(±)-Carnitine chloride (Monocamin) is a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine.

L-carnitine primarily facilitates the translocation of long-chain fatty acids across the inner mitochondrial membrane by transforming acyl-CoA into acyl-carnitine via carnitine palmitoyl transferase (CPT)-I activation. This acyl-carnitine is then converted back into acyl-CoA within the mitochondrial matrix by CPT-II. L-carnitine's introduction enhances palmitoyl-CoA-induced mitochondrial respiration, further accelerated by ADP, showcasing a concentration-dependent effect that reaches saturation at 5 mM L-carnitine[1]. Additionally, L-carnitine pre-treatment enhances Nrf2 nuclear translocation, its DNA binding activity, and heme oxygenase-1 (HO-1) expression in Water2-treated HL7702 cells, providing protection against Water2-induced cell damage through Akt-mediated Nrf2 signaling pathway activation[2].

L-carnitine has been shown to modulate the ubiquitin-proteasome pathway and enhance IGF-1 levels in animal studies. Its administration over two weeks can mitigate muscle mass and fiber size reduction in the soleus muscle caused by hindlimb suspension. Additionally, L-carnitine inhibits atrogin-1 mRNA expression, crucial for preventing muscle atrophy. Concurrent L-carnitine treatment also reduces renal fibrosis—associated with lowered plasma TGF-β1 levels—and addresses the enhanced oxidative and inflammatory states observed in L-NAME treated groups, alongside promoting PPAR-γ expression.

Mitochondria (0.6 mg protein/mL) are incubated in 2.5 mM Hepes (pH7.4) containing 225 mM mannitol, 75 mM sucrose and 100 μM ethylene glycol tetraacetic acid (EGTA) with or without 5 mM L-carnitine at 25°C. To measure oxygen uptake, 10 min after inorganic phosphate (Pi) 4 mM are added, the mitochondria are treated with palmitoyl-CoA (50 μM) and then ADP is added (200 μM). Oligomycin (5 μM) and rotenone (10 μM) are added 3-4 min after the ADP treatment. HPG (0-10 mM), which can specifically inhibit carnitine palmitoyl transferase (CPT)-I activity in the mitochondria, is added in the Hepes medium before incubation of the mitochondria[1].