Molecular mechanisms involved in the resistance of fibrin to clot lysis by plasmin in subjects with type 2 diabetes mellitus.
OBJECTIVE
The aim of this study was to determine the influence of type 2 diabetes on fibrinolysis by assessing interactions between the regulatory components of fibrinolysis and the fibrin clot, using fibrinogen purified from 150 patients with type 2 diabetes and 50 matched controls.


METHODS
Clot lysis rates were determined by confocal microscopy. Plasmin generation was measured using a plasmin-specific chromogenic substrate. Surface plasmon resonance was used to determine the binding interactions between fibrin, tissue-type plasminogen activator (t-PA) and Glu-plasminogen; cross-linkage of plasmin inhibitor to fibrin by factor XIII was determined using a microtitre plate assay.


RESULTS
Lysis of diabetic clots was significantly slower than that of controls (1.35 vs 2.92 microm/min, p<0.0001) and plasmin generation was significantly reduced. The equilibrium binding affinity between both t-PA and Glu-plasminogen and fibrin was reduced in diabetic subjects: t-PA, K (D)=0.91+/-0.3 micromol/l (control subjects), 1.21+/-0.5 micromol/l (diabetic subjects), p=0.001; Glu-plasminogen, K (D)=97+/-19 nmol/l (control subjects), 156+/-66 nmol/l (diabetic subjects), p=0.001. Cross-linkage of plasmin inhibitor to fibrin by factor XIII was enhanced in diabetic subjects, with the extent of in vitro cross-linkage correlating with in vivo glycaemic control (HbA(1c)) (r=0.59, p=0.001).


CONCLUSIONS
These results indicate that impairment of the fibrinolytic process in diabetic patients is mediated via a number of different mechanisms; these may be a consequence of post-translational modifications to fibrinogen molecules, resulting from their exposure to the abnormal metabolic milieu associated with diabetes.
Academic Unit of Molecular Vascular Medicine, Leeds Institute for Genetics, Health and Therapeutics, University of Leeds, Clarendon Way, Leeds LS1 3EX, UK.
E J
EJ
Dunn
H
H
Philippou
R A S
RA
Ariëns
P J
PJ
Grant
D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D004351:Drug Resistance; D004789:Enzyme Activation; D005176:Factor XIII / Q000302:isolation & purification; D005260:Female; D005337:Fibrin / Q000494:pharmacology*; D005340:Fibrinogen / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D005341:Fibrinolysin / Q000494:pharmacology*; D006442:Glycated Hemoglobin / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D012016:Reference Values; D020349:Surface Plasmon Resonance
D001786:Blood Glucose; D005176:Factor XIII; D005337:Fibrin; D005340:Fibrinogen; D005341:Fibrinolysin; D006442:Glycated Hemoglobin