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Endocrinology Vol. 145, No. 2 548-555
Copyright © 2004 by The Endocrine Society

High Dietary Fructose Induces a Hepatic Stress Response Resulting in Cholesterol and Lipid Dysregulation

Glen L. Kelley, Geoffrey Allan and Salman Azhar

Insmed Incorporated (G.L.K., G.A.), Richmond, Virginia 23058; and Geriatric Research, Education and Clinical Center (S.A.), Veterans Affairs Palo Alto Health Care System and Stanford University School of Medicine, Palo Alto, California 94304

Address all correspondence and requests for reprints to: Glen L. Kelley, Insmed Incorporated, 4851 Lake Brook Drive, Glen Allen, Virginia 23058. E-mail: gkelley{at}insmed.com.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
High-fructose feeding causes diet-induced alterations of lipid metabolism and decreased insulin sensitivity with alterations of hepatic pyruvate dehydrogenase and hepatic very low-density lipoprotein secretion. Inflammatory cytokines also induce dramatic changes in lipid metabolism, particularly in serum triglycerides via increased hepatic secretion and/or delayed clearance of very low-density lipoprotein. The aim of this study was to determine whether the mechanism of lipid dysregulation in the high-fructose diet is induced by stress response pathways. Animals were fed a high-fructose diet for 14 d to establish hypertriglyceridemia and then were treated with lipoxygenase inhibitors for 4 d concurrent with the diet. At the end of drug treatment, the animals were divided into two groups and treated with lipopolysaccharide or a vehicle. Serum samples were taken pretreatment and posttreatment, and liver tissue was harvested at the end of study. Serum samples were tested for metabolic parameters, and the tissue samples were tested for metabolic and stress pathway responses. Our results show that fructose-fed rats have changes in the c-Jun N-terminal kinase pathway with correspondingly elevated activator protein-1 activity, consistent with an inflammatory response. Treatment with lipoxygenase inhibitors reversed the hypertriglyceridemia and also reduced activator protein-1 activation, suggesting that the basis for lipid dysregulation in this model is due to activation of inflammatory pathways in the liver.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
HIGH-FRUCTOSE-FED (HFF) diets induce well-characterized metabolic dysfunction, typically resulting in a rapid elevation of serum triglycerides (TGs) with a corresponding increase in blood pressure within 2 wk. This diet also results in alterations of lipid metabolism and decreased insulin sensitivity as well as alterations of hepatic pyruvate dehydrogenase (1) and very low-density lipoprotein (VLDL) secretion (2). Inflammatory cytokines also induce dramatic changes in lipid metabolism, particularly in serum TGs via increased hepatic secretion and/or delayed clearance of VLDL (3). Since the introduction of high-fructose corn sweeteners in 1967, the amount of fructose consumption has steadily risen and now accounts for about 9% of daily caloric intake in the United States. Unlike glucose, which is widely used by tissues throughout the body, fructose is primarily metabolized in the liver (4, 5).

Animals maintained on a high-fructose diet for longer periods of time develop elevated free fatty acids (FFAs) and hyperinsulinemia at the expense of glycemic control. In this metabolic model, compounds that lower circulating lipid levels, increase insulin sensitivity, or inhibit TNF-{alpha} production reduce serum TGs and improve blood pressure (6, 7). Moreover, if animals are subjected to an exercise regimen, the diet-induced effects can be ameliorated (2). Thus, this animal model exhibits many of the hallmarks of an early stage of the metabolic syndrome (or syndrome X), in which a combination of physical inactivity and diet results in cardiovascular disease and metabolic complications.

We hypothesized that HFF animals exhibited altered lipid metabolism due to hepatic stress as a result of the burden of fructose metabolism. Additionally, fructose bypasses two regulatory steps of glycolysis, glucokinase and phosphofructokinase, thus potentially providing unregulated accumulation of glycolytic intermediates. Thus, these studies were conducted to determine whether chronic high-level fructose metabolism leads to activation of stress pathways.

Obesity and fatty acid-induced insulin resistance are thought to contribute to the progression of diabetes through the actions of the TNF-{alpha} pathway (8, 9). TNF-{alpha} has long been recognized to induce lipolysis and insulin resistance, although the exact mechanism(s) by which this occurs has not been fully elucidated (10, 11, 12). Recently, a relationship has been demonstrated between diet-induced obesity and c-Jun N-terminal kinase (JNK) activity (13). JNK can be activated by either TNF-{alpha} or reactive oxygen intermediates (ROS) that are generated as a result of hyperglycemia-induced oxidative stress through a Rac->cytosoloic phospholipase A2->arachadonic acid pathway that generates ROS (14). The metabolism of arachadonic acid suggests a role for lipoxygenases (LOs) in stress pathway signaling. Fructose-fed animals exhibit reduced peroxisome proliferator-activated receptor-{alpha} levels and a corresponding reduction of ß-oxidation (15). As such, metabolism of xenobiotics, including LO products, is likely impaired, which could result in their accumulation.

To address this hypothesis, we tested the effects of LO inhibitors on the metabolic and hepatic status of HFF rats. We chose to examine two structurally different LO inhibitors because nordihydroguaiaretic acid (NDGA), which has previously demonstrated effects in this model (16), also exhibits numerous other biological effects. This allowed us to minimize interpretation of effects that might not be related to its LO inhibitor activity. Here, we show that fructose induces a hepatic stress response that mimics a portion of the TNF-{alpha} acute phase response. This response occurs without overt hyperglycemia, obesity, or significantly elevated fatty acids, suggesting that other metabolic triggers can induce inflammatory pathways that result in metabolic dysfunction.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Animals and treatments
The treatment protocol is summarized in Fig. 1Go. Male Sprague Dawley rats weighing approximately 180–200 g first maintained on a rat chow diet were then divided into four groups, three of which were switched to a high-fructose diet (TD 89247; Harlan Teklad, Madison, WI) that provided 60% of total calories as fructose (d 1). On d 15 of treatment, the rats were fasted for 4 h and tail vein blood was collected for baseline measurements of serum TG, glucose, insulin, and FFA as previously described (17). The three groups of rats were then treated with vehicle (0.5% carboxymethyl cellulose), NDGA (250 mg/kg body weight), or 4,5-dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine (BW-755c) (100 mg/kg body weight) twice a day for 4 d, delivered by oral gavage. The chow group (diet control) was treated with vehicle. During the treatment regimen, the animals were maintained on the high-fructose diet. After 4 d of treatment, blood was collected from the tail vein 3 h after the last dose of vehicle, NDGA, or BW-755c, and serum samples were analyzed for TG, glucose, insulin, FFA, and total cholesterol as previously described (17, 18, 19). On d 20, four animals in each group were injected iv with 0.5 mg/kg body weight Salmonella enteritidis endotoxin [lipopolysaccharide (LPS)] or normal saline under light anesthesia. After 2 h, serum was collected for corticosterone measurement, as described previously (19); then the animals were killed, and tissues were removed, snap-frozen in liquid nitrogen, and stored at -80 C until analyzed. The local committee on animal care approved all animal protocols.



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  		FIG. 1. Animal treatment paradigm. Male rats were initially divided into HFF or chow (control) groups and maintained for 14 d on the prescribed diet. On d 15, the HFF groups were divided into three groups, vehicle, NDGA, and BW-755c (the chemical structures of NDGA and BW-755c are inset for illustration). On d 15–19, all groups were treated by oral gavage twice daily with either drug or vehicle. On d 15 and 19, serum was collected for analysis. On d 20, the groups were subdivided to receive either LPS or vehicle (saline). Post LPS treatment, the animals were killed, and their livers were isolated for analysis.

 
Measurement of lipid peroxidation by thiobarbituric acid-reactive substance (TBARS) assays
Membrane lipid peroxidation, as a measure of oxidative damage to lipids, was assessed by colorimetric determination of TBARS on hepatic microsomal fractions as described (20). TBARS formation was determined under basal condition (endogenous) and in the presence of Fe2+/ADP/NADPH (enzymatic) and Fe2+/ascorbate as prooxidents. Results are expressed as nanomoles TBARS (malondialdehyde equivalent) formed per hour per milligram protein.

Preparation of hepatic nuclear extracts and EMSAs
Hepatic nuclear extracts were prepared according to the procedure described previously from this laboratory (21). For EMSAs, the double-stranded oligonucleotide probes were end-labeled using [{gamma}-32P]ATP and T4 polynucleotide kinase, and unincorporated radioactivity in each preparation was removed by Sephadex G-50 spin column chromatography. The double-stranded sequences of the synthetic oligonucleotide containing activator protein-1 (AP-1) and specificity protein (SP)-1 recognition sequence (the consensus sequences shown in bold) were as follows:

AP-1 (TRE): 5'-CGCTTGATGAGTCAGCCGGAA-3' and 3'-GCGAACTACTCAGTCGGCCTT-5'

SP-1: 5'-ATTCGATCGGGGCGGGGCGAGC-3' and 3'-TAAGCTAGCCCCGCCCCGCTCG-5'

Each reaction mixture (20 µl) for AP-1 contained: 15 mM HEPES-NaOH (pH 7.9), 3 mM Tris-HCl (pH 7.9), 60 mM KCl, 0.5 mM EDTA, 1 mM MgCl2, 100 µg/ml poly (dI-dC), 0.5 mM dithiothreitol (DTT), 1% Nonidet P-40, 10% glycerol [32P]-labeled double-stranded oligonucleotide probe (~100,000 dpm), and 4.0–8.0 µg nuclear protein extract; for SP-1 (20 µl): 50 mM Tris-HCl (pH 7.9), 100 mM KCl, 12.5 mM MgCl2, 1 mM DTT, 100 µg/ml poly (dI-dC).poly (dI-dC), 1 mM DTT, 1% Nonidet P-40, 10% glycerol, [32P]-labeled double-stranded oligonucleotide probe (~100,000 disintegrations per minute), and 4.0–8.0 µg nuclear protein extract. The [32P]-oligonucleotide-nuclear protein complexes formed were separated from free oligonucleotide by PAGE. After electrophoresis, the gels were dried, exposed to Kodak X-OMAT film (Kodak, Rochester, NY) for an appropriate time (<=72 h), and then scanned; and the appropriate bands quantified by densitometry. The results are expressed as arbitrary units/10 µg nuclear protein extract.

Western blot analysis of total and phosphorylated forms of ERKs, p38 MAPK, and JNKs
Liver samples (~200 mg) were homogenized using a Potter-Elvehjem homogenizer in three volumes of detergent containing lysis buffer [20 mM HEPES (pH 7.4), 1% Triton X-100 (vol/vol), 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 20 mM NaF, 20 mM ß-glycerophosphate, 10 mM sodium pyrophosphate, 1 mM sodium vanadate, 10 nM okadaic acid, 1 mM DTT, 10 µg/ml aprotinin, 10 µg/ml leupeptin, 10 µg/ml pepstatin A, 0.5 mM 4-(2-aminoethyl)benzylsulfonyl fluoride (Roche Molecular Biochemicals, Indianapolis, IN), 10 µM E-64, and 50 µM bestatin] and incubated for 30 min at 4 C on an orbital shaker for complete lysis. The lysates were cleared by centrifugation at 15,000 x g for 10 min, the protein concentration of each solubilized lysate was determined, and samples were stored frozen until analyzed.

Samples containing an equal amount of protein (80 µg) were fractionated by SDS-PAGE (10% polyacrylamide gel with 4% stacking gel) and transferred to polyvinyllidene difluoride membrane (Immobilon, Millipore Corp., Bedford, MA). After transfer, the membrane was washed in Tris-buffered saline containing 0.1% Tween 20 (TTBS) and incubated in blocking buffer (TTBS containing 5% nonfat dry milk) for 90 min at room temperature, followed by overnight incubation at 4 C with primary antibody diluted in blocking buffer. Subsequently, the membrane was washed in TTBS and incubated for 2 h with horseradish peroxidase-conjugated secondary antibody in blocking buffer. The immunoreactive bands were then visualized using LumiGLO Chemiluminescent Detection System (Kirkegaard and Perry Laboratories, Inc., Gaithersburg, MD) followed by exposure to x-ray film (15–35 min) and quantified by Fluor-S-MultiImager scanning densitometry system (Bio-Rad, Hercules, CA). Polyclonal antibodies against total ERKs, JNKs/stress-activated protein kinases, and p38 MAPK were purchased from Cell Signaling Technology (Beverly, MA). Phospho-specific antibodies against phosphorylation of p38 MAPK [Thr (180)/Tyr (182)] and ERKs [Thr (202)/Tyr (204)] were also supplied by Cell Signaling Technology. Phospho-JNKs/phospho-stress-activated protein kinases [Thr (183)/Tyr (185)] antibody was obtained from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA).

Statistical analysis
Statistical analysis was performed by either paired or unpaired t test using GraphPad Prism version 3.00 for Windows (GraphPad Software, San Diego, CA). A difference between groups was considered significant if P was less than 0.05. Normalized Western blot data were obtained as a ratio of the units measured for phosphorylated protein divided by the units measured for total protein. Statistical analysis was performed on the normalized data.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
LO inhibitors reduce hypertriglyceridemia
As shown in Table 1Go, the high-fructose diet induced dramatic hypertriglyceridemia and significantly increased serum glucose and total cholesterol. Importantly, at this stage of treatment, these animals were not obese and did not exhibit elevated FFA, and their blood glucose levels were not dangerously high. After 4 d of treatment, both of the LO inhibitors reduced serum TG to chow-fed control levels, completely reversing the effects of the HFF diet (Table 2Go). During the treatment phase, the chow group exhibited a small, but significant decrease in serum TG and a statistically significant increase in serum FFA. The corresponding vehicle HFF group also exhibited a small, but significant increase in FFA. The effect of lowered serum TG and elevated FFA may have been due to generalized animal stress as a result of twice daily oral gavage treatment and was not considered a specific effect of the dietary treatment. Neither group receiving the LO inhibitors exhibited this increase in serum FFA. NDGA significantly decreased fasting serum insulin without significantly altering fasting blood glucose and significantly reduced serum total cholesterol. Neither of these effects was observed with BW-755c, suggesting that they are NDGA-specific and presumably unrelated to LO activity.


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  		TABLE 1. Baseline metabolic parameters of fructose-fed animals

 

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  		TABLE 2. Effect of LO inhibitors on serum metabolic components

 
Effects of fructose feeding on hepatic lipid metabolism
After the treatment protocol, we examined the hepatic lipid composition in the saline-treated animals to determine the effect of LO inhibitors on hepatic lipid metabolism. As seen in Fig. 2AGo, the total cholesterol content of HFF animals was elevated compared with chow controls. The LO inhibitors reduced total cholesterol, an effect consistent with restoration of normal hepatic VLDL metabolism. In contrast to serum lipids, liver TG content and liver FFA were not significantly elevated in the HFF animals (Fig. 2Go, B and C). This suggests that these HFF animals did not exhibit impaired hepatic TG or FFA secretion during the treatment period. Finally, we measured the extent of membrane lipid peroxidation, which increases under conditions of oxidative stress, and products of which are known to activate JNK and hence AP-1 (22). Liver microsomal fractions from HFF animals demonstrated similar susceptibility to lipid oxidation in response to enzymatic prooxidants and a reduced susceptibility to nonenzymatic prooxidants (Fig. 2Go, D and E). Animals from all groups that were treated with LPS exhibited similar sensitivity to microsomal lipid peroxidation, including negating the nonspecific antioxidant effects of the HFF diet.



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  		FIG. 2. Hepatic lipid composition chow diet is represented by clear bars; HFF diet, dotted bars; HFF diet + NDGA treatment, striped bars; and HFF + BW-755c treatment, hatched bars. All data are presented as mean ± SE (n = 4 per group). A, Total hepatic cholesterol of chow and HFF animals expressed as micrograms of cholesterol per 100 mg of tissue. B, Hepatic FFA content of chow and HFF animals expressed in nanoequivalent units/100 mg of tissue. C, Hepatic TG content of chow and HFF animals expressed in micrograms per 100 mg of tissue. D, Lipid peroxidation of chow and HFF hepatic microsomes by nonenzymatic TBARS assay. E, Lipid peroxidation of chow and HFF hepatic microsomes by enzymatic TBARS assay.

 
Fructose feeding induces a hepatic stress response
Due to the similarity between metabolic effects of high-fructose diets and inflammatory acute responses on serum lipids, we examined the effects of the HFF diet on certain elements of the stress pathway that have been associated with insulin resistance. As shown in Fig. 3Go, HFF animals exhibited significant reduction in the total protein of JNK p54 and p46, particularly p46. Despite the reduction of total protein, both isoforms of JNK exhibited significant phosphorylation, indicating that these pathways are activated on chronic fructose metabolism. The HFF animals did not exhibit significant changes to p38 MAPK, either total protein or phosphorylation state. ERK1/2 total protein levels were comparable between groups, but the phosphorylation state of these kinases was reduced by approximately 50% in HFF animals.



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  		FIG. 3. Western blot analysis of kinase activity. Chow diet, clear bars; HFF diet, dotted bars. The bar graphs indicate the ratio of phosphorylated kinase to total kinase protein of the individual samples expressed as the mean ± SE (n = 4 per group). A, Total and phosphorylated ERK1 and ERK1 Western blots for chow and HFF animals. B, Total and phosphorylated p38 MAPK Western blots for chow and HFF animals. C, Total and phosphorylated JNK-46 and JNK-54 Western blots for chow and HFF animals.

 
To corroborate the observation of JNK pathway activation in HFF animals, we examined the DNA binding activity of AP-1. As seen in Fig. 4AGo, the HFF diet increased the intensity of the AP-1 EMSA band by 86% compared with the chow diet. Treatment with both compounds significantly reduced AP-1 band intensity as compared with the HFF diet to levels that were nearly identical to the chow group. As a control, we compared the diet-induced changes of AP-1 activity to that of another transcription factor, SP-1 (Fig. 4BGo). Neither the fructose diet nor the LO inhibitors affected activity of SP-1 relative to the chow diet. The reduction of AP-1 activity in the LO inhibitor groups was due to the overall status of the liver and not an acute drug effect because the livers were harvested a full day after the last drug treatment, thus allowing drug clearance before AP-1 measurement. In support of this conclusion is the observation that all groups challenged with LPS exhibited a robust response to AP-1 (Fig. 4CGo).



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  		FIG. 4. Quantified EMSA analysis of hepatic AP-1 and SP-1. Chow diet, clear bars; HFF diet, dotted bars; HFF diet + NDGA treatment, striped bars; HFF + BW-755c treatment, hatched bars. All data are presented as mean ± SE (n = 4 per group). A, 3-d exposure of AP-1 for saline-treated groups. The densitometric intensity of each group is expressed as arbitrary units/10 µg nuclear protein extract and plotted on a graph to the right of the figure. B, The densitometric intensity of a 3-d exposure of SP-1 for saline-treated groups. C, The densitometric intensity of an overnight exposure of AP-1 for LPS-treated groups.

 
Hepatic lipid metabolism dysregulation in the HFF model is not due to corticosterone
In rats, fructose feeding increases serum levels of corticosterone, a glucocorticoid that, in part, regulates hepatic activity of phosphohydrolase and thus influences hepatic TG synthesis (23, 24, 25). Therefore, it is possible that one effect of LO inhibitors may be to suppress endogenous corticosterone production and thus indirectly influence hepatic lipogenesis. To address this question, we measured serum corticosterone in the groups after drug treatment. All animals exhibited elevated levels of serum corticosterone, which most likely was due to overall animal stress precipitated by repeated animal handling. Animals receiving NDGA and BW-755c exhibited slightly elevated serum levels of corticosterone, although these levels were not significantly higher than those for fructose-fed animals (Fig. 5AGo). LPS treatment resulted in a robust corticosterone response in all groups, with a slightly elevated, but not statistically significant, response in the BW-755c group (Fig. 5BGo). Collectively, the fructose-induced effects on hepatic TG production do not appear to be related to the adrenal stress response or general stress of the animals.



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  		FIG. 5. Serum corticosterone measurement chow diet, clear bars; HFF diet, dotted bars; HFF diet + NDGA treatment, striped bars; HFF diet + BW-755c treatment, hatched bars. All data presented as mean ± SE (n = 4 per group). A, Serum from d 20, saline-treated groups; B, serum from d 20, LPS-treated groups.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
These studies demonstrate that a high-fructose diet induces a hepatic response through the JNK/AP-1 pathway, which is similar to that observed for the inflammatory cytokine TNF-{alpha}. In addition to activation of the JNK pathway, it appears that the ERK1/2 pathway is suppressed, suggesting reduced mitogenic kinase activity in the presence of increased stress kinase activity. We demonstrated that two compounds, both LO inhibitors, reduced activation of AP-1 and reduced serum hypertriglyceridemia, which is the metabolic hallmark of this model. These results suggest a link between the hepatic inflammatory status and lipid dysregulation.

The mechanism by which these LO inhibitors reverse the stress response is unresolved. One mechanism by which these drugs may work is through inhibition of ROS generation, thus directly disrupting the JNK pathway, similar to that seen during hyperglycemic stress responses (14), although this appears unlikely because the HFF TBARS values (a crude measure of lipid peroxidation and oxidative damage to membranes) were unremarkable relative to chow controls. Moreover, ß-oxidation appears to be down-regulated due to an ample energy supply in the form of fructose. Therefore, this excludes lipid peroxidation as the primary cause of the AP-1 activation in the HFF model. Alternatively, hepatic metabolism of fructose may generate stress-activating molecules directly. Fructose is metabolized in the liver to yield dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde, which can be phosphorylated to glyceraldehyde-3-phosphate (G3P). DHAP and G3P are glycolytic intermediates and intermediates in TG synthesis. Because fructose metabolism is not regulated like glucose, it is theoretically possible that excess consumption of this sugar could lead to elevated levels of DHAP and G3P if they were not used (for example, in the case of rested rats). We propose a theory that accumulation of methylglyoxal (MG) and/or D-glyceraldehyde could provide substrate for glyceraldehyde-derived advanced glycation end products (Fig. 6Go). MG has been associated with nuclear factor-{kappa}B activation and diabetic complications (26), whereas D-glyceraldehyde has demonstrated increased transcription activation of AP-1 in endothelial cells (27). As such, LO inhibitors could inhibit JNK pathway activation from these aldehyde intermediates (28). This mechanism may account for the observation that rats fed a HFF diet in conjunction with exercise do not develop hypertriglyceridemia, because these glycolytic intermediates may be shuttled through glycolysis rather than accumulating and/or being used in alternative metabolic or chemical pathways.



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  		FIG. 6. Hepatic metabolism of fructose (F). F1P, Fructose-1-phosphate; MG AGE, MG advanced glycation end product. Fructose is metabolized in the liver to F1P by fructokinase and an aldolase to yield DHAP and D-glyceraldehyde. D-glyceraldehyde can be phosphorlyated to yield the glycolytic intermediate G3P. G3P can either be metabolized or can isomerize to yield DHAP. Alternatively, G3P may form advanced glycation end products through MG as a fragmentation intermediate. Theoretically, D-glyceraldehyde may directly conjugate with cellular proteins to yield advanced glycation end products.

 
Most data in the literature focus on inflammatory effects that are caused by or exacerbated by hyperglyceridemia, obesity, or elevated FFA. An evolving hypothesis is that metabolic disease and inflammation create a progressive cycle leading to disease progression and metabolic and cardiovascular complications (8). Our data agree with this hypothesis, and we propose that low-level inflammation may occur before the onset of overt metabolic disease, thus allowing one potential entry point into the cycle. Assuming this to be true, these data suggest that leukotriene inhibitors may be useful drugs to treat certain individuals with metabolic disease. These data further support the concept that diabetics and other groups at risk should evaluate their consumption of high levels of dietary fructose in light of possible dyslipidemia.


   Footnotes
 
The authors declare that they have no competing financial interests.

Abbreviations: AP-1, Activator protein-1; BW-755c, 4,5-dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; DHAP, dihydroxyacetone phosphate; DTT, dithiothreitol; FFA, free fatty acid; G3P, glyceraldehyde-3-phosphate; HFF, high-fructose-fed diet; JNK, c-Jun N-terminal kinase; LO, lipoxygenase; LPS, lipopolysaccharide; MG, methylglyoxal; NDGA, nordihydroguaiaretic acid; ROS, reactive oxygen intermediates; SP, specificity protein; TBARS, thiobarbituric acid-reactive substance; TG, triglyceride; TTBS, Tris-buffered saline containing 0.1% Tween 20; VLDL, very low-density lipoprotein.

Received September 4, 2003.

Accepted for publication October 17, 2003.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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