Microfilaments (or actin filaments) are the thinnest filaments of the cytoskeleton, having 6 nm in diameter, providing both stability and dynamics to neurons. In neurons, actin filaments are packed into networks and stabilized by interacting proteins (22). Microfilaments play a role in spine formation and spine volume stabilization (30), with the dynamics of actin leading to the formation of new synapses as well as increased cell communication. The actin cytoskeleton controls several cellular processes. In animal models of diabetes there is an impairment of slow axonal transport of cytoskeletal elements like tubulin and NF proteins (slow component a), and polypeptides such as actin (slow component b) (31-33). Actin undergoes glycation in the brain of STZ-induced diabetic rats and the appearance of glycated actin is prevented by administration of insulin (9, 34).

More recently, it was investigated if the receptor for advanced glycation end-product (RAGE) is involved in axonal transport impairment via interaction with its cytoplasmic domain binding partner mDia1, which is involved in actin structure modifications. Slow axonal transport in the peripheral nerves is indeed affected by diabetes, but in a RAGE-independent manner (35). Moreover, mDia1 axonal transport is impaired, suggesting that diabetes-induced changes affecting actin binding proteins are early events in the course of the pathology (35), and forward the hypothesis that mDia1 axonal transport impairment might be correlated with the extent of actin glycation (34).

Taken together, these studies in experimental diabetes indicate that post-translational modifications, as well as altered expression of cytoskeletal proteins (tubulin, neurofilament and actin), may interfere with cytoskeletal assembly, contributing to altered axonal transport and subsequent nerve dysfunction.