ProCaps Laboratories Acetyl L Carnitine 400 Acetyl l carnitine deficiency in patients with major depressive disorder PNAS Acetyl L carnitine physical chemical, metabolic, and therapeutic properties: relevance for its mode of action in Alzheimer's disease and geriatric depression Molecular Psychiatry Frontiers Discovery and validation of acetyl L carnitine in serum for diagnosis of major depressive disorder and remission status through metabolomic approach