N-acetyl mannosamine as a therapeutic agent

A method of treating a kidney disease or condition in a mammal in need thereof comprising administering orally an effective amount of a sialic acid precursor, N-acetyl mannosamine or a derivative thereof, to the mammal to thereby treat a kidney disease or condition in the mammal, wherein the derivative consists of Formula I;

• wherein:
• R1, R3, R4, or R5 is hydrogen, lower alkanoyl, carboxylate or lower alkyl;
• and R2 is lower alkyl, lower alkanoylalkyl, or lower alkyl alkanoyloxy, wherein the kidney disease or condition is selected from podocytopathy, minimal change nephrosis, focal and segmental glomerulosclerosis, membranous glomerulonephritis, glomerular basement membrane disease, nephrotic syndrome or other kidney disease or condition with hyposialylation.