Oxysterols formation: A review of a multifactorial process

Lipolysis and Sterol Stability and Bioaccessibility of Wholemeal Rye Bread Enriched with Plant Sterols Subjected to Adult and Elderly Digestion Conditions

This study evaluated the impact of different digestion conditions (adult and senior) on lipolysis and bioaccessibility of plant sterols (PS) and phytosterol oxidation products (POPs) in PS-enriched wholemeal rye bread. Under adult digestion conditions, the addition of gastric lipase (GL) reduced lipolysis products (by 6.1% for free fatty acids and 11.7% for monoacylglycerols) and the bioaccessibility of PS by 6.7%, compared to the control. In digestion with both GL and cholesterol esterase (CE), these reductions were 12.9, 20.1, and 11.3%, respectively. Both modifications (GL and GL + CE) increased the bioaccessibility of POPs by 4.5-4.0%. When simulating the elderly digestion, the modified gastric and intestinal phases did not alter PS bioaccessibility but decreased POPs bioaccessibility by 21.8% compared to control, along with reduced lipolysis. Incorporating GL and CE thus approached physiological conditions and influenced lipid digestion. Elderly simulated digestion conditions resulted in a positive outcome by maintaining PS bioaccessibility while reducing potentially harmful POPs.

Effects of Phenols from Olive Vegetation Water on Mutagenicity and Genotoxicity of Stored-Cooked Beef Patties

This explorative study aimed to assess the mutagenicity and genotoxicity of stored-cooked beef patties formulated with and without phenols (7.00 mg of phenols/80-g patty) extracted from olive vegetation water (OVW), as related to the formation of cholesterol oxidation products (COPs) and heterocyclic amines (HCAs). The patties were packaged in a modified atmosphere, sampled during cold storage (4 °C) for 9 days, and grilled at 200 °C. The genotoxicity was evaluated by the Comet assay. The patty extract was found to be genotoxic on primary peripheral blood mononuclear cells (PBMCs), while no mutagenicity was detected. The addition of OVW phenols significantly decreased the genotoxicity of the patty extract and reduced the total COPs content in stored-cooked patties (4.59 times lower than control); however, it did not affect the content of total HCAs (31.51-36.31 ng/patty) and the revertants' number. Therefore, these results demonstrate that the OVW phenols were able to counteract the formation of genotoxic compounds in stored-cooked beef patties.

Current and New Insights on Delivery Systems for Plant Sterols in Food

Plant sterols are minor bioactive components of food lipids, which are often used for the formulation of functional foods due to their cholesterol-lowering properties. However, they have low solubility and tend to crystallize, which may affect their biological effects, the sensory profile of the sterol-enriched food, and its consumer acceptability. Moreover, due to the unsaturated structure of sterols, they are susceptible to oxidation, so different encapsulation systems have been developed to improve their dispersibility/solubility, stability, delivery, and bioaccessibility. This chapter provides an overview of the main encapsulation systems currently used for plant sterols and their application in model and food systems, with a particular focus on their efficiency and impact on sterol bioaccessibility.

Natural antioxidants as strategy to minimize the presence of lipid oxidation products in canned fish: Research progress, current trends and future perspectives

Canned fish is one of the most popular forms of fish consumption due to its high nutritional value, availability, and practicality. However, canning may induce lipid oxidation. Thus, this study provides in-depth information on the impact of high temperatures applied during canning on fish lipids. The thermo-oxidation is evidenced, for example, by the high levels of both primary and secondary oxidation products determined in fish after canning, as well as the presence of harmful compounds such as cholesterol oxides. Given the role of lipid oxidation in canned fish, this study also presents a comprehensive review on using natural antioxidants to control it. The antioxidant properties of common liquid mediums (vegetable oils and sauces) are highlighted. Moreover, adding algae extracts, spices, and condiments to the liquid medium to enhance its antioxidant potential has been considered, while the exploitation of by-products and wastes from the food industry also emerges as a suitable strategy. Besides the promising results, these practices may promote positive impacts on other quality parameters (e.g. water and oil holding capacities, texture, microbiological growth). However, further studies are needed, including research on aspects related to safety, effective concentrations and application methods, without ignoring consumers' sensory acceptance.

Antioxidant addition improves cholesterol and astaxanthin stability in dry salted shrimp

BACKGROUND

Traditional production of dry salted shrimp enhances cholesterol oxidation and astaxanthin degradation in the product. The aim of this study was to evaluate the effect of addition of the antioxidants butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) to cooked shrimp on the formation of cholesterol oxidation products (COPs) and astaxanthin degradation during solar drying of shrimp.

RESULTS

The added antioxidants significantly inhibited COPs formation after the product was boiled in brine. Smaller amounts of COPs were formed in antioxidant-treated shrimps (~-23%) as compared to untreated samples. The antioxidants continued to significantly inhibit COPs formation (~-39%) during sun drying. Similarly, TBHQ and BHT reduced by 51.3% and 37.2%, respectively, the degradation rate of astaxanthin, favoring a higher retention of this carotenoid in the final product.

CONCLUSION

The use of the antioxidants BHT and TBHQ in the preparation of dry salted shrimp significantly inhibited the formation of COPs after cooking raw shrimp and during direct solar drying. They also protected astaxanthin contained in the cooked shrimp from photodegradation. These results are technologically relevant because it is possible to prepare a product with a higher content of astaxanthin and lower the presence of hazardous COPs. © 2022 Society of Chemical Industry.

Fatty acid profile, sterols, and squalene content comparison between two conventional (olive oil and linseed oil) and three non‐conventional vegetable oils (echium oil, hempseed oil, and moringa oil)

Abstract

New sources of bioactive compounds are constantly explored for reformulating healthier foods. This work aimed to explore and characterize the fatty acid profile and sterol content of three non‐conventional oils used in functional food products (hempseed oil, moringa oil, and echium oil) and to compare them with two conventional ones (extra virgin olive oil [EVOO] and linseed oil). Oxidative stability was assessed by determining their acidity value and peroxide content. All oils showed adequate values for acidity and oxidation status. Echium and hempseed oils showed a high content of polyunsaturated fatty acids (>70%), especially omega‐3 fatty acids, while moringa oil was rich in oleic acid. Echium oil, hempseed oil, and moringa oil presented higher sterol content than EVOO, but lower than that of linseed oil. Sitosterol was the most abundant sterol in all samples (97.88–275.36 mg/100 g oil), except in echium oil, where campesterol (170.62 mg/100 g oil) was the major sterol. Squalene was only found in significant amounts in EVOO. In conclusion, non‐conventional oils seem to be interesting sources of bioactive compounds and have great potential for the food industry.

Practical Application

Non‐conventional vegetable oils can be used as alternative sources of lipids in a variety of food products. Additionally, these oils have great potential to be included in the formulation of functional ingredients for the delivery of omega‐3 fatty acids, antioxidants, fiber, among others.

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.

Bioactive compounds of parsley (Petroselinum crispum), chives (Allium schoenoprasum L) and their mixture (Brazilian cheiro-verde) as promising antioxidant and anti-cholesterol oxidation agents in a food system

This study determined the bioactive composition and antioxidant potential of parsley, chives and their mixture (Brazilian cheiro-verde). Additionally, the effect of these herbs against cholesterol oxidation in grilled sardines (Sardinella brasiliensis) was also investigated. Ultra-high Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (UHPLC-ESI-MS) analyses revealed the presence of phenolic acids (caffeic, chlorogenic, and ferulic acids) and flavonoids (apigenin, kaempferol, catechin) in the herbs. Higher levels of phenolics (2.10 ± 0.02 mg GAE/g) and carotenoids (205.95 ± 0.17 µg/g) were determined in parsley extracts. Moreover, parsley also presented higher antioxidant capacity by DPPH (59.21 ± 0.07 %) and ORAC (109.94 ± 18.7 µM TE/g) than the other herbs. In vivo analyses demonstrated that the herbs' extracts decreased the damage on Saccharomyces cerevisiae cells exposed to H₂O₂, except the chives extract at 10 μg/mL. Higher levels of cholesterol oxidation products (COPs) were determined after grilling. The total COPs increased from 61.8 ± 0.7 (raw fish) to 139.7 ± 10.1 µg/g (control). However, the addition of herbs effectively reduced cholesterol oxides formation, this effect was more pronounced in fish containing 4% parsley and 4% cheiro-verde. Promising results were found for cheiro-verde; however, it did not present synergic antioxidant effects.

Dietary cholesterol oxidation products: Perspectives linking food processing and storage with health implications

Dietary cholesterol oxidation products (COPs) are heterogeneous compounds formed during the processing and storage of cholesterol-rich foods, such as seafood, meat, eggs, and dairy products. With the increased intake of COPs-rich foods, the concern about health implications of dietary COPs is rising. Dietary COPs may exert deleterious effects on human health to induce several inflammatory diseases including atherosclerosis, neurodegenerative diseases, and inflammatory bowel diseases. Thus, knowledge regarding the effects of processing and storage conditions leading to formation of COPs is needed to reduce the levels of COPs in foods. Efficient methodologies to determine COPs in foods are also essential. More importantly, the biological roles of dietary COPs in human health and effects of phytochemicals on dietary COPs-induced diseases need to be established. This review summarizes the recent information on dietary COPs including their formation in foods during their processing and storage, analytical methods of determination of COPs, metabolic fate, implications for human health, and beneficial interventions by phytochemicals. The formation of COPs is largely dependent on the heating temperature, storage time, and food matrices. Alteration of food processing and storage conditions is one of the potent strategies to restrict hazardous dietary COPs from forming, including maintaining relatively low temperatures, shorter processing or storage time, and the appropriate addition of antioxidants. Once absorbed into the circulation, dietary COPs can contribute to the progression of several inflammatory diseases, where the absorbed dietary COPs may induce inflammation, apoptosis, and autophagy in cells in the target organs or tissues. Improved intake of phytochemicals may be an effective strategy to reduce the hazardous effects of dietary COPs.

Lipid profile and high contents of cholesterol oxidation products (COPs) in different commercial brands of canned tuna

Canned fish is submitted to processes that may degrade its lipids and form harmful compounds called cholesterol oxidation products (COPs). Samples of Brazilian commercial canned tuna were analyzed to evaluate the influence of different liquid mediums (oil and brine) on the fatty acid composition and formation of COPs. The exchange between fish lipids and the constituents of the covering liquid was highlighted by the high levels of linoleic acid found in tuna conserved in oil. High amounts of COPs were found. However, higher contents of COPs were found in tuna in brine (933.14 to 1914.23 µg/g) than in oil (698.24 to 1167.88 µg/g). This result was mainly promoted by the presence of pro-oxidant elements such as salt, as well as greater heat transfer in brine than in oil. This study showed that canned tuna is a potential source of exogenous COPs, indicating the role of liquid mediums in oxidative processes.

Analytical Strategies to Analyze the Oxidation Products of Phytosterols, and Formulation-Based Approaches to Reduce Their Generation

Phytosterols are a class of lipid molecules present in plants that are structurally similar to cholesterol and have been widely utilized as cholesterol-lowering agents. However, the susceptibility of phytosterols to oxidation has led to concerns regarding their safety and tolerability. Phytosterol oxidation products (POPs) present in a variety of enriched and non-enriched foods can show pro-atherogenic and pro-inflammatory properties. Therefore, it is crucial to screen and analyze various phytosterol-containing products for the presence of POPs and ultimately design or modify phytosterols in such a way that prevents the generation of POPs and yet maintains their pharmacological activity. The main approaches for the analysis of POPs include the use of mass spectrometry (MS) linked to a suitable separation technique, notably gas chromatography (GC). However, liquid chromatography (LC)-MS has the potential to simplify the analysis due to the elimination of any derivatization step, usually required for GC-MS. To reduce the transformation of phytosterols to their oxidized counterparts, formulation strategies can theoretically be adopted, including the use of microemulsions, microcapsules, micelles, nanoparticles, and liposomes. In addition, co-formulation with antioxidants, such as tocopherols, may prove useful in substantially preventing POP generation. The main objectives of this review article are to evaluate the various analytical strategies that have been adopted for analyzing them. In addition, formulation approaches that can prevent the generation of these oxidation products are proposed.

Oxysterols and lipidomic profile of myocardium of rats supplemented with pomegranate seed oil and/or bitter melon aqueous extract - Cardio-oncological animal model research

A close link between cardiovascular diseases and cancer results from sharing the same modifiable risk factors (e.g. nutritional) and cardiotoxicity of anti-cancerous therapies. It justifies cardio-oncological preliminary studies on dietary factors, especially on those of possible anti-carcinogenic or cardioprotective properties. The main purpose was to evaluate the effect of pomegranate seed oil (PSO) and/or bitter melon extract (BME) supplementation of the diet of female rats suffering from mammary tumors on lipidomic profile (expressed as fatty acids, conjugated fatty acids (CFA), malondialdehyde (MDA), cholesterol and oxysterols content) of cardiac tissue. Total lipidomic profile and intensity of lipid peroxidation in hearts of DMBA-treated Sprague-Dawley rats and their healthy equivalents, both obtaining diet supplementation, were evaluated with different chromatographic techniques coupled with appropriate detection systems (GC-MS, GC-TOFMS, Ag+-HPLC-DAD, UF-HPLC-DAD). Dietary modifications neither diminished breast cancer incidence nor exerted explicit cardio-protective influence, however, they diminished cholesterol content, i.a. because of inhibition of the endogenous conversion of squalene to cholesterol in cardiac tissue. CFA were incorporated into cardiac tissue to a lesser extent in the cancerous process. PSO and BME anti-oxidant properties in pathological condition were only slightly reflected in MDA levels but not in oxysterols formation. Obtained results indicate considerable changes in dietary supplements' biological activity in pathological conditions and the need for clear distinction of drugs and dietary supplements, which is of utmost importance, especially for cancer survivors.

Linking phytosterols and oxyphytosterols from food to brain health: origins, effects, and underlying mechanisms

Phytosterols and their oxidation products, namely oxyphytosterols, are natural compounds present in plant foods. With increased intake of phytosterol-enriched functional food products, the exposure of both phytosterols and oxyphytosterols is rising. Over the past ten years, researches have been focused on their absorption and metabolism in human body, as well as their biological effects. More importantly, recent studies showed that phytosterols and oxyphytosterols can traverse the blood-brain barrier and accumulate in the brain. As brain health problems resulting from ageing being more serious, attenuating central nervous system (CNS) disorders with active compounds in food are becoming a hot topic. Phytosterols and oxyphytosterols have been shown to implicated in cognition altering and the pathologies of several CNS disorders, including Alzheimer's disease and multiple sclerosis. We will overview these findings with a focus on the contents of phytosterols and oxyphytosterols in food and their dietary intake, as well as their origins in the brain, and illustrate molecular pathways through which they affect brain health, in terms of inflammation, cholesterol homeostasis, oxidative stress, and mitochondria function. The existing scientific gaps of phytosterols and oxyphytosterols to brain health in knowledge are also discussed, highlighting research directions in the future.

Effect of DL-Methionine Supplementation on Tissue and Plasma Antioxidant Status and Concentrations of Oxidation Products of Cholesterol and Phytosterols in Heat-Processed Thigh Muscle of Broilers

In this study, the hypothesis that supplementation with methionine (Met) as DL-Met (DLM) in excess of the National Research Council (NRC) recommendations improves the antioxidant system in broilers was investigated. Day-old male Cobb-500 broilers (n = 72) were divided into three groups which were fed a control diet or diets supplemented with two levels of DLM in which the concentrations of Met + Cys exceeded the recommendations of NRC by 15-20% (group DLM 1) or 30-40% (group DLM 2), respectively. The three groups of broilers did not show differences in body weight gains, feed intake, and feed conversion ratio. However, broilers of groups DLM 1 and DLM 2 had higher concentrations of glutathione (GSH) in liver and thigh muscle and lower concentrations of cholesterol oxidation products (COPs) in heat-processed thigh muscle than broilers of the control group. Concentrations of several oxidation products of phytosterols in heat-processed thigh muscle were also reduced in groups DLM 1 and DLM 2; however, the concentration of total oxidation products of phytosterols was not different between the three groups. The study shows that DLM supplementation improved the antioxidant status due to an increased formation of GSH and reduced the formation of COPs during heat-processing in thigh muscle.

Quantification of Cooking Method Effect on COP Content in Meat Types Using Triple Quadrupole GC-MS/MS

A diet containing cholesterol is an essential component of biological function; however, cholesterol oxidation products (COPs) remain a major public health concern. This study investigated the effects of cooking methods (boiling and frying) on the production levels of COPs in processed foods. Samples, as represented by minced beef, chicken sausages, and fish fillets, were subjected to different cooking methods followed by COP extraction using a saponification method. Then, six common COPs, 5α-cholest, α-epoxy, β-epoxy, 25-HC, triol, and 7-keto, were quantified by triple quadrupole gas chromatography-mass spectrometry (GS-MS/MS). A significantly high number of COPs were detected in minced meat, of which 7-keto and triol were detected as major oxidation products, followed by chicken sausages and fish fillets (p ≤ 0.05). Compared to boiling, frying generated significantly more COPs, specifically triol (0.001-0.004 mg/kg) and 7-keto (0.001-0.200 mg/kg), in all samples. Interestingly, cholesterol level was found to be slightly (but not significantly) decreased in heat-treated samples due to oxidation during cooking, producing a higher number of COPs. Notably, the fish fillets were found to produce the fewest COPs due to the presence of a low amount of cholesterol and unsaturated fatty acids. In conclusion, adapting boiling as a way of cooking and choosing the right type of meat could serve to reduce COPs in processed foods.

Effects of Cooking Cycle Times of Marinating Juice and Reheating on the Formation of Cholesterol Oxidation Products and Heterocyclic Amines in Marinated Pig Hock

In this work the effects of cooking cycle times of marinating juice and reheating on the formation of cholesterol oxidation products (COPs) and heterocyclic amines (HAs) in marinated pig hock were investigated. After the 12th cycle, the total content of COPs was 3.3, 2.0, and 2.0 times higher than that after the 1st cycle in the skin, subcutaneous fat, and lean meat, respectively. The total content of HAs was 5.8, 6.0, and 5.6 times higher than that after the 1st cycle in the skin, subcutaneous fat, and lean meat, respectively. Notably, more COPs were present in the lean meat than in the skin and subcutaneous fat, whereas the content of HAs in the skin was the highest. Compared with the unreheated samples, the total content of COPs and HAs in all tissues increased after reheating at 95 °C for 30 min or at 121 °C for 25 min, but no significant difference was found between different reheating conditions.

The Effect of Diet Supplementation with Pomegranate and Bitter Melon on Lipidomic Profile of Serum and Cancerous Tissues of Rats with Mammary Tumours

The aim of this study was to present overall lipid profile of organisms with ongoing neoplastic process and applied diet supplementation with pomegranate seed oil (PSO) and bitter melon extract (BME). The following were quantified in serum and cancerous tissues of rats suffering from mammary tumours: fatty acids, conjugated fatty acids and sterols, their oxidised metabolites (malondialdehyde and oxysterols) and lipoxygenase (LOX) metabolites of polyunsaturated fatty acids. The obtained results indicate that abnormalities in lipid metabolism accompany neoplastic process. These differences concern all classes of lipids and most pathways of their transformation, with the special emphasis on lipid peroxidation and LOX-mediated metabolism. Cancer process appears to be so detrimental that it may conceal positive influence of dietary modifications. The lack of anticarcinogenic properties of PSO and BME in this model may be due to their antioxidant properties or elevated levels of conjugated linoleic acids (CLA), which change CLA isomer activity from anti- to pro-tumorigenic. As CLA are the product of conjugated linolenic acids (CLnA) endogenous metabolism, high CLA levels may be explained by applied diet enrichment.

Omics analysis of oxysterols to better understand their pathophysiological role

High amounts of cholesterol have been definitely associated with the pathogenesis of several diseases, including metabolic and neurodegenerative disorders, cardiovascular diseases, and cancer. In all these pathologies the exacerbation of pro-oxidant and inflammatory responses is a consistent feature. In this scenario, species derived from enzymatic and non-enzymatic cholesterol oxidation, namely oxysterols, are strongly suspected to play a primary role. The consideration of these bioactive lipids is therefore helpful in investigating pathological mechanisms and may also acquire clinical value for the diagnosis and treatment of diseases. For this purpose and considering that a great number of oxysterols may be present together in the body, the employment of lipidomics technology certainly represents a powerful strategy for the simultaneous detection and characterization of these compounds in biological specimens. In this review, we will discuss the applicability of the lipidomics approach in the study of the association between oxysterols and diseases.

Induction of peroxisomal changes in oligodendrocytes treated with 7-ketocholesterol: Attenuation by α-tocopherol

The involvement of organelles in cell death is well established especially for endoplasmic reticulum, lysosomes and mitochondria. However, the role of the peroxisome is not well known, though peroxisomal dysfunction favors a rupture of redox equilibrium. To study the role of peroxisomes in cell death, 158 N murine oligodendrocytes were treated with 7-ketocholesterol (7 KC: 25-50 μM, 24 h). The highest concentration is known to induce oxiapoptophagy (OXIdative stress + APOPTOsis + autoPHAGY), whereas the lowest concentration does not induce cell death. In those conditions (with 7 KC: 50 μM) morphological, topographical and functional peroxisome alterations associated with modifications of the cytoplasmic distribution of mitochondria, with mitochondrial dysfunction (loss of transmembrane mitochondrial potential, decreased level of cardiolipins) and oxidative stress were observed: presence of peroxisomes with abnormal sizes and shapes similar to those observed in Zellweger fibroblasts, lower cellular level of ABCD3, used as a marker of peroxisomal mass, measured by flow cytometry, lower mRNA and protein levels (measured by RT-qPCR and western blotting) of ABCD1 and ABCD3 (two ATP-dependent peroxisomal transporters), and of ACOX1 and MFP2 enzymes, and lower mRNA level of DHAPAT, involved in peroxisomal β-oxidation and plasmalogen synthesis, respectively, and increased levels of very long chain fatty acids (VLCFA: C24:0, C24:1, C26:0 and C26:1, quantified by gas chromatography coupled with mass spectrometry) metabolized by peroxisomal β-oxidation. In the presence of 7 KC (25 μM), slight mitochondrial dysfunction and oxidative stress were found, and no induction of apoptosis was detected; however, modifications of the cytoplasmic distribution of mitochondria and clusters of mitochondria were detected. The peroxisomal alterations observed with 7 KC (25 μM) were similar to those with 7 KC (50 μM). In addition, data obtained by transmission electron microcopy and immunofluorescence microscopy by dual staining with antibodies raised against p62, involved in autophagy, and ABCD3, support that 7 KC (25-50 μM) induces pexophagy. 7 KC (25-50 μM)-induced side effects were attenuated by α-tocopherol but not by α-tocotrienol, whereas the anti-oxidant properties of these molecules determined with the FRAP assay were in the same range. These data provide evidences that 7 KC, at concentrations inducing or not cell death, triggers morphological, topographical and functional peroxisomal alterations associated with minor or major mitochondrial changes.