LIFE IN THE 21ST CENTURY: Startups Flock to Turn Young Blood Into an Elixir of Youth. “Beneath all the hype is some striking science. Blood, particularly the yellow liquid part of it known as plasma, is chock full of proteins and other compounds that act like a readout of how all the cells in the body are functioning. Research has shown that the ratios of those components change as animals, including humans, age. Older blood carries more signs of tissue damage than young blood, which often contains compounds that can stimulate cell growth and repair. Elevian has singled out one of these proteins, a growth differentiation factor known as GDF11, as the chief source of young blood’s rejuvenating effects. At the outset, the company is developing drugs based on GDF11 to treat Alzheimer’s, coronary heart disease, and age-related muscle dysfunction. But its founders say any disease of the elderly is on the table.”