Methods for measuring the metabolism of neurally derived biomolecules in vivo
The present invention relates to methods of diagnosing, monitoring, and assessing treatment effects for neurological and neurodegenerative diseases and disorders, such as Alzheimer's Disease, early in the course of clinical disease or prior to the onset of brain damage and clinical symptoms. Methods of measuring the in vivo metabolism of biomolecules produced in the CNS in a subject are provided.
1. A method for measuring the in vivo metabolism of a protein in a subject, the protein being synthesized in the central nervous system, the method comprising:
(a) administering a labeled moiety to the subject, the labeled moiety being capable of crossing the blood brain barrier and incorporating into the protein as the protein is synthesized in the central nervous system of the subject;
(b) obtaining a biological sample from the subject, the biological sample comprising a protein fraction labeled with the moiety and a protein fraction not labeled with the moiety; and
(c) detecting the amount of labeled protein and the amount of unlabeled protein by mass spectrometry, wherein the ratio of labeled protein to unlabeled protein is directly proportional to the metabolism of the protein in the subject, wherein the protein is selected from the group consisting of apolipoprotein E, apolipoprotein J, synuclein, soluble amyloid precursor protein, Tau, alpha-2 macroglobulin, S100B, myelin basic protein, an interleukin, and TNF.
2. The method of claim 1 , wherein the protein synthesized is from a neuronal cell, glial cell, or other cell in the central nervous system.
3. The method of claim 1 , wherein the labeled moiety is an atom, or a molecule with a labeled atom.
4. The method of claim 3 , wherein the atom is a radioactive isotope.
5. The method of claim 3 , wherein the atom is a non-radioactive isotope.
6. The method of claim 5 , wherein the non-radioactive isotope is selected from the group consisting of 2 H, 13 C, 15 N, 17 O, 18 O, 33 S, 34 S, and 36 S.
7. The method of claim 6 , wherein the non-radioactive isotope is a component of or attached to an amino acid.
8. The method of claim 7 , wherein the amino acid is leucine and the non-radioactive isotope is 13 C.
9. The method of claim 1 , wherein the labeled moiety is administered to the subject intravenously, intra-arterially, subcutaneously, intraperitoneally, intramuscularly, or orally.
10. The method of claim 1 , wherein the biological sample is cerebral spinal fluid.
11. The method of claim 1 , further comprising separating the labeled protein fraction and the unlabeled protein fraction from the biological sample.
12. The method of claim 11 , wherein the protein factions are separated by immunoprecipitation.
13. The method of claim 1 , wherein the subject is human.