Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays a critical role in the formation of c... more Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays a critical role in the formation of cholesteryl esters from cholesterol and fatty acids, and is a potential target for treating hypercholesterolemia. We recently reported the significant effects of two human ACAT2 gene polymorphisms, 41A>G (Glu(14)Gly, rs9658625) and 734C>T (Thr(254)Ile, rs2272296), on plasma lipid levels and coronary artery disease susceptibility in a case-control association study. In the present study, we evaluated the possible biological influence of the two polymorphism using two approaches. In the first approach, the functional impact of the two polymorphisms was predicted in-silico using available web-based software, and in the second approach, the varying functions of the two polymorphisms were characterized in in vitro experiments, using ACAT2-deficient AC-29 cells. Our results show that the enzymatic activity of mutant Glu(14)Gly is approximately two times higher than wildtype, and that this increase is primarily due to the increased expression and/or stability of the mutant ACAT2 protein. These results suggest that the genetic variation at Glu(14)Gly is functionally important and may contribute to ACAT2 protein expression and stability.
This study investigated the early and long-term effects of atherogenic diet on hepatic gene expre... more This study investigated the early and long-term effects of atherogenic diet on hepatic gene expression, and the restorative effects of atorvastatin in treating hypercholesterolemia. Two groups of female C57BL/6J mice were fed standard chow or atherogenic diet for 1-week early phase study and two other groups for 10 weeks. The fifth group had daily 10 mg/kg atorvastatin injections for 3 weeks from week 8 of the atherogenic diet. Gene expression profiling was carried out with Affymetrix GeneChips. One-week atherogenic diet elevated 38 and inhibited 127 gene expressions, while 10-week atherogenic diet elevated 165 and inhibited 281 genes by more than twofold. Atorvastatin could restore 78.2% and 68%, respectively, of the genes to normal levels. Genes in the Insig (insulin-induced gene)-SREBP (sterol regulatory element binding proteins) pathway were mostly inhibited by atherogenic diet at week 1 but elevated at week 10. Of these, 65.2% were restored by atorvastatin. In conclusion, lipid...
Studies in health technology and informatics, 2007
Coronary artery disease (CAD) is a main cause of death in the world. Finding cost-effective metho... more Coronary artery disease (CAD) is a main cause of death in the world. Finding cost-effective methods to predict CAD is a major challenge in public health. In this paper, we investigate the combined effects of genetic polymorphisms and non-genetic factors on predicting the risk of CAD by applying well known classification methods, such as Bayesian networks, naïve Bayes, support vector machine, k-nearest neighbor, neural networks and decision trees. Our experiments show that all these classifiers are comparable in terms of accuracy, while Bayesian networks have the additional advantage of being able to provide insights into the relationships among the variables. We observe that the learned Bayesian Networks identify many important dependency relationships among genetic variables, which can be verified with domain knowledge. Conforming to current domain understanding, our results indicate that related diseases (e.g., diabetes and hypertension), age and smoking status are the most import...
This paper presents for the first time the design and fabrication of BioMEMS devices for living c... more This paper presents for the first time the design and fabrication of BioMEMS devices for living cells’ electrochemical impedance measurement under optical excitation. An interdigitated electrode design is adopted in order to increase the sensitivity of living cells’ impedance measurement. The magnitudes of the parasitic components were calculated and their influence on the chip performance was simulated. It is shown
The uTAS proposed the full incorporation of analytical procedures, which include sampling, sample... more The uTAS proposed the full incorporation of analytical procedures, which include sampling, sample preparation or pretreatment and actual analysis, into flowing systems. To incorporate a full uTAS, it is important to develop the individual microfluidic components. Microfilter is one of the microfluidic devices for sample preparation. This paper presents a fabrication method for a vertical silicon mesh structure depth filter as well as the application of white blood cell filtration. The results are also compared with another fabricated horizontal flow silicon filter.
ABSTRACT FSGS is a molecularly heterogeneous disease, and can be classified into primary or secon... more ABSTRACT FSGS is a molecularly heterogeneous disease, and can be classified into primary or secondary disease. Primary FSGS can be due to immune or genetic causes. To date, more than 20 genes have been implicated in FSGS. The discovery of so many FSGS genes, together with the advent of next-generation sequencing, has led to a paradigm shift in the genetic diagnosis and management of this disease. However, genetic screening in FSGS may not be so straightforward because of the difficulty in selection and prioritization of genes. It is challenging to appreciate the prevalence of mutations in the different genes based on the current literature due to heterogeneity of the studies and rarity of the disease. Clinicians need to understand the different methods of genetic screening available. These should be weighed against practical issues such as clinical urgency, financial costs, availability of expertise, and test accessibility. Clinicians should also consider the likelihood of a genetic etiology and the clinical impact of a genetic diagnosis to decide, with the patient and family, on the extent or “aggressiveness” of the genetic screening. The main impact of a genetic diagnosis in FSGS is on the use of immunosuppressive medications as well as on peri-transplant management involving the selection of live-related donors and risk of post-transplant recurrence.
An ultrasensitive electrochemical nucleic acid assay amplified by carbon nanotubes (CNTs)-based l... more An ultrasensitive electrochemical nucleic acid assay amplified by carbon nanotubes (CNTs)-based labels for the detection of leukemia oncogenes.
Henoch-Schönlein purpura (HSP) is a multifactorial inflammatory disease whose pathogenesis remain... more Henoch-Schönlein purpura (HSP) is a multifactorial inflammatory disease whose pathogenesis remains unknown. Pyrin encoded by the MEFV gene (NM_000243; OMIM 608107) is an important active member of the inflammasome and has been shown to affect the expression of many of the genes involved in immune and inflammatory responses. The aim of our study was to elucidate the possible roles of MEFV genetic variants on the susceptibility to HSP and its clinical outcomes in 78 patients with HSP and 189 controls in China. A significant association was found between the E148Q polymorphism (G->C) and HSP susceptibility (odds ratio 2.76, 95% confidence interval 1.76-4.34, P=0.0001). The C allele of E148Q was associated with joint involvement (P=0.014) but not with HSP nephritis (P=0.1). The clinical score was higher in subjects with the CC genotype than in those with the CG or GG genotype (4.13+/-3.53 vs. 1.94+/-1.70, respectively; P=0.011). P369S was not associated with HSP or other phenotypes. M694V and M680I were absent in our patients. Our results suggest that MEFV E148Q could be a contributory genetic factor to HSP and HSP-related joint syndromes.
This paper proposes a novel method to detect transparent living cells in a transparent microfluid... more This paper proposes a novel method to detect transparent living cells in a transparent microfluidic chamber by optical diffraction of an aperture or an aperture array. Through the analysis of the far-field diffraction pattern, one of the parameters of the cells, including the size, refractive index, or position, can be extracted by the analysis software developed in this paper. Calculations are carried out to discuss the key issues of this MEMS device, and our simulation is verified by diffraction patterns of transparent microparticles on fabricated apertures, recorded via a digital camera.
Reports on the immediate and long-term responses to high-fat and high-calorie (HFC) feeding are c... more Reports on the immediate and long-term responses to high-fat and high-calorie (HFC) feeding are controversial. Therefore, we examined the sequential effects of an HFC diet. C57BL/6J mice were randomly assigned to consume either the control (C) or the HFC diet. Body weights and food intake were measured weekly and other measurements at weeks 2, 4, and 10. Microarrays were used for screening the transcriptional response of the livers at the three time points. Genes, encoding enzymes regulating key steps of lipid metabolism, were then selected from the microarray data for validation by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) and their protein expression by western blot assays. Mice fed with HFC diet for 2 weeks showed no increase in food intake and no difference in weight gain compared to the C mice. At weeks 4 and 10, the HFC mice increased their food intake and gained more weight than their controls (by 1.4 times and 2.5 times, respectively) (P<0.01 at week 10). Genes involved in fatty acid oxidation (FAO) were initially upregulated and then downregulated, whereas the lipogenic genes and genes involved in cholesterol synthesis showed reverse trends. The differential mRNA expression of Cpt1L, Fas, and Hmgcr were confirmed by RT-PCR and their protein expression by western blot assays. Our findings suggested that when mice were fed an HFC diet, they could develop initial compensatory response to resist the increased energy balance; however, a prolonged consumption of an HFC diet appeared to disrupt this adaptation.
International Journal of Computational Engineering Science, 2003
In this work, a low cost micro-plate array is developed using flip-chip technique for thermal mul... more In this work, a low cost micro-plate array is developed using flip-chip technique for thermal multiplexing. The microplate is made of silicon chip with on-chip heater and temperature sensor for accurate control of temperature. These silicon chips are flip-chip bonded on a printed-circuit-board (PCB) and arranged in array for thermal multiplexing. By proper thermal design, high performance of thermal cycling has been achieved in this work. The micro-plate array has been used with a plastic chip together as multichamber micro-polymerase chain reaction (uPCR), which can perform independent protocol in each chamber simultaneously.
Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays a critical role in the formation of c... more Acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) plays a critical role in the formation of cholesteryl esters from cholesterol and fatty acids, and is a potential target for treating hypercholesterolemia. We recently reported the significant effects of two human ACAT2 gene polymorphisms, 41A>G (Glu(14)Gly, rs9658625) and 734C>T (Thr(254)Ile, rs2272296), on plasma lipid levels and coronary artery disease susceptibility in a case-control association study. In the present study, we evaluated the possible biological influence of the two polymorphism using two approaches. In the first approach, the functional impact of the two polymorphisms was predicted in-silico using available web-based software, and in the second approach, the varying functions of the two polymorphisms were characterized in in vitro experiments, using ACAT2-deficient AC-29 cells. Our results show that the enzymatic activity of mutant Glu(14)Gly is approximately two times higher than wildtype, and that this increase is primarily due to the increased expression and/or stability of the mutant ACAT2 protein. These results suggest that the genetic variation at Glu(14)Gly is functionally important and may contribute to ACAT2 protein expression and stability.
This study investigated the early and long-term effects of atherogenic diet on hepatic gene expre... more This study investigated the early and long-term effects of atherogenic diet on hepatic gene expression, and the restorative effects of atorvastatin in treating hypercholesterolemia. Two groups of female C57BL/6J mice were fed standard chow or atherogenic diet for 1-week early phase study and two other groups for 10 weeks. The fifth group had daily 10 mg/kg atorvastatin injections for 3 weeks from week 8 of the atherogenic diet. Gene expression profiling was carried out with Affymetrix GeneChips. One-week atherogenic diet elevated 38 and inhibited 127 gene expressions, while 10-week atherogenic diet elevated 165 and inhibited 281 genes by more than twofold. Atorvastatin could restore 78.2% and 68%, respectively, of the genes to normal levels. Genes in the Insig (insulin-induced gene)-SREBP (sterol regulatory element binding proteins) pathway were mostly inhibited by atherogenic diet at week 1 but elevated at week 10. Of these, 65.2% were restored by atorvastatin. In conclusion, lipid...
Studies in health technology and informatics, 2007
Coronary artery disease (CAD) is a main cause of death in the world. Finding cost-effective metho... more Coronary artery disease (CAD) is a main cause of death in the world. Finding cost-effective methods to predict CAD is a major challenge in public health. In this paper, we investigate the combined effects of genetic polymorphisms and non-genetic factors on predicting the risk of CAD by applying well known classification methods, such as Bayesian networks, naïve Bayes, support vector machine, k-nearest neighbor, neural networks and decision trees. Our experiments show that all these classifiers are comparable in terms of accuracy, while Bayesian networks have the additional advantage of being able to provide insights into the relationships among the variables. We observe that the learned Bayesian Networks identify many important dependency relationships among genetic variables, which can be verified with domain knowledge. Conforming to current domain understanding, our results indicate that related diseases (e.g., diabetes and hypertension), age and smoking status are the most import...
This paper presents for the first time the design and fabrication of BioMEMS devices for living c... more This paper presents for the first time the design and fabrication of BioMEMS devices for living cells’ electrochemical impedance measurement under optical excitation. An interdigitated electrode design is adopted in order to increase the sensitivity of living cells’ impedance measurement. The magnitudes of the parasitic components were calculated and their influence on the chip performance was simulated. It is shown
The uTAS proposed the full incorporation of analytical procedures, which include sampling, sample... more The uTAS proposed the full incorporation of analytical procedures, which include sampling, sample preparation or pretreatment and actual analysis, into flowing systems. To incorporate a full uTAS, it is important to develop the individual microfluidic components. Microfilter is one of the microfluidic devices for sample preparation. This paper presents a fabrication method for a vertical silicon mesh structure depth filter as well as the application of white blood cell filtration. The results are also compared with another fabricated horizontal flow silicon filter.
ABSTRACT FSGS is a molecularly heterogeneous disease, and can be classified into primary or secon... more ABSTRACT FSGS is a molecularly heterogeneous disease, and can be classified into primary or secondary disease. Primary FSGS can be due to immune or genetic causes. To date, more than 20 genes have been implicated in FSGS. The discovery of so many FSGS genes, together with the advent of next-generation sequencing, has led to a paradigm shift in the genetic diagnosis and management of this disease. However, genetic screening in FSGS may not be so straightforward because of the difficulty in selection and prioritization of genes. It is challenging to appreciate the prevalence of mutations in the different genes based on the current literature due to heterogeneity of the studies and rarity of the disease. Clinicians need to understand the different methods of genetic screening available. These should be weighed against practical issues such as clinical urgency, financial costs, availability of expertise, and test accessibility. Clinicians should also consider the likelihood of a genetic etiology and the clinical impact of a genetic diagnosis to decide, with the patient and family, on the extent or “aggressiveness” of the genetic screening. The main impact of a genetic diagnosis in FSGS is on the use of immunosuppressive medications as well as on peri-transplant management involving the selection of live-related donors and risk of post-transplant recurrence.
An ultrasensitive electrochemical nucleic acid assay amplified by carbon nanotubes (CNTs)-based l... more An ultrasensitive electrochemical nucleic acid assay amplified by carbon nanotubes (CNTs)-based labels for the detection of leukemia oncogenes.
Henoch-Schönlein purpura (HSP) is a multifactorial inflammatory disease whose pathogenesis remain... more Henoch-Schönlein purpura (HSP) is a multifactorial inflammatory disease whose pathogenesis remains unknown. Pyrin encoded by the MEFV gene (NM_000243; OMIM 608107) is an important active member of the inflammasome and has been shown to affect the expression of many of the genes involved in immune and inflammatory responses. The aim of our study was to elucidate the possible roles of MEFV genetic variants on the susceptibility to HSP and its clinical outcomes in 78 patients with HSP and 189 controls in China. A significant association was found between the E148Q polymorphism (G->C) and HSP susceptibility (odds ratio 2.76, 95% confidence interval 1.76-4.34, P=0.0001). The C allele of E148Q was associated with joint involvement (P=0.014) but not with HSP nephritis (P=0.1). The clinical score was higher in subjects with the CC genotype than in those with the CG or GG genotype (4.13+/-3.53 vs. 1.94+/-1.70, respectively; P=0.011). P369S was not associated with HSP or other phenotypes. M694V and M680I were absent in our patients. Our results suggest that MEFV E148Q could be a contributory genetic factor to HSP and HSP-related joint syndromes.
This paper proposes a novel method to detect transparent living cells in a transparent microfluid... more This paper proposes a novel method to detect transparent living cells in a transparent microfluidic chamber by optical diffraction of an aperture or an aperture array. Through the analysis of the far-field diffraction pattern, one of the parameters of the cells, including the size, refractive index, or position, can be extracted by the analysis software developed in this paper. Calculations are carried out to discuss the key issues of this MEMS device, and our simulation is verified by diffraction patterns of transparent microparticles on fabricated apertures, recorded via a digital camera.
Reports on the immediate and long-term responses to high-fat and high-calorie (HFC) feeding are c... more Reports on the immediate and long-term responses to high-fat and high-calorie (HFC) feeding are controversial. Therefore, we examined the sequential effects of an HFC diet. C57BL/6J mice were randomly assigned to consume either the control (C) or the HFC diet. Body weights and food intake were measured weekly and other measurements at weeks 2, 4, and 10. Microarrays were used for screening the transcriptional response of the livers at the three time points. Genes, encoding enzymes regulating key steps of lipid metabolism, were then selected from the microarray data for validation by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) and their protein expression by western blot assays. Mice fed with HFC diet for 2 weeks showed no increase in food intake and no difference in weight gain compared to the C mice. At weeks 4 and 10, the HFC mice increased their food intake and gained more weight than their controls (by 1.4 times and 2.5 times, respectively) (P<0.01 at week 10). Genes involved in fatty acid oxidation (FAO) were initially upregulated and then downregulated, whereas the lipogenic genes and genes involved in cholesterol synthesis showed reverse trends. The differential mRNA expression of Cpt1L, Fas, and Hmgcr were confirmed by RT-PCR and their protein expression by western blot assays. Our findings suggested that when mice were fed an HFC diet, they could develop initial compensatory response to resist the increased energy balance; however, a prolonged consumption of an HFC diet appeared to disrupt this adaptation.
International Journal of Computational Engineering Science, 2003
In this work, a low cost micro-plate array is developed using flip-chip technique for thermal mul... more In this work, a low cost micro-plate array is developed using flip-chip technique for thermal multiplexing. The microplate is made of silicon chip with on-chip heater and temperature sensor for accurate control of temperature. These silicon chips are flip-chip bonded on a printed-circuit-board (PCB) and arranged in array for thermal multiplexing. By proper thermal design, high performance of thermal cycling has been achieved in this work. The micro-plate array has been used with a plastic chip together as multichamber micro-polymerase chain reaction (uPCR), which can perform independent protocol in each chamber simultaneously.
Uploads
Papers by ChewKiat Heng