Control of the structural stability of α-crystallin under thermal and chemical stress: the role of carnosine

Carnosine and Beta-Alanine Supplementation in Human Medicine: Narrative Review and Critical Assessment

The dipeptide carnosine is a physiologically important molecule in the human body, commonly found in skeletal muscle and brain tissue. Beta-alanine is a limiting precursor of carnosine and is among the most used sports supplements for improving athletic performance. However, carnosine, its metabolite N-acetylcarnosine, and the synthetic derivative zinc-L-carnosine have recently been gaining popularity as supplements in human medicine. These molecules have a wide range of effects—principally with anti-inflammatory, antioxidant, antiglycation, anticarbonylation, calcium-regulatory, immunomodulatory and chelating properties. This review discusses results from recent studies focusing on the impact of this supplementation in several areas of human medicine. We queried PubMed, Web of Science, the National Library of Medicine and the Cochrane Library, employing a search strategy using database-specific keywords. Evidence showed that the supplementation had a beneficial impact in the prevention of sarcopenia, the preservation of cognitive abilities and the improvement of neurodegenerative disorders. Furthermore, the improvement of diabetes mellitus parameters and symptoms of oral mucositis was seen, as well as the regression of esophagitis and taste disorders after chemotherapy, the protection of the gastrointestinal mucosa and the support of Helicobacter pylori eradication treatment. However, in the areas of senile cataracts, cardiovascular disease, schizophrenia and autistic disorders, the results are inconclusive.

Ionophore Ability of Carnosine and Its Trehalose Conjugate Assists Copper Signal in Triggering Brain-Derived Neurotrophic Factor and Vascular Endothelial Growth Factor Activation In Vitro

l-carnosine (β-alanyl-l-histidine) (Car hereafter) is a natural dipeptide widely distributed in mammalian tissues and reaching high concentrations (0.7-2.0 mM) in the brain. The molecular features of the dipeptide underlie the antioxidant, anti-aggregating and metal chelating ability showed in a large number of physiological effects, while the biological mechanisms involved in the protective role found against several diseases cannot be explained on the basis of the above-mentioned properties alone, requiring further research efforts. It has been reported that l-carnosine increases the secretion and expression of various neurotrophic factors and affects copper homeostasis in nervous cells inducing Cu cellular uptake in keeping with the key metal-sensing system. Having in mind this l-carnosine ability, here we report the copper-binding and ionophore ability of l-carnosine to activate tyrosine kinase cascade pathways in PC12 cells and stimulate the expression of BDNF. Furthermore, the study was extended to verify the ability of the dipeptide to favor copper signaling inducing the expression of VEGF. Being aware that the potential protective action of l-carnosine is drastically hampered by its hydrolysis, we also report on the behavior of a conjugate of l-carnosine with trehalose that blocks the carnosinase degradative activity. Overall, our findings describe a copper tuning effect on the ability of l-carnosine and, particularly its conjugate, to activate tyrosine kinase cascade pathways.

Carnosine as an effective neuroprotector in brain pathology and potential neuromodulator in normal conditions

Carnosine (b-alanyl-L-histidine) is an endogenous dipeptide widely distributed in excitable tissues, such as muscle and neural tissues-though in minor concentrations in the latter. Multiple benefits have been attributed to carnosine: direct and indirect antioxidant effect, antiglycating, metal-chelating, chaperone and pH-buffering activity. Thus, carnosine turns out to be a multipotent protector against oxidative damage. However, the role of carnosine in the brain remains unclear. The key aspects concerning carnosine in the brain reviewed are as follows: its concentration and bioavailability, mechanisms of action in neuronal and glial cells, beneficial effects in human studies. Recent literature data and the results of our own research are summarized here. This review covers studies of carnosine effects on both in vitro and in vivo models of cerebral damage, such as neurodegenerative disorders and ischemic injuries and the data on its physiological actions on neuronal signaling and cerebral functions. Besides its antioxidant and homeostatic properties, new potential roles of carnosine in the brain are discussed.

Zinc, Carnosine, and Neurodegenerative Diseases

Zinc (Zn) is abundantly present in the brain, and accumulates in the synaptic vesicles. Synaptic Zn is released with neuronal excitation, and plays essential roles in learning and memory. Increasing evidence suggests that the disruption of Zn homeostasis is involved in various neurodegenerative diseases including Alzheimer's disease, a vascular type of dementia, and prion diseases. Our and other numerous studies suggest that carnosine (β-alanyl histidine) is protective against these neurodegenerative diseases. Carnosine is an endogenous dipeptide abundantly present in the skeletal muscles and in the brain, and has numerous beneficial effects such as antioxidant, metal chelating, anti-crosslinking, and anti-glycation activities. The complex of carnosine and Zn, termed polaprezinc, is widely used for Zn supplementation therapy and for the treatment of ulcers. Here, we review the link between Zn and these neurodegenerative diseases, and focus on the neuroprotective effects of carnosine. We also discuss the carnosine level in various foodstuffs and beneficial effects of dietary supplementation of carnosine.

On the Relationship between Energy Metabolism, Proteostasis, Aging and Parkinson's Disease: Possible Causative Role of Methylglyoxal and Alleviative Potential of Carnosine

Recent research shows that energy metabolism can strongly influence proteostasis and thereby affect onset of aging and related disease such as Parkinson's disease (PD). Changes in glycolytic and proteolytic activities (influenced by diet and development) are suggested to synergistically create a self-reinforcing deleterious cycle via enhanced formation of triose phosphates (dihydroxyacetone-phosphate and glyceraldehyde-3-phosphate) and their decomposition product methylglyoxal (MG). It is proposed that triose phosphates and/or MG contribute to the development of PD and its attendant pathophysiological symptoms. MG can induce many of the macromolecular modifications (e.g. protein glycation) which characterise the aged-phenotype. MG can also react with dopamine to generate a salsolinol-like product, 1-acetyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinaline (ADTIQ), which accumulates in the Parkinson's disease (PD) brain and whose effects on mitochondria, analogous to MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), closely resemble changes associated with PD. MG can directly damage the intracellular proteolytic apparatus and modify proteins into non-degradable (cross-linked) forms. It is suggested that increased endogenous MG formation may result from either, or both, enhanced glycolytic activity and decreased proteolytic activity and contribute to the macromolecular changes associated with PD. Carnosine, a naturally-occurring dipeptide, may ameliorate MG-induced effects due, in part, to its carbonyl-scavenging activity. The possibility that ingestion of highly glycated proteins could also contribute to age-related brain dysfunction is briefly discussed.