Cardiovascular autonomic dysfunction predicts acute ischaemic stroke in patients with Type 2 diabetes mellitus: a 7-year follow-up study

AIMS

We investigated whether cardiovascular autonomic neuropathy (CAN) is associated with acute ischaemic stroke in patients with Type 2 diabetes.

METHODS

From 1999 to 2000, cardiovascular autonomic function tests were conducted in patients with Type 2 diabetes (n = 1458). Patients were followed up between 2006 and 2007. Standard tests for CAN measured heart rate variability parameters [expiration-to-inspiration (E/I) ratio, responses to the Valsalva manoeuvre and standing]. Using the American Diabetes Association criteria, the CAN scores were determined from the results of each test as follows: 0 = normal, 1 = abnormal (total maximum score 3). We assessed the development of acute ischaemic stroke events.

RESULTS

The prevalence of CAN at baseline was 55.7% (E/I 17.1%, Valsalva 39.4%, posture 27.3%) (n = 1126). During follow-up, 131 patients (11.6%) developed acute ischaemic stroke. The vascular events were more frequent in older patients (P < 0.001) and in those with diabetes of longer duration (P = 0.022), hypertension (P < 0.001) or diabetic retinopathy (P = 0.03) than in patients without vascular events. Patients with ischaemic stroke had higher creatinine levels (P = 0.045) and higher urine albumin excretion (P = 0.025) than those of patients without stroke. Cox proportional hazard regression analysis revealed that the CAN score was associated with the development of acute ischaemic stroke (total score 0 vs. 3, adjusted hazard ratio 2.7, 95% CI 1.3-5.5, P = 0.006).

CONCLUSION

Cardiovascular autonomic dysfunction was significantly associated with the development of ischaemic stroke in patients with Type 2 diabetes.

Changes in gene expression in beta cells after islet isolation and transplantation using laser-capture microdissection

AIMS/HYPOTHESIS

The process of islet isolation can cause chemical and mechanical injury to beta cells. In addition, hyperglycaemia after islet transplantation can compromise beta cell function. The aim of this experiment was to evaluate changes in gene expression in endogenous islets using laser-capture microdissection (LCM).

MATERIALS AND METHODS

Islets from B6AF1 mice were studied in situ in the pancreas as well as those freshly isolated or cultured for 24 h. Fresh islets were transplanted under the kidney capsule of syngeneic diabetic (streptozocin-induced) and non-diabetic mice. Frozen sections from all the samples were prepared for LCM to obtain beta cell-enriched tissue; RNA was extracted and amplified using T7 polymerase. RT-PCR was used to assess expression of selected genes critical for beta cell function (Ins, Ipf1 [previously known as Pdx1], Slc2a2 [previously known as GLUT2] and Ldha) and the stress response (Hmox1 [previously known as HO-1], Gpx1, Tnfaip3 [previously known as A20] and Fas). Immunostaining was also performed.

RESULTS

In freshly isolated and cultured islets, insulin and Ipf1 mRNA levels were decreased by 40% (compared with islets in situ), while stress genes were upregulated. Comparison between in situ pancreatic islets and engrafted beta cells of cured mice showed declines in Ipf1 expression.

CONCLUSIONS/INTERPRETATION

Our experiment, the first report to investigate changes in gene expression in endogenous islets using LCM, indicate that beta cells following islet isolation and residing in a foreign graft environment have decreased expression of genes involved in insulin production and increased expression of stress genes. Our data suggest that an islet graft, even in successful transplantation, may be different from endogenous islets in gene expression.

Methods and evaluations of MRI content-adaptive finite element mesh generation for bioelectromagnetic problems

In studying bioelectromagnetic problems, finite element analysis (FEA) offers several advantages over conventional methods such as the boundary element method. It allows truly volumetric analysis and incorporation of material properties such as anisotropic conductivity. For FEA, mesh generation is the first critical requirement and there exist many different approaches. However, conventional approaches offered by commercial packages and various algorithms do not generate content-adaptive meshes (cMeshes), resulting in numerous nodes and elements in modelling the conducting domain, and thereby increasing computational load and demand. In this work, we present efficient content-adaptive mesh generation schemes for complex biological volumes of MR images. The presented methodology is fully automatic and generates FE meshes that are adaptive to the geometrical contents of MR images, allowing optimal representation of conducting domain for FEA. We have also evaluated the effect of cMeshes on FEA in three dimensions by comparing the forward solutions from various cMesh head models to the solutions from the reference FE head model in which fine and equidistant FEs constitute the model. The results show that there is a significant gain in computation time with minor loss in numerical accuracy. We believe that cMeshes should be useful in the FEA of bioelectromagnetic problems.

Expression of the intermediate filament vimentin in proliferating duct cells as a marker of pancreatic precursor cells

OBJECTIVES

The expression of the intermediate filament (IF) vimentin, usually considered a marker of mesenchymal cells, has been observed in the epithelial cells during embryogenesis, carcinogenesis, and dedifferentiation, suggesting that it might be useful as a marker of proliferating precursor cells in the pancreas.

METHODS

Rat pancreata at E18 and at different time points after partial pancreatectomy (Px) and human and neonatal pig pancreatic tissue sections and monolayer cultured pancreatic duct cells were observed. All tissues were simultaneously immunostained with pancytokeratin and vimentin antibodies. In costained duct cells, PDX-1 or PCNA expression was also analyzed using confocal microscope images.

RESULTS

In the rat embryonic pancreas at E18, all epithelial cells that formed ductlike structures expressed both cytokeratin and vimentin IF, whereas no duct cells costained for IF in the adult rat or neonatal pig pancreas. Such costaining reappeared in the following order: common pancreatic duct, main ducts, foci of regeneration and then disappeared completely at 30 days after Px. In humans, costaining was found in only 1 diabetic patient's pancreatic section, which was accompanied by massive duct cell proliferation. In monolayer culture, most of the duct cells of human and neonatal pigs coexpressed both IF proteins. Only a few costained duct cells also expressed PDX-1, and most of those cells were also stained with PCNA in rat embryonic pancreas and regenerating foci after partial Px.

CONCLUSIONS

Vimentin IF expression might be a useful marker for pancreatic precursor cells and could be used to investigate the concept of the dedifferentiation of fully matured duct cells during the process of the beta-cell neogenesis.

Hypodipsic hypernatremia with intact AVP response to non-osmotic stimuli induced by hypothalamic tumor: a case report

Anatomical lesions of hypothalamic area associated with hypodipsic hypernatremia have been reported only rarely. We report here a case of hypodipsic hypernatremia induced by a hypothalamic lesion. A 25-yr-old man, who had been treated with radiation for hypothalamic tumor 5-yr before, was admitted for evaluation of hypernatremia and hypokalemia. He never felt thirst despite the elevated plasma osmolality and usually refused to drink intentionally. Plasma arginine vasopressin (AVP) level was normal despite the severe hypernatremic hyperosmolar state and urine was not properly concentrated, while AVP secretion was rapidly induced by water deprivation and urine osmolality also progressively increased to the near maximum concentration range. All of these findings were consistent with an isolated defect in osmoregulation of thirst, which was considered as the cause of chronic hypernatremia in the patient without an absolute deficiency in AVP secretion. Hypokalemia could be induced by activation of the renin-angiotensin-aldosterone system as a result of volume depletion. However, inappropriately low values of plasma aldosterone levels despite high plasma renin activity could not induce symptomatic hypokalemia and metabolic alkalosis. The relatively low serum aldosterone levels compared with high plasma renin activity might result from hypernatremia. Hypernatremia and hypokalemia were gradually corrected by intentional water intake only.

The effect of cilostazol on glucose tolerance and insulin resistance in a rat model of non-insulin dependent diabetes mellitus

BACKGROUND

It has been reported that many peripheral vasodilating drugs might improve insulin resistance. Cilostazol, a antithrombotic agent, increases peripheral blood flow in non-insulin dependent diabetic patients. The effect of cilostazol treatment on insulin resistance in streptozotocin (STZ)-induced non-insulin dependent diabetic Wistar rats was examined.

METHODS

About a half of two-day old neonate siblings were injected intraperitoneally with STZ and maintained for six months, at which time they were compared with age-matched control rats for intraperitoneal glucose tolerance test (IPGTT) and for glucose infusion rate (GINF) in a euglycemic hyperinsulinemic glucose-clamp study. After that, these studies were also performed after feeding rat chow containing cilostazol (100 mg/kg/day) to rats with STZ-induced non-insulin dependent diabetes mellitus for four-weeks and compared with those of age-matched control rats.

RESULTS

In the intraperitoneal glucose tolerance test studies, plasma glucose levels of STZ-induced non-insulin dependent diabetic rats were significantly higher and plasma insulin levels significantly lower than those of age-matched control rats in the age of six months. Glucose infusion rate was lower in STZ-induced non-insulin dependent diabetic rats than those of age-matched control rats. However, after a four-week cilostazol treatment, glucose infusion rate of STZ-induced non-insulin dependent diabetic rats was not significantly different from that of control rats.

CONCLUSION

These findings suggested that cilostazol may improve insulin resistance in STZ-induced non-insulin dependent diabetic rats.

New ADA criteria in the Korean population: fasting blood glucose is not enough for diagnosis of mild diabetes especially in the elderly

BACKGROUND

To compare the 1997 American Diabetes Association (ADA) criteria with the 1985 World Health Organization (WHO) criteria in categorization of the diabetes diagnostic status of Koreans and to define clinical characteristics of subjects diagnosed differently by the two criteria.

METHODS

In 810 Korean subjects, we analyzed blood glucose and insulin response during 75 g oral glucose tolerance test (OGTT). According to current WHO criteria, the cutoff values of FPG which distinguish normal and IGT from diabetes were determined. Then the subjects were categorized according to both WHO and ADA criteria. The clinical characteristics of the subjects with different diagnostic categories by the two criteria were defined.

RESULTS

The FPG cut point distinguishing diabetes from IGT was 117 mg/dl, and from normal was 110 mg/dl. The overall agreement between the ADA criteria and the WHO criteria was moderate, as reflected in the kappa of 0.45. 141 of subjects categorized diabetes by WHO criteria were not diagnosed with ADA criteria. These discordant subjects were older in age and showed blunted early insulin response than concordant normal subjects.

CONCLUSION

These results suggest that mild diabetes by the WHO criteria, especially in the elderly, would not be diagnosed as diabetes by the ADA FPG criteria only. Thus, in a group at high risk for developing diabetes or in a relatively older age group, we should continue using the OGTT.

The effect of long-term glycaemic control on serum lipoprotein(a) levels in patients with Type 2 diabetes mellitus

AIMS

To examine whether long-term glycaemic control affects lipoprotein(a) (Lp(a)) levels in patients with Type 2 diabetes mellitus.

METHODS

Eighty-nine Type 2 diabetic patients (38 men, 51 women) were recruited from the diabetes clinic. Based on HbA1c concentrations at baseline, patients were divided into two groups: those with HbA1c < 8.0% (n =45) and those with HbA1c > or = 8.0% (n=44). Comparisons of Lp(a) levels were made between both groups. The effect of long-term glycaemic control on Lp(a) levels was investigated in a subgroup of 20 patients, selected from those with baseline HbA1c > or = 8%. All these patients were treated with a goal of HbA1c <7%.

RESULTS

Lp(a) levels were not significantly different between those with HbA1c< 8.0% and those with HbA1c, > or = 8.0%. No correlation between Lp(a) and HbA1c or fasting blood glucose levels was noted in diabetic patients as a whole. After 2 years of intensive glycaemic control, all patients exhibited remarkable improvement of therapy: their average HbA1c levels were 6.5 +/- 0.7%, being < 7% in 70% of patients. However, no change in Lp(a) levels were observed after 2 years (19.5 +/- 14.8-21.4 +/- 13.4 mg/dl, P = 0.390).

CONCLUSION

These results indicate that improvement of glycaemic control does not affect serum Lp(a) levels in patients with Type 2 diabetes mellitus.

Estimation of mean frequency and variance of ultrasonic Doppler signal by using second-order autoregressive model

In order to estimate the mean frequency and variance of the diagnostic ultrasound Doppler signal in the presence of clutter noise, a new estimator using a second-order autoregressive (AR) model, called the AR estimator, is proposed. The sampled signal that contains information of both the Doppler signal and clutter is described by the second-order AR model with two poles. The mean frequency and variance of a unidirectional Doppler signal can be estimated, respectively, from the phase and the magnitude of the pole, with larger phase between the two poles. If the clutter is not completely rejected, all conventional estimators, including the autocorrelation (AC) estimator, result in erroneous estimations for the mean frequency and variance of the Doppler signal, whereas the AR estimator gives an accurate estimation. In the absence of clutter, however, the performance of both the AC and AR estimators are similar. If the blood flows in both directions in a sample volume and the clutter is rejected to the extent that it no longer obscures the Doppler signal, the proposed method can estimate simultaneously the mean frequencies and variances of both the forward and reverse blood flows. The performance of the proposed AR estimator was compared with that of the AC estimator by computer simulations and experiments, and it was found that when the number of available sampled data is small, the AR estimator does not require the use of a clutter filter, which simplifies Doppler signal detection.