Urinary carnitine excretion in patients with heart failure

Acylcarnitines: Nomenclature, Biomarkers, Therapeutic Potential, Drug Targets, and Clinical Trials

Acylcarnitines are fatty acid metabolites that play important roles in many cellular energy metabolism pathways. They have historically been used as important diagnostic markers for inborn errors of fatty acid oxidation and are being intensively studied as markers of energy metabolism, deficits in mitochondrial and peroxisomal β -oxidation activity, insulin resistance, and physical activity. Acylcarnitines are increasingly being identified as important indicators in metabolic studies of many diseases, including metabolic disorders, cardiovascular diseases, diabetes, depression, neurologic disorders, and certain cancers. The US Food and Drug Administration-approved drug L-carnitine, along with short-chain acylcarnitines (acetylcarnitine and propionylcarnitine), is now widely used as a dietary supplement. In light of their growing importance, we have undertaken an extensive review of acylcarnitines and provided a detailed description of their identity, nomenclature, classification, biochemistry, pathophysiology, supplementary use, potential drug targets, and clinical trials. We also summarize these updates in the Human Metabolome Database, which now includes information on the structures, chemical formulae, chemical/spectral properties, descriptions, and pathways for 1240 acylcarnitines. This work lays a solid foundation for identifying, characterizing, and understanding acylcarnitines in human biosamples. We also discuss the emerging opportunities for using acylcarnitines as biomarkers and as dietary interventions or supplements for many wide-ranging indications. The opportunity to identify new drug targets involved in controlling acylcarnitine levels is also discussed. SIGNIFICANCE STATEMENT: This review provides a comprehensive overview of acylcarnitines, including their nomenclature, structure and biochemistry, and use as disease biomarkers and pharmaceutical agents. We present updated information contained in the Human Metabolome Database website as well as substantial mapping of the known biochemical pathways associated with acylcarnitines, thereby providing a strong foundation for further clarification of their physiological roles.

Impact of sleep-disordered breathing on myocardial damage and metabolism in patients with chronic heart failure

Sleep-disordered breathing (SDB) has a critical association with mortality and morbidity of patients with chronic heart failure (CHF). Troponin T is a marker of ongoing myocardial damage and predicts adverse clinical outcomes in patients with CHF. Carnitine plays an important role in the utilization of fatty acids in the myocardium. It has been reported that myocardial carnitine levels decrease in the failing heart. We hypothesized that plasma troponin T and carnitine are increased due to the leakage from damaged cardiomyocytes or the alteration of myocardial metabolism in CHF patients with SDB. We examined the relation of plasma troponin T and carnitine levels with severity of SDB in CHF. We used portable sleep monitor and measured the apnea-hypopnea index (AHI), plasma levels of high-sensitive troponin T and carnitine in 131 CHF patients. These patients were divided into three groups based on AHI: group A (None-mild SDB AHI < 15/h, n = 45), group B (Moderate SDB 15 ≤ AHI < 30/h, n = 32) and group C (Severe SDB AHI ≥ 30/h, n = 54). Levels of high-sensitive troponin T and plasm total carnitine were significantly higher in group C than in groups A and B [high-sensitive troponin T; group A 0.009 (0.005-0.016), group B 0.012 (0.006-0.021), group C 0.021 (0.011-0.039) ng/ml, total carnitine; group A 61.0 ± 15.1, group B 65.0 ± 13.5, group C 73.3 ± 17.5 μmol/l, P < 0.01 vs. group A and P < 0.05 vs. group B, respectively]. Furthermore, in the multiple regression analysis, the independent factors to determine plasma levels of log (high-sensitive troponin T) were high-sensitive C-reactive protein and AHI, and the independent factors to determine plasma levels of carnitine were glomerular filtration rate and AHI. The present study suggests that SDB is associated with latent myocardial damage and alteration of myocardial carnitine metabolism in patients with CHF, presented by higher circulating troponin T and carnitine levels.

Carnitine and its derivatives in cardiovascular disease

Carnitine and its derivative propionyl-L-carnitine are endogenous cofactors which enhance carbohydrate metabolism and reduce the intracellular buildup of toxic metabolites in ischemic conditions. The carnitines have been, and are being used in a spectrum of diseases including multiple cardiovascular conditions. These include angina, acute myocardial infarction, postmyocardial infarction, congestive heart failure, peripheral vascular disease, dyslipidemia, and diabetes. Most published data on carnitine, propionyl-L-carnitine, and other carnitine congeners are favorable but the clinical trials have been relatively small. In currently used doses, these substances are virtually devoid of significant side effects.