24S-hydroxycholesterol in plasma: a marker of cholesterol turnover in neurodegenerative diseases

Impairment of Renal and Hematopoietic Stem/Progenitor Cell Compartments in Frailty Syndrome: Link With Oxidative Stress, Plasma Cytokine Profiles, and Nuclear DNA Damage

Frailty is an age-related syndrome that drives multiple physiological system impairments in some older adults, and its pathophysiological mechanisms remain unclear. We evaluated whether frailty-related biological processes could impair stem cell compartments, specifically the renal stem compartment, given that kidney dysfunctions are frequent in frailty. A well-characterized in vitro nephrosphere model of human adult renal stem/progenitor cells has been instrumental to and was appropriate for verifying this hypothesis in our current research. Evaluating the effects of plasma from older individuals with frailty (frail plasma) on allogeneic renal stem/progenitor cells, we showed significant functional impairment and nuclear DNA damage in the treated cells of the renal stem compartment. The analysis of the frail plasma revealed mitochondrial functional impairment associated with the activation of oxidative stress and a unique inflammatory mediator profile in frail individuals. In addition, the plasma of frail subjects also contained the highest percentage of DNA-damaged autologous circulating hematopoietic progenitor/stem cells. The integration of both molecular and functional data obtained allowed us to discern patterns associated with frailty status, irrespective of the comorbidities present in the frail individuals. The data obtained converged toward biological conditions that in frailty caused renal and hematopoietic impairment of stem cells, highlighting the possibility of concomitant exhaustion of several stem compartments.

Immune Implications of Cholesterol-Containing Lipid Nanoparticles

The majority of clinically approved nanoparticle-mediated therapeutics are lipid nanoparticles (LNPs), and most of these LNPs are liposomes containing cholesterol. LNP formulations significantly alter the drug pharmacokinetics (PK) due to the propensity of nanoparticles for uptake by macrophages. In addition to readily engulfing LNPs, the high expression of cholesterol hydroxylases and reactive oxygen species (ROS) in macrophages suggests that they will readily produce oxysterols from LNP-associated cholesterol. Oxysterols are a heterogeneous group of cholesterol oxidation products that have potent immune modulatory effects. Oxysterols are implicated in the pathogenesis of atherosclerosis and certain malignancies; they have also been found in commercial liposome preparations. Yet, the in vivo metabolic fate of LNP-associated cholesterol remains unclear. We review herein the mechanisms of cellular uptake, trafficking, metabolism, and immune modulation of endogenous nanometer-sized cholesterol particles (i.e., lipoproteins) that are also relevant for cholesterol-containing nanoparticles. We believe that it would be imperative to better understand the in vivo metabolic fate of LNP-associated cholesterol and the immune implications for LNP-therapeutics. We highlight critical knowledge gaps that we believe need to be addressed in order to develop safer and more efficacious lipid nanoparticle delivery systems.

Aggregation Behavior of Amyloid Beta Peptide Depends Upon the Membrane Lipid Composition

Protein aggregation plays a crucial role in the development of several neurodegenerative diseases. It is important to understand the aggregation process for the detection of the onset of these diseases. Alzheimer's Disease (AD) is one of the most prevalent neurodegenerative diseases caused by the aggregation of Aβ-40 and Aβ-42 peptides. The smaller oligomers lead to the formation of protein plaque at the neural membranes leading to memory loss and other disorders. Interestingly, aggregation takes place at the neural membranes, therefore the membrane composition seems to play an important role in the aggregation process. Despite a large number of literatures on the effect of lipid composition on protein aggregation, there are very few concise reviews that highlight the role of membrane composition in protein aggregation. In this review, we have discussed the implication of membrane composition on the aggregation of amyloid beta peptide with a special emphasis on cholesterol. We have further discussed the role of the degree of unsaturation of fatty acids and the participation of apolipoprotein E4 (ApoE4) in the onset of AD.

Diagnostic Potential of Alternations of Bile Acid Profiles in the Plasma of Patients with Huntington's Disease

Huntington's disease (HD) is characterized by progressive involuntary chorea movements and cognitive decline. Recent research indicates that metabolic disturbance may play a role in its pathogenesis. Bile acids, produced during cholesterol metabolism in the liver, have been linked to neurodegenerative conditions. This study investigated variations in plasma bile acid profiles among individuals with HD. Plasma levels of 16 primary and secondary bile acids and their conjugates were analyzed in 20 healthy controls and 33 HD patients, including 24 with symptoms (symHD) and 9 carriers in the presymptomatic stage (preHD). HD patients exhibited significantly higher levels of glycochenodeoxycholic acid (GCDCA) and glycoursodeoxycholic acid (GUDCA) compared to healthy controls. Conversely, isolithocholic acid levels were notably lower in the HD group. Neurotoxic bile acids (glycocholic acid (GCA) + glycodeoxycholic acid (GDCA) + GCDCA) were elevated in symHD patients, while levels of neuroprotective bile acids (ursodeoxycholic acid (UDCA) + GUDCA + tauroursodeoxycholic acid (TUDCA)) were higher in preHD carriers, indicating a compensatory response to early neuronal damage. These results underscore the importance of changes in plasma bile acid profiles in HD and their potential involvement in disease mechanisms. The identified bile acids (GCDCA, GUDCA, and isolithocholic acid) could potentially serve as markers to distinguish between HD stages and healthy individuals. Nonetheless, further research is warranted to fully understand the clinical implications of these findings and their potential as diagnostic or therapeutic tools for HD.

Investigation of Liver X Receptor Gene Variants and Oxysterol Dysregulation in Autism Spectrum Disorder

The NR1H2 gene produces the Liver X Receptor Beta (LXRB) protein, which is crucial for brain cholesterol metabolism and neuronal development. However, its involvement in autism spectrum disorder (ASD) remains largely unexplored, aside from animal studies. This study is the first to explore the potential link between autism and rs2695121/rs17373080 single nucleotide polymorphisms (SNPs) in the regulatory regions of NR1H2, known for their association with neuropsychiatric functions. Additionally, we assessed levels of oxysterols (24-Hydroxycholesterol, 25-Hydroxycholesterol, 27-Hydroxycholesterol), crucial ligands of LXR, and lipid profiles. Our cohort comprised 107 children with ASD and 103 healthy children aged 2-18 years. Clinical assessment tools included the Childhood Autism Rating Scale, Autistic Behavior Checklist, and Repetitive Behavior Scale-Revised. Genotyping for SNPs was conducted using PCR-RFLP. Lipid profiles were analyzed with Beckman Coulter kits, while oxysterol levels were determined through liquid chromatography-tandem mass spectrometry. Significantly higher total cholesterol (p = 0.003), LDL (p = 0.008), and triglyceride (p < 0.001) levels were observed in the ASD group. 27-Hydroxycholesterol levels were markedly lower in the ASD group (p ≤ 0.001). ROC analysis indicated the potential of 27-Hydroxycholesterol to discriminate ASD diagnosis. The SNP genotype and allele frequencies were similar in both groups (p > 0.05). Our findings suggest that disturbances in oxysterol metabolism, previously linked to neurodegeneration, may constitute a risk factor for ASD and contribute to its heterogeneous phenotype.

Cytoprotective effects of α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol on 7-ketocholesterol - Induced oxiapoptophagy: Major roles of PI3-K / PDK-1 / Akt signaling pathway and glutathione peroxidase activity in cell rescue

On murine N2a cells, 7-ketocholesterol induced an oxiapotophagic mode of cell death characterized by oxidative stress (reactive oxygen species overproduction on whole cells and at the mitochondrial level; lipid peroxidation), apoptosis induction (caspase-9, -3 and -7 cleavage, PARP degradation) and autophagy (increased ratio LC3-II / LC3-I). Oxidative stress was strongly attenuated by diphenyleneiodonium chloride which inhibits NAD(P)H oxidase. Mitochondrial and peroxisomal morphological and functional changes were also observed. Down regulation of PDK1 / Akt signaling pathways as well as of GSK3 / Mcl-1 and Nrf2 pathways were simultaneously observed in 7-ketocholesterol-induced oxiapoptophagy. These events were prevented by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by LY-294002, a PI3-K inhibitor, demonstrated an essential role of PI3-K in cell rescue. The rupture of oxidative stress in 7-ketocholesterol-induced oxiapoptophagy was also associated with important modifications of glutathione peroxidase, superoxide dismutase and catalase activities as well as of glutathione peroxidase-1, superoxide dismutase-1 and catalase level and expression. These events were also counteracted by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol. The inhibition of the cytoprotection by mercaptosuccinic acid, a glutathione peroxidase inhibitor, showed an essential role of this enzyme in cell rescue. Altogether, our data support that the reactivation of PI3-K and glutathione peroxidase activities by α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, oleic acid and α-tocopherol are essential to prevent 7KC-induced oxiapoptophagy.

The Diagnostic Use of the Plasma Quantification of 24S-Hydroxycholesterol and Other Oxysterols in Neurodegenerative Disease

Cholesterol regulates fluidity and structure of cellular membranes. The brain is involved in signal transduction, synaptogenesis, and membrane trafficking. An impairment of its metabolism was observed in different neurodegenerative diseases, such as Multiple Sclerosis, Alzheimer, and Huntington diseases. Because of the blood-brain barrier, cholesterol cannot be uptaken from the circulation and all the cholesterol is locally synthetized. The excess cholesterol in neurons is converted into 24S-hydroxycholesterol (24OHC) by the cholesterol 24-hydroxylase (CYP46A1). The plasmatic concentration of 24OHC results in the balance between cerebral production and liver elimination. It is related to the number of metabolically active neurons in the brain. Several factors that affect the brain cholesterol turnover and the liver elimination of oxysterols, the genetic background, nutrition, and lifestyle habits were found to significantly affect plasma levels of 24OHC. Reduced levels of 24OHC were found related to the loss of metabolically active cells and the degree of brain atrophy. The dysfunction of the blood-brain barrier, inflammation, and increased cholesterol turnover might overlap with this progressive reduction giving temporary increased levels of 24OHC.The study of plasma 24OHC is likely to offer an insight into brain cholesterol turnover with a limited diagnostic power.

Enzymatically Formed Oxysterols and Cell Death

The side-chain hydroxylation of cholesterol by specific enzymes produces 24(S)-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol, and other products. These enzymatically formed side-chain oxysterols act as intermediates in the biosynthesis of bile acids and serve as signaling molecules that regulate cholesterol homeostasis. Besides these intracellular functions, an imbalance in oxysterol homeostasis is implicated in pathophysiology. Furthermore, growing evidence reveals that oxysterols affect cell proliferation and cause cell death. This chapter provides an overview of the pathophysiological role of side-chain oxysterols in developing human diseases. We also summarize our understanding of the molecular mechanisms underlying the induction of various forms of cell death by side-chain oxysterols.

Circulating oxysterols and prognosis among women with a breast cancer diagnosis: results from the MARIE patient cohort

BACKGROUND

Breast cancer is the most commonly diagnosed cancer in women worldwide, and underlying mechanistic pathways associated with breast cancer-specific and non-breast cancer-related deaths are of importance. Emerging evidence suggests a role of oxysterols, derivates of cholesterol, in multiple chronic diseases including breast cancer and coronary artery diseases. However, associations between oxysterols and survival have been minimally studied in women diagnosed with breast cancer. In this large breast cancer patient cohort, we evaluated associations between a panel of circulating oxysterols and mortality and recurrence outcomes.

METHODS

Concentrations of 13 circulating oxysterols representing different pathways of cholesterol metabolism were quantified using liquid-chromatography mass-spectrometry. Associations between baseline levels of oxysterols and cause-specific mortality outcomes and recurrence following a breast cancer diagnosis were assessed in 2282 women from the MARIE study over a median follow-up time of 11 years. We calculated hazard ratios (HR) and 95% confidence intervals (CI) using multivariable Cox proportional hazard models and competing risks models.

RESULTS

We observed no associations for circulating oxysterols and breast cancer-specific outcomes. Higher levels of six oxysterols were associated with an increased risk of cardiovascular disease death, including 24S-hydroxycholesterol (alternative bile acid pathway, HRlog2 = 1.73 (1.02, 2.93)), lanosterol (cholesterol biosynthesis pathway, HRlog2 = 1.95 (1.34, 2.83)), 7-ketocholesterol (HRlog2 = 1.26 (1.03, 1.55)), 5α,6α-epoxycholesterol (HRlog2 = 1.34 (1.02-1.77)), and 5a,6β-dihydroxycholestanol (HRlog2 = 1.34 (1.03, 1.76)). After adjusting for multiple comparisons, none of the associations were statistically significant.

CONCLUSION

We provide first evidence on a range of circulating oxysterols and mortality following a breast cancer diagnosis, contributing to a better understanding of associations between different pathways of cholesterol metabolism and prognosis in women with a breast cancer diagnosis. The findings of this study suggest circulating oxysterols may be associated with cardiovascular mortality among women diagnosed with breast cancer. Further studies are needed to evaluate these oxysterols as potential markers of risk for cardiovascular mortality among women with a breast cancer diagnosis as well as their clinical potential.

The translational potential of cholesterol-based therapies for neurological disease

Cholesterol is an important metabolite and membrane component and is enriched in the brain owing to its role in neuronal maturation and function. In the adult brain, cholesterol is produced locally, predominantly by astrocytes. When cholesterol has been used, recycled and catabolized, the derivatives are excreted across the blood-brain barrier. Abnormalities in any of these steps can lead to neurological dysfunction. Here, we examine how precise interactions between cholesterol production and its use and catabolism in neurons ensures cholesterol homeostasis to support brain function. As an example of a neurological disease associated with cholesterol dyshomeostasis, we summarize evidence from animal models of Huntington disease (HD), which demonstrate a marked reduction in cholesterol biosynthesis with clinically relevant consequences for synaptic activity and cognition. In addition, we examine the relationship between cholesterol loss in the brain and cognitive decline in ageing. We then present emerging therapeutic strategies to restore cholesterol homeostasis, focusing on evidence from HD mouse models.

The potential therapeutic effect of statins in multiple sclerosis: beneficial or detrimental effects

Multiple sclerosis (MS) is a chronic progressive disabling disease of the central nervous system (CNS) characterized by demyelination and neuronal injury. Dyslipidemia is observed as one of the imperative risk factors involved in MS neuropathology. Also, chronic inflammation in MS predisposes to the progress of dyslipidemia. Therefore, treatment of dyslipidemia in MS by statins may attenuate dyslipidemia-induced MS and avert MS-induced metabolic changes. Therefore, the present review aimed to elucidate the possible effects of statins on the pathogenesis and outcomes of MS. Statins adversely affect the cognitive function in MS by decreasing brain cholesterol CoQ10, which is necessary for the regulation of neuronal mitochondrial function. However, statins could be beneficial in MS by shifting the immune response from pro-inflammatory Th17 to an anti-inflammatory regulatory T cell (Treg). The protective effect of statins against MS is related to anti-inflammatory and immunomodulatory effects with modulation of fibrinogen and growth factors. In conclusion, the effects of statins on MS neuropathology seem to be conflicting, as statins seem to be protective in the acute phase of MS through anti-inflammatory and antioxidant effects. However, statins lead to detrimental effects in the chronic phase of MS by reducing brain cholesterol and inhibiting the remyelination process.

Quantitative characterizations of the cholesterol-related pathways in the retina and brain of hamsters

The retina and brain are separated from the systemic circulation by the anatomical barriers, which are permeable (the outer blood-retinal barrier) and impermeable (the blood-brain and inner blood-retina barriers) to cholesterol. Herein we investigated whether the whole-body cholesterol maintenance affects cholesterol homeostasis in the retina and brain. We used hamsters, whose whole-body cholesterol handling is more similar to those in humans than in mice and conducted separate administrations of deuterated water and deuterated cholesterol. We assessed the quantitative significance of the retinal and brain pathways of cholesterol input and compared the results with those from our previous studies in mice. The utility of the measurements in the plasma of deuterated 24-hydroxycholesterol, the major cholesterol elimination product from the brain, was investigated as well. We established that despite a 7-fold higher serum LDL to HDL ratio and other cholesterol-related differences, in situ biosynthesis remained the major source of cholesterol for hamster retina, although its quantitative significance was reduced to 53% as compared to 72-78% in mouse retina. In the brain, the principal pathway of cholesterol input was also the same, in situ biosynthesis, accounting for 94% of the total brain cholesterol input (96% in mice); the interspecies differences pertained to the absolute rates of the total cholesterol input and turnover. We documented the correlations between deuterium enrichments of the brain 24-hydroxycholesterol, brain cholesterol, and plasma 24-hydroxycholesterol, which suggested that deuterium enrichment of plasma 24-hydroxycholesteol could be an in vivo marker of cholesterol elimination and turnover in the brain.

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.

Lipid Mediated Brain Disorders: A Perspective

The brain, one of the most resilient organs of the body is highly enriched in lipid content, suggesting the essential role of lipids in brain physiological activities. Lipids constitute an important structural part of the brain and act as a rich source of metabolic energy. Besides, lipids in their bioactive form (known as bioactive lipids) play an essential signaling and regulatory role, facilitating neurogenesis, synaptogenesis, and cell-cell communication. Brain lipid metabolism is thus a tightly regulated process. Any alteration/dysregulation of lipid metabolism greatly impact brain health and activity. Moreover, since central nervous system (CNS) is the most metabolically active system and lacks an efficient antioxidative defence system, it acts as a hub for the production of reactive oxygen species (ROS) and subsequent lipid peroxidation. These peroxidation events are reported during pathological changes such as neuronal tissue injury and inflammation. Present review is a modest attempt to gain insights into the role of dysregulated bioactive lipid levels and lipid oxidation status in the pathogenesis and progression of neurodegenerative disorders. This may open up new avenues exploiting lipids as the therapeutic targets for improving brain health, and treatment of nervous system disorders.

The Pathological Effects of Circulating Hydrophobic Bile Acids in Alzheimer's Disease

Recent clinical studies have revealed that the serum levels of toxic hydrophobic bile acids (deoxy cholic acid, lithocholic acid [LCA], and glycoursodeoxycholic acid) are significantly higher in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) when compared to control subjects. The elevated serum bile acids may be the result of hepatic peroxisomal dysfunction. Circulating hydrophobic bile acids are able to disrupt the blood-brain barrier and promote the formation of amyloid-β plaques through enhancing the oxidation of docosahexaenoic acid. Hydrophobic bile acid may find their ways into the neurons via the apical sodium-dependent bile acid transporter. It has been shown that hydrophobic bile acids impose their pathological effects by activating farnesoid X receptor and suppressing bile acid synthesis in the brain, blocking NMDA receptors, lowering brain oxysterol levels, and interfering with 17β-estradiol actions such as LCA by binding to E2 receptors (molecular modelling data exclusive to this paper). Hydrophobic bile acids may interfere with the sonic hedgehog signaling through alteration of cell membrane rafts and reducing brain 24(S)-hydroxycholesterol. This article will 1) analyze the pathological roles of circulating hydrophobic bile acids in the brain, 2) propose therapeutic approaches, and 3) conclude that consideration be given to reducing/monitoring toxic bile acid levels in patients with AD or aMCI, prior/in combination with other treatments.

Cholesterol metabolism pathway in autism spectrum disorder: From animal models to clinical observations

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by a persistent impairment of social skills, including aspects of perception, interpretation, and response, combined with restricted and repetitive behavior. ASD is a complex and multifactorial condition, and its etiology could be attributed to genetic and environmental factors. Despite numerous clinical and experimental studies, no etiological factor, biomarker, and specific model of transmission have been consistently associated with ASD. However, an imbalance in cholesterol levels has been observed in many patients, more specifically, a condition of hypocholesterolemia, which seems to be shared between ASD and ASD-related genetic syndromes such as fragile X syndrome (FXS), Rett syndrome (RS), and Smith- Lemli-Opitz (SLO). Furthermore, it is known that alterations in cholesterol levels lead to neuroinflammation, oxidative stress, impaired myelination and synaptogenesis. Thus, the aim of this review is to discuss the cholesterol metabolic pathways in the ASD context, as well as in genetic syndromes related to ASD, through clinical observations and animal models. In fact, SLO, FXS, and RS patients display early behavioral markers of ASD followed by cholesterol disturbances. Several studies have demonstrated the role of cholesterol in psychiatric conditions and how its levels modulate brain neurodevelopment. This review suggests an important relationship between ASD pathology and cholesterol metabolism impairment; thus, some strategies could be raised - at clinical and pre-clinical levels - to explore whether cholesterol metabolism disturbance has a generally adverse effect in exacerbating the symptoms of ASD patients.

Identification of Side Chain Oxidized Sterols as Novel Liver X Receptor Agonists with Therapeutic Potential in the Treatment of Cardiovascular and Neurodegenerative Diseases

The nuclear receptors-liver X receptors (LXR α and β) are potential therapeutic targets in cardiovascular and neurodegenerative diseases because of their key role in the regulation of lipid homeostasis and inflammatory processes. Specific oxy(phyto)sterols differentially modulate the transcriptional activity of LXRs providing opportunities to develop compounds with improved therapeutic characteristics. We isolated oxyphytosterols from Sargassum fusiforme and synthesized sidechain oxidized sterol derivatives. Five 24-oxidized sterols demonstrated a high potency for LXRα/β activation in luciferase reporter assays and induction of LXR-target genes APOE, ABCA1 and ABCG1 involved in cellular cholesterol turnover in cultured cells: methyl 3β-hydroxychol-5-en-24-oate (S1), methyl (3β)-3-aldehydeoxychol-5-en-24-oate (S2), 24-ketocholesterol (S6), (3β,22E)-3-hydroxycholesta-5,22-dien-24-one (N10) and fucosterol-24,28 epoxide (N12). These compounds induced SREBF1 but not SREBP1c-mediated lipogenic genes such as SCD1, ACACA and FASN in HepG2 cells or astrocytoma cells. Moreover, S2 and S6 enhanced cholesterol efflux from HepG2 cells. All five oxysterols induced production of the endogenous LXR agonists 24(S)-hydroxycholesterol by upregulating the CYP46A1, encoding the enzyme converting cholesterol into 24(S)-hydroxycholesterol; S1 and S6 may also act via the upregulation of desmosterol production. Thus, we identified five novel LXR-activating 24-oxidized sterols with a potential for therapeutic applications in neurodegenerative and cardiovascular diseases.

CYP46A1 activation by low-dose efavirenz enhances brain cholesterol metabolism in subjects with early Alzheimer's disease

BACKGROUND

Efavirenz is an anti-HIV drug, and cytochrome P450 46A1 (CYP46A1) is a CNS-specific enzyme that metabolizes cholesterol to 24-hydroxycholesterol (24HC). We have previously shown that allosteric CYP46A1 activation by low-dose efavirenz in a transgenic mouse model of Alzheimer's disease (AD) enhanced both cholesterol elimination and turnover in the brain and improved animal performance in memory tests. Here, we sought to determine whether CYP46A1 could be similarly activated by a low-dose efavirenz in human subjects.  METHODS: This pilot study enrolled 5 subjects with early AD. Participants were randomized to placebo (n = 1) or two daily efavirenz doses (50 mg and 200 mg, n = 2 for each) for 20 weeks and evaluated for safety and CYP46A1 target engagement (plasma 24HC levels). A longitudinal mixed model was used to ascertain the statistical significance of target engagement. We also measured 24HC in CSF and conducted a unique stable isotope labeling kinetics (SILK) study with deuterated water to directly measure CYP46A1 activity changes in the brain.

RESULTS

In subjects receiving efavirenz, there was a statistically significant within-group increase (P ≤ 0.001) in the levels of plasma 24HC from baseline. The levels of 24HC in the CSF of subjects on the 200-mg dose of efavirenz were also increased. Target engagement was further supported by the labeling kinetics of 24HC by deuterated water in the SILK study. There were no serious adverse effects in any subjects.

CONCLUSIONS

Our findings suggest efavirenz target engagement in human subjects with early AD. This supports the pursuit of a larger trial for further determination and confirmation of the efavirenz dose that exerts maximal enzyme activation, as well as evaluation of this drug's effects on AD biomarkers and clinical symptomatology.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03706885.

Cholesterol in Brain Development and Perinatal Brain Injury: More than a Building Block

The central nervous system (CNS) is enriched with important classes of lipids, in which cholesterol is known to make up a major portion of myelin sheaths, besides being a structural and functional unit of CNS cell membranes. Unlike in the adult brain, where the cholesterol pool is relatively stable, cholesterol is synthesized and accumulated at the highest rate in the developing brain to meet the needs of rapid brain growth at this stage, which is also a critical period for neuroplasticity. In addition to its biophysical role in membrane organization, cholesterol is crucial for brain development due to its involvement in brain patterning, myelination, neuronal differentiation, and synaptogenesis. Thus any injuries to the immature brain that affect cholesterol homeostasis may have long-term adverse neurological consequences. In this review, we describe the unique features of brain cholesterol biosynthesis and metabolism, cholesterol trafficking between different cell types, and highlight cholesterol-dependent biological processes during brain maturation. We also discuss the association of impaired cholesterol homeostasis with several forms of perinatal brain disorders in term and preterm newborns, including hypoxic-ischemic encephalopathy. Strategies targeting the cholesterol pathways may open new avenues for the diagnosis and treatment of developmental brain injury.

Selected plasma oxysterols as a potential multi-marker biosignature panel for Behçet's Disease

Clinical, genetic, and medical evidence has shown the inflammatory vasculitis aspect of Behçet's Disease (BD). Whereas oxysterols are vital factors in inflammation and oxidative stress, it is still unknown whether they are involved in the pathophysiology of BD. The current study aims to explore the profile of oxysterols in plasma of BD patients. Thirty patients diagnosed with BD and forty healthy controls matched for age and gender were included. Results showed that the cholestane-3β,5α,6β-triol, 27-hydroxycholesterol (27-OHC) and cholestanol levels were higher in BD than controls. In addition, plasma levels of 7-ketocholesterol (7-KC) and 25-hydroxycholesterol (25-OHC) were lower in BD patient. However, levels of 24S-hydroxycholesterol (24-OHC) did not significantly differ. For BD patients, the plasma 7-KC level was negatively correlated with the BD activity index (BDAI) while 27-OHC was positively correlated with high-sensitivity C-reactive protein (hs-CRP) in patients with active course of the disease. According to ROC analysis, a remarkable increase in the area under the curve (AUC) with a higher sensitivity (Se) and specificity (Sp) for 7-KC, 25-OHC and 27-OHC combined markers was observed. The present study indicated that the identification of the predictive value of these three-selected biomarkers related to oxidative stress and inflammation in patients should lead to a better identification of the etiological mechanism of BD.

Neuroinflammation in Huntington's Disease: A Starring Role for Astrocyte and Microglia

Huntington's disease (HD) is a neurodegenerative genetic disorder caused by a CAG repeat expansion in the huntingtin gene. HD causes motor, cognitive, and behavioral dysfunction. Since no existing treatment affects the course of this disease, new treatments are needed. Inflammation is frequently observed in HD patients before symptom onset. Neuroinflammation, characterized by the presence of reactive microglia, astrocytes and inflammatory factors within the brain, is also detected early. However, in comparison to other neurodegenerative diseases, the role of neuroinflammation in HD is much less known. Work has been dedicated to altered microglial and astrocytic functions in the context of HD, but less attention has been given to glial participation in neuroinflammation. This review describes evidence of inflammation in HD patients and animal models. It also discusses recent knowledge on neuroinflammation in HD, highlighting astrocyte and microglia involvement in the disease and considering anti-inflammatory therapeutic approaches.

ATAD3A oligomerization promotes neuropathology and cognitive deficits in Alzheimer's disease models

Predisposition to Alzheimer's disease (AD) may arise from lipid metabolism perturbation, however, the underlying mechanism remains elusive. Here, we identify ATPase family AAA-domain containing protein 3A (ATAD3A), a mitochondrial AAA-ATPase, as a molecular switch that links cholesterol metabolism impairment to AD phenotypes. In neuronal models of AD, the 5XFAD mouse model and post-mortem AD brains, ATAD3A is oligomerized and accumulated at the mitochondria-associated ER membranes (MAMs), where it induces cholesterol accumulation by inhibiting gene expression of CYP46A1, an enzyme governing brain cholesterol clearance. ATAD3A and CYP46A1 cooperate to promote APP processing and synaptic loss. Suppressing ATAD3A oligomerization by heterozygous ATAD3A knockout or pharmacological inhibition with DA1 restores neuronal CYP46A1 levels, normalizes brain cholesterol turnover and MAM integrity, suppresses APP processing and synaptic loss, and consequently reduces AD neuropathology and cognitive deficits in AD transgenic mice. These findings reveal a role for ATAD3A oligomerization in AD pathogenesis and suggest ATAD3A as a potential therapeutic target for AD.

Oxysterols: From redox bench to industry

More and more attention is nowadays given to the possible translational application of a great number of biochemical and biological findings with the involved molecules. This is also the case of cholesterol oxidation products, redox molecules over the last years deeply investigated for their implication in human pathophysiology. Oxysterols of non-enzymatic origin, the excessive increase of which in biological fluids and tissues is of toxicological relevance for their marked pro-oxidant and pro-inflammatory properties, are increasingly applied in clinical biochemistry as molecular markers in the diagnosis and monitoring of several human and veterinary diseases. Conversely, oxysterols of enzymatic origin, the production of which is commonly under physiological regulation, could be considered and tested as promising pharmaceutical agents because of their antiviral, pro-osteogenic and antiadipogenic properties of some of them. Very recently, the quantification of oxysterols of non-enzymatic origin has been adopted in a systematic way to evaluate, monitor and improve the quality of cholesterol-based food ingredients, that are prone to auto-oxidation, as well as their industrial processing and the packaging and the shelf life of the finished food products. The growing translational value of oxysterols is here reviewed in its present and upcoming applications in various industrial fields.

Dysregulation of Neuronal Nicotinic Acetylcholine Receptor-Cholesterol Crosstalk in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a set of complex neurodevelopmental diseases that include impaired social interaction, delayed and disordered language, repetitive or stereotypic behavior, restricted range of interests, and altered sensory processing. The underlying causes of the core symptoms remain unclear, as are the factors that trigger their onset. Given the complexity and heterogeneity of the clinical phenotypes, a constellation of genetic, epigenetic, environmental, and immunological factors may be involved. The lack of appropriate biomarkers for the evaluation of neurodevelopmental disorders makes it difficult to assess the contribution of early alterations in neurochemical processes and neuroanatomical and neurodevelopmental factors to ASD. Abnormalities in the cholinergic system in various regions of the brain and cerebellum are observed in ASD, and recently altered cholesterol metabolism has been implicated at the initial stages of the disease. Given the multiple effects of the neutral lipid cholesterol on the paradigm rapid ligand-gated ion channel, the nicotinic acetylcholine receptor, we explore in this review the possibility that the dysregulation of nicotinic receptor-cholesterol crosstalk plays a role in some of the neurological alterations observed in ASD.

Cholesterol Hydroxylating Cytochrome P450 46A1: From Mechanisms of Action to Clinical Applications

Cholesterol, an essential component of the brain, and its local metabolism are involved in many neurodegenerative diseases. The blood-brain barrier is impermeable to cholesterol; hence, cholesterol homeostasis in the central nervous system represents a balance between in situ biosynthesis and elimination. Cytochrome P450 46A1 (CYP46A1), a central nervous system-specific enzyme, converts cholesterol to 24-hydroxycholesterol, which can freely cross the blood-brain barrier and be degraded in the liver. By the dual action of initiating cholesterol efflux and activating the cholesterol synthesis pathway, CYP46A1 is the key enzyme that ensures brain cholesterol turnover. In humans and mouse models, CYP46A1 activity is altered in Alzheimer’s and Huntington’s diseases, spinocerebellar ataxias, glioblastoma, and autism spectrum disorders. In mouse models, modulations of CYP46A1 activity mitigate the manifestations of Alzheimer’s, Huntington’s, Nieman-Pick type C, and Machao-Joseph (spinocerebellar ataxia type 3) diseases as well as amyotrophic lateral sclerosis, epilepsy, glioblastoma, and prion infection. Animal studies revealed that the CYP46A1 activity effects are not limited to cholesterol maintenance but also involve critical cellular pathways, like gene transcription, endocytosis, misfolded protein clearance, vesicular transport, and synaptic transmission. How CYP46A1 can exert central control of such essential brain functions is a pressing question under investigation. The potential therapeutic role of CYP46A1, demonstrated in numerous models of brain disorders, is currently being evaluated in early clinical trials. This review summarizes the past 70 years of research that has led to the identification of CYP46A1 and brain cholesterol homeostasis as powerful therapeutic targets for severe pathologies of the CNS.

New Insights into Multiple Sclerosis Mechanisms: Lipids on the Track to Control Inflammation and Neurodegeneration

Multiple sclerosis (MS) is a central nervous system disease with complex pathogenesis, including two main processes: immune-mediated inflammatory demyelination and progressive degeneration with axonal loss. Despite recent progress in our understanding and management of MS, availability of sensitive and specific biomarkers for these both processes, as well as neuroprotective therapeutic options targeted at progressive phase of disease, are still being sought. Given their abundance in the myelin sheath, lipids are believed to play a central role in underlying immunopathogenesis in MS and seem to be a promising subject of investigation in this field. On the basis of our previous research and a review of the literature, we discuss the current understanding of lipid-related mechanisms involved in active relapse, remission, and progression of MS. These insights highlight potential usefulness of lipid markers in prediction or monitoring the course of MS, particularly in its progressive stage, still insufficiently addressed. Furthermore, they raise hope for new, effective, and stage-specific treatment options, involving lipids as targets or carriers of therapeutic agents.

Oxysterols and multiple sclerosis: Physiopathology, evolutive biomarkers and therapeutic strategy

Multiple sclerosis is an autoimmune disease that affects the central nervous system. Dysfunction of the immune system leads to lesions that cause motor, sensory, cognitive, visual and/or sphincter disturbances. In the long term, these disorders can progress towards an irreversible handicap. The diagnosis takes time because there are no specific criteria to diagnose multiple sclerosis. To realize the diagnosis, a combination of clinical, biological, and radiological arguments is therefore required. Hence, there is a need to identify multiple sclerosis biomarkers. Some biomarkers target immunity through the detection of oligoclonal bands, the measurement of the IgG index and cytokines. During the physiopathological process, the blood-brain barrier can be broken, and this event can be identified by measuring metalloproteinase activity and diffusion of gadolinium in the brain by magnetic resonance imaging. Markers of demyelination and of astrocyte and microglial activity may also be of interest as well as markers of neuronal damage and mitochondrial status. The measurement of different lipids in the plasma and cerebrospinal fluid can also provide suitable information. These different lipids include fatty acids, fatty acid peroxidation products, phospholipids as well as oxidized derivatives of cholesterol (oxysterols). Oxysterols could constitute new biomarkers providing information on the form of multiple sclerosis, the outcome of the disease and the answer to treatment.

The Controversial Role of 24-S-Hydroxycholesterol in Alzheimer's Disease

The development of Alzheimer’s disease (AD) is influenced by several events, among which the dysregulation of cholesterol metabolism in the brain plays a major role. Maintenance of brain cholesterol homeostasis is essential for neuronal functioning and brain development. To maintain the steady-state level, excess brain cholesterol is converted into the more hydrophilic metabolite 24-S-hydroxycholesterol (24-OHC), also called cerebrosterol, by the neuron-specific enzyme CYP46A1. A growing bulk of evidence suggests that cholesterol oxidation products, named oxysterols, are the link connecting altered cholesterol metabolism to AD. It has been shown that the levels of some oxysterols, including 27-hydroxycholesterol, 7β-hydroxycholesterol and 7-ketocholesterol, significantly increase in AD brains contributing to disease progression. In contrast, 24-OHC levels decrease, likely due to neuronal loss. Among the different brain oxysterols, 24-OHC is certainly the one whose role is most controversial. It is the dominant oxysterol in the brain and evidence shows that it represents a signaling molecule of great importance for brain function. However, numerous studies highlighted the potential role of 24-OHC in favoring AD development, since it promotes neuroinflammation, amyloid β (Aβ) peptide production, oxidative stress and cell death. In parallel, 24-OHC has been shown to exert several beneficial effects against AD progression, such as preventing tau hyperphosphorylation and Aβ production. In this review we focus on the current knowledge of the controversial role of 24-OHC in AD pathogenesis, reporting a detailed overview of the findings about its levels in different AD biological samples and its noxious or neuroprotective effects in the brain. Given the relevant role of 24-OHC in AD pathophysiology, its targeting could be useful for disease prevention or slowing down its progression.

Disturbances of brain cholesterol metabolism: A new excitotoxic process associated with status epilepticus

The understanding of the excitotoxic processes associated with a severe status epilepticus (SE) is of major importance. Changes of brain cholesterol homeostasis is an emerging candidate for excitotoxicity. We conducted an overall analysis of the cholesterol homeostasis both (i) in fluids and tissues from patients with SE: blood (n = 63, n = 87 controls), CSF (n = 32, n = 60 controls), and post-mortem brain tissues (n = 8, n = 8 controls) and (ii) in a mouse model of SE induced by an intrahippocampal injection of kainic acid. 24-hydroxycholesterol levels were decreased in kainic acid mouse hippocampus and in human plasma and post-mortem brain tissues of patients with SE when compared with controls. The decrease of 24-hydroxycholesterol levels was followed by increased cholesterol levels and by an increase of the cholesterol synthesis. Desmosterol levels were higher in human CSF and in mice and human hippocampus after SE. Lanosterol and dihydrolanosterol levels were higher in plasma from SE patients. Our results suggest that a CYP46A1 inhibition could occur after SE and is followed by a brain cholesterol accumulation. The excess of cholesterol is known to be excitotoxic for neuronal cells and may participate to neurological sequelae observed after SE. This study highlights a new pathophysiological pathway involved in SE excitotoxicity.

High-Fat Diet Modulates Hepatic Amyloid β and Cerebrosterol Metabolism in the Triple Transgenic Mouse Model of Alzheimer's Disease

Obesity and diabetes are strongly associated not only with fatty liver but also cognitive dysfunction. Moreover, their presence, particularly in midlife, is recognized as a risk factor for Alzheimer's disease (AD). AD, the most common cause of dementia, is increasingly considered as a metabolic disease, although underlying pathogenic mechanisms remain unclear. The liver plays a major role in maintaining glucose and lipid homeostasis, as well as in clearing the AD neuropathogenic factor amyloid-β (Aβ) and in metabolizing cerebrosterol, a cerebral-derived oxysterol proposed as an AD biomarker. We hypothesized that liver impairment induced by obesity contributes to AD pathogenesis. We show that the AD triple transgenic mouse model (3xTg-AD) fed a chow diet presents a hepatic phenotype similar to nontransgenic controls (NTg) at 15 months of age. A high-fat diet (HFD), started at the age of 6 months and continued for 9 months, until sacrifice, induced hepatic steatosis in NTg, but not in 3xTg-AD mice, whereas HFD did not induce changes in hepatic fatty acid oxidation, de novo lipogenesis, and gluconeogenesis. HFD-induced obesity was associated with a reduction of insulin-degrading enzyme, one of the main hepatic enzymes responsible for Aβ clearance. The hepatic rate of cerebrosterol glucuronidation was lower in obese 3xTg-AD than in nonobese controls (P < 0.05) and higher compared with obese NTg (P < 0.05), although circulating levels remained unchanged. Conclusion: Modulation of hepatic lipids, Aβ, and cerebrosterol metabolism in obese 3xTg-AD mice differs from control mice. This study sheds light on the liver-brain axis, showing that the chronic presence of NAFLD and changes in liver function affect peripheral AD features and should be considered during development of biomarkers or AD therapeutic targets.

Serum 24S-hydroxycholesterol predicts long-term brain structural and functional outcomes after hypoxia-ischemia in neonatal mice

The major pathway of brain cholesterol turnover relies on its hydroxylation into 24S-hydroxycholesterol (24S-HC) using brain-specific cytochrome P450 46A1 (CYP46A1). 24S-HC produced exclusively in the brain normally traverses the blood-brain barrier to enter the circulation to the liver for excretion; therefore, the serum 24S-HC level is an indication of cholesterol metabolism in the brain. We recently reported an upregulation of CYP46A1 following hypoxia-ischemia (HI) in the neonatal mouse brain and a correlation between serum 24S-HC levels and acute brain damage. Here, we performed a longitudinal study to investigate whether the serum 24S-HC concentrations predict long-term brain structural and functional outcomes. In postnatal day 9 mice subjected to HI, the serum 24S-HC levels increased at 6 h and 24 h after HI and correlated with the infarct volumes measured histologically or by T2-weighted MRI. The 24 h levels were associated with white matter volume loss quantified by MBP immunostaining and luxol fast blue staining. The animals with higher serum 24S-HC at 6 h and 24 h corresponded to those with more severe motor and cognitive deficits at 35-40 days after HI. These data suggest that 24S-HC could be a novel and early blood biomarker for severity of neonatal HI brain damage and associated functional impairments.

Association Between Oxidative Stress and Altered Cholesterol Metabolism in Alzheimer's Disease Patients

BACKGROUND

Oxidative stress is the main feature of several diseases including Alzheimer's disease (AD). The involvement of oxysterols derivates has been recently reported.

OBJECTIVE

The aim of this study was to evaluate the implication of oxidative stress in cholesterol impairment in AD patients.

METHODS

A case-control study was conducted on 56 AD patients and 97 controls. Levels of oxidative biomarkers, including lipid peroxidation products and antioxidant enzyme activities were measured with spectrophotometric methods on red blood cells (RBCs) and plasma. Cholesterol precursors and oxysterols (7-Ketocholeterol (7KC), 7α-hydroxycholesterol (7α-OHC), 7β-hydroxycholesterol (7β-OHC), 24Shydroxycholesterol (24S-OH), 25-hyroxycholesterol (25-OHC), and 27-hydroxycholesterol (27-OHC), in plasma were quantified by gas chromatography coupled with mass spectrometry.

RESULTS

In RBCs and plasma of AD patients, a significant decrease of glutathione peroxidase (GPx) activity was detected associated with raised levels of malondialdehyde (MDA). A decreased level of lanosterol and an accumulation of 7β-OHC, 24S-OHC, 27-OHC, and 25-OHC that were higher in plasma of AD patients, compared to controls, were also observed in AD patients. Mini-Mental State Examination (MMSE) score was correlated with MDA and conjugated dienes (CD) levels in plasma. Besides, the MDA level in RBCs was correlated with 7β-OHC. Binary logistic regression revealed an association between GPx activity and AD (OR=0.895, 95%CI: 0.848-0.945. P<0.001).

CONCLUSION

Our data consolidate the relationship between the rupture of redox homeostasis and lipid and cholesterol oxidation in AD.

Blood Lipids and Cognitive Performance of Aging Polish Adults: A Case-Control Study Based on the PolSenior Project

Background: The demand for effective strategies for maintaining cognitive capableness and establishing early dementia diagnosis has been tremendous, especially in the context of population aging. However, studies on the elderly population and neurocognitive impairment had provided ambiguous results throughout, while potential blood biomarkers of cognitive decline are yet to be clearly understood.

Objectives: The present study is aimed at assessing the relationship between blood lipids—especially in the context of their usefulness as biomarkers of an early cognitive decline—and cognitive functioning of aging adults.

Materials and Methods: The study sample consisted of 230 participants—(109 women, 121 men) aged 65+ years. Plasma 24(S)-hydroxycholesterol [24(S)-OHC], serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL) were assessed. The analyses were conducted in three groups of cognitive performance: cognitively normal, mild cognitive impairment (MCI), and mild dementia, of which the subjects were divided with the Mini-Mental State Examination (MMSE).

Results: No significant differences in 24(S)-OHC plasma concentrations for different levels of cognitive performance were found. Significant differences were found in serum TC (p = 0.026) and LDL (p = 0.007) concentrations for different levels of cognitive performance. Concentrations of both parameters were highest in the MCI group and lowest in mild dementia and cognitive norm, respectively. No significant differences between serum HDL concentrations and cognitive performance were found.

Conclusions: To fully assess the potential of research on blood lipids in regards to a cognitive decline, cross-sectional or epidemiological studies aimed at further exploring blood lipid roles in both the early and advanced MCI and dementia, are needed.

Novel therapeutic strategies for Alzheimer's disease targeting brain cholesterol homeostasis

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia. Aβ plaques and tauopathy are two major concerns associated with AD. Moreover, excessive Aβ accumulation can lead to other nonspecific metabolic brain abnormalities. There are various genetic, environmental, and other risk factors associated with AD. Identification of risk factors and its mechanisms by which these factors impart role in AD pathology would be helpful for the prevention of AD progression. Altered cholesterol homeostasis could be considered as a risk factor for AD progression. Brain cholesterol dysmetabolism is recognized as one of the crucial attributes for AD that affect major hallmarks of AD including neurodegeneration. To fill the gap between altered cholesterol levels in the brain and AD, the researchers started focusing on statins as re-purposing drugs for AD treatment. The various other hypothesis has been suggested due to a lack of beneficial results of statins in clinical trials, such as reduced brain cholesterol could underlie poor cognition. Unfortunately, it is still unclear, whether an increase or decrease in brain cholesterol levels responsible for Alzheimer's disease or not. Presently, scientists believed that managing the level of cholesterol in the brain may help as an alternative treatment strategy for AD. In this review, we focused on the therapeutic strategies for AD by targeting brain cholesterol levels.

Orphan Nuclear Receptor RORα Regulates Enzymatic Metabolism of Cerebral 24S-Hydroxycholesterol through CYP39A1 Intronic Response Element Activation

Oxysterols, important regulators of cholesterol homeostasis in the brain, are affected by neurodegenerative diseases. Early-onset Alzheimer’s disease is associated with higher levels of circulating brain-derived 24S-hydroxycholesterol (24S-OHC). Conversion of cholesterol to 24S-OHC is mediated by cholesterol 24S-hydroxylase in the brain, which is the major pathway for oxysterol elimination, followed by oxidation through hepatic first-pass metabolism by CYP39A1. Abnormal CYP39A1 expression results in accumulation of 24S-OHC, influencing neurodegenerative disease-related deterioration; thus, it is important to understand the normal elimination of 24S-OHC and the system regulating CYP39A1, a selective hepatic metabolic enzyme of 24S-OHC. We examined the role of transcriptional regulation by retinoic acid receptor-related orphan receptor α (RORα), a nuclear receptor that responds to oxysterol ligands. In humans, the promoter and first intronic regions of CYP39A1 contain two putative RORα response elements (ROREs). RORα binding and responses of these ROREs were assessed using electrophoretic mobility shift, chromatin immunoprecipitation, and luciferase reporter assays. CYP39A1 was upregulated by RORα overexpression in HEK293 cells, while RORα knockdown by siRNA significantly downregulated CYP39A1 expression in human hepatoma cells. Additionally, CYP39A1 was induced by RORα agonist treatment, suggesting that CYP39A1 expression is activated by RORα nuclear receptors. This may provide a way to increase CYP39A1 activity using RORα agonists, and help halt 24S-OHC accumulation in neurodegenerative illnesses.

Cholesterol and Dementia: A Long and Complicated Relationship

BACKGROUND

There is a huge demand for efficient strategies for maintaining cognitive wellbeing with age, especially in the context of population aging. Dementia constitutes the main reason for disability and dependency in the elderly. Identification of potential risk and protective factors, as well as determinants of conversion from MCI to dementia, is therefore crucial. In case of Alzheimer's disease, the most prevalent dementia syndrome amongst the members of modern societies, neurodegenerative processes in the brain can begin many years before first clinical symptoms appear. First functional changes typically mean advanced neuron loss, therefore, the earliest possible diagnosis is critical for implementation of promising early pharmaceutical interventions.

OBJECTIVE

The study aimed to discuss the relationships between both circulating and brain cholesterol with cognition, and explore its potential role in early diagnosis of cognitive disorders.

METHODS

Literature review.

RESULTS

The causal role of high cholesterol levels in AD or MCI has not been confirmed. It has been postulated that plasma levels of 24(S)-OHC can potentially be used as an early biochemical marker of altered cholesterol homeostasis in the CNS. Some studies brought conflicting results, finding normal or lowered levels of 24(S)-OHC in dementia patients compared to controls. In spite of decades of research on the relationship between cholesterol and dementia, so far, no single trusted indicator of an early cognitive deterioration has been identified.

CONCLUSION

The current state of knowledge makes the use of cholesterol markers of cognitive decline in clinical practice impossible.

7-Ketocholesterol in disease and aging

7-Ketocholesterol (7KC) is a toxic oxysterol that is associated with many diseases and disabilities of aging, as well as several orphan diseases. 7KC is the most common product of a reaction between cholesterol and oxygen radicals and is the most concentrated oxysterol found in the blood and arterial plaques of coronary artery disease patients as well as various other disease tissues and cell types. Unlike cholesterol, 7KC consistently shows cytotoxicity to cells and its physiological function in humans or other complex organisms is unknown. Oxysterols, particularly 7KC, have also been shown to diffuse through membranes where they affect receptor and enzymatic function. Here, we will explore the known and proposed mechanisms of pathologies that are associated with 7KC, as well speculate about the future of 7KC as a diagnostic and therapeutic target in medicine.

Purple corn extract induces long-lasting reprogramming and M2 phenotypic switch of adipose tissue macrophages in obese mice

Background

Obesity is a chronic and systemic inflammatory disorder and an important risk factor for the onset of several chronic syndromes. Adipose tissue (AT) plays a crucial role in the development of obesity, promoting the infiltration and accumulation of leukocytes in the tissue and sustaining adipocyte expansion. Anthocyanins exert a broad range of health benefits, but their effect in improving obesity-related inflammation in vivo has been poorly characterized. We examined the effects of a purple corn cob extract in the context of AT inflammation in a murine diet-induced obesity (DIO) model.

Methods

Male C57BL/6J mice were subjected to control diet (CTR + H₂O), high fat diet (HF + H₂O) or high fat diet plus purple corn extract (HF + RED) for 12 weeks. Blood glucose, AT, and liver gene expression, metabolism, biochemistry, and histology were analysed and flow cytometry was performed on AT leukocytes and Kupffer cells.

Results

RED extract intake resulted in lower MCP-1 mediated recruitment and proliferation of macrophages into crown-like structures in the AT. AT macrophages (ATM) of HF + RED group upregulated M2 markers (ArgI, Fizz1, TGFβ), downregulating inflammatory mediators (TNF-α, IL-6, IL-1β, COX-2) thanks to the suppression of NF-kB signalling. ATM also increased the expression of iron metabolism-related genes (FABP4, Hmox1, Ferroportin, CD163, TfR1, Ceruloplasmin, FtL1, FtH1) associated with a reduction in iron storage and increased turnover. ATM from HF + RED mice did not respond to LPS treatment ex vivo, confirming the long-lasting effects of the treatment on M2 polarization. Adipocytes of HF + RED group improved lipid metabolism and displayed a lower inflammation grade. Liver histology revealed a remarkable reduction of steatosis in the HF + RED group, and Kupffer cell profiling displayed a marked switch towards the M2 phenotype.

Conclusions

RED extract attenuated AT inflammation in vivo, with a long-lasting reprogramming of ATM and adipocyte profiles towards the anti-inflammatory phenotype, therefore representing a valuable supplement in the context of obesity-associated disorders.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1972-6) contains supplementary material, which is available to authorized users.

Loss of Mevalonate/Cholesterol Homeostasis in the Brain: A Focus on Autism Spectrum Disorder and Rett Syndrome

The mevalonate (MVA)/cholesterol pathway is crucial for central nervous system (CNS) development and function and consequently, any dysfunction of this fundamental metabolic pathway is likely to provoke pathologic changes in the brain. Mutations in genes directly involved in MVA/cholesterol metabolism cause a range of diseases, many of which present neurologic and psychiatric symptoms. This raises the question whether other diseases presenting similar symptoms are related albeit indirectly to the MVA/cholesterol pathway. Here, we summarized the current literature suggesting links between MVA/cholesterol dysregulation and specific diseases, namely autism spectrum disorder and Rett syndrome.

Serum 24-hydroxycholesterol in probable Alzheimer's dementia: Reexploring the significance of a tentative Alzheimer's disease biomarker

OBJECTIVE

This study measured and analyzed the serum levels of 24-hydroxycholesterol in patients with probable Alzheimer's disease (AD) and age-/sex-matched controls.

METHODS

A case-control study involving 40 AD patients and 40 controls was performed at a tertiary neurological teaching hospital in eastern India. Blood and serum samples were collected for APOE genotyping and 24-hydroxycholesterol levels, respectively.

RESULTS

Serum 24-hydroxycholesterol was significantly lower in AD patients compared to controls (median concentration: controls, 47.14 ng/mL (interquartile range, 16.34); AD patients, 32.93 ng/mL (interquartile range, 9.45); P < 0.001) but showed no significant correlation with Mini Mental State Examination (MMSE) score in AD cases (r = -0.169, P = 0.298) or in controls (r = 0.18, P = 0.26). No statistically significant difference was observed between serum 24-hydroxycholesterol levels of the APOE4-positive and -negative subgroups in AD patients (P = 0.79). Findings were consistent and unchanged even when the ratio of serum 24-hydroxycholesterol to serum total cholesterol was considered.

CONCLUSION

The decreased 24-hydroxycholesterol level in peripheral circulation in AD cases observed in the present study may suggest its role in AD pathogenesis. The lack of a clear correlation between serum levels of 24-hydroxycholesterol and MMSE score-a surrogate marker of AD severity-raises the question as to whether 24-hydroxycholesterol level declines with decreasing neuronal mass or whether the steroid continues to play a protective role.

Oxysterols and apolipoproteins in multiple sclerosis: a 5 year follow-up study

The purpose of this work was to investigate whether changes in oxysterol and apolipoprotein levels over 5 years are associated with disease course and disability progression in multiple sclerosis (MS). This study included 139 subjects [39 healthy controls (HCs), 61 relapsing-remitting MS (RR-MS) patients, and 39 progressive MS (P-MS) patients]. Oxysterols [24-hydroxycholesterol (24HC), 25-hydroxycholesterol (25HC), 27-hydroxycholesterol (27HC), 7α-hydroxycholesterol (7αHC), and 7-ketocholesterol (7KC)] were measured at baseline and 5 years using a novel mass spectrometric method, and apolipoproteins were measured using immunoturbidometric diagnostic kits. Levels of 24HC (P = 0.004), 25HC (P = 0.029), and 27HC (P = 0.026) increased in P-MS patients. 7KC (P = 0.047) and 7αHC (P = 0.001) levels decreased in RR-MS patients, and there were no changes in any oxysterols in HCs. In MS patients, ApoC-II (all P ≤ 0.01) and ApoE (all P ≤ 0.01) changes were positively associated with all oxysterol levels. Increases in 24HC (P = 0.038) and ApoB (P = 0.038) and decreases in 7KC (P = 0.020) were observed in RR-MS patients who converted to secondary P-MS (SP-MS) at follow-up and in SP-MS patients compared with RR-MS patients. Oxysterols and their associations with apolipoproteins differed between MS patients and HCs over 5 years. Oxysterol and apolipoprotein changes were associated with conversion to SP-MS.

Donepezil effects on cholesterol and oxysterol plasma levels of Alzheimer's disease patients

Cholesterol is an essential component in the structure and function of cell membranes and has been associated with the major pathological signatures of Alzheimer's disease (AD). To maintain brain cholesterol homeostasis, it is converted into 24(S)-hydroxycholesterol (24OHC) which can be driven through the blood-brain barrier. Several studies have already described a decrease in 24OHC and an increase of 27(S)-hydroxycholesterol (27OHC) in AD, as a reflection of disease burden, the loss of metabolically active neurons and the degree of structural atrophy. It is also well known that peripheral cholesterol is altered in AD patients. However, there are no data regarding effects of AD treatment in this cholesterol pathway. Since a study from our group indicated a significant increase in membrane phospholipid metabolism by donepezil, the aim of this study was to evaluate the effect of short- and long-term donepezil treatment on cholesterol and metabolites 24OHC and 27OHC in plasma of AD patients and in healthy volunteers. At baseline, we found a decrease of 24OHC (p = 0.003) in AD patients. Cholesterol levels increased with donepezil treatment (p = 0.04) but no differences were observed regarding 24OHC and 27OHC. However, these results confirm and extend previous studies demonstrating disturbed cholesterol turnover in Alzheimer's disease.