Disclosed herein are methods of increasing the expression rate of epigenetic markers such as ELOVL2, KLF14, and PENK with administration of a therapeutic agent (e.g., vitamin C or its derivatives, analogs, metabolites, prodrugs, or pharmaceutically acceptable salts thereof). Also described herein are methods of modulating the methylation pattern of epigenetic markers such as ELOVL2, KLF14, and PENK with administration of a therapeutic agent (e.g., vitamin C or its derivatives, analogs, metabolites, prodrugs, or pharmaceutically acceptable salts thereof).