FIGURE 2.

Schematic representation of carnitine traffic. Carnitine (Car) traffic is described by continuous arrows; dotted arrows refer to the transport of some other substrates such as carnitine derivatives and trimethylamine (TMA) that are indirectly involved in carnitine traffic. The organic cation transporter novel 2 (OCTN2) mediates carnitine transport by a sodium dependent mechanism, which is not reported for the sake of clarity. ATB^0,+ mediates a sodium and chloride dependent transport, which is not reported for the sake of clarity. Carnitine/acylcarnitine carrier (CAC), the mitochondrial carnitine transporter, allows for the completion of β-oxidation (β-ox) and mediates acylcarnitine/carnitine antiport in mitochondria which is reported in details in Figure 3. The longest isoform of OCTN2, named OCTN2VT, is depicted in the endoplasmic reticulum (ER). The other transporters are depicted in the cell types in which they are expressed. The role of carnitine in the synthesis of the neurotransmitter acetylcholine (Ach) is reported in the sketch representing the brain tissue; the blood-brain barrier is indicated as BBB. Carnitine concentrations in the different tissues are reported. Synt, carnitine synthesis; CIC, citrate transporter; Citr, citrate; Exo, exosomes; VLDL, very low density lipoprotein; BBB, blood-brain barrier.