Differences in response to food stimuli in a rat model of obesity: in-vivo assessment of brain glucose metabolism.
OBJECTIVE
Food intake is regulated by factors that modulate caloric requirements as well as food's reinforcing properties. In this study, we measured brain glucose utilization to an olfactory stimulus (bacon scent), and we examined the role of food restriction and genetic predisposition to obesity on such brain metabolic activity.


METHODS
Zucker obese (Ob) and lean (Le) rats were divided into four groups: (1) Ob ad-libitum fed, (2) Ob food restricted (70% of ad libitum), (3) Le ad-libitum fed and (4) Le food restricted. Rats were scanned using micro-positron emission tomography and 2-[(18)F]-fluoro-2-deoxy-D-glucose under two conditions: (1) baseline scan (no stimulation) and (2) challenge scan (food stimulation, FS).


RESULTS
FS resulted in deactivation of the right and left hippocampus. Ob rats showed greater changes with FS than Le rats (deactivation of hippocampus and activation of the medial thalamus) and Ob but not Le animals deactivated the frontal cortex and activated the superior colliculus. Access to food resulted in an opposite pattern of metabolic changes to the food stimuli in olfactory nucleus (deactivated in unrestricted and activated in restricted) and in right insular/parietal cortex (activated in unrestricted and deactivated in restricted). In addition, restricted but not unrestricted animals activated the medial thalamus.


CONCLUSIONS
The greater changes in the Ob rats suggest that leptin modulates the regional brain responses to a familiar food stimulus. Similarly, the differences in the pattern of responses with food restriction suggest that FS is influenced by access to food conditions. The main changes with FS occurred in the hippocampus, a region involved in memory, the insular cortex, a region involved with interoception (perception of internal sensations), the medial thalamus (region involved in alertness) and in regions involved with sensory perception (olfactory bulb, olfactory nucleus, occipital cortex, superior colliculus and parietal cortex), which corroborates their relevance in the perception of food.
Thanos
P K
PK
Department of Medicine, Behavioral Neuropharmacology and Neuroimaging Laboratory, Brookhaven National Laboratory, Upton, NY, USA.
Michaelides
M
M
Gispert
J-D
JD
Pascau
J
J
Soto-Montenegro
M L
ML
Desco
M
M
Wang
R
R
Wang
G-J
GJ
Volkow
N D
ND
D000818:Animals; D001069:Appetite Regulation; D001921:Brain / Q000378:metabolism*; D004435:Eating; D019788:Fluorodeoxyglucose F18; D005508:Food Deprivation; D005947:Glucose / Q000378:metabolism*; D006624:Hippocampus / Q000000981:diagnostic imaging; D007091:Image Processing, Computer-Assisted; D020738:Leptin / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D023421:Models, Animal; D009765:Obesity / Q000378:metabolism*; D049268:Positron-Emission Tomography / Q000379:methods; D017397:Prefrontal Cortex / Q000000981:diagnostic imaging; D019275:Radiopharmaceuticals; D051381:Rats; D011924:Rats, Zucker
D020738:Leptin; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005947:Glucose