Resting Energy Expenditure and Systolic Blood Pressure Relationships in Women Across 4.5 Years

Recent studies have reported a strong association between blood pressure (BP) and resting energy expenditure (REE). However, it is not known whether this relationship persists over time. Therefore, the authors examined the temporal relationship between REE and systolic BP. In addition, the impact of sympathetic tone and anthropometric variables on this relationship was examined. All testing was performed on healthy, overweight African American and European American women aged 25 to 45 years over 4.5 years in the University of Alabama at Birmingham General Clinical Research Center. Repeated‐measures mixed‐models revealed REE as a significant determinant of systolic BP (β=0.0155, P<.0001), independent of catecholamines, leg fat, visceral fat, fat‐free mass, fat mass, height, relative skeletal muscle index, and resting heart rate. Observations that REE is predictive of systolic BP across 4.5 years support previous findings that REE may potentially mediate resting BP, independent of anthropometric variables and a marker for sympathetic tone.     

Paradoxical weight loss with extra energy expenditure at brown adipose tissue in adolescent patients with Duchenne muscular dystrophy

We examined the energy expenditure in patients with Duchenne muscular dystrophy(DMD) to evaluate the cause of the paradoxical weight loss observed in large numbers of adolescent patients before any obvious impairment of their swallowing function. In the morning, resting energy expenditure (REE)/m(2) was almost the same as that in normal controls despite a reduction in fat-free mass (FFM); thus, REE/m(2)/FFM was significantly increased in patients (median, 21.2 kcal/m(2)/FFM kg; range, 17.7 to 44.2, P =.012). A thermographic examination in the morning showed an obvious elevation of the body surface temperature on the back. This phenomenon was consistent with a paradoxical fall in the low frequency (LF)/high frequency (HF) ratio at night analyzed using the inter-RR spectrum by 24-hour electrocardiogram, which indicated relative activation of the sympathetic nervous system. The urinary secretion of norepinephrine at night was also significantly greater in patients (median, 0.119 microg/kg/h; range, 0.061 to 0.219, P =.011). These results suggest that paradoxical activation of the sympathetic nervous system may accelerate the production of heat in brown adipose tissue (BAT) and increase the level of energy consumption in patients, and that adolescent DMD patients may require greater caloric intake than expected to maintain body weight, which is important to improve the prognosis of their respiratory function.     

Relation of obesity and diet to sympathetic nervous system activity

The hypothesis that dietary intake and obesity stimulate the sympathetic nervous system was investigated in a cross-sectional study of 572 men aged 43-85 years from the Normative Aging Study. Habitus was represented by body mass index, as a measure of overall adiposity, and by the ratio of abdomen-to-hip circumference (abdomen/hip ratio), as a measure of centripetal fat distribution. Sympathetic activity was assessed by measurement of 24-hour urinary norepinephrine excretion. Increased body mass index and total caloric intake were independently associated with increased 24-hour urinary norepinephrine excretion (p = 0.0001 and p = 0.0055, respectively). In addition, mean urinary norepinephrine excretion was higher in subjects classified as either hyperglycemic (serum fasting glucose greater than or equal to 113 mg/dl) and hyperinsulinemic (serum fasting insulin greater than or equal to 19 microIU/ml) (p = 0.0023) or in subjects classified as either hyperglycemic or hyperinsulinemic (p = 0.0063) than the mean urinary norepinephrine excretion in normal subjects. These relations were demonstrated to be independent of age, smoking status, and physical activity. Our results are consistent with the hypothesis that insulin mediates sympathetic stimulation in response to dietary intake and increases sympathetic nervous system activity in the obese.     

Influence of sympathetic activity on blood pressure and vascular damage evaluated by means of urinary albumin excretion

To analyze the influence of sympathetic activity on blood pressure (BP) and its effects on urinary albumin excretion (UAE), the authors carried out a cross-sectional study in their local health coverage area. The following variables were monitored in a representative sample of the general population made up of 495 individuals: anthropometric parameters; blood glucose, creatinine, and lipid levels; 24-hour urinary albumin, norepinephrine, and epinephrine excretion; and BP of patients with known hypertension and newly discovered BP > or =140/90 mm Hg, evaluated by ambulatory monitoring. In the multivariate analysis, only gender, systolic BP, and UAE were associated with norepinephrine levels; only gender, systolic BP, and body mass index were associated with epinephrine. After excluding those patients with chronic kidney disease, the multivariate analysis showed a strong association between UAE > or =30 mg/d and elevated norepinephrine and epinephrine levels. The authors concluded that in the subject population there is an association between elevated adrenergic activity and higher UAE, independent of factors such as age and BP.     

Chronic sympathetic attenuation and energy metabolism in autonomic failure

The sympathetic nervous system regulates thermogenesis and energy homeostasis in humans. When activated it increases energy expenditure, particularly resting energy expenditure. Most human studies used acute infusion of β-blockers as a model to eliminate sympathetic stimulation and to examine the contribution of the sympathetic nervous system to energy metabolism and balance. Clinically, however, it is also important to assess the effect of chronic sympathetic attenuation on energy metabolism. In this context, we hypothesized that resting energy expenditure is decreased in patients with autonomic failure who, by definition, have low sympathetic tone. We measured 24-hour energy expenditure using whole-room indirect calorimeter in 10 adults with chronic autonomic failure (6 women; age, 64.9±9.1 years; body mass index, 25.2±4.4 kg/m(2)) and 15 sedentary healthy controls of similar age and body composition (8 women; age, 63.1±4.0 years; body mass index, 24.4±3.9 kg/m(2)). In 4 patients, we eliminated residual sympathetic activity with the ganglionic blocker trimethaphan. We found that, after adjusting for body composition, resting energy expenditure did not differ between patients with autonomic failure and healthy controls. However, resting energy expenditure significantly decreased when residual sympathetic activity was eliminated. Our findings suggest that sympathetic tonic support of resting energy expenditure is preserved, at least in part, in pathophysiological models of chronic sympathetic attenuation.     

Association between blood pressure and resting energy expenditure independent of body size

Obesity is an important risk factor for hypertension; however, the pathway through which it raises blood pressure (BP) is poorly understood. Body size is also the primary determinant of energy expenditure, and we therefore examined the joint relationship of energy expenditure and body size to blood pressure. Resting energy expenditure (REE) was measured using respiratory gas exchange in population-based samples of 997 Nigerians and 452 African Americans. In a third sample of 118 individuals, nonresting energy expenditure (ie, physical activity) was measured in addition to REE. The univariate correlation between REE and BP ranged from 0.10 to 0.22 in the 3 samples (P<0.001). In multivariate models, adiposity, whether defined by body mass, fat mass, or leptin, was no longer associated with BP, while REE remained highly significant (P<0.001). The REE-BP association also persisted after adjustment for physical activity measured with doubly labeled water. The odds ratio for hypertension among persons in the highest quartile versus the lowest quartile of REE, after adjustment for body size, was 1.7. This relationship was not the result of hypertension among the obese, because it did not vary across the range of BMI and was the same in lean Nigerians as in obese Americans. These data suggest that metabolic processes represented by REE may mediate the effect of body size on BP. The interrelationship of REE with sympathetic tone, transmembrane ion exchange, or other metabolic processes that determine energy costs at rest could provide physiological explanations for this observation.     

Tumor necrosis factor, interleukin-6,and epinephrine are associated with hypermetabolism in AIDS patients with acute opportunistic infections

During a 9-day period we investigated body composition, resting energy expenditure (REE), IL-6, TNF, and sTNFR-55 and sTNFR-75 plasma concentrations during infectious complications in 12 patients with HIV disease. At study entry, IL-6 was detectable in 5 and TNF in 10 patients. TNF was closely correlated with sTNFR-75 concentration (r = 0.84, p < 0.001) whereas sTNFR/sTNFR-55 ratio increased throughout the study. TNF concentrations were significantly correlated with the 24-hour excretion of epinephrine and norepinephrine (r = 0.64 and 0.69; each p < 0.01). Compared to expected values REE was increased by 34%. Body cell mass was the single best predictor of REE and explained 72% of its variance. In contrast, the deviation of measured from predicted REE was correlated with TNF and IL-6 concentrations (r = 0.9). We conclude that increased plasma concentrations of cytokines in complicated HIV disease display little biologic variability and relate to hypermetabolism in these patients.     

Neurohumoral mechanisms and left ventricular hypertrophy: effects of hygienic therapy

To determine the effects of hygienic (non-drug) therapy on blood pressure (BP) control and its relationship to sympathetic tone and left ventricular mass (LVM) in primary hypertension, plasma norepinephrine (NE) and renin activity (PRA), LVM, and nutritional and behavioral status were assessed in 76 borderline to mild hypertensives. Pretherapy plasma NE was related to diastolic blood pressure (DBP) and PRA (r = 0.24, P less than .05 and r = 0.37, P less than .01, respectively). Plasma NE of high renin patients (221 +/- 52) (mean +/- SD) was greater than that of normal renin patients (159 +/- 61, ng/l, P less than .01). LVM was related to systolic blood pressure (SBP) (P less than .001), DBP (P less than .01) and urinary sodium (P less than .05), and inversely related to PRA (P less than .01). Septal wall thickness was related to hostility (r = 0.42, P less than .05). After seven weeks of hygienic therapy, DBP was reduced by 6 mmHg (P less than .01). The change in SBP was related to baseline plasma NE (P less than .05) and inversely related to LVM (P less than .05). These results suggest that raised sympathetic tone may be a pathogenic factor in primary hypertension and that hygienic therapy lowers BP more effectively in patients with raised sympathetic tone and low LVM.     

Energy expenditure of rhesus monkeys subjected to 11 years of dietary restriction

Dietary restriction (DR) is currently the only paradigm that has consistently extended maximal life span and reduced the onset of age-related chronic diseases in all of the nonprimate species tested. Although it is controversial, some investigators have suggested that the underlying mechanisms may be mediated by adaptations in energy expenditure. We evaluated the extent to which DR alters energy metabolism in a unique cohort of rhesus monkeys submitted to DR for 11 yr. Total energy expenditure (doubly labeled water), resting energy expenditure (REE; indirect calorimetry), and nonbasal energy expenditure (calculated by difference) were measured in DR (n = 12) and control (n = 11) animals. Body composition was determined by dual energy x-ray absorptiometry. Both fat mass and fat-free mass were lower in the restricted animals (56 and 12%, respectively). DR induced a 17% lower total energy expenditure that was attributable to a 20% decrease in REE without changes in the nonbasal energy expenditure. Adjusted for fat-free mass, REE was 13% lower with DR (-250 kJ/d). Taken together with a reanalysis of previous DR experiments published in humans, rodents, and monkeys, these results suggest that DR may lower REE independent of the DR-induced changes in body composition. Whether this reduction in REE contributes to the life-extending properties of DR warrants further analysis, but it suggests that the long-standing debate regarding DR effects on metabolic rates may derive from the lack of consensus on how to adjust for body size and composition.     

Poor Sleep Quality and Sleep Apnea Are Associated with Higher Resting Energy Expenditure in Obese Individuals with Short Sleep Duration

Context: Epidemiological studies reported an inverse or U-shaped relationship between sleep duration and weight. The relationship between sleep and resting energy expenditure (REE) has not been well characterized. Objective: The aim of the study was to determine the relationship between sleep, REE, and stress hormones. Design and Setting: We conducted a cross-sectional evaluation of a prospective cohort study at a tertiary referral research clinical center. Subjects: Subjects included 126 obese individuals (30 males, 96 females; age, 40.5 ± 6.9 yr; body mass index, 38.6 ± 6.5 kg/m(2); sleep duration, 360 ± 50 min/night; and sleep efficiency, 79.5 ± 7.5%). Main Outcome Measure(s): REE and respiratory quotient (RQ) were assessed by indirect calorimetry. Sleep duration and sleep efficiency were assessed by actigraphy. Sleep quality was estimated by questionnaires, and sleep apnea was evaluated by respiratory disturbance index (RDI). Morning plasma ACTH, serum cortisol, and 24-h urinary free cortisol and catecholamines were also measured. Results: RDI was positively correlated with REE adjusted by fat-free mass (r = 0.307; P = 0.003) and RQ (r = 0.377; P < 0.001). Sleep efficiency was inversely correlated with RQ (r = -0.200; P = 0.033). The relationship of RDI score and REE was stronger in men than women (P = 0.03). In women, serum cortisol was positively correlated (r = 0.407; P < 0.001), and Epworth sleepiness score tended to be inversely (r = -0.190; P = 0.086) correlated with adjusted REE. The RQ was positively related to RDI in women, whereas subjective sleep time was related to RQ in men. In a multiple regression model, RDI, serum cortisol, and urinary norepinephrine were directly related to REE, whereas serum cortisol also directly related to adjusted REE. Conclusion: Poor sleep quality was associated with increased REE, a higher RQ indicating a shift from fat toward carbohydrate oxidation, and activation of the stress system.     

Elevated bound leptin correlates with energy expenditure in cirrhotics

BACKGROUND & AIMS: Leptin, found to be elevated in patients with liver cirrhosis, may contribute to the inadequate energy expenditure and malnutrition associated with a negative prognosis for these patients. Our aim was to characterize leptin components and their relationships to body composition, resting energy expenditure (REE), and substrate use in patients with posthepatic liver cirrhosis. METHODS: Using specific radioimmunoassays, we measured free leptin and bound leptin in 27 cirrhotics and 27 matched control subjects. In the cirrhotic group, body composition and REE were determined. RESULTS: Free leptin was not different in cirrhotics and control subjects and was related to body mass index (controls: r = 0.34, P < 0.05; cirrhotics: r = 0.55, P < 0.005) and to fat mass (cirrhotics: r = 0.76, P < 0.0001). Bound leptin was significantly higher in cirrhotic subjects than in controls (P < 0.001) and was related to REE x fat-free mass(-1) (r = 0.57, P < 0.005) or to the difference between measured and estimated REE (r = 0.55, P < 0.005). CONCLUSIONS: Free leptin reflects fat mass in controls and cirrhotics. Increased serum leptin in cirrhotics is a result of increased bound leptin serum concentrations, which are positively related to energy expenditure. Moreover, bound leptin may be a useful marker for inadequate energy expenditure in patients with liver cirrhosis.     

Highly active antiretroviral therapy-induced lipodystrophy has minor effects on human immunodeficiency virus-induced changes in lipolysis,but normalizes resting energy expenditure

Combination antiretroviral therapy for the treatment of human immunodeficiency virus type 1-infected patients is associated with development of the lipodystrophy syndrome (LD). We previously showed that plasma levels of free fatty acids are higher in patients with lipodystrophy. The purpose of this study was to evaluate the postabsorptive rate of lipolysis, using [(2)H(5)]glycerol infusion, the resting energy expenditure (REE) measured by indirect calorimetry, and the responses of both to epinephrine infusion ( approximately 15 ng/kg.min) in patients with LD. Results were compared with those obtained in five matched human immunodeficiency virus type 1-infected patients. The postabsorptive rate of appearance of glycerol did not differ between the two groups. There was no difference in the lipolytic response to epinephrine, although the response in the LD group was delayed (P < 0.001). The postabsorptive REE adjusted for lean body mass was lower and remained lower during epinephrine infusion in the LD group. Postabsorptive norepinephrine concentrations were higher and remained elevated during epinephrine infusion in the LD group. We conclude that the lipolytic response to epinephrine in the LD group was normal, albeit delayed. Norepinephrine concentrations were increased in patients with lipodystrophy, indicating increased sympathetic activity. Postabsorptive REE was lower in the patients with lipodystrophy. Our data suggest that highly active antiretroviral therapy-associated lipodystrophy normalizes the REE, but has only minor effects on lipolysis as a result of concomitant sympathetic stimulation of adipose tissue.     

Hormonal and physiological correlates of energy expenditure and substrate oxidation in middle-aged, premenopausal women.

An understanding of the hormonal and physiological correlates of energy expenditure and substrate oxidation in middle-aged women will increase our knowledge of factors that promote changes in energy balance and adiposity. We measured resting and postprandial energy expenditure and substrate oxidation in 59 middle-aged, premenopausal women (mean+/-sD age, 47+/-2 yr) to examine the hormonal and physiological correlates of energy and substrate metabolism. Energy expenditure and substrate oxidation were measured at rest using indirect calorimetry and urinary nitrogen excretion and for 180 min after the ingestion of a liquid meal (10 kcal/kg fat-free mass; 410+/-44 Cal). Fasting hormone levels were measured by RIA, glucose tolerance was determined by a 75-g oral glucose tolerance test, body composition was measured by dual energy x-ray absorptiometry, and peak aerobic capacity was determined by a treadmill test. Using stepwise regression analysis, we found that resting energy expenditure was predicted by fat-free mass and serum leptin concentration (r2 = 66%; P < 0.01), fat oxidation was predicted by resting energy expenditure (r2 = 17%; P < 0.01), and carbohydrate oxidation was predicted by serum leptin and appendicular skeletal muscle mass (r2 = 21%;P < 0.01). Novariables were related to postprandial energy expenditure or substrate oxidation. We conclude that in middle-aged, premenopausal women, variation in resting energy expenditure and substrate oxidation is primarily explained by fat-free mass and serum leptin levels. Thus, changes in metabolically active tissue mass or leptin concentration may partially contribute to changes in resting energy expenditure or substrate oxidation in middle-aged women.     

Resting energy expenditure in Duchenne patients using home mechanical ventilation.

Nutritional status is both important and difficult to assess in patients with Duchenne muscular dystrophy (DMD), particularly in those requiring mechanical ventilation (MV). The current authors evaluated body composition (bio-impedancemetry), resting energy expenditure (REE; indirect calorimetry) and energy intake in 20 adult patients with DMD using home MV (nocturnal: n = 13; continuous: n = 7) and 12 age-matched healthy controls. The patients were smaller in height than the controls and had a lower body weight. Most of the reduction in body mass index was accounted for by a reduction in fat free mass (FFM). REE (kJ) was significantly reduced in the patients (4559+/-853 kJ x 24 h(-1) versus 7407+/-1312 kJ x 24 h(-1)), but the difference disappeared after correction for FFM. REE and FFM were correlated in both the controls and patients, but less strongly in the latter, the lower strength of the association being due to the patients using continuous MV (REE and FFM uncorrelated). The food intake of the patients was 1.2+/-0.4 greater than their REE. This study shows that patients with advanced forms of Duchenne muscular dystrophy have balanced energy intakes and resting energy expenditure.     

Fat distribution and metabolic changes are strongly correlated and energy expenditure is increased in the HIV lipodystrophy syndrome

OBJECTIVE: To examine the relationships between protease inhibitor (PI) therapy, body fat distribution and metabolic disturbances in the HIV lipodystrophy syndrome. DESIGN: Cross-sectional study. SETTING: HIV primary care practices. PATIENTS: PI-treated patients with lipodystrophy (n= 14) and PI-treated (n= 13) and PI-naive (n= 5) patients without lipodystrophy. MAIN OUTCOME MEASURES: Body composition was assessed by physical examination, dual-energy X-ray absorptiometry and computed tomography. Insulin sensitivity (SI) was measured using the insulin-modified frequently sampled intravenous glucose tolerance test. Lipid profiles, other metabolic parameters, duration of HIV infection, CD4 lymphocyte counts, HIV-1 RNA load and resting energy expenditure (REE) were also assessed. RESULTS: PI-treated patients with lipodystrophy were significantly less insulin sensitive than PI-treated patients and PI-naive patients without any changes in fat distribution (SI(22) x 10(-4) (min(-1)/microU/ml) versus 3.2 x 10(-4) and 4.6 x 10(-4) (min(-1)/microU/ml), respectively; P < 0.001). Visceral adipose tissue area and other measures of central adiposity correlated strongly with metabolic disturbances as did the percent of total body fat present in the extremities; visceral adipose tissue was an independent predictor of insulin sensitivity and high density lipoprotein cholesterol levels. REE per kg lean body mass was significantly higher in the group with lipodystrophy compared to the groups without lipodystrophy (36.9 versus 31.5 and 29.4 kcal/kg lean body mass; P < 0.001), and SI was strongly correlated with and was an independent predictor of REE in this population. CONCLUSIONS: Body fat distribution and metabolic disturbances are strongly correlated in the HIV lipodystrophy syndrome and REE is increased.     

Relationship of arousals from sleep to sympathetic nervous system activity and BP in obstructive sleep apnea.

STUDY OBJECTIVE: Obstructive sleep apnea (OSA) patients have a high frequency of arousals. We hypothesized that arousals significantly influence tonic sympathetic nervous system function. DESIGN: We examined the association of 11 variables measuring sympathetic activity, including plasma norepinephrine (NE), urinary NE, and BP measurements, with movement and cortical arousals. PATIENTS: Sixty-seven subjects with various degrees of hypertension and OSA were evaluated. All patients were free from antihypertensive medications. RESULTS: The age (range, 35 to 60 years), weight (range, 100 to 150% of ideal body weight), and diet of the subjects were similar. The movement arousal index was correlated with daytime baseline plasma NE (BNE), daytime urine NE, mean daytime diastolic BP, and systolic BP during rapid eye movement sleep (r = 0.39 to 0.53; p < or = 0.002). Cortical arousals did not correlate with any of the variables. A multiple regression procedure was performed to examine how well movement arousals predicted those variables with significant correlations. The respiratory disturbance index (RDI) and nighttime pulse oxyhemoglobin saturation were included in the regression equation due to their close association with movement arousals. Movement arousals independently predicted BNE (t [48] = 2.06; p < 0.05). No other variable independently predicted any of the measurements of sympathetic activity. CONCLUSIONS: These findings suggest that movement arousals may influence daytime sympathetic tone independently of RDI and nighttime saturation.     

Beneficial effects of protease inhibitors on body composition and energy expenditure: a comparison between HIV-infected and AIDS patients

OBJECTIVES: (i) To investigate whether protease inhibitor (PI) (nelfinavir)-containing highly active antiretroviral therapy (HAART) affects body composition differently in HIV-infected and AIDS patients without wasting syndrome. (ii) To delineate the changes in resting energy expenditure (REE) under PI therapy, and to determine whether sustained reductions in HIV RNA would decrease REE. DESIGN: Prospective longitudinal cohort study with individually matched healthy controls. SETTING: Tertiary care centre at a University Hospital. METHODS: HIV-seropositive (n = 20) and AIDS patients (n = 17) with a plasma viral load of at least 10000 copies/ml and 37 healthy volunteers were enrolled. All participants were weight stable, free of acute opportunistic infections, and naive to PI therapy. Patients underwent testing of bioelectrical impedance analysis (BIA), indirect calorimetry and food intake, shortly before the initiation of HAART and 24 weeks thereafter. RESULTS: Both patient groups gained weight, body mass index (BMI), and fat-free mass (FFM) (P < 0.05 versus baseline), whereas only AIDS patients gained fat mass. Increases were more pronounced in the AIDS group. REE was elevated compared with corresponding controls at baseline, and decreased similarly in HIV and in AIDS patients during PI therapy (P < 0.05). The reduction in the viral burden preceded the decrease in REE by several weeks. CONCLUSION: Body composition and metabolic parameters improved during PI therapy in HIV-infected and AIDS patients without wasting. Although an early reduction in viral load as a result of HAART does not seem to influence REE directly, sustained viral load suppression may promote a decrease in energy expenditure.     

Elevated resting energy expenditure among HIV-seropositive persons receiving highly active antiretroviral therapy.

OBJECTIVES: To ascertain the relationships between resting energy expenditure (REE), HIV RNA in plasma, and highly active antiretroviral therapy (HAART). DESIGN: Cross-sectional analysis using data of a large cohort study of nutrition in relation to HIV disease. METHODS: HIV RNA in plasma, REE, fat-free mass (FFM), and medication regimens were assessed at 530 visits among 372 participants in a cohort study of HIV-seropositive men and women. RESULTS: HIV RNA in plasma was directly correlated with REE. After adjustment for FFM, age, CD4 cell count and HAART use, there was an increase in REE of 90 kJ/day per log10 copies/ml increase in HIV RNA [95% confidence interval (CI) 16-164; P = 0.02). HAART use had an independent effect on REE. In patients reporting HAART use, adjusted REE was 339 kJ/day higher than in those not reporting HAART use (95% CI 177-501; P = 0.0001). CONCLUSIONS: Viral load and HAART appear to exert independent effects on REE. Although HAART may decrease metabolic rate by lowering viral burden, it appears to increase metabolic demands through some mechanism(s) independent of its effect on viral burden. This may result in elevated REE despite control of viral replication.     

Do hormonal indices of maturation explain energy expenditure differences in African American and Caucasian prepubertal children?

OBJECTIVE: To examine the relationships between hormonal indices of maturation and total, resting and physical activity-related energy expenditure (TEE, REE and AEE) in African American and Caucasian prepubertal children. DESIGN: Cross-sectional study. SUBJECTS: Sixty-four African American and 48 Caucasian prepubertal children. MEASUREMENTS: TEE (by doubly labeled water), REE (by indirect calorimetry), fat mass and fat-free mass (by dual-energy X-ray absorptiometry), fasting serum dehydroepiandrosterone-sulfate (DHEAS), androstenedione, and estrone-sulfate (by radioimmunoassay). RESULTS: Serum concentrations of hormones correlated significantly with REE and TEE (r values range from 0.33 to 0.76, P<0.001). Only androstenedione correlated significantly with AEE (r = 0.23, P<0.05). However, these correlations were no longer significant after adjusting energy expenditure components for fat-free mass. In multiple regression models, ethnicity was not a significant determinant of any energy expenditure component after adjusting for body composition and hormone concentrations. CONCLUSION: Hormonal indices of maturation do not influence energy expenditure in this group of African American and Caucasian prepubertal children.     

Impact of aldosterone on left ventricular structure and function in young normotensive and mildly hypertensive subjects

Left ventricular (LV) hypertrophy is an independent risk factor for cardiovascular morbidity and mortality. Experimental data revealed that elevated circulating aldosterone is associated with increased collagen accumulation resulting in myocardial fibrosis. To analyze whether aldosterone is also associated with cardiac structural and functional changes in humans, we examined the effects of aldosterone on LV structure and function before and after suppression of aldosterone by increasing oral salt intake. The study group comprised 26 normotensive male white healthy control subjects (age 26 +/- 3 years) and 31 male white subjects (age 25 +/- 3 years) with mild essential hypertension (World Health Organization stages I to II). Two-dimensional-guided M-mode echocardiography and 24-hour ambulatory blood pressure (BP) monitoring was performed in each subject. Simultaneously, we measured 24-hour urinary sodium excretion, 24-hour urinary aldosterone, and serum aldosterone concentration at baseline and after increasing oral salt intake to suppress aldosterone secretion. In all subjects LV mass correlated with body mass index (r = 0.42, p <0.001) and both 24-hour ambulatory systolic (r = 0.28, p <0.05) and diastolic (r = 0.25, p <0.05) BP. Changes in urinary sodium excretion correlated inversely with changes in serum aldosterone concentration (r = -0.28; p <0.05). Urinary aldosterone concentration after salt loading decreased in normotensive (10.98 vs 7.44 microg/24 hours; p <0.02) but not in hypertensive (9.34 vs 10.51 microg/24 hours; p = NS) subjects. Serum and urinary aldosterone levels at baseline were not related to LV structure or function. In contrast, after increasing oral salt intake, urinary aldosterone concentration was related to LV mass (r = 0.43; p <0.01) and impaired midwall fractional fiber shortening (r = -0.33; p <0.02) in all subjects, independent of 24-hour ambulatory BP. Subgroup analysis revealed that this was significant only in hypertensive (r = 0.46; p <0.01 and r = -0.44; p <0.02, respectively) but not in normotensive (r = 0.28 and -0.16; p = NS for both, respectively) subjects. Consistently, the greater serum aldosterone remained after increasing oral salt intake, the greater was LV mass (r = 0.35; p <0.01). The latter was found in hypertensive subjects (r = 0.44; p <0.02), independent of 24-hour ambulatory BP, but not in normotensive subjects (r = 0.025; p = NS). Inadequate suppression of aldosterone in response to an increase in oral salt intake is related to LV structural and functional changes in hypertensive subjects. Thus, our results support experimental data indicating that aldosterone affects LV structure and function in humans and that this effect is BP independent.