Paediatric Obesity and Cardiovascular Dysfunction
Condition: Obesity, Childhood; Cardiovascular Diseases
MeSH terms: Cardiovascular Diseases; Obesity; Pediatric Obesity
Study type: Interventional

Summary: 
      Background Childhood obesity has been related to an impaired cardiovascular structure and
      function. Aims of this study will be to evaluate early cardiovascular abnormalities in a
      large population of obese children and adolescents compared with a normal weight counterpart,
      to investigate the potential association with insulin resistance (IR), serum uric acid (sUA),
      metabolic syndrome (MetS), plasmatic markers of inflammation and oxidative stress and
      adipokines, to evaluate changes in cardiovascular dysfunction after 6 and 12 months of a
      behavioral treatment (isocaloric Mediterranean balanced diet plus daily aerobic physical
      activity).

      Subjects and methods This was a single-center case-control study. Eighty obese (OB) subjects
      (6-16 years) and 20 normal weight (NW) matched controls were consecutively recruited. In the
      whole population we will perform an anthropometric and a cardiovascular assessment. OB
      patients will also undergo an OGTT and biochemical evaluations. In the OB group, all these
      evaluations will be performed at baseline and after 6 (T6) and 12 months (T12) of diet plus
      aerobic training.
    

Detailed description: 
      Background Childhood obesity causes a wide range of severe complications, increasing the risk
      of premature morbidity and mortality and raising public-health concerns. In addition, obese
      children are more prone to become obese adults, with higher risk of cardiovascular diseases
      (CVD). A cluster of CVD risk factors has been identified in children as young as 5 years of
      age. Furthermore, among adolescents and young adults, the presence of CVD risk factors
      correlates with asymptomatic coronary atherosclerosis. Childhood obesity has been related to
      an impaired cardiac structure and function.

      Atherogenesis and arterial wall damage begin during childhood and, there is evolving evidence
      that clinical indicators of atherosclerosis such as carotid artery intima-media thickness
      (CIMT), arterial stiffness, and endothelial function are altered in obese children. In
      addition, little is known on the potential association between early cardiovascular
      alterations and metabolic abnormalities in obese children. Metabolic syndrome (MetS) is a
      cluster of features, which includes dyslipidemia, hypertension, and visceral obesity,
      conferring with a higher risk of CVD and type 2 diabetes. Few studies investigated the
      association of MetS with cardiovascular changes during childhood. Hyperuricemia has been
      recognized as a risk factor for CVD in adults with a negative impact on longevity. However,
      data in pediatric age are still lacking and the association between hyperuricaemia and
      cardiovascular abnormalities in obese children is still unknown. Furthermore, obesity is a
      state of chronic low-level inflammation and increased oxidative stress. Oxidative stress
      plays an important role in the pathogenesis of cardiovascular alterations by either
      triggering or exacerbating the biochemical processes accompanying endothelial dysfunction.

      Moreover, adipose tissue acts as a secretory gland, releasing hormones and adipokines with
      pro- or anti-inflammatory activity. Clinical studies of obese adults have observed an
      association between plasma levels of adipokines and markers of inflammation and/or oxidative
      stress. Among various adipokines, adiponectin seems to play an important role. Indeed, in
      contrast to other adipokines which are up-regulated in obesity, secretion of adiponectin is
      markedly reduced in obese subjects. Second, adiponectin seems to exert mainly positive
      activities on metabolism, vascular tone and inflammatory reaction. Consequently, in contrast
      to other adipokines, which circulate in excess in obese subjects and exert unbeneficial
      effects when chronically elevated, deficiency rather than excess of adiponectin is implicated
      in obesity-associated complications. Finally, serum concentration of adiponectin is very high
      in comparison to other hormones and cytokines, which suggests that apart from binding to
      specific high-affinity receptors, this protein may also have some less specific low affinity
      targets. Adiponectin has been associated with endothelial improvement and vascular protection
      through the activation of an endothelial isoform of nitric oxide (eNOS)-related signalling
      and with anti-inflammatory properties and antiatherogenic effects. Thus, an impaired
      production of adipokines may be a key mechanism linking obesity with inflammation and
      oxidative stress. The understanding of these complex mechanisms and the identification of
      possible early markers of cardiovascular damage are therefore necessary in order to establish
      preventive and therapeutic measures in childhood and to decrease cardiovascular morbidity and
      mortality in adulthood.

      Subjects and methods This study is a single-centre longitudinal study. Subjects were
      recruited at Division of Pediatrics, Department of Health Sciences, University of Piedmont
      Orientale, Novara (Italy). The study protocol was in accordance with the ethical guidelines
      of the Declaration of Helsinki and has been approved by the local Ethical Committee. Informed
      written consent was obtained from all subjects and their parents before study. The
      investigators consecutively enrolled 80 Caucasian obese (OB) children and adolescents, aged 6
      to 16 years, and 20 normal weight, age and sex matched controls (NW). NW patients were
      evaluated only at baseline while OB subjects will be evaluated at baseline and after 6 (T6)
      and 12 months (T12) of an isocaloric Mediterranean balanced diet plus aerobic training.

      Assessment in both groups (OB and NW)

      Echocardiographic assessment Transthoracic echocardiogram using a Vivid 7 Pro ultrasound
      scanner (General Electric Healthcare, USA) will be performed by a sonographer and the images
      will be reviewed by an expert pediatric cardiologist, blinded to patients' clinical data.
      Measurements of left ventricle (LV end-diastolic diameter, LVEDD; LV end-systolic diameter,
      LVESD; interventricular septum at end diastole, IVSD; LV posterior wall at end diastole,
      LVPWD) and left atrium diameter (LAD) will be obtained according to established standards.
      The maximum LA volume will be calculated from apical 4- and 2-chamber zoomed views of the LA.
      LV end-diastolic and end-systolic volumes and the LV ejection fraction at rest will be
      computed from 2- and 4-chamber views, using a modified Simpson's biplane method. LV mass
      (LVM) will be derived from the Devereux formula and indexed to body surface area (left
      ventricular mass index [LVMI]). Relative wall thickness (RWT) will be calculated as the ratio
      (LVPWD x 2)/LVEDD. Using pulsed wave Doppler, mitral inflow velocities, peak early diastolic
      velocity (E), peak late diastolic velocity (A), E/A ratio, will be measured.

      Vascular assessment Vascular measurements will be performed with a high-resolution
      ultrasonography (Esaote MyLab25TM Gold, Esaote, Italy) using a 8-megaHertz (mHz) linear
      transducer and a 5 mHz convex transducer for the abdominal aorta, by an expert sonographer
      and images will be then reviewed offline by an expert vascular surgeon blinded to patients
      clinical status. Ultrasonography of the right and left carotid arteries will be performed in
      the supine position with the head turned 45° away from the side being imaged. CIMT will be
      defined as the mean distance from the leading edge of the lumen-intima interface to the
      leading edge of the media-adventitia interface of the far wall, approximately 10 mm distal to
      the common carotid artery. CIMT will be calculated by the average of three measurements
      performed at 0.2 mm intervals.

      The abdominal aortic diameter will be measured at maximum systolic expansion (Ds) and minimum
      diastolic expansion (Dd) at the mid-point between renal arteries origin and iliac carrefour.
      Aortic strain (S) will be calculated using the formula (S = (Ds-Dd)/Dd). Pressure strain
      elastic modulus (Ep) will be calculated from S using the formula (Ep=(Ps-Pd)/S; Ps= aortic
      systolic pressure; Pd= aortic diastolic pressure). Pressure strain normalized by diastolic
      pressure (Ep*), will be calculated using the formula (Ep* = Ep/Pd). While S is the mean
      strain of the aortic wall, Ep and Ep* are the mean stiffness of the aorta. To measure
      brachial artery flow-mediated dilation (FMD), a pneumatic cuff will be placed on the right
      forearm, 2 cm above the antecubital fossa and inflated to a suprasystolic level (300 mmHg)
      for 5 minutes. A continuous Doppler velocity assessment will be obtained simultaneously, and
      data will be collected using the lowest insonation angle (between 30° and 60°). Brachial
      artery diameters, peak systolic velocity (PSV) and end diastolic velocity (EDV) will be
      measured immediately after and 2 minutes after the cuff release and then compared to basal
      values taken immediately before the inflation. The maximum diameter recorded following
      reactive hyperemia will be reported as a percentage change of resting diameter (FMD = peak
      diameter - baseline diameter/baseline diameter).

      Anthropometric variables Height will be measured to the nearest 0.1 cm using a Harpenden
      stadiometer, and body weight to the nearest 0.1 kg using a manual weighing scale. Body mass
      index (BMI) will be calculated as body weight divided by squared height (kg/m2). Waist
      circumference (WC) will be measured at the high point of the iliac crest around the abdomen
      and was recorded to the nearest 0.1 cm. Hip circumference will be measured over the widest
      part of the gluteal region. Pubertal stages will be determined by physical examination, using
      the criteria of Marshall and Tanner. Systolic (SBP) and diastolic (DBP) blood pressure will
      be measured three times at 2-minute intervals using a standard mercury sphygmomanometer with
      an appropriate cuff size. Mean values will be used for the analysis.

      Assessment only in the OB group

      Biochemical variables After a 12-h overnight fast, blood samples will be taken for
      measurement of: glucose (mg/dL), insulin (μUI/mL), total cholesterol (mg/dL), high density
      lipoprotein-cholesterol (HDL-c, mg/dL), triglycerides (mg/dL), sUA (mg/dL), using
      standardized methods in the Hospital's Laboratory. Low density lipoprotein-cholesterol
      (LDL-c) will be calculated by the Friedwald formula. sUA (mg/dL) will be measured by Fossati
      method reaction using uricase with a Trinder-like endpoint.

      OB subjects will also undergo an oral glucose tolerance test (1.75 g of glucose solution per
      kg, maximum 75 g) and samples will be drawn for the determination of glucose and insulin
      every 30 min. Insulin-resistance at fasting will be calculated using the formula of
      homeostasis model assessment (HOMA)-IR. Insulin sensitivity at fasting and during OGTT will
      be calculated as the formula of the Quantitative Insulin-Sensitivity Check Index (QUICKI) and
      Matsuda index (ISI).

      Determination of interleukins (IL), tumor necrosis factor (TNF)α, plasminogen activator
      inhibitor-1 (PAI1), adiponectin and plasmatic markers of oxidative stress IL-8, IL-10, IL-6,
      TNFα, PAI-1, adiponectin, 3-nitrotyrosine, malondialdehyde (MDA), reactive oxygen species
      (ROS) generation, myeloperoxidase (MPO), reduced glutathione (GSH) and superoxide dismutase
      (SOD) will be measured using specific kits. NO will be quantified from blood samples by using
      the Griess reagent.

      Mitochondria morphology and function Mitochondria will be isolated from monocytes.
      Ultrastructural analyses of mitochondria (through transmission electron microscope ZEISS 109)
      will be performed to assess morphologic mitochondrial changes (mitochondrial swelling,
      decrease in matrix density, possible difference in the sub-plasmalemmal and intrafibrillar
      sub-fraction of mitochondria, fission-fusion dynamic mitochondrial propriety, mitophagy).
      Moreover, mitochondria will be used for in vitro assays of mitochondrial oxygen consumption,
      complex I activity (NAD+/NADH), transmembrane potential and mitochondrial dynamic proteins
      expression (fusion and fission ratio through mitofusin 1 and 2 Western blot analysis).

      Time course of measurements in the OB group All the evaluations previously described will be
      performed at baseline and after 6 (T6) and 12 months (T12) of an isocaloric Mediterranean
      balanced diet plus aerobic training.

      Nutritional analysis and interventions A well-trained and experienced clinical paediatric
      endocrinologist will assess food consumption in all subjects and will administer an
      isocaloric Mediterranean balanced diet in OB children. To assess food consumption, foods will
      be divided according to the classic basic food groups by the Italian Institute of Research on
      Food and Nutrition. Food frequencies questionnaires, validated for a wide range of ages, will
      be also completed by parents. The nutritional counselling will be performed at baseline and
      after 6 and 12 months, according to Italian LARN (Livelli di Assunzione di Riferimento di
      Nutrienti) Guidelines and the Italian food pyramid.

      Moreover, obese subjects will undergo an exercise training regimen. Exercise will be
      conducted daily and will consist of 60 minutes of aerobic physical activity. Parents will
      record every day, on a specific questionnaire, the training performed.
    

Intervention name(s): diet plus physical activity
Intervention type(s): Behavioral
Intervention description(s): OB subjects will undergo an isocaloric Mediterranen balanced diet plus a daily aerobic training for at least 60 minutes. All the evaluations will be performed at baseline and after 6 and 12 months of this behavioral therapy. To assess food consumption, foods will be divided according to the classic basic food groups by the Italian Institute of Research on Food and Nutrition. Food frequencies questionnaires, validated for a wide range of ages, will be also completed by parents. Physical activity will be recorded by parents daily on a specific questionnaire.
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Intervention model description: Only one group, the obese children group (OB) will be followed for one year. At baseline they received a behavioral intervention which comprises a Mediterranean balanced diet plus daily aerobic training.
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: paediatric obesity; cardiovascular dysfunction; metabolic syndrome; adipokines; inflammation; oxidative stress