Pomegranate supplementation alleviates dyslipidemia and the onset of non-alcoholic fatty liver disease in Wistar rats by shifting microbiota and producing urolithin-like microbial metabolites.

Non-alcoholic fatty liver disease (NAFLD), obesity and related chronic diseases are major non-communicable diseases with high mortality rates worldwide. While dietary sugars are known to be responsible for insulin resistance and metabolic syndrome (MetS), the underlying pathophysiological effects of sustained fructose consumption require further elucidation. We hypothesize that certain bioactive compounds (i.e. punicalagin and ellagic acid) from dietary pomegranate could counteract the harmful effects of sustained fructose consumption in terms of obesity and liver damage. The present study aimed to elucidate both the molecular mechanisms involved in the pathophysiology associated with fructose intake and the effect of a punicalagin-rich commercial pomegranate dietary supplement (P) used as a nutritional strategy to alleviate fructose-induced metabolic impairments. Thus, nineteen Wistar rats fed on a basal commercial feed were supplemented with either 30% (w/v) fructose in drinking water (F; n = 7) or 30% (w/v) fructose solution plus 0.2% (w/v) P (F + P; n = 6) for 10 weeks. The results were compared to those from a control group fed on the basal diet and provided with drinking water (C; n = 6). Body weight and energy intake were registered weekly. P supplementation decreased fat depots, counteracted the dyslipidemia caused by F and improved markers of liver injury including steatosis. The study of the microbiota by metagenomics and urine by untargeted MS-based metabolomics revealed microbial metabolites from P that may be responsible for these health benefits.

The utilisation of agricultural by-products in processed meat products: Effects on physicochemical, nutritional and sensory quality - Invited Review.

Several plant-based materials are discarded by the food industry due to oversupply, lack of transport, and inappropriate storage. These materials contain valuable essential micronutrients such as minerals, vitamins and bioactive components (e.g., polyphenol, tocopherols, ascorbic acid, carotenoids) with antioxidant, antimicrobial, and anti-inflammatory effects, among others. In the context of making our agriculture-food based economy more circular and sustainable, and to develop foods with clean labels and less E-numbers, fruits, vegetables, yams, cereal distillers, oilseeds and other plant by-products could be utilised and upcycled back into new food formulations. Meat products are a particularly suitable matrix for this purpose, due to their susceptibility to lipid and protein oxidation and microbial spoilage (which shorten their shelf life). This review brings together the latest (2020-23) reformulation efforts, preservative methods and other innovative pathways, including studies on by-products as plant-based additives and bio-actives. It will cover the use of plant-based by-products as natural additives into production of processed meat products such as burgers, fermented meats and sausages, produced from ruminant and monogastric animals (except poultry). The extraction methods, inclusion levels, processing methods used and the quality of the resulting meat products will be reported, including preservative effects (microbial growth, oxidative stability and shelf life) and effects on instrumental, nutritional and sensory quality. Furthermore, it will also critically discuss the gaps identified, recommendation of the most promising ingredients for quality enhancement, and provide directions for future research.

Unveiling the bioactivity and bioaccessibility of phenolic compounds from organic coffee husks using an in vitro digestion model.

BACKGROUND: The large quantities of by-products generated in the coffee industry are a problem. Studies related to the biological potential of organic coffee husks are still limited. The aim of this work was to investigate the occurrence of phenolic compounds in organic coffee husks and to evaluate their potential as a source of bioactive dietary components. RESULTS: To achieve this objective, three extracts were prepared, namely extractable polyphenols (EPs), hydrolyzable non-extractable polyphenols (H-NEPs), and non-extractable polyphenols (NEPs). These extracts were characterized and evaluated for their bioactive properties after simulated gastrointestinal digestion. The results show that the extraction process affected the occurrence of phenols from coffee peels, especially for caffeic acid, gallic acid, and chlorogenic acid. The free and bound polyphenols found in the extracts and digests not only showed antioxidant properties against 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals but were also strongly bioavailable and had good anticoagulant potential. CONCLUSION: These results highlight the potential health benefits of phytochemicals from coffee husks and open new perspectives for the use of such compounds in dietary supplements. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Emotional response to healthier foods: Influence of culture and health consciousness.

Sugar, salt, and fat content in processed products are important concerns for consumers. Hence, alternative "healthy" versions of conventional foods such as chocolate, potato chips, and yogurt are offered. This work aimed to define the emotional response of consumers from different cultural backgrounds (Spain vs. Brazil) evoked by healthier versions of conventional products and the relationship between hedonic responses and health consciousness. A total of 186 Brazilian and 152 Spanish consumers participated in this online cross-cultural study. Participants answered a Health Consciousness Questionnaire and an emotional check-all-that-applies questionnaire using picture stimuli of conventional chocolate, potato chips, and yogurt and their healthier versions with less sugar, salt, and fat content, respectively. The Brazilians' emotional responses were more diverse for all stimuli compared to the Spaniards'. However, participants from both cultures rated an average of "slightly agree" on the health consciousness scale; a higher level of consumption, liking, and willingness to buy; and a higher frequency of positive emotional terms for the stimuli of conventional products compared to their healthier versions. A higher frequency of evocation of "active" is strongly associated with higher levels of health consciousness. Strategic actions by the food industry and government must consider cultural, emotional, and health-conscious factors to encourage the consumption of healthier foods. PRACTICAL APPLICATION: Food manufacturers can use the information obtained from this study to create healthier versions of their products that appeal to consumers' emotional responses and health consciousness levels. The findings can assist in designing strategic actions to promote healthier food consumption by emphasizing the benefits of healthier food choices and making them more appealing to consumers. The methodology employed in this study can also be applied to further studies aimed to assess emotional responses to food stimuli across different cultures.

Impact of Sustained Fructose Consumption on Gastrointestinal Function and Health in Wistar Rats: Glycoxidative Stress, Impaired Protein Digestion, and Shifted Fecal Microbiota.

The gastrointestinal tract (GIT) is the target of assorted pathological conditions, and dietary components are known to affect its functionality and health. In previous in vitro studies, we observed that reducing sugars induced protein glycoxidation and impaired protein digestibility. To gain further insights into the pathophysiological effects of dietary sugars, Wistar rats were provided with a 30% (w/v) fructose water solution for 10 weeks. Upon slaughter, in vivo protein digestibility was assessed, and the entire GIT (digests and tissues) was analyzed for markers of oxidative stress and untargeted metabolomics. Additionally, the impact of sustained fructose intake on colonic microbiota was also evaluated. High fructose intake for 10 weeks decreased protein digestibility and promoted changes in the physiological digestion of proteins, enhancing intestinal digestion rather than stomach digestion. Moreover, at colonic stages, the oxidative stress was harmfully increased, and both the microbiota and the intraluminal colonic metabolome were modified.

Multi-Omics Approach Reveals Prebiotic and Potential Antioxidant Effects of Essential Oils from the Mediterranean Diet on Cardiometabolic Disorder Using Humanized Gnotobiotic Mice.

Essential oils sourced from herbs commonly used in the Mediterranean diet have demonstrated advantageous attributes as nutraceuticals and prebiotics within a model of severe cardiometabolic disorder. The primary objective of this study was to assess the influences exerted by essential oils derived from thyme (Thymus vulgaris) and oregano (Origanum vulgare) via a comprehensive multi-omics approach within a gnotobiotic murine model featuring colonic microbiota acquired from patients diagnosed with coronary artery disease (CAD) and type-2 diabetes mellitus (T2DM). Our findings demonstrated prebiotic and potential antioxidant effects elicited by these essential oils. We observed a substantial increase in the relative abundance of the Lactobacillus genus in the gut microbiota, accompanied by higher levels of short-chain fatty acids and a reduction in trimethylamine N-oxide levels and protein oxidation in the plasma. Moreover, functional enrichment analysis of the cardiac tissue proteome unveiled an over-representation of pathways related to mitochondrial function, oxidative stress, and cardiac contraction. These findings provide compelling evidence of the prebiotic and antioxidant actions of thyme- and oregano-derived essential oils, which extend to cardiac function. These results encourage further investigation into the promising utility of essential oils derived from herbs commonly used in the Mediterranean diet as potential nutraceutical interventions for mitigating chronic diseases linked to CAD and T2DM.

The pro-oxidant action of high-oxygen MAP on beef patties can be counterbalanced by antioxidant compounds from common hawthorn and rose hips.

The objective of this research was to evaluate the effectiveness of antioxidant-rich extracts from rose hip (Rosa canina L.; RC) and hawthorn (Crataegus monogyna Jacq.; CM) at minimizing the oxidative damage to proteins and lipids in beef patties subjected to a high­oxygen (HiOx-MAP) and vacuum (Vacuum) packaging atmosphere. The extracts of RC and CM were characterized by quantifying bioactive compounds, namely, phenolic compounds, tocopherols and vitamin C. Both fruits had high concentrations of bioactive compounds, with RC having the highest total phenolic and vitamin C content. Yet, CM was the most efficient in protecting beef patties against protein carbonylation, reducing, as a result, the instrumental toughness in cooked beef patties. The use of CM and RC extracts in beef patties significantly improved consumer purchase intention in HiOx-MAP packaging systems. The use of CM and RC extracts or their combination in future research would be an effective antioxidant means to decrease the pro-oxidative effects caused by HiOx-MAP in red meat.

Crosstalk between dietary pomegranate and gut microbiota: evidence of health benefits.

Gut microbiota (GM) is an invisible organ that plays an important role in human health. Increasing evidence suggests that polyphenols in pomegranate (punicalagin, PU) could serve as prebiotics to modulate the composition and function of GM. In turn, GM transform PU into bioactive metabolites such as ellagic acid (EA) and urolithin (Uro). In this review, the interplay between pomegranate and GM is thoroughly described by unveiling a dialog in which both actors seem to affect each other's roles. In a first dialog, the influence of bioactive compounds from pomegranate on GM is described. The second act shows how the GM biotransform pomegranate phenolics into Uro. Finally, the health benefits of Uro and that related molecular mechanism are summarized and discussed. Intake of pomegranate promotes beneficial bacteria in GM (e.g. Lactobacillus spp., Bifidobacterium spp.) while reducing the growth of harmful bacteria (e.g. Bacteroides fragilis group, Clostridia). Akkermansia muciniphila, and Gordonibacter spp., among others, biotransform PU and EA into Uro. Uro contributes to strengthening intestinal barrier and reducing inflammatory processes. Yet, Uro production varies greatly among individuals and depend on GM composition. Uro-producing bacteria and precise metabolic pathways need to be further elucidated therefore contributing to personalized and precision nutrition.

Gut microbiota plays a critical role in maintaining host health.Pomegranate is rich in bioactive components.Consumption of pomegranate positively modulates gut microbiota.Gut microbiota can transform ellagitannins in pomegranate into urolithin.Urolithin has high bioavailability and multiple health benefits.

Oxidative stability of white striping chicken breasts: effect of cold storage and heat treatments.

This study aimed to investigate the level of lipid and protein oxidation in poultry breasts with severe white striping (WS; striation thickness > 1 mm) and nonaffected meats (N; normal breast) during storage under refrigeration (1°C for 14 d) and freezing (-18°C for 90 d). WS presented higher lipid content, although no difference in protein content was detected, compared to normal broiler breast (N). Regarding oxidative damages, a reduction in malondialdehyde and carbonyl protein, hexanal, octanal and nonanal levels, alongside the interaction of these compounds with other compounds in raw, roasted, and reheated breasts was observed under refrigerated storage (14 d). Freezing storage promotes an increase in carbonyls proteins, hexanal, octanal and nonanal levels at 45 d of storage in poultry meats and subsequent decrease, indicating the evolution of oxidative reactions. Regardless of the type of storage, in general, breasts with WS myopathy have higher levels of lipid and protein oxidation.

Deciphering the underlying mechanisms of the oxidative perturbations and impaired meat quality in Wooden breast myopathy by label-free quantitative MS-based proteomics.

The study aimed to investigate biochemical mechanisms occurred in Wooden breast (WB) chicken meat, with attention to the impact on meat quality. Commercial chicken breasts were classified as Normal (N, n = 12), WB-M (moderate degree; focal hardness on cranial region, n = 12) and WB-S (severe degree; extreme and diffused hardness over the entire surface, n = 12). Samples were analyzed for physico-chemical properties, oxidative damage to lipids and proteins, and discriminating sarcoplasmic proteins by using a Q-Exactive mass spectrometer. WB meat presented impaired composition and functionality and higher levels of lipid and protein oxidation markers than N meat. The proteomic profile of WB-S presents a dynamic regulation of the relevant proteins involved in redox homeostasis, carbohydrate, protein and lipid metabolisms. Proteomics results demonstrate that the physiological and metabolic processes of muscles affected by WB myopathy are involved in combating the inflammatory process and in repairing the damaged tissue by oxidative stress.

Influence of fat reduction and flavor addition on the temporal sensory profile in potato chips using a multiple-intake approach.

BACKGROUND: Reducing the fat content of potato chips can negatively affect the overall perception of taste and texture. However, incorporating flavor can help mitigate negative effects. To measure and understand these changes, a technique describing the consumption experience must be used. The impact of low fat content and the presence of ham flavor in the formulation of potato chips was studied in relation to the dynamics of sensations perceived during consumption and, additionally, related to the hedonic aspects of these products. RESULTS: Three different varieties of commercially available potato chips, classical salted potato chips (PC-C), light (low fat content) potato chips (PC-L), and ham-flavored potato chips (PC-H), were analyzed by multiple-intake temporal dominance of sensations (TDS) sessions, showing the differences among PC-C, PC-L, and PC-H. Moreover, acceptability and purchase intention were also considered. The results showed that the lower fat content in the potato chips had a great impact on temporal dominance of texture attributes, whereas the presence of ham flavor in the formulation greatly modified the temporal dominance of flavor sensations during consumption with no effect on acceptability. CONCLUSION: Multiple intake TDS is a suitable method for revealing how modifications of formulation and composition of potato chips to achieve healthier or different versions affects consumers dynamic sensory perception and how it is related to preferences. © 2023 Society of Chemical Industry.

Ellagic Acid Triggers the Necrosis of Differentiated Human Enterocytes Exposed to 3-Nitro-Tyrosine: An MS-Based Proteomic Study.

To study the molecular basis of the toxicological effect of a dietary nitrosated amino acid, namely, 3-nitrotyrosine (3-NT), differentiated human enterocytes were exposed to dietary concentrations of this species (200 µM) and analyzed for flow cytometry, protein oxidation markers and MS-based proteomics. The possible protective role of a dietary phytochemical, ellagic acid (EA) (200 µM), was also tested. The results revealed that cell viability was significantly affected by exposure to 3-NT, with a concomitant significant increase in necrosis (p < 0.05). 3-NT affected several biological processes, such as histocompatibility complex class II (MHC class II), and pathways related to type 3 metabotropic glutamate receptors binding. Addition of EA to 3-NT-treated cells stimulated the toxicological effects of the latter by reducing the abundance of proteins involved in mitochondrial conformation. These results emphasize the impact of dietary nitrosated amino acids in intestinal cell physiology and warn about the potential negative effects of ellagic acid when combined with noxious metabolites.

Biodegradation of Punicalagin into Ellagic Acid by Selected Probiotic Bacteria: A Study of the Underlying Mechanisms by MS-Based Proteomics.

Pomegranate (Punica granatum L.) is a well-known source of bioactive phenolic compounds such as ellagitannins, anthocyanins, and flavanols. Punicalagin, one of the main constituents of pomegranate, needs to be biodegraded by bacteria to yield metabolites of medicinal interest. In this work, we tested 30 lactic acid bacteria (LAB) and their capacity to transform punicalagin from a punicalagin-rich pomegranate extract into smaller bioactive molecules, namely, ellagic acid and urolithins. These were identified and quantified by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS2). Further, we evaluated the molecular mechanism governing this transformation through label-free comparative MS-based proteomics. All tested LAB strains were capable of transforming punicalagin into ellagic acid, while the biosynthesis of urolithins was not observed. Proteomic analysis revealed an increase of generic transglycosylases that might have a hydrolytic role in the target phenolic molecule, coupled with an increase in the quantity of ATP-binding cassette (ABC) transporters, which might play a relevant role in transporting the resulting byproducts in and out of the cell.

Beneficial Effects of Essential Oils from the Mediterranean Diet on Gut Microbiota and Their Metabolites in Ischemic Heart Disease and Type-2 Diabetes Mellitus.

Ischemic heart disease (IHD) and type-2 diabetes mellitus (T2DM) remain major health problems worldwide and commonly coexist in individuals. Gut microbial metabolites, such as trimethylamine N-oxide (TMAO) and short-chain fatty acids (SCFAs), have been linked to cardiovascular and metabolic diseases. Previous studies have reported dysbiosis in the gut microbiota of these patients and the prebiotic effects of some components of the Mediterranean diet. Essential oil emulsions of savory (Satureja hortensis), parsley (Petroselinum crispum) and rosemary (Rosmarinus officinalis) were assessed as nutraceuticals and prebiotics in IHD and T2DM. Humanized mice harboring gut microbiota derived from that of patients with IHD and T2DM were supplemented with L-carnitine and orally treated with essential oil emulsions for 40 days. We assessed the effects on gut microbiota composition and abundance, microbial metabolites and plasma markers of cardiovascular disease, inflammation and oxidative stress. Our results showed that essential oil emulsions in mice supplemented with L-carnitine have prebiotic effects on beneficial commensal bacteria, mainly Lactobacillus genus. There was a decrease in plasma TMAO and an increase in fecal SCFAs levels in mice treated with parsley and rosemary essential oils. Thrombomodulin levels were increased in mice treated with savory and parsley essential oils. While mice treated with parsley and rosemary essential oils showed a decrease in plasma cytokines (INFÉ£, TNFα, IL-12p70 and IL-22); savory essential oil was associated with increased levels of chemokines (CXCL1, CCL2 and CCL11). Finally, there was a decrease in protein carbonyls and pentosidine according to the essential oil emulsion. These results suggest that changes in the gut microbiota induced by essential oils of parsley, savory and rosemary as prebiotics could differentially regulate cardiovascular and metabolic factors, which highlights the potential of these nutraceuticals for reducing IHD risk in patients affected by T2DM.

Effect of feeding carob (Ceratonia siliqua L.) pulp powder to broiler chicken on growth performance, intestinal microbiota, carcass traits, and meat quality.

In this study, the influence of a partial substitution of corn with carob (Ceratonia siliqua L.) pulp powder on broiler performance, intestinal microbiota, carcass traits, and meat quality, was investigated. Two dietary treatments were compared: the control group received a diet containing basically corn, soybean meal, and wheat bran for all the breeding periods while the experimental group received the same starter diet as the control group and grower and finisher diets containing 3% and 7% of carob pulp powder, respectively. Growth performance (weight gain, feed intake, and feed conversion ratio), carcass traits, lactic acid bacteria, and total coliforms were determined. Physicochemical parameters, proximate composition, fatty acid profiles, lipid oxidation index, and sensory characteristics of broiler thigh and breast muscles were determined. Dietary supplementation with carob pulp powder did not show an effect (P > 0.05) on growth performance and carcass traits except for slaughter yield and breast relative weight. An increase in sum lactic acid bacteria count and a decrease in total coliforms were observed in the experimental group. No effect (P > 0.05) of dietary carob was observed on pH, cooking losses, ash, mineral, and protein contents in breast and thigh muscles from broilers. However, the experimental diet decreased (P < 0.05) moisture and fat contents in thigh muscles but not in breast muscles. Both muscles from the experimental group of birds exhibited lower palmitic and oleic acids contents, and higher linoleic and linolenic acids levels than those from the control group. Whereas the polyunsaturated fatty acid contents in broiler breast and thigh meat was increased by dietary carob, the concentration of lipid oxidation products decreased in this group. The dietary intervention had no significant effect on the sensory profile of breast and thigh muscles. Thus, carob pulp powder can be applied to broiler diet at 7% as a nonconventional feed with no negative impact on growth performance and carcass traits and to increase the degree of unsaturation with no negative impact on oxidative stability or sensory traits.

Protein oxidation marker, α-amino adipic acid, impairs proteome of differentiated human enterocytes: Underlying toxicological mechanisms.

Protein oxidation and oxidative stress are involved in a variety of health disorders such as colorectal adenomas, inflammatory bowel's disease, neurological disorders and aging, among others. In particular, the specific final oxidation product from lysine, the α-amino adipic acid (α-AA), has been found in processed meat products and emphasized as a reliable marker of type II diabetes and obesity. Currently, the underlying mechanisms of the biological impairments caused by α-AA are unknown. To elucidate the molecular basis of the toxicological effect of α-AA, differentiated human enterocytes were exposed to dietary concentrations of α-AA (200 µM) and analyzed by flow cytometry, protein oxidation and proteomics using a Nanoliquid Chromatography-Orbitrap MS/MS. Cell viability was significantly affected by α-AA (p < 0.05). The proteomic study revealed that α-AA was able to alter cell homeostasis through impairment of the Na+/K+-ATPase pump, energetic metabolism, and antioxidant response, among other biological processes. These results show the importance of dietary oxidized amino acids in intestinal cell physiology and open the door to further studies to reveal the impact of protein oxidation products in pathological conditions.

Improving the poor texture and technological properties of chicken wooden breast by enzymatic hydrolysis and low-frequency ultrasound.

Wooden breast (WB) is a recurrent myopathy in fast-growing birds, which alters the appearance, functionality, and the texture of the breast muscle. The objectives of this study were (i) to evaluate the effect of a combined use of papain enzyme and ultrasound on the texture of WB chicken using response surface methodology and (ii) to assess the effect of marinating on the quality of WB chicken meat. Full factorial experimental design method was used to obtain the ideal conditions to soften the WB meat. The independent variables were the concentration of papain (0.1%-0.3%) and the time in ultrasonic bath (10-30 min); shear force (SF) was the dependent variable. The optimum results were obtained at a concentration of 0.2% papain and 20 min on ultrasound. Papain enzyme had a great influence on the texture of WB meat, reducing its hardness. However, the effect of the ultrasound time on the SF response was not observed. The marinated WB meat showed similar SF values and texture profile than those from normal (N) meat, with reduction in the parameters of protein and lipid oxidation. The use of papain without ultrasound bath proved to be an efficient means for improving the tenderness of WB breasts. PRACTICAL APPLICATION: This study shows the efficiency of the application of two technological procedures (enzymatic treatment and ultrasound) to improve the texture profile and technological properties of chicken breasts affected by the wooden breast myopathy. The economic loss caused by the world-wide occurrence of wooden breast is enormous, and the application of papain has been found to counteract the impaired properties of this abnormal chicken breasts. Since papain is already widely used in the food industry to tenderize meat, its application in improving the quality of WB meat is straightforward.

Exploring the prospects of the fifth quarter in the 21st century.

A variable proportion of slaughtered livestock, generally referred to as the fifth quarter, is not part of the edible dressed meat and regarded as animal byproduct. In order for the fifth quarter to play a significant role in the current effort toward a circular bio-based economy, it has to successfully support food security, social inclusivity, environmental sustainability, and a viable economy. The high volume of these low-value streams and their nutrient-dense nature can facilitate their position as a very important candidate to explore within the context of a circular bio-based economy to achieve some of the United Nations Sustainable Development Goals (UN-SDGs). While these sources have been traditionally used for various applications across different cultures and industries, it seems evident that their full potential has not yet been exploited, leaving these products more like an environmental burden rather than valuable resources. With innovation and well-targeted interdisciplinary collaborations, the potential of the fifth quarter can be fully realized. The present review intends to explore these low-value streams, their current utilization, and their potential to tackle the global challenges of increasing protein demands while preventing environmental degradation. Factors that limit widespread applications of the fifth quarter across industries and cultures will also be discussed.

An in vitro assay of the effect of lysine oxidation end-product, α-aminoadipic acid, on the redox status and gene expression in probiotic Lactobacillus reuteri PL503.

This study was designed to gain information about the underlying mechanisms of the effects of a food-occurring free oxidized amino acid, α-aminoadipic acid (AAA), on the probiotic Lactobacillus reuteri PL503. This bacterium was incubated in colonic-simulated conditions (37 °C for 24 h in microaerophilic conditions) and exposed to three food-compatible AAA concentrations, namely, 1 mM, 5 mM, and 10 mM. A control group with no AAA exposure was also considered. Each of the four experimental conditions was replicated three times and samplings were collected at 12, 16, 20, and 24 h. The downregulation of the uspA gene by AAA (0.5-fold decrease as compared to control) suggests that AAA is identified as a potential chemical threat. The dhaT gene, implicated in the antioxidant defense, was found to be upregulated in bacteria treated with 1 and 5 mM AAA (up to twofold increase, as compared to control), which suggest the ability of the oxidized amino acid to impair the redox status of the bacterium. In fact, AAA caused an increased production of reactive oxygen species (ROS) and the accretion of post-translational changes (protein carbonylation) in L. reuteri (up to 13 nmol allysine/mg protein vs 1.8 nmol allysine/mg protein in control). These results suggest that probiotic bacteria identify oxidized amino acids as harmful species and activate mechanisms that may protect themselves and the host against their noxious effects.

Molecular mechanisms of the disturbance caused by malondialdehyde on probiotic Lactobacillus reuteri PL503.

This study aimed to provide insight into the molecular and genetic mechanisms implicated in the responses of Lactobacillus reuteri against the oxidative stress induced by malondialdehyde (MDA) by analysing protein oxidation and assessing the uspA and the dhaT genes. Four experimental groups were evaluated depending on the concentration of MDA added in Man, Rogosa and Sharpe (MRS) broth: Control (L. reuteri), 5 µM (L. reuteri + 5 µM MDA), 25 µM (L. reuteri + 25 µM MDA) and 100 µM (L. reuteri + 100 µM MDA). Three replicates were incubated at 37 °C for 24 h in microaerophilic conditions and sampled at 12, 16, 20 and 24 h. The upregulation of the uspA gene by L. reuteri indicates the recognition of MDA as a potential DNA-damaging agent. The dhaT gene, encoding a NADH-dependent-oxidoreductase, was also upregulated at the highest MDA concentrations. This gene was proposed to play a role in the antioxidant response of L. reuteri. The incubation of L. reuteri with MDA increased the production of ROS and caused thiol depletion and protein carbonylation. L. reuteri is proposed to detoxify pro-oxidative species while the underlying mechanism requires further elucidation.