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Biomedical subjects

Michael I Goran

Publications and source records attributed to Michael I Goran.

At least 19 recordsLinked to original sources

Validity of new child-specific thoracic gas volume prediction equations for air-displacement plethysmography.

BACKGROUND: To determine the validity of the recently developed child-specific thoracic gas volume (TGV) prediction equations for use in air-displacement plethysmography (ADP) in diverse pediatric populations. METHODS: Three distinct populations were studied: European American and African American children living in Birmingham, Alabama and European children living in Lisbon, Portugal. Each child completed a standard ADP testing protocol, including a measured TGV according to the manufactures software criteria. Measured TGV was compared to the predicted TGV from current adult-based ADP proprietary equations and to the recently developed child-specific TGV equations of Fields et al. Similarly, percent body fat, derived using the TGV prediction equations, was compared to percent body fat derived using measured TGV. RESULTS: Predicted TGV from adult-based equations was significantly different from measured TGV in girls from each of the three ethnic groups (P < 0.05), however child-specific TGV estimates did not significantly differ from measured TGV in any of the ethnic or gender groups. Percent body fat estimates using adult-derived and child-specific TGV estimates did not differ significantly from percent body fat measures using measured TGV in any of the groups. CONCLUSION: The child-specific TGV equations developed by Fields et al. provided a modest improvement over the adult-based TGV equations in an ethnically diverse group of children.

Black or African American↗

Longitudinal changes in insulin sensitivity, insulin secretion, and beta-cell function during puberty.

OBJECTIVE: To determine longitudinal changes in insulin sensitivity (SI), insulin secretion, and beta-cell function during puberty in white and black youth. STUDY DESIGN: The tolbutamide-modified frequently sampled intravenous glucose tolerance test and minimal modeling were used to measure SI, the acute insulin response to glucose (AIRg), and beta-cell function (disposition index, DI) in white (n = 46) and black (n = 46) children (mean [+/-SD] age at baseline = 10.2 +/- 1.7 years). Growth curve models (including 272 observations) with SI, AIRg, and DI regressed on Tanner stage were run after adjusting for covariates. RESULTS: After adjusting for covariates, growth curve models revealed that SI decreased and subsequently recovered by the end of puberty in whites and blacks (both p < .05), AIRg decreased linearly across Tanner stages in both races (both p < .001), and DI decreased across puberty in blacks (p = .001) but not in whites (p = .2). CONCLUSIONS: White and black youth exhibited transient insulin resistance and diminished AIRg during puberty. The progressive decline in DI among blacks versus whites may reflect a unique effect of puberty on beta-cell compensation in blacks. Future studies are needed to identify whether this difference contributes to the increased risk of type II diabetes in young blacks.

Black or African American↗

Associations of adiposity with measured and self-reported academic performance in early adolescence.

OBJECTIVE: To examine the associations of adiposity with measured and self-reported academic performance independently of demographics and physical activity among U.S. adolescents. RESEARCH METHODS AND PROCEDURES: We surveyed 666 students 11 to 14 years old from seven middle schools in Los Angeles, CA. Weight and height were measured. Actual grade point average was obtained from school records. Self-reported school grades and physical activity time were measured by questionnaire. Adiposity measures included BMI, BMI percentile (> or =85th percentile defined as at-risk-of-overweight), and percentage body fat (bioimpedance). RESULTS: After adjusting for gender, ethnicity, age, and physical activity time, overweight at-risk status, BMI, and percentage body fat were negatively related to only self-reported (p < 0.01) but not measured grades. Level of moderate-to-vigorous physical activity time was negatively related to measured and self-reported grades, independently of adiposity (p < 0.01). DISCUSSION: To our knowledge, this is the first study to examine both body mass and body fat in relation to measured and self-reported school grades. Adiposity did not relate to actual academic performance in a sample of predominantly Latino and Asian-American adolescents. The use of measured vs. self-reported academic outcomes may represent different constructs and influence study conclusions. Cultural factors may also play a role in our findings, but this requires further study.

Achievement↗

Ethnic disparity in the relationship between obesity and plasma insulin-like growth factors: the multiethnic cohort.

Previous studies on the relationship between obesity and circulating insulin-like growth factor (IGF) hormones show inconsistent findings and have not considered the possibility of racial/ethnic-specific differences that may exist. We therefore examined the relationship between obesity status [as measured by body mass index (BMI)] and plasma levels of the IGF proteins, IGF-I, IGF-binding protein 3 (IGFBP-3), and the molar ratio of IGF-I/IGFBP-3 in Whites, African Americans, Latinos, Japanese Americans, and Native Hawaiians from the ongoing Hawaii and Los Angeles Multiethnic Cohort Study. We measured plasma IGF-I and IGFBP-3 by ELISA in a random sample of 811 Multiethnic Cohort participants (53% male, age range = 47-82 at blood draw). In a multivariate regression of IGF-I levels, we found a statistically significant interaction between race/ethnicity and obesity status (P = 0.005). Plasma IGF-I levels declined with increasing BMI most dramatically in Latinos and Japanese. This decline was attenuated in Whites and absent in African-American and Native Hawaiian subjects. In Japanese, the quadratic term (BMI(2)) was statistically significant in a multivariate model (P = 0.002). In Latinos, the adjusted least-squares mean IGF-I levels in ng/mL for BMI < 25, 25 to 29.99, and >or=30 were 184.6, 147.7, and 132.7, respectively. No interaction between race/ethnicity and BMI explained the plasma IGFBP-3 levels in these data. These results may help to resolve the uncertainty in the relationship between circulating IGF levels and obesity and highlight the potential importance of racial/ethnic-specific effects among these factors in explaining ethnic disparities in obesity-related cancers.

Aged↗

Effects of resistance training on insulin sensitivity in overweight Latino adolescent males.

PURPOSE: Insulin resistance is thought to be a core defect in the pathophysiology of obesity-related comorbidities in children, such as type 2 diabetes. Exercise training is known to improve insulin resistance and reduce the risk of type 2 diabetes in adults. However, very little is known regarding the effects of exercise on insulin resistance in youth. Therefore, we examined the effects of a 16-wk resistance training exercise intervention on insulin sensitivity in youth at high risk for developing type 2 diabetes. METHODS: Twenty-two overweight Latino adolescent males were randomly assigned to either a twice-per-week resistance training group (RT=11) or a nonexercising control group (C=11) for 16 wk. Strength was assessed by one-repetition maximum, body composition was quantified by dual-energy x-ray absorptiometry, and insulin sensitivity was determined by the frequently sampled intravenous glucose tolerance test with minimal modeling. RESULTS: Significant increases in upper- and lower-body strength were observed in the RT compared with the C group. The RT group significantly increased insulin sensitivity compared with the C group (P<0.05), and this increase remained significant after adjustment for changes in total fat mass and total lean tissue mass (P<0.05). Compared with baseline values, insulin sensitivity increased 45.1+/-7.3% in the RT group versus -0.9+/-12.9% in controls (P<0.01). CONCLUSION: A twice-per-week 16-wk resistance training program can significantly increase insulin sensitivity in overweight Latino adolescent males independent of changes in body composition.

Adolescent↗

Aerobic fitness among Caucasian, African-American, and Latino youth.

OBJECTIVE: The prevalence of obesity and related comorbidities has dramatically increased in the pediatric population in recent years, and youth from ethnic minorities appear to be disproportionately affected. Although several factors play a role in these ethnic health disparities, evidence suggests fitness may also be an important mediator of disease risk in children. Therefore, the purpose of the present investigation was to compare aerobic fitness (VO2peak) in healthy Caucasian (C), African-American (AA), and Latino (L) youth and to evaluate differences after controlling for gender, maturational stage, and body composition. MEASURES: Seventy-three healthy boys and girls [C (n=18), AA (n=19), and L (n=36)] aged 7-14 years participated in the study. VO2peak was evaluated using an all-out, progressive treadmill protocol, total body composition was estimated via dual-energy x-ray absorptiometry, and ethnicity was determined via parental questionnaire. RESULTS: VO2peak relative to total body mass (mL/kg/min) was significantly lower in Latinos compared to either Caucasian or African-American children. Further, after controlling for gender, maturational stage, and body composition, L (1.68 +/- 0.05 L/min) and AA (1.57 +/- 0.05 L/min) youth had significantly lower VO2peak compared to C (1.84 +/- 0.04 L/ min; P<.05) children. CONCLUSION: These results suggest that Latino and African-American children have lower aerobic fitness levels than Caucasian children and this effect is independent of gender, maturation, and body composition.

Adolescent↗

Early ethnic difference in insulin-like growth factor-1 is associated with African genetic admixture.

IGF-1 is a growth-promoting hormone. Numerous studies have reported higher systemic concentrations of IGF-1 among African Americans (AA) compared with European Americans (EA) before puberty. We conducted this cross-sectional analysis to determine whether African ancestral genetic background, dietary factors, energy expenditure, adiposity, and socioeconomic status contribute to this difference. Children were prepubertal, AA and EA males and females. Genetic admixture was assessed from approximately 20 ancestry informative genetic markers. Body composition was determined by dual-energy x-ray absorptiometry; intake of energy, carbohydrate, protein, and fat by 24-h dietary recall; activity-related energy expenditure by doubly labeled water and indirect calorimetry; and socioeconomic status (SES) according to the Hollingshead scale. IGF-1 and IGF binding protein-3 (IGFBP-3) were measured using immunoradiometric assays. AA children had significantly greater IGF-1 compared with EA children (p < 0.01). In addition, AA children had lower SES and greater protein intake relative to EAs (p < 0.05 for both). Multiple linear regression analysis revealed that the only significant independent predictors of IGF-1 were IGFBP-3 and African admixture (p < 0.01 for both). Thus, our data suggest that the greater IGF-1 of AA relative to EA children could have a genetic basis.

Adiposity↗

Dietary fat intake and insulin resistance in black and white children.

OBJECTIVE: The purpose of this study was to determine whether dietary fat intake above current Acceptable Macronutrient Distribution Range (AMDR) guidelines was associated with greater insulin resistance in black and white children. RESEARCH METHODS AND PROCEDURES: We studied 142 healthy children (n = 81 whites, n = 61 blacks), 6.5 to 14 years old. Dietary composition was determined by repeated 24-hour dietary recall, body composition by DXA, visceral fat by computed tomography, and insulin sensitivity (SI) and acute insulin response to glucose (AIRg) by frequently sampled intravenous glucose tolerance test. Subjects were categorized by ethnicity (white/black) and dietary fat intake (above-AMDR/within-AMDR guidelines), and differences were analyzed by 2 x 2 analysis of covariance, adjusting for covariates. RESULTS: After adjusting for total body fat, gender, and Tanner stage, subjects consuming dietary fat above AMDR intake guidelines had lower SI and higher AIRg. This effect was specific to black children (32% lower SI and 62% higher AIRg in above-AMDR compared with within-AMDR blacks) and was not seen in whites. DISCUSSION: In black, but not white, children, those with dietary fat intake above current AMDR guidelines had lower SI and higher AIRg than those who met AMDR guidelines. These findings support current AMDR guidelines for dietary fat in black children and adolescents. The mechanism(s) underlying the ethnic differences in the relationship between dietary fat intake and SI in children require further investigation.

Adolescent↗

Interactive multimedia for promoting physical activity (IMPACT) in children.

OBJECTIVE: To develop and examine the efficacy of a computer-based interactive multimedia curriculum for promoting physical activity in fourth grade children. RESEARCH METHODS AND PROCEDURES: The participants were 209 fourth grade children (mean age of 9.5 +/- 0.4 years) from four schools. Two schools received an 8-week multimedia intervention delivered by interactive CD-ROM, supplemented by four classroom and four homework assignments. Two control schools received educational CD-ROMS not related to health outcomes. Measures conducted before and after intervention included height, weight, percentage body fat (bioimpedance analysis), physical activity (5-day accelerometry), and psychosocial aspects of physical activity by questionnaire. All outcomes were examined using general linear models. RESULTS: There was a significant treatment effect for obesity reduction in girls but not in boys. There were no significant treatment effects on total physical activity by accelerometry (total counts per minute), but there was an overall treatment effect on reducing percent of time in moderate-intensity activity (16.5% to 15% of the time) and significant sex-by- treatment interactions for light-intensity activities (reduction in boys from 78% to 75% of the time and an increase in girls from 78% to 81% of the time). There were marginal/significant treatment effects for improvements in behavioral outcomes, including self-efficacy (p = 0.06), social norms (p = 0.07), and outcome expectancies (p = 0.049). DISCUSSION: The interactive multimedia curriculum favored an improvement in obesity indices in girls and was associated with subtle changes in physical activity in girls and general improvement in psychosocial outcomes related to physical activity.

Body Composition↗

Estimating energy requirements: regression based prediction equations or multiples of resting metabolic rate.

Energy requirements have traditionally been determined based on multiples of resting metabolic rate (RMR), known as Physical Activity Levels (PAL). With more data from doubly labelled water studies alternative approaches for estimating energy requirements have been suggested. Statistical analysis reveals that body weight explains more of the variance in total energy expenditure (TEE) than does RMR. The explanation for this phenomenon is that body weight contributes to the variance of both RMR and the other major determinant of TEE, i.e. physical activity related energy expenditure. Thus, in effect, the regression-based approach provides a more physiological appropriate model for TEE. Its major departure from tradition, difference from current adult proposals, and time taken for acceptance are the disadvantages of the regression-based approach.

Basal Metabolism↗

The relation of sugar intake to beta cell function in overweight Latino children.

BACKGROUND: Few studies have investigated the association between sugar intake and insulin dynamics in children, and none have examined this association in overweight Latino youth. OBJECTIVE: We aimed to examine the relation between dietary components, especially sugar intake, and insulin dynamics in overweight Latino youth. DESIGN: We examined 63 overweight Latino children aged 9-13 y. Dietary intake was determined by 3-d records, and body composition was measured with dual-energy X-ray absorptiometry. Insulin sensitivity (S(I)), acute insulin response (AIR), and disposition index (an index of beta cell function) were measured by using a frequently sampled intravenous-glucose-tolerance test and minimal modeling. Hierarchical regression analysis ascertained the potential independent relation between insulin dynamics and dietary components. RESULTS: The relation between macronutrient intake and any variable related to insulin dynamics was not significant. However, higher total sugar intake, although not related to S(I), was significantly associated with lower AIR (beta = -0.296, P = 0.045) and lower beta cell function (beta = -0.421, P = 0.043), independent of the covariates age, sex, body composition, Tanner stage, and energy intake. Sugar-sweetened beverage intakes trended toward inverse association with lower AIR (beta = -0.219, P = 0.072) and beta cell function (beta = -0.298, P = 0.077). CONCLUSIONS: In overweight Latino children, higher intakes of sugar and sugar-sweetened beverages were associated with lower AIR and disposition index, which suggested that these children already have early signs of poor beta cell function. These results emphasize the need for early nutritional interventions to reduce daily sugar intake in overweight Latino children and potentially reduce their risk for type 2 diabetes.

Absorptiometry, Photon↗

Adiponectin is lower among African Americans and is independently related to insulin sensitivity in children and adolescents.

Adiponectin is inversely related to adiposity and positively correlated with insulin sensitivity (S(i)). Sparse data exist on the contributions of ethnicity and body fat distribution to variance in serum adiponectin. Hypotheses tested were that adiponectin would be lower in African Americans compared with Caucasians; that adiponectin would be inversely related to central, not peripheral, fat; that adiponectin would be positively associated with S(i); and that baseline adiponectin would predict change in S(i) over 2 years in 150 African-American and Caucasian youth. Multiple linear regression modeling showed that adiponectin was lower in African-American versus Caucasian children (adjusted means 10.8 +/- 0.5 vs. 12.3 +/- 0.5 microg/ml, respectively; P < 0.05); inversely related to trunk fat (P < 0.05); and positively related to limb fat (P < 0.01). Addition of the acute insulin response to glucose to the model eliminated the significance of ethnicity. S(i), which was positively related to adiponectin (P < 0.05), was lower in African Americans (P < 0.001) and girls (P < 0.05). Baseline adiponectin did not predict change in S(i) over 2 years. In conclusion, adiponectin was positively correlated with S(i), inversely related to central fat, and positively related to peripheral fat. In addition, higher acute insulin response to glucose explained lower adiponectin among African-American children.

Adipose Tissue↗

Decreased beta-cell function in overweight Latino children with impaired fasting glucose.

OBJECTIVE: To determine whether overweight Latino children with impaired fasting glucose (IFG) (> or = 100 mg/dl) have increased insulin resistance or decreased beta-cell function compared with those with normal fasting glucose (NFG). RESEARCH DESIGN AND METHODS: We studied 207 healthy overweight Latino children, aged 8-13 years, with a family history of type 2 diabetes. Fasting and 2-h glucose and insulin were assessed by oral glucose tolerance test. Insulin sensitivity (S(i)), the acute insulin response to glucose (AIRg), and the disposition index (DI; an index of beta-cell function) were determined using the insulin-modified intravenous glucose tolerance test and minimal modeling. Body composition was determined by dual-energy X-ray absorptiometry. RESULTS: There were no differences in body composition between NFG (n = 182) and IFG (n = 25) children. Compared with children with NFG, children with IFG had higher fasting and 2-h glucose values and higher fasting insulin. After adjusting for covariates, children with IFG had no difference in S(i) but 15% lower DI than NFG children (2,224 +/- 210 vs. 2,613 +/- 76, P < 0.05). Multivariate linear regression showed that AIRg and DI, but not S(i), were significant predictors of fasting blood glucose. CONCLUSIONS: In overweight Latino adolescents with a family history of type 2 diabetes, IFG is associated with impaired beta-cell function and therefore may identify children likely to be at risk for progression to type 2 diabetes. The actual risk of progression of IFG to type 2 diabetes remains to be determined by prospective longitudinal studies.

Adolescent↗

Impaired glucose tolerance and bone mineral content in overweight latino children with a family history of type 2 diabetes.

OBJECTIVE: Research on the skeletal status of pre-diabetic (type 2 diabetic) children is warranted. We examined the hypothesis that bone mineral content (BMC) and bone mineral density (BMD) will be lower in children with impaired glucose tolerance (IGT) versus normal glucose tolerance (NGT). RESEARCH DESIGN AND METHODS: Total body BMC and BMD of 184 overweight Latino children (106 boys, 78 girls, 11.9 +/- 1.7 years) with a family history of type 2 diabetes were measured using dual-energy X-ray absorptiometry. Glucose tolerance was assessed by 2-h glucose after an oral glucose tolerance test. Area under the insulin curve (AUC) assessed the cumulative insulin response to oral glucose. Acute insulin response to glucose (AIR) was determined by an intravenous glucose tolerance test. RESULTS: Partial correlations revealed an inverse relationship between BMC and AIR (r = -0.29, P = 0.00), AUC (r = -0.28, P = 0.00), fasting insulin (r = -0.16, P = 0.04), and 2-h insulin (r = -0.16, P = 0.04). There was no significant difference in BMC or BMD between children with IGT (n = 46) or NGT (n = 138). Stepwise multiple linear regression revealed that 89% of the variance in BMC is attributed to lean mass (87%), age (1%), and AIR (1%). BMD was explained by lean mass (69%), Tanner stage (3%), and AUC (2%). CONCLUSIONS: The findings of this study suggest that in overweight children, lean mass is the primary predictor of BMC and BMD, whereas age, Tanner stage, and the acute and cumulative insulin responses to oral glucose make subtle independent contributions to the total variances. In addition, poor glycemic control does not seem to be detrimental to bone mass of pre-diabetic children.

Absorptiometry, Photon↗

Cardiovascular fitness and the metabolic syndrome in overweight latino youths.

PURPOSE: To determine whether cardiovascular fitness (.)VO(2max) is associated with the metabolic syndrome and its individual features in overweight Latino youths. METHODS: A total of 163 overweight Latino boys and girls (body mass index (BMI) percentile = 97.0 +/- 3.1; age = 11.2 +/- 1.7 yr) with a family history of Type 2 diabetes participated in this investigation. The metabolic syndrome was defined as having three or more of the following risk factors: abdominal obesity, high blood pressure, low HDL-cholesterol, high triglycerides, and impaired glucose tolerance. (.)VO(2max) was determined by a progressive treadmill test to exhaustion, and body composition was assessed using dual energy x-ray absorptiometry. RESULTS: (.)VO(2max) was not correlated with any individual risk factor of the metabolic syndrome after adjusting for gender, age, and body composition in partial analysis. Furthermore, ANCOVA revealed that children with zero, one, two, or three or more risk factors did not differ in regards to fitness levels. CONCLUSION: (.)VO(2max) is not independently associated with the metabolic syndrome or any individual feature in overweight youths of Latino ethnicity after controlling for differences in confounding variables.

Adolescent↗

The metabolic syndrome in children and adolescents.

The metabolic syndrome was recently defined by the Adult Treatment Panel III. Despite a lack of uniform definition of the syndrome in pediatrics, recent studies have shown that the syndrome develops during childhood and is highly prevalent among overweight children and adolescents. The hypothesized central role of insulin resistance and obesity as a common underlying feature of the metabolic syndrome also appears to be already manifested in childhood. In view of the current obesity epidemic in children and adolescents, there is a vital need to provide adequate guidelines for the definition of the metabolic syndrome in pediatrics and for the development of screening and treatment strategies. This article focuses on the above issues, as well as on the impact of the syndrome on two major disease outcomes, type 2 diabetes and cardiovascular disease.

Adolescent↗

Insulin sensitivity, cardiorespiratory fitness, and physical activity in overweight Hispanic youth.

OBJECTIVE: To determine whether cardiorespiratory fitness and/or physical activity (PA) were related to measures of insulin sensitivity and secretion independent of body composition in overweight Hispanic children. RESEARCH METHODS AND PROCEDURES: Ninety-five Hispanic children (n = 55 boys; n = 40 girls; 8 to 13 years old) participated in this investigation. The frequently sampled intravenous glucose tolerance test was used to determine the insulin sensitivity index (SI), the acute insulin response, and the disposition index. Cardiorespiratory fitness [maximal oxygen uptake (VO(2max))] was evaluated using a treadmill protocol, and PA was determined by an interviewer-administered questionnaire. Body composition was measured using DXA. RESULTS: Unadjusted correlations indicated that VO(2max) (milliliters of O(2) per minute) was negatively related to SI (r = -0.46, p < 0.05) and disposition index (r = -0.31, p < 0.05) and positively associated with fasting insulin (r = 0.29, p < 0.05), but these relationships were no longer significant once gender, Tanner stage, fat mass, and soft lean tissue mass were included as covariates (all p > 0.05). Multivariate linear regression analysis showed that body fat mass explained 53% of the variance in SI and that VO(2max) (milliliters of O(2) per minute) was not independently related to SI. Cardiorespiratory fitness was positively related to both fat mass (r = 0.43, p < 0.001) and soft lean tissue mass (r = 0.89, p < 0.001). PA was not related to any measure of insulin sensitivity and secretion. DISCUSSION: Cardiorespiratory fitness, as determined by VO(2max) (milliliters of O(2) per minute), was not independently related to insulin sensitivity or secretion, suggesting that VO(2max) influences insulin dynamics indirectly through fat mass.

Adolescent↗

The metabolic syndrome in overweight Hispanic youth and the role of insulin sensitivity.

The prevalence of the metabolic syndrome is highest among Hispanic adults. However, studies exploring the metabolic syndrome in overweight Hispanic youth are lacking. Subjects were 126 overweight children (8-13 yr of age) with a family history for type 2 diabetes. The metabolic syndrome was defined as having at least three of the following: abdominal obesity, low high-density lipoprotein (HDL) cholesterol, hypertriglyceridemia, hypertension, and/or impaired glucose tolerance. Insulin sensitivity was determined by the frequently sampled iv glucose tolerance test and minimal modeling. The prevalence of abdominal obesity, low HDL cholesterol, hypertriglyceridemia, systolic and diastolic hypertension, and impaired glucose tolerance was 62, 67, 26, 22, 4, and 27%, respectively. The presence of zero, one, two, or three or more features of the metabolic syndrome was 9, 22, 38, and 30%, respectively. After controlling for body composition, insulin sensitivity was positively related to HDL cholesterol (P < 0.01) and negatively related to triglycerides (P < 0.001) and systolic (P < 0.01) and diastolic blood pressure (P < 0.05). Insulin sensitivity significantly decreased (P < 0.001) as the number of features of the metabolic syndrome increased. In conclusion, overweight Hispanic youth with a family history for type 2 diabetes are at increased risk for cardiovascular disease and type 2 diabetes, and this appears to be due to decreased insulin sensitivity. Improving insulin resistance may be crucial for the prevention of chronic disease in this at-risk population.

Adolescent↗