Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome

Post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (PI-ME/CFS) is a disabling disorder, yet the clinical phenotype is poorly defined, the pathophysiology is unknown, and no disease-modifying treatments are available. We used rigorous criteria to recruit PI-ME/CFS participants with matched controls to conduct deep phenotyping. Among the many physical and cognitive complaints, one defining feature of PI-ME/CFS was an alteration of effort preference, rather than physical or central fatigue, due to dysfunction of integrative brain regions potentially associated with central catechol pathway dysregulation, with consequences on autonomic functioning and physical conditioning. Immune profiling suggested chronic antigenic stimulation with increase in naïve and decrease in switched memory B-cells. Alterations in gene expression profiles of peripheral blood mononuclear cells and metabolic pathways were consistent with cellular phenotypic studies and demonstrated differences according to sex. Together these clinical abnormalities and biomarker differences provide unique insight into the underlying pathophysiology of PI-ME/CFS, which may guide future intervention.

Randomized controlled trial of N-acetylcysteine therapy for RYR1-related myopathies

Objective

To investigate the efficacy of N-acetylcysteine (NAC) for decreasing elevated oxidative stress and increasing physical endurance in individuals with ryanodine receptor 1-related myopathies (RYR1-RM).

Methods

In this 6-month natural history assessment (n = 37) followed by a randomized, double-blinded, placebo-controlled trial, 33 eligible participants were block-randomized (1:1) to receive NAC (n = 16) or placebo (n = 17), orally for 6 months (adult dose 2,700 mg/d; pediatric dose 30 mg/kg/d). The primary endpoint was urine 15-F2t isoprostane concentration and the clinically meaningful co-primary endpoint was 6-minute walk test (6MWT) distance.

Results

When compared to the general population, participants had elevated baseline 15-F2t isoprostane concentrations and most had a decreased 6MWT distance (mean ± SD 3.2 ± 1.5 vs 1.1 ± 1.7 ng/mg creatinine and 468 ± 134 vs 600 ± 58 m, respectively, both p < 0.001). 15-F2t isoprostane concentration and 6MWT distance did not change over the 6-month natural history assessment (p = 0.98 and p = 0.61, respectively). NAC treatment did not improve 15-F2t isoprostane concentration (least squares means difference 0.1 [95% confidence interval [CI] −1.4 to 1.6] ng/mg creatinine, p = 0.88) or 6MWT distance (least squares means difference 24 [95% CI −5.5 to 53.4] m, p = 0.11). NAC was safe and well-tolerated at the doses administered in this study.

Conclusion

In ambulatory RYR1-RM–affected individuals, we observed stable disease course, and corroborated preclinical reports of elevated oxidative stress and decreased physical endurance. NAC treatment did not decrease elevated oxidative stress, as measured by 15-F2t isoprostane.

Classification of evidence

This study provides Class I evidence that, for people with RYR1-RM, treatment with oral NAC does not decrease oxidative stress as measured by 15-F2t isoprostane.

Clinicaltrials.gov identifier

NCT02362425.

Reliability and Validity of Self-Report Questionnaires as Indicators of Fatigue in RYR1-Related Disorders

BACKGROUND

RYR1-related disorders (RYR1-RD), are a spectrum of genetic neuromuscular disorders. Affected individuals frequently experience fatigue yet appropriate tools to assess RYR1-RD-associated fatigue remain underdeveloped.

OBJECTIVE

This study assessed the reliability and validity of two self-report questionnaires, the multidimensional fatigue inventory (MFI-20) and adult/pediatric functional assessment of chronic illness-fatigue (FACIT-F/Peds-FACIT-F) as potential fatigue measures in RYR1-RD affected individuals.

METHODS

Participants (n = 37) were enrolled in an RYR1-RD combined natural history study and clinical trial. At baseline, participants completed fatigue questionnaires, six-minute walk test (6MWT), cardiopulmonary exercise test (CPET) and saliva collection for fatigue biomarker index (FBI) quantification.

RESULTS

All questionnaires exhibited good test-retest reliability (n = 18, ICC > 0.80). MFI-20 (n = 37), and FACIT-F (n = 28) also showed good internal consistency (Cronbach's α> 0.80). All MFI-20 subscales, except mental fatigue, and FACIT-F demonstrated evidence of criterion validity when correlated against percent predicted 6MWT distance (MFI-20 n = 37; r = -0.34 to -0.47, all p < 0.05, mental fatigue, r = -0.16, p = 0.35; FACIT-F n = 28, r = 0.41, p = 0.03). This was not the case for percent predicted VO2 peak (all p > 0.05). FBI correlated with MFI-20 general fatigue dimension only (r = -0.35, p = 0.03). Comparison of standardized questionnaire scores revealed that RYR1-RD affected individuals experience significantly greater fatigue than the general population.

CONCLUSIONS

MFI-20 and FACIT-F are valid and reliable tools for assessing RYR1-RD-associated fatigue, a symptom centrally implicated in this rare disorder.

Oxygen uptake on-kinetics before and after aerobic exercise training in individuals with traumatic brain injury

Objective: The high prevalence of fatigue among persons with traumatic brain injury (TBI) may be related to poor cardiorespiratory fitness observed in this population. Oxygen uptake on-kinetics is a method of assessing cardiorespiratory fitness and may be used to examine performance fatigability (decline in performance during a given activity) in persons with TBI.Purpose: To examine the effect of aerobic exercise training on oxygen uptake on-kinetics during treadmill walking in individuals with TBI.Methods: Seven ambulatory adults with chronic non-penetrating TBI performed short moderate-intensity (3-6 metabolic equivalents) walking bouts on a treadmill, prior to and following an aerobic exercise training program (clinicaltrials.gov: NCT01294332). The 12-week training program consisted of vigorous-intensity exercise on a treadmill for 30 min, 3 times a week. Breath-by-breath pulmonary gas exchange was measured throughout the bouts, and oxygen uptake on-kinetics described the time taken to achieve a steady-state response.Results: Faster oxygen uptake on-kinetics was observed after exercise training, for both the absolute and relative intensity as pre-training.Conclusions: Faster oxygen uptake on-kinetics following aerobic exercise training suggests an attenuated decline in physical performance during a standardized walking bout and improved performance fatigability in these individuals with TBI.Implications for rehabilitationSevere fatigue is a common complaint among persons with traumatic brain injury (TBI).Oxygen uptake on-kinetics may be used as an objective physiological measure of performance fatigability in persons with TBI.Faster oxygen uptake on-kinetics following aerobic exercise training suggests improved performance fatigability in these individuals with TBI.Aerobic exercise training appeared beneficial for reducing performance fatigability and may be considered as part of the rehabilitative strategy for those living with TBI.

Changes in fatigability following intense aerobic exercise training in patients with interstitial lung disease

OBJECTIVE

To determine if, in patients with interstitial lung disease (ILD), fatigue might be lessened after vigorous aerobic exercise.

METHODS

13 physically inactive patients (5 men and 8 women; age 57.2 ± 9.1 years, BMI 28.2 ± 4.6 kgm(-2)) with ILD of heterogeneous etiology and able to walk on a motor driven treadmill without physical limitation were enrolled. Subjects underwent cardiopulmonary exercise (CPET) and 6-min walk (6MWT) tests and completed Fatigue Severity Scale and Human Activity Profile questionnaires before and after an aerobic exercise-training regimen. The training regimen required participation in at least 24 of 30 prescribed aerobic exercise training sessions at a target heart rate of 70-80% of the heart rate reserve, 30 min per session, 3 times per week for 10 weeks.

RESULTS

After training, a 55% (p < 0.001) increase in time to anaerobic threshold on the CPET, and an 11% (p = 0.045) reduction in performance fatigability index (PFI), calculated from the performance on the 6MWT were observed. Distance walked on the 6MWT (6MWD) increased by 49.7 ± 46.9 m (p = 0.002). Significant improvements in scores on the Fatigue Severity Scale (p = 0.046) and Human Activity Profile (AAS p = 0.024; MAS p = 0.029) were also observed. No adverse events related to the training regimen were noted.

CONCLUSION

After training, the decrease in fatigability appeared to result in increased 6MWD and was associated with physical activity. Since significant declines in 6MWD may be a marker for impending mortality in ILD, a better understanding of the etiological state of fatigue in patients with ILD and its reversal might provide fundamental insight into disease progression and even survival. [ClinicalTrials.gov identifier NCT00678821].

Benefits of intensive treadmill exercise training on cardiorespiratory function and quality of life in patients with pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) restricts the ability to engage in physical activity and decreases longevity. We examined the impact of aerobic exercise training on function and quality of life in patients with World Health Organization group 1 PH.

METHODS

Patients were randomized to a 10-week education only (EDU) or education/exercise combined (EXE) group. The exercise program consisted of 24-30 sessions of treadmill walking for 30-45 min per session at 70% to 80% of heart rate reserve. Outcome variables included changes in 6-min walk test (6MWT) distance, time to exercise intolerance, peak work rate (WR) from a cardiopulmonary treadmill test, and quality-of-life measures, including the Short Form Health Survey, version 2 (SF-36v2) and Cambridge Pulmonary Hypertension Outcome Review (CAMPHOR).

RESULTS

Data are presented as mean SD. Twenty-three women (age, 54 11 years; BMI, 31 7 kg/m 2 ) were randomized to the EDU (n 5 13) or EXE (n 5 10) groups. Following 10 weeks of intervention, patients in the EXE group demonstrated an improvement in 6MWT distance (56 45 m; P 5 .002), increased time to exercise intolerance (1.9 1.3 min; P 5 .001), and peak WR (26 23 W; P 5 .004). Additionally, the EXE group scored significantly ( P , .050) better on six of the eight scales on SF-36v2, and fi ve of the six scales on CAMPHOR. In contrast, no significant improvement was observed for any of the outcome measures following EDU. No adverse events were noted in either group.

CONCLUSION

Ten weeks of brisk treadmill walking improved 6MWT distance, cardiorespiratory function, and patient-reported quality of life in female patients with group 1 PH.

Metabolic effects of liothyronine therapy in hypothyroidism: a randomized, double-blind, crossover trial of liothyronine versus levothyroxine

CONTEXT

Levothyroxine (L-T(4)) therapy is based on the assumption that the conversion of T(4) into T(3) provides adequate amounts of active hormone at target tissues. However, in rodents, L-T(4) alone does not restore a euthyroid state in all tissues. Previous combination L-T(4)/liothyronine (L-T(3)) therapy trials focused on quality-of-life endpoints, and limited information is available on the effects on other measures of thyroid hormone action.

OBJECTIVE

Our objective was to evaluate the efficacy of thyroid hormone replacement with L-T(4) or L-T(3) at doses producing equivalent normalization of TSH.

PARTICIPANTS, DESIGN, AND SETTING

Fourteen hypothyroid patients participated in this randomized, double-blind, crossover intervention at the National Institutes of Health Clinical Center.

INTERVENTIONS

L-T(3) or L-T(4) were administered thrice daily to achieve a target TSH from 0.5-1.5 mU/liter. Volunteers were studied as inpatients after 6 wk on a stable dose and at the target TSH.

MAIN OUTCOME MEASURES

Serum thyroid hormones, lipid parameters, and indices of glucose metabolism were evaluated.

RESULTS

No difference was observed in TSH between L-T(3) and L-T(4) treatments. L-T(3) resulted in significant weight loss [L-T(4), 70.6 ± 12.5, vs. L-T(3), 68.5 ± 11.9 kg (P = 0.009)] and in a 10.9 ± 10.0% decrease in total cholesterol (P = 0.002), 13.3 ± 12.1% decrease in low-density lipoprotein-cholesterol (P = 0.002), and an 18.3 ± 28.6% decrease in apolipoprotein B (P = 0.018). No significant differences were observed in high-density lipoprotein-cholesterol, heart rate, blood pressure, exercise tolerance, or insulin sensitivity.

CONCLUSIONS

The substitution of L-T(3) for L-T(4) at equivalent doses (relative to the pituitary) reduced body weight and resulted in greater thyroid hormone action on the lipid metabolism, without detected differences in cardiovascular function or insulin sensitivity.

Adrenomedullary function in patients with nonclassic congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is classified into three types based on disease severity: classic salt-wasting, classic simple virilizing, and nonclassic. Adrenomedullary dysplasia and epinephrine deficiency have been described in classic CAH, resulting in glucose dysregulation. Our objective was to investigate adrenomedullary function in nonclassic CAH and to evaluate adrenomedullary function according to disease severity. Adrenomedullary function was evaluated in response to a standardized cycle ergonometer test in 23 CAH patients (14 females, age 9-38 years; 6 salt-wasting, 7 simple virilizing, 5 nonclassic receiving glucocorticoid treatment, 5 nonclassic not receiving glucocorticoid), and 14 controls (7 females, age 12-38 years). Epinephrine, glucose, and cortisol were measured at baseline and peak exercise. CAH patients and controls were similar in age and anthropometric measures. Patients with nonclassic CAH who were not receiving glucocorticoid and controls experienced the expected stress-induced rise in epinephrine, glucose, and cortisol. Compared to controls, patients with all types of CAH receiving glucocorticoid had impaired exercise-induced changes in epinephrine (salt-wasting: p=0.01;simple virilizing: p=0.01; nonclassic: p=0.03), and cortisol (salt-wasting: p=0.004; simple virilizing: p=0.006; nonclassic: p=0.03). Salt-wasting patients displayed the most significant impairment, including impairment in glucose response relative to controls (p=0.03). Hydrocortisone dose was negatively correlated with epinephrine response (r=-0.58; p=0.007) and glucose response (r=-0.60; p=0.002). The present study demonstrates that untreated patients with nonclassic CAH have normal adrenomedullary function. The degree of epinephrine deficiency in patients with CAH is associated with the severity of adrenocortical dysfunction, as well as glucocorticoid therapy.

Prediction of maximal oxygen uptake by bioelectrical impedance analysis in overweight adolescents

AIM

Maximal oxygen uptake (VO(2max)), the gold standard for measurement of cardiorespiratory fitness, is frequently difficult to assess in overweight individuals due to physical limitations. Reactance and resistance measures obtained from bioelectrical impedance analysis (BIA) have been suggested as easily obtainable predictors of cardiorespiratory fitness, but the accuracy with which ht(2)/Z can predict VO(2max) has not previously been examined in overweight adolescents.

METHODS

The impedance index was used as a predictor of VO(2max) in 87 overweight girls and 47 overweight boys ages 12 to 17 with mean BMI of 38.6 + or - 7.3 and 42.5 + or - 8.2 in girls and boys respectively. The Bland Altman procedure assessed agreement between predicted and actual VO(2max).

RESULTS

Predicted VO(2max) was significantly correlated with measured VO(2max) (r(2)=0.48, P<0.0001). Using the Bland Altman procedure, there was significant magnitude bias (r(2)=0.10; P<0.002). The limits of agreement for predicted relative to actual VO(2max) were -589 to 574 mL O(2)/min.

CONCLUSIONS

The impedance index was highly correlated with VO(2max) in overweight adolescents. However, using BIA data to predict maximal oxygen uptake over-predicted VO(2max) at low levels of oxygen consumption and under-predicted VO(2max) at high levels of oxygen consumption. This magnitude bias, along with the large limits of agreement of BIA-derived predicted VO(2max), limit its usefulness in the clinical setting for overweight adolescents.

Recruitment to a physical activity intervention study in women at increased risk of breast cancer

Background

Physical activity is being studied as a breast cancer prevention strategy. Women at risk of breast cancer report interest in lifestyle modification, but recruitment to randomized physical activity intervention studies is challenging.

Methods

We conducted an analysis of recruitment techniques used for a prospective, randomized pilot study of physical activity in women at risk of breast cancer. We evaluated differences in proportion of eligible patients, enrolled patients, and successful patients identified by each individual recruitment method. The Fisher-Freeman-Halton test (an extension of Fisher's exact test from 2 × 2 tables to general row by column tables) was used to compare the success of different recruitment strategies.

Results

We received 352 inquiries from women interested in participating, of whom 171 (54%) were eligible. Ninety-nine women completed a baseline activity evaluation, and 58 (34% of eligible; 16% of total inquiries) were randomized. Recruitment methods fell into three broad categories: media techniques, direct contact with potential participants, and contacts with health care providers. Recruitment strategies differed significantly in their ability to identify eligible women (p = 0.01), and women who subsequently enrolled in the study (p = 0.02).

Conclusion

Recruitment techniques had varying success. Our data illustrate the challenges in recruiting to behavior modification studies, and provide useful information for tailoring future recruitment efforts for lifestyle intervention trials.

Trial Registration No(s)

CDR0000393790, NCI-04-C-0276, NCI-NAVY-B05-001

Oxygen-uptake efficiency slope as a determinant of fitness in overweight adolescents

PURPOSE

Peak oxygen uptake (VO2peak) is frequently difficult to assess in overweight individuals; therefore, submaximal measures that predict VO2peak are proposed as substitutes. Oxygen uptake efficiency slope (OUES) has been suggested as a submaximal measurement of cardiorespiratory fitness that is independent of exercise intensity. There are few data examining its value as a predictor of V O2peak in severely overweight adolescents.

METHODS

One hundred seven severely overweight (BMI Z 2.50 +/- 0.34) and 43 nonoverweight (BMI Z 0.13 +/- 0.84) adolescents, performed a maximal cycle ergometer test with respiratory gas-exchange measurements. OUES was calculated through three exercise intensities: lactate inflection point (OUES LI), 150% of lactate inflection point (OUES 150), and VO2peak (OUES PEAK).

RESULTS

When adjusted for lean body mass, VO2peak and OUES at all exercise intensities were lower in overweight subjects (VO2peak: 35.3 +/- 6.4 vs 46.8 +/- 7.9 mL.kg(-1) LBM.min(-1), P < 0.001; OUES LI: 37.9 +/- 10.0 vs 43.7 +/- 9.2 mL.kg(-1) LBM.min(-1).logL(-1) P < 0.001; OUES 150: 41.6 +/- 9.0 vs 49.8 +/- 11.1 mL.kg(-1) LBM.min(-1).logL(-1) P < 0.001; and OUES PEAK: 45.1 +/- 8.7 vs 52.8 +/- 9.6 mL.kg(-1) LBM.min(-1).logL(-1) P < 0.001). There was a significant increase in OUES with increasing exercise intensity in both groups (P < 0.001). OUES at all exercise intensities was a significant predictor of VO2peak for both groups (r2 = 0.35-0.83, P < 0.0001). However, limits of agreement for predicted VO2peak relative to actual VO2peak were wide (+/- 478 to +/- 670 mL.min(-1)).

CONCLUSIONS

OUES differs significantly in overweight and nonoverweight adolescents. The wide interindividual variation and the exercise intensity dependence of OUES preclude its use in clinical practice as a predictor of VO2peak.

Patients with classic congenital adrenal hyperplasia have decreased epinephrine reserve and defective glycemic control during prolonged moderate-intensity exercise

CONTEXT

Patients with classic congenital adrenal hyperplasia (CAH) have adrenomedullary dysplasia and hypofunction, and their lack of adrenomedullary reserve has been associated with a defective glucose response to brief high-intensity exercise.

OBJECTIVE

Our objective was to assess hormonal, metabolic, and cardiovascular response to prolonged moderate-intensity exercise comparable to brisk walking in adolescents with classic CAH.

SUBJECTS AND METHODS

We compared six adolescents with classic CAH (16-20 yr old) with seven age-, sex-, and body mass index group-matched controls (16-23 yr old) using a 90-min standardized ergometer test. Metabolic, hormonal, and cardiovascular parameters were studied during exercise and recovery.

RESULTS

Glucose did not change throughout exercise and recovery for controls, whereas CAH patients showed a steady decline in glucose during exercise with an increase in glucose in the postexercise period. Glucose levels were significantly lower in CAH patients at 60 (P = 0.04), 75 (P = 0.01), and 90 (P = 0.03) min of exercise and 15 (P = 0.02) min post exercise, whereas glucose levels were comparable between the two groups early in exercise and at 30 min (P = 0.19) post exercise. As compared with controls, CAH patients had significantly lower epinephrine (P = 0.002) and cortisol (P < or = 0.001) levels throughout the study and similar norepinephrine, glucagon, and GH levels. Patients with CAH and controls had comparable cardiovascular parameters and perceived level of exertion. Despite having lower glucose levels, insulin levels were slightly higher in CAH patients during the testing period (P = 0.17), suggesting insulin insensitivity.

CONCLUSION

CAH patients have defective glycemic control and altered metabolic and hormonal responses during prolonged moderate-intensity exercise comparable to brisk walking.

Influence of excess adiposity on exercise fitness and performance in overweight children and adolescents

OBJECTIVE

Relatively little is known about how excess body mass affects adolescents' capacity to perform sustained exercise. We hypothesized that most of the difficulty that severely overweight adolescents have with sustained exercise occurs because the metabolic costs of moving excess mass result in use of a high proportion of their total oxygen reserve.

METHODS

We compared results from a maximal cycle ergometry fitness test in 129 severely overweight adolescents who had BMIs of 41.5 +/- 9.7 kg/m2 and ages of 14.5 +/- 1.8 years (range: 12.1-17.8 years) and 34 nonoverweight adolescents who had BMIs of 20.1 +/- 2.9 kg/m2 and ages of 14.5 +/- 1.5 years (range: 12.0-18.1 years). Oxygen uptake (Vo2) was compared at 3 times: during a 4-minute period of unloaded cycling (ULVo2), at the lactate threshold estimated by gas exchange (LTVo2), and at maximal exertion (Vo2 max). Heart rate was obtained at rest and at Vo2 max. Participants also completed a 12-minute walk/run performance test to obtain distance traveled (D12) and heart rate.

RESULTS

Absolute LTVo2 and Vo2 max and LTVo2 as a percentage of Vo2 max were not different in overweight and nonoverweight adolescents during the cycle test. However, absolute ULVo2 was significantly greater in overweight adolescents: ULVo2 accounted for 35 +/- 8% of Vo2 max (and 63 +/- 15% of LTVo2) in overweight adolescents but only 20 +/- 5% of Vo2 max (and 39 +/- 12% of LTVo2) in nonoverweight adolescents. Resting heart rate before initiating the cycle test was significantly greater in overweight than nonoverweight adolescents (94 +/- 14 vs 82 +/- 15 beats per minute). However, maximal heart rate during the cycle test was significantly lower in overweight adolescents (186 +/- 13 vs 196 +/- 11 beats per minute). During the walk/run test, mean D12 was significantly shorter for overweight than for nonoverweight adolescents (1983 +/- 323 vs 1159 +/- 194 m). D12 was negatively related to BMI SDS (r = -0.81) and to ULVo2 (r = -0.98).

DISCUSSION

Overweight and nonoverweight adolescents had similar absolute Vo2 at the lactate threshold and at maximal exertion, suggesting that overweight adolescents are more limited by the increased cardiorespiratory effort required to move their larger body mass through space than by cardiorespiratory deconditioning. The higher percentage of oxygen consumed during submaximal exercise indicates that overweight adolescents are burdened by the metabolic cost of their excess mass. Their greater oxygen demand during an unloaded task predicted poorer performance during sustained exercise. Exercise prescriptions for overweight adolescents should account for the limited exercise tolerance imposed by excess body mass, focusing on activities that keep demands below lactate threshold so that exercise can be sustained.

Stress dose of hydrocortisone is not beneficial in patients with classic congenital adrenal hyperplasia undergoing short-term, high-intensity exercise

Classic congenital adrenal hyperplasia (CAH) is associated with impaired function of the adrenal cortex and medulla leading to decreased production of cortisol and epinephrine. As a result, the normal exercise-induced rise in blood glucose is markedly blunted in such individuals. We examined whether an extra dose of hydrocortisone, similar to that given during other forms of physical stress such as intercurrent illness, would normalize blood glucose levels during exercise in patients with CAH. We studied hormonal, metabolic, and cardiorespiratory parameters in response to a standardized high-intensity exercise protocol in nine adolescent patients with classic CAH. Patients were assigned to receive either an additional morning dose of hydrocortisone or placebo, in addition to their usual glucocorticoid and mineralocorticoid replacement in a randomized, double-blind, crossover design 1 h before exercising. Although plasma cortisol levels approximately doubled after administration of the additional hydrocortisone dose compared with the usual single dose, fasting and exercise-induced blood glucose levels did not differ. In addition, no differences were observed in the serum concentrations of the glucose-modulating hormones epinephrine, insulin, glucagon, and GH and of the metabolic parameters lactate and free fatty acids. Although maximal heart rate was slightly higher after stress dosing (193 +/- 3 vs. 191 +/- 3 beats/min, mean +/- sem, P < 0.05), this did not affect exercise performance or perceived exertion. We conclude that patients with classic CAH do not benefit from additional hydrocortisone during short-term, high-intensity exercise. Although this has not been tested with long-term exercise, a high degree of caution should be used when considering the frequent use of additional hydrocortisone administration with exercise, given the adverse side effects of glucocorticoid excess.

Patients with classic congenital adrenal hyperplasia have decreased epinephrine reserve and defective glucose elevation in response to high-intensity exercise

Classic congenital hyperplasia (CAH) is characterized by impaired adrenocortical function with a decrease in cortisol and aldosterone secretion and an increase in androgen secretion. Adrenomedullary function is also compromised due to developmental defects in the formation of the adrenal medulla, leading to decreased production of epinephrine. To examine the response to a natural stressful stimulus in patients with classic CAH, we studied hormonal, metabolic, and cardiorespiratory parameters in response to a standardized high-intensity exercise protocol in nine adolescent patients with CAH and nine healthy controls matched for gender, age, and percent body fat. The same relative workload was applied, based on individual maximal aerobic capacity, and all patients received their usual glucocorticoid and mineralocorticoid replacement. When compared with their normal counterparts, patients with CAH had significantly lower epinephrine levels both at baseline and at peak exercise (P < 0.01), whereas norepinephrine levels did not differ. Blood glucose concentrations were similar at baseline, but the normal exercise-induced rise observed in the healthy controls was significantly blunted in the CAH patients (P < 0.01). Peak heart rate was also lower in CAH patients than healthy controls (P < 0.05). As expected, the normal exercise-induced increase in cortisol was not observed in patients with CAH. No significant differences were found in serum levels of insulin, glucagon, GH, lactate and free fatty acids, blood pressure, or ability to sustain exercise between the two groups. Patients with CAH replaced with glucocorticoids have decreased adrenomedullary reserve and impaired exercise-induced changes in glucose but normal short-term high-intensity exercise performance. Whether the combination of epinephrine and cortisol deficiency poses a risk for hypoglycemia and/or decreased endurance during long-term physical stress has to be determined.

Improvement in hypertrophic cardiomyopathy after significant weight loss: case report

A 17-year-old obese boy found to have familial apical hypertrophic cardiomyopathy on routine screening was enrolled in a weight loss program on the basis of the hypothesis that significant weight loss would improve his cardiac status. He was followed with serial dual-energy x-ray absorptiometry, electrocardiography, echocardiography, and blood pressure and pulse rate measurements. Within 1 year, he lost 49 kg, with a body mass index reduction from 43.6 to 28.1 kg/m2 and associated reductions in systolic blood pressure, diastolic blood pressure, pulse pressure, mean heart rate, rate pressure product, and echocardiographic indices of left ventricular mass that resulted in a change from the initial geometric finding of eccentric left ventricular hypertrophy to a "normal" left ventricular mass with minimal asymmetric apical left ventricular thickening. Significant weight loss in an obese adolescent with presumed familial apical hypertrophic cardiomyopathy was associated with striking improvement in cardiac functional indices, which could have profound implications for long-term cardiovascular risk.

Decreased aerobic capacity in children with juvenile dermatomyositis

OBJECTIVE

To determine whether patients with juvenile dermatomyositis (DM) have limited aerobic capacity compared with healthy controls.

METHODS

Fourteen juvenile DM patients with inactive to moderately active, stable disease (age range 7-17 years) and 14 age- and sex-matched controls performed a maximal exercise test using a cycle ergometer. Oxygen uptake and power were measured at peak exercise (VO(2peak) and W(peak), respectively) and at anaerobic threshold (AT and W(AT)). Juvenile DM disease activity and damage were also assessed.

RESULTS

Patients with juvenile DM had significantly reduced VO(2peak) (19.6 ml O(2)/kg/minute in juvenile DM versus 31.1 ml O(2)/kg/minute in controls), peak heart rate (166 versus 184 beats per minute), W(peak) (1.6 versus 2.7 watts/kg), AT (11.1 versus 18.0 ml O(2)/kg/minute) and W(AT) (0.6 versus 1.4 watts/kg), compared to controls (P <or= 0.05 for each). Aerobic exercise parameters correlated with physician global disease activity and damage, T1-weighted magnetic resonance imaging, and Childhood Myositis Assessment Scale scores (r(s) = 0.58 - 0.82, P <or= 0.05).

CONCLUSION

Patients with juvenile DM with a range of disease activity have a decreased aerobic and work capacity compared to healthy children. Aerobic exercise limitation in juvenile DM correlates best with measures of disease damage (global damage assessment, T1-weighted magnetic resonance imaging, and disease duration). Aerobic exercise testing may be valuable in the assessment of physical endurance, and aerobic training may be indicated as part of the therapeutic regimen in myositis patients with inactive to moderately active, stable disease.

Relationships between walk/run performance and cardiorespiratory fitness in adolescents who are overweight

BACKGROUND AND PURPOSE

Little is known about the methods used to assess the physical fitness of adolescents who are overweight. We investigated the relationship between walk/run performance and cardiorespiratory fitness in adolescents who are overweight.

SUBJECTS

Eight African-American adolescents (5 female, 3 male) and 10 Caucasian adolescents (5 female, 5 male) who were overweight (mean age=14.5 years, SD=2.0, range=12-17; mean body mass index [BMI]=42.9 kg/m2, SD=11.5) participated in this study.

METHODS

Subjects performed a 12-minute walk/run test. The distances traveled at both 9 minutes (D9) and 12 minutes (D12) were recorded, and the distance traveled between 9 and 12 minutes (D9-12) was calculated. Subjects also completed a maximal cycle ergometry test, during which peak oxygen uptake (VO2peak), anaerobic threshold (AT), peak power (Wpeak), and power at the anaerobic threshold (WAT) were determined. Body composition was determined by air displacement plethysmography.

RESULTS

The mean percentage of body fat was 48.6% (SD=5.3%, range=40.3%-60.4%). Percentage of body fat and BMI were each inversely related to D9, D12, and VO2peak (all P<.005). Peak oxygen uptake (r=.72, P=.0001), VO2peak/kg lean body mass (r=.60, P<.005), Wpeak (r=.88, P<.0001), and WAT (r=.72, P=.0007) were all related to D12, with greater r values than for D9. If D9-12was included in regression analyses, D9 did not account for additional variance in any of the cycle ergometry variables.

DISCUSSION AND CONCLUSION

These results suggest that an easily obtained measurement of physical performance (distance traveled during a 12-minute walk/run test) is related to cardiorespiratory fitness and to body composition in adolescents who are overweight. The 12-minute walk/run distance is more predictive of cycle ergometry test results than the 9-minute distance.

Hypothalamic-pituitary-adrenal axis activity during exercise in African American and Caucasian women

African American women have a greater prevalence of obesity than Caucasian women, but the reasons for this difference are not known. We have investigated whether activity of the hypothalamic-pituitary adrenal axis plays a role in this phenomenon. Previous studies have shown that plasma ACTH immunoreactivity (ACTH-IR) of African American women, measured after ovine CRH (oCRH) stimulation, is significantly greater than ACTH-IR of Caucasian women, but is not accompanied by greater plasma cortisol concentrations. Analysis by high pressure liquid chromatography has demonstrated that after oCRH stimulation, the plasma ACTH-IR of African American women contains many nonintact ACTH fragments not found in Caucasians. To determine whether these racial differences in ACTH-IR secretion are an artifact of exogenous oCRH administration or are also found after a physiological stimulus for ACTH secretion, we measured hormones of the hypothalamic-pituitary adrenal axis before and after a standardized, maximal exercise treadmill test in 16 African American and 19 Caucasian healthy women matched for age, socioeconomic status, and body mass index. The intensity of exercise performed was similar in the two groups, as determined by duration of exercise, perceived intensity of exertion, plasma lactate, maximal heart rate, and maximum oxygen uptake. Basal ACTH-IR measured by RIA or immunoradiometric assay and cortisol were similar in African Americans and Caucasians. Plasma ACTH-IR, measured 10 min after completion of exercise, was significantly greater in African Americans than in Caucasians [by RIA: mean +/- SD ACTH-IR, 47.1 +/- 30.9 vs. 25.4 +/- 16.7 pmol/L (P < 0.01); by immunoradiometric assay: ACTH-IR, 45.9 +/- 43.2 vs. 21.1 +/- 14.6 pmol/L (P < 0.05)]. However, plasma cortisol after exercise was not different (450.2 +/- 157.7 vs. 483.6 +/- 180.4 nmol/L; P = 0.57). We conclude that ACTH-IR is significantly greater in African American than in Caucasian women after intense exercise. The ACTH-IR of African Americans and Caucasians does not appear to be equipotent at adrenal melanocortin-2 receptors, because the greater ACTH-IR of African Americans does not lead to greater cortisol secretion. Whether some components of the ACTH-IR detected in African Americans affect signal transduction of the hypothalamic melanocortin-4 receptors implicated in body weight regulation and thus predispose African American women to weight gain without altering plasma cortisol remains to be determined.