Neuroprotective features of carnosine in oxidative driven diseases

Carnosine (β-alanyl-L-histidine) is a natural dipeptide widely and abundantly distributed in excitable tissues of several animal tissues. Although its physiological role has not been completely understood yet, many beneficial actions have been attributed to carnosine, such as being an antioxidant, antiglycating and ion-chelating agent, a wound healing promoter and a free-radical scavenger. The role of carnosine in the neuroprotection of oxidative stress-driven disorders has been reviewed. The effects of carnosine have been extensively studied both in vivo and in vitro models of cerebral damages, such as neurodegenerative disorders and hypoxia-ischemia injuries. Beside the classical sacrificial agent, carnosine has been reevaluated as a molecular chaperon and an inducer of antioxidant systems in oxidative stress conditions. Thus, beneficial effects on most of the common biochemical events that characterize neurological disorders make carnosine a very promising molecule among all the endogenous compounds in the treatment and/or prevention of oxidative driven diseases.     

Carnosine and protein carbonyl groups: a possible relationship

Carnosine has been shown to react with low-molecular-weight aldehydes and ketones and has been proposed as a naturally occurring anti-glycating agent. It is suggested here that carnosine can also react with ("carnosinylate") proteins bearing carbonyl groups, and evidence supporting this idea is presented. Accumulation of protein carbonyl groups is associated with cellular ageing resulting from the effects of reactive oxygen species, reducing sugars, and other reactive aldehydes and ketones. Carnosine has been shown to delay senescence and promote formation of a more juvenile phenotype in cultured human fibroblasts. It is speculated that carnosine may intracellularly suppress the deleterious effects of protein carbonyls by reacting with them to form protein-carbonyl-carnosine adducts, i.e., "carnosinylated" proteins. Various fates of the carnosinylated proteins are discussed including formation of inert lipofuscin and proteolysis via proteosome and RAGE activities. It is proposed that the anti-ageing and rejuvenating effects of carnosine are more readily explainable by its ability to react with protein carbonyls than its well-documented antioxidant activity.     

New glycoside derivatives of carnosine and analogs resistant to carnosinase hydrolysis: synthesis and characterization of their copper(II) complexes

Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide widely and abundantly distributed in muscle and nervous tissues of several animal species. Many functions have been proposed for this compound, such as antioxidant and metal ion-chelator properties. However, the main limitation on therapeutic use of carnosine on pathologies related to increased oxidative stress and/or metal ion dishomeostasis is associated with the hydrolysis by the specific dipeptidase carnosinase. Several attempts have been made to overcome this limitation. On this basis, we functionalized carnosine and its amide derivative with small sugars such as glucose and lactose. The resistance of these derivatives to the carnosinase hydrolysis was tested and compared with that of carnosine. We found that the glycoconjugation protects the dipeptide moiety from carnosinase hydrolysis, thus potentially improving the availability of carnosine. The copper(II) binding properties of all the new synthesized compounds were investigated by spectroscopic (UV-Visible and circular dichroism) and ESI-MS studies. Particularly, the new family of amide derivatives that are not significantly hydrolyzed by carnosinase is a very promising class of carnosine derivatives. The sugar moiety can act as a recognition element. These new derivatives are potentially able to act as chelating agents in the development of clinical approaches for the regulation of metal homeostasis in the field of medicinal inorganic chemistry.     

Biological role of histidine-containing dipeptides

The biological role of histidine-containing dipeptides is reviewed. The role of carnosine and anserine in muscle function is discussed from the evolutionary viewpoint. Evidence on the antioxidative effect of carnosine and its protection of biological membranes against lipid peroxidation-induced damages is presented. The effects of presently known natural antioxidative agents and carnosine on lipid peroxidation are compared. Carnosine has been shown to be a more universal protector of membranes as compared to free radical scavengers.     

Effect of beta-alanine supplementation on muscle carnosine concentrations and exercise performance

High-intensity exercise results in reduced substrate levels and accumulation of metabolites in the skeletal muscle. The accumulation of these metabolites (e.g. ADP, Pi and H⁺) can have deleterious effects on skeletal muscle function and force generation, thus contributing to fatigue. Clearly this is a challenge to sport and exercise performance and, as such, any intervention capable of reducing the negative impact of these metabolites would be of use. Carnosine (β-alanyl-l-histidine) is a cytoplasmic dipeptide found in high concentrations in the skeletal muscle of both vertebrates and non-vertebrates and is formed by bonding histidine and β-alanine in a reaction catalysed by carnosine synthase. Due to the pKa of its imidazole ring (6.83) and its location within skeletal muscle, carnosine has a key role to play in intracellular pH buffering over the physiological pH range, although other physiological roles for carnosine have also been suggested. The concentration of histidine in muscle and plasma is high relative to its K _m with muscle carnosine synthase, whereas β-alanine exists in low concentration in muscle and has a higher K _m with muscle carnosine synthase, which indicates that it is the availability of β-alanine that is limiting to the synthesis of carnosine in skeletal muscle. Thus, the elevation of muscle carnosine concentrations through the dietary intake of carnosine, or chemically related dipeptides that release β-alanine on absorption, or supplementation with β-alanine directly could provide a method of increasing intracellular buffering capacity during exercise, which could provide a means of increasing high-intensity exercise capacity and performance. This paper reviews the available evidence relating to the effects of β-alanine supplementation on muscle carnosine synthesis and the subsequent effects on exercise performance. In addition, the effects of training, with or without β-alanine supplementation, on muscle carnosine concentrations are also reviewed.     

The Sod Like Activity of Copper: Arnosine,Copper: Anserine and Copper: Homocarnosine Complexes

Carnosine, anserine and homocarnosine are natural compounds which are present in high concentrations (2–20 mM) in skeletal muscles and brain of many vertebrates. We have demonstrated in a previous work that these compounds can act as antioxidants, a result of their ability to scavenge peroxyl radicals, singlet oxygen and hydroxyl radicals. Carnosine and its analogues have been shown to be efficient chelating agents for copper and other transition metals. Since human skeletal muscle contains one-third of the total copper in the body (20–47 mmol/kg) and the concentration of carnosine in this tissue is relatively high, the complex of carnosine:copper may be of biological importance. We have studied the ability of the coppenarnosine (and other carnosine derivatives) complexes to act as superoxide dismutasc. The results indicate that the complex of copper:carnosine can dismute superoxide radicals released by neutrophils treated with PMA in an analogous mechanism to other amino acids and copper complexes. Copper:anserine failed to dismute superoxide radicals and coppwhomocarnosine complex was efficient when the cells were treated with PMA or with histone-opsonized streptococci and cytochalasine B. The possible role of these compounds to act as physiological antioxidants that possess superoxide dismutase activity is discussed.     

Carnosine and its constituents inhibit glycation of low-density lipoproteins that promotes foam cell formation in vitro

Glycation of low-density lipoprotein (LDL) by reactive aldehydes, such as glycolaldehyde, can result in the cellular accumulation of cholesterol in macrophages. In this study, it is shown that carnosine, or its constituent amino acids beta-alanine and l-histidine, can inhibit the modification of LDL by glycolaldehyde when present at equimolar concentrations to the modifying agent. This protective effect was accompanied by inhibition of cholesterol and cholesteryl ester accumulation in human monocyte-derived macrophages incubated with the glycated LDL. Thus, carnosine and its constituent amino acids may have therapeutic potential in preventing diabetes-induced atherosclerosis.     

Problems and perspectives in studying the biological role of carnosine

In describing carnosine among the constituents of muscle tissue in 1900, V. Gulevitsch opened the question of its real biological role. Investigation of carnosine-related phenomena occurred simultaneously with the study of its metabolic transformation within the cell. It has now been demonstrated that carnosine has the ability to protect cells against oxidative stress as well as to increase their resistance toward functional exhaustion and accumulation of senile features. Mechanisms of such protection are explained in terms of proton buffering, heavy metal chelating, as well as free radical and active sugar molecule scavenging, preventing modification of biomacromolecules and keeping their native functional activity under oxidative stress. Several carnosine derivatives are characterized by different rates of splitting by tissue carnosinase and by different biological efficiencies, thus the biological significance of enzymatic modification of carnosine during its tissue metabolism may be increased resistance of cells operating under unfavorable conditions.     

Carnosine enhances diabetic wound healing in the db/db mouse model of type 2 diabetes

Diabetes mellitus (DM) is a progressive disorder with severe late complications. Normal wound healing involves a series of complex and well-orchestrated molecular events dictated by multiple factors. In diabetes, wound healing is grossly impaired due to defective, and dysregulated cellular and molecular events at all phases of wound healing resulting in chronic wounds that fail to heal. Carnosine, a dipeptide of alanine and histidine and an endogenous antioxidant is documented to accelerate healing of wounds and ulcers. However, not much is known about its role in wound healing in diabetes. Therefore, we studied the effect of carnosine in wound healing in db/db mice, a mice model of Type 2 DM. Six millimeter circular wounds were made in db/db mice and analyzed for wound healing every other day. Carnosine (100?mg/kg) was injected (I.P.) every day and also applied locally. Treatment with carnosine enhanced wound healing significantly, and wound tissue analysis showed increased expression of growth factors and cytokines genes involved in wound healing. In vitro studies with human dermal fibroblasts and microvascular-endothelial cells showed that carnosine increases cell viability in presence of high glucose. These effects, in addition to its known role as an antioxidant and a precursor for histamine synthesis, provide evidence for a possible therapeutic use of carnosine in diabetic wound healing.     

Antioxidant effect of carnosine treatment on renal oxidative stress in streptozotocin-induced diabetic rats

Nitric oxide (NO) plays a significant role in the development of diabetic nephropathy. We investigated the effects of an antioxidant, carnosine, on streptozotocin (STZ)-induced renal injury in diabetic rats. We used four groups of eight rats: group 1, control; group 2, carnosine treated; group 3, untreated diabetic; group 4, carnosine treated diabetic. Kidneys were removed and processed, and sections were stained with periodic acid-Schiff (PAS) and subjected to eNOS immunohistochemistry. Examination by light microscopy revealed degenerated glomeruli, thickened basement membrane and glycogen accumulation in the tubules of diabetic kidneys. Carnosine treatment prevented the renal morphological damage caused by diabetes. Moreover, administration of carnosine decreased somewhat the oxidative damage of diabetic nephropathy. Appropriate doses of carnosine might be a useful therapeutic option to reduce oxidative stress and associated renal injury in diabetes mellitus.     

Carnosine: biological role and prospects for use in medicine]

The biological role of the histidine-containing dipeptide carnosine (beta-alanyl-L-histidine) has been reviewed. The properties and putative biological role of the dipeptide in vertebrate tissues are considered. The antioxidative activity of carnosine and related compounds is described. The author's conception of the membranoprotective effect of carnosine on cells, tissues, and whole organism has been formulated. The properties of carnosine as an antistressory radioprotective agent are discussed. The data presented suggest that carnosine is a perspective immunomodulating tool which has many applications in medicine.     

Carnosine and anserine act as effective transglycating agents in decomposition of aldose-derived Schiff bases

There are numerous publications describing the positive effects of carnosine (beta-alanyl-histidine) and anserine (beta-alanyl-1-N-methyl-histidine) on cell and organ function. Of special interest to us is the fact that these dipeptides act to retard and (in one instance) reverse non-enzymatic glycation. To date, the primary explanation for these anti-glycating effects has been the fact that carnosine and anserine can serve as alternative and competitive glycation targets, thereby protecting proteins from this deleterious process. In this paper, we document another mechanism by which these two peptides can retard or reverse glycation. The process involves decomposition of the very first intermediates of the non-enzymatic glycation cascade (aldosamines a.k.a. Schiff bases) by nucleophilic attack of carnosine and/or anserine on the preformed aldosamine such as glucosyl-lysine. If future research shows this reaction is to be physiologically important, this mechanism could explain some of the beneficial effects of carnosine and anserine as anti-glycating agents.     

Effects of carnosine on contractile apparatus Ca²⁺ sensitivity and sarcoplasmic reticulum Ca²⁺ release in human skeletal muscle fibers

There is considerable interest in potential ergogenic and therapeutic effects of increasing skeletal muscle carnosine content, although its effects on excitation-contraction (EC) coupling in human muscle have not been defined. Consequently, we sought to characterize what effects carnosine, at levels attained by supplementation, has on human muscle fiber function, using a preparation with all key EC coupling proteins in their in situ positions. Fiber segments, obtained from vastus lateralis muscle of human subjects by needle biopsy, were mechanically skinned, and their Ca(2+) release and contractile apparatus properties were characterized. Ca(2+) sensitivity of the contractile apparatus was significantly increased by 8 and 16 mM carnosine (increase in pCa(50) of 0.073 ± 0.007 and 0.116 ± 0.006 pCa units, respectively, in six type I fibers, and 0.063 ± 0.018 and 0.103 ± 0.013 pCa units, respectively, in five type II fibers). Caffeine-induced force responses were potentiated by 8 mM carnosine in both type I and II fibers, with the potentiation in type II fibers being entirely explicable by the increase in Ca(2+) sensitivity of the contractile apparatus caused by carnosine. However, the potentiation of caffeine-induced responses caused by carnosine in type I fibers was beyond that expected from the associated increase in Ca(2+) sensitivity of the contractile apparatus and suggestive of increased Ca(2+)-induced Ca(2+) release. Thus increasing muscle carnosine content likely confers benefits to muscle performance in both fiber types by increasing the Ca(2+) sensitivity of the contractile apparatus and possibly also by aiding Ca(2+) release in type I fibers, helping to lessen or slow the decline in muscle performance during fatiguing stimulation.     

Carnosine: New concept for the function of an old molecule

In this review, the development of understanding of the biological functions of carnosine is briefly discussed. Carnosine was first described as a component of meat in 1900 by V. S. Gulevitch. Changes in the concepts of the role of carnosine in metabolism are followed starting from the early suggestion that it is the end product of protein degradation to the modern ideas based on demonstrating its specific involvement in intracellular signaling regulation in excitable tissue cells. The discovery of the ability of carnosine to regulate expression of early response genes broadens the concept about carnosine as a cellular peptide regulator. The first attempts for application of carnosine in sport and medical practice are described.     

A re-evaluation of the antioxidant activity of purified carnosine

The antioxidant activity of carnosine has been re-evaluated due to the presence of contaminating hydrazine in commercial carnosine preparations. Purified carnosine is capable of scavenging peroxyl radicals. Inhibition of the oxidation of phosphatidylcholine liposomes by purified carnosine is greater in the presence of copper than iron, a phenomenon likely to be due to the copper chelating properties of carnosine. Purified carnosine is capable of forming adducts with aldehydic lipid oxidation products. Adduct formation is greatest for alpha,beta-monounsaturated followed by polyunsaturated and saturated aldehydes. While the ability of carnosine to form adducts with aldehydic lipid oxidation products is lower than other compounds such as glutathione, the higher concentrations of carnosine in skeletal muscle are likely to make it the most important molecule that forms aldehyde adducts. Monitoring changes in carnosine concentrations in oxidizing skeletal muscle shows that carnosine oxidation does not occur until the later stages of oxidation suggesting that carnosine may not be as effective free radical scavenger in vivo as other antioxidants like alpha-tocopherol.     

Carnosine: from exercise performance to health

Carnosine was first discovered in skeletal muscle, where its concentration is higher than in any other tissue. This, along with an understanding of its role as an intracellular pH buffer has made it a dipeptide of interest for the athletic population with its potential to increase high-intensity exercise performance and capacity. The ability to increase muscle carnosine levels via β-alanine supplementation has spawned a new area of research into its use as an ergogenic aid. The current evidence base relating to the use of β-alanine as an ergogenic aid is reviewed here, alongside our current thoughts on the potential mechanism(s) to support any effect. There is also some emerging evidence for a potential therapeutic role for carnosine, with this potential being, at least theoretically, shown in ageing, neurological diseases, diabetes and cancer. The currently available evidence to support this potential therapeutic role is also reviewed here, as are the potential limitations of its use for these purposes, which mainly focusses on issues surrounding carnosine bioavailability.     

Vibrational characterisation and biological activity of carnosine and its metal complexes

The spectroscopic characterisation of free carnosine and its coordination compounds with Cu(II), Zn(II) and Co(II) ions are discussed. Raman and IR studies on metal-carnosine systems have been performed, obtaining a relationship between the vibrational spectra and the structure of the predominant species formed. The biological activity of free carnosine and of its complexes is briefly considered.     

Reverse structure of carnosine-induced sedative and hypnotic effects in the chick under acute stress

In the central nervous system, beta-alanine is thought to act as an inhibitory neurotransmitter, but the role or precise mechanism of beta-alanine in the brain has not been clearly defined. beta-Alanine is found in high levels in the chicken brain as a component of the dipeptides carnosine (beta-alanyl-L-histidine) and anserine, or as a free amino acid. We focused on the position of beta-alanine, i.e., at the carboxyl terminus. In Experiment 1, the central effects of glycyl-beta-alanine, L-histidyl-beta-alanine and L-valyl-beta-alanine were compared with a saline control in chicks. L-Histidyl-beta-alanine significantly induced sedative and hypnotic effects. In Experiment 2, the effects of carnosine, its reverse (L-histidyl-beta-alanine), and their combination were investigated. Central carnosine-induced hyperactivity while reverse carnosine-induced hypoactivity, and the behaviors were intermediate following the combination of the two peptides. Finally, the central effect of reverse carnosine was compared with beta-alanine alone and L-seryl-beta-alanine in Experiment 3. Reverse carnosine showed similar effects to beta-alanine. In conclusion, L-histidyl-beta-alanine not only has the reverse structure of carnosine, but also reverse function. Thus, we propose to name reverse carnosine (L-histidyl-beta-alanine) rev-carnosine.