Spatial Learning and Memory Impairment in Growing Mice Induced by Major Oxidized Tyrosine Product Dityrosine

Novel insights into whey protein among Yak, Yellow Cattle, and Cattle-Yak milk

This study identified characteristic whey proteins from Zhongdian Yak (ZY), Diqing Yellow Cattle (DYC), and Cattle Yak (CY), revealing insights into their potential functions and released peptides. A total of 118 whey proteins were quantified in milk obtained from the three breeds of cattle, including seven characteristic proteins (IGL@ protein, 40S ribosomal protein S9, calreticulin, etc.) in CY milk and two characteristic proteins (RNA helicase and uncharacterized protein (A0A3Q1LFQ2)) in ZY milk. These characteristic proteins are involved in the phagosome and Fc gamma R-mediated phagocytosis pathways, exhibiting immunoprotective activities, verified through molecular docking. Furthermore, the molecular docking results showed five whey proteins (IGL@ protein, rho GDP-dissociation inhibitor 1, small monomeric GTPase, action-like protein 3, and adenylyl cyclase-associated protein) interacted with TLR4 through multiple hydrogen and hydrophobic bonds. Therefore, these proteins may exert immunomodulatory functions by inhibiting TLR4. Meanwhile, whey proteins produced bioactive peptides, such as antioxidant peptides and ACE inhibitory peptides after simulated gastrointestinal digestion (SGID). The whey proteins and bioactive peptides from CY exhibited more types and activities than the ZY and DYC whey proteins. This study provides a theoretical basis for promoting formula milk powder production.

Effects of Dityrosine on Lactic Acid Metabolism in Mice Gastrocnemius Muscle During Endurance Exercise via the Oxidative Stress-Induced Mitochondria Damage

Dityrosine (Dityr) has been detected in commercial food as a product of protein oxidation and has been shown to pose a threat to human health. This study aims to investigate whether Dityr causes a decrease in lactic acid metabolism in the gastrocnemius muscle during endurance exercise. C57BL/6 mice were administered Dityr or saline by gavage for 13 weeks and underwent an endurance exercise test on a treadmill. Dityr caused a severe reduction in motion displacement and endurance time, along with a significant increase in lactic acid accumulation in the blood and gastrocnemius muscle in mice after exercise. Dityr induced significant mitochondrial defects in the gastrocnemius muscle of mice. Additionally, Dityr induced serious oxidative stress in the gastrocnemius muscle, accompanied by inflammation, which might be one of the causes of mitochondrial dysfunction. Moreover, significant apoptosis in the gastrocnemius muscle increased after exposure to Dityr. This study confirmed that Dityr induced oxidative stress in the gastrocnemius muscle, which further caused significant mitochondrial damage in the gastrocnemius muscle cell, resulting in decreased capacity of lactic acid metabolism and finally affected performance in endurance exercise. This may be one of the possible mechanisms by which highly oxidized foods cause a decreased muscle energy metabolism.

Dityrosine Aggravates Hepatic Insulin Resistance in Obese Mice by Altering Gut Microbiota and the LPS/TLR4/NF-κB Inflammatory Pathway

SCOPE

Dityrosine is the main product of protein oxidation, which has been proved to be a threat to human health. This study aims to investigate whether dityrosine exacerbates insulin resistance by inducing gut flora disturbance and associated inflammatory responses.

METHODS AND RESULTS

Mice fed with normal diet or high-fat diet (HFD) received daily gavage of dityrosine (320 µg kg-1 BW) or saline for consecutive 13 weeks. The effects of dityrosine on gut microbiota are verified by in vitro fermentation using fecal microbiota from db/m mice and db/db mice. As a result, dityrosine causes the insulin resistance in mice fed normal diet, and aggravates the effects of HFD on insulin sensitivity. Dityrosine increases the levels of lipopolysaccharide (LPS), lipopolysaccharide-binding protein (LBP), toll-like receptor 4 (TLR4), nuclear factor kappa-B (NF-κB), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) but decreases levels of interleukin-10 (IL-10) in the plasma of CON and HFD-fed mice. The changes of gut flora composition caused by dityrosine are significantly correlated with the changes of inflammatory biomarkers.

CONCLUSION

The effects of dityrosine on insulin resistance may be attributed to the reshaping of the gut microbiota composition and promoting the activity of the LPS/TLR4/NF-κB inflammatory pathway in HFD-induced obese individuals.

Potential implications of oxidative modification on dietary protein nutritional value: A review

During food processing and storage, proteins are sensitive to oxidative modification, changing the structural characteristics and functional properties. Recently, the impact of dietary protein oxidation on body health has drawn increasing attention. However, few reviews summarized and highlighted the impact of oxidative modification on the nutritional value of dietary proteins and related mechanisms. Therefore, this review seeks to give an updated discussion of the effects of oxidative modification on the structural characteristics and nutritional value of dietary proteins, and elucidate the interaction with gut microbiota, intestinal tissues, and organs. Additionally, the specific mechanisms related to pathological conditions are also characterized. Dietary protein oxidation during food processing and storage change protein structure, which further influences the in vitro digestion properties of proteins. In vivo research demonstrates that oxidized dietary proteins threaten body health via complicated pathways and affect the intestinal microenvironment via gut microbiota, metabolites, and intestinal morphology. This review highlights the influence of oxidative modification on the nutritional value of dietary proteins based on organs and the intestinal tract, and illustrates the necessity of appropriate experimental design for comprehensively exploring the health consequences of oxidized dietary proteins.

Dityrosine in food: A review of its occurrence, health effects, detection methods, and mitigation strategies

Protein and amino acid oxidation in food products produce many new compounds, of which the reactive and toxic compound dityrosine, derived from oxidized tyrosine, is the most widely studied. The high reactivity of dityrosine enables this compound to induce oxidative stress and disrupt thyroid hormone function, contributing to the pathological processes of several diseases, such as obesity, diabetes, cognitive dysfunction, aging, and age-related diseases. From the perspective of food safety and human health, protein-oxidation products in food are the main concern of consumers, health management departments, and the food industry. This review highlights the latest research on the formation pathways, toxicity, detection methods, occurrence in food, and mitigation strategies for dityrosine. Furthermore, the control of dityrosine in family cooking and food-processing industry has been discussed. Food-derived dityrosine primarily originates from high-protein foods, such as meat and dairy products. Considering its toxicity, combining rapid high sensitivity dityrosine detection techniques with feasible control methods could be an effective strategy to ensure food safety and maintain human health. However, the current dityrosine detection and mitigation strategies exhibit some inherent characteristics and limitations. Therefore, developing technologies for rapid and effective dityrosine detection and control at the industrial level is necessary.

Bifidobacterium breve CCFM1078 Alleviates Collagen-Induced Arthritis in Rats via Modulating the Gut Microbiota and Repairing the Intestinal Barrier Damage

This study focused on the effects of Bifidobacterium breve CCFM1078 on the intestinal barrier and systemic inflammation of collagen-induced arthritis (CIA) rats. Female rats were divided into three groups with daily intragastric administration of either saline (control group and model group) or B. breve CCFM1078 (CCFM1078 group, 3 × 10⁹cfu/rat per day) for 5 weeks. In the Model and CCFM1078 groups, arthritis was induced by subcutaneous collagen injection. We found that B. breve CCFM1078 can repair the intestinal barrier, reduce LPS translocation, regulate gut microbiota composition, and increase short-chain fatty acids in the intestine. Then, it can reduce pro-inflammatory cytokines release, adjust immune dysfunction, and inhibit TLR4-MyD88-dependent pathways and downstream inflammatory pathways to alleviate joint inflammation in CIA rats. These findings suggest that B. breve CCFM1078 may alleviate joint inflammation by adjusting the profile of gut microbiota and enhancing the intestinal barrier.

Microbiota-assisted therapy for systemic inflammatory arthritis: advances and mechanistic insights

Research on the influence of gut microbiota on systemic inflammatory arthritis has exploded in the past decade. Gut microbiota changes may be a crucial regulatory component in systemic inflammatory arthritis. As a result of advancements in the field, microbiota-assisted therapy has evolved, but this discipline is still in its infancy. Consequently, we review the limitations of current systemic inflammatory arthritis treatment, analyze the connection between the microbiota and arthritis, and summarize the research progress of microbiota regulating systemic inflammatory arthritis and the further development aspects of microbiota-assisted therapy. Finally, the partial mechanisms of microbiota-assisted therapy of systemic inflammatory arthritis are being discussed. In general, this review summarizes the current progress, challenges, and prospects of microbiota-assisted therapy for systemic inflammatory arthritis and points out the direction for the development of microbiota-assisted therapy in the future.

Effects of oxidized rice bran protein induced by rancidity on the hepatic function in mice

Rice bran protein (RBP) is a great resource of premium protein. However, rice bran (RB) rancidity, which inevitably occurs during rice milling, can induce RBP oxidation, further affecting the nutritional value of RBP. This study focused on the impact of RBP rancidity on the nutritional value of oxidized RBP. RBP with varying oxidation degrees and doses was given to mice via a 12-week intragastric administration. Oxidized RBP interfered with hepatic function and inflammation, and decreased the antioxidant capacities of the liver. Oxidized RBP also disturbed the hepatic lipid metabolism, and excessively oxidized RBP caused intrahepatic lipid accumulation and hepatic damage. Furthermore, oxidized RBP triggered the MyD88/NF-κB pathway but inhibited the Keap1-Nrf2/ARE pathway in the liver. Correlation analysis revealed that the protein expression of the Nrf2 pathway was negatively correlated with the NF-κB pathway. Results implied that oxidized RBP induced hepatic damage and hepatic dysfunction, indicating the deteriorating nutrition of oxidized RBP. The results exhibited the nutritional value of RBP after oxidative modification, and implied the importance of optimizing food-processing strategies to reduce the degree of protein oxidation, thereby avoiding the nutritional loss of dietary protein.

Lycopene Regulates Dietary Dityrosine-Induced Mitochondrial-Lipid Homeostasis by Increasing Mitochondrial Complex Activity

SCOPE

Dityrosine (DT), a marker of protein oxidation, is widely found in many high-protein foods. Dietary intake of DT induces myocardial oxidative stress injury and impairs energy metabolism. Lycopene is a common dietary supplement with antioxidant and mitochondrial-lipid homeostasis modulating abilities. This study aimed to examine the effects of lycopene on DT-induced disturbances in myocardial function and energy metabolism.

METHODS AND RESULTS

Four-week-old C57BL/6J mice received intragastric administration of either tyrosine (420 µg kg^-1 BW), DT (420 µg kg^-1 BW), or lycopene at high (10 mg kg^-1 BW) and low (5 mg kg^-1 BW) doses for 35 days. Lycopene administration effectively reduced oxidative stress, cardiac fatty acid accumulation, and cardiac hypertrophy and improved mitochondrial performance in DT-induced mice. In vitro experiments in H9c2 cells showed that DT directly inhibited the activity of the respiratory chain complex, whereas oxidative phosphorylation and β-oxidation gene expression is upregulated. Lycopene enhanced the activity of the complexes and inhibited ROS production caused by compensatory regulation.

CONCLUSION

Lycopene improves DT-mediated myocardial energy homeostasis disorder by promoting the activity of respiratory chain complexes I and IV and alleviates the accumulation of cardiac fatty acids and myocardial hypertrophy.

Oxidized Milk Induces Spatial Learning and Memory Impairment by Altering Gut Microbiota in Offspring Mice during Pregnancy and Lactation

Early adverse diet exposures are known to be associated with increased risk of learning and memory injury in offspring, yet whether oxidized milk is involved in such an effect has been largely unknown. Here, we focused on oxidized milk intake in mice during pregnancy and lactation to measure the changes in the learning and memory ability in offspring and also probed into the relevant association with gut microbiota. Milk was oxidized with H₂O₂-Cu or HClO, resulting in different degrees of oxidative damage. KM female mice were fed H₂O₂-Cu, HClO, or normal control diets immediately after caging until their offspring were 3-weeks old. Behavioral tests were then performed to test the learning and memory ability, and 16S rRNA sequencing was completed with harvested fecal contents. As analyzed, fecal microflora in mice with oxidized milk was affected, mainly reflected in decreased mucin-degrading bacteria, Akkermansia and Lactobacillus, and in reversely increased pro-inflammatory bacteria Shigella, pathobiont Mucispirillum, nervous associated bacteria Ruminococcus, Escherichia, and Desulfovibrio. In the meantime, the inflammation developed in mice was aggravated accompanied by increased expression of relevant genes, while the genes and proteins associated with the learning and memory ability were down-regulated. Further behavioral tests proved impairment of the learning and memory ability in offspring. In general, milk of oxidative damage is a risk factor of the impaired transgenerational ability in learning and memory, which is associated with gut microbiota and intestinal mucosa conditions. This finding may help support the potential of early adverse diet as a harmful factor in learning and memory.

Dietary Dityrosine Induces Mitochondrial Dysfunction by Diminished Thyroid Hormone Function in Mouse Myocardia

Oxidized tyrosine products (OTP) have been detected in commercial foods with high protein content, such as meat and milk products. OTP intake induces tissue oxidative stress and affects the normal activity of the hypothalamic-pituitary-thyroid axis (HPT). This study aims to investigate the effects of OTP and their main product, dityrosine (Dityr), on mouse myocardial function and myocardial energy metabolism. Mice received daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), Dityr (420 μg/kg body weight), or OTP (1909 μg/kg body weight) for 35 days. Additionally, H9c2 cells were incubated with various concentrations of Dityr for 72 h. We found that OTP and pure Dityr induced oxidative stress in growing mice and in H9c2 cells, resulting in a redox state imbalance, myocardial injury, mitochondrial dysfunction, and energy metabolism disorder. Dityr interferes with T3 regulation of the myocardium via the PI3K/AKT/GSK3β pathway, leading to myocardial mitochondrial damage and energy metabolism disorders. Food-borne OTP, especially Dityr, can disrupt thyroid hormone function in mouse myocardia leading to mitochondrial dysfunction, energy metabolism disorder, and oxidative stress.

Noxious effects of selected food-occurring oxidized amino acids on differentiated CACO-2 intestinal human cells

The harmful effects of food-occurring oxidized amino acids, namely, aminoadipic acid (AAA), dityrosine (DTYR), L-kynurenine (KN), kynurenic acid (KA) and 3-nitrotyrosine (3NT), were studied on differentiated CACO-2 cells by flow cytometry and quantification of glutathione (GSH), and allysine. Cells were exposed to food-relevant doses (200 μM) of each compound for 4 or 72h and compared to a control (no stimulated cells). All oxidized amino acids induced apoptosis and results indicated that underlying mechanisms depended on the chemical nature of the species. AAA, KN and KA caused ROS generation and severe oxidative stress in 96%, 98% and 89% of exposed cells (77% in control cells), leading to significant GSH depletion and allysine accretion (1.5, 1.5 and 1.6 nmol allysine/mg protein, respectively at 4h; control: 0.22 nmol/mg protein; p < 0.05). DTYR and 3NT induced significant apoptosis to 29% and 25% of cells (control: 16%; p < 0.05) and necrosis to 28% and 26% of cells (control: 23%) at 72h by ROS-independent mechanisms. KN and KA were found to induce a cycle arrest effect on CACO-2 cells. These findings emphasize the potential harmful effects of the intake of oxidized proteins and amino acids and urge the necessity of carrying out further molecular studies.

Dityrosine suppresses the cytoprotective action of thyroid hormone T3 via inhibiting thyroid hormone receptor-mediated transcriptional activation

Dityrosine (Dityr) is the most common oxidized form of tyrosine. In the previous studies of mice treated with dityrosine, cell death in the pancreas, kidneys, and liver was detected in the presence of enhanced plasma triiodothyronine (T3) content. Due to its structural similarity with the thyroid hormone T3, we hypothesized that dityrosine might disrupt T3-dependent endocrine signaling. The cytotoxic effect of dityrosine was studied in C57BL/6 mice by gavage with a dityrosine dose of 320 μg per kg per day for 10 weeks. Cell death in the liver was detected in the presence of enhanced plasma thyroid hormone content in mice treated with dityrosine. The antagonistic effect of dityrosine on T3 biofunction was studied using HepG2 cells. Dityrosine incubation reduced T3 transport ability and attenuated the T3-mediated cell survival via regulation of the PI3k/Akt/MAPK pathway. Furthermore, dityrosine inhibited T3 binding to thyroid hormone receptors (TRs) and suppressed the TR-mediated transcription. Dityrosine also downregulated the expressions of T3 action-related factors. Taken together, this study demonstrates that dityrosine inhibits T3-dependent cytoprotection by competitive inhibition, resulting in downstream gene suppression. Our findings offer insights into how dityrosine acts as an antagonist of T3. These findings shed new light on cellular processes underlying the energy metabolism disorder caused by dietary oxidized protein, thus contributing to a better understanding of the diet-health axis at a cellular level.

Oxidative-Antioxidant Imbalance and Impaired Glucose Metabolism in Schizophrenia

Schizophrenia is a neurodevelopmental disorder featuring chronic, complex neuropsychiatric features. The etiology and pathogenesis of schizophrenia are not fully understood. Oxidative-antioxidant imbalance is a potential determinant of schizophrenia. Oxidative, nitrosative, or sulfuric damage to enzymes of glycolysis and tricarboxylic acid cycle, as well as calcium transport and ATP biosynthesis might cause impaired bioenergetics function in the brain. This could explain the initial symptoms, such as the first psychotic episode and mild cognitive impairment. Another concept of the etiopathogenesis of schizophrenia is associated with impaired glucose metabolism and insulin resistance with the activation of the mTOR mitochondrial pathway, which may contribute to impaired neuronal development. Consequently, cognitive processes requiring ATP are compromised and dysfunctions in synaptic transmission lead to neuronal death, preceding changes in key brain areas. This review summarizes the role and mutual interactions of oxidative damage and impaired glucose metabolism as key factors affecting metabolic complications in schizophrenia. These observations may be a premise for novel potential therapeutic targets that will delay not only the onset of first symptoms but also the progression of schizophrenia and its complications.