Retinol binding protein 4 is associated with adiposity-related co-morbidity risk factors in children.

OBJECTIVE: In adults, elevated levels of retinol binding protein 4 (RBP4) have been associated with biochemical markers of adiposity-related co-morbidities including insulin resistance, dyslipidemia, hypertension, and abdominal obesity. This study examined the relationship between RBP4 and risk factors for co-morbidities of adiposity in a population of ethnically diverse children in early- to mid-adolescence in the public school system of New York City. MATERIALS/METHODS: We analyzed anthropometric (body mass index, % body fat, waist circumference), metabolic (lipids, glucose), and inflammatory (TNF-alpha, interleukin-6, C-reactive protein, adiponectin) markers for adiposity-related co-morbidities and serum alanine aminotransferase (ALT) in 106 school children (65 males, 41 females) 11-15 years of age (mean +/- SD = 13.0 +/- 0.1 years) who were enrolled in the Reduce Obesity and Diabetes (ROAD) project. Insulin sensitivity was assessed by quantitative insulin sensitivity check index. Insulin secretory capacity was measured as acute insulin response and glucose disposal index. RESULTS: Serum RBP4 was significantly correlated directly with ALT, triglycerides, and triglyceride z-score, and inversely correlated with adiponectin. Correlations with ALT and adiponectin remained significant when corrected for % body fat, age, and gender. There were significant ethnic differences in the relationship of RBP4 to ALT, glucose disposal index and adiponectin. CONCLUSIONS: In early- to mid-adolescents, circulating concentrations of RBP4 are correlated with multiple risk factors for adiposity-related co-morbidities. The observation that many associations persisted when corrected for % body fat, suggests that RBP4 can be viewed as an independent marker of adiposity-related co-morbidity risk in children.

Utility of early insulin response and proinsulin to assess insulin resistance.

OBJECTIVE: To determine whether obesity and premature adrenarche are additive events increasing the risk of insulin resistance and beta-cell failure, using early insulin response (EIR) or the insulinogenic index and proinsulin (PI) as markers. STUDY DESIGN: This was a prospective case-control study conducted at a tertiary care academic medical center involving 81 prepubertal, predominantly Hispanic children (34 males, 47 females), classified as lean controls (4 males, 6 females; mean age, 6.5 +/- 1.2 years; mean body mass index [BMI] z-score, 0.08 +/- 0.6), obese controls (20 males, 10 females; mean age, 7.2 +/- 1.5 years; mean BMI z-score, 2.5 +/- 0.5), lean premature adrenarche (3 males, 11 females; mean age, 7.1 +/- 1.2 years; mean BMI z-score, 0.09 +/- 0.6), and obese premature adrenarche (7 males, 20 females; mean age, 7.3 +/- 1.0; mean BMI z-score, 2.2 +/- 0.4). Fasting glucose (G(0)), insulin (I(0)), PI(0), androgen levels, insulin-like growth factor 1, insulin-like growth factor binding protein 1, and lipid levels were obtained. An oral glucose tolerance test was performed. EIR was calculated as (I(30) - I(0))/(G(30) - G(0)). Between-group differences were assessed by 2-way analysis of variance, with interactions and associations explored with correlation/regression. RESULTS: EIR was greater in the obese subjects with and without premature adrenarche. Combined analysis of the independent variables obesity and premature adrenarche showed that the obese premature adrenarche group had the highest EIR. The obese subjects with premature adrenarche had greater fasting PI levels than their lean counterparts. The differences in fasting PI/I ratio among the groups were not statistically significant. CONCLUSIONS: Using EIR and PI as markers to assess the risk of insulin resistance and impaired insulin secretion indicates that obese children with premature adrenarche may be at greater risk for the development of prediabetes and type 2 diabetes mellitus compared with their lean counterparts.

Racial/ethnic differences in clinical and biochemical type 2 diabetes mellitus risk factors in children.

OBJECTIVE: To examine whether periadolescent children demonstrate the significant racial/ethnic differences in body fatness relative to BMI and in the prevalence and relationship of body composition to risk factors for type 2 diabetes (T2DM) as in adults. DESIGN AND METHODS: Family history of obesity and T2DM, anthropometry, insulin sensitivity and secretory capacity, lipids, and cytokines (IL-6, CRP, TNF-α, and adiponectin) were examined in a cohort of 994 middle school students (47% male, 53%, female; 12% African American, 14% East Asian, 13% South Asian, 9% Caucasian, 44% Hispanic, and 8% other). RESULTS: Fractional body fat content was significantly greater at any BMI among South Asians. There were racial/ethnic specific differences in lipid profiles, insulin secretory capacity, insulin sensitivity, and inflammatory markers corrected for body fatness that are similar to those seen in adults. Family history of T2DM was associated with lower insulin secretory capacity while family history of obesity was more associated with insulin resistance. CONCLUSIONS: Children show some of the same racial/ethnic differences in risk factors for adiposity-related comorbidities as adults. BMI and waist circumference cutoffs to identify children at-risk for adiposity-related comorbidities should be adjusted by racial/ethnic group as well as other variables such as birthweight and family history.

Bone age advancement in prepubertal children with obesity and premature adrenarche: possible potentiating factors.

Obesity and premature adrenarche (PA) are both associated with bone age (BA) advancement of unclear etiology, which may lead to earlier puberty, suboptimal final height and obesity in adulthood. Our objective was to understand the hormonal and anthropometric characteristics of BA advancement in a spectrum of prepubertal children with and without obesity and PA. In this cross-sectional study of 66 prepubertal children (35 PA, 31 control, 5-9 years), BMI z-score, hormonal values and response to an oral glucose tolerance test were the main outcome measures. Subjects were divided into tertiles by BA divided by chronological age (BA/CA), an index of BA advancement. Subjects in the top tertile for BA/CA had the highest dehydroepiandrosterone sulfate (DHEAS), free testosterone (%), hemoglobin A(1C), BMI z-score, and weight (P < 0.05). BMI z-score (r = 0.47), weight (r = 0.40), free testosterone (%) (r = 0.34), and DHEAS (r = 0.30) correlated with BA/CA (P < 0.02). Regression analysis showed greater BA/CA in PA compared to controls after controlling for weight (0.21 ± 0.56, P < 0.004). An exploratory stepwise regression model showed that weight, estradiol, and DHEAS were the strongest predictors of BA/CA accounting for 24% of its variance. Obesity was highly associated with BA advancement in this study of prepubertal children. In addition, children with PA had greater BA/CA at any given weight when compared to controls. These findings suggest a possible hormonal factor, which potentiates the effect of obesity on BA advancement in children with obesity and/or PA.