Martha L. Cruz

Insulin Sensitivity and Blood Pressure in Black and White Children

Although insulin sensitivity is correlated with high blood pressure in adults, it is unclear whether such a relationship exists in children across ethnic groups. Therefore, the aims of the study were to establish (1) if body composition and insulin sensitivity were related to blood pressure in children, and (2) if any differences in blood pressure between white and black children were explained by body composition and/or insulin sensitivity. Insulin sensitivity and the acute insulin response were established by the minimal model and body composition by dual-energy X-ray absorptiometry. Blood pressure was recorded in the supine position. Body composition, fasting insulin (P <0.01), and the acute insulin response (P <0.05) were positively related to systolic blood pressure but not to diastolic blood pressure, and insulin sensitivity (P <0.001) was negatively related to systolic blood pressure but not to diastolic blood pressure. Insulin sensitivity was negatively associated with systolic and diastolic blood pressure after adjustment for body composition (P <0.01). Black children had higher systolic (110±9.2 versus 105±8.5 mm Hg, P =0.01) and diastolic (59±7.0 versus 54±8.0 mm Hg, P <0.01) blood pressure than did white children. The ethnic difference in blood pressure was not explained by body composition, fasting insulin, acute insulin response, or insulin sensitivity. In conclusion, the relationship between insulin sensitivity and systolic blood pressure is evident early in life. Black ethnicity and low insulin sensitivity contribute independently to higher blood pressure in children.

Deterioration of insulin sensitivity and beta-cell function in overweight Hispanic children during pubertal transition: A longitudinal assessment

PURPOSE To examine 1-year changes in insulin dynamics in overweight Hispanic children at high-risk of type 2 diabetes as a function of body composition and pubertal transition. EXPERIMENTAL DESIGN Longitudinal changes in insulin dynamics, body composition and maturation were determined in 132 Hispanic children (70 boys/62 girls; aged 10.9 +/- 1.8 years). METHODS Body composition was determined by dual energy x-ray absorptiometry and Tanner stage by physical examination. Insulin sensitivity (SI), the acute insulin response to glucose (AIR) and the disposition index (DI; an index of beta-cell function) were determined using an insulin modified intravenous glucose tolerance test. These measures were conducted at baseline and 1-year later. RESULTS Fat mass increased by 13% (3.0 kg) and SI declined by 24%. In repeated measures analysis of variance, the fall in insulin sensitivity over 1 year remained highly significant even after adjusting for baseline fat mass, age, gender and change in fat mass. The fall in SI was not significantly influenced by Tanner stage. However, subjects in earlier maturation showed a compensatory increase in AIR (i.e. appropriate beta-cell compensation), whereas subjects in the latter stages of maturation did not (i.e. poor compensation). CONCLUSIONS These results indicate that failure to increase AIR in response to the fall in SI may be one factor in the pathogenesis of the progression of pediatric type 2 diabetes in this at risk population.

Predicting abdominal adipose tissue in overweight Latino youth

OBJECTIVES 1) Examine associations between visceral adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAAT), and anthropometric and demographic variables; 2) generate and cross-validate prediction equations for estimating VAT and SAAT in overweight Latino children. STUDY DESIGN Cross-sectional. PARTICIPANTS 196 overweight 8-13-year-old Latino youth. Two-thirds (n = 131) were randomly assigned to a development group to generate prediction equations for VAT and SAAT; one-third (n = 65) was used as a cross-validation group. METHODS AND PROCEDURES Anthropometric measurements (height, weight, skinfold thicknesses, and circumferences) were performed. VAT and SAAT were measured using magnetic resonance imaging (MRI). RESULTS The strongest univariate correlate for VAT was waist circumference (WC) (r = 0.65, p < 0.01) while the strongest correlate for SAAT was hip circumference (r = 0.88, p < 0.001). Regression analyses showed approximately 50% of the variance in VAT was explained by WC (43.8%), Tanner stage (4.2%) and calf skinfold (1.7%). Variance in the SAAT model was explained by WC (77.8%), triceps skinfold (4.2%) and gender (2.3%). Residual analyses showed no bias in either equation. Though mean differences between measured and predicted VAT and SAAT were small, there was a large degree of variability at the individual level especially for VAT. CONCLUSIONS Both VAT and SAAT prediction equations performed well at the group level, but the relatively high degree of variability suggests limited clinical utility of the VAT equation. MRI is currently required to derive an accurate measure of VAT at the individual level.

Birth weight, puberty, and systolic blood pressure in children and adolescents: a longitudinal analysis

We examined the association between birth weight and systolic blood pressure (SBP) from pre-puberty to late puberty in a cohort of American children. Ninety-eight children aged 4–12 years at baseline were followed annually for 2–6 years with at least two Tanner stages. Annual measures included SBP, age, gender, race, birth weight, Tanner stage, and body composition using dual-energy X-ray absorptiometry and computed tomography. Birth weight was inversely correlated with SBP in pre-pubertal children (r=−0.23, P<0.05), especially in white children. SBP persisted at a higher level from pre-puberty through late puberty among children with low birth weight (<2500 g). However, SBP significantly increased from pre-puberty to early or late puberty among children with high birth weight (⩾4000 g). After adjusting for visceral fat, one unit change of birth weight category was associated with a 2.6 mm Hg reduction in SBP (P<0.05), but this association was attenuated as puberty progressed. The changes in SBP across puberty followed different trajectories in children with low vs high birth weight. Attenuation in the association between birth weight and SBP from pre-puberty to late puberty may be influenced by sexual maturation.

Insulin sensitivity, insulin secretion and β -cell function during puberty in overweight Hispanic children with a family history of type 2 diabetes

OBJECTIVE:To examine cross-sectional differences in insulin sensitivity, insulin secretion and β-cell function during puberty in overweight Hispanic boys and girls with a family history of type 2 diabetes.STUDY DESIGN AND PARTICIPANTS:This cross-sectional, observational study included 214 8–13-y-old Hispanic children with a BMI percentile ≥85th percentile and family history of type 2 diabetes.METHODS AND ANALYSES:Participants underwent a physical examination, body composition measures, oral glucose tolerance test (OGTT), and frequently-sampled intravenous glucose tolerance test. Unadjusted and adjusted general linear models (GLM) tested whether insulin/glucose dynamics differed by Tanner stage and gender.RESULTS:Unadjusted group comparisons showed that fasting insulin increased whereas insulin sensitivity (SI) and the disposition index (DI) (a measure of pancreatic β-cell function) decreased across Tanner stage groups (all P<0.05). No differences in the acute insulin response to glucose (AIRg), fasting glucose or 2-h glucose were found. After adjusting for covariates, there was no independent effect of Tanner stage on SI (P=0.9) or AIRg (P=0.2), but DI was slightly lower in later Tanner stages suggesting decreased β-cell function in the more mature groups (P=0.10).CONCLUSIONS:Overweight Hispanic children with a family history of type 2 diabetes may represent a unique population given that pubertal insulin resistance was not evident once analyses controlled for body composition. Longitudinal analyses are required to determine whether the slightly diminished β-cell function in later Tanner stages plays a role in the development of type 2 diabetes.

Cardiovascular fitness and physical activity in children with and without impaired glucose tolerance.

Objective:To examine differences in cardiovascular fitness (VO2max) and physical activity levels in overweight Hispanic children with normal glucose tolerance (NGT) vs impaired glucose tolerance (IGT).Participants:A total of 173 overweight (BMI percentile 97.0±3.1) Hispanic children ages 8–13 years with a family history of type 2 diabetes.Methods:VO2max was measured via a maximal effort treadmill test and open circuit spirometry. Physical activity was determined by questionnaire. Glucose tolerance was established by a 2-h oral glucose challenge (1.75 g of glucose/kg body weight). IGT was defined from an oral glucose tolerance test as a 2-h plasma glucose level ⩾140 and <200 mg/dl.Results:IGT was detected in 46 of the 173 participants (∼27%); no cases of type 2 diabetes were identified. No significant differences were found between youth with NGT and those with IGT in absolute VO2max (2.2±0.6 vs 2.1±0.5 l/min), VO2max adjusted for gender, age, and body composition (2.2±0.2 vs 2.1±0.2 l/min), or recreational physical activity levels (8.7±8.2 vs 6.9±6.2 h/week).Conclusion:Overweight Hispanic youth with IGT exhibit similar levels of VO2max and physical activity compared to their NGT counterparts. Longitudinal analyses are necessary to determine whether fitness/activity measures contribute significantly to diabetes risk over time in this group.

Fatty liver in adolescents on the U.S.‐Mexico border

Purpose: To describe the physical and metabolic characteristics of children diagnosed with fatty liver disease in a gastroenterology clinic in El Paso, Texas. Data Sources: A retrospective chart review of 31 patients aged 8‐18 diagnosed with fatty liver was conducted. Conclusions: These children were diagnosed with fatty liver by elevated alanine aminotransferase (ALT) levels (mean ALT levels 126 ± 08 U/L) and increased hepatic echogenicity measured via ultrasound. The majority of children were adolescents (12‐17 years of age) and Mexican American. All subjects were overweight (body mass index [BMI] ≥ 95th percentile) based on Centers for Disease Control and Prevention standards. In a subset of children for whom results from laboratory test were available, we found 40% had high triglycerides (≥ 150 mg/dL), 53% had low high‐density lipoprotein cholesterol (≤ 35 mg/dL), and 17% had prediabetes (fasting glucose ≥ 100 mg/dL). The clinical and laboratory findings in this patient population with fatty liver are consistent with a diagnosis of nonalcoholic fatty liver disease (NAFLD). Implications for Practice: Despite the increasing trend in overweight among children and adolescents, data suggest low rates of diagnosis and management of overweight and related comorbidities by healthcare providers. Overweight has been associated with fatty liver disease in the pediatric population and includes other comorbidities such insulin resistance and features of metabolic syndrome. Screening for overweight in children should constitute the first step in identifying children at risk for NAFLD. Nurse practitioners should include in the evaluation of pediatric patients calculation of BMI and waist circumference for age and screening for other overweight‐related comorbidities.

Physical activity, cardiorespiratory fitness, and metabolic syndrome in young Mexican and Mexican-American women

Young adult women have had the greatest increase in prevalence of metabolic syndrome (MetS) over time, and prevalence is highest in Hispanic women, compared with women of other ethnicities. Factors contributing to the high prevalence of MetS in Hispanic women are unknown. This study was conducted to determine if physical activity or fitness were associated with individual features of MetS in young Mexican and Mexican-American women, and if the associations were independent of fat mass. Sixty young Mexican and Mexican-American women participated in the study. MetS was defined according to the Adult Treatment Panel III. A fasting blood sample was drawn for the measurement of glucose, insulin, high-density lipoprotein cholesterol (HDL-c), and triglycerides. Physical activity was assessed by questionnaire and accelerometer. Fitness was assessed by progressive treadmill test to exhaustion and ventilatory threshold. Body composition was assessed with Bod Pod. Multivariate regression was used to establish the independent contributions of physical activity and fitness to the individual features of MetS. After controlling for fat mass and fat-free mass, physical activity was found to be independently related to HDL-c and fitness was found to be independently related to triglycerides (p < 0.05). The independent associations between physical activity, fitness, and features of MetS were mediated by, rather than independent of, fat mass. Fat mass was independently related to triglycerides, systolic blood pressure, and diastolic blood pressure. Although physical activity and fitness were related to features of MetS, these associations were not independent of fat mass.

Cardiorespiratory Fitness Is Strongly Related to the Metabolic Syndrome in Adolescents Response to Janssen and Cramp

The recent report by Janseen and Cramp (1), describing the independent associations between cardiorespiratory fitness (CRF) and the metabolic syndrome in adolescents participating in the National Health and Nutrition Examination Survey 1999–2002, addresses a critical issue related to fitness and chronic disease risk in youth. However, the authors’ findings and interpretation should be received with caution. First, the authors suggest that CRF is an objective measure of physical …

Frequency of hypoglycaemia during the intravenous glucose tolerance test in overweight children

The study aimed to assess the frequency of hypoglycaemia during the insulin-modified, frequently sampled intravenous glucose tolerance test (FSIVGTT) in overweight Hispanic children. The study included 210 children, mean age=11+/-1.7 years, BMI percentile=97.2+/-2.9 who where enrolled in a longitudinal study to explore risk factors for type 2 diabetes. Two fasting blood samples were collected to determine basal glucose and insulin concentrations. At time 0, glucose (0.3 g/kg body weight) was administered intravenously. Eleven blood samples were collected until 180 min post glucose injection. Insulin (0.02 U/kg body weight) was injected intravenously at 20 min. Plasma was analyzed for glucose and insulin and used for the determination of insulin sensitivity. Hypoglycaemia, defined as a plasma glucose<50 mg/dl, was observed in one asymptomatic subject (<0.5% subjects). In addition, only 1.9% of subjects (n=4) had plasma glucose<60 mg/dl at any time during the FSIVGTT. The frequency of hypoglycaemia during the insulin modified FSIVGTT is very low in overweight Hispanic youth.