Growth in children with cystic fibrosis-related diabetes

Screening strategies for glucose tolerance abnormalities and diabetes in people with cystic fibrosis

The increase in life expectancy of patients with cystic fibrosis has come with new comorbidities, particularly diabetes. The gradual development of glucose tolerance abnormalities means that 30 to 40% of adults will be diabetic. Cystic fibrosis-related diabetes is a major challenge in the care of these patients because it is a morbidity and mortality factor at all stages of the disease. Early glucose tolerance abnormalities observed from childhood, before the stage of diabetes, are also associated with a poor pulmonary and nutritional outcome. The long asymptomatic period justifies systematic screening with an annual oral glucose tolerance test from the age of 10 years. However, this strategy does not take into account the new clinical profiles of patients with cystic fibrosis, recent pathophysiological knowledge of glucose tolerance abnormalities, and the emergence of new diagnostic tools in diabetology. In this paper, we summarise the challenges of screening in the current context of new patient profiles - patients who are pregnant, have transplants, or are being treated with fibrosis conductance transmembrane regulator modulators - and put forward an inventory of the various screening methods for cystic fibrosis-related diabetes, including their applications, limitations and practical implications.

Distribution of OGTT-Related Variables in Patients with Cystic Fibrosis from Puberty to Adulthood: An Italian Multicenter Study

Background: Insulin secretion and glucose tolerance is annually assessed in patients with cystic fibrosis (PwCF) through oral glucose tolerance tests (OGTTs) as a screening measure for cystic fibrosis-related diabetes. We aimed to describe the distribution and provide reference quartiles of OGTT-related variables in the Italian cystic fibrosis population. Methods: Cross-sectional study of PwCF receiving care in three Italian cystic fibrosis centers of excellence, from 2016 to 2020. We performed a modified 2-h OGTT protocol (1.75 g/kg, maximum 75 g), sampling at baseline and at 30-min intervals, analyzing plasma glucose, serum insulin, and C-peptide. The modified OGTT allowed for the modeling of β cell function. For all variables, multivariable quantile regression was performed to estimate the median, the 25th, and 75th percentiles, with age, sex, and pancreatic insufficiency as predictors. Results: We have quantified the deterioration of glucose tolerance and insulin secretion with age according to sex and pancreatic insufficiency, highlighting a deviation from linearity both for patients <10 years and >35 years of age. Conclusions: References of OGTT variables for PwCF provide a necessary tool to not only identify patients at risk for CFRD or other cystic fibrosis-related complications, but also to evaluate the effects of promising pharmacological therapies.

Cystic Fibrosis-Related Diabetes: Clinical approach and knowledge gaps

Cystic Fibrosis-Related Diabetes (CFRD) is a unique type of diabetes mellitus that shares some features with both type 1 and type 2 diabetes. Yet, its distinguishing feature of acute pulmonary complications associated with hyperglycemia and the catabolic metabolism associated with a relative insulin deficiency poses challenges to the application of traditional definitions and treatments for diabetes mellitus. People with CF (pwCF) undergo rigorous annual screening starting at age 10, a process that is challenging for patients and limited by sensitivity, specificity, and reproducibility. As pwCF continue to live longer, over 50% are expected to develop CFRD over their lifetime, including up to 20% of adolescents. Increasing numbers of people with CFRD will make this disease increasingly relevant to diabetes practitioners. Evidence-guided practice in CFRD care is limited by small and short studies. Our current understanding of CFRD may change significantly with the recent introduction of CF Transmembrane Regulator (CFTR) modulator medications. This review will explore current challenges in the diagnosis and management of CFRD, specifically highlighting knowledge gaps in the pathophysiology of CFRD, optimal screening methods, priorities for research and provide guidance with regards to screening, diagnosis, and treatment.

Auxological and Endocrinological Features in Children and Adolescents with Cystic Fibrosis

Cystic fibrosis (CF) is a multisystem autosomal recessive disease caused by mutations that lead to deficient or dysfunctional CF transmembrane conductance regulator (CFTR) proteins. Patients typically present malnutrition resulting from the malabsorption of fundamental nutrients and recurring lung infections, with a progressive worsening of the respiratory function. For these reasons, the clinical management of CF requires a multidisciplinary team. From an endocrinological point of view, patients often present major complications, such as diabetes, bone disease, thyroid disorders, delayed growth and puberty, hypogonadism and infertility, which negatively affect their quality of life and, in some cases, significantly reduce life expectancy. These complications can arise as a direct result of CFTR dysfunction and/or as a consequence of a deterioration in the function of the organs affected. The objective of this review is to analyze all the possible endocrinological complications that can occur in patients with CF by evaluating the most recent papers in the literature.

Prepuberal insulin secretory indices are long-term predictors of short adult stature in cystic fibrosis

Objective

Diabetes is a frequent comorbidity in cystic fibrosis (CF), related to multiple unfavorable outcomes. During the progression of β-cell dysfunction to diabetes, insulin deficiency could possibly reduce the anabolic support to grow even in the absence of significant glycemic derangements. To test this hypothesis, we evaluated whether prepuberal insulin secretory indices are independent predictors of adult height.

Design

Observational cohort study.

Research design and methods

A longitudinal analysis of 66 CF patients (33 females) from an ongoing cohort received at prepuberal age (median age of 12 years) modified 3-h oral glucose tolerance tests with 30-min insulin and C-peptide sampling, modeling of insulin secretory and sensitivity parameters, anthropometric evaluation. The latter was repeated when adults after a median follow-up of 9 years.

Results

In alternative models, we found a positive association with either basal insulin secretion (mean 0.22, 95% CI 0.01, 0.44 z-scores) or prepuberal β-cell glucose sensitivity (mean 0.23, 95% CI 0.00, 0.46 z-scores) and adult height, while total insulin secretion was negatively related to adult height (mean -0.36, 95% CI -0.57, -0.15 z-scores or mean -0.42, 95% CI -0.69, -0.16 z-scores, respectively). The high total insulin secretion of low adult height patients was mainly due to late (>60 min) secretion and was associated with a worse glucose response during OGTT.

Conclusions

Abnormal insulin secretion associated with high glucose response during OGTT predicts a decrease in adult height z-score. Our results suggest that insulin secretory defects in CF affect growth prior to the development of fasting hyperglycemia.

Most Short Children with Cystic Fibrosis Do Not Catch Up by Adulthood

Poor linear growth is common in children with cystic fibrosis (CF) and predicts pulmonary status and mortality. Growth impairment develops in infancy, prior to pulmonary decline and despite aggressive nutritional measures. We hypothesized that growth restriction during early childhood in CF is associated with reduced adult height. We used the Cystic Fibrosis Foundation (CFF) patient registry to identify CF adults between 2011 and 2015 (ages 18–19 y, n = 3655) and had height for age (HFA) records between ages 2 and 4 y. We found that only 26% CF adults were ≥median HFA and 25% were <10th percentile. Between 2 and 4 years, those with height < 10th percentile had increased odds of being <10th percentile in adulthood compared to children ≥ 10th percentile (OR = 7.7). Of HFA measured between the 10th and 25th percentiles at ages 2–4, 58% were <25th percentile as adults. Only 13% between the 10th and 25th percentile HFA at age 2–4 years were >50th percentile as adults. Maximum height between ages 2 and 4 highly correlated with adult height. These results demonstrate that low early childhood CF height correlates with height in adulthood. Since linear growth correlates with lung growth, identifying both risk factors and interventions for growth failure (nutritional support, confounders of clinical care, and potential endocrine involvement) could lead to improved overall health.

Nutritional status between 5-10 years is associated with cystic fibrosis-related diabetes in adolescence

BACKGROUND

Cystic fibrosis-related diabetes (CFRD) is a risk factor for adverse clinical outcomes including poor nutritional status, deterioration in lung functions, and increased mortality. The association between nutritional status between 5 and 10 years of age and later diagnosis of CFRD is not known.

METHODS

A retrospective chart review was performed for our patients with CF between 10 and 18 years. Data was collected at age 5 and 10 years. Comparison made between patients with and without CFRD.

RESULTS

Two groups were comparable for age and sex. At age 5, groups had no differences in weight, height, and body mass index. At age 10, the CFRD group had a lower body mass index (40.2 ± 24.7 vs. 61.5 ± 22.5 percentile, p = 0.02). Spirometry was similar between groups at 5 and 10 years. Patients with CFRD had lower growth velocity (5 ± 0.9 vs. 5.7 ± 0.9 cm/year, p = 0.03) and reduced weight gain rate (2.2 ± 0.9 vs. 3.2 ± 1.2 kg/year, p = 0.03) compared to patients without CFRD between 5 and 10 years. Patients with a weight gain less than 2.5 kg/year between 5 and 10 years were nine times more likely to develop CFRD in adolescence (Unadjusted Odds Ratio: 8.9; 95% CI:1.4, 47.2; p = 0.01).

CONCLUSION

Patients who later developed CFRD had significantly lower weight gain rate and height growth between 5 and 10 years of age than those without diabetes. Close monitoring of nutritional status in before age 10 years may help identify CF patients at-risk of developing CFRD.

Diabetes outbreak during COVID19 lock-down in a prediabetic patient with cystic fibrosis long treated with glargine

BACKGROUND

Cystic Fibrosis Related Diabetes (CFRD) is a frequent comorbidity of patients with Cystic Fibrosis (CF). A worsening of clinical conditions appears before CFRD. It has been demonstrated a decline in pulmonary function and nutritional status also in patients with prediabetes. Few trials show that insulin may be beneficial in prediabetic CF patients, to date guidelines do not recommend for this condition.

CASE PRESENTATION

We report a case of a patient treated with insulin glargine at 13 years, due to glycemic intolerance, and with Lumacaftor/Ivacaftor at 15 years. A reduction of pulmonary exacerbations was observed after glargine therapy, also confirmed after the starting of Lumacaftor/ Ivacaftor in this patient. Pulmonary function improved only after the first year of glargine therapy, then a deterioration appeared due to the natural history of CF lung damage. During the COVID-19 lockdown, poor adherence to care contributed to diabetes mellitus onset needing high insulin requirements. After two weeks the patient returned to prediabetic condition and his previous dose of glargine.

CONCLUSIONS

our case highlights firstly that insulin glargine has contributed to preserve him from further clinical worsening due to prediabetes in the years before pandemic, secondly the negative impact of COVID-19 lockdown on the clinical course of a chronic disease as CF.

Growth failure and treatment in cystic fibrosis

Poor growth has long been a characteristic feature of cystic fibrosis (CF) and is significantly linked to lung function and overall health status. Improvements in pulmonary and nutrition care for patients with cystic fibrosis (CF) have resulted in better growth outcomes; however, height gains have not paralleled the improvements in weight in children with CF, and patients with more severe CF mutations remain significantly more affected. Many factors affect the growth hormone-IGF-1 axis and the growth plate of the long bones, including the chronic inflammatory state associated with CF. There are also increasing data on the direct effects of CFTR on bone and implications for CFTR modulators in attaining optimal growth. Treatments aimed at improving growth in CF are also reviewed here.

Rapid early increase in BMI is associated with impaired longitudinal growth in children with cystic fibrosis

BACKGROUND

We aimed to assess whether final height in children with cystic fibrosis (CF) is affected by body mass index (BMI), BMI increase, pulmonary function, and cystic fibrosis-related diabetes (CFRD).

STUDY DESIGN

A longitudinal, retrospective study was performed in a cohort of 57 patients with CF (30 boys, 27 girls) born between 1997 and 2001. Height and weight were recorded annually from ages 0.5 to 10 years and biannually up to the age of 18. Measurements were converted to height-for-age-adjusted-for-target-height (HFA-TH) and BMI-for-age z-scores. Analyses were performed using the independent t tests and the Pearson's correlation.

RESULTS

For both boys and girls, HFA-TH and BMI-for-age z-scores were significantly lower in the first year of life, these scores increased rapidly until the age of 11 and 8 years, respectively. In boys, HFA-TH z-scores declined during puberty, with subsequently significantly impaired final height (z-score, -0.56, n = 30, standard deviation [SD] = 0.81, P = 0.001). In girls, HFA-TH z-scores briefly declined after the age of 8 years, but then increased to a z-score of -0.21 (n = 27, SD = 0.87) at age 18, which is not significantly lower than the national average (P = 0.22). Pulmonary function and the presence of CFRD were not associated with final height. However, rapid BMI increase between ages 1 and 6 was negatively associated with final height in boys (n = 29, r =-0.420; P = 0.023) and girls (n = 25, r =-0.466; P = 0.019).

CONCLUSIONS

In boys and girls, early BMI increase was associated with impaired final height. We suggest that early childhood serves as a "window" in which nutritional variations may program subsequent growth. Further refinement of nutritional strategies could be needed.

Cystic-fibrosis related-diabetes (CFRD) is preceded by and associated with growth failure and deteriorating lung function

BACKGROUND

Impaired glucose metabolism and cystic fibrosis (CF)-related diabetes (CFRD) are associated with insufficient weight gain and impaired lung function in children and adolescents with CF. We have asked whether imminent CFRD may be a cause of poor growth in children and adolescents.

METHODS

A retrospective case control study including 32 patients with CF with or without diabetes was conducted. Sixteen pairs, matched according to age, gender and exocrine pancreatic insufficiency, were analysed. Standard deviation scores (SDS) of height, growth, weight, body mass index (BMI), forced vital capacity (FVC), forced expiratory volume in the first second (FEV1) and forced expiratory flow at 75% of expired FVC (FEF75) were recorded during a mean observation period of 13 years per patient.

RESULTS

SDS of height and weight were reduced in CF patients with diabetes compared to those without, not only at the point of diagnosis (both p<0.05) but years before the evidence of diabetes. Afterwards there was a significant decline in height (p<0.001) and weight (p<0.01) SDS in CFRD patients and an increasing difference between the height and weight of CF patients with or without diabetes. In contrast, no significant reduction of BMI-SDS was observed in CFRD patients. All analysed lung function parameters showed a marked decline in CFRD patients starting 1 year prior to the diagnosis of diabetes.

CONCLUSIONS

Deteriorating growth, reduced weight and impaired lung function are related to the development of CFRD and are obvious several years before the actual diagnosis of diabetes.

Endocrine Disorders in Cystic Fibrosis

Cystic fibrosis is frequently complicated by endocrine disorders. Diabetes can be expected to affect most with CF and pancreatic insufficiency and varies widely in age of onset, but early identification and treatment improve morbidity and mortality. Short stature can be exacerbated by relative delay of puberty and by use of inhaled corticosteroids. Bone disease in CF causes fragility fractures and should be assessed by monitoring bone mineral density and optimizing vitamin D status. Detecting and managing endocrine complications in CF can reduce morbidity and mortality in CF. These complications can be expected to become more common as the CF population ages.

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.

Glucose tolerance affects pubertal growth and final height of children with cystic fibrosis

There are few data about the impact of cystic fibrosis-related diabetes (CFRD) on growth. We analyzed 17 children with cystic fibrosis (CF) presenting with newly diagnosed CFRD during puberty, in comparison with a matched control group of 52 CF children with normal glucose tolerance (NGT). Anthropometric evaluation showed that body mass index at CFRD diagnosis was significantly reduced in children with CFRD, in comparison with children with NGT (CFRD: -0.48 ± 1.08 vs. NGT: 0.2 ± 0.99; P=0.01), and the same difference remained evident at the end of follow up (CFRD: -0.49 ± 0.95 vs. NGT: 0.13 ± 0.89; P=0.04). Height standard deviation score (SDS) at baseline was slightly but not significantly lower in CFRD children (CFRD: -0.71 ± 0.83 vs. NGT: -0.25 ± 1.08; P=0.08), while final height SDS was significantly reduced (CFRD: -1.61 ± 1.12 vs. NGT: -0.61 ± 1.15; P=0.003). Mean final height SDS of the whole group was lower than mean target height SDS (final height SDS: -0.86 ± 1.2 vs. target height SDS: -0.3 ± 0.85; P<0.001). Target adjusted final height was lower in CFRD children, although the difference between CFRD and NGT children did not reach statistical significance (CFRD: -0.8 ± 1.03 vs. NGT: -0.47 ± 0.9; P=0.09). Pubertal growth and final height are negatively affected by CFRD. Intensive insulin treatment does not appear to be effective in normalizing growth, even when treatment is started early in the course of the disease, before the onset of clinical deterioration.

Growth failure and nutrition considerations in chronic childhood wasting diseases

Growth failure is a common problem in many children with chronic diseases. This article is an overview of the most common causes of growth failure/growth retardation that affect children with a number of chronic diseases. We also briefly review the nutrition considerations and treatment goals. Growth failure is multifactorial in children with chronic conditions, including patients with cystic fibrosis, chronic kidney disease, chronic liver disease, congenital heart disease, human immunodeficiency virus, inflammatory bowel disease, short bowel syndrome, and muscular dystrophies. Important contributory factors to growth failure include increased energy needs, increased energy loss, malabsorption, decreased energy intake, anorexia, pain, vomiting, intestinal obstruction, and inflammatory cytokines. Various metabolic and pathologic abnormalities that are characteristic of chronic diseases further lead to significant malnutrition and growth failure. In addition to treating disease-specific abnormalities, treatment should address the energy and protein deficits, including vitamin and mineral supplements to correct deficiencies, correct metabolic and endocrinologic abnormalities, and include long-term monitoring of weight and growth. Individualized, age-appropriate nutrition intervention will minimize the malnutrition and growth failure seen in children with chronic diseases.

Comparison of cystic fibrosis-related diabetes with type 1 diabetes based on a German/Austrian Pediatric Diabetes Registry

OBJECTIVE

The prevalence of cystic fibrosis-related diabetes (CFRD) has increased with improved life expectancy of patients. Clinical and care characteristics were compared with type 1 diabetes mellitus (T1DM) in a multicenter analysis of pediatric data.

RESEARCH DESIGN AND METHODS

Auxological and treatment data from 47,227 patients aged younger than 21 years with CFRD or T1DM in the German/Austrian Diabetes Prospective Documentation Initiative registry were analyzed by multivariable mixed regression modeling.

RESULTS

Diabetes onset (mean [interquartile range]) occurred later in individuals with CFRD (14.5 [11.8-16.3] years) than in individuals with T1DM (8.5 [4.9-11.8] years), with female preponderance in CFRD (59.1% vs. 47.5%; P < 0.01). CFRD patients had lower BMI standard deviation scores (-0.85 [-1.59 to -0.12] vs. +0.52 [-0.10 to +1.16]; P < 0.01) and lower HbA(1c) (6.87% vs. 7.97%; P < 0.01). Self-monitoring of blood glucose was more frequent in patients with T1DM (4.5 vs. 3.5; P < 0.01); 72% of CFRD patients received insulin. In insulin-treated patients, insulin dosage adjusted for age, sex, and diabetes duration differed significantly (T1DM: 0.79 IE per kilogram of body weight; CFRD: 0.83 IE per kilogram of body weight). Use of short-acting and long-acting insulin analogs was significantly more frequent in T1DM (47% vs. 39% and 37% vs. 28%; both P < 0.05). Metabolic control in CFRD patients without insulin was better compared with CFRD on insulin (HbA(1c): 6.00 vs. 7.12; P < 0.01), but duration of disease was significantly shorter (0.8 years [0.1-2.4] compared with 2.4 years [0.6-4.6]). There was no significant difference for BMI standard deviations scores between CFRD patients with or without insulin treatment.

CONCLUSIONS

Pediatric patients with CFRD show clear auxological and metabolic differences from those with T1DM, with different treatment choices.

Abnormal endocrine pancreas function at birth in cystic fibrosis ferrets

Diabetes is a common comorbidity in cystic fibrosis (CF) that worsens prognosis. The lack of an animal model for CF-related diabetes (CFRD) has made it difficult to dissect how the onset of pancreatic pathology influences the emergence of CFRD. We evaluated the structure and function of the neonatal CF endocrine pancreas using a new CFTR-knockout ferret model. Although CF kits are born with only mild exocrine pancreas disease, progressive exocrine and endocrine pancreatic loss during the first months of life was associated with pancreatic inflammation, spontaneous hyperglycemia, and glucose intolerance. Interestingly, prior to major exocrine pancreas disease, CF kits demonstrated significant abnormalities in blood glucose and insulin regulation, including diminished first-phase and accentuated peak insulin secretion in response to glucose, elevated peak glucose levels following glucose challenge, and variably elevated insulin and C-peptide levels in the nonfasted state. Although there was no difference in lobular insulin and glucagon expression between genotypes at birth, significant alterations in the frequencies of small and large islets were observed. Newborn cultured CF islets demonstrated dysregulated glucose-dependent insulin secretion in comparison to controls, suggesting intrinsic abnormalities in CF islets. These findings demonstrate that early abnormalities exist in the regulation of insulin secretion by the CF endocrine pancreas.

Maintenance of nutritional status in patients with cystic fibrosis: new and emerging therapies

Poor clinical outcomes in cystic fibrosis are often associated with undernutrition. Normal growth and development should be achieved in cystic fibrosis, and nutritional counseling is paramount at all ages. Prevention and early detection of growth failure is the key to successful nutritional intervention. The advance in nutritional management is certainly one factor that has contributed to the improved survival in recent decades. This review outlines the major nutritional parameters in the management of the patient with cystic fibrosis, including recent advances in pancreatic enzyme replacement therapy and fat-soluble vitamin therapy. There are sections on complicated clinical situations which directly affect nutrition, for example, before and after lung transplantation, cystic fibrosis-related diabetes, and bone health.

The role of exercise in maintaining health in cystic fibrosis

PURPOSE OF REVIEW

Consensus statements about the care of people with cystic fibrosis (CF) recommend exercise as part of a wider management strategy. Many of these recommendations are based on high-quality evidence that regular exercise improves some important clinical outcomes, such as lung function and quality of life. However, the evidence about the effect of exercise on other clinical outcomes is less extensive or lower in quality. This article will review the physiological effects of exercise on a range of outcomes in people with CF, the mechanisms by which exercise may improve these outcomes and the quality and findings of clinical research into the effects of exercise in the management of CF.

RECENT FINDINGS

Substantial evidence confirms that exercise significantly reduces the rate of decline in lung function in people with CF, at least in part by increasing mucus clearance. Regular exercise training over 6 months improves aerobic exercise capacity. Bone health is often poor in people with CF, but only indirect evidence supports that increasing the amount of exercise will have a beneficial effect on bone density. CF-related diabetes is also a common sequela of the disease, but again only evidence from type-2 diabetes exists to support exercise as a way of managing it.

SUMMARY

Although its effects on some outcomes are unclear, the overall effect of exercise on quality of life is substantially beneficial and the evidence available for other specific outcomes is directly or indirectly supportive, so it appears appropriate to recommend it in clinical practice.

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.

Recent trends in cystic fibrosis-related diabetes

PURPOSE OF REVIEW

To provide an updated literature review highlighting important aspects of cystic fibrosis-related diabetes (CFRD) including epidemiology, pathogenesis, complications, screening, and management.

RECENT FINDINGS

Although CFRD continues to be associated with increased rates of mortality in the cystic fibrosis (CF) population, this has improved over the past several years, and the previous sex difference is no longer present. Recent studies support that CFRD is primarily caused by insulin deficiency due to loss of beta cells, which may occur via a number of mechanisms including oxidative stress. Aggressive screening programs with oral-glucose tolerance testing and early treatment with insulin for patients with CFRD with or without fasting hyperglycemia have led to improvements in nutritional states and lung function. Oral agents do not appear to be effective in CFRD.

SUMMARY

CFRD is the most common comorbidity in the CF population and is associated with microvascular complications and protein catabolism leading to worse health outcomes. Recognition of glycemic abnormalities through aggressive screening has led to improvements in nutritional status, pulmonary function, and mortality rates.