Obesity: Harshfield GA

Urbina E, Alpert B, Flynn J, Hayman L, Harshfield GA, Jacobson M, Mahoney L, McCrindle B, Mietus-Snyder M, Steinberger J, Daniels S, Anonymous00015. · American Heart Association, Public Information, 7272 Greenville Ave, Dallas, TX75231-4596, USA. · Hypertension. · Pubmed #18678786 No free full text.

This publication has no abstract.

Harshfield GA, Dong Y, Kapuku GK, Zhu H, Hanevold CD. · Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-4534, USA. · Curr Hypertens Rep. · Pubmed #19146798 No free full text.

Abstract: Hypertension--an important health problem in industrialized nations--is particularly significant in blacks and obese individuals, in whom it is hypothesized to result from impaired renal sodium regulation. We reviewed studies that identified individuals with impaired sodium regulation by examining the natriuretic response to mental stress. A significant percentage of black and obese individuals retain or have a diminished natriuretic response to mental stress despite increased blood pressure (BP). This contributes a volume component to the normal resistance-mediated BP increase, and BP remains elevated after the stressor ceases until the volume expansion diminishes. The stress exposes these individuals to greater cardiovascular load. This response pattern has been linked to renin-angiotensin-aldosterone system activity, and is associated with premature target-organ damage. Assessing stress-induced sodium retention provides a method to identify patients with impaired sodium regulation without using a dietary protocol that poses adherence difficulties, or complicated laboratory assessments. Furthermore, research using this technique indicates the effectiveness of renin-angiotensin-aldosterone system blockers in correcting impaired sodium regulation and consequent hypertension in these individuals.

Yan W, Yao H, Dai J, Cui J, Chen Y, Yang X, Harshfield GA, Wang X. · Division of Epidemiology and Biostatistics, School of Public Health, Xinjiang Medical University, Urumqi, Xinjiang, China. · Obesity (Silver Spring). · Pubmed #18451779 No free full text.

Abstract: OBJECTIVE: To examine the distribution of age- and gender-specific waist circumference (WC) and to identify optimal cutoffs for predicting cardiovascular (CV) risk factors in Chinese Han and Uygur children. METHODS AND PROCEDURES: In total 4,224 Han and Uygur children aged 7-18 were randomly selected from schools in Urumqi city, China. WC, height, and weight were accurately measured in all subjects. Blood pressure, fasting lipids, glucose, and insulin were determined in 258 overweight/obese children and 370 age-, gender-, and ethnicity-matched normal-weight controls selected from the same study sample. LMS (lambda-mu-sigma) method was used to construct WC centile curves. Optimal WC cutoffs were determined by comparing the performance of five sets of WC cutoffs in predicting CV risk factors. RESULTS: Han boys and girls had higher WC at all percentiles and ages except for girls over the age of 16. Uygur girls also showed a greater increase in WC corresponding with age (2.1 cm/year vs. 1.6 cm/year for the median) than Han girls. Compared with the other four sets of cutoffs, the 85th WC percentile showed the best combination of sensitivity (81.0%) and specificity (71.4%). The two sets of WC cutoffs constructed by allowing centile curves passing through the adult cutoffs for central adiposity using the fitted LMS curves provided poor sensitivities in predicting the presence of cluster of CV risk factors. DISCUSSION: The growth pattern of WC varies with gender and ethnicity. The 85th percentile of WC is an appropriate cutoff for Chinese Han and Uygur children in the prediction of CV risks.

Wilson ME, Harshfield GA, Ortiz L, Hanevold C, Kapuka G, Mackey L, Gillis D, Edmonds L, Evans C. · Georgia Prevention Institute and the Department of Pediatrics, Medical College of Georgia, Augusta, Georgia, USA. · Am J Hypertens. · Pubmed #15533728 No free full text.

Abstract: BACKGROUND: The contribution of stress to obesity-related cardiovascular disease is uncertain. The purpose of this study was to examine the influence of body composition on stress-induced pressure natriuresis. METHODS: Dual energy x-ray absorptiometry was performed in 127 African American and white youths to assess lean body mass (LBM), fat mass (FM), and total percentage of body fat (%BF). The stress protocol was comprised of a 2-h baseline period, 1-h video game competition stressor, and 2-h recovery period. Blood and urine samples were collected hourly and blood pressure (BP) was obtained at 15-min intervals. RESULTS: Both BP and urinary sodium excretion(U(Na)V) increased from baseline to stress and returned to prestress levels after stress (P = .001 for each). The BP levels and changes were positively correlated with LBM. In contrast, levels and changes in sodium excretion U(Na)V were inversely correlated with FM and %BM. Multiple regression analyses that included ethnicity, sex, angiotensin II (Ang II), and measures of body composition in the models indicated the following: a) LBM was the best predictor of stress systolic BP and independently contributed with ethnicity to stress diastolic BP; b) ethnicity was the only independent predictor of the stress-related change in systolic and diastolic BP; c) LBM was the only independent predictor of the change in BP from stress to recovery for both systolic and diastolic BP; and d) total percent body fat accounted for 11.2% of the variance of stress U(Na)V, with Ang II contributing an additional 6.1%. CONCLUSIONS: Based on the results of this study, ethnicity and body composition are related to stress-induced pressure natriuresis.

Barbeau P, Litaker MS, Harshfield GA. · Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta, Georgia 30912, USA. · Obes Res. · Pubmed #12805395 No free full text.

Abstract: OBJECTIVE: To compare the response and recovery of blood pressure (BP) and sodium excretion (U(Na)V) in response to a behavioral stressor in overweight/obese and lean adolescents. RESEARCH METHODS AND PROCEDURES: Twenty-five lean (12% to 20% body fat) and 59 overweight/obese (>25% body fat) normotensive adolescents were provided all meals for 3 days (average sodium intake, 4000 +/- 200 mg/d), before performing the stressor on the third day. There was a 2-hour pre-stress rest, followed by a 1-hour stress (involving a video game task), and a 2-hour recovery. Percentage of body fat was obtained from DXA. U(Na)V was measured hourly, whereas systolic BP and diastolic BP measurements were obtained at 15-minute intervals, and averaged for each 1-hour period. RESULTS: There was no significant difference between the lean and overweight/obese group for the response of systolic BP and diastolic BP (group by time interaction, p = 0.60 and p = 0.64, respectively). However, the lean group had a significantly greater increase in U(Na)V in response to the stressor compared with the overweight/obese group (p = 0.02). U(Na)V remained elevated compared with baseline in both groups at the 1-hour (p <or= 0.0001) and 2-hour (p <or= 0.0001) post-time points. Furthermore, there was a tendency for a larger number of sodium retainers in the overweight/obese group compared with the lean group (39.0% vs. 20.0%; chi(2) = 2.85, df = 1, p = 0.09). DISCUSSION: This study provided evidence that sodium regulation was impaired during a behavioral stress in overweight/obese individuals compared with lean individuals.

Snieder H, Harshfield GA, Treiber FA. · Georgia Prevention Institute, Medical College of Georgia, Bldg HS-1640, Augusta, GA 30912, USA. · Hypertension. · Pubmed #12719445 links to  free full text

Abstract: Hypertension prevalence is much higher in African-Americans (AAs) than in European-Americans (EAs). It is unknown whether this difference is related to potential ethnic differences in the relative contribution of genes and environment to population variation in blood pressure and underlying hemodynamics. We studied 308 EA and 226 AA twin pairs, including monozygotic and dizygotic twins, of the same as well as the opposite sex (mean+/-SD age, 14.7+/-3.1 years). Supine resting systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure, and heart rate (HR) were measured by a Dinamap instrument and hemodynamics (stroke volume, cardiac index, and total peripheral resistance [TPR] index) by impedance cardiography. Ethnic and sex effects on genetic and environmental contributions to resting blood pressure and hemodynamics were estimated by genetic model fitting. For most measures, the best-fitting model showed no differences in heritability between AAs and EAs or between males and females, with heritabilities of 0.50 for cardiac index, of 0.64 for HR, and of SBP, pulse pressure, and stroke volume in between. Heritability of DBP was 0.45 in EAs and 0.58 in AAs with no effect of sex. For TPR index in EAs, 46% of the variance could be attributed to familial effects, but no significant distinction could be made between shared environmental and genetic factors. Heritability of TPR index in AAs was 0.51. Adjustment for obesity yielded virtually identical heritabilities. In summary, relative influences of genetic and environmental factors on blood pressure and hemodynamics in AA and EA youth are similar and independent of (genes for) obesity.