Carnosine protects cardiac myocytes against lipid peroxidation products

Simultaneous Analysis of Imidazole Dipeptides, Constituent Amino Acids, and Taurine in Meats Using the Highly Sensitive Labeling Reagent l-FDVDA and PBr Column

Imidazole dipeptides (IDPs) are found in the skeletal muscles and brains of various animals, and they exhibit unique functions like antioxidant and antiaging properties. Despite their importance, the metabolic mechanisms and physiological roles of IDPs remain unclear. Herein, we propose a method for the simultaneous analysis of IDPs, their constituent amino acids, and taurine, which are difficult to separate using conventional labeling reagents or columns, using liquid chromatography-single quadrupole mass spectrometry with PBr column and our highly sensitive labeling reagent, 1-fluoro-2,4-dinitrophenyl-5-l-valine-N,N-dimethylethylenediamineamide (l-FDVDA). This method successfully separated histidine and carnosine enantiomers as well as l-2-oxocarnosine with high antioxidant activity under the same conditions. Our labeling reagent was more stable than the other reagents and did not degrade and desorb from the analytes for at least 1 week at 4 °C. Furthermore, our method allows for the accurate analysis of IDPs, amino acids, and taurine in meats from various animal species, tissues, and breeds.

Histidine containing dipeptides protect epithelial and endothelial cell barriers from methylglyoxal induced injury

Integrity of epithelial and endothelial cell barriers is of critical importance for health, barrier disruption is a hallmark of numerous diseases, of which many are driven by carbonyl stressors such as methylglyoxal (MG). Carnosine and anserine exert some MG-quenching activity, but the impact of these and of other histidine containing dipeptides on cell barrier integrity has not been explored in detail. In human proximal tubular (HK-2) and umbilical vein endothelial (HUVEC) cells, exposure to 200 µM MG decreased transepithelial resistance (TER), i.e. increased ionic permeability and permeability for 4-, 10- and 70-kDa dextran, membrane zonula occludens (ZO-1) abundance was reduced, methylglyoxal 5-hydro-5-methylimidazolones (MG-H1) formation was increased. Carnosine, balenine (ß-ala-1methyl-histidine) and anserine (ß-ala-3-methyl-histidine) ameliorated MG-induced reduction of TER in both cell types. Incubation with histidine, 1-/3-methylhistidine, but not with ß-alanine alone, restored TER, although to a lower extent than the corresponding dipeptides. Carnosine and anserine normalized transport and membrane ZO-1 abundance. Aminoguanidine, a well-described MG-quencher, did not mitigate MG-induced loss of TER. Our results show that the effects of the dipeptides on epithelial and endothelial resistance and junction function depend on the methylation status of histidine and are not exclusively explained by their quenching activity.

Exploring Secondary Amine Carnosine Derivatives: Design, Synthesis, and Properties

Carnosine is a naturally occurring dipeptide that has been advocated by some authors as an interesting scaffold for the development of potential therapeutic agents in view of the positive outcomes of its supplementation in animal models of human diseases. Its mode of action seems to depend on the quenching of toxic electrophiles, such as 4-hydroxynonenal (HNE). However, carnosine's bioavailability in humans is lower than that in other mammals. The main reason for such an unfavorable pharmacokinetic profile is the activity of the enzyme human serum carnosinase (E.C. 3.4.13.20), which rapidly hydrolyzes carnosine upon absorption. Therefore, some studies have focused on the design of carnosinase-resistant derivatives that retain binding activity toward toxic electrophiles. Nevertheless, the structural modification of the N-terminus amino group of carnosine has rarely been considered, possibly because of its key role in the electrophile scavenging mechanism. This was proven, since some carnosine N-terminus modification generated inactive compounds, despite some derivatives retaining oral bioavailability and gaining resistance to carnosinase hydrolysis. Herein, we therefore report a study aimed at exploring whether the amino group of carnosine can be conveniently modified to develop carnosinase-resistant derivatives retaining the dipeptide activity toward toxic electrophiles.

Evaluation of supplementary carnosine accumulation and distribution: an initial analysis of participants in the Nucleophilic Defense Against PM Toxicity (NEAT) clinical trial

Carnosine is an endogenous dipeptide that buffers intracellular pH and quenches toxic products of lipid peroxidation. Used as a dietary supplement, it also supports exercise endurance. However, the accumulation and distribution of carnosine after supplementation has not been rigorously evaluated. To do this, we randomized a cohort to receive daily supplements of either placebo or carnosine (2 g/day). Blood and urine samples were collected twice over the subsequent 12 week supplementation period and we measured levels of red blood cell (RBC) carnosine, urinary carnosine, and urinary carnosine-propanol and carnosine-propanal conjugates by LC/MS-MS. We found that, when compared with placebo, supplementation with carnosine for 6 or 12 weeks led to an approximate twofold increase in RBC carnosine, while levels of urinary carnosine increased nearly sevenfold. Although there were no changes in the urinary levels of carnosine propanol, carnosine propanal increased nearly twofold. RBC carnosine levels were positively associated with urinary carnosine and carnosine propanal levels. No adverse reactions were reported by those in the carnosine or placebo arms, nor did carnosine supplementation have any effect on kidney, liver, and cardiac function or blood electrolytes. In conclusion, irrespective of age, sex, or BMI, oral carnosine supplementation in humans leads to its increase in RBC and urine, as well as an increase in urinary carnosine-propanal. RBC carnosine may be a readily accessible pool to estimate carnosine levels. Clinical trial registration: This study is registered with ClinicalTrials.gov (Nucleophilic Defense Against PM Toxicity (NEAT Trial)-Full Text View-ClinicalTrials.gov), under the registration: NCT03314987.

Quantitative Analysis of Glutathione and Carnosine Adducts with 4-Hydroxy-2-nonenal in Muscle in a hSOD1G93A ALS Rat Model

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the dysfunction and death of motor neurons through multifactorial mechanisms that remain unclear. ALS has been recognized as a multisystemic disease, and the potential role of skeletal muscle in disease progression has been investigated. Reactive aldehydes formed as secondary lipid peroxidation products in the redox processes react with biomolecules, such as DNA, proteins, and amino acids, resulting in cytotoxic effects. 4-Hydroxy-2-nonenal (HNE) levels are elevated in the spinal cord motor neurons of ALS patients, and HNE-modified proteins have been identified in the spinal cord tissue of an ALS transgenic mice model, suggesting that reactive aldehydes can contribute to motor neuron degeneration in ALS. One biological pathway of aldehyde detoxification involves conjugation with glutathione (GSH) or carnosine (Car). Here, the detection and quantification of Car, GSH, GSSG (glutathione disulfide), and the corresponding adducts with HNE, Car-HNE, and GS-HNE, were performed in muscle and liver tissues of a hSOD1G93A ALS rat model by reverse-phase high-performance liquid chromatography coupled to electrospray ion trap tandem mass spectrometry in the selected reaction monitoring mode. A significant increase in the levels of GS-HNE and Car-HNE was observed in the muscle tissue of the end-stage ALS animals. Therefore, analyzing variations in the levels of these adducts in ALS animal tissue is crucial from a toxicological perspective and can contribute to the development of new therapeutic strategies.

Effect of Scoparia dulcis Extract on Lipid Oxidation in Fish Feed, Growth Performance, and Hypoxia Tolerance in Juvenile Jian Carp (Cyprinus carpio var. Jian)

Lipid oxidation and hypoxia can lead to oxidative damage in aquatic animals. This study explored the effects of Scoparia dulcis extracts (SDE) on lipid oxidation, fish growth performance, digestive ability, antioxidant capacity, and hypoxia tolerance ability. The results showed that SDE decreased malonaldehyde (MDA), conjugated diene (CD), and peroxide value (PO) in the linoleic acid and linolenic acid as well as in fish feed. Broken-line analysis revealed that the optimal acetone extract of S. dulcis (AE) supplements was 4.02, 4.01, and 4.01 g kg-1 determined from PO, CD, and MDA, respectively. Dietary AE supplementation increased feed intake and specific growth rate and activities of amylase, trypsin, and lipase as well as alkaline phosphatase in fish hepatopancreas and gut. Polynomial regression analysis showed that optimal dietary AE supplement was 3.61 g kg-1 diet determined from weight gain. Furthermore, dietary AE supplementation decreased MDA content and increased glutathione content and the activities of glutathione peroxidase, catalase, superoxide dismutase, and glutathione reductase in fish digestive organs, gills, erythrocytes, and muscle. Dietary AE supplementation increased durative time (DT) and oxygen consumption rate (OCR) under hypoxia condition. Based on polynomial regression analysis, optimal dietary AE supplements were 4.73 and 4.60 g kg-1 diet determined from DT and OCR for hypoxia tolerance in fish, respectively. According to our current research, SDE's antioxidant capacity may be attribute to their phenolic chemicals.

Comparative evaluation of different modalities for measuring in vivo carnosine levels

Carnosine is an endogenous di-peptide (β-alanine -L- histidine) involved in maintaining tissue homeostasis. It is most abundant in skeletal muscle where its concentration has been determined in biopsy samples using tandem mass spectrometry (MS-MS). Carnosine levels can also be assessed in intact leg muscles by proton magnetic resonance spectroscopy (1H-MRS) or in blood and urine samples using mass spectrometry. Nevertheless, it remains uncertain how carnosine levels from these distinct compartments are correlated with each other when measured in the same individual. Furthermore, it is unclear which measurement modality might be most suitable for large-scale clinical studies. Hence, in 31 healthy volunteers, we assessed carnosine levels in skeletal muscle, via 1H-MRS, and in erythrocytes and urine by MS-MS. While muscle carnosine levels were higher in males (C2 peak, p = 0.010; C4 peak, p = 0.018), there was no sex-associated difference in urinary (p = 0.433) or erythrocyte (p = 0.858) levels. In a linear regression model adjusted for age, sex, race, and diet, there was a positive association between erythrocyte and urinary carnosine. However, no association was observed between 1H-MRS and erythrocytes or urinary measures. In the relationship between muscle versus urinary and erythrocyte measures, females had a positive association, while males did not show any association. We also found that 1H-MRS measures were highly sensitive to location of measurement. Thus, it is uncertain whether 1H-MRS can accurately and reliably predict endogenous carnosine levels. In contrast, urinary and erythrocyte carnosine measures may be stable and in greater synchrony, and given financial and logistical concerns, may be a feasible alternative for large-scale clinical studies.

Carnosine facilitates lysosomal release of inhibitors of T cell surveillance

Cancer metabolism produces large fluxes of lactate and H+, which are extruded by membrane transporters. However, H+ production and extrusion must be coupled by diffusion, facilitated by mobile buffers. Yan et al. propose that carnosine, generated by CARNS2, provides this mobile buffering and enables lysosomal functions that block T cell surveillance.

Intakes of folate, vitamin B6, and vitamin B12 and cardiovascular disease risk: a national population-based cross-sectional study

Background

Only a few studies that investigated dietary intakes of folate, vitamin B6, and vitamin B12 in relation to cariovascular disease (CVD). This study aimed to assess the association of dietary folate, vitamin B6, and vitamin B12 with CVD in the United States population.

Methods

A cross-sectional analysis of 65,322 adults aged ≥ 20 years who participated in the Third National Health and Nutrition Examination Survey (NHANES III) and NHANES 1999-2018. Before 2003, dietary intake data were assessed using a 24-hour dietary call, and two 24-hour dietary calls were used during 2003 and 2018. Odds ratios and 95% confidence intervals (CIs) for CVD associated with dietary folate, vitamin B6, and vitamin B12 were estimated using multivariate logistic regression models.

Results

Dietary vitamin B6 intake were inversely associated with the odds of CVD. In males, the multivariable OR for the highest vs. lowest quartiles of vitamin B6 was 0.77 (95%CI: 0.61-0.97, Ptrend = 0.013) for the odds of CVD. In females, the adjusted OR for the highest quartile of vitamin B6 compared with the lowest quartile was 0.73 (95%CI: 0.56-0.95, Ptrend = 0.038) for the odds of CVD. No significant association was observed between dietary folate and vitamin B12 intakes and the odds of CVD.

Conclusions

Our findings indicate that higher intake of dietary vitamin B6 may be associated with lower prevalence of CVD, suggesting that dietary vitamin B6 has major public health implications in the prevention of CVD in the United States population.

Ferroptosis in Parkinson's disease: Molecular mechanisms and therapeutic potential

Parkinson's Disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra (SN), leading to motor and non-motor symptoms. While the exact mechanisms remain complex and multifaceted, several molecular pathways have been implicated in PD pathology, including accumulation of misfolded proteins, impaired mitochondrial function, oxidative stress, inflammation, elevated iron levels, etc. Overall, PD's molecular mechanisms involve a complex interplay between genetic, environmental, and cellular factors that disrupt cellular homeostasis, and ultimately lead to the degeneration of dopaminergic neurons. Recently, emerging evidence highlights ferroptosis, an iron-dependent non-apoptotic cell death process, as a pivotal player in the advancement of PD. Notably, oligomeric α-synuclein (α-syn) generates reactive oxygen species (ROS) and lipid peroxides within cellular membranes, potentially triggering ferroptosis. The loss of dopamine, a hallmark of PD, could predispose neurons to ferroptotic vulnerability. This unique form of cell demise unveils fresh insights into PD pathogenesis, necessitating an exploration of the molecular intricacies connecting ferroptosis and PD progression. In this review, the molecular and regulatory mechanisms of ferroptosis and their connection with the pathological processes of PD have been systematically summarized. Furthermore, the features of ferroptosis in PD animal models and clinical trials targeting ferroptosis as a therapeutic approach in PD patients' management are scrutinized.

Research on ferroptosis as a therapeutic target for the treatment of neurodegenerative diseases

Ferroptosis is an iron- and lipid peroxidation (LPO)-mediated programmed cell death type. Recently, mounting evidence has indicated the involvement of ferroptosis in neurodegenerative diseases, especially in Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and so on. Treating ferroptosis presents opportunities as well as challenges for neurodegenerative diseases. This review provides a comprehensive overview of typical features of ferroptosis and the underlying mechanisms that contribute to its occurrence, as well as their implications in the pathogenesis and advancement of major neurodegenerative disorders. Meanwhile, we summarize the utilization of ferroptosis inhibition in both experimental and clinical approaches for the treatment of major neurodegenerative disorders. In addition, we specifically summarize recent advances in developing therapeutic means targeting ferroptosis in these diseases, which may guide future approaches for the effective management of these devastating medical conditions.

Melatonin promotes parthenogenetic development of vitrified-warmed mouse MII oocytes, potentially by reducing oxidative stress through SIRT1

Previous studies have demonstrated that melatonin could ameliorate oxidative stress during the cryopreservation of mouse MII oocytes and their in vitro culture after parthenogenetic activation. However, the underlying molecular mechanism remained poorly understood. This study was conducted to investigate whether melatonin could modulate the oxidative stress in the parthenogenetic 2-cell embryos derived from vitrified-warmed oocytes through SIRT1. The results showed that the reactive oxygen species levels increased, the glutathione levels and SIRT1 expression decreased significantly in parthenogenetic 2-cell embryos derived from cryopreserved oocyte, and the parthenogenetic blastocyst formation rates significantly decreased when compared to those derived from control oocytes. These unfavorable phenomena were prevented by the addition of either 10-9 mol/L melatonin or 10-6 mol/L SRT-1720 (SIRT1 agonist), and it was restored by the supplementation of 10-9 mol/L melatonin in combination with 2 × 10-5 mol/L EX527 (SIRT1 inhibitor). Therefore, the findings from the present study concluded that melatonin may reduce oxidative stress via regulating SIRT1, and potentially promote the parthenogenetic development of vitrified-warmed mouse MII oocytes.

Carnosine alleviates kidney tubular epithelial injury by targeting NRF2 mediated ferroptosis in diabetic nephropathy

Diabetic nephropathy (DN) can promote the occurrence of end-stage renal disease (ESRD). The injury of renal tubular epithelial cells is a significant reason for the occurrence of ESRD. A recent research demonstrated that ferroptosis was associated with renal tubular injury in DN. Ferroptosis is a kind of cell death brought on by the buildup of iron ions and lipid peroxidation brought on by ROS. Because carnosine (CAR) is a scavenger of iron ions and reactive oxygen species, we investigated whether CAR can improve DN by regulating ferroptosis. The results show that both CAR and Fer-1 significantly reduced kidney damage and inhibited ferroptosis in STZ mice. In addition, ferroptosis caused by HG or erastin (an inducer of ferroptosis) in human kidney tubular epithelial cell (HK2) was also rescued by CAR treatment. It was discovered that the protective effect of CAR against HG-induced ferroptosis was abolished when NRF2 was specifically knocked down in HK2 cells.

Acute balenine supplementation in humans as a natural carnosinase-resistant alternative to carnosine

Balenine possesses some of carnosine's and anserine's functions, yet it appears more resistant to the hydrolysing CN1 enzyme. The aim of this study was to elucidate the stability of balenine in the systemic circulation and its bioavailability in humans following acute supplementation. Two experiments were conducted in which (in vitro) carnosine, anserine and balenine were added to plasma to compare degradation profiles and (in vivo) three increasing doses (1-4-10 mg/kg) of balenine were acutely administered to 6 human volunteers. Half-life of balenine (34.9 ± 14.6 min) was respectively 29.1 and 16.3 times longer than that of carnosine (1.20 ± 0.36 min, p = 0.0044) and anserine (2.14 ± 0.58 min, p = 0.0044). In vivo, 10 mg/kg of balenine elicited a peak plasma concentration (Cmax) of 28 µM, which was 4 and 18 times higher than with 4 (p = 0.0034) and 1 mg/kg (p = 0.0017), respectively. CN1 activity showed strong negative correlations with half-life (ρ = - 0.829; p = 0.0583), Cmax (r = - 0.938; p = 0.0372) and incremental area under the curve (r = - 0.825; p = 0.0433). Overall, balenine seems more resistant to CN1 hydrolysis resulting in better in vivo bioavailability, yet its degradation remains dependent on enzyme activity. Although a similar functionality as carnosine and anserine remains to be demonstrated, opportunities arise for balenine as nutraceutical or ergogenic aid.

No Effect of Acute Balenine Supplementation on Maximal and Submaximal Exercise Performance in Recreational Cyclists

Carnosine (β-alanyl-L-histidine) and its methylated analogues anserine and balenine are highly concentrated endogenous dipeptides in mammalian skeletal muscle that are implicated in exercise performance. Balenine has a much better bioavailability and stability in human circulation upon acute ingestion, compared to carnosine and anserine. Therefore, ergogenic effects observed with acute carnosine and anserine supplementation may be even more pronounced with balenine. This study investigated whether acute balenine supplementation improves physical performance in four maximal and submaximal exercise modalities. A total of 20 healthy, active volunteers (14 males; six females) performed cycling sprints, maximal isometric contractions, a 4-km TT and 20-km TT following either preexercise placebo or 10 mg/kg of balenine ingestion. Physical, as well as mental performance, along with acid-base balance and glucose concentration were assessed. Balenine was unable to augment peak power (p = .3553), peak torque (p = .3169), time to complete the 4 km (p = .8566), nor 20 km time trial (p = .2660). None of the performances were correlated with plasma balenine or CN1 enzyme activity. In addition, no effect on pH, bicarbonate, and lactate was observed. Also, the supplement did not affect mental performance. In contrast, glucose remained higher during and after the 20 km time trial following balenine ingestion. In conclusion, these results overall indicate that the functionality of balenine does not fully resemble that of carnosine and anserine, since it was unable to elicit performance improvements with similar and even higher plasma concentrations.

Mass Spectrometry Analysis of DNA and Protein Adducts as Biomarkers in Human Exposure to Cigarette Smoking: Acrolein as an Example

Acrolein is a major component in cigarette smoke and a product of endogenous lipid peroxidation. It is difficult to distinguish human exposure to acrolein from exogenous sources versus endogenous causes, as components in cigarette smoke can stimulate lipid peroxidation in vivo. Therefore, analysis of acrolein-induced DNA and protein adducts by the highly accurate, sensitive, and specific mass spectrometry-based methods is vital to estimate the degree of damage by this IARC Group 2A carcinogen. This Perspective reviews the analyses of acrolein-induced DNA and protein adducts in humans by mass spectrometry focusing on samples accessible for biomonitoring, including DNA from leukocytes and oral cells and abundant proteins from blood, i.e., hemoglobin and serum albumin.

Acrolein-inducing ferroptosis contributes to impaired peripheral neurogenesis in zebrafish

Introduction

Diabetes mellitus (DM) is associated with physiological disorders such as delayed wound healing, diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy (DPN). Over 50% of diabetic patients will develop DPN, characterized by motor dysfunction and impaired sensory nerve function. In a previous study, we have uncovered acrolein (ACR) as an upstream initiator which induced impaired glucose homeostasis and microvascular alterations in zebrafish. Whether ACR has specific effects on peripheral neurogenesis and mediates DPN, is still waiting for clarification.

Methods

To evaluate the function of ACR in peripheral nerve development, in vivo experiments were performed in Tg(hb9:GFP) zebrafish. In addition, a series of rescue experiments, metabolomics assessment, and bioinformatics analysis was performed aimed at identifying the molecular mechanisms behind ACR's function and impaired neurogenesis.

Results

Impaired motor neuron development was confirmed in wild-type embryos treated with external ACR. ACR treated embryos displayed ferroptosis and reduction of several amino acids and increased glutathione (GSH). Furthermore, ferroptosis inducer caused similarly suppressed neurogenesis in zebrafish embryos, while anti-ACR treatment or ferroptosis inhibitor could successfully reverse the detrimental phenotypes of ACR on neurogenesis in zebrafish.

Discussion

Our data indicate that ACR could directly activate ferroptosis and impairs peripheral neurogenesis. The data strongly suggest ACR and activated ferroptosis as inducers and promising therapeutic targets for future DPN studies.

Trehalose-Carnosine Prevents the Effects of Spinal Cord Injury Through Regulating Acute Inflammation and Zinc(II) Ion Homeostasis

Spinal cord injury (SCI) leads to long-term and permanent motor dysfunctions, and nervous system abnormalities. Injury to the spinal cord triggers a signaling cascade that results in activation of the inflammatory cascade, apoptosis, and Zn(II) ion homeostasis. Trehalose (Tre), a nonreducing disaccharide, and L-carnosine (Car), (β-alanyl-L-histidine), one of the endogenous histidine dipeptides have been recognized to suppress early inflammatory effects, oxidative stress and to possess neuroprotective effects. We report on the effects of the conjugation of Tre with Car (Tre-car) in reducing inflammation in in vitro and in vivo models. The in vitro study was performed using rat pheochromocytoma cells (PC12 cell line). After 24 h, Tre-car, Car, Tre, and Tre + Car mixture treatments, cells were collected and used to investigate Zn²⁺ homeostasis. The in vivo model of SCI was induced by extradural compression of the spinal cord at the T6-T8 levels. After treatments with Tre, Car and Tre-Car conjugate 1 and 6 h after SCI, spinal cord tissue was collected for analysis. In vitro results demonstrated the ionophore effect and chelating features of L-carnosine and its conjugate. In vivo, the Tre-car conjugate treatment counteracted the activation of the early inflammatory cascade, oxidative stress and apoptosis after SCI. The Tre-car conjugate stimulated neurotrophic factors release, and influenced Zn²⁺ homeostasis. We demonstrated that Tre-car, Tre and Car treatments improved tissue recovery after SCI. Tre-car decreased proinflammatory, oxidative stress mediators release, upregulated neurotrophic factors and restored Zn²⁺ homeostasis, suggesting that Tre-car may represent a promising therapeutic agent for counteracting the consequences of SCI.

Integrated Multilayer Omics Reveals the Genomic, Proteomic, and Metabolic Influences of Histidyl Dipeptides on the Heart

Background

Histidyl dipeptides such as carnosine are present in a micromolar to millimolar range in mammalian hearts. These dipeptides facilitate glycolysis by proton buffering. They form conjugates with reactive aldehydes, such as acrolein, and attenuate myocardial ischemia–reperfusion injury. Although these dipeptides exhibit multifunctional properties, a composite understanding of their role in the myocardium is lacking.

Methods and Results

To identify histidyl dipeptide–mediated responses in the heart, we used an integrated triomics approach, which involved genome‐wide RNA sequencing, global proteomics, and unbiased metabolomics to identify the effects of cardiospecific transgenic overexpression of the carnosine synthesizing enzyme, carnosine synthase (Carns), in mice. Our result showed that higher myocardial levels of histidyl dipeptides were associated with extensive changes in the levels of several microRNAs, which target the expression of contractile proteins, β‐fatty acid oxidation, and citric acid cycle (TCA) enzymes. Global proteomic analysis showed enrichment in the expression of contractile proteins, enzymes of β‐fatty acid oxidation, and the TCA in the Carns transgenic heart. Under aerobic conditions, the Carns transgenic hearts had lower levels of short‐ and long‐chain fatty acids as well as the TCA intermediate—succinic acid; whereas, under ischemic conditions, the accumulation of fatty acids and TCA intermediates was significantly attenuated. Integration of multiple data sets suggested that β‐fatty acid oxidation and TCA pathways exhibit correlative changes in the Carns transgenic hearts at all 3 levels.

Conclusions

Taken together, these findings reveal a central role of histidyl dipeptides in coordinated regulation of myocardial structure, function, and energetics.

Physiological Roles of Carnosine in Myocardial Function and Health

Carnosine is a pleiotropic histidine-containing dipeptide synthesized from β-alanine and l-histidine, with the intact dipeptide and constituent amino acids being available from the diet. The therapeutic application of carnosine in myocardial tissue is promising, with carnosine playing a potentially beneficial role in both healthy and diseased myocardial models. This narrative review discusses the role of carnosine in myocardial function and health, including an overview of the metabolic pathway of carnosine in the myocardial tissue, the roles carnosine may play in the myocardium, and a critical analysis of the literature, focusing on the effect of exogenous carnosine and its precursors on myocardial function. By so doing, we aim to identify current gaps in the literature, thereby identifying considerations for future research.

[The anti-ischemic and antioxidant activity of the pharmacological agonist of galanin receptor GalR2 and carnosine in in vitro and in vivo model systems]

Antioxidant and anti-ischemic properties of the pharmacological agonist of galanin receptor GalR2 WTLNSAGYLLGPβAH (Gal) and its C-terminal fragment, dipeptide carnosine (βAH), were studied in the model of regional ischemia and reperfusion of the rat heart in vivo in the dose range of 0.5-5.0 mg/kg and Cu²⁺-induced free radical oxidation of low density lipoproteins (LDL) of human plasma in vitro for peptide concentrations of 0.01 mM and 0.1 mM. Gal was obtained by automatic solid phase synthesis using the Fmoc methodology; its structure was characterized by 1H-NMR spectroscopy and MALDI-TOF mass spectrometry. Intravenous administration of the optimal dose of Gal (1 mg/kg) to rats after ischemia was more effective than carnosine in reducing of the myocardial infarct size and the activity of creatine kinase-MB and lactate dehydrogenase in blood plasma at the end of reperfusion. It also improved the metabolic state of the reperfused myocardium and reduced the formation of peroxidation products during reperfusion. Gal reduced more effectively the formation of adducts of hydroxyl radicals in the interstitium of the area at risk (AAR) of the rat heart than carnosine. Carnosine at a dose of 1 mg/kg more effectively increased the activity of catalase and glutathione peroxidase in the AAR by the end of reperfusion compared to Gal. In a model of Cu²⁺-initiated oxidation of human plasma LDL 0.1 mM carnosine demonstrated a significantly more pronounced reduction in the formation of lipid radicals compared to Gal. The results show that Gal can be considered as a promising agent that reduces myocardial injury during reperfusion and oxidative stress.

Unveiling the Hidden Therapeutic Potential of Carnosine, a Molecule with a Multimodal Mechanism of Action: A Position Paper

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous dipeptide and an over-the-counter food supplement with a well-demonstrated multimodal mechanism of action that includes the detoxification of reactive oxygen and nitrogen species, the down-regulation of the production of pro-inflammatory mediators, the inhibition of aberrant protein formation, and the modulation of cells in the peripheral (macrophages) and brain (microglia) immune systems. Since its discovery more than 100 years ago, a plethora of in vivo preclinical studies have been carried out; however, there is still substantial heterogeneity regarding the route of administration, the dosage, the duration of the treatment, and the animal model selected, underlining the urgent need for "coordinated/aligned" preclinical studies laying the foundations for well-defined future clinical trials. The main aim of the present position paper is to critically and concisely consider these key points and open a discussion on the possible "alignment" for future studies, with the goal of validating the full therapeutic potential of this intriguing molecule.

Roles of transient receptor potential channel 6 in glucose-induced cardiomyocyte injury

BACKGROUND

Diabetic cardiomyopathy (DCM) is a serious complication of end-stage diabetes that presents symptoms such as cardiac hypertrophy and heart failure. The transient receptor potential channel 6 (TRPC6) protein is a very important selective calcium channel that is closely related to the development of various cardiomyopathies.

AIM

To explore whether TRPC6 affects cardiomyocyte apoptosis and proliferation inhibition in DCM.

METHODS

We compared cardiac function and myocardial pathological changes in wild-type mice and mice injected with streptozotocin (STZ), in addition to comparing the expression of TRPC6 and P-calmodulin-dependent protein kinase II (P-CaMKII) in them. At the same time, we treated H9C2 cardiomyocytes with high glucose and then evaluated the effects of addition of SAR, a TRPC6 inhibitor, and KN-93, a CaMKII inhibitor, to such H9C2 cells in a high-glucose environment.

RESULTS

We found that STZ-treated mice had DCM, decreased cardiac function, necrotic cardiomyocytes, and limited proliferation. Western blot and immunofluorescence were used to detect the expression levels of various appropriate proteins in the myocardial tissue of mice and H9C2 cells. Compared to those in the control group, the expression levels of the apoptosis-related proteins cleaved caspase 3 and Bax were significantly higher in the experimental group, while the expression of the proliferation-related proteins proliferating cell nuclear antigen (PCNA) and CyclinD1 was significantly lower. In vivo and in vitro, the expression of TRPC6 and P-CaMKII increased in a high-glucose environment. However, addition of inhibitors to H9C2 cells in a high-glucose environment resulted in alleviation of both apoptosis and proliferation inhibition.

CONCLUSION

The inhibition of apoptosis and proliferation of cardiomyocytes in a high-glucose environment may be closely related to activation of the TRPC6/P-CaMKII pathway.

Comprehending Cardiac Dysfunction by Oxidative Stress: Untargeted Metabolomics of In Vitro Samples

Cardiovascular diseases (CVDs) are noncommunicable diseases known for their complex etiology and high mortality rate. Oxidative stress (OS), a condition in which the release of free radical exceeds endogenous antioxidant capacity, is pivotal in CVC, such as myocardial infarction, ischemia/reperfusion, and heart failure. Due to the lack of information about the implications of OS on cardiovascular conditions, several methodologies have been applied to investigate the causes and consequences, and to find new ways of diagnosis and treatment as well. In the present study, cardiac dysfunction was evaluated by analyzing cells’ alterations with untargeted metabolomics, after simulation of an oxidative stress condition using hydrogen peroxide (H₂O₂) in H9c2 myocytes. Optimizations of H₂O₂ concentration, cell exposure, and cell recovery times were performed through MTT assays. Intracellular metabolites were analyzed right after the oxidative stress (oxidative stress group) and after 48 h of cell recovery (recovery group) by ultra-high-performance liquid chromatography coupled to mass spectrometry (UHPLC-MS) in positive and negative ESI ionization mode. Significant alterations were found in pathways such as “alanine, aspartate and glutamate metabolism”, “glycolysis”, and “glutathione metabolism”, mostly with increased metabolites (upregulated). Furthermore, our results indicated that the LC-MS method is effective for studying metabolism in cardiomyocytes and generated excellent fit (R²Y > 0.987) and predictability (Q² > 0.84) values.

Synergistic Effect of L-Carnosine and Hyaluronic Acid in Their Covalent Conjugates on the Antioxidant Abilities and the Mutual Defense against Enzymatic Degradation

Hyaluronic acid (Hy) is a natural linear polymer that is widely distributed in different organisms, especially in the articular cartilage and the synovial fluid. During tissue injury due to oxidative stress, Hy plays an important protective role. All the beneficial properties of Hy make the polymer attractive for many biomedical uses; however, the low stability and short biological half-life limit Hy application. To overcome these problems, the addition of small antioxidant molecules to Hy solution has been employed to protect the molecular integrity of Hy or delay its degradation. Carnosine (β-alanyl-L-histidine, Car) protects cells from the damage due to the reactive species derived from oxygen (ROS), nitrogen (RNS) or carbonyl groups (RCS). Car inhibits the degradation of hyaluronan induced by free radical processes in vitro but, like Hy, the potential protective action of Car is drastically hampered by the enzymatic hydrolysis in vivo. Recently, we conjugated Hy to Car and the derivatives (HyCar) showed protective effects in experimental models of osteoarthritis and rheumatoid arthritis in vivo. Here we report the antioxidant activity exerted by HyCar against ROS, RNS and RCS. Moreover, we tested if the covalent conjugation between Hy and Car inhibits the enzymatic hydrolysis of the polymer and the dipeptide backbone. We found that the antioxidant properties and the resistance to the enzymatic hydrolysis of Hy and Car are greatly improved by the conjugation.

Absence of endogenous carnosine synthesis does not increase protein carbonylation and advanced lipoxidation end products in brain, kidney or muscle

Carnosine and other histidine-containing dipeptides are expected to be important anti-oxidants in vertebrates based on various in vitro and in vivo studies with exogenously administered carnosine or its precursor β-alanine. To examine a possible anti-oxidant role of endogenous carnosine, mice lacking carnosine synthase (Carns1^−/−) had been generated and were examined further in the present study. Protein carbonylation increased significantly between old (18 months) and aged (24 months) mice in brain and kidney but this was independent of the Carns1 genotype. Lipoxidation end products were not increased in 18-month-old Carns1^−/− mice compared to controls. We also found no evidence for compensatory increase of anti-oxidant enzymes in Carns1^−/− mice. To explore the effect of carnosine deficiency in a mouse model known to suffer from increased oxidative stress, Carns1 also was deleted in the type II diabetes model Lepr^db/db mouse. In line with previous studies, malondialdehyde adducts were elevated in Lepr^db/db mouse kidney, but there was no further increase by additional deficiency in Carns1. Furthermore, Lepr^db/db mice lacking Carns1 were indistinguishable from conventional Lepr^db/db mice with respect to fasting blood glucose and insulin levels. Taken together, Carns1 deficiency appears not to reinforce oxidative stress in old mice and there was no evidence for a compensatory upregulation of anti-oxidant enzymes. We conclude that the significance of the anti-oxidant activity of endogenously synthesized HCDs is limited in mice, suggesting that other functions of HCDs play a more important role.

Endogenous dipeptide-carnosine supplementation ameliorates hypobaric hypoxia-induced skeletal muscle loss via attenuating endoplasmic reticulum stress response and maintaining proteostasis

High altitude is an environmental stress that is accompanied with numerous adverse biological responses, including skeletal muscle weakness and muscle protein loss. Skeletal muscle wasting is an important clinical problem, progressing to critical illness, associated with increased morbidity and mortality. The present study explores the protective efficacy of endogenous dipeptide, carnosine (CAR), supplementation in ameliorating skeletal muscle protein loss under hypobaric hypoxia (HH). Male Sprague-Dawley rats (n = 5) were randomly divided into control group, HH-exposed group (3 days HH exposure equivalent to 7,620 m), and HH-exposed rats supplemented with carnosine (3 days; 150 mg/kg b.w, orally) (HH + CAR). HH-exposed rats supplemented with CAR ameliorated HH-induced oxidative protein damage, lipid peroxidation, and maintained pro-inflammatory cytokines levels. HH-associated muscle protein degradative pathways, including calpain, ubiquitination, endoplasmic reticulum stress, autophagy, and apoptosis were also regulated in carnosine-supplemented rats. Further, the muscle damage marker, the levels of serum creatine phosphokinase were also reduced in HH + CAR co-supplemented rats which proved the protective efficacy of CAR against hypobaric hypoxia-induced muscle protein loss. Altogether, CAR supplementation ameliorated HH-induced skeletal muscle protein loss via performing multifaceted ways, mainly by maintaining redox homeostasis and proteostasis in skeletal muscle.

Ferroptosis as a Major Factor and Therapeutic Target for Neuroinflammation in Parkinson's Disease

Mounting evidence suggests that ferroptosis is not just a consequence but also a fundamental contributor to the development and progression of Parkinson’s disease (PD). Ferroptosis is characterized as iron-dependent regulated cell death caused by excessive lipid peroxidation, leading to plasma membrane rupture, release of damage-associated molecular patterns, and neuroinflammation. Due to the crucial role of intracellular iron in mediating the production of reactive oxygen species and the formation of lipid peroxides, ferroptosis is intimately controlled by regulators involved in many aspects of iron metabolism, including iron uptake, storage and export, and by pathways constituting the antioxidant systems. Translational and transcriptional regulation of iron homeostasis and redox status provide an integrated network to determine the sensitivity of ferroptosis. We herein review recent advances related to ferroptosis, ranging from fundamental mechanistic discoveries and cutting-edge preclinical animal studies, to clinical trials in PD and the regulation of neuroinflammation via ferroptosis pathways. Elucidating the roles of ferroptosis in the survival of dopaminergic neurons and microglial activity can enhance our understanding of the pathogenesis of PD and provide opportunities for the development of novel prevention and treatment strategies.

Carnosine quenches the reactive carbonyl acrolein in the central nervous system and attenuates autoimmune neuroinflammation

Background

Multiple sclerosis (MS) is a chronic autoimmune disease driven by sustained inflammation in the central nervous system. One of the pathological hallmarks of MS is extensive free radical production. However, the subsequent generation, potential pathological role, and detoxification of different lipid peroxidation-derived reactive carbonyl species during neuroinflammation are unclear, as are the therapeutic benefits of carbonyl quenchers. Here, we investigated the reactive carbonyl acrolein and (the therapeutic effect of) acrolein quenching by carnosine during neuroinflammation.

Methods

The abundance and localization of acrolein was investigated in inflammatory lesions of MS patients and experimental autoimmune encephalomyelitis (EAE) mice. In addition, we analysed carnosine levels and acrolein quenching by endogenous and exogenous carnosine in EAE. Finally, the therapeutic effect of exogenous carnosine was assessed in vivo (EAE) and in vitro (primary mouse microglia, macrophages, astrocytes).

Results

Acrolein was substantially increased in inflammatory lesions of MS patients and EAE mice. Levels of the dipeptide carnosine (β-alanyl-l-histidine), an endogenous carbonyl quencher particularly reactive towards acrolein, and the carnosine-acrolein adduct (carnosine-propanal) were ~ twofold lower within EAE spinal cord tissue. Oral carnosine treatment augmented spinal cord carnosine levels (up to > tenfold), increased carnosine-acrolein quenching, reduced acrolein-protein adduct formation, suppressed inflammatory activity, and alleviated clinical disease severity in EAE. In vivo and in vitro studies indicate that pro-inflammatory microglia/macrophages generate acrolein, which can be efficiently quenched by increasing carnosine availability, resulting in suppressed inflammatory activity. Other properties of carnosine (antioxidant, nitric oxide scavenging) may also contribute to the therapeutic effects.

Conclusions

Our results identify carbonyl (particularly acrolein) quenching by carnosine as a therapeutic strategy to counter inflammation and macromolecular damage in MS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02306-9.

Carnosine alleviates podocyte injury in diabetic nephropathy by targeting caspase-1-mediated pyroptosis

Diabetic nephropathy (DN) is a main complication of diabetes and often develops into end-stage nephropathy. Histologically, DN progresses as the gradual loss of podocytes with the loss of glomerular podocytes being the earliest sign of DN. Pyroptosis is a new type of programmed cell death and has been mechanistically correlated with podocyte injury in DN. The current study aimed to evaluate the protective effects of carnosine on glomerular podocytes in DN, both in vivo and in vitro. Using high glucose-treated cultured MPC5 cells and a streptozotocin (STZ)-induced diabetic mouse model, we evaluated the effects of carnosine on alleviating podocyte injury in DN. We found that carnosine significantly reversed albuminuria and histopathological lesions and alleviated renal inflammatory and pyroptosis responses in STZ-induced diabetic mice for 12 weeks. The results also showed that carnosine strongly inhibited podocyte inflammation and podocyte pyroptosis in vitro. Cellular Thermal Shift Assay (CETSA) and molecular docking results revealed that mechnaistically caspase-1 was the target of carnosine. We then found that silencing caspase-1 eliminated the protective effect of carnosine. Interestingly, we also found that caspase-1 and gasdermin D expression were increased in renal biopsy tissue of patients with DN. Our study is the first to demonstrate the novel role of carnosine in alleviating podocyte injury by inhibiting pyroptosis via the targeting of caspase-1. Carnosine may have potential as a therapeutic agent in treating DN by targeting caspase-1.

Diet and redox state in maintaining skeletal muscle health and performance at high altitude

High altitude exposure leads to compromised physical performance with considerable weight loss. The major stressor at high altitude is hypobaric hypoxia which leads to disturbance in redox homeostasis. Oxidative stress is a well-known trigger for many high altitude illnesses and regulates several key signaling pathways under stressful conditions. Altered redox homeostasis is considered the prime culprit of high altitude linked skeletal muscle atrophy. Hypobaric hypoxia disturbs redox homeostasis through increased RONS production and compromised antioxidant system. Increased RONS disturbs the cellular homeostasis via multiple ways such as inflammation generation, altered protein anabolic pathways, redox remodeling of RyR1 that contributed to dysregulated calcium homeostasis, enhanced protein degradation pathways via activation calcium-regulated protein, calpain, and apoptosis. Ultimately, all the cellular signaling pathways aggregately result in skeletal muscle atrophy. Dietary supplementation of phytochemicals could become a safe and effective intervention to ameliorate skeletal muscle atrophy and enhance the physical performance of the personnel who are staying at high altitude regions. The present evidence-based review explores few dietary supplementations which regulate several signaling mechanisms and ameliorate hypobaric hypoxia induced muscle atrophy and enhances physical performance. However, a clinical research trial is required to establish proof-of-concept.

Dimeric Histidine as a Novel Free Radical Scavenger Alleviates Non-Alcoholic Liver Injury

Non-alcoholic liver injury (NLI) is a common disease worldwide. Since free radical damage in the liver is a crucial initiator leading to diseases, scavenging excess free radicals has become an essential therapeutic strategy. To enhance the antioxidant capacity of histidine, we synthesized a protonated dimeric histidine, H-bihistidine, and investigated its anti-free radical potential in several free-radical-induced NLI. Results showed that H-bihistidine could strongly scavenge free radicals caused by H₂O₂, fatty acid, and CCl₄, respectively, and recover cell viability in cultured hepatocytes. In the animal model of nonalcoholic fatty liver injury caused by high-fat diet, H-bihistidine reduced the contents of transaminases and lipids in serum, eliminated the liver’s fat accumulation, and decreased the oxidative damage. Moreover, H-bihistidine could rescue CCl₄-induced liver injury and recover energy supply through scavenging free radicals. Moreover, liver fibrosis prepared by high-fat diet and CCl₄ administration was significantly alleviated after H-bihistidine treatment. This study suggests a novel nonenzymatic free radical scavenger against NLI and, potentially, other free-radical-induced diseases.

2-Oxo-Imidazole-Containing Dipeptides Play a Key Role in the Antioxidant Capacity of Imidazole-Containing Dipeptides

There is substantial evidence for the antioxidant functions of imidazole-containing dipeptides (IDPs), including carnosine and anserine, under physiological and pathological conditions in vivo. However, the detailed mechanism underlying the antioxidant functions is still poorly understood. Recently, we discovered the endogenous production of 2-oxo-imidazole-containing dipeptides (2-oxo-IDPs), such as 2-oxo-carnosine and 2-oxo-anserine, as novel derivatives of IDPs in mouse tissues and revealed that the antioxidant capacity of 2-oxo-carnosine was much greater than that of carnosine. However, the antioxidant capacity of 2-oxo-IDPs still remains unclear. In this study, we evaluated 2-oxo-carnosine and 2-oxo-anserine by multiple in vitro assays, such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing/antioxidant power, and oxygen radical absorbance capacity assays in comparison with the corresponding IDPs, carnosine and anserine. All the assays employed herein demonstrated that 2-oxo-carnosine and 2-oxo-anserine exhibited a greater antioxidant capacity than that of the corresponding IDPs. Quantitative high-performance liquid chromatography tandem mass spectrometry revealed that commercial IDPs standards were contaminated with a certain amount of 2-oxo-IDPs, which was correlated with the antioxidant capacity. DPPH radical scavenging assay revealed that the elimination of contaminated 2-oxo-IDPs from the IDPs standards caused a significant decrease in the antioxidant capacity compared to the original IDPs standards. These results suggest that the main driver of the antioxidant capacity of IDPs is 2-oxo-IDPs; accordingly, the conversion of IDPs to 2-oxo-IDPs may be a critical step in the antioxidant functions.

Emerging cardioprotective mechanisms of vitamin B6: a narrative review

Although overt vitamin B6 deficiency is rare, marginal vitamin B6 deficiency is frequent and occurs in a consistent proportion of the population. The marginal vitamin B6 deficiency appears to relate to an increased risk of inflammation-related diseases, such as cardiovascular diseases and cancers. Of all the cardiovascular diseases, heart failure is a complex clinical syndrome associated with a high mortality rate. So far, information regarding the cardioprotective mechanisms of vitamin B6 has been limited. Meanwhile, recent studies have revealed that vitamin B6 treatment increases cardiac levels of imidazole dipeptides (e.g., carnosine, anserine, and homocarnosine), histamine, and γ-aminobutyric acid (GABA) and suppresses P2X7 receptor-mediated NLRP3 inflammasome. These modulations may imply potential cardioprotective mechanisms of vitamin B6. These modulations may also be involved in the underlying mechanisms through which vitamin B6 suppresses oxidative stress and inflammation. This review provides an up-to-date evaluation of our current understanding of the cardioprotective mechanisms of vitamin B6.

A chemical field guide to histone nonenzymatic modifications

Histone nonenzymatic covalent modifications (NECMs) have recently emerged as an understudied class of posttranslational modifications that regulate chromatin structure and function. These NECMs alter the surface topology of histone proteins, their interactions with DNA and chromatin regulators, as well as compete for modification sites with enzymatic posttranslational modifications. NECM formation depends on the chemical compatibility between a reactive molecule and its target site, in addition to their relative stoichiometries. Here we survey the chemical reactions and conditions that govern the addition of NECMs onto histones as a manual to guide the identification of new physiologically relevant chemical adducts. Characterizing NECMs on chromatin is critical to attain a comprehensive understanding of this new chapter of the so-called "histone code".

Isolation of balenine from opah (Lampris megalopsis) muscle and comparison of antioxidant and iron-chelating activities with other major imidazole dipeptides

Balenine (Bal) in opah muscle was extracted using hot water and purified by ion-exchange chromatography and recrystallization to provide 41 g of over 95% pure Bal from 1 kg of opah muscle. The structure of purified Bal was identical to that of an authentic Bal standard by NMR analysis. The antioxidant (ORAC and HORAC values) and Fe(II) ion-chelating abilities of purified Bal were examined by comparison with two major imidazole dipeptides, carnosine (Car) and anserine (Ans). Opah-derived Bal showed significantly higher ORAC and HORAC values and Fe(II) ion-chelating ability at 0.3 mM. In silico molecular simulation revealed that Bal and Car formed hydrogen bonds between the hydrogen atom of the imidazole imino group and the carboxyl carbonyl oxygen, whereas Ans did not. The proposed method for extracting and purifying Bal from opah muscle suggests that opah can be utilized as a functional food or Bal resource.

Metabolomics approach based on LC-HRMS for the fast screening of iron(II)-chelating peptides in protein hydrolysates

Production of iron-chelating peptides from protein hydrolysates requires robust and adequate screening methods to optimize their purification and subsequently valorize their potential antioxidant properties. An original methodology was developed for direct and sensitive screening of iron(II)-chelating peptides based on ion-pair reverse phase liquid chromatography (IP-RPLC) coupled to high-resolution mass spectrometry (HRMS). Peptide mixture was first added to iron(II) solution to form iron(II)-peptide complexes. Then IP-RPLC-HRMS analysis was conducted on this iron-peptide mixture and on the iron-free peptide solution for comparative mass spectra analysis. This protocol, initially applied to a range of low molecular weight standard peptides, allowed detection of [(Peptide-H)+⁵⁶Fe^II]⁺ complex ion for iron(II)-chelating peptides (GGH, EAH, DAH, βAH, DMH, DTH, DSH). GGH was added in complex peptide mixtures and targeted analysis of [(GGH-H)+⁵⁶Fe^II]⁺ complex showed a limit of detection (LOD) below 0.77 mg L^-1 of GGH. This protocol was finally tested in combination with metabolomics software and additional digital processing for non-targeted search for iron(II)-chelating peptides. Applicability of this new screening methodology has been validated by detection of GGH as iron(II)-chelating peptide when added at 0.77 mg L^-1 in casein hydrolysate. Graphical abstract.

Carnosine synthase deficiency is compatible with normal skeletal muscle and olfactory function but causes reduced olfactory sensitivity in aging mice

Carnosine (β-alanyl-l-histidine) and anserine (β-alanyl-3-methyl-l-histidine) are abundant peptides in the nervous system and skeletal muscle of many vertebrates. Many in vitro and in vivo studies demonstrated that exogenously added carnosine can improve muscle contraction, has antioxidant activity, and can quench various reactive aldehydes. Some of these functions likely contribute to the proposed anti-aging activity of carnosine. However, the physiological role of carnosine and related histidine-containing dipeptides (HCDs) is not clear. In this study, we generated a mouse line deficient in carnosine synthase (Carns1). HCDs were undetectable in the primary olfactory system and skeletal muscle of Carns1-deficient mice. Skeletal muscle contraction in these mice, however, was unaltered, and there was no evidence for reduced pH-buffering capacity in the skeletal muscle. Olfactory tests did not reveal any deterioration in 8-month-old mice lacking carnosine. In contrast, aging (18-24-month-old) Carns1-deficient mice exhibited olfactory sensitivity impairments that correlated with an age-dependent reduction in the number of olfactory receptor neurons. Whereas we found no evidence for elevated levels of lipoxidation and glycation end products in the primary olfactory system, protein carbonylation was increased in the olfactory bulb of aged Carns1-deficient mice. Taken together, these results suggest that carnosine in the olfactory system is not essential for information processing in the olfactory signaling pathway but does have a role in the long-term protection of olfactory receptor neurons, possibly through its antioxidant activity.

Cardiospecific Overexpression of ATPGD1 (Carnosine Synthase) Increases Histidine Dipeptide Levels and Prevents Myocardial Ischemia Reperfusion Injury

BACKGROUND Myocardial ischemia reperfusion (I/R) injury is associated with complex pathophysiological changes characterized by pH imbalance, the accumulation of lipid peroxidation products acrolein and 4-hydroxy trans-2-nonenal, and the depletion of ATP levels. Cardioprotective interventions, designed to address individual mediators of I/R injury, have shown limited efficacy. The recently identified enzyme ATPGD1 (Carnosine Synthase), which synthesizes histidyl dipeptides such as carnosine, has the potential to counteract multiple effectors of I/R injury by buffering intracellular pH and quenching lipid peroxidation products and may protect against I/R injury. METHODS AND RESULTS We report here that β-alanine and carnosine feeding enhanced myocardial carnosine levels and protected the heart against I/R injury. Cardiospecific overexpression of ATPGD1 increased myocardial histidyl dipeptides levels and protected the heart from I/R injury. Isolated cardiac myocytes from ATPGD1-transgenic hearts were protected against hypoxia reoxygenation injury. The overexpression of ATPGD1 prevented the accumulation of acrolein and 4-hydroxy trans-2-nonenal-protein adducts in ischemic hearts and delayed acrolein or 4-hydroxy trans-2-nonenal-induced hypercontracture in isolated cardiac myocytes. Changes in the levels of ATP, high-energy phosphates, intracellular pH, and glycolysis during low-flow ischemia in the wild-type mice hearts were attenuated in the ATPGD1-transgenic hearts. Two natural dipeptide analogs (anserine and balenine) that can either quench aldehydes or buffer intracellular pH, but not both, failed to protect against I/R injury. CONCLUSIONS Either exogenous administration or enhanced endogenous formation of histidyl dipeptides prevents I/R injury by attenuating changes in intracellular pH and preventing the accumulation of lipid peroxidation derived aldehydes.

Therapeutic Potential of Carnosine and Its Derivatives in the Treatment of Human Diseases

Despite significant progress in the pathogenesis, diagnosis, treatment, and prevention of cancer and neurodegenerative diseases, their occurrence and mortality are still high around the world. The resistance of cancer cells to the drugs remains a significant problem in oncology today, while in the case of neuro-degenerative diseases, therapies reversing the process are still yet to be found. Furthermore, it is important to seek new chemotherapeutics reversing side effects of currently used drugs or helping them perform their function to inhibit progression of the disease. Carnosine, a dipeptide constisting of β-alanine and l-histidine, has a variety of functions to mention: antioxidant, antiglycation, and reducing the toxicity of metal ions. It has therefore been proposed to act as a therapeutic agent for many pathological states. The aim of this paper was to find if carnosine and its derivatives can be helpful in treating various diseases. Literature search presented in this review includes review and original papers found in SciFinder, PubMed, and Google Scholar. Searches were based on substantial keywords concerning therapeutic usage of carnosine and its derivatives in several diseases including neurodegenerative disorders and cancer. In this paper, we review articles and find that carnosine and its derivatives are potential therapeutic agents in many diseases including cancer, neurodegenerative diseases, diabetes, and schizophrenia. Carnosine and its derivatives can be used in treating neurodegenerative diseases, cancer, diabetes, or schizophrenia, although their usage is limited. Therefore, there's an urge to synthesize and analyze new substances, overcoming the limitation of carnosine itself.

Activation Effects of Carnosine- and Histidine-Containing Dipeptides on Human Carbonic Anhydrases: A Comprehensive Study

l-Carnosine (β-Ala-l-His) and several other histidine-containing peptides, including two N-methylated forms on the imidazole ring (l-anserine and l-balenine), two derivatives modified on the carboxyl function (carcinine and l-carnosinamide), two analogues differing in the length of the N-terminal residue (l-homocarnosine and Gly-l-His) and the N-acetyl derivatives, were investigated as activators of four isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). The four human isoforms hCA I, II, VA and IX were activated in the low to high micromolar range, with a rather complex structure activity relationship. A performed computational study allowed us to rationalize these results and to propose a binding mode of these activators within the enzyme active site. Similarly to other CA activators, the here studied peptides could find relevant pharmacological applications such as in the management of CA deficiencies, for therapy memory and enhancing cognition or for artificial tissues engineering.

Scientific Papers and Patents on Substances with Unproven Effects

It is evident from reviewing scientific literature that the quality of argumentation in some areas of medical research has deteriorated during the last decades. Publication of a series of questionable reliability has continued without making references to the published criticism; examples are discussed in this review. Another tendency is that drugs without proven efficiency are advertised, corresponding products patented and marketed as evidence-based medications. Professional publications are required to register drugs and dietary supplements to obtain permissions for the practical use; and such papers appeared, sometimes being of questionable reliability. Several examples are discussed in this review when substances without proven effects were patented and introduced into practice being supported by publications of questionable reliability. Some of the topics are not entirely clear; and the arguments provided here can induce a constructive discussion.

LC-ESI-MS/MS quantification of carnosine, anserine, and balenine in meat samples

The histidine-containing imidazole dipeptide carnosine and its methylated analogs anserine and balenine are present at high concentrations in vertebrate tissues. Although the physiological functions of the imidazole dipeptides have not been elucidated yet, it has been suggested that they play significant biological roles in animals. Despite increasing interest, few studies have challenged the quantifications of carnosine, anserine, and balenine by a single HPLC run because they have similar retention times. In this study, we developed a method to quantify these imidazole dipeptides in meat samples using an LC-ESI-MS/MS triple-quadrupole mass spectrometer. We improved the liquid chromatographic separation of the imidazole dipeptides by applying a mix-mode column, which provides both normal phase and ion exchange separations, and developed multiple reaction-monitoring of the transitions for quantification of m/z 227 → 110 for carnosine, m/z 241 → 126 for anserine, m/z 241 → 124 for balenine, and m/z 269 → 110 for L-histidyl-L-leucine (internal standard). The established method met all pre-defined validation criteria. Intra- and inter-day accuracy and precision were ±10.0% and ≤14.8%, respectively. The ranges of quantifications were 14.7 ng/mL to 1.5 mg/mL for carnosine, 15.6 ng/mL to 1.6 mg/mL for anserine, and 15.6 ng/mL to 1.6 mg/mL for balenine. In conclusion, the validated method was successfully applied to the quantification of imidazole dipeptides in biological samples without derivatization.

Reactive Oxygen Species-Induced Lipid Peroxidation in Apoptosis, Autophagy, and Ferroptosis

Reactive oxygen species- (ROS-) induced lipid peroxidation plays a critical role in cell death including apoptosis, autophagy, and ferroptosis. This fundamental and conserved mechanism is based on an excess of ROS which attacks biomembranes, propagates lipid peroxidation chain reactions, and subsequently induces different types of cell death. A highly evolved sophisticated antioxidant system exists that acts to protect the cells from oxidative damage. In this review, we discussed how ROS propagate lipid peroxidation chain reactions and how the products of lipid peroxidation initiate apoptosis and autophagy in current models. We also discussed the mechanism of lipid peroxidation during ferroptosis, and we summarized lipid peroxidation in pathological conditions of critical illness. We aim to bring a more global and integrative sight to know how different ROS-induced lipid peroxidation occurs among apoptosis, autophagy, and ferroptosis.

Metabolic Profiling Associates with Disease Severity in Nonischemic Dilated Cardiomyopathy

BACKGROUND

Metabolomic profiling may have diagnostic and prognostic value in heart failure. This study investigated whether targeted blood and urine metabolomics reflects disease severity in patients with nonischemic dilated cardiomyopathy (DCM) and compared its incremental value on top of N-terminal prohormone of brain natriuretic peptide (NT-proBNP).

METHODS AND RESULTS

A total of 149 metabolites were measured in plasma and urine samples of 273 patients with DCM and with varying stages of disease (patients with DCM and normal left ventricular reverse remodeling, n = 70; asymptomatic DCM, n = 72; and symptomatic DCM, n = 131). Acylcarnitines, sialic acid and glutamic acid are the most distinctive metabolites associated with disease severity, as repeatedly revealed by unibiomarker linear regression, sparse partial least squares discriminant analysis, random forest, and conditional random forest analyses. However, the absolute difference in the metabolic profile among groups was marginal. A decision-tree model based on the top metabolites did not surpass NT-proBNP in classifying stages. However, a combination of NT-proBNP and the top metabolites improved the decision tree to distinguish patients with DCM and left ventricular reverse remodeling from symptomatic DCM (area under the curve 0.813 ± 0.138 vs 0.739 ± 0.114; P = 0.02).

CONCLUSION

Functional cardiac recovery is reflected in metabolomics. These alterations reveal potential alternative treatment targets in advanced symptomatic DCM. The metabolic profile can complement NT-proBNP in determining disease severity in nonischemic DCM.

Proximate Composition and Nutritional Profile of Rainbow Trout (Oncorhynchus mykiss) Heads and Skipjack tuna (Katsuwonus Pelamis) Heads

In order to evaluate the application potential of rainbow trout (Oncorhynchus mykiss) heads and skipjack tuna (Katsuwonus pelamis) heads; proximate composition, amino acids, fatty acids, carnosine, and anserine contents were analyzed in this study. Rainbow trout heads showed significantly higher protein (29.31 g/100 g FW, FW is abbreviation of fresh weight) and lipid (6.03 g/100 g FW) contents than skipjack tuna heads (18.47 g/100 g FW protein and 4.83 g/100 g FW lipid) (p < 0.05). Rainbow trout heads and skipjack tuna heads exhibited similar amino acid composition. Essential amino acids constituted more than 40% of total amino acids in both rainbow trout head and skipjack tuna head. The fatty acid profile was different between rainbow trout heads and skipjack tuna heads. Rainbow trout heads mainly contained 38.64% polyunsaturated fatty acids (PUFAs) and 38.57% monounsaturated fatty acids (MUFAs), whereas skipjack tuna heads mainly contained 54.46% saturated fatty acids (SFAs). Skipjack tuna heads contained 4563 mg/kg FW anserine and 1761 mg/kg FW carnosine, which were both significantly higher than those of rainbow trout heads (p < 0.05). These results demonstrate that both rainbow trout heads and skipjack tuna heads may be used as materials for recycling high-quality protein. Meanwhile, rainbow trout heads can be used to extract oil with high contents of unsaturated fatty acids, while skipjack tuna heads may be a source for obtaining carnosine and anserine.