desmosterol and Alzheimer-Disease

Evidence is emerging that during the development of Alzheimer's disease (AD), changes in the synthesis and metabolism of cholesterol and progesterone are occurring that may or may not affect the progression of the disease. The concept arose from the recognition that dehydrocholesterol 24-reductase (DHCR24/Seladin-1), one of the nine enzymes in the endoplasmic reticulum that determines the transformation of lanosterol to cholesterol, is selectively reduced in late AD. As a consequence, the tissue level of desmosterol increases, affecting the expression of ABC transporters and the structure of lipid rafts, both determinants of amyloid-β processing. However, the former effect is considered beneficial and the latter detrimental to processing. Other determinants of desmosterol tissue levels are 24,25 epoxycholesterol and the ABCG1 and ABCG4 transporters. Progesterone and its metabolites are determinants of tissue levels of desmosterol and several other sterol intermediates in cholesterol synthesis. Animal models indicate marked elevations in the tissue levels of these sterols at early time frames in the progression of neurodegenerative diseases. The low level of neuroprogesterone and metabolites in AD are consonant with the low level of desmosterol and may have a role in amyloid-β processing. The sparse data that has accumulated appears to be a sufficient basis for proposing a systematic evaluation of the biologic roles of sterol intermediates in the slowly progressive neurodegeneration characteristic of AD.

Topics: Aged; Alzheimer Disease; Amyloidogenic Proteins; Animals; ATP Binding Cassette Transporter, Subfamily G; ATP Binding Cassette Transporter, Subfamily G, Member 1; ATP-Binding Cassette Transporters; Brain; Cholesterol; Desmosterol; Disease Models, Animal; Disease Progression; Humans; Mice; Nerve Tissue Proteins; Oxidoreductases Acting on CH-CH Group Donors; Progesterone

Desmosterol is a C27 sterol intermediate in cholesterol synthesis generated during the metabolic pathway that transforms lanosterol into cholesterol. It has become of particular interest in the pathogenesis of Alzheimer's disease (AD) because of the report that the activity of the gene coding for the enzyme DHCR24, which metabolizes desmosterol to cholesterol, is selectively reduced in the affected areas of the brain. Any change in the pattern of C27 sterol intermediates in cholesterol synthesis merits investigation with respect to the pathogenesis of AD, since neurosteroids such as progesterone can modulate the tissue levels. We therefore analyzed the C27 sterol composition using a metabolomics approach that preserves the proportion of the different sterol intermediates. In AD, the proportion of desmosterol was found to be less than that of age-matched controls. The findings do not directly support the focus on Seladin-1, although they could reflect different stages of a slowly progressive disease.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Brain; Desmosterol; Female; Humans; Male; Middle Aged; Nerve Tissue Proteins

We performed unbiased analysis of steroid-related compounds to identify novel Alzheimer's disease (AD) plasma biomarkers using liquid chromatography-atmospheric pressure chemical ionization-mass spectroscopy. The analysis revealed that desmosterol was found to be decreased in AD plasma versus controls. To precisely quantify variations in desmosterol, we established an analytical method to measure desmosterol and cholesterol. Using this LC-based method, we discovered that desmosterol and the desmosterol/cholesterol ratio are significantly decreased in AD. Finally, the validation of this assay using 109 clinical samples confirmed the decrease of desmosterol in AD as well as a change in the desmosterol/cholesterol ratio in AD. Interestingly, we could also observe a difference between mild cognitive impairment and control. In addition, the decrease of desmosterol was somewhat more significant in females. Receiver operating characteristic (ROC) analysis between controls and AD, using plasma desmosterol shows a score of 0.80, indicating a good discrimination power for this marker in the two reference populations and confirms the potential usefulness of measuring plasma desmosterol levels for diagnosing AD. Further analysis showed a significant correlation of plasma desmosterol with Mini-Mental State Examination scores. Although larger sample populations will be needed to confirm this diagnostic marker sensitivity, our studies demonstrate a sensitive and accurate method of detecting plasma desmosterol concentration and suggest that plasma desmosterol could become a powerful new specific biomarker for early and easy AD diagnosis.

Topics: Aged; Alzheimer Disease; Biomarkers; Case-Control Studies; Cholesterol; Chromatography, Liquid; Desmosterol; Female; Humans; Male; Mass Spectrometry; Metabolomics; Sex Factors

Disturbances in cerebral cholesterol metabolism have been implicated in the pathogenesis of Alzheimer's disease (AD). Here, we provide evidence that alterations in brain cholesterol homeostasis also can be a consequence of disease progression. We found that APPSLxPS1mut mice, at the age of 9 months when AD-like pathology starts to develop, display increased levels of the cholesterol precursor desmosterol and of the cholesterol metabolite 27-hydroxy(OH)cholesterol in their cerebellum in comparison with wild-type controls. At the age of 21 months, when APPSLxPS1mut brain contains abundant amyloid deposits, desmosterol levels had further increased (> 200% in comparison with wild-type mice) in all brain regions examined. 24(S)-OHcholesterol levels were increased in hippocampus and cerebellum of the APPSLxPS1mut mice, while 27-OHcholesterol levels were increased in cerebellum exclusively. Brain cholesterol levels remained unaffected. In line with the fact that desmosterol and 24(S)-OHcholesterol are Liver X Receptor (LXR) activators, the LXR-target genes Abca1 and Apoc1 were upregulated predominantly in hippocampus of APPSLxPS1mut mice at both ages evaluated. The reduced expression of the enzyme that converts desmosterol into cholesterol, the Selective AD indicator 1 gene (Seladin-1/Dhcr24), in both cortex and cerebellum may underlie the increased desmosterol levels in 21 month-old APPSLxPS1mut mice.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Brain; Cholesterol; Desmosterol; Disease Models, Animal; Mice; Mice, Inbred C57BL; Mice, Neurologic Mutants; Mice, Transgenic; Nerve Tissue Proteins; Oxidoreductases Acting on CH-CH Group Donors; Presenilin-1

Cerebral and extracerebral cholesterol metabolism are altered in Alzheimer's disease (AD) as indicated by reduced plasma levels of the cholesterol elimination products 24S-hydroxycholesterol, which is of cerebral origin, and of 27-hydroxycholesterol, which is formed extracerebrally. However, it has to be evaluated, if changes of cholesterol metabolism in the whole body or in the CNS are exclusively due to the altered elimination of cholesterol or are also due to altered de novo synthesis in AD. We investigated CSF and plasma levels of cholesterol and of its precursors lanosterol, lathosterol and desmosterol in AD patients and non-demented controls. We found CSF levels of cholesterol (p=0.011), absolute levels of all investigated cholesterol precursors (each p<0.001) and ratios of cholesterol precursors/cholesterol (each <0.01) to be lower in AD patients as compared to controls. In plasma, the absolute levels of lanosterol (p=0.026) and lathosterol (p<0.001) and the ratio of lathosterol/cholesterol (p=0.002) but none of the other investigated parameters were reduced in AD patients (p>0.1). Furthermore, ratios of desmosterol/lathosterol in CSF (p=0.023) and plasma (p=0.009) were higher in AD patients as compared to controls. Our data support the hypothesis that cholesterol metabolism is altered in AD and further suggest that especially cholesterol de novo synthesis within the CNS of AD patients might be reduced. These findings raise doubt on a beneficial effect of cholesterol lowering treatment in manifest AD.

Topics: Aged; Aged, 80 and over; Alleles; Alzheimer Disease; Apolipoprotein E4; Case-Control Studies; Cholesterol; Desmosterol; Female; Gene Frequency; Humans; Lanosterol; Male; Middle Aged; Models, Biological