Effects of coenzyme Q10 and α-lipoic acid supplementation in fructose fed rats.

This study was conducted to investigate the effects of α-lipoic acid and coenzyme Q10 on plasma levels of lipids, asymmetric dimethylarginine, oxidative stress in fructose fed rats which provide a model of dietary-induced insulin resistance and to evaluate vascular changes developing in these rats by histologically. Male Sprague Dawley rats were used in this study. The animals were divided into 4 groups. Group 1 did not receive any medication and served as a control. Group 2 received a regular diet and water ad libitum and fructose was administered as % 10 solution in drinking water. Group 3 received α-lipoic acid (100 mg/kg/day) i.p. for 5 weeks and Group 4 received coenzyme Q10 (10 mg/kg/day) i.p. for 5 weeks. For determination of plasma asymmetric dimethylarginine, glutathione and malondialdehyde levels, high-performance liquid chromatography system was used. Homeostatic model assessment as a measure of insulin resistance was calculated. Lipid profile measurements were determined using enzymatic assay on an Auto analyzer. The high fructose diet was significantly associated with an increase in levels of plasma LDL, VLDL and total cholesterol and decrease in level of HDL cholesterol. Plasma asymmetric dimethylarginine, malondialdehyde and glutathione levels were also increase in these rats. α-lipoic acid or coenzyme Q10 supplementation was found to have some positive effect on these parameters. These findings were also demonstrated by morphological observation of the aorta. We demonstrated that administration of α-lipoic acid and coenzyme Q10 notably suppresses oxidative and nitrative stress, hyperinsulinemia, insulin resistance developing in fructose fed rats, a model of metabolic syndrome (MS). These positive effects of α-lipoic acid or coenzyme Q10 can be attributed to its antioxidant activity.

Introduction

Metabolic syndrome (MS) characterized by hyperglycemia, hyperlipidemia and hypertension is a significant risk factor for cardiovascular disease.( Insulin resistance (IR) is a central component of metabolic syndrome.( Fructose-fed rats (FFRs) provide a model of dietary-induced insulin resistance to indicate the pathophysiological mechanisms (metabolic and cardiovascular changes) associated with MS.( The metabolic effect of a fructose diet is associated with oxidative stress,( but the precise mechanism is not fully understood. Reactive oxygen species (ROS) play a physiological role in the vessel wall. Dietary factors play a key role in the development or prevention of various human diseases, including cardiovascular disease and MS.( Some studies suggest a strong association between IR and endothelial dysfunction.( Endothelium-derived nitric oxide (NO) is the most potent endogenous substance which is synthesized by the endothelial enzyme NO synthase (e-NOS) from the amino acid L-arginine.( Experimental and clinical data show that endogenous inhibitors of e-NOS, such as asymmetric dimethylarginine (ADMA), may be responsible for endothelial dysfunction in which ADMA plasma levels have been found elevated.( Therefore, ADMA plasma levels appear to be dynamically regulated and can be correlated with measure of NO bioavailability. Endothelial dysfunction induces a reduction in vascular relaxation, linked to a decrease in the bioavailability of nitric oxide (NO)( and an increase in levels of oxidative stress( following the overproduction of super oxide anion (O2•−). The role of oxidative stress in the development of IR has been demonstrated by several studies.( Furthermore, systemic oxidative stress is associated with insulin resistance.(

Coenzyme Q10 (CoQ10) is an electron carrier in the mitochondrial respiratory chain. In addition to its role in mitochondria, CoQ10 acts as an antioxidant, scavenging free radicals and inhibiting lipid peroxidation.( Recent studies have provided beneficial effects of CoQ10 in various disorders related to oxidative stress like hypertension and heart failure.( It has been reported that CoQ10 concentrations and redox status are associated with components of MS.(

α-lipoic acid (ALA), also known as 6,8-thioctic acid has generated considerable clinical interest as a redox-modulating agent.( Biologically, α-lipoic acid functions as a cofactor of oxidative decarboxylation reactions in glucose metabolism to provide energy.( It has been used in the western world for a long time to treat complications associated with diabetes.( In addition to its role in glucose metabolism, but may also acts as an antioxidant in vitro and in vivo.( In vitro experiments have shown that ALA is potent scavengers of reactive oxygen species which quenches singlet oxygen, hydroxyl radical and hypochlorus acid.(

Thus, it would be important to establish whether exogenous administration of CoQ10 and ALA are effective for prophylaxis and therapy of MS. This study aimed to investigate the effect of exogenous CoQ10 and ALA administration in the fructose-fed rat on the levels of lipids, ADMA, NO and glutathione. We also investigated the possible protective effects of coenzyme Q10 and ALA on the vascular changes developed in these rats by histologically.

Materials and Methods

Animals and treatment

Male Sprague Dawley rats of body weight ranging from 210 to 230 g were used in this study. They were housed in an animal room under controlled conditions on a 12-h light/dark cycle and constant temperature (22°C). Food and water were supplied ad libitum. All rats were fed a standard rat chow before beginning the study and continued to consume standard rat chow composed of 21% protein, 4% fat, 50% carbohydrate (vegetable starch), and 4.5% cellulose for the entire study duration. Both diets contained a standard mineral and vitamin mixture. All protocols described were reviewed and approved by the Local Institutional Committee for the Ethical Use of Animals. The animals were divided into 4 groups and were maintained as follows:

Group 1 (CON) (n = 7) – This group received regular diet and water ad libitum. This group did not receive any medication and served as a control. After 8 weeks, this group recieved serum physiologic (SF) (0.5 mL/day) intraperitoneally (i.p.) for 5 weeks.

Group 2 (FRU) (n = 9) – This group received a regular diet and water ad libitum and fructose was administered as % 10 solution in drinking water. After 8 weeks, this group recieved SF (0.5 mL/day) i.p. for 5 weeks.

The other groups of rats were given one of the following treatments (Group 3 and 4).

Group 3 (FRU + ALA) (n = 9) – This group received a regular diet and water ad libitum and fructose was administered as % 10 solution in drinking water. After 8 weeks, this group received ALA (100 mg/kg/day) i.p. for 5 weeks.

Group 4 (FRU + CoQ10) (n = 9) – This group received a regular diet and water ad libitum and fructose was administered as % 10 solution in drinking water. After 8 weeks, this group received CoQ10 (10 mg/kg/day) i.p. for 5 weeks.

Body weights of animals were recorded at the baseline and after the treatment. Blood samples from animals were collected by decapitation and serum was separated by centrifugation and samples were kept at −70°C until the measurements were performed.

Biochemical analysis

Serum samples were analyzed for glucose, triglyceride (TG), HDL-cholesterol, LDL-cholesterol and total cholesterol (TC). Glucose and lipid profile measurement were determined using enzymatic assay on an Auto analyzer (Olympus AU 600, Hamburg, Germany). Quantitative determination of serum insulin concentration was performed with rat/mouse Enzyme-linked immunosorbent assay (ELISA) kit (Linco research). Insulin levels were expressed as ng/mL in ELISA kit and they were converted to mU/ml. Homeostatic model assessment (HOMA) as a measure of insulin resistance was calculated by the formula: insulin (mU/ml) × [glucose (mmol/l/22.5)].

For determination of plasma ADMA levels, HPLC system was used. This method allows to analized the asymmetric dimethylarginine (ADMA) with clean-up columns procedure and derivatization. Besides this method allow to analyze the arginine and symmetric dimethylarginine (SDMA). After derivatization, 50 µl of solution are injected in HPLC system and analized by Fluorescence. The sensitivity of this method was <0.01 µmol/l and linearity was >16,00 µmol/l.

Determinations of total and reduced glutathione (GSH) were determined by HPLC. EDTA-blood was used in this test system. For the determination of glutathione the sample is divided in two aliquots. One is reduced and the total amount of glutathione is measured. The other aliquot is treated without reduction solution, which determines only the reduced glutathione. During the derivatisation reaction glutathione is converted into a fluorescent probe. The following precipitation step removes high molecular substances. After centrifugation the fluorescent probe is cooled (2–8°C) and injected into the HPLC system. The isocratic separation via HPLC at 30°C using a reversed phase column in two runs. One run lasts 4 min. The chromatograms are recorded by a fluorescence detector. The quantification is performed with the delivered EDTA-blood calibrator; the concentration is calculated by the internal standard method. The amount of oxidized glutathione is calculated by substraction of: Glutathionetotal– Glutathionereduced the difference was divided by two because oxidized glutathione (GSSG) consists of two reduced GSH molecules. Intra-Assay CV for GSHtotal is 1.2% (551 µmol/l) and for GSHreduced is 1.2% (286 µmol/l). Inter-Assay CV for GSHtotal is 2.8% (554 µmol/l) and for GSHreduced is 3.5% (271 µmol/l).

Determination of plasma MDA level was also determined by HPLC. For the determination of malondialdehyde a derivatisation step, in which protein bound malondialdehyde is hydrolysed and converted into a fluorescent probe (60 min at 95°C) is performed. The fluorescent probe is then cooled (2–8°C), centrifuged, mixed with a reaction solution and injected into the HPLC system. The isocratic separation via HPLC at 30°C, using a ’reversed phase’ column, lasts 4 min for one sample. The chromatograms are recorded by a fluorescence detector. The quantification is performed with the delivered calibrator; the concentration is calculated via integration of the peak heights. Intra-Assay CV: 6.4% (2.55 µmol/l) Inter-Assay CV: 7.5% (2.50 µmol/l) [n = 6].

Plasma NO levels were measured in triplicate after conversion of nitrate to nitrite by nitrate reductase, and nitrite was measured by using the Griess reaction, as described previously.( The results were expressed as µmol/ml.

Vascular histological analysis

Fixations of vessel samples obtained from control and other groups were made in % 10 formaldehyde. After that, paraffin sections at 4 micron thickness obtained from routine pathological processes were stained with hematoxylin-eosin and examined by light microscopy.

Statistical analysis

The results are expressed as mean ± SD. Analysis of the data was performed by one-way analysis of variance (ANOVA) and subsequent analysis was performed using the Tukey test. The p values smaller than 0.05 were selected to indicate statistical significance between groups.

Results

Body weight, glucose, HOMA-IR and lipid profile

Fructose fed rats had a significant increase in body weight. Fructose fed rats had a higher body weight compared with controls (p<0.0001). ALA and CoQ10 treatment given to fructose fed rats for 8 weeks affect body weight gain during the experimental period. Body weights were decreased during the treatment of ALA and CoQ10 at the end of the experiment compared with only fructose fed rats (p<0.05, p<0.01). Serum levels of LDL, TG and total cholesterol were increased and HDL cholesterol was decreased in fructose fed rats compared with control rats at the end of the experiment (p<0.0001). The treatment of ALA and coenzyme Q10 at the end of experiment improved the lipid levels. Serum levels of LDL, TG and total cholesterol were significantly decreased and HDL cholesterol was significantly increased in group 3 and 4 compared with fructose fed rats (p<0.0001). But there were no significant difference between ALA treatment and Coenzyme Q10 treatment (Table 1).

Table 1

Changes in body weight and serum lipids

	Group 1 (CONTROL)	Group 2 (FRU)	Group 3 (FRU + ALA)	Group 4 (FRU + CoQ10)
	n = 7	n = 9	n = 9	n = 9
Body weight (g) (Initial)	212.57 + 11.04	218.66 + 9.65	219.44 + 15.28	220.55 + 13.21
Body weight (g) (Final)	312.71 ± 6.15	362.11 ± 20.03a,b,c	345.22 ± 13.31a	342.11 ± 12.46a
Glucose (mg/dl)	98.57 ± 6.42	147.88 ± 8.97a	115.44 ± 6.98a,e	109.66 ± 4.58d,e
LDL-C (mg/dl)	28.28 ± 3.19	59.88 ± 3.68a	38.55 ± 6.10a,e	34.22 ± 4.43f,e
VLDL-C (mg/dl)	20.48 ± 1.37	33.97 ± 1.68a	25.26 ± 1.54a,e	24.82 ± 1.36a,e
Trigliserid (mg/dl)	102.42 ± 6.87	169.88 ± 8.44a	126.33 ± 7.71a,e	124.11 ± 6.80a,e
Total-C (mg/dl)	82.57 ± 4.15	118.22 ± 3.89a	97.22 ± 8.52a,e	96.00 ± 6.63a,e
HDL-C (mg/dl)	34.14 ± 2.79	25.11 ± 4.13a	35.77 ± 5.09e	37.11 ± 4.07e

ap<0.0001, compared with control; bp<0.05, compared with group 3; cp<0.01, compared with group 4; dp<0.005, compared with control; ep<0.0001, compared with group 2; fp<0.05, compared with control.

In the end of the experiments, the highest levels of glucose and HOMA-IR were observed in the fructose fed group compared with control, group 3 and group 4 (p<0.0001, p<0.05, p<0.01 respectively). Administration of ALA and CoQ10 were improved the glucose and HOMA-IR levels. Treatment with ALA and CoQ10 were significantly decreased the glucose level compared with fructose fed rats (p<0.0001), but as shown in lipid levels, there were no significant difference in glucose levels between ALA and CoQ10 treatment. HOMA-IR level was decreased in ALA treatment group compared with fructose fed group (p<0.001). Coenzyme Q10 administration more improved HOMA-IR than ALA treatment, HOMA-IR was significantly decreased in this group compared with fructose fed rats (p<0.0001).

Levels of ADMA, MDA, NO, total glutathione, reduced glutathione and NO

The high fructose diet was significantly associated with an increase in levels of plasma ADMA (0.95 ± 0.21 µmol/L vs 2.51 ± 1.19 µmol/L, p<0.0001) leading to a significant reduction in the L-arginine level (81.39 ± 6.92 µmol/l vs 71.08 ± 8.35 µmol/l, p<0.05). No significant difference was seen in the levels of SDMA between control and fructose fed rats. ALA and CoQ10 administration were decreased ADMA levels compared with controls (p<0.01, p<0.001, respectively). MDA and NO levels were lead similar effects as shown in ADMA levels. These parameters were increased in high fructose diet group compared with controls (p<0.0001) and treatment with ALA or CoQ10 decreased the levels of MDA and NO levels (Table 2). In contrast, total and reduced glutathione levels were decreased in high fructose diet group compared with controls (p<0.0001) and treatment with ALA or CoQ10 increased the levels of these parameters (Table 2).

Table 2

Effects of ALA and CoQ10 treatments on plasma variables in rats

	Group 1 (CONTROL)	Group 2 (FRU)	Group 3 (FRU + ALA)	Group 4 (FRU + CoQ10)
	n = 7	n = 9	n = 9	n = 9
ADMA (µmol/l)	0.95 ± 0.21	2.51 ± 1.19a	1.61 ± 0.27b	1.39 ± 0.30c
SADMA (µmol/l)	0.66 ± 0.14	0.87 ± 0.42	0.46 ± 0.09d,e	0.75 ± 0.24
ARJININ (µmol/l)	81.39 ± 6.92	71.08 ± 8.35f	74.54 ± 6.08	82.54 ± 11.56b
Insulin (ng/ml)	0.41 ± .14	0.93 ± 0.14a	0.68 ± 0.11a,g	0.67 ± 0.12a,g
HOMA	2.44 ± 0.98	8.19 ± 1.69a	4.67 ± 1.01i,c	4.41 ± 1.00h,g
Reduced glutathione (µmol/l)	829.42 ± 35.00	682.44 ± 76.61a	732.11 ± 38.72a,j	757.88 ± 16.03h,k
Total glutathione (µmol/l)	848.57 ± 34.23	736.11 ± 74.70a	753.66 ± 42.06a	778.66 ± 17.08h
MDA (µmol/l)	1.98 ± 0.47	3.21 ± 0.47a	2.66 ± 0.88f	2.52 ± 0.21j
NO (µmol/ml)	56.82 ± 10.39	84.67 ± 15.93a	71.01 ± 14.12f,j	71.71 ± 6.64f,j

ap<0.0001, compared with control; bp<0.01, compared with group 2; cp<0.001, compared with group 2; dp<0.05, compared with group 4; ep<0.005, compared with group 2; fp<0.05, compared with control; gp<0.0001, compared with group 2; hp<0.01, compared with control; ip<0.001, compared with control; jp<0.05, compared with group 2; kp<0.005, compared with group 2.

To further investigate the relationships between biochemical characteristics and HOMA-IR as continuous variables, the following statistical correlations were identified: ADMA (r = 0.55, p = 0.001), glutathionetotal (r = −0.46, p = 0.006), glutathionereduced (r = −0.60, p = 0.0001), MDA (r = 0.49, p = 0.003) and NO (r = 0.44, p = 0.001) (Table 3).

Table 3

Correlation HOMA and some of biochemical parameters

	r	p
ADMA	0.55	0.001
Reduced glutathione	–0.6	0.0001
Total glutathione	–0.46	0.006
NO	0.44	0.009

Morphological observation of the aorta

When compared with control group (Fig. 1), histopathological examination of vessels of group 2 revealed that there were lymphocytic infiltration in place, hypertrophy of smooth muscles and edema (Fig. 2, 3,4); in ALA-administered group, it was noted that perivascular lymphocytic infiltration was significiantly decreased and even disappeared completely in place (Fig. 5). In CoQ10-administered group, appearances of vessels were almost same with control group and poor lymphocytic infiltration was seen in perivascular area (Fig. 6).

Fig. 1

Aorta in a rat from group 1 (HE ×200).

Fig. 2

Perivascular inflammation in group 2 (HE ×400).

Fig. 3

Smooth muscle hypertrophy in group 2(HE ×400).

Fig. 4

Edema in a vessel in group 2 (HE ×200).

Fig. 5

Edema and infiltration is reduced in group 3 (HE ×100).

Fig. 6

Edema and infiltration is also reduced in group 4 (HE ×100).

Discussion

In this study, we found that ALA or Coenzyme Q10 administration prevent the increase of ADMA, the development of insulin resistance, oxidative stress, and vascular changes in an experimental model of metabolic syndrome induced by fructose administration. Insulin resistance has been implicated as a central pathogenic feature of MS in human and animal models.( As shown in previous studies reported by a group,( in our study, FFRs developed insulin resistance and increased oxidative stress, plasma ADMA level and histological vascular alterations. Chronic administration of ALA and CoQ10 not only prevented the increase in ADMA and oxidative stress but also reduced vascular perivascular lymphocytic infiltration and edema in FFRs.

The fructose rich diet used in our experimental model( induced the development of pathophysiological characteristics associated with metabolic syndrome, including hyperglycemia and dyslipidemia.( Our results are in accordance with a recent study( which indicated that fructose-fed Sprague–Dawley rats manifested major characteristics of human metabolic syndrome. Fructose is a simple carbohydrate, with interesting physico-chemical properties such as its strong sweetening power and its hygroscopic nature. The highest concentration of fructose found in natural foods is about 42%, and it is the principal sugar added to processed foods.( Unlike glucose, fructose does not directly stimulate insulin secretion because pancreatic beta-cells have very low levels of the fructose transporter GLUT5.( An additional important observation in this study pertained to the weight loss noted with ALA. α-lipoic acid has been described to have appetite suppressant effect through an AMP kinase mechanism in the hypothalamus.(

The present study had shown that fructose rich diet in rats leads to dyslipidemia condition. The increase in TC, LDL-C, and triglycerides as well as decrease in HDL-C concentrations may be as a result of reduced lipoprotein lipase activity secondary to reduced in plasma insulin levels.( Cholesterol ester transfer protein, which is important in regulating lipoprotein lipid composition, was increased in DM condition, which may have contributed to the dyslipidemia.( ALA and coenzyme Q10 supplementation corrected the dyslipidemia occurred. The mechanism action of ALA is believed through the controlling the activity of enzyme that involved in lipid metabolism. ALA was found to increase 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity and increase lipoprotein lipase and lecithin cholesterol acyl transferase (LCAT).(

Glucose autoxidation and glycation of protein leads to generation of oxygen free radicals, which can enhance lipid peroxidation and oxidation of LDL.( Fructose fed rats showed significant increase in serum total cholesterol, triglycerides, VLDL, LDL and decrease in HDL levels. Treatment with CoQ10 significantly decreased serum cholesterol, triglycerides, VLDL, LDL and increased HDL levels in diabetic treated rats. Singh et al.( reported that HDL-C concentrations significantly increased in the group treated by 120 mg/day of CoQ10 than in the control group. The reduction in lipid levels and increase in HDL levels may be due to inhibition of LDL oxidation and reduce oxidative stress.

We found that a long-term fructose-rich diet was associated with an increase in oxidative stress. The increased production of MDA, nitric oksit, total glutatione and reduced glutathione in plasma was detected. In the present experiments, CoQ10 and ALA were used to test the effects of antioxidants on high-fructose diets CoQ10 and ALA were associated with statistically significant positive effects. Previous work carried out on ’ALA supplementation using the same dose in diabetic rats’ demonstrated beneficial effects via changes in the oxidative state.( Previous reports confirmed that ALA scavenges hydroxyl radicals, hydrogen peroxide (H2O2), singlet oxygen, superoxide radicals, and peroxyl radicals thereby preventing the free radicals-mediated lipid peroxidation.( GSH is the intracellular non-protein sulfhydryl compound that act as both nucleophile and an effective reductant by interacting with various electrophilic and oxidized compounds, and its depletion results in increased defenselessness of cell to oxidative stress.( The consequence of decrease in cellular GSH levels is an increase of free radical intermediates leading to oxidative stress and potent cellular damage. The reduced form of GSH becomes readily oxidized to oxidized glutathione (GSSG) with the Glutatyon peroksidaz (GSH-Px) on interacting with free radicals.( In our present study, pretreatment of the rats with ALA significantly increased the concentration of GSH. It has been known that the ALA plays an important role in improving the GSH status through the mechanism of increasing the cystine availability because cystine is the rate-limiting factor in GSH biosynthesis. ALA induces the cystine uptake and thereby increases GSH synthesis. In our present investigation, pretreatment with ALA augments the serum GSH level which is in accordance with the previous studies.(

Impaired endothelium-dependent relaxation has been demonstrated in various vascular beds in different animal models of diabetes. The potent antioxidant capacity of ALA, which reduces oxidative stress both at systemic and local levels, was responsible for its beneficial action on atherosclerosis and vascular relaxation. In a recent study,( ALA was directly linked to ability to reduce significantly the elevated total nitrate/nitrite levels of combination-treated rats. The ability of ALA to modify nitric oxide production was previously documented, where ALA inhibits lipopolysaccharide-induced NO production in isolated rat Kupffer’s cells and in murine macrophages.( Furthermore, pre-treatment with ALA prevents NO over production.( It has been reported that ALA is able to decrease the synthesis of NO by preventing the upregulation of iNOS.( Another explanation for the reduction of NO level might be due to the direct scavenging effect of NO by the sulphydryl group of ALA.( Moreover, it has been shown that ALA is a very potent protector against peroxynitrite-mediated nitration of L-tyrosine, direct oxidation of glutathione and cellular damage.(

CoQ10 has been considered for improving glycemic control through various mechanisms, including a decrease in oxidative stress.( A study of subjects with type 2 diabetes showed that CoQ10 therapy lowered blood pressure, improved glycemic control with a modest decrement in glycated hemoglobin levels.( In fructose rich diet due to oxidative stress there is generation of free radical which promotes lipid peroxidation. CoQ10 supplementation was associated with significant reduction in thiobarbituric acid reactive substances, malondealdehyde and diene conjugates in coronary artery disease patients.( In present study CoQ10 significantly decreased the lipid peroxidation which may be due to decreased oxidative stress.

Miyazaki et al.( were the first to point to a possible association between ADMA and metabolic pathways. In their cross-sectional study, they found that patients with the worst insulin tolerance had the highest plasma concentrations of ADMA. Lin et al.( proposed possible mechanisms by which high glucose levels, a consequence of insulin resistance, lead to elevated ADMA levels. The initiation of streptozotocin-induced diabetes in rats reduced the activity of dimethylarginine dimethylaminohydrolase (DDAH), which was associated with elevated plasma ADMA levels. Increasing evidence has demonstrated that ADMA, an endogenous NOS inhibitor, is involved in a large number of disorders characterized by endothelial dysfunction.( It is also becoming apparent that DDAH, the metabolizing enzyme for ADMA, has a potential to regulate NO synthesis through the modulation of ADMA level.( In our study, ALA decreased serum NO levels. However, the molecular mechanism of ALA’s effect on NO production and endothelial function is not fully understood. In this study, we demonstrated that ALA decreases ADMA level. A recent study reported that 12-week treatment of ALA in End stage renal disease (ESRD) patients significantly decreased plasma ADMA levels.( Similar to this clinical observation, we demonstrate here that ALA treatment decreased ADMA level. In our study we also observed that CoQ10 administration decreased ADMA level but this is the first report on effect of CoQ10 administration in ADMA levels.

The morphological findings of this study have shown that ultrastructural organization of aorta is disturbed in fructose-induced metabolic syndrome rats. In the current study, various morphological changes in endothelial cells indicate of endothelial injury. Infiltration of lymphocytes in the subendothelial space and edema of smooth muscle cells were observed in fructose rich diet rats. These finding were considered to be early events in the development of the atherosclerotic lesion.( In ALA-administered group, perivascular lymphocytic infiltration was significantly decreased and even disappeared completely as shown in Fig. 5. In CoQ10-administered group edema was relatively mild as shown in Fig. 6; appearances of vessels were almost same with control group.

In conclusion, our findings suggest that the elevation in insulin resistance, plasma levels of ADMA and oxidative stress induced by a fructose diet can be improve by administration of CoQ10 and ALA. The beneficial effects of CoQ10 or ALA can be attributed to its antioxidant activity. The protective effects of CoQ10 and ALA via alterations in the biochemical pathway will be further investigated.