QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chen, H.-W. Articles by Lii, C.-K. Search for Related Content PubMed PubMed Citation Articles by Chen, H.-W. Articles by Lii, C.-K.

---

Articles

Dietary Fat and Garlic Oil Independently Regulate Hepatic Cytochrome P₄₅₀ 2B1 and the Placental Form of Glutathione S-Transferase Expression in Rats¹

Haw-Wen Chen, Jaw-Ji Yang^*, Chia-Wen Tsai, Jyh-Jong Wu, Lee-Yan Sheen^**, Chu-Chyn Ou and Chong-Kuei Lii²

Department of Nutrition, Chung Shan Medical College; Department of Food Science, National Chung-Hsing University; ^** Department of Nutrition, China Medical College, Taichung 402; and ^* Institute of Molecular Biology, National Chung Cheng University, Min-Hsiung 621, Taiwan

²To whom correspondence should be addressed. E-mail: cklii{at}mercury.csmc.edu.tw

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The individual and combined effects of dietary fat and garlic oil on two drug-metabolizing enzymes, cytochrome P₄₅₀ 2B1 and the placental form of glutathione (GSH) S-transferase (PGST), in rat liver were examined in this study. Rats were fed a low corn oil, high corn oil or high fish oil diet and received various amount of garlic oil (0, 30, 80, 200 mg/kg body) orally three times per week for 6 wk. The fat energy in the low and high fat diets accounted for 11.6 and 45.7% of total energy, respectively. Final body weights did not differ among the three dietary fat groups and were not affected by garlic oil treatment. The fatty acid profile in hepatic phospholipids revealed higher eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] levels in the fish oil–fed group than in the low and high corn oil–fed groups (P < 0.05). In contrast, the corn oil–fed groups had greater hepatic phospholipid arachidonic acid [20:4(n-6)] levels (P < 0.05). Both dietary fat and garlic oil significantly affected hepatic cytochrome 7-pentoxyresorufin O-dealkylase (PROD) activity and GST activity toward ethacrynic acid. Rats fed the high fish oil diet had 85 and 51% higher PROD activity compared with those fed the low or the high corn oil diet, respectively (P < 0.05). The GST activity in the high fish oil and the high corn oil groups was 33 and 18% higher than that in the low corn oil group (P < 0.05), respectively, and the GST activity in rats fed the high fish oil diet was higher than in those fed the high corn oil diet (P < 0.05). Garlic oil dose-dependently increased GST activity. No interaction between dietary fat and garlic oil on PROD or GST activity was noted. Northern and Western blot analysis revealed that dietary fish oil increased both cytochrome P₄₅₀ 2B1 and PGST mRNA and protein levels. Cytochrome P₄₅₀ 2B1 and PGST mRNA and protein levels were also dose-dependently increased by garlic oil treatment. The effects of garlic oil and dietary fat on P₄₅₀ 2B1 and PGST mRNA and protein expression were independent. These results indicate that dietary fat and garlic oil independently modulate P₄₅₀ 2B1 and PGST expression at transcriptional and/or post-transcriptional stages.

KEY WORDS: • fish oil • garlic oil • cytochrome P₄₅₀ 2B1 • glutathione S-transferase • rats

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The hepatic bioactivation and detoxification system plays an important role in carcinogenesis. This system is composed of phase I and phase II enzymes. Phase I enzymes, mainly the cytochrome P₄₅₀, are involved in the bioactivation of chemical carcinogens, the biotransformation of many endogenous compounds and the detoxification of numerous xenobiotics (1 ,2) . The physiologic function of phase II enzymes such as glutathione (GSH)³ (3) S-transferases (GST) is to catalyze the conjugation of small water-soluble molecules to xenobiotics and facilitate their excretion. There is a strong inverse association between tissue levels of detoxifying enzymes and susceptibility to chemical carcinogenesis (4 5 6) .

GST are a family of dimeric enzymes composed of at least seven gene products (3) . Overexpression of the placental form of GST (PGST) has attracted great interest because of its relationship to carcinogenesis and human cancers (7 ,8) . GST and cytochrome P₄₅₀ are highly inducible in animals and humans, and their expression is affected by nutritional as well as nonnutritional factors. The dietary factors include lipid (9 10 11) , vitamin E (12 ,13) , water-soluble vitamins (14) , garlic components (15) and green tea polyphenols (16) . Recently, animal studies showed that rats fed a high fish oil diet (20.5 g/100 g) had significantly higher 7-pentoxyresorufin O-dealkylase (PROD) activity than rats fed a low or high corn oil diet (17) . In addition to the source of dietary lipid, the amount of dietary lipid also plays an important role in the modulation of hepatic N-nitrosodimethylamine demethylase activity and cytochrome P₄₅₀ 2E1 protein expression (10) . A higher degree of unsaturation of polyunsaturated fatty acids present in liver microsomal membranes may be associated with the increases in the rate of drug metabolism and drug oxidation (18) .

The role of natural foods in disease prevention has been studied extensively in recent years. Among these natural foods, garlic has attracted a great deal of attention. During the past 15 y, most studies on garlic have been in the fields of cardiovascular and cancer research (19) . Previous studies have found that ingestion of garlic is inversely related to the incidence of hyperlipidemia, atherosclerosis and thrombosis (19) . Among the active garlic components, the organosulfur compounds are considered to be the most potent agents in chemoprevention (15) , and their chemopreventive capabilities have been shown to be related to their modulation of drug-metabolizing enzymes involved in the activation or detoxification of carcinogens (20 ,21) . Garlic oil is rich in numerous active organosulfur compounds such as diallyl sulfide, diallyl disulfide and diallyl trisulfide. Diallyl sulfide has been shown to increase the activities of cytochrome P₄₅₀ 2B1 and GST (22 23 24) .

Although dietary lipid and garlic modulate the activity of drug-metabolizing enzymes, the combined effect of garlic oil and fish oil on the drug metabolism system has not been studied. Recently, coadministration of garlic and fish oil was shown to ameliorate hyperlipidemia in hypercholesterolemic men (25) . This study was designed to investigate the individual and combined action of fish oil and garlic oil on cytochrome P₄₅₀ 2B1 and GST, particularly the placental form (PGST). The results of this study may help to clarify the extent of interaction between fish oil and garlic oil in carcinogen bioactivation and xenobiotic detoxification.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Materials.

2,4-Chloro-dinitrobenzene (CDNB), 7-pentoxyresorufin and other biochemical reagents were purchased from Sigma Chemical (St. Louis, MO). Trizol was ordered from Gibco BRL (Grand Island, NY). Anti-P₄₅₀ 2B1 polyclonal antibody was purchased from Oxford Biomedical Research (Oxford, MI). Antibody against PGST was purchased from Biotrin (Dublin, Ireland).

Garlic oil preparation.

Garlic cloves were purchased from a local market. In each preparation, 1.5 kg of garlic cloves was blended with 3 L of distilled water in a Waring blender. Volatile components were extracted for 4 h with boiling distilled water. The extract was dried with anhydrous Na₂SO₄ and then filtered through nitrocellulose acetate membranes (26) . The oily product was designated garlic oil. An average of 2.5 g of garlic oil was extracted from 1 kg of garlic cloves. The garlic oil constitutes were analyzed by a gas chromatography-mass spectrometry system (G1800, Hewlett Packard, Palo Alto, CA); the levels of the four major organosulfur compounds, diallyl sulfide, diallyl disulfide, diallyl trisulfide and allyl methyl trisulfide, were 5, 39, 34, and 10 g/100 g, respectively.

Animals and treatments.

Male Sprague-Dawley rats (4 wk old) were purchased from the National Animal Breeding and Research Center (Taipei, Taiwan). After 1 wk of acclimation, rats were assigned to each experimental group by weight and housed in stainless steel wire cages, on a 12-h light:dark cycle. Rats were fed a diet containing 5 g/100 g corn oil (low corn oil, LCO) or 23.5 g/100 g corn oil (high corn oil, HCO) or 20.5 g/100 g fish oil + 3.0 g/100 g corn oil (high fish oil, HFO) (Table 1 ) as described by Reddy and Sugie (27) . The composition of all experimental diets was adjusted so that rats in all of the dietary groups received the same dosage of vitamins, minerals and fiber (27) . The addition of corn oil (3%) to the HFO diet was to prevent essential fatty acid deficiency. Diets were prepared every 2 wk and stored at -4°C. The diets provided to rats were changed every other day. Throughout the experiment, rats were administered 0, 30, 80 or 200 mg/kg body garlic oil (corn oil as a vehicle, 1 mL/kg body) by oral intubation three times per week. Rats were allowed free access to water and food. Body weight was measured weekly. Rats were treated in compliance with NIH guidelines (28) .

Hepatic phospholipid fatty acid composition.

Liver lipids were extracted according to the method of Folch et al. (29) ; total phospholipids were then isolated by TLC with hexane/diethyl ether/formic acid (80:20:2, v/v/v). After visualizing by spraying with 2',7'-dichlorofluorescein (1 g/L methanol) and marking under UV light (366 nm), spots were scraped off and collected into glass tubes for fatty acid analysis. Fatty acid analysis was performed as described by Lepage and Roy (30) using a Supelco fused silica column with an i.d. of 0.25 mm (Bellefonte, PA). The integration of the peak area of each individual fatty acid was determined and its relative percentage of the sum of the peak area of all detectable fatty acids was calculated.

Hepatic PROD and GST activity assays.

Livers were homogenized in 4 volumes of a buffer (pH 7.4) containing 10 mmol/L potassium phosphate and 150 mmol/L KCl, and centrifuged at 10,000 x g for 30 min at 4°C. The resultant supernatant was further ultracentrifuged at 105,000 x g for 1 h, and the final cytosolic supernatant was stored at -80°C until analysis. The microsomal pellets were resuspended in 50 mmol/L potassium phosphate, 1 mmol/L EDTA buffer (pH 7.6), and the activity of PROD was measured with a fluorescence spectrophotometer (F4500, Hitachi, Tokyo, Japan) as previously described (31) . Cytosolic GST activity was assayed by the method of Habig et al. (32) , with CDNB as the substrate. Ethacrynic acid, which shows higher substrate specificity for PGST, was used as an alternative GST substrate (32 ,33) .

cDNA probes.

Two pairs of oligonucleotide primers were designed on the basis of the published sequences of 2B1 (forward: 5'-GGATGGGAAAGAGGAGTGTGGA-3', backward: 5'-CTGGAGGAT GGTGGTGAAGAAG-3') and PGST (forward: 5'-TTCAAGGCTCGCTCAAGTCCAC-3', backward: 5'-CTTGAT-CTTGGGGCGGGCACTG-3'). mRNA obtained from rat liver tissues was used as the template for reverse transcriptase-polymerase chain reaction (RT-PCR). The PCR conditions were set as follows: denaturing at 94°C for 1 min, annealing at 55°C for 1 min and extension at 72°C for 1 min, for 35 cycles followed by a 7-min extension at 72°C. Bands corresponding to the DNA fragment of 2B1 and PGST were labeled with -³²P-dCTP through NEBlot kit (New England Biolabs, Beverly, MA) and used as probes for Northern blot analysis.

RNA preparation and Northern blot analysis.

Fresh liver (100 mg) was homogenized in 1 mL Trizol reagent using a power homogenizer. The homogenates were allowed to react at room temperature for 5 min; 0.2 mL of chloroform was then added followed by incubation for an additional 3 min. The samples were centrifuged at 12,000 x g for 15 min at 4°C. The aqueous phase was transferred to a fresh tube and the RNA was precipitated by adding 0.5 mL isopropyl alcohol. The RNA samples remained at room temperature for 10 min followed by centrifugation at 12,000 x g for 10 min at 4°C. The resultant RNA pellets were washed twice with ice-cold ethanol.

For Northern blot analysis, 20 µg of each RNA sample was electrophoretically separated by 1% agarose gel containing 6% formaldehyde and transferred to HyBond membrane as previously described (34) . For hybridization with cDNA, the membrane was prehybridized for 2 h at 42°C in a solution containing 10X Denhardt’s reagent (0.2% Ficoll, 2 g/L polyvinylpyrolidone, 2 g/L bovine serum albumin), 5X SSPE (750 mmol/L NaCl, 50 mmol/L NaH₂PO₄, 5 mmol/L EDTA), 20 g/L SDS, 50% foramide, and 100 mg/L of single-strand sheared salmon sperm DNA. The membrane was then hybridized in the same solution with ³²P-labeled 2B1 cDNA probe at 4°C overnight. The membrane was washed 4 times with 2X SSC (300 mmol/L NaCl and 30 mmol/L sodium citrate)-0.5 g/L SDS at room temperature and twice with 0.1X SSC-1 g/L SDS at 52°C. Autoradiography was performed by exposing the membrane to Kodak SuperRx X-ray film at -80°C with an intensifying screen. For rehybridization with PGST cDNA probe, the membrane was deprobed by washing twice with boiling 1 g/L SDS. The bands on the X-ray film were measured with an AlphaImager 2000 (Alpha Innotech, San Leandro, CA).

SDS-polyacrylamide gel electrophoresis and immunodetection.

Equal amounts of liver microsomal or cytosolic fractions were applied to 10% SDS-polyacrylamide gels. After electrophoresis, proteins separated on gels were transferred to polyvinylidiene difluoride membranes and were immunostained as described by Towbin et al. (35) . The membranes were incubated with 50 g/L nonfat dry milk in 15 mmol/L Tris, 150 mmol/L NaCl buffer, pH 7.4, at 4°C overnight to block nonspecific binding. The membranes were then incubated with anti-P₄₅₀ 2B1 and PGST antibodies at 37°C for 1 h followed by peroxidase-labeled goat anti-rabbit immunoglobulin G. Hydrogen peroxide and tetrahydrochloride diaminbenzidine were used for color development.

Statistical analysis.

Data were analyzed by means of one-way ANOVA and Tukey’s test was used to test the significance of the effect of garlic oil treatments in each dietary fat–fed group. Two-way ANOVA was used to test the effects of both dietary fat and garlic oil and their interaction. When variances were heterogeneous, data were log-transformed before ANOVA. All statistical analyses were performed with commercially available software (SAS Institute, Cary, NC). A value of P < 0.05 was considered significant.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Differences in dietary lipid amount and source had no effect on the growth of rats (Table 2 ). Final body weight of rats fed different dosages of garlic oil was also not significantly different. Differences in dietary lipid amount had a significant effect on liver weight and relative liver weight of rats (P < 0.05). Rats fed the HCO and HFO diets had significantly greater absolute and relative liver weights than rats fed the LCO diet (P < 0.05) (Table 2) . However, garlic oil did not affect liver weight.

View larger version (64K): [in this window] [in a new window]   Figure 1. Hepatic P450 2B1 and placental glutathione S-transferase (PGST) mRNA level in rats fed low corn oil (LCO), high corn oil (HCO) or high fish oil (HFO) diets and treated with 0, 30, 80 or 200 mg/kg garlic oil for 6 wk. Total RNA was extracted by Trizol as described in Materials and Methods. An equal amount of RNA was subjected to Northern blot analysis (20 µg/lane). The filter was first hybridized with a P450 2B1 cDNA and then rehybridized with a PGST cDNA after deprobing. The fold of induction was quantitated by densitometry based on the relative amount of 18S RNA. A representative experiment is shown. The average values of P450 2B1 mRNA induction of three separate experiments were (from left to right) 1.0 ± 0, 1.47 ± 0.57, 1.92 ± 1.07, 3.39 ± 0.70, 1.54 ± 0.55, 2.24 ± 0.40, 3.63 ± 1.00, 9.96 ± 2.91, 7.17 ± 3.20, 9.07 ± 3.33, 14.06 ± 1.65, 17.91 ± 2.06, respectively, and those of PGST mRNA were 1.0 ± 0, 0.93 ± 0.31, 1.48 ± 0.52, 2.05 ± 0.93, 1.08 ± 0.41, 1.38 ± 0.51, 1.76 ± 0.37, 1.98 ± 0.65, 1.88 ± 0.41, 2.65 ± 0.84, 2.70 ± 0.63, 3.61 ± 1.0, respectively.

View larger version (27K): [in this window] [in a new window]   Figure 2. Immunoblot analysis of P450 2B1 and placental glutathione S-transferase (PGST) in rats treated with 0, 30, 80 or 200 mg/kg garlic oil and fed low corn oil (LCO), high corn oil (HCO) or high fish oil (HFO) diets for 6 wk. Proteins were separated on 10% SDS-polyacrylamide gels and electrophoretically transferred to polyvinylidene difluoride membranes. The amount of protein in each lane for P450 2B1 and PGST immunostaining was 6 and 3 µg, respectively. Protein level was quantitated by densitometry and the value in rats fed the LCO diet and receiving no garlic oil was regarded as 1.0. A representative experiment is shown. The average fold inductions of P450 2B1 of three separate experiments were (from left to right) 1.0 ± 0, 1.50 ± 0.36, 1.91 ± 0.36, 3.98 ± 0.37, 1.75 ± 0.77, 3.29 ± 0.96, 4.33 ± 1.99, 6.99 ± 1.72, 5.70 ± 1.46, 10.0 ± 3.80, 9.60 ± 3.20, 14.3 ± 5.19, respectively, and those of PGST were 1.0 ± 0, 1.43 ± 0.19, 1.46 ± 0.14, 1.76 ± 0.35, 1.03 ± 0.18, 1.23 ± 0.20, 1.56 ± 0.17, 1.69 ± 0.23, 1.33 ± 0.19, 1.71 ± 0.38, 1.94 ± 0.21, 2.30 ± 0.40, respectively.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

Cytochrome P₄₅₀ 2B1 protein and mRNA levels were affected by both the amount and source of dietary lipid with an order of influence of HFO > HCO > LCO. Hepatic P₄₅₀ 2B1 is one of the microsomal enzymes, and microsomal enzymes are embedded within the microsomal membranes. Any changes in the fatty acid composition in membrane phospholipids affects the fluidity of the microsomal membrane matrix and possibly alters the activity of cytochrome P₄₅₀ via electron transfer from NADPH to cytochrome P₄₅₀ (36) . In addition to the microsomal P₄₅₀ 2B1, changes in protein and mRNA levels of the cytosolic PGST suggest that, other than the alteration of enzyme conformation in membrane matrix, regulation of protein expression at the transcriptional and/or translational stages by the amount and source of dietary fat is possible. Numerous studies have suggested that dietary fatty acids can directly and indirectly modulate receptor-mediated signaling pathways at multiple levels and therefore the gene expression [see review in Hwang and Rhee (37) ]. Elucidating the molecular and cellular mechanisms of such responses requires further study. Hepatic P₄₅₀ 2B1 is inducible by phenobarbital, a hepatopromoter. The role of hepatic P₄₅₀ 2B1 in carcinogenesis is not fully understood, but previous studies in rats indicate that it is involved in the activation of aflatoxin B₁ (AFB₁) to AFB₁-8,9-epoxide (38) . In this study, we noted that the increase of P₄₅₀ 2B1 protein and mRNA levels by garlic oil in rats fed the HCO and HFO diets was not consistent with the changes of PROD activity. This discrepancy was attributed in part to the characteristic wide substrate spectrum of P₄₅₀. Thus, PROD activity may not be fully representative of P₄₅₀ 2B1.

In this study, GST activities toward CDNB and ethacrynic acid were affected by dietary lipid amount and source, and garlic oil treatment. However, no interaction that affected hepatic GST activity was found among these factors (Table 4) . Among the GST isoforms, the expression of the placental form, which is highly inducible in hepatocarcinogenesis, is of particular interest (Figs. 1 , 2) . Similar to P₄₅₀ 2B1, a HFO diet showed the greatest effect on PGST transcripts and protein levels. In this study, CDNB and ethacrynic acid were used as the substrates for GST activity assay, and PGST protein and mRNA expression patterns were more consistent with enzyme activity toward ethacrynic acid rather than CDNB. PGST is one of the GST isoenzmes, and GST activity toward CDNB may not truly reflect the PGST protein level due to the limited substrate specificity (33) . The difference in enzyme activities toward CDNB, ethacrynic acid and PGST expression suggests that GST isoforms other than the placental form, such as Ya, Yb and Yc, may also be modulated in a different pattern by dietary lipid and/or garlic oil (39) .

Recent studies found that the molecular mechanisms involved in the regulation of PGST gene are mediated by an antioxidant-responsive element (ARE) and the activator protein-1-responsive element; both are located on PGST gene promoter and/or enhancer regions (40 ,41) . The role of garlic in chemoprevention has been attributed to its modulation of bioactivation and/or detoxification systems (20 ,21) . However, the molecular mechanism of garlic effect is not clear, and it is compelling to investigate whether garlic oil mediation of the PGST gene is through the ARE pathway and/or the Fos/Jun binding to AP-1 binding site.

The growth of rats was not significantly affected by dietary lipid amount or source or by garlic oil treatment (Table 2) . This result is not consistent with our previous study (42) , which showed that oral intubation of 200 mg/kg garlic oil three times per week for 7 wk significantly decreased body weight gain of rats compared with oral intubation of 2 mL/kg corn oil as the control in both the high fat and low fat groups. This discrepancy may have been due to the age of rats used in the experiments and the duration of the experiments. The age of rats used in the present study was 5 wk, whereas that in the previous study was 4 wk. The experimental period in this study was 6 wk and that in the previous study was 7 wk. In a previous study (43) , soft feces were found in rats treated with 200 mg/kg garlic oil; however, this phenomenon was not observed in the present study. This difference may have been due to the greater maturity of the gastrointestinal system of rats in the present study because the gastrointestinal systems of younger rats are more susceptible to the irritant effect of garlic oil. Lower intestinal mucosa protein contents noted in rats receiving the high dose of garlic oil indicated the possible effect of garlic oil on the gastrointestinal tract function (data not shown). In this study, absolute and relative liver weights of rats were significantly affected by dietary lipid amount; those results are consistent with those of a previous study (42) and were related to the difference in the hepatic bioactivation/detoxification system.

The aim of the present study was to investigate the individual and combined effects of fish oil and garlic oil on the bioactivation and/or detoxification systems in rats. Both of these compounds are involved in the regulation of P₄₅₀ 2B1 and PGST. An increase in phase II enzyme systems enhances the detoxification potential of animals. However, an increase in phase I enzyme systems may not always be beneficial because induction of pathways protective against one group of compounds may potentiate the toxic effects of another class of toxins. The balance between activation and detoxification determines the net effect (44) . In this study, both fish oil and garlic oil were active modulators and no interaction between these two factors on P₄₅₀ 2B1 and PGST was identified.

	FOOTNOTES

 
¹ Supported by a grant, NSC 89–2320-B-040–033, from the National Science Council of the ROC.

³ Abbreviations used: AFB₁, aflatoxin B₁; ARE, antioxidant-responsive element; CDNB, 1-chloro-2,4-dinitrobenzene; GSH, glutathione; GST, glutathione S-transferase; HCO, high corn oil diet, HFO, high fish oil diet; LCO, low corn oil diet; PCR, polymerase chain reaction; PGST, placental GSH S-transferase; PROD, 7-pentoxyresorufin O-dealkylase.

Manuscript received November 6, 2000. Initial review completed December 15, 2000. Revision accepted February 20, 2001.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

1. Conney A. H. Induction of microsomal enzymes by foreign chemicals and carcinogenesis by polycyclic aromatic hydrocarbons: G.H.A. Clowes Memorial Lecture. Cancer Res 1982;42:4875-4917[Free Full Text]

2. Guengerich F. P., Shimada P. Oxidation of toxic and carcinogenic chemicals by human cytochrome P-450 enzymes. Chem. Res. Toxicol. 1991;4:391-407[Medline]

3. Pickett C. B., Lu A.Y.H. Glutathione S-transferases: gene structure, regulation, and biological function. Annu. Rev. Biochem. 1989;58:743-764[Medline]

4. Kensler T. W. Chemoprevention by inducers of carcinogen detoxication enzymes. Environ. Health Perspect. 1997;105(suppl. 4):965-970

5. Talalay P., Fahey J. W., Holtzclaw W. D., Prestera T., Zhang Y. Chemoprotection against cancer by phase 2 enzyme induction. Toxicol. Lett. 1995;82/83:173-179

6. Wattenberg L.W. An overview of chemoprevention: current status and future prospects. Proc. Soc. Exp. Biol. Med. 1997;216:133-141[Abstract]

7. Katagiri A., Tomita Y., Nishiyama T., Kimura M., Sato S. Imminohistochemical detection of P-glycoprotein and GSTP1–1 in testis cancer. Br. J. Cancer 1993;68:125-129[Medline]

8. Hamada S., Kamada M., Furumoto H., Hirao T., Aono T. Expression of glutathione S-transferase-pi in human ovarian cancer as an indicator or resistance to chemotherapy. Gynecol. Oncol. 1994;52:313-319[Medline]

9. Chen H. W., Lii C. K., Wu M. H., Ou C. C., Sheen L. Y. Amount and type of dietary lipid modulate rat hepatic cytochrome P-450 activity. Nutr. Cancer 1997;29:174-180[Medline]

10. Yoo J.-S.H., Ning S. M., Pantuck C. B., Pantuck E. J., Yang C. S. Regulation of hepatic microsomal cytochrome P450IIE1 level by dietary lipids and carbohydrates in rats. J. Nutr. 1991;121:959-965

11. Yoo J.-S.H., Smith T. J., Ning S. M., Lee M.-J., Thomas P. E., Yang C. S. Modulation of the levels of cytochrome P450 in rat liver and lung by dietary lipid. Biochem. Pharmacol. 1992;43:2535-2542[Medline]

12. Chen H. W., Lii C. K., Sung W. C., Ko Y. J. Effect of vitamin E on rat hepatic cytochrome P-450 activity. Nutr. Cancer 1998;31:178-183[Medline]

13. Lii C. K., Sung W. C., Ko Y. J., Chen H. W. -Tocopherol acetate supplementation enhances rat hepatic cytochrome PROD activity in the presence of phenobarbital induction. Nutr. Cancer 1998;32:37-42[Medline]

14. Guengerich F. P. Influence of nutrients and other dietary materials on cytochrome P-450 enzymes. Am. J. Clin. Nutr. 1995;61(suppl.):651S-658S[Abstract/Free Full Text]

15. Yang C. S., Smith T. J., Hong J. Y. Cytochrome P-450 enzymes as targets for chemoprevention against chemical carcinogenesis and toxicity: opportunities and limitations. Cancer Res 1994;54:1982s-1986s[Medline]

16. Chou F.-P., Chu Y.-C., Hsu J.-D., Chiang H.-C., Wang C.-J. Specific induction of glutathione S-transferase GSTM2 subunit expression by epigallocatechin gallate in rat liver. Biochem. Pharmacol. 2000;60:643-650[Medline]

17. Lii C.-K., Ou C.-C., Liu K.-L., Liu J.-Y., Lin W.-L., Chen H.-W. Suppression of altered hepatic foci development by a high fish oil diet compared with a high corn oil diet in rats. Nutr. Cancer 2000;38:50-59[Medline]

18. Choi Y. J., Yang L. K., Park J. S., Cha Y. N. Enhancement of hepatic drug metabolism in 3-week-old pups by maternal feeding of n-3 polyunsaturated fatty acid diets. J. Nutr. Biochem. 1992;3:580-586

19. Agarwal K. C. Therapeutic actions of garlic constituents. Med. Res. Rev. 1996;16:111-124[Medline]

20. Brady J. F., Wang M. H., Hong J. Y., Xiao F., Li Y., Yoo J. S., Ning S. M., Lee M. J., Fukuto J. M., Gapac J. M., Yang C. S. Modulation of rat hepatic microsomal monooxygenase activities and cytotoxicity by diallyl sulfide. Toxicol. Appl. Pharmacol. 1991;108:342-354[Medline]

21. Reicks M. M., Crankshaw D. L. Modulation of rat hepatic cytochrome P-450 activity by garlic organosulfur compounds. Nutr. Cancer 1996;25:241-248[Medline]

22. Harber D., Siess M. H., Canivenc-Lavier M. C., Le Bon A. M., Suschetet M. Differential effects of dietary diallyl sulfide and diallyl disulfide on rat intestinal and hepatic drug-metabolizing enzymes. J. Toxicol. Environ. Health 1995;44:423-434[Medline]

23. Pan J., Hong J. Y., Ma B. L., Ning S. M., Paranawithana S. R., Yang C. S. Transcriptional activation of P-450 2B1/2 genes in rat liver by diallyl sulfide, a compound derived from garlic. Arch. Biochem. Biophys. 1993;302:337-342[Medline]

24. Sparnins V. L., Barany G., Wattenberg L. W. Effects of organosulfur compounds from garlic and onions on benzo[a]pyrene-induced neoplasia and glutathione S-transferase activity in the mouse. Carcinogenesis 1988;9:131-134[Abstract/Free Full Text]

25. Adler A. J., Holub B. J. Effect of garlic and fish-oil supplementation on serum lipid and lipoprotein concentrations in hypercholesterolemic men. Am. J. Clin. Nutr. 1997;65:445-450[Abstract/Free Full Text]

26. Sheen L. Y., Lin S. Y., Tsai S. J. Odor assessments for volatile compounds of garlic and ginger essential oils by sniffing method of gas chromatography. J. Chin. Agric. Chem. Soc. 1992;30:14-24

27. Reddy B. S., Sugie S. Effect of different levels of omega-3 and omega-6 fatty acids on azoxymethane-induced colon carcinogenesis in F344 rats. Cancer Res 1988;48:6642-6647[Abstract/Free Full Text]

28. National Research Council Guide for the Care and Use of Laboratory Animals 1985 National Institutes of Health Bethesda, MD. Publication no. 85–23 (rev.)

29. Folch J., Lees M., Sloane-Stanley G. H. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 1957;226:497-507[Free Full Text]

30. Lepage G., Roy C. C. Direct transesterification of all classes of lipids in one-step reaction. J. Lipid Res. 1986;27:114-120[Abstract]

31. Lubet R. A., Mayer R. T., Cameron J. W., Nims R. W., Burke M. D., Wolf T., Guengerich F. P. Dealkylation of pentoxyresorufin: a rapid and sensitive assay for measuring induction of cytochrome(s) P-450 by phenobarbital and other xenobiotics in the rats. Arch. Biochem. Biophys. 1985;238:43-48[Medline]

32. Habig W. H., Pabst M. J., Jakoby W. B. Glutathione S-transferase. The first enzymatic step in mercapturic acid formation. J. Biol. Chem. 1974;249:7130-7139[Abstract/Free Full Text]

33. Mannervik B., Alin P., Guthenberg C., Jensson H., Tahir M. K., Warholm M., Jornvall H. Identification of three classes of cytosolic glutathione transferase common to several mammalian species: correlation between structural and enzymatic properties. Proc. Natl. Acad. Sci. U.S.A. 1985;82:7202-7206[Abstract/Free Full Text]

34. Yang J. J., Krauss R. S. Extracellular ATP induces anchorage-independent expression of cyclin A and rescues the transformed phenotype of a Ras-resistant mutant cell line. J. Biol. Chem. 1997;272:3103-3108[Abstract/Free Full Text]

35. Towbin H., Staehelin T., Gordon J. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc. Natl. Acad. Sci. U.S.A. 1979;76:4350-4354[Abstract/Free Full Text]

36. Yang C. S. The organization and interaction of monooxygenase enzymes in the microsomal membrane. Life Sci 1977;21:1047-1058[Medline]

37. Hwang D., Rhee S. H. Receptor-mediated signaling pathways: potential targets of modulation by dietary fatty acids. Am. J. Clin. Nutr. 1999;70:545-556[Abstract/Free Full Text]

38. Ishii K., Maeda K., Kamataki T., Kato R. Mutagenic activation of aflatoxin AFB₁ by several forms of purified cytochrome P450. Mutat. Res. 1986;174:85-88[Medline]

39. Maurya A. K., Singh S. V. Differential induction of glutathione transferase isoenzymes of mice stomach by diallyl sulfide, a naturally occurring anticarcinogen. Cancer Lett 1991;57:121-129[Medline]

40. Henderson C. J., McLaren A. W., Moffat G. J., Bacon E. J., Wolf C. R. Pi-class glutathione S-transferase: regulation and function. Chem.-Biol. Interact. 1998;111–112:69-82

41. Okuda A., Imagawa M., Maeda Y., Sakai M., Muramatsu M. Structural and functional analysis of an enhancer GPE1 having a phorbol 12-O-tetradecanoate 13-acetate responsive element-like sequence found in the rat glutathione transferase P gene. J. Biol. Chem. 1989;264:16919-16926[Abstract/Free Full Text]

42. Sheen L. Y., Chen H. W., Kung Y. L., Liu C. T., Lii C. K. Effects of garlic oil and its organosulfur compounds on the activities of hepatic drug-metabolizing and antioxidant enzymes in rats fed high- and low-fat diets. Nutr. Cancer 1999;35:160-166[Medline]

43. Liu C. T., Chen H. W., Sheen L. Y., Kung Y. L., Chen C.H.P., Lii C. K. Effect of garlic oil on hepatic arachidonic acid content and immune response in rats. J. Agric. Food Chem. 1998;46:4642-4647

44. O’Brien K., Moss E., Judah D. J., Neal G. E. Metabolic basis of the species difference to aflatoxin AFB₁ induced hepatotoxicity. Biochem. Biophys. Res. Commun. 1983;114:813-821[Medline]

45. American Institute of Nutrition Report of the American Institute of Nutrition ad hoc committee on standards for nutritional studies. J. Nutr. 1977;107:1340-1348

This article has been cited by other articles:

				J. T. Pinto, B. F. Krasnikov, and A. J. L. Cooper Redox-Sensitive Proteins Are Potential Targets of Garlic-Derived Mercaptocysteine Derivatives J. Nutr., March 1, 2006; 136(3): 835S - 841S. [Abstract] [Full Text] [PDF]

				C.-W. Tsai, J.-J. Yang, H.-W. Chen, L.-Y. Sheen, and C.-K. Lii Garlic Organosulfur Compounds Upregulate the Expression of the {pi} Class of Glutathione S-Transferase in Rat Primary Hepatocytes J. Nutr., November 1, 2005; 135(11): 2560 - 2565. [Abstract] [Full Text] [PDF]

				C.-W. Tsai, H.-W. Chen, J.-J. Yang, K.-L. Liu, and C.-K. Lii Sulfur Amino Acid Restriction Induces the {pi} Class of Glutathione S-Transferase Expression in Primary Rat Hepatocytes J. Nutr., May 1, 2005; 135(5): 1034 - 1039. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chen, H.-W. Articles by Lii, C.-K. Search for Related Content PubMed PubMed Citation Articles by Chen, H.-W. Articles by Lii, C.-K.