Unconventional ferroelectric transition in the multiferroic compound TbMnO3 revealed by the absence of an anomaly in c-polarized phonon dispersion

TbMnO(3) exhibits a spontaneous electric polarization along c concomitantly with a spiral spin ordering modulated along b below T_{C} = 28 K. We have performed inelastic x-ray scattering measurements on a single crystal of TbMnO(3) to clarify whether phonon anomalies related to the ferroelectricity exist. We measured transverse modes, especially the Mn-O-Mn bending mode polarized along c and propagating along b, which we expect is most relevant to the ferroelectricity. However, no anomaly was found in the phonon dispersion below 50 meV across T_{C}. The present result suggests that the mechanism of ferroelectricity in TbMnO(3) is different from that of a conventional displacive-type ferroelectric. The weak coupling between electric polarization and lattice in TbMnO(3) strongly suggests that the ferroelectricity is mainly derived from the spiral spin ordering.

Waist circumference as a cardiovascular and metabolic risk in Japanese patients with type 2 diabetes

Excess waist circumference (WC) is a frequently used indicator of abdominal obesity and/or cardiovascular disease (CVD) risk. Nonetheless, search of the literature revealed no prospective studies on the association between WC and CVD events in diabetic patients. In this study, the clinical significance and implications of WC as a cardiovascular and metabolic risk indicator was prospectively investigated in Japanese patients with type 2 diabetes. For this purpose, baseline data on WC, hypertension, and dyslipidemia were collected and subsequent CVD (coronary heart disease and stroke) events during the following 8 years were studied in 1,424 Japanese type 2 diabetic patients, and the cross-sectional/longitudinal associations between WC and CVD risk factors/events were analyzed. Mean WC levels were significantly increased according to the number of coexisting risk factors. However, no significant difference in mean WC between subgroups with and without CVD events was noted, and excess WC alone was not predictive of subsequent CVD events either in male or female subjects even after adjustment for age, smoking, hypertension, and dyslipidemia. In female patients, excess WC (> or =80 cm) was predictive of CVD events only with the coexistence of hypertension. In Japanese diabetic patients, excess WC alone, although a good marker for clustering of CVD risk factors, did not raise the risk of CVD events unless accompanied by hypertension in female patients. Further investigations are necessary before WC as a risk factor can be utilized in clinical settings for the management of diabetes in this population.

Combined effect of oxidative stress-related gene polymorphisms on atherosclerosis

It is well known that oxidative stress plays critical roles in the pathogenesis of atherosclerosis. In this study, we enrolled 1746 type 2 diabetic subjects, determined 4 common genetic variants related to oxidative stress (glutamate-cysteine ligase modifier subunit (GCLM) C-588T, myeloperoxidase G-463A, human paraoxonase 1 Gln192Arg and NAD(P)H oxidase p22phox C242T polymorphisms), and measured carotid intima-media thickness (IMT) as a surrogate marker for atherosclerosis. GCLM C-588T polymorphism was associated with average IMT (AveIMT) (r=0.090, p=0.0008), but the association between the other 3 polymorphisms and AveIMT did not reach the statistical significance. However, AveIMT was significantly greater as the total number of 4 concomitant "pro-oxidant alleles" in each subject was increased (r=0.108, p<0.0001). Furthermore, the number of "pro-oxidant alleles" was a risk factor for a high AveIMT independently of conventional risk factors (p=0.0003). In conclusion, accumulation of oxidative stress-associated alleles was associated with carotid atherosclerosis in type 2 diabetic patients.

Role of copper ion in the pathogenesis of type 2 diabetes

Reactive oxygen species (ROS) are induced under diabetic conditions and are likely associated with the development of type 2 diabetes. It is also known that ROS production is facilitated in the presence of copper ion through the Fenton reaction. The aim of this study was to examine the involvement of copper ion in the pathogenesis of type 2 diabetes and to evaluate the potential usefulness of a copper chelating agent for the treatment of type 2 diabetes. First, both serum copper ion and ROS levels in diabetic C57BL/KsJ-db/db mice were significantly higher compared to those in nondiabetic mice. Second, we treated diabetic db/db mice with a copper chelating agent tetrathiomolybdate and examined the effects on the development of type 2 diabetes. As the results, both serum copper ion and ROS levels were significantly decreased by the treatment, which were equivalent to those in non-diabetic mice. Consequently, the treatment with a copper chelating agent reduced insulin resistance and ameliorated glucose intolerance in diabetic db/db mice. In addition, serum triglyceride levels were also decreased by the treatment. In conclusion, our present results suggest that copper ion is involved in the development of type 2 diabetes and thereby a potential therapeutic target for diabetes.

Pioglitazone reduces ER stress in the liver: direct monitoring of in vivo ER stress using ER stress-activated indicator transgenic mice

It is known that endoplasmic reticulum (ER) stress is provoked under diabetic conditions and is possibly involved in the development of insulin resistance. In this study, using ER stress-activated indicator (ERAI) transgenic mice which express green fluorescent protein under ER stress conditions, we directly evaluated the effects of a diabetic agent pioglitazone on in vivo ER stress under diabetic conditions. In high fat and high sucrose diet-induced diabetic ERAI transgenic mice, 8 weeks of pioglitazone treatment reduced the accumulation of fat droplets in the liver and attenuated the development of insulin resistance. In the liver of the ERAI transgenic mice, ERAI fluorescence activity was clearly reduced as early as after 4 weeks of pioglitazone treatment, preceding the improvement of insulin resistance. In addition, after the pioglitazone treatment, serum free fatty acid and triglyceride levels were decreased, and serum adiponectin levels were increased. These data indicate that pioglitazone treatment suppresses ER stress in the liver which may explain, at least in part, the pharmacological effects of pioglitazone to reduce insulin resistance.

Evidence for an electric-dipole active continuum band of spin excitations in multiferroic TbMnO3

The wide range optical spectra on a multiferroic prototype TbMnO3 have been investigated to clarify the origin of spin excitations observed in the far-infrared region. We elucidate the full band structure, whose high energy edge (133 cm;{-1}) exactly corresponds to twice of the highest-lying magnon energy. Thus the origin of this absorption band is clearly assigned to two-magnon excitation driven by the electric field of light. There is an overlap between the two-magnon and phonon energy ranges, where the strong coupling between them is manifested by the frequency shift and transfer of oscillator strength of the phonon mode.

Serum endogenous secretory RAGE level is an independent risk factor for the progression of carotid atherosclerosis in type 1 diabetes

OBJECTIVE

Advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE) system plays an important role in the development of atherosclerosis. It has been recently reported that endogenous secretory RAGE (esRAGE) and total soluble RAGE (sRAGE) levels are associated with diabetic complications. The aim of the present study is to longitudinally evaluate the association between esRAGE and sRAGE levels and the progression of carotid intima-media thickness (IMT), a surrogate marker of atherosclerosis.

METHODS AND RESULTS

Japanese type 1 diabetic patients (n=47, aged 24.0+/-3.1 years) were enrolled into a 4-year follow-up study and annual measurements of serum esRAGE and sRAGE levels and IMTs were performed. At baseline, mean-IMT was inversely correlated with circulating esRAGE levels (r=-0.317, p=0.0292), whereas there was not statistical significance between mean-IMT and sRAGE levels. Mean-IMT significantly increased during the follow-up period (from 0.63+/-0.10 to 0.67+/-0.10mm, p=0.0022). Annual increase in mean-IMT (=(mean-IMT after 4 years-mean-IMT at baseline)/4) was positively correlated with the arithmetic average of systolic blood pressure (r=0.310, p=0.0332) and triglyceride (r=0.337, p=0.0201), and inversely correlated with circulating esRAGE levels (r=-0.360, p=0.0124) and sRAGE levels (r=-0.406, p=0.0042) during the follow-up period. Furthermore, stepwise multivariate regression analyses revealed that continuous low levels of circulating esRAGE and sRAGE were determinants of the progression of mean-IMT independently of conventional risk factors.

CONCLUSIONS

Circulating esRAGE level as well as sRAGE level was an independent risk factor for the progression of carotid IMT in type 1 diabetic subjects.

Endogenous secretory RAGE but not soluble RAGE is associated with carotid atherosclerosis in type 1 diabetes patients

Advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE) system play an important role in the development of diabetic complications. The soluble form of RAGE (sRAGE) that potentially counteracts AGEs consists of several forms, including endogenous secretory RAGE (esRAGE; a splice variant of RAGE) and cleaved-type soluble RAGE derived from cell-surface RAGE. The aim of this study was to compare sRAGE and esRAGE directly in patients with type 1 diabetes. The associations of both total sRAGE and esRAGE with markers of glycaemic control and with carotid intima-media thickness (IMT) as a marker of atherosclerosis were examined in 130 type 1 diabetes patients (aged 23.6+/-4.9 years) and 22 age-matched non-diabetic subjects. IMT was inversely correlated with esRAGE (r=-0.254, p=0.0015) but neither with sRAGE nor subtracted soluble RAGE values (that is, circulating total sRAGE values - circulating esRAGE values). Furthermore, a stepwise multivariate regression analysis revealed that esRAGE (F=7.3), but not sRAGE, was a variable that interacted independently of IMT. It is likely that circulating sRAGE and esRAGE are distinct markers and that circulating esRAGE levels, but not sRAGE levels, are associated with the status of early-stage atherosclerosis.

Cycloidal spin order in the a-axis polarized ferroelectric phase of orthorhombic perovskite manganite

The ferroelectric state in an orthorhombic perovskite RMnO3 (R=Gd0.7Tb0.3) was proved by neutron scattering studies to show the cycloidal spin state with the ab-spiral plane and the spin-helicity dependent polarization vector along the a axis, sharing the microscopic origin (inverse Dzyaloshinskii-Moriya interaction) with the more widely observed P||c state (e.g., for R=Tb and Dy) with the bc-spiral plane. The magnetic-field induced polarization flop from P||c to P||a as well known for RMnO3 is thus assigned to the orthogonal flop of the spin spiral plane from bc to ab.

The impact of new-onset diabetes on arterial stiffness after renal transplantation

New-onset diabetes after renal transplantation (NODAT) is known to be a potent risk factor for cardiovascular events. We therefore investigated the incidence and risk factors for NODAT, and evaluated surrogate endpoints of atherosclerosis in Japanese patients with stable renal function after renal transplantation. Seventy-nine patients were enrolled in the study, and a 75 g oral glucose tolerance test (OGTT) was performed in subjects excluding patients with known NODAT. We evaluated the risk factors for NODAT and the degree of atherosclerosis, determined by brachial-ankle pulse wave velocity (baPWV), ankle-brachial blood pressure index (ABPI) and intima-media thickness (IMT) of the carotid artery. Eleven patients diagnosed as NODAT had significantly higher fasting plasma glucose before transplantation, blood pressure, and incidence of hepatitis C virus (HCV) infection than patients without NODAT. Multivariate regression analysis revealed that the independent determinant of NODAT was fasting plasma glucose pre-transplantation, HCV infection and systolic blood pressure. The baPWV in patients with NODAT was significantly higher compared to that in patients without NODAT. In addition, the independent determinant of baPWV evaluated by multivariate regression analysis was an increase in systolic blood pressure and age, and a decrease of adiponectin levels. In conclusion, we found that high fasting plasma glucose prior to transplantation, HCV infection and high blood pressure are risk factors for NODAT in Japanese patients after renal transplantation. Since NODAT patients have advanced arterial stiffness probably due to high blood pressure, strict control of blood pressure will be important for preventing the development of cardiovascular disease in NODAT.

Increased serum pigment epithelium-derived factor levels in type 1 diabetic patients with diabetic retinopathy

Serum pigment epithelium-derived factor (PEDF) levels were significantly higher in type 1 diabetic patients with retinopathy (n=20, 10.38+/-3.87 microg/ml) compared to the patients without it (n=57, 7.68+/-2.80 microg/ml) (p=0.0013). Elevated PEDF levels may be related to the progression of diabetic retinopathy.

Glycated albumin is a better indicator for glucose excursion than glycated hemoglobin in type 1 and type 2 diabetes

To determine the impact of blood glucose profile, involving fluctuation and excursion of blood glucose levels, on glycated proteins, we evaluated the association among the daily profile of blood glucose, and glycated albumin (GA) and HbA1c levels in patients with type 1 diabetes (n = 93) and type 2 diabetes (n = 75). GA levels were strongly correlated with HbA1c levels in type 1 (r = 0.85, P<0.0001) and type 2 diabetes (r = 0.61, P<0.0001), respectively. HbA1c levels were similar between patients with type 1 and type 2 diabetes, while GA levels were significantly higher in type 1 diabetes. Thus the ratio of GA levels to HbA1c levels was significantly higher in type 1 diabetes than that in type 2 diabetes (3.32 0.36 vs. 2.89 0.44, p<0.001). The degrees of GA levels and HbA1c levels correlated with maximum and mean blood glucose levels in patients with type 1 and type 2 diabetes. Stepwise multivariate analysis revealed that GA levels independently correlated with maximum blood glucose levels in type 1 diabetes (F = 43.34, P<0.001) and type 2 diabetes (F = 41.57, P<0.001). HbA1c levels also independently correlated with maximum blood glucose levels in type 1 diabetes (F = 34.78, P<0.001), as well as being correlated with mean blood glucose levels in type 2 diabetes (F = 11.28, P<0.001). In summary, GA could be a better marker for glycemic control than glycated hemoglobin in diabetic patients, especially for evaluating glycemic excursion, which is considered to be a major cause of diabetic angiopathy.

PDX-1 functions as a master factor in the pancreas

Various pancreatic transcription factors are involved in pancreas development and beta-cell differentiation. Among them, pancreatic and duodenal homeobox factor-1 (PDX-1) plays a crucial role in pancreas development and beta-cell differentiation, and maintaining mature beta-cell function. MafA is a recently isolated beta-cell-specific transcription factor and functions as a potent activator of insulin gene transcription. These pancreatic transcription factors also play a crucial role in inducing surrogate beta-cells from non-beta-cells and thus could be therapeutic targets for diabetes. On the other hand, under diabetic conditions, expression and/or activities of PDX-1 and MafA in beta-cells are reduced, which leads to suppression of insulin biosynthesis and secretion. Thus, it is likely that alteration of such transcription factors explains, at least in part, the molecular mechanism for beta-cell glucose toxicity found in diabetes.

PDX-1 and MafA play a crucial role in pancreatic beta-cell differentiation and maintenance of mature beta-cell function

Pancreatic and duodenal homeobox factor-1 (PDX-1) plays a crucial role in pancreas development, beta-cell differentiation, and maintenance of mature beta-cell function. PDX-1 expression is maintained in pancreatic precursor cells during pancreas development but becomes restricted to beta-cells in mature pancreas. In mature beta-cells, PDX-1 transactivates the insulin and other genes involved in glucose sensing and metabolism such as GLUT2 and glucokinase. MafA is a recently isolated beta-cell-specific transcription factor which functions as a potent activator of insulin gene transcription. Furthermore, these transcription factors play an important role in induction of insulin-producing cells in various non-beta-cells and thus could be therapeutic targets for diabetes. On the other hand, under diabetic conditions, expression and/or activities of PDX-1 and MafA in beta-cells are reduced, which leads to suppression of insulin biosynthesis and secretion. It is likely that alteration of such transcription factors explains, at least in part, the molecular mechanism for beta-cell glucose toxicity found in diabetes.

Evaluation of lengthened callus by callotasis with analysis of mathematical morphology

BACKGROUND

Callotasis has become an established option for reconstruction of congenital anomalies and after resection of bone tumors. However, fracture after removal of the lengthener remains one of the most serious complications. Mathematical morphology is an image processing technique that allows the skeletal patterns of trabecular bone to be selectively extracted as binary images from computed radiographic (CR) images. We evaluated the strength of the lengthened callus by analysis using mathematical morphology and examined the utility of this method in a biomechanical study.

METHODS

Three Japanese white rabbits per time point were euthanized at the 2-, 3-, 4-, 6-, and 8-week points after completion of the lengthening and were evaluated by CR images and analysis with mathematical morphology.

RESULTS

The changes of the number and continuity of trabecular bone were obtained visually and could be evaluated quantitatively. In some cases corticalization appeared to be complete in the CR images, but it was not complete on the morphological images. Such cases were found to be weaker than those in which corticalization appeared to be complete on both CR and morphological images.

CONCLUSION

Analysis with mathematical morphology is useful for evaluating the lengthened callus after callotasis.

Correlation between spin helicity and an electric polarization vector in quantum-spin chain magnet LiCu2O2

Measurements of polarized neutron scattering were performed on a S=1/2 chain multiferroic LiCu2O2. In the ferroelectric ground state with the spontaneous polarization along the c axis, the existence of transverse spiral spin component in the bc plane was confirmed. When the direction of electric polarization is reversed, the vector spin chirality as defined by C_(ij)=S_(i)xS_(j) (i and j being the neighboring spin sites) is observed to be reversed, indicating that the spin-current model or the inverse Dzyaloshinskii-Moriya mechanism is applicable even to this e_(g)-electron quantum-spin system. Differential scattering intensity of polarized neutrons shows a large discrepancy from that expected for the classical-spin bc-cycloidal structure, implying the effect of large quantum fluctuation.

Oxidative stress and the JNK pathway are involved in the development of type 1 and type 2 diabetes

Failure of pancreatic beta-cells is the common characteristic of type 1 and type 2 diabetes. Type 1 diabetes mellitus is induced by destruction of pancreatic beta-cells which is mediated by an autoimmune mechanism and consequent inflammatory process. Various inflammatory cytokines and oxidative stress are produced during this process, which has been proposed to play an important role in mediating beta-cell destruction. The JNK pathway is also activated by such cytokines and oxidative stress, and is involved in beta-cell destruction. Type 2 diabetes is the most prevalent and serious metabolic disease, and beta-cell dysfunction and insulin resistance are the hallmark of type 2 diabetes. Under diabetic conditions, chronic hyperglycemia gradually deteriorates beta-cell function and aggravates insulin resistance. This process is called "glucose toxicity". Under such conditions, oxidative stress is provoked and the JNK pathway is activated, which is likely involved in pancreatic beta-cells dysfunction and insulin resistance. In addition, oxidative stress and activation of the JNK pathway are also involved in the progression of atherosclerosis which is often observed under diabetic conditions. Taken together, it is likely that oxidative stress and subsequent activation of the JNK pathway are involved in the pathogenesis of type 1 and type 2 diabetes.