Is Carnosine a Naturally Occurring Suppressor of Oxidative Damage in Olfactory Neurones?

GADL1 is a multifunctional decarboxylase with tissue-specific roles in β-alanine and carnosine production

Carnosine and related β-alanine-containing peptides are believed to be important antioxidants, pH buffers, and neuromodulators. However, their biosynthetic routes and therapeutic potential are still being debated. This study describes the first animal model lacking the enzyme glutamic acid decarboxylase-like 1 (GADL1). We show that Gadl1^-/- mice are deficient in β-alanine, carnosine, and anserine, particularly in the olfactory bulb, cerebral cortex, and skeletal muscle. Gadl1^-/- mice also exhibited decreased anxiety, increased levels of oxidative stress markers, alterations in energy and lipid metabolism, and age-related changes. Examination of the GADL1 active site indicated that the enzyme may have multiple physiological substrates, including aspartate and cysteine sulfinic acid. Human genetic studies show strong associations of the GADL1 locus with plasma levels of carnosine, subjective well-being, and muscle strength. Together, this shows the multifaceted and organ-specific roles of carnosine peptides and establishes Gadl1 knockout mice as a versatile model to explore carnosine biology and its therapeutic potential.

Protective activity of carnosine and anserine against zinc-induced neurotoxicity: a possible treatment for vascular dementia

Carnosine (β-alanyl-L-histidine) is a small dipeptide with numerous beneficial effects, including the maintenance of the acid-base balance, antioxidant properties, chelating agent, anti-crosslinking, and anti-glycation activities. High levels of carnosine and its analogue anserine (1-methyl carnosine) are found in skeletal muscle and the brain. Zinc (Zn)-induced neurotoxicity plays a crucial role in the pathogenesis of vascular dementia (VD), and carnosine inhibits Zn-induced neuronal death. Here, the protective activity of carnosine against Zn-induced neurotoxicity and its molecular mechanisms such as cellular Zn influx and Zn-induced gene expression were investigated using immortalised hypothalamic neurons (GT1-7 cells). Carnosine and anserine protected against Zn-induced neurotoxicity not by preventing increases in intracellular Zn(2+) but by participating in the regulation of the endoplasmic reticulum (ER) stress pathway and the activity-regulated cytoskeletal protein (Arc). Accordingly, carnosine and anserine protected against neurotoxicity induced by ER-stress inducers thapsigargin and tunicamycin. Hence, carnosine and anserine are expected to have future therapeutic potential for VD and other neurodegenerative diseases.

Would carnosine or a carnivorous diet help suppress aging and associated pathologies?

Carnosine (beta-alanyl-L-histidine) is found exclusively in animal tissues. Carnosine has the potential to suppress many of the biochemical changes (e.g., protein oxidation, glycation, AGE formation, and cross-linking) that accompany aging and associated pathologies. Glycation, generation of advanced glycosylation end-products (AGEs), and formation of protein carbonyl groups play important roles in aging, diabetes, its secondary complications, and neurodegenerative conditions. Due to carnosine's antiglycating activity, reactivity toward deleterious carbonyls, zinc- and copper-chelating activity and low toxicity, carnosine and related structures could be effective against age-related protein carbonyl stress. It is suggested that carnivorous diets could be beneficial because of their carnosine content, as the dipeptide has been shown to suppress some diabetic complications in mice. It is also suggested that carnosine's therapeutic potential should be explored with respect to neurodegeneration. Olfactory tissue is normally enriched in carnosine, but olfactory dysfunction is frequently associated with neurodegeneration. Olfactory administration of carnosine could provide a direct route to compromised tissue, avoiding serum carnosinases.

Glycation, ageing and carnosine: Are carnivorous diets beneficial?

Non-enzymic protein glycosylation (glycation) plays important roles in ageing and in diabetes and its secondary complications. Dietary constituents may play important roles in accelerating or suppressing glycation. It is suggested that carnivorous diets contain a potential anti-glycating agent, carnosine (beta-alanyl-histidine), whilst vegetarians may lack intake of the dipeptide. The possible beneficial effects of carnosine and related structures on protein carbonyl stress, AGE formation, secondary diabetic complications and age-related neuropathology are discussed.