Purpose: Our purpose is to determine the concentration and biological activity of Insulin-like Growth Factor I and II (IGF-I and II), soluble Cluster of Differentiation 163 (sCD-163), Nerve Growth Factor (NGF), Vascular Endothelial Growth Factor (VEGF) and Brain-derived Neurotropic Factor (BDNF) in cerebrospinal fluid and in blood in patients with diabetes and/or nerve disease (especially diabetic polyneuropathy) as well as in healthy control subjects. We will furthermore relate the findings to peripheral nerve function. In addition the composition of the cerebrospinal fluid will be analyzed using mass spectrometry.