Normal energy expenditure in the infant with presymptomatic cystic fibrosis

Serum metabolomics indicate altered cellular energy metabolism in children with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a multi-system disease affecting multiple organs and cells besides the respiratory system. Metabolomic profiling allows simultaneous detection of biochemicals originating from cells, organs, or exogenous origin that may be valuable for monitoring of disease severity or in diagnosis.

AIM

We hypothesized that metabolomics using serum from children would differentiate CF from non-CF lung disease subjects and would provide insight into metabolism in CF.

METHODS

Serum collected from children with CF (n = 31) and 31 age and gender matched children with other lung diseases was used for metabolomic profiling by gas- and liquid-chromatography. Relative concentration of metabolites was compared between the groups using partial least square discriminant analyses (PLS-DA) and linear modeling.

RESULTS

A clear separation of the two groups was seen in PLS-DA. Linear model found that among the 459 detected metabolites 92 differed between CF and non-CF. These included known biochemicals in lipid metabolism, oxidants, and markers consistent with abnormalities in bile acid processing. Bacterial metabolites were identified and differed between the groups indicating intestinal dysbiosis in CF. As a novel finding several pathways were markedly different in CF, which jointly point towards decreased activity in the β-oxidation of fatty acids. These pathways include low ketone bodies, low medium chain carnitines, elevated di-carboxylic acids and decreased 2-hydroxybutyrate from amino acid metabolism in CF compared to non-CF.

CONCLUSION

Serum metabolomics discriminated CF from non-CF and show altered cellular energy metabolism in CF potentially reflecting mitochondrial dysfunction. Future studies are indicated to examine their relation to the underlying CF defect and their use as biomarkers for disease severity or for cystic fibrosis transmembrane regulator (CFTR) function in an era of CFTR modifying drugs.

Physical activity recommendations for children with specific chronic health conditions: Juvenile idiopathic arthritis, hemophilia, asthma and cystic fibrosis

As a group, children with a chronic disease or disability are less active than their healthy peers. There are many reasons for suboptimal physical activity, including biological, psychological and social factors. Furthermore, the lack of specific guidelines for 'safe' physical activity participation poses a barrier to increasing activity. Physical activity provides significant general health benefits and may improve disease outcomes. Each child with a chronic illness should be evaluated by an experienced physician for activity counselling and for identifing any contraindications to participation. The present statement reviews the benefits and risks of participation in sport and exercise for children with juvenile arthritis, hemophilia, asthma and cystic fibrosis. Guidelines for participation are included.

Physical activity recommendations for children with specific chronic health conditions: juvenile idiopathic arthritis, hemophilia, asthma, and cystic fibrosis

As a group, children with a chronic disease or disability are less active than their healthy peers. There are many reasons for suboptimal physical activity, including biological, psychological, and social factors. Furthermore, the lack of specific guidelines for 'safe' physical activity participation poses a barrier to increasing activity. Physical activity provides significant general health benefits and may improve disease outcomes. Each child with a chronic illness should be evaluated by an experienced physician for activity counselling and for identifying any contraindications to participation. The present statement reviews the benefits and risks of participation in sport and exercise for children with juvenile arthritis, hemophilia, asthma, and cystic fibrosis. Guidelines for participation are included.

Energy expenditure in extremely low birth weight infants near time of hospital discharge

OBJECTIVE

To test the hypothesis that total energy expenditure is significantly higher in extremely low birth weight (ELBW) infants compared with healthy term infants near the time of discharge.

STUDY DESIGN

This study was designed to determine total energy expenditure and body composition in a group of ELBW infants nearing discharge receiving full-volume enteral feedings of fortified breast milk or postdischarge formula (Neosure) (n = 10; mean birth weight, 0.8 +/- 0.1 kg; mean gestational age, 26 +/- 0.8 weeks; mean age at study, 68 +/- 9 days; mean postconceptional age, 36 +/- 1 weeks) and compare them with healthy term newborns all receiving breast milk (n = 14; mean birth weight, 3.5 +/- 0.5 kg; mean gestational age, 39.0 +/- 1.4 weeks; mean age at study, 2.3 +/- 1 days). Body composition and total energy expenditure were measured using the doubly labeled water method over a 7-day period.

RESULTS

Mean total energy expenditure was significantly higher in the ELBW infants compared with the term infants (89 +/- 22 kcal/kg/day vs 58 +/- 19 kcal/kg/day; P <or= .001). Total energy expenditure normalized to fat-free mass was also significantly greater in the ELBW infants (98 +/- 3 kcal/kg/day vs 73 +/- 20 kcal/kg/day; P <or= .01).

CONCLUSIONS

The rate of total energy expenditure is greater in ELBW infants nearing discharge compared with normal healthy term infants. In the ELBW infants, higher energy intake compensates for their higher total energy expenditure.

Nutrition and Lung Disease in Cystic Fibrosis

Among patients who have cystic fibrosis (CF), lung disease is a significant contributor to morbidity. From a clinical perspective, the link between malnutrition and lung dysfunction in CF is well established; however, the causal relationship remains unclear. Nutritional intervention for CF patients is predicated on the hypothesis that improved nutritional status improves pulmonary function. Which interventions will be of most value and have sustained gains is not completely clear from the available data. Taking into account that several factors condition the deficits that lead to malnutrition in CF, multidisciplinary interventions are likely to give the best results. More research is needed to better dissect the nutritional factors involved in lung disease and to identify effective and safe interventions through systematic controlled trials.

Energy balance and the accuracy of reported energy intake in preadolescent children with cystic fibrosis

BACKGROUND

Suboptimal growth and nutritional status are common among children with cystic fibrosis (CF) and pancreatic insufficiency (PI). A better understanding of energy balance is required to improve prevention and treatment of malnutrition.

OBJECTIVE

Our objective was to characterize energy balance and the reporting accuracy of dietary intake in children with CF by evaluating the relations between energy intake (EI), energy expenditure (EE), fecal energy loss, nutritional status, and growth.

DESIGN

The subjects were participants of a 24-mo prospective study of children 6-10 y of age with CF and PI. EE, EI, fecal energy loss, and anthropometric measures were obtained at baseline and at 24 mo.

RESULTS

The children (n = 69) had suboptimal growth at baseline (x +/- SD: weight-for-age z score, -0.53 +/- 1.19; adjusted height-for-age z score, -0.67 +/- 1.06; body mass index z score, -0.29 +/- 1.12), and these variables remained suboptimal at 24 mo. The median ratios of EI to EE at baseline and 24 mo were 1.15 and 1.18, respectively, which decreased to 1.09 and 1.10, respectively, when adjusted for fecal energy loss (EI(-FL):EE). At baseline, 7% of subjects were underreporters, 64% were accurate reporters, and 23% were overreporters of energy intake; the percentages were similar at 24 mo.

CONCLUSIONS

Although EI(-FL):EE ratios were higher than expected at both baseline and 24 mo, this cohort showed only age-appropriate weight gain. Self-reported dietary intake data at the individual level should be interpreted with caution, and weight gain velocity may serve as an objective measure of long-term energy balance.

Energy cost of activity and exercise in children and adolescents with cystic fibrosis

In cystic fibrosis (CF), perturbations of total daily energy expenditure (TDEE) may be a major determinant of altered nutrition and growth. Measurement of TDEE is problematic, though the flex-heart rate method (FHRM) provides a close estimation of TDEE, as compared to the cost-prohibitive, gold standard, the double-labeled water method, and permits estimates of the energy cost of daily activities (ECA) above resting energy expenditure (REE). We hypothesize that alterations in ECA affects TDEE in CF.

PURPOSE

To measure components of TDEE in adolescents with CF and normal lung function compared with controls, and to determine whether ECA can be improved by diet and exercise.

METHODS

Clinically stable CF subjects (aged 9-13, n=12) and age- and gender-matched controls (n=13) had repeated measurements of TDEE by FHRM, REE, and maximal cardiopulmonary exercise testing (CPET) during a 6-week exercise and diet program.

RESULTS

While the mean REE was similar in both groups, ECA was significantly lower in CF adolescents as compared to controls (p=0.02). During CPET, maximal exercise in CF was characterized by hyperventilation, which was unrelated to ventilation-perfusion mismatching. There were no changes in REE after dietary intervention.

CONCLUSION

ECA in CF adolescents with normal lung function is lower when compared to healthy controls. These findings support the hypothesis that clinically stable patients with CF have inefficient energy metabolism or alternatively conserve energy during activities of daily living.

[Technical aspects and relevance of energy expenditure and physical activity assessment in clinical research for cystic fibrosis patients]

Cystic fibrosis (CF) is characterized by deteriorating lung function and mal-digestion, which result in growth failure and/or under-nutrition. Several factors, alone or combined, contribute to malnutrition in CF: poor energy intake, elevation of energy loss as a result of malabsorption, increasing resting energy expenditure due to genetic mutation and/or pulmonary exacerbation. Several techniques have been used to assess energy expenditure and physical activity in order to better understand mechanisms of malnutrition in CF and follow therapeutic interventions. Indirect calorimetry (IC) studies have shown that resting energy expenditure (REE) was 10-22% higher than predictive values. This increase could be attributed to chronic inflammation as a result of Pseudomonas aeruginosa (PA) infection. Indeed, intravenous antibiotic therapy decreases REE. Doubly labelled water technique and heart rate monitoring calibrated against IC techniques shows that total energy expenditure (TEE) was not different than in healthy children. Physical activity level assessed by the ratio TEE-REE is also not different between CF of healthy children. Recently, new accelerometry technics, easier to use and less invasive have been successfully used in order to assess physical activity level in CF. Precise and ambulatory assessment of energy expenditure and physical activity permit to check and adapt dietary allowances in CF. These techniques could be simultaneously used and be helpful to assess efficacy of intervention studies.

Association of nutritional status and pulmonary function in children with cystic fibrosis

PURPOSE OF REVIEW

Multiple studies have shown that nutritional status is a strong predictor of morbidity and mortality in patients with cystic fibrosis (CF). Since CF is characterized by progressive lung disease, it could be argued that the underlying lung disease is what determines the nutritional failure seen in most patients. This review will summarize the data available from studies that have attempted to better define this relation and also present a review of the possible mechanisms involved taken from both observational and interventional studies.

RECENT FINDINGS

Longitudinal studies with sufficiently large follow-up times have demonstrated that young underweight patients have worst pulmonary function outcomes. More importantly, these studies concur in that the yearly change in growth parameters has a significant effect on the rate at which pulmonary function develops. Although the mechanisms behind this important association are yet unclear, there is some suggestion from interventional studies that the accrual of lean body mass is the factor that is involved in the preservation of lung function.

SUMMARY

Nutritional status strongly influences pulmonary health among CF patients. Therefore, aggressive nutritional support aiming at achieving normal growth patterns should lead to adequate development of lung function and maintenance of pulmonary health. However, more research is required with long-term longitudinal studies to better identify the most critical nutritional characteristics influencing this process as well as the most effective nutritional interventions.

Energy expenditure, nutrition status, and body composition in children with cystic fibrosis

OBJECTIVE

Undernutrition is a frequent complication in patients with cystic fibrosis (CF). Elevated energy requirements have been found to be 4% to 33% higher than in controls in some studies. Whether or not this is caused by a primary defect or energy metabolism is still a matter of controversy. To this end, we assessed energy expenditure, nutrition status, and body composition of clinically stable CF outpatients.

METHODS

Fifteen clinically stable CF patients, ages 2 to 15 y, were paired with 15 healthy control children. Measurements consisted of anthropometry and body composition. Plasma tocopherol, retinol, and hair zinc content were measured. Resting energy expenditure was determined by indirect calorimetry. Physical activity and dietary intake were recorded by recall methods.

RESULTS

Two children were nutritionally at risk according to the weight/height index, eight were normal, three were overweight, and two were obese. Body composition was similar in both groups. Zinc, tocopherol, and retinol levels were low in three, two, and three patients, respectively. Resting energy expenditures were 4.7 MJ/d (1127 +/- 220 kcal/d) in CF children and 4.63 MJ/d (1108 +/- 191 kcal/d) in control children (P = not significant). Physical activity level was sedentary in 86.6% of CF patients; the rest had a light physical activity pattern. Energy intake represented 141% of the estimated daily energy expenditure.

CONCLUSIONS

Non-oxygen-dependent CF children, without acute respiratory infection, had resting energy expenditures comparable to those of matched controls. Total energy expenditure was similar to or slightly lower than that in healthy children. Dietary recommendations for CF patients need to be reassessed.

Impact of intravenous antibiotic therapy on total daily energy expenditure and physical activity in cystic fibrosis children with Pseudomonas aeruginosa pulmonary exacerbation

Resting energy expenditure (REE) increases during pulmonary exacerbation by Pseudomonas aeruginosa in cystic fibrosis (CF) patients, and decreases after i.v. anti-Pseudomonas aeruginosa antibiotic therapy (IVAT). However, the impact of IVAT on total energy expenditure (TEE) is unknown. The aim of this study was to assess the changes in TEE and its main components after IVAT administered at home. Body composition measured by skinfold thickness and bio-impedance analysis, energy intake (EI) assessed by a weekly diary, REE measured by indirect calorimetry (IC), TEE assessed by a technique using 24-h heart-rate monitoring method and physical activity (PA) monitored using an activity diary (AD) were assessed in 16 patients (9 boys and 7 girls) aged 12.1 +/- 2.3 y (range, 7.1-14.6 y), before and after 28 +/- 4 d including a 14-d IVAT course. After IVAT, weight increased significantly by 1.9% (32.1 +/- 7.5 versus 32.7 +/- 7.6 kg; p < 0.05), while fat mass and fat free mass increased non significantly. EI increased by 4.6% (10,797 +/- 3039 versus 11320 +/- 3074 kJ/d; p < 0.05). TEE was not affected by IVAT (7014 +/- 1929 versus 7081 +/- 1478 kJ/d) whereas REE decreased by 4.1% (5295 +/- 909 versus 5093 +/- 837 kJ/d; p < 0.05), resulting in 9.3% increase in PA assessed by AD converted to metabolic equivalent tasks (MET) (37.0 +/- 3.1 versus 40.7 +/- 4.5 MET; p < 0.05). The improvement in nutritional status after IVAT is not related to a decrease in TEE, but probably to an increase in EI and a decrease of REE after IVAT. After IVAT, the reduction in REE is probably compensated by an increase in PA in CF patients.

Longitudinal investigation of energy expenditure in infants with cystic fibrosis

OBJECTIVE

To determine when energy expenditure becomes elevated in infants with cystic fibrosis (CF).

DESIGN

Longitudinal studies of total energy expenditure (TEE) using doubly labeled water were conducted in infants identified with CF by newborn screening through the first year of life.

SETTING

Hospital and community based studies in Denver, Colorado, USA and Cambridge, UK.

RESULTS

Eight of the 12 infants enrolled had begun enzyme therapy but were clinically asymptomatic. Four of the 12 infants were heterozygous for the delta F508 mutation, however no difference was seen in TEE from the remaining homozygous infants. TEE was compared to control cohorts at 2, 6 and 12 months of age. There was no difference from the control groups in TEE/kg fat free mass (FFM)/day at 2 months. However, by 6 months of age TEE/kg FFM/day in infants with CF exceeded that of age-matched controls by 25% (P<0.001). This elevation in TEE continued at 12 months of age exceeding that of controls by 30% (P<0.05).

CONCLUSIONS

These results indicate that infants with CF have increased energy needs by 6 months of age and that early diagnosis alone does not prevent the development of increased caloric requirements. These findings emphasize the need for close nutritional monitoring to prevent suboptimal growth during infancy in this population.

SPONSORSHIP

This research was supported by grant number 5 MO1 RR00069, General Clinical Research Centers Program, National Center for Research Resources, NIH.

Understanding chronic malnutrition in childhood and old age: role of energy balance research

Undernutrition is commonly associated with chronic disease in children and the elderly. Overnutrition is also, but less commonly, associated with chronic illness. In most diseases malnutrition arises because energy intake does not match energy output. Traditionally, the focus of research has been on abnormalities in energy expenditure, in the belief that these factors were the main determinants of energy imbalance. Recent studies using the doubly-labelled-water method to measure total energy expenditure, combined with more complex study design, have suggested an alternative conclusion. In many chronic diseases patient behaviour, and particularly energy intake, is responsible for energy imbalance and malnutrition. Energy balance studies have therefore provided a useful foundation for the design of strategies aimed at preventing or managing chronic malnutrition. However, modifying patient behaviour is an ambitious undertaking which may not be within the scope of existing clinical nutrition services. A number of non-traditional models of managing chronic malnutrition in children and the elderly are promising. Increasing recognition of the value of systematic review will also provide improved strategies for prevention and management of chronic malnutrition.

Energy metabolism in infants with cystic fibrosis

OBJECTIVE

To determine whether a defect in energy metabolism exists in infants with cystic fibrosis (CF).

DESIGN

Unselected, newly-diagnosed subjects with CF (n = 46) and 24 healthy infants aged <20 weeks had measurements of resting energy expenditure (REE), total energy expenditure (TEE) (n = 25), and body composition. Metabolizable energy intake (MEI) was calculated. Genotype, energy intake, and pancreatic status was determined in all subjects with CF, and 24 underwent bronchial lavage.

RESULTS

At diagnosis, infants with CF detected by newborn screening had significant anthropometric deficits (mean [SD] z-weight = 0.5 [1.0], z-length = 0.7 [1.3]) associated with pancreatic insufficiency. Their REE, TEE, or MEI (absolute measurements, per unit body weight or fat-free mass) were not increased. No relationship between REE, TEE, or MEI and Delta F(508) genotype, and no proportional differences in individual components of MEI between subjects with CF and controls, or between subjects with CF who were homozygotes or compound heterozygotes for Delta F(508) were observed. REE and TEE were not correlated with bronchial infection or inflammation.

CONCLUSION

Growth impairment during the first weeks of life in infants with CF is associated with pancreatic insufficiency. However, there is no evidence for a defect of energy metabolism related to Delta F(508), and in infants with CF, minimal lung disease is unaccompanied by increased energy expenditure.

Acute respiratory infection in patients with cystic fibrosis with mild pulmonary impairment: comparison of two physiotherapy regimens

Chest physiotherapy is an essential part of the management of cystic fibrosis, yet comparatively few studies have investigated the commonly used forms of chest physiotherapy during acute respiratory exacerbations. Fifteen subjects with cystic fibrosis and predominantly mild pulmonary impairment completed a randomised cross-over trial with 24 hours between treatments. The active cycle of breathing techniques (ACBT) assisted by a physiotherapist was compared with the ACBT performed independently by the patient. Measurement outcomes included pulmonary function tests, indirect calorimetry and oximetry parameters. Energy expenditure was not significantly different between the two treatment regimens, though significant improvements in pulmonary function were apparent 24 hours following the therapist-assisted ACBT. In this group of subjects, neither form of treatment proved superior in terms of energy consumption, but a reduction in airways obstruction was observed as a carry-over effect following the therapist-assisted ACBT.

Nutritional challenges of infants with cystic fibrosis

Nutrition plays an essential role in the management of cystic fibrosis (CF), particularly in infants with their high energy requirement due to rapid growth. Most infants are already malnourished at the time of clinical diagnosis due to an energy imbalance with increased losses and needs not compensated by energy intake. Even in very young asymptomatic CF patients diagnosed by neonatal screening programs, nutritional deficits can be detected in a high proportion of infants, since about half of all CF patients have evidence of pancreatic insufficiency at the time of birth. This review provides recommendations for assessment of the nutritional status at diagnosis and nutritional management including supplementation with pancreatic enzymes during the first year of life.

Energy expenditure and the body cell mass in cystic fibrosis

Poor nutritional status in patients with cystic fibrosis (CF) is associated with severe lung disease, and possible causative factors include inadequate intake, malabsorption, and increased energy requirements. Body cell mass (which can be quantified by measurement of total body potassium) provides an ideal standard for measurements of energy expenditure. The aim of this study was to compare resting energy expenditure (REE) in patients with CF with both predicted values and age-matched healthy children and to determine whether REE was related to either nutritional status or pulmonary function. REE was measured by indirect calorimetry and body cell mass by scanning with total body potassium in 30 patients with CF (12 male, mean age = 13.07 +/- 0.55 y) and 18 healthy children (six male, mean age = 12.56 +/- 1.25 y). Nutritional status was expressed as a percentage of predicted total body potassium. Lung function was measured in the CF group by spirometry and expressed as the percentage of predicted forced expiratory volume in 1 s. Mean REE was significantly increased in the patients with CF compared with healthy children (119.3 +/- 3.1% predicted versus 103.6 +/- 5% predicted, P < 0.001) and, using multiple regression techniques, REE for total body potassium was significantly increased in patients with CF (P = 0.0001). There was no relation between REE and nutritional status or pulmonary disease status in the CF group. In conclusion, REE is increased in children and adolescents with CF but is not directly related to nutritional status or pulmonary disease.

Metabolic and inflammatory responses to pulmonary exacerbation in adults with cystic fibrosis

BACKGROUND

We hypothesized that increased resting energy expenditure in adults with cystic fibrosis was related to chronic inflammation secondary to pulmonary infection and could be modified by treatment of the underlying infection.

METHOD

To determine the relationship between resting energy expenditure and the inflammatory and metabolic responses, we studied 22 adults with cystic fibrosis and chronic Pseudomonas aeruginosa infection before and after treatment of a respiratory exacerbation. Resting energy expenditure was measured by indirect calorimetry. Spirometry and circulating concentrations of C-reactive protein, neutrophil elastase alpha1-antiproteinase complex, catecholamines, non-esterified fatty acids and glycerol were determined.

RESULTS

The mean (95% confidence interval)% predicted FEV1 was 28.5% (20.6, 36.4) and mean body weight 50.7 kg (47.4, 54.1). Following treatment, 1-s forced expiratory volume (FEV1) and weight increased, while C-reactive protein (P<0.0001) and neutrophil elastase alpha1-antiproteinase complex concentrations (P<0.0001) were reduced. Resting energy expenditure decreased from 6.8 (6.3, 7.2) to 6.25 (5.9, 6.6) MJ day-1 by day 15 (P<0.001). Changes in resting energy expenditure and C-reactive protein were related (r = 0.66, P< 0.0001). Weight gain was inversely related to resting energy expenditure (r = 0.43, P = 0.02) and unrelated to energy intake (r = 0.02, P = 0.47). Post-treatment reduction in norepinephrine was related to changes in heart rate (r = 0.57, P<0.01), resting energy expenditure (r = 0.51, P = 0.001) and non-esterified fatty acids (r = 0.42, P< 0.05).

CONCLUSIONS

A parallel reduction in the host inflammatory and catabolic responses followed treatment of a respiratory exacerbation and may have contributed to weight gain.

Physiological and psychosocial contributors to malnutrition in children with cystic fibrosis: review

Malnutrition was once thought to be an inevitable consequence of cystic fibrosis (CF). It is now considered preventable but still contributes considerable morbidity in children. Malnutrition is linked to poorer pulmonary function, reduced survival and quality of life. As the anticipated lifespan of children with CF continues to lengthen, the prevention of malnutrition attains greater importance. This review explores the complex organic and psychosocial factors implicated in the aetiology of malnutrition associated with CF.

Adequacy of clinical formulae for estimation of energy requirements in children with cystic fibrosis

BACKGROUND

Two clinical formulae (CF conference formula and estimation based on 120% of average requirement for energy) have been recommended for the estimation of energy requirements in cystic fibrosis but their accuracy is unknown.

AIM

To compare the accuracy of estimates of energy requirement derived from the two formulae.

METHODS

Energy requirement, defined as total daily energy expenditure, was measured using the doubly labelled water method in 15 patients (six girls, nine boys; mean (SD) age, 10.0 (2.4) years) who were well and clinically stable. The accuracy of the formulae was assessed using calculation of biases and limits of agreement relative to measured energy requirement.

RESULTS

Estimates from the CF conference formula were lower than measured values (mean paired difference, 0.52 MJ/day; 95% confidence interval (CI), -1.10 to 0. 10), but this bias was not significant, and was smaller than that from the alternative formula (mean paired difference, 0.77 MJ/day; 95% CI, -0.20 to 1.74). Limits of agreement relative to measured total daily energy expenditure were narrower for the CF conference formula (-2.72 to 1.68 MJ/day) than for that based on 120% of estimated average requirement (-2.75 to 4.29 MJ/day), but with both formulae errors in estimation at the individual level were large.

CONCLUSIONS

The CF conference formula offers improved prediction of energy requirements, but the accuracy of both formulae at the individual level is not sufficiently good for clinical purposes.

Energy expenditure and energy intake during dexamethasone therapy for chronic lung disease

Dexamethasone is commonly administered to ventilator-dependent preterm infants with chronic lung disease. Infants receiving dexamethasone therapy frequently exhibit decreased rates of weight gain. The purpose of this investigation was to determine whether decreased growth in infants receiving dexamethasone therapy is caused by increased energy expenditure. Twelve infants were studied: 6 received dexamethasone treatment at 2 wk of age and crossed over to receive placebo treatment at 4 wk; the treatment order was reversed in the other 6 infants. The doubly labeled water method was used to determine energy expenditure for a 1-wk period during each treatment phase. The rate of weight gain during dexamethasone treatment was 6.5+/-10.6 and 20.0+/-5.7 g/kg/d during placebo treatment. Energy expenditure was 93.1+/-34.6 kcal/kg/d during dexamethasone treatment and 88.3+/-37.1 kcal/kg/d during placebo treatment. Energy intake was 119.2+/-29.0 kcal/kg/d during dexamethasone treatment and 113.8+/-23.7 kcal/kg/d during placebo treatment. The difference between intake and expenditure, or the energy available for growth, was 26.2+/-36.8 kcal/kg/d during dexamethasone treatment and 25.5+/-37.4 kcal/kg/d during placebo treatment. No significant differences were found in energy expenditure or energy intake between the treatment phases. The reduced growth seen in infants receiving dexamethasone treatment cannot be explained by increased energy expenditure or decreased energy intake, but may be due to differences in the composition of newly accreted tissue.

Nutritional imperatives in cystic fibrosis therapy

Patients with CF who receive optimal nutrition have better growth, maintain better nutritional reserves, and have better pulmonary function than patients with CF who have poor nutrition. These factors influence quality of life as well as survival. The metabolic and immunologic response to infection, as well as the increased work of breathing, escalates calorie requirements in this patient population. No single strategy works for every patient. Therefore, close monitoring of growth, symptoms, and changes in respiratory status that could increase calorie requirements is necessary.

Cystic fibrosis: nutritional consequences and management

Malnutrition is an adverse prognostic factor in cystic fibrosis, influencing the course of pulmonary disease and correlating inversely with survival. A positive energy balance between energy intake and the combination of total energy expenditure, energy losses and growth-related energy cost is essential to maintain normal nutritional status. Before starting nutritional supplementation, it is important to rule out pathological conditions that may have a deleterious effect on nutritional status: persistent exocrine pancreatic insufficiency, chronic bacterial pulmonary colonization, impaired glucose tolerance, specific nutritional deficits and associated disorders leading to a decrease of energy intake. Several methods are available, ranging from boosted oral nutrition to behavioural intervention, oral supplementation, enteral nutrition and, rarely, parenteral nutrition. The use of elemental nutrients for either oral supplementation or enteral nutrition seems of no nutritional benefit and is more expensive than conventional polymeric nutrients. Provided that the goals of the nutritional supplementation are fulfilled, simpler is often better.

Inspiratory muscle function and body composition in cystic fibrosis

Loss of body mass, which occurs in the later stages of cystic fibrosis (CF), probably affects all body compartments. We hypothesized that loss of skeletal muscle mass would include inspiratory muscles and impair their function. To test this, we determined the effect of body mass index (BMI) and lean body mass (LBM) depletion on handgrip (HG) force and inspiratory muscle function (IMF). The maximum inspiratory pressure (MIP) and the sustained maximum inspiratory pressure (SMIP) were measured with a computerized system. The relationship of IMF and reduced BMI to survival was studied in 49 patients, and a further 25 patients were studied to define the link between IMF and LBM. LBM was assessed by anthropometry. In the survival study a BMI < 20 kg/m2 was associated with a low SMIP (p < 0.001) and reduced survival, whereas MIP was relatively preserved. In the cross-sectional study SMIP (p < 0.001), MIP (p < 0.01), and HG (p < 0.01) were all reduced in the low LBM group, but not when related to total LBM. C-reactive protein and LBM were inversely related (r = -0.71, p < 0.01). Impaired IMF was chiefly a loss of sustained muscle contraction secondary to a reduced skeletal muscle mass, which may be related to pulmonary inflammation.

Nutrition and cystic fibrosis

Cystic fibrosis is commonly associated with energy deficiency in children and adults. Chronic undernutrition will lead to failure to thrive, wasting, and stunting of linear growth; nutrition and survival are intimately related in cystic fibrosis. These problems can simply be considered as energy imbalance, and management centers on restoration of energy balance. Specific nutrient deficiencies, such as fat soluble vitamins, are common in cystic fibrosis. Recent work has highlighted problems with bone density and also the prevalence of vitamin K deficiency. Management of nutritional problems can be complex, and injudicious treatment can further worsen the situation, as the relationship between high daily doses of pancreatic enzymes and the development of fibrosing colonopathy illustrates.

Resting energy expenditure, pulmonary inflammation, and genotype in the early course of cystic fibrosis

To further investigate the early course of cystic fibrosis (CF), specifically to examine factors contributing to energy imbalance, we examined resting energy expenditure (REE) (by indirect calorimetry) per unit body weight and metabolically active body cell mass (by total body potassium), in relation to CF genotype (by genomic DNA analysis), CF pancreatic phenotype, and markers of pulmonary inflammation (from bronchoalveolar lavage fluid). Eighteen subjects with presymptomatic CF who were less than 2 years of age (n = 11, delta F508/ delta F508 genotype; n = 15, pancreatic insufficiency phenotype), identified by newborn screening, were compared with age-, sex-, and length-matched control subjects (n = 13). Those with the delta F508/ delta F508 genotype had significantly higher mean REE expressed per unit body weight (125%) and body cell mass (115%; p < 0.03). Those with other genotypes (n = 7) did not, as a group, have significantly different mean REEs, but individuals with known "severe" genotypes had REEs in the high range and those with a pancreatic-sufficient phenotype had significantly lower REE than those with a pancreatic-insufficient phenotype (p < 0.05), and REEs were in the normal range. Examination of bronchoalveolar lavage fluid revealed positive culture results (7/10) but variable colony counts, neutrophil percentages, and concentrations of interleukin-8 and interleukin-1 beta equally in both CF genotype groups. These markers of pulmonary inflammation were not correlated, individually or collectively, with REE or genotype. We conclude that genotypic variations in energy balance are detectable early in CF unrelated to lung inflammation. Subclinical defects in body composition and pulmonary integrity occur early in CF and, in combination with increased cellular metabolic activity, have important clinical implications with respect to early diagnosis and management.