Relationship Between Obesity and 8-hydroxy-2-deoxy Guanosine as an Oxidative Marker in Obese Adolescents of Giza
Nayera Elmorsi Hassan,
Salwa el Zayat,
This study was conducted to assess the relationship between obesity markers (Body mass index (BMI), fat percentage) and DNA oxidation marker 8-hydroxy-guanosine (OHG) , as a predictor for future clinical problems in obese adolescents of Giza. The study was conducted on 103 adolescents aged 13-18 years (22 boy, 81 girl). BMI was calculated as body weight (kg) divided by height (m2) squared and obesity was defined as BMI of 95 percentile. Fat percentage was determined by using Biological impedance technique. Oxidative stress markers as 8- hydroxyl guanosine, superoxide and glutathione were measured. The adolescents were divided according to BMI into two groups. Group I with BMI >95 percentile and less than 97 percentile (obese) and Group II with BMI >97 percentile (severely obese). Significant differences were detected between the two groups (Group I and II) of the study as regard obesity markers (BMI, fat%) and oxidative stress markers (lipid oxidation, superoxide dismutase enzyme activity, glutathione peroxidase enzyme activity, 8-hydroxyl guanosine) (p<0.0005). Significant positive correlations were detected between obesity markers and oxidative stress markers among adolescent severely obese cases (group II). Obesity is highly associated with states of oxidative stress in adolescents, with elevated levels of oxidative stress markers, with a positive relation with 8-hydroxy-guanosine and obesity markers and other oxidative markers, suggesting that this marker might play an important role in the prediction of future development of some clinical diseases.
to cite this article:
Amany Elwakkad, Nayera Elmorsi Hassan, Hiba Sibaii, Salwa el Zayat, Lobna Sherif, Enas-R-Abdel Hameed and Azza-Abdel Shaheed, 2011. Relationship Between Obesity and 8-hydroxy-2-deoxy Guanosine as an Oxidative Marker in Obese Adolescents of Giza. Journal of Medical Sciences, 11: 231-235.
Received: August 01, 2011;
Accepted: October 14, 2011;
Published: December 07, 2011
Oxidative stress has been defined as an elevation in the steady state concentration
of various Reactive Oxygen State species (ROS) on a cellular level, such as
the hydroxyl radical (OH), super oxide anion radical and the nitric acid radicals
(Guilder et al., 2006). Antioxidants defense
mechanisms begin to work by preventing ROS formation and their induced damage
through a number of enzymatic and non-enzymatic systems. Under normal physiological
conditions, there is a balance maintained between endogenous oxidants and antioxidants,
when imbalance occurs, through the excessive generation of oxidants or a decrease
of antioxidants, this abnormal oxidant system then enters what is called oxidative
stress (Di Renzo et al., 2010). Various markers
of oxidative damage have been identified (Keaney et al.,
2003), the most popular markers designed for lipid peroxidation, were malondialdehyde
(MDH) and oxidized low density lipoprotein (ox LDL). Recently 8-hydroxy-2-deoxy
guanosine (8-oH-2-deoxy Guanosine) (8-OH-dG) emerged as a marker for oxidative
stress and acts as a reliable biomarker for DNA oxidative damage (Taylor
et al., 2010). Excess weight has a great impact on the health and
quality of life of individuals. Obesity is reported to be associated with hypertension
and elevated serum levels of total and -LDL-cholesterol. It is also a risk factor
for diabetes mellitus (Paek and Chun, 2010), cardiovascular
diseases, (Guilder et al., 2006) and certain
neoplasm such as colorectal cancer (Furukawa et al.,
2004). The exact mechanisms are not well understood, some studies have provided
evidence that obesity could contribute to oxidative stress (Keaney
et al., 2003). In the present study we aim to determine the relation
between the degree of obesity and 8- hydroxy-2- deoxy guanosine as a marker
of oxidative stress in obese adolescents of Giza.
MATERIALS AND METHODS
This study was conducted by a team from the National Research Center, Egypt, to estimate the prevalence of obesity and metabolic syndrome among school children and adolescents and the potential risk factors for these diseases. It was a cross-sectional survey. Four local public schools situated in Giza governorate were included in the study). The study was performed during the period of October 2007 to April 2009. Permission to perform the study was granted by the Ministry of Education and the protocol was approved by the Ethical Committee of the National Research Centre. Of the total sample, one hundred and three obese adolescents meet the inclusion criteria (22 boys and 81 girls), were included in the current research after obtaining written informed consent from their parents. Adolescents assent was also obtained.
The participated adolescents must meet the following inclusion criteria: age
from 13-18 years and Body Mass Index (BMI) greater than the 95 percentile for
age and gender based on the CDC Charts (Uhegbu et al.,
Adolescents were excluded if they had major illness, specially, type 1 or 2 diabetes, under medications or had a condition known to influence body composition, or insulin action (e.g., glucocorticoid therapy, hypothyroidism and Cushings disease).
Each adolescent underwent a complete physical examination, including anthropometric measures. Height was measured to the nearest 0.5 cm on a Holstein portable anthropometry and weight was determined to the nearest 0.1 kg on a Seca Balance with the subject dressed minimum clothes and no shoes.
Body Mass Index (BMI) was calculated as weight (in kilograms) divided by height (in meters squared). Fat% was measured using Holten Body composition analyzer.
Each measurement was taken as the mean of three consecutive readings following
the recommendations of the International Biological program Hiernaux and (Hiernaux
and Tanner, 1969). Human Cu/Zn SOD activity was estimated in serum by using
Enzyme-linked immuno-sorbent assay ELISA kit produced by Bender Med system GmbH,
Austria, Europe, the limit of detection (sensitivity) was determined to be 0.04
Glutathione peroxidase activity was estimated in erythrocyte lysate by using ELISA kit produced by Bender Med system GmbH, Austria, Europe, the limit of detection (sensitivity) was determined to be 0.04 mg mL-1.
8-hydroxy-2-deoxyguanosine (8-oH-2-dG) was measured by using Enzyme-linked immuno-sorbent assay ELISA kit, which is fast and sensitive competitive immunoassay for the detection and quantitation of 8-oH-2-dG in serum from Biovender. The inter-assay coefficient of variation of stressgen 8-oH-2-dG ELISA has been determined to be <10%, where the intra-assay coefficient of variation was determined to be <10%.
Lipid peroxidation was determined by using Lipid Peroxide (LPO) assay kit catalogue number 705003 from cayman chemical company. The dynamic range of the kit was 0.25-5 nmol hydroperoxide per assay tube.
The participated adolescents were divided into two groups according to BMI
percentile: Group I: with BMI >95 percentile and less than 97 percentile
which include 6 boys and 33 girls, GroupII: with BMI >97 percentile which
include 16 boys and 48 girls (Uhegbu et al., 2012).
Statistical analysis: All subjects values were recorded and tabulated in excel sheets for Microsoft offices xp. SPSS 9.0 was used for analysis of the variables. Quantitative variables were expressed by mean and Standard Deviation (SD). Comparison between group I and group II was done using t-student test. In all tests p-value was considered significant when less than 0.05 and highly significant when less than 0.01. Pearson correlation well used for correlation between different variables.
Body Mass Index percentile (BMI) 97.92±0.64 and fat percentage (fat
%) 44.38±6.76 (markers of obesity), were increased in group II versus
group I with a high significant difference (p>0.0005) (Table
|| Markers of obesity in the two groups
|Results are expressed as Mean±SD
|| Markers of oxidative stress in the study groups
|Results are expressed as Mean±SD
||Correlations between obesity and oxidative stress markers
among group II, with referring to correlation between lipid per oxidation
and other stress markers
|| Effects of Gender on levels of 8-hydroxyl Guanosine
As regard oxidative stress markers, all oxidative stress markers used in this
study were highly increased in group II over group I with highly significant
difference (p<0.0005) (Table 2). Correlations between obesity
markers (BMI and Fat %) and oxidative stress markers (GPx, SOD, 8-oH-2-dG) among
group II (severely obese adolescents) were discussed in Table
3. A highly positive correlation between BMI and 8-oH-2-dG (r = 0.886),
SOD (r = 0.939) and GPx (r = 0.931), respectively were detected. Fat % as one
of the obesity markers also, showed a high positive correlation with 8-oH-2-dG
(r = 0.788), SOD (r = 0.788) and GPx, (r = 0.889).
The fourth parameter of oxidative stress, lipid per oxidation level was significantly correlated to 8-hydroxyl guanosine (r = 0.891), to super oxide dismutase activity (r = 0.874) and to glutathione peroxidase activity (r = 0.784), respectively (Table 3). Our data revealed l6 out of 22 (88%) obese male adolescent with mean level of serum 8-oH-2-dG (8.83±2.36) compared to 48 (60%) out of obese female adolescent with 8-oH-2-dG (6.93±0.11) with p<0.05 (Table 4).
Obesity is defined by the Body Mass Index (BMI) and Fat % was used for the
measure of the degree of body fatness (Wang et al.,
2008). Various markers of oxidative damage have been identified. The most
popular markers were designed for lipid peroxidation, such as Malondialaldehyde
(MDA), oxidized LDL (ox LDL) (Channon and Guzik, 2002).
Recently 8-hydroxy-2-deoxy guanosine has been emerged as a marker for oxidative
DNA damage (Fruebis et al., 2001). The latter
results from reaction between hydroxyl radical and guanine and acts as reliable
biomarker for oxidative damage of DNA (Matsuzawa et al.,
The estimation of the degree of oxidative damage and antioxidant status, in obese
patients, by appropriate techniques appears to be of interest. Increased oxidative
stress and activated antioxidant defense mechanisms, were clearly seen in this
study, where the markers of oxidative stress
represented by 8-hydroxy-2-deoxy
guanosine, showed significant increase in the higher obese (BMI>97 percentile)
group compared to the obese (BMI<97 percentile) one. These findings support
the results of the study of Karaouzene et al. (2011)
as they concluded that the oxidative stress
markers levels are elevated in human
obesity as well as, the markers of antioxidant defense mechanisms represented
by the activity of Glutathione Peroxidase (GPx) and the Superoxide Dismutase (SOD)
which showed the same significance. Our results clearly showed systemic oxidative
damage of DNA associated with sufficient or increased defense mechanisms against
ROS which has been already present in obese children and adolescents. In the current
study, group II where found to have significantly higher mean of serum 8-hydroxy
-2- deoxy guanosine level compared to group I. This finding, was consistent with
that reported by Wiegand et al. (2010)
that elevated 8 -hydroxy-2-deoxy guanosine among obese. Our finding confirmed
that measuring 8-OHG is a novel convenient method for evaluating oxidative DNA
damage which may contribute to development of future diseases.
In addition, our result revealed high level of 8-hydroxy-2-deoxy guanosine
in boys more that in girls obese adolescent, this gender effect was in reverse
to that of Keaney et al. (2003) who found high
prevalence of oxidative stress markers among females more than in males and
also of that reported by Paek and Chun (2010) While
this finding supports the result of Taylor et al.
(2010) on the gender effect on oxidative stress markers. Our findings confirmed
that, the 8-hydroxy-2-deoxy guanosine is a reliable method for evaluating oxidative
DNA damage in obese person.
Association between obesity markers and oxidative stress markers have been
reported in this work as significant positive correlations among obese cases
(Table 3) these results are identical to those of Ostrow
et al. (2011) in which, they concluded that oxidative stress is correlated
with adiposity. The mechanism of such relations between obesity and oxidative
stress are unclear. Even if several theories have been proposed (Furukawa
et al., 2004) it has been suggested that oxidative stress in obesity
may result, partially, from the accumulation of triglycerides (Ostrow
et al., 2011). Specifically, intra cellular triglycerides are supposed
to elevate super oxide radical generation within the electron transport chain
by inhibiting the mitochondria adenosine nucleotide transporter (Bakker
et al., 2000). The inhibition of this transporter leads to a diminution
in intra-mitochondrial Adenosine Diphosphate (ADP), that in turn, reduces the
proton flux through the adenosine triphosphate- synthetics reaction (Berg
et al., 2002).
As a conclusion present findings confirmed that measuring 8- OHG is a novel
convenient method for evaluating oxidative DNA damage which may contribute to
development of future diseases. Biochemical investigations aimed at promptly
detecting the danger of an oxidative imbalance and restoring antioxidant reservoir
for triggering the irreversible damage cascade and thus mandatory, they should
be performed in the future as routine and repeated along the treatment plan
to monitor the efficacy of antioxidants compounds. We can't exclude, in the
future, that an oxidative status check-up followed by immediate targeted treatment
will achieve better social health perspectives, especially preventing major
illness and heavier social cost burden.
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