THEORY OF OBJECTS. ARTICLE 4. 2 META-COMPARTMENT: INTERSTITIAL FLUID. INTERSTITIAL FLUID AS A LATENT ENVIRONMENT FOR METABOLIC AGING: PP/IT PROFILE AND RESTORATION OF TISSUE HOMEOSTASIS IN PEOPLE 55+

Interstitial fluid is a medium of direct contact with cells, ensuring the delivery of nutrients, the removal of metabolic products, and the transfer of signaling molecules. After the age of 55, the metabolomic diversity of the interstitium decreases sharply: the number of detectable metabolites drops from 300–600 (potentially more than 10,000) to a critical threshold of less than 100, which corresponds to severe tissue ischemia, fibrosis, and loss of tissue homeostasis. However, no standard clinical analysis evaluates interstitial fluid. The article shows how the theory of objects allows you to measure the metabolic depletion of the interstitium, what diseases are associated with it, and how foods with a high PP/IT profile, including biogenic nutrition, restore tissue diversity. The PP/IT profile is a format for representing two independent indices: the density of objects (PP) and the toxicity index (IT). The record 49/2 means 49 beneficial molecular species and 2 harmful ones per 100 g of product — this is not a fraction, but two independent numbers next to each other, like blood pressure of 120/80. The profile is tied to the vector of product parameters: variety, origin, method of production, condition, freshness, and storage conditions. A monitoring protocol and practical recommendations for people 55+ are proposed.