The Journal of Nutrition Vol. 128 No. 6 June 1998, pp. 967-972

Lipogenic Enzyme Gene Expression Is Quickly Suppressed in Rats by a Small Amount of Exogenous Polyunsaturated Fatty Acids^1,2

Nobuko Iritani³, Masumi Komiya, Hitomi Fukuda, and Tomomi Sugimoto

Tezukayama Gakuin College, Sakai, Osaka 590-01, Japan

	ABSTRACT

Abstract Introduction Methods Results Discussion References

An examination was conducted of the time courses of incorporation of polyunsaturated fatty acids (PUFA) into lipids of plasma, liver and its nuclei, and the time courses of hepatic lipogenic enzyme gene expression after oral administration of perilla oil by a stomach tube to rats fed a fat-free diet. Linolenic acid, 18:3(n-3), and eicosapentaenoic acid, 20:5(n-3), were considered indices of exogenous fatty acids. In total lipids of liver and its nuclei, linolenic acid was detected 1 h after the intubation, continued to increase during the first 4 h, then decreased and almost disappeared by 48 h. Eicosapentaenoic acid also increased within only 1 h of intubation, reached a maximum after 8 h and then gradually decreased. In contrast with the increase of exogenous PUFA, the mRNA concentrations of hepatic lipogenic enzymes began to decrease 2 h after the perilla oil intubation, were at a minimum at 8 h, and then increased. In another experiment to examine the effects of dietary perilla oil concentration on PUFA incorporation and gene expression, rats were given diets containing 0-10% perilla oil (supplemented with hydrogenated fat to 10% fat) for 3 d. Only 1% perilla oil elevated the exogenous PUFA concentrations in liver and its nuclei in comparison with concentrations in rats fed a hydrogenated fat diet. Perilla oil at 2% of the diet was sufficient to suppress lipogenic enzyme gene expressions, which were suppressed to the minimum level by 5% perilla oil in the diet. Thus, lipogenic enzyme gene expression was quickly suppressed by a small amount of exogenous PUFA, in contrast with the increase of PUFA incorporation into liver and its nuclei. Newly incorporated exogenous PUFA appear to be involved in suppression of lipogenic enzyme gene expression.

	INTRODUCTION

Abstract Introduction Methods Results Discussion References

Lipogenic enzyme gene expression in rat liver is elevated by a fat-free/high carbohydrate diet and suppressed by feeding polyunsaturated fat (Iritani 1993). The mechanisms of stimulation and suppression of lipogenic enzyme gene expression have begun to be elucidated and the cis-acting elements of genes are involved in the expression (Fukuda et al. 1996a, 1996b, 1997a and 1997b, Kim 1997, Moustaid et al. 1994, Towle et al. 1997). Recently, the polyunsaturated fatty acid (PUFA)⁴ response elements have been reported to be localized in the promoter region of the L-pyruvate kinase gene (Limatta et al. 1994) and also in that of S14 (Clarke and Jump 1994, Jump et al. 1993); their gene expressions were regulated by nutritional and hormonal manipulations, similarly to lipogenic enzyme gene expression. We mapped the sequences responsive to glucose/insulin stimulation and PUFA suppression in the proximal promoter regions of the fatty acid synthase gene and the ATP citrate-lyase gene (Fukuda et al. 1996a, 1996b, 1997a and 1997b). However, these regions may not have to contain cis-acting elements responsive to PUFA because PUFA may inhibit the insulin signaling pathway from the insulin receptor to the gene (Iritani and Fukuda 1995).

We previously found that the fatty acid compositions in liver nuclei were influenced by dietary fatty acids and were roughly similar to those in the microsomes (Iritani et al. 1988). By feeding a diet containing corn oil or fish oil to rats, the proportions of (n-6) or (n-3) PUFA, respectively, were increased in phospholipids of the liver nuclei. To clarify the effects of exogenous PUFA on lipogenic enzyme gene expression in vivo, we examined the time courses for changes in incorporation of dietary PUFA into liver and its nuclei, and changes in suppression of the lipogenic enzyme gene expressions in liver after oral administration of perilla oil to rats. The effects of the dietary amount of perilla oil on the incorporation of dietary PUFA into liver and its nuclei, and on the suppression of lipogenic enzyme gene expression were also examined.

	MATERIALS AND METHODS

Abstract Introduction Methods Results Discussion References

Chemicals.  [-³²P]dCTP (111 TBq/mmol) was purchased from ICN Pharmaceuticals (Costa Mesa, CA). Nylon filter (Hybond N) was purchased from Amersham (Buckinghamshire, UK). -Actin cDNA and other reagents were obtained mainly from Wako Pure Chemical (Osaka, Japan) and Sigma Chemical (St. Louis, MO). Triolein was from Wako.

Animals. 

Experiments 1 and 2.  Male Wistar rats (Japan SLC, Hamamatsu, Japan), 5 wk old, were fed a fat-free diet (Table 1) for 1 wk, and then were orally given 5 g perilla oil or triolein (control)/kg body weight by a stomach tube at 0900 h. The rats were kept under an automatic lighting schedule from 0800 to 2000 h at 24°C. The rats were allowed to consume water ad libitum. Rats were killed 1, 2, 4, 6 and 8 h after intubation in Experiment 1, and after 8, 16, 24, 48, 72 and 96 h in Experiment 2. Other procedures were the same in Experiments 1 and 2. Rats were killed by decapitation while under diethyl ether anesthesia. An aliquot of liver was quickly removed to obtain liver nuclei, as described below. Another aliquot of liver was quickly removed and homogenized with three volumes of 0.25 mol/L sucrose. The 10,000 × g supernatant of the homogenate was centrifuged at 105,000 × g for 45 min (Model L5, Type 40 rotor, Beckman Instruments, Palo Alto, CA). The 105,000 × g supernatant was used for measurement of lipogenic enzyme activities. The other aliquots of liver were immediately frozen in liquid nitrogen and stored at 80°C to measure the mRNA and DNA concentrations and to extract total lipids for measurement of fatty acid composition as described below. Care and treatment of experimental animals were in accordance with the Guide for the Care and Use of Laboratory Animals (NRC 1985).

Experiment 3.  The rats were deprived of food for 2 d and then given 10% fat diets (containing 1, 2, 5 or 10 g perilla oil/100 g diet, supplemented with hydrogenated fat achieve a level of 10 g/100 g diet) as a substitute for the sucrose of the fat-free diet (Table 1). Diets were fed for 3 d after which rats were killed by decapitation while under diethyl ether anesthesia. The fatty acid composition of perilla oil is shown in Table 1. Other details were as described above.

Preparation of nuclei.  Rat liver nuclei were prepared according to the procedure of Blobel and Potter (1966). The livers were homogenized in ice-cold 250 mmol/L sucrose in TKM buffer (50 mmol/L Tris-HCl, pH 7.5, 20 mmol/L KCl, 5 mmol/L MgCl₂) and nuclear pellets were separated by centrifugation.

Dot blot hybridization assay.  The cDNA species were cloned as described in our previous reports (Fukuda et al. 1992, Katsurada et al. 1987, 1989, 1990a and 1990b). The genomic clone of rat rRNA was obtained from the Japanese Cancer Research Resources Bank (Mishima, Japan). A BamHI/EcoRI fragment (~1 Kb) of this clone was isolated and used as a probe for 18S rRNA. Total RNA was isolated from the liver by the method of acid guanidium thiocyanate/phenol/chloroform extraction (Chomczynski and Sacchi 1987). To measure the mRNA concentrations of lipogenic enzymes, total RNA (10-30 µg) was denatured with formamide, spotted on nylon filter and then radiated with ultraviolet light for 5 min. The filter was prehybridized and then hybridized with ³²P-labeled cDNA as described previously (Katsurada et al. 1990a). Relative densities of the hybridization signals were determined by scanning the autoradiograms at 525 nm (Model CS-9000, Shimadzu, Kyoto, Japan) and normalizing to the values of 18S rRNA. The validity of the determination was established previously (Iritani et al. 1992). The mRNA concentrations of -actin were determined in the same manner as the control for lipogenic enzyme mRNA concentrations.

Lipid extraction, fractionation and analysis.  Total lipids of plasma, liver and liver nuclei were extracted according to the method of Folch et al. (1957) and separated by TLC on silica gel H (Merck, Darmstadt, Germany). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were separated by TLC with a solvent of chloroform/methanol/water (65:25:4, v/v/v). The silica gel zones corresponding to PC and PE were identified by comparison with authentic standards, which were visualized by exposure to iodine vapor. The silica gel zones were scraped and the lipids were extracted with chloroform/methanol (1:1, v/v). After saponification of the lipids with 1.79 mol KOH/L ethanol at 60°C for 1 h, the aqueous phase was washed with petroleum ether and acidified. Fatty acids were extracted with petroleum ether, methylated with m-trifluoromethylphenyltrimethylammonium hydroxide and applied onto a Shimadzu 9A gas chromatograph equipped with a hydrogen flame detector. A capillary column of CBP-M20-025 (Shimadzu) poly(ethylene glycol) coated in a tube 0.25 mm × 25 m was programmed to increase from 60 to 230°C at 6°C/min and to remain at 230°C for 20 min. The carrier gas was nitrogen. Fatty acid concentrations were expressed as milligrams or micrograms per milligram DNA. The DNA concentrations were measured by the method of Ceriotti (1955).

Lipogenic enzyme activities.  Acetyl-CoA carboxylase (EC 6.4.1.2) activity was assayed by the H¹⁴CO₃-fixation method (Nakanishi and Numa 1970). To attain full activity, the enzyme was first preincubated with 10 mmol/L citrate. Fatty acid synthase (EC 2.3.1.85) activity was assayed according to Hsu et al. (1969). Malic enzyme (EC 1.1.1.40) was assayed according to Ochoa (1955) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49), according to Glock and McLean (1953). ATP-citrate lyase (EC 4.1.3.8) activity was assayed as described by Takeda et al. (1969). The enzyme activities in the supernatant of the liver homogenates are shown as mU/mg protein, where 1 mU is the amount catalyzing the formation of nanomoles product/min at 37°C for acetyl-CoA carboxylase, fatty acid synthase and ATP-citrate lyase, and the utilization of NADP for malic enzyme and glucose-6-phosphate dehydrogenase. Protein was determined by the method of Lowry et al. (1951).

Statistical analysis.  One-way or two-way ANOVA was followed by inspection of all differences between pairs of means by using the least significant difference test (Snedecor and Cochran 1967). Differences were considered significant at P < 0.05. Values in the text are means ± SD.

	RESULTS

Abstract Introduction Methods Results Discussion References

Changes in plasma and liver polyunsaturated fatty acid concentrations after intubation of perilla oil.  The time courses for fatty acid concentrations of plasma, liver and liver nuclei of rats were followed after the intubation of perilla oil. The results of both Experiments 1 and 2 are shown in Figure 1 (upper and lower panels, respectively). No linolenic acid and very little eicosapentaenoic acid (EPA) as found in plasma and liver of the rats after feeding a fat-free diet (before the intubation). However, the concentrations of linoleic acid and archidonic acid in plasma and liver were not lowered to the same extent. Therefore linolenic acid and EPA were considered proper indices for following the incorporation of exogenous fatty acids into tissue fatty acids.

View larger version (43K): [in this window] [in a new window]   Fig 1. Changes in polyunsaturated fatty acid (PUFA) concentrations of total lipids of plasma, liver and liver nuclei, and PUFA compositions of liver nuclear phospholipids after intubation of perilla oil to rats fed a fat-free diet. Rats fed a fat-free diet for 1 wk were given perilla oil orally (5 g/k g body wt), and changes in the fatty acid compositions in plasma (A), liver (B) and liver nuclei (C) were measured. The upper and lower panels show data for 8 h (Experiment 1) and for 96 h (Experiment 2), respectively, after the intubation. Percent(%) shows mol/100 mol. Data were tested by two-way ANOVA (fatty acid × time). Means in each panel with different letters are significantly different (P < 0.05). Values are means ± SD (n = 6). PC, phosphatidylcholine; PE, phosphatidylethanolamine.

In total lipids of plasma (Fig. 1A), the linolenic acid and EPA concentrations were 0.73 ± 0.01 and 0.12 ± 0.001 mmol/L, respectively, 4 h after the perilla oil intubation. The concentrations of linolenic acid reached a maximum at 4 h, but those of EPA reached a maximum (0.18 ± 0.01 mmol/L) at 8 h. Linolenic acid was markedly elevated in plasma, but rapidly decreased. The maximum concentration of linolenic acid was higher than that of EPA in the plasma, but the reverse was seen in liver.

In total hepatic lipids (Fig. 1B), linolenic acid appeared 1 h after the intubation, continued to increase markedly, reached a maximum at 4 h, then began to decrease after 4 h and almost disappeared after 48 h. EPA in the total lipids significantly increased after 2 h, reached a maximum after 8 h, then began to decrease, and did not return to the initial level even at 48 h. The concentrations of arachidonic acid and docosahexaenoic acid were always high and were unaltered as were those of EPA, but reached maximum levels 16-24 h after the administration and quickly returned to the initial levels after 48 h.

When triolein was given similarly to rats as a control for perilla oil, the concentrations of linoleic acid and arachidonic acid were not changed in the plasma and liver (Table 2). No linolenic acid was found. The concentrations of EPA were very small and not changed by triolein intubation.

In total lipids of liver nuclei (Fig. 1C), linolenic acid appeared 1 h after the perilla oil intubation and was clearly detected at 2 h, reached a maximum at 8 h, began to decrease at 16 h and disappeared by 48 h. EPA began to increase 1 h after the intubation, had significantly increased after 2 h, reached a maximum after 8 h, began to decrease after 24 h and did not return to the initial level even after 96 h. The maximum concentration of EPA in total lipids of liver nuclei was 7.34 ± 1.45 µmol/g DNA, whereas that of linolenic acid was only 1.48 ± 0.38 µmol/g DNA. The concentrations of linoleic acid changed similarly over time as those of EPA, but were always higher than those of EPA. The concentrations of arachidonic acid and docosahexaenoic acid were not so markedly changed as those of linoleic acid, linolenic acid and EPA after the intubation. The concentrations of linolenic acid in the liver and its nuclei reached a maximum 4 h after the perilla oil intubation, whereas the concentrations of EPA were maximal after 8 h.

In phosphatidylcholine (PC) of liver nuclei, linoleic acid, linolenic acid and EPA began to increase significantly 2 h after the perilla oil intubation, but increased at 4 h in phosphatidylethanolamine (PE). EPA and linolenic acid began to increase earlier and more markedly in PC than in PE.

Changes in lipogenic enzyme gene expression after intubation of perilla oil.  The mRNA concentrations of lipogenic enzymes in the liver were significantly decreased 2 h after the intubation of perilla oil to rats. The mRNA concentrations were at minimum levels 8-16 h after perilla oil intubation, then gradually increased and returned to the initial levels at 48-96 h (Fig. 2). When triolein was given similarly to rats as a control for perilla oil, the mRNA concentrations of lipogenic enzymes were not suppressed. The mRNA concentrations were significantly lowered 2 h after the perilla oil intubation in comparison with the mRNA concentrations after the triolein intubation. Thus, dietary PUFA were quickly incorporated into liver nuclei and quickly suppressed the lipogenic enzyme gene expressions inversely to the increase in PUFA in liver and its nuclei. However, the enzyme activities were not changed by the single intubation of perilla oil or triolein. Although the half-lives of lipogenic enzyme mRNAs were 4-6 h, those of the enzymes were 20-30 h (Iritani 1993). Because of the long half-lives of the enzymes, the activities should not be affected by the single intubation of perilla oil.

View larger version (37K): [in this window] [in a new window]   Fig 2. Changes in hepatic lipogenic enzyme gene expression after intubation of perilla oil or triolein to rats fed a fat-free diet. The mRNA concentrations of lipogenic enzymes are shown in the upper panels (Experiment 1) and in the middle panels (Experiment 2). The enzyme activities are shown in the lower panels (Experiment 2). The enzyme activities were not significantly changed by the single intubation of triolein (data not shown). The mRNA concentrations are normalized to the values at 0 time. Means with different letters are significantly different by two-way ANOVA (oil intubation × time) in each panel (P < 0.05). Values are means ± SD (n = 6).

Effects of dietary PUFA concentration on plasma and liver PUFA.  In Experiment 3, the rats were given 10% fat diets containing 1, 2, 5 or 10 g perilla oil (supplemented with hydrogenated fat to a level of 10 g fat/100 g diet) for 3 d. Even in rats given the diet containing only 1% perilla oil, the concentrations of linolenic acid and EPA were high in plasma, liver and liver nuclei (Fig. 3). The concentrations were elevated with increasing dietary perilla oil concentration. The incorporation ratio of EPA from liver into its nuclei was higher than that of linolenic acid.

View larger version (33K): [in this window] [in a new window]   Fig 3. Effects of dietary perilla oil concentration on polyunsaturated fatty acid (PUFA) concentrations of total lipids of plasma, liver and liver nuclei, and PUFA compositions of liver nuclear phospholipids (Experiment 3). Rats deprived of diet for 2 d were given 10% fat diets containing 0, 1, 2, 5 or 10 g perilla oil (supplemented with hydrogenated fat to a level of 10 g fat/100 g diet) for 3 d. The rats, weighing 174 ± 12.5 g, were given diets containing equal energy for the same body. Mean values of PUFA concentrations in the tissues of six rats are shown (SD not shown). Means with different letters are significantly different by two-way ANOVA (each fatty acid × diet) in each panel (P < 0.05). Black bars of the bottom show the contents of 18:3(n-3), with ANOVA letters shown at the bottom. *No 18:3(n-3) was detected in rats fed the diet containing no perilla oil/10% hydrogenated fat. PC, phosphatidylcholine; PE, phosphatidylethanolamine.

The compositions of EPA in PC and PE of liver nuclei were elevated to 4-5% in rats given the 1% perilla oil diet and to 9-12% in those given the 5% perilla oil diet, whereas linolenic acid was not as greatly elevated. In the phospholipids of liver nuclei, arachidonic acid was lowered with increasing dietary amounts of perilla oil, inversely to EPA in PE. EPA replaced arachidonic acid in the PE. In PC, however, even though EPA was elevated, arachidonic acid was not lowered.

Effects of dietary PUFA concentration on lipogenic enzyme gene expression.  In the rats described above, the effects of dietary PUFA on the lipogenic enzyme gene expression in the liver were examined (Fig. 4). In the livers of rats given even the 2% perilla oil diet, the mRNA concentrations of the lipogenic enzymes were significantly less than those of rats given the no perilla oil/10% hydrogenated fat diet. The mRNA concentrations were lowered to minimum levels (30-50%) in rats given the 5% perilla oil diet, and enzyme activities were lowered to 40-65% (minimum levels) in those rats.

View larger version (42K): [in this window] [in a new window]   Fig 4. Effects of dietary perilla oil concentration on lipogenic enzyme gene expression in rat liver (Experiment 3). The mRNA concentrations (upper panel) and enzyme activities (lower panel) in the rats are shown. The mRNA concentrations are normalized to the values of the diet containing no perilla oil/10% hydrogenated fat. Means with different letters are significantly different in each panel (P < 0.05). Values are means ± SD (n = 6).

	DISCUSSION

Abstract Introduction Methods Results Discussion References

Exogenous PUFA were quickly (within 1 h) incorporated into liver and its nuclei, and the lipogenic enzyme gene expression was quickly (within 2 h) suppressed. The gene expression was suppressed by intake of a small amount of PUFA (2% dietary perilla oil). We previously investigated the regulatory DNA sequences required for insulin/glucose stimulation and PUFA suppression of fatty acid synthase and ATP citrate lyase genes in CAT assays by using primary cultured hepatocytes (Fukuda et al. 1996a and 1996b). The CAT activities stimulated by insulin/glucose were reduced by the addition of PUFA. We mapped the sequences responsive to glucose/insulin stimulation and PUFA suppression in the proximal promoter regions of the fatty acid synthase and ATP citrate-lyase genes (Fukuda et al. 1996a, 1996b, 1997a and 1997b). The PUFA-responsive elements have been reported to be localized in the promoter region of the L-pyruvate kinase gene (Limatta et al. 1994) and also in that of S14 (Clarke and Jump 1994, Jump et al. 1993), and their gene expressions were regulated by nutritional and hormonal manipulations, similarly to lipogenic enzyme gene expression. Therefore the liver nuclear PUFA should be involved in the PUFA suppression of lipogenic enzymes. However, the mechanisms are not known.

The concentration of EPA was 3.21 ± 0.28 µmol/g liver nuclear DNA 2 h after perilla oil intubation. The level of EPA, which was considered to be an index of exogenous PUFA in this experiment, was sufficient to suppress the lipogenic enzyme gene expression. Although linolenic acid was well incorporated into liver fatty acids, it was only slightly incorporated into liver nuclear fatty acids compared with EPA. Linolenic acid appeared to be quickly metabolized to EPA or selectively incorporated into the phospholipids. EPA should be more directly involved than linolenic acid in the PUFA-induced suppression of the lipogenic enzyme gene expression. Because the gene expression was suppressed inversely to the incorporation of exogenous PUFA into liver, newly incorporated exogenous PUFA could be involved in the suppression of lipogenic enzyme gene expression.

	FOOTNOTES

Manuscript received 12 September 1997. Initial reviews completed 11 November 1997. Revision accepted 11 February 1998.

	LITERATURE CITED

Abstract Introduction Methods Results Discussion References

• Blobel, G. & Potter, Van R. (1966) Nuclei from rat liver: isolation method that combines purity with high yield. Science (Washington, DC), 14: 1662-1665.
• Ceriotti G. Determination of nucleic acids in animal tissues. J. Biol. Chem. 1955; 214:59-70[Free Full Text]
• Chomczynski P., Sacchi N. Single-step method of RNA isolation by acid guanidium thiocyanate-phenol-chloroform extraction. Anal. Biochem. 1987; 163:156-159
• Clarke S. D., Jump D. B. Dietary polyunsaturated fatty acid regulation of gene transcription. Annu. Rev. Nutr. 1994; 14:83-98[Medline]
• Folch J., Lees M., Sloane-Stanley G. H. A simple method for isolation and purification of total lipides from animal tissues. J. Biol. Chem. 1957; 226:497-509[Free Full Text]
• Fukuda H., Iritani N., Katsurada A., Noguchi T. Insulin- and polyunsaturated fatty acid-responsive region(s) of rat ATP citrate lyase gene promoter. FEBS Lett. 1996a; 380:204-207[Medline]
• Fukuda H., Iritani N., Katsurada A., Noguchi T. Insulin/glucose-, pyruvate- and polyunsaturated fatty acid-responsive region(s) of rat fatty acid synthase gene promoter. Biochem. Mol. Biol. Int. 1996b; 38:987-996[Medline]
• Fukuda H., Iritani N., Noguchi T. Transcriptional regulatory regions for expression of the rat fatty acid synthase. FEBS Lett. 1997a; 406:243-248[Medline]
• Fukuda H., Iritani N., Noguchi T. Transcriptional regulatory regions for expression of the rat ATP citrate lyase. Eur. J. Biochem. 1997b; 247:479-502
• Fukuda H., Katsurada A., Iritani N. Effects of nutrients and hormones on gene expression of ATP citrate-lyase in rat liver. Eur. J. Biochem. 1992; 209:217-222[Medline]
• Glock G. E., McLean P. Further studies on the properties and assay of glucose-6-phosphate dehydrogenase and 6-phospho-gluconate dehydrogenase of rat liver. Biochem. J. 1953; 55:400-408[Medline]
• Hsu R. Y., Butterworth P.H.W., Porte J. W. Pigeon liver fatty acid synthetase. Methods Enzymol. 1969; 14:233-239
• Iritani N. A review, nutritional and hormonal regulation of lipogenic enzyme gene expression in rat liver. Eur. J. Biochem. 1993; 205:433-442[Medline]
• Iritani N., Fukuda H. Polyunsaturated fatty acid-mediated suppression of insulin-dependent gene expression of lipogenic enzymes in rat liver. J. Nutr. Sci. Vitaminol. 1995; 41:207-216
• Iritani N., Fukuda H., Matsumura Y. Effects of corn oil- and fish oil-supplemented diets on phospholipid fatty acid composition of rat liver nuclei. Biochim. Biophys. Acta 1988; 963:224-230[Medline]
• Iritani N., Nishimoto N., Katsurada A., Fukuda H. Regulation of hepatic lipogenic enzyme gene expression by diet quantity in rats fed a fat-free, high carbohydrate diet. J. Nutr. 1992; 122:28-36
• Jump D. B., Clarke S. D., Macdougald O., Thelen A. Polyunsaturated fatty acids inhibit S14 gene transcription in rat liver and cultured hepatocytes. Proc. Natl. Acad. Sci. U.S.A. 1993; 90:8454-8458[Abstract/Free Full Text]
• Katsurada A., Iritani N., Fukuda H., Matsumura Y., Nishimoto N., Noguchi T., Tanaka T. Effects of nutrients and insulin on transcriptional and post-transcriptional regulation of glucose-6-phosphate dehydrogenase in rat liver. Biochim. Biophys. Acta 1989; 1006:104-110[Medline]
• Katsurada A., Iritani N., Fukuda H., Matsumura Y., Nishimoto N., Noguchi T., Tanaka T. Effects of nutrients and hormones on transcriptional and post-transcriptional regulation of fatty acid synthase in rat liver. Eur. J. Biochem. 1990a; 190:427-433[Medline]
• Katsurada A., Iritani N., Fukuda H., Matsumura Y., Nishimoto N., Noguchi T., Tanaka T. Effects of nutrients and hormones on transcriptional and post-transcriptional regulation of acetyl-CoA carboxylase in rat liver. Eur. J. Biochem. 1990b; 190:435-441[Medline]
• Katsurada A., Iritani N., Fukuda H., Noguchi T., Tanaka T. Influence of diet on transcriptional and post-transcriptional regulation of malic enzyme induction in rat liver. Eur. J. Biochem. 1987; 168:487-491[Medline]
• Kim K.-H. Regulation of mammalian acetyl-CoA carboxylase. Annu. Rev. Nutr. 1997; 17:77-99[Medline]
• Limatta M., Towle H. C., Clarke S., Jump D. B. Dietary polyunsaturated fatty acids interfere with the insulin/glucose activation of L-type pyruvate kinase gene transcription. Mol. Endocrinol. 1994; 8:1147-1153[Abstract/Free Full Text]
• Lowry O. H., Rosebrough N. J., Faar A. L., Randall R. J. Protein measurement with the Folin phenol reagent. J. Biol. Chem. 1951; 193:265-275[Free Full Text]
• Moustaid N., Beyer R. S., Sul H. S. Identification of an insulin response element in the fatty acid synthase promoter. J. Biol. Chem. 1994; 269:5629-5634[Abstract/Free Full Text]
• Nakanishi S., Numa S. Purification of rat liver acetyl coenzyme A carboxylase and immunochemical studies on its synthesis and degradation. Eur. J. Biochem. 1970; 16:161-173[Medline]
• National Research Council (1985) Guide for the Care and Use of Laboratory Animals, National Institutes of Health Publication No. 85-23 (rev.). U.S. Government Printing Office, Washington, DC.
• Ochoa S. Malic enzyme. Methods Enzymol. 1955; 1:739-753
• Reeves P. G., Nielsen F. H., Fahey G. C. Jr. AIN-93 Purified diets for laboratory rodents: final report of the American Institute of Nutrition ad hoc writing committee on the reformation of the AIN-76A rodent diet. J. Nutr. 1993; 123:1939-1951
• Snedecor, G. W. & Cochran, W. G. (1967) Statistical Methods, pp. 285-338. Iowa State University Press, Ames, IA.
• Takeda Y., Suzuki F., Inoue H. ATP-citrate lyase (citrate-cleavage enzyme). Methods Enzymol. 1969; 13:153-160
• Towle H. C., Kayter E. N., Shia H.-M. Regulation of the expression of lipogenic enzyme genes by carbohydrate. Annu. Rev. Nutr. 1997; 17:405-433[Medline]

0022-3166/98 $3.00 ©1998 American Society for Nutritional Sciences