7-Ketocholesterol: Effects on viral infections and hypothetical contribution in COVID-19.

7-Ketocholesterol, which is one of the earliest cholesterol oxidization products identified, is essentially formed by the auto-oxidation of cholesterol. In the body, 7-ketocholesterol is both provided by food and produced endogenously. This pro-oxidant and pro-inflammatory molecule, which can activate apoptosis and autophagy at high concentrations, is an abundant component of oxidized Low Density Lipoproteins. 7-Ketocholesterol appears to significantly contribute to the development of age-related diseases (cardiovascular diseases, age-related macular degeneration, and Alzheimer's disease), chronic inflammatory bowel diseases and to certain cancers. Recent studies have also shown that 7-ketocholesterol has anti-viral activities, including on SARS-CoV-2, which are, however, lower than those of oxysterols resulting from the oxidation of cholesterol on the side chain. Furthermore, 7-ketocholesterol is increased in the serum of moderately and severely affected COVID-19 patients. In the case of COVID-19, it can be assumed that the antiviral activity of 7-ketocholesterol could be counterbalanced by its toxic effects, including pro-oxidant, pro-inflammatory and pro-coagulant activities that might promote the induction of cell death in alveolar cells. It is therefore suggested that this oxysterol might be involved in the pathophysiology of COVID-19 by contributing to the acute respiratory distress syndrome and promoting a deleterious, even fatal outcome. Thus, 7-ketocholesterol could possibly constitute a lipid biomarker of COVID-19 outcome and counteracting its toxic effects with adjuvant therapies might have beneficial effects in COVID-19 patients.

Oxysterol species generated by auto-oxidation in subclinical hypothyroidism.

BACKGROUND: Auto-oxidized oxysterols are implicated in the pathogenesis of various chronic diseases. Their concentrations are indicators of oxidative stress in vivo and associated with atherosclerosis. Subclinical hypothyroidism is related with cardiac diseases and oxidative stress, but the exact mechanisms underlying these associations are not clear yet. OBJECTIVE: To investigate the auto-oxidized oxysterols, 7-ketocholesterol (7-KC) and cholestane-3ß,5α,6ß-triol (chol-triol), in patients with subclinical hypothyroidism, as well as to evaluate the impact of restoring euthyroidism on oxysterol concentrations. METHODS: In this prospective observational study, 64 patients with newly diagnosed autoimmune thyroiditis (41 with subclinical hypothyroidism and 23 euthyroidism), and 45 healthy controls were enrolled. Age, gender, and body mass index were matched among patient groups and healthy controls. Anthropometric measurements were obtained and fasting plasma 7-ketocholesterol and cholestane-3ß,5α,6ß-triol concentrations were measured by using liquid chromatography coupled with tandem mass spectrometry. Levothyroxine was then administered to all patients with subclinical-hypothyroidism. After three months, measurements of the oxysterols and serum cholesterols from the patients who have become euthyroid were repeated. RESULTS: Concentrations of 7-ketocholesterol and cholestane-3ß,5α,6ß-triol were significantly higher in patients with subclinical-hypothyroidism when compared to both euthyroid patients and healthy controls (p < 0.001 for both oxysterols). After restoration of euthyroidism, concentrations of 7-ketocholesterol and cholestane-3ß,5α,6ß-triol decreased significantly and reached similar concentrations observed in healthy controls (p < 0.001 for both oxysterols). CONCLUSIONS: Auto-oxidized oxysterol species are higher in patients with mild thyroid dysfunction, and supported the rationale for treating subclinical-hypothyroidism.

A combination of 7-ketocholesterol, lysosphingomyelin and bile acid-408 to diagnose Niemann-Pick disease type C using LC-MS/MS.

BACKGROUND: Niemann-Pick disease type C (NPC) is an autosomal recessive disorder caused by mutations of NPC1 or NPC2, which encode the proteins that are responsible for intracellular cholesterol trafficking. Loss of this function results in the accumulation of cholesterol-related products, such as oxysterols, sphingolipids, and NPC-related bile acids, which were recently used as biochemical biomarkers for the diagnosis of NPC. Bile acid-408 is a new significant compound we found in Japanese NPC patients, and it likely belongs to the category of bile acids. However, the diagnosis of NPC using a single biomarker is not satisfactory for clinical application because of the high instance of false negatives or positives. Therefore, we proposed an application of NPC diagnosis using a combination of 7-ketocholesterol (7-KC), lysosphingomyelin (lysoSM), bile acid-408 and/or glucosylsphingosine (lysoGL-1). METHODS AND FINDINGS: 7-KC, lysoSM and lysoGL-1 in sera and bile acid-408 in dried blood spots (DBS) were quantified within 17 minutes using tandem mass spectrometry and high-resolution mass spectrometry, respectively. We measured these biomarkers in NPC patients (n = 19), X-linked adrenoleukodystrophy (X-ALD) patients (n = 5), patients with other lysosomal diseases (n = 300), newborns (n = 124) and healthy people (n = 74). Our results showed a promising accuracy (97%) for NPC diagnosis using the combination of 7-KC, lysoSM and bile acid-408. However, contrary to our expectations, lysoGL-1 levels did not present at a significantly greater amount in NPC patients than other patients and negative controls. CONCLUSIONS: The combination of 7-KC, lysoSM and bile acid-408 improves the accuracy of NPC diagnosis and is feasible for mass screening due to its simple sample preparation and measurement. Future research should investigate the chemical structure of bile acid-408 to further facilitate its advantage in diagnosis.

Evaluation of oxysterol levels of patients with silicosis by LC-MS/MS method.

Silicosis is one of the prolonged and irreversible occupational diseases. Crystalline silica dust, which has been linked with silicosis, occurs in different industrial areas such as constructions, ceramic, quarry, and pottery. There are significant numbers of newly diagnosed cases every year in Turkey. Patients with silicosis suffer from inflammatory respiratory disorders and silicosis-related complications such as rheumatoid arthritis, systemic sclerosis, and vasculitis. Oxysterols are defined as 27-carbon intermediates or end products of cholesterol. They are also implicated in the etiology of disease states such as atherosclerosis, neurodegenerative, and inflammatory diseases. The aim of the study is to evaluate cholesterol oxidation products in the patients with silicosis and determination of sphingosine-1-phosphate (S1P) levels which is a sphingolipid metabolite. In addition to these parameters, it is aimed to determine the possible lipid peroxidation by different parameters. For this purpose, blood samples and urine were collected from 47 patients and 30 healthy individual with their consents. In order to evaluate oxysterols, 7-ketocholesterol and cholestan 3ß,5α,6ß-triol levels were measured by LC-MS/MS method. The measured levels of 7-KC were 0.101 ± 0.005 µmol/l in patient and 0.050 ± 0.003 µmol/l in control plasma samples. Triol levels were measured as 0.038 ± 0.005 µmol/l in patient group and 0.033 ± 0.004 µmol/l in control group (p < 0.001). In addition, lipid peroxidation products were measured by human-8-isoprostane, human-4-hydroxynonenal (4-HNE), and human malondialdehyde (MDA) ELISA kits. The measured levels of HNE in the patient and control groups were 735.14 ± 288.80 pg/ml and 595.72 ± 108.62 pg/ml in plasma and 606.02 + 118.23 pg/ml and 531.84 + 107.18 pg/ml in urine, respectively (p < 0.05). F2-iP results of patients and controls were 450.0 + 101.40 pg/dl and 386.9 + 112.7 pg/ml for urine and 432.7 ± 188,8 pg/dl and 321.9 ± 69.4 pg/dl for plasma, respectively (p < 0.05). MDA levels of plasma were measured as 44.1 ± 14.6 nmol/ml in the patient and 31.9 ± 10.5 nmol/ml in the control (p < 0.05). Levels of MDA for urine samples were 30.15 + 5.06 nmol/ml and 25.15 + 6.07 nmol/ml in patients and controls, respectively (p < 0.05). S1P levels were decreased in patients compared to control group (49.05 ± 10.87 and 67.57 ± 16.25, p < 0.001). The results not only indicate a correlation between cholesterol oxidation, lipid peroxidation, and silicosis, but also provide better understanding of the role of the lipids in the mechanism of this inflammatory disease.

Human Herpesvirus 8 infection may contribute to oxidative stress in diabetes type 2 patients.

OBJECTIVE: To investigate the link between Human Herpesvirus 8 (HHV8) infection and plasma oxidative stress in patients with diabetes mellitus type 2 (DM2). RESULTS: Blood samples collected from DM2 and control subjects were screened for the presence of antibodies against HHV8 and for biomarkers of oxidative stress. We determined the products of radical damage on the plasma lipid fraction, such as malondialdehyde (MDA), fatty acid hydroperoxides (HP) and 7-ketocholesterol (7-keto), the oxidation products of unsaturated fatty acids (UFA) and cholesterol, respectively. The level of plasma antioxidant α-tocopherol (α-toc) was also assessed. Relevant differences were observed in the redox status in DM2 and either HHV8-positive or -negative control subjects. The level of α-toc significantly decreased in both DM2 and HHV8-positive subjects. Levels of MDA, HP and 7-keto were much higher in HHV8-positive and DM2 subjects, indicating that plasma oxidative stress is a common feature in both DM2 and HHV8-infection. In addition, 7-keto was further increased in HHV8-positive DM2 patients. We hypothesized that the HHV8-infection may contribute to the production of ROS, and hence to the oxidative stress closely related to the pathogenesis and development of DM2.

Enhanced endoplasmic reticulum and mitochondrial stress in abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is a degenerative vascular disease with a complex aetiology that remains to be fully elucidated. Clinical management of AAA is limited to surgical repair, while an effective pharmacotherapy is still awaited. Endoplasmic reticulum (ER) stress and mitochondrial dysfunction have been involved in the pathogenesis of cardiovascular diseases (CVDs), although their contribution to AAA development is uncertain. Therefore, we aimed to determine their implication in AAA and investigated the profile of oxysterols in plasma, specifically 7-ketocholesterol (7-KC), as an ER stress inducer.In the present study, we determined aortic ER stress activation in a large cohort of AAA patients compared with healthy donors. Higher gene expression of activating transcription factor (ATF) 6 (ATF6), IRE-1, X-binding protein 1 (XBP-1), C/EBP-homologous protein (CHOP), CRELD2 and suppressor/enhancer of Lin-12-like (SEL1L) and greater protein levels of active ATF6, active XBP1 and of the pro-apoptotic protein CHOP were detected in human aneurysmatic samples. This was accompanied by an exacerbated apoptosis, higher reactive oxygen species (ROS) production and by a reduction in mitochondrial biogenesis in the vascular wall of AAA. The quantification of oxysterols, performed by liquid chromatography-(atmospheric pressure chemical ionization (APCI))-mass spectrometry, showed that levels of 7-KC were significantly higher while those of 7α-hydroxycholesterol (HC), 24-HC and 27-HC were lower in AAA patients compared with healthy donors. Interestingly, the levels of 7-KC correlate with the expression of ER stress markers.Our results evidence an induction of ER stress in the vascular wall of AAA patients associated with an increase in circulating 7-KC levels and a reduction in mitochondrial biogenesis suggesting their implication in the pathophysiology of this disease.

Oxysterol concentrations are associated with cholesterol concentrations and anemia in pediatric patients with sickle cell disease.

Sickle cell disease (SCD) causes anemia, oxidative stress, chronic inflammation, and lipid abnormalities. Oxysterols are oxidized derivatives of cholesterol and affect cholesterol metabolism and eryptosis. Our aim was to determine whether the plasma concentrations of 7-ketocholesterol (7-KC) and cholestane-3ß,5α,6ß-triol (C-triol) were associated with hemolysis and lipid profile in patients with SCD. A total of 32 steady-state pediatric patients with SCD (22 HbSS and 10 HbSß+) and 25 healthy controls were included in the study. Hemolysis parameters, ferritin, serum iron, lipids, 7-KC and C-triol concentrations of all subjects were measured. Oxysterols were quantified with N,N-dimethylglycine derivatization via LC-MS/MS. 7-KC and C-triol concentrations were found to be increased in SCD patients, while there was no difference between the HbSS and HbSß+ subgroups. 7-KC concentrations s were correlated negatively with hemoglobin and positively with lactate dehydrogenase concentrations, while C-triol concentrations were negatively correlated with HDL cholesterol. Furthermore, while 7-KC and C-triol concentrations were highly correlated among controls, there was no correlation in patients. The findings of our study suggest that 7-KC and C-triol may have a role in SCD pathophysiology. The lack of correlation in patients' 7-KC and C-triol concentrations suggest alterations in oxysterol production in patients with SCD.

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.

Metabolism of Non-Enzymatically Derived Oxysterols: Clues from sterol metabolic disorders.

Cholestane-3ß,5α,6ß-triol (3ß,5α,6ß-triol) is formed from cholestan-5,6-epoxide (5,6-EC) in a reaction catalysed by cholesterol epoxide hydrolase, following formation of 5,6-EC through free radical oxidation of cholesterol. 7-Oxocholesterol (7-OC) and 7ß-hydroxycholesterol (7ß-HC) can also be formed by free radical oxidation of cholesterol. Here we investigate how 3ß,5α,6ß-triol, 7-OC and 7ß-HC are metabolised to bile acids. We show, by monitoring oxysterol metabolites in plasma samples rich in 3ß,5α,6ß-triol, 7-OC and 7ß-HC, that these three oxysterols fall into novel branches of the acidic pathway of bile acid biosynthesis becoming (25R)26-hydroxylated then carboxylated, 24-hydroxylated and side-chain shortened to give the final products 3ß,5α,6ß-trihydroxycholanoic, 3ß-hydroxy-7-oxochol-5-enoic and 3ß,7ß-dihydroxychol-5-enoic acids, respectively. The intermediates in these pathways may be causative of some phenotypical features of, and/or have diagnostic value for, the lysosomal storage diseases, Niemann Pick types C and B and lysosomal acid lipase deficiency. Free radical derived oxysterols are metabolised in human to unusual bile acids via novel branches of the acidic pathway, intermediates in these pathways are observed in plasma.

High Cholesterol Diet-Induced Changes in Oxysterol and Scavenger Receptor Levels in Heart Tissue.

Involvement of high cholesterol and oxidative stress in cardiovascular diseases is well studied, as it can be hypothesized that various products originated from lipid peroxidation, such as oxysterols, or affected protein expression might lead to cardiomyocyte damage followed by the pathological modifications. Although oxidation of excessive cholesterol to oxysterols in elevated stress conditions is identified by a number of studies, the role of a high cholesterol diet in regulating fatty acid and oxysterol accumulation, together with scavenger receptor mRNA levels, in the heart remains little investigated. Our study provides a detailed analysis of the changes in fatty acid, oxysterol, and scavenger receptor profiles and its relation with histological alterations in the heart tissue. We evaluated alterations of fatty acid composition, by the GC-MS method, while 4ß-, 25-, and 27-hydroxycholesterol and 7-ketocholesterol levels by means of LC-MS/MS in high cholesterol diet-fed rabbits. Additionally, a number of proteins related to lipid metabolism and scavenger receptor mRNA expressions were evaluated by Western blotting and RT-PCR. According to our in vivo results, a high cholesterol diet enhances a number of unsaturated fatty acids, oxysterols, and LXRα, in addition to CD36, CD68, CD204, and SR-F1 expressions while α-tocopherol supplementation decreases LXRα and SR expressions together with an increase in 27-hydroxycholesterol and ABCA1 levels. Our results indicated that the high cholesterol diet modulates proteins related to lipid metabolism, which might result in the malfunction of the heart and α-tocopherol shows its beneficial effects. We believe that this work will lead the generation of different theories in the development of heart diseases.

Unravelling new pathways of sterol metabolism: lessons learned from in-born errors and cancer.

PURPOSE OF REVIEW: To update researchers of recently discovered metabolites of cholesterol and of its precursors and to suggest relevant metabolic pathways. RECENT FINDINGS: Patients suffering from inborn errors of sterol biosynthesis, transport and metabolism display unusual metabolic pathways, which may be major routes in the diseased state but minor in the healthy individual. Although quantitatively minor, these pathways may still be important in healthy individuals. Four inborn errors of metabolism, Smith-Lemli-Opitz syndrome, cerebrotendinous xanthomatosis and Niemann Pick disease types B (NPB) and C (NPC) result from mutations in different genes but can generate elevated levels of the same sterol metabolite, 7-oxocholesterol, in plasma. How this molecule is metabolized further is of great interest as its metabolites may have an important role in embryonic development. A second metabolite, abundant in NPC and NPB diseases, cholestane-3ß,5α,6ß-triol (3ß,5α,6ß-triol), has recently been shown to be metabolized to the corresponding bile acid, 3ß,5α,6ß-trihydroxycholanoic acid, providing a diagnostic marker in plasma. The origin of cholestane-3ß,5α,6ß-triol is likely to be 3ß-hydroxycholestan-5,6-epoxide, which can alternatively be metabolized to the tumour suppressor dendrogenin A (DDA). In breast tumours, DDA levels are found to be decreased compared with normal tissues linking sterol metabolism to cancer. SUMMARY: Unusual sterol metabolites and pathways may not only provide markers of disease, but also clues towards cause and treatment.

Plasma 7-ketocholesterol levels and the risk of incident cardiovascular events.

OBJECTIVE: 7-Ketocholesterol (7-KC), a major oxidation product of cholesterol, is found in human atherosclerotic plaque and more atherogenic than cholesterol in animal models. This study was designed to investigate the association of plasma 7-KC level with the incident cardiovascular disease (CVD) events in general population. METHODS: We measured plasma 7-KC concentrations at baseline in 1944 participants free from CVD in a community-based cohort study. The primary endpoint was incident of a major adverse cardiovascular event. A Cox proportional hazards model was used to calculate the HRs with 95% CI. RESULTS: A total of 101 incident CVD events were recorded during the 5.2 year median follow-up. The baseline plasma 7-KC levels were associated with a higher risk of incident CVD events; compared with quartile 1, participants in quartile 4 had an unadjusted HR of 2.38 (2.03-2.85, p<0.001) and an adjusted HR of 1.70 (1.45-1.91, p=0.004) after adjusting for traditional risk factors. Plasma 7-KC levels improved all of the metrics of discrimination and reclassification when added to the intima-media thickness (C-statistic: p=0.002; net reclassification improvement (NRI): p<0.001; integrated discrimination improvement (IDI): p<0.001), family history of myocardial infarction (C-statistic: p=0.011; NRI: p=0.004; IDI: p=0.003) and elevated high-sensitivity C reactive protein (C-statistic: p=0.008; NRI: p=0.015; IDI: p=0.009). CONCLUSIONS: Elevated plasma 7-KC levels are associated with the incident CVD events in a population-based cohort. Further studies are needed to confirm this observation.

Association of Plasma 7-Ketocholesterol With Cardiovascular Outcomes and Total Mortality in Patients With Coronary Artery Disease.

RATIONALE: 7-Ketocholesterol (7-KC), a form of cholesterol oxidation product, plays an essential role in the atherogenesis in animal models. OBJECTIVE: We sought to determine the association of circulating 7-KC with clinical cardiovascular outcomes and total mortality in patients with stable coronary artery disease. METHODS AND RESULTS: We measured the plasma 7-KC levels by high-performance liquid chromatography in a prospective cohort study of 1016 patients (mean age, 63.2 years; male 61.1%) with stable coronary artery disease who were recruited from December 2008 to December 2011 and followed up for a median of 4.6 years. We adjudicated myocardial infarction, hospitalization of heart failure, cardiovascular death, all-cause death, and composite end points of myocardial infarction/heart failure/death by review of medical records and death certificates. We used multivariable Cox proportional hazards analysis to compare the incidence rate of cardiovascular events and all-cause death according to the quartile of the plasma 7-KC. During the median 4.6 years follow-up, totally 221 participants (21.8%) experienced a cardiovascular event or death. The adjusted risk of the composite end points was higher in the highest 7-KC quartile than in the lowest quartile (hazard ratio, 1.76; 95% confidence interval, 1.42-2.21; P<0.001). After adjustment for demographic and clinical variables and other biomarkers, including high-sensitivity C-reactive protein and NT-proBNP (N-terminal pro-B-type natriuretic peptide), 1 SD increase in the 7-KC level remained associated with a 36% higher rate of composite outcomes (hazard ratio, 1.36; 95% confidence interval, 1.22-1.48; P=0.007). Plasma 7-KC clearly improved various model performance measures, including C statistics, integrated discrimination, and category-free net reclassification. CONCLUSIONS: High 7-KC levels are associated with increased risk of cardiovascular events, total death, and composite outcomes in patients with stable coronary artery disease.

7-Ketocholesterol is increased in the plasma of X-ALD patients and induces peroxisomal modifications in microglial cells: Potential roles of 7-ketocholesterol in the pathophysiology of X-ALD.

X-linked adrenoleukodystrophy (X-ALD) is a genetic disorder induced by a mutation in the ABCD1 gene, which causes the accumulation of very long-chain fatty acids in tissue and plasma. Oxidative stress may be a hallmark of X-ALD. In the plasma of X-ALD patients with different forms of the disease, characterized by high levels of C24:0 and C26:0, we observed the presence of oxidative stress revealed by decreased levels of GSH, α-tocopherol, and docosahexaenoic acid (DHA). We showed that oxidative stress caused the oxidation of cholesterol and linoleic acid, leading to the formation of cholesterol oxide derivatives oxidized at C7 (7-ketocholesterol (7KC), 7ß-hydroxycholesterol (7ß-OHC), and 7α-hydroxycholesrol (7α-OHC)) and of 9- and 13-hydroxyoctadecadienoic acids (9-HODE, 13-HODE), respectively. High levels of 7KC, 7ß-OHC, 7α-OHC, 9-HODE and 13-HODE were found. As 7KC induces oxidative stress, inflammation and cell death, which could play key roles in the development of X-ALD, the impact of 7KC on the peroxisomal status was determined in microglial BV-2 cells. Indeed, environmental stress factors such as 7KC could exacerbate peroxisomal dysfunctions in microglial cells and thus determine the progression of the disease. 7KC induces oxiapoptophagy in BV-2 cells: overproduction of H2O2 and O2-, presence of cleaved caspase-3 and PARP, nuclear condensation and/or fragmentation; elevated [LC3-II/LC3-I] ratio, increased p62 levels. 7KC also induces several peroxisomal modifications: decreased Abcd1, Abcd2, Abcd3, Acox1 and/or Mfp2 mRNA and protein levels, increased catalase activity and decreased Acox1-activity. However, the Pex14 level was unchanged. It is suggested that high levels of 7KC in X-ALD patients could foster generalized peroxisomal dysfunction in microglial cells, which could in turn intensify brain damage.

[Blood 7-ketocholesterol level, clinical features and gene mutation analysis of 18 children with Niemann-Pick disease type C].

OBJECTIVE: To investigate 7-ketocholesterol (7-KC) level in the blood, clinical features and gene mutation of Niemann-Pick disease type C (NPC). METHOD: Eighteen patients diagnosed as NPC in Shanghai Xinhua Hospital seen from February 2013 to October 2014 were enrolled in this study. They included 13 males and 5 females and aged from 5 months to 21 years. The plasma 7-KC concentrations, clinical features and gene mutations of NPC patients were reviewed retrospectively. RESULT: Fourteen NPC patients had neurological symptoms with the age of neurological onset from 1 year to 16 years. In seven cases the disease was early-infantile subtype, in 1 late-infantile subtype, in five juvenile subtype and in one adult subtype. The 7-KC value in the plasma of NPC patients was higher than the normal range, (348.5±168.7) µg/L in the early-infantile subtype, 150.6 µg/L in the late-infantile subtype, (145.0±46.3) µg/L in the juvenile subtype, and 32.0 µg/L in the adult subtype, respectively, additionally, four NPC patients had no observable neuropsychiatric disability when confirmed to be NPC by genetic testing, with the plasma 7-KC value (345.6±134.2) µg/L; 16 of 18 patients had splenomegaly or hepatosplenomegaly. Among 18 patients, 34 different mutations in the NPC1 gene were identified including 27 reported mutations, 1 novel small deletion 3609_3610delAC, five novel exonic point mutations, c. 3683T>C(M1228T), c. 3679A>T(R1227W), c. 1070C>T(S357L), c. 1456A>C(N486H) and c. 1142G>A(W381X) and 1 novel intronic mutation c. 881+ 3A>G. CONCLUSION: The 7-KC levels in the blood of patient was remarkably increased, and there was a tendency that 7-KC levels inversely correlated with the age of neurological onset. Most NPC patient had splenomegaly or hepatosplenomegaly. Among 18 patients, 34 different mutations in the NPC1 gene were identified including seven novel mutations, which enriched the gene mutation spectrum.

Evaluation of plasma cholestane-3ß,5α,6ß-triol and 7-ketocholesterol in inherited disorders related to cholesterol metabolism.

Oxysterols are intermediates of cholesterol metabolism and are generated from cholesterol via either enzymatic or nonenzymatic pathways under oxidative stress conditions. Cholestan-3ß,5α,6ß-triol (C-triol) and 7-ketocholesterol (7-KC) have been proposed as new biomarkers for the diagnosis of Niemann-Pick type C (NP-C) disease, representing an alternative tool to the invasive and time-consuming method of fibroblast filipin test. To test the efficacy of plasma oxysterol determination for the diagnosis of NP-C, we systematically screened oxysterol levels in patients affected by different inherited disorders related with cholesterol metabolism, which included Niemann-Pick type B (NP-B) disease, lysosomal acid lipase (LAL) deficiency, Smith-Lemli-Opitz syndrome (SLOS), congenital familial hypercholesterolemia (FH), and sitosterolemia (SITO). As expected, NP-C patients showed significant increase of both C-triol and 7-KC. Strong increase of both oxysterols was observed in NP-B and less pronounced in LAL deficiency. In SLOS, only 7-KC was markedly increased, whereas in both FH and in SITO, oxysterol concentrations were normal. Interestingly, in NP-C alone, we observed that plasma oxysterols correlate negatively with patient's age and positively with serum total bilirubin, suggesting the potential relationship between oxysterol levels and hepatic disease status. Our results indicate that oxysterols are reliable and sensitive biomarkers of NP-C.

Comprehensive Evaluation of Plasma 7-Ketocholesterol and Cholestan-3ß,5α,6ß-Triol in an Italian Cohort of Patients Affected by Niemann-Pick Disease due to NPC1 and SMPD1 Mutations.

Niemann-Pick C disease (NPCD) is a rare autosomal recessive neurovisceral disorder with a heterogeneous clinical presentation. Cholestan-3ß,5α,6ß-triol and 7-ketocholesterol have been proposed as biomarkers for the screening of NPCD. In this work, we assessed oxysterols levels in a cohort of Italian patients affected by NPCD and analyzed the obtained results in the context of the clinical, biochemical and molecular data. In addition, a group of patients affected by Niemann-Pick B disease (NPBD) were also analyzed. NPC patients presented levels of both oxysterols way above the cut off value, except for 5 siblings presenting the variant biochemical phenotype who displayed levels of 3ß,5α,6ß-triol below or just above the cut-off value; 2 of them presented also normal levels of 7-KC. Both oxysterols were extremely high in a patient presenting the neonatal systemic lethal phenotype. All NPB patients showed increased oxysterols levels. In conclusion, the reported LC-MS/MS assay provides a robust non-invasive screening tool for NPCD. However, false negative results can be obtained in patients expressing the variant biochemical phenotype. These data strengthen the concept that the results should always be interpreted in the context of the patients' clinical picture and filipin staining and/or genetic studies might still be undertaken in patients with normal levels of oxysterols if symptoms are highly suggestive of NPCD. Both oxysterols are significantly elevated in NPB patients; thus a differential diagnosis should always be performed in patients presenting isolated hepatosplenomegaly, a common clinical sign of both NPCD and NPBD.

Quantification of oxysterols in human plasma and red blood cells by liquid chromatography high-resolution tandem mass spectrometry.

Oxysterols are important intermediates in numerous metabolic and catabolic pathways and their biological significance is also proven. The present paper describes a reliable and short liquid chromatography-high-resolution mass spectrometry method (LC-MS/HR-MS) for the quantification of 8 different oxysterols (24(S)-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol, 4ß-hydroxycholesterol, 7α-hydroxycholesterol, 7ß-hydroxycholesterol, 7-ketocholesterol and cholestan-3ß,5α,6ß-triol) in human plasma and red blood cells. Oxysterols were extracted with iso-octane after saponification of esterified sterols. Due to the poor ionization efficiency of the target compounds in electrospray ionization (ESI) derivatization of the molecules has been performed with N,N-dimethylglycine (DMG). Within less than 8 min we were able to achieve baseline separation of the isobaric 24(S)-hydroxycholesterol, 25-hydroxycholesterol, 27-hydroxycholesterol, 4ß-hydroxycholesterol, 7α-hydroxycholesterol and 7ß-hydroxycholesterol. Moreover, high mass resolution was advantageously applied to resolve quasi-isobaric interferences. The method was validated based on the recommendations of US Food and Drug Administration and the European Medicines Agency guidelines. Oxysterol concentrations were determined in human plasma and red blood cells from healthy volunteers. Furthermore, the applicability for clinical use has been proven by the analysis of oxysterols as biomarkers in Niemann-Pick type C or cerebrotendinous xanthomatosis patients.

Cholestane-3ß,5α,6ß-triol: high levels in Niemann-Pick type C, cerebrotendinous xanthomatosis, and lysosomal acid lipase deficiency.

Niemann-Pick type C (NPC) is a progressive neurodegenerative disease characterized by lysosomal/endosomal accumulation of unesterified cholesterol and glycolipids. Recent studies have shown that plasma cholestane-3ß,5α,6ß-triol (CT) and 7-ketocholesterol (7-KC) could be potential biomarkers for the diagnosis of NPC patients. We aimed to know the sensitivity and specificity of these biomarkers for the diagnosis of NPC compared with other diseases that can potentially lead to oxysterol alterations. We studied 107 controls and 122 patients including 16 with NPC, 3 with lysosomal acid lipase (LAL) deficiency, 8 with other lysosomal diseases, 5 with galactosemia, 11 with cerebrotendinous xanthomatosis (CTX), 3 with Smith-Lemli-Opitz, 14 with peroxisomal biogenesis disorders, 19 with unspecific hepatic diseases, 13 with familial hypercholesterolemia, and 30 with neurological involvement and no evidence of an inherited metabolic disease. CT and 7-KC were analyzed by HPLC-ESI-MS/MS as mono-dimethylglycine derivatives. Levels of 7-KC were high in most of the studied diseases, whereas those of CT were only high in NPC, LAL, and CTX patients. Consequently, although CT is a sensitive biomarker of NPC disease, including those cases with doubtful filipin staining, it is not specific. 7-KC is a very unspecific biomarker.

LC-MS/MS based assay and reference intervals in children and adolescents for oxysterols elevated in Niemann-Pick diseases.

BACKGROUND: Niemann-Pick type C (NP-C) is a rare progressive neurodegenerative lipid storage disorder with heterogeneous clinical presentation and challenging diagnostic procedures. Recently oxysterols have been reported to be specific biomarkers for NP-C but knowledge on the intra-individual variation and on reference intervals in children and adolescents are lacking. METHODS: We established a LC-MS/MS assay to measure Cholestane-3ß, 5α, 6ß-triol (C-triol) and 7-Ketocholesterol (7-KC) following Steglich esterification. To assess reference intervals and intra-individual variation we determined oxysterols in 148 children and adolescents from 0 to 18 years and repeat measurements in 19 of them. RESULTS: The reported method is linear (r>0.99), sensitive (detection limit of 0.03 ng/mL [0.07 nM] for C-triol, and 0.54 ng/mL [1.35 nM] for 7-KC) and precise, with an intra-day imprecision of 4.8% and 4.1%, and an inter-day imprecision of 7.0% and 11.0% for C-triol (28 ng/ml, 67 nM) and 7-KC (32 ng/ml, 80 nM), respectively. Recoveries for 7-KC and C-triol range between 93% and 107%. The upper reference limit obtained for C-triol is 40.4 ng/mL (95% CI: 26.4-61.7 ng/mL, 96.0 nM, 95% CI: 62.8-146.7 nM) and 75.0 ng/mL for 7-KC (95% CI: 55.5-102.5 ng/mL, 187.2 nM, 95% CI: 138.53-255.8 nM), with no age or gender dependency. Both oxysterols have a broad intra-individual variation of 46%±23% for C-triol and 52%±29% for 7-KC. Nevertheless, all Niemann-Pick patients showed increased C-triol levels including Niemann-Pick type A and B patients. CONCLUSIONS: The LC-MS/MS assay is a robust assay to quantify C-triol and 7-KC in plasma with well documented reference intervals in children and adolescents to screen for NP-C in the pediatric population. In addition our results suggest that especially the C-triol is a biomarker for all three Niemann-Pick diseases.