Plasma 24S-hydroxycholesterol Research Articles

The Effects of Gender and CYP46 and Apo E Polymorphism on 24S-Hydroxycholesterol Levels in Alzheimers Patients Treated with Statins

To examine the effect of gender and polymorphisms of CYP46 and apo E on plasma levels of 24S-hydroxycholesterol in Alzheimer's disease (AD) patients and to determine whether these factors contribute to the variability in responses to statin treatment. Fifty-three AD patients had measurement of plasma levels of 24S-hydroxycholesterol, plasma and lipoprotein cholesterol and genotyping of CYP46 and apo E. Thirty-nine of the subjects subsequently participated in a statin trial for 6 weeks, and had a repetition of the baseline measurements. Baseline levels of 24S-hydroxycholesterol were higher in women than in men. There was a positive and significant correlation of plasma oxysterol levels with levels of total plasma cholesterol (women: r = .72, P < .0001; men: r = .47, P = .02) and non-HDL cholesterol (women: r = .68, P < .0001; men: r = 0.51, P = .01) (and LDL cholesterol) but not HDL cholesterol levels. There was no association of CYP46 or apo E polymorphisms with plasma levels of 24S-hydroxycholesterol. AD subjects treated with statins had a similar percent reduction in lathosterol, 24S-hydroxycholesterol, total cholesterol and non-HDL (and LDL) cholesterol regardless of gender and polymorphisms of CYP46. Subjects with the 4/4 polymorphism had less reduction in the ratios of 24S-hydroxycholesterol-LDL cholesterol. Women with AD had higher levels of plasma 24S-hydroxycholesterol levels than men. Women also showed a very strong correlation of plasma levels of 24S-hydroxycholesterol-to-total and non-HDL cholesterol. This may suggest that the oxysterol may be an important marker of AD risk instead of total cholesterol, as suggested by others. Polymorphisms of CYP46 or apo E do not explain levels of oxysterol or non-HDL cholesterol or the responsiveness to statin treatment in this study.

Plasma levels of 24S-hydroxycholesterol in patients with neurological diseases

The brain is the exclusive or almost exclusive site of formation of 24S-hydroxycholesterol and we have shown that the circulating level of 24S-hydroxycholesterol is dependent upon the relation between cerebral production and hepatic clearance. In the present work we determined plasma levels of 24S-hydroxycholesterol in patients with various neurological diseases. Eleven subjects with brain death occurring 6–10 h before collection of the plasma samples had markedly reduced circulating levels of 24S-hydroxycholesterol (−43%, P<0.001). Patients with advanced Alzheimer's disease and cerebral inflammatory diseases had slightly lower levels of 24S-hydroxycholesterol in plasma when compared to matched controls. Patients with acute ischemic stroke, multiple sclerosis and primary brain tumors had levels not significantly different from those of controls. The conditions leading to reduced plasma levels of 24S-hydroxycholesterol had no significant effect on plasma levels of another side-chain oxidized oxysterol, 27-hydroxycholesterol. Except for conditions characterized by very marked destruction of the central nervous system, different severe neurological diseases seem to have relatively small effects on the flux of 24S-hydroxycholesterol from the brain.

Plasma 24S-hydroxycholesterol: a peripheral indicator of neuronal degeneration and potential state marker for Alzheimer's disease.

The conversion of brain cholesterol into 24S-hydroxycholesterol and its subsequent release into the periphery is probably an important step for the maintenance of brain cholesterol homeostasis. Recent findings suggest that plasma 24S-hydroxycholesterol may be elevated in Alzheimer's disease (AD) and vascular dementia at least at some stage of the disease, suggesting increased brain cholesterol turnover during neurodegeneration. We investigated whether plasma 24S-hydroxycholesterol concentrations depend on the severity of AD and on the apolipoprotein E (apoE) genotype. Severity of AD and inheritance of the apoE4 allele were independently associated with reduced plasma 24S-hydroxycholesterol/cholesterol ratios. The results suggest that the decrease of plasma 24S-hydroxycholesterol/cholesterol in severely affected AD patients is a peripheral marker for loss of cholesterol 24S-hydroxylase in the CNS. Inheritance of the apoE4 allele may be associated with increased apoE-mediated transport of brain cholesterol to the periphery or with decreased activity of the 24S-hydroxylase. Longitudinal studies will assess the validity of the ratio plasma 24S-hydroxycholesterol/cholesterol as a state marker for AD.

Plasma levels of 24S-hydroxycholesterol reflect the balance between cerebral production and hepatic metabolism and are inversely related to body surface

We have previously presented evidence that most of the 24S-hydroxycholesterol present in the circulation originates from the brain and that most of the elimination of this oxysterol occurs in the liver. Plasma 24S-hydroxycholesterol levels decline by a factor of about 5 during the first decades of life. The concentration of the enzyme cholesterol 24S-hydroxylase in the brain is, however, about constant from the first year of life, and reduced enzyme levels thus cannot explain the decreasing plasma levels during infancy. In the present work we tested the hypothesis that the plasma levels of 24S-hydroxycholesterol may reflect the size of the brain relative to the capacity of the liver to eliminate the substance. It is shown here that the age-dependent changes in absolute as well as cholesterol-related plasma level of 24S-hydroxycholesterol closely follow the changes in the ratio between estimated brain weight and estimated liver volume. The size of the brain is increased only about 50% whereas the size of the liver is increased by about 6-fold after the age of 1 year. Liver volume is known to be highly correlated to body surface, and in accordance with this the absolute as well as the cholesterol-related plasma level of 24S-hydroxycholesterol was found to be highly inversely correlated to body surface in 77 healthy subjects of varying ages (r2 = 0.74). Two chondrodystrophic dwarves with normal size of the brain but with markedly reduced body area had increased levels of 24S-hydroxycholesterol when related to age but normal levels when related to body surface. It is concluded that the balance between cerebral production and hepatic metabolism is a critical determinant for plasma levels of 24S-hydroxycholesterol at different ages and that endocrinological factors are less important. The results are discussed in relation to the possibility to use 24S-hydroxycholesterol in the circulation as a marker for cholesterol homeostasis in the brain.—Bretillon, L., D. Lütjohann, L. Ståhle, T. Widhe, L. Bindl, G. Eggertsen, U. Diczfalusy, and I. Björkhem. Plasma levels of 24S-hydroxycholesterol reflect the balance between cerebral production and hepatic metabolism and are inversely related to body surface. J. Lipid Res. 2000. 41: 840–845.

Plasma 24S-hydroxycholesterol (cerebrosterol) is increased in Alzheimer and vascular demented patients

Alzheimer's disease (AD) is characterized by the presence of senile plaques, neurofibrillary tangles, and neuronal cell loss associated with membrane cholesterol release. 24S-hydroxycholesterol (24S-OH-Chol) is an enzymatically oxidized product of cholesterol mainly synthesized in the brain. We tested the hypothesis that plasma levels of this oxysterol could be used as a putative biochemical marker for an altered cholesterol homeostasis in the brain of AD patients. Thirty patients with clinical criteria for AD, 30 healthy volunteers, 18 depressed patients, and 12 patients with vascular dementia (non-Alzheimer demented) were studied. Plasma concentrations of 24S-OH-Chol were assayed by isotope dilution–mass spectrometry, cholesterol was measured enzymatically, and apolipoprotein E (apoE) was genotyped by polymerase chain reaction and restricted fragment length polymorphism. The concentration of 24S-OH-Chol in AD and non-Alzheimer demented patients was modestly but significantly higher than in healthy controls and in depressed patients. There was no significant difference in the concentrations of 24S-OH-Chol between depressed patients and healthy controls nor between AD and non-Alzheimer demented patients. The apoE ϵ4 allele influences plasma 24S-OH-Chol. However, this influence could be completely accounted for by the elevated plasma cholesterol in apoE4 hetero- or homozygotes. Plasma 24S-OH-Chol levels correlated negatively with the severity of dementia. AD and vascular demented patients appear to have higher circulating levels of 24S-OH-Chol than depressed patients and healthy controls. We speculate that 24S-OH-Chol plasma levels may potentially be used as an early biochemical marker for an altered cholesterol homeostasis in the central nervous system. —Lütjohann, D., A. Papassotiropoulos, I. Björkhem, S. Locatelli, M. Bagli, R. D. Oehring, U. Schlegel, F. Jessen, M. L. Rao, K. von Bergmann, and R. Heun. Plasma 24S-hydroxycholesterol (cerebrosterol) is increased in Alzheimer and vascular demented patients.