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To establish widespread cell therapy for type 1 diabetes mellitus, we aimed to develop an effective protocol for generating insulin-producing cells (IPCs) from adipose-derived stem cells (ADSCs). We established a 3D culture using a human recombinant peptide (RCP) petaloid μ-piece with xeno-antigen free reagents. Briefly, we employed our two-step protocol to differentiate ADSCs in 96-well dishes and cultured cells in xeno-antigen free reagents with 0.1 mg/mL RCP μ-piece for 7 days (step 1), followed by addition of histone deacetylase inhibitor for 14 days (step 2). Generated IPCs were strongly stained with dithizone, anti-insulin antibody at day 21, and microstructures resembling insulin secretory granules were detected by electron microscopy. Glucose stimulation index (maximum value, 4.9) and MAFA mRNA expression were significantly higher in 3D cultured cells compared with conventionally cultured cells (P < 0.01 and P < 0.05, respectively). The hyperglycaemic state of streptozotocin-induced diabetic nude mice converted to normoglycaemic state around 14 days after transplantation of 96 IPCs under kidney capsule or intra-mesentery. Histological evaluation revealed that insulin and C-peptide positive structures existed at day 120. Our established xeno-antigen free and RCP petaloid μ-piece 3D culture method for generating IPCs may be suitable for clinical application, due to the proven effectiveness in vitro and in vivo.

Background: Glucose values of continuous glucose monitoring (CGM) have time delays compared with plasma glucose (PG) values. The artificial pancreas (STG-55, Nikkiso, Japan) (AP), which measures venous blood glucose directly, also has a time delay because of the long tubing lines from sampling vessel to the glucose sensor. We investigate accuracy and time delay of CGM and AP in comparison with PG values during 2-step glucose clamp study., Methods: Seven patients with type 2 diabetes and 2 healthy volunteers were included in this study. CGM (Enlite sensor, Medtronic, Northridge, CA, USA) was attached on the day before the experiment. Hyperglycemic (200 mg/dL) clamp was performed for 90 minutes, followed by euglycemic (100 mg/dL) hyperinsulinemic (100 μU/mL) clamp for 90-120 minutes using AP. CGM sensor glucose was calibrated just before and after the clamp study. AP and CGM values were compared with PG values., Results: AP values were significantly lower than PG values at 5, 30 minute during hyperglycemic clamp. In comparison, CGM value at 0 minute was significantly higher, and its following values were almost significantly lower than PG values. The time delay of AP and CGM values to reach maximum glucose levels were 5.0 ± 22.3 (NS) and 28.6 ± 32.5 ( P < .05) min, respectively. Mean absolute rate difference of CGM was significantly higher than AP (24.0 ± 7.6 vs 15.3 ± 4.6, P < .05) during glucose rising period (0-45 min); however, there were no significant differences during other periods., Conclusions: Both CGM and AP failed to follow plasma glucose values during nonphysiologically rapid glucose rising, but indicated accurate values during physiological glucose change.

Dosing guidelines for patients with type 1 diabetes using continuous subcutaneous insulin infusion (CSII), which are historically based on clinical experience and retrospective studies of patients consuming an American diet, recommend that basal insulin should represent approximately 50 % of the total daily dose (TDD). Recent prospective studies in the USA and Japan conclude that the more appropriate proportion is closer to 30-40 % of TDD. In addition, currently used formulas for calculating the carbohydrate-to-insulin ratio (CIR) and correction factor (CF) may lead to underdosing of bolus insulin by as much as 12.8-50 % for a hypothetical patient. The discrepancies between traditional formulas and data from newer studies can be accounted for by the more rigorous design of the newer studies (e.g., prospective design, controlled diets, meal omission, and frequent glucose monitoring). International differences in diet composition may also be important to consider when developing dosing recommendations for CSII.

We herein report the case of a 37-year-old type 1 diabetic pregnant woman treated with an insulin pump. Although the patient's glycemic control deteriorated following progesterone treatment for the prevention of preterm delivery and miscarriage, it was improved by adjusting the basal insulin rate on the days of progesterone treatment. Excess progesterone is known to impair both insulin sensitivity and secretion. The present case is the first report to evaluate deterioration of glycemic control induced by progesterone treatment and to determine the dose of insulin required in a type 1 diabetic pregnant woman whose insulin secretion was completely depleted.

Background: To optimize insulin dose using insulin pump, basal and bolus insulin doses are widely calculated from total daily insulin dose (TDD). It is recommended that total daily basal insulin dose (TBD) is 50% of TDD and that the carbohydrate-to-insulin ratio (CIR) equals 500 divided by TDD. We recently reported that basal insulin requirement is approximately 30% of TDD. We therefore investigated CIR after adjustment of the proper basal insulin rate., Subjects and Methods: Forty-five Japanese patients with type 1 diabetes were investigated during several weeks of hospitalization. The patients were served standard diabetes meals (25-30 kcal/kg of ideal body weight). Each meal omission was done to confirm basal insulin rate. Target blood glucose level was set at 100 and 150 mg/dL before and 2 h after each meal, respectively. After the basal insulin rate was fixed and target blood glucose levels were achieved, TBD, CIR, TDD, and their products were determined., Results: Mean (±SD) blood glucose levels before and 2 h after meals were 121±47 and 150±61 mg/dL, respectively. TDD was 31.5±9.0 U, and TBD was 27.0±6.5% of TDD. CIR×TDD of breakfast was significantly lower than those of lunch and supper (288±73 vs. 408±92 and 387±83, respectively; P<0.01)., Conclusions: CIR has diurnal variance and is estimated from the formula CIR=300/TDD at breakfast or CIR=400/TDD at lunch and supper in type 1 diabetes patients. These results indicate that the insulin dose has been underestimated by using previously established calculations.

In type 2 diabetes mellitus, glucose homeostasis is tightly maintained through insulin secretion and insulin sensitivity. Therefore, finding an accurate method to assess insulin secretion and sensitivity using clinically available data would enhance the quality of diabetic medical care. In an effort to find such a method, we developed a computational approach to derive indices of these factors using a 2-h oral glucose tolerance test (OGTT). To evaluate our method, clinical data from subjects who received an OGTT and a glucose clamp test were examined. Our insulin secretion index was significantly correlated with an analogous index obtained from a hyperglycemic clamp test (r = 0.90, n = 46, p < 0.001). Our insulin sensitivity index sensitivity was also significantly correlated with an analogous index obtained from a hyperinsulinemic-euglycemic clamp test (r = 0.56, n = 79, p < 0.001). These results suggest that our method can potentially provide an accurate and convenient tool toward improving the management of diabetes in clinical practice by assessing insulin secretion and insulin sensitivity.

Objective: To investigate the basal insulin requirement in total daily insulin dose in Japanese type 1 diabetic patients who use the insulin pump., Research Design and Methods: The basal insulin requirement in 35 type 1 diabetic patients without detectable C-peptide using the insulin pump (Paradigm 712) was investigated during 2-3 weeks of hospitalization. The patients were served diabetic diets of 25-30 kcal/kg ideal body weight. Each meal omission was done to confirm stable blood glucose levels within 30 mg/dL variance until the next meal. Target blood glucose level was set at 100 mg/dL before each meal and 150 mg/dL at 2 h after each meal., Results: Total daily insulin dose was 31.6 ± 8.5 units, and total basal insulin requirement was 8.7 ± 2.9 units, which was 27.7 ± 6.9% of the total daily dose., Conclusions: Basal insulin requirement is ~30% of the total daily dose in Japanese type 1 diabetic patients who use the insulin pump.

Objective: Progressive β-cell dysfunction and loss of β-cell mass are fundamental pathogenic features of type 2 diabetes. To examine if anti-diabetic reagents, such as insulin, pioglitazone (pio), and alogliptin (alo), have protective effects on β-cell mass and function in vivo, we treated obese diabetic db/db mice with these reagents., Methods: Male db/db mice were treated with a chow including pio, alo, or both of them from 8 to 16 weeks of age. Insulin glargine (gla) was daily injected subcutaneously during the same period., Results: At 16 weeks of age, untreated db/db mice revealed marked increase of HbA1c level, whereas those treated with pio, pio+alo, or insulin revealed the almost same HbA1c levels as non-diabetic db/m mice. Islet mass evaluated by direct counting in the whole pancreas and insulin content in isolated islets were preserved in pio, pio+alo and gla groups compared with untreated or alo groups, and there was no difference among pio, pio+alo and gla groups. To precisely evaluate islet β-cell functions, islet perifusion analysis was performed. In pio, pio+alo and gla groups, biphasic insulin secretion was preserved compared with untreated or alo groups. In particular, pio+alo as well as gla therapy preserved almost normal insulin secretion, although pio therapy improved partially. To examine the mechanism how these reagents exerted beneficial effects on β-cells, we evaluated expression levels of various factors which are potentially important for β-cell functions by real-time RT-PCR and immunohistochemistry. The results showed that expression levels of MafA and GLP-1 receptor were markedly decreased in untreated and alo groups, but not in pio, pio+alo and gla groups., Conclusion: Combination therapy with pio and alo almost completely normalized β-cell functions in vivo, which was comparable with gla treatment., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The hallmarks of type 2 diabetes are pancreatic beta-cell dysfunction and insulin resistance. It has been suggested that Rho/Rho-kinase is a mediator of insulin signaling, and thereby involved in the development of insulin resistance, regulation of insulin action, and glucose homeostasis, but the role of Rho/Rho-kinase in beta-cells remained unknown. The aim of this study was to examine the possible role of Rho/Rho-kinase in beta-cell function. Immunostaining showed that RhoA was expressed in mature beta-cells, with higher expression observed in beta-cells of diabetic C57BL/KsJ-db/db mice compared to non-diabetic mice. In addition, to examine the functional role of Rho/Rho-kinase in beta-cells, we evaluated the effect of Rho-kinase inhibitors on insulin biosynthesis. Northern blot analysis showed that insulin mRNA levels were markedly increased by Rho-kinase inhibitors, Y-27632 and fasudil, in beta-cell-derived HIT-T15 cells. Furthermore, using the luciferase reporter gene assay, insulin promoter activity was also dramatically increased by Y-27632, which was associated with an increase in the insulin mRNA level. These results suggest that suppression of Rho/Rho-kinase increases insulin promoter activity, which leads to an increase in insulin mRNA level. Taken together, Rho/Rho-kinase is activated in beta-cells under diabetic conditions and suppression of the Rho/Rho-kinase pathway increases insulin gene transcription. These results imply that Rho/Rho-kinase activation is involved in the suppression of insulin expression found in diabetes and that suppression of the Rho/Rho-kinase pathway could be a useful tool to augment insulin gene transcription.

Diabetes is the most prevalent and serious metabolic disease, and the number of diabetic patients worldwide is increasing. The reduction of insulin biosynthesis in pancreatic beta-cells is closely associated with the onset and progression of diabetes, and thus it is important to search for ways to induce insulin-producing cells in non-beta-cells. In this study, we showed that a modified form of the pancreatic and duodenal homeobox factor 1 (PDX-1) carrying the VP16 transcriptional activation domain (PDX-1/VP16) markedly increases insulin biosynthesis and induces various pancreas-related factors in the liver, especially in the presence of NeuroD or neurogenin 3 (Ngn3). Furthermore, in streptozotocin-induced diabetic mice, PDX-1/VP16 overexpression, together with NeuroD or Ngn3, drastically ameliorated glucose tolerance. Thus PDX-1/VP16 expression, together with NeuroD or Ngn3, markedly induces insulin gene transcription and ameliorates glucose tolerance. This approach warrants further investigation and may have utility in the treatment of diabetes.

We previously reported that insulin receptor substrate-2 (IRS-2)-deficient mice develop diabetes as a result of insulin resistance in the liver and failure of beta-cell hyperplasia. In this study we introduced the IRS-2 gene specifically into the liver of Irs2(-/-) mice with adenovirus vectors. Glucose tolerance tests revealed that the IRS-2 restoration in the liver ameliorated the hyperglycemia, but the improvement in hyperinsulinemia was only partial. Endogenous glucose production (EGP) and the rate of glucose disappearance (Rd) were measured during hyperinsulinemic-euglycemic clamp studies: EGP was increased 2-fold in the Irs2(-/-) mice, while Rd decreased by 50%. Restoration of IRS-2 in the liver suppressed EGP to a level similar to that in wild-type mice, but Rd remained decreased in the Adeno-IRS-2-infected Irs2(-/-) mice. Irs2(-/-) mice also exhibit obesity and hyperleptinemia associated with impairment of hypothalamic phosphatidylinositol 3-kinase activation. Continuous intracerebroventricular leptin infusion or caloric restriction yielded Irs2(-/-) mice whose adiposity was comparable to that of Irs2(+/+) mice, and both the hyperglycemia and the hyperinsulinemia of these mice improved with increased Rd albeit partially. Finally combination treatment consisting of adenovirus-mediated gene transfer of IRS-2 and continuous intracerebroventricular leptin infusion completely reversed the hyperglycemia and hyperinsulinemia in Irs2(-/-) mice. EGP and Rd also became normal in these mice as well as in mice treated by caloric restriction plus adenoviral gene transfer. We therefore concluded that a combination of increased EGP due to insulin signaling defects in the liver and reduced Rd due to obesity accounts for the systemic insulin resistance in Irs2(-/-) mice.

Aims/Introduction: To investigate the basal insulin requirement in patients with type 1 diabetes who are on multiple daily injections (MDI) and to assess the patient characteristics that affect the percent of total daily basal insulin dose to the total daily insulin dose (%TBD/TDD). Materials and Methods: The subjects of this study were 67 inpatients with type 1 diabetes who were served diabetic meals of 25–30 kcal/kg standard body weight during several weeks of hospitalization. The basal insulin requirement was adjusted to keep the blood glucose level from bedtime to before breakfast within a 30 mg/dL difference. The bolus insulin dose before the meal was adjusted to keep the blood glucose level below 140 and 200 mg/dL before and 2 h after each meal, respectively. The total daily insulin dose (TDD), the percent of total daily basal insulin dose (TBD) to TDD (%TBD/TDD), and clinical characteristics were collected. Results: The median (Q1, Q3) of TDD was 33.0 (26.0, 49.0) units, and the %TBD/TDD was 24.1 ± 9.8%. The %TBD/TDD was positively correlated with the body mass index (BMI) and negatively correlated with the age at the onset and at the examination according to a univariate analysis. However, the %TBD/TDD was dependent on the BMI (β = 0.340, P = 0.004) and the age at examination (β = −0.288, P = 0.012) according to the multiple regression analysis. Conclusions: The average %TBD/TDD in patients with type 1 diabetes on MDI was approximately 24% under inpatient conditions. The basal insulin requirement was dependent on the BMI and the age at examination. [ABSTRACT FROM AUTHOR]

Severe hypoglycaemia (SH) remains a challenge to people with type 1 diabetes (T1DM), and new‐generation basal insulins may improve patient outcomes. This post hoc meta‐analysis explored the risk of SH with insulin glargine 300 U/mL (Gla‐300) versus glargine 100 U/mL (Gla‐100) in a pooled population with T1DM from three randomized, multicentre, 6‐month similarly designed phase 3 trials: EDITION 4, EDITION JP 1 and EDITION JUNIOR. Endpoints included incidence and time to first occurrence of SH. Among 629 and 626 participants randomized to Gla‐300 and Gla‐100, respectively, glycated haemoglobin reductions were similar. Fewer participants experienced ≥1 SH event with Gla‐300 (6.2%) than with Gla‐100 (9.3%). From baseline to month 6, the risk of a first SH event was lower with Gla‐300: hazard ratio 0.65 [95% confidence interval (CI) 0.44–0.98; stratified log‐rank test P = 0.038]. SH event rates were numerically lower with Gla‐300 versus Gla‐100 from baseline to month 6 [relative risk (RR) 0.80 (95% CI 0.49–1.29); P = 0.356] and baseline to week 8 [RR 0.73 (95% CI 0.37–1.44); P = 0.369]. Thus, Gla‐300 demonstrated similar glycaemic control with lower risk of SH versus Gla‐100, particularly during the titration period. [ABSTRACT FROM AUTHOR]

The objective of the present study was to investigate the correlations between serum undercarboxylated osteocalcin (ucOC) or osteocalcin (OC) concentrations and %body fat, serum adiponectin and free-testosterone concentration, muscle strength and dose of exogenous insulin in patients with type 1 diabetes. We recruited 73 Japanese young adult patients with childhood-onset type 1 diabetes. All participants were receiving insulin replacement therapy. The correlations between logarithmic serum ucOC or OC concentrations and each parameter were examined. Serum ucOC and OC concentrations were inversely correlated with %body fat (r = -0.319, P = 0.007; r = -0.321, P = 0.006, respectively). Furthermore, multiple linear regression analyses were performed to determine whether or not serum ucOC or OC concentrations were factors associated with %body fat. Serum ucOC and OC concentrations remained significant factors even after adjusting for gender, HbA1c, body weight-adjusted total daily dose of insulin and duration of diabetes (β = -0.260, P = 0.027; β = -0.254, P = 0.031, respectively). However, serum ucOC and OC concentrations were not correlated with serum adiponectin or free-testosterone concentrations, muscle strength or dose of exogenous insulin. In conclusion, our study demonstrates the inverse correlation between serum ucOC or OC concentrations and body fat in patients with type 1 diabetes. [ABSTRACT FROM AUTHOR]

Background: Experimental studies have suggested that dipeptidyl peptidase-4 (DPP-4) inhibitors provide cardiovascular protective effects. We performed a randomized study to evaluate the effects of sitagliptin added on to the conventional therapy compared with conventional therapy alone (diet, exercise, and/or drugs, except for incretin-related agents) on the intima-media thickness (IMT) of the carotid artery, a surrogate marker for the evaluation of atherosclerotic cardiovascular disease, in people with type 2 diabetes mellitus (T2DM).Methods and Findings: We used a multicenter PROBE (prospective, randomized, open label, blinded endpoint) design. Individuals aged ≥30 y with T2DM (6.2% ≤ HbA1c < 9.4%) were randomly allocated to receive either sitagliptin (25 to 100 mg/d) or conventional therapy. Carotid ultrasound was performed at participating medical centers, and all parameters were measured in a core laboratory. Of the 463 enrolled participants with T2DM, 442 were included in the primary analysis (sitagliptin group, 222; conventional therapy group, 220). Estimated mean (± standard error) common carotid artery IMT at 24 mo of follow-up in the sitagliptin and conventional therapy groups was 0.827 ± 0.007 mm and 0.837 ± 0.007 mm, respectively, with a mean difference of -0.009 mm (97.2% CI -0.028 to 0.011, p = 0.309). HbA1c level at 24 mo was significantly lower with sitagliptin than with conventional therapy (6.56% ± 0.05% versus 6.72% ± 0.05%, p = 0.008; group mean difference -0.159, 95% CI -0.278 to -0.041). Episodes of serious hypoglycemia were recorded only in the conventional therapy group, and the rate of other adverse events was not different between the two groups. As it was not a placebo-controlled trial and carotid IMT was measured as a surrogate marker of atherosclerosis, there were some limitations of interpretation.Conclusions: In the PROLOGUE study, there was no evidence that treatment with sitagliptin had an additional effect on the progression of carotid IMT in participants with T2DM beyond that achieved with conventional treatment.Trial Registration: University Hospital Medical Information Network Clinical Trials Registry UMIN000004490. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to examine the association between ectopic fat and organ-specific insulin resistance (IR) in insulin-target organs in patients with nonalcoholic fatty liver disease (NAFLD). Methods: Organ-specific IR in the liver (hepatic glucose production (HGP)×fasting plasma insulin (FPI) and suppression of HGP by insulin [%HGP]), skeletal muscle (insulin-stimulated glucose disposal [Rd]), and adipose tissue (suppression of FFA by insulin [%FFA]) was measured in 69 patients with NAFLD using a euglycemic hyperinsulinemic clamp with tracer infusion ([6,6-2H2]glucose). Liver fat, intramyocellular lipid (IMCL), and body composition were measured by liver biopsy, proton magnetic resonance spectroscopy, and bioelectrical impedance analysis, respectively. Results: HGP×FPI was significantly correlated with Rd (r = −0.57, P<0.001), %HGP with %FFA (r = 0.38, P<0.01), and Rd with %FFA (r = 0.27, P<0.05). Liver steatosis score was negatively associated with Rd (r = −0.47, P<0.001) as well as with HGP×FPI (r = 0.43, P<0.001). Similarly, intrahepatic lipid was negatively associated with Rd (r = −0.32, P<0.05). IMCL was not associated with Rd (r = −0.16, P = 0.26). Fat mass and its percentage were associated with HGP×FPI (r = 0.50, P<0.001; r = 0.48, P<0.001, respectively) and Rd (r = −0.59, P<0.001; r = −0.52, P<0.001, respectively), but not with %FFA (r = −0.21, P = 0.10; r = −0.001, P = 0.99, respectively). Conclusion: Unexpectedly, fat accumulation in the skeletal muscle and adipose tissue was not associated with organ-specific IR. Instead, liver fat was associated not only with hepatic IR but also with skeletal muscle IR, suggesting a central role of fatty liver in systemic IR and that a network exists between liver and skeletal muscle. [ABSTRACT FROM AUTHOR]

The aim of the present study was to compare the usefulness of premeal rapid-acting and regular insulin in type 2 diabetes patients. A total of 56 type 2 diabetic patients were investigated during hospitalization. Premeal rapid-acting insulin was applied instead of other medications. Premeal insulin was titrated to adjust premeal and bedtime blood glucose levels to 81-120 mg/ dL. Premeal rapid-acting insulin was changed to regular insulin just before a meal at the same dosage if the postmeal blood glucose level was lower than the premeal blood glucose level. A total of 15 patients changed to regular insulin, and 41 patients continued rapid-acting insulin. The blood glucose level was comparable between these two groups. Body mass index was significantly lower in the patients using regular insulin. According to the multivariate logistic regression analysis, low body mass index was an independent variable accounting for the usefulness of regular insulin. Regular insulin, rather than rapid-acting insulin, is a suitable choice for premeal insulin in lean type 2 diabetic patients. [ABSTRACT FROM AUTHOR]

Aims: This study investigated the hypoglycemia risk in people with type 2 diabetes (T2D) who initiated or switched to insulin glargine 300 U/mL (Gla-300) by stratifying them by age and renal function.Methods: We examined data from 4621 people with T2D (1227 insulin-naïve and 3394 insulin-experienced) of the X-STAR study, a prospective, observational, 12-month study conducted from December 2015 to August 2018 in Japan. Participants were stratified by age (<65, 65 to <75, and ≥75 years) and estimated glomerular filtration rate (eGFR) (≥90, 60 to <90, 30 to <60, and <30 mL/min/1.73 m2). Hypoglycemia was defined according to the Ministry of Health, Labour and Welfare manual of Japan.Results: No apparent increase in the proportion of people who experienced hypoglycemia was found in all subgroups. The proportions were 2.9-3.5% and 2.7-5.2% of insulin-naïve and insulin-experienced people, respectively, for age subgroups, and 2.4-4.7% and 4.6-4.8%, respectively, for eGFR subgroups. The result was similar for HbA1c levels below and at or above 7.0% in all age subgroups.Conclusions: Our study found no apparent increase in the hypoglycemia risk in people with older age and renal impairment who were administered Gla-300. These results would provide reassuring information on Gla-300 use. [ABSTRACT FROM AUTHOR]

Background: Continuous subcutaneous insulin infusion (CSII) is associated with improved glycemic control, a reduced incidence of hypoglycemia, and improved quality of life (QOL). To date, however, there has been no QOL scale specific to CSII. The objective of this study was to develop and validate a scale to measure CSII-QOL for people with type 1 diabetes (T1D). Methods: A total of 50 people with T1D aged ≥15 years who used CSII (28% males; age, 47.6 ± 17.0 years; duration of diabetes, 14.7 ± 9.7 years; duration of CSII use, 6.1 ± 3.3 years; HbA1c, 7.4% ± 0.8%) took part in the CSII-QOL study. Twenty-eight potential CSII-QOL items were developed in a combined approach consisting of semistructured patient interviews, expert input, and a literature search. The resulting CSII-QOL was tested for factor analysis, validity, reliability, and influencing factors. Results: The final 25-item questionnaire had a 3-domain structure ("convenience," "social restriction," and "psychological problems"), high internal consistency (Cronbach's alpha = 0.870), and substantial test-retest reliability (intraclass correlation coefficient = 0.65). The CSII-QOL score was correlated negatively with the Problem Areas in Diabetes score. Conclusion: The CSII-QOL is the first CSII-related QOL scale for people with T1D. This short, validated, and reliable instrument might potentially be useful in future clinical studies and routine clinical patient care. Further validation is required to confirm these issues because of the small and potentially biased sample (UMIN-CTR: UMIN000031595). [ABSTRACT FROM AUTHOR]

Abstract: Pancreatic β-cell-specific insulin gene expression is regulated by a variety of pancreatic transcription factors and the conserved A3, C1 and E1 elements in the insulin gene enhancer region are very important for activation of insulin gene. Indeed, PDX-1 binding to the A3 element and NeuroD binding to the E1 element are crucial for insulin gene transcription. Recently, C1 element-binding transcription factor was identified as MafA, which is a basic-leucine zipper transcription factor and functions as a potent transactivator for the insulin gene. Under diabetic conditions, chronic hyperglycemia gradually deteriorates pancreatic β-cell function, which is accompanied by decreased expression and/or DNA binding activities of MafA and PDX-1. Furthermore, MafA overexpression, together with PDX-1 and NeuroD, markedly induces insulin biosynthesis in various non-β-cells and thereby is a useful tool to efficiently induce insulin-producing surrogate β-cells. These results suggest that MafA plays a crucial role in pancreatic β-cells and could be a novel therapeutic target for diabetes. [Copyright &y& Elsevier]

Abstract: It is well known that pancreatic and duodenal homeobox gene-1 (PDX-1) plays a crucial role in β-cell differentiation, and maintaining mature β-cell function. Thus, it is important to understand how pdx-1 gene is regulated under various pathophysiological conditions in vivo. In this study, to non-invasively and quantitatively monitor pdx-1 promoter activity in vivo, we constructed a pdx-1 promoter-SEAP-IRES-GFP reporter plasmid. In this construct, the −4.6kb pdx-1 promoter region sufficient for driving β-cell-selective PDX-1 expression was inserted to the upstream of the secreted alkaline phosphatase (SEAP) reporter gene. It is noted here that the pdx-1 promoter-mediated SEAP activity can be distinguished from endogenous alkaline phosphatase activity. First, we transfected the construct in mouse β-cell line MIN6 and human hepatocellular carcinoma cell line HepG2. SEAP activity was readily detected in the media of MIN6 cells, but not in HepG2 cells. These results indicate that this construct specifically reports β-cell-specific pdx-1 promoter activity in a cell culture system. Based on these in vitro findings, we next generated transgenic mice using the same construct. SEAP activity was readily detected in serum of the transgenic mice, but not in their littermate mice. Furthermore, SEAP activity was detected in protein extract from the transgenic pancreas and slightly from the transgenic duodenum, but not from the liver, and brain. These results indicate that serum SEAP activity likely represents in vivo pdx-1 promoter activity. This transgenic mouse model would be useful to non-invasively monitor in vivo pdx-1 promoter activity and to screen new molecules which regulate PDX-1 expression. [Copyright &y& Elsevier]

The c-Jun N-terminal kinase (JNK) pathway is known to be activated under diabetic conditions and to possibly be involved in the progression of insulin resistance. In this study, we examined the effects of modulation of the JNK pathway in liver on insulin resistance and glucose tolerance. Overexpression of dominant-negative type JNK in the liver of obese diabetic mice dramatically improved insulin resistance and markedly decreased blood glucose levels. Conversely, expression of wild type JNK in the liver of normal mice decreased insulin sensitivity. The phosphorylation state of crucial molecules for insulin signaling was altered upon modification of the JNK pathway. Furthermore, suppression of the JNK pathway resulted in a dramatic decrease in the expression levels of the key gluconeogenic enzymes, and endogenous hepatic glucose production was also greatly reduced. Similar effects were observed in high fat, high sucrose diet-induced diabetic mice. Taken together, these findings suggest that suppression of the JNK pathway in liver exerts greatly beneficial effects on insulin resistance status and glucose tolerance in both genetic and dietary models of diabetes. [ABSTRACT FROM AUTHOR]

We previously reported that insulin receptor substrate-2 (IRS-2)-deficient mice develop diabetes as a re. suit of insulin resistance in the liver and failure of β-cell hyperplasia. In this study we introduced the IRS-2 gene specifically into the liver of Irs2-1- mice with adenovirus vectors. Glucose tolerance tests revealed that the IRS-2 restoration in the liver ameliorated the hyperglycemia, but the improvement in hyperinsulinemia was only partial. Endogenous glucose production (EGP) and the rate of glucose disappearance (Rd) were measured during hyperinsulinemic-euglycemic clamp studies: EGP was increased 2-fold in the Irs2-1- mice, while Rd decreased by 50%. Restoration of IRS-2 in the liver suppressed EGP to a level similar to that in wild-type mice, but Rd remained decreased in the Adeno-IRS-2-infected Irs2-1- mice. Irs2-1- mice also exhibit obesity and hyperleptinemia associated with impairment of hypothalamic phosphatidylinositol 3-kinase activation. Continuous intracerebroventricular leptin infusion or caloric restriction yielded Irs2-1- mice whose adiposity was comparable to that of Irs2+/+ mice, and both the hyperglycemia and the hyperinsulinemia of these mice improved with increased Rd albeit partially. Finally combination treatment consisting of adenovirus-mediated gene transfer of IRS-2 and continuous intracerebroventricular leptin infusion completely reversed the hyperglycemia and hyperinsulinemia in Irs2-/- mice. EGP and Rd also became normal in these mice as well as in mice treated by caloric restriction plus adenoviral gene transfer. We therefore concluded that a combination of increased EGP due to insulin signaling defects in the liver and reduced Rd due to obesity accounts for the systemic insulin resistance in Irs2-/- mice. [ABSTRACT FROM AUTHOR]