© Whole Foods Magazine

October 1992

Tuning Up Metabolism

Vitamins, minerals and key biochemicals can aid in cancer prevention and help delay signs of aging.

An interview with Bruce N. Ames, Ph.D.

Part 1: Mutations, Genetic Diseases, and Slowing Aging

By Richard A. Passwater, Ph.D.

There is exciting news about research on slowing the aging process and preventing degenerative diseases such as cancer! The excitement is coming from the laboratory of Bruce N. Ames, Ph.D., professor of biochemistry and molecular biology at the University of California, Berkeley. The exciting news is coming on several fronts, including the mental rejuvenation of laboratory animals with nutrients. Ames’s review article in the American Journal of Clinical Nutrition showed that megavitamin therapy is effective against more than 50 genetic diseases, most of them inborn metabolic diseases due to defective enzymes.

There is so much that we have learned from Dr. Ames that it is difficult to choose where to start, even if it were possible to spend the next year or so chatting with him about his many, many studies. Much of what we understand today about the genetic material that gives our bodies the chemical instructions for making all of the biochemicals and components we need—our deoxyribonucleic acid (DNA)—is the result of work done by Dr. Ames and his colleagues. He is one of the most cited scientists of all time, thanks to his more than 450 research reports and his development of the Ames Test.

Dr. Ames is a member of the National Academy of Sciences, and he was on the organization’s Commission on Life Sciences. He was a member of the board of directors of the National Cancer Institute and the National Cancer Advisory Board, from 1976 to 1982. He was the recipient of the General Motors Cancer Research Foundation Prize (1983), the Tyler Environmental Prize (1985), the Gold Medal Award of the American Institute of Chemists (1991), the Glenn Foundation Award of the Gerontological Society of America (1992), the Lovelace Institutes Award for Excellence in Environmental Health Research (1995), the Honda Prize of the Honda Foundation, Japan (1996), the Japan Prize (1997), the Kehoe Award, American College of Occupational and Environmental Medicine (1997), the Medal of the City of Paris (1998), the U.S. National Medal of Science (1998), the Linus Pauling Institute Prize for Health Research (2001), and the American Society for Microbiology Lifetime Achievement Award (2001).

Passwater: Dr. Ames, you have been researching free radicals and antioxidants for more than 30 years. What piqued your curiosity about antioxidants and free radicals?

Ames: My main interest was DNA damage and how to prevent it. DNA damage can lead to cancer and other diseases. From studying various lines of evidence, I became convinced that much of human DNA damage was likely to be due to oxidation, and that slowly got me into the free radical and antioxidant field.

Passwater: It seems as if you have particularly been interested in DNA damage that leads to cancer. One of your most important contributions has been the Ames Mutagenicity Test, which is commonly called simply the "Ames Test." What has the Ames Test enabled us to do?

Ames: I had training in both genetics and biochemistry, and, as I mentioned, I had a long-term interest in DNA damage. I was studying gene regulation in bacteria and I was mutating the bacteria to select mutants that had regulation damaged in certain ways. This prompted me to start reading about mutagens—compounds that can alter DNA.

In the course of doing this, I became interested in developing a practical test for screening mutagens. I started to develop bacterial tester strains to detect the known mutagens. I then became interested in the relation of mutagens to carcinogens. I started testing carcinogens in the test. This led to putting a homogenate of rat liver in the test to mimic mammalian metabolism. The "Ames Test" was the result in the late ’60s. This test became widely used to quickly and cheaply screen for compounds that were mutagenic and candidates for further testing for carcinogenic activity.

Passwater: That was probably the major reason why you were the 23rd most quoted scientist in all fields between 1973 and 1984! One of the first things scientists ask about compounds that are going to be consumed or put into the environment is, "Is it mutagenic in the Ames Test?"

Vitamin E is the common name for two families of compounds called "tocopherols" and "tocotrienols." Each of these families contains four vitamers classified as "alpha-," "beta-," "gamma-" and "delta-." The most familiar and most researched form of vitamin E is alpha-tocopherol because, historically, it is the most effective in maintaining fertility (which was the focus of research that led to the discovery of vitamin E). It is the most powerful antioxidant of the tocopherols, and is the form most often used in supplements.

I have discussed these eight vitamers of vitamin E extensively in previous columns, especially in my chats with Dr. Maret Traber (November and December 1997, and January 1998) and Dr. Marvin Barenbaum (February 1998). I like to discuss the chemical structure of vitamin E in terms of the molecule having a "head" which is actually a "chromane ring" and a "tail" which is a phytyl chain. Please do not confuse the fact that natural vitamin E has eight vitamers with the coincidence in numbers that synthetic vitamin E has eight variants called enatomorphs. Synthetic vitamin E is a mixture of eight variants of alpha-tocopherol, most of which have little or no vitamin E activity nor other biochemical value. These essentially useless variants of alpha-tocopherol in synthetic vitamin E have alterations in the phytyl "tail" of the normal vitamin E molecule. The discussion here is of natural vitamin E forms that include true alpha-tocopherol (chemically called RRR- alpha-tocopherol) as well as another natural vitamin E form called gamma-tocopherol. There is no synthetic gamma-tocopherol.

Dr. Ames, recently, you have been investigating the role of one of the forms of vitamin E called "gamma-tocopherol" in comparison to "alpha-tocopherol." Are there distinct roles for gamma-tocopherol. Should dietary supplements be balanced with gamma-tocopherol?

Ames: Gamma-tocopherol is the main form of vitamin E in the American diet, though it has attracted little interest in comparison to alpha-tocopherol, the form found in supplements. The reason for this neglect is that alpha-tocopherol is a better antioxidant than gamma-tocopherol and is preferentially taken up by the body so that plasma concentrations of alpha-tocopherol are higher than those of gamma-tocopherol.

Dr. Stephan Christen in my lab, following up on some work of Dr. Robert Cooney, showed that gamma-tocopherol, however, is an excellent nucleophile (electron-rich), unlike alpha-tocopherol, and can react with and inactivate electrophilic (electron-poor) mutagens such as the nitrogen oxides generated by smoking or chronic inflammation.

Dr. Qing Jiang in my lab also has shown that gamma-tocopherol, unlike alpha-tocopherol, is an excellent anti-inflammatory agent at physiological concentrations and is effective in inhibiting the synthesis of the pro-inflammatory eicosanoids both in vitro and in vivo. Cronic inflammation has been implicated in heart disease, Alzheimer's disease, cancer, and other degenerative diseases. Dr. Jiang has written a review pointing out the many reasons why gamma-tocopherol may be important for health and deserves more attention.

Nuts are particularly rich in gamma-tocopherol, and a number of epidemiological studies have found an inverse relation between nut, or gamma-tocopherol, consumption, and various degenerative diseases. A strong protective effect was found between gamma-tocopherol level and prostate cancer.

Passwater: The chemical structural difference between the alpha- and gamma-forms of tocopherol is that the alpha-tocopherol head of the molecule (the chromane ring) has all available positions filled, whereas gamma-tocopherol has an open position. This apparently allows better interaction with nitric oxide and other nitrogen radicals. Similarly, the large phenolic oligomeric flavonoids found in Pycnogenol® are effective against nitric oxide and nitrogen radicals for the same reason.

Markers of inflammation such as the enzyme protein kinase C (PKC) or C-reactive protein (CRP) can be lowered by alpha-tocopherol. Are there other considerations to the inflammatory process that have different reactions from the alpha-tocopherol and gamma-tocopherol forms of vitamin E, such as the eicosanoids or superoxide anion radicals?

And if inflammation is a risk factor in heart disease, as oxidized low-density lipoprotein (LDL) may be, how do we balance the new findings about gamma-tocopherol with the 1993 epidemiological studies of Dr. Eric Rimm et al. and Dr. Meir Stampfer et al.? Their studies suggest a protective effect of alpha-tocopherol supplements against heart disease. Is it that both gamma-tocopherol and alpha-tocopherol share the same, or some of the same, anti-inflammatory pathways, possibly with different degrees of effectiveness? Or is it that each form has its own distinct anti-inflammatory pathway? Could a relatively large amount of alpha-tocopherol overcome a diet low in gamma-tocopherol? Would you expect adding gamma-tocopherol to supplements would improve their protective effect?

Ames: We are not saying that one should substitute gamma-tocopherol for alpha-tocopherol. We think they both have their functions. Alpha-tocopherol is a better antioxidant, and gamma-tocopherol is a better anti-inflammatory and mutagen scavenger. Most supplements, however have only alpha-tocopherol, even though gamma-tocopherol is the main form in the diet.

Passwater: A very good point. It reminds me of the advice I offered in Let’s Live in September 1975 in an article entitled "Which Kind of Vitamin E should I take?" The article discussed my personal preference for mixed-tocopherols as opposed to straight alpha-tocopherol for my vitamin E. I explained that alpha-tocopherol was the most powerful antioxidant of the various forms of vitamin E, but there may be a reason for nature providing the other forms. It didn’t seem that nature was just using the other forms of vitamin E as precursors to alpha-tocopherol.

It could be that the other forms of vitamin E had specific uses in the plants that form them, but it could also be that there was a difference that was important to humans, and it we just didn’t know about it yet. Perhaps this use is what you have finally elucidated. The amount of gamma-tocopherol present in what has traditionally been called "mixed tocopherols" is about 35 to 50 milligrams per 400 IU of alpha-tocopherol. Based on your research, it may be even better to take an additional 100 to 200 milligrams of gamma-tocopherol daily, an even better yet to include one with generous amounts of tocotrienols as well.

One of your research interests is in tuning-up human metabolism. Metabolism is affected by several parameters including genetics and aging. What is the benefit of tuning-up metabolism?

Ames: We need to get everyone up to required levels of the essential vitamins and minerals. Their metabolism is out of tune if they are too low in any of them. We are interested in determining optimum vitamin, mineral and other micronutrient intakes for minimizing DNA damage as an aid in the prevention of cancer and other degenerative diseases of aging. I believe this is likely to be a major way to minimize DNA damage, improve health, and prolong healthy lifespan.

Mitochondria are the power plants of the cells. The decay of mitochondria with age—due to oxidation of RNA/DNA, proteins, and lipids—is another major interest of mine and my laboratory. We are making progress in reversing some of this decay in old rats by feeding them normal mitochondrial metabolites at high levels, and are extending the research to humans.

Passwater: One of your most recent discoveries is that mitochondria from old rats can be "rejuvenated" and the rats’ memory improved with a diet high in acetyl-l-carnitine and lipoic acid. What are your findings?

Ames: Mitochondria decay with age. Membrane potential, cardiolipin (a key lipid in the mitochondria), and oxygen utilization decrease with age. Oxidants, oxidized RNA in brain neurons, and lipid peroxidation products increase with age.

Feeding old rats acetyl carnitine, a normal mitochondrial biochemical, for a few weeks restores membrane potential, oxygen utilization, and cardiolipin, however it does not lower the level of oxidants, oxidized RNA, or lipid peroxidation products. These are lowered by feeding old rats another mitochondrial biochemical, the antioxidant lipoic acid.

Passwater: Is the combination of acetyl-l-carnitine and lipoic acid synergistic?

Ames: Yes, for several parameters that we measured. The old rats fed the mixture of the two biochemicals have mitochondria that are more like those of young animals and in addition the old animals have brain function and ambulatory activity more like that of young animals. This work was started by Dr. Tory Hagen when he was a postdoc in my lab and continued as a collaboration with him now that he is at Oregon State at the Linus Pauling Instittue. It has been continued in my lab by Dr. Jiankang Liu, first as a postdoc and now as a research scientist. Dr. Liu and I have established a mechanism by which high levels of acetyl-carnitine can restore mitochondrial activity.

Dr. Hagen and I formed a company, Juvenon, which licensed the patent the university took out on our mixture. This company is doing clinical trials in humans.

Passwater: Why did you choose acetyl-l-carnitine over l-carnitine to use in your studies?

Ames: We used acetyl-carnitine because it was fed to old rats by an Italian group and improved mitochondrial transcription. Some evidence suggests that it passes the blood brain barrier better than carnitine. Carnitine is used in mitochondria for transporting fatty acid fuel. The body synthesiszes carnitine, but the levels of acetyl carnitine present in blood plasma, decline with age. The levels in the diet are minimal. It is sold in Italy as a pep pill.

Passwater: Why lipoic acid as the antioxidant?

Ames: Lipoic acid is reduced in mitochondria to a coenzyme for assimilating carbohydrate energy, and it is also an antioxidant. It is used in diabetes.

Passwater: Would supplemental coenzyme Q-10 also help?

Ames: It might, but we have not investigated that yet.

Passwater: Does improved metabolic efficiency affect mitochondrial free-radical production?

Ames: I would think it would decrease free radical leakage.

Passwater: Which is a goal that several of us have been working toward for about 45 years. Let’s stop here for the time being and pick up on your research on how vitamins, minerals and other micronutrients can help overcome genetic diseases and other biochemical shortcomings. Dr. Ames, thank you for sharing your research with us. WF