Colorectal and Other Digestive Tract Cancers

Several randomized trials have shown no reduction in colorectal cancer risk with -carotene supplementation (8,10). However, two trials indicated that among regular alcohol users b-carotene supplementation decreases colon cancer risk (12,13). The carotenoid supplementation in alcohol users may be more effective because their serum b-carotene levels appear to be lower than in nonusers (14,15). In another study (16), b-carotene was not effective in preventing colorectal adenoma (a precursor of...

References

Beta-carotene, carotenoids and disease prevention in humans. FASEB J 1996 10 690-701. 2. Ziegler RG, Mayne ST, Swanson CA. Nutrition and lung cancer. Cancer Causes Control 1996 7 157-177. 3. Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, Keogh JP, Meyskens FL, Valanis B, Williams JH, Barnhart S, Hammar S. Effects of a combination of -carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med 1996 334 1150-1155. 4. The Alpha-tocopherol,...

Carotenoids and the Insulin Like Growth Factor System

The identification of risk factors for various types of cancer can lead to appropriate preventive measures. The importance of the sex steroids estradiol and testosterone for the development and progression of breast and prostate cancers, respectively, is well known. Recently, a similar role has been proposed for insulin-like growth factor-I (IGF-I). Chan et al. (102) found a strong positive association between IGF-I levels and prostate cancer risk in participants of the Physicians' Health...

Lipoprotein Transport of Carotenoids in Plasma

As early as 1936, Willstaedt and Lindquist identified the predominant carotenoids (lutein, zeaxanthin, lycopene, and -carotene, as well as several unidentified carotenoids, most likely -cryptoxanthin) in human serum and liver (43), but they did not provide dietary intake data on their subjects. The carotenoids that have been identified in human plasma samples are listed in Table 1. A number of experiments have delineated the time-course of carotenoid concentrations on specific lipoprotein...

Factors Involved In The Prooxidant Activity Of Carotenoids

Increasing evidence suggests that the antioxidant activity of carotenoids may shift into a pro-oxidant one in biological models, depending on several factors. Some of them have been recently reviewed (8-10) and are summarized in Table 1. As Burton and Ingold suggested (12), carotenoids do not have the structural features commonly associated with chain-breaking antioxidants. The extensive system of conjugated double bonds may impart a pro-oxidant character to the carotenoid molecule and may make...

Carotenoids and Gap Junctional Intercellular Communication

Among the various biological activities of carotenoids, their stimulatory effects on gap junctional intercellular communication GJIC have been discussed as one of the possible biochemical mechanisms underlying their cancer-preventive properties 114-117 . Although only limited data from in vivo studies are available, a number of cell culture experiments provide evidence for such a mechanism. Gap junctions are specialized microdomains of the plasma membrane that provide a specific pathway for...

Carotenoids and Radicals Interactions with Other Nutrients

Carotene Structure

Keele University, Keele, Staffordshire, England A nutrient is defined as any substance that has nutritious qualities, i.e., that nourishes or promotes growth, and one that can be metabolized by an organism to give energy and build tissue. In this chapter a nutrient is assumed to be an amino acid, carotenoid, vitamin C, vitamin E, and other antioxidants such as polyphenols Fig. 1 shows the structures of some important antioxidants discussed in chapter . While carotenoids, vitamin E, and vitamin...

Heterochromatic Flicker Photometry

Heterochromatic Flicker Photometry

The most commonly used method to measure macular pigment levels noninvasively in the human eye is the psychophysical technique known as heterochromatic flicker photometry HFP . This technique was initially described by several investigators in the 1970s, and at that time it usually required rather extensive apparatus utilizing Maxwellian view optics, xenon arc lamps, and fixed optical tables 25,26 . In recent years, newer versions using free-view Newtonian optics and simpler light sources such...

Retinoid Receptors

Retinoic acid is the parent compound of ligands known as retinoids. It exerts multiple effects on cell proliferation and differentiation through two classes of nuclear receptors termed retinoic acid receptors RARs and retinoid X receptors RXRs . All-trans retinoic acid binds only to RAR, whereas its isomer, 9-cis-retinoic acid, binds to both RAR and RXR. Upon DNA binding, RXR RAR heterodimers regulate gene expression of retinoic acid target genes in a ligand-dependent manner. RXR is also...

Synergistic Inhibition Of Cancer Cell Growth By Combination Of Various Carotenoids And Other Micronutrients

The use of a single plant-derived compound in human prevention studies has not been particularly successful as evidenced from the large intervention studies carried out with -carotene 7-9,11,16 . These results seem to indicate that the beneficial effects of diets rich in vegetables and fruit are not related to the action of a single compound but rather to the concerted action of several micronutrients, which when used alone are active only at high and sometimes toxic concentrations. To support...

Conclusion

In studies using cell and animal models, carotenoids have been shown to influence diverse molecular and cellular processes that can form the basis for the beneficial effects of carotenoids on human health and disease prevention. However, despite the promising results it is difficult at the moment to directly relate available experimental data to human pathophysiology. One problem is that many results were obtained in studies using carotenoid levels that are much higher than those achievable in...

Modulation By Carotenoids Of Cytochrome P450 Enzyme Activities In Animal Studies

The initial studies on this issue involved investigation of the effects of dietary supplements of -carotene 20, 100, 500 mg kg diet on hepatic microsomal drug-metabolizing enzyme activities in mice 4 . Supplementation for 14 days resulted in strong diminution of hepatic cytochrome P450 content and biphenyl- 4-hydroxylase activity, but unchanged activities of aminopyrine N-demethylase and p-nitroanisol o-demethylase. Red palm oil RPO from Elaris guineensis has been reported to be the richest...

Series Introduction

Overwhelming evidence indicates that oxidative stress can lead to cell and tissue injury. However, the same free radicals that are generated during oxidative stress are produced during normal metabolism and thus are involved in both human health and disease. Free radicals are molecules with an odd number of electrons. The odd, or unpaired, electron is highly reactive as it seeks to pair with another free electron. Free radicals are generated during oxidative...

Regulation of Cell Cycle by Carotenoids

The carotenoid-induced reduction in cancer cell proliferation reported in the in vivo and in vitro studies mentioned above can result from cell death or from inhibition of cell cycle progression or both. Several studies have shown that at high concentrations 20 mM and higher carotenoids decrease cell viability by inducing apoptosis 71,86 . On the other hand, we have demonstrated that the inhibitory effects of low lycopene concentrations 1-4 mM on the growth of cancer cells are not accompanied...

Antiproliferative Effects Of Carotenoids On Cancer Cells

Numerous in vitro studies have been performed to verify the role of carotenoids in cell proliferation and differentiation. In a study on both estrogen receptor-positive MCF-7 and negative Hs578T and MDA-MB-231 human breast cancer cells 65 , -carotene significantly inhibited the growth of MCF-7 and Hs578T cells and lycopene inhibited the growth of MCF-7 and MDA-MB-231 cells, whereas cantaxanthin did not affect the proliferation of any of the three cell lines. The same group also studied the...

Reflectance Measurement of Carotenoids in Skin

300 Chroma Meter

Objective noninvasive optical methods to measure carotenoids are challenging since skin is a semiopaque tissue that is prone to considerable light scattering. Jungmann and colleagues developed a reflectometry-based system 85 that has been useful for monitoring relative changes in skin carotenoid content in small groups of volunteer subjects after supplementation 86 . In this method, a region of the skin is illuminated with a 5-W halogen lamp via a fiberoptic reflection bundle, and the reflected...

Basic Carotenoid Chemistry

Iupac Beta Carotene

Norwegian University of Science and Technology, Trondheim, Norway This chapter deals with the chemical foundation for the other chapters in this book. For more detailed treatments reference is made particularly to comprehensive recent treatments, including the Carotenoids book series published by Birkhauser, namely Vol. 1A, Isolation and Analysis 1 Vol. 1B, Spectroscopy 2 Vol. 2, Synthesis 3 and Vol. 3, Biosynthesis and Metabolism 4 . Other useful references are the Key to Carotenoids 5 and the...

Contributors

Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, U.S.A. Eileen Ang The University of Melbourne, Melbourne, Victoria, Australia Arun B. Barua, Ph.D. Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, U.S.A. Paul S. Bernstein, M.D., Ph.D. Department of Ophthalmology and Visual Sciences, Moran Eye Center, School of Medicine, University of Utah, Salt Lake...