OCTN2Organic Cation Transporter Number 2
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Under these conditions, activation of peroxisome proliferator-activated receptor-alpha (PPAR[alpha]) by nonesterified FAs (NEFAs) from adipose tissue increases the expression of [gamma]-BBH and OCTN2 to facilitate the oxidation of FAs in tissues.
Samples (20 [micro]g) were subjected to immunoblot analysis with the use of antibodies against OCTN2, [gamma]-BBH, PPAR[alpha], and TMLD (Santa Cruz Biotechnology Inc., Dallas, TX).
To confirm that the decrease in free carnitine reflects active uptake, we determined the expression of OCTN2 in liver and heart.
Evidence shows that conditions associated with elevated rates of FA oxidation stimulate PPAR[alpha] expression in liver and genes involved in FA disposal, including [gamma]-BBH and OCTN2 [7].
Indeed, increased protein expression of OCTN2 was detected in liver and heart from exercising mice.
Early studies have indicated that carnitine biosynthesis and OCTN2 expression in liver are dependent on the activation of PPAR[alpha] [14], a lipid-sensing nuclear receptor that functions as a regulator of FA metabolism [15].
An interesting finding of this study was that acute exercise increased the expression of OCTN2 and TMLD in heart.
Primary carnitine deficiency is a rare autosomal recessive disorder with an incidence of one in 120,000, caused by mutations in the SLC22A5 gene, located on chromosome 5q23.3, which encodes OCTN2 [2].
Mutations of OCTN2, an organic cation/carnitine transporter, lead to deficient cellular carnitine uptake in primary carnitine deficiency.
El fallo hereditario en el transportador de carnitina (OCTN2) se conoce como deficiencia primaria de carnitina (Mckusick 212140) (1).
El material biologico empleado fueron los fibroblastos de 2 pacientes con deficiencia de OCTN2. Esta deficiencia se confirmo por estudios moleculares.
Cuadro 1 Oxidacion de [9, [10.sup.3]H]-acidos grasos en pacientes con deficiencias de OCTN2 Oxidacion[9,[10.sup.3]H]- palmitato miristato Deficiencia n nmol/hora/mg nmol/hora/mg proteina (X + DS) proteina (X + DS) Controles 20 4.7 [+ o -] 0.23 4.4 [+ o -] 0.15 OCTN2 2 1.6 [+ o -] 0.23 1.6 [+ o -] 0.18 OCTN2 + 2 4.6 [+ o -] 0.20 4.6 [+ o -] 0.22 Carnitina Oxidacion[9,[10.sup.3]H]- palmitato miristato Deficiencia % % Controles 100 100 OCTN2 34 37 OCTN2 + 100 100 Carnitina