Indu Singh | Griffith University (original) (raw)

Papers by Indu Singh

Research paper thumbnail of An Investigation into Gilbert's Syndrome: Understanding the Role of Unconjugated Bilirubin in Targeting Platelet and Haemostatic Mechanisms Associated with Thrombotic Risk Factors

Gilbert's syndrome (GS) is a common genetic condition associated with mildly elevated unconju... more Gilbert's syndrome (GS) is a common genetic condition associated with mildly elevated unconjugated bilirubin (UCB) concentrations and increased protection against development of cardiovascular disease (CVD). Mutation in the uridine diphosphate glucuronosyltransferase (UGT1A1) gene causing a reduction in UGT1A1 enzyme activity that is responsible for conjugation and elimination of UCB, is considered as the cause for GS. Numerous studies have shown that elevated levels of UCB are negatively associated with risk of developing CVD. While, several in vitro and in vivo trials have shown that UCB at physiological concentrations can improve endothelial function, lipid profile and reduce vascular inflammation, thereby imparting its cardiovascular protection. Cardiovascular disease is a major cause of death globally, an estimated 17.3 million CVD related deaths are reported annually by the World Health Organization (WHO), making it the largest cause of human mortality. Furthermore, severa...

Research paper thumbnail of Anthocyanin supplementation inhibits secretion of pro-inflammatory cytokines in overweight and obese individuals

Journal of Functional Foods, 2019

Research paper thumbnail of The Synergistic Effect of Taurine and Caffeine on Platelet Activity and Hemostatic Function

Several studies have shown the deleterious effects of energy drinks, containing taurine and caffe... more Several studies have shown the deleterious effects of energy drinks, containing taurine and caffeine, on cardiac health. This study aimed to examine synergistic effect of taurine and caffeine on platelets and haemostasis because platelet hyperactivity is a known predictor of cardiovascular diseases. Blood from twelve healthy volunteers aged 18 – 60 years was incubated with 500 μM taurine and 700 μM caffeine individually or together. Platelet activity was evaluated using platelet aggregation assays induced by ADP and collagen, and, haemostatic function by coagulation profile testing, glucose, lipid profile and inflammation marker C- reactive protein assessment (CRP). The optimal time and doses of taurine and caffeine required to inhibit platelet hyperactivity in vitro were established. A combined action of lower doses of taurine and caffeine (T+C) inhibited platelet aggregation, induced by ADP and collagen, greater than taurine or caffeine individually (p < 0.05). Taurine and T+C ...

Research paper thumbnail of The ex vivo antiplatelet activation potential of fruit phenolic metabolite hippuric acid

Food & Function, 2015

Active metabolite of polyphenol intake, hippuric acid, reduces platelet activation-related confor... more Active metabolite of polyphenol intake, hippuric acid, reduces platelet activation-related conformational change and de-granulationex vivothereby alleviating thrombogenesis.

Research paper thumbnail of Diet containing cocoa powder with flavanols and procyanidins inhibits platelet function

Flavanols and their related procyanidins are flavonoids found in foods such as tea, wine and coco... more Flavanols and their related procyanidins are flavonoids found in foods such as tea, wine and cocoa powder, and are powerful antioxidants in vitro (1). The consumption of a high intake of a cocoa beverage, containing 897 mg total flavanols and oligomeric procyanidins, inhibited platelet activation and function in an acute study (6 hours) in humans (2). The current study investigated the long-term effect of a lower dose of flavanols and procyanidins from cocoa powder using a double blind, randomised, placebo-controlled study with 32 subjects. Subjects were stratified into active and placebo groups based on plasma vitamin C levels prior to the study. Subjects on the active diet consumed 234 mg of flavanols and procyanidins (CocoaPro™, Mars Inc) per day for 4 weeks, while subjects on the placebo tablet consumed an identical tablet made from cocoa powder with a low level of flavanols and procyanidins (< 1mg) for 4 weeks. Dietary restrictions were implemented to control the amount of flavonoids from the diet. Weighed food records, anthropometric measurements and fasting blood tests were performed at day 0 and 28. Plasma was analysed for F 2-isoprostanes, TBARS, TRAP, the flavanols catechin and epicatechin, vitamin C, E, A, carotenoids and uric acid to determine the effect of oxidative damage. Plasma was also analysed for lipids and lipoproteins, while whole blood was analysed for platelet aggregation and platelet activation using flow cytometry. Results showed that the plasma levels of epicatechin, catechin and vitamin C were significantly increased in the active group at day 28 and that platelet aggregation and activation (% of activated platelets) was significantly lower in the active group (p < 0.05) compared with the control, using two different agonists, at day 28. There were no significant differences between groups for vitamin E, A, the carotenoids nor plasma lipids and lipoproteins. In terms of antioxidant protection, there were no significant differences in TBARS, TRAP and F2-isoprostanes between groups. These results with a relatively low intake of cocoa flavanols and procyanidins over a 4-week period support the short-term data showing benefits on platelet function. In vitro data suggest that flavonoids inhibit platelet function by reducing H 2 O 2 production, and in turn, phospholipase C activation in the platelet (3). Further investigations with different levels of supplementation are recommended.

Research paper thumbnail of Consumption of anthocyanin-rich Queen Garnet plum juice reduces platelet activation related thrombogenesis in healthy volunteers

Journal of Functional Foods, 2015

Research paper thumbnail of A review of the mechanisms and effectiveness of dietary polyphenols in reducing oxidative stress and thrombotic risk

Journal of Human Nutrition and Dietetics, 2013

Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, 5 ... more Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, 5 flavonols, catechins and phenolic acids possess antioxidant properties, therefore, might be important 6 in preventing oxidative-stress-induced platelet activation and attenuate adverse haemostatic function. 7 Free radicals including reactive oxygen and nitrogen species promote oxidative stress, leading to 8 platelet hyper-activation and risk of thrombosis. Consumption of antioxidant/polyphenol rich foods 9 might, therefore, impart anti-thrombotic and cardiovascular protective effects via their inhibition of 10 platelet hyper-activation or aggregation. Most commonly used antiplatelet drugs such as aspirin block 11 the cyclooxygenase-1 (COX-1) pathway of platelet activation similar to the action of antioxidants in 12 neutralizing hydrogen peroxide with a similar effect on thromboxane production via COX-1 pathway. 13 Polyphenols also target various additional platelet activation pathways e.g. by blocking platelet-ADP, 14 collagen receptors; alleviating fibrinogen binding to platelet surface (GPIIb-IIIa) receptors reducing 15 further platelet recruitment for aggregation and inhibiting platelet degranulation. Due to the ability of 16 polyphenols to target additional pathways of platelet activation, they may have the potential to 17 substitute or complement currently used anti-platelet drugs in sedentary, obese, pre-diabetic or 18 diabetic populations who can be resistant or sensitive to pharmacological antiplatelet therapy. 19 20 21 22

Research paper thumbnail of Effects of gamma-tocopherol supplementation on thrombotic risk factors

The antioxidant activity of vitamin E is derived primarily from alpha-tocopherol (α-T) and gammat... more The antioxidant activity of vitamin E is derived primarily from alpha-tocopherol (α-T) and gammatocopherol (γ-T). Results of epidemiological studies have demonstrated an inverse relationship between vitamin E intake and coronary disease. However, the results of clinical trials using α-T are equivocal. We determined the effect of 5 weeks of 100 mg/d or 200 mg/d γ-T supplementation on thrombotic markers such as platelet reactivity, lipid profile and the inflammation marker C-reactive protein (CRP). Methods and results: Fourteen healthy subjects consumed 100 mg/day while 13 consumed 200 mg/d of γ-T and 12 received placebo (soybean capsules with less than 5 mg/d γ-T) in a double-blinded parallel study design. Fasting pre and post dose blood samples were analysed. Blood γ-T concentrations increased significantly (p<0.05) relative to dose during the intervention period. Both groups receiving active ingredients showed significantly lower platelet activation after supplementation (p<0.05). Subjects consuming 100 mg/d γ-T had significantly decreased LDL cholesterol, platelet aggregation and mean platelet volume (MPV) (p<0.05). Little effect of γ-T was observed on other parameters. Conclusions: These data suggest that γ-T supplementation may have a permissive role in decreasing the risk of thrombotic events by improving lipid profile and reducing platelet activity.

Research paper thumbnail of The effects of polyphenols in olive leaves on platelet function

Nutrition Metabolism and Cardiovascular Diseases, 2008

Introduction: The phenolic compounds of olive leaves and olive oils in the Mediterranean diet hav... more Introduction: The phenolic compounds of olive leaves and olive oils in the Mediterranean diet have been associated with a reduced incidence of heart disease. Accordingly, antioxidant-rich diets may prevent the deleterious effects of oxidative metabolism by scavenging free radicals, thus inhibiting oxidation and delaying atherosclerosis. The process involves phospholipase C activation and arachidonic acid metabolism, and is thought to reduce hydrogen peroxide (H 2 O 2 ). In our study, an extract of Olea europaea L. leaves was used. The active phenolic compounds in this extract are part of the secoiridoid family, known for their capacity to scavenge H 2 O 2 . The results from this study will help to improve our understanding of effects of polyphenol antioxidants in olive leaf extract on platelet function. Methods: Full blood examination (FBE), platelet aggregation, and ATP release were performed on samples from fasting, normal, healthy male subjects. Platelet function at increasing concentrations of oleuropein was investigated through measures of platelet aggregation and ATP release from activated platelets. Results: Blood analysis (n [ 11) revealed a significant dose-dependant reduction in platelet activity with olive extract concentrations of 1.0% v/v (P < 0.001). ATP Release showed a similar pattern (P [ 0.02). Conclusions: Olive leaf polyphenols derived from O. europaea L. leaves inhibited in vitro platelet activation in healthy, non-smoking males. Further bioavailability studies need to be undertaken to determine the in vivo effect of extract on platelet function and to validate the present results. ª

Research paper thumbnail of Oxidative stress-induced insulin resistance in skeletal muscle cells is ameliorated by gamma-tocopherol treatment

European Journal of Nutrition, 2008

Background Oxidative stress-induced reactive oxygen species are associated with the clinical mani... more Background Oxidative stress-induced reactive oxygen species are associated with the clinical manifestation of insulin resistance. Evidence suggests that antioxidant treatment may reduce this incidence. Aim of the study This study determined whether glucose oxidase (GO)-induced insulin resistance in cultured skeletal muscle cells could be ameliorated by pre-treatment with gamma-tocopherol (GT). Methods Insulin sensitivity in L6 myotubes was assessed by 2-deoxy-d-[3H]-glucose uptake. The phosphorylation of distal insulin signaling proteins Akt and the Akt substrate AS160 were determined by western blot. Results One hour treatment with 100 mU/ml GO decreased insulin-stimulated glucose uptake (P P Conclusions High-dose (200 µM) GT treatment ameliorated oxidative stress-induced insulin resistance in cultured rat L6 skeletal muscle cells.

Research paper thumbnail of Effects of Seal Oil and Tuna-Fish Oil on Platelet Parameters and Plasma Lipid Levels in Healthy Subjects

Lipids, 2010

Fish are a rich source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two long-ch... more Fish are a rich source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two long-chain polyunsaturated n-3 fatty acids (LC n-3 PUFA) with cardiovascular benefits. A related but less-investigated LC n-3 PUFA, docosapentaenoic acid (DPA), is more common in seal oil and pasture-fed red meats. This study compared indicators of platelet function and plasma lipids in healthy volunteers given supplements containing these different fatty acids (FA) for 14 days. Subjects, randomised into three groups of ten, consumed capsules of tuna oil (210 mg EPA, 30 mg DPA, 810 mg DHA), seal oil (340 mg EPA, 230 mg DPA, 450 mg DHA) or placebo (sunola) oil. Supplementary LC n-3 PUFA levels were approximately 1 g/day in both fish and seal oil groups. Baseline dietary FA and other nutrient intakes were similar in all groups. Both fish and seal oil elevated platelet DHA levels (P P P = 0.01), a platelet activation marker negatively associated with DPA (P = 0.03) and EPA (P P = 0.03) and HDL-cholesterol levels increased (P = 0.01) with seal oil only. Hence, seal oil may be more efficient than fish oil at promoting healthy plasma lipid profiles and lowering thrombotic risk, possibly due to its high DPA as well as EPA content.

Research paper thumbnail of An Investigation into Gilbert's Syndrome: Understanding the Role of Unconjugated Bilirubin in Targeting Platelet and Haemostatic Mechanisms Associated with Thrombotic Risk Factors

Gilbert's syndrome (GS) is a common genetic condition associated with mildly elevated unconju... more Gilbert's syndrome (GS) is a common genetic condition associated with mildly elevated unconjugated bilirubin (UCB) concentrations and increased protection against development of cardiovascular disease (CVD). Mutation in the uridine diphosphate glucuronosyltransferase (UGT1A1) gene causing a reduction in UGT1A1 enzyme activity that is responsible for conjugation and elimination of UCB, is considered as the cause for GS. Numerous studies have shown that elevated levels of UCB are negatively associated with risk of developing CVD. While, several in vitro and in vivo trials have shown that UCB at physiological concentrations can improve endothelial function, lipid profile and reduce vascular inflammation, thereby imparting its cardiovascular protection. Cardiovascular disease is a major cause of death globally, an estimated 17.3 million CVD related deaths are reported annually by the World Health Organization (WHO), making it the largest cause of human mortality. Furthermore, severa...

Research paper thumbnail of Anthocyanin supplementation inhibits secretion of pro-inflammatory cytokines in overweight and obese individuals

Journal of Functional Foods, 2019

Research paper thumbnail of The Synergistic Effect of Taurine and Caffeine on Platelet Activity and Hemostatic Function

Several studies have shown the deleterious effects of energy drinks, containing taurine and caffe... more Several studies have shown the deleterious effects of energy drinks, containing taurine and caffeine, on cardiac health. This study aimed to examine synergistic effect of taurine and caffeine on platelets and haemostasis because platelet hyperactivity is a known predictor of cardiovascular diseases. Blood from twelve healthy volunteers aged 18 – 60 years was incubated with 500 μM taurine and 700 μM caffeine individually or together. Platelet activity was evaluated using platelet aggregation assays induced by ADP and collagen, and, haemostatic function by coagulation profile testing, glucose, lipid profile and inflammation marker C- reactive protein assessment (CRP). The optimal time and doses of taurine and caffeine required to inhibit platelet hyperactivity in vitro were established. A combined action of lower doses of taurine and caffeine (T+C) inhibited platelet aggregation, induced by ADP and collagen, greater than taurine or caffeine individually (p < 0.05). Taurine and T+C ...

Research paper thumbnail of The ex vivo antiplatelet activation potential of fruit phenolic metabolite hippuric acid

Food & Function, 2015

Active metabolite of polyphenol intake, hippuric acid, reduces platelet activation-related confor... more Active metabolite of polyphenol intake, hippuric acid, reduces platelet activation-related conformational change and de-granulationex vivothereby alleviating thrombogenesis.

Research paper thumbnail of Diet containing cocoa powder with flavanols and procyanidins inhibits platelet function

Flavanols and their related procyanidins are flavonoids found in foods such as tea, wine and coco... more Flavanols and their related procyanidins are flavonoids found in foods such as tea, wine and cocoa powder, and are powerful antioxidants in vitro (1). The consumption of a high intake of a cocoa beverage, containing 897 mg total flavanols and oligomeric procyanidins, inhibited platelet activation and function in an acute study (6 hours) in humans (2). The current study investigated the long-term effect of a lower dose of flavanols and procyanidins from cocoa powder using a double blind, randomised, placebo-controlled study with 32 subjects. Subjects were stratified into active and placebo groups based on plasma vitamin C levels prior to the study. Subjects on the active diet consumed 234 mg of flavanols and procyanidins (CocoaPro™, Mars Inc) per day for 4 weeks, while subjects on the placebo tablet consumed an identical tablet made from cocoa powder with a low level of flavanols and procyanidins (< 1mg) for 4 weeks. Dietary restrictions were implemented to control the amount of flavonoids from the diet. Weighed food records, anthropometric measurements and fasting blood tests were performed at day 0 and 28. Plasma was analysed for F 2-isoprostanes, TBARS, TRAP, the flavanols catechin and epicatechin, vitamin C, E, A, carotenoids and uric acid to determine the effect of oxidative damage. Plasma was also analysed for lipids and lipoproteins, while whole blood was analysed for platelet aggregation and platelet activation using flow cytometry. Results showed that the plasma levels of epicatechin, catechin and vitamin C were significantly increased in the active group at day 28 and that platelet aggregation and activation (% of activated platelets) was significantly lower in the active group (p < 0.05) compared with the control, using two different agonists, at day 28. There were no significant differences between groups for vitamin E, A, the carotenoids nor plasma lipids and lipoproteins. In terms of antioxidant protection, there were no significant differences in TBARS, TRAP and F2-isoprostanes between groups. These results with a relatively low intake of cocoa flavanols and procyanidins over a 4-week period support the short-term data showing benefits on platelet function. In vitro data suggest that flavonoids inhibit platelet function by reducing H 2 O 2 production, and in turn, phospholipase C activation in the platelet (3). Further investigations with different levels of supplementation are recommended.

Research paper thumbnail of Consumption of anthocyanin-rich Queen Garnet plum juice reduces platelet activation related thrombogenesis in healthy volunteers

Journal of Functional Foods, 2015

Research paper thumbnail of A review of the mechanisms and effectiveness of dietary polyphenols in reducing oxidative stress and thrombotic risk

Journal of Human Nutrition and Dietetics, 2013

Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, 5 ... more Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, 5 flavonols, catechins and phenolic acids possess antioxidant properties, therefore, might be important 6 in preventing oxidative-stress-induced platelet activation and attenuate adverse haemostatic function. 7 Free radicals including reactive oxygen and nitrogen species promote oxidative stress, leading to 8 platelet hyper-activation and risk of thrombosis. Consumption of antioxidant/polyphenol rich foods 9 might, therefore, impart anti-thrombotic and cardiovascular protective effects via their inhibition of 10 platelet hyper-activation or aggregation. Most commonly used antiplatelet drugs such as aspirin block 11 the cyclooxygenase-1 (COX-1) pathway of platelet activation similar to the action of antioxidants in 12 neutralizing hydrogen peroxide with a similar effect on thromboxane production via COX-1 pathway. 13 Polyphenols also target various additional platelet activation pathways e.g. by blocking platelet-ADP, 14 collagen receptors; alleviating fibrinogen binding to platelet surface (GPIIb-IIIa) receptors reducing 15 further platelet recruitment for aggregation and inhibiting platelet degranulation. Due to the ability of 16 polyphenols to target additional pathways of platelet activation, they may have the potential to 17 substitute or complement currently used anti-platelet drugs in sedentary, obese, pre-diabetic or 18 diabetic populations who can be resistant or sensitive to pharmacological antiplatelet therapy. 19 20 21 22

Research paper thumbnail of Effects of gamma-tocopherol supplementation on thrombotic risk factors

The antioxidant activity of vitamin E is derived primarily from alpha-tocopherol (α-T) and gammat... more The antioxidant activity of vitamin E is derived primarily from alpha-tocopherol (α-T) and gammatocopherol (γ-T). Results of epidemiological studies have demonstrated an inverse relationship between vitamin E intake and coronary disease. However, the results of clinical trials using α-T are equivocal. We determined the effect of 5 weeks of 100 mg/d or 200 mg/d γ-T supplementation on thrombotic markers such as platelet reactivity, lipid profile and the inflammation marker C-reactive protein (CRP). Methods and results: Fourteen healthy subjects consumed 100 mg/day while 13 consumed 200 mg/d of γ-T and 12 received placebo (soybean capsules with less than 5 mg/d γ-T) in a double-blinded parallel study design. Fasting pre and post dose blood samples were analysed. Blood γ-T concentrations increased significantly (p<0.05) relative to dose during the intervention period. Both groups receiving active ingredients showed significantly lower platelet activation after supplementation (p<0.05). Subjects consuming 100 mg/d γ-T had significantly decreased LDL cholesterol, platelet aggregation and mean platelet volume (MPV) (p<0.05). Little effect of γ-T was observed on other parameters. Conclusions: These data suggest that γ-T supplementation may have a permissive role in decreasing the risk of thrombotic events by improving lipid profile and reducing platelet activity.

Research paper thumbnail of The effects of polyphenols in olive leaves on platelet function

Nutrition Metabolism and Cardiovascular Diseases, 2008

Introduction: The phenolic compounds of olive leaves and olive oils in the Mediterranean diet hav... more Introduction: The phenolic compounds of olive leaves and olive oils in the Mediterranean diet have been associated with a reduced incidence of heart disease. Accordingly, antioxidant-rich diets may prevent the deleterious effects of oxidative metabolism by scavenging free radicals, thus inhibiting oxidation and delaying atherosclerosis. The process involves phospholipase C activation and arachidonic acid metabolism, and is thought to reduce hydrogen peroxide (H 2 O 2 ). In our study, an extract of Olea europaea L. leaves was used. The active phenolic compounds in this extract are part of the secoiridoid family, known for their capacity to scavenge H 2 O 2 . The results from this study will help to improve our understanding of effects of polyphenol antioxidants in olive leaf extract on platelet function. Methods: Full blood examination (FBE), platelet aggregation, and ATP release were performed on samples from fasting, normal, healthy male subjects. Platelet function at increasing concentrations of oleuropein was investigated through measures of platelet aggregation and ATP release from activated platelets. Results: Blood analysis (n [ 11) revealed a significant dose-dependant reduction in platelet activity with olive extract concentrations of 1.0% v/v (P < 0.001). ATP Release showed a similar pattern (P [ 0.02). Conclusions: Olive leaf polyphenols derived from O. europaea L. leaves inhibited in vitro platelet activation in healthy, non-smoking males. Further bioavailability studies need to be undertaken to determine the in vivo effect of extract on platelet function and to validate the present results. ª

Research paper thumbnail of Oxidative stress-induced insulin resistance in skeletal muscle cells is ameliorated by gamma-tocopherol treatment

European Journal of Nutrition, 2008

Background Oxidative stress-induced reactive oxygen species are associated with the clinical mani... more Background Oxidative stress-induced reactive oxygen species are associated with the clinical manifestation of insulin resistance. Evidence suggests that antioxidant treatment may reduce this incidence. Aim of the study This study determined whether glucose oxidase (GO)-induced insulin resistance in cultured skeletal muscle cells could be ameliorated by pre-treatment with gamma-tocopherol (GT). Methods Insulin sensitivity in L6 myotubes was assessed by 2-deoxy-d-[3H]-glucose uptake. The phosphorylation of distal insulin signaling proteins Akt and the Akt substrate AS160 were determined by western blot. Results One hour treatment with 100 mU/ml GO decreased insulin-stimulated glucose uptake (P P Conclusions High-dose (200 µM) GT treatment ameliorated oxidative stress-induced insulin resistance in cultured rat L6 skeletal muscle cells.

Research paper thumbnail of Effects of Seal Oil and Tuna-Fish Oil on Platelet Parameters and Plasma Lipid Levels in Healthy Subjects

Lipids, 2010

Fish are a rich source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two long-ch... more Fish are a rich source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two long-chain polyunsaturated n-3 fatty acids (LC n-3 PUFA) with cardiovascular benefits. A related but less-investigated LC n-3 PUFA, docosapentaenoic acid (DPA), is more common in seal oil and pasture-fed red meats. This study compared indicators of platelet function and plasma lipids in healthy volunteers given supplements containing these different fatty acids (FA) for 14 days. Subjects, randomised into three groups of ten, consumed capsules of tuna oil (210 mg EPA, 30 mg DPA, 810 mg DHA), seal oil (340 mg EPA, 230 mg DPA, 450 mg DHA) or placebo (sunola) oil. Supplementary LC n-3 PUFA levels were approximately 1 g/day in both fish and seal oil groups. Baseline dietary FA and other nutrient intakes were similar in all groups. Both fish and seal oil elevated platelet DHA levels (P P P = 0.01), a platelet activation marker negatively associated with DPA (P = 0.03) and EPA (P P = 0.03) and HDL-cholesterol levels increased (P = 0.01) with seal oil only. Hence, seal oil may be more efficient than fish oil at promoting healthy plasma lipid profiles and lowering thrombotic risk, possibly due to its high DPA as well as EPA content.