Dietary oxidized tyrosine (O-Tyr) stimulates TGF-β1-induced extracellular matrix production via the JNK/p38 signaling pathway in rat kidneys

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.

Lycium barbarum Oligosaccharides Alleviate Hepatic Steatosis by Modulating Gut Microbiota in C57BL/6J Mice Fed a High-Fat Diet

High-fat diets (HFD) can promote the development of hepatic steatosis by altering the structure and composition of gut flora. In this study, the potential therapeutic mechanism of Lycium barbarum oligosaccharide (LBO) against hepatic steatosis was investigated by analyzing the changes in the intestinal flora and metabolites in mice. Mice on an HFD were administered LBO by gavage once daily for a continuous period of eight weeks. Compared with the HFD group, the levels of triglyceride (TG), alanine aminotransferase (ALT) in the serum, and hepatic TG were significantly reduced in the LBO group, and liver lipid accumulation was obviously improved. In addition, LBO could regulate the HFD-induced alteration of intestinal flora. The HFD increased the proportion of Barnesiellaceae, Barnesiella, and CHKCI001. LBO increased the proportion of Dubosiella, Eubacterium, and Lactobacillus. LBO also altered the fecal metabolic profile. Significantly different metabolites between LBO and the HFD, such as taurochenodeoxycholate, taurocholate, fluvastatin, and kynurenic acid, were related to the cholesterol metabolism, bile acid metabolism, and tryptophan metabolic pathways. In light of the above, LBO can alleviate HFD-induced NAFLD by modulating the components of the intestinal flora and fecal metabolites.

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.

Signaling Pathways Related to Oxidative Stress in Diabetic Cardiomyopathy

Diabetes is a chronic metabolic disease that is increasing in prevalence and causes many complications. Diabetic cardiomyopathy (DCM) is a complication of diabetes that is associated with high mortality, but it is not well defined. Nevertheless, it is generally accepted that DCM refers to a clinical disease that occurs in patients with diabetes and involves ventricular dysfunction, in the absence of other cardiovascular diseases, such as coronary atherosclerotic heart disease, hypertension, or valvular heart disease. However, it is currently uncertain whether the pathogenesis of DCM is directly attributable to metabolic dysfunction or secondary to diabetic microangiopathy. Oxidative stress (OS) is considered to be a key component of its pathogenesis. The production of reactive oxygen species (ROS) in cardiomyocytes is a vicious circle, resulting in further production of ROS, mitochondrial DNA damage, lipid peroxidation, and the post-translational modification of proteins, as well as inflammation, cardiac hypertrophy and fibrosis, ultimately leading to cell death and cardiac dysfunction. ROS have been shown to affect various signaling pathways involved in the development of DCM. For instance, OS causes metabolic disorders by affecting the regulation of PPARα, AMPK/mTOR, and SIRT3/FOXO3a. Furthermore, OS participates in inflammation mediated by the NF-κB pathway, NLRP3 inflammasome, and the TLR4 pathway. OS also promotes TGF-β-, Rho-ROCK-, and Notch-mediated cardiac remodeling, and is involved in the regulation of calcium homeostasis, which impairs ATP production and causes ROS overproduction. In this review, we summarize the signaling pathways that link OS to DCM, with the intention of identifying appropriate targets and new antioxidant therapies for DCM.

Chemical Stability of Proteins in Foods: Oxidation and the Maillard Reaction

Protein is a major nutrient present in foods along with carbohydrates and lipids. Food proteins undergo a wide range of modifications during food production, processing, and storage. In this review, we discuss two major reactions, oxidation and the Maillard reaction, involved in chemical modifications of food proteins. Protein oxidation in foods is initiated by metal-, enzyme-, or light-induced processes. Food protein oxidation results in the loss of thiol groups and the formation of protein carbonyls and specific oxidation products of cysteine, tyrosine, tryptophan, phenylalanine, and methionine residues, such as disulfides, dityrosine, kynurenine, m-tyrosine, and methionine sulfoxide. The Maillard reaction involves the reaction of nucleophilic amino acid residues with reducing sugars, which yields numerous heterogeneous compounds such as α-dicarbonyls, furans, Strecker aldehydes, advanced glycation end-products, and melanoidins. Both protein oxidation and the Maillard reaction result in the loss of essential amino acids but may positively or negatively impact food structure and flavor. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Oxidative Crosslinking of Peptides and Proteins: Mechanisms of Formation, Detection, Characterization and Quantification

Covalent crosslinks within or between proteins play a key role in determining the structure and function of proteins. Some of these are formed intentionally by either enzymatic or molecular reactions and are critical to normal physiological function. Others are generated as a consequence of exposure to oxidants (radicals, excited states or two-electron species) and other endogenous or external stimuli, or as a result of the actions of a number of enzymes (e.g., oxidases and peroxidases). Increasing evidence indicates that the accumulation of unwanted crosslinks, as is seen in ageing and multiple pathologies, has adverse effects on biological function. In this article, we review the spectrum of crosslinks, both reducible and non-reducible, currently known to be formed on proteins; the mechanisms of their formation; and experimental approaches to the detection, identification and characterization of these species.

Oxidized Pork Induces Hepatic Steatosis by Impairing Thyroid Hormone Function in Mice

SCOPE

Recent studies have linked high consumption of red and processed meats to an increased risk of non-alcoholic fatty liver disease, and cooking-induced oxidation of proteins and amino acids might be contributing factors. Herein, this study investigates the influence of oxidized pork and the protein oxidation biomarker dityrosine (Dityr) on hepatic steatosis in mice.

METHODS AND RESULTS

Low- and high-oxidative injury pork (LOP and HOP) are freeze-dried to prepare mouse diets. Mice are fed a diet of either the control, LOP, HOP, LOP+Dityr, or Dityr for 12 weeks. HOP and Dityr intake induced oxidative stress and inflammation that impaired thyroid function and peripheral metabolism (reduced type 1 deiodinase activity) of thyroid hormones (THs). These lead to a decrease in the circulating as well as liver THs and induced hepatic steatosis. This process might be regulated through reduced TH levels and altered TH target genes and proteins related to hepatic lipid metabolism that ultimately inhibited hepatic energy metabolism, as indicated by increased hepatic lipid synthesis, decreased hepatic lipid catabolism, and fatty acid oxidation.

CONCLUSION

HOP intake could induce hepatic steatosis by impairing TH function. Dityr plays an important role in the HOP-induced harmful effects.

Point mutations in Candida glabrata 3-hydroxy-3-methylglutaryl-coenzyme A reductase (CgHMGR) decrease enzymatic activity and substrate/inhibitor affinity

3-Hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) is a crucial enzyme in the ergosterol biosynthesis pathway. The aim of this study was to obtain, purify, characterize, and overexpress five point mutations in highly conserved regions of the catalytic domain of Candida glabrata HMGR (CgHMGR) to explore the function of key amino acid residues in enzymatic activity. Glutamic acid (Glu) was substituted by glutamine in the E680Q mutant (at the dimerization site), Glu by glutamine in E711Q (at the substrate binding site), aspartic acid by alanine in D805A, and methionine by arginine in M807R (the latter two at the cofactor binding site). A double mutation, E680Q-M807R, was included. Regarding recombinant and wild-type CgHMGR, in vitro enzymatic activity was significantly lower for the former, as was the in silico binding energy of simvastatin, alpha-asarone and the HMG-CoA substrate. E711Q displayed the lowest enzymatic activity and binding energy, suggesting the importance of Glu711 (in the substrate binding site). The double mutant CgHMGR E680Q-M807R exhibited the second lowest enzymatic activity. Based on the values of the kinetic parameters KM and Vmax, the mutated amino acids appear to participate in binding. The current findings provide insights into the role of residues in the catalytic site of CgHMGR.

Adverse Effects of Thermal Food Processing on the Structural, Nutritional, and Biological Properties of Proteins

Thermal processing is one of the most important processing methods in the food industry. However, many studies have revealed that thermal processing can have detrimental effects on the nutritional and functional properties of foods because of the complex interactions among food components. Proteins are essential nutrients for humans, and changes in the structure and nutritional properties of proteins can substantially impact the biological effects of foods. This review focuses on the interactions among proteins, sugars, and lipids during thermal food processing and the effects of these interactions on the structure, nutritional value, and biological effects of proteins. In particular, the negative effects of modified proteins on human health and strategies for mitigating these detrimental effects from two perspectives, namely, reducing the formation of modified proteins during thermal processing and dietary intervention in vivo, are discussed.

Apremilast interferes with the TGFβ1-induced transition of human skin fibroblasts into profibrotic myofibroblasts: in vitro study

OBJECTIVES

Fibroblast-to-myofibroblast transition and extracellular matrix overproduction represent progressive events in chronic inflammatory and fibrotic diseases, in which TGFβ1 is one of the key mediators. Phosphodiesterase 4 (PDE4) acts as a proinflammatory enzyme through the degradation of cyclic adenosine monophosphate and it is overexpressed in skin fibroblasts. The study investigated how apremilast (a PDE4 inhibitor) interferes with the intracellular signalling pathways responsible for the TGFβ1-induced fibroblast-to-myofibroblast transition and profibrotic extracellular matrix protein synthesis.

METHODS

Cultured human skin fibroblasts were stimulated with TGFβ1 (10 ng/ml) alone or combined with apremilast (1 and 10 μM) for 4, 16 and 24 h. Other aliquots of the same cells were previously stimulated with TGFβ1 and then treated with apremilast (1 and 10 μM) for 4, 16 and 24 h, always under stimulation with TGFβ1. Gene and protein expression of αSMA, type I collagen (COL1) and fibronectin were evaluated, together with the activation of small mothers against decapentaplegic 2 and 3 (Smad2/3) and extracellular signal-regulated kinase (Erk1/2) proteins.

RESULTS

Apremilast reduced the TGFβ1-induced increase in αSMA, COL1 and fibronectin gene expression at 4 and 16 h, and protein synthesis at 24 h of treatment in cultured fibroblasts, even for cells already differentiated into myofibroblasts by way of a previous stimulation with TGFβ1. Apremilast inhibited the TGFβ1-induced Smad2/3 and Erk1/2 phosphorylation at 15 and 30 min.

CONCLUSION

Apremilast seems to inhibit in vitro the fibroblast-to-myofibroblast transition and the profibrotic activity induced by TGFβ1 in cultured human skin fibroblasts by downregulating Smad2/3 and Erk1/2 intracellular signalling pathways.

Analysis of Protein Oxidation in Food and Feed Products

Food and feed proteins are subject to oxidation reactions during production, processing, and storage. Several individual oxidized amino acids have been described in model systems and food; however, protein oxidation in food is still mostly assessed by the analysis of protein carbonylation. In the present review, the chemistry of protein oxidation and its implications for protein functionality, food flavor, and nutritional physiology are briefly summarized. Limitations of generic methods targeting redox-relevant functional groups and properties of typical reaction products, such as the determination of protein carbonyls and fluorescence spectroscopy, are presented. Methods for the quantitation of individual oxidation products of susceptible amino acids, such as cysteine, methionine, phenylalanine, tyrosine, and tryptophan, are reported. Special regard is paid to limitations resulting from the required hydrolysis procedures and unintended formation of the analytes during sample pretreatment. If available, results from food analysis obtained by different methods are compared. Suggestions and requirements for future works on protein oxidation in food and nutrition are given.

Alogliptin attenuates cyclophosphamide-induced nephrotoxicity: a novel therapeutic approach through modulating MAP3K/JNK/SMAD3 signaling cascade

Cyclophosphamide (CP) is widely used as a chemotherapy against various types of cancers. However, CP is accompanied with multiple organ toxicity due to production of reactive oxygen species (ROS), induction of inflammation and consequently apoptosis. Alogliptin (Alo) is a dipeptidyl peptidase 4 (DPP-IV) inhibitor, which is booming as an antidiabetic agent. Interestingly, gliptins are currently studied for their counter-regulatory effects against oxidative stress and inflammation via multiple pathways, among which is the mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinase (JNK) pathway. This cascade can reduce inflammation via mitigating the activity of mothers against decapentaplegic homolog 3 (SMAD3) and c-Jun. However, Alo effect against CP-induced kidney injury has not been previously elucidated. This tempted us to investigate the possible beneficial effect of Alo against CP-induced kidney injury via modulating the MAP3K/JNK/SMAD3 signaling cascade. Thirty-two male Wistar rats were randomly allocated into four groups. CP-treated group received a single dose of CP (200 mg/kg; i.p.). Alo-treated group received Alo (20 mg/kg/day; p.o.) for 7 days with single CP injection on day 2. Marked decrease in renal injury was observed upon Alo treatment, as evidenced through declined serum kidney function markers, oxidative stress and apoptosis markers, MAP3K expression, phospho (p)-SMAD3, p-JNK, and p-c-Jun levels. These cellular effects were reflected in reduced transforming growth factor beta (TGF-β) and tumor necrosis factor alpha (TNF-α) fibrotic and inflammatory mediators, coinciding with improved histopathological portrait. In conclusion, the current study provides novel application of Alo as a therapeutic modality against CP-induced nephrotoxicity.

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.

Whey proteins: targets of oxidation, or mediators of redox protection

Bovine whey proteins are highly valued dairy ingredients. This is primarily due to their amino acid content, digestibility, bioactivities and their processing characteristics. One of the reported bioactivities of whey proteins is antioxidant activity. Numerous dietary intervention trials with humans and animals indicate that consumption of whey products can modulate redox biomarkers to reduce oxidative stress. This bioactivity has in part been assigned to whey peptides using a range of biochemical or cellular assays in vitro. Superimposing whey peptide sequences from gastrointestinal samples, with whey peptides proven to be antioxidant in vitro, allows us to propose peptides from whey likely to exhibit antioxidant activity in the diet. However, whey proteins themselves are targets of oxidation during processing particularly when exposed to high thermal loads and/or extensive processing (e.g. infant formula manufacture). Oxidative damage of whey proteins can be selective with regard to the residues that are modified and are associated with the degree of protein unfolding, with α-Lactalbumin more susceptible than β-Lactoglobulin. Such oxidative damage may have adverse effects on human health. This review summarises how whey proteins can modulate cellular redox pathways and conversely how whey proteins can be oxidised during processing. Given the extensive processing steps that whey proteins are often subjected to, we conclude that oxidation during processing is likely to compromise the positive health attributes associated with whey proteins.

Protein Oxidation and In Vitro Gastric Digestion of Processed Soy-Based Matrices

Process conditions that are applied to make structured soy-protein-based food commonly include high temperatures. Those conditions can induce protein oxidation, leading to a decrease in their susceptibility to proteolysis by digestive enzymes. We aimed to investigate the effects of thermomechanical processing on oxidation and in vitro gastric digestion of commercial soy protein ingredients. Samples were sheared at 100 to 140 °C and characterized for acid uptake, carbonyl content, electrophoresis, and surface hydrophobicity. The enzymatic hydrolysis was determined in simulated gastric conditions. Protein ingredients were already oxidized and showed higher surface hydrophobicity and hydrolysis rate compared with those of the processed matrices. However, no clear correlation between the level of carbonyls and the hydrolysis rate was found. Therefore, we conclude that gastric digestion is mostly driven by the matrix structure and composition and the available contact area between the substrate and proteolytic enzymes.

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

This study focused on the effects of oxidized tyrosine products (OTPs) and major component dityrosine (DT) on the brain and behavior of growing mice. Male and female mice were treated with daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), DT (420 μg/kg body weight), or OTPs (1909 μg/kg body weight) for 35 days. We found that pure DT and OTPs caused redox state imbalance, elevated levels of inflammatory factors, hippocampal oxidative damage, and neurotransmitter disorders while activating the mitochondrial apoptosis pathway in the hippocampus and downregulating the genes associated with learning and memory. These events eventually led to growing mice learning and memory impairment, lagging responses, and anxiety-like behaviors. Furthermore, the male mice exhibited slightly more oxidative damage than the females. These findings imply that contemporary diets and food-processing strategies of the modern world should be modified to reduce oxidized protein intake.

The role of high fat diet in the regulation of MAP kinases activity in left ventricular fibrosis

It is well known that obesity contributes to the development of systemic inflammatory responses, which in turn may be involved in the process of interstitial fibrosis and left ventricular (LV) remodelling. Activation of pro-inflammatory factors such as transforming growth factor β (TGF-β) can directly stimulate mitogen-activated protein kinase (MAPK) p38 and JNK. The aim of the study was to evaluate the level of TGF-β and MAPK p38 and JNK in the LV in Sprague Dawley (SPRD) rats maintained on a high fat diet (HFD). The SPRD rats from 4 weeks of age were on a normal fat diet (NFD) or a HFD for 12 weeks (NFD-16-week-old rats, NFD 16-wk; or HFD-16-week-old rats, HFD 16-wk) or 16 weeks (NFD-20-week-old rats, NFD 20-wk; or HFD-20-week-old rats, HFD 20-wk). At the end of the experiment, blood and LV were collected from all rats for further analysis (biochemical, Real Time PCR and immunohistochemical analysis). TGF-β mRNA expression did not differ between the study groups of rats. However, p38 MAPK mRNA expression was significantly lower in the HFD 20-wk rats than in both the HFD 16-wk rats and the NFD 20-wk rats. c-jun mRNA expression was significantly higher in the HFD 16-wk rats than in the NFD 16-wk rats. There was significantly lower expression of c-jun mRNA in the HFD 20-wk rats and in the NFD 20-wk rats than in the HFD 16-wk rats and in the NFD 16-wk rats, respectively. TGF-β type II receptor (TβRII) protein demonstrated only cytoplasmic reactivity, while p38 MAPK protein and c-jun protein showed both nuclear and cytoplasmic reactivity. The results suggest that a high fat diet and in two time intervals significantly influence the expression of p38 MAPK and JNK in the LV. However, demonstrating their potential involvement in the processes of interstitial myocardial fibrosis and left ventricular remodeling requires further research.

Aggregation of α- and β- caseins induced by peroxyl radicals involves secondary reactions of carbonyl compounds as well as di-tyrosine and di-tryptophan formation

The present work examined the role of Tyr and Trp in oxidative modifications of caseins, the most abundant milk proteins, induced by peroxyl radicals (ROO^•). We hypothesized that the selectivity of ROO^• and the high flexibility of caseins (implying a high exposure of Tyr and Trp residues) would favor radical-radical reactions, and di-tyrosine (di-Tyr) and di-tryptophan (di-Trp) formation. Solutions of α- and β-caseins were exposed to ROO^• from thermolysis and photolysis of AAPH (2,2'-azobis(2-methylpropionamidine)dihydrochloride). Oxidative modifications were examined using electrophoresis, western blotting, fluorescence, and chromatographic methodologies with diode array, fluorescence and mass detection. Exposure of caseins to AAPH at 37 °C gave fragmentation, cross-linking and protein aggregation. Amino acid analysis showed consumption of Trp, Tyr, Met, His and Lys residues. Quantification of Trp and Tyr products, showed low levels of di-Tyr and di-Trp, together with an accumulation of carbonyls indicating that casein aggregation is, at least partly, associated with secondary reactions between carbonyls and Lys and His residues. AAPH photolysis, which generates a high flux of free radicals increased the extent of formation of di-Tyr in both model peptides and α- and β- caseins; di-Trp was only detected in peptides and α-casein. Thus, in spite of the high flexibility of caseins, which would be expected to favor radical-radical reactions, the low flux of ROO^• generated during AAPH thermolysis disfavours the formation of dimeric radical-radical cross-links such as di-Tyr and di-Trp, instead favoring other O₂-dependent crosslinking pathways such as those involving secondary reactions of initial carbonyl products.

Dietary methionine restriction regulated energy and protein homeostasis by improving thyroid function in high fat diet mice

Methionine-restricted diets (MRD) show an integrated series of beneficial health effects, including improving insulin sensitivity, limiting fat deposition, and decreasing oxidative stress, and inflammation responses. We aimed to explore the systemic responses to a MRD in mice fed with a high fat (HFD) and clarify the possible mechanism. Mice were fed with a control diet (0.86% methionine + 4% fat, CON), HFD (0.86% methionine + 20% fat), or MRD (0.17% methionine + 20% fat) for 22 consecutive weeks. HFD-fed mice showed widespread systemic metabolic disorders and thyroid dysfunction. A MRD significantly increased energy expenditure (e.g. fatty acid oxidation, glycolysis, and tricarboxylic acid cycle metabolism), regulated protein homeostasis, improved gut microbiota functions, prevented thyroid dysfunction, increased plasma thyroxine and triiodothyronine levels, decreased plasma thyroid stimulating hormone levels, increased type 2 deiodinase (DIO2) activity, and up-regulated mRNA and protein expression levels of DIO2 and thyroid hormone receptor α1 in the skeletal muscle. These results suggest that a MRD can improve the metabolic disorders induced by a HFD, and especially regulate energy and protein homeostasis likely through improved thyroid function. Thus, reducing methionine intake (e.g. through a vegan diet) may improve metabolic health in animals and humans.

New insights into TGF-β/Smad signaling in tissue fibrosis

Transforming growth factor-β1 (TGF-β1) is considered as a crucial mediator in tissue fibrosis and causes tissue scarring largely by activating its downstream small mother against decapentaplegic (Smad) signaling. Different TGF-β signalings play different roles in fibrogenesis. TGF-β1 directly activates Smad signaling which triggers pro-fibrotic gene overexpression. Excessive studies have demonstrated that dysregulation of TGF-β1/Smad pathway was an important pathogenic mechanism in tissue fibrosis. Smad2 and Smad3 are the two major downstream regulator that promote TGF-β1-mediated tissue fibrosis, while Smad7 serves as a negative feedback regulator of TGF-β1/Smad pathway thereby protects against TGF-β1-mediated fibrosis. This review presents an overview of the molecular mechanisms of TGF-β/Smad signaling pathway in renal, hepatic, pulmonary and cardiac fibrosis, followed by an in-depth discussion of their molecular mechanisms of intervention effects both in vitro and in vivo. The role of TGF-β/Smad signaling pathway in tumor or cancer is also discussed. Additionally, the current advances also highlight targeting TGF-β/Smad signaling pathway for the prevention of tissue fibrosis. The review reveals comprehensive pathophysiological mechanisms of tissue fibrosis. Particular challenges are presented and placed within the context of future applications against tissue fibrosis.

LncRNAs: Proverbial Genomic "Junk" or Key Epigenetic Regulators During Cardiac Fibrosis in Diabetes?

Long non-coding RNAs (lncRNAs) are critical regulators in a multitude of biological processes. Recent evidences demonstrate potential pathogenetic implications of lncRNAs in diabetic cardiomyopathy (DCM); however, the majority of lncRNAs have not been comprehensively characterized. While the precise molecular mechanisms underlying the functions of lncRNAs remain to be deciphered in DCM, emerging data in other pathophysiological conditions suggests that lncRNAs can have versatile features such as genomic imprinting, acting as guides for certain histone-modifying complexes, serving as scaffolds for specific molecules, or acting as molecular sponges. In an effort to better understand these features of lncRNAs in the context of DCM, our review will first summarize some of the key molecular alterations that occur during fibrosis in the diabetic heart (extracellular proteins and endothelial-to-mesenchymal transitioning), followed by a review of the current knowledge on the crosstalk between lncRNAs and major epigenetic mechanisms (histone methylation, histone acetylation, DNA methylation, and microRNAs) within this fibrotic process.

Health Effects of Dietary Oxidized Tyrosine and Dityrosine Administration in Mice with Nutrimetabolomic Strategies

This study aims to investigate the health effects of long-term dietary oxidized tyrosine (O-Tyr) and its main product (dityrosine) administration on mice metabolism. Mice received daily intragastric administration of either O-Tyr (320 μg/kg body weight), dityrosine (Dityr, 320 μg/kg body weight), or saline for consecutive 6 weeks. Urine and plasma samples were analyzed by NMR-based metabolomics strategies. Body weight, clinical chemistry, oxidative damage indexes, and histopathological data were obtained as complementary information. O-Tyr and Dityr exposure changed many systemic metabolic processes, including reduced choline bioavailability, led to fat accumulation in liver, induced hepatic injury, and renal dysfunction, resulted in changes in gut microbiota functions, elevated risk factor for cardiovascular disease, altered amino acid metabolism, induced oxidative stress responses, and inhibited energy metabolism. These findings implied that it is absolutely essential to reduce the generation of oxidation protein products in food system through improving modern food processing methods.

Effects of dietary oxidized tyrosine products on insulin secretion via the thyroid hormone T3-regulated TRβ1–Akt–mTOR pathway in the pancreas

Oxidized tyrosine products (OTPs) have been detected in commercial foods with high protein content.

Metabolomic studies on the systemic responses of mice with oxidative stress induced by short-term oxidized tyrosine administration

Oxidized tyrosine (O-Tyr) has attracted more interest in recent years because many researchers have discovered that it and its product (dityrosine) are associated with pathological conditions, especially various age-related disorders in biological systems.