Scientists have caused cancer development in rats by treating them with specific cancer-causing chemicals. This causes pre-cancerous lesions in the liver that are low in dna methylation and high in oncogene expression-that is, use of genes that under certain conditions can cause normal cells to become cancerous. Later, these rats develop liver cancer. At least three different cancer-causing procedures have now been used to show that this progress toward cancer can be halted in most cases by extended treatment with SAMe. SAMe not only reduces oncogene expression, but also increases dna methylation. SAMe also greatly reduces the number of animals that later develop liver cancer (Pascale et al. 1992, 1995; Simile et al. 1996).
Betaine has been shown to increase SAMe in rats (Barak et al. 1994) and mice (Wise et al. 1997), and thus both SAMe supplements and methyl supplements that include betaine make good choices in trying to prevent spontaneous cancer in rats.
Because I knew that dna methylation was dependent on methyl metabolism, several years ago I proposed that one reason we lose methylation with age is that our metabolisms just weren't up to snuff as far as maintaining our dna methylation, keeping our homocysteine low or handling other longevity-assuring aspects of methyl metabolism (Cooney 1993, 1994). I also proposed that most of our cells have inherent, built-in deficiencies that compromise methyl metabolism, this leads in turn to a gradual loss of dna methylation, and that these deficiencies and their effects are a mechanism of aging. As such, they contribute to limited normal cell growth, dna breaks, aging and cancer.
On the surface, built-in deficiencies in our dna methylation system or in methyl metabolism seem like a cruel trick of nature. But if we look at it from an evolutionary point of view, it makes a lot of sense. Let's use mice as an example. In nature, most mice will die either of starvation or be killed by predators, disease, drought or other environmental hazards long before they are greatly affected by aging. Likewise, those mice that survive will generally reproduce long before they are greatly affected by aging.
These considerations make a long-lived mouse unlikely and unnecessary. Why? Because it takes lots resources, including energy, essential fatty acids, choline, zinc, folic acid and more to keep an animal healthy and well-maintained for a long life, and these resources would be better expended on reproduction and immediate survival early in life.
So in most animals all metabolism should be quite sufficient-in fact, optimized- for immediate and short-term needs, such as youthful reproduction. This is a fundamental requirement of evolution. It should come as no surprise, then, that various aspects of our metabolisms and dna methylation machinery are not set on "healthful longevity" with an outlook of hundreds of years, but are instead set on a "just-do-it" 5-minute-to-10-year horizon.
Very recently we have shown that epigenetics during embryonic development of mice is changed by methyl-supplemented diets fed to their mothers during pregnancy. These epigenetic factors are very important for health and longevity. We showed this with yellow mice, in which an epigenetically controlled gene both affects coat color and their health and longevity. Even though these mice are genetically identical, their health-that is, their propensity for diabetes, cancer, obesity, longevity-varies greatly (Wolff et al. 1998).
In our new project, we will study rats not only according to their specific ages, but also by following rats periodically over their lifetimes, regardless of how long they live. One of the things we hope to learn from this is which changes actually act as biomarkers for aging and which represent survival mechanisms of special long-lived minorities.
Rats will be maintained as control, methyl-supplemented, or SAMe-supplemented groups, and several determinations will be made. Their longevity will be determined by time of natural death, and also will be monitored at a specific time-point for age-related pathology. Blood will be collected at two-month intervals from specific rats of each group and the parameters of blood plasma homocysteine, red blood cell SAMe (RBCSAM, Wise et al. 1997) and leukocyte dna methylation (Cooney et al. 1997) will be determined. These measures of dna methylation, SAMe and homocysteine will be correlated with the longevity of these individuals.
These studies will use specific methyl supplements and SAMe supplements based on our prior successful studies of metabolism, dna methylation and epigenetics in rats and mice. They should tell us how these supplements affect SAMe, sah, dna methylation and homocysteine, as well as a number of more common measures, such as cholesterol and glucose. They also will demonstrate how these supplements affect age-related pathology and overall longevity. And they should give us information on how the parameters might be used as biomarkers to predict length of life and, more importantly, how to increase length of life.
The recent cloning demonstrations-such as Dolly the cloned sheep and Cumulina the cloned mouse-show that mammals can be cloned from adult cells. This has lots of implications for those of us interested in epigenetics and longevity (Wilmut et al. 1997, Wakayama et al. 1998).
The ability to clone almost certainly means that dna sequence is unchanged from embryonic cells to those adult cells. This underscores that it is largely epigenetics that makes up the "thin blue line" between normal cells and cancer and aged cells. Even as cloning and related techniques make it easier to produce organs, bodies or stem cells, you still need to maintain the epigenetics of tissues and cells; otherwise these will suffer the same fate as the originals. These new discoveries in cloning emphasize that epigenetics is our next big frontier.
The cloning of animals is not just important to our basic understanding of biology and to practical advances in longevity research. It also is an inspiration to those who know that a vastly longer, healthy life is attainable. Ian Wilmut and his team, the cloners of Dolly the sheep, simply didn't believe the many scientists who said that "you can't clone mammals from adult cells." Likewise, those who say we can't live past a certain life span, or that supplements don't improve health, will need to reevaluate their suppositions or risk being left far behind.
We have in front of us a great frontier for supplement research and great opportunities to improve our health and lengthen our lives. Because many of us have been taking supplements for years, epidemiologists now have been able to prove that supplements have health benefits. But this is only the beginning. Optimal levels and optimal combinations of supplements are not known because supplement research has been neglected in the past. Supplement research will now expand greatly, and holds enormous promise to vastly improve our health, well being and longevity.
Rev 55, p145-149. Barak AJ, Beckenhauer HC, Tuma DJ (1994) S-adenosylmethionine generation and prevention of alcoholic fatty liver by betaine. Alcohol 11, p501-503.
Bestor TH (1998) The host defence function of genomic methylation patterns. Novartis Found Symp 214, p187-195.
Bestor TH (1992) Activation of mammalian DNA methyltransferase by cleavage of a Zn binding regulatory domain. EMBO J 11, 2611-2617.
Blackwell BN, Bucci TJ, Hart RW, Turturro A (1995) Longevity, body weight, and neoplasia in ad libitum-fed and diet-restricted C57BL6 mice fed NIH-31 open formula diet. Toxicol Pathol 23, 570-582.
Brattstrom L, Lindgren A, Israelsson B, Andersson A, Hultberg B (1994) Homocysteine and cysteine: determinants of plasma levels in middle-aged and elderly subjects. J Intern Med 236 p633-641.
Cooney CA (1993) Are somatic cells inherently deficient in methylation metabolism? A proposed mechanism for DNA methylation loss, senescence and aging. Growth Dev Aging 57, p261-273.
Cooney CA (1994) Methylation metabolism has a central role in mammalian longevity. AGE 17, p166-167.
Cooney, C. A., Wise, C.W., Poirier, L.A. (1997) An Improved Sample Preparation Method for the Quantitative HPLC Determination of 5-Methyldeoxycytidine in Animal Tissue DNA. J Liq Chrom 20, p1279-1293.
Cooney CA, Wise CK, Poirier LA, Ali SF (1998) Methamphetamine treatment affects blood and liver S-adenosylmethionine (SAM) in mice. Correlation with dopamine depletion in the striatum. Ann N Y Acad Sci 30, p191-200.
Counts JL, Sarmiento JI, Harbison ML, Downing JC, McClain RM, Goodman JL (1996) Cell proliferation and global methylation status changes in mouse liver after phenobarbital and/or choline-devoid, methionine-deficient diet administration. Carcinogenesis 17, p1251-1257.
Counts JL, Goodman JI (1995) Hypomethylation of DNA: a possible epigenetic mechanism involved in tumor promotion. Prog Clin Biol Res 391, p81-101.
Fava M, Giannelli A, Rapisarda V, Patralia A, Guaraldi GP (1995) Rapidity of onset of the antidepressant effect of parenteral S-adenosyl-L-methionine. Psychiatry Res 56, p295-297.
Finch CE (1990) Longevity, Senescence and the Genome. Chicago: Univ. Chicago Press.
Frankel P and Mitchell T (1997) Homocysteine. Homocysteine and heart attacks. Life Extension July 1997 p8-17.
Holliday R (1986) Strong effects of 5-azacytidine on the in vitro lifespan of human diploid fibroblasts. Exp Cell Res 166, p543-552.
Kagan BL, Sultzer DL, Rosenlicht N, Gerner RH (1990) Oral S-adenosylmethionine in depression: a randomized, double-blind, placebo-controlled trial. Am J Psychiatry 147, p591-595.
Kim E, Lowenson JD, MacLaren DC, Clarke S, Young SG (1997) Deficiency of a protein-repair enzyme results in the accumulation of altered proteins, retardation of growth, and fatal seizures in mice. Proc Natl Acad Sci U S A 94, p6132-6137.
Li E, Bestor TH, Jaenisch R (1992) Targeted mutation of the DNA methyltransferase gene results in embryonic lethality. Cell 69, 915-926.
McCully K (1997) The Homocysteine Revolution. Keats Publishing, New Canaan CT.
Millian NS, Garrow TA (1998) Human betaine-homocysteine methyltransferase is a zinc metalloenzyme. Arch Biochem Biophys 356, p93-98.
Mitchell T (1998) Methylation. A little known but essential process. Life Extension. August 1998 p23-26.
Orentreich N, Matias JR, DeFelice A, Zimmerman JA (1993) Low methionine ingestion by rats extends life span. J Nutr 123, 269-274.
Pascale RM, Simile MM, De Miglio MR, Nufris A, Daino L, Seddaiu MA, Rao PM, Rajalakshmi S, Sarma DS, Feo F (1995) Chemoprevention by S-adenosyl-L-methionine of rat liver carcinogenesis nitiated by 1,2-dimethylhydrazine and promoted by orotic acid. Carcinogenesis 16, p427-430.
Pascale RM, Marras V, Simile MM, Daino L, Pinna G, Bennati S, Carta M, Seddaiu MA, Massarelli G, Feo F (1992) Chemoprevention of rat liver carcinogenesis by S-adenosyl-L-methionine: a long-term study. Cancer Res 52, p4979-4986.
Poirier LA (1994) Methyl group deficiency in hepatocarcinogenesis. Drug Metab. Rev. 26, 185-199.
Romanov GA, Vanyushin BF (1981) Methylation of reiterated sequences in mammalian DNAs. Effects of the tissue type, age, malignancy and hormonal induction. Biochim Biophys Acta 653, p204-218.
Simile MM, Saviozzi M, De Miglio MR, Muroni MR, Nufris A, Pascale RM, Malvaldi G, Feo F (1996) Persistent chemopreventive effect of S-adenosyl-L-methionine on the development of liver putative preneoplastic lesions induced by thiobenzamide in diethylnitrosamine-initiated rats. Carcinogenesis 17, 1533-1537.
Singhal RP, Mays-Hoopes LL, Eichhorn GL (1987) DNA methylation in aging of mice. Mech Ageing Dev 41, p199-210.
Vanyushin BF, Nemirovsky LE, Klimenko VV, Vasiliev VK, Belozersky AN (1973) The 5-methylcytosine in DNA of rats. Tissue and age specificity and the changes induced by hydrocortisone and other agents. Gerontologia 19, p138-152.