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

Abstract

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 ( cftr 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.

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

“…In fact, despite modern pancreatic enzyme replacement therapy, many CF patients exhibit a degree of fat malabsorption [ 66 ]. Most CF mice exhibit similar fatty acid abnormalities as humans [ 11 , 20 , 32 , 33 , 36 , 38 ], despite mice having CF pathology mainly limited to the gastrointestinal tract. Here, we find that two non-rodent models that broadly recapitulate the histopathology of CF also develop fatty acid composition abnormalities that overlap those observed in humans.…”

“…Fatty acid composition has been studied extensively in mouse models of CF but with mixed results, depending in part on the strain and Cftr mutation under study [ 32 ]. Linoleic acid concentrations in CF mice have been reported to be low [ 11 , 20 , 32 , 33 ] or normal [ 34 , 35 ]. Yet several mouse studies focused on docosahexaenoic acid and arachidonic acid (20:4n6) did not report linoleic acid levels [ 36–38 ].…”

“…Interestingly, one study found that low linoleic acid in mouse adipose tissue normalized at 6 weeks [ 39 ]. Diet also impacts fatty acid composition in mice [ 32 , 34 ]. However, there are several reasons that mice may not be an optimal model of lipid imbalance in CF disease.…”

Severe Genotype, Pancreatic Insufficiency and Low Dose of Pancreatic Enzymes Associate with Abnormal Serum Sterol Profile in Cystic Fibrosis

“…Standard CF therapy includes a high-energy, high-fat diet (with pancreatic enzyme replacement therapy) [ 13 , 51 ], and it is recommended to use good-quality fats comprising polyunsaturated fatty acids from oils, nuts and avocados (products that are also a source of plant sterols) [ 13 , 30 , 52 ]. Regardless of the guidelines, the phytosterol intake in the present study was comparable in CF patients and HS as a result of the high consumption of saturated fatty acids, butter, eggs and dairy, which was also documented by our previous research [ 53 ].…”

Specialized Pro-Resolving Lipid Mediators in Cystic Fibrosis

“…These lipid abnormalities were mainly explained by the fat malabsorption caused by the pancreatic insufficiency present in 85% of the patients [ 34 , 35 ]. In addition, CFTR dysfunction has been related to increased expression and activity of phospholipase A2 (PLA2) [ 36 , 37 , 38 , 39 , 40 , 41 ]. Since the release of AA by phospholipases is rate-limiting for the eicosanoid synthesis, an abnormal activity of PLA2 is a possible mechanism involved in increased AA levels in CF [ 42 ].…”