Adiponectin, IL-6 and hsC-RP in Relation to Carotid Intima-media Thickness in B-thalassemia Patients

β-thalassemia result from a decrease in β- globin chains which result in a relative excess of α-globin chains . Approximately 1.5% of the population is estimated to be carriers for β-thalassemia . Around 60,000 new births are recorded to be affected by β-thalassemia per year in the world . In Egypt, it was estimated that 1000/1.5 million live births per year suffer from thalassemia; β -thalassemia is the most common type, with a carrier rate starting from 5.3%-9% . Depending on severity of hematological and clinical conditions, β-thalassemia is classified into three types, namely, β-thalassemia minor (β-TMI) (also called as carrier), β-thalassemia intermedia (β-TI) and β-thalassemia major (β-TM). The clinical severity of β-thalassemia intermedia has ranged from asymptomatic carrier state to severe transfusion-dependent type. β-Thalassemia minor is clinically asymptomatic but can be characterized by specific hematological features .

A high incidence of thromboembolic event has been observed in patients with β -thalassemia. Endothelial dysfunction occurred in those patients was attributed to peroxidative tissue injury because of continuous blood transfusions . Carotid atherosclerosis was positively associated with serum ferritin independent of traditional cardiovascular risk factors and transfusion-related iron overload in β-thalassemia major (β-TM) has been associated with the onset of cardiovascular complications, including cardiac dysfunction and vascular anomalies. Increased iron overload has also been reported in patients with non-transfusion dependent thalassemia (NTDT) Direct iron-related injury is responsible for different kinds of cardiovascular abnormalities, including progressive worsening of diastolic and systolic ventricular function, increased arterial stiffness and pulmonary hypertension .

It has previously demonstrated that both patients with β-TM and β-TI exhibit a global impairment of arterial vasorelaxation and increased carotid intima-media thickness (cIMT) as compared with control healthy subjects , those findings strongly support the notion that the severe arterial dysfunction in thalassemia may indicate an additional clinical vulnerability for venous thromboembolism. Epidemiologically, vascular events appear at a relatively young age with a four times higher incidence in β-TI as compared with β-TM patients . Carotid intima-media thickness is related both with incident and prevalent cardiovascular disease and is accepted measure of subclinical atherosclerosis . It also increases the risk for future myocardial infarction (MI) .

Lipid abnormalities have been detected in different types of β -thalassemia, and also in various hematological disorders including sickle cell disease, glucose-6-phosphate dehydrogenase (G6PD) deficiency, spherocytosis, aplastic anemia and myelodysplastic syndrome . Patients with β - thalassemia are at risk of developing premature atherosclerosis because of those abnormalities .

Inflammatory biomarkers including C-reactive proteins and cytokines (IL-6) are found to be increased in various inflammatory conditions and have been used by a number of workers as biomarker of inflammation in thalassemia . The iron laden insult to the tissues in transfusion dependent thalassemic patients has been monitored using the high sensitive C-reactive proteins as biomarker of inflammation and vascular risk .

High Sensitive C-reactive protein(hsC-RP)is clinically proven as a method to predict vascular risk and to enhance event rates in clinical trials. As hsC-RP and IL-6 levels measured in apparently healthy populations also predict future vascular risk; hsC-RP and IL-6 levels have been shown to correlate with endothelial dysfunction, arterial stiffness, and extent of subclinical atherosclerosis . IL-6 signaling has also been linked to plaque initiation and destabilization , to microvascular flow dysfunction , and to adverse outcomes in the setting of acute ischemia .

Adiponectin, an adipose tissue secreted protein, has been well recognized to exhibit insulin-sensitizing, anti-inflammatory and anti-atherosclerotic properties . Its level is associated with atherosclerosis markers such as inflammation, oxidative stress, and endothelial dysfunction . Its anti-inflammatory action, resulting in decreased production and inhibition of tumor necrosis factor-α (TNF-α) action, decreased IL-6 production, and human studies previously reported an inverse association between adiponectin level and C-RP , TNF-α and IL-6 .

Adiponectin varies according to body mass index with lower levels in obese individuals , in type 2 diabetes mellitus (T2DM) and in hypertensive patients.

Circulating low adiponectin levels (hypoadiponectinemia) is considered an independent risk factor for endothelial dysfunction and modulating vessel wall health . It has been correlated with elevated risk factors of atherosclerotic cardiovascular disease and associated with hypertension, dyslipidemia, and inflammation in both the general population and in diabetic patients .