Overall survival in the OlympiA phase III trial of adjuvant olaparib in patients with germline pathogenic variants in BRCA1/2 and high-risk, early breast cancer

BACKGROUND

The randomized, double-blind OlympiA trial compared 1 year of the oral poly(adenosine diphosphate-ribose) polymerase inhibitor, olaparib, to matching placebo as adjuvant therapy for patients with pathogenic or likely pathogenic variants in germline BRCA1 or BRCA2 (gBRCA1/2pv) and high-risk, human epidermal growth factor receptor 2-negative, early breast cancer (EBC). The first pre-specified interim analysis (IA) previously demonstrated statistically significant improvement in invasive disease-free survival (IDFS) and distant disease-free survival (DDFS). The olaparib group had fewer deaths than the placebo group, but the difference did not reach statistical significance for overall survival (OS). We now report the pre-specified second IA of OS with updates of IDFS, DDFS, and safety.

PATIENTS AND METHODS

One thousand eight hundred and thirty-six patients were randomly assigned to olaparib or placebo following (neo)adjuvant chemotherapy, surgery, and radiation therapy if indicated. Endocrine therapy was given concurrently with study medication for hormone receptor-positive cancers. Statistical significance for OS at this IA required P < 0.015.

RESULTS

With a median follow-up of 3.5 years, the second IA of OS demonstrated significant improvement in the olaparib group relative to the placebo group [hazard ratio 0.68; 98.5% confidence interval (CI) 0.47-0.97; P = 0.009]. Four-year OS was 89.8% in the olaparib group and 86.4% in the placebo group (Δ 3.4%, 95% CI -0.1% to 6.8%). Four-year IDFS for the olaparib group versus placebo group was 82.7% versus 75.4% (Δ 7.3%, 95% CI 3.0% to 11.5%) and 4-year DDFS was 86.5% versus 79.1% (Δ 7.4%, 95% CI 3.6% to 11.3%), respectively. Subset analyses for OS, IDFS, and DDFS demonstrated benefit across major subgroups. No new safety signals were identified including no new cases of acute myeloid leukemia or myelodysplastic syndrome.

CONCLUSION

With 3.5 years of median follow-up, OlympiA demonstrates statistically significant improvement in OS with adjuvant olaparib compared with placebo for gBRCA1/2pv-associated EBC and maintained improvements in the previously reported, statistically significant endpoints of IDFS and DDFS with no new safety signals.

Cross-calibration of body-composition techniques against dual-energy X-ray absorptiometry in young children

Using dual-energy X-ray absorptiometry (DXA) as a standard method for determining body composition in children, we evaluated the accuracy of skinfold-thickness measurements (with the Slaughter et al equations, which are based on triceps and calf skinfold-thickness measurements), bioelectrical resistance (BR; with the Kushner el al equations and age-specific hydration constants), and other clinical measurements (individual skinfold thicknesses and body mass index) for the assessment of body fat in children. We studied a heterogenous group of 49 boys and 49 girls, aged 6.6 +/- 1.4 y and weighing 24.1 +/- 5.9 kg. Fat mass estimated by DXA was significantly lower than fat mass measured by skinfold thickness, even though fat mass measurements by these two techniques were strongly related to each other. Fat mass estimated by DXA was also significantly lower than fat mass measured by BR, and the model R2 and SEE were not as strong as for the skinfold-thickness technique. Fat mass estimated by DXA also correlated with other clinical indexes such as triceps skinfold thickness, body mass index, body weight, and subscapular skinfold thickness. In forward-regression analysis, subscapular skinfold thickness, body weight, triceps skinfold thickness, sex, and height2/resistance estimated the value for fat mass measured by DXA with a model R2 of 0.91 and an SEE of 0.94 kg fat mass. These studies suggest that existing techniques for assessing body fat in children may be inaccurate. We provide new anthropometric equations based on the use of DXA as a criterion that provide accurate and precise measures of body fat and fat-free mass in white children aged 4-9 y. This approach provides estimates of body fat standardized to a known laboratory standard of chemical analysis of carcasses.

Visceral fat, insulin sensitivity, and lipids in prepubertal children

In adults, visceral fat accumulation is associated with insulin resistance and dyslipidemia. The cause-and-effect nature of these relationships is not clear. The objective of the present study was to determine if similar relationships exist in prepubertal children. Specifically, we determined whether visceral fat was associated with fasting insulin, insulin sensitivity (Si), serum triglyceride (TG) concentration, or serum HDL cholesterol (HDL-C) concentration; whether visceral fat or Si was independently related to lipids; and whether ethnicity influenced the relationship between visceral fat and risk factors. Subjects were 61 prepubertal African-American and Caucasian children. Total body fat was determined by dual-energy X-ray absorptiometry, visceral fat by computed tomography, and insulin sensitivity by the tolbutamide-modified, frequently sampled intravenous glucose tolerance test with minimal modeling. In multiple linear regression analysis (adjusting for total fat, sex, and ethnicity), visceral fat was independently related to TG (P < 0.05) and fasting insulin (P < 0.001), but not Si (P = 0.425). Total body fat was independently related to Si (P < 0.001). Si was independently related to fasting insulin (P < 0.001) but not to TG or HDL-C (P = 0.941 and 0.201, respectively). Si in African-Americans was 42% lower than in Caucasians (0.50 +/- 0.05 vs. 0.86 +/- 0.11 x 10(-5) min(-1) x pmol(-1) x l, mean +/- SE after adjusting for total fat, P < 0.001). Nonetheless, ethnicity was not independently related to either TG or HDL-C (P = 0.075 and 0.619, respectively, after adjusting for total and visceral fat and sex). The slopes of the relationships of total and visceral fat with risk factors did not differ with ethnicity. In conclusion, visceral fat appears metabolically unique in children, being independently associated with elevated TG and insulin but not Si. Obese children and African-American children were more insulin resistant, independent of visceral fat accumulation. Lower Si was associated with higher, faster insulin, but not dyslipidemia. Thus, obesity, visceral fat accumulation, and ethnicity in children may confer negative, but independent, health risks.

Precision and accuracy of dual-energy X-ray absorptiometry for determining in vivo body composition of mice

OBJECTIVE

To evaluate the precision and accuracy of dual-energy X-ray absorptiometry (DXA) for the measurement of total-bone mineral density (TBMD), total-body bone mineral (TBBM), fat mass (FM), and bone-free lean tissue mass (LTM) in mice.

RESEARCH METHODS AND PROCEDURES

Twenty-five male C57BL/6J mice (6 to 11 weeks old; 19 to 29 g) were anesthetized and scanned three times (with repositioning between scans) using a peripheral densitometer (Lunar PIXImus). Gravimetric and chemical extraction techniques (Soxhlet) were used as the criterion method for the determination of body composition; ash content was determined by burning at 600 degrees C for 8 hours.

RESULTS

The mean intraindividual coefficients of variation (CV) for the repeated DXA analyses were: TBMD, 0.84%; TBBM, 1.60%; FM, 2.20%; and LTM, 0.86%. Accuracy was determined by comparing the DXA-derived data from the first scan with the chemical carcass analysis data. DXA accurately measured bone ash content (p = 0.942), underestimated LTM (0.59 +/- 0.05g, p < 0.001), and overestimated FM (2.19 +/- 0.06g, p < 0.001 ). Thus, DXA estimated 100% of bone ash content, 97% of carcass LTM, and 209% of carcass FM. DXA-derived values were then used to predict chemical values of FM and LTM. Chemically extracted FM was best predicted by DXA FM and DXA LTM [FM = -0.50 + 1.09(DXA FM) - 0.11(DXA LTM), model r2 = 0.86, root mean square error (RMSE) = 0.233 g] and chemically determined LTM by DXA LTM [LTM = -0.14 + 1.04(DXA LTM), r2 = 0.99, RMSE = 0.238 g].

DISCUSSION

These data show that the precision of DXA for measuring TBMD, TBBM, FM, and LTM in mice ranges from a low of 0.84% to a high of 2.20% (CV). DXA accurately measured bone ash content but overestimated carcass FM and underestimated LTM. However, because of the close relationship between DXA-derived data and chemical carcass analysis for FM and LTM, prediction equations can be derived to more accurately predict body composition.

Developmental changes in energy expenditure and physical activity in children: evidence for a decline in physical activity in girls before puberty

OBJECTIVE

To examine individual changes in energy expenditure and physical activity during prepubertal growth in boys and girls.

METHODS

Total energy expenditure (TEE), resting energy expenditure, physical activity-related energy expenditure, reported physical activity, and fat and fat-free mass were measured three times over 5 years in 11 boys (5.3 +/- 0.9 years at baseline) and 11 girls (5.5 +/- 0.9 years at baseline).

RESULTS

Four-year increases in fat ( approximately 6 kg) and fat-free mass ( approximately 10 kg) and resting energy expenditure ( approximately 200 kcal/day) were similar in boys and girls. In boys, TEE increased at each measurement year, whereas in girls, there was an initial increase from age 5.5 (1365 +/- 330 kcal/day) to age 6.5 (1815 +/- 392 kcal/day); however, by age 9.5, TEE was reduced significantly (1608 +/- 284 kcal/day) with no change in energy intake. The gender difference in TEE changes over time was explained by a 50% reduction in physical activity (kcal/day and hours/week) in girls between the ages of 6.5 and 9.5.

CONCLUSIONS

These data suggest a gender dimorphism in the developmental changes in energy expenditure before adolescence, with a conservation of energy use in girls achieved through a marked reduction in physical activity.

Retinal pigmented epithelial cells induced to transdifferentiate to neurons by laminin

Although the regeneration of nervous tissue in the vertebrate is very limited, there are a few remarkable examples of this process. Understanding the factors that regulate CNS regeneration in those areas of the nervous system where it occurs, will doubtless provide generally applicable, essential information about the process. It has been known for some time that the amphibian retina regenerates following its destruction. Transplant studies, confirmed later by in vitro experiments, have shown that one source of new neurons in regenerating retina is the retinal pigmented epithelium (RPE). RPE cells can transdifferentiate to either neurons or lens cells in culture, but little is known about the factors that regulate this process. A recent study in vivo of retinal regeneration provided evidence that the association of RPE cells with the retinal vascular membrane is an important step in transdifferentiation. We report here that transdifferentiation in vitro is profoundly influenced by the substrate on which the cells are cultured; RPE cells plated on laminin-containing substrates frequently transdifferentiate into neurons. In addition, we have found a high concentration of laminin in the Rana retinal vascular membrane. Therefore, we propose that retinal regeneration is initiated by changes in the composition of the extracellular matrix that RPE cells contact early in the process.

Do adaptive changes in metabolic rate favor weight regain in weight-reduced individuals? An examination of the set-point theory

BACKGROUND

Obese persons generally regain lost weight, suggesting that adaptive metabolic changes favor return to a preset weight.

OBJECTIVE

Our objective was to determine whether adaptive changes in resting metabolic rate (RMR) and thyroid hormones occur in weight-reduced persons, predisposing them to long-term weight gain.

DESIGN

Twenty-four overweight, postmenopausal women were studied at a clinical research center in four 10-d study phases: the overweight state (phase 1, energy balance; phase 2, 3350 kJ/d) and after reduction to a normal-weight state (phase 3, 3350 kJ/d; phase 4, energy balance). Weight-reduced women were matched with 24 never-overweight control subjects. After each study phase, assessments included RMR (by indirect calorimetry), body composition (by hydrostatic weighing), serum triiodothyronine (T(3)), and reverse T(3) (rT(3)). Body weight was measured 4 y later, without intervention.

RESULTS

Body composition-adjusted RMR and T(3):rT(3) fell during acute (phase 2) and chronic (phase 3) energy restriction (P: < 0.01), but returned to baseline in the normal-weight, energy-balanced state (phase 4; mean weight loss: 12.9 +/- 2.0 kg). RMR among weight-reduced women (4771 +/- 414 kJ/d) was not significantly different from that in control subjects (4955 +/- 414 kJ/d; P: = 0.14), and lower RMR did not predict greater 4-y weight regain (r = 0.27, NS).

CONCLUSIONS

Energy restriction produces a transient hypothyroid-hypometabolic state that normalizes on return to energy-balanced conditions. Failure to establish energy balance after weight loss gives the misleading impression that weight-reduced persons are energy conservative and predisposed to weight regain. Our findings do not provide evidence in support of adaptive metabolic changes as an explanation for the tendency of weight-reduced persons to regain weight.

Monoclonal antibodies for high-resolution localization of NHE3 in adult and neonatal rat kidney

Previous immunochemical studies have shown that NHE3 is an apical Na+/H+ exchanger in some renal epithelia. The purpose of the present study was to develop high-affinity, isoform-specific monoclonal antibodies (MAbs) that would be useful for carrying out high-resolution immunocytochemical studies of NHE3 in the adult and neonatal mammalian kidney. Three MAbs were developed to a fusion protein containing amino acids 702-832 of rabbit NHE3. Specificity was established by immunoblotting membranes from NHE-deficient LAP cells that had been transfected with either NHE1,-2, -3, or -4. With the use of high-resolution immunocytochemical techniques, NHE3 was found in vesicles in the apical cytoplasm of proximal tubule cells, as well as in the apical plasma membrane of the proximal tubule, and in both the thin and thick limbs of the loop of Henle. When localized in the 1-day-old rat kidney, NHE3 was first detected in the late stages of the S-shaped body. In later stages of nephron development, the pattern of NHE3 staining was similar to that seen in the adult. This study demonstrates 1) the specificity of three MAbs for Na+/H+ exchanger isoform NHE3; 2) NHE3 is present in an intracellular vesicular compartment in cells of the proximal tubule, consistent with possible regulation by membrane recycling; and 3) NHE3 is expressed on the apical membrane in early stages of the developing nephron.

Cross-calibration of fat and lean measurements by dual-energy X-ray absorptiometry to pig carcass analysis in the pediatric body weight range

The objective of this study was to cross-calibrate measurements of body composition by dual-energy X-ray absorptiometry (DXA) with chemical analysis of carcasses of pigs in the pediatric range of body weight. Eighteen pigs (25.5 +/- 7.0 kg; 9.9-32.8% body fat) were scanned in duplicate by using DXA with a Lunar DPX-L densitometer in the pediatric medium and adult fast-detail scan modes. Pigs were then killed and their carcasses analyzed completely. Carcass lean and fat contents were highly correlated with DXA measurement in both scan modes (Pearson r values > 0.98). For lean mass, the relation between carcass content and DXA measures was not significantly different from the line of identity in the adult mode, but was in the pediatric mode. For fat mass, the relations between carcass content and DXA measures were significantly different from the line of identity in both the adult and pediatric modes. In duplicate scans, the reliability of DXA measures of lean mass and fat mass was excellent in both scan modes. Because neither the adult nor the pediatric scan mode provided accurate measures of fat and lean mass, we derived specific correction factors to improve the measurement of total fat and lean compartments, thereby calibrating the Lunar DPX-L to the laboratory standard of carcass analysis in pigs.

Prediction of intra-abdominal and subcutaneous abdominal adipose tissue in healthy pre-pubertal children

OBJECTIVE

To examine the relationship of intra-abdominal adipose tissue (IAAT) and subcutaneous abdominal adipose tissue (SAAT) with body composition and anthropometry in children.

DESIGN

Cross-sectional data analysis.

SUBJECTS

113 healty Caucasian and African-American, pre-pubertal children aged 4-10 y.

MEASUREMENTS

IAAT and SAAT by single slice computed tomography at the level of the umbilicus; total fat and trunk fat by dual energy X-ray absorptiometry (DEXA); anthropometric evaluation by skinfolds and circumferences.

RESULTS

IAAT was most strongly correlated with abdominal skinfold (r = 0.88) and trunk fat by DEXA (r = 0.87), and SAAT with trunk fat by DEXA (r = 0.96), total fat by DEXA (r = 0.93) and waist circumference (r = 0.93). In stepwise regression, IAAT was best predicted by trunk fat from DEXA, total fat from DEXA, and abdominal skinfold (R2 = 0.85); SAAT was best predicted by trunk fat from DEXA, body weight, waist circumference and abdominal skinfold (R2 = 0.96). In the absence of DEXA data, IAAT was best predicted by abdominal skinfold, ethnicity and subscapular skinfold (R2 = 0.82) and SAAT was best predicted by waist circumference subscapular skinfold, height and abdominal skinfold (R2=0.92). The prediction equations with and without DEXA were successfully cross-validated in an independent sample of 12 additional measures of IAAT and SAAT.

CONCLUSION

These data provide useful information that can help in the interpretation of anthropometric data with regard to body fat distribution. IAAT and SAAT can be accurately estimated in Caucasian and African-American prepubertal children from anthropometry with and without the availability of DEXA data.

Visceral fat in white and African American prepubertal children

The objectives of this study were 1) to examine interrelations among intraabdominal adipose tissue (IAAT) and other adiposity indexes, 2) to identify a visceral obesity index that is independent of total adiposity, and 3) to examine sex and ethnic (white compared with African American) differences in IAAT. We measured IAAT and subcutaneous abdominal adipose tissue (SAAT) using computed tomography, and total fat mass (FM) by dual-energy X-ray absorptiometry in a heterogenous sample of 101 children aged 7.7 +/- 1.6 y weighing 33.2 +/- 12.6 kg. IAAT was highly variable (mean +/- SE; 31 +/- 22 cm2; range: 7-107 cm2) and related to SAAT (r = 0.87) and FM (r = 0.81). The regression slope between IAAT and SAAT was significantly lower in African Americans (0.17 +/- 0.02 cm2 IATT/cm2 SAAT) than in whites (0.23 +/- 0.02 cm2 IAAT/cm2 SAAT). Within each ethnic group there was no effect of sex on IAAT adjusted for SAAT (mean +/- SE: 40.2 +/- 3.1 and 43.2 +/- 2.7 cm2 in white boys and girls, respectively; 26.4 +/- 1.9 and 25.1 +/- 1.6 cm2 in African American boys and girls, respectively). We conclude that in children 1) there is wide variation in visceral fatness; 2) IAAT relative to SAAT is an index of visceral fat, independent of FM, allowing examination of the unique effects of IAAT; and 3) the relative distribution of adipose tissue in the intraabdominal compared with the subcutaneous abdominal region is significantly lower in African Americans than in whites.

Longitudinal changes in fatness in white children: no effect of childhood energy expenditure

Reduced energy expenditure may predispose children to the development of obesity, but there are limited longitudinal studies to support this theory. We studied 75 white, preadolescent children over 4 y by taking annual measures of body composition and resting energy expenditure (by indirect calorimetry) and two annual measures of total energy expenditure and physical-activity-related energy expenditure (by doubly labeled water). Body composition of parents was assessed at the onset of the study with use of underwater weighing. The major outcome variable was the individual rate of change in fat mass (FM) adjusted for fat-free mass (FFM). The influence of sex, energy expenditure components, initial FM, and parental FM on the rate of change in FM was analyzed by hierarchical linear modeling and analysis of variance. The rate of change in absolute FM was 0.89 +/- 1.08 kg/y (range: -0.44 to 5.6 kg/y). The rate of change in FM adjusted for FFM was 0.08 +/- 0.64 kg/y (range: -1.45 to 2.22 kg/y) and was similar among children of two nonobese parents and children with one nonobese or one obese parent, but was significantly higher in children with two obese parents (0.61 +/- 0.87 kg/y). The major determinants of change in FM adjusted for FFM were sex (greater fat gain in girls), initial fatness, and parental fatness. None of the components of energy expenditure were inversely related to change in FM. The main predictors of change in FM relative to FFM during preadolescent growth are sex, initial fatness, and parental fatness, but not reduced energy expenditure.

Physical activity related energy expenditure and fat mass in young children

OBJECTIVE

To examine whether body fat content in pre-pubertal children is influenced by physical activity related energy expenditure (AEE) and/or more qualitative aspects of physical activity.

DESIGN

Cross-sectional study.

SUBJECT

101 pre-pubertal children were examined in Study 1: (age: 5.3 +/- 0.9 y; weight: 20.2 +/- 3.6 kg). In Study 2: 68 of the original children were re-examined (age: 6.3 +/- 0.9 y; weight: 23.6 +/- 5.0 y).

MEASUREMENT

Fat mass (FM) and fat free mass (FFM) were determined by bioelectrical resistance and skinfolds; AEE was estimated from the difference between total energy expenditure (TEE) by doubly labeled water and post-prandial resting energy expenditure (REE) by indirect calorimetry; qualitative information on activity was derived by questionnaire.

RESULTS

AEE was significantly correlated with FFM (r = 0.32 in both Studies) and body weight (r = 0.28 in Study 1; r = 0.29 in Study 2), but not FM. There were no significant relationships between AEE and any of the variables from the activity questionnaire in children (including TV time, playing time, and an accumulated activity index in h/week). After adjusting for FFM, age, and gender, FM was inversely related to activity time in h/week (partial r = -0.24 in Study 1; partial r = -0.32 in Study 2) but not AEE (P > 0.5).

CONCLUSION

After adjusting for FFM, age, and gender, a small portion of the variance in body fat mass in children (approximately 10%) is explained by time devoted to recreational activity, whereas none of the variance is explained by the combined daily energy expenditure related to physical activity.

Specific association of megalin and the Na+/H+ exchanger isoform NHE3 in the proximal tubule

We investigated whether the renal brush border Na+/H+ exchanger NHE3 exists in assemblies with other proteins in native kidney membranes. To this end we generated monoclonal antibodies (mAbs) against affinity purified NHE3 protein complexes. Hybridomas were selected based on ability to immunoprecipitate NHE3. One of the resulting mAbs (10A3) labeled a high molecular mass (>200 kDa) protein and stained primarily the coated pit region of the proximal tubule in a manner similar to that described for megalin (gp330). We then confirmed that both mAb 10A3 and a known anti-megalin mAb immunoprecipitated and immunoblotted the same protein, namely megalin. mAb 10A3 specifically co-precipitated NHE3 but not villin or NaPi-2 from solubilized renal membranes, indicating specificity of the NHE3-megalin interaction. When immunoprecipitations were performed using either 10A3 or anti-NHE3 mAb 2B9 after separation of solubilized renal proteins by sucrose velocity gradient centrifugation, we found that NHE3 exists in two states with distinct sedimentation coefficients, a 9.6 S megalin-free form and a 21 S megalin-bound form, and that when NHE3 assembles with megalin, epitopes within the carboxyl-terminal 131 amino acids of NHE3 are blocked. Taken together, these findings indicate that a significant pool of NHE3 exists as a multimeric complex with megalin in the brush border of the proximal tubule.

Association of Na(+)-H(+) exchanger isoform NHE3 and dipeptidyl peptidase IV in the renal proximal tubule

In an attempt to identify proteins that assemble with the apical membrane Na(+)-H(+) exchanger isoform NHE3, we generated monoclonal antibodies (mAbs) against affinity-purified NHE3 protein complexes isolated from solubilized renal microvillus membrane vesicles. Hybridomas were selected based on their ability to immunoprecipitate NHE3. We have characterized in detail one of the mAbs (1D11) that specifically co-precipitated NHE3 but not villin or NaPi-2. Western blot analyses of microvillus membranes and immunoelectron microscopy of kidney sections showed that mAb 1D11 recognizes a 110-kDa protein highly expressed on the apical membrane of proximal tubule cells. Immunoaffinity chromatography was used to isolate the antigen against which mAb 1D11 is directed. N-terminal sequencing of the purified protein identified it as dipeptidyl peptidase IV (DPPIV) (EC ), which was confirmed by assays of DPPIV enzyme activity. We also evaluated the distribution of the NHE3-DPPIV complex in microdomains of rabbit renal brush border. In contrast to the previously described NHE3-megalin complex, which principally resides in a dense membrane population (coated pits) in which NHE3 is inactive, the NHE3-DPPIV complex was predominantly in the microvillar fraction in which NHE3 is active. Serial precipitation experiments confirmed that anti-megalin and anti-DPPIV antibodies co-precipitate different pools of NHE3. Taken together, these studies revealed an unexpected association of the brush border Na(+)-H(+) exchanger NHE3 with dipeptidyl peptidase IV in the proximal tubule. These findings raise the possibility that association with DPPIV may affect NHE3 surface expression and/or activity.

Predicting body composition from anthropometry in pre-adolescent children

The objectives of this paper were to: a) evaluate the accuracy and precision of previously published pediatric body composition prediction equations and b) develop additional prediction equations from a large, heterogeneous group of Caucasian (n = 133) and African-American (n = 69) children. The combined cohort of 202 children included a wide range of ages (4.0-10.9 y), weights (14.0-70.8 kg), fat mass (FM: 1.2-28.5 kg) and percent body fat (% body fat: 6.2-49.6%). Skinfold measurements were obtained using a Lange caliper and body fat was measured with a Lunar DPX-L densitometer. The previously published equations of Slaughter et al and Goran et al did not accurately predict body fat. The entire cohort was randomly divided into two sub-groups for purposes of deriving and cross-validating a new prediction equation. In stepwise regression analysis in the development group (n = 135), weight, triceps skinfold, gender, ethnicity and abdominal skinfold estimated FM measured by dual energy x-ray absorptiometry (DEXA) with a model R2 of 0.95. The new prediction equation was cross-validated in the control group (n = 67) and each ethnic and gender subgroup. We conclude that a) the equations of Slaughter et al and Goran et al did not accurately predict FM in a heterogeneous group of children and b) a new anthropometric prediction equation is proposed that may provide accurate estimates of FM in both Caucasian and African-American children aged 4-10 y with a wide range of FM and body composition.

Antipsychotic drug-induced weight gain: development of an animal model

OBJECTIVE

Weight gain is a prominent effect of most atypical antipsychotic drugs (AAPDs); yet, the mechanisms are not fully understood and no well-established mouse models exist for investigating the mechanisms. Thus, we developed a mouse model to evaluate the effects of AAPDs on eating, body weight (BW), and body composition.

METHODS

Female C57BL/6J mice were used to test olanzapine, quetiapine, ziprasidone, and risperidone. Mice were acclimated to individual housing, given ad libitum access to chow and water, dosed with placebo peanut butter pills for 1 week, and then dosed daily with AAPD-laced peanut butter pills for 4 weeks. Weekly food intakes and BWs were measured, and body compositions were determined at the end of each experiment.

RESULTS

After 4 weeks of treatment, olanzapine, quetiapine, ziprasidone, and risperidone caused significant weight increases, but only olanzapine and quetiapine were associated with significantly increased food intake. Body composition data revealed that olanzapine-treated mice had more relative fat mass and risperidone-treated mice had more relative lean mass than did control mice. Quetiapine and ziprasidone did not significantly affect relative body composition even though BW was increased.

CONCLUSIONS

Oral AAPD administration causes increased BW in female mice. Our mouse model of AAPD-induced weight gain resembles the human response to these medications and will be used to investigate the mechanisms for weight gain and fat accumulation.

Cholesterol potentiates ABCG2 activity in a heterologous expression system: improved in vitro model to study function of human ABCG2

ABCG2, a transporter of the ATP-binding cassette family, is known to play a prominent role in the absorption, distribution, metabolism, and excretion of xenobiotics. Drug-transporter interactions are commonly screened by high-throughput systems using transfected insect and/or human cell lines. The determination of ABCG2-ATPase activity is one method to identify ABCG2 substrate and inhibitors. We demonstrate that the ATPase activities of the human ABCG2 transfected Sf9 cell membranes (MXR-Sf9) and ABCG2-overexpressing human cell membranes (MXR-M) differ. Variation due to disparity in the glycosylation level of the protein had no effect on the transporter. The influence of cholesterol on ABCG2-ATPase activity was investigated because the lipid compositions of insect and human cells are largely different from each other. Differences in cholesterol content, shown by cholesterol loading and depletion experiments, conferred the difference in stimulation of basal ABCG2-ATPase of the two cell membranes. Basal ABCG2-ATPase activity could be stimulated by sulfasalazine, prazosin, and topotecan, known substrates of ABCG2 in cholesterol-loaded MXR-Sf9 and MXR-M cell membranes. In contrast, ABCG2-ATPase could not be stimulated in MXR-Sf9 or in cholesterol-depleted MXR-M membranes. Moreover, cholesterol loading significantly improved the drug transport into inside-out membrane vesicles prepared from MXR-Sf9 cells. MXR-M and cholesterol-loaded MXR-Sf9 cell membranes displayed similar ABCG2-ATPase activity and vesicular transport. Our study indicates an essential role of membrane cholesterol for the function of ABCG2.

Voluntary sucrose ingestion, like corticosterone replacement, prevents the metabolic deficits of adrenalectomy

We tested whether corticosterone replacement causes increased sucrose drinking in adrenalectomized (ADX) rats compared to sham-ADX (sham) rats. ADX rats given high doses of corticosterone drank as much sucrose as sham rats, whereas at three lower doses of corticosterone, drinking was similar between groups and was only approximately 40% of that ingested by shams. Compared to sham rats, ADX rats drinking saline, or saline and saccharin, gain weight more slowly, contain less white adipose tissue, and have higher sympathetic outflow as assessed by uncoupling protein content in brown adipose tissue. Allowing sucrose as well as saline to drink restored all of these variables to normal in ADX rats with no- or low-corticosterone. All endpoints from sucrose-drinking ADX rats with no-or low-corticosterone were indistinguishable from those in water-drinking shams. By contrast, sucrose-drinking ADX rats that were given high doses of corticosterone exhibited the usual catabolic effects of corticosterone on body weight gain and, unlike sucrose-drinking shams, were obese. We conclude that (i) high corticosterone stimulates the potability of sucrose and inhibits sympathetic stimulation of uncoupling protein; (ii) sucrose, without corticosterone, normalizes metabolic deficits in ADX rats probably through actions mediated both peripherally and by the central nervous system; and (iii) ADX rats have a distinct sucrose appetite.

Corticosterone facilitates saccharin intake in adrenalectomized rats: does corticosterone increase stimulus salience?

Unlike normal rats, adrenalectomized rats do not voluntarily drink sweet saccharin solutions. To test whether this is a function of corticosterone in the circulation, and if corticosterone also increases the impetus for drinking saccharin after a period of withdrawal, we performed the following experiments. Young male rats were sham adrenalectomized (sham) or adrenalectomized (ADX); the ADX rats were provided with subcutaneous pellets containing (percent replacement of corticosterone, %B) 0%B, 15%B, 30%B or 100%B. Sham and ADX rats were immediately provided with saline (0.5%) and saccharin (2 mM) bottles in their home cages. Saccharin was allowed for 4 days on, 3 days off, 4 days on, 3 days off and a final day on, over the 15 days experiment. The dose of corticosterone determined both how much saccharin was voluntarily drunk by the ADX rats and the degree of overshoot after days off. Corticosterone also determined energy balance of the groups of ADX rats. The 30%B pellets restored food intake, body weight gain, insulin and caloric efficiency to the normal levels observed in sham rats. White fat depot weights and uncoupling protein concentration in brown adipose tissue were restored to sham levels by 100%B, suggesting that these variables which depend on activity in the sympathetic nervous system require considerable glucocorticoid receptor occupancy. We conclude that corticosterone increases the willingness to ingest sweetened water in a unimodal, dose-related manner, while moderate doses of corticosterone restore energy balance.

All three surface tryptophans in Type IIa cellulose binding domains play a pivotal role in binding both soluble and insoluble ligands

The three surface tryptophans of the Type IIa cellulose binding domain of Pseudomonas fluorescens subsp. cellulosa xylanase A (CBD(XYLA)) were independently mutated to alanine, to create the mutants W13A, W49A and W66A. The three mutant proteins were purified, and their capacity to bind to a variety of ligands was determined. The mutant proteins have native-like structures but exhibited much weaker affinity for crystalline and amorphous cellulose and for cellohexaose than the wild type. These data indicate that all three tryptophans are important for binding to cellulose, and support a model in which the three tryptophans form an aromatic strip on the surface of the protein that binds to a single cellulose.

Fat distribution and insulin response in prepubertal African American and white children

Ethnic differences in obesity-related disease prevalence may relate to differences in fat distribution or metabolism. We conducted a study in 73 African American and white children to examine the relation between fat distribution and insulin and to determine whether ethnic differences in fat distribution or in adiposity-insulin relations contribute to differences in insulin concentrations. Fasting and postchallenge insulin concentrations were determined by oral-glucose-tolerance test, total body fat by dual-energy X-ray absorptiometry, and subcutaneous abdominal (SAAT) and intraabdominal (IAAT) adipose tissue by computerized tomography. African Americans had greater fasting insulin (x +/- SD: 79 +/- 37 compared with 55 +/- 23 pmol/L, P < 0.01), incremental 30-min insulin (567 +/- 438 compared with 300 +/- 304 pmol/L, P < 0.001), and incremental area under the insulin curve (AUC; 262 +/- 209 compared with 164 +/- 156 pmol/L, P < 0.01). In multiple linear regression, fasting insulin was independently related to total fat within both ethnic groups (model R2 = 0.42 and 0.52 for African Americans and whites, respectively), incremental 30-min insulin to total fat and IAAT in whites only (model R2 = 0.71), and AUC to SAAT in African Americans only (model R2 = 0.49). Adjusting insulin indexes for adiposity did not eliminate the significant effect of ethnicity. In general, relations between adiposity and insulin were stronger in whites than in African Americans. African American children had higher insulin concentrations than white children after total body fat, IAAT, and SAAT were controlled for. However, strong relations between adiposity (total and abdominal) and insulin in both groups suggest that obesity may contribute to disease risk regardless of ethnicity.

A possible role for the vascular membrane in retinal regeneration in Rana catesbienna tadpoles

We have studied the process of retinal regeneration in Rana catesbienna tadpoles using a recently developed monoclonal antibody (2D3) directed against frog neurons and germinitive neuroepithelium. We have found that, following retinal degeneration induced by devascularization, new retina is generated in the posterior eye from transdifferentiating pigment epithelial (RPE) cells and in the anterior eye from increased proliferation at the normal growth zone in the ora serrata. This demonstrates that the anuran retina regenerates in a manner similar to that observed previously in urodeles. In addition, the use of MAb-2D3 has allowed us to study the process of RPE transdifferentiation more accurately than was previously possible, and consequently we have found a high degree of association of migratory pigment cells with the retinal vascular membrane at the time of the initial RPE transdifferentiation to retinal neuroblasts.

Solution structure of the CBM10 cellulose binding module from Pseudomonas xylanase A

Plant cell wall hydrolases generally have a modular structure consisting of a catalytic domain linked to one or more noncatalytic carbohydrate-binding modules (CBMs), whose common function is to attach the enzyme to the polymeric substrate. Xylanase A from Pseudomonas fluorescens subsp. cellulosa (Pf Xyn10A) consists of a family 10 catalytic domain, an N-terminal family IIa cellulose-binding module, and an internal family 10 cellulose-binding module. The structure of the 45-residue family 10 CBM has been determined in solution using NMR. It consists of two antiparallel beta-sheets, one with two strands and one with three, with a short alpha-helix across one face of the three-stranded sheet. There is a high density of aromatic residues on one side of the protein, including three aromatic residues (Tyr8, Trp22, and Trp24), which are exposed and form a flat surface on one face, in a classical polysaccharide-binding arrangement. The fold is closely similar to that of the oligonucleotide/oligosaccharide-binding (OB) fold, but appears to have arisen by convergent evolution, because there is no sequence similarity, and the presumed binding sites are on different faces.

Influence of sex, seasonality, ethnicity, and geographic location on the components of total energy expenditure in young children: implications for energy requirements

BACKGROUND

There are limited data on the influence of body composition, sex, seasonality, ethnicity, and geographic location on the components of energy expenditure in children.

OBJECTIVE

The objective was to examine the determinants of total energy expenditure (TEE), resting energy expenditure (REE), and activity-related energy expenditure (AEE) in children.

DESIGN

Cross-sectional data from 232 children (4-10 y of age) from 4 ethnic groups (white American, African American, Guatemalan Mestizo, and Native American Mohawk) were examined.

RESULTS

In 104 white children studied in Vermont and Alabama, TEE was significantly higher in spring than in fall, higher in boys than in girls, and higher in children in Vermont (all effects: approximately 0.42 MJ/d, P < 0.05). The significant effect of sex was explained through REE; the influences of season and location were explained through AEE. In all children, there was no effect of sex but a significant effect of ethnicity (P < 0.01) on TEE: a significant effect of sex (P < 0.01) and no effect of ethnicity (P = 0.16) on REE; and no effect of sex and a significant effect of ethnicity on AEE. The significant effects of ethnicity were due to lower values in Guatemalan children. TEE correlated most strongly with weight (r = 0.81) and fat-free mass (r = 0.79-0.81); REE with weight (r = 0.85) and fat-free mass (r = 0.80-0.87); and AEE with maximal oxygen consumption (r = 0.54), fat-free mass (r = 0.50), and fat mass (r = 0.49).

CONCLUSIONS

1) Season and location influenced TEE in children through their effects on AEE, 2) a higher REE in boys was consistent across all groups examined, 3) Guatemalan children had lower TEE due to a lower AEE, 4) body weight may be the best predictor of TEE, and 5) maximal oxygen consumption was the strongest marker of AEE.