Relation between essential fatty acid metabolism and gastrointestinal symptoms in cystic fibrosis

Fatty acid abnormalities in cystic fibrosis-the missing link for a cure?

The care for cystic fibrosis (CF) has dramatically changed with the development of modulators, correctors, and potentiators of the CFTR molecule, which lead to improved clinical status of most people with CF (pwCF). The modulators influence phospholipids and ceramides, but not linoleic acid (LA) deficiency, associated with more severe phenotypes of CF. The LA deficiency is associated with upregulation of its transfer to arachidonic acid (AA). The AA release from membranes is increased and associated with increase of pro-inflammatory prostanoids and the characteristic inflammation is present before birth and bacterial infections. Docosahexaenoic acid is often decreased, especially in associated liver disease Some endogenously synthesized fatty acids are increased. Cholesterol and ceramide metabolisms are disturbed. The lipid abnormalities are present at birth, and before feeding in transgenic pigs and ferrets. This review focus on the lipid abnormalities and their associations to clinical symptoms in CF, based on clinical studies and experimental research.

Changes of Erythrocyte Fatty Acids after Supplementation with Highly Concentrated Docosahexaenoic Acid (DHA) in Pediatric Cystic Fibrosis: A Randomized Double-Blind Controlled Trial

We characterized the fatty acid profiles in the erythrocyte membrane of pediatric patients with cystic fibrosis (CF) receiving highly concentrated docosahexaenoic acid (DHA) supplementation (Tridocosahexanoin-AOX^® 70%) at 50 mg/kg/day (n = 11) or matching placebo (n = 11) for 12 months. The mean age was 11.7 years. The DHA group showed a statistically significant improvement in n-3 polyunsaturated fatty acids (PUFAs), which was observed as early as 6 months and further increased at 12 months. Among the n-3 PUFAs, there was a significant increase in DHA and eicosapentaenoic acid (EPA). Additionally, a statistically significant decrease in n-6 PUFAs was found, primarily due to a decrease in arachidonic acid (AA) levels and elongase 5 activity. However, we did not observe any changes in linoleic acid levels. The long-term administration of DHA over one year was safe and well tolerated. In summary, the administration of a high-rich DHA supplement at a dose of 50 mg/kg/day for one year can correct erythrocyte AA/DHA imbalance and reduce fatty acid inflammatory markers. However, it is important to note that essential fatty acid alterations cannot be fully normalized with this treatment. These data provide timely information of essential fatty acid profile for future comparative research.

Nutrition in Cystic Fibrosis—Some Notes on the Fat Recommendations

Nutrition is important in cystic fibrosis (CF) because the disease is associated with a higher energy consumption, special nutritional deficiencies, and malabsorption mainly related to pancreatic insufficiency. The clinical course with deterioration of lung function has been shown to relate to nutrition. Despite general recommendation of high energy intake, the clinical deterioration is difficult to restrain suggesting that special needs have not been identified and specified. It is well-known that the CF phenotype is associated with lipid abnormalities, especially in the essential or conditionally essential fatty acids. This review will concentrate on the qualitative aspects of fat metabolism, which has mainly been neglected in dietary fat recommendations focusing on fat quantity. For more than 60 years it has been known and confirmed that the patients have a deficiency of linoleic acid, an n-6 essential fatty acid of importance for membrane structure and function. The ratio between arachidonic acid and docosahexaenoic acid, conditionally essential fatty acids of the n-6 and n-3 series, respectively, is often increased. The recently discovered relations between the CFTR modulators and lipid metabolism raise new interests in this field and together with new technology provide possibilities to specify further specify personalized therapy.

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.

Cutaneous Manifestations of Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive affliction triggered by genetic mutations in the cystic fibrosis transmembrane conductance regulator. The lung and pancreas are the most frequently affected organs in cystic fibrosis, cutaneous involvement is undervalued and underdiag-nosed. Skin lesions observed in patients diagnosed with cystic fibrosis are not well known and can create confusions with other dermatological diseases. The diagnosis of cutaneous lesions as signs of cystic fibrosis by pediatricians or dermatologists, despite their overlapping with different nutritional deficiencies, would allow earlier diagnosis and proper treatment and could improve quality of life and outcomes.

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.

Fatty acid metabolism in cystic fibrosis

Despite identification twenty years ago of the gene responsible for cystic fibrosis transmembrane conductance regulator (CFTR), the protein defective in cystic fibrosis (CF), research of this monogenetic disease has not provided an explanation for the divergent symptoms, and a treatment breakthrough is still awaited. This review discusses different aspects of disturbances in lipid metabolism seen in CF. These include increased release of arachidonic acid (AA) from cell membrane phospholipids and a low status of linoleic and docosahexaenoic acids. Recent research has explored more complicated lipid associations. Disturbances in annexins and ceramides might act in concert to explain the impact on inflammation and AA release. The connections to CFTR and between the disturbances in essential fatty acid metabolism are reviewed. The metabolic interactions, some of which might be compensating, possibly explain the difficulties in understanding the fatty acid disturbances in relation to different symptoms and their relation to the defective CFTR.

Effects of essential fatty acid deficiency on enterohepatic circulation of bile salts in mice

Essential fatty acid (EFA) deficiency in mice has been associated with increased bile production, which is mainly determined by the enterohepatic circulation (EHC) of bile salts. To establish the mechanism underlying the increased bile production, we characterized in detail the EHC of bile salts in EFA-deficient mice using stable isotope technique, without interrupting the normal EHC. Farnesoid X receptor (FXR) has been proposed as an important regulator of bile salt synthesis and homeostasis. In Fxr(-/-) mice we additionally investigated to what extent alterations in bile production during EFA deficiency were FXR dependent. Furthermore, we tested in differentiating Caco-2 cells the effects of EFA deficiency on expression of FXR-target genes relevant for feedback regulation of bile salt synthesis. EFA deficiency-enhanced bile flow and biliary bile salt secretion were associated with elevated bile salt pool size and synthesis rate (+146 and +42%, respectively, P < 0.05), despite increased ileal bile salt reabsorption (+228%, P < 0.05). Cyp7a1 mRNA expression was unaffected in EFA-deficient mice. However, ileal mRNA expression of Fgf15 (inhibitor of bile salt synthesis) was significantly reduced, in agreement with absent inhibition of the hepatic bile salt synthesis. Bile flow and biliary secretion were enhanced to the same extent in EFA-deficient wild-type and Fxr(-/-) mice, indicating contribution of other factors besides FXR in regulation of EHC during EFA deficiency. In vitro experiments show reduced induction of mRNA expression of relevant genes upon chenodeoxycholic acid and a selective FXR agonist GW4064 stimulation in EFA-deficient Caco-2 cells. In conclusion, our data indicate that EFA deficiency is associated with interrupted negative feedback of bile salt synthesis, possibly because of reduced ileal Fgf15 expression.

Serum linoleic acid status as a clinical indicator of essential fatty acid status in children with cystic fibrosis

BACKGROUND

Children with cystic fibrosis (CF) and pancreatic insufficiency (PI) are at increased risk for essential fatty acid (EFA) deficiency.

OBJECTIVES

To investigate serum markers of EFA status in children with CF and PI and their association with growth, body composition, and lung function.

PATIENTS AND METHODS

Serum phospholipid fatty acid, growth, and forced expiratory volume at 1 second (FEV1, percentage predicted) status were assessed at baseline and 12 months in 77 children with CF and PI, 7 to 10 years old. Longitudinal mixed-effects models were used to compare associations of the triene:tetraene ratio (ratio of eicosatrienoic acid to arachidonic acid) and serum linoleic acid (as a molar percentage of total serum phospholipid fatty acids, or mol%) with the clinical outcomes. Controls for serum fatty acid were 23 healthy white age- and sex-matched children.

RESULTS

Children with CF and PI had higher median triene:tetraene ratio and lower linoleic acid than healthy controls. Depending on the triene:tetraene ratio cutoff point used (0.04 or 0.02), either 17% or 52% of the children with CF had EFA deficiency, respectively. Only linoleic acid was significantly and positively associated with z scores for weight, height, body mass index, upper arm muscle area, and FEV1 at baseline. Children with linoleic acid at 21 mol% or higher had significantly better growth and pulmonary status than those with lower concentrations.

CONCLUSIONS

Serum phospholipid linoleic acid at 21 mol% or higher was associated with better growth, body composition, and FEV1. No clinical outcome associations were found with the triene:tetraene ratio. These findings suggest that linoleic acid concentration was a more clinically relevant biomarker of EFA status than the triene:tetraene ratio in children with CF and PI. Further research is warranted to validate this specific percentage of linoleic acid cutoff point as a new recommendation for clinical use.

Cutaneous manifestations of cystic fibrosis

Cystic fibrosis is an autosomal recessive disease reported in 1 in 2500 live births in Northern American and Northern European Caucasian populations. Classic disease findings include chronic bacterial infection of airways and sinuses, malabsorption of fat, infertility in men, and elevated concentrations of chloride in sweat. Less well-recognized findings associated with cystic fibrosis include cutaneous findings, which can be primary or secondary manifestations of the disease process. Patients demonstrate more atopic and drug hypersensitivity reactions than the general population, but have similar rates of urticaria compared with the general population. In atypical presentations of cystic fibrosis, the nutrient deficiency dermatitis of the disease may aid with diagnosis, and notably can be the presenting sign. Other dermatologic manifestations of cystic fibrosis include early aquagenic skin wrinkling and cutaneous vasculitis, which can be associated with arthralgias. Familiarity with the nutrient deficiency dermatitis of this entity may play a role in the timely diagnosis of the disease, and the other cutaneous findings add to our understanding of the protean nature of its manifestations.

Nutrition in patients with cystic fibrosis: a European Consensus

This document is the result of an European Consensus conference which took place in Artimino, Tuscany, Italy, in March 2001 involving 33 experts on nutrition in patients with cystic fibrosis, organised by the European Cystic Fibrosis Society, and sponsored by Axcan-Scandipharm, Baxter, Dr Falk Pharma, Fresenius, Nutricia, SHS International, Solvay Pharmaceuticals (major sponsor). The purpose of the conference was to develop a consensus document on nutrition in patients with cystic fibrosis based on current evidence.

Effects of pregnancy on health: certain aspects of importance for women with cystic fibrosis

More women with cystic fibrosis (CF) now reach reproductive age and wish to become pregnant. Although women with CF have reduced fertility, many of them can become mothers. A pregnancy ought to be carefully planned since several studies have shown that pregnancy is well tolerated if good medical care is provided, and the CF woman is in a stable good condition. A short review of the implications of pregnancy for women with CF is presented. A suggested schedule for pregnant women with CF is given.

No indications for altered essential fatty acid metabolism in two murine models for cystic fibrosis

A deficiency of essential fatty acids (EFA) is frequently described in cystic fibrosis (CF), but whether this is a primary consequence of altered EFA metabolism or a secondary phenomenon is unclear. It was suggested that defective long-chain polyunsaturated fatty acid (LCPUFA) synthesis contributes to the CF phenotype. To establish whether cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction affects LCPUFA synthesis, we quantified EFA metabolism in cftr-/-CAM and cftr+/+CAM mice. Effects of intestinal phenotype, diet, age, and genetic background on EFA status were evaluated in cftr-/-CAM mice, DeltaF508/DeltaF508 mice, and littermate controls. EFA metabolism was measured by 13C stable isotope methodology in vivo. EFA status was determined by gas chromatography in tissues of cftr-/-CAM mice, DeltaF508/DeltaF508 mice, littermate controls, and C57Bl/6 wild types fed chow or liquid diet. After enteral administration of [13C]EFA, arachidonic acid (AA) and docosahexaenoic acid (DHA) were equally 13C-enriched in cftr-/-CAM and cftr+/+CAM mice, indicating similar EFA elongation/desaturation rates. LA, ALA, AA, and DHA concentrations were equal in pancreas, lung, and jejunum of chow-fed cftr-/-CAM and DeltaF508/DeltaF508 mice and controls. LCPUFA levels were also equal in liquid diet-weaned cftr-/-CAM mice and littermate controls, but consistently higher than in age- and diet-matched C57Bl/6 wild types. We conclude that cftr-/-CAM mice adequately absorb and metabolize EFA, indicating that CFTR dysfunction does not impair LCPUFA synthesis. A membrane EFA imbalance is not inextricably linked to the CF genotype. EFA status in murine CF models is strongly determined by genetic background.

Manifestations digestives au cours de la mucoviscidose

The prognosis of cystic fibrosis (CF) is strongly linked to the pulmonary status, nevertheless digestive disorders should be taken into account in order to prevent malnutrition which may increase pulmonary surinfections and speed up the deterioration of the respiratory function. Digestion, gut motility and absorption are the three major functions of the gastrointestinal tract. Functional disorders may involve the whole gut; in addition to pancreatic insufficiency we describe the failure of chloride secretion with dehydration of bowel content. Insufficient knowledge of the pathophysiology stresses the need for further studies to allow development of more rational and effective therapy.

Essential fatty acid deficiency in relation to genotype in patients with cystic fibrosis

OBJECTIVE

To determine if the serum phospholipid fatty acid pattern in patients with cystic fibrosis (CF) was related to the major cystic fibrosis transmembrane conductance regulator gene mutations.

METHODS

Patients with CF (n = 110) aged 3 months to 56 years were studied. Serum samples were analyzed for phospholipid fatty acid with gas-liquid chromatography, and cystic fibrosis transmembrane conductance regulator mutations were determined with standard methods.

RESULTS

Patients with CF had significantly lower molar percentages of linoleic acid and docosahexaenoic acid in the serum phospholipid than healthy controls (mean +/- standard deviation, 20.3 +/- 4.5 and 2.6 +/- 0.9 vs 22.4 +/- 2.2 and 3.1 +/- 0.7, respectively; P <.001). Palmitoleic and oleic acids were significantly increased (P <.001) but arachidonic acid was not different from controls. Homozygotes for DeltaF508 and heterozygotes/homozygotes for 394delTT showed significantly lower concentrations of linoleic acid and docosahexaenoic acid than the other groups. Low values were not correlated to anthropometric data or lung function. Patients with pancreatic insufficiency showed similar differences to those with sufficient pancreatic function, reflecting the different genotypes.

CONCLUSION

Serum concentrations of linoleic acid and docosahexaenoic acid were significantly lower in patients with severe cystic fibrosis transmembrane conductance regulator mutations, suggesting an association between the basic defect and abnormal essential fatty acid metabolism in CF patients.

[Nutritional management of cystic fibrosis in children]

A major goal in the management of cystic fibrosis patients is to maintain a good nutritional status as it improves long-term survival. A link is clearly established between the degree of malnutrition and the severity of the disease. Clinical and biological follow-up, better knowledge of energy requirements, dietary counseling and nutritional intervention help to optimize the growth of these patients through childhood and adolescence.

Intestinal permeability in cystic fibrosis in relation to genotype

BACKGROUND

The purpose of this study was to investigate whether the increase intestinal permeability (IP) seen in patients with cystic fibrosis (CF) is correlated with the basic defect, as revealed by the patient's genotype, and/or whether the intestinal disturbance reflects secondary abnormalities such as essential fatty acid deficiency.

METHODS

Nineteen CF patients were compared with nine age- and sex-matched healthy controls. IP was evaluated by studying urinary excretion for 5 hours after a test meal containing lactulose, L-rhamnose and xylose in water. Urine was analyzed for carbohydrates, and blood samples were taken for determination of the fatty acid pattern of serum phospholipids. The CF patients were grouped according to genotype: homozygous for delta F508, heterozygous for alpha F508, or unidentified.

RESULTS

Patients who were homozygous (n = 9) or heterzygous (n = 6) for delta F508 had significantly higher lactulose/L-rhamnose excretion ratios (mean(range) values of 0.08(0.05-0.13) and 0.09(0.03-0.13), respectively) than patients (n = 4) with unidentified genotypes [0.03(0.02-0.05); p = 0.005] or healthy controls [0.02(0.003-0.06); p = 0.002]. CF patients with EFAD (n = 6) did not differ from those with a normal pattern of serum phospholipid fatty acids, the lactulose/L-rhamnose excretion ratio being 0.08(0.02-0.13) and 0.07(0.03-0.12), respectively.

CONCLUSIONS

These data show that the IP in CF was related to patient genotype; those homozygozous or heterozygous for delta F508 having a significantly increased IP compared with patients with unidentified genotypes, who had IP values within the normal range.

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.

Defective inhibition by dexamethasone of leukotriene B4 and C4 production by leukocytes in patients with cystic fibrosis

To investigate the effects of glucocorticoids on leukotriene (LT) generation in patients with cystic fibrosis (CF), we evaluated calcium ionophore A23187-induced LTB4 and LTC4 production by leukocytes with and without pretreatment with dexamethasone. The CF patients were in good condition and did not have acute infection. There were no significant differences in LTB4 and LTC4 production without dexamethasone pretreatment between the CF patients and controls. However, the ratios of LTB4 and LTC4 production by leukocytes preincubated with dexamethasone to those of leukocytes without dexamethasone pretreatment were significantly higher in the CF patients than in the controls (both p < 0.05). Our data suggest that the response of LTB4 and LTC4 production to dexamethasone is disturbed in patients with CF. The generation of LTs may be enhanced due to a disturbance in glucocorticoid suppression.

The chloride channel blocker anthracene 9-carboxylate inhibits fatty acid incorporation into phospholipid in cultured human airway epithelial cells

This study investigated whether making epithelial cell membranes impermeable to Cl- movement affects incorporation of fatty acids into membrane constituents. Epithelial cells were isolated from human nasal polyps, cultured for 5-7 days, and used to test the effect of anthracene 9-carboxylate (9-AC), known to inhibit Cl- conductance across the epithelial membrane, on the incorporation and desaturation of [1-14C]linoleic acid (C18:2,n-6) in experiments of up to 4 h duration. 9-AC (5 mM) reduced C18:2,n-6 incorporation into phospholipid by 60-70%, and increased incorporation of C18:2,n-6 into triacylglycerol by 50-100%. The decrease in C18:2,n-6 incorporation into phospholipid was rapid and dependent on the concentration of 9-AC. Substitution of extracellular Cl- with gluconate significantly decreased C18:2,n-6 incorporation into phospholipid, suggesting that the effect of 9-AC may occur by inhibiting Cl- conductance. Lipid analysis of cells exposed to 50 microM-C18:2 revealed that, as a consequence of the effect of 9-AC, the level of C18:2,n-6 in cell membrane phospholipid was significantly lowered. The relative rate of C18:2,n-6 desaturation was not apparently changed by 9-AC. These data suggest that Cl- conductance may play a role in fatty acid incorporation into epithelial cell membrane phospholipids.