Methods for measuring the metabolism of neurally derived biomolecules in vivo

Abstract

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.

What is claimed is: 
     
         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, wherein the ratio of labeled protein to unlabeled protein is directly proportional to the metabolism of the protein in the subject.   
     
     
         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 non-radioactive isotope. 
     
     
         5 . The method of  claim 4 , 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. 
     
     
         6 . The method of  claim 5 , wherein the non-radioactive isotope is a component of or attached to an amino acid. 
     
     
         7 . The method of  claim 6 , wherein the amino acid is leucine, the nonradioactive isotope is  13 C, and the protein is amyloid-beta. 
     
     
         8 . The method of  claim 1 , wherein the labeled moiety is administered to the subject intravenously, intra-arterially, subcutaneously, intraperitoneally, intramuscularly, or orally. 
     
     
         9 . The method of  claim 1 , further comprising separating the labeled protein fraction and the unlabeled protein fraction from the biological sample. 
     
     
         10 . The method of  claim 9 , wherein the protein is separated by immunoprecipitation. 
     
     
         11 . The method of  claim 1 , wherein the amount of labeled biomolecule and the amount of unlabeled biomolecule is detected by mass spectrometry. 
     
     
         12 . A kit for detecting the in vivo metabolism of a protein in a subject, the kit comprising:
 (a) a labeled amino acid;   (b) means for administering the labeled amino acid to the subject, whereby the labeled amino acid is capable of crossing the blood brain barrier and incorporating into and labeling a protein as the protein is being synthesized in the central nervous system of the subject;   (c) means for obtaining a biological sample at regular time intervals from the subject, the biological sample comprising a labeled protein fraction and an unlabeled protein fraction; and   (d) instructions for detecting and determining the ratio of labeled to unlabeled protein over time so that the in vivo metabolism may be calculated.   
     
     
         13 . The kit of  claim 12 , wherein the protein synthesized is from a neuronal cell, glial cell, or other cell in the central nervous system. 
     
     
         14 . The kit of  claim 12 , wherein the protein is selected from the group consisting of amyloid-beta, apolipoprotein E, apolipoprotein J, synuclein, soluble amyloid precursor protein, Tau, alpha-2 macroglobulin, S100B, myelin basic protein, an interleukin, and TNF. 
     
     
         15 . The kit of  claim 12 , wherein the labeled amino acid has a radioactive or a non-radioactive atom. 
     
     
         16 . The kit of  claim 15 , 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. 
     
     
         17 . The kit of  claim 15 , wherein the amino acid is leucine, the non-radioactive isotope is  13 C, and the protein is amyloid-beta. 
     
     
         18 . The kit of  claim 12 , wherein the labeled amino acid is administered to the subject intravenously, intra-arterially, subcutaneously, intraperitoneally, intramuscularly, or orally. 
     
     
         19 . The kit of  claim 12 , wherein the ratio of labeled protein to unlabeled protein is determined from the amounts of labeled and unlabeled protein detected by mass spectrometry. 
     
     
         20 . The kit of  claim 12 , wherein the metabolic index comprises the fractional synthesis rate (FSR) and the fractional clearance rate (FCR).