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.

OBJECTIVE: To describe pancreatic function during the first year of life in infants diagnosed with cystic fibrosis (CF) using serial fecal elastase measurements. STUDY DESIGN: This was a longitudinal study of 82 infants diagnosed with CF through newborn screening. Monthly stool samples were sent to a central laboratory for fecal elastase measurements. RESULTS: A total of 61 infants had an initial stool sample obtained at age 9 months. Twenty-six of 29 infants with a fecal elastase value /g at study entry had a fecal elastase value /g (the accepted cutoff value for pancreatic insufficiency) on all measurements during the year; all 29 had a value /g at the end of the study. Of the 48 infants with initial fecal elastase value /g, 13 had at least 1 fecal elastase value >200 mug/g but had a final stool fecal elastase value /g; however, 4 infants with an initial fecal elastase value /g ended the year with a value >200 mug/g. Eleven of 13 infants with an initial fecal elastase value of >200 mug/g still had a value >200 mug/g at the end of the first year. CONCLUSION: Infants with CF exhibit variability in fecal elastase values during the first year. Infants with a fecal elastase level of 50-200 mug/g at diagnosis should be treated with pancreatic enzyme replacement therapy, but fecal elastase should be remeasured at age 1 year to ensure that those with a falsely low value do not continue to receive pancreatic enzyme replacement therapy unnecessarily. Those with a fecal elastase value >200 mug/g initially can become pancreatic insufficient with time.