Oxidative Stress and Biochemical Parameters in Childhood Obesity

  

    
Factors
    
Gender
    
History of CVD
    
Sedentary lifestyle
    
Breastfeeding
  
  

    
 
    
Female
      
(n=12)
    
Male
      
(n=19)
    
Yes
      
(n=12)
    
No
      
(n=19)
    
Yes
      
(n=20)
    
No
      
(n=11)
    
Yes
      
(n=19)
    
No
      
(n=12)
  
  

    
 
    
 
    
 
    
 
    
 
    
 
    
 
    
 
    
 
  
  

    
Factor 1
    
-0,53±1,65
    
0,33±1,52
    
-0,04±1,49
    
0,02±1,71
    
0,19±1,63
    
-0,35±1,57
    
0,16±1,54
    
-0,26±1,74
  
  

    
p*
    
0,161
    
0,921
    
0,370
    
0,496
  
  

    
Factor 2
    
0,85±0,87
    
-0,53±1,11
    
0,13±1,65
    
-0,08±0,88
    
0,15±1,21
    
-0,27±1,24
    
0,19±1,16
    
-0,30±1,29
  
  

    
p*
    
0,001
    
0,678
    
0,368
    
0,295
  
  

    
Factor 3
    
-0,08±1,06
    
0,05±1,16
    
-0,25±0,791
    
0,16±1,26
    
-0,08±1,22
    
0,15±0,907
    
0,31±1,09
    
-0,49±0,31
  
  

    
p*
    
0,748
    
0,275
    
0,562
    
0,047
  
  

    
*T test;    Factor 1: Increase or decrease the levels of TC, LDLc, TG and VLDL-c; Factor    2: increased levels of TC and LDLc and reduced MDA, TG and VLDL-c or vice    versa; Factor 3: increased levels of LDLc and reduced levels of HDLc or vice    versa. TC: total cholesterol; LDLc: fraction of cholesterol low-density    lipoprotein; HDLc: cholesterol fraction of high-density lipoprotein; VLDL-C: fraction    of cholesterol and very low-density lipoprotein; TG: triglycerides; CVD:    cardiovascular disease; p:    significance level 
  

Table 4: Correlation of the major components identified as factors 1, 2 and 3 and the personal history of eutrophic group in both genders.

Discussion

This study confirms the association between obesity and high levels of TG and VLDL-c and oxidative stress in childhood, in positive correlation with MDA levels. The current epidemic of obesity among children has increased the need for health professionals to know risk factors for CVD and implement changes aimed at preventing this disease or early clinical intervention5. Admittedly, childhood obesity is a complex disease with different genetic components; metabolic, environmental and behavioral factors are interrelated, making it difficult to define the causal pathways.

Although recognized that atherosclerosis develops in childhood, the determinants of this preclinical phase still remain unclear. Freedman et al. [13] in a study of students between 5 and 17 years of age found that overweight individuals were more likely to present altered concentrations of CT and its fractions and TG.

In this study, the altered concentrations of TC and LDLc were more frequent in females, corroborating other studies that confirm higher frequency of high levels of TC in girls (37.5 and 32.2%) compared to boys (32.4 and 29.2%) [14]. Risk factors for obesity modify up according to age and may depend on the timing of sexual maturation, differences in locations, sample size and cultural or socioeconomic causes [14,15].

In relation to nutritional status in this study, children with obesity had higher concentrations of VLDL-c and TG compared to normal weight children. Moreover, obese male children showed higher frequency of high levels of LDLc to the controls of the same sex, corroborating with a Brazilian study, which showed that 50% of overweight boys had undesirable levels of LDLc [9]. Although the present study did not show difference in CT concentrations between groups, Friedland et al. [16] found TC and TG concentrations higher in obese compared with eutrophic; however does not detect the degree of obesity effect in the lipid profile, whereas a BMI between 85 and 95 % compared to values above 95%. However, controversy is a causal relationship between obesity and hypercholesterolemia, being relatively common observation of individuals with severe obesity and desirable concentrations of CT [17].

In this study there was no difference of LDLc and HDLc concentrations between groups with obesity and normal weight. However, Lamb et al. [18], in the analysis of risk factors for clinical and metabolic complications among adolescents with obesity, highlighted lower levels of HDL-c in obese compared with nonobese, results in agreement with other studies [8,17].

It was observed in this study, higher concentrations of MDA in children with obesity compared to normal weight, corroborating studies in Brazilian17 and Spanish children [19]. In contrast, reduced MDA values were observed in a study of children with severe obesity compared to normal children [20]. Lima et al. [9] also observed that high concentrations of MDA are more prevalent in males, contrasting with the findings of this study, which revealed a similarity of MDA concentrations between the genders.

This study showed MDA values within the desirable limit in normal children, disagreeing with the findings of Lima et al. [9]. MDA is one of the most abundant aldehydes resulting from tissue lipid peroxidation, enabling the indirect analysis of the resulting oxidative damage of lipid peroxidation [19]. Obesity in children has been linked to increased oxidative stress, which favors the development of comorbidities [8]. Previous studies have shown that the degree of childhood obesity is closely related to cardiovascular morbidity in the adult21. Adverse cardiovascular outcomes are more likely when several risk factors are present. Recently, it has been suggested that an evaluation of the oxidative state can help to identify patients at increased risk for subsequent cardiovascular and metabolic complications [22].

Targets phospholipids on the particle surface of LDLc, and lipid particle and internal proteins are exposed to oxidation with consequent formation of oxidized LDL (oxLDL) and accumulation of byproducts such as MDA [23], which is often used as a marker oxidative stress. In this context, it is disturbing the findings of this study showing the high frequency of children with increased levels of LDLc in the groups with (31.4%) or without obesity (22.6%), although the average levels of LDLc in both groups remained in the desirable limit.

Further, the BMI is associated not only with increased oxidative stress, but also with high systemic inflammation and activation of the coagulation cascade [24,25]. The elevation of coagulation factors and, therefore, blood hypercoagulability may be associated with hypertriglyceridemia [24]. This confirms the importance of controlling TG levels in childhood, especially children with obesity that in the present study showed increased concentrations of TG, considered an independent risk factor for CVD in positive correlation with levels of VLDL-c and MDA.

The main cause of increased oxidative stress in individuals with obesity is not yet fully elucidated. The Framingham Heart Study [26] confirms the association between markers of this process and BMI and waist / hip ratio, adiposity is the main factor, suggesting that higher fat mass also determines greater degree of oxidative stress [27]. Other factors in addition to oxidative stress should be highlighted for obesity. In this study, multivariate principal component analysis identified the association between changes in the lipid profile and MDA and the correlation with sex, sedentary lifestyle, breastfeeding and familial history of CVD. Thus it was possible to identify the profile of children with and without obesity. In this context, it is possible that exercise, in addition to power, influencing the total body fat by their effect on fat tissue and intracellular TG, can reduce systemic inflammation and oxidative stress [19,27], in order that adipocytes produce cytokines that stimulate the oxidative pathway [27].

In this study, considering the equivalent factors the combinations of variables was also related to breastfeeding, suggesting greater protection against oxidative stress and cardiovascular disease in children with obesity. Thus, it is likely that exclusive breastfeeding for more than four months is associated with slower weight gain during the second semester of the first year, which could be part of the reason behind the reduced risk of later overweight or obese [28]. There is also evidence that breastfeeding provides likely beneficial effects on blood pressure and blood cholesterol levels in adulthood [28].

Given the association between obesity, cardiovascular disease and family history of CVD in this study as well as in clinical studies in general, these data were recorded based on the parent information, becoming a limiting factor in the data analysis. The potential risk factor for child becoming obese, with consequent chronic complications, is the sum of genetic influences and environmental factors such as eating habits and family lifestyle [13]. The literature is scarce in relation to the prevention studies involving obesity, dyslipidemia and markers of lipid peroxidation, especially in children and adolescents [9,10,19]. Weight loss programs, including diet and physical activity should be encouraged in childhood to reduce the risk admittedly increased cardiovascular diseases.

In conclusion, data from this study shows that high levels of TG and MDA are associated with obesity in childhood, increasing the risk for CVD in men with also increased levels of LDLc. Moreover, in females, increased age is related to higher degree of obesity, suggesting that controlling for BMI may delay the manifestation of CVD and that for normal weight children to breastfeeding history associated with high levels of HDL-c, suggests its protective effect for CVD. Like other authors [8], we suggest that pediatricians should be aware of the importance of assessing the degree of oxidative stress in children with obesity in an attempt to reverse this condition as soon as possible and thereby preventing the development of comorbidities.

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