Fat cell size, insulin sensitivity, and inflammation in obese children
ABSTRACT To assess the association between adiposity indexes (body mass index [BMI], fat mass, adipocyte size) and circulating inflammation markers with known metabolic relevance or insulin sensitivity in overweight/obese children.
Twenty-eight children (males/females: 13/15) with different degrees of overweight (BMI z-score: 1.64-3.1; fat mass: 14.1-49.8 kg) were studied. BMI, body composition (dual-energy x-ray absorptiometry scanning), subcutaneous adipocyte diameter (needle biopsy of subcutaneous abdominal fat), blood tumor necrosis factor-alpha and interleukin-6 concentrations and insulin sensitivity (frequently sampled intravenous glucose tolerance test) were assessed.
Adipocyte diameter, more than BMI and fat mass, was significantly associated with interleukin-6 (r = 0.62, P < .001) and tumor necrosis factor-alpha (r = 0.61, P < .001). Moreover adipocyte size was associated with insulin sensitivity (R2 = 0.15, F = 4.69, P = .04) independently from fat mass.
Adipocyte size is a factor linked to both inflammation and insulin resistance in overweight/obese children. This is similar to the findings in adults and lends support to the tenet that the earlier obesity ensues, the more severe the biologic consequences may be.
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ABSTRACT: Androgens regulate body composition in youth and declining testosterone that occurs with aging is associated with muscle wasting, increased fat mass and osteopenia. Transgenic mice with targeted androgen receptor (AR) over-expression in mesenchymal stem cells (MSC) were generated to explore the role of androgen signaling in the regulation of body composition. Transgenic males, but not females, were shorter and have reduced body weight and visceral fat accumulation. Dual-energy X-ray absorptiometry (DXA) revealed significant reductions in fat mass with a reciprocal increase in lean mass, yet no difference in food consumption or locomotor activity was observed. Adipose tissue weight was normal in brown fat but reduced in both gonadal and perirenal depots, and reduced hyperplasia was observed with smaller adipocyte size in visceral and subcutaneous white adipose tissue. Although serum leptin, adiponectin, triglyceride, and insulin levels were no different between the genotypes, intraperitoneal glucose tolerance testing (IPGTT) showed improved glucose clearance in transgenic males. High levels of the AR transgene are detected in MSCs but not in mature fat tissue. Reduced fibroblast colony forming units indicate fewer progenitor cells resident in the marrow in vivo. Precocious expression of glucose transporter 4 (GLUT4), peroxisome proliferator-activated receptor γ (PPARγ), and CCAAT enhancer-binding protein α (C/EBPα) was observed in proliferating precursor cultures from transgenic mice compared to controls. In more mature cultures, there was little difference between the genotypes. We propose a mechanism where enhanced androgen sensitivity can alter lineage commitment in vivo to reduce progenitor number and fat development, while increasing the expression of key factors to promote smaller adipocytes with improved glucose clearance.Journal of Cellular Biochemistry 07/2011; 112(7):1773-86. DOI:10.1002/jcb.23098 · 3.37 Impact Factor
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ABSTRACT: The impact of obesity as a systemic low-grade inflammatory process has only partially been explored. To this effect, 704 community-based school-aged children (354 obese children and 350 age-, gender-, and ethnicity-matched controls) were recruited and underwent assessment of plasma levels of fasting insulin and glucose, lipids, and a variety of proinflammatory mediators that are associated with cardiometabolic dysfunction. Obese children were at higher risk for abnormal HOMA and cholesterol levels. Furthermore, BMI z score, HOMA, and LDL/HDL ratio strongly correlated with levels of certain inflammatory mediators. Taken together, obesity in children is not only associated with insulin resistance and hyperlipidemia, but is accompanied by increased, yet variable, expression of markers of systemic inflammation. Future community-based intervention and phenotype correlational studies on childhood obesity will require inclusion of expanded panels of inflammatory biomarkers to provide a comprehensive assessment of risk on specific obesity-related morbidities.International Journal of Pediatrics 01/2010; 2010(1687-9740):846098. DOI:10.1155/2010/846098