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L-carnosine

Is a substance that protects and nourishes our functional life bases - cells, proteins, DNA lipids - can in good conscience be called an agent for longevity. If this substance is safe, naturally present in food and in the body, and proven to extend lifespan in animals and human cell cultures, then it belongs in any program that focuses on healthy life extension. Mountains of research show that carnosine has such anti-aging potential. Carnosine is a multifunctional dipeptide and is a combination of the amino acids beta-alanine and L-histidine. Long-lived cells such as nerve cells (neurons) and muscle cells (myocytes) show high carnosine levels. The carnosine level in the muscle of animals is related to their maximum lifespan (Hipkiss AR et al., 1995). Laboratory studies on cell ageing (at the end of the cycle of dividing cells) suggest that the above-mentioned fact is no coincidence. Carnosine has the remarkable ability to rejuvenate cells at this stage, restoring their normal appearance and extending cellular lifespan. How does this cell-rejuvenating effect come about? We still don't know the full answer, but its abilities may point us to key mechanisms of tissue and cell aging as well as measures to counteract them. Carnosine embodies the biochemical paradox of life: elements that make up and sustain life - oxygen, glucose, lipids, protein, trace elements - while at the same time it can destroy life by inhibiting it. However, it protects against this destructive property through its potent antioxidant, antiglycolating, aldehyde quenching and metal chelating properties (Quinn PJ et al., 1999, Hipkiss AR and Preston JE et al., 1998). The greatest beneficiaries are the most important building blocks of the body - the proteins. Our bodies are largely made up of proteins. Unfortunately, proteins tend to undergo destructive changes during their aging process due to oxidation and interactions with sugars or aldehydes. These protein modifications are caused by oxidation, carbonization, cross-linking, glycolization and the end product of advanced glycolization (AGE) and are expressed in all the typical features of the aging process such as wrinkling of the skin, cataracts and neurodegeneration. Carnosine has been shown in studies to be effective against all these forms of protein modification. As an antioxidant, carnosine neutralizes the most damaging free radicals such as hydroxyl radicals, superoxide radicals, singlet oxygen and peroxide radicals. Surprisingly, carnosine has also been shown to protect chromosomes from oxidative damage. Carnosine's ability to rejuvenate connective tissue explains its beneficial effect on wound healing. The ageing of the skin is linked to protein modification. Damaged proteins accumulate, form cross-links in the skin, form wrinkles and cause loss of elasticity. In the lens of the eye, protein cross-links are part of cataract formation. Carnosine eye drops can delay vision loss with up to 100% success in primary senile cataract and up to 80% success in cases of massive senile cataract (Wang AM et al., 2000). Carnosine levels decrease with age. Carnosine levels in muscle decrease by 63% between the ages of 10 and 70, which corresponds to the normal age-related decline in muscle mass and function (Stuerenberg HJ et al.,). Since carnosine has the effect of a pH buffer, it can protect muscle cell membranes from oxidation under acidic conditions of muscular tension. Carnosine enables the heart muscle to increase contraction efficiency by increasing the calcium reaction in the heart muscle cells (Zaloga GP et al., 1997). The high carnosine levels in the brain serve as a natural protection against external toxins, copper and zinc damage, protein cross-linking and glycolization, but especially against oxidation of cell membranes. Animal studies show widespread protection in simulated strokes. As more and more people are moving away from eating meat - the main source of carnosine - an additional supplement is becoming increasingly important. Carnosine is completely safe and absolutely non-toxic, even at doses of 500mg per kilogram of body weight in animal studies (Quinn PJ et al., 1992). It is particularly advantageous that carnosine is safe even at high doses, as the body would then neutralize smaller amounts of carnosine. The enzyme carnosinase (Quinn PJ et al., 1992) must be supplied with a larger amount of carnosine than it is eventually able to neutralize in order to have sufficient free carnosine available for the rest of the body.

Biological rejuvenation

It is well known that our cells have a limited ability to divide during life. Human fetal fibroblasts (precursors of fibrocytes (spindle-shaped cells of connective tissue)) do not divide more than about 60 to 80 times in laboratory cultures. In young adults, fibroblasts still have 30 to 40 cell divisions to go, whereas at an older age only 10 to 20 remain. When cultured cells reach the Hayflick limit, they divide less frequently and take on conspicuously irregular shapes. They no longer arrange themselves in parallel formation, take on a granular shape and deviate from their normal size and shape (McFarland GA et al., 1994). This disturbed appearance is referred to as the senescent phenotype. They announce themselves in the intermediate stage of cellular aging, which until recently was considered irreversible. In a remarkable series of experiments, scientists at an Australian research institute have shown that carnosine rejuvenates cells as they approach the ageing stage. What is special about carnosine's ability is that it can reverse the signs on the threshold of ageing. When the scientists transferred "late passer" fibroblasts to a medium containing carnosine, they showed a rejuvenated appearance and often an increased ability to divide. They grew again in their original arrangements of young fibroblasts and showed a uniform appearance. However, when the fibroblasts were returned to the carnosine-free medium, the signs of ageing soon reappeared. The carnosine-containing medium also prolonged the lifespan, even in old cells. The number of PDs, the doubling of populations, provides an excellent measure of cell division. When "late passager" lung fibroblasts were placed in the carnosine-containing medium after 55 PDs (population doublings), they lived from 69 to 70 PDs, compared to 57 to 61 PDs of fibroblasts without carnosine addition. In addition, the fibroblasts transferred to the carnosine-containing medium reached a total life span of 413 days, compared to 126 to 139 days of the control fibroblasts. Carnosine increased the chronological lifespan much more than the PD's in the Australian experiments. When cells from the carnosine-containing medium eventually reach the stage of cell senescence, they still maintain a normal or at least less senescent stage. The ability of carnosine to maintain or restore the youthful phenotype suggests that it may help to maintain cellular homeostasis (maintenance of the body's internal environment). Two Japanese studies demonstrate the ability of carnosine to stabilize and protect cultured fibroblasts. The first study shows that carnosine is able to stimulate a factor called vimentin, which in turn promotes the robustness of fibroblasts. (Ikeda D et al., 1999). Vimentin is a structured protein that gives fibroblasts and endothelial cells strength and stability. The second Japanese study shows that carnosine is able to maintain the integrity of rat fibroblasts in a deficient medium (Kantha SS et al., 1996). The fibroblasts in the deficient medium lost their characteristic shape after only one week, while the fiboblasts in the carnosine-containing medium retained their healthy appearance. After four weeks, the fibroblasts from the carnosine-containing medium still showed their cellular integrity, while the others were no longer viable. This study further investigated the 8-hydroxydeoxyguanosine (8-OH dG) level, a marker for oxidative damage to DNA in fibroblast cultures with and without carnosine. They found that carnosine was able to significantly reduce the 8-hydroxydeoxyguanosine level in the fibroblasts after four weeks. Oxidation of DNA is thought to be a major contributor not only to cellular aging but also to carcinogenesis, and it appears that 8-hydroxydeoxyguanosine should indeed be considered a marker for cancer risk (Kasai H, 1997). The revitalizing effect of carnosine on cultured fibroblasts may provide an explanation for the improved post-surgical wound healing with appropriate levels of carnosine. Another Japanese study shows that carnosine supports granulation, a healing process in which proliferated fibroblasts and blood vessels temporarily fill a tissue defect (Nagai K et al., 1986). A Brazilian study showed that granulation tissue developed and strengthened faster in rats under extra carnosingaben at a higher level of collagen synthesis (Vizoli MR et al., 1983). The Japanese study also provided evidence that carnosine was able to restore the body's regenerative potential when this had been suppressed by conventional drugs. Can the rejuvenating effect of carnosine on cells and cell cultures be transferred to the whole organism? Comparable anti-ageing effects have now been observed in mice. A recent Russian study investigated the effect of carnosine on lifespan and aging indicators in mice at an advanced stage of aging (Yuneva MO et al., 1999; Boldyrev AA et al., 1999). Half of the mice received additional doses of carnosine in their drinking water starting at the age of 10 months. This extended the lifespan by an average of 20% compared to the mice without carnosine supplementation. Although carnosine could not exceed the 15-month maximum lifespan of the age-accelerated mouse group, it significantly increased the number of mice that survived into old age. Of the mice that had received the additional carnosine doses, about twice as many reached the mature age of 12 months compared to the mice that had not received additional carnosine doses. At the same time, the measured aging indicators showed a much more favorable result at this advanced age of 10 months. Carnosine significantly improved the overall appearance of the old mice, whose fur and color were much more reminiscent of that of the young mice. Mice treated with further increased levels of carnosine had a shiny coat (44% versus 5%), while at the same time there were significantly fewer skin ulcers (14% versus 36%). However, carnosine did not appear to have any effect on hair loss or hair structure. In contrast, carnosine significantly reduced spinal lordokyphosis (curvature of the spine) and periophthalmic damage (damage to the eye), but had no effect on impaired corneal opacity (the degree to which the cornea of the eye transmits incident light intensity). However, the greatest contrast between treated and untreated mice was observed in their behavior. Only 9% of the untreated mice showed normal reaction behavior, compared to 58% of the mice treated with carnosine. The investigators also measured biochemical indicators related to brain aging. The brain membranes of the carnosine-fed mice showed a significantly lower level of MDA (malondialdehyde), a highly toxic product of lipid metabolism in the membranes. MAO-B (monoamine oxidase B) activity was 44% lower in carnosine-treated mice, indicating the maintenance of dopamine metabolism. Glutamate binding to cellular receptors almost doubled in the carnosine-treated group. Since glutamate (one of the starting materials for glutamine) is one of the most important activating neurotransmitters, this could explain the much more natural reaction behavior of the mice fed with carnosine. This study shows that carnosine improves most of the measurable parameters for overall appearance and behavior, physiological health, behavior, brain biochemistry as well as extended lifespan in aging mice. The investigators thus conclude that mice supplied with carnosine can be described as more resistant to the physiological processes of ageing (Boldyrev AA et al., 1999).

Protein carboxylation (catalyzing protein molecules by introducing CO2)

The reason that older people - and animals - look different from the young has to do with changes in the body's proteins. Proteins are probably the most responsible and important so-called building blocks of the living and functioning body, so that damage to them can have such dramatic effects on function and appearance. Oxidation (and by free radicals) and processes such as glycolization (protein-sugar reactions). Carnosine targets the main triggers of protein glycolization through its antioxidant and antiglycolating effects, its ability to neutralize reactive aldehydes and chelate metals and lipid peroxidation. Carnosine corresponds to the properties of protein metabolization to such an extent that one is tempted to speculate that evolution itself has created carnosine specifically for this task in order to protect our proteins from carbolization and other harmful modifications. An excellent example of the broad spectrum of carnosine to protect against protein modification is provided by MDA (malondialdehyde). This toxic product of lipid peroxidation causes protein modification, cross-linking, glycolization and AGE formation (Burcham PC et al., 1997). Carnosine prevents MDA from carbolizing albumin (major serum protein) and crystallin (four-fraction protein of the crystalline lens containing an insoluble albinoid) in a concentration-dependent manner. MDA glycolizes albumin, leading to cross-linking and end products of glycolization (AGE), but can be prevented by carnosine. Table 1 summarizes some of the many results from laboratory studies to provide an overview of the extent to which carnosine is able to protect our proteins from a wide variety of damaging agents.

Glycolization and AGE formation

AGE shows its damaging effects on two levels. The most obvious is the physical damage to proteins, DNA and lipids by altering their chemical properties. They act as cellular signals by triggering a cascade of destructive processes when they enter into their cellular binding (see the intermediate text entitled "AGE and RAGE"). The result is an up to 50-fold increase in free radicals. Oxidative stress is often referred to as fixed AGE formation, a dangerous cycle of oxidative stress and AGE accumulation. Carnosine is by far the safest and most effective natural antiglycating agent. A large number of studies with wide-ranging experimental models demonstrate that carnosine prevents protein glycolization and AGE formation Due to its structural similarity to the glycolating agents that attack proteins, carnosine is often seen as the "chosen savior". When carnosine is glycolized, it saves proteins from the same fate. Glycolized carnosine is not mutagenic in contrast to amino acids such as lysine, which becomes mutagenic by glycolization according to the well-known Ames test (Hipkiss AR, Michaelis J, Syrris P, et al., 1995). Carnosine not only prevents the formation of AGE, it can also protect the normal proteins from the toxic effect of the already formed AGE. This finding was confirmed by an elegant experiment at King's College, University of London (Brownson C et al., 2000; Hipkiss AR et al., 2000). The scientists used a glycolating agent called methylglyoxal (MG), which reacts with the lysine and arginine found in body proteins. The study shows that carnosine can prevent transfer to healthy proteins. Furthermore, evidence was found that carnosine reacts with them and is even able to remove carbonyl groups from glycolized proteins. This study demonstrates the unique three-step protection of carnosine against the accumulation of damaged proteins: carnosine protects against protein carboxylation, prevents damaged proteins from infecting healthy proteins and supports the proteolytic system (degradation of proteins and peptides by hydrolytic cleavage of the peptide bond with release of the amino acids) in the removal of damaged and unusable proteins.

Genome protection

DNA (deoxyribonucleic acid - DNA) is organized in chromosomes, each of which forms an appropriately structured double helix containing genes. Oxidative stress causes breaks and other abnormalities in the chromosomes and leads to clumping with increasing age. A fascinating experiment shows the paradoxical effects of antioxidants on oxidatively damaged chromosomes (Gille JJ et al., 1991). This study uses hyperoxia (an increase in the partial pressure of oxygen in the blood and body tissues), a depletion of almost pure oxygen (90%) as a physiologically natural oxidative factor. Hyperoxia generates free radicals in exactly those places where they normally form in the course of life. The scientists investigated the ability of various antioxidants - including vitamin C, N-acetylcysteine (NAC), vitamin E, carnosine and a form of glatathione - to protect the chromosomes in the ovaries of Chinese hamsters from oxidative damage. However, some of the antioxidants tested were pro-oxidant: they increased oxidative damage and exacerbated the effects of hyperoxia. It is a well-known phenomenon that individual antioxidants sometimes turn into pro-oxidants in the body. This is one of the reasons for those in the know to take not just one antioxidant, but a whole range of them. In this study, a significant reduction in chromosome damage was only observed for one antioxidant and that was carnosine. Cell cultures without any addition of antioxidants showed 133 chromosomal abnormalities in 100 cells. Carnosine reduced this level of damage by 2 thirds to only 44 chromosomal aberrations in 100 cells. Carnosine was able to keep 68% of all cells fully functional, compared to only 46% in the control cells.

Neurodegeneration

The rich supply of oxygenium, glucose, membrane lipids and metals to the brain could explain why it is normally also abundantly supplied with carnosine. Carnosine reduces: oxidative stress, protein-sugar interactions leading to AGE (see above), lipid peroxidation and toxic copper and zinc stress. Furthermore, the ability of carnosine to rejuvenate ageing cells is thought to be responsible for the longevity of neurons, as they do not divide to form new cells. The following is an overview of the neuron-protective properties of carnosine, with particular reference to Alzheimer's disease. Brain ageing and degeneration are marked by protein carboxylation. Therefore, a special, highly sensitive assay for carbonyl proteins has recently been developed. Applied to human brain tissue, this assay suggests that the carbonyl content of neurons is several times higher than in Alzheimer's disease patients and controls of the same age (Smith MA et al., 1998). Advances in cell culture technology have allowed scientists to observe neurons in culture over long periods of time for the first time. For example, scientists at the University of Kentucky have used this technique for the first time to study "aging in experiments" (Aksenova MV et al., 1999). They found that protein carbonyl levels began to increase one week before visible changes in the viability of cultured neurons from the rat fetal hippocampus. At a point where only 10 to 20% of the neurons were no longer viable, protein carbonyl levels had already doubled and swollen, unhealthy cell bodies appeared in many cells with high carbonyl levels. The Kentucky study also supported the findings of previous studies on the relationship between protein oxidation and reduced activity of the energy transfer enzyme creatine kinase, which is very sensitive to oxidation. This leads to reduced energy metabolism in the brain - a key feature of Alzheimer's disease.

Excitotoxicity and stroke

An underlying pathology of many neurological disorders is excitotoxicity. It is caused by excessive release by or excessive sensitivity to glutamate, an important neuronal transmitter of excitation. Excitotoxicity leads to a cascade of events including cell death through membrane polarization. Oxidative stress and excitotoxicity can even reinforce each other in a virtuous circle. It is possible that excitotoxicity with complications determines the effects of a stroke. With regard to Alzheimer's disease, laboratory experiments have shown that beta-amyloid-cultured neurons can lead to excitotoxic death (Doble A, 1999).

Carnosine and glutamate are found together in presynaptic terminals in the brain. Experimental results show that carnosine is able to protect cells from excitotoxic death, which supports the assumption that carnosine serves the same purpose in our brain. An interesting Russian study shows that rat brain cells exposed to carnosine are resistant to excitotoxic death by the glutamate analog NMDA (Boldyrev A et al., 1999). Scientists exposed rat neurons to physiological concentrations of copper and zinc and the neurons died, whereas even moderate doses of carnosine were able to protect the neurons from the toxic effects of these metals (Horning MS et al., 2000). A flood of recent research papers show the central role of copper and zinc in the development of Alzheimer's disease. The levels of these substances are elevated in the brains of Alzheimer's patients, but particularly in the beta-amyloid plaque ("senile plaque"), which is the central cause of this disease (see also the intermediate text "Copper, zinc and Alzheimer's") A breakthrough to new knowledge was achieved in a study that led to the discovery that chelating agents for copper and zinc are able to dissolve beta-amyloid deposits in post-mortem human tissue samples from the brains of Alzheimer's patients Cherry RA et al., 1999). The scientists concluded that "agents that chelate specifically with copper and zinc ions but contain Mg(II) and Ca(II) could be of great therapeutic benefit in the treatment of Alzheimer's disease". Carnosine meets these requirements and also has the ability to buffer pH and neutralize hydroxyl radicals. Not only is carnosine able to form chelates with copper and zinc, but the presence of copper and zinc ions can further enhance the potential of carnosine to neutralize superoxide radicals (Gulyaeva NV, 1987). This is particularly important because beta-amyloid is able to damage endothelial cells (in the walls of blood vessels) in the brain particularly quickly and causes oxidative stress even at low concentrations, especially in the form of superoxide radicals (Thomas T er al., 1996). Microvascular damage is the precursor to Alzheimer's disease, which precedes all other pathological manifestations. One theory of the development of Alzheimer's disease claims that the observed microvascular damage is the actual cause of the disease, as it impairs the nutritional supply to the brain cells (de la Torre JC, 1997). An experiment with endothelial cells from the rat brain shows that carnosine is able to provide sufficient protection against such damage. When the endothelial beta-amyloid was exposed to a physiological carnosine solution, the damage to the endothelial cells was significantly reduced or disappeared completely (Preston JE et al. 1998). Another experiment conducted by the same British team demonstrated that carnosine is able to protect endothelial brain cells from damage caused by MDA (malondialdehyde), a toxic product of lipid peroxidation. Carnosine prevented protein carboxylation and cross-linking while protecting cellular and mitochondrial functions (Hipkiss AR et al., 1997). A third experiment showed that carnosine was also able to protect these cells from damage caused by acetaldehydes as alcohol degradation products HipKiss AR et al., 1998).

AGE and amyloid deposits (plaque)

Carnosine works along many metabolic pathways to protect against amyloid plaques, provides protection against intoxication by these plaques, prevents them and can even support the degradation of these plaques as laboratory experiments have shown. An investigation into how the deposits reveal an additional metabolic pathway. The first step in plaque formation occurs slowly and consists of the reversible development of a nucleus, followed by a phase of rapid cross-linking and growth. AGE (see "Glycolization and AGE formation") accelerates these two steps by cross-linking soluble monomers to form insoluble aggregates. The investigators hypothesize that the crucial step is the formation of a stable amyloid core and the cross-linking of beta-amyloid by AGE (Munch G et al., 1997). The scientists found that beta-amyloid cross-linking was inhibited by three AGE factors: The pharmaceuticals aminoguanadine and tenilsetam and carnosine. Tenilsetam has demonstrated clinical utility in Alzheimer's disease. The investigators incubated beta-amyloid with fructose, which makes up a large proportion of the brain and cross-bonds with proteins up to ten times faster than glucose. Soluble amyloid disappears and the insoluble aggregates form, driven by AGE cross-links. All three AGE inhibitors were able to prevent cross-linking of beta-amyloid and keep it almost 100% soluble. Considering the dependence of the brain on glucose for the necessary energy metabolism and the unusually high ratio of fructose to glucose (about 1:4 compared to 1:20 in plasma), it seems that carnosine acts as a kind of natural protection against the glycolization process.

Need in sport

Carnosine has a positive effect on both muscle strength and endurance by neutralizing the lactic acid produced during exercise. It also leads to an increase in muscle volume, similar to creatine. It also promotes muscle volume and acts as an antioxidant. In this way, it can both promote muscle growth and reduce muscle damage caused by intensive training. Approximately 1-1.5g taken twice a day should be sufficient. It is best to take carnosine at the same time as taurine, glutamine and creatine.

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