Acidic and neutral sialidase in the erythrocyte membrane of type 2 diabetic patients.
The behavior of the 2 sialidase forms present in the erythrocyte membrane was investigated in 117 subjects with type 2 diabetes mellitus versus 95 healthy controls. A significant increase of the acidic form of sialidase, which is anchored to the membrane by a glycosylphosphatidylinositol bridge, was observed in erythrocyte resealed membranes. On the contrary, the neutral form of the enzyme, the only one capable of removing lipid- and protein-bound sialic acid from endogenous and exogenous sialoderivatives, was significantly reduced with a consequent increase of erythrocyte membrane total sialic acid content. Disease duration, therapy, glycemia, parameters of metabolic control, and presence of complications, except nephropathies, had no influence on the tested enzyme activities. Diabetic subjects showed a different erythrocyte age distribution, with an almost double proportion of young red cells and only one quarter of senescent ones compared with controls. In young erythrocytes, diabetic and control subjects had the same distribution of the 2 enzymes, while in senescent cells the acidic enzyme was increased 3.5-fold and the neutral form was reduced by half in the diabetic subjects. The increase of both acidic sialidase and total membrane-bound sialic acid, together with an overpresence of young red cells in diabetics, suggests that in this pathological condition there might be an altered aging process with a diminished expression of the neutral form of the enzyme and an increase of bound sialic acid. It has been suggested that the expression of the neutral enzyme requires some activation mechanism that is impaired in diabetes.
Venerando
Bruno
B
Department of Medical Chemistry and Biochemistry, School of Medicine, University of Milan, LITA, Via Fratelli Cervi, 93-20090 Segrate, Milan, Italy. bruno.venerando@unimi.it
Fiorilli
Amelia
A
Croci
Gianluigi
G
Tringali
Cristina
C
Goi
Giancarlo
G
Mazzanti
Laura
L
Curatola
Giovanna
G
Segalini
Giovanni
G
Massaccesi
Luca
L
Lombardo
Adriana
A
Tettamanti
Guido
G
D000328:Adult; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D004905:Erythrocyte Aging; D004910:Erythrocyte Membrane / Q000201:enzymology* / Q000378:metabolism; D004912:Erythrocytes / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008875:Middle Aged; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D009439:Neuraminidase / Q000378:metabolism*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010738:Type C Phospholipases / Q000378:metabolism
D010738:Type C Phospholipases; D009439:Neuraminidase; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D019158:N-Acetylneuraminic Acid