Download High dietary fat induces NADPH oxidase-associated

Experimental Neurology 191 (2005) 318 – 325
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High dietary fat induces NADPH oxidase-associated oxidative stress and
inflammation in rat cerebral cortex
Xiaochun Zhang, Feng Dong, Jun Ren, Meghan J. Driscoll, Bruce Culver*
Division of Pharmaceutical Sciences and Graduate Neuroscience Program, University of Wyoming, Dept. 3375, 10,000 E. University Avenue,
Laramie, WY 82071-3375, USA
Received 25 May 2004; revised 13 October 2004; accepted 18 October 2004
Available online 9 December 2004
Abstract
Epidemiological and experimental studies have suggested that high dietary intake of fats is associated with cognitive decline and a
significantly increased risk of dementia. Since oxidative stress and inflammation have been speculated to be critical mechanisms underlying
neurodegenerative diseases, we hypothesized that a high fat (HF) diet might induce cerebral oxidative stress or neural inflammation and
subsequently contribute to the high risk of dementia. To test this hypothesis, male rats were placed on either a HF diet or a low fat (LF) diet
starting at 1 month of age and lasting for 5 months. Intracellular reactive oxidative species (ROS) generation in the cerebral cortex was
measured by the oxidant-sensitive dye 5-(6)-chloromethyl-2V,7V-dichlorodihydrofluorescein diacetate (CM-H2DCFDA). Cortical tissue
concentration of prostaglandin E2 (PGE2) was determined using an enzymatic immunoassay. Expression of NADPH oxidase subunits,
cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), nuclear transcription factor NFkappa-B (NF-nB) p65 subunit, Ikappa B(InB), and
phospho-Ikappa B(phospho-InB) was evaluated by Western blot analysis. The HF diet significantly increased ROS generation and expression
of gp91phox, p22phox, p47phox, and p67phox NADPH oxidase subunits in cerebral cortex. Elevated PGE2 levels and markedly increased COX-2
expression suggested a neural inflammatory response in response to excessive fat intake. These findings were further supported by
significantly increased phospho-InB and nuclear NF-nB expression that suggested a role of InB phosphorylation in HF diet-induced NF-nB
translocation. The present study revealed that HF diet induced neural oxidative stress, inflammation, and NF-nB activation in rat cerebral
cortex, and provided novel evidence regarding the link between high dietary fat and increased risk of dementia.
D 2004 Elsevier Inc. All rights reserved.
Keywords: High fat diet; Oxidative stress; NADPH oxidase; Inflammation; PGE2; COX-1; COX-2; NF-nB
Introduction
It is becoming well accepted that lifestyle plays a
critical role in maintaining neural function throughout the
life span of individuals. In particular, dietary fat was
found to be a significant risk factor for the development
of vascular dementia and Alzheimer’s disease (AD), the
two most important subtypes of dementias, and to
contribute to cognitive decline in aging (Grant et al.,
2002; Kalmijn, 2000, Kalmijn et al., 1997b; Knopman et
al., 2001). Kalmijn (2000) showed that high intakes of
* Corresponding author. Fax: +1 307 766 2953.
E-mail address: [email protected] (B. Culver).
0014-4886/$ - see front matter D 2004 Elsevier Inc. All rights reserved.
doi:10.1016/j.expneurol.2004.10.011
total fat (relative risk (RR) = 2.4), saturated fat (RR =
1.9), and cholesterol (RR = 1.7) were associated with an
increased risk of dementia after adjustment for confounders. Cholesterol has been known to be a risk factor for
AD since the early 1990s (Sparks, 1997, 1994), and
recently, cholesterol-ester levels were directly correlated
with beta-amyloid production (Shie et al., 2002). Levels
of circulating cholesterol are affected to a large extent by
diet (Kasim-Karakas et al., 2000; Nicolosi et al., 2001).
Dietary sugars and fats, especially saturated fats, contribute to the formation of serum cholesterol (Fuentes et al.,
2001; Jansen et al., 2000). Moreover, a recent investigation supported the link between high fat (HF) intake
and cognitive impairment by revealing that a high-fat,
refined sugar diet reduces hippocampal brain-derived
X. Zhang et al. / Experimental Neurology 191 (2005) 318–325
neurotrophic factor, neuronal plasticity, and learning in
rats (Molteni et al., 2002).
A number of intriguing hypotheses for an association
between fatty acids and cognitive function or dementia
have been proposed, which include mechanisms involving
atherosclerosis and thrombosis, inflammation, accumulation of beta-amyloid, or effects on brain development and
membrane function (Kalmijn, 2000). However, most of the
existing studies assume that the effects of high dietary fat
on neural function result primarily from cardiovascular
dysfunction such as atherosclerosis (Kalmijn, 2000; Molteni et al., 2002), and evidence of direct effects of diet on
the brain is still lacking. Neuroinflammation and oxidative
stress are thought to play an essential role in neural
degenerative diseases as well as aging, so the possibility
exists that a high fat diet could induce neuroinflammation
or oxidative stress to increase vulnerability of the brain to
numerous neurological diseases and to aging-associated
deficits. Therefore, it is important to determine whether
high dietary fat intake can induce oxidative stress and
inflammation directly in the brain.
Among numerous biochemical effects of reactive oxygen
species (ROS), particular emphasis should be given to their
interference with NF-nB function, whose role in the
pathophysiology of neurodegenerative disorders is gaining
increasing attention (Lipton, 1997; O’Neill and Kaltschmidt,
1997). NF-nB, also known as a hallmark of oxidative stress
(Flohe et al., 1997; Tanaka et al., 2002), is an inducible and
ubiquitously expressed transcription factor responsible for
regulating the expression of genes involved in cell survival,
cell adhesion, inflammation, differentiation, and growth
(O’Neill and Kaltschmidt, 1997). However, the effect of
high fat diet on cerebral cortex NF-nB activation has not
been reported.
Cyclooxygenase (COX) is the rate-limiting enzyme in
prostaglandin biosynthesis and plays an essential role in
neuroinflammation. Two distinct isoforms of COX have
been identified from various species of animals: COX-1 is
constitutively expressed in most tissues and produces
prostaglandins that generally serve a housekeeping function, while COX-2 was initially characterized as an
inducible enzyme that is expressed in response to
inflammatory stimuli, cytokines, and mitogens (Warner
and Mitchell, 2004). In the CNS, COX enzymes are
localized in neurons, astrocytes, and microglia cells, and
can be induced under various conditions (Consilvio et al.,
2004). A growing body of evidence indicates that NF-nB
also exerts an important role in general inflammatory
responses. The promoter region of COX-2 contains two
putative NF-nB binding sites, and NF-nB has been shown
to be a positive regulator of COX-2 expression in a
number of murine and human cells (Chun and Surh, 2004).
Together, these markers will be measured in the cerebral
cortex of rats fed a high fat diet to evaluate the possibility
of dietary-induced neuroinflammation and oxidative stress
in the brain.
319
Methods
Animals and diet
The experimental procedures used in this study were
approved by the University of Wyoming Animal Use and
Care Committee. Male Sprague–Dawley rats (Charles
River, Wilmington, MA), 1 month of age, were housed
in a climate-controlled environment, and animals were
randomly divided into two groups and fed either a high
fat diet (Diet #D12451, Research Diets Inc., New
Brunswick, NJ) containing 177.5 g/kg lard or a low fat
(LF) diet (Diet #D1245B, Research Diets Inc.) containing
20 g/kg lard for 5 months. Body weight (BW) and
systolic blood pressure were measured with a laboratory
scale and a semi-automated tail cuff device (IITC, Inc.,
Woodland Hills, CA).
In situ measurement of reactive oxygen species
The determination of intracellular oxidant formation was
based on the oxidation of the membrane-permeable probe
5-(6)-chloromethyl-2V,7V-dichlorodihydrofluorescein diacetate (CM-H2DCFDA) (Molecular Probes, Eugene, OR) to
yield an intracellular-trapped fluorescent compound whose
emissions at 530 nm can be captured when excited at 480
nm. Brain segments were obtained from control and high
fat diet rats, embedded in tissue freezing medium (TBS,
Fisher), frozen, cut into 30-Am-thick sections, and placed
on glass slides. The sections were exposed to 10 Amol/L
CM-H2DCFDA in Krebs/HEPES buffer and slides were
incubated in a light-protected humidified chamber at 378C
for 30 min. Fluorescence was then observed using an
Olympus BX51 fluorescent microscope equipped with a
digital camera and captured fluorescent images were
quantified using Microsuite software (Soft Imaging System,
Lakewood, CO). Low and high fat diet tissue sections were
processed and imaged in parallel (Brennan et al., 2003).
PGE2 enzyme immunoassay
After homogenization on ice, tissue samples were
centrifuged (30 min, 14,000 rpm at 48C) and the supernatant
was used for prostaglandin E2 (PGE2) measurement. Cortical
tissue concentrations of PGE2 were determined using a
commercially available enzyme immunoassay ELISA kit
(Assay designs, INC. Ann Arbor, MI) according to the
manufacturer’s instructions.
Nuclear protein and total protein samples preparation
Nuclear proteins were extracted from the cerebral cortex
according to the following protocol (Ezquer and Seltzer,
2003). Cortical tissues were rapidly removed and homogenized in a buffer containing 10 mM Tris, pH 7.6, 0.5 M
sucrose, 1.5 mM MgCl2, 10 mM KCl, 10% glycerol, 1 mM
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X. Zhang et al. / Experimental Neurology 191 (2005) 318–325
EDTA, 1 mM dithiothreitol, and a protease inhibitor cocktail
(PIC). The crude nuclear fraction was isolated by centrifugation at 4000 g for 5 min at 48C. The nuclear pellet was
resuspended in lysis buffer containing 20 mM Tris, pH 7.4,
20% glycerol, 1.5 mM MgCl2, 0.2 mM EDTA, 300 mM
NaCl, 0.5 mM dithiothreitol, and 1% PIC. Nuclear proteins
were derived from the supernatant following centrifugation at
12,000 g for 20 min at 48C. Total proteins were prepared as
described previously (Zhang et al., 2003). In brief, tissue
samples from cerebral cortex were removed and homogenized in a lysis buffer containing 20 mM Tris (pH 7.4), 150
mM NaCl, 1 mM EDTA, 1 mM EGTA, 1% Triton, 0.1%
SDS, and 1% PIC. Samples were then sonicated for 15 s and
centrifuged at 12,000 g for 20 min at 48C. The protein
concentration of the supernatant was evaluated using Protein
Assay Reagent (Bio-Rad, Hercules, CA).
Western blot analysis of NADPH oxidase subunits, COX-1,
COX-2, IjB, phospho-Ij B, and NF-jB p65 subunit
Equal amounts (50 Ag protein/lane) of nuclear protein (for
NF-nB p65) or total protein and prestained molecular weight
markers (Gibco-BRL, Gaithersburg, MD) were separated on
10% (p47phox), 7% (gp91phox, p67phox, COX-1, COX-2, NFnB p65, InB, and Phospho-InB), or 15% (p22phox) SDSpolyacrylamide gels in a minigel apparatus (Mini-PROTEAN II, Bio-Rad) and transferred electrophoretically to
polyvinylidene difluoride membranes. The membranes were
incubated for 2 h in a blocking solution containing 5%
skimmed milk in TBS, then membranes were washed briefly
in TBS and incubated overnight at 48C with the appropriate
dilution of antibodies: anti-p47phox (1:1000), anti-COX-1
(1:1000), anti-COX-2 (1:500), anti-NF-nB p65 (1:1000),
anti-InB (1:1000), and anti-Phospho-InB (1:1000). Antip47phox, anti-gp91phox, anti-p67phox, and anti-p22phox monoclonal antibody was kindly provided by Dr. Mark T. Quinn
from Montana State University (Bozeman, MT). COX-2
polyclonal antibody was purchased from Santa Cruz Biotechnology, Inc., Santa Cruz, CA. COX-1 monoclonal
antibody was obtained from Cayman Chemical, Ann Arbor,
MI. Anti-NF-nB p65, InB, and Phospho-InB polyclonal
antibodies were from Cell Signaling Technology, Beverly,
MA. After washing blots to remove excess primary antibody
binding, blots were incubated for 1 h with the appropriate
horseradish peroxidase (HRP)-conjugated secondary antibody (1:5000). Antibody binding was detected using
enhanced chemiluminescence (Amersham Pharmacia), and
the film was scanned and the intensity of immunoblot bands
was detected with a Bio-Rad Calibrated Densitometer
(Model: GS-800) (Zhang et al., 2003).
Results
General features of rats fed with low and high fat diets
As expected, rats fed the HF diet exhibited significantly
elevated body weights (23.5%) compared to their LF diet
counterparts. There was also a significant elevation in
systolic blood pressure in HF rats compared to the LF
group, but heart rates were similar for the two groups
(Table 1). These results are consistent with other reports
that chronic consumption of a high fat, refined carbohydrate diet results in hypertension (Roberts et al., 2000,
2002, 2003).
High dietary fat intake induced ROS production in rat
cerebral cortex: involvement of NADPH oxidase
Results depicted in Fig. 1 reveal that the cerebral
cortex of animals fed the high fat diet for 5 months
exhibited significantly enhanced ROS generation as
detected by DCF fluorescent intensity. This finding is
consistent with similar studies on other tissues (Kalmijn
et al., 1997a; Scheuer et al., 2000). The significantly
upregulated protein expression of the gp91phox, p22phox,
p47phox, and p67phox subunits of NADPH oxidase (Fig. 2)
detected in cerebral cortical tissue suggests an involvement of NADPH oxidase in high dietary fat-induced
oxidative stress.
High dietary fat intake increased prostaglandin E2 (PGE2)
levels and expression of cyclooxygenases in rat cerebral
cortex
PGE2, the most common prostanoid, is a marker for
inflammation. It can be produced by a wide variety of
cells and tissues and has a broad range of bioactivity.
As shown in Fig. 3, cortical tissue PGE2 levels were
increased by 29.7% in the high fat diet group. A
slightly upregulated (23.1%) constitutive cyclooxygenase-1 (COX-1) and a markedly elevated (71.5%)
expression of inducible cyclooxygenase-2 (COX-2) were
elicited in cerebral cortex by feeding high fat diet for 5
months (Fig. 4). Together, these data are indicative of
an inflammatory response in brains of rats fed the HF
diet.
Table 1
General features of Sprague–Dawley rats fed the high fat diet or low fat diet
for 5 months
Group
Body
weight (g)
Systolic
blood pressure
(mm Hg)
Heart rate
(beats/min)
Low fat diet
High fat diet
501.19 F 13.15
618.71 F 17.15*
125.33 F 3.75
140.57 F 3.41*
373.71 F 13.74
375.89 F 11.85
Statistical analysis
All data are expressed as mean F SEM. Two group
comparisons were evaluated by t tests. A P value less than
0.05 was considered statistically significant.
Mean F SEM, n = 8 rats per group.
* P b 0.05 compared with low fat diet group.
X. Zhang et al. / Experimental Neurology 191 (2005) 318–325
321
Fig. 1. Effect of high fat diet on ROS generation in rat cerebral cortex. ROS was detected by DCF fluorescence using fluorescent microscopy. Panel A: negative
control, brain slice from low fat diet group without CM-H2DCFDA; panels B and C depict the fluorescent images in cerebral cortex slices from rats fed low and
high fat diets, respectively, after exposure to 10 Amol/L CM-H2DCFDA. Panels AV, BV, and CVshow corresponding images under the light microscope. Panel D
presents the pooled data displayed as percentage of the DCF fluorescence increase from the low fat group. Means F SEM, n = 6, *P b 0.05 compared to low
fat diet group.
Effects of high fat diet on NF-jB signaling pathway
activation
Western blot analysis of nuclear extracts from cerebral
cortex revealed that nuclear levels of p65 subunits were
increased by 26.8% in rats fed the HF diet compared to the low
fat diet group (Fig. 5), suggesting an enhancement of NF-nB
nuclear translocation following high dietary fat consumption.
Phosphorylation and degradation of InB are essential for NFnB translocation (Dhanalakshmi et al., 2002). To find out if
HF diet enhanced NF-nB translocation via the InB pathway,
we examined the total and phosphorylated InB. Results
shown in Fig. 6 reveal that while HF diet failed to alter total
levels of InB expression, it significantly elevated (37.5%)
phospho-InB, suggesting a role of InB phosphorylation in
high fat diet-induced NF-nB translocation.
Discussion
The present study provides novel evidence that high
dietary fat intake promoted neuronal oxidative stress and
inflammation. Our major finding revealed that a high dietary
fat intake directly enhanced ROS generation and triggered
PGE2 production in cerebral cortex accompanied by
elevated expression of NADPH oxidase subunits and
cyclooxygenases. To the best of our knowledge, this is the
first report that NF-nB, an important downstream effector of
both oxidative stress and inflammation, can be activated by
phosphorylation of InB by consuming a high fat diet. The
results herein described strengthen the link between the
western society diet and the increased risk of dementia.
Oxidative stress is hypothesized to be an important
contributor to the pathogenesis of AD and other types of
dementia (Grant et al., 2002; Smith et al., 2000). There is
substantial evidence that the brain, which consumes large
amounts of oxygen, is particularly vulnerable to oxidative
damage (Esposito et al., 2002). An increasing scientific
literature provides ample direct or indirect evidence that
overproduction of ROS can induce cellular damage via
oxidation of critical cellular components such as membrane
lipids, proteins, and DNA (Halliwell, 2001; Kruman et al.,
1997; Markesbery and Carney, 1999; See and Loeffler,
2001), ultimately leading to neuronal death by apoptosis or
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X. Zhang et al. / Experimental Neurology 191 (2005) 318–325
Fig. 2. Effect of high fat diet on cortical protein expression of NADPH
oxidase subunits. The upper panel shows the results of immunoblots
analyzed in cerebral cortex tissue from low fat diet and high fat diet-treated
rats and probed with antibodies against gp91phox, p22phox, p47phox, and
p67phox, as indicated. The bar graphs show the results of densitometric
necrosis (Beal, 1996; Behl et al., 1994; Ishikawa et al.,
1999; Mattson, 2003). NADPH oxidase, which consists of
at least six subunits, the membrane-bound gp91phox and
p22phox heterodimer, the cytoplasmic complex of p40phox,
p47phox, p67phox, and the small GTPase Rac2 (Bokoch and
Knaus, 2003), is the most important source of ROS other
than the mitochondria, and has been best characterized in
phagocytic cells. However, it is now well accepted that
nonphagocytic cell types also express components of
NADPH oxidase en route to generation of ROS (Serrano
et al., 2003; Tammariello et al., 2000). A recent study
revealed a wide distribution of NADPH oxidase immunoreactivity throughout the brain with particularly prominent
Fig. 3. Effect of high fat diet on PGE2 level in rats’ cerebral cortex tissue.
PGE2 concentration in the supernatants of cerebral cortex homogenates was
measured by an ELISA assay as described in Methods. Data are expressed
as mean F SEM, n = 8 (**P b 0.01 high fat diet vs. low fat diet).
Fig. 4. COX-2 enzyme expression in cerebral cortex is markedly increased
by high fat diet treatment. Representative blots showing immunostaining
with anti-COX-1 or anti-COX-2 antibodies. Data are expressed as percent
increase from low fat diet. Mean F SEM, n = 4, *P b 0.05 compared with
low fat diet group.
localizations in the cerebral cortex, hippocampus, amygdala,
striatum, and thalamus (Serrano et al., 2003). Our data
demonstrated a significantly elevated ROS production in the
cerebral cortex from rats treated with HF diet, which is
consistent with studies of the effects of high fat diets on
other tissues or cells (Hong et al., 2002; Mohanty et al.,
2002; Roberts et al., 2002; Stokes et al., 2002). The
mechanism underlying ROS generation in brains of rats
fed HF diet requires further investigation. The present study
showed for the first time that cerebral cortical NADPH
oxidase subunits (gp91phox, p22phox, p47phox, and p67phox)
were significantly upregulated by high dietary fat intake,
suggesting that high levels of dietary fatty acids might
induce brain oxidative stress via the NADPH oxidase
pathway. It should be noted that although direct measure-
Fig. 5. Enhancement of immunoreactivity for the NF-nB p65 subunit in the
cerebral cortex nuclear extraction from brain of the high diet-treated rats.
X. Zhang et al. / Experimental Neurology 191 (2005) 318–325
Fig. 6. Effect of high fat diet on total InB expression and InB
phosphorylation. Representative blots showing immunostaining with antiInB or anti-phospho-InB antibodies. Means F SEM, n = 4, *P b 0.05
compared with low fat diet group.
ment of NADPH oxidase activity (superoxide anion
production) would provide strong evidence of effects of
high dietary fat intake on this enzyme, technical difficulties
precluded us from measuring activity of this enzyme in this
study.
Another index of oxidative stress is the activation of NFnB (Behl et al., 1994; Tanaka et al., 2002). A large body of
evidence indicates that ROS can act as a second messenger
mediating intracellular responses, including NF-nB activation (Dalton et al., 1999; Flohe et al., 1997; Li and Karin,
1999; Pinkus et al., 1996). However, ROS generation is not
the only permissive factor for activation of NF-nB, with the
latter being considered as a common downstream signaling
molecule and can be induced by various intercellular
signals, including inflammatory mediators (Mattson et al.,
2000; O’Neill and Kaltschmidt, 1997; Terai et al., 1996).
NF-nB is a heterodimer composed of p50 and p65 subunits
and, under resting conditions, the dimer is retained in the
cytoplasm in an inactive state through interaction with InB.
NF-nB can be rapidly activated in response to a variety of
inflammatory stimuli that lead to degradation of InB (Terai
et al., 1996). Our results showed consumption of a high fat
diet enhanced InB phosphorylation and p65 subunit
activation in rat cerebral cortex, which supports our
observation of HF diet-induced neural oxidative stress
and inflammation. However, the effect of fatty acids on the
NF-nB pathway is still highly controversial. Activation, no
change, and inactivation have all been reported. Liao et al.
(1993) reported that a high fat, high cholesterol
batherogenicQ diet induced considerably greater hepatic
expression of several inflammatory and oxidative stressresponsive genes and significant NF-nB activation that is
consistent with our findings. However, another study
revealed an unaltered NF-nB activity in brains of rabbits
fed a high cholesterol diet (Kalman et al., 2001). Moreover,
downregulated NF-nB activation was shown in human
323
CaCo-2 colon cells when treated with omega-3 fatty acid
docosahexaenoic acid (DHA) as well as in oleic acidtreated human umbilical vein endothelial cells (Carluccio et
al., 1999; Narayanan et al., 2003). Thus, the effect of fatty
acids on NF-nB might depend on the category of fatty acid
(probably the most important factor), as well as on tissue or
cell type, and the dose and duration of treatment.
Interestingly, while the NF-nB signaling pathway certainly
appears to be involved in AD as well as in other
neurodegenerative diseases (Esposito et al., 2002; Kaltschmidt et al., 1997), the explanation for the conflicting
results concerning an anti-apoptotic vs. pro-apoptotic role
of NF-nB activation is still not clear and has been
described as bjanus facesQ of NF-nB (Lipton, 1997). Thus,
the meaning (neurotoxic or neuroprotective effect) of high
fat diet-induced NF-nB activation revealed in the present
study is unclear.
Our data also demonstrated pro-inflammatory actions of
high fat diet in cerebral cortical tissue, this finding being in
agreement with some early studies describing increased
expression of mediators of inflammation in other tissues and
cells induced by high fat diets (Lee et al., 2001; Lin et al.,
1996; Rao et al., 2001). The PGE2 level in the cerebral
cortex was increased significantly by excess consumption of
fat. Moreover, both COX-1 and COX-2 isoforms were
upregulated in the cerebral cortex of rats fed the high fat
diet, with the most dramatic increase occurring in COX-2
expression, which indicates that COX-2 might be a critical
mediator in dietary fat-induced neural inflammation. Saturated fatty acids, but not unsaturated fatty acids, were
reported to induce the expression of COX-2 in macrophages, suggesting that the saturated fatty acids in the high
fat diet might be the dominating contributors to the
increased COX-2 (Lee et al., 2001). Furthermore, it was
found that saturated fatty acid-induced COX-2 expression is
mediated through the activation of NF-nB in RAW 264.7
cells, which suggests that excess consumption of dietary fat
induced-inflammation might result from hyperlipidemiainitiated oxidative stress rather than a parallel occurrence. A
chain of events with ROS production resulting in NF-nB
activation, COX-2 mRNA induction, COX-2 protein production, and PGE2 synthesis is supported by an increasing
number of studies (Barbieri et al., 2003; Kiritoshi et al.,
2003).
In conclusion, excessive dietary fat intake-induced
NADPH oxidase related oxidative stress as well as
inflammatory response represented by increased PGE2
levels, increased COX-1, and particularly COX-2 expression, and promoted NF-nB activation via InB phosphorylation. The present finding may help to explain the
increased risk of dementia by excess fat consumption.
High fat diet consumption may active NADPH oxidase
and overproduction of ROS, which in turn, activates the
NF-nB pathway and upregulates COX-2, thus contributing
to neural injury underlying cognitive impairment and
dementia.
324
X. Zhang et al. / Experimental Neurology 191 (2005) 318–325
Acknowledgments
This research was supported in part by NIH grants
NCRR BRIN P20 RR15640 (R.O. Kelley, P.I) and NCRR
COBRE P20 RR15640 (F.W. Flynn, P.I.) awarded to the
University of Wyoming.
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