Diabetes & Metabolism Journal

Original Articles

Migration of Vascular Smooth Muscle Cells by High Glucose is Reactive Oxygen Dependent.: Yong Seong An, Ji Hae Kwon, Yang Ho Kang, In Ju Kim, Yong Ki Kim, Seok Man Son; Korean Diabetes J. 2008;32(3):185-195. Published online June 1, 2008; DOI: https://doi.org/10.4093/kdj.2008.32.3.185

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Abstract PDF: BACKGROUND
Oxidative stress contributes to vascular diseases in patients with diabetes. As the mechanism of development and progression of diabetic vascular complications is poorly understood, this study was aimed to assess the potential role of hyperglycemia-induced oxidative stress and to determine whether the oxidative stress is a major factor in hyperglycemia-induced migration of vascular smooth muscle cells (VSMCs). METHODS: We treated primary cultured rat aortic smooth muscle cells for 72 hours with medium containing 5.5 mM D-glucose (normal glucose), 30 mM D-glucose (high glucose) or 5.5 mM D-glucose plus 24.5 mM mannitol (osmotic control). We measured the migration of VSMCs and superoxide production. Immunoblotting of PKC isozymes using phoshospecific antibodies was performed, and PKC activity was also measured. RESULTS: Migration of VSMCs incubated under high glucose condition were markedly increased compared to normal glucose condition. Treatment with diphenyleneiodonium (DPI, 10 micromol/L) and superoxide dismutase (SOD, 500 U/mL) significantly suppressed high glucose-induced migration of VSMCs. Superoxide production was significantly increased in high glucose condition and was markedly decreased after treatment with DPI and SOD. High glucose also markedly increased activity of PKC-delta isozyme. When VSMCs were treated with rottlerin or transfected with PKC-delta siRNA, nitro blue tetrazolium (NBT) staining and NAD(P)H oxidase activity were significantly attenuated in the high glucose-treated VSMCs. Furthermore, inhibition of PKC-delta markedly decreased VSMC migration by high glucose. CONCLUSION: These results suggest that high glucose-induced VSMC migration is dependent upon activation of PKC-delta, which may responsible for elevated intracellular ROS production in VSMCs, and this is mediated by NAD(P)H oxidase.

Transcriptional Regulation of Insulin and CXCL10 Gene by Peroxisome Proliferator Activated Receptor gamma Coactivator-1alpha.: Won Gu Jang, In Kyu Lee, Eun Jung Kim, Seong Yeol Ryu, Bo Wan Kim, Jung Guk Kim; Korean Diabetes J. 2007;31(4):326-335. Published online July 1, 2007; DOI: https://doi.org/10.4093/jkda.2007.31.4.326

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Abstract PDF: BACKGROUND
Peroxisome proliferator-activated receptor-gamma coactivator 1alpha (PGC-1alpha), which act as a coactivator of nuclear receptors and several other transcription factors. This study was performed to evaluate the expressional regulation of insulin and inflammatory response genes by PGC-1alpha. METHODS: Transient transfection assays were performed to measure the promoter activity of the insulin and CXCL10 gene. The insulin gene expression levels in INS-1 cells were determined by Northern blot analysis. Differentially expressed genes by PGC-1alpha overexpression in HASMCs were confirmed using DNA microarray, real-time PCR and Northen blot analysis. RESULTS: Insulin promoter activity and mRNA levels were suppressed by GR and Ad-PGC-1alpha. Northern blot analysis of the INS-1 cells revealed that infection with Ad-PGC-1alpha markedly reduced the amount of insulin mRNA and treatment of Dex enhanced this effect in an additive manner. The PGC-1alpha-specific siRNA decreased insulin expression that was induced by Dex in the GR-expressing INS-1 cells was nearly restored by this siRNA treatment. We found that when vascular smooth muscle cells (VSMCs) overexpressed PGC-1alpha, immune or inflammatory response genes were highly expressed. For example, promoter activity and mRNA level of CXCL10 gene were increased by PGC-1alpha. CONCLUSION: PGC-1alpha overexpression inhibited insulin promoter activity in INS-1 cells and enhanced expressions of inflammatory response genes (CXCL10, CXCL11, TNFLSF10) in VSMCs.

The Effect of Alpha-lipoic Acid on the Cell Cycle Arrest and Apoptosis in Rat Vascular Smooth Muscle Cells.: Hye Jin Kim, In Kyu Lee, Young Ho Kim, Soon Young Shin, Young Han Lee, Jung Guk Kim, Bo Wan Kim, Hye Soon Kim, Mi Kyoung Kim, Keun Gyu Park, Seong Yeol Ryu; Korean Diabetes J. 2007;31(3):200-207. Published online May 1, 2007; DOI: https://doi.org/10.4093/jkda.2007.31.3.200

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Abstract PDF: BACKGROUND
The proliferation of vascular smooth muscle cells (VSMCs) is a hallmark of atheroscelrosis and post-angioplasty restenosis. We previously showed that alpha-lipoic acid (ALA) inhibited neointimal hyperplasia and has potential anti-atherosclerosis effect in rat carotid artery balloon injured model. Here, we investigated whether alpha-lipoic acid inhibited proliferation of cells and induced apoptosis in rat vascular smooth muscle cells. METHODS: VSMCs were treated with ALA under each condition, harvested and protein was extracted. Same amount of protein was loaded into SDS-PAGE and western blot analysis was performed with various cell cycle regulation protein. To examine ALA induce apoptosis in VSMCs, FACS and DNA fragmentation assay were performed. Antioxidant effect of ALA was determined by DCF-DA staining. RESULTS: ALA induced VSMCs cell cycle arrest and induced p21, p27 and p53 proteins. Also ALA induced PTEN expression and AMPK phosphorylation. Increased AMPK phosphorylation reduced Erk-2 phosphorylation and finally arrested cell cycle promotion. The apoptotic effect was also shown by ALA treatment. Also we confirmed that ALA reduced ROS generation in VSMCs. CONCLUSION: The present data suggest that ALA has anti-proliferative effect and arrests cell proliferation. Therefore, ALA may provide new strategies for the prevention of neointimal hyperplasia after angioplasty.

High Glucose Modulates Vascular Smooth Muscle Cell Proliferation Through Activation of PKC-sigma-dependent NAD(P)H oxidase.: Bo Hyun Kim, Chang Won Lee, Jung Lae Park, Yang Ho Kang, In Ju Kim, Yong Ki Kim, Seok Man Son; Korean Diabetes J. 2006;30(6):416-427. Published online November 1, 2006; DOI: https://doi.org/10.4093/jkda.2006.30.6.416

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Abstract PDF

BACKGROUND
Oxidative stress is thought to be one of the causative factors contributing to macrovascular complications in diabetes. However, the mechanisms of development and progression of diabetic vascular complications are poorly understood. We hypothesized that PKC-sigma isozyme contributes to ROS generation and determined their roles in the critical intermediary signaling events in high glucose-induced proliferation of vascular smooth muscle (VSM) cells. METHODS: We treated primary cultured rat aortic smooth muscle cells for 72 hours with medium containing 5.5 mmol/L D-glucose (normal glucose), 30 mmol/L D-glucose (high glucose) or 5.5 mmol/L D-glucose plus 24.5 mmol/L mannitol (osmotic control). We then measured cell number, BrdU incorporation, cell cycle and superoxide production in VSM cells. Immunoblotting of PKC isozymes using phoshospecific antibodies was performed, and PKC activity was also measured. RESULTS: High glucose increased VSM cell number and BrdU incorporation and displayed significantly greater percentages of S and G2/M phases than compared to 5.5 mmol/L glucose and osmotic control. The nitroblue tetrazolium (NBT) staining in high glucose-treated VSM cell was more prominent compared with normal glucose-treated VSM cell, which was significantly inhibited by DPI (10 micrometer), but not by inhibitors for other oxidases. High glucose also markedly increased activity of PKC-sigma isozyme. When VSM cells were treated with rottlerin, a specific inhibitor of PKC-sigma or transfected with PKC-sigma siRNA, NBT staining and NAD(P)H oxidase activity were significantly attenuated in the high glucose-treated VSM cells. Furthermore, inhibition of PKC-sigma markedly decreased VSM cell number by high glucose. CONCLUSION: These results suggest that high glucose-induced VSM cell proliferation is dependent upon activation of PKC-sigma, which may responsible for elevated intracellular ROS production in VSM cells, and this is mediated by NAD(P)H oxidase.

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High Glucose and/or Free Fatty Acid Damage Vascular Endothelial Cells via Stimulating of NAD(P)H Oxidase-induced Superoxide Production from Neutrophils
Sang Soo Kim, Sun Young Kim, Soo Hyung Lee, Yang Ho Kang, In Ju Kim, Yong Ki Kim, Seok Man Son
Korean Diabetes Journal.2009; 33(2): 94. CrossRef

Alpha-Lipoic acid Inhibits TNF-alpha-Induced Fractalkine Expression in Rat aortic Smooth Muscle Cells.: Keun Gyu Park, Hye Soon Kim, Seong Yeol Ryu, Chang Wook Nam, Byung Kyu Chae, Eui Dal Jung, Jung Guk Kim, Bo Wan Kim, In Kyu Lee; Korean Diabetes J. 2005;29(5):409-417. Published online September 1, 2005

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Abstract PDF: BACKGOUND: The induction of vascular inflammation via the proinflammatory cytokine/ nuclear factor (NF)-kappaB pathway is one of the key mechanisms in the development and progression of atherosclerosis. Accumulating evidence suggests a recently identified chemokine, fractalkine, is involved in arterial inflammation and atherogenesis; however, few studies have examined the effects of pharmacological agents on this process. The purposes of this study were to determine if alpha-lipoic acid (ALA) inhibits the expression of tumor necrosis factor (TNF)-alpha-stimulated fractalkine in vascular smooth muscle cells(VSMCs). METHODS: Rat VSMCs were isolated and cultured. Northern and Western blot analyses were performed to evaluate the effects of ALA on the expression of TNF-alpha-stimulated fractalkine in VSMCs. A gel shift assay was performed to examine the mechanism by which ALA inhibits the expression of fractalkine. RESULTS: TNF-alpha markedly induced the expression of fractalkine in primary cultured VSMCs. ALA inhibited the expression of TNF-alpha-stimulated fractalkine in cultured VSMCs. The result of the gel shift assay suggested the inhibitory effects of AS-6 on the expression of TNF-alpha-stimulated fractalkine were mediated via the NF-kappaB pathway. CONCLUSION: This study has shown that ALA has anti-inflammatory effects on VSMCs, which are mediated by the inhibitoin, at least in part, of the NF-kappaB dependent inflammatory signal-stimulated expression of fractalkine. Our data suggest the possibility that antioxidants, such as ALA, inhibit the NF-kappaB pathway, which may be used to prevent the development and progression of atherosclerosis.

Ascochlorin Derivative, AS-6, Inhibits TNF-alpha-Induced fractalkine, MCP-1 and VCAM-1 Expression in Rat Aortic Smooth Muscle Cells.: Young Yun Jang, Sang Yoon Kim, Nam Keong Kim, Mi Kyung Kim, Hee Kyoung Kim, Hye Soon Kim, Chang Wook Nam, Seong Yeol Ryu, Sung Il Nam, Keun Gyu Park; Korean Diabetes J. 2005;29(5):401-408. Published online September 1, 2005

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Abstract PDF: BACKGOUND: Inflammation is one of the key mechanisms in the development and progression of atherosclerosis. Accumulating evidence suggests that peroxisome proliferators- activated receptorgamma(PPARgamma) plays an important role in the prevention of arterial inflammation and the formation of atherogenesis. This study was designed to evaluate whether the new synthetic PPARgamma, ascochlorin-6(AS-6) has anti-inflammatory and anti-atherogenic effects in primary cultured rat vascular smooth muscle cells(VSMCs). METHODS: Rat VSMCs were isolated and cultured. Northern and Western blot analyses were performed to evaluate the effects of AS-6 on the expressions of tumor necrosis factor (TNF)-alpha-stimulated fractalkine, monocyte chemoattractant protein(MCP)-1 and vascular cell adhesion molecule (VCAM)-1 in VSMCs. A gel shift assay was performed to examine the mechanism by which AS-6 inhibits the expressions of fractalkine, MCP-1 and VCAM-1. RESULTS: TNF-alpha markedly induced the expressions of fractalkine, MCP-1 and VCAM-1 in primary cultured VSMCs. AS-6 inhibited the expressions of TNF-alpha-stimulated fractalkine, MCP-1 and VCAM-1 in primary cultured VSMCs. The result of the gel shift assay suggested the inhibitory effects of AS-6 on the expressions of TNF-alpha-stimulated fractalkine, MCP-1 and VCAM-1 were mediated through a nuclear factor kappaB associated pathway. CONCLUSION: The present study shows that AS-6 has anti-inflammatory effects on VSMCs, suggesting the possibility for the use of AS-6 for prevention of the development and progression of atherosclerosis.

The Effect of High Glucose on the Proliferation and Migration of Vascular Smooth Muscle Cells.: Mi Kyoung Kim, Yang Ho Kang, Seok Man Son, In Ju Kim, Yong Ki Kim; Korean Diabetes J. 2004;28(5):407-415. Published online October 1, 2004

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Abstract PDF: BACKGROUND
Oxidative stress contributes to vascular diseases for patients with diabetes by promoting vascular smooth muscle cell (VSMC) proliferation, monocyte/macrophage infiltration, and vascular tone alteration. As the mechanism of development and progression of diabetic vascular complications is poorly understood, this study was aimed to assess the potential role of hyperglycemia-induced oxidative stress and to determine whether thise oxidative stress is a major factor in hyperglycemia-induced migration and proliferation of VSMCs. METHODS: Rat aortic VSMCs were incubated for 48 hours in either a normal glucose (NG, 5.5 mM) or a high glucose (HG, 30 mM) condition. We then measured the proliferation and migration of VSMCs and the superoxide production. RESULTS: The migration and proliferation of VSMCs incubated under a HG condition were markedly increased compared to the NG condition. Treatment with diphenyleneiodonium (DPI, 10 M) and superoxide dismutase (SOD, 500 U/mL) significantly suppressed the HG-induced migration and proliferation of VSMCs. Superoxide production was significantly increased in the HG condition, and it was markedly decreased after a treatment with DPI and SOD. CONCLUSION: These data suggest that HG-induced VSMC migration and proliferation are related to the production of superoxide anion that is derived from NAD(P)H oxidase.

Insulin Enhances Suppressive Effect of Lipopolysaccharide on Glucose-induced Proliferation of Vascular Smooth Muscle Cells.: Hyoung Chul Choi, Hyuk Jin Kwon, Kwang Youn Lee; Korean Diabetes J. 2004;28(4):265-272. Published online August 1, 2004

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Abstract PDF: BACKGROUND
Vascular smooth muscle cell (VSMC) proliferation is a major pathologic finding of atherosclerotic vessels in diabetes mellitus. Lipopolysaccharide (LPS) inhibits the VSMC proliferation by NO production via iNOS expression. This study attempted to investigate the effect of LPS on the glucose-induced proliferation of VSMC and its mechanism of action. The effects of insulin on glucose induced VSMC proliferation and on the expression of iNOS were also investigated. METHODS: VSMCs were primarily cultured from rat aorta. A proliferation assay for VSMC was performed by a cell count. The concentrations of nitrite in culture media were measured using the Griess reaction. Western blots were performed to analyze for iNOS protein. RESULTS: D-glucose induced VSMC proliferation in a concentration-dependent manner. LPS inhibited the D-glucose induced VSMC proliferation by increasing ing nitrite production. Insulin suppressed the D-glucose induced VSMC proliferation and potentiated the LPS-induced inhibition of VSMC proliferation by increasing the nitrite production. Insulin potentiated the LPS-induced expression of iNOS. CONCLUSION: These results suggest that in diabetes mellitus, glucose induces VSMC proliferation, and LPS and insulin inhibit the stimulatory action of glucose on VSMC proliferation, and insulin potentiates the inhibitory action of LPS on VSMC proliferation via a increase in the expression of iNOS.

Effect of Glucose Concentrations on the Cell Proliferation and Expression of L-type Calcium Channel mRNA in Cultured Rat Aortic Vascular Smooth Muscle Cells.: Young Jung Cho, Hyung Joon Yoo, Hong Woo Nam, Ji Young Suh, In Kyung Jeong, Sung Hee Ihm, Hyeon Kyu Kim, Cheol Young Park, Jae Myung Yoo, Doo Man Kim, Moon Gi Choi, Sung Woo Park; Korean Diabetes J. 2003;27(3):253-259. Published online June 1, 2003

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Abstract PDF: BACKGROUND
Vascular smooth muscle cell (VSMC) proliferation is one of the major pathogenic mechanisms for atherosclerosis. It is known that L-type calcium channels play a role in VSMC proliferation in diabetic rats. However, there have been no studies that show an association between the L-type calcium channels and the VSMC proliferation due to various glucose concentrations in the culture media. Therefore, the association between the voltage-dependent L-type calcium channels of the VSMCs, and the growth of vascular smooth muscle cells, was examined. METHODS: Rat aortic VSMCs were isolated from the aorta of Sprague-Dawley and OLETF rats, using an enzymic method. The VSMCs were cultured in various concentrations of glucose (5.5, 11.0, 16.6, 25, 30 and 40 mM). The VSMCs (1x10(4) cells in 24-well plates) were incubated in the presence of Bay K 8644 (10(-6)M), both with and without verapamil (10(-6)M), for 48 hours. The proliferation was then assessed by the MTT (methylthiazole tetrazolium) assay, and the expression of L-type calcium channel mRNA by RT-PCR. RESULTS: The vascular smooth muscle cell proliferation was significantly increased, in a dose-dependent manner, with glucose concentrations below 25 mM in both in a dose-dependent manner, with glucose concentrations below 25 mM in both kinds of rat. However, the increase in the VSMC proliferation of the OLETF rat was significantly higher than in the Sprague-Dawley rat. After the Bay K 8644 treatment, with the same glucose concentration, the VSMC proliferation and the expression of L-type calcium channel mRNA were significantly increased in both kinds of rat. After treatment with verapamil, the increased VSMC proliferation and expression of L-type calcium channel mRNA, due to the Bay K 8644, were suppressed to control levels in both kinds of rat. CONCLUSION: The results suggest that below certain concentrations of glucose, 25 mM, the L-type calcium channels may play a role in the VSMC proliferation of OLETF and Sprague-Dawley rats. The growth of the VSMCs in OLETF rats, due to various glucose concentrations (< 25 mM), was significantly higher than in the Sprague-Dawley rats.

Effect of Transforming Growth Factor-Induced Gene Product, beta ig-h3 on Proliferation, Migration, and Adhesion of Aortic Smooth Muscle Cells Cultured in High Glucose.: Sung Woo Ha, Gui Hwa Jung, He Jin Yeo, Jong Sup Bae, Soon Hee Lee, Jung Guk Kim, Rang Woon Park, In San Kim, Bo Wan Kim; Korean Diabetes J. 2002;26(4):286-295. Published online August 1, 2002

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Abstract PDF: BACKGROUND
Diabetes mellitus is associated with a substantial increase in the prevalence of atherosclerotic disease. There are many factors which are involved in development of these processes. Transforming growth factor (TGF-beta) is known to be an important factor in the pathogenesis of diabetic vascular complications. TGF-beta-induced gene-h3 (beta ig-h3) is an adhesive molecule whose expression is induced by TGF-beta. Considering that TGF-beta plays an important role in diabetic complications and that beta ig-h3 is induced by TGF-beta, we hypothesized that beta ig-h3 may also play a role in the development of diabetic angiopathy. Then, we examined the effects of beta ig-h3 on biologic function of vascular smooth muscle cells (VSMCs) and potential roles of beta ig-h3 in the pathognesis of diabetic angiopathy. METHODS: VSMCs were isolated from rat thoracic aorta. We conditioned cells with different concentration of TGF-beta or glucose. We measured TGF-beta and beta ig-h3 protein in cell supernatant by ELISA. We also examined whether TGF-beta involves in high glucose-induced beta ig-h3 expression. Finally, we did proliferation, migration, and adhesion assay to investigate biologic function of beta ig-h3 in VSMCs. RESULTS: Our results demonstrated that TGF-beta induced beta ig-h3 expression in VSMCs in dose dependent manners. High glucose induced TGF expression as well as beta ig-h3 protein. Finally, beta ig-h3 was found to support the proliferation, migration, and adhesion of rat VSMCs. CONCLUSION: These results suggest that high glucose-and TGF-beta-induced beta ig-h3 may play an important role in diabetic angiopathy by regulating proliferation, migration, and adhesion of VSMCs.

Effect of Advanced Glycation End Products on Rat Aortic Vascular Smooth Muscle Cells.: Jin Young Song, Sung Hee Ihm, Ji Young Suh, Young Joong Cho, Hyung Joon Yoo, Sung Woo Park, Ja Hei Ihm; Korean Diabetes J. 2002;26(2):91-99. Published online April 1, 2002

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Abstract PDF: BACKGROUND
Diabetes mellitus is an epidemiologically proven risk factor for atherosclerosis. Advanced glycation end products (AGE) have been implicated in the pathogenesis of many diabetic vascular complications. AGE not only change the physicochemical properties of proteins, but also induce a wide range of cell-mediated responses. However, biological effects of AGE on the vascular smooth muscle cells (VSMCs) have not been fully explained despite of presence of an AGE-receptor on the VSMCs. METHODS: In order to test whether AGE promotes atherosclerosis by stimulation of the growth promoting signal transduction pathways in the VSMCs, the proliferation of rat aortic VSMCs cultured in the presence of AGE-BSA with/without anti-AGE antibodies, the MAP kinase inhibitor and antioxidants was measured. The VSMCs (1 x 104 cells in 24-well plates) isolated from the aorta of Sprague-Dawley rats were incubated for 48 hours and the proliferation was assessed by a MTT assay. RESULTS: AGE-BSA increased the proliferation of rat aortic VSMCs by 1.5~1.6 fold at the g/mL level. The stimulatory effect of AGE-BSA (5 microgram/mL) was blocked by the anti-AGE antibodies (100 microgram/mL). PD98059 at 50 M inhibited the AGE - BSA - induced VSMC proliferation, suggesting that MAP kinase activation might be responsible for the proliferative response of the VSMCs to AGE. AGE - BSA - induced VSMC proliferation was also attenuated by N-acetylcysteine (1 micro M) and butylated hydroxyanisole (10 micro M), implying that increased intracellular oxidative stress might be also involved in the proliferative response to AGE. CONCLUSION: These results suggest AGE play a role in diabetic atherosclerosis by stimulating of the growth promoting signal transduction pathways in the VSMCs.

Insulin Gene Therapy using Vascular Smooth Muscle Cells in Diabetic Rats.: Tae Geun Oh, Mi Ja Lee, Young Ku Kim, Seung Tak Kim; Korean Diabetes J. 2002;26(1):32-46. Published online February 1, 2002

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Abstract PDF: BACKGROUND
Type 1 diabetes mellitus is caused by a lack of insulin. The purpose of this study was to test whether blood glucose control in severe diabetic animals can be achieved by transplanting of rat vascular smooth muscle cells which are transduced with the insulin gene using a retroviral vector system. METHODS: After cloning the recombinant retroviral plasmid including human mutated proinsulin cDNA which contains furin endopeptidase cleavage site, the resulting plasmid, LInABCSN, was transfected into the retroviral packaging cell line (PA317/LhInABCSN). The resulting retrovirus in the supernatant of PA317/ LhInABCSN infected the F344 rat vascular smooth muscle cell (SMC) and produced the SMC/LhInABCSN cells. After transplanting SMC/LInABCSN cells into the internal carotid artery of the rat, diabetes was induced by an intraperitoneal streptozotocin (STZ) injection (50 mg/kg) 2 week later. The blood glucose and insulin levels, percent weight change and the survival rates between the control group (SMC/LNFZ) and the treatment group (SMC/LInABCSN) were compared. RESULTS: The insulin concentrations in the supernatant of the SMC/LhInABCSN mice were 160.2 IU/mL in 24 hours, 243.6 IU/mL in 48 hours and 350.2 IU/mL in 72 hours, but the proinsulin concentrations in 24, 48 and 72 hours were all lower than 1 pmol/L. After 1 day and 3 days of the STZ injection, there were no differences in glucose concentrations between treatment group (n=10) and control group (n=10). There were no statistical differences in the percent weight change between the control and treatment group but the treated rats showed bad a lower weight loss than control rats. After 3 days of the STZ injection, serum insulin concentration of treatment group showed slightly higher levels than the control group (2.7+/-.5 IU/mL vs. 1.6+/-.1 IU/mL, p=0.077). The survival showed a significant increase in treatment group (median survival: 29 days, 9-104 days) compared to the control group (median survival: 6 days, 3-49 days, p < 0.05). CONCLUSION: Although this study did not show a normal glucose concentration in treated rats, it did show significantly higher survival compared to control rats. It is believed that gene therapy using rat vascular smooth muscle cells which transduced the insulin gene may be a new insulin delivery method.

The Effects of Troglitazone on Vascular Smooth Muscle Cell Proliferation.: Yun Jae Chung, Kyeong Min Min, Eun Young Oh, Jae Hoon Chung, Yong Ki Min, Myung Shik Lee, Moon Kyu Lee, Kwang Won Kim; Korean Diabetes J. 2000;24(3):348-355. Published online January 1, 2001

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Abstract PDF: BACKGROUND
Elevated fasting and postprandial insulin levels are frequently observed in patients with obesity and hypertension as well as type 2 diabetes mellitus. This phenomenon has been suggested as an independent risk factors for atherosclerotic cardiovascular diseases. Troglitazone, an insulin-sensitizing antidiabetic agent, has been shown to inhibit atherosclerotic process, but its mechanism of action is not yet elucidated. This study was undertaken to examine the effects of troglitazone, a peroxisome proliferator- activated receptor- (PPAR ) ligand, on vascular smooth muscle cell proliferation. METHODS: Aortic smooth muscle cells were isolated from Sprague-Dawley rats and the effects of several different agonists (insulin, ET-I, IGF-I) on cellular DNA synthesis were measured and compared with the effects of troglitazone. In addition, the mRNA of PPARgamma gene in rat aortic smooth muscle cells(RASMCs) was detected by RT-PCR methods. RESULTS:1. Insulin, endothelin-I and IGF-I significantly stimulated DNA synthesis in RASMCs (p<0.05). 2. Insulin-induced DNA synthesis was not significantly inhibited by coincubation with wortmannin or LY294002 but inhibited by PD98059. 3. Troglitazone significantly inhibited insulin, endothelin-I and IGF-I-induced DNA synthesis in RASMCs (p<0.05, respectively). 4. PPAR mRNA was detected in RASMCs by RT-PCR and its expression did not significantly increase by troglitazone treatment. CONCLUSION: Troglitazone could inhibit agonist-induced proliferation of vascular smooth muscle cells and might be a useful agent for treatment as well as prevention of atherosclerosis.

Proliferative Ability of Aortic Smooth Muscle Cells and Lipid Peroxidation of Red Blood Cell Membrane in Diabetic Rats.: Sae Young Park, Hyung Joon Yoo, Kyun Soo Kim, Hyun Kyu Kim, Doo Man Kim, Jae Myung Yoo, Sung Hee Ihm, Moon Gi Choi, Sung Woo Park; Korean Diabetes J. 1999;23(6):785-792. Published online January 1, 2001

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Abstract PDF: BACKGROUND
Diabetes mellitus is a known risk factor for atherosclerosis, and lipid peroxidation, expression of oxidative stress, is also known to related to diabetes mellitus. The purpose of this study was to investigate the proliferative behaviour of cultured vascular smooth muscle cells (VSMCs) and the alteration of lipid peroxidation in relation to the pathogenesis of diabetic atherosclerosis. METHODS: Seven streptozotocin-induced insulin dependent diabetic Sprague Dawley rats and 7 normal rats were studied. Using enzyme method, aortic VSMCs was cultured in diabetic rats. and proliferation was compared between normal and diabetic rat. The membrane lipid peroxidaton of erythrocytes was determined by measurement of malonyl- dialdehyde(MDA), an end-product of fatty acid peroxidation with thiobarbituric acid (TBA) reaction. MDA-TBA colored complex concentration was calculated with the extinction coefficient of MDA-TBA complex at 532nm = 1.56X105cm-lM-1. RESULT: 1. The proliferative ability of cultured VSMCs was much higher in diabetic rats than in nondiabetic ones (p<0.05). 2. Compared with normal control rats, MDA concentration of diabetic rats was significantly increased (p<0.05). CONCLUSION: We concluded that proliferation of cultured VSMCs is due to oxidative stress in diabetes mellitus as a result of the increased proliferative ability of cultured VSMCs combined with increased lipid pemxidation in diabetic rats.

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