Essential fatty acid and lipoprotein status in pediatric cystic fibrosis: Impact of cystic fibrosis transmembrane conductance regulator modulators

ABSTRACT

Background: Dyslipidemias and essential fatty acid deficiencies (EFADs) are well established complications of cystic fibrosis (CF). In the general population, a diet high in saturated fat is associated with hyperlipidemia and greater risk of cardiovascular disease and type 2 diabetes. Increasing life expectancy in CF brings concern about the risks of the "legacy" high-fat CF diet. The impact of CFTR modulators on CF-related dyslipidemia and EFAD is not known. Previous studies reported dyslipidemia in people with CF (PwCF) using traditional lipid measures. This study aimed to evaluate the lipoprotein and fatty acid profiles in children and adolescents with CF and to correlate biochemical results with clinical and molecular findings. Plasma and red blood cell (RBC) samples were studied to compare the ability of each method to identify EFAD markers. Method(s) Blood samples (n = 171) were obtained from 142 (78 female) children with CF aged 9.8 +/- 4.7 (range 4 months to 18 years) during routine laboratory draws at pediatric CF center clinic visits. Pancreatic insufficiency was present in 92% and glucose intolerance or diabetes in 14%. Body mass index percentile (BMI%ile) for age z-scorewas 0.23 +/- 0.89 (range -2.4-2.6). F508del mutation was homozygous for 56% and heterozygous for 41%. CFTR modulator therapy had been initiated 3 or more months before for 62% of samples. Sample collection began in September 2019, paused during the COVID-19 pandemic, and resumed in July 2021. An accredited, regional laboratory with expertise in fatty acid analysis processed all samples. Serum was separated and refrigerated for lipoprotein analysis, plasmawas separated and frozen, and RBCs were washed and frozen for fatty acid analysis. Nuclear magnetic resonance lipoprotein assayswere conducted to determine particle number and size of lipoprotein classes. Triglyceride, total cholesterol, and high-density lipoprotein cholesterol (HDL-C) were measured directly (Roche). Low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C) were calculated. To correlate laboratory results with clinical findings, medical records were reviewed, and a CF clinic dietitian conducted 24-hour dietary recalls concurrent with study labs. Result(s) Of PwCF homozygous F508del/F508del, 43% tested positive for EFAD biomarkers (RBC linoleic acid, RBC mead acid, RBC triene/tetraene ratio), compared with 13% of PwCF heterozygous F508del ( p <=0.01) (Figure 1). There was no significant difference in concentrations of fatty acid and EFAD biomarkers between those who had or had not initiated CFTR modulator therapy. Lipoprotein abnormalities were identified in 69% of samples with low HDL-C and 39% with large HDL-C, 87% with large VLDL-C particle size and 52% with large VLDL-C particle number, and 5% with high LDL-C or small LDL-C particle numbers. High total cholesterol was found in 15% and high triglycerides in 17%. HDL-C was low in 24%, and 3% had high LDL-C. (Figure Presented) Figure 1. Differences in concentrations of red blood cell (RBC) linoleic and mead acids and triene/tetraene (T/T) ratio between F508del homozygous and F508del heterozygous individuals Conclusion(s) Despite clinical advances and use of CFTR modulator therapy, EFAD remains prevalent and underrecognized in the pediatric CF population. Of PwCF, those homozygous for f508del may have a higher risk of EFAD. Limitations of this study (four different CFTR modulator therapies and small sample sizes in each group) may have precluded significant findings for EFAD and lipid profiles, but PwCF receiving modulator therapy appear to have healthier lipid profiles than those not receiving therapy. Lipids and fatty acid are not routinely evaluated in PwCF, but evaluation should be included in the standard of care for timely dietary interventionsCopyright © 2022, European Cystic Fibrosis Society. All rights reserved