DOI 10.1515/jpem-2013-0337 J Pediatr Endocr Met 2014; 27(7-8): 667–675
Emel Torun*, Selim Gökçe, İlker Tolga Ozgen, Sinem Aydın and Yasar Cesur
Serum paraoxonase activity and oxidative stress and their relationship with obesity-related metabolic syndrome and non-alcoholic fatty liver disease in obese children and adolescents Abstract Objective: Oxidative stress has been reported to be involved in the pathogenesis of metabolic disorders related with obesity. The aim of the study was to investigate the association of oxidative stress and paraoxonase activities with non-alcoholic fatty liver disease (NAFLD) as well as metabolic syndrome. Materials and methods: A total of 109 obese children and adolescents and 44 healthy and lean control subjects were enrolled in the study. According to their ultrasonographic steatosis scores, they were classified into four groups as follows: healthy children; obese, non-NAFLD; obese, grade I-NAFLD; and obese, grade II–III NAFLD. The biochemical parameters and insulin resistance (HOMA-IR) were evaluated from fasting samples. The plasma total antioxidant status (TAS), total oxidant status (TOS), and serum paraoxonase activities were measured and then oxidative stress index (OSI) was calculated as the indicator of degree of oxidative stress. Results: As the steatosis increased, the alanine aminotransferase, C-reactive protein, HOMA-IR, total cholesterol, and LDL cholesterol increased, whereas HDL cholesterol decreased. The TAS measurements were higher in the obese NAFLD group compared with that of the healthy control group. The TOS and OSI measurements did not differ between the groups. Paraoxonase activities increased significantly as steatosis increased. Conclusions: Among the children in this study, no relationship could be demonstrated between obesity with/ without steatosis and oxidant/antioxidant status. Keywords: hepatosteatosis; paraoxonase; total antioxidant stress; total oxidant stress. *Corresponding author: Emel Torun, MD, Department of Pediatrics, Bezmialem Vakif University Hospital, Adnan Menderes Avenue, P.K.: 3409 Fatih, Istanbul, Phone: +0090/212 453-1700, Fax: +0090/212 621-7580, E-mail: dr.emeltorun@gmail Selim Gökçe: Department of Pediatric Gastroenterology, Bezmialem Vakif University Medical Faculty, Istanbul
İlker Tolga Ozgen and Yasar Cesur: Department of Pediatric Endocrinology and Metabolism, Bezmialem Vakif University Medical Faculty, Istanbul Sinem Aydın: Department of Radiology, Bezmialem Vakif University Medical Faculty, Istanbul
Introduction There is a growing interest in the obesity and obesity-related metabolic disorders both in the children and adults. Considerable progress has been made toward understanding the pathogenesis of steatosis and the roles played in the process by insulin resistance (IR), dyslipidemia, hypertension, and metabolic syndrome (MetS). Non-alcoholic fatty liver disease (NAFLD) is a clinico-histopathological entity associated with obesity that is generally recognized as the hepatic manifestation of MetS (1). The factors that determine the presence and extent of necroinflammation are not yet fully understood, although, several possible mechanisms have been theorized. For example, IR has been supposed to play a key role in hepatic steatosis (2). Even oxidative stress has also been supposed to be involved in the pathogenesis of NAFLD (3). Another area of interest which has emerged in recent years is the risk and mechanism of atherosclerosis with regard to MetS in childhood obesity. The MetS is defined as the existence of obesity, IR, glucose intolerance, hypertension, and dyslipidemia (4). Both MetS and obesity-related NAFLD have been shown to impact cardiovascular mortality and morbidity (4). Several reports have indicated that obesity-related MetS and NAFLD may alter oxidative stress, which contributes to atherosclerosis-related cardiovascular events (1). Lipid peroxide-induced damage was supposed to initiate and progress the atherosclerotic lesions, therefore, the enzymes of high-density lipoprotein (HDL) impeding the atherosclerosis are critical for obesity-related cardiovascular events (5). Paraoxonase (PON1) is an HDL-attached, extracellular esterase that contributes to the anti-atherogenic and anti-inflammatory properties of HDL (6). PON1 is also involved in the prevention of lipid peroxidation and
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 10:27 AM
668 Torun et al.: Serum paraoxonase activity and oxidative stress and their relationship with obesity has been associated with diseases characterized by high oxidative stress such as cardiovascular disease and diabetes (7–9). Taking into account the anti-atherogenic and antiinflammatory properties of PON1, its plasma levels might correlate with the oxidative stress and risk of metabolic disturbances in childhood obesity. We aimed to determine the association between PON1 activity, oxidative stress, and obesity-related metabolic abnormalities, inflammation, and steatohepatitis in obese children and adolescents. The present study is the first of its kind which had detected the paraoxonase activity in the obese children and adolescents with non-alcoholic fatty liver disease.
Materials and methods Study population and clinical examinations This study included 109 consecutive obese children and a control group of 44 healthy non-obese children. The study participants were recruited from the Bezmialem Vakif University Pediatric Endocrinology and Metabolism Outpatient Clinic between January 2011 and February 2013. Each participant underwent a detailed physical examination which included anthropometric measurements, the degree of obesity, and systolic and diastolic blood pressure (BP). The children whose obesity was the result of a syndrome problem (Prader Willi, Laurence-Moon Biedl syndrome, etc.) were excluded, as well as those whose obesity had an endocrinal cause such as Cushing’s syndrome or hypothyroidism. Those with systemic disease including cystic fibrosis and inflammatory bowel disease, hepatitis, drug use, history of parenteral nutrition, cigarette use, alcohol use, and family history of hereditary hyperlipidemia, and/or premature atherosclerosis were also excluded. The patients were screened for antibodies against hepatotropic viruses, serum seruloplasmin level, serum α1 antitrypsin level, autoantibodies against nuclear smooth muscle, and liver-kidney microsomal type-1 antigens in order to exclude infectious, metabolic, and autoimmune liver pathologies in patients with steatosis. Obesity is defined as a body mass index (BMI) equal to or greater than the 95th percentile for gender and age, BMI%, and BMI standard deviation (10). Standing height was measured to the nearest 0.1 cm with a Harpenden fixed stadiometer. The body weight (kg) was measured on a SECA balance scale to the nearest 0.1 kg, with each subject dressed in a light T-shirt and shorts. The BMI was calculated by dividing weight by height (kg/m2). The BP was measured three separate times after the children had been sitting for 10 min, and the second and third measurements were averaged. The children with systolic BP and/or diastolic BP > 95th percentile – adjusted for height, age, and gender – were considered to have high BP (11).
Biochemical parameters All the blood analyses were performed on fasting samples in both the study and control groups. Cholesterol, HDL, low density lipoprotein (LDL), and triglycerides (TGs) were measured using the homogenous
colorimetric enzyme technique (Roche, Cobas 8000, Indianapolis, USA). Glucose was measured using the glucose oxidase technique (Siemens Advia 1800, Erlangen, Germany) and insulin levels were analyzed with the direct chemiluminescence technique (Siemens Centaur, USA). The insulin resistance was estimated from fasting plasma measurements using HOMA-IR [insulin (mU/L) × glucose (mmol/L)/22.5] (12). The insulin resistance criteria were HOMA-IR > 2.5 for prepubertal children and HOMA-IR > 4.0 for adolescents (13). The MetS was diagnosed based on a modification of the National Cholesterol Education Program’s Adult Treatment Panel Criteria (14). As the body proportions normally change during the pubertal development and vary according to the individual, waist circumference can be difficult to interpret in the children. For this reason, the BMI was used according to the previously defined criteria. The MetS was defined as the presence of any three of the following five constituent risks: hypertension (elevated BP as systolic or diastolic BP ≥ 95th percentile for age and gender); low HDL cholesterol values ( ≤ 5th percentile for age and gender); hypertriglyceridemia (TGs above the 95th percentile for age and gender); obesity (BMI ≥ 95th percentile for age and gender); and glucose impairment, using pediatric reference standards. According to the criteria reported by the World Health Organization, TGs
Emel Torun*, Selim Gökçe, İlker Tolga Ozgen, Sinem Aydın and Yasar Cesur
Serum paraoxonase activity and oxidative stress and their relationship with obesity-related metabolic syndrome and non-alcoholic fatty liver disease in obese children and adolescents Abstract Objective: Oxidative stress has been reported to be involved in the pathogenesis of metabolic disorders related with obesity. The aim of the study was to investigate the association of oxidative stress and paraoxonase activities with non-alcoholic fatty liver disease (NAFLD) as well as metabolic syndrome. Materials and methods: A total of 109 obese children and adolescents and 44 healthy and lean control subjects were enrolled in the study. According to their ultrasonographic steatosis scores, they were classified into four groups as follows: healthy children; obese, non-NAFLD; obese, grade I-NAFLD; and obese, grade II–III NAFLD. The biochemical parameters and insulin resistance (HOMA-IR) were evaluated from fasting samples. The plasma total antioxidant status (TAS), total oxidant status (TOS), and serum paraoxonase activities were measured and then oxidative stress index (OSI) was calculated as the indicator of degree of oxidative stress. Results: As the steatosis increased, the alanine aminotransferase, C-reactive protein, HOMA-IR, total cholesterol, and LDL cholesterol increased, whereas HDL cholesterol decreased. The TAS measurements were higher in the obese NAFLD group compared with that of the healthy control group. The TOS and OSI measurements did not differ between the groups. Paraoxonase activities increased significantly as steatosis increased. Conclusions: Among the children in this study, no relationship could be demonstrated between obesity with/ without steatosis and oxidant/antioxidant status. Keywords: hepatosteatosis; paraoxonase; total antioxidant stress; total oxidant stress. *Corresponding author: Emel Torun, MD, Department of Pediatrics, Bezmialem Vakif University Hospital, Adnan Menderes Avenue, P.K.: 3409 Fatih, Istanbul, Phone: +0090/212 453-1700, Fax: +0090/212 621-7580, E-mail: dr.emeltorun@gmail Selim Gökçe: Department of Pediatric Gastroenterology, Bezmialem Vakif University Medical Faculty, Istanbul
İlker Tolga Ozgen and Yasar Cesur: Department of Pediatric Endocrinology and Metabolism, Bezmialem Vakif University Medical Faculty, Istanbul Sinem Aydın: Department of Radiology, Bezmialem Vakif University Medical Faculty, Istanbul
Introduction There is a growing interest in the obesity and obesity-related metabolic disorders both in the children and adults. Considerable progress has been made toward understanding the pathogenesis of steatosis and the roles played in the process by insulin resistance (IR), dyslipidemia, hypertension, and metabolic syndrome (MetS). Non-alcoholic fatty liver disease (NAFLD) is a clinico-histopathological entity associated with obesity that is generally recognized as the hepatic manifestation of MetS (1). The factors that determine the presence and extent of necroinflammation are not yet fully understood, although, several possible mechanisms have been theorized. For example, IR has been supposed to play a key role in hepatic steatosis (2). Even oxidative stress has also been supposed to be involved in the pathogenesis of NAFLD (3). Another area of interest which has emerged in recent years is the risk and mechanism of atherosclerosis with regard to MetS in childhood obesity. The MetS is defined as the existence of obesity, IR, glucose intolerance, hypertension, and dyslipidemia (4). Both MetS and obesity-related NAFLD have been shown to impact cardiovascular mortality and morbidity (4). Several reports have indicated that obesity-related MetS and NAFLD may alter oxidative stress, which contributes to atherosclerosis-related cardiovascular events (1). Lipid peroxide-induced damage was supposed to initiate and progress the atherosclerotic lesions, therefore, the enzymes of high-density lipoprotein (HDL) impeding the atherosclerosis are critical for obesity-related cardiovascular events (5). Paraoxonase (PON1) is an HDL-attached, extracellular esterase that contributes to the anti-atherogenic and anti-inflammatory properties of HDL (6). PON1 is also involved in the prevention of lipid peroxidation and
Brought to you by | University of California - San Francisco Authenticated Download Date | 2/17/15 10:27 AM
668 Torun et al.: Serum paraoxonase activity and oxidative stress and their relationship with obesity has been associated with diseases characterized by high oxidative stress such as cardiovascular disease and diabetes (7–9). Taking into account the anti-atherogenic and antiinflammatory properties of PON1, its plasma levels might correlate with the oxidative stress and risk of metabolic disturbances in childhood obesity. We aimed to determine the association between PON1 activity, oxidative stress, and obesity-related metabolic abnormalities, inflammation, and steatohepatitis in obese children and adolescents. The present study is the first of its kind which had detected the paraoxonase activity in the obese children and adolescents with non-alcoholic fatty liver disease.
Materials and methods Study population and clinical examinations This study included 109 consecutive obese children and a control group of 44 healthy non-obese children. The study participants were recruited from the Bezmialem Vakif University Pediatric Endocrinology and Metabolism Outpatient Clinic between January 2011 and February 2013. Each participant underwent a detailed physical examination which included anthropometric measurements, the degree of obesity, and systolic and diastolic blood pressure (BP). The children whose obesity was the result of a syndrome problem (Prader Willi, Laurence-Moon Biedl syndrome, etc.) were excluded, as well as those whose obesity had an endocrinal cause such as Cushing’s syndrome or hypothyroidism. Those with systemic disease including cystic fibrosis and inflammatory bowel disease, hepatitis, drug use, history of parenteral nutrition, cigarette use, alcohol use, and family history of hereditary hyperlipidemia, and/or premature atherosclerosis were also excluded. The patients were screened for antibodies against hepatotropic viruses, serum seruloplasmin level, serum α1 antitrypsin level, autoantibodies against nuclear smooth muscle, and liver-kidney microsomal type-1 antigens in order to exclude infectious, metabolic, and autoimmune liver pathologies in patients with steatosis. Obesity is defined as a body mass index (BMI) equal to or greater than the 95th percentile for gender and age, BMI%, and BMI standard deviation (10). Standing height was measured to the nearest 0.1 cm with a Harpenden fixed stadiometer. The body weight (kg) was measured on a SECA balance scale to the nearest 0.1 kg, with each subject dressed in a light T-shirt and shorts. The BMI was calculated by dividing weight by height (kg/m2). The BP was measured three separate times after the children had been sitting for 10 min, and the second and third measurements were averaged. The children with systolic BP and/or diastolic BP > 95th percentile – adjusted for height, age, and gender – were considered to have high BP (11).
Biochemical parameters All the blood analyses were performed on fasting samples in both the study and control groups. Cholesterol, HDL, low density lipoprotein (LDL), and triglycerides (TGs) were measured using the homogenous
colorimetric enzyme technique (Roche, Cobas 8000, Indianapolis, USA). Glucose was measured using the glucose oxidase technique (Siemens Advia 1800, Erlangen, Germany) and insulin levels were analyzed with the direct chemiluminescence technique (Siemens Centaur, USA). The insulin resistance was estimated from fasting plasma measurements using HOMA-IR [insulin (mU/L) × glucose (mmol/L)/22.5] (12). The insulin resistance criteria were HOMA-IR > 2.5 for prepubertal children and HOMA-IR > 4.0 for adolescents (13). The MetS was diagnosed based on a modification of the National Cholesterol Education Program’s Adult Treatment Panel Criteria (14). As the body proportions normally change during the pubertal development and vary according to the individual, waist circumference can be difficult to interpret in the children. For this reason, the BMI was used according to the previously defined criteria. The MetS was defined as the presence of any three of the following five constituent risks: hypertension (elevated BP as systolic or diastolic BP ≥ 95th percentile for age and gender); low HDL cholesterol values ( ≤ 5th percentile for age and gender); hypertriglyceridemia (TGs above the 95th percentile for age and gender); obesity (BMI ≥ 95th percentile for age and gender); and glucose impairment, using pediatric reference standards. According to the criteria reported by the World Health Organization, TGs
