Measurement of oxysterols and alpha-tocopherol in plasma and tissue samples as indices of oxidant stress status

Cholestane-3β,5α,6β-triol Induces Multiple Cell Death in A549 Cells via ER Stress and Autophagy Activation

Cholestane-3β,5α,6β-triol (CT) and its analogues are abundant in natural sources and are reported to demonstrate cytotoxicity toward different kinds of tumor cells without a deep probe into their mechanism of action. CT is also one of the major metabolic oxysterols of cholesterol in mammals and is found to accumulate in various diseases. An extensive exploration of the biological roles of CT over the past few decades has established its identity as an apoptosis inducer. In this study, the effects of CT on A549 cell death were investigated through cell viability assays. RNA-sequencing analysis and western blot of CT-treated A549 cells revealed the role of CT in inducing endoplasmic reticulum (ER) stress response and enhancing autophagy flux, suggesting a putative mechanism of CT-induced cell-death activation involving reactive oxygen species (ROS)-mediated ER stress and autophagy. It is reported for the first time that the upregulation of autophagy induced by CT can serve as a cellular cytotoxicity response in accelerating CT-induced cell death in A549 cells. This research provides evidence for the effect of CT as an oxysterol in cell response to oxidative damage and allows for a deep understanding of cholesterol in its response in an oxidative stress environment that commonly occurs in the progression of various diseases.

7-Ketocholesterol plays a key role in cholesterol-induced hepatitis via macrophage and neutrophil infiltration

This study sought to explore the role of 7-ketocholesterol (7-KC) in liver damage caused by high cholesterol intake and its potential pathological mechanism in mice. Our in vivo findings indicated that mice fed a high-cholesterol diet had elevated serum levels of 7-KC, accompanied by liver injury and inflammation, similar to human nonalcoholic steatohepatitis. Furthermore, the high-cholesterol diet induced neutrophil infiltration, which played a critical role in liver damage through myeloperoxidase (MPO) activity. Upon stimulation with 7-KC, macrophages exhibited increased expression of C-X-C motif chemokine ligand 1 (CXCL1) and CXCL2, as well as ATP-binding cassette transporter A1 (ABCA1) and ABCG1. Hepatocytes, on the other hand, exhibited increased expression of CXCL2 and ABCG1. The infiltration of neutrophils in the liver was primarily caused by CXCL1 and CXCL2, resulting in hepatocyte cell death due to elevated MPO activity. Our data also revealed that the activation of macrophages by 7-KC via ABCA1 or ABCG1 was not associated with lipid accumulation. Collectively, these findings suggest that high cholesterol-induced hepatitis in mice involves, at least partially, the recruitment of neutrophils to the liver by 7-KC-activated macrophages. This is mediated by increased expression of CXCL1 and CXCL2 through ABCA1 or ABCG1, which act as 7-KC efflux transporters. Additionally, hepatocytes contribute to this process by increased expression of CXCL2 through ABCG1. Therefore, our findings suggest that 7-KC may play a role in high cholesterol-induced hepatitis in mice by activating macrophages and hepatocytes, ultimately leading to neutrophil infiltration.

Inflammation and oxidative stress markers in type 2 diabetes patients with Advanced Carotid atherosclerosis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a major global health issue and a significant risk factor for atherosclerosis. Atherosclerosis in T2DM patients has been associated with inflammation, insulin resistance, hyperglycemia, dyslipidemia, and oxidative stress. Identifying molecular features of atherosclerotic plaques in T2DM patients could provide valuable insights into the pathogenesis of the disease.

METHODS

The MASCADI (Arachidonic Acid Metabolism in Carotid Stenosis Plaque in Diabetic Patients) study aimed to investigate the increase of 2-arachidonoyl-lysophatidylcholine (2-AA-LPC) in carotid plaques from T2DM and control patients and to explore its association with plaque vulnerability as well as with blood and intra-plaque biomarkers altered during diabetes.

RESULTS

In a population of elderly, polymedicated patients with advanced stage of atherosclerosis, we found that T2DM patients had higher systemic inflammation markers, such as high-sensitivity C-reactive protein (hsCRP) and IL-1β, higher levels of oxysterols, increased triglyceride levels, and decreased HDL levels as compared to control patients. Furthermore, 2-AA-LPC was significantly enriched in plaques from diabetic patients, suggesting its potential role in diabetic atherosclerosis. Interestingly, 2-AA-LPC was not associated with systemic markers related to diabetes, such as hsCRP, triglycerides, or HDL cholesterol. However, it was significantly correlated with the levels of inflammatory markers within the plaques such as lysophospholipids and 25-hydroxycholesterol, strengthening the link between local inflammation, arachidonic acid metabolism and diabetes.

CONCLUSION

Our study is in line with a key role for inflammation in the pathogenesis of diabetic atherosclerosis and highlights the involvement of 2-AA-LPC. Further research is needed to better understand the local processes involved in the alteration of plaque composition in T2DM and to identify potential therapeutic targets.

TRIAL REGISTRATION

The MASCADI was registered on ClinicalTrials.gov (clinical registration number: NCT03202823).

Plasma sterols and vitamin D are correlates and predictors of ozone-induced inflammation in the lung: A pilot study

BACKGROUND

Ozone (O3) exposure causes respiratory effects including lung function decrements, increased lung permeability, and airway inflammation. Additionally, baseline metabolic state can predispose individuals to adverse health effects from O3. For this reason, we conducted an exploratory study to examine the effect of O3 exposure on derivatives of cholesterol biosynthesis: sterols, oxysterols, and secosteroid (25-hydroxyvitamin D) not only in the lung, but also in circulation.

METHODS

We obtained plasma and induced sputum samples from non-asthmatic (n = 12) and asthmatic (n = 12) adult volunteers 6 hours following exposure to 0.4ppm O3 for 2 hours. We quantified the concentrations of 24 cholesterol precursors and derivatives by UPLC-MS and 30 cytokines by ELISA. We use computational analyses including machine learning to determine whether baseline plasma sterols are predictive of O3 responsiveness.

RESULTS

We observed an overall decrease in the concentration of cholesterol precursors and derivatives (e.g. 27-hydroxycholesterol) and an increase in concentration of autooxidation products (e.g. secosterol-B) in sputum samples. In plasma, we saw a significant increase in the concentration of secosterol-B after O3 exposure. Machine learning algorithms showed that plasma cholesterol was a top predictor of O3 responder status based on decrease in FEV1 (>5%). Further, 25-hydroxyvitamin D was positively associated with lung function in non-asthmatic subjects and with sputum uteroglobin, whereas it was inversely associated with sputum myeloperoxidase and neutrophil counts.

CONCLUSION

This study highlights alterations in sterol metabolites in the airway and circulation as potential contributors to systemic health outcomes and predictors of pulmonary and inflammatory responsiveness following O3 exposure.

Liver X Receptor Activation Attenuates Oxysterol-Induced Inflammatory Responses in Fetoplacental Endothelial Cells

Oxysterols are oxidized cholesterol derivatives whose systemic levels are found elevated in pregnancy disorders such as gestational diabetes mellitus (GDM). Oxysterols act through various cellular receptors and serve as a key metabolic signal, coordinating inflammation. GDM is a condition of low-grade chronic inflammation accompanied by altered inflammatory profiles in the mother, placenta and fetus. Higher levels of two oxysterols, namely 7-ketocholesterol (7-ketoC) and 7β-hydroxycholesterol (7β-OHC), were observed in fetoplacental endothelial cells (fpEC) and cord blood of GDM offspring. In this study, we tested the effects of 7-ketoC and 7β-OHC on inflammation and investigated the underlying mechanisms involved. Primary fpEC in culture treated with 7-ketoC or 7β-OHC, induced the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NFκB) signaling, which resulted in the expression of pro-inflammatory cytokines (IL-6, IL-8) and intercellular cell adhesion molecule-1 (ICAM-1). Liver-X receptor (LXR) activation is known to repress inflammation. Treatment with LXR synthetic agonist T0901317 dampened oxysterol-induced inflammatory responses. Probucol, an inhibitor of LXR target gene ATP-binding cassette transporter A-1 (ABCA-1), antagonized the protective effects of T0901317, suggesting a potential involvement of ABCA-1 in LXR-mediated repression of inflammatory signaling in fpEC. TLR-4 inhibitor Tak-242 attenuated pro-inflammatory signaling induced by oxysterols downstream of the TLR-4 inflammatory signaling cascade. Taken together, our findings suggest that 7-ketoC and 7β-OHC contribute to placental inflammation through the activation of TLR-4. Pharmacologic activation of LXR in fpEC decelerates its shift to a pro-inflammatory phenotype in the presence of oxysterols.

Role of reactive oxygen species in regulating 27-hydroxycholesterol-induced apoptosis of hematopoietic progenitor cells and myeloid cell lines

Oxysterols are oxygenated derivatives of cholesterol that contain an additional hydroxy, epoxide, or ketone group in the sterol nucleus and/or a hydroxyl group in the side chain of the cholesterol molecule. 27-Hydroxycholesterol (27HC) is a side-chain oxysterol that is oxygenated at the 27th carbon atom of cholesterol. The oxysterol (27HC) is produced via oxidation by sterol 27-hydroxylase (CYP27A1) and metabolized via oxysterol 7a-hydroxylase (CYP7B1) for bile acid synthesis in the liver. A previous study has demonstrated that treatment with the alternative Estrogen receptor alpha (ERα) ligand 27HC induces ERα-dependent hematopoietic stem cell (HSC) mobilization. In addition, Cyp27a1-deficient mice demonstrate significantly reduced 27HC levels and HSC mobilization. Here, we report that exogenous 27HC treatment leads to a substantial reduction in the hematopoietic stem and progenitor cell (HSPC) population owing to significantly increased reactive oxygen species (ROS) levels and apoptosis in the bone marrow (BM). However, 27HC does not influence the population of mature hematopoietic cells in the BM. Furthermore, exogenous 27HC treatment suppresses cell growth and promotes ROS production and apoptosis in leukemic cells. Moreover, acute myeloid leukemia (AML) patients with high CYP7B1 expression (expected to have inhibition of 27HC) had significantly shorter survival than those with low CYP7B1 expression (expected to have an elevation of 27HC). Single-cell RNA-sequencing (scRNA seq) analysis revealed that the expression of CYP7B1 was significantly increased in AML patients. Thus, our study suggests that 27HC may serve as a potent agent for regulating pools of HSPCs and may have an application as a novel therapeutic target for hematological malignancies. Collectively, pharmacological inhibition of CYP7B1 (expected to have an elevation of 27HC) would potentially have fewer long-term hematological side effects, particularly when used in combination with chemotherapy or radiation for the treatment of leukemia patients.

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.

Plasma oxyphytosterols most likely originate from hepatic oxidation and subsequent spill-over in the circulation

We evaluated oxyphytosterol (OPS) concentrations in plasma and various tissues of two genetically modified mouse models with either increased cholesterol (apoE KO mice) or increased cholesterol and plant sterol (PS) concentrations (apoExABCG8 dKO mice). Sixteen female apoE KO and 16 dKO mice followed the same standard, low OPS-chow diet. Animals were euthanized at 36 weeks to measure PS and OPS concentrations in plasma, brain, liver and aortic tissue. Cholesterol and oxysterol (OS) concentrations were analyzed as reference for sterol oxidation in general. Plasma campesterol (24.1 ± 4.3 vs. 11.8 ± 3.0 mg/dL) and sitosterol (67.4 ± 12.7 vs. 4.9 ± 1.1 mg/dL) concentrations were severely elevated in the dKO compared to the apoE KO mice (p < 0.001). Also, in aortic and brain tissue, PS levels were significantly elevated in dKO. However, plasma, aortic and brain OPS concentrations were comparable or even lower in the dKO mice. In contrast, in liver tissue, both PS and OPS concentrations were severely elevated in the dKO compared to apoE KO mice (sum OPS: 7.4 ± 1.6 vs. 4.1 ± 0.8 ng/mg, p < 0.001). OS concentrations followed cholesterol concentrations in plasma and all tissues suggesting ubiquitous oxidation. Despite severely elevated PS concentrations, OPS concentrations were only elevated in liver tissue, suggesting that OPS are primarily formed in the liver and plasma concentrations originate from hepatic spill-over into the circulation.

7-ketocholesterol enhances autophagy via the ROS-TFEB signaling pathway in osteoclasts

Oxysterols play a critical role in human health and diseases associated with high cholesterol and oxidative stress. Given that a positive correlation was observed between cholesterol and collagen type 1 fragment (CTX-1) or serum reactive oxygen species (ROS) in humans, we hypothesized that oxidized cholesterol metabolites may participate in cholesterol-induced bone loss. Therefore, this study aimed to identify the metabolite responsible for cholesterol-associated bone loss and evaluate its effect on osteoclasts (OCs) leading to bone loss. An atherogenic diet in mice increased the levels of the oxysterol, 7-ketocholesterol (7-KC) in bone, as well as serum ROS. 7-KC increased the number and activity of OCs by enhancing autophagy via the ROS-transcription factor EB signaling pathway. These findings suggest that 7-KC acts as a cholesterol metabolite and is at least partially responsible for cholesterol-induced bone loss by inducing autophagy in OCs.

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-3β,5α,6β-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-3β,5α,6β-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-3β,5α,6β-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-3β,5α,6β-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.

Safety of the extension of use of plant sterol esters as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of an extension of use of the novel food 'plant sterol esters' when added to vegetable fat spreads and to liquid vegetable fat-based emulsions for cooking and baking purposes pursuant to Regulation (EU) 2015/2283. Member States expressed concerns in relation to plant sterol oxidation products (POP) and consumption by non-target population groups. The median (0.5%) and P90 (2.28%) value of the oxidation rates of plant sterols determined by a wide range of cooking experiments were used together with exposure estimates for plant sterol when added and cooked with vegetable fat spreads and liquids. The no-observed adverse effect level (NOAEL) of a subchronic rat study and an applied default uncertainty factor of 200 served to derive levels (i.e. 0.64 mg POP/kg body weight (bw) per day) considered safe for humans. This safe level of exposure would be exceeded at the P95 by all age groups when considering the P90 oxidation rate and using EFSA's comprehensive food consumption database for assessing the potential exposure. When considering the median oxidation rate, the safe level of 0.64 mg POP/kg bw per day would be exceeded at the highest P95 intake estimates in children below 9 years of age. When considering an intake of the maximum authorised use level of 3 g plant sterols/person per day and oxidation rates of 0.5% and 2.28%, the resulting daily POP intakes per kg bw by an adult weighing 70 kg would be 0.21 and 0.98 mg/kg bw per day, respectively, the latter value exceeding 0.64 mg/kg bw per day. The Panel concludes that the safety of the intended extension of use of plant sterol esters under the proposed conditions of use has not been established.

Nuclear Factor E2-Related Factor 2 Mediates Oxidative Stress-Induced Lipid Accumulation in Adipocytes by Increasing Adipogenesis and Decreasing Lipolysis

Aims: Nuclear factor E2-related factor 2 (Nrf2) is a regulator of cellular oxidative stress and is also involved in lipid metabolism in adipocytes. However, it remains unknown as to whether Nrf2 is the link between oxidative stress and the induction of lipid accumulation in adipocytes. Results: Here, we show that oxidative stress is markedly increased in white adipose tissue from mice with high-fat diet-induced or genetically (ob/ob)-induced obesity and from human subjects with obesity. Notably, in response to oxidative stress, Nrf2 expression and activity were induced, further promoting lipid accumulation in adipocytes and exacerbating the development of obesity. In contrast, Nrf2 ablation alleviated oxidative stress-induced lipid accumulation. Mechanistically, oxidative stress promoted Nrf2 recruitment to the sterol regulatory element binding protein 1 promoter, inducing target gene transcription and subsequent lipogenesis. In addition, Nrf2 mediated oxidative stress-inhibited lipolysis in adipocytes via the protein kinase A pathway. Innovation and Conclusion: Our data provide a novel insight that Nrf2, as a critical signaling node, links oxidative stress to the induction of fat accumulation in adipocytes.

Cholest-4,6-Dien-3-One Promote Epithelial-To-Mesenchymal Transition (EMT) in Biliary Tree Stem/Progenitor Cell Cultures In Vitro

Human biliary tree stem/progenitor cells (hBTSCs), reside in peribiliary glands, are mainly stimulated by primary sclerosing cholangitis (PSC) and cholangiocarcinoma. In these pathologies, hBTSCs displayed epithelial-to-mesenchymal transition (EMT), senescence characteristics, and impaired differentiation. Here, we investigated the effects of cholest-4,6-dien-3-one, an oxysterol involved in cholangiopathies, on hBTSCs biology. hBTSCs were isolated from donor organs, cultured in self-renewal control conditions, differentiated in mature cholangiocytes by specifically tailored medium, or exposed for 10 days to concentration of cholest-4,6-dien-3-one (0.14 mM). Viability, proliferation, senescence, EMT genes expression, telomerase activity, interleukin 6 (IL6) secretion, differentiation capacity, and HDAC6 gene expression were analyzed. Although the effect of cholest-4,6-dien-3-one was not detected on hBTSCs viability, we found a significant increase in cell proliferation, senescence, and IL6 secretion. Interestingly, cholest-4.6-dien-3-one impaired differentiation in mature cholangiocytes and, simultaneously, induced the EMT markers, significantly reduced the telomerase activity, and induced HDAC6 gene expression. Moreover, cholest-4,6-dien-3-one enhanced bone morphogenic protein 4 (Bmp-4) and sonic hedgehog (Shh) pathways in hBTSCs. The same pathways activated by human recombinant proteins induced the expression of EMT markers in hBTSCs. In conclusion, we demonstrated that chronic exposition of cholest-4,6-dien-3-one induced cell proliferation, EMT markers, and senescence in hBTSC, and also impaired the differentiation in mature cholangiocytes.

Secosterol-B affects endoplasmic reticulum structure in endothelial cells

Oxysterols, oxidized derivatives of cholesterol found in LDL and atherosclerotic plaques, trigger several biological responses involved in the initiation and progression of atherosclerosis. Endothelial dysfunction, which occurs when vascular homeostasis is altered, plays a key role in the pathogenesis of several metabolic diseases. The contribution of endoplasmic reticulum (ER) stress to endothelial disfunction is a relatively recent area of investigation. There is a well-established link between LDL oxidation and ER stress but the role played by specific products of lipid oxidation into this interaction is still to be defined. The present study shows that secosterol-B (SEC-B), 3β-hydroxy-5β-hydroxy-B-norcholestane-6βcarboxaldehyde, a cholesterol autoxidation product recently identified in the atherosclerotic plaque, is able to induce ER stress in HUVEC cells, as revealed by significant expansion and change of structure. At low doses, i.e. 1 and 5 μM, cells try to cope with this stress by activating autophagy and the ubiquitin proteasome system in the attempt to restore ER function. However, at higher doses, i.e. 20 μM, cell apoptosis occurs in a pathway that involves early phosphorylation of eIF2α and NF-kB activation, suggesting that the adaptive program fails and the cell activates the apoptotic program. These findings provide additional insight about the role of oxysterols in endothelial dysfunction and its potential involvement in atherosclerotic pathophysiology.

Brain cholesterol metabolism and Parkinson's disease

BACKGROUND

Circulating cholesterol levels have been linked to PD, but not directly to brain physiology.

OBJECTIVE

To assess whether brain cholesterol metabolism is related to PD.

METHODS

Sixty PD patients and 64 controls were recruited from an academic movement disorder clinic (2009-2012). Thirty-five PD patients and 33 controls returned approximately 36 months later. Fasting plasma (S)24-OH-cholesterol (brain-derived cholesterol metabolite) and 27-OH-cholesterol (peripheral cholesterol metabolite) were quantified. Odds ratios for PD were derived from logistic regression models, adjusting for potential confounders. Relationships between the oxysterols and clinical measurements were explored using Spearman correlation coefficients.

RESULTS

Mean age of PD subjects was 63.8 ± 8.3 years and disease duration was 5.0 ± 5.4 years. Plasma (S)24-OH-cholesterol levels were inversely associated with the odds of having PD, with an odds ratio of 0.92 (95% confidence interval: 0.87-0.97) for each 1-ng/mL increase (P = 0.004). Compared to the lowest tertile, the odds ratio was 0.34 (0.12-0.98) for the second tertile (P = 0.045) and 0.08 (0.02-0.31) for the highest tertile (P < 0.001). Higher (S)24-OH-cholesterol levels also were correlated with better sense of smell (r = 0.35; P = 0.01). No significant associations were found between clinical measures and 27-OH-cholesterol, a peripheral cholesterol metabolite. Furthermore, (S)24-OH-cholesterol levels were stable over time, whereas 27-OH-cholesterol decreased with time in both cases and controls.

CONCLUSIONS

Results indicate that plasma (S)24-OH-cholesterol (possibly reflecting brain cholesterol metabolism) is inversely linked to PD, is relatively stable over time, and may serve as a new biomarker for PD. Further investigation is necessary to determine the mechanistic and clinical implications. © 2019 International Parkinson and Movement Disorder Society.

Oxysterol species: reliable markers of oxidative stress in diabetes mellitus

PURPOSE

To assess the plasma oxysterol species 7-ketocholesterol (7-Kchol) and cholestane-3β,5α,6β-triol (chol-triol) as biomarkers of oxidative stress in type 1 and type 2 diabetes mellitus (DM).

METHODS

In total, 26 type 1 and 80 type 2 diabetes patients, along with 205 age- and gender-matched healthy controls, were included in this study. Oxysterols were quantified by liquid chromatography coupled with tandem mass spectrometry and N,N-dimethylglycine derivatization. Correlations between oxysterols and clinical/biochemical characteristics of the diabetes patients, and factors affecting 7-Kchol and chol-triol, were also determined.

RESULTS

Plasma 7-Kchol and chol-triol levels were significantly higher in type 1 and type 2 diabetes patients compared to healthy controls (P < 0.001). Significant positive correlations were observed between oxysterol levels and levels of glycated hemoglobin (HbA1c), glucose, serum total cholesterol, low-density lipoprotein, very-low-density lipoprotein, and triglycerides, as well as the number of coronary risk factors. Statins, oral hypoglycemic agents, and antihypertensive agents reduced the levels of oxysterols in type 2 diabetes patients. Statin use, HbA1c levels, and the number of coronary risk factors accounted for 98.8% of the changes in 7-Kchol levels, and total cholesterol, smoking status, and the number of coronary risk factors accounted for 77.3% of the changes in chol-triol levels in type 2 diabetes patients.

CONCLUSIONS

Plasma oxysterol levels in DM, and particularly type 2 DM, may yield complementary information regarding oxidative stress for the clinical follow-up of diabetes patients, especially those with coronary risk factors.

Heme Oxygenase-1 and Brain Oxysterols Metabolism Are Linked to Egr-1 Expression in Aged Mice Cortex, but Not in Hippocampus

Throughout life, stress stimuli act upon the brain leading to morphological and functional changes in advanced age, when it is likely to develop neurodegenerative disorders. There is an increasing need to unveil the molecular mechanisms underlying aging, in a world where populations are getting older. Egr-1 (early growth response 1), a transcriptional factor involved in cell survival, proliferation and differentiation – with a role also in memory, cognition and synaptic plasticity, can be implicated in the molecular mechanism of the aging process. Moreover, Heme Oxygenase-1a (HO), a 32 kDa heat-shock protein that converts heme to iron, carbon monoxide and biliverdin, is a key enzyme with neuroprotective properties. Several in vitro and in vivo studies reported that HO-1 could regulate the metabolism of oxysterols, oxidation products of cholesterol that include markers of oxidative stress. Recently, a link between Egr-1 and HO-1 has been demonstrated in mouse lung cells exposed to cigarette smoke. In view of these data, we wanted to investigate whether Egr-1 can be implicated also in the oxysterol metabolism during brain aging. Our results show that Egr-1 expression is differently expressed in the cortex and hippocampus of old mice, as well as the oxysterol profile between these two brain areas. In particular, we show that the cortex experiences in an age-dependent fashion increasing levels of the Egr-1 protein, and that these correlate with the level of HO-1 expression and oxysterol abundance. Such a situation was not observed in the hippocampus. These results are further strenghtened by our observations made with Egr-1 KO mice, confirming our hypothesis concerning the influence of Egr-1 on oxysterol production and accumulation via regulation of the expression of HO-1 in the cortex, but not the hippocampus, of old mice. It is important to notice that most of the oxysterols involved in this process are those usually stimulated by oxidative stress, which would then represent the triggering factor for this mechanism.

Microtubule-Associated Protein 1 Light Chain 3B, (LC3B) Is Necessary to Maintain Lipid-Mediated Homeostasis in the Retinal Pigment Epithelium

Like other neurons, retinal cells utilize autophagic pathways to maintain cell homeostasis. The mammalian retina relies on heterophagy and selective autophagy to efficiently degrade and metabolize ingested lipids with disruption in autophagy associated degradation contributing to age related retinal disorders. The retinal pigment epithelium (RPE) supports photoreceptor cell renewal by daily phagocytosis of shed photoreceptor outer segments (OS). The daily ingestion of these lipid-rich OS imposes a constant degradative burden on these terminally differentiated cells. These cells rely on Microtubule-Associated Protein 1 Light Chain 3 (LC3) family of proteins for phagocytic clearance of the ingested OS. The LC3 family comprises of three highly homologous members, MAP1LC3A (LC3A), MAP1LC3B (LC3B), and MAP1LC3C (LC3C). The purpose of this study was to determine whether the LC3B isoform plays a specific role in maintaining RPE lipid homeostasis. We examined the RPE and retina of the LC3B^-/- mouse as a function of age using in vivo ocular imaging and electroretinography coupled with ex vivo, lipidomic analyses of lipid mediators, assessment of bisretinoids as well as imaging of lipid aggregates. Deletion of LC3B resulted in defects within the RPE including increased phagosome accumulation, decreased fatty acid oxidation and a subsequent increase in RPE and sub-RPE lipid deposits. Age-dependent RPE changes included elevated levels of oxidized cholesterol, deposition of 4-HNE lipid peroxidation products, bisretinoid lipofuscin accumulation, and subretinal migration of microglia, collectively likely contributing to loss of retinal function. These observations are consistent with a critical role for LC3B-dependent processes in the maintenance of normal lipid homeostasis in the aging RPE, and suggest that LC3 isoform specific disruption in autophagic processes contribute to AMD-like pathogenesis.

Circulating malondialdehyde concentrations in patients with stable chronic obstructive pulmonary disease: a systematic review and meta-analysis

The aim of this meta-analysis was to review the available evidence regarding the blood concentrations of the oxidative stress marker malondialdehyde (MDA) in chronic obstructive pulmonary disease (COPD) patients in comparison to healthy individuals. 14 studies were included in the meta-analysis (from inception to October 2017) with a total of 817 COPD patients and 530 healthy controls. Pooled MDA concentrations were significantly higher in patients with COPD than controls (standardized mean differences = 2.39 μmol/l, 95% CI: 1.50-3.28 μmol/l; p < 0.001). Our meta-analysis showed that the blood concentrations of MDA are consistently higher in patients with COPD when compared with healthy controls, suggesting an important role of lipid peroxidation, and thus oxidative stress, in the pathogenesis of COPD.

Oxidant-specific biomarkers of oxidative stress. Association with atherosclerosis and implication for antioxidant effects

The unregulated oxidative modification of lipids, proteins, and nucleic acids induced by multiple oxidants has been implicated in the pathogenesis of many diseases. Antioxidants with diverse functions exert their roles either directly or indirectly in the physiological defense network to inhibit such deleterious oxidative modification of biological molecules and resulting damage. The efficacy of antioxidants depends on the nature of oxidants. Therefore, it is important to identify the oxidants which are responsible for modification of biological molecules. Some oxidation products produced selectively by specific oxidant enable to identify the responsible oxidants, while other products are produced by several oxidants similarly. In this review article, several oxidant-specific products produced selectively by peroxyl radicals, peroxynitrite, hypochlorous acid, lipoxygenase, and singlet oxygen were summarized and their potential role as biomarker is discussed. It is shown that the levels of specific oxidation products including hydroxylinoleate isomers, nitrated and chlorinated products, and oxysterols produced by the above-mentioned oxidants are elevated in the human atherosclerotic lesions, suggesting that all these oxidants may contribute to the development of atherosclerosis. Further, it was shown that the reactivities of physiological antioxidants toward the above-mentioned oxidants vary extensively, suggesting that multiple antioxidants effective against these different oxidants are required, since no single antioxidant alone can cope with these multiple oxidants.

Assessment of Micronutrient Status in Critically Ill Children: Challenges and Opportunities

Micronutrients refer to a group of organic vitamins and inorganic trace elements that serve many functions in metabolism. Assessment of micronutrient status in critically ill children is challenging due to many complicating factors, such as evolving metabolic demands, immature organ function, and varying methods of feeding that affect nutritional dietary intake. Determination of micronutrient status, especially in children, usually relies on a combination of biomarkers, with only a few having been established as a gold standard. Almost all micronutrients display a decrease in their serum levels in critically ill children, resulting in an increased risk of deficiency in this setting. While vitamin D deficiency is a well-known phenomenon in critical illness and can predict a higher need for intensive care, serum concentrations of many trace elements such as iron, zinc, and selenium decrease as a result of tissue redistribution in response to systemic inflammation. Despite a decrease in their levels, supplementation of micronutrients during times of severe illness has not demonstrated clear benefits in either survival advantage or reduction of adverse outcomes. For many micronutrients, the lack of large and randomized studies remains a major hindrance to critically evaluating their status and clinical significance.

Improvement of 5,6α-epoxycholesterol, 5,6β-epoxycholesterol, cholestane-3β,5α,6β-triol and 6-oxo-cholestan-3β,5α-diol recovery for quantification by GC/MS

5,6α-epoxycholesterol (5,6α-EC) and 5,6β-epoxycholesterol (5,6β-EC) are oxysterols involved in the anticancer pharmacology of the widely used antitumor drug tamoxifen. They are both metabolized into cholestane-3β,5α,6β-triol (CT) by the cholesterol-5,6-epoxide hydrolase (ChEH) enzyme, and CT is metabolized by an as-yet uncharacterized enzyme into 6-oxo-cholestan-3β,5α-diol (OCDO). A recent feasibility study showed that the 5,6-ECs may represent surrogate markers of tamoxifen activity in breast cancer patients undergoing endocrine therapy, thus there is a growing interest in their accurate quantification. These oxysterols are usually quantified by gas-liquid chromatography coupled to mass spectrometry (GC/MS), using an isotope dilution methodology with the corresponding deuterated oxysterol. This method is considered to be relative quantitative since all of the standards used are deuterated oxysterols, however it is not known whether the preparation of each oxysterol is affected in the same way by the extraction, pre-purification by solid phase extraction (SPE) and trimethylsilylation steps, particularly when using biological samples that contain many other reactive compounds. Thus, in this study we investigated the yield of the 5,6-ECs, CT and OCDO recovery from patient serum samples at different stages of their work-up and trimethylsilylation prior to GC/MS analysis, using [¹⁴C]-labeled analogs to follow these oxysterols at each step. We measured a 40 to 60% loss of material for the 5,6-ECs and OCDO, however we also describe the conditions that improved their recovery. Our data also show that the use of deuterated 5,6α-EC, 5,6β-EC, CT and OCDO is an absolute requirement for their accurate quantification.

Circulating oxysterol metabolites as potential new surrogate markers in patients with hormone receptor-positive breast cancer: Results of the OXYTAM study

Accumulating evidence indicates that cholesterol oxygenation products, also known as oxysterols (OS), are involved in breast cancer (BC) promotion. The impact of Tam, as well as aromatase inhibitors (AI), an alternative BC endocrine therapy (ET), on OS metabolism in patients is currently unknown. We conducted a prospective clinical study in BC patients receiving Tam (n=15) or AI (n=14) in adjuvant or in metastatic settings. The primary end point was the feasibility of detecting and quantifying 11 different OS in the circulation of patients before and after 28days of treatment with Tam or AI. Key secondary end points were the measurements of variations in the concentrations of OS according to differences between patients and treatments. OS profiling in the serum of patients was determined by gas chromatography coupled to mass spectrometry. OS profiling was conducted in all patients both at baseline and during treatment regimens. An important inter-individual variability was observed for each OS. Interestingly 5,6β-epoxycholesterol relative concentrations significantly increased in the entire population (p=0.0109), while no increase in Cholestane-triol (CT) levels was measured. Interestingly, we found that, in contrast to AI, Tam therapy significantly decreased blood levels of 24-hydroxycholesterol (24-HC), 7α-HC and 25-HC (a tumor promoter) (p=0.0007, p=0.0231 and p=0.0231, respectively), whereas 4β-HC levels increased (p=0.0010). Interestingly, levels of 27-HC (a tumor promoter) significantly increased in response to AI (p=0.0342), but not Tam treatment. According to these results, specific OS are promising candidate markers of Tam and AI efficacy. Thus, further clinical investigations are needed to confirm the use of oxysterols as biomarkers of both prognosis and/or the efficacy of ET.

Lipid Peroxidation: Kinetics, Mechanisms, and Products

Recent advances in our understanding of lipid peroxidation, a degenerative process that is believed to play a key role in the pathogenesis of many diseases, are highlighted. In particular, the factors that control the kinetics and regio-/stereochemical outcomes of the autoxidation of both polyunsaturated fatty acids and sterols and the subsequent decomposition of the hydroperoxide products to cytotoxic derivatives are discussed. These advances promise to help clarify the role of lipid peroxidation in cell death and human disease.

Sterol Analysis by Quantitative Mass Spectrometry

Analysis of sterols by mass spectrometry is a fundamental technique allowing for both qualitative and quantitative characterization of sterol molecular lipid species. Lipids are isolated from matrix or matrices by homogenization and solvent extraction, and converted into species amenable for ionization either by derivatization or adduct formation. Chromatogaphy (either gas or liquid phase) can assist with the resolution of sterols. Tandem mass spectrometry allows the precise identification of sterol lipid species, while comparison to internal standards added during extraction enables accurate quantification.

Modified Lipids and Lipoproteins in Chronic Kidney Disease: A New Class of Uremic Toxins

Chronic kidney disease (CKD) is associated with an enhanced oxidative stress and deep modifications in lipid and lipoprotein metabolism. First, many oxidized lipids accumulate in CKD and were shown to exert toxic effects on cells and tissues. These lipids are known to interfere with many cell functions and to be pro-apoptotic and pro-inflammatory, especially in the cardiovascular system. Some, like F2-isoprostanes, are directly correlated with CKD progression. Their accumulation, added to their noxious effects, rendered their nomination as uremic toxins credible. Similarly, lipoproteins are deeply altered by CKD modifications, either in their metabolism or composition. These impairments lead to impaired effects of HDL on their normal effectors and may strongly participate in accelerated atherosclerosis and failure of statins in end-stage renal disease patients. This review describes the impact of oxidized lipids and other modifications in the natural history of CKD and its complications. Moreover, this review focuses on the modifications of lipoproteins and their impact on the emergence of cardiovascular diseases in CKD as well as the appropriateness of considering them as actual mediators of uremic toxicity.

Free Radical-derived Oxysterols: Novel Adipokines Modulating Adipogenic Differentiation of Adipose Precursor Cells

CONTEXT

Increased oxidative stress in adipose tissue emerges as an inducer of obesity-linked insulin resistance. Here we tested whether free-radical derived oxysterols are formed by, and accumulate in, human adipocytes. Moreover, we asked whether increased accumulation of oxysterols characterizes the adipose cells of obese patients with type 2 diabetes (T2D) (OBT2D) compared with lean, nondiabetic controls (CTRLs). Finally, we studied the effects of the free radical-derived oxysterols on adipogenic differentiation of adipose-derived stem cells (ASCs).

MAIN OUTCOME MEASURES

Adipocytes and ASCs were isolated from sc abdominal adipose tissue biopsy in four OBT2D and four CTRL subjects. Oxysterols in adipocytes were detected by gas chromatography/mass spectrometry. The cellular and molecular effects of oxysterols were then evaluated on primary cultures of ASCs focusing on cell viability, adipogenic differentiation, and "canonical" WNT and MAPK signaling pathways.

RESULTS

7-ketocholesterol (7κ-C) and 7β-hydroxycholesterol were unambiguously detected in adipocytes, which showed higher oxysterol accumulation (P < .01) in OBT2D, as compared with CTRL individuals. Notably, the accumulation of oxysterols in adipocytes was predicted by the adipose cell size of the donor (R² = 0.582; P < .01). Challenging ASCs with free radical-derived type I (7κ-C) and type II (5,6-Secosterol) oxysterols led to a time- and concentration-dependent decrease of cell viability. Meaningfully, at a non-toxic concentration (1μM), these bioactive lipids hampered adipogenic differentiation of ASCs by sequential activation of WNT/β-catenin, p38-MAPK, ERK1/2, and JNK signaling pathways.

CONCLUSION

Free radical-derived oxysterols accumulate in the "diabetic" fat and may act as novel adipokines modulating the adipogenic potential of undifferentiated adipose precursor cells.

Mass spectrometry profiling of oxysterols in human sperm identifies 25-hydroxycholesterol as a marker of sperm function

Cholesterol is a main lipid component of sperm cell that is essential for sperm membrane fluidity, capacitation, and acrosomal reaction. Recent data obtained in bovine sperm showed that sperm capacitation is associated to the formation of oxysterols, oxidized products of cholesterol. The aim of this study was to profile oxysterol content in human semen, and to investigate their potential role in sperm pathophysiology. Among the 12 oxysterols analyzed, 25-hydroxycholesterol (25-HC) resulted the most represented in normozoospermic samples, and its concentration positively correlated with spermatozoa number. We detected Cholesterol 25-hydroxylase, the enzyme responsible for 25-HC production, in human spermatozoa at the level of the neck and the post acrosomal area. Upon incubation with spermatozoa, 25-HC induced calcium and cholesterol transients in connection with the acrosomal reaction. Our results support a role for 25-HC in sperm function.

Circulating biomarkers of oxidative stress in chronic obstructive pulmonary disease: a systematic review

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by airflow limitation associated with an abnormal inflammatory response of the lungs to noxious particles and gases, caused primarily by cigarette smoking. Increased oxidative burden plays an important role in the pathogenesis of COPD. There is a delicate balance between the toxicity of oxidants and the protective function of the intracellular and extracellular antioxidant defense systems, which is critically important for the maintenance of normal pulmonary functions. Several biomarkers of oxidative stress are available and have been evaluated in COPD. In this review, we summarize the main literature findings about circulating oxidative stress biomarkers, grouped according to their method of detection, measured in COPD subjects.

Defective cholesterol metabolism in amyotrophic lateral sclerosis

As neurons die, cholesterol is released in the central nervous system (CNS); hence, this sterol and its metabolites may represent a biomarker of neurodegeneration, including in amyotrophic lateral sclerosis (ALS), in which altered cholesterol levels have been linked to prognosis. More than 40 different sterols were quantified in serum and cerebrospinal fluid (CSF) from ALS patients and healthy controls. In CSF, the concentration of cholesterol was found to be elevated in ALS samples. When CSF metabolite levels were normalized to cholesterol, the cholesterol metabolite 3β,7α-dihydroxycholest-5-en-26-oic acid, along with its precursor 3β-hydroxycholest-5-en-26-oic acid and product 7α-hydroxy-3-oxocholest-4-en-26-oic acid, were reduced in concentration, whereas metabolites known to be imported from the circulation into the CNS were not found to differ in concentration between groups. Analysis of serum revealed that (25R)26-hydroxycholesterol, the immediate precursor of 3β-hydroxycholest-5-en-26-oic acid, was reduced in concentration in ALS patients compared with controls. We conclude that the acidic branch of bile acid biosynthesis, known to be operative in-part in the brain, is defective in ALS, leading to a failure of the CNS to remove excess cholesterol, which may be toxic to neuronal cells, compounded by a reduction in neuroprotective 3β,7α-dihydroxycholest-5-en-26-oic acid.

Effects of dietary fatty acids and cholesterol excess on liver injury: A lipidomic approach

Lipid accumulation is the hallmark of Non-alcoholic Fatty Liver Disease (NAFLD) and has been suggested to play a role in promoting fatty liver inflammation. Previous findings indicate that during oxidative stress conditions excess cholesterol autoxidizes to oxysterols. To date, the role of oxysterols and their potential interaction with fatty acids accumulation in NASH pathogenesis remains little investigated. We used the nutritional model of high fatty acids (HFA), high cholesterol (HCh) or high fat and high cholesterol (HFA+FCh) diets and explored by a lipidomic approach, the blood and liver distribution of fatty acids and oxysterols in response to dietary manipulation. We observed that HFA or HCh diets induced fatty liver without inflammation, which was otherwise observed only after supplementation of HFA+HCh. Very interestingly, the combination model was associated with a specific oxysterol fingerprint. The present work provides a complete analysis of the change in lipids and oxysterols profile induced by different lipid dietary model and their association with histological alteration of the liver. This study allows the generation of interesting hypotheses on the role of interaction of lipid and cholesterol metabolites in the liver injury during NAFLD development and progression. Moreover, the changes in the concentration and quality of oxysterols induced by a combination diet suggest a novel potential pathogenic mechanism in the progression from simple steatosis to steatohepatitis.

Changes in brain oxysterols at different stages of Alzheimer's disease: Their involvement in neuroinflammation

Alzheimer's disease (AD) is a gradually debilitating disease that leads to dementia. The molecular mechanisms underlying AD are still not clear, and at present no reliable biomarkers are available for the early diagnosis. In the last several years, together with oxidative stress and neuroinflammation, altered cholesterol metabolism in the brain has become increasingly implicated in AD progression. A significant body of evidence indicates that oxidized cholesterol, in the form of oxysterols, is one of the main triggers of AD. The oxysterols potentially most closely involved in the pathogenesis of AD are 24-hydroxycholesterol and 27-hydroxycholesterol, respectively deriving from cholesterol oxidation by the enzymes CYP46A1 and CYP27A1. However, the possible involvement of oxysterols resulting from cholesterol autooxidation, including 7-ketocholesterol and 7β-hydroxycholesterol, is now emerging. In a systematic analysis of oxysterols in post-mortem human AD brains, classified by the Braak staging system of neurofibrillary pathology, alongside the two oxysterols of enzymatic origin, a variety of oxysterols deriving from cholesterol autoxidation were identified; these included 7-ketocholesterol, 7α-hydroxycholesterol, 4β-hydroxycholesterol, 5α,6α-epoxycholesterol, and 5β,6β-epoxycholesterol. Their levels were quantified and compared across the disease stages. Some inflammatory mediators, and the proteolytic enzyme matrix metalloprotease-9, were also found to be enhanced in the brains, depending on disease progression. This highlights the pathogenic association between the trends of inflammatory molecules and oxysterol levels during the evolution of AD. Conversely, sirtuin 1, an enzyme that regulates several pathways involved in the anti-inflammatory response, was reduced markedly with the progression of AD, supporting the hypothesis that the loss of sirtuin 1 might play a key role in AD. Taken together, these results strongly support the association between changes in oxysterol levels and AD progression.

New methods for analysis of oxysterols and related compounds by LC-MS

Oxysterols are oxygenated forms of cholesterol or its precursors. They are formed enzymatically and via reactive oxygen species. Oxysterols are intermediates in bile acid and steroid hormone biosynthetic pathways and are also bioactive molecules in their own right, being ligands to nuclear receptors and also regulators of the processing of steroid regulatory element-binding proteins (SREBPs) to their active forms as transcription factors regulating cholesterol and fatty acid biosynthesis. Oxysterols are implicated in the pathogenesis of multiple disease states ranging from atherosclerosis and cancer to multiple sclerosis and other neurodegenerative diseases including Alzheimer's and Parkinson's disease. Analysis of oxysterols is challenging on account of their low abundance in biological systems in comparison to cholesterol, and due to the propensity of cholesterol to undergo oxidation in air to generate oxysterols with the same structures as those present endogenously. In this article we review the mass spectrometry-based methods for oxysterol analysis paying particular attention to analysis by liquid chromatography-mass spectrometry (LC-MS).

The role of oxysterols in vascular ageing

The ageing endothelium progressively loses its remarkable and crucial ability to maintain homeostasis of the vasculature, as it acquires a proinflammatory phenotype. Cellular and structural changes gradually accumulate in the blood vessels, and markedly in artery walls. Most changes in aged arteries are comparable to those occurring during the atherogenic process, the latter being more marked: pro-oxidant and proinflammatory molecules, mainly deriving from or triggered by oxidized low density lipoproteins (oxLDLs), are undoubtedly a major driving force of this process. Oxysterols, quantitatively relevant components of oxLDLs, are likely candidate molecules in the pathogenesis of vascular ageing, because of their marked pro-oxidant, proinflammatory and proapoptotic properties. An increasing bulk of experimental data point to the contribution of a variety of oxysterols of pathophysiological interest, also in the age-related genesis of endothelium dysfunction, intimal thickening due to lipid accumulation, and smooth muscle cell migration and arterial stiffness due to increasing collagen deposition and calcification. This review provides an updated analysis of the molecular mechanisms whereby oxysterols accumulating in the wall of ageing blood vessels may 'activate' endothelial and monocytic cells, through expression of an inflammatory phenotype, and 'convince' smooth muscle cells to proliferate, migrate and, above all, to act as fibroblast-like cells.

Streptococcal serum opacity factor promotes cholesterol ester metabolism and bile acid secretion in vitro and in vivo

Plasma high density lipoprotein-cholesterol (HDL-C) concentrations negatively correlate with atherosclerotic cardiovascular disease. HDL is thought to have several atheroprotective functions, which are likely distinct from the epidemiological inverse relationship between HDL-C levels and risk. Specifically, strategies that reduce HDL-C while promoting reverse cholesterol transport (RCT) may have therapeutic value. The major product of the serum opacity factor (SOF) reaction versus HDL is a cholesteryl ester (CE)-rich microemulsion (CERM), which contains apo E and the CE of ~400,000 HDL particles. Huh7 hepatocytes take up CE faster when delivered as CERM than as HDL, in part via the LDL-receptor (LDLR). Here we compared the final RCT step, hepatic uptake and subsequent intracellular processing to cholesterol and bile salts for radiolabeled HDL-, CERM- and LDL-CE by Huh7 cells and in vivo in C57BL/6J mice. In Huh7 cells, uptake from LDL was greater than from CERM (2-4X) and HDL (5-10X). Halftimes for [(14)C]CE hydrolysis were 3.0±0.2, 4.4±0.6 and 5.4±0.7h respectively for HDL, CERM and LDL-CE. The fraction of sterols secreted as bile acids was ~50% by 8h for all three particles. HDL, CERM and LDL-CE metabolism in mice showed efficient plasma clearance of CERM-CE, liver uptake and metabolism, and secretion as bile acids into the gall bladder. This work supports the therapeutic potential of the SOF reaction, which diverts HDL-CE to the LDLR, thereby increasing hepatic CE uptake, and sterol disposal as bile acids.

Evidence for altered cholesterol metabolism in Huntington's disease post mortem brain tissue

AIMS

Cholesterol plays an essential role in membrane structure and function, being especially important in the brain. Alteration of brain cholesterol synthesis and metabolism has been demonstrated in several Huntington's disease (HD) mouse and cell models; however, less is known about these alterations in human tissue. This study aimed to identify alterations to cholesterol synthetic and metabolic pathways in human HD brain tissue.

METHODS

A broad range of cholesterol synthetic precursors, metabolites and oxidation products were measured by gas chromatography-tandem mass spectrometry in five regions of human post mortem HD brain and compared with age- and sex-matched control tissues. The level of enzymes that regulate cholesterol homeostasis, cholesterol 24-hydroxylase and delta(24)-sterol reductase were investigated by Western blotting and qPCR in putamen.

RESULTS

The most significant changes were localized to the putamen, where a 60% decrease in 24(S)-hydroxycholesterol, 30% increase in cholesterol and 100-200% increase in synthetic precursors (lathosterol, zymosterol and desmosterol) was detected. The enzymes cholesterol 24-hydroxylase and delta(24)-sterol reductase were also significantly decreased in HD putamen as compared with control tissues. Free radical-generated cholesterol oxidation products 7-keto cholesterol and 7β-hydroxycholesterol were also increased by 50-70% in HD putamen.

CONCLUSION

Human HD brain has significantly decreased cholesterol metabolism and disrupted cholesterol homeostasis. Our data also indicate that lipid oxidative stress accompanies HD pathology.

Neopterin and 7,8-dihydroneopterin are generated within atherosclerotic plaques

Plasma neopterin correlates with the level of cardiovascular disease. Neopterin is the oxidation product of 7,8-dihydroneopterin, which is released by γ-interferon-stimulated macrophages. 7,8-Dihydroneopterin is a potent antioxidant, which inhibits lipid oxidation, macrophage cell death and scavenger receptor CD36 expression. The concentration of neopterin within atherosclerotic plaques was measured in tissue removed from carotid and femoral arteries. The excised plaques were cut into 3-mm-thick sections, and each section was analysed for neopterin, total neopterin, cholesterol, lipid peroxides, α-tocopherol and protein-bound 3,4-dihydroxyphenylalanine. Selected plaques were placed in tissue culture, and the media was analysed for 7,8-dihydroneopterin and neopterin release. Total neopterin levels ranged from 14 to 18.8 nmol/g of tissue. Large ranges of values were seen both within the same plaque and between plaques. No correlation between neopterin and any of the other analytes was observed, nor was there any significant trend in levels along the length of the plaques. γ-Interferon stimulation of cultured plaque generated total neopterin concentrations from 1 to 4 nmol/(g 24 h). The level of 7,8-dihydroneopterin generated within the plaque was within the range that inhibits lipid oxidation. The data show that atherosclerotic plaques are extremely dynamic in biochemistry and are the likely source of the plasma 7,8-dihydroneopterin and neopterin.

Effect of obesity and metabolic syndrome on plasma oxysterols and fatty acids in human

BACKGROUND

Obesity and the related entity metabolic syndrome are characterized by altered lipid metabolism and associated with increased morbidity risk for cardiovascular disease and cancer. Oxysterols belong to a large family of cholesterol-derived molecules known to play crucial role in many signaling pathways underlying several diseases. Little is known on the potential effect of obesity and metabolic syndrome on oxysterols in human.

OBJECTIVES

In this work, we questioned whether circulating oxysterols might be significantly altered in obese patients and in patients with metabolic syndrome. We also tested the potential correlation between circulating oxysterols and fatty acids.

METHODS

60 obese patients and 75 patients with metabolic syndrome were enrolled in the study along with 210 age- and sex-matched healthy subjects, used as control group. Plasma oxysterols were analyzed by isotope dilution GC/MS, and plasma fatty acids profiling was assessed by gas chromatography coupled with flame ionization detection.

RESULTS

We found considerable differences in oxysterols profiling in the two disease groups that were gender-related. Compared to controls, males showed significant differences only in 4α- and 4β-hydroxycholesterol levels in obese and metabolic syndrome patients. In contrast, females showed consistent differences in 7-oxocholesterol, 4α-hydroxycholesterol, 25-hydroxycholesterol and triol. Concerning fatty acids, we found minor differences in the levels of these variables in males of the three groups. Significant changes were observed in plasma fatty acid profile of female patients with obesity or metabolic syndrome. We found significant correlations between various oxysterols and fatty acids. In particular, 4β-hydroxycholesterol, which is reduced in obesity and metabolic syndrome, correlated with a number of saturated and mono-unsaturated fatty acids that are end-products of de novo lipogenesis.

CONCLUSIONS

Our data provide the first evidence that obesity and metabolic syndrome are associated with major, gender-specific, changes in circulating oxysterols and fatty acids. These findings suggest a metabolic link between oxysterols and fatty acids, and that oxysterols may contribute to the epidemic diseases associated with obesity and metabolic syndrome in female.

Cholesterol metabolites exported from human brain

The human brain contains approximately 25% of the body's cholesterol. The brain is separated from the circulation by the blood brain barrier. While cholesterol will not passes this barrier, oxygenated forms of cholesterol can cross the barrier. Here by measuring the difference in the oxysterol content of blood plasma in the jugular vein and in a forearm vein by mass spectrometry (MS) we were able to determine the flux of more than 20 cholesterol metabolites between brain and the circulation. We confirm that 24S-hydroxycholesterol is exported from brain at a rate of about 2-3mg/24h. Gas chromatography (GC)-MS data shows that the cholesterol metabolites 5α-hydroxy-6-oxocholesterol (3β,5α-dihydroxycholestan-6-one), 7β-hydroxycholesterol and 7-oxocholesterol, generally considered to be formed through reactive oxygen species, are similarly exported from brain at rates of about 0.1, 2 and 2mg/24h, respectively. Although not to statistical significance both GC-MS and liquid chromatography (LC)-MS methods indicate that (25R)26-hydroxycholesterol is imported to brain, while LC-MS indicates that 7α-hydroxy-3-oxocholest-4-enoic acid is exported from brain.

Gas chromatography-mass spectrometry microanalysis of alpha- and gamma-tocopherol in plasma and whole blood

BACKGROUND

Assessing vitamin E status in humans is critical for nutritional evaluation and verification of clinical and biological compliance of supplemented subjects. An accurate analytical method for measuring the two main vitamin E isoforms, i.e. α- and γ-tocopherol (α- and γ-TOH) in small volumes of plasma can facilitate the application of this analysis to clinical trials and in situations where a limited amount of sample is available.

METHODS

We have developed a micro method, which uses only 5 μL plasma, based on isotope dilution, trimethylsilation and GC-MS. The method was validated according to the guidelines of the International Conference on Harmonization of analytical procedures. The method was also applied to 5 μL of whole blood for the potential use in conditions were the availability of specimens is limited.

RESULTS

Accurate quantitation of α-TOH and γ-TOH was achieved at levels ≥ 0.417 μM and ≥ 0.007 μM, respectively. Within-day coefficient of variation was 1.31% and 4.70% for α-TOH and γ-TOH, respectively. Between-day coefficient of variation was 1.32% and 2.88% for α-TOH and γ-TOH, respectively. Recovery, assessed at three concentration levels, ranged 98-103% and 100-102% for α-TOH and γ-TOH, respectively. The method allowed the detection of α-TOH and γ-TOH in 5 μL whole blood and in membranes of red blood cells washed from 5 μL of blood as well. The analytical performance was assessed in plasma from a cohort of Italian healthy subjects (n = 205). The mean plasma concentrations were 28.01 ± 6.31 and 0.68 ± 0.48 μM (mean ± SD) for α-TOH and γ-TOH, respectively. Alpha-TOH correlated with total cholesterol (r = 0.617, p < 0.0001) and triglycerides (r = 0.420, p < 0.0001) while γ-TOH correlated modestly with total cholesterol (r = 0.213, p < 0.0001) but not with triglycerides. γ-TOH, but not α-TOH, was significantly lower in smokers than in non-smokers (0.72 ± 0.50 vs. 0.56 ± 0.37, μM, mean ± SD, p = 0.017). Given the high sensitivity, the method allowed to be applied to 5 μM whole blood without specific modification.

CONCLUSIONS

This micro-method represents an analytical advancement in α- and γ-TOH assay that is available to accurately verify the nutritional status and compliance after supplementation in large-scale settings, and to measure the two vitamers in conditions where sample availability is limited.

Survival signaling elicited by 27-hydroxycholesterol through the combined modulation of cellular redox state and ERK/Akt phosphorylation

The oxysterol 27-hydroxycholesterol (27-OH) is increasingly considered to be involved in a variety of pathophysiological processes, having been shown to modulate cell proliferation and metabolism, and also to exert proinflammatory and proapoptotic effects. This study aimed to elucidate the molecular pathways whereby 27-OH may generate survival signals in cells of the macrophage lineage, and to clarify whether its known prooxidant effect is involved in that process. A net up-regulation of survival signaling, involving the extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt phosphorylation pathways, was observed in U937 promonocytic cells cultivated over time in the presence of a low micromolar concentration of the oxysterol. Interestingly, the up-regulation of both kinases was shown to be closely dependent on an early 27-OH-induced intracellular increase of reactive oxygen species (ROS). In turn, stimulation of ERK and PI3K/Akt both significantly quenched ROS steady state and markedly phosphorylated Bad, thereby determining a marked delay of the oxysterol׳s proapoptotic action. The 27-OH-induced survival pathways thus appear to be redox modulated and, if they occur within or nearby inflammatory cells during progression of chronic diseases such as cancer and atherosclerosis, they could significantly impact the growth and evolution of such diseases.