Brain energy metabolism during hypoglycaemia in healthy and type 1 diabetic subjects.
OBJECTIVE
This study aimed to examine brain energy metabolism during moderate insulin-induced hypoglycaemia in Type 1 diabetic patients and healthy volunteers.


METHODS
Type 1 diabetic patients (mean diabetes duration 13 +/- 2.5 years; HbA1c 6.8 +/- 0.3%) and matched controls were studied before, during (0-120 min) and after (120-240 min) hypoglycaemic (approximately 3.0 mmol/l) hyperinsulinaemic (1.5 mU x kg(-1) min(-1)) clamp tests. Brain energy metabolism was assessed by in vivo 31P nuclear magnetic resonance spectroscopy of the occipital lobe (3 Tesla, 10-cm surface coil).


RESULTS
During hypoglycaemia, the diabetic patients showed blunted endocrine counter-regulation. Throughout the study, the phosphocreatine:gamma-ATP ratios were lower in the diabetic patients (baseline: controls 3.08 +/- 0.29 vs diabetic patients 2.65 +/- 0.43, p<0.01; hypoglycaemia: 2.97 +/- 0.38 vs 2.60 +/- 0.35, p<0.05; recovery: 3.01 +/- 0.28 vs 2.60 +/- 0.35, p<0.01). Intracellular pH increased in both groups, being higher in diabetic patients (7.096 +/- 0.010 vs. 7.107 +/- 0.015, p<0.04), whereas intracellular magnesium concentrations decreased in both groups (controls: 377 +/- 33 vs 321 +/- 39; diabetic patients: 388 +/- 47 vs 336 +/- 68 micromol/l; p<0.05).


CONCLUSIONS
Despite a lower cerebral phosphocreatine:gamma-ATP ratio in Type 1 diabetic patients at baseline, this ratio does not change in control or diabetic patients during modest hypoglycaemia. However, both groups exhibit subtle changes in intracellular pH and intracellular magnesium concentrations.
Division of Endocrinology and Metabolism, Department of Internal Medicine III, University of Vienna Medical School, Austria.
M G
MG
Bischof
V
V
Mlynarik
A
A
Brehm
E
E
Bernroider
M
M
Krssak
E
E
Bauer
C
C
Madl
M
M
Bayerle-Eder
W
W
Waldhäusl
M
M
Roden
D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001923:Brain Chemistry / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D015309:Glucose Clamp Technique; D006728:Hormones / Q000097:blood; D006801:Humans; D007003:Hypoglycemia / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D010725:Phosphocreatine / Q000378:metabolism
D001786:Blood Glucose; D006728:Hormones; D010725:Phosphocreatine; D000255:Adenosine Triphosphate