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Effects of dietary anticarcinogens on rat gastrointestinal glutathione peroxidase activity
E M van Lieshout1, M P Ekkel, M M Bedaf
1Department of Gastroenterology, St. Radboud University Hospital, 6500 HB Nijmegen, The Netherlands.
Abstract:
Several naturally occurring and synthetic food components reduce gastrointestinal cancer. Many of these compounds are scavengers of free radicals, formed during oxidative stress. Glutathione peroxidases (GPxs) protect against free radicals by catalysing their inactivation, thereby consuming glutathione (GSH). This might be one of the mechanisms leading to cancer prevention. We studied the effect of several dietary anticarcinogens on gastrointestinal GPx enzyme activities in male Wistar rats. Total as well as selenium-dependent and non-selenium-dependent GPx (t-GPx, Se-GPx and nSe-GPx) enzyme activities were determined in cytosolic fractions of oesophagus, gastric and colonic mucosa and liver. d-Limonene induced all three types of GPx activities in the oesophagus. d-Limonene and PEITC induced colonic t-GPX and nSe-GPx activity. beta-Carotene induced all three colonic GPx activities and hepatic t-GPx and Se-GPx activity. Coumarin and alpha-tocopherol induced gastric t-GPx and colonic nSe-GPx activity. Oltipraz enhanced oesophageal and gastric t-GPx and oesophageal, gastric and colonic Se-GPx. All other anticarcinogens induced one type of GPx activity at one site. In conclusion, the specific enhancement of GPx enzyme activities by dietary anticarcinogens might lead to a more efficient reduction of organic hydroperoxides and hydrogen peroxide and thus add to prevention of carcinogenesis in these organs.
Insights
Dietary anticarcinogens enhance glutathione peroxidases (GPx) enzyme activity in the gastrointestinal tract. This specific enhancement may contribute to cancer prevention by reducing harmful oxidative stress compounds.
Area of Science:
- Biochemistry
- Oncology
- Nutritional Science
Background:
- Oxidative stress from free radicals contributes to gastrointestinal cancer.
- Glutathione peroxidases (GPxs) are key enzymes in neutralizing free radicals.
- Dietary compounds may influence GPx activity and offer cancer protection.
Purpose of the Study:
- To investigate the impact of various dietary anticarcinogens on gastrointestinal GPx enzyme activities.
- To determine the effects on total GPx (t-GPx), selenium-dependent GPx (Se-GPx), and non-selenium-dependent GPx (nSe-GPx).
Main Methods:
- Male Wistar rats were used as the study model.
- Administration of several naturally occurring and synthetic dietary anticarcinogens.
- Measurement of GPx enzyme activities in cytosolic fractions of oesophagus, gastric, colonic mucosa, and liver.
Main Results:
- d-Limonene boosted all GPx types in the oesophagus.
- d-Limonene and PEITC increased colonic t-GPx and nSe-GPx.
- beta-Carotene elevated all colonic GPx types and hepatic t-GPx and Se-GPx.
- Coumarin and alpha-tocopherol enhanced gastric t-GPx and colonic nSe-GPx.
- Oltipraz significantly increased oesophageal and gastric t-GPx and Se-GPx across multiple sites.
Conclusions:
- Specific dietary anticarcinogens can selectively enhance GPx enzyme activities in the gastrointestinal tract.
- This targeted enhancement of GPx may improve the detoxification of hydroperoxides and hydrogen peroxide.
- Increased GPx activity is a potential mechanism for the chemopreventive effects of these dietary compounds against gastrointestinal cancers.