Carnosine and advanced glycation end products: a systematic review

Determination of Imidazole Dipeptides and Related Amino Acids in Natural Seafoods by Liquid Chromatography-Tandem Mass Spectrometry Using a Pre-Column Derivatization Reagent

Imidazole dipeptides (IDPs) and taurine (Tau) have several health benefits and are known to be contained in natural seafoods. However, their levels vary widely in different natural seafoods, making their simultaneous determination desirable. Herein, we employ a liquid chromatography-tandem mass spectrometry approach using a novel amino group derivatization reagent, succinimidyl 2-(3-((benzyloxy)carbonyl)-1-methyl-5-oxoimidazolidin-4-yl) acetate ((R)-CIMa-OSu), for the simultaneous quantification of IDPs (carnosine (Car) and anserine (Ans)), their related amino acids, and Tau in natural seafoods. Each seafood sample contained different concentrations of IDPs (Car: ND to 1.48 mmol/100 g-wet, Ans: ND to 4.67 mmol/100 g-wet). The Car levels were considerably higher in eel, while Tau was more abundant in squid, boiled octopus, and scallop. Thus, the derivatization reagent (R)-CIMa-OSu provides a new approach to accurately assess the nutritional composition of seafoods, thereby providing valuable insight into its dietary benefits.

Accumulation of advanced glycation end products in skin and increased vascular ageing in the general population: the Malmö Offspring Study

OBJECTIVES

Advanced glycation end product (AGE) is an established risk marker for diabetic vascular disease, and associated with the degree of diabetes complications, renal failure, and atherosclerosis in middle-aged and older individuals. The relationship between AGEs and aortic stiffness has not been thoroughly examined in the younger general population. We aimed to evaluate the association between AGEs and aortic stiffness in the general population of young and middle-aged adults.

METHODS

We analysed cross-sectionally 2518 participants from a Swedish population-based cohort, the Malmö Offspring Study (mean age 41.8 ± 14.5 years, 52.2%). Advanced glycation end-products (AGEs) were measured by a well validated, noninvasive method using skin autofluorescence with AGE-Reader. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (PWV) and augmentation index (Aix) was calibrated to a standard heart rate of 75 bpm at the arteria radialis using SphygmoCor. Multivariable linear regression was performed stratified by age to analyse the association between skin AGE and aortic stiffness.

RESULTS

Increased levels of AGEs were significantly associated with higher direct measurements of aortic stiffness (vascular ageing) in younger individuals (PWV β 0.55 m/s, P  < 0.001) after adjustment for traditional cardiometabolic risk factors, however, not in older individuals (PWV β 0.23 m/s, P  = 0.10). Indirect vascular ageing was also significantly associated with higher levels of AGEs in both younger (Aix β 7.78, P  < 0.001) and older individuals (Aix β 3.69, P  < 0.001).

CONCLUSION

Higher levels of skin autofluorescence-AGEs are positively associated with increased vascular ageing in younger adults from the general population, independent of cardiometabolic risk factors.

Analysis of the efficacy of blunt separation combined with uncrosslinked sodium hyaluronate composite solution for the treatment of tear trough deformity in Asians

BACKGROUND

Filling therapy is becoming increasingly popular for correcting tear trough deformities (TTD). However, its therapeutic effect and retention time are limited.

AIMS

To improve the clinical efficacy and safety of TTD treatment in Asians, we used a blunt separation technique to break the adhesion site of periorbital subcutaneous tissue, and while repairing skin dermis after injury, it was combined with uncrosslinked hyaluronic acid compound solution to promote collagen regeneration and treat TTDs.

PATIENTS/METHODS

Twenty-six Chinese patients (21 women and 5 men) with TTD, with a mean age of 34.54 ± 9.21 (range, 20-56) years, were enrolled. Symptom improvement, recurrence rates, treatment safety, and patient satisfaction were evaluated.

RESULTS

All patients' tear trough rating scale (TTRS) scores decreased significantly immediately after treatment. The TTRS scores at 1, 3, and 6 months, and 1 year after treatment demonstrated significant differences from those before treatment (all p < 0.05). All patients' experienced mild pain, erythema, and swelling during the treatment. Three patients developed postinjection bruising after treatment, which lasted for 6-7 days and subsequently disappeared. No other adverse reactions were observed during the follow-up. There were no recurrent cases, and patient satisfaction was very high.

CONCLUSIONS

Blunt separation combined with an uncrosslinked sodium hyaluronate composite solution is safe and effective for treating TTDs in Asians with few side effects and has good clinical application prospects.

Inhibitory Potential of Carnosine and Aminoguanidine Towards Glycation and Fibrillation of Albumin: In-vitro and Simulation Studies

Carnosine is beta-alanyl histidine, a dipeptide, endogenously produced in our body by the carnosine synthase enzyme. It is an antioxidant, thus protecting from the deleterious effect of advanced glycation end products (AGEs). Similarly, aminoguanidine (AG) also prevents AGEs formation by scavenging free radicals such as reactive oxygen species (ROS)/reactive carbonyl species (RCS). This study used experimental and computational techniques to perform a comparative analysis of carnosine and AG and their inhibiting properties against glycated human serum albumin (HSA). Fructose-mediated glycation of albumin produced fluorescent structures, such as pentosidine and malondialdehyde. These AGEs were significantly reduced by carnosine and AG. At 20 mM, carnosine and AG quenches pentosidine fluorescence by 66% and 83%, respectively. A similar inhibitory effect was observed for malondialdehyde. Protein hydrophobicity and tryptophan fluorescence were restored in the presence of carnosine and AG. Aminoguanidine decreased fibrillation in HSA, while carnosine did not significantly affect aggregation/fibrillation. In addition, molecular docking study observed binding scores of -5.90 kcal/mol and -2.59 kcal/mol by HSA-aminoguanidine and HSA-carnosine complex, respectively. Aminoguanidine forms one conventional hydrogen bond with ARG A:10 and a salt bridge with ASP A:13, ASP A:259, ASP A:255, and ASP A:256 from the amine group. Similarly, carnosine forms only hydrogen bonds with GLU A:501 and GLN A:508 from the amine and hydroxy group. The root mean square deviation (RMSD) calculated from simulation studies was 1 nm upto 70 ns for the HSA-aminoguanidine complex and the spectrum of HSA-carnosine was significantly deviated and not stabilized. The superior inhibitory activity of aminoguanidine could be due to additional salt bridge bonding with albumin. Conclusively, aminoguanidine can be the better treatment choice for diabetes-associated neurological diseases.

Combinatorial protein engineering and transporter engineering for efficient synthesis of L-Carnosine in Escherichia coli

L-Carnosine has various physiological functions and is widely used in cosmetics, medicine, food additives, and other fields. However, the yield of L-Carnosine obtained by biological methods is far from the level of industrial production. Herein, a cell factory for efficient synthesis of L-Carnosine was constructed based on transporter engineering and protein engineering. Firstly, a dipeptidase (SmpepD) was screened from Serratia marcescens through genome mining to construct a cell factory for synthesizing L-Carnosine. Subsequently, through rationally designed SmPepD, a double mutant T168S/G148D increased the L-Carnosine yield by 41.6% was obtained. Then, yeaS, a gene encoding the exporter of L-histidine, was deleted to further increase the production of L-Carnosine. Finally, L-Carnosine was produced by one-pot biotransformation in a 5 L bioreactor under optimized conditions with a yield of 133.2 mM. This study represented the highest yield of L-Carnosine synthesized in microorganisms and provided a biosynthetic pathway for the industrial production of L-Carnosine.

Oxidative stress in intervertebral disc degeneration: Molecular mechanisms, pathogenesis and treatment

Low back pain (LBP) is a leading cause of labour loss and disability worldwide, and it also imposes a severe economic burden on patients and society. Among symptomatic LBP, approximately 40% is caused by intervertebral disc degeneration (IDD). IDD is the pathological basis of many spinal degenerative diseases such as disc herniation and spinal stenosis. Currently, the therapeutic approaches for IDD mainly include conservative treatment and surgical treatment, neither of which can solve the problem from the root by terminating the degenerative process of the intervertebral disc (IVD). Therefore, further exploring the pathogenic mechanisms of IDD and adopting targeted therapeutic strategies is one of the current research hotspots. Among the complex pathophysiological processes and pathogenic mechanisms of IDD, oxidative stress is considered as the main pathogenic factor. The delicate balance between reactive oxygen species (ROS) and antioxidants is essential for maintaining the normal function and survival of IVD cells. Excessive ROS levels can cause damage to macromolecules such as nucleic acids, lipids, and proteins of cells, affect normal cellular activities and functions, and ultimately lead to cell senescence or death. This review discusses the potential role of oxidative stress in IDD to further understand the pathophysiological processes and pathogenic mechanisms of IDD and provides potential therapeutic strategies for the treatment of IDD.

Biochemical Mechanisms of Beneficial Effects of Beta-Alanine Supplements on Cognition

Using nutritional interventions to cure and manage psychiatric disorders is a promising tool. In this regard, accumulating documents support strong relationships between the diet and brain health throughout the lifespan. Evidence from animal and human studies demonstrated that β-alanine (Beta-alanine; BA), a natural amino acid, provides several benefits in fight against cognitive decline promoting mental health. This review summarizes and reports state-of-the-art evidence on how BA affects cognitive health and argues existence of potential unrevealed biochemical mechanisms and signaling cascades. There is a growing body of evidence showing that BA supplement has a significant role in mental health mediating increase of the cell carnosine and brain-derived neurotrophic factor (BDNF) content. BDNF is one of the most studied neurotrophins in the mammalian brain, which activates several downstream functional cascades via the tropomyosin-related kinase receptor type B (TrkB). Activation of TrkB induces diverse processes, such as programmed cell death and neuronal viability, dendritic branching growth, dendritic spine formation and stabilization, synaptic development, cognitive-related processes, and synaptic plasticity. Carnosine exerts its main effect via its antioxidant properties. This critical antioxidant also scavenges hypochlorous acid (HOCl), another toxic species produced in mammalian cells. Carnosine regulates transcription of hundreds of genes related to antioxidant mechanisms by increasing expression of the nuclear erythroid 2-related factor 2 (Nrf2) and translocating Nrf2 to the nucleus. Another major protective effect of carnosine on the central nervous system (CNS) is related to its anti-glycating, anti-aggregate activities, anti-inflammatory, metal ion chelator activity, and regulation of pro-inflammatory cytokine secretion. These effects could be associated with the carnosine ability to form complexes with metal ions, particularly with zinc (Zn2+). Thus, it seems that BA via BDNF and carnosine mechanisms may improve brain health and cognitive function over the entire human lifespan.

Anti-inflammatory and antioxidant traditional Chinese Medicine in treatment and prevention of osteoporosis

A metabolic bone disorder called osteoporosis is characterized by decreased bone mass and compromised microarchitecture. This condition can deteriorate bones and raise the risk of fractures. The two main causes of osteoporosis are an increase in osteoclast activity or quantity and a decrease in osteoblast viability. Numerous mechanisms, including estrogen shortage, aging, chemical agents, and decreased mechanical loads, have been linked to osteoporosis. Inflammation and oxidative stress have recently been linked to osteoporosis, according to an increasing number of studies. The two primary medications used to treat osteoporosis at the moment are bisphosphonates and selective estrogen receptor modulators (SERMs). These medications work well for osteoporosis brought on by aging and estrogen deprivation, however, they do not target inflammation and oxidative stress-induced osteoporosis. In addition, these drugs have some limitations that are attributed to various side effects that have not been overcome. Traditional Chinese medicine (TCM) has been applied in osteoporosis for many years and has a high safety profile. Therefore, in this review, literature related to botanical drugs that have an effect on inflammation and oxidative stress-induced osteoporosis was searched for. Moreover, the pharmacologically active ingredients of these herbs and the pathways were discussed and may contribute to the discovery of more safe and effective drugs for the treatment of osteoporosis.

Effects of carnosine on the embryonic development and TiO2 nanoparticles-induced oxidative stress on Zebrafish

Oxidative stress is due to an unbalance between pro-oxidants, such as reactive oxygen (ROS) and nitrogen (RNS) species, and antioxidants/antioxidant system. Under physiological conditions these species are involved in different cellular processes such as cellular homeostasis and immune response, while an excessive production of ROS/RNS has been linked to the development of various diseases such as cancer, diabetes, and Alzheimer's disease. In this context, the naturally occurring dipeptide carnosine has shown the ability to scavenge ROS, counteract lipid peroxidation, and inhibit proteins oxidation. Titanium dioxide nanoparticles (TiO₂-NPs) have been widely used to produce cosmetics, in wastewater treatment, in food industry, and in healthcare product. As consequence, these NPs are often released into aquatic environments. The Danio rerio (commonly called zebrafish) embryos exposure to TiO₂-NPs did not affect the hatching rate, but induced oxidative stress. According to this scenario, in the present study, we first investigated the effects of carnosine exposure and of a sub-toxic administration of TiO₂-NPs on the development and survival of zebrafish embryos/larvae measured through the acute embryo toxicity test (FET-Test). Zebrafish larvae represent a useful model to study oxidative stress-linked disorders and to test antioxidant molecules, while carnosine was selected based on its well-known multimodal mechanism of action that includes a strong antioxidant activity. Once the basal effects of carnosine were assessed, we then evaluated its effects on TiO₂-NPs-induced oxidative stress in zebrafish larvae, measured in terms of total ROS production (measured with 2,7-dichlorodihydrofluorescein diacetate probe) and protein expression by immunohistochemistry of two cellular stress markers, 70 kDa-heat shock protein (Hsp70) and metallothioneins (MTs). We demonstrated that carnosine did not alter the phenotypes of both embryos and larvae of zebrafish at different hours post fertilization. Carnosine was instead able to significantly decrease the enhancement of ROS levels in zebrafish larvae exposed to TiO₂-NPs and its antioxidant effect was paralleled by the rescue of the protein expression levels of Hsp70 and MTs. Our results suggest a therapeutic potential of carnosine as a new pharmacological tool in the context of pathologies characterized by oxidative stress such as neurodegenerative disorders.

Effect of Carnosine on the Activity of Matrix Metalloproteinase-2 and Oxidative Stress in the Kidneys in Experimental Urate Nephrolithiasis

The effect of carnosine on MMP-2 activity and oxidative stress in the kidneys in experimental urate nephrolithiasis was studied. Urate nephrolithiasis was modeled in Wistar rats by intragastric administration of a mixture of oxonic and uric acids. Carnosine was administered intragastrically through a tube in a dose of 15 mg/kg. In rats treated with carnosine, the concentration of MMP-2 in the urine decreased by 3.7 times, and the excretion of MMP-2 with urine decreased by 4.3 times. In the homogenate of the kidneys from rats treated with carnosine, the concentration of TBA-reactive substances decreased by 5 times and the concentration of MMP-2 decreased by 12.7%. After treatment with carnosine, the number of histologically confirmed cases of urate nephrolithiasis decreased by 2 times, while the mean size of urate deposits decreased by 2.7 times. Thus, carnosine inhibits MMP-2 and reduces the intensity of oxidative stress in the kidneys, which prevents the development of urate nephrolithiasis.

Serum levels of carnosine may be associated with the duration of MDD episodes

BACKGROUND

Major depressive disorder (MDD) is a recurrent disorder that incurs a high societal burden. However, the etiology of MDD remains unclear. The functioning of several systems associated with the etiopathogenesis of MDD, such as inflammatory and stress systems, is partially modulated by the dipeptide carnosine.

METHODS

The study comprised 99 MDD patients and 253 non-depressed controls aged 20-71 years. Fasting serum samples were analyzed using ultra-performance liquid chromatography coupled to mass spectrometry to determine the serum levels of carnosine and its constituent, histidine. We compared these metabolites in three different settings: 1) MDD patients vs. non-depressed controls and 2) remitted vs. non-remitted MDD patients, as well as 3) changes in the metabolite levels during the follow-up period within a) the remitted group and b) the non-remitted group. In addition, we assessed the possible effect of medications on the measured metabolites.

RESULTS

We observed higher serum levels of carnosine in the MDD group compared to the control group at baseline (OR = 1.895, 95%CI = 1.223-2.937, p = 0.004). Elevated serum levels of carnosine were also associated with a longer duration of the depressive episode (Z = 0.406, p = 0.001). However, the use of any antipsychotic medication (n = 36) was associated with lowered carnosine levels (p = 0.010 for use vs. non-use). At the follow-up, remitted and non-remitted participants displayed no significant differences in their carnosine levels (Z = -0.14, p = 0.891) or histidine (Z = -1.39 p = 0.164).

CONCLUSIONS

An increase in circulating carnosine may characterize depressive episodes and may represent a protective homeostatic reaction against MDD-related oxidative stress and inflammation.

Quantitative Determination of 2-Oxo-Imidazole-Containing Dipeptides by High-Performance Liquid Chromatography/Tandem Mass Spectrometry

2-Oxo-imidazole-containing dipeptides (2-oxo-IDPs), novel imidazole-containing dipeptide (IDP) derivatives, exhibit a much higher antioxidant capacity than that of IDPs. However, quantitative methods have only been developed for IDPs, and methods for the quantitative analysis of 2-oxo-IDPs are needed. In this study, we developed methods for the quantitative analysis of 2-oxo-IDPs by high-performance liquid chromatography with online electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) coupled with a stable isotope dilution method. First, we prepared stable isotope-labeled IDP and 2-oxo-IDP standards for MS analyses. Next, using these standards, we established highly sensitive, selective, and absolute quantitative analysis methods for five IDPs and five 2-oxo-IDPs by HPLC-ESI-MS/MS, achieving a limit of detection in the fmol range. Finally, we applied the method to various types of meat, such as beef, pork, chicken, and whale meat, demonstrating the detection of both IDPs and 2-oxo-IDPs. Furthermore, we provide the first evidence for the endogenous production of 2-oxo-balenine in meats. The methods developed in this study enable the detection of trace levels of 2-oxo-IDPs in biological samples and could be helpful for understanding the biological relevance of 2-oxo-IDPs.

Research Advances on the Damage Mechanism of Skin Glycation and Related Inhibitors

Our skin is an organ with the largest contact area between the human body and the external environment. Skin aging is affected directly by both endogenous factors and exogenous factors (e.g., UV exposure). Skin saccharification, a non-enzymatic reaction between proteins, e.g., dermal collagen and naturally occurring reducing sugars, is one of the basic root causes of endogenous skin aging. During the reaction, a series of complicated glycation products produced at different reaction stages and pathways are usually collectively referred to as advanced glycation end products (AGEs). AGEs cause cellular dysfunction through the modification of intracellular molecules and accumulate in tissues with aging. AGEs are also associated with a variety of age-related diseases, such as diabetes, cardiovascular disease, renal failure (uremia), and Alzheimer's disease. AGEs accumulate in the skin with age and are amplified through exogenous factors, e.g., ultraviolet radiation, resulting in wrinkles, loss of elasticity, dull yellowing, and other skin problems. This article focuses on the damage mechanism of glucose and its glycation products on the skin by summarizing the biochemical characteristics, compositions, as well as processes of the production and elimination of AGEs. One of the important parts of this article would be to summarize the current AGEs inhibitors to gain insight into the anti-glycation mechanism of the skin and the development of promising natural products with anti-glycation effects.

Carnosine as a potential therapeutic for the management of peripheral vascular disease

AIMS

To evaluate the potential role of carnosine in the management of peripheral vascular disease.

DATA SYNTHESIS

Peripheral vascular disease is growing in its burden and impact; however it is currently under researched, and there are a lack of strong, non-invasive therapeutic options for the clinicians. Carnosine is a dipeptide stored particularly in muscle and brain tissue, which exhibits a wide range of physiological activities, which may be beneficial as an adjunct treatment for peripheral vascular disease. Carnosine's strong anti-inflammatory, antioxidant and antiglycating actions may aid in the prevention of plaque formation, through protective actions on the vascular endothelium, and the inhibition of foam cells. Carnosine may also improve angiogenesis, exercise performance and vasodilatory response, while protecting from ischemic tissue injury.

CONCLUSIONS

Carnosine may have a role as an adjunct treatment for peripheral vascular disease alongside typical exercise and surgical interventions, and may be used in high risk individuals to aid in the prevention of atherogenesis.

CLINICAL RECOMMENDATION

This review identifies a beneficial role for carnosine supplementation in the management of patients with peripheral vascular disease, in conjunction with exercise and revascularization. Carnosine as a supplement is safe, and associated with a host of beneficial effects in peripheral vascular disease and its key risk factors.

Efficacy of 12 weeks oral beta-alanine supplementation in patients with chronic obstructive pulmonary disease: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Beta-alanine (BA) supplementation increases muscle carnosine, an abundant endogenous antioxidant and pH buffer in skeletal muscle. Carnosine loading promotes exercise capacity in healthy older adults. As patients with chronic obstructive pulmonary disease (COPD) suffer from elevated exercise-induced muscle oxidative/carbonyl stress and acidosis, and from reduced muscle carnosine stores, it was investigated whether BA supplementation augments muscle carnosine and induces beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress in patients with COPD.

METHODS

In this double-blind, randomized, placebo (PL)-controlled trial (clinicaltrials.gov identifier: NCT02770417), 40 patients (75% male) with COPD (mean ± standard deviation: age 65 ± 6 years; FEV₁ % predicted 55 ± 14%) were assigned to 12 weeks oral BA or PL supplementation (3.2 g/day). The primary outcome, i.e. muscle carnosine, was quantified from m. vastus lateralis biopsies obtained before and after intervention. Co-primary outcomes, i.e. incremental and constant work rate cycle capacity, were also assessed. Linear mixed model analyses were performed. Compliance with and side effects of supplement intake and secondary outcomes (quadriceps strength and endurance, and muscle oxidative/carbonyl stress) were also assessed.

RESULTS

Beta-alanine supplementation increased muscle carnosine in comparison with PL in patients with COPD (mean difference [95% confidence interval]; +2.82 [1.49-4.14] mmol/kg wet weight; P < 0.001). Maximal incremental cycling capacity (VO₂ peak: +0.5 [-0.7 to 1.7] mL/kg/min; P = 0.384, Wpeak: +5 [-1 to 11] W; P = 0.103) and time to exhaustion on the constant work rate cycle test (+28 [-179 to 236] s; P = 0.782) did not change significantly. Compliance with supplement intake was similar in BA (median (quartile 1-quartile 3); 100 (98-100)%) and PL (98 (96-100)%) (P = 0.294) groups, and patients did not report side effects possibly related to supplement intake. No change was observed in secondary outcomes.

CONCLUSIONS

Beta-alanine supplementation is efficacious in augmenting muscle carnosine (+54% from mean baseline value) without side effects in patients with COPD in comparison with PL. However, accompanied beneficial changes in exercise capacity, quadriceps function, and muscle oxidative/carbonyl stress were not observed.

Deneysel hipertiroidide fiziksel ve vital bulguların ve karnozinin etkisinin değerlendirilmesi

Purpose: This study aims to investigate the effects of experimental hyperthyroidism and carnosine which is known to have antioxidant properties on physical and vital findings in rats, and to determine the relationship between these parameters and free T3 (FT3) levels. Materials and Methods: Rats were analyzed in 7 groups (each containing 12 animals); control (CONT), hyperthyroidism-1 (T:10-day L-thyroxine (L-T4) administration), hyperthyroidism-2 (T-T: 20-day L-T4 administration), Carnosine (10 day carnosine administration), Hyperthyroidism-1 + Carnosine (T-C), Hyperthyroidism-2 + Carnosine (T-TC), and Carnosine + Hyperthyroidism-1 (C-T). In order to create a hyperthyroidism model, L-thyroxine (L-T4) doses of 300 µg/kg rat weight/day and carnosine doses of 300 µg/kg rat weight/ day were intraperitoneally (ip) administered to the rats. Results: After 10 and 20 days of thyroxine administration, FT3 levels (T:3.640.51pg/mL, T-T: 4.060.91pg/mL) and body temperature (T:37.10.3oC, T-T: 37.60.3oC), significantly increased while body weight decreased (T:240.722.0g, T-T:263.028.7g). Carnosine administration only prevented the increase of FT3 levels, but had no effect on other parameters. Conclusion: The increased FT3 levels observed with L-T4 administration were consistent with the physical and vital findings, but carnosine administration did not reflect the expected effects on the physical findings observed in the hyperthyroid condition.

Skeletal muscle oxidative stress and inflammation in aging: Focus on antioxidant and anti-inflammatory therapy

With aging, the progressive loss of skeletal muscle will have negative effect on multiple physiological parameters, such as exercise, respiration, thermoregulation, and metabolic homeostasis. Accumulating evidence reveals that oxidative stress and inflammation are the main pathological characteristics of skeletal muscle during aging. Here, we focus on aging-related sarcopenia, summarize the relationship between aging and sarcopenia, and elaborate on aging-mediated oxidative stress and oxidative damage in skeletal muscle and its critical role in the occurrence and development of sarcopenia. In addition, we discuss the production of excessive reactive oxygen species in aging skeletal muscle, which reduces the ability of skeletal muscle satellite cells to participate in muscle regeneration, and analyze the potential molecular mechanism of ROS-mediated mitochondrial dysfunction in aging skeletal muscle. Furthermore, we have also paid extensive attention to the possibility and potential regulatory pathways of skeletal muscle aging and oxidative stress mediate inflammation. Finally, in response to the abnormal activity of oxidative stress and inflammation during aging, we summarize several potential antioxidant and anti-inflammatory strategies for the treatment of sarcopenia, which may provide beneficial help for improving sarcopenia during aging.

Salidroside protects against osteoporosis in ovariectomized rats by inhibiting oxidative stress and promoting osteogenesis via Nrf2 activation

BACKGROUND

Osteoporosis (OP) is characterized as low bone mass, bone microarchitecture breakdown and bone fragility. The increase of oxidative stress could lead to breakdown in the balance of bone formation and resorption which gives rise to OP. Nrf2 is a transcription factor which takes part in oxidative stress and recently was reported that it can regulate the occurrence of OP. Salidroside (SAL) with the efficacies of anti-oxidation, anti-aging and bone-protection is one of the active ingredients in Ligustri Lucidi Fructus, a traditional Chinese medicinal herb. Nevertheless, few studies have explored the potential mechanism of SAL preventing OP development from the perspective of oxidative stress intervention.

PURPOSE

This study aimed to investigate the pharmacological effect and molecular mechanisms of SAL on OP.

STUDY DESIGNS AND METHODS

A tert-butyl hydroperoxide (t-BHP)-induced oxidative stress model was applied for investigating the effects of SAL in vitro, and an ovariectomized (OVX) model was used for in vivo study on the effect of SAL for OP. Related pharmacodynamic actions and molecular mechanisms of SAL were explored in both rat osteoblasts (ROBs) and OVX rats. Network biology and cell metabolomics were performed for further investigating the correlation and association among potential biomarkers, targets and pathways.

RESULTS

SAL reduced levels of ROS and lipid peroxidation (LPO), increased activities of antioxidant enzymes like GPx and SOD, and enhanced osteogenic differentiation in t-BHP-induced ROBs and OVX rats. Mechanistic studies showed SAL prevented OP development and reduced oxidative damage in ROBs and OVX rats through up-regulating Nrf2 expression and facilitating its nuclear translocation. The joint analysis of network biology and cell metabolomics revealed that galactose metabolism and fatty acid metabolism could be the major influenced pathways following treatment with SAL.

CONCLUSION

SAL could protect against OP by inhibiting oxidative stress, promoting osteogenesis through the up-regulation of Nrf2 and intervening galactose metabolism and fatty acid metabolism. Our study implied that SAL may be a potential drug to treat OP.

Antioxidant and Neuroprotective Effects of Carnosine: Therapeutic Implications in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) constitute a global challenge to human health and an important social and economic burden worldwide, mainly due to their growing prevalence in an aging population and to their associated disabilities. Despite their differences at the clinical level, NDs share fundamental pathological mechanisms such as abnormal protein deposition, intracellular Ca²⁺ overload, mitochondrial dysfunction, redox homeostasis imbalance and neuroinflammation. Although important progress is being made in deciphering the mechanisms underlying NDs, the availability of effective therapies is still scarce. Carnosine is a natural endogenous molecule that has been extensively studied during the last years due to its promising beneficial effects for human health. It presents multimodal mechanisms of action, being able to exert antioxidant, anti-inflammatory and anti-aggregate activities, among others. Interestingly, most NDs exhibit oxidative and nitrosative stress, protein aggregation and inflammation as molecular hallmarks. In this review, we discuss the neuroprotective functions of carnosine and its implications as a therapeutic strategy in different NDs. We summarize the existing works that study alterations in carnosine metabolism in Alzheimer’s disease and Parkinson’s disease, the two most common NDs. In addition, we review the beneficial effect that carnosine supplementation presents in models of such diseases as well as in aging-related neurodegeneration.

Separation and identification of the DL-forms of short-chain peptides using a new chiral resolution labeling reagent

There are several reports of D-amino acids being the causative molecules of serious diseases, resulting in the formation of, for example, prion protein and amyloid β. D-Amino acids in peptides and proteins are typically identified by sequencing each residue by Edman degradation or by hydrolysis with hydrochloric acid for amino acid analysis. However, these approaches can result in racemization of the L-form to the D-form by hydrolysis and long pre-treatment for hydrolysis. To address these problems, we aimed to identify the DL-forms of amino acids in peptides without hydrolysis. Here, we showed that the DL-forms in peptides which are difficult to separate on a chiral column can be precisely separated by labeling with 1-fluoro-2,4-dinitrophenyl-5-D-leucine-N,N-dimethylethylenediamine-amide (D-FDLDA). Additionally, the peptides could be quantitatively analyzed using the same labeling method as for amino acids. Furthermore, the detection sensitivity of a sample labeled with D-FDLDA was higher than that of the conventional reagents Nα-(5-fluoro-2,4-dinitrophenyl)-L-alaninamide (L-FDAA) and Nα-(5-fluoro-2,4-dinitrophenyl)-L-leucinamide (L-FDLA) used in Marfey's method. The proposed method for identifying DL-forms of amino acids in peptides is a powerful tool for use in organic chemistry, biochemistry, and medical science.

Metabolomics Analysis for Nitrite Degradation by the Metabolites of Limosilactobacillus fermentum RC4

Nitrite (NIT), a commonly used food additive, especially in pickled and cured vegetables and meat products, might cause acute and chronic diseases. Fermentation with lactic acid bacteria (LAB) is an effective method for degrading NIT and improving the flavor of pickled and cured foods. In this study, Limosilactobacillus fermentum (L. fermentum) RC4 with a high NIT degradation ability was found to degrade NIT in a new manner when compared with reported enzymatic and acid degradation, namely, metabolite degradation during fermentation in MRS broth, which shows a synergistic effect with acid to increase NIT degradation. Liquid chromatography–mass spectrometry analysis identified 134 significantly different metabolites, of which 11 metabolites of L. fermentum RC4, namely, γ-aminobutyric acid (GABA), isocitric acid, D-glucose, 3-methylthiopropionic acid (MTP), N-formyl-L-methionine, dimethyl sulfone (MSM), D-ribose, mesaconate, trans-aconitic acid, L-lysine, and carnosine, showed significant NIT degradation effects compared with the control group (MRS broth). Verification experiments showed that adding the above 11 metabolites to 100 mg/L NIT and incubating for 24 h resulted in NIT degradation rates of 5.07%, 4.41%, 6.08%, 16.93%, 5.28%, 2.41%, 0.93%, 18.93%, 12.25%, 6.42%, and 3.21%, respectively. Among these, three metabolites, namely, mesaconate, MTP, and trans-aconitic acid, showed efficient NIT degradation abilities that might be related to the degradation mechanism involving decarboxylation reactions. This is the first systematic study of NIT degradation by LAB, resulting in the identification of a new metabolite degradation pathway and three efficient NIT degradation metabolites.

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.

Carnosine, oxidative and carbonyl stress, antioxidants and muscle fiber characteristics of quadriceps muscle of patients with COPD

BACKGROUND

Oxidative/carbonyl stress is elevated in lower-limb muscles of patients with Chronic Obstructive Pulmonary Disease (COPD). Carnosine is a skeletal muscle antioxidant particularly present in fast-twitch fibers.

AIMS

To compare muscle carnosine, oxidative/carbonyl stress, antioxidants and fiber characteristics between patients with COPD and healthy controls (HCs), and between patients after stratification for airflow limitation (mild/moderate vs. severe/very-severe). To investigate correlates of carnosine in patients with COPD.

METHODS

A vastus lateralis muscle biopsy was obtained from 40 patients with stable COPD and 20 age/sex matched HCs. Carnosine, oxidative/carbonyl stress, antioxidants, fiber characteristics, quadriceps strength and endurance (QE), VO₂peak (incremental cycle test) and physical activity (PA) were determined.

RESULTS

Patients with COPD had a similar carnosine concentration (4.16 mmol/kg wet weight (WW) (SD 1.93)) to HCs (4.64 mmol/kgWW (SD 1.71)) and significantly higher percentage of fast-twitch fibers and lower QE, VO₂peak and PA vs. HCs. Patients with severe/very-severe COPD had a 30% lower carnosine concentration (3.24 mmol/kgWW (SD 1.79); n=15) vs. patients with mild/moderate COPD (4.71 mmol/kgWW (SD 1.83); n=25; P=0.02) and significantly lower VO₂peak and PA vs. patients with mild/moderate COPD. Carnosine correlated significantly with QE (r_s=0.427), VO₂peak (r_s=0.334), PA (r_s=0.379) and lung function parameters in patients with COPD.

CONCLUSION

Despite having the highest proportion of fast-twitch fibers, patients with severe/very-severe COPD displayed a 30% lower muscle carnosine concentration compared to patients with mild/moderate COPD. As no oxidative/carbonyl stress markers, nor antioxidants were affected, the observed carnosine deficiency is thought to be a possible first sign of muscle redox balance abnormalities.

Carnosine, Small but Mighty-Prospect of Use as Functional Ingredient for Functional Food Formulation

Carnosine is a dipeptide synthesized in the body from β-alanine and L-histidine. It is found in high concentrations in the brain, muscle, and gastrointestinal tissues of humans and is present in all vertebrates. Carnosine has a number of beneficial antioxidant properties. For example, carnosine scavenges reactive oxygen species (ROS) as well as alpha-beta unsaturated aldehydes created by peroxidation of fatty acid cell membranes during oxidative stress. Carnosine can oppose glycation, and it can chelate divalent metal ions. Carnosine alleviates diabetic nephropathy by protecting podocyte and mesangial cells, and can slow down aging. Its component, the amino acid beta-alanine, is particularly interesting as a dietary supplement for athletes because it increases muscle carnosine, and improves effectiveness of exercise and stimulation and contraction in muscles. Carnosine is widely used among athletes in the form of supplements, but rarely in the population of cardiovascular or diabetic patients. Much less is known, if any, about its potential use in enriched food. In the present review, we aimed to provide recent knowledge on carnosine properties and distribution, its metabolism (synthesis and degradation), and analytical methods for carnosine determination, since one of the difficulties is the measurement of carnosine concentration in human samples. Furthermore, the potential mechanisms of carnosine's biological effects in musculature, metabolism and on immunomodulation are discussed. Finally, this review provides a section on carnosine supplementation in the form of functional food and potential health benefits and up to the present, neglected clinical use of carnosine.

Ecofriendly Synthesis of l-Carnosine in Metabolically Engineered Corynebacterium glutamicum by Reinforcing Precursor Accumulation

Biobased processes to minimize environmental pollutants have attracted much attention. l-Carnosine has been produced by chemical synthesis, and as an alternative to this method, we newly developed engineered Corynebacterium glutamicum synthesizing l-carnosine. To develop the strain, the pentose phosphate pathway (PPP) was enhanced by attenuating flux to nonoxidative PPP. Enhanced PPP strengthened the histidine pathway and produced 5.0 g/L l-histidine and 3.9 mg/L l-carnosine. Then, the histidine synthetic pathway was reinforced by overexpressing HisG and Rel. This pathway reduced feedback inhibition by l-histidine and strengthened the flux of the histidine pathway; thus, it produced 552.20 mg/g _DCW l-histidine. As a result, enhancement of the PPP accumulates more l-histidine than the histidine pathway; thus, the PPP was further enhanced by pgi gene alteration. For sufficient β-alanine products, PanD was overexpressed and produced 99.17 mg/L l-carnosine. The final strain, Car15, which consolidated all three pathways, produced 323.26 mg/L l-carnosine via fed-batch fermentation. Finally, we confirmed the antioxidant and antiglycation effects of biologically synthesized l-carnosine, and the biologically synthesized l-carnosine showed inhibitory activity similar to that of commercial l-carnosine. Consequently, this study suggested a new biosynthetic process for l-carnosine and showed potential as a treatment for metabolic disorders through the assessment of its functions.

Histidine dipeptides are key regulators of excitation-contraction coupling in cardiac muscle: Evidence from a novel CARNS1 knockout rat model

Histidine-containing dipeptides (HCDs) are abundantly expressed in striated muscles. Although important properties have been ascribed to HCDs, including H⁺ buffering, regulation of Ca²⁺ transients and protection against oxidative stress, it remains unknown whether they play relevant functions in vivo. To investigate the in vivo roles of HCDs, we developed the first carnosine synthase knockout (CARNS1^−/−) rat strain to investigate the impact of an absence of HCDs on skeletal and cardiac muscle function. Male wild-type (WT) and knockout rats (4 months-old) were used. Skeletal muscle function was assessed by an exercise tolerance test, contractile function in situ and muscle buffering capacity in vitro. Cardiac function was assessed in vivo by echocardiography and cardiac electrical activity by electrocardiography. Cardiomyocyte contractile function was assessed in isolated cardiomyocytes by measuring sarcomere contractility, along with the determination of Ca²⁺ transient. Markers of oxidative stress, mitochondrial function and expression of proteins were also evaluated in cardiac muscle. Animals were supplemented with carnosine (1.8% in drinking water for 12 weeks) in an attempt to rescue tissue HCDs levels and function. CARNS1^−/− resulted in the complete absence of carnosine and anserine, but it did not affect exercise capacity, skeletal muscle force production, fatigability or buffering capacity in vitro, indicating that these are not essential for pH regulation and function in skeletal muscle. In cardiac muscle, however, CARNS1^−/− resulted in a significant impairment of contractile function, which was confirmed both in vivo and ex vivo in isolated sarcomeres. Impaired systolic and diastolic dysfunction were accompanied by reduced intracellular Ca²⁺ peaks and slowed Ca²⁺ removal, but not by increased markers of oxidative stress or impaired mitochondrial respiration. No relevant increases in muscle carnosine content were observed after carnosine supplementation. Results show that a primary function of HCDs in cardiac muscle is the regulation of Ca²⁺ handling and excitation-contraction coupling.

Biomarkers of Senescence during Aging as Possible Warnings to Use Preventive Measures

Human life expectancy is increasing significantly over time thanks to the improved possibility for people to take care of themselves and the higher availability of food, drugs, hygiene, services, and assistance. The increase in the average age of the population worldwide is, however, becoming a real concern, since aging is associated with the rapid increase in chronic inflammatory pathologies and degenerative diseases, very frequently dependent on senescent phenomena that occur alongside with senescence. Therefore, the search for reliable biomarkers that can diagnose the possible onset or predict the risk of developing a disease associated with aging is a crucial target of current medicine. In this review, we construct a synopsis of the main addressable biomarkers to study the development of aging and the associated ailments.

Association of dietary intake, medication and anthropometric indices with serum levels of advanced glycation end products, caspase-3, and matrix metalloproteinase-9 in diabetic patients

Background and objective

Increased serum levels of advanced glycation end products (AGEs), caspase-3 (Cas-3) and matrix metalloproteinase-9 (MMP-9) have been reported in diabetic patients. This study aimed to evaluate association of anthropometric, dietary, and therapeutic factors with serum levels of methylglyoxal (MGO), carboxymethyl lysine (CML), pentosidine (Pen), Cas-3, and MMP-9 in diabetic patients.

Methods

The current study included 36 diabetic subjects. Dietary intake of the participants was assessed using three-day 24-h recall survey and anthropometric indices were measured. Demographic factors and medication intake of every subject were obtained. Serum levels of CML, MGO, Pen, MMP-9, and Cas-3 were measured using ELISA method.

Results

Gliclazide consumption was positively correlated with MMP-9 and Cas-3, but not AGEs levels. Females had higher MGO level compared with males. Further, CML levels were negatively correlated with BMI and WHR. Dietary protein intake was positively correlated with MMP-9, Cas-3, and MGO levels. As well as dietary energy and fat intake had significant positive relationship with serum Cas-3 concentration.

Conclusion

It is concluded that anthropometric characteristics, dietary intake, and therapeutic medications are possible factors that may determine the circulating levels of AGEs, MMP-9, and Cas-3 in patients with diabetes.

Kinetics of Muscle Carnosine Decay after β-Alanine Supplementation: A 16-wk Washout Study

PURPOSE

This study aimed to describe the kinetics of carnosine washout in human skeletal muscle over 16 wk.

METHODS

Carnosine washout kinetics were studied in 15 young, physically active omnivorous men randomly assigned to take 6.4 g·d-1 of β-alanine (n = 11) or placebo (n = 4) for 8 wk. Muscle carnosine content (M-Carn) was determined before (PRE), immediately after (POST), and 4, 8, 12, and 16 wk after supplementation. High-intensity exercise tests were performed at these same time points. Linear and exponential models were fitted to the washout data, and the leave-one-out method was used to select the model with the best fit for M-Carn decay data. Repeated-measures correlation analysis was used to assess the association between changes in M-Carn and changes in performance.

RESULTS

M-Carn increased from PRE to POST in the β-alanine group only (+91.1% ± 29.1%; placebo, +0.04% ± 10.1%; P < 0.0001). M-Carn started to decrease after cessation of β-alanine supplementation and continued to decrease until week 16 (POST4, +59% ± 40%; POST8, +35% ± 39%; POST12, +18% ± 32%; POST16, -3% ± 24% of PRE M-Carn). From week 12 onward, M-Carn was no longer statistically different from PRE. Both linear and exponential models displayed very similar fit and could be used to describe carnosine washout, although the linear model presented a slightly better fit. The decay in M-Carn was mirrored by a similar decay in high-intensity exercise tolerance; M-Carn was moderately and significantly correlated with total mechanical work done (r = 0.505; P = 0.032) and time to exhaustion (r = 0.72; P < 0.001).

CONCLUSIONS

Carnosine washout takes 12-16 wk to complete, and it can be described either by linear or exponential curves. Changes in M-Carn seem to be mirrored by changes in high-intensity exercise tolerance. This information can be used to optimize β-alanine supplementation strategies.

Metabolomic characterisation of progression and spontaneous regression of melanoma in the melanoma-bearing Libechov minipig model

Melanoma-bearing Libechov minipig (MeLiM) represents a large animal model for melanoma research. This model shows a high incidence of complete spontaneous regression of melanoma - a phenomenon uncommon in humans. Here, we present the first metabolomic characterisation of the MeLiM model comparing animals with progressing and spontaneously regressing melanomas. Plasma samples of 19 minipigs with progression and 27 minipigs with evidence of regression were analysed by a targeted metabolomic assay based on mass spectrometry detection. Differences in plasma metabolomics patterns were investigated by univariate and multivariate statistical analyses. Overall, 185 metabolites were quantified in each plasma sample. Significantly altered metabolomic profile was found, and 42 features were differentially regulated in plasma. Besides, the machine learning approach was used to create a predictive model utilising Arg/Orn and Arg/ADMA ratios to discriminate minipigs with progressive disease development from minipigs with regression evidence. Our results suggest that progression of melanoma in the MeLiM model is associated with alteration of arginine, glycerophospholipid and acylcarnitines metabolism. Moreover, this study provides targeted metabolomics characterisation of an animal model of melanoma with progression and spontaneous regression of tumours.

Peptidomimetics - An infinite reservoir of metal binding motifs in metabolically stable and biologically active molecules

The involvement of metal ions in interactions with therapeutic peptides is inevitable. They are one of the factors able to fine-tune the biological properties of antimicrobial peptides, a promising group of drugs with one large drawback - a problematic metabolic stability. Appropriately chosen, proteolytically stable peptidomimetics seem to be a reasonable solution of the problem, and the use of D-, β-, γ-amino acids, unnatural amino acids, azapeptides, peptoids, cyclopeptides and dehydropeptides is an infinite reservoir of metal binding motifs in metabolically stable, well-designed, biologically active molecules. Below, their specific structural features, metal-chelating abilities and antimicrobial potential are discussed.

Urinary Levels of the Acrolein Conjugates of Carnosine Are Associated with Cardiovascular Disease Risk

Carnosine is a naturally occurring dipeptide (β-alanine-L-histidine) which supports physiological homeostasis by buffering intracellular pH, chelating metals, and conjugating with and neutralizing toxic aldehydes such as acrolein. However, it is not clear if carnosine can support cardiovascular function or modify cardiovascular disease (CVD) risk. To examine this, we measured urinary levels of nonconjugated carnosine and its acrolein conjugates (carnosine-propanal and carnosine-propanol) in participants of the Louisville Healthy Heart Study and examined associations with indices of CVD risk. We found that nonconjugated carnosine was significantly associated with hypertension (p = 0.011), heart failure (p = 0.015), those categorized with high CVD risk (p < 0.001), body mass index (BMI; p = 0.007), high sensitivity C-reactive protein (hsCRP; p = 0.026), high-density lipoprotein (HDL; p = 0.007) and certain medication uses. Levels of carnosine-propanal and carnosine-propanol demonstrated significant associations with BMI, blood glucose, HDL and diagnosis of diabetes. Carnosine-propanal was also associated with heart failure (p = 0.045) and hyperlipidemia (p = 0.002), but no associations with myocardial infarction or stroke were identified. We found that the positive associations of carnosine conjugates with diabetes and HDL remain statistically significant (p < 0.05) in an adjusted, linear regression model. These findings suggest that urinary levels of nonconjugated carnosine, carnosine-propanal and carnosine-propanol may be informative biomarkers for the assessment of CVD risk—and particularly reflective of skeletal muscle injury and carnosine depletion in diabetes.

Antioxidative Characteristics of Chicken Breast Meat and Blood after Diet Supplementation with Carnosine, L-histidine, and β-alanine

The objective of the study was to test the effect of diets supplemented with β-alanine, L-histidine, and carnosine on the histidine dipeptide content and the antioxidative status of chicken breast muscles and blood. One-day-old Hubbard Flex male chickens were assigned to five treatments: control diet (C) and control diet supplemented with 0.18% L-histidine (ExpH), 0.3% β-alanine (ExpA), a mix of L-histidine\β-alanine (ExpH+A), and 0.27% carnosine (ExpCar). After 28 days, chicken breast muscles and blood samples were analyzed for the antioxidant enzyme activity (catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD)), carnosine and anserine content, amino acid profile, and anti-radical activity (ABTS, DPPH, ferric reducing antioxidant power (FRAP)). The results of the study showed that carnosine supplementation effectively increased body weight and breast muscle share in chicken carcasses. Carnosine and L-histidine supplementation with or without β-alanine increased carnosine content in chicken breast muscles up to 20% (p = 0.003), but the boost seems to be too low to affect the potential antioxidant capacity and amino acid content. The β-alanine-enriched diet lowered dipeptide concentration in chicken blood serum (p = 0.002) and activated catalase in chicken breast muscles in relation to the control group (p = 0.003). It can be concluded that histidine or dipeptide supplementation of chicken diets differently affected the total antioxidant potential: in breast muscles, it increased dipeptide content, while in blood cell sediment (rich in erythrocytes), increased SOD and GPx activities were observed.

Deorphaning a solute carrier 22 family member, SLC22A15, through functional genomic studies

The human solute carrier 22A (SLC22A) family consists of 23 members, representing one of the largest families in the human SLC superfamily. Despite their pharmacological and physiological importance in the absorption and disposition of a range of solutes, eight SLC22A family members remain classified as orphans. In this study, we used a multifaceted approach to identify ligands of orphan SLC22A15. Ligands of SLC22A15 were proposed based on phylogenetic analysis and comparative modeling. The putative ligands were then confirmed by metabolomic screening and uptake assays in SLC22A15 transfected HEK293 cells. Metabolomic studies and transporter assays revealed that SLC22A15 prefers zwitterionic compounds over cations and anions. We identified eight zwitterions, including ergothioneine, carnitine, carnosine, gabapentin, as well as four cations, including MPP⁺ , thiamine, and cimetidine, as substrates of SLC22A15. Carnosine was a specific substrate of SLC22A15 among the transporters in the SLC22A family. SLC22A15 transport of several substrates was sodium-dependent and exhibited a higher Km for ergothioneine, carnitine, and carnosine compared to previously identified transporters for these ligands. This is the first study to characterize the function of SLC22A15. Our studies demonstrate that SLC22A15 may play an important role in determining the systemic and tissue levels of ergothioneine, carnosine, and other zwitterions.

Zinc enhances carnosine inhibitory effect against structural and functional age-related protein alterations in an albumin glycoxidation model

Age-related complications including protein alterations seen in diabetes and Alzheimer's disease are a major issue due to their accumulation and deleterious effects. This report aims to investigate the effect of zinc supplementation on the anti-glycoxidation activity of carnosine on the in vitro model of albumin-based protein modification. Besides, the therapeutic effect of this combination was tested through the addition of the molecules in tandem (co-treatment) or post initiation (post-treatment) of the protein modification process. Glycation was induced via the addition of glucose to which carnosine (5 mM) alone or with various zinc concentrations (125, 250, and 500 μM) were added either at 0 h or 24 h post-glycation induction. On the other hand, protein oxidation was induced using chloramine T (20 mM) and treated in the same way with carnosine and zinc. The different markers of glycation (advanced glycation end products (AGEs), dityrosine, and beta-sheet formation (aggregation)) and oxidation (AOPP, advanced oxidation protein products) were estimated via fluorescence and colorimetric assays. Zinc addition induced a significant enhancement of carnosine activity by reducing albumin modification that outperformed aminoguanidine both in the co- and post-treatment protocols. Zinc demonstrated a supplementary effect in combination with carnosine highlighting its potential in the protection against age-related protein modifications processes such as the ones found in diabetes.

Evaluation of Antioxidant Activity and Amino Acids in the Mucus of Mackerel for Cosmetic Applications

To identify antioxidants for improving rough skin, we aimed to analyze the amino acid composition of fish mucus and antioxidant activity of the mucus component. Specifically, we aimed to examine the antioxidant properties of dialyzed mucus components secreted from mackerel, which can be used as raw materials for producing cosmetics. The amino acid composition of hydrolyzed mucus was examined by ultra-high-performance liquid chromatography after dialyzing mucus. In addition, the antioxidant activity of the mucus was evaluated via oxygen radical absorption capacity and Trolox equivalent antioxidant capacity assays. The amino acid composition differed between the low-molecular-weight and high-molecular-weight fractions. Moreover, the low-molecular-weight fraction of farmed mackerel mucus exhibited antioxidant activity with high specificity. The results suggest that antioxidant peptides or free amino acids are present in the low-molecular-weight fraction of farmed mackerel mucus.

The Muscle Carnosine Response to Beta-Alanine Supplementation: A Systematic Review With Bayesian Individual and Aggregate Data E-Max Model and Meta-Analysis

Beta-alanine (BA) supplementation increases muscle carnosine content (MCarn), and has many proven, and purported, ergogenic, and therapeutic benefits. Currently, many questions on the nature of the MCarn response to supplementation are open, and the response to these has considerable potential to enhance the efficacy and application of this supplementation strategy. To address these questions, we conducted a systematic review with Bayesian-based meta-analysis of all published aggregate data using a dose response (Emax) model. Meta-regression was used to consider the influence of potential moderators (including dose, sex, age, baseline MCarn, and analysis method used) on the primary outcome. The protocol was designed according to PRISMA guidelines and a three-step screening strategy was undertaken to identify studies that measured the MCarn response to BA supplementation. Additionally, we conducted an original analysis of all available individual data on the MCarn response to BA supplementation from studies conducted within our lab (n = 99). The Emax model indicated that human skeletal muscle has large capacity for non-linear MCarn accumulation, and that commonly used BA supplementation protocols may not come close to saturating muscle carnosine content. Neither baseline values, nor sex, appeared to influence subsequent response to supplementation. Analysis of individual data indicated that MCarn is relatively stable in the absence of intervention, and effectually all participants respond to BA supplementation (99.3% response [95%CrI: 96.2–100]).

ALKBH7 mediates necrosis via rewiring of glyoxal metabolism

Alkb homolog 7 (ALKBH7) is a mitochondrial α-ketoglutarate dioxygenase required for DNA alkylation-induced necrosis, but its function and substrates remain unclear. Herein, we show ALKBH7 regulates dialdehyde metabolism, which impacts the cardiac response to ischemia-reperfusion (IR) injury. Using a multi-omics approach, we find no evidence ALKBH7 functions as a prolyl-hydroxylase, but we do find Alkbh7^-/- mice have elevated glyoxalase I (GLO-1), a dialdehyde detoxifying enzyme. Metabolic pathways related to the glycolytic by-product methylglyoxal (MGO) are rewired in Alkbh7^-/- mice, along with elevated levels of MGO protein adducts. Despite greater glycative stress, hearts from Alkbh7^-/- mice are protected against IR injury, in a manner blocked by GLO-1 inhibition. Integrating these observations, we propose ALKBH7 regulates glyoxal metabolism, and that protection against necrosis and cardiac IR injury bought on by ALKBH7 deficiency originates from the signaling response to elevated MGO stress.

AGE-RAGE Axis in the Pathophysiology of Chronic Lower Limb Ischemia and a Novel Strategy for Its Treatment

This review focuses on the role of advanced glycation end products (AGEs) and its cell receptor (RAGE) and soluble receptor (sRAGE) in the pathogenesis of chronic lower limb ischemia (CLLI) and its treatment. CLLI is associated with atherosclerosis in lower limb arteries. AGE-RAGE axis which comprises of AGE, RAGE, and sRAGE has been implicated in atherosclerosis and restenosis. It may be involved in atherosclerosis of lower limb resulting in CLLI. Serum and tissue levels of AGE, and expression of RAGE are elevated, and the serum levels of sRAGE are decreased in CLLI. It is known that AGE, and AGE-RAGE interaction increase the generation of various atherogenic factors including reactive oxygen species, nuclear factor-kappa B, cell adhesion molecules, cytokines, monocyte chemoattractant protein-1, granulocyte macrophage-colony stimulating factor, and growth factors. sRAGE acts as antiatherogenic factor because it reduces the generation of AGE-RAGE-induced atherogenic factors. Treatment of CLLI should be targeted at lowering AGE levels through reduction of dietary intake of AGE, prevention of AGE formation and degradation of AGE, suppression of RAGE expression, blockade of AGE-RAGE binding, elevation of sRAGE by upregulating sRAGE expression, and exogenous administration of sRAGE, and use of antioxidants. In conclusion, AGE-RAGE stress defined as a shift in the balance between stressors (AGE, RAGE) and antistressor (sRAGE) in favor of stressors, initiates the development of atherosclerosis resulting in CLLI. Treatment modalities would include reduction of AGE levels and RAGE expression, RAGE blocker, elevation of sRAGE, and antioxidants for prevention, regression, and slowing of progression of CLLI.

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.

Magnetic Resonance Spectroscopy as a Non-invasive Method to Quantify Muscle Carnosine in Humans: a Comprehensive Validity Assessment

Carnosine is a dipeptide abundantly found in human skeletal muscle, cardiac muscle and neuronal cells having numerous properties that confers performance enhancing effects, as well as a wide-range of potential therapeutic applications. A reliable and valid method for tissue carnosine quantification is crucial for advancing the knowledge on biological processes involved with carnosine metabolism. In this regard, proton magnetic resonance spectroscopy (1H-MRS) has been used as a non-invasive alternative to quantify carnosine in human skeletal muscle. However, carnosine quantification by 1H-MRS has some potential limitations that warrant a thorough experimental examination of its validity. The present investigation examined the reliability, accuracy and sensitivity for the determination of muscle carnosine in humans using in vitro and in vivo experiments and comparing it to reference method for carnosine quantification (high-performance liquid chromatography - HPLC). We used in vitro 1H-MRS to verify signal linearity and possible noise sources. Carnosine was determined in the m. gastrocnemius by 1H-MRS and HPLC to compare signal quality and convergent validity. 1H-MRS showed adequate discriminant validity, but limited reliability and poor agreement with a reference method. Low signal amplitude, low signal-to-noise ratio, and voxel repositioning are major sources of error.

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.

Synthetic Evidence of the Amadori-Type Alkylation of Biogenic Amines by the Neurotoxic Metabolite Dopegal

The neurotransmitter metabolite 3,4-dihydroxy-phenylglycolaldehyde (dopegal) damages neurons and the myocardium by protein cross-linking, resulting in conglomerations and cell death. We investigated this process on a synthetic scale, leading to the discovery of an Amadori-type rearrangement of dopegal in the reaction with several amino acids and neuropeptides. This alkylation also occurs with neurotransmitters, suggesting an influence of dopegal on neurochemical processes. The rearrangement occurs readily under physiological conditions.

The impact of resveratrol on toxicity and related complications of advanced glycation end products: A systematic review

Accumulation of advanced glycation end products (AGEs) promotes the generation of free radicals, which leads to chronic oxidative stress predisposing to chronic oxidative stress, inflammation, and related diseases. This systematic review aimed to determine the effect of resveratrol (RSV) on AGE-induced toxicity and its deleterious consequences. A comprehensive search was performed through literature were published until December 2018 using relevant keywords. The databases that were used for the search were PubMed, Scopus, Embase, ProQuest, and Google Scholar. A total of 29 eligible studies were found and included in the review for the analysis. Except one, all studies showed suppressing effects for RSV on the production of AGEs or receptor for advanced glycation end products (RAGE) and its detrimental consequences including oxidative stress, inflammatory response, cellular immune reactions, insulin response, and atherosclerosis. RSV exerts its effects through influencing RAGE, nuclear factor kappa B (NF-κB), peroxisome proliferator-activated receptor (PPAR) γ, and transforming growth factor (TGF)-β activities. This review suggests that RSV has got potential to decrease AGEs toxicity and inhibit the AGE-induced complications. More clinical trials are suggested to evaluate the beneficial effect of RSV on AGEs in chronic metabolic diseases.

Profiling and targeting of cellular mitochondrial bioenergetics: inhibition of human gastric cancer cell growth by carnosine

L-Carnosine (β-alanyl-L-histidine) is a naturally occurring dipeptide distributed in various organs of mammalians. We previously showed that carnosine inhibited proliferation of human gastric cancer cells through targeting both mitochondrial bioenergetics and glycolysis pathway. But the mechanism underlying carnosine action on mitochondrial bioenergetics of tumor cells remains unclear. In the current study we investigated the effect of carnosine on the growth of human gastric cancer SGC-7901 cells in vitro and in vivo. We firstly showed that hydrolysis of carnosine was not a prerequisite for its anti-gastric cancer effect. Treatment of SGC-7901 cells with carnosine (20 mmol/L) significantly decreased the activities of mitochondrial respiratory chain complexes I-IV and mitochondrial ATP production, and downregulated 13 proteins involved in mitochondrial bioenergetics. Furthermore, carnosine treatment significantly suppressed the phosphorylation of Akt, while inhibition of Akt activation with GSK690693 significantly reduced the localization of prohibitin-1 (PHB-1) in the mitochondria of SGC-7901 and BGC-823 cells. In addition, we showed that silencing of PHB-1 gene with shRNA markedly reduced the mitochondrial PHB-1 in SGC-7901 cells, and significantly decreased the colony formation capacity and growth rate of the cells. In SGC-7901 cell xenograft nude mice, administration of carnosine (250 mg kg/d, ip, for 3 weeks) significantly inhibited the tumor growth and decreased the expression of mitochondrial PHB-1 in tumor tissue. Taken together, these results suggest that carnosine may act on multiple mitochondrial proteins to down-regulate mitochondrial bioenergetics and then to inhibit the growth and proliferation of SGC-7901 and BGC-823 cells.