Blood coagulation and aortic wall integrity in rats with obesity-induced insulin resistance

Abstract

Obesity is an important factor in pathogenesis of disorders caused by chronic inflammation. Diet-induced obesity leads to dyslipidemia and insulin resistance (IR) that in turn provoke the development of type 2 diabetes and cardiovascular diseases. Thus, the aim of this work was to investigate the possible pro-atherogenic effects in the blood coagulation system and aortic wall of rats with obesity-induced IR. The experimental model was induced by a 6-month high-fat diet (HFD) in white rats. Blood samples were collected from 7 control and 14 obese IR rats. Prothrombin time (PT) and partial activated thromboplastin time (APTT) were performed by standard methods using Coagulometer Solar СТ 2410. Fibrinogen concentration in the blood plasma was determined by the modified spectrophotometric method. Levels of protein C (PC), prothrombin and factor X were measured using specific chromogenic substrates and activa­ting enzymes from snake venoms. Platelet aggregation was measured and their count determined using Aggregometer Solar AP2110. The aorta samples were stained by hematoxylin and eosin according to Ehrlich. Aortic wall thickness was measured using morphometric program Image J. Statistical analysis was performed using Mann-Whitney U Test. The haemostasis system was characterized by estimation of the levels of individual coagulation factors, anticoagulant system involvement and platelet reactivity. PT and APTT demonstrated that blood coagulation time strongly tended to decrease in obese IR rats in comparison to the control group. It was also detec­ted that 30% of studied obese IR rats had decreased factor X level, 40% had decreased level of prothrombin whereas fibrinogen concentration was slightly increased up to 3 mg/ml in 37% of obese IR rats. A prominent decrease of anticoagulant PC in blood plasma of obese rats was detected. Obese IR rats also had increased platelet count and higher rate of platelet aggregation in comparison to control animals. Histological analysis identified the disruption of aorta endothelium and tendency for the thickening of the aorta wall in the group with obesity-induced IR compared to the group of control rats. Changes of individual coagulation factors were assumed as the evidence of imbalance in the blood coagulation system. Increase of fibrinogen level, drop in PC concentration and pathological platelet reactivity were taken to corroborate the development of low-grade inflammation in obese IR rats. Instant generation of small amounts of thrombin in their blood plasma is expected. Since the aorta morphology assay detected the trend of its wall to thicken and the emergence of disruptions, we assumed there were initial stages of atherosclerosis and the danger of developing atherothrombosis. We detected an increase of blood coagulability and changes in aorta morphology in rats with obesity-induced IR which we assume indicate early development of atherosclerosis.

Keywords

• atherosclerosis
• blood coagulation
• fibrinogen
• haemostasis
• inflammation
• insulin resistance
• obesity