Resistance training and diastolic myocardial tissue velocities in obese children.

PURPOSE: The primary purpose of this study was to determine the effects of resistance exercise training on early diastolic myocardial velocities (E') in an obese pediatric population. METHODS: Twenty-three obese adolescents were selected to participate in either a resistance-based training program (RT; n = 13, 12.2 +/- 0.4 yr, body mass index [BMI] = 32.5 +/- 1.9 kg m(-2)) or a nonexercise control intervention (n = 10, 13.6 +/- 0.7 yr, BMI = 30.2 +/- 2.6 kg m(-2)) for 8 wk. All subjects had repeated echocardiographic assessments to determine left ventricular (LV) geometry, early transmitral flow velocity (E), and E'. RESULTS: LV mass and wall thicknesses did not significantly change with training or in controls. RT improved E' (11.9 +/- 0.5 to 13.3 +/- 0.5 cm s(-1), P< 0.01) in the presence of a decrease in E/E' (8.17 +/- 0.39 to 7.06 +/- 0.30 cm s(-1), P < 0.01), a marker of left atrial pressure. No changes were evident in the inactive control subjects. CONCLUSIONS: A supervised 8-wk RT exercise program improved early diastolic tissue velocity in obese children, independent of changes in LV morphology.

Measurement of the heme affinity for yeast dap1p, and its importance in cellular function.

Current studies on the Saccharomyces cerevisiae protein Dap1p have demonstrated a heme-related function within the ergosterol biosynthetic pathway. Here we present data to further the understanding of the role of heme in the proper biological functioning of Dap1p in cellular processes. First, we examined the role of Dap1p in stabilizing the P450 enzyme, Erg11p, a key regulatory protein in ergosterol biosynthesis. Our data indicate that the absence of Dap1p does not affect Erg11p mRNA, protein expression levels, or the protein degradation rates in S. Cerevisaie. Second, in order to probe the role of heme in the biological functioning of Dap1p, we measured ferric and ferrous heme binding affinities for Dap1p and the mutant Dap1pY138F, as well as equilibrium midpoint reduction potentials of the Fe(III)/Fe(II) couples. Our results show that both wild-type and mutant proteins bind heme in a 1:1 fashion, possessing tight ferric heme affinities, KD values of 400 pM and 200 nM, respectively, but exhibiting weak ferrous affinities, 2 and 10 microM, respectively. Additionally, the measured reduction potential of Dap1p, which was found to be -307 mV, is similar to that of other monotyrosinate hemoproteins. Although previous reports show the weaker affinity of Dap1pY138F for ferric heme lowers the production of ergosterol with respect to wild-type Dap1p in S. pombe, we find that Dap1pY138F expression is still sufficient to rescue the growth sensitivity of dap1Delta to fluconazole and methyl methanesulfonate in S. cerevisiae. Various interpretations of these results are discussed with respect to Dap1p function in the cell.

Exercise alone reduces insulin resistance in obese children independently of changes in body composition.

CONTEXT: The number of obese children with insulin resistance and type 2 diabetes is increasing, but the best management strategy is not clear. OBJECTIVE: The objective of this study was to assess the effect of a structured 8-wk exercise training program on insulin resistance and changes in body composition in obese children. DESIGN: The study was 8 wk of structured supervised exercise intervention with outcome measures before and after the exercise period. SUBJECTS: Fourteen obese children (12.70 +/- 2.32 yr; eight male, six female) with high fasting insulin levels were enrolled into the study. INTERVENTION: INTERVENTION consisted of 8 wk of supervised circuit-based exercise training, composed of three fully supervised 1-h sessions per week. OUTCOME MEASURES: Outcome measures were assessed pretraining program and posttraining program and included insulin sensitivity (euglycemic-hyperinsulinemic clamp studies), fasting insulin and glucose levels, body composition using dual energy x-ray absorptiometry scan, lipid profile, and liver function tests. RESULTS: Insulin sensitivity improved significantly after 8 wk of training (M(lbm) 8.20 +/- 3.44 to 10.03 +/- 4.33 mg/kg.min, P < 0.05). Submaximal exercise heart rate responses were significantly lower following the training (P < 0.05), indicating an improvement in cardiorespiratory fitness. Dual energy x-ray absorptiometry scans revealed no differences in lean body mass or abdominal fat mass. CONCLUSION: An 8-wk exercise training program increases insulin sensitivity in obese children, and this improvement occurred in the presence of increased cardiorespiratory fitness but is independent of measurable changes in body composition.

Increasing body mass index z-score is continuously associated with complications of overweight in children, even in the healthy weight range.

CONTEXT: Overweight/obesity in children is increasing. Incidence data for medical complications use arbitrary cutoff values for categories of overweight and obesity. Continuous relationships are seldom reported. OBJECTIVES: The objective of this study is to report relationships of child body mass index (BMI) z-score as a continuous variable with the medical complications of overweight. DESIGN: This study is a part of the larger, prospective cohort Growth and Development Study. SETTING: Children were recruited from the community through randomly selected primary schools. Overweight children seeking treatment were recruited through tertiary centers. PARTICIPANTS: Children aged 6-13 yr were community-recruited normal weight (n = 73), community-recruited overweight (n = 53), and overweight treatment-seeking (n = 51). Medical history, family history, and symptoms of complications of overweight were collected by interview, and physical examination was performed. Investigations included oral glucose tolerance tests, fasting lipids, and liver function tests. MAIN OUTCOME MEASURE: Adjusted regression was used to model each complication of obesity with age- and sex-specific child BMI z-scores entered as a continuous dependent variable. RESULTS: Adjusted logistic regression showed the proportion of children with musculoskeletal pain, obstructive sleep apnea symptoms, headaches, depression, anxiety, bullying, and acanthosis nigricans increased with child BMI z-score. Adjusted linear regression showed BMI z-score was significantly related to systolic and diastolic blood pressure, insulin during oral glucose tolerance test, total cholesterol, high-density lipoprotein, triglycerides, and alanine aminotransferase. CONCLUSION: Child's BMI z-score is independently related to complications of overweight and obesity in a linear or curvilinear fashion. Children's risks of most complications increase across the entire range of BMI values and are not defined by thresholds.

Spectroscopic and biochemical characterization of heme binding to yeast Dap1p and mouse PGRMC1p.

Yeast damage-associated response protein (Dap1p) and mouse progesterone receptor membrane component-1 protein (mPGRMC1p) belong to a highly conserved class of putative membrane-associated progesterone binding proteins (MAPR), with Dap1p and inner zone antigen (IZA), the rat homologue of mPGRMC1p, recently being reported to bind heme. While primary structure analysis reveals similarities to the cytochrome b(5) motif, neither of the two axial histidines responsible for ligation to the heme is present in any of the MAPR proteins. In this paper, EPR, MCD, CD, UV-vis, and general biochemical methods have been used to characterize the nature of heme binding in both Dap1p and a His-tagged, membrane anchor-truncated mPGRMC1p. As isolated, Dap1p is a tetramer which can be converted to a dimer upon addition of 150 mM salt. The heme is noncovalently attached, with a maximal, in vitro, heme loading of approximately 30%, for both proteins. CD and fluorescence spectroscopies indicate a well-ordered structure, suggesting the low level of heme loading is probably not due to improperly folded protein. EPR confirmed a five-coordinate, high-spin, ferric resting state for both proteins, indicating one axial amino acid ligand, in contrast to the six-coordinate, low-spin, ferric state of cytochrome b(5). The MCD spectrum confirmed this conclusion for Dap1p and indicated the axial ligand is most likely a tyrosine and not a histidine, or a cysteine; however, an aspartic acid residue could not be conclusively ruled out. Potential axial ligands, which are conserved in all MAPRs, were mutated (Y78F, D118A, and Y138F) and purified to homogeneity. The Y78F and D118A mutants were found to bind heme; however, Y138F did not. This result is consistent with the MCD data and indicates that Tyr138 is most likely the axial ligand to the heme in Dap1p.