Avinash Kundur

Bilirubin, platelet activation and heart disease: A missing link to cardiovascular protection in Gilbert's syndrome?

Gilberts syndrome (GS) is a relatively common condition, inducing a benign, non-hemolytic, unconjugated hyperbilirubinemia. Gilberts Syndrome is associated with mutation in the Uridine Glucuronosyl Transferase 1A1 (UGT1A1) gene promoter, reducing UGT1A1 activity, which normally conjugates bilirubin allowing its elimination from the blood. Individuals with GS demonstrate mildly elevated plasma antioxidant capacity caused by elevated levels of unconjugated bilirubin (UCB), reduced thiols and glutathione. Interestingly, the development of, and risk of mortality from, cardiovascular disease is remarkably reduced in GS individuals. An explanation for this protection may be explained by bilirubins ability to inhibit multiple processes that induce platelet hyper-reactivity and thrombosis, thus far under-appreciated in the literature. Reactive oxygen species are produced continuously via metabolic processes and have the potential to oxidatively modify proteins and lipids within cell membranes, which may encourage the development of thrombosis and CVDs. Oxidative stress induced platelet hyper-reactivity significantly increases the risk of thrombosis, which can potentially lead to tissue infarction. Here, we discuss the possible mechanisms by which increased antioxidant status might influence platelet function and link this to cardiovascular protection in GS. In summary, this is the first article to discuss the possible role of bilirubin as an anti-thrombotic agent, which inhibits platelet activation and potentially, organ infarction, which could contribute to the reduced mortality rate in mildly hyperbilirbinemic individuals.

Unconjugated bilirubin inhibits collagen induced platelet activation

Gilberts syndrome (GS) individuals have mildly elevated serum unconjugated bilirubin (UCB) concentrations and are protected against the development of cardiovascular diseases (CVD). Although UCB has antioxidant properties, which could delay atherosclerotic plaque development, evidence suggests UCB might also affect haemostasis, subsequently influencing thrombus formation after atherosclerotic plaque rupture. The aim of this study was to reveal the in-vitro effect of UCB on platelet function and haemostatic factors at physiologically relevant concentrations seen in GS. Blood samples were collected from 16 healthy volunteers (mean age 25 ± 5) for full blood examination. A final concentration of approximately 35 ± 4.0 µmol/L of UCB was obtained by adding 1.25 µL of UCB stock solution to 250 µL of sample, to study its effect on platelet aggregation, coagulation and lipid profile. Collagen induced platelet aggregation was significantly inhibited in platelet rich plasma treated with UCB. Coagulation and lipid profile did not change by the in-vitro addition of UCB. These data are the first to show that mildly (but physiologically) elevated UCB inhibits platelet activity in plasma via a mechanism specifically related to collagen induced platelet activation. These findings support a novel mechanism which might further explain protection from CVD by mildly elevated levels of UCB, thus reducing the risk of thrombus formation by inhibition of collagen-induced platelet aggregation.

Occupational health and metabolic risk factors: A pilot intervention for transport workers.

OBJECTIVES Heavy vehicle transport workers have a high risk of obesity and obesity-related disorders including cardiovascular disease and diabetes. Sedentary nature of their work makes a healthy work and lifestyle balance difficult to achieve. Educational interventions that promote behavioral changes have been shown to be effective in various group settings. The aims of this study were to determine the prevalence of metabolic risk factors among a population of urban bus drivers; to deliver a 3-month educational intervention specifically tailored for the workplace environment of transport workers; and to evaluate the efficacy of the intervention through quantitative measurements and qualitative feedback. MATERIAL AND METHODS Thirty-three bus drivers from depots in south Queensland were recruited for the study. Baseline metabolic data were collected through anthropometric measurements, blood collection and diet/lifestyle questionnaires. Metabolic risk factors that were analyzed included: waist circumference, blood pressure, fasting glucose, blood triglycerides and high density lipoprotein cholesterol (HDL-C). Three interactive seminars were delivered over a 3-month period. At the end of the period, data collection was repeated. RESULTS At the commencement of the study, 35% of the participants exhibited ≥ 3 of the metabolic risk factors that characterize metabolic syndrome. This is higher than the reported prevalence in the general Australian population (22.1%). A total 21 of the 33 participants remained committed to the intervention and provided pre and post intervention data. Of these, 28% (N = 6) showed a decrease in one or more of the risk factors associated with metabolic syndrome. There was a significant increase in the average HDL-C after the intervention. Qualitative feedback indicated that the workers benefited from the program, especially regarding their awareness of the risks associated with their profession. CONCLUSIONS This pilot study demonstrates that lifestyle education seminars specifically tailored for the workplace can have an impact on the health behaviors of transport workers.

Mildly elevated unconjugated bilirubin is associated with reduced platelet activation-related thrombogenesis and inflammation in Gilbert’s syndrome

Abstract Gilbert’s syndrome (GS) is associated with a mild unconjugated hyperbilirubinemia, increased circulating antioxidant capacity, and reduced cardiovascular disease (CVD) risk. The current study investigated whether mildly elevated circulating unconjugated bilirubin (UCB) is negatively associated with multiple thrombotic risk factors including platelet activity, hemostatic function, and inflammation in individuals with GS. Blood samples were collected from matched GS and control subjects (14 per group). Activation-dependent platelet surface marker expression of PAC-1 (binds to GPIIb/IIIa surface receptors on activated platelets) and CD62P (marker for P-selectin released from activated degranulated platelets) was assessed in adenosine diphosphate (ADP)-stimulated platelets using flow cytometry. Exogenous agonists, ADP, collagen, and arachidonic acid (AA), were used to stimulate platelet aggregation. A statistically significant decrease in the expression of P-selectin (P = 0.030) on activated platelets was observed in GS subjects. Collagen and AA-induced platelet aggregation were significantly (P = 0.018; P = 0.032 for respective agonists) reduced in GS versus control group. Elevated UCB (P = 0.001) and high density lipoprotein (P = 0.033) in addition to reduced low density lipoprotein (P = 0.024) and high sensitive C-reactive protein (P = 0.043) were also observed in GS when compared to the control group. Reduced P-selectin expression suggests decreased platelet activation-dependent degranulation, while reduced platelet aggregation by AA and collagen indicates a quantitative decrease in platelet aggregation consequently targeting the cyclooxygenase-1 and GP VI pathways, respectively. These findings are the first to demonstrate that the activation of platelets is mildly inhibited in individuals with GS, an effect that might contribute to protection from platelet hyperactivation-induced thrombosis and thus cardiovascular mortality in individuals with benign hyperbilirubinemia.

Oxidative stress biomarkers in type 2 diabetes mellitus for assessment of cardiovascular disease risk

AIMS Type-2 Diabetes Mellitus (T2DM) is one of the most prevalent and progressive metabolic conditions affecting approximately 8.5% of the global population. Individuals with T2DM have a significantly increased risk of developing chronic conditions such as cardiovascular disease (CVD) and its associated complications, therefore, it is of great importance to establish strategies for combatting T2DM and its associated chronic conditions. Current literature has identified several biomarkers that are known to play a key role in the pathogenesis of CVD. Many of these biomarkers affecting CVD are influenced by an increase in oxidative stress as seen in T2DM. The purpose of this review is to analyse and correlate the oxidative stress-related biomarkers that have been identified in the literature to provide an updated summary of their significance in CVD risk factors. DATA SYNTHESIS This review has analysed current research on T2DM, CVD, and oxidative stress. Four key cardiovascular risk factors: thrombosis, inflammation, vascular homeostasis and cellular proliferation were searched to identify potential biomarkers for this review. These biomarkers stem from seven major cellular pathways; NF-κB, Keap1-Nrf2, protein kinase-C, macrophage activation, arachidonic acid mobilisation, endothelial dysfunction and advanced glycation end products. CONCLUSIONS The pathways and biomarkers were analysed to show their role as contributing factors to CVD development and a summary is made regarding the assessment of cardiovascular risk in T2DM individuals.

Plasma Cell Disorders

This chapter presents two cases of plasma cell disorder. The final diagnoses are plasma cell leukaemia and plasma cell myeloma. There are blood film images of the diagnostic morphology for each case and these include images of plasma cell and rouleaux presentation.

Nonimmune Haemolytic Disorders (RBC Metabolic Abnormalities)

This chapter presents two cases of nonimmune haemolytic disorders (RBC metabolic disorders). The final diagnosis for these cases was G6PD deficiency and pyruvate kinase deficiency. Differential diagnoses considered were sickle cell anaemia, hereditary spherocytosis, drug-induced haemolytic anaemia, autoimmune haemolytic anaemia, thalassaemia, and haemoglobin E disease. There are blood film images of the diagnostic morphology for each case and these include anisocytosis, polychromasia, bite cells, blister cells, target cells spherocytes, and Pappenheimer cells.

Myeloproliferative/Myelodysplastic Disorders

This chapter presents six examples of myeloproliferative/myelodysplastic disorders. Final diagnoses include chronic myeloid leukaemia (CML), polycythaemia vera (PV), essential thrombocytopenia (ET), myelofibrosis (MF), chronic myelomonocytic leukaemia (CMML), refractory anaemia with ring sideroblasts (RARS), and refractory anaemia with excess blasts (RAEB). Each case also lists the bone marrow, cytogenetic tests, molecular tests, biochemistry, and NAP score results that led to the final diagnosis. There are also blood film images of the diagnostic features for each diagnosis, e.g. basophils, eosinophils, giant platelets, teardrop cells, hypersegmentation, hypogranular neutrophils, and blasts.

Nonimmune Haemolytic Disorders (RBC Membrane Abnormalities)

This chapter presents six cases. The final diagnosis includes hereditary spherocytosis, hereditary elliptocytosis, hereditary stomatocytosis, Melanesian ovalocytosis, hereditary pyropoikilocytosis, and paroxysmal nocturnal haemoglobinuria. The pathophysiology of each condition is explained and the tests listed that confirm the diagnosis. There are blood film images of the diagnostic morphology for each case and these include spherocytosis, elliptocytosis, stomatocyte, target cell, poikilocytosis, and polychromasia.

Chronic Lymphoproliferative Disorders

This chapter presents four cases of chronic lymphoproliferative disorders. Final diagnoses include chronic lymphocytic leukaemia (CLL), prolymphocytic leukaemia (PLL), and hairy cell leukaemia (HCL). Each case details the bone marrow, immunophenotype, cytogenetic, and cytochemistry test results that led to the diagnosis. Differential diagnoses are also listed. There are also blood film images of the diagnostic features for each diagnosis and these include smear cells, abnormal lymphocytes, spherocytes, prolymphocyte, and hairy cells.