24-Hydroxy-Cholesterol Synthesis Rate Measured in Blood in a Preclinical Mouse Model Suggests a Non-invasive Biomarker of Brain Demyelination and Remyelination (P2.199)

OBJECTIVE: Assess changes in syntheses of myelin in brain and of blood sterols, during demyelination and remyelination and in response to thyroid hormone (T3) treatment in the mouse cuprizone model. BACKGROUND: In mice, dietary cuprizone produces brain demyelination and spontaneous remyelination is induced upon return to normal chow. Deuterated water ( 2 H 2 O) labeling combined with mass spectrometry is useful to measure brain de novo cholesterol synthesis, de novo lipogenesis, as well as synthesis of galactocereboside (GalC) and myelin proteins. 24-hydroxy cholesterol (24-OHC), the major metabolite of brain cholesterol, is detected in blood and thought to reflect CNS cholesterol metabolism. DESIGN/METHODS: Mice were fed cuprizone for 4 weeks, then returned to control diet and treated with either placebo or T3 (0.005 mg/day). 2 H 2 O labeling was performed for the last 14 days of cuprizone diet, and for either 8, 14 or 21 days during recovery, after which blood and corpus callosum (CC) samples were collected (n=5/time point/treatment). 2 H incorporation into cholesterol and 24-OHC in blood and CC, as well as into palmitate in phospholipids, GalC, myelin basic protein (MBP) and 29,39-cyclic-nucleotide 39-phosphodiesterase (CNPase) in CC were measured by mass spectrometry. RESULTS: Cuprizone diet significantly (p<0.05) decreased syntheses of cholesterol, 24-OHC, GalC, MBP, CNPase and palmitate in the CC and these effects were reversed during recovery. T3 treatment significantly (p<0.05) increased syntheses of cholesterol, 24-OHC and palmitate as compared to placebo. 24-OHC synthesis rates indicated that majority of blood 24-OHC is derived from the brain and most importantly, blood 24-OHC reflected brain sterol changes produced by cuprizone and T3. CONCLUSIONS: These preclinical mouse data indicate that dynamic changes in synthesis of several lipid and protein components occur during demyelination and remyelination in the brain, and suggest that 24-OHC in blood has the potential to be a non-invasive marker of brain de novo cholesterol synthesis. Disclosure: Dr. Shankaran has received personal compensation for activities with KineMed, Inc. as an employee. Dr. Tsang has received personal compensation for activities with KineMed, Inc. as an employee. Dr. Mohammed has received personal compensation for activities with KineMed, Inc. as an employee. Dr. Wong has received personal compensation for activities with KineMed, Inc. as an employee. Dr. Protasio has received personal compensation for activities with KineMed, Inc. as an employee. Dr. Bernard has received personal compensation for activities with EMD Serono as an employee. Dr. Chang has received personal compensation for activities with EMD Serono as an employee. Dr. Dellovade has received personal compensation for activities with EMD Serono as an employee. Dr. Turner has received personal compensation for activities with KineMed, Inc. as an employee.