Clinical Antiaging Medicine: Antiaging Medicine from the Perspective of the Kidneys

The kidneys are the main organs that eliminate unnecessary by-products of metabolism and excess body fluids. About 20–25% of cardiac output flows into the kidneys, and 150 L of blood is filtered daily, 99% of which is reabsorbed, producing 1.5 L of urine. Therefore, under physiological conditions, the kidneys are highly metabolically active organs, prone to oxidative stress, and highly susceptible to the effects of aging. The kidney volume does not change relatively until the age of 50, but it is known to decrease with age thereafter. Such changes are mainly due to a decrease in the volume of the renal cortex, and histologically, they present various characteristic pathological findings such as arteriosclerosis, glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Against the background of such pathological changes, the glomerular filtration rate (GFR), a functional indicator of the kidneys, decreases with age, leading to chronic kidney disease (CKD), which is a year-on-year decrease in GFR. Currently, Japan is one of the most aged societies in the world, with people aged 65 and over accounting for more than 25% of the total population, and CKD itself is a risk factor that determines the prognosis of life, including cardiovascular diseases, attracting social attention as an important issue.