Effects of 1,5-anhydro-D-glucitol on insulin secretion both in in vitro and ex vivo pancreatic preparations.

Organ bath experiments are conventionally used to investigate the physiological actions and effects of hormones and drugs on organ responses. We developed an experimental method to reproduce insulin secretion from isolated rat pancreas preparations, to investigate substances that promote insulin secretion ex vivo. 1,5-anhydro-D-glucitol (1,5-AG) is found in foods, and exists in humans and rodents; however, whether 1,5-AG stimulates insulin secretion remains unclear. This study aimed to assess the effects of short-term 1,5-AG stimulation on insulin secretion in both ex vivo and in INS-1E (rat-derived) cells in vitro. Our results indicated that 1,5-AG had no potency to increase the proportion of insulin outflow both in ex vivo and in vitro experiments. Insulin outflow significantly increased upon stimulation with 10 µM glimepiride, a member of the sulfonylurea class of drugs, ex vivo. Glucose-stimulated insulin secretion was observed not only in INS-1E cells but also in rat pancreatic preparations. Our findings demonstrated that short-term exposure to 1,5-AG had no effect on insulin secretion in rats.

The Effects of Trypsin Inhibitor on Insulin Secretion Using Rat Pancreas in an Organ Bath.

BACKGROUND/AIM: We developed an experimental method to reproduce insulin secretion from isolated rat pancreas preparations using an organ bath system. However, secretion of trypsin, another pancreatic enzyme, interferes with insulin production in such systems. We aimed to ascertain the minimum trypsin inhibitor (TI), dose for obtaining a sustained, stable rate of insulin secretion. MATERIALS AND METHODS: The action of TI (1-10 µg/ml) on pancreatic preparations of male Wistar-Imamichi rats in organ bath experiments was assessed by measuring insulin, amylase, and trypsin activity. RESULTS: The level of insulin outflow remained steady in the TI-treated samples, in contrast to that in the untreated control, where insulin secretion decreased over time. The level of amylase outflow did not change significantly. Trypsin activity was significantly lower in the TI-treated samples than in the control. CONCLUSION: Even low concentrations of TI can maintain insulin secretion by inhibiting trypsin activity in organ bath experiments.

Development of an organ bath technique for isolated rat pancreas preparations to assess the effect of 1,5-AG on insulin secretion.

To investigate substances related to insulin secretion, we reported a convenient experimental method to reproduce insulin secretion from isolated rat pancreas preparations using an organ bath. While the method has experimental utility for investigating insulin secretion, optimization of the experimental design is still needed. The level of insulin outflow in the control decreased over time in our previous study. Decreasing serum 1,5-anhydroglucitol (1,5-AG) levels is also known to be shown in patients with worsening glycemic control. There is one in vitro report demonstrated that 1,5-AG induced insulin release. It appears that discussion needs to be deepened further on it. In this study, we investigated the effect of 1,5-AG on insulin secretion through to optimize the condition of endocrine function using the ex vivo organ bath technique. The level of insulin outflow in the control and 1,5-AG groups decreased over time in the organ bath experiment. To analyze the effect of trypsin on reduced insulin secretion, pancreas preparation was treated with soybean trypsin inhibitor (TI). Insulin outflow levels of the TI group were significantly higher than the control group. An enzyme indicator of tissue damage tended to be lower in the TI group. There was no significant enhancement of insulin secretion by 1,5-AG. The present study demonstrated the utility of TI application for the organ bath technique. This finding supported the development of an organ bath technique for the assessment of the effects of novel therapeutics on insulin secretion.

Uric acid lowering in relation to HbA1c reductions with the SGLT2 inhibitor tofogliflozin.

An integrated analysis was performed with data from 4 phase 2 and phase 3 studies of tofogliflozin in which patients with type 2 diabetes mellitus received the sodium-glucose cotransporter 2 inhibitor tofogliflozin for up to 24 weeks. Sex differences, baseline haemoglobin A1c (HbA1c) and serum uric acid (UA) levels, and log10 -transformed urinary N-acetyl-ß-D-glucosaminidase ratio were significantly correlated with the reduction in serum UA levels at both 4 and 24 weeks in multivariate analysis (respectively, P < .0001). The decrease in HbA1c levels was greatest in the group with the highest baseline HbA1c level (quartile 4; HbA1c > 8.6%) and lowest in the group with the lowest baseline HbA1c level (quartile 1; HbA1c ≤ 7.4%). The decrease in serum UA levels was greatest in the quartile 1 group and lowest in the quartile 4 group. In most groups, the maximum decrease in serum UA levels was seen in the first 4 weeks, while the maximum decrease in HbA1c was seen at week 24. Thus, serum UA levels were significantly decreased in patients with moderate HbA1c levels.

Relationship between daily and day-to-day glycemic variability and increased oxidative stress in type 2 diabetes.

AIMS: To determine the association of daily and day-to-day glucose variability with oxidative stress. METHODS: This was a cross-sectional analysis of 68 patients with type 2 diabetes mellitus (T2DM) over 72h of continuous glucose monitoring. Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) were measured before breakfast on day 1. Glucose variability, mean glucose level (MGL), mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD) in glucose levels and area under the postprandial plasma glucose curve (AUCPP) were measured on days 2 and 3. Plasma oxidant capacity against N,N-diethylparaphenylenediamine was measured with the diacron-reactive oxygen metabolites (d-ROMs) test on day 1. RESULTS: Overall, 66.2% males with the mean age of 63.2±12.6years, diabetes duration of 12.9±10.4years, and HbA1c level of 8.1±1.6% (65±17mmol/mol) were included. MGL (r=0.330), HbA1c (r=0.326), MAGE (r=0.565), MODD (r=0.488), and AUCPP (r=0.254) exhibited significant correlations with d-ROMs and not FPG; these correlations remained significant after adjustment for clinical factors (sex, age, duration of diabetes, smoking habit, insulin use, statin use, angiotensin II receptor blocker use, BMI, LDL-C, HDL-C, TG, eGFR, and systolic blood pressure) (R2=0.268, R2=0.268, R2=0.417, R2=0.314, and R2=0.347, respectively). MAGE was significantly correlated with MODD (r=0.708) and MAGE and MODD were independently correlated with d-ROMs by multivariate analysis. CONCLUSIONS: Therefore, oxidative stress is associated with daily and day-to-day glucose variability in patients with T2DM.

Association between pulse wave velocity and a marker of renal tubular damage (N-acetyl-ß-D-glucosaminidase) in patients without diabetes.

The authors assessed the association between the ratio of urinary activity of N-acetyl-ß-D-glucosaminidase (NAG) to creatinine and the brachial-ankle pulse wave velocity (baPWV) in patients without overt diabetes mellitus (DM). This was a cross-sectional study of 233 patients who had an estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m(2) and no history of kidney disease. Patients were divided into two groups: high NAG group (>5.8 U/g creatinine) and low NAG group (≤5.8 U/g creatinine). Mean baPWVs of the high NAG group were significantly higher than those of the low NAG group in both the eGFR ≥30 and <60 tertiles and the eGFR ≥60 and <90 tertiles. The baPWV was positively correlated with NAG in all patients (r=0.341, P<.001). Stepwise multivariate regression analysis showed that the baPWV was significantly related with NAG, age, and systolic blood pressure. Elevated NAG is related to elevated arterial stiffness in patients without DM.

Change of carotid intima-media thickness is associated with age in elderly Japanese patients without a history of cardiovascular disease.

AIM: The present study aimed to evaluate the relationship between the change of carotid intima-media thickness (CIMT) and clinical characteristics in Japanese patients without a history of cardiovascular disease. METHODS: The study participants were 149 Japanese patients without a history of cardiovascular disease treated in our outpatient department. The in all participants CIMT was measured with ultrasonography at baseline and after a mean interval of 2.4 years. Study participants were divided into a middle-aged group (younger than 65 years: n = 59) and an elderly group (65 years or older: n = 90). The annual CIMT change (ΔCIMT) was calculated, and the associations between ΔCIMT and clinical characteristics, including age, were evaluated in both groups. RESULTS: The ΔCIMT was significantly correlated with age in all participants (r = 0.222; P < 0.05) and in elderly participants (r = 0.234; P < 0.05), but was not correlated with other risk factors. The annual ΔCIMT was significantly higher in elderly participants (0.015 ± 0.096 mm) than in middle-aged participants (-0.018 ± 0.088 mm; P < 0.05). Multivariate linear regression analysis with ΔCIMT as a dependent variable and risk factors as independent variables showed that ΔCIMT was significantly associated with age in all participants (ß = 0.002; P < 0.05) and in elderly participants (ß = 0.004; P < 0.05), but not with other risk factors. CONCLUSIONS: Annual CIMT change is associated with age, rather than with other clinical characteristics, including traditional cardiovascular risk factors, such as diabetes and hypertension, in elderly Japanese patients without a history of cardiovascular disease.

Postprandial glycemic control conditions in relation to urinary N-acetyl-ß-D-glucosaminidase in patients with type 2 diabetes mellitus without low glomerular filtration rate.

BACKGROUND: This study assessed the relationship between the serum level of 1,5-anhydroglucitol (1,5-AG), a marker of postprandial hyperglycemia, and the ratio of the urinary activity of N-acetyl-ß-D-glucosaminidase (NAG) to creatinine (NAG index) in patients with type 2 diabetes mellitus. SUBJECTS AND METHODS: This was a cross-sectional study with 153 patients who had an estimated glomerular filtration rate of ≥60 mL/min/1.73 m(2) and no proteinuria and who had never been treated with oral hypoglycemic agents or insulin. On the basis of 1,5-AG levels, the patients were divided into a High 1,5-AG group (>14.0 µg/mL) and a Low 1,5-AG group (≤14.0 µg/mL). RESULTS: The logarithmically transformed NAG index was significantly higher in the Low 1,5-AG group than in the High 1,5-AG group when all glycated hemoglobin (HbA1c) levels were included. The logarithmically transformed NAG index was lowest in the High 1,5-AG group with an HbA1c level of ≤6.4% and was highest in the Low 1,5-AG group with an HbA1c level of ≥7.5%. Multivariate regression analysis showed that the NAG index had a higher independent association with 1,5-AG than with HbA1c or the fasting plasma glucose level. In all models, multivariate regression analyses showed that the NAG index was correlated with age. CONCLUSIONS: These results suggest that postprandial hyperglycemia correlates with early renal tubule injury in type 2 diabetes mellitus.

Change in urinary N-acetyl-ß-d-glucosaminidase levels relevant to postprandial glycemic control conditions in subjects without diabetes mellitus.

BACKGROUND: To assess the relationship between the serum level of 1,5-anhydroglucitol (1,5-AG), a marker of postprandial hyperglycemia, and the ratio of the urinary activity of N-acetyl-ß-d-glucosaminidase to creatinine (NAG index) in subjects without diabetes mellitus (DM). METHODS: This was a cross-sectional study with 495 subjects without DM who had an estimated glomerular filtration rate≥30ml/min/1.73m(2). Subjects were divided into tertiles based on serum 1,5-AG levels: high (>21.0µg/ml), middle (14.0-21.0µg/ml), and low (<14.0µg/ml). Adjusted odds ratios for an elevated urinary NAG index (>5.8U/g creatinine) according to the HbA1c (≤5.4%, 5.5%-5.9%, and 6.0%-6.4%) and 1,5-AG tertiles were calculated. RESULTS: The NAG index was negatively correlated with the serum 1,5-AG level in all subjects. The slopes of the regression lines for these variables did not differ significantly between elderly (≥65y) and nonelderly subjects. As compared with high 1,5-AG and HbA1c≤5.4%, the odds ratios for an elevated urinary NAG index increased progressively to 7.71 across the categories of low 1,5-AG and HbA1c of 6.0% to 6.4%. CONCLUSION: Poor control of postprandial glucose is related to an elevated urinary NAG index in persons without DM.

Improving in the fasting, but not the postprandial, glucose level is associated with reduction of plasma d-ROMs level in patients with type 2 diabetes.

AIMS: This study aimed to evaluate the relationship between improvement of glucose metabolism and plasma levels of diacron-reactive oxygen metabolites (d-ROMs) in patients with type 2 diabetes. METHODS: As the first daily profile, the plasma levels of glucose and d-ROMs were determined on admission. Then, after treatment to lower plasma glucose levels, the second daily profile of these levels was evaluated. Fasting plasma glucose (FPG), the total area under the curve (AUC) of the daily plasma glucose profile (AUCDP), the AUC of the postprandial plasma glucose levels (AUCPP), the AUC of the daily plasma d-ROMs profile (AUCd-ROMs), the coefficient of variation (CV) of plasma glucose (CVPG), and the mean amplitude of glycemic excursions (MAGE) were calculated. The relationship between the improvement of glucose metabolism and that of oxidative stress in patients with type 2 diabetes was evaluated. RESULTS: The second determinations of FPG, AUCDP, AUCPP, MAGE, and AUCd-ROMs were significantly lower than those of the first determinations, but no significant difference was observed in CVPG. Linear regression analysis demonstrated significant associations between the changes in AUCd-ROMs and the changes in both FPG and AUCDP, whereas no significant association was observed between the change in AUCd-ROMs and the change in AUCPP, CVPG, or MAGE. CONCLUSIONS: This study has demonstrated that improvement of the FPG level, but not of the postprandial glucose level, is associated with a reduction of the plasma level of d-ROMs in patients with type 2 diabetes.

What characteristics at baseline are associated with the glucose-lowering effect of colestimide in patients with type 2 diabetes and hypercholesterolemia according to response to treatment?

Colestimide, an anion exchange resin, reportedly improves glycemic control in patients with type 2 diabetes. However, no studies of the glucose-lowering effect of colestimide have identified responders and nonresponders. In the present study, we compared glycemic control, lipids, and body-mass index (BMI) among patients with type 2 diabetes receiving colestimide (n=59) until 24 weeks after the start of treatment. Subjects were classified as responders to treatment (n=40), who showed a 15% or greater decrease in glycated hemoglobin (HbA1c) or a 20% or greater decrease in plasma glucose level or both after 24 weeks of colestimide treatment as compared with baseline; nonresponders showed HbA1c>11.5% or fasting plasma glucose (FPG)>250 mg/dL during the course of the study and <15% decrease in HbA1c levels or <20% decrease in FPG levels or both after 24 weeks of colestimide treatment as compared with baseline. In responders, FPG decreased significantly from 196 ± 91 mg/dL to 125 ± 47 mg/dL after 24 weeks (P<0.001), and HbA1c decreased from 9.1% ± 2.0% to 7.0% ± 0.9% (P<0.001). In nonresponders, HbA1c decreased significantly from 7.7% ± 2.9% to 7.6% ± 1.2% (P<0.05). Multiple logistic regression analysis revealed that baseline HbA1c and the presence of cholelithiasis were significant determinants of the response to colestimide treatment when corrected for sex, age, triglyceride levels, and BMI at baseline and the presence of fatty liver. In conclusion, baseline HbA1c and the presence of cholelithiasis have strong and independent influences on the glucose-lowering effect of colestimide.

Serum uric acid in relation to serum 1,5-anhydroglucitol levels in patients with and without type 2 diabetes mellitus.

OBJECTIVES: The aim of this study was to examine the relationship between serum levels of uric acid (UA) and 1,5-anhydroglucitol (1,5-AG) in elderly subjects (60 years or older; mean age, 73.0±7.2 years) with and without type 2 diabetes mellitus (DM). METHODS: Subjects with DM (n=97) and without DM (n=360) were recruited from among our outpatients (estimated glomerular filtration rate≥45 mL min⁻¹ 1.73 m⁻², and urine protein equivalent to <1.0 g/L), and a cross-sectional study was performed with simple linear regression and stepwise multiple linear regression analyses. RESULTS: The mean serum UA levels of men were significantly higher than those of women in both groups. The mean serum 1,5-AG levels of men were significantly higher than those of women in the non-DM group. There were positive correlations (indicated by Pearson's correlation coefficients) between serum UA levels and 1,5-anhydroglucitol levels in all patients and in both men and women. Simple linear regression and multiple linear regression analyses showed that the serum 1,5-AG levels were significantly and positively correlated with the serum UA level in both the non-DM group and the DM group. In the non-DM group, HbA1c levels, as well as 1,5-AG levels, were positively correlated with serum UA levels. Furthermore, the correlation between 1,5-AG and UA levels was stronger in subjects with DM than in subjects without DM. CONCLUSIONS: These results suggest that the serum 1,5-AG level is an independent factor associated with serum UA levels in the nondiabetic state, as in DM.

Low-molecular-weight lipoprotein (a) and low relative lymphocyte concentration are significant and independent risk factors for coronary heart disease in patients with type 2 diabetes mellitus: Lp(a) phenotype, lymphocyte, and coronary heart disease.

BACKGROUND: The aim of the present prospective study was to examine whether lipoprotein (a) [Lp(a)] phenotypes and/or low relative lymphocyte concentration (LRLC) are independently associated with coronary heart disease (CHD) in patients with type 2 diabetes mellitus (T2DM). METHODS: Serum Lp(a) concentration, Lp(a) phenotypes, and RLC were analyzed in 214 subjects. Lp(a) phenotypes were classified into 7 subtypes according to sodium dodecyl sulfate-agarose gel electrophoresis by Western blotting. Subjects were assigned to the low-molecular-weight (LMW (number of KIV repeats: 11-22) ) and high-molecular-weight (HMW( number of KIV repeats: >22 )) Lp(a) groups according to Lp(a) phenotype and to the LRLC (RLC: <20.3%) and normal RLC (NRLC; RLC: ≥20.3%) groups according to RLC. A CHD event was defined as the occurrence of angina pectoris or myocardial infarction during the follow-up period. RESULTS: During the follow-up period, 30 cases of CHD events were verified. Neutrophil count showed no correlation with CHD, while relative neutrophil concentration and RLC showed positive and negative correlations, respectively, with CHD. The Cox proportional hazard model analysis revealed the following hazard ratios adjusted for LMW Lp(a), LRLC, and LMW Lp(a) + LRLC: (4.31; 95% confidence interval [CI], 1.99-9.32; P < 0.01, 3.621; 95% CI, 1.50-8.75; P < 0.05, and 7.15; 95% CI, 2.17-23.56; P < 0.01, respectively). CONCLUSIONS: Our results suggest that both LMW Lp(a) and LRLC are significant and independent risk factors for CHD and that the combination thereof more strongly predicts CHD in patients with T2DM.

Relationship between postprandial glucose level and carotid artery stiffness in patients without diabetes or cardiovascular disease.

BACKGROUND: The aim of this study was to evaluate the relationship between postprandial glucose level and atherosclerosis in patients without diabetes and cardiovascular disease by determining carotid ultrasonographic variables and serum levels of 1,5-anhydroglucitol (1,5-AG). METHODS: The subjects were 72 patients without diabetes and cardiovascular disease being treated for hypertension or dyslipidemia. The clinical characteristics of all subjects, including the serum level of 1,5-AG, which appears to be well suited for monitoring postprandial hyperglycemia, were evaluated after an overnight fast. The average intima-media thickness (IMT) and the average pulsatility index (PI) of the right and left common carotid arteries were determined with high-resolution ultrasonography and used as ultrasonographic variables. The subjects were divided into a lower 1,5-AG group (n = 36) and a higher 1,5-AG group (n = 36). We evaluated the relationship between clinical characteristics and ultrasonographic variables of the carotid artery in both groups. RESULTS: The average PI in the Lower 1,5-AG group was significantly higher than that in the Higher 1,5-AG group, but the average IMT did not differ between the groups. Linear regression analysis, with the ultrasonographic variables as the dependent variables, with 1,5-AG as the independent variable, and adjusted for other clinical characteristics, showed significant correlation between 1,5-AG and the PI but not between 1,5-AG and IMT. CONCLUSION: Our results suggest that postprandial hyperglycemia increases carotid artery stiffness, but not morphological change, in patients without diabetes or cardiovascular disease.

Aortic arch calcification detectable on chest X-ray films is associated with plasma diacron-reactive oxygen metabolites in patients with type 2 diabetes but without cardiovascular disease.

AIMS: This study aimed to evaluate the relationship between aortic arch calcification (AAC) detectable on chest X-ray films and plasma diacron-reactive oxygen metabolites (d-ROMs) in patients with type 2 diabetes but without cardiovascular disease. METHODS: Forty-nine patients with type 2 diabetes but without cardiovascular disease were evaluated with chest X-ray examinations and divided into those with AAC (n=26) and those without AAC (n=23). Biochemical variables, including plasma levels of d-ROMS, high-sensitivity C-reactive protein (hsCRP), plasminogen activator inhibitor-1 (PAI-1), and lipoprotein(a) (Lp(a)), were evaluated after an overnight fast. The relationships of AAC with both inflammation and oxidative-stress variables were evaluated. RESULTS: The plasma level of d-ROMs in subjects with AAC was significantly higher than that in subjects without AAC, whereas plasma levels of hsCRP, PAI-1, and Lp(a) in subjects with AAC were higher, but not significantly so, than those in subjects without AAC. Multivariate linear regression analysis with AAC grade as the dependent variable and plasma levels of d-ROMs, hsCRP, PAI-1, or Lp(a) as independent variables demonstrated a significant association of AAC grade with plasma levels of d-ROMs but not with plasma levels of hsCRP, PAI-1, or Lp(a). CONCLUSIONS: The plasma level of d-ROMs is associated with AAC in patients with type 2 diabetes but without cardiovascular disease. Hence, the results of the present study suggest that AAC in these patients is strongly associated with oxidative stress. Furthermore, patients with type 2 diabetes and AAC may be at high risk for the development and progression of various diabetic complications induced by oxidative stress.

[Overview of drug therapy in elderly diabetic patients].

General treatment principles for elderly diabetic patient with type 2 diabetes are the same as those of adult care. However, hypoglycemia and other adverse effects of glucose-lowering treatment are more common in older patients. Understanding the advantages and disadvantages of each antihyperglycemic drug class helps clinicians individualize therapy for elderly patients. Especially, given the heterogeneity of the older adult population, the risk of hypoglycemia must be carefully considered before using sulfonylureas and insulin regimen. Less stringent goals for glycemic control are recommended for frail elderly diabetic patients with limited life expectancy, advanced diabetes complications, or extensive comorbid conditions. The aggressive management of cardiovascular risk factors, such as hypertension, dyslipidemia, obesity, inactivity or smoking, is likely to have even greater benefits.

Urinary N-acetyl-ß-D-glucosaminidase levels are positively correlated with 2-hr plasma glucose levels during oral glucose tolerance testing in prediabetes.

BACKGROUND: Urinary N-acetyl-ß-D-glucosaminidase (NAG) excretion is increased in patients with impaired glucose tolerance (IGT). This study investigated when during the oral glucose tolerance test (OGTT) the plasma glucose, urine glucose, and insulin levels correlate most strongly with urinary N-acetyl-ß-d-glucosaminidase (NAG) levels in prediabetic subjects. METHODS: The OGTT was administered to 80 subjects who had not yet received a diagnosis of diabetes mellitus (DM) and in whom HbA1c levels were ≤6.8% and fasting plasma glucose levels were <7.0 mmol/l. Forty-two subjects had normal glucose tolerance (NGT), 31 had impaired glucose tolerance (IGT), and 7 had DM according to World Health Organization criteria. Serum levels of cystatin C, the estimated glomerular filtration rate, the urinary albumin-to-creatinine (Cr) ratio, urinary and serum ß2-microglobulin, and urinary NAG were measured as markers of renal function. RESULTS: NAG levels were significantly higher in subjects with DM and in subjects with IGT than in subjects with NGT. No significant associations were observed between glycemic status and other markers of renal function. Multiple linear regression analysis showed that the NAG level was positively correlated with plasma glucose levels at 120 min of the OGTT and was associated with the glycemic status of prediabetic patients. CONCLUSION: These results suggest that postprandial hyperglycemia is an independent factor that causes renal tubular damage in prediabetes patients.