Butyrobetaine (BB), carnitine (C0), total carnitine (tC0), acetylcarnitine (C2), propionylcarnitine (C3), butyrylcarnitine (C4), isovalerylcarnitine (iC5), hexanoylcarnitine (C6), octanoylcarnitine (C8), decanoylcarnitine (C10), dodecanoylcarnitine (C12), myristoylcarnitine (C14), palmitoylcarnitine (C16), stearoylcarnitine (C18), oleoylcarnitine (C18:1), linoleylcarnitine (C18:2).
Acylcarnitine esters are formed from the CoASH esters of acetate, propionate, butyrate, medium-chain, long-chain and very-long-chain fatty acids. Acylcarnitines cross the mitochondrial membrane, and such transport is required for beta-oxidation of long-chain fatty acids for energy production.
Carnitine is mainly obtained through the diet, can be consumed as supplement, but about 30 per cent is supplied by de novo synthesis from trimethyllysine (TML), which takes place in liver and kidney. The final step in the synthesis is catalyzed by the α-ketoglutarate-dependent enzyme, gamma-butyrobetaine dioxygenase (BBOX) that converts gamma-butyrylbetaine into carnitine.
Circulating levels of carnitine and acylcarnitines have been related to risk of insulin resistance, diabetes 2, NAFLD and cardiovascular disease (1).
To investigate the metabolomic signature of human diseases.
Matrix: EDTA plasma or serum.
Volume: Minimum volume is 60 µL, but 200 µL is optimal and allows reanalysis.
Preparation and stability: Samples should be put on ice immediately after collection and stored at -80 °C.
Reported values (µmol/L): BB: 0.4-2; C0: 20-80; tC0: 30-90; C2: 3-15; C3: 0.2-1.5; C4: 0.1-0.5; iC5: 0.06-0.2; C6: 0.01-1.2; C8: 0.06-0.3; C10: 0.2-1; C12: < 0.4; C14: 0.01-0.22; C16: 0.04-0.31; C18: 0.04-0.1; C18:1: 0.04-0.41; C18:2: 0.01-0.29.
Intraclass correlation coefficients (ICCs): C2: 0.63; C3: 0.62; iC5: 0.68; C8: 0.4; C14: 0.38; C16: 0.49; C18: 0.40; C18:1: 0.66.
1. Bene, J., Szabo, A., Komlósi, K., & Melegh, B. (2020). Mass spectrometric analysis of L-carnitine and its esters: Potential biomarkers of disturbances in carnitine homeostasis. Curr Mol Med, 20, 336-354.