Lycopene animal studies

Oxidative stress is now recognized as an important etiological factor in the causation of several chronic diseases including cancer, cardiovascular diseases, osteoporosis, and diabetes. Antioxidants play an important role in mitigating the damaging effects of oxidative stress on cells. Lycopene, a carotenoid antioxidant, has received considerable scientific interest in recent years. Epidemiological, tissue culture, and animal studies provide... 

Coenzyme QIO is a powerful antioxidant naturally occurring in the mitochondria of myocardium, and it is an electron carrier in the mitochondrial synthesis of ATP. Patients with heart failure have lower myocardial levels of coenzyme QIO, but supplementation has been demonstrated to have variable benefits in randomized controlled trials. One meta-analysis on the use in congestive heart failure showed improvements in stroke volume, ejection fraction, cardiac output, cardiac index, and end diastolic volume index. " Another antioxidant associated with beneficial effects in cardiac patients is lycopene, a natural constituent of tomatoes. Lycopene is the major carotenoid found in human serum, and epidemiological studies have indicated an effect of dietary supplementation in reducing heart disease. Few dietary interventions have been reported one study showed a mild but significant hypocholesterolemic effect, and another showed a significant reduction in LDL oxidation. " Animal studies show an antiatherogenic effect of DHEA, and a review of the clinical trials and studies on DHEA in males with coronary heart disease reported a favorable or neutral effect. Plasma levels of DHEA are decreased in patients with chronic heart failure in proportion to its severity. ... 

Interestingly, many more lycopene-based studies have been conducted in animal models or in human subjects rather than in cell culture. The explanation for this may be seen as two-fold. Firstly, because of the high lipophilic nature of lycopene, it is most commonly solubilized in tetrahydrofuran, which, in itself, is toxic to cells. Second, since lycopene, a phytochemical, is a natural product and, in most studies, was either supplied to subjects in its natural form (tomato juice, etc.) rather than supplements or indirectly deduced from dietary questioimaires, ethical committee approval was relatively easy to obtain. Substantial evidence has been produced relating the consumption of lycopene to a decreased risk of acquiring degenerative diseases, such as certain kinds of cancers and cardiovascular disease. In addition, the usefulness of lycopene has, on several accounts, been shown in the treatment of cancers. Thus it becomes increasingly important to understand in detail the molecular mechanism of action of lycopene in varions model cell systems. 

ANIMAL STUDIES OF LYCOPENE EFFECTS ON EXPERIMENTAL TUMORS... 

From the literature reviewed in the present chapter, it appears that lycopene is an important compound in coimection with the onset and the progression of cancer. Important epidemiological studies have traced the path that has been followed by the first clinical interventions and by the animal studies. Cellular mechanisms have appeared as well to show that the human and animal results are based on specific molecular events correlated with regulation of the cell cycle. An additional step in understanding the... 

Lycopene has been shown to inhibit the incidence and growth of the chemically induced breast tumors in laboratory animal studies [12, 107]. A protective effect of lycopene was found on DMBA-induced rat mammary tumors. When compared with placebo or control rats, the lycopene fed rats had the smallest average size of tumors, but the difference was not statistically significant. The number of tumors that developed over 135 days was much lower in the... 

Epidemiologic studies, in vitro, and in vivo animal studies have suggested that tomato and lycopene have beneficial effects in the treatment of head and neck... 

In this chapter, we have summarized the potential effects of lycopene in prevention and treatment of cancer. Lycopene intake and plasma levels of lycopene have been inversely associated with cancer risk in most of the case-control studies and animal studies. Clinical trials need to be craiducted to investigate lycopene in prevention of cancer and as an adjunct to standard cancer therapy. Until more data is available regarding lycopene supplementation, it is suggested that the potential health benefits of lycopene can best be achieved through a diet rich in a variety of fruits and vegetables, which include tomatoes. 

Most of the indications with respect to cancer comes from human studies linking tomato intake, total estimated lycopene intake, and serum or plasma lycopene concentrations to the subsequent development of cancers (Table 5). There is a small amount of evidence from experimental animal studies, for instance, rat and mouse dimethylbenzanthracene-... 

Animal studies demonstrating a reduction of oxidation-induced damage or disease with lycopene supplements or with lycopene-rich foods such as tomatoes or tomato products. 

Population studies associate tomato consumption with reduced risk to prostate cancer. The most positive associations have come from cohort studies performed before the prostate-specific antigen (PSA)-screening era, and these studies have suggested that the tomato/lycopene effect was the strongest for clinically relevant prostate cancers (Giovannucci 2007). Small human studies have shown in vivo antioxidant effects for tomato products but evidence for lycopene alone is weak (Chen et al. 2001, Porrini and Riso 2000, Riso et al. 2004, Zhao et al. 2006). Animal and tissue culture studies have been... 

Awareness of lycopene as a potentially beneficial carotenoid in the nutritional and medical sciences is less than 10 years old. Therefore, comparatively few scientific data are available from animal and human studies. But in this short time, a number of features of lycopene have emerged that are unique among the common carotenoids, quite apart from its exceptionally high singlet oxygen quenching capacity in vitro. The most obvious distinction is that unlike the other hydrocarbon carotenoids, a- and P-carotene, lycopene has no provitamin A activity. 

With increasing interest in undertaking animal experimental and human clinical and intervention studies to evaluate the role of lycopene in cancer prevention, it is important that well-established molecular and clinical markers of cancer be used in these studies. In general, the main clinical end points used in animal and human experiments are the tumor burden and volume and survival rates. Now that our understanding of cancer pathology has advanced, several molecular events are beginning to be recognized and used in research to evaluate the outcomes from intervention studies. A brief overview of some of the more important molecular markers of cancer that can and should be used in future studies is presented in this section. 

These types of technique have been employed to identify a number of carotenoids in multiple types of samples. Recently GC-MS and authentic standards were used to identify volatile carotenoid metabolites from plant tissues (Vogel et ah, 2008) and numerous studies have identified P-carotene metabolites in animals and humans using a variety of analytical techniques (Hu et ah, 2006 Ho et ah, 2007). These techniques have also been used to identify lycopene metabolites in both foods and biological samples (Khachik et ah, 1997 Bouvier et ah, 2003 Kopec et ah, 2010) and the metabolism of lutein, zeaxanthin, and P-cryptox-anthin (Bernstein et ah, 2001 Prasain et ah, 2005 Mein et ah, 2011). 

Three major types of research have emerged (Levy et al., 1995) epidemiological studies involving patients with various malignancies, studies on the direct effect of lycopene on the proliferation of various tumors in cell lines and in animal models, and studies on the biochemical and immunological mechanisms of lycopene action. 

Together, such studies demonstrate that lycopene can function as an antioxidant In vivo and In vitro and can reduce genetic damage In humans, animal models, and cell systems. 

Cohen, L.A., A review of animal model studies of tomato carotenoids, lycopene, and cancer prevention, Exp. Biol. Med., Ill, 864, 2002. 

To date, only eight studies in animal models have been pubhshed on the cancer chemopreventive effects of lycopene or tomato carotenoids (Table 32.3), with the majority showing a protective effect of lycopene. A positive correlation between lycopene or tomato product intake and cancer... 

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