Effects of myo-Inositol ingestion on human brain myo-inositol levels: A proton magnetic resonance spectroscopic imaging study

Background: Cerebrospinal fluid levels of myo-Inositol (m-Ino) are reported to be deer-eased in patients with affective disorder; and dietary suppleme nts of m-Ino have been shown to reduce the symptoms of major depression. My o-Inositol transport across the blood-brain barrier is mediated by a low ca pacity saturable system. This study tests whether dietary m-Ino increases b rain m-Ino or changes brain metabolism of m-Ino, possibly explaining the ab ility of this compound to alter mood Methods: Using proton magnetic resonance spectroscopic imaging, we measured m-Ino Levels in occipital gray and parietal white matter of seventeen heal thy subjects. Magnetic resonance spectroscopic imaging was performed twice at baseline as well as at day 4 and day 8 while subjects ingested 6 g of m- Ino twice a day, Results: Following 4 days of m-Ino, m-Ino/Cr was 20% higher than baseline l evels in occipital gray matter (p < 0.04) and 8% higher in parietal white m atter (p = ns). By clay 8, m-Ino/Cr ratios had returned to baseline values. Conclusions: Brain m-Ino levels initially increase during m-Ino administrat ion and subsequently return to baseline levels. The rime-limited increases observed for brain m-Ino may reflect homeostatic mechanisms, possibly assoc iated with the role of m-lna as a cerebral osmolyte, or with changes in bra in phosphoinositide metabolism. (C) 1999 Society of Biological Psychiatry.