Short communicationAssociation between some endocrine-disrupting chemicals and childhood obesity in biological samples of young girls: A cross-sectional study
Introduction
Overweight and obesity are defined by the WHO (World Health Organization) as abnormal or excessive fat accumulation that presents a risk to health. Obesity has dramatically increased worldwide in recent decades, becoming a major global health concern. Like adults, the prevalence rate for child and adolescent obesity has increased all over the world. Childhood obesity increased from 7% in 1980 to nearly 20% in 2008 in the United States, and increased from 5.8% in 1997 to 9.7% in 2005 in Korea (Oh et al., 2008). Obesity is a complex disease for which no single cause or cure exists. Obesity is most likely caused by a complicated interaction between genetic, behavioral, and environmental factors. However, the most common causes are overeating, lack of physical activity and genetic susceptibility (Ogden et al., 2012, Tang-Peronard et al., 2011). One environmental factor that has been receiving attention recently is the contribution of endocrine-disrupting chemicals (EDCs) such as phthalates, bisphenol A and alkylphenols to the high prevalence of obesity. Endocrine-disrupting chemicals (EDCs) interfere by mimicking, blocking, or altering hormones and endocrine systems. Children are more vulnerable than adults to the effects of EDCs (Tang-Peronard et al., 2011).
Phthalates are industrial chemicals used in many consumer products, such as children's toys, baby powder, food packaging, and building materials. Phthalates have anti-androgenic effects in animal experiments, and some phthalate activities are dependent on PPARs, which are receptors that regulate the development and maturation of adipogenesis (Hatch et al., 2010). Animal and human data have detected an association between phthalates-, such as MEP, and increasing obesity and body size (Hatch et al., 2008). Bisphenol A (BPA) and alkylphenols (APs) are the industrial chemicals that have received much attention due to their high production and extensive usage. BPA is used in the production of polycarbonate plastic and epoxy resins and is also found in baby bottles, microwave ovenware and the inner coating of cans for food and beverages. BPA acts as an androgen receptor antagonist and, in combination with insulin, accelerates adipocyte formation (Braun et al., 2009, Shankar et al., 2012). In rodents, exposure to low doses of BPA leads to obesity and high lipid levels in utero (Honma et al., 2002). Limited human data have suggested a positive association between BPA exposure and obesity (Trasande et al., 2012, Wang et al., 2012). Alkylphenols are the nonionic surfactants widely used in industry. The compound 4-nonlyphenol (4-NP) has been investigated to determine whether there is an association with adipocytes in vitro, and perinatal exposure to 4-NP showed an increase in body weight and fat mass. The compound 4-NP also activated PPARγ and its target genes in adipose tissue. A few studies have suggested that the increase in body weight was associated with developmental exposure to some estrogenic chemicals (Lopez-Espinosa et al., 2009, Masuno et al., 2003). The compound 4-tert-octylphenol (t-OP), an alkylphenols, is also a known estrogenic chemical together with 4-nonylphenol and BPA.
In this study, we examined the association between obesity classified by BMI and EDCs which was suspected as one of the causes of obesity in young girls. We also examined the change in the levels of endogenous steroids which were expected to be associated with EDCs.
Specially, we selected only the young girls in this experiment and examined the effects of EDCs to estrogen. 7 Phthalates [mono-ethyl (MEP), di-n-butyl (DBP), mono-n-butyl (MBP), di-2-ethylhexyl (DEHP), mono-2-ethylhexyl (MEHP), mono-benzyl (MBzP) phthalate, phthalic acid (PA)], bisphenol A, and 2 alkylphenols [4-nonylphenol (4-NP) and 4-tert-octylphenol (t-OP)], all of which are endocrine-disrupting chemicals, were assayed and measured in terms of their levels in the urine and serum of a control group and an obese group. And endogenous steroids were dehydroepiandrosterone (DHEA), androsterone (A), estrone (E1), dihydrotestosterone (DHT), epitestosterone (epi-T), testosterone (T), estradiol (E2), progesterone (P) and estriol (E3).
Section snippets
Instruments and equipments
A GC/MS instrument consisting of a 6890 gas chromatograph (GC) and a 5975 mass selective detector (MSD) from Agilent Technologies (Palo Alto, CA, USA) was used to detect the target compounds. The column for the GC was an Ultra-1 (50 m × 0.2 mm i.d., 0.11 μm film thickness). Distilled water was purified through a Milli Q water system (Millipore; Billerica, MA, USA). An HS501D shaker from IKA (Staufen, Germany) was used to mix the samples and the organic solvents. A Varifuge-F system from Heraeus
Validation of analytical assays of the target compounds
The experimental method for analyzing the urine and serum samples was validated in terms of precision, recovery and reproducibility using GC/MS. For this investigation, 3 different concentrations were used (n = 5). In the case of the EDCs, DEHP and MBzP were used at a concentration of 5, 50 and 100 ng/mL, and the others were used at concentrations of 2, 20, and 100 ng/mL. Endogenous steroids were used at a concentration of 1, 10 and 50 ng/mL. The recovery rates of the EDCs were 83.18% (20 ng/mL of
Conclusion
We studied the association between childhood obesity and endocrine-disrupting chemicals that were detected in urine and serum. PA in urine showed a statistically significant relationship to childhood obesity. MEP, DBP and PA in serum showed a statistically significant relationship to childhood obesity. We concluded that these substances can affect the development of obesity. In the case of endogenous steroids, DHEA (p = 0.012), in particular, showed a statistically significant difference in serum
Conflict of interest
Nothing declared.
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