Identification of a new SERPINC1 mutation in a Kazak family that alters the heparin binding capacity of antithrombin

Exploring antithrombin: insights into its physiological features, clinical implications and analytical techniques

Antithrombin is an essential protein that acts as a natural anticoagulant in the human body. It is synthesized by the liver and belongs to the serine protease inhibitors, which are commonly referred to as the SERPINS superfamily. The antithrombin molecule comprises 432 amino acids and has a molecular weight of approximately 58 200 D. It consists of three domains, including an amino-terminal domain, a carbohydrate-rich domain, and a carboxyl-terminal domain. The amino-terminal domain binds with heparin, whereas the carboxyl-terminal domain binds with serine protease. Antithrombin is a crucial natural anticoagulant that contributes approximately 60-80% of plasma anticoagulant activities in the human body. Moreover, antithrombin has anti-inflammatory effects that can be divided into coagulation-dependent and coagulation-independent effects. Furthermore, it exhibits antitumor activity and possesses a broad range of antiviral properties. Inherited type I antithrombin deficiency is a quantitative disorder that is characterized by low antithrombin activity due to low plasma levels. On the other hand, inherited type II antithrombin deficiency is a qualitative disorder that is characterized by defects in the antithrombin molecule. Acquired antithrombin deficiencies are more common than hereditary deficiencies and are associated with various clinical conditions due to reduced synthesis, increased loss, or enhanced consumption. The purpose of this review was to provide an update on the structure, functions, clinical implications, and methods of detection of antithrombin.

Heparin sensitivity and postoperative blood loss in patients undergoing cardiac surgery with cardiopulmonary bypass

BACKGROUND

Heparin-associated coagulation disorder is an important factor related to postoperative bleeding in patients undergoing cardiac surgery with cardiopulmonary bypass. Currently, the relationship between heparin sensitivity and postoperative bleeding is unknown.

OBJECTIVE

To investigate the relationship between individual heparin sensitivity and postoperative blood loss in patients undergoing cardiac surgery.

DESIGN

Prospective controlled study.

SETTING

Tertiary teaching hospital, Urumqi, Xinjiang, PR China. The study was conducted from January 2016 to August 2018.

PATIENTS

A total of 195 adult patients undergoing cardiac valve replacement surgery were included.

INTERVENTION

After initial heparin dosing (2.5 mg kg), patients were divided into three groups according to the whole blood activated clotting time (ACT): group A, insensitive group (ACT < 480 s); group B, sensitive group (480 s < ACT < 750 s); group C, hypersensitive group (ACT > 750 s).

MAIN OUTCOME MEASURES

First, intra-operative and 24-h postoperative blood loss. Second, antithrombin (AT) and factor X mRNA levels. Third, the plasma levels of AT-III and factor X. Fourth, heparin sensitivity index.

RESULTS

Blood loss was approximately 20 to 25% lower in group B than in groups A and C, which was statistically significant (P < 0.01). The AT-III mRNA levels increased from groups A to C and was positively associated with heparin sensitivity; the factor X mRNA levels changed in the opposite direction; a significant difference was observed between groups A and C (P < 0.05). The factor X plasma level showed the same trend as its mRNA. The AT-III plasma level was significantly lower in group B than in groups A and C (P < 0.05).

CONCLUSION

Postoperative blood loss is related to heparin sensitivity in patients undergoing cardiac surgery, and the moderately sensitive patients have the least postoperative bleeding. Individual variation in heparin sensitivity is related to the mRNA and plasma levels of AT-III and factor X.

TRIAL REGISTRATION

Registration number ChiCTR-RPC-17012259.

Heparin, coumarin, protein C, antithrombin, fibrinolysis and other clotting related resistances: old and new concepts in blood coagulation

The concept of resistance in blood coagulation has become important. In the past it was limited to the resistance shown by some patients to heparin, coumarin or aspirin. Subsequently, it was demonstrated that a mutation in a single clotting factor, FV, showed resistance to activated protein C. Since activated protein C is supposed to downregulate aFV and aFVIII, their persistence in the circulation gives origin to a hypercoagulable state. Recently antithrombin resistance has been defined. Several prothrombin abnormalities (dysprothrombinemias) have been shown to be resistant to the action of antithrombin. This is associated with the occurrence of a trombophilic state. Prothrombin may therefore be associated like FV with both a bleeding condition (prothrombin deficiency) and a thrombophilic state (some dysprothrombinemias). Finally, thrombomodulin resistance has been defined in liver cirrhosis. These patients often show an increased ratio between FVIII levels and protein C. This imbalance may be partly responsible for the frequent presence of portal vein thrombosis seen in these patients. All these studies have greatly increased the complexity of the clotting mechanisms and interactions. They have cast light on clinical events which had remained unknown or ill-defined.