Serum fatty acid profiles in cystic fibrosis patients and their parents

The fatty acid imbalance of cystic fibrosis exists at birth independent of feeding in pig and ferret models

Persons with cystic fibrosis (CF) exhibit a unique alteration of fatty acid composition, marked especially among polyunsaturates by relative deficiency of linoleic acid and excess of Mead acid. Relative deficiency of docosahexaenoic acid is variably found. However, the initial development of these abnormalities is not understood. We examined fatty acid composition in young CF ferrets and pigs, finding abnormalities from the day of birth onward including relative deficiency of linoleic acid in both species. Fatty acid composition abnormalities were present in both liver and serum phospholipids of newborn CF piglets even prior to feeding, including reduced linoleic acid and increased Mead acid. Serum fatty acid composition evolved over the first weeks of life in both non-CF and CF ferrets, though differences between CF and non-CF persisted. Although red blood cell phospholipid fatty acid composition was normal in newborn animals, it became perturbed in juvenile CF ferrets including relative deficiencies of linoleic and docosahexaenoic acids and excess of Mead acid. In summary, fatty acid composition abnormalities in CF pigs and ferrets exist from a young age including at birth independent of feeding and overlap extensively with the abnormalities found in humans with CF. That the abnormalities exist prior to feeding implies that dietary measures alone will not address the mechanisms of imbalance.

Essential Fatty Acid Deficiency in Cystic Fibrosis Disease Progression: Role of Genotype and Sex

Adequate intake of nutrients such as essential fatty acids (EFA) are critical in cystic fibrosis (CF). The clinical course of deterioration of lung function in people with CF has been shown to relate to nutrition. Independent of the higher energy consumption and malabsorption due to pancreatic insufficiency, EFA deficiency is closely associated with the risk of pulmonary infection, the most significant pathology in CF. This review will focus on the EFA deficiency identified in people with CF, as well as the limited progress made in deciphering the exact metabolic pathways that are dysfunctional in CF. Specifically, people with CF are deficient in linoleic acid, an omega 6 fatty acid, and the ratio of arachidonic acid (omega 6 metabolite) and docosahexaenoic acid (omega 3 metabolite) is increased. Analysis of the molecular pathways in bronchial cells has identified changes in the enzymes that metabolise EFA. However, fatty acid metabolism primarily occurs in the liver, with EFA metabolism in CF liver not yet investigated, indicating that further research is required. Despite limited understanding in this area, it is well known that adequate EFA concentrations are critical to normal membrane structure and function, and thus are important to consider in disease processes. Novel insights into the relationship between CF genotype and EFA phenotype will be discussed, in addition to sex differences in EFA concentrations in people with CF. Collectively, investigating the specific effects of genotype and sex on fatty acid metabolism may provide support for the management of people with CF via personalised genotype- and sex-specific nutritional therapies.

Role for animal models in understanding essential fatty acid deficiency in cystic fibrosis

Essential fatty acid deficiency has been observed in most patients with Cystic Fibrosis (CF); however, pancreatic supplementation does not restore the deficiency, suggesting a different pathology independent of the pancreas. At this time, the underlying pathological mechanisms are largely unknown. Essential fatty acids are obtained from the diet and processed by organs including the liver and intestine, two organs significantly impacted by mutations in the cystic fibrosis transmembrane conductance regulator gene (Cftr). There are several CF animal models in a variety of species that have been developed to investigate molecular mechanisms associated with the CF phenotype. Specifically, global and systemic mutations in Cftr which mimic genotypic changes identified in CF patients have been generated in mice, rats, sheep, pigs and ferrets. These mutations produce CFTR proteins with a gating defect, trafficking defect, or an absent or inactive CFTR channel. Essential fatty acids are critical to CFTR function, with a bidirectional relationship between CFTR and essential fatty acids proposed. Currently, there are limited analyses on the essential fatty acid status in most of these animal models. Of interest, in the mouse model, essential fatty acid status is dependent on the genotype and resultant phenotype of the mouse. Future investigations should identify an optimal animal model that has most of the phenotypic changes associated with CF including the essential fatty acid deficiencies, which can be used in the development of therapeutics.

DeltaF508 CFTR Hetero- and Homozygous Paediatric Patients with Cystic Fibrosis Do Not Differ with Regard to Nutritional Status

The purpose of this study was to compare the nutritional status between deltaF508 CFTR hetero- and homozygous paediatric patients with cystic fibrosis. We assessed the percentage profiles of fatty acids measured in erythrocyte membranes and the serum levels of vitamins A, D3, E and K1 in the studied groups. We also measured the weights and heights and calculated the body mass indexes (BMIs). The studied groups consisted of 34 heterozygous and 30 homozygous patients. No statistically significant differences were found in the serum vitamins or erythrocyte membrane fatty acid profiles between the hetero- and homozygous patient groups, except for heptadecanoic acid (p = 0.038). The mean percentiles of height, weight and BMI did not differ significantly between the two groups. The homozygous and heterozygous paediatric patients with cystic fibrosis were similar in terms of their nutritional statuses.

Is the ENaC Dysregulation in CF an Effect of Protein-Lipid Interaction in the Membranes?

While approximately 2000 mutations have been discovered in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR), only a small amount (about 10%) is associated with clinical cystic fibrosis (CF) disease. The discovery of the association between CFTR and the hyperactive epithelial sodium channel (ENaC) has raised the question of the influence of ENaC on the clinical CF phenotype. ENaC disturbance contributes to the pathological secretion, and overexpression of one ENaC subunit, the β-unit, can give a CF-like phenotype in mice with normal acting CFTR. The development of ENaC channel modulators is now in progress. Both CFTR and ENaC are located in the cell membrane and are influenced by its lipid configuration. Recent studies have emphasized the importance of the interaction of lipids and these proteins in the membranes. Linoleic acid deficiency is the most prevailing lipid abnormality in CF, and linoleic acid is an important constituent of membranes. The influence on sodium excretion by linoleic acid supplementation indicates that lipid-protein interaction is of importance for the clinical pathophysiology in CF. Further studies of this association can imply a simple clinical adjuvant in CF therapy.

Abnormal n-6 fatty acid metabolism in cystic fibrosis contributes to pulmonary symptoms

Cystic fibrosis (CF) is a recessively inherited fatal disease that is the subject of extensive research and ongoing development of therapeutics targeting the defective protein, cystic fibrosis transmembrane conductance regulator (CFTR). Despite progress, the link between CFTR and clinical symptoms is incomplete. The severe CF phenotypes are associated with a deficiency of linoleic acid, which is the precursor of arachidonic acid. The release of arachidonic acid from membranes via phospholipase A₂ is the rate-limiting step for eicosanoid synthesis and is increased in CF, which contributes to the observed inflammation. A potential deficiency of docosahexaenoic acid may lead to decreased levels of specialized pro-resolving mediators. This pathophysiology may contribute to an early and sterile inflammation, mucus production, and to bacterial colonization, which further increases inflammation and potentiates the clinical symptoms. Advances in lipid technology will assist in elucidating the role of lipid metabolism in CF, and stimulate therapeutic modulations of inflammation.

Low linoleic and high docosahexaenoic acids in a severe phenotype of transgenic cystic fibrosis mice

Low linoleic acid concentration is a common finding in patients with cystic fibrosis and associated with severe clinical phenotype. Low docosahexaenoic and arachidonic acids are more inconsistently found in patients, but arachidonic/docosahexaenoic ratio is usually high. In animal models with cftr mutations or KO animals for the cftr gene, linoleic acid deficiency has not been consistently reported and some report docosahexaenoic deficiency as the major fatty acid abnormality. We hereby describe fatty acid profile in a severe clinical cystic fibrosis phenotype in mice with a duplication of exon 3 generated in the cystic fibrosis gene of C57B1/6J mice ( cftrm1Bay allele). In 43/50 animals, plasma phospholipid fatty acids were repeatedly analyzed (mean three times/animal) covering ages between 7 and 235 days. Linoleic acid concentrations were significantly lower in cftr-/- mice compared to heterozygotes ( P = 0.03) and wild type mice ( P < 0.001). Females had significantly lower linoleic acid than males, not related to age. Arachidonic acid did not differ but docosahexaenoic acid was higher in cftr-/- than in wild type mice ( P < 0.001). The arachidonic/docosahexaenoic acid ratio did not differ but arachidonic/linoleic acid ratio was higher in cftr-/- mice compared to wild type mice ( P = 0.007). Similar to clinical studies, type of mutation is important for lipid abnormality with low linoleic acid most consistently found in the animals. Rodents differ in metabolism by synthesizing docosahexaenoic acid more efficiently comparing to humans, suggesting greater influence by diet. Precaution seems important when comparing animal and humans. Impact statement In translational research, animal models are important to investigate the effect of genetic mutations in specific diseases and their metabolism. Special attention has to be given to differences in physiology and metabolism between species and humans, which otherwise can hazard the conclusions. Our work illustrates that the different synthesis capacity in mice and humans for DHA would explain different results in different models for cystic fibrosis and different influences of diets. To avoid disappointing clinical results, these facts have to be considered before extensive clinical studies are started based on results from single animal studies.

Complex Relation Between Diet and Phospholipid Fatty Acids in Children With Cystic Fibrosis

OBJECTIVES

Altered total plasma n-6 and n-3 fatty acids are common in cystic fibrosis (CF). Whether alterations extend to plasma phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and are explained by diet is unclear. The present study was to describe the dietary intake of a large group of children with CF and to determine whether dietary fat composition explains differences in plasma PC and PE fatty acids between children with and without CF.

METHODS

Dietary intake was assessed using a food frequency questionnaire. Venous blood was collected. Plasma PC and PE were separately analyzed for fatty acids.

RESULTS

Children with CF, n = 74, consumed more calories and fat (g/day and % energy), with significantly more saturates mainly from dairy foods and less polyunsaturates including linoleic acid (LA), arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) (% fat) than reference children, n = 71. A subset of children with CF, not differing in dietary intake from the larger group, had significantly lower LA and DHA, but higher EPA in plasma PC and had higher LA and lower ARA and DHA in plasma PE, compared to a subset of reference children. In both groups, LA intake and LA in plasma PC and PE were not associated. EPA and DHA intakes were positively associated with EPA and DHA, respectively, in plasma PC, but not PE, in reference children only.

CONCLUSIONS

The fatty acid composition of plasma PC and PE is altered in CF. Fatty acid differences between children with and without CF are inconsistent between PC and PE and are not explained by dietary fat.

Determinants of Serum Glycerophospholipid Fatty Acids in Cystic Fibrosis

The etiology of altered blood fatty acid (FA) composition in cystic fibrosis (CF) is understood only partially. We aimed to investigate the determinants of serum glycerophospholipids’ FAs in CF with regard to the highest number of FAs and in the largest cohort to date. The study comprised 172 CF patients and 30 healthy subjects (HS). We assessed Fas’ profile (gas chromatography/mass spectrometry), CF transmembrane conductance regulator (CFTR) genotype, spirometry, fecal elastase-1, body height and weight Z-scores, liver disease, diabetes and colonization by Pseudomonas aeruginosa. The amounts of saturated FAs (C14:0, C16:0) and monounsaturated FAs (C16:1n-7, C18:1n-9, C20:1n-9, C20:3n-9) were significantly higher in CF patients than in HS. C18:3n-6, C20:3n-6 and C22:4n-6 levels were also higher in CF, but C18:2n-6, C20:2n-6 and C20:4n-6, as well as C22:6n-3, were lower. In a multiple regression analysis, levels of seven FAs were predicted by various sets of factors that included age, genotype, forced expiratory volume in one second, pancreatic status and diabetes. FA composition abnormalities are highly prevalent in CF patients. They seem to be caused by both metabolic disturbances and independent clinical risk factors. Further research into the influence of CFTR mutations on fat metabolism and desaturases’ activity is warranted.

Abnormal unsaturated fatty acid metabolism in cystic fibrosis: biochemical mechanisms and clinical implications

Cystic fibrosis is an inherited multi-organ disorder caused by mutations in the CFTR gene. Patients with this disease exhibit characteristic abnormalities in the levels of unsaturated fatty acids in blood and tissue. Recent studies have uncovered an underlying biochemical mechanism for some of these changes, namely increased expression and activity of fatty acid desaturases. Among other effects, this drives metabolism of linoeate to arachidonate. Increased desaturase expression appears to be linked to cystic fibrosis mutations via stimulation of the AMP-activated protein kinase in the absence of functional CFTR protein. There is evidence that these abnormalities may contribute to disease pathophysiology by increasing production of eicosanoids, such as prostaglandins and leukotrienes, of which arachidonate is a key substrate. Understanding these underlying mechanisms provides key insights that could potentially impact the diagnosis, clinical monitoring, nutrition, and therapy of patients suffering from this deadly disease.

Lung transplantation in cystic fibrosis normalizes essential fatty acid profiles

BACKGROUND

Cystic fibrosis (CF) can be a devastating disease. Disorders in essential fatty acid state are increasingly reported and various supplementation trials have been performed in an attempt to improve outcomes. However, the mechanisms leading to these disturbances remain elusive. We wanted to investigate the role of the diseased CF lung on fatty acid profiles.

METHODS

We compared fatty acid profiles in patients with CF after lung transplantation (n=11) to age-matched healthy controls and homozygous F508del patients (n=22 each).

RESULTS

Compared to healthy controls, in patients with CF, there are decreased levels of docosahexaenoic, linoleic and arachidonic acid and increased levels of mead acid. In patients that underwent a lung transplantation, levels of docosahexaenoic, linoleic and arachidonic acid were normal. Mead acid did not decrease significantly.

CONCLUSIONS

The diseased CFTR deficient lung is a major determinant in the disturbed fatty acid profile in CF.

Renal function in pediatric cystic fibrosis patients in the first decade of life

With increasing life expectancy and the need for lung transplantation in the cystic fibrosis (CF) population, there are increasing reports of chronic kidney disease (CKD). However, values for baseline or longitudinal glomerular filtration rate (GFR) as measured by exogenous clearance markers are lacking in this population. Retrospective cross-sectional study in 2 to 18-year-olds cared for at a single CF center who had a GFR measured by plasma disappearance of Technetium-99 m diethylenetriaminepentaacetic acid (mGFR). The primary outcome was evidence of renal dysfunction as defined by CKD stage II or below (mGFR <90 ml/min/1.73 m(2), persistent abnormalities in urinary sediment, abnormal renal imaging). Of 63 patients evaluated, four had apparent renal dysfunction, one demonstrated decreased mGFR, and three others had persistent microscopic hematuria. The mean mGFR was substantially higher (140 ± 24 ml/min/1.73 m(2)) than expected or previously reported for healthy children. We did not demonstrate the presence of significant renal impairment after limited aminoglycoside exposure in the first decade following diagnosis with CF. However, we did document the presence of glomerular hyperfiltration in a significant proportion of our CF patients.

CFTR knockdown stimulates lipid synthesis and transport in intestinal Caco-2/15 cells

Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel highly expressed in epithelial cells of the gastrointestinal tract. Mutations in the CFTR gene cause cystic fibrosis (CF), a disease characterized by pancreatic insufficiency, fat malabsorption, and steatorrhea. Despite the administration of pancreatic enzymes to normalize malabsorption, CF patients still experienced lipid fecal loss, nutritional deficiencies, and abnormalities in serum lipid profile, suggesting the presence of intrinsic defects in the intestinal handling of nutrients. The objective of the present study was to assess the impact of CFTR gene knockdown on intracellular lipid metabolism of the intestinal Caco-2/15 cell line. Partial CFTR gene inactivation led to cellular lipid accretion of phospholipids, triglycerides, and cholesteryl esters. Likewise, secretion of these lipid fractions was significantly increased following CFTR gene manipulation. As expected from these findings, the output of triglyceride-rich lipoproteins showed the same increasing pattern. Investigation of the mechanisms underlying these changes revealed that CFTR knockdown resulted in raised levels of apolipoproteins in cells and media and microsomal transfer protein activity, two important factors for the efficient assembly and secretion of lipoproteins. Similarly, scrutiny of the enzymatic monoacylglycerol acyltransferase and diacylglycerol acyltransferase, which exhibit dynamic function in triacylglycerol resynthesis and chylomicron formation in enterocytes, revealed a significant augmentation in their activity. Conversely, cholesterol uptake mediated by Niemann-Pick C1 like 1, Scavenger Receptor Class B Type I, and ATP-binding cassette G8 remains unaffected by genetic modification of CFTR. Collectively, these results highlight the role played by CFTR in intestinal handling of lipids and may suggest that factors other than defective CFTR are responsible for the abnormal intracellular events leading to fat malabsorption in CF patients.

A novel lipidomic strategy reveals plasma phospholipid signatures associated with respiratory disease severity in cystic fibrosis patients

The aim of this study was to search for lipid signatures in blood plasma from cystic fibrosis (CF) patients using a novel MALDI-TOF-ClinProTools strategy, initially developed for protein analysis, and thin layer chromatography coupled to MALDI-TOF (TLC-MALDI). Samples from 33 CF patients and 18 healthy children were subjected to organic extraction and column chromatography separation of lipid classes. Extracts were analyzed by MALDI-TOF, ion signatures were compared by the ClinProTools software and by parallel statistical analyses. Relevant peaks were identified by LC-MSn. The ensemble of analyses provided 11 and 4 peaks differentially displayed in CF vs healthy and in mild vs severe patients respectively. Ten ions were significantly decreased in all patients, corresponding to 4 lysophosphatidylcholine (18:0, 18:2, 20:3, and 20:5) and 6 phosphatidylcholine (36:5, O-38:0, 38:4, 38:5, 38:6, and P-40:1) species. One sphingolipid, SM(d18:0), was significantly increased in all patients. Four PC forms (36:3, 36:5, 38:5, and 38:6) were consistently downregulated in severe vs mild patients. These observations were confirmed by TLC-MALDI. These results suggest that plasma phospholipid signatures may be able to discriminate mild and severe forms of CF, and show for the first time MALDI-TOF-ClinProTools as a suitable methodology for the search of lipid markers in CF.

Lipid metabolism in cystic fibrosis

PURPOSE OF REVIEW

Expression of defective cystic fibrosis transmembrane conductance regulator (CFTR), the cause for cystic fibrosis, affects fatty acid, cholesterol and sphingolipid metabolism. This review summarizes recent observations and evaluates current understanding of mechanisms.

RECENT FINDINGS

Recent observations implicate CFTR, in addition to known effects on fatty acid and cholesterol metabolism, in the regulation of sphingolipid metabolism and suggest that this pathway is relevant to inflammation and infection. A common mechanism on how CFTR affects such a wide spectrum of lipid classes is currently not known. One mechanism for low linoleic acid, amenable to inhibition by docosahexaenoic acid, is increased metabolism in the n-6 fatty acid pathway. Accumulation of free cholesterol in distinct perinuclear compartments, reversible by overexpression of rab9, suggests that cystic fibrosis and the lysosomal storage disease Niemann-Pick-C could share similar cell signaling defects, in addition to increased cAMP signaling and sterol-regulatory element binding protein (SREBP) expression that affect cholesterol metabolism. Novel is the recognition that CFTR modulates ceramide mass and uptake of sphingosine-1- phosphate. Experiments in different cystic fibrosis-mouse models, although not able to establish whether ceramide mass is increased or decreased, suggest that normalization of ceramide decreases infection and selected parameters of inflammation, of relevance to the complex phenotype that characterizes cystic fibrosis.

SUMMARY

Expression of defective CFTR has profound effects on fatty acid, cholesterol and sphingolipid metabolism, for which mechanisms are currently poorly understood. Recent studies in different cystic fibrosis models suggest a causal relationship between altered ceramide mass and increased inflammation and susceptibility to infection. Studies in cystic fibrosis knockout mouse models suggest that normalization of ceramide decreases infection and inflammation. Studies that evaluate the diagnostic and clinical relevance of sphingolipids in patients with cystic fibrosis are needed.

Dislipidemia relacionada à fibrose cística

Esse artigo tem por objetivo rever o conhecimento atual sobre a fisiopatologia, o diagnóstico e a abordagem da dislipidemia relacionada à fibrose cística (DFC). A pesquisa bibliográfica utilizou os bancos de dados Medline e Literatura Latino-Americana e do Caribe em Ciências da Saúde (1987-2007), selecionando os artigos mais relevantes sobre o tema. A DFC é caracterizada por hipertrigliceridemia e/ou hipocolesterolemia e deficiência de ácidos graxos essenciais. Seus principais fatores de risco são: insuficiência pancreática, dieta rica em carboidratos, hepatopatias, estado inflamatório e corticoterapia. Não existem recomendações específicas sobre a triagem, que habitualmente é realizada a partir do diagnóstico e, em intervalos regulares, com maior freqüência, nos indivíduos pertencentes aos grupos de risco. O tratamento inclui: dieta balanceada, reposição de micronutrientes, vitaminas e fibras, além de exercício físico regular de acordo com a tolerância individual. Na grande maioria dos casos, a hipertrigliceridemia da DFC não atinge valores que indiquem o uso de hipolipemiantes. Conclui-se que existem poucos trabalhos na literatura sobre a freqüência, etiologia e manejo da DFC. A recomendações preventivas e terapêuticas para a hipertrigliceridemia são extrapoladas de diretrizes para indivíduos sem fibrose cística. Mais pesquisas são necessárias para investigar a associação da deficiência de ácidos graxos essenciais com a fisiopatologia da fibrose cística. Como a hipertrigliceridemia é um importante fator de risco para doença arterial coronariana, estudos prospectivos irão contribuir para o melhor entendimento da história natural dessa complicação bem como definir maneiras de preveni-la e tratá-la.

A mechanism accounting for the low cellular level of linoleic acid in cystic fibrosis and its reversal by DHA

Specific fatty acid alterations have been described in the blood and tissues of cystic fibrosis (CF) patients. The principal alterations include decreased levels of linoleic acid (LA) and docosahexaenoic acid (DHA). We investigated the potential mechanisms of these alterations by studying the cellular uptake of LA and DHA, their distribution among lipid classes, and the metabolism of LA in a human bronchial epithelial cell model of CF. CF (antisense) cells demonstrated decreased levels of LA and DHA compared with wild type (WT, sense) cells expressing normal CFTR. Cellular uptake of LA and DHA was higher in CF cells compared with WT cells at 1 h and 4 h. Subsequent incorporation of LA and DHA into most lipid classes and individual phospholipids was also increased in CF cells. The metabolic conversion of LA to n-6 metabolites, including 18:3n-6 and arachidonic acid, was upregulated in CF cells, indicating increased flux through the n-6 pathway. Supplementing CF cells with DHA inhibited the production of LA metabolites and corrected the n-6 fatty acid defect. In conclusion, the evidence suggests that low LA level in cultured CF cells is due to its increased metabolism, and this increased LA metabolism is corrected by DHA supplementation.

Fatty acid alterations and n-3 fatty acid supplementation in cystic fibrosis

Specific fatty acid alterations have been described in the blood and tissues of cystic fibrosis (CF) patients. The two most consistent alterations include decreased levels of linoleic acid (LA) and decreased levels of docosahexaenoic acid (DHA). Increased arachidonic acid (AA) release from membrane phospholipids, as well as changes in levels of AA and other monounsaturated and polyunsaturated fatty acids (PUFAs) have also been described in CF. Although mechanisms of fatty acid alterations have not yet been determined, these alterations may have an important role in the progression of the CF disease. There have been several clinical trials in which CF patients were supplemented with n-3 fatty acids. Most trials resulted in an increase in the levels of the supplemental fatty acids in the blood of CF patients in the absence of significant clinical improvement. It is recommended that future trials include a larger population of CF patients and measure multiple clinical outcomes.

An overview of monitoring and supplementation of omega 3 fatty acids in cystic fibrosis

Essential fatty acid deficiency has been increasingly reported in patients with cystic fibrosis. The purpose of this work is to critically summarize previous data on fatty acid status and omega3 supplementation in cystic fibrosis. Although the reported abnormalities differ from study to study, the two most consistent features appeared to be reduced circulating levels of linoleic acid and docosahexaenoic acid (DHA). On the assumption that the fatty acid composition of erythrocyte cell membranes may be similar to that of other organs, it seems appropriate to monitor the phospholipid profile from erythrocyte membranes together with circulating blood levels. Formulations containing widely variable DHA doses, ranging from 300 mg to 5 g per day, have been administered to patients with cystic fibrosis with discrepant outcomes. Randomized controlled trials are needed in order to draw firm conclusions on the therapeutic effect of omega3 fatty acid supplementation in cystic fibrosis.

Fatty acids in blood and intestine following docosahexaenoic acid supplementation in adults with cystic fibrosis

The objective of this study was to investigate the effect of docosahexaenoic acid (DHA) supplementation on blood and intestinal DHA levels and lung function in mild/moderately affected adult CF patients with the DeltaF508 genotype.

BACKGROUND

Cystic Fibrosis (CF) patients often present with plasma fatty acid levels indicating low levels of linoleic (18:2n-6) and docosahexaenoic (22:6n-3) acids and an increased level of arachidonic acid (20:4n-6). Improved dietary fat intake or reducing fat malabsorption with pancreatic enzymes has failed to normalize this biochemical deficiency of DHA.

METHODS

Five CF patients, aged 18-43, received 70 mg of DHA/kg body weight/d for six weeks. At baseline and at six weeks a physical exam, lung function, 3-day dietary intake, duodenal mucosal biopsy and blood sample were assessed. The blood was analyzed for plasma vitamin A, D and E levels, liver function tests, clinical chemistry (CBC, differential and electrolytes). Plasma and red blood cell fatty acid levels were also analyzed. At three weeks, assessment included a physical exam, lung function test and fasting blood sample (vitamin levels, liver function and clinical chemistry only).

RESULTS

Pre- and post-measurements were compared for the four subjects who completed the study. An increase in DHA content (% w/w) was observed in all phospholipid fractions of plasma, red blood cell and mucosal samples. No significant differences in vitamin levels, liver function or lung function were observed.

CONCLUSIONS

The study proves the concept that an increase in tissue DHA levels in CF patients can be achieved by supplementing for six weeks with 70 mg/kg/d DHA.

Bioavailability and safety of a high dose of docosahexaenoic acid triacylglycerol of algal origin in cystic fibrosis patients: a randomized, controlled study

OBJECTIVE

Several studies have reported omega-3 and omega-6 fatty acid imbalances in patients with cystic fibrosis (CF). Whether these imbalances contribute to or are manifestations of the pathophysiology of CF is unknown. The study objective was to determine bioavailability, tissue accretion, and safety of a large dose of an algal source of docosahexaenoic acid (DHA) triacylglycerol and to observe effects on lung function in patients with CF.

METHODS

Twenty subjects with CF (8 to 20 y of age) were randomly assigned to receive algal oil providing 50 mg of DHA per kilogram per day (1 to 4.2 g of DHA per subject per day) or placebo for 6 mo. Fatty acids, liver enzymes, and lipid soluble antioxidants were measured in blood at baseline and at 1, 3, and 6 mo. Rectal biopsy specimens were collected at baseline and at 3 mo for fatty acid analysis. Lung function, anthropometrics, and adverse experiences were monitored throughout the study.

RESULTS

Compared with placebo, DHA supplementation increased plasma, erythrocyte, and rectal DHA levels four- to five-fold (P < 0.001) with concomitant decreases in blood arachidonic acid levels and the ratio of arachidonic acid to DHA. Supplementation was well tolerated, with no treatment-related changes in liver enzymes, growth, or antioxidant status. DHA supplementation had no detectable effect on lung function during the course of this study.

CONCLUSIONS

Algal DHA triacylglycerol oil is readily absorbed, well tolerated, and increases blood and tissue DHA levels in patients with CF. No adverse developments were associated with this large dose of DHA oil. Larger studies of longer duration are needed to determine whether DHA supplementation results in any clinically significant benefits in patients with CF.

Association of cystic fibrosis with abnormalities in fatty acid metabolism

BACKGROUND

Patients with cystic fibrosis have altered levels of plasma fatty acids. We previously demonstrated that arachidonic acid levels are increased and docosahexaenoic acid levels are decreased in affected tissues from cystic fibrosis-knockout mice. In this study we determined whether humans with mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have a similar fatty acid defect in tissues expressing CFTR.

METHODS

Fatty acids from nasal- and rectal-biopsy specimens, nasal epithelial scrapings, and plasma were analyzed from 38 subjects with cystic fibrosis and compared with results in 13 obligate heterozygotes, 24 healthy controls, 11 subjects with inflammatory bowel disease, 9 subjects with upper respiratory tract infection, and 16 subjects with asthma.

RESULTS

The ratio of arachidonic to docosahexaenoic acid was increased in mucosal and submucosal nasal-biopsy specimens (P<0.001) and rectal-biopsy specimens (P=0.009) from subjects with cystic fibrosis and pancreatic sufficiency and subjects with cystic fibrosis and pancreatic insufficiency, as compared with values in healthy control subjects. In nasal tissue, this change reflected an increase in arachidonic acid levels and a decrease in docosahexaenoic acid levels. In cells from nasal mucosa, the ratio of arachidonic to docosahexaenoic acid was increased in subjects with cystic fibrosis (P<0.001), as compared with healthy controls, with values in obligate heterozygotes intermediate between these two groups (P<0.001). The ratio was not increased in subjects with inflammatory bowel disease. Subjects with asthma and those with upper respiratory tract infection had values intermediate between those in subjects with cystic fibrosis and those in healthy control subjects.

CONCLUSIONS

These data indicate that alterations in fatty acids similar to those in cystic fibrosis-knockout mice are present in CFTR-expressing tissue from subjects with cystic fibrosis.

Molecular species compositions of lung and pancreas phospholipids in the cftr(tm1HGU/tm1HGU) cystic fibrosis mouse

Fatty acid analysis of phospholipid compositions of lung and pancreas cells from a cystic fibrosis transmembrane regulator (CFTR) negative mouse (cftr(-/-))suggested that a decreased concentration of docosahexaenoate (22:6(n-3)) and increased arachidonate (20:4(n-6)) may be related to the disease process in cystic fibrosis (CF). Consequently, we have determined compositions of the major phospholipids of lung, pancreas, liver, and plasma from a different mouse model of CF, the cftr(tm1HGU/tm1HGU) mouse, compared with ZTM:MF-1 control mice. Electrospray ionization mass spectrometry permitted the quantification of all of the individual molecular species of phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn), phosphatidylglycerol (PtdGly), phosphatidylserine (PtdSer), and phosphatidylinositol (PtdIns). There was no deficiency of 22:6(n-3) in any phospholipid class from lung, pancreas, or liver from mice with the cftr(tm1HGU/tm1HGU). Instead, the concentration of 20:4(n-6) was significantly decreased in plasma PtdCho species and in pancreas and lung species of PtdEtn, PtdSer, and PtdIns. These results demonstrate the variability of membrane phospholipid compositions in different mouse models of CF and suggest that in cftr(tm1HGU/tm1HGU) mice, the apparent deficiency was of 20:4n-6- rather than of 22:6n-3-containing phospholipid species. They highlight a need for detailed phospholipid molecular species analysis of cells expressing mutant CFTR from children with CF before the therapeutic effects of administering high doses of 22:6(n-3)-containing oils to children with CF can be fully evaluated.

Abnormal lipid concentrations in cystic fibrosis

BACKGROUND

Concentrations of cholesterol and triacylglycerol are commonly believed to be low in persons with cystic fibrosis and thus not of concern.

OBJECTIVE

The goal was to determine whether concentrations of cholesterol and triacylglycerol are related to glucose tolerance or nutritional status in patients with cystic fibrosis.

DESIGN

Fasting lipid profiles were measured in 192 patients ( +/- SD age: 21 +/- 11 y) in conjunction with an oral-glucose-tolerance test.

RESULTS

Cystic fibrosis patients in all age groups had higher triacylglycerol (1.51 +/- 0.95 mmol/L) and lower cholesterol (3.57 +/- 0.96 mmol/L) concentrations than US population means. Thirty patients (16%) had hypertriglyceridemia (3.22 +/- 1.22 mmol/L), and 8 patients (4%) had elevated cholesterol (6.05 +/- 1.32 mmol/L). In most cases, hypertriglyceridemia was isolated; only 3 subjects had elevation of both cholesterol and triacylglycerol. Lipid concentrations were not related to body mass index, weight, glucose tolerance, the areas under the curve for glucose or insulin, or glycated hemoglobin. Lipid concentrations also did not correlate with cystic fibrosis genotype, use of systemic steroids, blood pressure, liver enzymes, C-reactive protein, or pulmonary function.

CONCLUSIONS

Isolated hypertriglyceridemia appears to be common in cystic fibrosis, whereas cholesterol concentrations are generally low. Hypertriglyceridemia may be related to chronic low-grade inflammation or to a dietary macronutrient imbalance with excessive simple carbohydrate absorption relative to fat absorption. Whether it is associated with a risk of cardiovascular disease in this population is uncertain, but the clinical significance of triacylglycerol elevation may become important as survival improves.

Role of polyunsaturated fatty acids in lung disease

DF Horrobin hypothesized that the low prevalence of lung disease among Eskimos is the result of their diet, which is high in n-3 fatty acids. The n-3 and n-6 fatty acids shunt eicosanoid production away from the arachidonic acid pathway, and hence decrease the production of bronchoconstrictive leukotrienes. Animal studies showed that eicosapentaenoic acid or gamma-linolenic acid supplementation of animals exposed to endotoxins results in decreased effects on thromboxane B(2) and pulmonary vascular resistance. Small human trials confirmed that supplementation with eicosapentaenoic acid results in increased eicosapentaenoic acid in phospholipids and decreased generation of leukotrienes by neutrophils. Hence, a protective effect of such fatty acids in lung disease is biologically plausible. The results of human intervention studies looking at respiratory outcomes have been mixed, but they do suggest a possible difference between long-term and short-term effects. Epidemiologic studies showed possible protective effects against asthma in children, but weak to no evidence of such effects in adults. Results for bronchitis are more positive, although intervention trials are lacking. Recently, a cross-sectional analysis of data from the first National Health and Nutrition Examination Survey reported an approximately 80-mL difference in forced expiratory volume at 1 s between adults with high compared with low fish consumption. This response was not limited to asthmatic subjects. Others found that both fish consumption and n-3 fatty acid consumption (as estimated from food-frequency questionnaires) were protective against physician-diagnosed emphysema and chronic bronchitis and low spirometry values. Only smokers were included in this analysis. These results suggest that dietary fatty acids may play a role in lung disease; further work is needed to elucidate that role.

Several mechanisms contribute to the abnormal fatty acid composition of serum phospholipids and cholesterol esters in cholestatic children with extrahepatic biliary atresia

The fatty acid compositions of serum phospholipids and cholesterol esters and direct bilirubinemia were determined in 11 children with cholestasis due to extrahepatic biliary atresia. The levels of the different fatty acids in these lipid classes were compared with those of 22 appropriate controls and correlations with conjugated bilirubinemia were calculated. Significant differences were found in the levels of several fatty acids in these lipid classes, some of which were related to conjugated bilirubinemia. Relationships between fatty acids in phospholipids and cholesterol esters which exist in the control group were either absent or different in the patient group. The results found are compatible with the concept that malabsorption, overflow in blood of phospholipids, which are excreted in bile in healthy individuals, and liver disease per se contribute to the deviating fatty acid compositions. They suggest that administration in the diet may be required of preformed long chain polyunsaturated fatty acids in an easily absorbable form.

Prostanoid biosynthesis in patients with cystic fibrosis

The urinary excretion rate (ng/h/1.73 m2) of prostanoids was determined with a capillary gas-liquid chromatographic mass spectrometric method in 19 patients with cystic fibrosis (CF) aged 1-29 years. Patients with CF showed an increased excretion of prostaglandin E2 metabolites (PGE-M) and thromboxane B2 and its metabolites at all ages. An imbalance in the excretion pattern of thromboxane B2 metabolites also suggested a relative impairment of beta-oxidation. There was no increased excretion of dinor-6-keto-PGF1 alpha, indicating normal prostacyclin biosynthesis. No correlation was found to genotype, clinical score, lung function or bacterial colonization but a significant negative relation was found between the main prostanoids in the urine and serum phospholipid levels of essential fatty acids. The results show that, contrary to the generally accepted decrease of prostanoid excretion in essential fatty acid deficiency, patients with CF increase their production parallel to the development of the deficiency. Since prostanoid synthesis is rate limited by arachidonic acid release, our data support a previously presented hypothesis about a pathological regulation of the release of arachidonic acid in CF.