers; these effects were mimicked qualitatively by intravenous glucose. In contrast to a mixed meal, protein load reduced the BOLD fMRI signal in the amygdala. BOLD fMRI signal changes were inversely correlated with circulating concentrations of amylin, insulin, peptide YY, and glucagon-like peptide-1.
  
  
  CONCLUSIONS
  The caloric content of a meal is signaled from the gut to the brain and affects activity in homeostatic and non-homeostatic centers; blood glucose concentrations have an important role. The satiety effects of protein are associated with activity changes specifically in the amygdala.
authors.affiliation: Gastrointestinal Research Group, Calvin, Phoebe and Joan Snyder Institute of Infection, Immunity and Inflammation, University of Calgary, Calgary, Alberta, Canada.
authors.forename: David K
authors.initials: DK
authors.lastname: Min
authors.forename: Ursula I
authors.initials: UI
authors.lastname: Tuor
authors.forename: Henry S
authors.initials: HS
authors.lastname: Koopmans
authors.forename: Prasanth K
authors.initials: PK
authors.lastname: Chelikani
mesh_terms: D000679:Amygdala / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000187:drug effects* / Q000502:physiology*; D004044:Dietary Proteins / Q000494:pharmacology*; D005502:Food; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology; D007328:Insulin / Q000097:blood; D058228:Islet Amyloid Polypeptide / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D023421:Models, Animal; D019894:Peptide YY / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D012528:Satiety Response / Q000187:drug effects / Q000502:physiology; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology; D013788:Thalamus / Q000187:drug effects / Q000502:physiology
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D007328:Insulin; D058228:Islet Amyloid Polypeptide; D019894:Peptide YY; D052216:Glucagon-Like Peptide 1