Cobalamin as a regulator of serum and cerebrospinal fluid levels of normal prions

We have previously demonstrated that the concentration of normal prion proteins (PrPC) is increased in the serum and cerebrospinal fluid (CSF) of rats deficient in vitamin B12 (cobalamin, Cbl). In this study, we investigated whether similar increases also occur in the serum and CSF of patients deficient in Cbl (Cbl-D), and whether the increase in serum levels can be corrected by Cbl therapy. The study involved two sample populations. The first consisted of 45 patients (13 patients with pernicious anemia [PA], 19 with other forms of anemia, and 13 healthy controls); and the second, 68 patients (five with subacute combined degeneration [SCD], 18 with amyotrophic lateral sclerosis, 22 with multiple sclerosis [MS], and 23 neurological controls). Serum PrPC levels were measured using an enzyme-linked-immunosorbent-assay before as well as after Cbl therapy. The mean serum PrPC levels in patients with PA were significantly higher than those of the controls (p = 0.0017) but normalized after Cbl therapy; there was no significant change in the patients with other forms of anemia. Mean CSF PrPC levels in the patients with SCD were significantly higher than in the neurological controls (p < 0.03). The serum and CSF PrPC levels of patients with PA and those with SCD were correlated significantly with serum (p = 0.004) and CSF (p = 0.0018) Cbl levels. In patients with MS, CSF PrPC concentrations were significantly lower than those of the controls regardless of their CSF Cbl levels. We found a correlation between Cbl and PrPC levels in the serum and CSF of Cbl-D patients, which suggests that Cbl may regulate the PrPC levels in the serum and CSF in humans.