Min Ho Cho

Structural transition of crystalline Y2O3 film on Si(111) with substrate temperature

Abstract Crystalline Y 2 O 3 films on Si(111) were grown by ionized cluster beam (ICB) deposition in an ultra high vacuum (UHV). The crystallinity of the films deposited at several different temperatures was studied using X-ray diffraction (XRD) and reflection of high-energy electron diffraction (RHEED), and the chemical states of the films was investigated using X-ray photoelectron spectroscopy (XPS). The transformation from monoclinic to cubic structure was observed upon the increase of the substrate temperature from 100°C to 500°C. The single crystal cubic structure was obtained at substrate temperatures over 500°C. The stoichiometry and binding state in the films were gradually changed to a cubic Y 2 O 3 structure with the increase of the substrate temperature. The transformation of the film structure from a monoclinic structure to a cubic structure was also observed by post annealing treatment in an oxygen ambient.

Predictive Clinical Parameters for the Therapeutic Efficacy of Sitagliptin in Korean Type 2 Diabetes Mellitus

Background Sitagliptin is a highly selective dipeptidyl peptide-4 (DPP-4) inhibitor that increases blood levels of active glucagon-like peptide (GLP)-1 and glucose-dependent insulinotrophic polypeptide (GIP), resulting in increased insulin secretion. While studies conducted in other countries have indicated the efficacy and safety of using sitagliptin to treat type 2 diabetes mellitus (T2DM), its predictors of effects to sitagliptin are not well understood. Therefore, we evaluated the predictive clinical parameters for the therapeutic benefits of sitagliptin when added to an ongoing metformin or sulfonylurea therapy in Korean T2DM subjects. Methods We obtained data from 251 Korean T2DM subjects who had recently started taking sitagliptin as add-on therapy. Exclusion criteria included any insulin use. Changes in HbA1c (ΔHbA1c) and fasting plasma glucose (ΔFPG) were assessed by comparing baseline levels prior to sitagliptin administration to levels 12 and 24 weeks after treatment. Responders were defined as subjects who experienced decrease from baseline of >10% in ΔHbA1c or >20% in ΔFPG levels at 24 weeks. Results We classified 81% of the subjects (204 out of 251) as responders. The responder group had a lower mean body mass index (23.70±2.40 vs. 26.00±2.26, P≤0.01) and were younger (58.83±11.57 years vs. 62.87±12.09 years, P=0.03) than the non-responder group. Conclusion In Korean T2DM subjects, sitagliptin responders had lower body mass index and were younger compared to non-responders.

Insulin resistance independently influences arterial stiffness in normoglycemic normotensive postmenopausal women.

Objective:Cardiovascular disease risk increases after menopause, which may be related to insulin resistance, and arterial stiffness is a significant predictor of atherosclerosis. We investigated the relationships among insulin resistance, adiponectin, and arterial stiffness in normoglycemic normotensive postmenopausal women. Methods:From 9,555 participants who had routine health checkups, 455 normoglycemic normotensive postmenopausal women were enrolled. Serum concentrations of glucose, total cholesterol, triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) and adiponectin were measured. Insulin resistance was estimated by the insulin resistance index of homeostasis model assessment (HOMA-IR). Pulse wave velocity (PWV) was evaluated to assess arterial stiffness. Results:The women were stratified into three groups according to their HOMA-IR values, and comparisons were made among the three groups. There were significant differences in metabolic parameters between the groups. The mean age, body mass index, waist circumference, fasting plasma glucose, TG, systolic blood pressure (SBP), diastolic blood pressure (DBP), aortic PWV, and peripheral PWV increased sequentially with the degree of insulin resistance. Meanwhile, HDL-C and adiponectin levels decreased with the worsening of insulin resistance. Age, body mass index, fasting plasma glucose, TG, insulin, SBP, HOMA-IR, aortic PWV, and peripheral PWV were significantly higher in women with central obesity, and HDL-C and adiponectin were significantly lower in women with central obesity. Aortic PWV and peripheral PWV were significantly correlated with age, waist circumference, total cholesterol, SBP, DBP, insulin, and HOMA-IR, but adiponectin was not associated with PWV. The results of multiple regression analysis indicated that SBP, DBP, and insulin resistance were independently correlated with PWV. Conclusions:Insulin resistance was independently associated with PWV in normoglycemic normotensive postmenopausal women.

Effect of pioglitazone on serum concentrations of osteoprotegerin in patients with type 2 diabetes mellitus

Objective Osteoprotegerin (OPG) acts as an important regulatory molecule in atherosclerosis. Recent studies report that thiazolidinediones could affect OPG expression. We investigated the relationship between OPG and inflammatory cytokines and the effects of pioglitazone (a PPARγ (PPARG) agonist) versus metformin on serum OPG levels in type 2 diabetic patients. Design and methods Sixty-seven type 2 diabetic patients were included in this study. They were assigned to pioglitazone (15 mg/day, n=34) or metformin (1000 mg/day, n=33) during 24 weeks. Various anthropometric and metabolic parameters, OPG, interleukin 6 (IL6), C-reactive protein (CRP), adiponectin, and homeostasis model assessment of insulin resistance (HOMA-IR), were measured at baseline and at 6 months of treatment. Results Serum OPG levels correlated significantly with fasting plasma glucose (FPG), HbAlc, HOMA-IR, IL6, and CRP, and inversely correlated with adiponectin after adjusting for age (P<0.05). Multiple regression analysis showed that FPG, HbAlc, and adioponectin were independently correlated with OPG level. After 6 months of treatment, the reduction in FPG and HbAlc levels was similar between the two groups. Pioglitazone treatment significantly increased body mass index (P<0.05) and waist circumference (P<0.05) and decreased triglycerides (P<0.05) and HOMA-IR (P<0.01). The adiponectin concentration was increased (P<0.05), and OPG and CRP levels were decreased in the pioglitazone group (P<0.05), but were unchanged in the metformin group. The changes in serum OPG in the pioglitazone group showed significant correlation with changes in FPG, HbAlc, and adiponectin. Conclusions In type 2 diabetic patients, pioglitazone decreases OPG levels, and this decrease in OPG levels might be associated with the increase in adiponectin.

The activation of NF-κB and AP-1 in peripheral blood mononuclear cells isolated from patients with diabetic nephropathy

We evaluated the role of oxidative stress in diabetic nephropathy by measuring intracellular reactive oxygen species (ROS) and redox-sensitive transcription factors in isolated peripheral mononuclear cells (PBMC) in 66 diabetic patients with or without diabetic nephropathy (Groups III and II, respectively) and 49 normal controls (Group I). Stimulated ROS was significantly higher in Group III compared to Group II (increment of H(2)O(2)-induced ROS production: 21.8+/-2.2% vs. 11.1+/-2.0%; increment of PMA-induced ROS production 23.5+/-4.5% vs. 21.6+/-2.2%; both respectively), and the activity of nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1), but not specificity protein 1 (Sp1) was significantly higher in Group III than in Group II (2.53-fold vs. 2.0-fold vs. 1.43-fold, respectively). Both PBMC- and urinary TGF-beta1 levels were higher in Group III than Group II (3.23+/-0.39 ng/g vs. 1.99+/-0.68 ng/g in PBMCs, 16.88+/-6.84 (ng/g Cr) vs. 5.61+/-1.57 (ng/g Cr) in urine, both respectively), and they correlated with the activity of NF-kappaB and AP-1 and 24-h urine albumin excretion (UAE). Increased intracellular ROS generation in PBMCs of diabetic patients is involved in the pathogenesis of diabetic nephropathy via activation NF-kappaB and AP-1 and an increased expression of TGF-beta1.

The association of insulin resistance and carotid atherosclerosis with thigh and calf circumference in patients with type 2 diabetes.

BackgroundThe relationship between body composition parameters such as thigh and calf circumference and insulin resistance or atherosclerosis in type 2 diabetes is poorly understood. The aim of this study was to investigate the relationship between insulin resistance, atherosclerosis, and thigh and calf circumference in patients with type 2 diabetes.MethodsA total of 4,427 subjects with type 2 diabetes were enrolled in this study. Insulin sensitivity was assessed according the rate constant for plasma glucose disappearance (Kitt) determined via the short insulin tolerance test. Biochemical and anthropometric profiles were measured according to a standardized protocol. Visceral fat thickness and carotid intima media thickness (IMT) were measured by ultrasonography.ResultsInsulin sensitivity index (Kitt) was significantly correlated with weight adjusted thigh and calf circumference. Thigh circumference was inversely associated with IMT in men and women and calf circumference was negatively correlated with IMT in women. Multiple stepwise regression analysis revealed that thigh circumference was independently correlated with insulin sensitivity index (Kitt) and IMT. Furthermore, in multivariate logistic regression analysis, thigh circumference was an independent determinant factor for carotid atherosclerosis in patients with type 2 diabetes even after adjusting for other cardiovascular risk factors.ConclusionsThigh and calf circumference were correlated with insulin resistance and carotid atherosclerosis, and thigh circumference was independently associated with insulin resistance and carotid atherosclerosis in patients with type 2 diabetes.

Adiponectin is independently associated with apolipoprotein B to A-1 ratio in Koreans.

Apolipoprotein B to A-1 (apo B/A-1) ratio is reportedly a better predictor of atherosclerotic vascular disease than low-density lipoprotein cholesterol (LDL-C). The aim of this study was to assess the association of serum apo B/A-1 ratio with insulin resistance and adiponectin in patients with different grades of glucose intolerance. Patients were divided according to glucose tolerance into 3 groups: normal glucose tolerance without metabolic syndrome (n = 229), impaired fasting glucose (subjects with fasting plasma glucose level between 100 and 125 mg/dL, n = 658), and type 2 diabetes mellitus (n = 381). Serum concentrations of apo B, apo A-1, glucose, total cholesterol (TC), triglycerides, and high-density lipoprotein cholesterol (HDL-C) and adiponectin were measured. Insulin resistance was estimated by the homeostasis model assessment of insulin resistance index (HOMA-IR). There were significant differences in metabolic parameters among the groups, including waist circumference, insulin, HOMA-IR, and apo B/A-1 ratio, which increased sequentially with glucose intolerance, whereas adiponectin level decreased with increasing severity of glucose intolerance. The apo B/A-1 ratio was significantly correlated with TC, triglycerides, LDL-C, HDL-C, adiponectin, and HOMA-IR in normal glucose tolerance, impaired fasting glucose, and type 2 diabetes mellitus. Multiple regression analysis showed that apo B/A-1 ratio was significantly associated with TC, LDL-C, HDL-C, and adiponectin. In conclusion, apo B/A-1 ratio was significantly associated with insulin resistance according to glucose intolerance; and serum adiponectin was an important independent factor associated with apo B/A-1 ratio in Koreans.

Heteroepitaxial growth of Y2O3 films on Si(100) by reactive ionized cluster beam deposition

Abstract Heteroepitaxial Y 2 O 3 films on Si(100) have been grown by the technique of reactive ionized cluster beam (ICB) deposition. The composition of deposited film is investigated by using the X-ray photoelectron spectroscopy (XPS). It was found that the composition ratio of Y to O is 1 to 1.46. Using reflection high energy electron diffraction (RHEED) and glancing angle X-ray diffraction (GXRD), we study the crystallinity of the films. It was noticed that the orientation of deposited film is mainly determined by the substrate temperature and the cluster acceleration energy. We also found that, without acceleration below 800°C, Y 2 O 3 films were grown as polycrystalline. Under the condition of 5 kV acceleration voltage above 650°C, we noticed the heteroepitaxial growth of Y 2 O 3 film on Si(100) substrate. The epitaxial relationship between Y 2 O 3 and Si(100) is presented as Y 2 O 3 (110)//Si(100) and Y 2 O 3 [110]//Si[100] or Y 2 O 3 (110)//Si(100) and Y 2 O 3 [100]//Si[100].

Enhancement of Thermal Stability in Ni Silicides on Epi-Si1 − x C x by Pt Addition

The thermal stability of nickel silicides from the Ni-Pt alloy on strained epitaxial Si 1―x C x layers was evaluated. C atoms in the epitaxial Si 1―x C x layer remain in the Ni(Pt)Si/Si 1―x C x interface during Ni(Pt)Si formation. The decrease in interfacial energy by C segregation at the grain boundaries and interfaces enhanced the thermal stability of NiSi. The thermal stability of NiSi was greatly enhanced when Pt was added during the silicidation process. Upon increasing annealing temperatures, the sheet resistance of Ni-Pt(5 and 10 atom %)/Si 0.998 C 0.012 decreased to a lower value because a stable Ni(Pt)Si layer is formed on the epitaxial Si 0.998 C 0.012 layer. The formation of a stable Ni(Pt)Si phase suppressed the agglomeration of NiSi as well as the formation of a NiSi 2 phase.

Visceral Fat Thickness Predicts Fatty Liver in Koreans with Type 2 Diabetes Mellitus

Our aim was to study whether visceral adiposity is a predictor of diabetic fatty liver in Korean type 2 diabetes mellitus. In this study, abdominal ultrasonography was used to assess the presence of fatty liver in 1,898 patients with type 2 diabetes. We measured visceral fat thickness by high-resolutional ultrasonography and insulin resistance by Kitt. Half of the cohort had a fatty liver (50.2%). High visceral fat thickness had the highest odds ratio for developing fatty liver in both sexes (odds ratio [S.D]: 3.14 [2.24-4.69], p<0.00 in male, 2.84 [2.04-3.93], p<0.00 in female). In addition, visceral fat thickness of 42.45 and 37.7 mm in men and women, respectively, were chosen as the discriminating value to predict the presence of fatty liver with a sensitivity of 71% and 73% and a specificity of 70% and 70% in men and women, respectively. The area under the receiver-operating characteristics curve was 0.759 in men and 0.764 in women. Therefore we could conclude that the degree of visceral adiposity predicts the presence of fatty liver type 2 diabetes mellitus, whether centrally obese or not, suggesting that hepatic fat accumulation in a diabetic fatty liver may be influenced by visceral fat accumulation regardless of waist circumference.