Combined examination of glyceryl trinitrate-mediated vascular dilation with flow-mediated vascular dilation is essential for assessment of vascular function in type 2 diabetes.

AIMS/INTRODUCTION: In order to characterize the impaired vascular function in type 2 diabetes (DM) patients, we evaluated the flow-mediated vascular dilation (FMD) with glyceryl trinitrate-mediated vascular dilation (NMD) using ultrasonography. MATERIALS AND METHODS: A total of 111 DM patients and 42 healthy control participants were studied. The maximal dilatation of FMD and NMD (%FMD and %NMD, respectively), the beginning time (T) of dilatation after stimulation and the velocity (V) of the vascular dilatation were also measured. RESULTS: Among DM patients, 49% had impaired %NMD, which affects the results of %FMD. In DM patients with normal %NMD, the %FMD was also significantly lower than that in control participants, although the T and the V were not impaired. In contrast, both the T and the V were disturbed in the DM patients with low %NMD. Multiple linear regression analysis showed that %NMD was independently correlated with albuminuria. Our results indicate that the impaired FMD in DM is be affected by low NMD, and impaired endothelial function already exists even in DM patients whose vascular smooth muscle function is still retained, and also albuminuria is the clinical feature of DM with low %NMD. CONCLUSIONS: Examination of NMD, not only FMD, should be carried out as it offers the possibility of clarifying vascular function in DM patients.

Protective role of human insulin against the cytotoxicity associated with human mutant S20G islet amyloid polypeptide.

AIMS/INTRODUCTION: Islet amyloid polypeptide (IAPP) is a main component of islet amyloid in type 2 diabetes and cosecreted from ß-cell with insulin. Clinical evidence from the patients with S20G mutation of the IAPP gene, as well as experimental evidence that insulin could inhibit amyloid formation of IAPP, suggests that a gradual reduction of insulin could be related to the cytotoxicity associated with S20G-IAPP through long-term deterioration of ß-cells in type 2 diabetes. Our objective was to show an effect of human insulin on S20G-IAPP associated cytotoxicity. MATERIALS AND METHODS: We analyzed the cytotoxicity associated with S20G-IAPP by controlling human insulin expression using adenovirus vectors with micro ribonucleic acid specifically against human insulin in endocrine AtT-20ins cells, which express human insulin permanently. Additionally, we carried out a follow-up study of circulating IAPP and insulin in type 2 diabetic patients. RESULTS: S20G-IAPP expression was associated with a decrease in viability and an increase in terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling-positive cells in AtT-20ins cells. Furthermore, downregulation of human insulin enhanced the cytotoxicity associated with S20G-IAPP, and induced the cytotoxicity associated with wild-type (WT)-IAPP. Reduction of ubiquitin carboxy-terminal hydrolase L1 activity enhanced cytotoxicity under the downregulation of human insulin expression in both S20G- and WT-IAPP transduced cells. A 5-year follow up of type 2 diabetic patients showed a disproportionate increase of serum fasting IAPP-to-insulin ratio from baseline. CONCLUSIONS: Human insulin plays a protective role against the cytotoxicity associated with S20G-IAPP, as well as WT-IAPP. The findings could suggest long-term deterioration of insulin secretion associates with IAPP linked cytotoxicity in type 2 diabetes.

Kir6.2 E23K polymorphism is related to secondary failure of sulfonylureas in non-obese patients with type 2 diabetes.

AIMS/INTRODUCTION: The Kir6.2 E23K polymorphism was studied with a special reference to secondary sulfonylurea (SU) failure in non-obese patients with type 2 diabetes. MATERIALS AND METHODS: We recruited 278 non-obese (body mass index ≤30.0 kg/m(2)) Japanese patients with type 2 diabetes who had a history of SU treatment (for 11.2 ± 6.3 years) and compared the frequency of the secondary SU failure among the genotypes of the polymorphism. Genotyping of the Kir6.2 E23K was carried out by polymerase chain reaction-restriction fragment length polymorphism. RESULTS: The genotype frequencies of the polymorphism were similar to those previously reported in Japanese patients with type 2 diabetes. The frequency with which patients deteriorated into secondary SU failure was significantly higher in those with the KK genotype than those with EE or EK genotypes. Among 214 patients who eventually received insulin therapy because of secondary SU failure, the period of SU treatment in those with the KK genotype was significantly shorter than those with the EE or EK genotype, although the period from diagnosis to the start of SU treatment was not significantly different. CONCLUSIONS: These data suggest that the Kir6.2 E23K polymorphism is related to the acceleration of secondary SU failure in non-obese Japanese patients with type 2 diabetes.

[Evaluation of seasonal changes in hemoglobin A1c in diabetic patients].

In order to evaluate seasonal changes in hemoglobin A1c (HbA1c) values, we examined HbA1c values among 34,590 patients in 2010, and calculated the monthly average of HbA1c values through the year. HbA1c values were the highest in March and the lowest in October with a difference of 0.30%. The similar annual pattern was observed in HbA1c values from 2006 to 2009. Then we selected 453 diabetic patients whose treatment did not change through the year, and calculated average HbA1c values in four seasons each. There were also significant seasonal changes in diabetic patients, which were the highest in the spring and the lowest in the autumn, especially found in patients with insulin therapy. These effects may be caused by cold climate, decreased physical activity, over food intake and body weight gain in the winter. These seasonal changes in HbA1c should be concerned in the case of health service research, clinical trials and evaluation of the effects of medical treatment.

[Clinical evaluation of insulin measuring kit not cross-react with insulin analogue preparations].

Clinical evaluation of insulin assay system reacting with only human insulin molecule (kit B) was performed by comparing it with conventional insulin assay system (kit A) cross-reacting with insulin analogue as well as human insulin preparation. In vitro, the kit B was confirmed to cross-react with only human insulin, not with insulin analogue preparations such as insulin aspart, lyspro and glargine. In non-insulin treated diabetic patients, postprandial and post-insulin injected serum immunoreactive insulin (IRI) concentrations measured by kit B were almost the same as those measured by the kit A. On the other hand, in diabetic patients treated with insulin analogue preparations, postprandial and post-insulin injected serum IRI levels measured by kit B were obviously low compared with those by kit A. After intravenous injection of insulin analogue preparations (0.1 unit/kg), insulin lyspro or insulin aspart, serum IRI levels measured by the kit B were not increased but gradually decreased in contrast to the obviously increased serum IRI level measured by the kit A. From these results, the kit B was confirmed not to measure the insulin analogue preparations in vitro and in vivo.

The angiotensin II receptor blocker telmisartan improves insulin resistance and has beneficial effects in hypertensive patients with type 2 diabetes and poor glycemic control.

The angiotensin II receptor blocker (ARB) telmisartan has a molecular structure that confers it partial agonist properties similar to those of peroxisome proliferators-activated receptor-gamma molecule, which is thought to modulate tissue response to insulin. In order to investigate the effects of telmisartan on insulin sensitivity and glucose metabolism, we enrolled 14 hypertensive patients under treatment with ARB other than telmisartan who had insulin resistance [homeostasis model for insulin resistance (HOMA-IR)>2.0] but no severe glucose tolerance (HbA1c<6.5%), and HOMA-IR was compared before and after the displacement by telmisartan. We also enrolled 27 obese (body mass index>25kg/m(2)) and hypertensive patients with type 2 diabetes under treatment with ARB other than telmisartan, and HbA1c was assessed before and after the displacement by telmisartan. The telmisartan significantly improved HOMA-IR in hypertensive patients and also significantly decreased HbA1c in type 2 diabetic patients especially in the patients with poor glycemic control (HbA1c>==8.0%). These results indicate that telmisartan improves insulin resistance and gives beneficial effects in hypertensive patients with type 2 diabetes and a poor glycemic control.