Showing papers by "Barbara A. Gower published in 2008"

Resistance Training Conserves Fat‐free Mass and Resting Energy Expenditure Following Weight Loss

Abstract: Objective: To determine what effect diet-induced ∼12 kg weight loss in combination with exercise training has on body composition and resting energy expenditure (REE) in premenopausal African-American (AA) and European-American (EA) women. Methods and Procedures: This study was a longitudinal, randomized weight loss clinical intervention, with either aerobic (AT), resistance (RT), or no exercise training (NT). Forty-eight AA and forty-six EA premenopausal overweight (BMI between 27 and 30) women underwent weight loss to a BMI <25. Body composition (densitometry), REE (indirect calorimetry), maximal oxygen uptake (VO2max), and muscular strength (isometric elbow flexion) were evaluated when subjects were in energy balance. Results: AA women lost less fat-free mass (FFM, P ≤ 0.05) (47.0 ± 4.6 to 46.9 ± 5.0 kg) than EA women (46.4 ± 4.9 to 45.2 ± 4.6 kg). Regardless of race, RT maintained FFM (P ≤ 0.05) following weight loss (46.9 ± 5.2 to 47.2 ± 5.0 kg) whereas AT (45.4 ± 4.2 to 44.4 ± 4.1 kg) and NT (47.9 ± 4.7 to 46.4 ± 5.1 kg) decreased FFM (P ≤ 0.05). Both AT and NT decreased in REE with weight loss but RT did not. Significant time by group interactions (all P ≤ 0.05) for strength indicated that RT maintained strength and AT did not. Discussion: AA women lost less FFM than EA women during equivalent weight losses. However, following weight loss in both AA and EA, RT conserved FFM, REE, and strength fitness when compared to women who AT or did not train.

Resistance training conserves fat-free mass and resting energy expenditure following weight loss

Abstract: Objective: To determine what effect diet-induced 12 kg weight loss in combination with exercise training has on body composition and resting energy expenditure (REE) in premenopausal African-American (AA) and European-American (EA) women.--- Methods and Procedures: This study was a longitudinal, randomized weight loss clinical intervention, with either aerobic (AT), resistance (RT), or no exercise training (NT). Forty-eight AA and forty-six EA premenopausal overweight (BMI between 27 and 30) women underwent weight loss to a BMI <25. Body composition (densitometry), REE (indirect calorimetry), maximal oxygen uptake (VO2max), and muscular strength (isometric elbow flexion) were evaluated when subjects were in energy balance.--- Results: AA women lost less fat-free mass (FFM, P 0.05) (47.0 4.6 to 46.9 5.0 kg) than EA women (46.4 4.9 to 45.2 4.6 kg). Regardless of race, RT maintained FFM (P 0.05) following weight loss (46.9 5.2 to 47.2 5.0 kg) whereas AT (45.4 4.2 to 44.4 4.1 kg) and NT (47.9 4.7 to 46.4 5.1 kg) decreased FFM (P 0.05). Both AT and NT decreased in REE with weight loss but RT did not. Significant time by group interactions (all P 0.05) for strength indicated that RT maintained strength and AT did not.--- Discussion: AA women lost less FFM than EA women during equivalent weight losses. However, following weight loss in both AA and EA, RT conserved FFM, REE, and strength fitness when compared to women who AT or did not train.

Associations among Insulin, Estrogen, and Fat Mass Gain over the Pubertal Transition in African-American and European-American Girls

Abstract: Context: Age at menarche (AgeM) is earlier in African-American (AA) than in European-American (EA) girls. Neither the physiological cause nor the health implications of this difference are known. Objective: We tested the hypotheses that higher insulin among AA vs. EA precipitates an earlier elevation of estradiol (E2), an associated earlier AgeM, and greater gain in body fat. Setting: The study was conducted at a university research laboratory and General Clinical Research Center. Participants: Subjects were 137 girls (57 AA and 80 EA) aged 7–15 yr. Design: The study had a longitudinal design. Annual evaluations were conducted for body composition by dual-energy X-ray absorptiometry, acute insulin response to glucose (AIRg) by iv glucose tolerance test, and reproductive-endocrine profile. Main Outcome Measures: Multiple linear regression modeling and mixed model analyses were used to identify independent predictors of AgeM and E2 concentration at menarche. Results: AgeM was significantly earlier in AA vs....

Adiponectin multimers and metabolic syndrome traits: relative adiponectin resistance in African Americans.

Abstract: African Americans (AAs) tend to have lower total adiponectin levels compared to European Americans (EA); however, it is not known whether race affects adiponectin multimer distribution and their relationships to metabolic traits. We measured total adiponectin, high molecular weight (HMW), low molecular weight (LMW) (i.e., hexamer), and trimer adiponectin in 132 normoglycemic premenopausal women (75 AAs, 57 EAs), together with measures of total and abdominal fat, plasma lipids, insulin sensitivity (Si), and genetic admixture estimates. We found that lower total adiponectin in AAs was explained by reduced LMW, and trimer forms because levels of HMW did not differ between races. In EAs, HMW was highly correlated with multiple metabolic syndrome traits. In contrast, the LMW and trimer forms were most highly correlated with metabolic traits in AAs, including abdominal adiposity, lipids, and Si. At similar levels of visceral adiposity, AAs exhibited significantly lower LMW adiponectin than EAs. Similarly, at comparable levels of HMW and LMW adiponectin, AAs were more insulin resistant than their EA counterparts. In conclusion, (i) serum adiponectin is lower in AAs predominantly as a result of reduced concentrations of LMW and trimers multimeric forms; (ii) LMW and trimer, not HMW, are most broadly correlated with metabolic traits in AAs. Thus, HMW adiponectin may exert less bioactivity in explaining the metabolic syndrome trait cluster in populations of predominant African genetic background.

Longitudinal analysis of the insulin-like growth factor system in African-American and European American children and adolescents.

Abstract: Context: IGF-I and its binding proteins influence growth, development, and disease risk. Studies have revealed ethnic variations in the IGF system. Objective: This longitudinal study was undertaken to test the hypothesis that the ethnic differences in the IGF system exist throughout the pubertal transition, and these differences are mediated at least in part by inherent differences in insulin dynamics. Design: This was a longitudinal study. Annual evaluations were conducted for pubertal maturation, body composition, acute insulin response to glucose (AIRg), and reproductive-endocrine profile. Hormones and binding proteins were determined using standard assays, the AIRg during a frequently sampled iv glucose tolerance test, and body composition by dual-energy x-ray absorptiometry. Mixed model analyses were used to identify and characterize ethnic differences in the IGF system across the pubertal transition after adjusting for ethnicity, sex, age, maturation status, body composition, and reproductive hormones, and to identify the contribution of insulin to IGF binding protein (IGFBP)-1. Participants: Subjects included African-American (AA) and European American children (n = 162 at baseline) aged 7–16 yr, evaluated across the pubertal transition. Main Outcome Measures: Annual data on IGF-I, IGFBP-1, and IGFBP-3 were examined. Results: IGF-I was higher in AA children at pubertal stage 1 only (P < 0.001). However, IGFBP-3 and IGFBP-1 concentrations were lower in AAs through much of puberty (P < 0.05). The lower IGFBP-1 of AAs was in part explained by greater AIRg. Conclusions: Our data suggest that the higher IGF-I and lower IGFBP-1 and IGFBP-3 levels in AAs as compared with European Americans during puberty suggest potential ethnic differences in circulating bioavailable IGF-I. In addition, higher AIRg in AAs may lead to greater bioavailable IGF-I. Whether these differences in the IGF system account for disparities in disease risk warrants further investigation.

Genetic variation in a member of the laminin gene family affects variation in body composition in Drosophila and humans

Abstract: The objective of the present study was to map candidate loci influencing naturally occurring variation in triacylglycerol (TAG) storage using quantitative complementation procedures in Drosophila melanogaster. Based on our results from Drosophila, we performed a human population-based association study to investigate the effect of natural variation in LAMA5 gene on body composition in humans. We identified four candidate genes that contributed to differences in TAG storage between two strains of D. melanogaster, including Laminin A (LanA), which is a member of the α subfamily of laminin chains. We confirmed the effects of this gene using a viable LanA mutant and showed that female flies homozygous for the mutation had significantly lower TAG storage, body weight, and total protein content than control flies. Drosophila LanA is closely related to human LAMA5 gene, which maps to the well-replicated obesity-linkage region on chromosome 20q13.2-q13.3. We tested for association between three common single nucleotide polymorphisms (SNPs) in the human LAMA5 gene and variation in body composition and lipid profile traits in a cohort of unrelated women of European American (EA) and African American (AA) descent. In both ethnic groups, we found that SNP rs659822 was associated with weight (EA: P = 0.008; AA: P = 0.05) and lean mass (EA: P= 0.003; AA: P = 0.03). We also found this SNP to be associated with height (P = 0.01), total fat mass (P = 0.01), and HDL-cholesterol (P = 0.003) but only in EA women. Finally, significant associations of SNP rs944895 with serum TAG levels (P = 0.02) and HDL-cholesterol (P = 0.03) were observed in AA women. Our results suggest an evolutionarily conserved role of a member of the laminin gene family in contributing to variation in weight and body composition.

Ethnicity and weight status affect the accuracy of proxy indices of insulin sensitivity.

Abstract: This study tested the hypotheses that correlations between direct measures of insulin sensitivity and proxy indices of insulin sensitivity derived from fasting values, (i) would not be affected by ethnicity, and (ii) would be stronger in overweight vs. weight-reduced states. We further hypothesized that associations between proxy indices and fat distribution would be similar to those between directly measured insulin sensitivity and fat distribution. Testing was performed in weight-stable conditions in 59 African-American (AA) and 62 white-American (WA) overweight, premenopausal women before and after a weight loss intervention. Subjects were retested 1 year following weight loss. Proxy indices were correlated against the insulin sensitivity index SI determined via minimal modeling. Fat distribution was assessed using computed tomography. Correlations between Si and proxy indices were consistently stronger among overweight women (r = 0.44–0.52) vs. weight-reduced women (r = 0.18–0.32), and among AA (r = 0.49–0.56, baseline; 0.24–0.36, weight-reduced) vs. WA (r = 0.38–0.46, baseline; 0.19–0.31, weight-reduced). Among subjects who regained >3 kg after 1 year, correlations between SI and proxy indices were similar to those observed at baseline, whereas correlations were weak among women who maintained their reduced body weight. SI and all proxy indices were similarly correlated with intra-abdominal adipose tissue (IAAT) at baseline, but not after weight loss. In conclusion, correlations between SI and proxy indices were affected by both ethnicity and weight status. If proxy indices are used in multiethnic populations, or in populations including both lean and overweight/obese subjects, data should be interpreted with caution.

IAAT, catecholamines, and parity in African-American and European-American women.

Abstract: Objective: We have recently reported that parous European-American (EA) women have disproportionately more intra-abdominal adipose tissue (IAAT) than their nulliparous counterparts. Mediating mechanisms for IAAT accumulation remain unknown; however, some evidence suggests a possible catecholamine link. The objective of this study was to determine whether the IAAT-parity relationship found in EA women exists in African-American (AA) women and to determine whether catecholamines play a mediating role. Methods and Procedures: Subjects included 44 EA and 47 AA premenopausal women. Free-living physical activity by doubly labeled water (activity-related time equivalent (ARTE)), body composition (air plethysmography, computed tomography), and 24-h fractionated urinary catecholamines were measured. Results: Repeated measures ANOVA revealed parous EA and AA women had significantly higher IAAT than their nulliparous counterparts (100.1 ± 28.5 and 76.2 ± 34.8 cm2 vs. 75.9 ± 29.1 and 59.6 ± 15.0 cm2). In AA women and nulliparous women, 24-h urinary dopamine was significantly higher (AA parous 260.8 ± 88; EA parous 197.2 ± 78.8; AA nulliparous 376.5 ± 81; EA nulliparous 289.6 ± 62). Multiple regression analysis for modeling IAAT indicated that race, parity, dopamine, ARTE, and VO2max were all significant and independent contributors to the model (Unstandardized βs: race −32.6 ± 7.4; parity (number of births) 10.0 ± 3.4; 24-h urinary dopamine 0.08 ± 0.04; ARTE (min/day) −0.09 ± 0.04; VO2max (ml/kg/min) −2.8 ± 1.0). Discussion: Independent of the potential confounders: age, race, percent body fat, IAAT, 24-h fractionated urinary catecholamines, physical activity, and VO2max, parous EA and AA women had more IAAT than their nulliparous counterparts. Of the catecholamines, dopamine was found to be significantly lower in parous women and higher in AA's. Dopamine, however, did not explain racial or parity differences in IAAT.

Baseline inflammatory markers do not modulate the lipid response to weight loss

Abstract: Recent studies have found that baseline inflammatory status affected the response of the lipid profile to diet intervention. The goal of this study was to determine whether baseline inflammatory status, as reflected in C-reactive protein, interleukin 6, and tumor necrosis factor alpha, affected the lipid and insulin response to a weight loss intervention. A second goal was to determine whether inflammatory markers were related to traditional metabolic risk factors, such as lipids and insulin, in our sample of 190 overweight (body mass index, 27-30 kg/m2) premenopausal women. Body composition, fat distribution, serum lipids, insulin sensitivity (Si), and markers of inflammation were assessed at baseline and after weight loss to body mass index<25 kg/m2. All measurements were taken after a 4-week period of weight maintenance. Mixed-model, repeated-measures analysis was used to determine whether the interaction of baseline inflammatory status and time was significant in determining the changes in metabolic risk factors (Si and lipids) with weight loss. Weight loss was associated with significant reductions in total cholesterol, low-density lipoprotein cholesterol, triglycerides, and insulin, and increases in high-density lipoprotein cholesterol and Si. Triglycerides were higher (P=.054) and Si lower (P=.057) with increasing C-reactive protein tertile. The interaction of baseline inflammatory status and time was not significant for any outcome variable of interest. These results do not support the hypothesis that baseline inflammatory status affects the lipid and insulin response to a weight loss intervention. However, in these young, healthy women, weight loss had a beneficial impact on both inflammatory status and risk factors for chronic metabolic disease.