Taipei, Taiwan
Taipei, Taiwan

Time filter

Source Type

Lee H.-C.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
Advances in Experimental Medicine and Biology | Year: 2012

Aging is a degenerative process that is associated with progressive accumulation of deleterious changes with time, reduction of physiological function and increase in the chance of disease and death. Studies in several species reveal a wide spectrum of alterations in mitochondria and mitochondrial DNA (mtDNA) with aging, including (1) increased disorganization of mitochondrial structure, (2) decline in mitochondrial oxidative phosphorylation (OXPHOS) function, (3) accumulation of mtDNA mutation, (4) increased mitochondrial production of reactive oxygen species (ROS) and (5) increased extent of oxidative damage to DNA, proteins, and lipids. In this chapter, we outline the common alterations in mitochondria of the aging tissues and recent advances in understanding the role of mitochondrial H 2O 2 production and mtDNA mutation in the aging process and lifespan determination. In addition, we discuss the effect of caloric restriction on age-associated mitochondrial changes and its role in longevity. Taking these findings together, we suggest that decline in mitochondrial energy metabolism, enhanced mitochondrial oxidative stress, and accumulation of mtDNA mutations are important contributors to human aging. © 2012 Springer Science+Business Media B.V.

Wang C.-H.,National Yang Ming University | Wang C.-C.,National Yang Ming University | Huang H.-C.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
FEBS Journal | Year: 2013

Adipocytes play an integrative role in the regulation of energy metabolism and glucose homeostasis in the human body. Functional defects in adipocytes may cause systemic disturbance of glucose homeostasis. Recent studies revealed mitochondrial abnormalities in the adipose tissue of patients with type 2 diabetes. In addition, patients with mitochondrial diseases usually manifest systemic metabolic disorder. However, it is unclear how mitochondrial dysfunction in adipocytes affects the regulation of glucose homeostasis. In this study, we induced mitochondrial dysfunction and overproduction of reactive oxygen species (ROS) by addition of respiratory inhibitors oligomycin A and antimycin A and by knockdown of mitochondrial transcription factor A (mtTFA), respectively. We found an attenuation of the insulin response as indicated by lower glucose uptake and decreased phosphorylation of Akt upon insulin stimulation of adipocytes with mitochondrial dysfunction. Furthermore, the expression of glucose transporter 4 (Glut4) and secretion of adiponectin were decreased in adipocytes with increased ROS generated by defective mitochondria. Moreover, the severity of insulin insensitivity was correlated with the extent of mitochondrial dysfunction. These results suggest that higher intracellular ROS levels elicited by mitochondrial dysfunction resulted in impairment of the function of adipocytes in the maintenance of glucose homeostasis through attenuation of insulin signaling, downregulation of Glut4 expression, and decrease in adiponectin secretion. Our findings substantiate the important role of mitochondria in the regulation of glucose homeostasis in adipocytes and also provide a molecular basis for the explanation of the manifestation of diabetes mellitus or insulin insensitivity in a portion of patients with mitochondrial diseases such as MELAS or MERRF syndrome. © 2012 The Authors Journal compilation © 2012 FEBS.

Hsu S.-H.,National Yang Ming University | Chen C.-T.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
Stem Cells | Year: 2013

We previously demonstrated that metabolic switch and mitochondrial activation are required for osteogenic differentiation of human mesenchymal stem cells (hMSCs). However, stem cells in niches or transplanted into injured tissues constantly encounter hypoxic stress that hinders aerobic metabolism. Therefore, we investigated the effects of oxygen tension (1%vs. 21%) on metabolism and osteogenic differentiation of hMSCs. We found that hypoxia impaired osteogenic differentiation as indicated by attenuation of alkaline phosphatase activity and expression of osteogenic markers core binding factor a-1 and osteopontin. In addition, differentiationinduced mitochondrial activation was compromised as shown by the decrease in the expression of respiratory enzymes and oxygen consumption rate. On the contrary, anaerobic metabolism was augmented as revealed by the upregulation of glycolytic enzymes and increase of lactate production, rendering the cells to rely more on anaerobic glycolysis for energy supply. Moreover, administration of 2-deoxyglucose (a glycolytic inhibitor) but not antimycin A (a respiratory inhibitor) significantly decreased intracellular ATP levels of hMSCs differentiating under hypoxia. Treatment with cobalt chloride, a hypoxia-inducible factor-1α (HIF-1α) stabilizer, recapitulated the inhibitory effects of hypoxia, suggesting that HIF-1α is involved in the compromise of hMSCs differentiation. These results suggest that hypoxia inhibits metabolic switch and mitochondrial function and therefore suppresses osteogenic differentiation of hMSCs. Stem Cells. © AlphaMed Press.

Chen C.-T.,National Yang Ming University | Hsu S.-H.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
Biochimica et Biophysica Acta - General Subjects | Year: 2012

Background: The self-renewal ability and pluripotent differentiation potential of stem cells hold great promise for regenerative medicine. Many studies focus on the lineage-specific differentiation and expansion of stem cells, but little is known about the regulation of glycolysis and mitochondrial biogenesis and function during these processes. Recent studies have demonstrated a strong correlation between cellular metabolism and the pluripotency and differentiation potential of stem cells, which indicates the importance of bioenergetic function in the regulation of stem cell physiology. Scope of review: We summarize recent findings in the control of stem cell competence through the regulation of bioenergetic function in embryonic, hematopoietic, mesenchymal, and induced pluripotent stem cells, and discuss the up-to-date understanding of the molecular mechanisms involved in these biological processes. Major conclusions: It is believed that the metabolic signatures are highly correlated with the stemness status (high glycolytic flux) and differentiation potential (mitochondrial function) of stem cells. Besides, mitochondrial rejuvenation has been observed to participate in the reprogramming process. General significance: Understanding the metabolic regulation of stem cells will have great value in the characterization and isolation of stem cells with better differentiation potential. It also provides novel strategies of metabolic manipulation to increase the efficiency of cellular reprogramming. This article is part of a Special Issue entitled Biochemistry of Mitochondria, Life and Intervention 2010. © 2011 Elsevier B.V.

Wu Y.-T.,Mackay Medical College | Wu S.-B.,Mackay Medical College | Wei Y.-H.,Mackay Medical College | Wei Y.-H.,National Yang Ming University
Free Radical Research | Year: 2014

In addition to serving as the power house of mammalian cells, mitochondria are crucial for the maintenance of cellular homeostasis in response to physiological or environmental changes. Several lines of evidence suggest that posttranslational modification (PTM) of proteins plays a pivotal role in the regulation of the bioenergetic function of mitochondria. Among them, reversible lysine acetylation of mitochondrial proteins has been established as one of the key mechanisms in cellular response to energy demand by modulating the flux of a number of key metabolic pathways. In this article, we focus on the role of Sirt3-mediated deacetylation in: (1) flexibility of energy metabolism, (2) activation of antioxidant defense, and (3) maintenance of cellular redox status in response to dietary challenge and oxidative stress. We suggest that oxidative stress-elicited down-regulation of Sirt3 plays a role in the pathophysiology of diabetes, cardiac hypotrophy, mitochondrial diseases, and age-related diseases. Besides, the physiological role of newly identified lysine acylation mediated by Sirt5 and its biochemical effects on oxidative metabolism are also discussed. Moreover, we have integrated the regulatory function of several protein kinases that are involved in the phosphorylation of mitochondrial enzymes during oxidative stress. Finally, the functional consequence of the synergistic regulation through diverse protein modifications is emphasized on the maintenance of the bioenergetic homeostasis and metabolic adaptation of the animal and human cells. Together, we have provided an updated review of PTM in mitochondrial biology and their implications in aging and human diseases through an intricate regulation of energy metabolism under oxidative stress. © 2014 Informa UK, Ltd.

Wu Y.-T.,National Yang Ming University | Lee H.-C.,National Yang Ming University | Liao C.-C.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
Biochimica et Biophysica Acta - Molecular Basis of Disease | Year: 2013

Sirt3, a mitochondrial NAD+-dependent deacetylase, is regarded as a potential regulator in cellular metabolism. However, the role of Sirt3 in the regulation of mitochondrial FoF1ATPase and the linkage to mitochondrial diseases is unclear. In this study, we demonstrated a role of Sirt3 in the regulation of FoF1ATPase activity in human cells. Knockdown of Sirt3 in 143B cells by shRNA transfection caused increased acetylation levels of the α and OSCP subunits of FoF1ATPase. We showed that Sirt3 physically interacted with the OSCP and led to its subsequent deacetylation. By incubation of mitochondria with the purified Sirt3 protein, Sirt3 could regulate FoF1ATPase activity through its deacetylase activity. Moreover, suppression of Sirt3 reduced the FoF1ATPase activity, consequently decreased the intracellular ATP level, diminished the capacity of mitochondrial respiration, and compromised metabolic adaptability of 143B cells to the use of galactose as the energy source. In human cells harboring ≅85% of mtDNA with 4977bp deletion, we showed that oxidative stress induced a reduction of Sirt3 expression, and an increased acetylation of the OSCP subunit of FoF1ATPase. Importantly, the expression of Sirt3 was also decreased in the skin fibroblasts from patients with CPEO syndrome. We further demonstrated that oxidative stress induced by 5-10μM of menadione impaired the Sirt3-mediated deacetylation and activation on FoF1ATPase activity through decreasing the protein level of Sirt3. Our findings suggest that increased intracellular ROS levels might modulate the expression of Sirt3 which deacetylates and activates FoF1ATPase in human cells with mitochondrial dysfunction caused by a pathogenic mtDNA mutation. © 2012 Elsevier B.V.

Wu S.-B.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
Biochimica et Biophysica Acta - Molecular Basis of Disease | Year: 2012

We report that the energy metabolism shifts to anaerobic glycolysis as an adaptive response to oxidative stress in the primary cultures of skin fibroblasts from patients with MERRF syndrome. In order to unravel the molecular mechanism involved in the alteration of energy metabolism under oxidative stress, we treated normal human skin fibroblasts (CCD-966SK cells) with sub-lethal doses of H 2O 2. The results showed that several glycolytic enzymes including hexokinase type II (HK II), lactate dehydrogenase (LDH) and glucose transporter 1 (GLUT1) were up-regulated in H 2O 2-treated normal skin fibroblasts. In addition, the glycolytic flux of skin fibroblasts was increased by H 2O 2 in a dose-dependent manner through the activation of AMP-activated protein kinase (AMPK) and phosphorylation of its downstream target, phosphofructokinase 2 (PFK2). Moreover, we found that the AMPK-mediated increase of glycolytic flux by H 2O 2 was accompanied by an increase of intracellular NADPH content. By treatment of the cells with glycolysis inhibitors, an AMPK inhibitor or genetic knockdown of AMPK, respectively, the H 2O 2-induced increase of NADPH was abrogated leading to the overproduction of intracellular ROS and cell death. Significantly, we showed that phosphorylation levels of AMPK and glycolysis were up-regulated to confer an advantage of survival for MERRF skin fibroblasts. Taken together, our findings suggest that the increased production of NADPH by AMPK-mediated increase of the glycolytic flux contributes to the adaptation of MERRF skin fibroblasts and H 2O 2-treated normal skin fibroblasts to oxidative stress. © 2011 Elsevier B.V.

Wu S.-B.,National Yang Ming University | Wu Y.-T.,National Yang Ming University | Wu T.-P.,National Yang Ming University | Wei Y.-H.,National Yang Ming University | Wei Y.-H.,Mackay Medical College
Biochimica et Biophysica Acta - General Subjects | Year: 2014

Background Mitochondrial DNA (mtDNA) mutations are an important cause of mitochondrial diseases, for which there is no effective treatment due to complex pathophysiology. It has been suggested that mitochondrial dysfunction-elicited reactive oxygen species (ROS) plays a vital role in the pathogenesis of mitochondrial diseases, and the expression levels of several clusters of genes are altered in response to the elevated oxidative stress. Recently, we reported that glycolysis in affected cells with mitochondrial dysfunction is upregulated by AMP-activated protein kinase (AMPK), and such an adaptive response of metabolic reprogramming plays an important role in the pathophysiology of mitochondrial diseases. Scope of review We summarize recent findings regarding the role of AMPK-mediated signaling pathways that are involved in: (1) metabolic reprogramming, (2) alteration of cellular redox status and antioxidant enzyme expression, (3) mitochondrial biogenesis, and (4) autophagy, a master regulator of mitochondrial quality control in skin fibroblasts from patients with mitochondrial diseases. Major conclusion Induction of adaptive responses via AMPK-PFK2, AMPK-FOXO3a, AMPK-PGC-1α, and AMPK-mTOR signaling pathways, respectively is modulated for the survival of human cells under oxidative stress induced by mitochondrial dysfunction. We suggest that AMPK may be a potential target for the development of therapeutic agents for the treatment of mitochondrial diseases. General significance Elucidation of the adaptive mechanism involved in AMPK activation cascades would lead us to gain a deeper insight into the crosstalk between mitochondria and the nucleus in affected tissue cells from patients with mitochondrial diseases. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research. © 2013 Elsevier B.V.

Wu T.-W.,Mackay Medical College | Lin H.H.,Tzu Chi General Hospital | Lin H.H.,Tzu Chi University | Wang L.-Y.,Mackay Medical College | Wang L.-Y.,Taipei Medical University
Hepatology | Year: 2013

Hepatitis B virus (HBV) infection is a global health issue. Universal infantile hepatitis B (HB) vaccination is very efficacious. However, HBV infections among those immunized subjects have been reported. The long-term efficacy of postnatal passive-active HB vaccination in high-risk subjects is not well explored. A total of 8,733 senior high school students who were born after July 1987 were assayed for hepatitis B surface antigen (HBsAg) and antibodies to HBsAg (anti-HBs). The overall HBsAg and anti-HBs-positive rates were 1.9% and 48.3%, respectively. The HBsAg-positive rate was 15% in HB immunoglobulin (HBIG) recipients (adjusted odds ratio [OR]: 15.63; 95% confidence interval [CI]: 10.99-22.22). Among students who did not receive HBIG, there was a significantly negative association between HB vaccination dosage and HBsAg-positive rate (P for trend = 0.011). Adjusted ORs for those who received 4, 3, and 1 to 2 doses were 1.00, 1.52 (95% CI: 0.91-2.53), and 2.85 (95% CI: 1.39-5.81), respectively. Among HBIG recipients, the HBsAg-positive rate was significantly higher in subjects with maternal hepatitis B e antigen (HBeAg) positivity and who received HBIG off-schedule. A booster dose of HB vaccination was administered to 1974 HBsAg- and anti-HBs-negative subjects. Prebooster and a postbooster blood samples were drawn for anti-HBs quantification. The proportions of postbooster anti-HBs titer <10 mIU/mL was 27.9%. Subjects with prebooster anti-HBs titers of 1.0-9.9 mIU/mL had significantly higher postbooster anti-HBs titers than those with prebooster anti-HBs titers of <1.0 mIU/mL (P < 0.0001). Conclusion: Having maternal HBeAg positivity is the most important determinant for HBsAg positivity in adolescents who received postnatal passive-active HB vaccination 15 years before. A significant proportion of complete vaccinees may have lost their immunological memories against HBsAg. (HEPATOLOGY 2013) © 2012 American Association for the Study of Liver Diseases.

Huang S.-M.,Mackay Medical College
Cancer Nursing | Year: 2016

BACKGROUND:: Previous studies indicate that women with cancer experience infertility after cancer-related treatment. With the rapid progress in fertility science, women face diverse and uncertain choices regarding pregnancy. OBJECTIVE:: The aim of this study is to understand the decision-making process regarding fertility choices among reproductive-age women with cancer in Taiwan. METHODS:: Grounded theory methodology guided data collection using in-depth interviews with 18 women diagnosed and treated for cancer. Verbatim transcriptions were analyzed using constant comparative analysis and open, axial, and selective coding. RESULTS:: The core category that describes the decision-making process regarding fertility among reproductive-age women with cancer is “searching for balance in life and creating value in life.” The decision process was divided into 3 phases: needing to have children before treatment, struggling with self-living during cancer treatment, and returning to life after treatment. The style of cancer participantsʼ decision making in pregnancy was divided into 3 patterns: action taking, hesitation, and persistence. CONCLUSIONS:: Decision making regarding fertility among women with cancer was affected by the need for children before treatment and their experience during treatment. IMPLICATIONS FOR PRACTICE:: Health providers should be aware of and understand the needs of women with cancer to balance their need for children with their perception of their cancer prognosis and its effects on fertility, and help them with pregnancy planning if desired. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved

Loading Mackay Medical College collaborators
Loading Mackay Medical College collaborators