Regional brain activation during hypoglycemia in type 1 diabetes.
BACKGROUND
Mechanisms underlying the brain response to hypoglycemia are not well understood.


OBJECTIVE
Our objective was to determine the blood glucose level at which the hypothalamus and other brain regions are activated in response to hypoglycemia in type 1 diabetic patients and control subjects.


METHODS
This was a cross-sectional study evaluating brain activity using functional magnetic resonance imaging in conjunction with a hyperinsulinemic hypoglycemic clamp to lower glucose from euglycemia (90 mg/dl) to hypoglycemia (50 mg/dl).


METHODS
The study was performed at the Brain Imaging Center in the McLean Hospital.


METHODS
Seven type 1 diabetic patients between 18 and 50 yr old and six matched control subjects were included in the study.


METHODS
Hyperinsulinemic hypoglycemic clamp was performed.


METHODS
Blood glucose level at peak hypothalamic activation, amount of regional brain activity during hypoglycemia in both groups, and difference in regional brain activation between groups were calculated.


RESULTS
The hypothalamic region activates at 68 +/- 9 mg/dl in control subjects and 76 +/- 8 mg/dl in diabetic patients during hypoglycemia induction. Brainstem, anterior cingulate cortex, uncus, and putamen were activated in both groups (P < 0.001). Each group also activated unique brain areas not active in the other group.


CONCLUSIONS
This application of functional magnetic resonance imaging can be used to identify the glucose level at which the hypothalamus is triggered in response to hypoglycemia and whether this threshold differs across patient populations. This study suggests that a core network of brain regions is recruited during hypoglycemia in both diabetic patients and control subjects.
Musen
Gail
G
Research Division, Joslin Diabetes Center, 1 Joslin Place Room 350, Boston, Massachusetts 02215, USA. gail.musen@joslin.harvard.edu
Simonson
Donald C
DC
Bolo
Nicolas R
NR
Driscoll
Amy
A
Weinger
Katie
K
Raji
Annaswamy
A
Théberge
Jean
J
Renshaw
Perry F
PF
Jacobson
Alan M
AM
D000328:Adult; D000367:Age Factors; D001786:Blood Glucose / Q000032:analysis; D001921:Brain / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007003:Hypoglycemia / Q000503:physiopathology*; D007031:Hypothalamus / Q000502:physiology; D008297:Male; D008875:Middle Aged
D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human