Effects of abstinence from alcohol on the broad phospholipid signal in human brain: an in vivo 31P magnetic resonance spectroscopy study.

BACKGROUND: In vivo phosphorus magnetic resonance spectroscopy (31P MRS) at a magnetic field strength of 1.5 T allows measurement of fairly mobile membrane phospholipids in the human brain. We previously showed that subjects who are heavy drinkers had a smaller signal and a shorter transverse relaxation time (T2) of white matter phospholipids than light drinkers, which suggested lower concentrations and molecular mobility of phospholipids in heavy drinkers. The purpose of the present study was to measure if such chronic alcohol-induced white matter tissue changes are persistent in long-term abstinent alcoholics. METHODS: Fourteen abstinent alcoholics (mean age 45 years, seven men and seven women) were studied by localized 31P MRS in the centrum semiovale and were compared with 13 male, alcohol-dependent, heavy drinkers and 23 nondependent light drinkers (17 men, 6 women) of similar age. Methods for measurements of the broad membrane phospholipid signal and its relaxation time were described previously. RESULTS: Phospholipid concentrations and relaxation times in alcoholics abstinent for an average of 31 months were not significantly different from those measured in light drinkers. The contribution of fast and slowly relaxing signal components to the broad phospholipid signal, however, was still different in abstinent alcoholics compared with light drinkers. No effects of sex or of family history of alcoholism were noted on any of our spectroscopic measures within the light-drinking or abstinent groups. CONCLUSIONS: Most of our results suggest at least partial recovery of chronic alcohol-induced white matter phospholipid damage with long-term abstinence. They offer myelination changes and/or dendritic rearborization as a possible mechanism for the commonly observed white matter volume gain with prolonged abstinence. But the results also suggest a persistent abnormality in the nature and/or physical properties of white matter phospholipids in long-term abstinent alcoholics.

Effects of chronic alcohol consumption on the broad phospholipid signal in human brain: an in vivo 31P MRS study.

BACKGROUND: Phosphorus magnetic resonance spectroscopy (31P MRS) allows for the measurement of phospholipids and their breakdown products in the human brain. Fairly mobile membrane phospholipids give rise to a broad signal that co-resonates with metabolic phosphodiesters. Chronic alcohol exposure increases the rigidity of isolated brain membranes and, thus, may affect the amount and transverse relaxation times (T2) of MRS-detectable phospholipids. We tested the hypothesis that subjects who were heavy drinkers have stiffer membranes than controls who were light drinkers, as reflected in a smaller broad signal component and a shorter T2 of the broad signal in 31P MR spectra of the brain. METHODS: Thirteen alcohol-dependent heavy drinkers (mean age 44 years) were studied by localized 31P MRS in the centrum semiovale and compared with 17 nondependent light drinkers of similar age. The broad component signal was separated from the metabolite signal by convolution difference, which is based on the large difference in line widths of these two signals. Longitudinal and T2 relaxation times were measured using standard methods. RESULTS: The broad component integral was 13% lower in the brain of heavy drinkers compared with light drinkers (p < 0.001) and remained significantly smaller after corrections for both longitudinal and transverse relaxations (p < 0.01). The T2 distribution of the broad component consistently showed two resolvable components in both groups. The fast relaxing component had the same T2 in both groups (T2 = 1.9 msec). The slower relaxing component T2 was 0.6 msec shorter in heavy drinkers compared with light drinkers (p = 0.08). CONCLUSIONS: These results, observed in the absence of white matter volume loss, are consistent with biochemical alterations and higher rigidity of white matter phospholipids associated with long-term chronic alcohol abuse. The observed smaller broad signal component in these relatively young heavy drinkers is a sensitive measure of white matter phospholipid damage.