Nutritional rehabilitation in cystic fibrosis: controlled studies of effects on nutritional growth retardation, body protein turnover, and course of pulmonary disease

Evolution of nutritional management in children with cystic fibrosis - a narrative review

Nutrition has played a central role in the management and outcomes of people with cystic fibrosis (pwCF) since the 1970s. Advances in therapies and practices in recent decades have led to a significant change in the patient landscape with dramatic improvements in life expectancy, as well as quality of life, bringing with it new issues. Historically, cystic fibrosis was a condition associated with childhood and malnutrition; however, changes in patient demographics, nutritional assessment and fundamental nutritional management have evolved, and it has become an increasingly prevalent adult disease with new nutritional challenges, including obesity. This paper aims to describe these changes and the impact and challenges they bring for those working in this field. Nutritional professionals will need to evolve, adapt and remain agile to the wider range of situations and support required for a new generation of pwCF. Specialised nutrition support will continue to be required, and it will be additionally important to improve and optimise quality of life and long-term health.

A Gastroenterologist's Guide to Care Transitions in Cystic Fibrosis from Pediatrics to Adult Care

Cystic Fibrosis is a chronic disease affecting multiple systems, including the GI tract. Clinical manifestation in patients can start as early as infancy and vary across different age groups. With the advent of new, highly effective modulators, the life expectancy of PwCF has improved significantly. Various GI aspects of CF care, such as nutrition, are linked to an overall improvement in morbidity, lung function and the quality of life of PwCF. The variable clinical presentations and management of GI diseases in pediatrics and adults with CF should be recognized. Therefore, it is necessary to ensure efficient transfer of information between pediatric and adult providers for proper continuity of management and coordination of care at the time of transition. The transition of care is a challenging process for both patients and providers and currently there are no specific tools for GI providers to help ensure a smooth transition. In this review, we aim to highlight the crucial features of GI care at the time of transition and provide a checklist that can assist in ensuring an effective transition and ease the challenges associated with it.

Comparison of continuous glucose monitoring to reference standard oral glucose tolerance test for the detection of dysglycemia in cystic Fibrosis: A systematic review

Aims

Increasing evidence for benefit of early detection of cystic fibrosis related diabetes (CFRD) coupled with limitations of current diagnostic investigations has led to interest and utilisation of continuous glucose monitoring (CGM). We conducted a systematic review to assess current evidence on CGM compared to reference standard oral glucose tolerance test for the detection of dysglycemia in people with cystic fibrosis without confirmed diabetes.

Methods

MEDLINE, Embase, CENTRAL, Evidence-Based Medicine Reviews, grey literature and six relevant journals were searched for studies published after year 2000. Studies reporting contemporaneous CGM metrics and oral glucose tolerance test results were included. Outcomes on oral glucose tolerance tests were categorised into a) normal, b) abnormal (indeterminate and impaired) or c) diabetic as defined by American Diabetes Association criteria. CGM outcomes were defined as hyperglycemia (≥1 peak sensor glucose ≥ 200 mg/dL), dysglycemia (≥1 peak sensor glucose ≥ 140–199 mg/dL) or normoglycemia (all sensor glucose peaks < 140 mg/dL). CGM hyperglycemia in people with normal or abnormal glucose tolerances was used to define an arbitrary CGM-diagnosis of diabetes. The Quality Assessment of Diagnostic Accuracy Studies tool was used to assess risk of bias. Primary outcome was relative risk of an arbitrary CGM-diagnosis of diabetes compared to the oral glucose tolerance test.

Results

We identified 1277 publications, of which 19 studies were eligible comprising total of 416 individuals with contemporaneous CGM and oral glucose tolerance test results. Relative risk of an arbitrary CGM-diagnosis of diabetes compared to oral glucose tolerance test was 2.92. Studies analysed were highly heterogenous, prone to bias and inadequately assessed longitudinal associations between CGM and relevant disease-specific sequela.

Conclusions

A single reading > 200 mg/dL on CGM is not appropriate for the diagnosis of CFRD. Prospective studies correlating CGM metrics to disease-specific outcomes are needed to determine appropriate cut-points.

The Changing Landscape of Nutrition in Cystic Fibrosis: The Emergence of Overweight and Obesity

Cystic fibrosis has historically been characterized by malnutrition, and nutrition strategies have placed emphasis on weight gain due to its association with better pulmonary outcomes. As treatment for this disease has significantly improved, longevity has increased and overweight and obesity have emerged issues in this population. The effect of excess weight and adiposity on CF clinical outcomes is unknown but may produce similar health consequences and obesity-related diseases as those observed in the general population. This review examines the prevalence of overweight and obesity in CF, the medical and psychological impact, as well as the existing evidence for treatment in the general population and how this may be applied to people with CF. Clinicians should partner with individuals with CF and their families to provide a personalized, interdisciplinary approach that includes dietary modification, physical activity, and behavioral intervention. Additional research is needed to identify the optimal strategies for preventing and addressing overweight and obesity in CF.

Difference in Performance of EPI Pigs Fed Either Lipase-Predigested or Creon®-Supplemented Semielemental Diet

Pancreatic enzyme replacement therapy (PERT) and fat predigestion are key in ensuring the optimal growth of patients with cystic fibrosis. Our study attempted to highlight differences between fat predigestion and conventional PERT on body composition of young pigs with exocrine pancreatic insufficiency (EPI). EPI and healthy pigs were fed with high-fat diet for six weeks. During the last two weeks of the study, all pigs received additional nocturnal alimentation with Peptamen AF (PAF) and were divided into three groups: H—healthy pigs receiving PAF; P—EPI pigs receiving PAF+PERT; and L—EPI pigs receiving PAF predigested with an immobilized microbial lipase. Additional nocturnal alimentation increased the body weight gain of EPI pigs with better efficacy in P pigs. Humerus length and area in pigs in groups L and P were lower than that observed in pigs in group H (p value 0.005-0.088). However, bone mineral density and strength were significantly higher in P and L as compared to that of H pigs (p value 0.0026-0.0739). The gut structure was improved in P pigs. The levels of neurospecific proteins measured in the brain were mainly affected in P and less in L pigs as compared to H pigs. The beneficial effects of the nocturnal feeding with the semielemental diet in the prevention of EPI pigs' growth/development retardation are differently modified by PERT or fat predigestion in terms of growth, bone properties, neurospecific protein distribution, and gut structure.

Whole Body Protein Turnover and Net Protein Balance After Pediatric Thoracic Surgery: A Noninvasive Single-Dose 15 N Glycine Stable Isotope Protocol With End-Product Enrichment

BACKGROUND

We used the 15 N glycine urinary end-product enrichment technique to quantify whole body protein turnover following thoracic surgery.

MATERIALS AND METHODS

A single dose of 15 N glycine (2 mg/kg) was administered orally on postoperative day 1 to children (1-18 years) following thoracic surgery. 15 N enrichment of ammonia and urea was measured in mixed urine after 12 and 24 hours, respectively, and protein synthesis, breakdown, and net balance determined. Nitrogen balance (dietary intake minus urinary excretion) was calculated. Urinary 3-methylhistidine:creatinine ratio was measured as a marker of skeletal muscle protein breakdown.

RESULTS

We enrolled 19 subjects-median (interquartile range): age, 13.8 years (12.2-15.1); weight, 49.2 kg (38.4-60.8)-who underwent thoracotomy (n = 12) or thoracoscopic (n = 7) surgery. Protein synthesis and breakdown by 15 N enrichment were 7.1 (5.5-9) and 7.1 (5.6-9) g·kg-1 ·d-1 with ammonia (12 hours) as the end product, and 5.8 (3.8-6.7) and 6.7 (4.5-7.6) with urea (24 hours), respectively. Net protein balance by the 15 N glycine and urinary urea nitrogen methods were -0.34 (-0.47, -0.3) and -0.48 (-0.65, -0.28) g·kg-1 ·d-1 , respectively (rs = 0.828, P < .001). Postoperative change in 3-methylhistidine:creatinine ratio did not correlate significantly with protein breakdown or balance.

CONCLUSION

The single-dose oral administration of 15 N glycine stable isotope with measurement of urinary end-product enrichment is a feasible and noninvasive method to investigate whole body protein turnover in children. After major surgery, children manifest increased protein turnover and net negative balance due to increased protein breakdown.

Body composition and lung function in children with cystic fibrosis and meconium ileus

The aim of this study was to explore whether history of meconium ileus (MI) at birth in children and adolescents with cystic fibrosis (CF) adversely affects body composition and lung function in later life. Data of children and adolescents with CF who underwent spirometry and DXA as part of their routine care were analyzed. Associations between MI (explanatory variable) and areal bone mineral density (total body less head-TBLH aBMD), lean tissue mass (LTM), and fat mass (FM) (outcomes) were assessed using general linear models. Potential relationships of TBLH aBMD, LTM, and FM with FEV₁ (additional outcome) were also explored. One hundred and one subjects with CF (mean age 14 ± 3 years) were included, 19 (18.8%) of whom had history of MI. Negative associations were demonstrated between history of MI and FEV₁ (P = 0.04), TBLH aBMD (P = 0.03), and FM (P < 0.01) but not between history of MI and LTM (P = 0.07) after adjustment for other variables. Lung function was positively associated with TBLH aBMD (P < 0.01) and LTM (P = 0.02) but not with FM (P = 0.20).

CONCLUSION

Among children and adolescents with CF, those with history of MI have lower bone mineral density, FM, and lung function. What is Known: • Among children and adolescents with cystic fibrosis, those with history of meconium ileus in the neonatal period are at risk of having lower body mass index percentile and FEV ₁ percent predicted. What is New: • Children and adolescents with cystic fibrosis and history of meconium ileus have decreased bone mineral density and fat mass compared to patients without such history. • Lower lung function in children with MI coexists with suboptimal bone mineral density.

Nutritional and health benefits of semi-elemental diets: A comprehensive summary of the literature

AIM: To critically review and summarize the literature on nutritional and health outcomes of semi-elemental formulations on various nutritionally vulnerable patient populations who are unable to achieve adequate nutrition from standard oral diets.

METHODS: We conducted a comprehensive literature search of Pubmed and Embase databases. We manually screened articles that examined nutritional and health outcomes (e.g., growth, disease activity, gastrointestinal impairment, mortality, and economic impact) among various patient groups receiving semi-elemental diets. This review focused on full-text articles of randomized controlled clinical trials and other intervention studies, but pertinent abstracts and case studies were also included. Results pertaining primarily to tolerance, digestion, and absorption were summarized for each patient population in this systematic review.

RESULTS: Results pertaining primarily to tolerance, digestion, and absorption were summarized for each patient population. The efficacy of semi-elemental whey hydrolyzed protein (WHP) diet have been reported in various nutritionally high risk patient populations including - Crohn’s disease, short bowel syndrome, acute and chronic pancreatitis, cerebral palsy, cystic fibrosis, cerebrovascular accidents, human immunodeficiency virus, critically ill, and geriatrics. Collectively, the evidence from the medical literature indicates that feeding with a semi-elemental diet performs as well or better than parenteral or amino acid based diets in terms of tolerance, digestion, and nutrient assimilation measures across various disease conditions.

CONCLUSION: Based on this comprehensive review of the literature, patient populations who have difficulty digesting or absorbing standard diets may be able to achieve improved health and nutritional outcomes through the use of semi-elemental WHP diets.

Growth and the Growth Hormone-Insulin Like Growth Factor 1 Axis in Children With Chronic Inflammation: Current Evidence, Gaps in Knowledge, and Future Directions

Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt are often seen during adolescence. The underlying inflammatory state mediated by proinflammatory cytokines, prolonged use of glucocorticoid, and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the GH-IGF axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biological therapy may lead to improvement of growth in some of these children, but approximately one-third continue to grow slowly. There is increasing evidence that the use of relatively high-dose recombinant human GH may lead to partial catch-up growth in chronic inflammatory conditions, although long-term follow-up data are currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis, systemic abnormalities of the GH-IGF axis, and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human GH in these conditions and discussed the role of recombinant human IGF-1.

Advances in the detection and management of cystic fibrosis related diabetes

PURPOSE OF REVIEW

This review will outline the screening, diagnosis and management of cystic fibrosis related diabetes (CFRD). It will also discuss advances in the detection of early glucose abnormalities, their clinical significance and the emerging role for early insulin therapy.

RECENT FINDINGS

Before the onset of diabetes (as currently defined), patients with cystic fibrosis (CF) display glucose abnormalities, detectable either by 30-minutely sampled oral glucose tolerance testing (OGTT), or by continuous ambulatory interstitial glucose monitoring (CGM). These early glucose abnormalities are associated with the presence of glucose in airway fluid, potentially promoting the growth of airway pathogens and contributing to the progression of respiratory disease. Progressive insulin deficiency underlies these glucose abnormalities, and insulin deficiency also causes catabolism. Pilot studies of once-daily insulin therapy in the early stages of insulin deficiency show improved lung function and weight gain (important predictors of survival in CF).

SUMMARY

Early stages of insulin deficiency may be contributing to catabolism and deteriorating lung function in CF. It is plausible that early insulin therapy may prevent this deterioration, a view supported by pilot studies. Randomized controlled trials of early insulin therapy will now determine whether insulin therapy should be commenced earlier than current practice in CF.

Longitudinal trends in nutritional status and the relation between lung function and BMI in cystic fibrosis: a population-based cohort study

BACKGROUND

A high-calorie diet has been a standard of care in cystic fibrosis (CF) for >3 decades. However, energy requirements may have changed with new treatments and milder genotypes.

OBJECTIVES

The objectives of this study were to describe longitudinal trends in nutritional status and to evaluate the relation between nutritional status and lung function.

DESIGN

This longitudinal cohort study included 909 individuals followed at the Adult CF Clinic in Toronto from 1985 to 2011. Nutritional status was classified on the basis of WHO BMI guidelines. Multivariable linear regression with the use of generalized estimating equations was applied to evaluate the relation between BMI and lung function.

RESULTS

The proportion of underweight individuals decreased from 20.6% before 1990 to 11.1% in the most recent decade, whereas the proportion of overweight and obese subjects increased from 7.0% to 18.4% (P < 0.001). Overweight and obese subjects were older, had better lung function, had milder genotypes, and were more often male and pancreatic sufficient. Multivariable regression analyses showed that within the underweight group, an increase in BMI resulted in improved lung function, whereas this effect was half of that in overweight individuals. The greatest advantage of improved nutrition on lung function was observed in the underweight group and in pancreatic- insufficient patients.

CONCLUSIONS

Modification to a high-fat diet may be required in some individuals with CF to optimize nutritional health. Higher BMI is associated with improvements in lung function, although the lung function benefit of increasing one's BMI (in kg/m(2)) to >25 is small and needs to be balanced against the known health risks of obesity.

Nutritional care in children with cystic fibrosis: are our patients becoming better?

Over the last 30 years, major advances have occurred in our understanding of the disorder cystic fibrosis (CF) with the discoveries of the underlying chloride transport defect and the 'CF gene', the CF transmembrane conductance regulator gene. Equally important from a clinical and patient perspective are the improvements in median survival from less than 10 to 20 years prior to 1980, approaching 30 years during the 1980s and over 45 years more recently. Improved antibiotic regimens and lung clearance therapy contributed to the enhanced survival, but a key factor accredited as adding a further 10 years to the median survival was improving and then maintaining normal growth and nutrition. In the main, the latter were achieved by adherence to a 'high-fat high-energy' diet rather than the advocated virtually universal policy of the 'low fat', which was associated with wasting and linear growth failure. The high-fat diet in conjunction with better control of malabsorption due to microspheric pancreatic enzyme replacement therapy, attention to adequate fat-soluble vitamin supplementation and newborn screening has ensured that at least 80-90% of children with CF will achieve better health and survival through their adult years.

Hypoalbuminemia and early mortality after lung transplantation: a cohort study

Hypoalbuminemia predicts disability and mortality in patients with various illnesses and in the elderly. The association between serum albumin concentration at the time of listing for lung transplantation and the rate of death after lung transplantation is unknown. We examined 6808 adults who underwent lung transplantation in the United States between 2000 and 2008. We used Cox proportional hazard models and generalized additive models to examine multivariable-adjusted associations between serum albumin and the rate of death after transplantation. The median follow-up time was 2.7 years. Those with severe (0.5-2.9 g/dL) and mild hypoalbuminemia (3.0-3.6 g/dL) had posttransplant adjusted mortality rate ratios of 1.35 (95% CI: 1.12-1.62) and 1.15 (95% CI: 1.04-1.27), respectively. For each 0.5 g/dL decrease in serum albumin concentration the 1-year and overall mortality rate ratios were 1.48 (95% CI: 1.21-1.81) and 1.26 (95% CI: 1.11-1.43), respectively. The association between hypoalbuminemia and posttransplant mortality was strongest in recipients with cystic fibrosis and interstitial lung disease. Hypoalbuminemia is an independent risk factor for death after lung transplantation.

Successful prolonged use of recombinant human insulin-like growth factor-1 in a child with cystic fibrosis

Growth failure is a common and complicated process in children with cystic fibrosis (CF). Growth hormone, which is becoming a more commonly used agent in such patients, has demonstrated beneficial effects aside from increased growth velocity. Recently, insulin-like growth factor-1 has gained significant attention in the understanding of growth failure in children with CF. We report the successful prolonged use of recombinant human insulin-like growth factor-1 in an adolescent boy with CF, who demonstrated significant clinical benefits from the therapy.

Cystic fibrosis related diabetes (CFRD)--the end stage of progressive insulin deficiency

In cystic fibrosis, gradual pancreatic destruction causes progressive insulin deficiency, culminating in cystic fibrosis related diabetes (CFRD). As a consequence of insulin deficiency, elevated glucose levels can be detected (well before the diagnosis of CFRD), by continuous ambulatory subcutaneous interstitial fluid glucose monitoring or 30-min sampled oral glucose tolerance test (OGTT). Current diagnostic criteria for CFRD (based on 0 and 120-min OGTT blood glucose levels) were originally designed to forecast microvascular disease in type 2 diabetes, rather than CF-specific outcomes such as declining weight or lung function. In CF, decline in either weight or lung function predicts early mortality. Both may precede the diagnosis of CFRD by several years. Insulin, a potent anabolic hormone, is recommended treatment for CFRD, but use in earlier stages of insulin deficiency is not established. Conventional dosing (with four or more insulin injections per day) is burdensome and carries substantial risk of hypoglycemia. However, recent uncontrolled trials suggest that once-daily injection of intermediate or long-acting insulin improves weight and lung function, with minimal hypoglycemia risk, in CFRD and also in early insulin deficiency. It is plausible that insulin may be of greater benefit to respiratory function when given prior to the diagnosis of CFRD, after which structural lung disease may be irreversible. It is also plausible that early insulin treatment may prolong the lifespan of the remaining insulin-secreting β-cells. Randomized controlled trials are now needed to determine whether or not current clinical practice should be altered toward the earlier commencement of insulin in CF.

Body composition assessed by the 4-component model and association with lung function in 6-12-y-old children with cystic fibrosis

BACKGROUND

Malnutrition is an indicator of a poor prognosis in patients with cystic fibrosis (CF). Previous body-composition (BC) studies in children with CF used 2-component models (2CMs) to assess fat mass (FM) and fat-free mass (FFM), but to our knowledge no study has used the gold-standard 4-component model (4CM), which allows for a more accurate evaluation of the nature of both elements.

OBJECTIVE

We measured BC by using the 4CM in 6-12-y-old children with CF to 1) compare findings with those of healthy, matched control children and reference data; 2) relate BC to lung spirometry [forced expired volume in 1 s (FEV₁)]; and 3) compare findings with those from more commonly used 2CM techniques.

DESIGN

One hundred clinically stable children with CF (57% girls) aged 6-12 y were measured by using the 4CM. Children with CF underwent spirometry (FEV₁).

RESULTS

Girls with CF had significantly less FM than did healthy girls, even after adjustment for height and pubertal status; boys with CF had higher body mass index SD scores than did healthy boys. FM in girls was positively associated with the FEV₁ percentage predicted. The 2CM FM was significantly different from the 4CM FM, with differences dependent on sex and condition, although most techniques identified a relation between FM and FEV₁ in girls.

CONCLUSIONS

Although shorter than healthy children, boys with CF were heavier and had a BC within the normal range; however, girls with CF had lower FM than did healthy girls, and this was associated with poorer lung function. Given the worse prognosis in girls, this finding merits more attention. The reliability of 2CM techniques varied with sex and health status.

Natural history of glucose intolerance in patients with cystic fibrosis: ten-year prospective observation program

OBJECTIVE

To determine prospectively the long-term natural history of glucose homeostasis in adult patients with cystic fibrosis (CF).

STUDY DESIGN

Between 1996 and 2005, a total of 971 modified oral glucose tolerance tests (OGTTs) were performed in 329 patients with CF without recognized CF-related diabetes (CFRD). Patients were classified as having normal glucose tolerance (NGT), impaired glucose tolerance (IGT), CFRD without fasting hyperglycemia (FH), or CFRD with FH. Data were collected at baseline from the Toronto Cystic Fibrosis database.

RESULTS

On first OGTT, 63% of the 257 patients with pancreatic insufficiency (PI) had NGT, 23% had IGT, 11% had CFRD without FH, and 3% had CFRD with FH. Burkholderia cepacia complex colonization was correlated with worsening glucose tolerance category. There was a weak inverse relationship among weight, body mass index, forced expiratory volume in 1 minute, and 2-hour plasma glucose obtained during OGTT. Of the 168 PI patients who had a second OGTT, 17% improved their category of glucose tolerance, 70% remained unchanged, and 13% worsened. A similar trend was seen during the progression between any one test to a subsequent test.

CONCLUSIONS

Annual screening of glucose tolerance in patients with CF reveals highly variable results over time. Fluctuating levels of insulin resistance, probably with variable degrees of ongoing inflammation, affect the results and hinder prediction of future development of CFRD. Home glucose monitoring following abnormal OGTT results was essential in establishing the diagnosis of CFRD.

Cystic fibrosis related diabetes

Diabetes is a frequent complication seen in cystic fibrosis patients as they reach adulthood. Cystic fibrosis related diabetes (CFRD) is distinguished as a separate entity with features that include progressive loss of islet beta cell mass and insulin deficiency, as well as insulin resistance. Abnormalities in glucose tolerance may be detectable for many years prior to the development of overt diabetes. Therefore oral glucose tolerance testing is the preferred screening method for the identification of those patients at the highest risk for progression to diabetes. Progression to diabetes has been linked to poor outcomes in CF including loss of pulmonary function and increased mortality among females. Given the role that insulin deficiency plays in CFRD, insulin replacement therapy remains the only recommended intervention. In the absence of definitive supportive data, the use of oral antidiabetic agents is not considered standard therapy and needs further study. As with other forms of diabetes, CFRD patients also experience microvascular complications and should be periodically evaluated for manifestations.

Insulin-like growth factor-I levels predict weight, height and protein catabolism in children and adolescents with cystic fibrosis

Multiple reports have demonstrated the benefit of growth hormone (GH) treatment in children with cystic fibrosis (CF) and previous studies have demonstrated low to normal insulin-like growth factor-I (IGF-I) levels in these patients. Most biological effects of GH are mediated by IGF-I; however, the relationship between height, weight and rate of growth has not been systematically studied in CF. We conducted a retrospective analysis of 52 patients (including control volunteers with CF) who had participated in previous studies of GH treatment to determine the relationship between levels of IGF-I and growth in children with CF. In a subset of these patients, we also evaluated the relationship between protein catabolism and IGF-I. Baseline IGF-I levels and IGF-I z-scores were correlated with same day measures of height, weight, height and weight z-scores. In a subset of patients, IGF-I levels were also correlated with leucine rate of appearance (a measure of protein catabolism). IGF-I levels were obtained every six months during our studies and were correlated with same day height, weight and protein turnover. Height and weight velocity were calculated every six months from study baseline and were correlated with IGF-I levels. In all patients, whether treated with GH or controls, we found a positive linear correlation between IGF-I levels and height (r = 0.66, p < 0.0001) and weight (r = 0.61, p < 0.0001), as well as height and weight velocity. There was also a strong relationship between leucine rate of appearance and IGF-I. These results suggest a strong correlation between IGF-I and height, weight and protein catabolism and emphasize the need to normalize IGF-I levels in children with cystic fibrosis.

Growth and long-term lung function in cystic fibrosis: a longitudinal study of patients diagnosed by neonatal screening

OBJECTIVE

So far there is no long-term analysis relating the achievement of growth milestones (such as prepubertal and pubertal take-off and peak velocity) to the course of respiratory function from childhood to adulthood in cystic fibrosis. This study was designed to evaluate linear growth and severity of lung disease, find a correlation between growth and disease severity throughout childhood.

PATIENTS

One hundred sixty-three patients from one center were selected according to: diagnosis by neonatal screening, complete follow-up available (four height measurements/year) until the age of 20, respiratory tests available from the age of 5-6 years until adulthood, lung transplantation, or death. Disease was classified as mild or severe according to FEV(1) (group 1 and group 2). A third group of patients (group 3) consisted of those who died or underwent lung transplantation before the age of 18.

METHODS

Individual growth profiles were fitted with a seven-constant nonlinear growth function. A multivariate linear model was fitted, with gender and severity of disease as covariates, and age, height, and height velocity at growth milestones as dependent variables. Data were compared with those of the normal Italian population.

RESULTS

Lung disease severity correlates with delayed prepubertal and pubertal growth milestones. Peak height velocities were significantly reduced in relation to the severity of the disease.

CONCLUSIONS

Patients with severe forms of cystic fibrosis exhibit reduced growth velocity values at an early age, before a clear decline in pulmonary function.

Compliance in cystic fibrosis: an examination of infection control guidelines

The goal of this research was to begin the process of evaluating acceptability of infection control (IC) recommendations to CF patients and their families, determine whether compliance with IC guidelines differs from compliance with traditional CF medical treatment with respect to the variables predictive of compliance, and assess which patients are most likely to comply with IC recommendations. Participants were recruited during routine outpatient visits at a regional CF center located in a pediatric hospital. The sample included 44 child and adolescent patients, aged 9-18 years and their guardian, and 27 adult patients. All patients completed questionnaires and interviews. Results of this preliminary study suggest that many individuals with CF are unaware of or unconcerned with the risks involved in infection transmission via social contact with other CF patients. Further, most participants reported that they could benefit from friendships with other CF patients. Health belief variables were found to be predictive of compliance with both IC guidelines and traditional medical treatments in the adult and parent sample, but not in the child sample. Possible explanations for study findings are discussed and recommendations for future research on IC compliance are highlighted.

Nutrition support in clinical practice: review of published data and recommendations for future research directions

In the last 30 years, marked advances in enteral feeding techniques, venous access, and enteral and parenteral nutrient formulations have made it possible to provide nutrition support to almost all patients. Despite the abundant medical literature and widespread use of nutritional therapy, many areas of nutrition support remain controversial. Therefore, the leadership at the National Institutes of Health, The American Society for Parenteral and Enteral Nutrition, and The American Society for Clinical Nutrition convened an advisory committee to perform a critical review of the current medical literature evaluating the clinical use of nutrition support; the goal was to assess our current body of knowledge and to identify the issues that deserve further investigation. The panel was divided into five groups to evaluate the following areas: nutrition assessment, nutrition support in patients with gastrointestinal diseases, nutrition support in wasting diseases, nutrition support in critically ill patients, and perioperative nutrition support. The findings from each group are summarized in this report. This document is not meant to establish practice guidelines for nutrition support. The use of nutritional therapy requires a careful integration of data from pertinent clinical trials, clinical expertise in the illness or injury being treated, clinical expertise in nutritional therapy, and input from the patient and his/her family.

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.

Long term nutritional rehabilitation by gastrostomy in Israeli patients with cystic fibrosis: clinical outcome in advanced pulmonary disease

OBJECTIVES

Several studies have shown a linear correlation between nutritional status and pulmonary function in patients with cystic fibrosis. Our study aims were: 1) To evaluate the effect of nutritional supplementation via gastrostomy on nutritional, clinical, and pulmonary parameters, and 2) To identify predicting factors for success of long-term nutritional rehabilitation.

METHODS

Twenty-one Israeli patients, aged 8 months to 20 years, underwent gastrostomy insertion from 1992 to 2001. All patients were pancreatic insufficient, and all carried severe mutations (W1282X in 62% of the patients). Anthropometric and clinical data were obtained for each patient: 0-12 months before and 6-12 months and 18-24 months after gastrostomy placement. Standard deviation scores (SDS) for height, weight, and body mass index as well as percent of height-appropriate body weight were calculated.

RESULTS

The mean percent-of-predicted forced expiratory volume in 1 second (FEV1) decreased significantly during the first year of gastrostomy feeding (n = 16), from 44.2% +/- 13.9 to 41% +/- 13.3 (P = 0.05). However, during the second year of therapy (n = 10), a trend toward improvement was observed (from 39.4 +/- 12.1 to 41.4 +/- 16.1). Weight, and BMI z-scores as well as weight percent-of ideal body weight increased significantly. Height z-score for age decreased during the first year (from -1.9 +/- 1.3 to -2.1 +/- 1.4), However, a trend toward improvement was observed during the second year. A significant correlation was found between the change in weight z-score and height z-score during the first (r = 0.488, P = 0.016) and the second (r = 0.825, P < 0.001) years. There was no difference between compliers and noncompliers regarding height, weight, and BMI either before or after gastrostomy placement. A significant correlation between age at insertion of gastrostomy and improvement in height z-score (r = 0.52, P = 0.016) was observed. Cystic fibrosis related diabetes (n = 8) did not affect the response to supplemental feeding.

CONCLUSIONS

We observed a trend toward improvement of pulmonary disease during the second year, and a significant improvement in weight, height, and BMI z-scores. Compliance, diabetes, and young age prior to tube insertion did not predict success of nutritional rehabilitation.

The metabolic effects of pregnancy in cystic fibrosis

OBJECTIVE

Our purpose was to determine glucose tolerance in pregnant women with cystic fibrosis (CF) and to relate glucose tolerance to insulin sensitivity, hepatic glucose production, and protein turnover.

METHODS

We studied 8 CF women during pregnancy (CFPreg). Results were compared with those from 9 pregnant controls (PregCont) and 8 nonpregnant CF women (CFCont). The following metabolic studies were conducted: oral glucose tolerance test (OGTT), hyperinsulinemic euglycemic clamp, stable isotope infusion of [1-13C]leucine and [6,6-2H2]glucose for measurement of whole body protein turnover and hepatic glucose production (HGP), respectively. Indirect calorimetry was used to measure resting energy expenditure (REE), and food intake was measured by 3-day food journals. Fat-free mass was measured by total body potassium 40K scan.

RESULTS

All but one CFPreg developed diabetes by the end of the second trimester and had significantly lower insulin secretion and more insulin resistance than PregCont. Hepatic glucose production was significantly higher and suppression by insulin was less in CF subjects, and protein breakdown was significantly higher. Insulin resistance and HGP increased during pregnancy similarly in CFPreg and PregCont groups.

CONCLUSION

Pregnancy in CF is associated with decreased insulin sensitivity and high HGP, in addition to inherent decreased insulin secretion. Pregnancy in CF is also associated with increased protein turnover and less response to insulin's anticatabolic effect. These changes appear to predispose the pregnant CF women to early development of diabetes and poor weight gain.

Circulating markers to assess nutritional therapy in cystic fibrosis

Cystic fibrosis (CF) is the most commonly occurring lethal autosomal recessive disorder. The gene defect causes defective sodium and chloride transport across epithelial cells of the respiratory, hepatobiliary, gastrointestinal and reproductive tracts, resulting in thick mucus secretions. In the respiratory tract, mucus traps bacteria, causing repeated lung infections, progressive bronchiectasis and eventual death due to respiratory failure. In the gastrointestinal tract, mucus prevents pancreatic enzymes reaching the gut, leading to nutrient malabsorption. Careful nutritional management has a dramatic effect on growth and survival rates in CF. Appropriate nutritional support includes pancreatic enzyme replacement therapy, a high-fat/high-energy diet and essential nutrient supplementation, specifically fat-soluble vitamins and essential fatty acids (EFA). Long-term studies are required to examine the effects of nutritional interventions on key clinical outcomes in CF, such as the rate of decline of lung function. The use of circulating markers to assess the influence of nutritional therapy allows short-term intervention studies to predict the potential for clinical improvements. This article provides an overview of the biomarkers useful in the prediction of the efficacy of nutritional therapy on improvements in quality and quantity of life in CF.

Short-term protein intake and stimulation of protein synthesis in stunted children with cystic fibrosis

BACKGROUND

Stunted children with cystic fibrosis (CF) have less net protein anabolism than do children without CF, and the result is retarded growth in the CF patients. It is not known whether protein intake above that recommended by the Cystic Fibrosis Foundation would further stimulate whole-body protein synthesis.

OBJECTIVE

We studied the effects of 3 amounts of protein intake on whole-body protein synthesis and breakdown by using isotopic infusion of [1-(13)C]valine and [(15)N(2)]urea in children with stable CF who required tube feeding.

DESIGN

In 8 pediatric CF patients, we administered 3 randomly allocated isocaloric diets with normal (NP), intermediate (IP), and high (HP) amounts of protein (1.5, 3, and 5 g . kg(-1) . d(-1), respectively) by continuous drip feeding during a 4-d period at 6-wk intervals. Each patient acted as his or her own control. On the fourth day of feeding, whole-body protein synthesis and breakdown were measured.

RESULTS

Protein synthesis was significantly higher in the HP group (x +/- SEM: 1.78 +/- 0.07 micromol . kg(-1) . min(-1)) than in the IP (1.57 +/- 0.08 micromol . kg(-1) . min(-1); P=0.001) and NP (1.37 +/- 0.07 micromol . kg(-1) . min(-1); P < 0.001) groups. There were no significant differences in protein breakdown. Net retention of nitrogen was significantly higher in the HP group (12.93 +/- 1.42 micromol . kg(-1) . min(-1)) than in the IP (7.61 +/- 1.40 micromol . kg(-1) . min(-1); P=0.01) and HP (2.48 +/- 0.20 micromol . kg(-1) . min(-1); P < 0.001) groups.

CONCLUSION

In stunted children with CF requiring tube feeding, the highest stimulation of whole-body protein synthesis was achieved with a short-term dietary protein intake of 5 g . kg(-1) . d(-1).

Clinical importance of cystic fibrosis-related diabetes

The prevalence of cystic fibrosis-related diabetes (CFRD) and glucose intolerance (IGT) has risen dramatically over the past 20 years as survival has increased for people with cystic fibrosis (CF). Diabetes is primarily caused by pancreatic damage, which reduces insulin secretion, but glucose tolerance is also modified by factors that alter insulin resistance, such as intercurrent illness and infection. CFRD not only causes the symptoms and micro and macrovascular complications seen in type 1 and type 2 diabetes in the general population, but also is associated with accelerated pulmonary decline and increased mortality. Pulmonary effects are seen some years before the diagnosis of CFRD, implying that impaired glucose tolerance may be detrimental. Current practice is to screen for changes in glucose tolerance by regular measurement of fasting blood glucose, by oral glucose tolerance test or a combination of these approaches with symptom review and measurement of HbA1C. Treatment is clearly indicated for those with CFRD and fasting hyperglycaemia to control symptoms and reduce complications. As nutrition is critical in people with CF to maintain body mass and lung function, blood glucose should be controlled in CFRD by adjusting insulin doses to the requirements of adequate food intake and not by calorie restriction. It is less clear whether blood glucose control will have clinical benefits in the management of patients with CFRD without fasting hyperglycaemia or with impaired glucose tolerance and further studies are required to establish the best treatment for this patient group.

Factors affecting clinical outcome in gastrostomy-fed children with cystic fibrosis

In order to assess the effects of gastrostomy feeding on nutritional status, respiratory function, and survival in children with cystic fibrosis (CF), we studied all patients undergoing gastrostomy between 1989-1997 at the Royal Children's Hospital, Melbourne. Clinical information was collected from medical records, including serial measurements of weight-for-age standard deviation scores (WAZ) and forced expired volume in 1 sec (FEV1) (percent predicted). Measurements were compared for 2 years before and 2 years after gastrostomy placement. Data on gastroesophageal reflux (GER), adherence to the gastrostomy feeding program, and sputum culture were also assessed. Of 37 children (22 male; mean age, 11.6 +/- 4.8 years; range, 3-20), 11 died during the study period (7 female, 4 male). Female patients were more likely to die within 2 years of gastrostomy placement (OR = 3.9; 95% CI, 0.72-23.2; P = 0.07). Mortality was significantly associated with a WAZ score < -2 (OR = 10.7; 95% CI, 1.07-466.6; P = 0.02) and predicted FEV1 < 50% (OR = 10.8; 95% CI, 1.07-512.9; P = 0.02) at time of gastrostomy. Patients with clinical evidence of GER (n = 11) had significantly lower weight gain after gastrostomy (delta WAZ, -0.32 +/- 0.26 vs. 0.03 +/- 0.39; P = 0.03). In conclusion, the presence of advanced lung disease, GER, and female gender were factors associated with a poor clinical outcome after gastrostomy placement.

Cystic fibrosis-related diabetes

Diabetes mellitus (DM) has been recognized as a complication of cystic fibrosis (CF) for almost 50 years and commonly develops around 20 years of age. The prevalence increases with age and, with improved survival of those with CF, approaches 30% in certain centres. Its development appears to have a significant impact on pulmonary function and may increase mortality by up to six-fold. Subjects with CF are rarely ketosis-prone and phenotypically lie between Type 1 and Type 2 DM. Microvascular complications are recognized, although paucity of data does not permit a clear description of their natural history. An annual oral glucose tolerance test from the age of 10 years is recommended for screening, but logistical difficulties have led some groups to develop specific algorithms to aid diagnosis. Insulin sensitivity in CF is much debated and may depend upon the degree of glucose intolerance. Insulin resistance occurs in the presence of infection, corticosteroid usage and hyperglycaemia, whilst hepatic insulin resistance is considered an adaptation to CF. There is no universal consensus on the treatment of hyperglycaemia. With increased longevity of individuals with CF, greater numbers will develop diabetes and the diabetes physician is destined to play a greater role in the multidisciplinary CF team.

Effects of megestrol acetate on weight gain, body composition, and pulmonary function in patients with cystic fibrosis

OBJECTIVES

Malnutrition is a negative prognostic indicator in patients with cystic fibrosis (CF) and may accentuate pulmonary decline. We tested whether megestrol acetate would have beneficial effects on growth in patients with CF and pancreatic insufficiency.

STUDY DESIGN

We performed a randomized, double-blind, placebo controlled study. All patients were taking replacement enzymes to compensate for pancreatic insufficiency. Patients (n = 17) were randomly assigned to receive either megestrol acetate or placebo.

RESULTS

The treatment group had a significant increase in weight-for-age z scores compared with placebo and reached 100% of their ideal body weight within 3 months of initiating therapy. Weight gain included both fat and fat-free mass. Improved pulmonary function (forced vital capacity and forced expiratory volume in 1 second) was noted in the treatment group compared with placebo (P <.04). Reversible adrenal suppression was observed in the majority of patients who received megestrol acetate.

CONCLUSIONS

Short-term use of megestrol acetate results in significant weight gain and improved pulmonary function in malnourished subjects with CF. Our study provides a controlled basis for this intervention, identifies important side effects, and provides the foundation for multiyear, longitudinal trials in a larger number of patients with CF.

Effect of insulinlike growth factor-1 treatment in children with cystic fibrosis

OBJECTIVES

Malnutrition is common in cystic fibrosis (CF) and adversely affects survival. Because insulinlike growth factor-1 (IGF-1) has insulinlike effects in terms of carbohydrate metabolism and is growth promoting, the authors hypothesized that its use would increase linear growth rate and decrease insulin requirements in children with CF.

METHODS

The authors used a double-blind placebo-controlled crossover design. Seven prepubertal children aged 9.6 to 13 years (5 boys and 2 girls) were treated with placebo or IGF-1 for 6 months. After a 6-month washout period, patients received the alternative therapy for 6 months. The primary outcome measure was linear growth rate. Secondary outcome measures were changes in body mass index, body composition determined by dual energy x-ray absorptiometry, forced expiratory volume (FEV(1)), and the blood glucose/insulin ratio.

RESULTS

The mean height z score at baseline was -1.5 +/- 0.8. At entry, the mean serum IGF-1 level was 124 +/- 25 ng/mL (normal range, 110-771 ng/mL). With treatment, mean serum IGF-1 levels increased twofold to threefold for all patients. The half-life for IGF-1 was 10.3 hours. We observed no significant difference in linear growth rate, weight gain, rate of accretion of lean body mass, or mean FEV(1) during treatment with IGF-1 compared with placebo. The glucose/insulin ratio, an indirect index of insulin sensitivity, was significantly increased with IGF-1 treatment compared with placebo ( P < 0.02). No adverse events related to IGF-1 were detected.

CONCLUSIONS

Treatment with IGF-1 for 6 months did not promote linear growth in prepubertal children with CF. However, the glucose/insulin ratio was increased without changing blood glucose levels with IGF-1 treatment suggesting increased insulin sensitivity.

Insulin and glucose excursion following premeal insulin lispro or repaglinide in cystic fibrosis-related diabetes

OBJECTIVE

Insulin and glucose levels in response to premeal insulin lispro or repaglinide were evaluated in adult patients with cystic fibrosis-related diabetes (CFRD) without fasting hyperglycemia.

RESEARCH DESIGN AND METHODS

Seven patients with CFRD were fed 1,000-kcal liquid mixed meals. Three study conditions were administered in random order on separate mornings: 1) no premeal diabetes medication, 2) insulin lispro, 0.1 unit/kg body wt premeal and 3) repaglinide 1 mg premeal. Glucose and insulin levels were measured every 20 min for 5 h.

RESULTS

Fasting insulin and glucose levels were normal in patients with CFRD, but the peak glucose level was elevated. Insulin lispro significantly decreased the peak glucose level (P = 0.0004) and the 2-h (P = 0.001) and 5-h (P < 0.0001) glucose area under the curve (AUC). Repaglinide significantly decreased the 5-h glucose AUC (P = 0.03). Neither drug completely normalized cystic fibrosis glucose excursion at the doses used for this study. Insulin lispro significantly increased the 5-h insulin AUC (P = 0.04).

CONCLUSIONS

In response to subcutaneous insulin lispro, postprandial glucose excursion was significantly diminished and insulin secretion was enhanced compared with a control meal in which no medication was given to patients with CFRD. The oral agent repaglinide resulted in lesser corrections in these parameters. Neither drug completely normalized glucose or insulin levels, suggesting that the doses chosen for this study were suboptimal. Placebo-controlled longitudinal studies comparing the effectiveness of repaglinide and insulin on glucose metabolic control as well as overall nutrition and body weight are needed to help determine optimal medical treatment of CFRD.

Height and weight fail to detect early signs of malnutrition in children with cystic fibrosis

BACKGROUND

Many children with cystic fibrosis grow poorly and are malnourished. This study was undertaken to determine whether extensive anthropometry could detect early signs of malnutrition in prepubertal children with cystic fibrosis to prevent deficits in height and weight.

METHODS

Height, weight, six skin folds (triceps, subscapular, supraspinale, abdominal, front thigh, and medial calf) and five girths (arm relaxed, forearm, chest, thigh, and calf) were measured in a cross-sectional study of children aged 6 to 11 years with cystic fibrosis.

RESULTS

The children with cystic fibrosis were shorter and lighter for their age and gender than those in the reference groups. The mean weight and height z scores for the girls with cystic fibrosis were lower than those for the boys, significantly so for z weight ( P < 0.05). Although, the mean percent ideal body weight value of 98.6% suggested that the children with cystic fibrosis were adequately nourished, most of the measures of muscularity and adiposity of the children with cystic fibrosis were significantly lower than those of the reference group ( P < 0.05). The z scores of the anthropometric measures revealed that the deficit in muscularity of the children with cystic fibrosis was relatively much greater than the deficit in adiposity.

CONCLUSIONS

The percent ideal body weight index does not seem to be an adequate measure of nutritional status in children with cystic fibrosis. Anthropometric assessments should include skin-fold and circumference measurements of numerous sites on the upper and lower body, the trunk, and the limbs to detect deterioration in nutritional status early. Early detection of deficits in nutritional status may result in the adverse effects of malnutrition on height and weight, and possibly clinical status, being prevented.

Estado nutricional e ingestão alimentar de pessoas com fibrose cística

A mucoviscidose é uma doença que afeta o estado nutricional por interferir na ingestão e absorção adequadas de nutrientes. Este estudo avaliou 22 pacientes mucoviscidóticos atendidos no Ambulatório de Nutrição do Hospital Infantil Joana de Gusmão em Florianópolis, SC, no período de agosto de 1998 a janeiro de 1999. O estado nutricional foi determinado através de medidas antropométricas e dados de consumo alimentar. Quanto ao estado nutricional, 42,9% dos menores de 2 anos e 28,6% dos maiores de 10 anos estavam desnutridos; na faixa etária de 2 a 10 anos não houve nenhuma criança desnutrida. Quanto ao consumo alimentar, 33,3% atingiram a recomendação de energia e 95,2% atingiram a recomendação de proteína. Podemos concluir que a mucoviscidose afeta o estado nutricional das crianças em períodos críticos de crescimento e desenvolvimento, e que a qualidade da dieta destes pacientes pode ser melhorada através de um cuidado nutricional adequado.

Protein metabolism in clinically stable adult cystic fibrosis patients with abnormal glucose tolerance

Cystic fibrosis (CF) patients are reported to experience chronic protein catabolism. Since diabetes or impaired glucose tolerance (IGT) is common in CF, we hypothesized that their protein catabolic state is related to reduced insulin secretion or reduced insulin action. A total of 12 clinically stable adult CF patients with abnormal glucose tolerance and 12 age-, sex-, and lean body mass-matched healthy control subjects underwent protein turnover studies using L-[1-(13)C]leucine, L-[(15)N]phenylalanine, and L-[(2)H(4)]tyrosine, with and without exogenous insulin infusion. In the baseline fasting state, protein metabolism was entirely normal in CF patients, with no evidence of increased protein catabolism. In contrast, striking abnormalities were seen in CF patients when insulin was infused, since they did not experience normal suppression of the appearance rates of leucine, phenylalanine, or tyrosine (indexes of protein breakdown). At an insulin concentration of 45 +/- 2 microU/ml, normal control subjects suppressed the leucine appearance rate by 19 +/- 5% (P < 0.01), ketoisocaproate appearance rate by 10 +/- 3% (P = 0.03), tyrosine appearance rate by 11 +/- 2% (P = 0.03), and phenylalanine appearance rate by 6 +/- 3% (P = 0.07). Phenylalanine conversion to tyrosine decreased by 22 +/- 7% (P = 0.03). At a similar insulin concentration of 44 +/- 3 microU/ml, normal suppression of amino acid appearance did not occur in CF. The leucine appearance rate decreased by 4 +/- 2% (P = 0.65), ketoisocaproate appearance rate by 1 +/- 2% (P = 0.94), tyrosine appearance rate by 0 +/- 6% (P = 0.56), phenylalanine appearance rate by 5 +/- 6% (P = 0.34), and phenylalanine conversion to tyrosine by 5 +/- 6% (P = 0.95). Poor suppression of the amino acid appearance rate in CF was not related to previously documented glucose tolerance status (IGT or CF-related diabetes without fasting hyperglycemia), fasting insulin levels, the acute insulin response, insulin sensitivity, cytokine or counterregulatory hormone levels, resting energy expenditure, caloric intake, pulmonary function, or clinical status. Protein synthesis was not significantly affected by insulin infusion in either normal control subjects or CF patients. In conclusion, clinically stable adult CF patients have normal indexes of protein breakdown and synthesis in the fasting state. In contrast, elevation of plasma insulin to physiological postprandial levels fails to normally suppress indexes of protein breakdown. It is therefore likely that inability to spare protein during the postprandial state is the cause of protein catabolism in these patients.

Pathogenesis of malnutrition in cystic fibrosis, and its treatment

PATHOGENESIS

We have developed a model of the pathogenesis of malnutrition in cystic fibrosis. It consists of the relationship between nutrient balance and nutrient requirement. The validation has been conducted with respect to energy, but the same general principals can be applied to any nutrient. A patient with CF either loses weight or fails to grow normally if their absorbed energy intake is less than their total daily energy expenditure. Multiple factors have the potential to contribute to reduced energy intake including, anorexia, gastroeosophageal (GE) reflux leading to vomiting and hence food loss, as well as maldigestion. Another more recently recognized source of energy loss, is glucosuria as a result of CF related diabetes (CFRD). Conversely, lung inflammation appears to be related to increases in resting metabolic rate (RMR). Acute exacerbations of the chronic lung disease increases RMR which returns to a basal level some weeks after the inflammation is treated. In clinically stable patients with CF, RMR rises in a quadratic fashion as lung function falls. When FEV(1)is >85% predicted RMR is not different from controls, but it rises in a curvilinear fashion as FEV(1)falls. Initially it appears that patients adapt to their increased RMR by reducing their activity so their total daily energy expenditure (TDEE) is often no higher than controls. But this is by no means always the case. Furthermore good lung care requires CF patients to be involved in aerobic activities, hence their TDEE would rise. Although there has been considerable interest as to whether the genetic defect has an energy wasting effect, it appears genetic factors have little or no effect on RMR.

TREATMENT

This starts with making an energy diagnosis. First, a 3 day faecal fat balance study is conducted. This provides information with regard to intake as well as to maldigestion. In addition a history of GE reflux is sought, since it can readily be treated with H(2)-blockers. If significant fat malabsorption exists, efforts are made to improve pancreatic enzyme dose and function. The possibility of CFRD also needs to be considered. We measure the RMR of the patient using open circuit indirect calorimetry. Recommendations for diet therapy are based on estimated TDEE, which is determined from RMR taking into account faecal losses. Diet therapy places the emphasis on increasing the fat content of the diet. We have conducted a study to determine whether or not oral supplements help increase TDEE and they did not; they merely replaced food energy. Conversely, nocturnal gastrostomy supplemental feeding, while reducing voluntary food energy intake by about 20%, does result in a significant increase in total daily energy intake. Our target is to achieve a completely normal nutritional status. Long term follow-up of these patients has shown significantly better survival in patients who achieve normal nutritional status. The advent of lung transplantation has added another dimension. In our experience, following a successful lung transplant, most patients no longer need their supplemental gastrostomy feeding.

SUMMARY

Our clinic policy is to encourage a high fat diet (35-40% total energy) and our patients grow normally in height and weight until their lung disease deteriorates significantly. Patients who develop a negative energy balance seldom if ever respond to diet therapy and hence are candidates for supplemental nocturnal gastrostomy feeds. Gastrostomy fed patients constitute 3 to 5% of our total CF population of approximately 590 patients.