Life Extension Update Exclusive
Cysteine recommended for digestive tract cancer prevention
Researchers at the University of Helsinki in Finland have suggested the addition of the amino acid L-cysteine to tablets and chewing gum to help prevent upper digestive tract cancers. Cysteine can help protect against mouth, pharynx and esophageal cancers due to its ability to neutralize the effects of acetaldehyde, a compound formed when people drink alcohol or smoke. Smoking and drinking is believed to be responsible for up to 80 percent of upper digestive tract cancers.
University of Helsinki professor Mikko Salaspuro, had previously published the hypothesis that normal human digestive tract flora locally produce acetaldehyde from alcohol, rendering these areas at increased risk of digestive tract cancers. Dr Salaspuro’s research was supported by the finding of an increased risk of digestive tract cancer among Japanese drinkers, who have a genetically reduced ability to neutralize acetaldehyde. After a drinking a small amount of alcohol, Asians with this mutation have up to three times higher levels of acetaldehyde in their saliva than those without the mutation.
Because of L-cysteine’s known ability to bind with acetaldehyde, Dr Salaspuro, along with professor Martii Marvola, also of the University of Helsinki, developed slow-release L-cysteine tablets that eliminate acetaldehyde in the mouth and saliva when drinking or smoking. The patented methods developed by the researchers have been used in a new chewing gum launched at the 11th International Congress of Oral Cancer this month.
"We know that with this chewing gum it is possible to eliminate acetaldehyde totally from the saliva during smoking,” Dr Salaspuro stated. “We do hope that this will in the future turn out to be a novel method for the prevention of alcohol and tobacco smoking associated oral cancers. However, long term randomized controlled trials are naturally needed before the possible cancer preventive effects can be proved. We are currently planning that type of studies."
While L-cysteine tablets or gum can help eliminate acetaldehyde from the upper digestive tract, the carcinogen can also be produced in the stomach by the action of oral microbes on foods with a high sugar or carbohydrate content, particularly among individuals who produce insufficient hydrochloric acid, a condition associated with an increased risk of gastric cancer. Other products that contain L-cysteine are being developed that will slowly release the amino acid in different parts of the gastrointestinal tract, so that acetaldehyde can be eliminated in the stomach or intestine.
Cancer adjuvant therapy
N-acetyl-cysteine (NAC) is the acetylated precursor of the amino acids L-cysteine and reduced glutathione. Historically, it is used as a mucolytic agent in respiratory illnesses as well as an antidote for acetaminophen hepatotoxicity, but more recently its credits have grown. Animal and human studies have shown it to be a powerful antioxidant and a potential therapeutic agent in the treatment of cancer (Bongers et al. 1995; van Zandwijk 1995).
The biological value of NAC is attributed to its sulfhydryl group, while its acetyl-substituted amino group offers protection against oxidative and metabolic processes (Bonanomi et al. 1980; Sjodin et al. 1989). In vitro studies showed NAC to be directly antimutagenic and anticarcinogenic; in vivo, NAC inhibited mutagenicity of a number of mutagenic materials (De Flora et al. 1986, 1992). NAC has both chemopreventive and therapeutic potential in malignancies arising in the lung, skin, breast, liver, head, and neck (van Zandwijk 1995; Izzotti 1998).
NAC is effective in inhibiting tumor cell growth in melanoma, prostate cells, and astrocytoma cell lines (the latter is a primary tumor in the brain) (Albini et al. 1995; Arora-Kuruganti et al. 1999; Chiao et al. 2000). Neovascularization (new blood vessel growth) is crucial for tumor mass expansion and metastasis. NAC inhibited invasion and metastasis of malignant cells by up to 80% by preventing angiogenesis (De Flora et al. 1996).
L-cysteine is a conditionally essential amino acid, one of only three sulfur-containing amino acids, the others being taurine (which can be produced from L-cysteine) and L-methionine from which L-cysteine can be produced in the body by a multi-step process. Cysteine plays a role in the sulfation cycle, acting as a sulfur donor in phase II detoxification and as a methyl donor in the conversion of homocysteine to methionine. Cysteine also helps synthesize glutathione, one of the body’s most important natural detoxifiers.
N-acetyl cysteine is the more efficiently absorbed and used form of the amino acid, L-cysteine. L-cysteine plays a role in the sulfation cycle, acting as a sulfur donor in phase II detoxification and as a methyl donor in the conversion of homocysteine to methionine. N-acetyl cysteine has antioxidant properties, and helps to maintain healthy levels of the liver’s natural detoxifier, glutathione.
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