Gillingham, Melanie B.

ABSTRACT 3‐hydroxy acylcarnitines (3‐OH‐ACs) are key biomarkers for screening of long‐chain 3‐hydroxyacyl‐CoA dehydrogenase and trifunctional protein deficiencies (LCHADD/TFPD). The utility of this biomarker for disease monitoring in identified patients remains debated, and recent suggestions have highlighted the potential use of lipidomics for diagnosis, monitoring, prognosis, and/or identification of new biomarkers. We evaluated the use of omics in LCHADD/TFPD patients by analyzing plasma acylcarnitine profiles, metabolomics, and lipidomics, combined with genotype, visual assessments, and dietary records. Fasting plasma from 39 participants with LCHADD/TFPD and 32 control subjects were analyzed through untargeted metabolomic and lipidomic analyses. In LCHADD/TFPD participants, acylcarnitine profiling, visual and retinal function assessments were performed, and 3‐day diet records were collected. Relationships between acylcarnitines, metabolomics, lipidomics, along with visual outcomes and dietary intake were investigated. Plasma of LCHADD/TFPD participants exhibited elevated 3‐OH‐ACs, which correlated with genotype and visual outcomes. Metabolomics successfully distinguished LCHADD/TFPD from controls, and the biggest divergence was observed in lipid pathways. Metabolomic profiles tightly correlated with 3‐OH‐ACs, genotype, and visual outcomes. Lower concentrations of total lipids and some individual lipid species such as phosphoethanolamines (PE) were detected in LCHADD/TFPD, except for elevations in several certain triglycerides. LCHADD/TFPD participants followed a diet low in long‐chain fat (LCFA) as recommended. LCFA intake did not correlate with either plasma 3‐OH‐ACs or metabolomics. 3‐OH‐ACs are strong consistent biomarkers of LCHADD/TFPD that are associated with clinical parameters of vision and genotype. We did not observe a relationship between dietary LCFA intake and 3‐OH‐ACs.

Abstract Medical nutrition therapy for long‐chain fatty acid oxidation disorders (LC‐FAODs) currently emphasizes fasting avoidance, restricted dietary long‐chain fatty acid intake, supplementation with medium chain triglycerides, and increased carbohydrate intake. We hypothesize that increasing dietary protein intake relative to carbohydrate intake would preserve metabolic control yet induce physical benefits including reduced hepatic lipogenesis. Therefore, we compared two dietary approaches with similar fat intake but different carbohydrate to protein ratios in participants diagnosed with LC‐FAODs. Thirteen participants were enrolled and randomized into either a high‐protein (PRO) or a high‐carbohydrate (CHO) diet for 4 months. Baseline and 4‐month assessments included body composition, ectopic lipid deposition, and resting energy expenditure. End of study assessments also included total energy expenditure, metabolic responses to oral feedings, and whole‐body fatty acid oxidation capacity. At the end of the dietary intervention, both groups had similar energy expenditure, fat and glucose oxidation rates, and glucolipid responses to mixed meal and oral glucose loads. Neither dietary group experienced worsening symptoms related to their LC‐FAOD. Compared to the CHO group, the PRO group exhibited increased blood levels of short‐chain acylcarnitines, reduced intrahepatic lipid content, and maintained lean body mass while the CHO group lost lean mass. In patients with LC‐FAODs, increasing protein intake maintained metabolic control, reduced liver fat without risk of metabolic decompensation, and helped preserve lean body mass. We propose that a modest increase in dietary protein along with fasting avoidance and fat restriction may improve body composition and energy expenditure in patients with LC‐FAODs.

AbstractBackgroundObservational reports suggest that supplementation that increases citric acid cycle intermediates via anaplerosis may have therapeutic advantages over traditional medium‐chain triglyceride (MCT) treatment of long‐chain fatty acid oxidation disorders (LC‐FAODs) but controlled trials have not been reported. The goal of our study was to compare the effects of triheptanoin (C7), an anaplerotic seven‐carbon fatty acid triglyceride, to trioctanoin (C8), an eight‐carbon fatty acid triglyceride, in patients with LC‐FAODs.MethodsA double blinded, randomized controlled trial of 32 subjects with LC‐FAODs (carnitine palmitoyltransferase‐2, very long‐chain acylCoA dehydrogenase, trifunctional protein or long‐chain 3‐hydroxy acylCoA dehydrogenase deficiencies) who were randomly assigned a diet containing 20% of their total daily energy from either C7 or C8 for 4 months was conducted. Primary outcomes included changes in total energy expenditure (TEE), cardiac function by echocardiogram, exercise tolerance, and phosphocreatine recovery following acute exercise. Secondary outcomes included body composition, blood biomarkers, and adverse events, including incidence of rhabdomyolysis.ResultsPatients in the C7 group increased left ventricular (LV) ejection fraction by 7.4% (p = 0.046) while experiencing a 20% (p = 0.041) decrease in LV wall mass on their resting echocardiogram. They also required a lower heart rate for the same amount of work during a moderate‐intensity exercise stress test when compared to patients taking C8. There was no difference in TEE, phosphocreatine recovery, body composition, incidence of rhabdomyolysis, or any secondary outcome measures between the groups.ConclusionsC7 improved LV ejection fraction and reduced LV mass at rest, as well as lowering heart rate during exercise among patients with LC‐FAODs.Clinical Trial Registration: Clinicaltrials.gov NCT01379625.

AbstractBlood and urine acylcarnitine profiles are commonly used to diagnose long‐chain fatty acid oxidation disorders (FAOD: i.e., long‐chain hydroxy‐acyl‐CoA dehydrogenase [LCHAD] and carnitine palmitoyltransferase 2 [CPT2] deficiency), but the global metabolic impact of long‐chain FAOD has not been reported. We utilized untargeted metabolomics to characterize plasma metabolites in 12 overnight‐fasted individuals with FAOD (10 LCHAD, two CPT2) and 11 healthy age‐, sex‐, and body mass index (BMI)‐matched controls, with the caveat that individuals with FAOD consume a low‐fat diet supplemented with medium‐chain triglycerides (MCT) while matched controls consume a typical American diet. In plasma 832 metabolites were identified, and partial least squared‐discriminant analysis (PLS‐DA) identified 114 non‐acylcarnitine variables that discriminated FAOD subjects and controls. FAOD individuals had significantly higher triglycerides and lower specific phosphatidylethanolamines, ceramides, and sphingomyelins. Differences in phosphatidylcholines were also found but the directionality differed by metabolite species. Further, there were few differences in non‐lipid metabolites, indicating the metabolic impact of FAOD specifically on lipid pathways. This analysis provides evidence that LCHAD/CPT2 deficiency significantly alters complex lipid pathway flux. This metabolic signature may provide new clinical tools capable of confirming or diagnosing FAOD, even in subjects with a mild phenotype, and may provide clues regarding the biochemical and metabolic impact of FAOD that is relevant to the etiology of FAOD symptoms.

The development of insulin resistance has been associated with impaired mitochondrial fatty acid oxidation (FAO), but the exact relationship between FAO capacity and glucose metabolism continues to be debated. To address this controversy, patients with long-chain 3-hydroxy acyl-CoA dehydrogenase (LCHAD) deficiency underwent an oral glucose tolerance test (OGTT) and measurement of energy expenditure, body composition, and plasma metabolites. Compared with controls, patients with LCHAD deficiency had a trend toward higher total body fat and extramyocellular lipid deposition but similar levels of intramyocelluar and intrahepatic lipids. Resting energy expenditure was similar between the groups, but respiratory quotient was higher and total energy expenditure was lower in LCHAD-deficient patients compared with controls. High-molecular-weight (HMW) adiponectin levels were lower and plasma long-chain acylcarnitines were higher among LCHAD-deficient patients. Fasting and post-OGTT levels of glucose, insulin, and ghrelin, along with estimates of insulin sensitivity, were the same between the groups. Despite decreased capacity for FAO, lower total energy expenditure and plasma HMW adiponectin, and increased plasma acylcarnitines, LCHAD-deficient patients exhibited normal glucose tolerance. These data suggest that inhibition of the FAO pathway in humans is not sufficient to induce insulin resistance.