Cerebrospinal Fluid 7-Ketocholesterol Level is Associated with Amyloid-ß42 and White Matter Microstructure in Cognitively Healthy Adults.

BACKGROUND: Abnormal cholesterol metabolism changes the neuronal membrane and may promote amyloidogenesis. Oxysterols in cerebrospinal fluid (CSF) are related to Alzheimer's disease (AD) biomarkers in mild cognitive impairment and dementia. Cholesterol turnover is important for axonal and white matter (WM) microstructure maintenance. OBJECTIVE: We aim to demonstrate that the association of oxysterols, AD biomarkers, and WM microstructure occurs early in asymptomatic individuals. METHODS: We studied the association of inter-individual variability of CSF 24-hydroxycholesterol (24-OHC), 27-hydroxycholesterol (27-OHC), 7-ketocholesterol (7-KC), 7ß-hydroxycholesterol (7ß-OHC), amyloid-ß42 (Aß42), total-tau (t-tau), phosphorylated-tau (p-tau), neurofilament (NfL), and WM microstructure using diffusion tensor imaging, generalized linear models and moderation/mediation analyses in 153 healthy adults. RESULTS: Higher 7-KC levels were related to lower Aß42, indicative of greater AD pathology (p = 0.041) .  Higher 7-KC levels were related to lower fractional anisotropy (FA) and higher mean (MD), axial (AxD), and radial (RD) diffusivity. 7-KC modulated the association between AxD and NfL in the corpus callosum splenium (B = 39.39, p = 0.017), genu (B = 68.64, p = 0.000), and fornix (B = 10.97, p = 0.000). Lower Aß42 levels were associated to lower FA and higher MD, AxD, and RD in the fornix, corpus callosum, inferior longitudinal fasciculus, and hippocampus. The association between AxD and Aß42 was moderated by 7K-C (p = 0.048). CONCLUSION: This study adds clinical evidence to support the role of 7K-C on axonal integrity and the involvement of cholesterol metabolism in the Aß42 generation process.

The importance of steroidomics in the study of neurodegenerative disease and ageing.

In this mini review, the importance of experimental steroidomics in the study of neurodegenerative disease and aging is discussed. Attention is focused on just one class of lipid which is based on the cyclopentanoperhydro-phenanthrene ring system. Experimental methods for steroidomic analysis are reviewed, and the potential to use these methods to diagnose disease and to gain a better understanding of neurodegenerative disorders is examined.

Levels of 7-oxocholesterol in cerebrospinal fluid are more than one thousand times lower than reported in multiple sclerosis.

In a recent publication [Diestel, A., O. Aktas, D. Hackel, I. Hake, S. Meier, C. S. Raine, R. Nitsch, F. Zipp, and O. Ullrich. 2003. Activation of microglial poly (ADP-ribose)-polymerase-1 by cholesterol breakdown products during neuroinflammation: a link between demyelination and neuronal damage. J. Exp. Med. 198: 1729-1740], extremely high levels of 7-oxocholesterol were reported in cerebrospinal fluid (CSF) of 11 patients with multiple sclerosis (MS) [7.4 +/- 0.3 mg/l (mean +/- SEM)]. The corresponding level of 12 subjects with other kinds of neurological diseases was reported to be 0.5 +/- 0.1 mg/l. Such high levels of 7-oxocholesterol were found to cause neuronal damage of living brain tissues. Using a highly accurate method for an assay of 7-oxocholesterol based on isotope dilution-mass spectrometry and anaerobic conditions during workup, we found that the level of 7-oxocholesterol in CSF from 29 Swedish patients with MS was only 1.2 microg/l (median, ranging from 0.4 to 4.6 microg/l), less than 1/1,000 th of the previously reported level. The level of 7-oxocholesterol in CSF from 24 Swedish control patients was 0.9 microg/l (0.3-2.3 microg/l), slightly but significantly lower than the CSF level in MS patients (P=0.002). In vitro-induced lipid peroxidation of the endogenous cholesterol in CSF increased the level of 7-oxygenated cholesterol metabolites, particularly 7-oxocholesterol, up to approximately 0.3 mg/l. These results are discussed in relation to the fact that 7-oxygenated steroids are easily artificially formed by autoxidation of cholesterol during workup procedures and analysis of sterols and oxysterols from biological samples.

Activation of microglial poly(ADP-ribose)-polymerase-1 by cholesterol breakdown products during neuroinflammation: a link between demyelination and neuronal damage.

Multiple sclerosis (MS) is a chronic demyelinating disease in which it has only recently been suggested that damage to neuronal structures plays a key role. Here, we uncovered a link between the release of lipid breakdown products, found in the brain and cerebrospinal fluid (CSF) of MS patients as well as in experimental autoimmune encephalomyelitis, and neuronal damage mediated by microglial activation. The concentrations of the breakdown product 7-ketocholesterol detected in the CSF of MS patients were capable of inducing neuronal damage via the activation and migration of microglial cells in living brain tissue. 7-ketocholesterol rapidly entered the nucleus and activated poly(ADP-ribose)-polymerase (PARP)-1, followed by the expression of migration-regulating integrins CD11a and intercellular adhesion molecule 1. These findings reveal a novel mechanism linking demyelination and progressive neuronal damage, which might represent an underlying insidious process driving disease beyond a primary white matter phenomenon and rendering the microglial PARP-1 a possible antiinflammatory therapeutic target.