Proton magnetic resonance spectroscopy studies on human brain myo-inositol in hypo-osmolarity and hepatic encephalopathy.
OBJECTIVE
Recent in vivo studies using proton magnetic resonance (1H-MR) spectroscopy showed low levels of myo-inositol in the brain in hepatic encephalopathy; the pathogenetic relevance of this observation is unclear.


METHODS
Myo-inositol and glutamine levels in the brain were studied in vivo by 1H-MR spectroscopy in patients with hypo-osmolarity and hepatic encephalopathy.


RESULTS
A patient with severe plasma hypo-osmolarity (222 mOsm/L) had almost undetectable signals for myo-inositol and glutamine/glutamate in the brain. Both signals reappeared after normalization of plasma osmolarity, suggesting that both myo-inositol and glutamine were released as organic osmolytes from the brain. A decreased cerebral myo-inositol signal is also found in low-grade hepatic encephalopathy but is accompanied by an increased glutamine signal. Cirrhotics without hepatic encephalopathy have near-normal inositol signals, and patients with acquired immunodeficiency syndrome encephalopathy have increased inositol signals.


CONCLUSIONS
The 1H-MR spectroscopic myo-inositol signal in the human brain predominantly reflects an osmosensitive inositol pool. It is hypothesized that its depletion in latent hepatic encephalopathy points to a disturbance of cell volume homeostasis in the brain as an early pathogenetic event. This may partly be caused by a hyperammonemia-induced glutamine accumulation in the brain.
Häussinger
D
D
Medizinische und Radiologische Universitätsklinik Freiburg, Germany.
Laubenberger
J
J
vom Dahl
S
S
Ernst
T
T
Bayer
S
S
Langer
M
M
Gerok
W
W
Hennig
J
J
D000163:Acquired Immunodeficiency Syndrome / Q000150:complications; D000328:Adult; D000368:Aged; D001923:Brain Chemistry; D001927:Brain Diseases / Q000209:etiology / Q000378:metabolism; D005260:Female; D005973:Glutamine / Q000032:analysis; D006501:Hepatic Encephalopathy / Q000378:metabolism*; D006801:Humans; D007294:Inositol / Q000032:analysis*; D008103:Liver Cirrhosis / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011522:Protons; D014883:Water-Electrolyte Imbalance / Q000378:metabolism*
D011522:Protons; D005973:Glutamine; D007294:Inositol