Compositions and Methods for Modulating Circulating Factors

A method of preparing a sample that is useful for detecting a likelihood of developing a disease or condition in a subject, comprising:

• a) obtaining or having obtained a sample from the subject;
• b) adding a protease inhibitor, a control peptide, a standard peptide, or a combination thereof to the sample to prepare a sample that is useful for detecting a likelihood of developing cancer;
• and
• c) quantifying an expression or activity of a target protein identified in the Sequence Listing, in Table A, or a variant of the foregoing, in the sample prepared in step b),
• wherein the disease or condition is selected from aging, senescence, fibrosis, a metabolic disease, a cardiovascular disease, an endocrine-associated disorder, a genetic disease, cancer, an infection, an immunological disease, an indication treated with hormone, growth factor and/or protein replacement, or a combination thereof.

A method for identifying an agent that modulates the expression or activity of a target protein identified in the Sequence Listing, in Table A, or a of the foregoing, comprising:

• a) contacting a protein identified in the Sequence Listing, in Table A, or a variant of the foregoing with an agent;
• and
• b) determining whether the agent modulates the expression or activity of the target protein,
• wherein a difference in the expression or activity of the target protein that has been contacted with the agent compared to a reference for the expression or activity of the target protein indicates that the agent modulates the expression or activity of the target protein.