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Original Articles |
B Suppressive and Inhibitor-B Stimulatory Effects of Troglitazone in Obese Patients with Type 2 Diabetes: Evidence of an Antiinflammatory Action?1
Division of Endocrinology, Diabetes, and Metabolism, State University of New York, and Kaleida Health, Buffalo, New York 14209
Address all correspondence and requests for reprints to: Paresh Dandona, M.D., Ph.D., Diabetes-Endocrinology Center of Western New York, 3 Gates Circle, Buffalo, New York 14209. E-mail: pdandona{at}kaleidahealth.org
Abstract
It has been shown recently that troglitazone exerts an
anti-inflammatory effect, in vitro, and in
experimental animals. To test these properties in humans, we
investigated the effect of troglitazone on the
proinflammatory transcription factor nuclear factor-
B and its
inhibitory protein IB in mononuclear cells (MNC) and plasma soluble
intracellular adhesion molecule-1, monocyte chemoattractant
protein-1, plasminogen activator inhibitor-1, and
C-reactive protein. We also examined the effect of
troglitazone on reactive oxygen species generation,
p47phox subunit expression, 9-hydroxyoctadecadienoic acid
(9-HODE), 13-HODE, o-tyrosine, and
m-tyrosine in obese patients with type 2 diabetes. Seven
obese patients with type 2 diabetes were treated with
troglitazone (400 mg/day) for 4 weeks. Blood samples were
obtained at weekly intervals. Nuclear factor-B binding activity in
MNC nuclear extracts was significantly inhibited after
troglitazone treatment at week 1 and continued to be
inhibited up to week 4. On the other hand, IB protein levels
increased significantly after troglitazone treatment at
week 1, and this increase persisted throughout the study. Plasma
monocyte chemoattractant protein-1 and soluble intracellular
adhesion molecule-1 concentrations did not decrease
significantly after troglitazone treatment, although there
was a trend toward inhibition. Reactive oxygen species generation by
polymorphonuclear cells and MNC, p47phox subunit protein
quantities, plasminogen activator inhibitor-1, and C-reactive
protein levels decreased significantly after troglitazone
intake. 13-HODE/linoleic acid and 9-HODE/linoleic acid ratios also
decreased after troglitazone intake. However,
o-tyrosine/phenylalanine and
m-tyrosine/phenylalanine ratios did not change
significantly. These data show that troglitazone has
profound antiinflammatory effects in addition to antioxidant effects in
obese type 2 diabetics; these effects may be relevant to the recently
described beneficial antiatherosclerotic effects of
troglitazone at the vascular level.
TROGLITAZONE IS A thiazolidinedione, a
class of drugs known for their insulin-sensitizing effect. These drugs
are used in the treatment of type 2 diabetes, a condition associated
with insulin resistance. Troglitazone has been shown to
have antioxidant activity in vitro (1, 2). It
has recently been suggested that thiazolidinediones may have an
antiinflammatory effect (3, 4). This effect has hitherto
been attributed to those thiazolidinediones that have peroxisome
proliferator-activated receptor-
(PPAR) agonist activities, such
as troglitazone and pioglitazone. However, in
a mouse model of inflammatory bowel disease with experimental colitis
induced by 4% dextran sodium sulfate for 7 days, rosiglitazone
markedly reduce colonic inflammation (5). Rosiglitazone
binds to PPAR
specifically, but not to PPAR (6). As
rosiglitazone binds only to PPAR and not to PPAR
(7), it would appear that PPAR also mediates
antiinflammatory activity. Thus, troglitazone would be
expected to have a profound antiinflammatory effect, because it binds
to both PPAR and PPAR. More recently, we have demonstrated that
troglitazone administration to obese patients causes a
reduction in reactive oxygen species (ROS) generation by leukocytes, an
inhibition of lipid peroxidation, and an improvement in
endothelium-dependent (postischemic flow-mediated) and
endothelium-independent vasodilatation in the brachial artery
(8). The reduction of ROS generation by leukocytes is also
suggestive of the antiinflammatory effect of
troglitazone.
It has recently been shown that troglitazone may cause a reduction in carotid intimal medial thickness and thus a reversal of atherosclerosis (9). It is now agreed that atherosclerosis is an inflammatory process involving the arterial wall, a concept suggested by Ross several decades ago (10). Indeed, the plasma concentration of C-reactive protein (CRP), a marker of inflammation, has now been shown to be predictive of coronary heart disease (CHD) and events related to it (11, 12).
We have now investigated the possibility that
troglitazone may also exert an antiinflammatory effect in
obese subjects with type 2 diabetes. The effects of
troglitazone on ROS generation by MNC and
polymorphonuclear cells (PMN) and on the expression of
p47phox subunit of NADPH oxidase, the enzyme
responsible for the superoxide
(O·2-)
radical production (13) were examined.
O·2- has
been shown to be a modulator of nuclear factor-B (NFB), the
transcription factor responsible for the expression of proinflammatory
cytokines and genes modulating ROS generation (14). We
measured the concentrations of intranuclear NFB and its inhibitory
protein IB in MNC before and after troglitazone
treatment in obese subjects with type II diabetes. Plasma
concentrations of proinflammatory cytokines, soluble intracellular
adhesion molecule-1 (sICAM-1), and monocyte chemoattractant
protein-1 (MCP-1), were used as indexes of inflammation, and we
hypothesized that troglitazone would reduce the plasma
concentrations of sICAM-1 and MCP-1. ICAM-1 is an adhesion molecule
expressed by endothelial cells; it mediates the adhesion of leukocytes
to the endothelium and thus promotes inflammation (15, 16). Its expression increases acutely after endotoxin challenge
in vitro and in vivo (17) and also
in patients with atherosclerosis (18). An increase in
sICAM-1 concentrations is associated with an increase in coronary
events (19). MCP-1 has been detected in atherosclerotic
lesions. MCP-1 messenger ribonucleic acid expression has been detected
in endothelial cells, macrophages, and vascular smooth muscle cells in
atherosclerotic arteries of patients undergoing revascularization
(20).
In addition, CRP concentrations were measured, because it is considered as a general marker of inflammation. CRP is a protein produced by the liver that increases during episodes of acute inflammation (21, 22). CRP may contribute to the activation of monocytes. There are reports showing that CRP concentrations prognosticate increased risk of myocardial infarction in patients with angina pectoris (23). We also measured plasminogen activator inhibitor-1 (PAI-1) levels before and after troglitazone treatment, because its increase has been associated with insulin resistance (24) as well as endotoxin-induced inflammation (25). PAI-1 inhibits fibrinolytic activity and thus promotes thrombosis.
Subjects and Methods
Patients
Seven patients with type 2 diabetes mellitus and obesity (age
range, 32–47 yr; mean, 42.7 ± 2.3 yr), all with body mass index
(BMI) greater than 30 kg/m2, (body weight range,
88–171.5 kg; mean, 114.0 ± 10.7 kg; BMI range, 33–57; mean,
41 ± 3 kg/m2) were included in this study
(Table 1
). There were five females and
two male subjects. There were five Caucasians and two African
Americans. None of the patients was taking vitamin A, E, or C or any
other antioxidant therapy. The subjects were not advised to follow any
special diet, and none of them was actively trying to lose weight
during the duration of the study. There was no significant change in
weight or blood pressure at the end of the study. The drugs that the
patients were taking were not altered for the duration of this study;
all patients had been taking these drugs for 3 months at the current
dose level. The institutional review board of State University of New
York (Buffalo, NY) based at Millard Fillmore Hospitals approved the
study. Written informed consent was obtained from all subjects.
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Baseline liver function tests were carried out in each patient. The patients were then given 400 mg troglitazone daily for 4 weeks. A weekly follow-up was performed to note any side-effects of the drug and to collect fasting blood samples at each weekly visit. Tablet count was performed every week to verify compliance. Liver function tests were repeated at the end of 4 weeks.
PMN and MNC isolation
Blood samples were collected in sodium-ethylenediamine tetraacetate as an anticoagulant. An anticoagulated blood sample (3.5 mL) was carefully layered over 3.5 mL PMN medium (Robbins Scientific Corp., Sunnyvale, CA). Samples were centrifuged at 450 x g in a swing-out rotor for 30 min at 22 C. At the end of the centrifugation, two bands separated out at the top of the red blood cell pellet. The top band consisted of MNC, and the bottom band consisted of PMN. The bands were harvested with a Pasteur pipette, repeatedly washed with HBSS, and reconstituted to a concentration of 4 x 105 cells/mL in HBSS. This method provides yields greater than 95% pure PMN and MNC suspensions.
MNC nuclear protein extract preparation
DNA-binding protein extracts were prepared from MNC by the
method described by Andrews et al. (26). Total
protein concentrations were determined using the bicinchoninic acid
protein assay (Pierce Chemical Co., Rockford, IL). The
NFB gel retardation assay was performed using the NFB-binding
protein detection kit (Life Technologies, Inc., Grand
Island, NY). Briefly, the double stranded oligonucleotide containing a
tandem repeat of the consensus sequence for the NFB-binding site was
radiolabeled with -32P by T4 kinase. Then, 5
µg nuclear extract were mixed with the incubation buffer, and the
mixture was preincubated at 4 C for 15 min. Labeled oligonucleotide
(60,000 cpm) was added, and the mixture was incubated at room
temperature for 20 min. Samples were then applied to wells of 6%
nondenaturing polyacrylamide gel. The gel was dried under vacuum and
exposed to x-ray film. Densitometry was performed using molecular
analyst software (Bio-Rad Laboratories, Inc., Hercules,
CA). These measurements were carried out at 0, 1, 2, and 4 weeks.
IB and p47phox subunit Western
blotting
MNC cell lysates were prepared by adding 1 mL boiling lysis
buffer (1% SDS, 1 mmol/L sodium orthovanadate, and 10 mmol/L Tris, pH
7.4) to the MNC pellets. Total protein concentrations were determined
using bicinchoninic acid protein assay (Pierce Chemical Co.). Sixty micrograms of total cell lysate were electrophoresed
on 12% SDS-PAGE for IB and 10% SDS-PAGE for
p47phox subunit. The proteins were transferred to
a polyvinylidene difluoride membrane, blocked for 1 h in 5%
nonfat dry milk, and then incubated for 1 h with polyclonal
antibodies against IB (Rockland, Gilbertsville, PA) or monoclonal
antibodies against p47phox (Transduction Laboratories, Inc., San Diego, CA). Finally, the membrane was
washed and developed using supersignal chemiluminescence reagent
(Pierce Chemical Co.). Densitometry was performed using
molecular analyst software (Bio-Rad Laboratories, Inc.).
These measurements were carried out at 0, 1, 2, and 4 weeks.
Plasma sICAM-1, MCP-1, PAI-1, CRP, and insulin measurements
Plasma sICAM-1 and MCP-1 were assayed with enzyme-linked immunosorbent assay (ELISA) kits from R & D Systems, Inc. (Minneapolis, MN). The CRP ELISA kit was purchased from Diagnostics Systems Laboratories, Inc. (Webster, TX). Plasma PAI-1 levels were measured using TintElize PAI-1 kit (Biopool International, Ventura, CA). Insulin was measured in fasting plasma samples using an ELISA kit from Diagnostics Systems Laboratories, Inc. sICAM-1, MCP-1, PAI-1, CRP, and insulin concentrations were measured at 0, 1, and 4 weeks.
ROS generation assay
Five hundred microliters of PMN or MNC (2 x 105 cells) were delivered into a Chronolog (Havertown, PA) Lumi-Aggregometer cuvette to which a spin bar was added. Fifteen microliters of 10 mmol/L luminol were then added, followed by 1.0 µL 10 mmol/L formylmethionyl leucinyl phenylalanine. Chemiluminescence was recorded for 15 min (a protracted record after 15 min did not alter the relative amounts of chemiluminescence produced by various cell samples). Our method, developed independently (27), is similar to that described by Tosi and Hamedani (28). In this assay system the release of superoxide radical, as measured by chemiluminescence, has been shown to be linearly correlated with that measured by the ferricytochrome c method. We further established that in our assay system there is a dose-dependent inhibition of chemiluminescence by superoxide dismutase and catalase as well as diphenylene iodonium (data not shown), a specific inhibitor of NADPH oxidase, the enzyme responsible for the production of superoxide radicals. The specific inhibitory effect of diphenylene iodonium on NADPH oxidase has been established by Hancock and Jones (29). The variation in ROS generation by PMN and MNC in normal or obese subjects varied by less than 8% over a period of 2 weeks.
13-Hydroxyoctadecadienoic acid (13-HODE), 9-HODE, and linoleic acid measurements
Hydroxypolyunsaturated fatty acids were measured by a modification of the high pressure liquid chromatography-based method of Brown and Armstrong (30). Total lipid extracts were made from 0.5 mL ethylenediamine tetraacetate plasma according to a modification of the method described by Hara and Radin using hexane-isopropanol (3:2). Extracts were then saponified in 0.5 mol/L ethanolic NaOH to release the free acids according to the method reported by Thomas and Jackson (31).
o-Tyrosine, m-tyrosine, and phenylalanine measurements
o-Tyrosine, m-tyrosine, and phenylalanine determinations in serum were performed using high pressure liquid chromatography-fluorometric detection as described by Ishimitsu et al. with modification (32).
Statistical analysis
Statistical analysis was performed using SigmaStat software (Jandel Scientific, San Rafael, CA). All data for ROS generation, PAI-1, and CRP were normalized to a baseline of 100% in view of the interindividual variability. Paired t test was used to compare 13-HODE/linoleic acid, 9-HODE/linoleic acid, o-tyrosine/phenylalanine, and m-tyrosine/phenylalanine ratios, which were measured at baseline and 4 weeks after troglitazone treatment. Kruskal-Wallis one-way ANOVA on ranks was used to compare the rest of the indexes measured in this study. The results are expressed as the mean ± SD.
Results
Glucose, insulin, cholesterol, and triglycerides
The body weight of the obese subjects did not change over the
4-week treatment period with troglitazone. Hemoglobulin
A1c levels did not change during the study.
Plasma glucose concentration also did not alter significantly (week 0,
5.89 ± 1.27 mmol/L; week 1, 5.17 ± 0.97 mmol/L; week 4,
5.28 ± 0.77 mmol/L). Cholesterol and triglycerides levels did not
change significantly during the study (Table 2). The fasting serum insulin levels in
patients not taking insulin was 241.0 ± 56.6 nmol/L before
troglitazone and 177.6 ± 15.2 nmol/L at week 1 and
179.8 ± 25.4 nmol/L at week 4 of treatment. The fall in insulin
was not statistically significant.
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B and IB levels in MNC
NFB-binding activity in MNC nuclear extracts was inhibited
after troglitazone treatment. This inhibition was
significant at week 1 and continued to be inhibited up to week 4
(P < 0.01; Fig. 1). On
the other hand, IB protein levels increased significantly after
troglitazone treatment at week 1 as shown in Fig. 2. This increase persisted throughout the
study (P < 0.05). This suggests that nuclear NFB
inhibition is due to either IB induction or inhibition of IB
kinase, which phosphorylates IB and causes its degradation.
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Plasma MCP-1 and sICAM-1 concentrations were measured before and 1 and 4 weeks after troglitazone treatment. MCP-1 concentrations decreased from a basal level of 163.5 ± 12.4 to 139.1 ± 10.1 pg/mL at week 4. This fall was not significant, as compared by Kruskal-Wallis one-way ANOVA on ranks (P = 0.125). The plasma sICAM-1 concentration also declined from a basal level of 345 ± 34.7 to 323 ± 38.5 ng/mL at week 4. The fall in plasma sICAM-1 was not statistically significant either (P = 0.266).
Plasma PAI-1 concentrations
There was about a 25% reduction in plasma PAI-1 levels
after troglitazone treatment. PAI-1 levels were
significantly inhibited after 1 week of troglitazone
intake. PAI-1 concentrations decreased from a basal level of 110.6
± 14.7 to 92.6 ± 15.7 ng/mL at week 1 and 83.4 ± 11.3
ng/mL at week 4 (P < 0.05; Fig. 3).
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CRP levels decreased significantly in all the patients after
troglitazone treatment. CRP levels fell at week 1 from
1.82 ± 0.21 to 1.53 ± 0.18 ng/mL and further to 1.32
± 0.09 ng/mL at week 4 (Fig. 4). This
fall was also statistically significant (P <
0.05).
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ROS generation by PMN and MNC was measured at baseline and
1, 2, 3, and 4 weeks. ROS generation by PMN and MNC decreased
significantly after 400-mg troglitazone intake as shown in
Figs. 5 and 6. This decrease was evident after 1 week
and continued until week 4. ROS generation by PMN fell from 335 ±
95 mV (100%) to 58.7 ± 15.6% of the basal level at week 1,
66.2 ± 19.0% of the basal level at week 2, 73.0 ± 17.7%
of the basal level at week 3, and 57.3 ± 21.9% of the basal
level at week 4 (P < 0.05). ROS generation by MNC fell
significantly from 404 ± 73 mV (100%) to 68.7 ± 11.3% of
the basal level at week 1, 54.2 ± 9.4% of the basal level at
week 2, 63.8 ± 21.5% of the basal level at week 3, and 54.7
± 29.5% of the basal level at week 4 (P < 0.05). The
fall in ROS generation by both MNC and PMN was less in the obese
patients with type 2 diabetes compared with obese subjects without type
2 diabetes mellitus. These falls in ROS generation by PMN and MNC were
far greater than the variation observed in normal or obese subjects
over a period of 2 weeks (<8%).
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The protein quantities of p47phox subunit of
NADPH oxidase in MNC homogenates fell significantly at week 1 and
continued to be inhibited until week 4. Densitometry was performed on
these blots and showed a fall to 68 ± 13%, 64 ± 11%, and
62 ± 14% of the basal level at weeks 1, 2, and 4 respectively
(P < 0.05; Fig. 7).
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13-HODE/linoleic acid and 9-HODE/linoleic acid ratios declined significantly after troglitazone treatment. The 13-HODE/linoleic acid ratio decreased from a basal level of 1.008 ± 0.113 to 0.940 ± 0.103 pmol/µg at week 4 (P < 0.05). The 9-HODE/linoleic acid ratio also fell from a basal level of 1.014 ± 0.117 to 0.950 ± 0.104 pmol/µg at week 4 (P < 0.05).
o-Tyrosine/phenylalanine and m-tyrosine/phenylalanine ratios
The plasma o-tyrosine/phenylalanine ratio fell from 0.575 ± 0.045 to 0.568 ± 0.046 mmol/mol at week 4, and the m-tyrosine/phenylalanine ratio fell from 0.604 ± 0.046 to 0.593 ± 0.047 mmol/mol at week 4. The decreases in both o-tyrosine/phenylalanine and m-tyrosine/phenylalanine ratios were not statistically significant.
Discussion
Our data demonstrate clearly that troglitazone caused
a reduction in intranuclear NFB-binding activity and induced an
increase in the expression of IB, which binds to NFB and reduces
the ability of this transcription factor to move from the cytosol into
the nucleus (14). Diminution of intranuclear
NFB-binding activity leads to a fall in the transcription of
proinflammatory cytokines, adhesion molecules, and enzymes involved in
ROS generation. In this respect, it is noteworthy that glucocorticoids
have previously been shown by us to produce similar antiinflammatory
effects (33) in circulating MNC acutely after an injection
in vivo in humans. Furthermore, we have recently shown that
troglitazone induces similar effects in the nondiabetic
obese (34). These data are consistent with our recent
demonstration that insulin may be antiinflammatory. ICAM-1 and MCP-1
expression in human aortic endothelial cells falls after incubation
with insulin (35, 36). In addition, insulin reduces NFB
levels in the nucleus of these cells (36). Thus, insulin
and troglitazone have a similar effect.
Endothelial ICAM-1 ensures the adhesion of leukocytes to endothelial cells through leukocyte function-associated antigen-1, the corresponding ligand on the leukocyte surface (15). This process is proinflammatory and promotes atherosclerosis; thus, plasma sICAM-1 concentrations have been shown to relate to future coronary events (19). MCP-1 is a chemokine secreted by the endothelial cells, which attracts monocytes to the inflamed/injured site and thus, also promotes inflammation (37). We have previously demonstrated that troglitazone intake causes a fall in plasma sICAM-1 and MCP-1 concentrations in nondiabetic obese subjects. The reduction in ICAM-1 and MCP-1 concentrations has implications for an antiinflammatory effect and a potential antiatherogenic effect of troglitazone. Although the decreases in sICAM-1 and MCP-1 were not statistically significant in this study, there was a trend toward a fall in the plasma levels of sICAM-1 and MCP-1 after troglitazone treatment. A larger number of patients or a longer period of treatment may be necessary for this inhibitory effect to be statistically significant.
Troglitazone administration resulted in a significant
reduction in plasma concentrations of CRP, an established marker of
inflammation. CRP is known to bind to the receptor FcRIIa on the PMN
surface and to activate it (38). The reduction in CRP may
well contribute to the reduction in ROS generation by leukocytes, as
FcRII may mediate the stimulation of ROS generation
(39). An increase in plasma CRP concentrations has been
shown in observational studies to be associated with an increase in the
incidence of CHD and cerebrovascular disease-associated events
(21).
An increase in PAI-1 has been associated with insulin resistance as well as endotoxin-induced inflammation (24, 25). PAI-1 fell significantly during the short treatment period. PAI-1 not only prognosticates for CHD, but also is involved in the pathogenesis of atherosclerosis and inflammation. It inhibits the action of tissue plasminogen activator and thus inhibits fibrinolysis and promotes thrombosis. The inhibition of PAI-1 would reduce thrombosis, promote fibrinolysis, and potentially reduce the frequency of vascular events (40, 41).
The mechanism underlying these effects of troglitazone
requires comment. Similar antiinflammatory and antioxidant effects have
been observed in patients and normal subjects given vitamin E. We have
demonstrated antioxidant effects in subjects given 800 IU vitamin E
(42). The magnitude of the changes seen with 800 IU
vitamin E was comparable to that seen with 400 mg
troglitazone. As 400 mg of troglitazone
contains less than 200 mg (200 IU) of -tocopherol, it would appear
that a significant proportion of the antioxidant and antiinflammatory
effects of troglitazone is probably due to the
thiazolidinedione moiety. Indeed, a dose of 400 IU vitamin E does not
exert an effect on ROS generation or lipid peroxidation (Jialal, I.,
personal communication).
It has recently been shown that some thiazolidinediones activate the
PPAR receptor, which is known to mediate antiinflammatory effects
(43). It is thus possible that the antiinflammatory
effects of troglitazone may be PPAR mediated. However,
there is at least one report that rosiglitazone, which binds
specifically to PPAR receptors, may also have a potent
antiinflammatory effect (5). Thus, the antiinflammatory
actions of troglitazone may be mediated by both PPAR
and PPAR receptors.
Our data also demonstrate clearly that in patients with type 2 diabetes and obesity the administration of troglitazone at a dose of 400 mg daily for 4 weeks results in a marked reduction in ROS generation by MNC and PMN and that this inhibition is evident within 1 week of starting treatment. This effect persists and develops further over the following 3 weeks. This is probably due to a biological effect of troglitazone on ROS generation by leukocytes and is not a chemical antioxidant effect, as any drug in plasma would be washed away in the process of preparing the leukocytes, and all tests for ROS generation are conducted while the cells are suspended in HBSS. The magnitude of this effect (to 40% of the basal level) is less than that observed in the nondiabetic obese (to 60% of the basal level) and was observed in each of the patients regardless of gender, race, age, BMI, or previous antidiabetic treatment. The marked fall in ROS generation in the absence of a consistent significant change in plasma glucose concentrations suggests that this effect is also independent of glucose concentrations in these patients. This is also particularly true of the effects observed at 1 and 2 weeks; a marked fall in ROS generation was observed, whereas changes in blood glucose were erratic and not significant.
Of relevance is the recent work of Shoelson et al.
demonstrating that aspirin reduces blood glucose concentrations in
Zucker rats with diabetes while inducing IB kinase at the cellular
level (44, 45). Thus, the antiinflammatory effect of
aspirin may be linked to its hypoglycemic effect.
Recently, it has been shown that troglitazone treatment over months has beneficial effects in patients with vasospastic angina, and it improves postischemic endothelium-mediated vasodilation of the brachial artery (46). The reduction in ROS generation by PMN and MNC after troglitazone treatment may allow a greater bioavailability of nitric oxide (NO), which combines with superoxide radical (O·2-) under conditions of increased ROS generation. In conditions associated with increased O·2- generation, NO bioavailability may be diminished, thus reducing the ability of the blood vessels to dilate. An increase in the vasodilatory potential in patients with atherosclerosis by troglitazone may be through a reduction of O·2- generation and by the restoration of the bioavailability of NO.
Consistent with the reduction in ROS generation by leukocytes, there was a parallel reduction in p47phox subunit protein content. p47phox subunit is a cardinal protein component of NADPH oxidase, the membrane enzyme in the MNC that converts molecular O2 into the O·2- (13). These effects are similar to the effects of troglitazone on leukocytes prepared from nondiabetic obese patients who we have investigated. Troglitazone also resulted in a fall in 9-HODE and 13-HODE, the ROS-mediated peroxidation products of linoleic acid. A reduction in lipid peroxidation would reduce the conversion of low density lipoprotein to oxidized low density lipoprotein and potentially reduce the formation of foam cells from monocytes/macrophages, thus potentially reducing atherosclerosis.
Troglitazone is no longer available for clinical use, but
our observations are relevant in all probability to other
thiazolidinediones and other PPAR and PPAR agonists, such as
pioglitazone. Our data will provide the baseline to which
further data on other agents can be compared.
We conclude that troglitazone exerts a potent antiinflammatory effect in addition to ROS suppressive and antioxidant effects. The combination of antioxidant and antiinflammatory effects suggests a potential antiatherogenic action of this drug. This may lead to a reduction of atherosclerosis, myocardial infarction, and cerebrovascular disease associated with type 2 diabetes. If indeed this antiinflammatory effect of troglitazone is relevant to atherosclerosis and if all thiazolidinediones have this effect, the choice of antidiabetic drugs in the future may depend not only on their glucose-lowering effect, but also on their potential antiatherosclerotic effect.
Footnotes
1 This work was supported in part by the William G. McGowan
Charitable Fund (Washington, D.C.) and Parke-Davis. 
Received December 4, 2000.
Accepted January 30, 2001.
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 F. Mittermayer, G. Schaller, J. Pleiner, K. Krzyzanowska, S. Kapiotis, M. Roden, and M. Wolzt Rosiglitazone Prevents Free Fatty Acid-Induced Vascular Endothelial Dysfunction J. Clin. Endocrinol. Metab., July 1, 2007; 92(7): 2574 - 2580. [Abstract] [Full Text] [PDF]
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 S. Ohga, K. Shikata, K. Yozai, S. Okada, D. Ogawa, H. Usui, J. Wada, Y. Shikata, and H. Makino Thiazolidinedione ameliorates renal injury in experimental diabetic rats through anti-inflammatory effects mediated by inhibition of NF-{kappa}B activation Am J Physiol Renal Physiol, April 1, 2007; 292(4): F1141 - F1150. [Abstract] [Full Text] [PDF]
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H. Ghanim, S. Dhindsa, A. Aljada, A. Chaudhuri, P. Viswanathan, and P. Dandona Low-Dose Rosiglitazone Exerts an Antiinflammatory Effect with an Increase in Adiponectin Independently of Free Fatty Acid Fall and Insulin Sensitization in Obese Type 2 Diabetics J. Clin. Endocrinol. Metab., September 1, 2006; 91(9): 3553 - 3558. [Abstract] [Full Text] [PDF]
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 L. Gao, F. Wang, B. Wang, B. Gong, J. Zhang, X. Zhang, and J. Zhao Cilostazol Protects Diabetic Rats from Vascular Inflammation via Nuclear Factor-{kappa}B-Dependent Down-Regulation of Vascular Cell Adhesion Molecule-1 Expression J. Pharmacol. Exp. Ther., July 1, 2006; 318(1): 53 - 58. [Abstract] [Full Text] [PDF]
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 S. Y. Lee, E. J. Kang, G. Y. Hur, K. H. Jung, H. C. Jung, S. Y. Lee, J. H. Kim, C. Shin, K. H. In, K. H. Kang, et al. Peroxisome proliferator-activated receptor-{gamma} inhibits cigarette smoke solution-induced mucin production in human airway epithelial (NCI-H292) cells Am J Physiol Lung Cell Mol Physiol, July 1, 2006; 291(1): L84 - L90. [Abstract] [Full Text] [PDF]
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H. Sourij, R. Zweiker, and T. C. Wascher Effects of Pioglitazone on Endothelial Function, Insulin Sensitivity, and Glucose Control in Subjects With Coronary Artery Disease and New-Onset Type 2 Diabetes Diabetes Care, May 1, 2006; 29(5): 1039 - 1045. [Abstract] [Full Text] [PDF]
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 E. A. Jankowska, S. von Haehling, A. Czarny, E. Zaczynska, A. Kus, S. D. Anker, W. Banasiak, and P. Ponikowski Activation of the NF-{kappa}B system in peripheral blood leukocytes from patients with chronic heart failure Eur J Heart Fail, October 1, 2005; 7(6): 984 - 990. [Abstract] [Full Text] [PDF]
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 A Consoli and E Devangelio Thiazolidinediones and inflammation Lupus, September 1, 2005; 14(9): 794 - 797. [Abstract] [PDF]
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S. Dhindsa, D. Tripathy, N. Sanalkumar, S. Ravishankar, H. Ghanim, A. Aljada, and P. Dandona Free Fatty Acid-Induced Insulin Resistance in the Obese Is Not Prevented by Rosiglitazone Treatment J. Clin. Endocrinol. Metab., September 1, 2005; 90(9): 5058 - 5063. [Abstract] [Full Text] [PDF]
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 P. Dandona, A. Aljada, A. Chaudhuri, P. Mohanty, and R. Garg Metabolic Syndrome: A Comprehensive Perspective Based on Interactions Between Obesity, Diabetes, and Inflammation Circulation, March 22, 2005; 111(11): 1448 - 1454. [Full Text] [PDF]
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P. Mohanty, A. Aljada, H. Ghanim, D. Hofmeyer, D. Tripathy, T. Syed, W. Al-Haddad, S. Dhindsa, and P. Dandona Evidence for a Potent Antiinflammatory Effect of Rosiglitazone J. Clin. Endocrinol. Metab., June 1, 2004; 89(6): 2728 - 2735. [Abstract] [Full Text] [PDF]
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 V. Fonseca, C. Desouza, S. Asnani, and I. Jialal Nontraditional Risk Factors for Cardiovascular Disease in Diabetes Endocr. Rev., February 1, 2004; 25(1): 153 - 175. [Abstract] [Full Text] [PDF]
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M. Wolf, J. Sauk, A. Shah, K. Vossen Smirnakis, R. Jimenez-Kimble, J. L. Ecker, and R. Thadhani Inflammation and Glucose Intolerance: A prospective study of gestational diabetes mellitus Diabetes Care, January 1, 2004; 27(1): 21 - 27. [Abstract] [Full Text] [PDF]
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D. Tripathy, P. Mohanty, S. Dhindsa, T. Syed, H. Ghanim, A. Aljada, and P. Dandona Elevation of Free Fatty Acids Induces Inflammation and Impairs Vascular Reactivity in Healthy Subjects Diabetes, December 1, 2003; 52(12): 2882 - 2887. [Abstract] [Full Text] [PDF]
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M. B. Davidson Is Treatment of Insulin Resistance Beneficial Independent of Glycemia? Diabetes Care, November 1, 2003; 26(11): 3184 - 3186. [Full Text] [PDF]
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P. Dandona, V. Kumar, A. Aljada, H. Ghanim, T. Syed, D. Hofmayer, P. Mohanty, D. Tripathy, and R. Garg Angiotensin II Receptor Blocker Valsartan Suppresses Reactive Oxygen Species Generation in Leukocytes, Nuclear Factor-{kappa}B, in Mononuclear Cells of Normal Subjects: Evidence of an Antiinflammatory Action J. Clin. Endocrinol. Metab., September 1, 2003; 88(9): 4496 - 4501. [Abstract] [Full Text] [PDF]
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P. Dandona, A. Aljada, A. Chaudhuri, and A. Bandyopadhyay The Potential Influence of Inflammation and Insulin Resistance on the Pathogenesis and Treatment of Atherosclerosis-Related Complications in Type 2 Diabetes J. Clin. Endocrinol. Metab., June 1, 2003; 88(6): 2422 - 2429. [Full Text] [PDF]
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 G. G. L. Biondi-Zoccai, A. Abbate, G. Liuzzo, and L. M. Biasucci Atherothrombosis, inflammation, and diabetes J. Am. Coll. Cardiol., April 2, 2003; 41(7): 1071 - 1077. [Abstract] [Full Text] [PDF]
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A. Avogaro, E. Pagnin, and L. Calo Monocyte NADPH Oxidase Subunit p22phox and Inducible Hemeoxygenase-1 Gene Expressions Are Increased in Type II Diabetic Patients: Relationship with Oxidative Stress J. Clin. Endocrinol. Metab., April 1, 2003; 88(4): 1753 - 1759. [Abstract] [Full Text] [PDF]
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F. Zangeneh, Y. C. Kudva, and A. Basu Insulin Sensitizers Mayo Clin. Proc., April 1, 2003; 78(4): 471 - 479. [Abstract] [PDF]
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 D. C. Chan, G. F. Watts, P. H. R. Barrett, L. J. Beilin, and T. A. Mori Effect of Atorvastatin and Fish Oil on Plasma High-Sensitivity C-Reactive Protein Concentrations in Individuals with Visceral Obesity Clin. Chem., June 1, 2002; 48(6): 877 - 883. [Abstract] [Full Text] [PDF]
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J. Pfeilschifter, R. Koditz, M. Pfohl, and H. Schatz Changes in Proinflammatory Cytokine Activity after Menopause Endocr. Rev., February 1, 2002; 23(1): 90 - 119. [Abstract] [Full Text] [PDF]
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