Oxidation of Cholesterol in Foods and Its Importance for Human Health

The CaCo-2 cell junction derangement exerted by the single addition of oxysterols commonly detected in foods is markedly quenched when they are in mixture

The selective permeability of the gut epithelial barrier is heavily reliant on the stability of cell junctions, often challenged by a variety of dietary stressors, including non-enzymatic cholesterol oxidation products (COPs). A marked decrease of the tight junctions claudin-1 and occludin, and of the adherens junction E-cadherin was previously detected in differentiated CaCo-2 monolayers challenged by a single addition of 7β-hydroxycholesterol (7βOHC) or 7-ketocholesterol (7KC) in the lowest micromolar range. However, in the diet, oxysterols are occurring in a mixture. Hence, the aim of the present study was to evaluate whether cell incubation with all the main dietary COPs together quench the intercellular junction derangement previously observed as exerted by 7βOHC and 7KC singularly added. Two chocolate prototypes, respectively made with fresh (oxy-Mix1) or six-months stored whole milk powder (oxy-Mix2), were compared. The second prototype showed an almost double content of total COPs (3.34 µM, approximately 1337 ng /g of chocolate) than the first one (1.69 µM, approximately 675 ng /g of chocolate). Importantly, even in the CaCo-2 cell monolayers treated with six-months stored mixture of COPs oxy-Mix2, no alterations were observed of those cell junctions markedly affected by identical concentration of 7βOHC or 7KC used alone. The junctions' derangement started to be significantly evident when oxy-Mix2 was used at higher concentration (5 µM, approximately 2 µg oxysterols/g of product) or when treatments were carried out with repeated doses of oxy-Mix2 every 24 hours. Although achieved in a still widely adopted in vitro model system, these findings could orientate the definition of a safe shelf-life for dairy products, certainly for milk chocolate.

Immune Implications of Cholesterol-Containing Lipid Nanoparticles

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

Excipient-related impurities in liposome drug products

Liposomes are widely used in the pharmaceutical industry as drug delivery systems to increase the efficacy and reduce the off-target toxicity of active pharmaceutical ingredients (APIs). The liposomes are more complex drug delivery systems than the traditional dosage forms, and phospholipids and cholesterol are the major structural excipients. These two excipients undergo hydrolysis and/or oxidation during liposome preparation and storage, resulting in lipids hydrolyzed products (LHPs) and cholesterol oxidation products (COPs) in the final liposomal formulations. These excipient-related impurities at elevated concentrations may affect liposome stability and exert biological functions. This review focuses on LHPs and COPs, two major categories of excipient-related impurities in the liposomal formulations, and discusses factors affecting their formation, and analytical methods to determine these excipient-related impurities.

Cholesterol and Its Oxidation Derivatives Content in Market Dairy Products

Cholesterol oxidation products (COPs) are contaminants of food of animal origin. Increased levels of these compounds in the human body are associated with an increased risk of many non-communicable diseases. Dairy products are mentioned among the main sources of these compounds in the diet. The objective of this study was to evaluate the contents of cholesterol and its oxidized derivatives in eleven groups of dairy products, willingly consumed in European countries. The levels of COPs were determined by applying the GC-TOF/MS method. In the tested products, cholesterol and its oxidation derivatives, such as 7-ketocholesterol, 7α-hydroxycholesterol, 7β-hydroxycholesterol, 5,6β-epoxycholesterol and 5,6α-epoxycholesterol, were determined. The studied dairy products differed in their contents and profiles of oxysterols. The highest contents of COPs were found in cheese with internal mold (13.8 ± 2.5 mg kg-1) and Cheddar (11.7 ± 3.5 mg kg-1), while the lowest levels were detected in yoghurt (0.94 ± 0.30 mg kg-1) and kefir (0.57 ± 0.11 mg kg-1). 7-ketocholesterol and 5,6β-epoxycholesterol were the dominant oxysterols. The ratio of oxidized derivatives to total cholesterol was on average 1.7%. Our results confirmed that dairy products are an important dietary source of COPs. Their levels should be monitored in dairy products to provide the best health quality.

A Novel Method for the Determination of Squalene, Cholesterol and Their Oxidation Products in Food of Animal Origin by GC-TOF/MS

Cholesterol present in food of animal origin is a precursor of oxysterols (COPs), whose high intake through diet can be associated with health implications. Evaluation of the content of these contaminants in food is associated with many analytical problems. This work presents a GC-TOF/MS method for the simultaneous determination of squalene, cholesterol and seven COPs (7-ketocholesterol, 7α-hydroxycholesterol, 7β-hydroxycholesterol, 25-hydroxycholesterol, 5,6α-epoxycholesterol, 5,6β-epoxycholesterol, cholestanetriol). The sample preparation procedure includes such steps as saponification, extraction and silylation. The method is characterized by high sensitivity (limit of quantification, 0.02-0.25 ng mL-1 for instrument, 30-375 μg kg of sample), repeatability (RSD 2.3-6.2%) and a wide linearity range for each tested compound. The method has been tested on eight different animal-origin products. The COP to cholesterol content ratio in most products is about 1%, but the profile of cholesterol derivatives differs widely (α = 0.01). In all the samples, 7-ketocholesterol is the dominant oxysterol, accounting for 31-67% of the total COPs level. The levels of the other COPs range between 0% and 21%. In none of the examined products are cholestanetriol and 25-hydroxycholesterol present. The amount of squalene, which potentially may inhibit the formation of COPs in food, ranges from 2 to 57 mg kg-1.

Research progress on quality deterioration mechanism and control technology of frozen muscle foods

Freezing can prolong the shelf life of muscle foods and is widely used in their preservation. However, inevitable quality deterioration can occur during freezing, frozen storage, and thawing. This review explores the eating quality deterioration characteristics (color, water holding capacity, tenderness, and flavor) and mechanisms (irregular ice crystals, oxidation, and hydrolysis of lipids and proteins) of frozen muscle foods. It also summarizes and classifies the novel physical-field-assisted-freezing technologies (high-pressure, ultrasound, and electromagnetic) and bioactive antifreeze (ice nucleation proteins, antifreeze proteins, natural deep eutectic solvents, carbohydrate, polyphenol, phosphate, and protein hydrolysates), regulating the dynamic process from water to ice. Moreover, some novel thermal and nonthermal thawing technologies to resolve the loss of water and nutrients caused by traditional thawing methods were also reviewed. We concluded that the physical damage caused by ice crystals was the primary reason for the deterioration in eating quality, and these novel techniques promoted the eating quality of frozen muscle foods under proper conditions, including appropriate parameters (power, time, and intermittent mode mentioned in ultrasound-assisted techniques; pressure involved in high-pressure-assisted techniques; and field strength involved in electromagnetic-assisted techniques) and the amounts of bioactive antifreeze. To obtain better quality frozen muscle foods, more efficient technologies and substances must be developed. The synergy of novel freezing/thawing technology may be more effective than individual applications. This knowledge may help improve the eating quality of frozen muscle foods.

Recent advances in the development of healthier meat products

Meat products are an excellent source of high biological value proteins, in addition to the high content of minerals, vitamins, and bioactive compounds. However, meat products contain compounds that can cause a variety of adverse health effects and pose a serious health threat to humans. In this sense, this chapter will address recent strategies to assist in the development of healthier meat products. The main advances about the reduction of sodium and animal fat in meat products will be presented. In addition, strategies to make the lipid profile of meat products more nutritionally advantageous for human health will also be discussed. Finally, the reduction of substances of safety concern in meat products will be addressed, including phosphates, nitrites, polycyclic aromatic hydrocarbons, heterocyclic aromatic amines, as well as products from lipid and protein oxidation.

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.

The Influence of Supplementation with Zinc in Micro and Nano Forms on the Metabolism of Fatty Acids in Livers of Rats with Breast Cancer

The aim of this study was to investigate the effect of zinc supplementation (in the form of nano or microparticles) on the profile and metabolism of fatty acids in the liver microsomes of rats with induced breast cancer. The activity of desaturases (Δ5, Δ6, Δ9) and the level of cholesterol and its oxidized derivatives were measured. The aim of this study was also to determine the effect of various forms of zinc supplements on rats that were on 5-, 12- and 15-hydroxyeicosatetraenoic (5-, 12- and 15-HETE) and hydroxyoctadecadienoic (HODE) acids, and the level of prostaglandin E2 (PGE2). Female Spraque-Dawley rats (n = 24) were divided into 2 groups that were supplemented with zinc in the micro form (342 nm) or nano form (99 nm) particles, respectively, and a group with a standard diet (control group). All animals received 7,12-dimethylbenz[a]anthracene twice for the induction of breast cancer. Dietary nano-Zn supplementation increased vaccenic acid content (p = 0.032) and decreased Δ6-desaturase activity (p = 0.006), whereas micro-Zn increased cholesterol (p = 0.006), ∑COPs (total cholesterol-oxidation products) (p = 0.019) and PGE2 (p = 0.028) content. Dietary enrichment with Zn microparticles resulted in lower concentrations of the metabolites 15-, 12- and 5-HETE and HODE. Our study indicates that the effect of zinc supplementation on the metabolism of fatty acids in the liver microsomes under neoplastic conditions depends on the form in which it is administered.

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.

Effect of Cold Plasma on Meat Cholesterol and Lipid Oxidation

Cold atmospheric plasma (CAP) is a novel non-thermal technology with potential applications in inactivating microorganisms in food products. However, its impact on food quality is not yet fully understood. The aim of this research is to study the impact of in-package plasma technology on the stability of cholesterol and total lipid in four different types of meat (beef, pork, lamb and chicken breast). Additionally, any changes in the primary or secondary lipid oxidation, which is undesirable from a health perspective, is investigated. CAP was not found to have any impact on the cholesterol or lipid content. However, higher peroxide and thiobarbituric acid reactive substances (TBARS) values were found for the treated samples, indicating that plasma can induce the acceleration of primary and secondary lipid oxidation. Finally, color was not affected by the treatment supporting the suitability of the technology for meat products.

Effect of Different Egg Products on Lipid Oxidation of Biscuits

Egg products are one of the main ingredients used in bakery industries, and they contain cholesterol. Cholesterol suffers several chemical changes during the food processes, allowing some potentially toxic compounds called cholesterol oxidized products (COPs). Thus, the aim of this work was to study the evolution of lipid oxidation from eggs to egg products, and to evaluate the influence of egg products on COPs formation in biscuits formulated with them. The results confirmed that spray-drying technology improves the cholesterol oxidation 2.6 times compared to pasteurized eggs. Biscuit samples showed a COPs content that is strictly related to the egg products used. Samples formulated with spray-dried eggs noticed lower amounts of COPs compared to those formulated with pasteurized eggs. It is important to stress that COPs composition was different between the two samples, underlining that the kinetic of COPs formation is dependent on the type of egg products.

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.

Conjugated Linoleic Acid and Cholesterol Oxidative Products Generated in Hot Boned Beef Semimembranosus Muscle as Affected by Rigor Temperature, Ageing and Display Time

The present study investigated the effect of processing parameters comprising rigor temperature, ageing and display time on conjugated linoleic acid (CLA) concentrations, stability and the development of cholesterol oxidation products in hot boned beef semimembranosus muscles. Meat samples, having attained rigor mortis at 5 °C and 25 °C, were vacuum packed and aged for 7 and 14 days and then displayed under aerobic conditions for 7 days at 4 °C. Lipid was extracted at each time interval then ¹H NMR and GC-FID were used for CLA quantification. The cholesterol oxidation products (COPs) were separated from lipids via column chromatography and derivatized for GC-FID. The CLA content was not affected by the rigor temperature, ageing and display time (p > 0.05). The cholesterol oxidative stability was not affected by rigor temperature (p > 0.05) but was affected by ageing and display time (p < 0.05). The COPs, 7α- and 7β-hydroxycholesterol, and 7-ketocholesterol were positively identified and their quantities increased with ageing and display time (p < 0.05). These results demonstrate that the production of COPs in semimembranosus muscle was significantly altered by the ageing and display time parameters but not by the rigor temperature used in this study.

Formation of oxysterols during thermal processing and frozen storage of cooked minced meat

BACKGROUND

Cholesterol is susceptible to oxidation and the formation of oxysterols, which could have a negative health effect. The formation and distribution of oxysterols was investigated in meatloaves prepared under different baking regimes with an increased temperature or prolonged time. The effect of frozen storage and marjoram addition on the level of oxysterols was also investigated.

RESULTS

The effect of baking regime on the content and distribution of oxysterols was determined. Temperature was the most important factor affecting 7-ketocholesterol formation in baked meatloaf. Its content was significantly higher after baking at 250 °C compared to at 180 °C. The content of 7-ketocholesterol increased from the centre (87 µg kg^-1 ) to the surface (122 µg kg^-1 ) of baked meatloaves prepared under standard conditions. The level of α-tocopherol and its distribution was also affected by the baking regime. A higher level of 7-ketocholesterol was found in baked meatloaves after their frozen storage. The addition of marjoram did not change this level.

CONCLUSION

Inadequate culinary conditions used for preparation of baked meat can contribute to an increased oxysterol intake in the diet. Frozen storage did not stop oxysterol formation. The inhibition effect of marjoram on sterols oxidation was not confirmed. © 2017 Society of Chemical Industry.

Microwave assisted direct saponification for the simultaneous determination of cholesterol and cholesterol oxides in shrimp

A novel microwave-assisted direct saponification method for the simultaneous determination of cholesterol and cholesterol oxides in shrimp was developed and validated. Optimal saponification conditions, determined by means of an experimental design, were achieved using 500mg of sample and 20mL of 1mol/L KOH ethanol solution for 16min at 45°C at maximum power at 200W and magnetic stirring at 120rpm. Higher extraction of cholesterol oxides in a reduced saponification time (∼75 times) was achieved in comparison with the direct cold saponification method. The new method showed low detection (≤0.57μg/mL) and quantification (≤1.73μg/mL) limits, good repeatability (≤10.50% intraday and ≤8.56% interday) and low artifact formation (evaluated by using a deuterated cholesterol-D6 standard). Raw, salted and dried-salted shrimps were successfully analyzed by the validated method. The content of cholesterol oxides increased after salting and decreased after drying.

Health Risks of Food Oxidation

The impact of dietary habits on our health is indisputable. Consumer's concern on aging and age-related diseases challenges scientists to underline the potential role of food on the extension and guarantee of lifespan and healthspan. While some dietary components and habits are generally regarded as beneficial for our health, some others are being found to exert potential toxic effects and hence, contribute to the onset of particular health disorders. Among the latter, lipid and protein oxidation products formed during food production, storage, processing, and culinary preparation have been recently identified as potentially harmful to humans. Upon intake, food components are further degraded and oxidized during the subsequent digestion phases and the pool of compounds formed in the lumen is in close contact with the lamina propria of the intestines. Some of these oxidation products have been found to promote inflammatory conditions in the gut (i.e., bowel diseases) and are also reasonably linked to the onset of carcinogenic processes. Upon intestinal uptake, some species are distributed by the bloodstream causing an increase in oxidative stress markers and impairment of certain physiological processes through alteration of specific gene expression pathways. This chapter summarizes the most recent discoveries on this topic with particular stress on challenges that we face in the near future: understanding the molecular basis of disease, the suitability of using living animals vs in vitro model systems and the necessity of using massive genomic techniques and versatile mass spectrometric technology.

Cholesterol Oxidation in Fish and Fish Products

Fish and fish products are important from a nutritional point of view due to the presence of high biological value proteins and the high content of polyunsaturated fatty acids, especially those of the n-3 series, and above all eicosapentaenoic acid and docosahexaenoic acid. However, these important food products also contain significant amounts of cholesterol. Although cholesterol participates in essential functions in the human body, it is unstable, especially in the presence of light, oxygen, radiation, and high temperatures that can cause the formation of cholesterol oxidation products or cholesterol oxides, which are prejudicial to human health. Fish processing involves high and low temperatures, as well as other methods for microbiological control, which increases shelf life and consequently added value; however, such processes favor the formation of cholesterol oxidation products. This review brings together data on the formation of cholesterol oxides during the preparation and processing of fish into food products which are recognized and recommended for their nutritional properties.

Effect of dietary linseed on the nutritional value and quality of pork and pork products: systematic review and meta-analysis

Nutritional quality of pork is a significant factor for consumers' health. Feeding n-3 PUFA to pigs, using linseed, improves pork nutritional quality. A meta-analysis involving 1006 pigs reported in 24 publications was carried out to assess the effects of dietary linseed on alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) content in muscle and adipose tissue. Data showed positive effects of n-3 PUFA on muscle fatty acid composition: ALA+137%, EPA+188%, DPA+51% and DHA+12%. Same results were observed in adipose tissue: ALA+297%, EPA+149%, DPA+88% and DHA+18%. A positive correlation between dietary treatment and ALA and EPA content in muscle (P<0.001) and adipose tissue (P=0.036) was observed. A significant association between DPA (P=0.04) and DHA (P=0.011) and live weight in muscle was observed. Feeding linseed to pig improves the nutritional pork quality, raising the n-3 PUFA content in muscle and adipose tissue.