Increased elongase 6 and Δ9-desaturase activity are associated with n-7 and n-9 fatty acid changes 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.

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.

Saturated Fatty Acid Intake Is Associated With Increased Inflammation, Conversion of Kynurenine to Tryptophan, and Delta-9 Desaturase Activity in Healthy Humans

Saturated fat ingestion has previously been linked to increases in inflammation. However the relationship between saturated fatty acid (SFA) intake and the kynureine:tryptophan ratio ([Kyn]:[Trp]), a marker of inflammation, has not been previously investigated. This study evaluated in healthy, middle aged, individuals (men = 48, women = 52), potential relationships between SFA intake, red blood cell (RBC) membrane SFAs and monounsaturated fatty acids (MUFA), the [Kyn]:[Trp] ratio, C-reactive protein (CRP), TNF-α and Δ9 desaturase activity. [Kyn]:[Trp] was positively associated with increases in Total fat (P = .034) intake, including Total SFA (P = .029) and Total MUFA (P = .042) intakes. Unexpectedly the [Kyn]:[Trp] ratio was inversely associated with the percentage of Total SFA (P = .004) and positively associated with percentage of Total MUFA (P = .012) present in the RBC membrane. We found a positive association between Δ9 desaturase activity, responsible for the desaturation of a various SFAs to MUFAs, and [Kyn]:[Trp] (P = .008). [Kyn]:[Trp] was also positively associated with CRP (P = .044), however no significant relationship between [Kyn]:[Trp] and TNF-α was found. This study shows for the first time that SFA consumption increases inflammatory pathways linked to increased tryptophan to kynurenine conversion, even in healthy humans. Our data also suggests that SFA linked increases in inflammation occur concomitantly with an upregulation of Δ9 desaturase activity resulting in increased desaturation of SFA substrates to their MUFA derivatives.

Impaired Ratio of Unsaturated to Saturated Non-Esterified Fatty Acids in Saliva from Patients with Cystic Fibrosis

Impaired salivary non-esterified fatty acids (NEFA) levels have been previously observed in cystic fibrosis (CF). This study aimed to characterize the salivary NEFA profile in CF and to examine whether the alterations are related to the pancreatic status and/or lung disease severity. We analyzed salivary NEFA, cholesterol and interleukin-6 (IL-6) in CF patients (n = 66) and healthy subjects (n = 48). CF patients showed higher salivary levels of cholesterol, total NEFA (that was negatively correlated with serum triglycerides), unsaturated NEFA/saturated NEFA (U/S NEFA) ratio and IL-6 than controls. The U/S NEFA ratio was positively correlated with IL-6 in both patients and controls, suggesting an association between this parameter and local inflammation independently from the disease. No correlation between salivary lipids and pancreatic status was observed, while the U/S NEFA ratio was higher in patients with severe lung disease than mild/moderate severity and may represent a prognostic marker of lung disease in CF.

The Efficacy of MAG-DHA for Correcting AA/DHA Imbalance of Cystic Fibrosis Patients

Omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementations are thought to improve essential fatty acid deficiency (EFAD) as well as reduce inflammation in Cystic Fibrosis (CF), but their effectiveness in clinical studies remains unknown. The aim of the study was to determine how the medical food containing docosahexaenoic acid monoglyceride (MAG-DHA) influenced erythrocyte fatty acid profiles and the expression levels of inflammatory circulating mediators. We conducted a randomized, double blind, pilot trial including fifteen outpatients with Cystic Fibrosis, ages 18–48. The patients were divided into 2 groups and received MAG-DHA or a placebo (sunflower oil) for 60 days. Patients took 8 × 625 mg MAG-DHA softgels or 8 × 625 mg placebo softgels every day at bedtime for 60 days. Lipid analyses revealed that MAG-DHA increased docosahexaenoic acid (DHA) levels and decrease arachidonic acid (AA) ratio (AA/DHA) in erythrocytes of CF patients following 1 month of daily supplementation. Data also revealed a reduction in plasma human leukocyte elastase (pHLE) complexes and interleukin-6 (IL-6) expression levels in blood samples of MAG-DHA supplemented CF patients. This pilot study indicates that MAG-DHA supplementation corrects erythrocyte AA/DHA imbalance and may exert anti-inflammatory properties through the reduction of pHLE complexes and IL6 in blood samples of CF patients. Trial registration: Pro-resolving Effect of MAG-DHA in Cystic Fibrosis (PREMDIC), NCT02518672.

Tissue expression profiles and transcriptional regulation of elongase of very long chain fatty acid 6 in bovine mammary epithelial cells

In mammals, very long chain fatty acids (VLCFAs) perform pleiotropic roles in a wide range of biological processes, such as cell membrane formation, cell signal transduction, and endocrine regulation. Beef and milk are abundant of palmitic acid which can be further elongated into stearic acid for synthesizing VLCFAs. Elongase of very long chain fatty acid 6 (ELOVL6) is a rate-limiting enzyme for converting palmitic acid to stearic acid. Consequently, investigating the tissue expression patterns and transcriptional regulation of bovine ELOVL6 can provide new insights into improving the composition of beneficial fats in cattle and expanding the knowledge of transcriptional regulation mechanism among domestic animals. In the current study, we found that bovine ELOVL6 expressed ubiquitously. Dual-luciferase reporter assay identified that the core promoter region (-130/-41 bp) was located in the second CpG island. In addition, the deletion mutation of binding sites demonstrated that sterol regulatory element binding transcription factor 1 (SREBF1) and specific protein 1 (SP1) both were able to stimulate bovine ELOVL6 promoter activity independently, while resulting the similar effect. To confirm these findings, further RNA interference assays were executed in bovine mammary epithelial cells (BMECs). In summary, these data suggest that bovine ELOVL6 expressed ubiquitously and is activated by SREBF1 and SP1, via two binding sites present in the ELOVL6 promoter region between -130 bp to -41bp.

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.

The effects of ivacaftor on CF fatty acid metabolism: An analysis from the GOAL study

BACKGROUND

Ivacaftor has produced significant improvement in certain individuals with cystic fibrosis (CF), though the full metabolic effects of treatment remain unknown. Abnormalities in fatty acid metabolism have previously been shown to be a characteristic of CFTR dysfunction. We hypothesized that as a reflection of this clinical improvement, ivacaftor would improve plasma fatty acid levels and decrease urine prostaglandin E metabolite levels.

METHODS

This study analyzed plasma fatty acid levels and urine prostaglandin E metabolites (PGE-M) in 40 subjects with CF participating in the G551D observational (GOAL) study who demonstrated response to the medication by a significant decrease in sweat Cl levels. Paired samples were analyzed before and after 6months of ivacaftor treatment.

RESULTS

Linoleic acid and docosahexaenoic acid levels, which are typically low in individuals with CF, did not significantly increase with ivacaftor treatment. However, arachidonic acid levels did decrease with ivacaftor treatment and there was a significant decrease in the arachidonic acid metabolite PGE-M as measured in the urine [median: before treatment 17.03ng/mg Cr; after treatment 9.06ng/mg Cr; p<0.001]. Furthermore, there were fatty acid age differences observed, including pediatric participants having significantly greater linoleic acid levels at baseline.

CONCLUSION

Ivacaftor reduces inflammatory PGE without fully correcting the plasma fatty acid abnormalities of CF. Age-related differences in fatty acid levels were observed, that may be a result of other clinical factors, such as diet, clinical care, or drug response.

Chronic pancreatitis and the composition of plasma phosphatidylcholine fatty acids

Chronic pancreatitis (CP) is an irreversible inflammatory disorder characterized by the destruction of both exocrine and endocrine tissue. There is growing evidence that dysregulation of fatty acid (FA) metabolism is connected with many diseases; however, there are few data concerning FA composition in CP. Therefore, we analyzed FA profiles in plasma phosphatidylcholines in 96 patients with CP and in 108 control subjects (CON). The patients with CP had, in comparison with CON, increased sum of monounsaturated FA (ΣMUFA) and decreased content of polyunsaturated FA (PUFA) in both n-6 and n-3 families. Moreover, CP patients had increased indexes for delta-9, delta-6 desaturases, and fall in activity of delta-5 desaturase. Increased ratio of 16:1n-7/18:2n-6 (marker of essential n-6 FA deficiency), was more prevalent among CP patients. These changes implicated decreased fat intake, including n-3 as well as n-6 PUFA, and intrinsic changes in FA metabolism due to the alteration of delta desaturase activities.

Inflammation, oxidative stress, and cardiovascular disease risk factors in adults with cystic fibrosis

Cystic fibrosis (CF) represents one of a number of localized lung and non-lung diseases with an intense chronic inflammatory component associated with evidence of systemic oxidative stress. Many of these chronic inflammatory diseases are accompanied by an array of atherosclerotic processes and cardiovascular disease (CVD), another condition strongly related to inflammation and oxidative stress. As a consequence of a dramatic increase in long-lived patients with CF in recent decades, the specter of CVD must be considered in these patients who are now reaching middle age and beyond. Buttressed by recent data documenting that CF patients exhibit evidence of endothelial dysfunction, a recognized precursor of atherosclerosis and CVD, the spectrum of risk factors for CVD in CF is reviewed here. Epidemiological data further characterizing the presence and extent of atherogenic processes in CF patients would seem important to obtain. Such studies should further inform and offer mechanistic insights into how other chronic inflammatory diseases potentiate the processes leading to CVDs.

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.

Abnormal n-6 fatty acid metabolism in cystic fibrosis is caused by activation of AMP-activated protein kinase

Cystic fibrosis (CF) patients and model systems exhibit consistent abnormalities in PUFA metabolism, including increased metabolism of linoleate to arachidonate. Recent studies have connected these abnormalities to increased expression and activity of the Δ6- and Δ5-desaturase enzymes. However, the mechanism connecting these changes to the CF transmembrane conductance regulator (CFTR) mutations responsible for CF is unknown. This study tests the hypothesis that increased activity of AMP-activated protein kinase (AMPK), previously described in CF bronchial epithelial cells, causes these changes in fatty acid metabolism by driving desaturase expression. Using CF bronchial epithelial cell culture models, we confirm elevated activity of AMPK in CF cells and show that it is due to increased phosphorylation of AMPK by Ca(2+)/calmodulin-dependent protein kinase kinase β (CaMKKβ). We also show that inhibition of AMPK or CaMKKβ reduces desaturase expression and reverses the metabolic alterations seen in CF cells. These results signify a novel AMPK-dependent mechanism linking the genetic defect in CF to alterations in PUFA metabolism.

Tissue fatty acid composition in obstructive sleep apnea and recurrent tonsillitis

OBJECTIVE

Tonsillar hypertrophy cells appear to have an altered lipid metabolism as evidenced by modulated inflammatory cytokines that affect tissue lipid metabolism. The aim of this study was to investigate differences in tissue fat composition between obstructive sleep apnea (OSA) and recurrent infective tonsillitis (RT) in children.

METHODS

Tonsillar tissues were collected from 114 patients with OSA and 92 patients with RT, aged 4-10 years, during tonsillectomy. The tissue lipid extracts were analyzed by gas liquid chromatography for a comprehensive fatty acid profile.

RESULTS

In the tonsillitis tissue, the levels of palmitoleic acid (16:1n-7; P=0.002) and oleic acid (18:1n-9; P=0.003) were higher, and the level of stearic acid (18:0; P=0.004) was lower than that in the hyperplastic tonsillar tissue. Overall, tonsillar tissue of patients with RT had a significant increase in the total monounsaturated fatty acids (+9.9%; P<0.001) and the fatty acid desaturation index (+20.5%; P<0.001). Furthermore, oleic acid content of tonsillar tissue was positively correlated with BMI (r=0.20, P=0.004), snoring (r=0.16, P=0.022) and hypertrophy grade (r=0.18, P=0.023), which remain significant in the subgroup analysis by hypertrophy type.

CONCLUSIONS

The change in the fatty acid composition may be regarded as an indicator of altered lipid metabolism occurring in vivo during human tonsillar hypertrophy, which might be linked to the severity or type of the tissue damage.

Interactions of linoleic and alpha-linolenic acids in the development of fatty acid alterations in cystic fibrosis

Patients with cystic fibrosis (CF) exhibit characteristic polyunsaturated fatty acid abnormalities, including low linoleic acid and high arachidonic acid levels that are thought to contribute to the pathophysiology of this disease. Recent studies indicate that changes in fatty acid metabolism are responsible for these abnormalities. This study examines the role of fatty acid substrate concentrations in the development of these alterations in a cultured cell model of CF. By incubating cells with varying concentrations of exogenous fatty acids, it shows that increasing the concentration of substrates from the parallel n-3 and n-6 polyunsaturated fatty acid pathways (linoleic acid and alpha-linolenic acid, respectively) not only increases formation of the products in that pathway, but also reduces metabolism in the parallel pathway. In particular, we demonstrate that high levels of linoleic acid and low levels of alpha-linolenic acid are required to observe the typical fatty acid alterations of cystic fibrosis. These results shed light on the mechanisms of fatty acid metabolic abnormalities in cystic fibrosis. They also have implications for the nutritional therapy of CF, highlighting the importance of specific fatty acid content, and in understanding the anti-inflammatory effects of n-3 fatty acids.

Metabolomic profiling of regulatory lipid mediators in sputum from adult cystic fibrosis patients

Retained respiratory tract (RT) secretions, infection, and exuberant inflammatory responses are core abnormalities in cystic fibrosis (CF) lung disease. Factors contributing to the destructive CF airway inflammatory processes remain incompletely characterized. The pro-oxidative inflammatory CF RT milieu is known to contain enzymatically and nonenzymatically produced regulatory lipid mediators, a panel of structurally defined oxidized metabolites of polyunsaturated fatty acids known to play a role in pathology related to inflammation. Using an extraction protocol that maximizes recoveries of sputum-spiked deuterated standards, coupled with an LC/MS/MS detection system, this study presents a metabolomic method to assess a broad spectrum of regulatory lipid mediators in freshly obtained sputum from CF patients. A broad range of both proinflammatory and anti-inflammatory lipid mediators was detected, including PGE2, PGD2, TXB2, LTB4, 6-trans-LTB4, 20-OH-LTB4, 20-COOH-LTB4, 20-HETE, 15-HETE, 11-HETE, 12-HETE, 8-HETE, 9-HETE, 5-HETE, EpETrEs, diols, resolvin E1, 15-deoxy-PGJ2, and LXA4. The vast majority of these oxylipins have not been reported previously in CF RT secretions. Whereas direct associations of individual proinflammatory lipid mediators with compromised lung function (FEV-1) were observed, the relationships were not robust. However, multiple statistical analyses revealed that the regulatory lipid mediators profile taken in aggregate proved to have a stronger association with lung function in relatively stable outpatient adult CF patients. Our data reveal a relative paucity of the anti-inflammatory lipid mediator lipoxin A4 in CF sputum. Patients displaying detectable levels of the anti-inflammatory lipid mediator resolvin E1 demonstrated a better lung function compared to those patients with undetectable levels. Our data suggest that comprehensive metabolomic profiling of regulatory lipid mediators in CF sputum should contribute to a better understanding of the molecular mechanisms underlying CF RT inflammatory pathobiology. Further studies are required to determine the extent to which nutritional or pharmacological interventions alter the regulatory lipid mediators profile of the CF RT and the impact of potential modulations of RT regulatory lipid mediators on the clinical progression of CF lung disease.

Effect of omega-3 fatty acids on the modification of erythrocyte membrane fatty acid content including oleic acid in peritoneal dialysis patients

Erythrocyte membrane fatty acids (FA), such as oleic acid, are related to acute coronary syndrome. There is no report about the effect of omega-3 FA on oleic acid in peritoneal dialysis (PD) patients. We hypothesized that omega-3 FA can modify erythrocyte membrane FA, including oleic acid, in PD patients. In a double-blind, randomized, placebo-controlled study, 18 patients who were treated with PD for at least 6 months were randomized to treatment for 12 weeks with omega-3 FA or placebo. Erythrocyte membrane FA content was measured by gas chromatography at baseline and after 12 weeks. The erythrocyte membrane content of eicosapentaenoic acid and docosahexaenoic acid was significantly increased and saturated FA and oleic acid were significantly decreased in the omega-3 FA supplementation group after 12 weeks compared to baseline. In conclusion, erythrocyte membrane FA content, including oleic acid, was significantly modified by omega-3 FA supplementation for 12 weeks in PD patients.

DHA and EPA reverse cystic fibrosis-related FA abnormalities by suppressing FA desaturase expression and activity

Patients and models of cystic fibrosis (CF) exhibit consistent abnormalities of polyunsaturated fatty acid composition, including decreased linoleate (LA) and docosahexaenoate (DHA) and variably increased arachidonate (AA), related in part to increased expression and activity of fatty acid desaturases. These abnormalities and the consequent CF-related pathologic manifestations can be reversed in CF mouse models by dietary supplementation with DHA. However, the mechanism is unknown. This study investigates this mechanism by measuring the effect of exogenous DHA and eicosapentaenoate (EPA) supplementation on fatty acid composition and metabolism, as well as on metabolic enzyme expression, in a cell culture model of CF. We found that both DHA and EPA suppress the expression and activity of Δ5- and Δ6-desaturases, leading to decreased flux through the n-3 and n-6 PUFA metabolic pathways and decreased production of AA. The findings also uncover other metabolic abnormalities, including increased fatty acid uptake and markedly increased retroconversion of DHA to EPA, in CF cells. These results indicate that the fatty acid abnormalities of CF are related to intrinsic alterations of PUFA metabolism and that they may be reversed by supplementation with DHA and EPA.