1-Deoxysphingolipids (1-deoxySLs) are atypical neurotoxic sphingolipids that are formed by the serine-palmitoyltransferase (SPT). Pathologically elevated 1-deoxySL concentrations cause hereditary sensory and autonomic neuropathy type 1 (HSAN1), an axonal neuropathy associated with several missense mutations in SPT. Oral L-serine supplementation suppressed the formation of 1-deoxySLs in patients with HSAN1 and preserved nerve function in an HSAN1 mouse model. Because 1-deoxySLs also are elevated in patients with type 2 diabetes mellitus, L-serine supplementation could also be a therapeutic option for diabetic neuropathy (DN). This was tested in diabetic STZ rats in a preventive and therapeutic treatment scheme. Diabetic rats showed significantly increased plasma 1-deoxySL concentrations, and L-serine supplementation lowered 1-deoxySL concentrations in both treatment schemes (P < 0.0001). L-serine had no significant effect on hyperglycemia, body weight, or food intake. Mechanical sensitivity was significantly improved in the preventive (P < 0.01) and therapeutic schemes (P < 0.001). Nerve conduction velocity (NCV) significantly improved in only the preventive group (P < 0.05). Overall NCV showed a highly significant (P = 5.2E-12) inverse correlation with plasma 1-deoxySL concentrations. In summary, our data support the hypothesis that 1-deoxySLs are involved in the pathology of DN and that an oral L-serine supplementation could be a novel therapeutic option for treating DN.

Since the introduction into clinical practice of vinca alkaloids, tubulin has become a key and well-established target of modern antineoplastic chemotherapy. When taxanes became available their broad spectrum of activity was striking and opened up new horizons for cancer patients treatment. However, taxanes susceptibility to drug resistance caused by the drug efflux pump protein, P-glycoprotein, is not infrequent and their use may be limited by poor solubility, synthetic problems and toxicity. The epothilones are a new class of chemotherapeutic agents with a mechanism of action similar to that of taxanes, but different enough to escape, for example, the multidrug resistance caused by P-glycoprotein. Moreover, the epothilones (that are strong promoters of tubulin polymerization) have significant antitumor activity against human cancer cells that are taxane-resistant, express the multidrug resistance gene MDR-1, and have acquired tubulin mutations. Finally, starting from the natural molecules, several synthetic analogues have been developed. Besides their antineoplastic efficacy, all the antitubulin drugs share a common toxicity on the peripheral nervous system and peripheral neurotoxicity is a major, potentially dose-limiting side effect also of the epothilones. The current knowledge regarding the features of epothilones peripheral neurotoxicity and their comparison with taxanes will be reviewed.