Cholesterol 24-hydroxylase (CYP46A1) polymorphisms are associated with faster cognitive deterioration in Chinese older persons: a two-year follow up study

Plant sterols and cholesterol metabolism are associated with five-year cognitive decline in the elderly population

Dysregulations in cholesterol metabolism are associated with neurodegenerative and vascular pathologies, and dementia. Diet-derived plant sterols (phytosterols) have cholesterol-lowering, anti-inflammatory, and antioxidant properties and may interfere with neurodegeneration and cognitive decline. Here we performed multivariate analysis in 720 individuals enrolled in a population-based prospective study to determine whether circulating cholesterol precursors and metabolites, triglycerides, and phytosterols, are associated with cognitive impairment and decline in the older population. We report specific dysregulations of endogenous cholesterol synthesis and metabolism, and diet-derived phytosterols, and their changes over time associated with cognitive impairment, and decline in the general population. These findings suggest circulating sterols levels could be considered in risk evaluation and are relevant for the development of strategies to prevent cognitive decline in older people.

The CH24H metabolite, 24HC, blocks viral entry by disrupting intracellular cholesterol homeostasis

Cholesterol-24-hydroxylase (CH24H or Cyp46a1) is a reticulum-associated membrane protein that plays an irreplaceable role in cholesterol metabolism in the brain and has been well-studied in several neuro-associated diseases in recent years. In the present study, we found that CH24H expression can be induced by several neuroinvasive viruses, including vesicular stomatitis virus (VSV), rabies virus (RABV), Semliki Forest virus (SFV) and murine hepatitis virus (MHV). The CH24H metabolite, 24-hydroxycholesterol (24HC), also shows competence in inhibiting the replication of multiple viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 24HC can increase the cholesterol concentration in multivesicular body (MVB)/late endosome (LE) by disrupting the interaction between OSBP and VAPA, resulting in viral particles being trapped in MVB/LE, ultimately compromising VSV and RABV entry into host cells. These findings provide the first evidence that brain cholesterol oxidation products may play a critical role in viral infection.

Intestinal Microbiota Remodeling Protects Mice from Western Diet-Induced Brain Inflammation and Cognitive Decline

It has been shown that the Western diet (WD) induces systemic inflammation and cognitive decline. Moreover, probiotic supplementation and antibiotic treatment reduce diet-induced hepatic inflammation. The current study examines whether shaping the gut microbes by Bifidobacterium infantis (B. infantis) supplementation and antibiotic treatment reduce diet-induced brain inflammation and improve neuroplasticity. Furthermore, the significance of bile acid (BA) signaling in regulating brain inflammation was studied. Mice were fed a control diet (CD) or WD for seven months. B. infantis was supplemented to WD-fed mice to study brain inflammation, lipid, metabolomes, and neuroplasticity measured by long-term potentiation (LTP). Broad-spectrum coverage antibiotics and cholestyramine treatments were performed to study the impact of WD-associated gut microbes and BA in brain inflammation. Probiotic B. infantis supplementation inhibited diet-induced brain inflammation by reducing IL6, TNFα, and CD11b levels. B. infantis improved LTP and increased brain PSD95 and BDNF levels, which were reduced due to WD intake. Additionally, B. infantis reduced cecal cholesterol, brain ceramide and enhanced saturated fatty acids. Moreover, antibiotic treatment, as well as cholestyramine, diminished WD-induced brain inflammatory signaling. Our findings support the theory that intestinal microbiota remodeling by B. infantis reduces brain inflammation, activates BA receptor signaling, and improves neuroplasticity.

Association of cholesterol 7α-hydroxylase (CYP7A1) promoter polymorphism (rs3808607) and cholesterol 24S-hydroxylase (CYP46A1) intron 2 polymorphism (rs754203) with serum lipids, vitamin D levels, and multiple sclerosis risk in the Turkish population

BACKGROUND

Patients with multiple sclerosis (MS) have significantly lower vitamin D levels. Cholesterol is known to be the precursor for vitamin D synthesis, and cholesterol removal is regulated by cholesterol 7α-hydroxylase (CYP7A1) in the liver and cholesterol 24S-hydroxylase (CYP46A1) in the brain. In this study, single nucleotide polymorphisms (SNPs) within the genes CYP7A1 (rs3808607) and CYP46A1 (rs754203) were investigated for their effects on serum lipid profiles, vitamin D levels, and the risk of developing MS.

METHODS

Patients with MS (n = 191) and controls (n = 100) were tested using the PCR-RFLP method to determine their genotypes for rs3808607 and rs754203 SNPs.

RESULTS

The minor (C) allele frequency for CYP7A1 rs3808607 variation was 0.380 in patients with MS and 0.305 in control subjects (P = .074). For CYP46A1 rs754203, the frequencies of the minor (C) allele were 0.272 and 0.250 in patients and control subjects, respectively (P = .563). Serum vitamin D (25(OH)D3) concentrations were significantly lower in patients than in control subjects (P = .002). The CYP46A1 rs754203 SNP was associated with total cholesterol levels in patients, whereas the CYP7A1 rs3808607 variant was not associated with serum lipid parameters or vitamin D levels in patients or control subjects.

CONCLUSION

CYP7A1 rs3808607 and CYP46A1 rs754203 variations are not likely to confer an independent risk for MS development in the Turkish population. To the best of our knowledge, this is the first study to investigate the association between CYP46A1 rs754203 and MS risk.

Identification of 74 cytochrome P450 genes and co-localized cytochrome P450 genes of the CYP2K, CYP5A, and CYP46A subfamilies in the mangrove killifish Kryptolebias marmoratus

BACKGROUND

The mangrove killifish Kryptolebias marmoratus is the only vertebrate that reproduces by self-fertilizing and is an important model species in genetics and marine ecotoxicology. Using whole-genome and transcriptome sequences, we identified all members of the cytochrome P450 (CYP) family in this model teleost and compared them with those of other teleosts.

RESULTS

A total of 74 cytochrome P450 genes and one pseudogene were identified in K. marmoratus. Phylogenetic analysis indicated that the CYP genes in clan 2 were most expanded, while synteny analysis with other species showed orthologous relationships of CYP subfamilies among teleosts. In addition to the CYP2K expansions, five tandem duplicated gene copies of CYP5A were observed. These features were unique to K. marmoratus.

CONCLUSIONS

These results shed a light on CYP gene evolution, particularly the co-localized CYP2K, CYP5A, and CYP46A subfamilies in fish. Future studies of CYP expression could identify specific endogenous and exogenous environmental factors that triggered the evolution of tandem CYP duplication in K. marmoratus.

Association of angiotensin-converting enzyme, CYP46A1 genes polymorphism with senile cataract

Background:

Senile cataract is the most common type of cataract characterized by gradual progressive thickening of the lens of the eye. Previously, many studies investigated the association between genetic polymorphism and senile cataract. Angiotensin-converting enzyme (ACE) I/D polymorphism is the potential risk factor for many eye-related diseases such as retinopathy and glaucoma. CYP46A1 enzyme converts cholesterol to 24S-hydroxycholesterol; human lens' membranes contain the highest cholesterol content. Defects in enzymes of cholesterol metabolism can be associated with cataracts. Hence, the present study was carried out to investigate the association of ACE and CYP46A1 genes polymorphism with senile cataract cases and controls.

Materials and Methods:

ACE (rs 4646994) and CYP46A1 (rs 754203) genes polymorphism in cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism.

Results:

This study included 103 senile cataract cases (55 were males and 48 were females) and 102 controls (53 were males and 49 were females). Mean age of cases in this study was 52.02 ± 12.11 years while in control group 53.74 ± 11.87 years. Frequencies of ACE ID, DD, and II genotypes in senile cataract cases were 64.07%, 4.85%, and 31.06% and controls were 61.76%, 26.47%, and 11.76%, respectively. The CYP46A1 gene CT, CC, and TT genotype frequencies were 48.54%, 8.73%, and 42.71% in senile cataract cases and 28.43%, 3.92%, and 67.64% in healthy controls, respectively. ACE DD and II genotypes (P < 0.001,P = 0.0008) and CYP46A1 CT and TT genotypes (P = 0.003,P = 0.0003) were significantly associated with senile cataract cases compared to the controls.

Conclusion:

Findings of this study suggest that ACE and CYP46A1 genes polymorphism may be a predictive marker for early identification of population at risk of senile cataract. This potential role of ACE and CYP46A1 genes polymorphism as a marker of susceptibility to senile cataract needs further validation in studies involving larger number of patients from different regions.

Cholesterol 24-hydroxylase: Brain cholesterol metabolism and beyond

Dysfunctions in brain cholesterol homeostasis have been extensively related to brain disorders. The major elimination pathway of brain cholesterol is its hydroxylation into 24 (S)-hydroxycholesterol by the cholesterol 24-hydroxylase (CYP46A1). Interestingly, there seems to be an association between CYP46A1 and high-order brain functions, in a sense that increased expression of this hydroxylase improves cognition, while a reduction leads to a poor cognitive performance. Moreover, increasing amount of epidemiological, biochemical and molecular evidence, suggests that CYP46A1 has a role in the pathogenesis or progression of neurodegenerative disorders, in which up-regulation of this enzyme is clearly beneficial. However, the mechanisms underlying these effects are poorly understood, which highlights the importance of studies that further explore the role of CYP46A1 in the central nervous system. In this review we summarize the major findings regarding CYP46A1, and highlight the several recently described pathways modulated by this enzyme from a physiological and pathological perspective, which might account for novel therapeutic strategies for neurodegenerative disorders.

Neuronal cholesterol metabolism increases dendritic outgrowth and synaptic markers via a concerted action of GGTase-I and Trk

Cholesterol 24-hydroxylase (CYP46A1) is responsible for brain cholesterol elimination and therefore plays a crucial role in the control of brain cholesterol homeostasis. Altered CYP46A1 expression has been associated with several neurodegenerative diseases and changes in cognition. Since CYP46A1 activates small guanosine triphosphate-binding proteins (sGTPases), we hypothesized that CYP46A1 might be affecting neuronal development and function by activating tropomyosin-related kinase (Trk) receptors and promoting geranylgeranyl transferase-I (GGTase-I) prenylation activity. Our results show that CYP46A1 triggers an increase in neuronal dendritic outgrowth and dendritic protrusion density, and elicits an increase of synaptic proteins in the crude synaptosomal fraction. Strikingly, all of these effects are abolished by pharmacological inhibition of GGTase-I activity. Furthermore, CYP46A1 increases Trk phosphorylation, its interaction with GGTase-I, and the activity of GGTase-I, which is crucial for the enhanced dendritic outgrowth. Cholesterol supplementation studies indicate that cholesterol reduction by CYP46A1 is the necessary trigger for these effects. These results were confirmed in vivo, with a significant increase of p-Trk, pre- and postsynaptic proteins, Rac1, and decreased cholesterol levels, in crude synaptosomal fractions prepared from CYP46A1 transgenic mouse cortex. This work describes the molecular mechanisms by which neuronal cholesterol metabolism effectively modulates neuronal outgrowth and synaptic markers.

Recent research about mild cognitive impairment in China

The rapid aging of the Chinese population has spurred interest in research about the cause and prevention of dementia and its precursor, mild cognitive impairment (MCI). This review summarizes the last decade of research in China about MCI. Extensive research about the epidemiology, neuropsychological characteristics, diagnosis, genetic etiology, neuroimaging and electrophysiological changes, and treatment of MCI has provided some new insights but few breakthroughs. Further advances in the prevention and treatment of MCI will require a greater emphasis on multi-disciplinary prospective studies with large, representative samples that use standardized methods to assess and monitor changes in cognitive functioning over time.

Effects of metabolic syndrome, apolipoprotein E, and CYP46 on cognition among Taiwanese Chinese

The combined effects of metabolic syndrome and the apolipoprotein E and CYP46 genotypes on the risk of cognitive decline has yet to be determined among Taiwanese Chinese. Two hundred and nine mentally healthy middle-aged and older adults were assessed for metabolic syndrome, cognitive function using the Cognitive Abilities Screening Instrument, Mini-Mental State Examination, ApoE, and CYP46 polymorphisms. There were no differences in cognitive performance, ApoE epsilon4 (ε4) carrier status, or CYP46 genotypes between participants with and those without metabolic syndrome. The ε4 carriers and participants with the AA allele of CYP46 had significantly lower mental manipulation score. Metabolic syndrome and ε4 had synergistic effects on cognitive decline. Therefore, the ε4 carriers and participants with the AA allele of CYP46 have decreased mental manipulation ability. The metabolic syndrome may play a role in subtle cognitive dysfunction in ε4 carriers among Taiwanese Chinese.

Cytochrome P450s in the synthesis of cholesterol and bile acids--from mouse models to human diseases

The present review describes the transgenic mouse models that have been designed to evaluate the functions of the cytochrome P450s involved in cholesterol and bile acid synthesis, as well as their link with disease. The knockout of cholesterogenic Cyp51 is embrionally lethal, with symptoms of Antley-Bixler syndrome occurring in mice, whereas the evidence for this association is conflicting in humans. Disruption of Cyp7a1 from classic bile acid synthesis in mice leads to either increased postnatal death or a milder phenotype with elevated serum cholesterol. The latter is similar to the case in humans, where CYP7A1 mutations associate with high plasma low-density lipoprotein and hepatic cholesterol content, as well as deficient bile acid excretion. Disruption of Cyp8b1 from an alternative bile acid pathway results in the absence of cholic acid and a reduced absorption of dietary lipids; however, the human CYP8B1 polymorphism fails to explain differences in bile acid composition. Unexpectedly, apparently normal Cyp27a1(-/-) mice still synthesize bile acids that originate from the compensatory pathway. In humans, CYP27A1 mutations cause cerebrotendinous xanthomatosis, suggesting that only mice can compensate for the loss of alternative bile acid synthesis. In line with this, Cyp7b1 knockouts are also apparently normal, whereas human CYP7B1 mutations lead to a congenital bile acid synthesis defect in children or spastic paraplegia in adults. Mouse knockouts of the brain-specific Cyp46a1 have reduced brain cholesterol excretion, whereas, in humans, CYP46A1 polymorphisms associate with cognitive impairment. At present, cytochrome P450 family 39 is poorly characterized. Despite important physiological differences between humans and mice, mouse models prove to be an invaluable tool for understanding the multifactorial facets of cholesterol and bile acid-related disorders.

The effects of cholesterol on learning and memory

Cholesterol is vital to normal brain function including learning and memory but that involvement is as complex as the synthesis, metabolism and excretion of cholesterol itself. Dietary cholesterol influences learning tasks from water maze to fear conditioning even though cholesterol does not cross the blood brain barrier. Excess cholesterol has many consequences including peripheral pathology that can signal brain via cholesterol metabolites, pro-inflammatory mediators and antioxidant processes. Manipulations of cholesterol within the central nervous system through genetic, pharmacological, or metabolic means circumvent the blood brain barrier and affect learning and memory but often in animals already otherwise compromised. The human literature is no less complex. Cholesterol reduction using statins improves memory in some cases but not others. There is also controversy over statin use to alleviate memory problems in Alzheimer's disease. Correlations of cholesterol and cognitive function are mixed and association studies find some genetic polymorphisms are related to cognitive function but others are not. In sum, the field is in flux with a number of seemingly contradictory results and many complexities. Nevertheless, understanding cholesterol effects on learning and memory is too important to ignore.