Biomedical subjects

Marc J Weigensberg

Publications and source records attributed to Marc J Weigensberg.

11 recordsLinked to original sources

PubMed2006

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↗

PubMed2006

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↗

PubMed2005

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↗

PubMed2005

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↗

PubMed2005

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↗

PubMed2005

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↗

PubMed2004

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↗

PubMed2004

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↗

PubMed2004

Impaired glucose tolerance and reduced beta-cell function in overweight Latino children with a positive family history for type 2 diabetes.

The objective of this study was to examine relationships between impaired glucose tolerance (IGT) and body composition and insulin-related phenotypes in 150 overweight Latino children with a family history of type 2 diabetes. Glucose tolerance was assessed by an oral glucose challenge. Body composition was assessed by dual energy x-ray absorptiometry and magnetic resonance imaging. Insulin sensitivity, the acute insulin response, and the disposition index (DI), as an index of beta-cell function, were determined by an iv glucose tolerance test and compared between normal glucose-tolerant and IGT children. IGT was present in 28% of children, and was similar across obesity groups, but higher in children exposed to gestational diabetes mellitus (41% IGT). There were no significant differences in body composition, fat distribution, insulin sensitivity, or acute insulin response, but DI was significantly lower in IGT children by 16% (P < 0.02), and DI was inversely related to age. In conclusion, IGT is present in 28% of overweight Latino children with a family history of type 2 diabetes, is not influenced by obesity, is more prevalent in children exposed to gestational diabetes mellitus, and is related to poor beta-cell function, which shows signs of deterioration with age in this population.

Absorptiometry, Photon↗

PubMed2004

Relation between acanthosis nigricans and insulin sensitivity in overweight Hispanic children at risk for type 2 diabetes.

OBJECTIVE: To investigate in a population of Hispanic children if 1) the presence of acanthosis nigricans (AN) is related to insulin sensitivity (S(i)) independent of adiposity and 2) scale scoring AN severity adds to the clinical estimation of insulin sensitivity, above and beyond the presence or absence AN alone. RESEARCH DESIGN AND METHODS: The study population, 131 Hispanic overweight children (mean BMI percentile 97.0 +/- 3.1, 72 boys, 59 girls, ages 8-13 years, mean Tanner stage 2.4 +/- 1.5) with a family history of type 2 diabetes, underwent a physical examination of the neck to determine AN absence or presence (0-1), AN extent score (0-4 scale), AN texture score (0-3 scale), and an AN combined score (extent + texture; 0-7 scale). S(i) was measured by the frequently sampled intravenous glucose tolerance test and minimal modeling. Multivariate linear regression analysis was used to determine the role of BMI and AN in predicting S(i). RESULTS: BMI was the main predictor of S(i), explaining approximately 41% of the variance. The presence of AN explained an additional 4% of the variability in S(i); scale scoring of AN extent or texture did not significantly improve the prediction. CONCLUSIONS: Although AN is an independent risk factor for insulin resistance in overweight Hispanic children at risk for type 2 diabetes, body adiposity is the primary determinant of insulin sensitivity. In addition, scale scoring AN seems of minimal usefulness in clinically estimating the severity of insulin resistance over and above assessing the presence or absence of AN and calculating BMI.

Acanthosis Nigricans↗

PubMed2003

Association between insulin sensitivity and post-glucose challenge plasma insulin values in overweight Latino youth.

OBJECTIVE: To determine associations between directly measured insulin sensitivity (SI) and oral glucose tolerance test (OGTT)-derived plasma insulin values, or calculated SI indices, in overweight peripubertal Latino children at risk for type 2 diabetes. RESEARCH DESIGN AND METHODS: Thirty overweight Latino children with a family history of type 2 diabetes, aged 8-13 years, Tanner stages 1-2, underwent an OGTT. Fasting and 2-h plasma insulin values and OGTT-derived SI indices were compared with SI derived from a frequently sampled intravenous glucose tolerance test (FSIGTT) with minimal model analysis, before and after adjustment for total body fat and lean tissue mass, or BMI. RESULTS: FSIGTT-derived SI for all subjects was 1.62 +/- 0.78 x 10(-4) min (-1) x (microU/ml), with no sex differences. SI correlated (all P values < 0.001) with fasting (r = -0.57) and 2-h (r = -0.58) plasma insulin and all SI indices (r = -0.57 to 0.67). After adjusting for total body fat and lean tissue mass, or BMI, the associations between SI and either fasting insulin or fasting SI indices were no longer significant. However, the 2-h insulin and post-glucose challenge SI indices maintained significant independent associations with SI, even after adjustment for body composition. CONCLUSIONS: In overweight, peripubertal Latino children at risk for type 2 diabetes, the 2-h plasma insulin value and postchallenge SI indices are better independent correlates of SI than fasting values, after accounting for body composition. The 2-h insulin may therefore be superior to fasting insulin as a single blood sample value for clinical or epidemiological estimates of SI, especially when combined with assessment of body composition.

Adipose Tissue↗