Fatty acid abnormalities in cystic fibrosis.

Fatty acids were measured by gas chromatography in lipid extracts of plasma and tissues obtained from three categories of 46 patients with cystic fibrosis. Low levels of the major essential fatty acid linoleate were found in plasma total lipids of patients who had malabsorption but not in those without evidence of steatorrhea. Circulating arachidonic acid was only slightly decreased, and the unusual triene reflecting pathologically altered fatty acid metabolism (20:3 omega 9) was generally not detected, nor was the triene/tetraene ratio abnormal except for in two patients. There was no correlation between plasma linoleate and age, clinical severity score, or vitamin E status. Decreased linoleate did correlate with two indices of malabsorption, namely plasma carotene (r = 0.64) and fecal fat excretion (r = 0.76). Our data therefore indicate that the abnormality in linoleate is associated with (secondary to) malabsorption of dietary fat despite pancreatic enzyme replacement therapy and consumption of a regular diet. The frequency of this alteration was determined to be quite high in 40 patients with steatorrhea, 85% of whom showed values below the lower limit of normal for plasma linoleate. It was of interest to find markedly decreased levels of linoleate in adipose tissue, cardiac muscle, and lung and lesser reductions in liver and psoas muscle taken at autopsies. Tissue arachidonic acid percentage was normal, however, and 20:3 omega 9 was rarely present. Thus, the physiological significance of this common abnormality in CF patients with malabsorption remains to be determined.