Telenutrition Education Is Effective for Glycemic Management in People with Type 2 Diabetes Mellitus: A Non-Inferiority Randomized Controlled Trial in Japan.

This study examined the non-inferior efficacy of telenutrition education compared with face-to-face nutrition education in managing glycemic control in people with type 2 diabetes mellitus (T2DM). Participants had T2DM and a glycated hemoglobin (HbA1c) ranged 6.5-9.5%. Thirty participants were randomly assigned to either the telenutrition or face-to-face nutrition education group. During the 32-week intervention period, the participants received four sessions on nutrition education from a registered dietitian at the hospital. The telenutrition group received remote education via a videoconferencing platform. Face-to-face nutrition education was conducted using paper-based instructions. The main outcome measure was the non-inferiority of HbA1c levels in the telenutrition group compared to the face-to-face nutrition group. The non-inferiority of telenutrition education was considered valid if the intergroup difference in the mean values of the change in HbA1c had a bilateral 95% confidence interval (CI) upper limit below 0.40%. The intergroup difference in the mean HbA1c change from baseline to the fourth nutrition education session was -0.11 (95% CI -0.54-0.32) for both groups. The upper limit of the bilateral 95% CI was 0.32%, which was below the 0.40% non-inferiority margin (non-inferiority test; p = 0.011). Telenutrition education was not inferior to face-to-face nutrition education for glycemic management in people with T2DM.

Albuminuria and Serum Tumor Necrosis Factor Receptor Levels in Patients with Type 2 Diabetes on SGLT2 Inhibitors: A Prospective Study.

INTRODUCTION: Large-scale clinical trials of sodium-glucose cotransporter 2 inhibitors (SGLT2i) demonstrate proteinuria-reducing effects in diabetic kidney disease, even after treatment with renin-angiotensin inhibitors. The precise mechanism for this favorable effect remains unclear. This prospective open-label single-arm study investigated factors associated with a reduction in proteinuria after SGLT2i administration. METHODS: Patients with type 2 diabetes (T2DM) who had glycated hemoglobin (HbA1c) levels ≥ 6.5% despite dietary and/or oral hypoglycemic monotherapy were recruited and administered the recommended daily dose of SGLT2i for 4 months. Dual primary outcomes were changes in the urine albumin-to-creatinine ratio (uACR) and urine liver-type fatty acid-binding protein (L-FABP)-to-creatinine ratio (uL-FABPCR) at month 4 from baseline. Changes in kidney injury, inflammation, and oxidative stress biomarkers were investigated as secondary endpoints to examine the effects of this treatment on the kidney. The correlation between renal outcomes and clinical indicators, including circulating tumor necrosis factor receptors (TNFR) 1 and 2, was evaluated using univariate and multivariate analyses. RESULTS: Participants (n = 123) had a mean age of 64.1 years (SD 13.4), with 50.4% being male. The median BMI was 25.8 kg/m2 (interquartile range (IQR) 23.1-28.9), and the median HbA1c level was 7.3% (IQR 6.9-8.3). After SGLT2i administration, the uACR declined from 19.2 mg/gCr (IQR 7.1-48.7) to 13.3 mg/gCr (IQR 7.5-31.6), whereas the uL-FABPCR was not influenced. In univariate analysis, the change in log-transformed uACR due to SGLT2i administration showed a positive correlation with the change in serum TNFR1 level (R = 0.244, p < 0.01). Multivariate regression analysis, including confounding factors, showed that the changes in serum TNFR1 level were independently associated with the changes in the log-transformed uACR (independent t = 2.102, p < 0.05). CONCLUSION: After the 4-month SGLT2i administration, decreased albuminuria level was associated with decreased serum TNFR level in patients with T2DM. TRIAL REGISTRATION NUMBER: UMIN000031947.

Previous studies have demonstrated the synergistic proteinuria-reducing effect of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in combination therapy with renin­angiotensin system blockers; however, the underlying mechanisms of this effect are poorly understood. This study was based on our hypothesis that the proteinuria-reducing effect is associated with the anti-inflammatory effects of SGLT2i beyond the effect on glycemic control. In total, 123 patients with type 2 diabetes mellitus (T2DM) were administered the recommended daily dose of SGLT2i for 4 months. Dual primary outcomes were changes in the urine albumin-to-creatinine ratio (uACR) and urine liver-type fatty acid-binding protein (L-FABP)-to-creatinine ratio (uL-FABPCR) as markers of glomerular and proximal tubular damage at 4 months from the baseline. Secondary outcomes included changes in kidney injury biomarkers, inflammation, and oxidative stress to examine the effects of treatment on the kidneys. The correlation between renal outcomes and clinical indicators, including circulating tumor necrosis factor receptors (TNFR) 1 and 2, was evaluated using univariate and multivariate analyses. We found that administration of SGLT2i decreased the urine albumin-to-creatinine ratio but did not affect the urine liver-type fatty acid-binding protein-to-creatinine ratio. Further, SGLT2i may exert a proteinuria-reducing effect dependent on the anti-inflammatory effect in patients with T2DM. The inflammation-reducing and renoprotective mechanisms of SGLT2i remain to be fully clarified, but this study provides novel evidence regarding the mechanism. The study findings can help in developing anti-inflammatory agents for metabolic diseases.

Novel method utilizing bisulfite conversion with dual amplification-refractory mutation system polymerase chain reaction to detect circulating pancreatic ß-cell cfDNA.

AIMS/INTRODUCTION: Several research groups have reported methods for quantifying pancreatic beta cell (ß-cell) injury by measuring ß-cell-specific CpG unmethylation of the insulin gene in circulation using digital droplet PCR or next-generation sequencing. However, these methods have certain disadvantages, such as the need to consider the background signal owing to the small number of target CpG sites and the need for unique equipment. MATERIALS AND METHODS: We established a novel method for detecting four CpG unmethylations of the insulin gene using two-step amplification refractory mutation system PCR. We applied it to type 1 diabetes (T1D) patients with a wide range of disease durations and to healthy adults. RESULTS: The assay showed high linearity and could detect a single copy of unmethylated insulin DNA in experiments using methylated and unmethylated plasmid DNA. The unmethylated insulin DNA level in the type 1 diabetes group, whose ß-cell mass was considerably reduced, was similar to that of healthy adults. An inverse correlation was observed between copy number and disease duration in patients with unmethylated insulin DNA-positive type 1 diabetes. CONCLUSIONS: We developed a novel method for detecting unmethylated insulin DNA in circulation that can be performed using a conventional real-time PCR system. This method would be useful for analyzing dynamic profiles of ß-cells in human disease such as type 1 diabetes.

Characterisation of Ppy-lineage cells clarifies the functional heterogeneity of pancreatic beta cells in mice.

AIMS/HYPOTHESIS: Pancreatic polypeptide (PP) cells, which secrete PP (encoded by the Ppy gene), are a minor population of pancreatic endocrine cells. Although it has been reported that the loss of beta cell identity might be associated with beta-to-PP cell-fate conversion, at present, little is known regarding the characteristics of Ppy-lineage cells. METHODS: We used Ppy-Cre driver mice and a PP-specific monoclonal antibody to investigate the association between Ppy-lineage cells and beta cells. The molecular profiles of endocrine cells were investigated by single-cell transcriptome analysis and the glucose responsiveness of beta cells was assessed by Ca2+ imaging. Diabetic conditions were experimentally induced in mice by either streptozotocin or diphtheria toxin. RESULTS: Ppy-lineage cells were found to contribute to the four major types of endocrine cells, including beta cells. Ppy-lineage beta cells are a minor subpopulation, accounting for 12-15% of total beta cells, and are mostly (81.2%) localised at the islet periphery. Unbiased single-cell analysis with a Ppy-lineage tracer demonstrated that beta cells are composed of seven clusters, which are categorised into two groups (i.e. Ppy-lineage and non-Ppy-lineage beta cells). These subpopulations of beta cells demonstrated distinct characteristics regarding their functionality and gene expression profiles. Ppy-lineage beta cells had a reduced glucose-stimulated Ca2+ signalling response and were increased in number in experimental diabetes models. CONCLUSIONS/INTERPRETATION: Our results indicate that an unexpected degree of beta cell heterogeneity is defined by Ppy gene activation, providing valuable insight into the homeostatic regulation of pancreatic islets and future therapeutic strategies against diabetes. DATA AVAILABILITY: The single-cell RNA sequence (scRNA-seq) analysis datasets generated in this study have been deposited in the Gene Expression Omnibus (GEO) under the accession number GSE166164 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE166164 ).

Development of monoclonal mouse antibodies that specifically recognize pancreatic polypeptide.

Pancreatic polypeptide (PP) is a 36-amino acid peptide encoded by the Ppy gene, which is produced by a small population of cells located in the periphery of the islets of Langerhans. Owing to the high amino acid sequence similarity among neuropeptide Y family members, antibodies against PP that are currently available are not convincingly specific to PP. Here we report the development of mouse monoclonal antibodies that specifically bind to PP. We generated Ppy knockout (Ppy-KO) mice in which the Ppy-coding region was replaced by Cre recombinase. The Ppy-KO mice were immunized with mouse PP peptide, and stable hybridoma cell lines producing anti-PP antibodies were isolated. Firstly, positive clones were selected in an enzyme-linked immunosorbent assay for reactivity with PP coupled to bovine serum albumin. During the screening, hybridoma clones producing antibodies that cross-react to the peptide YY (PYY) were excluded. In the second screening, hybridoma clones in which their culture media produce no signal in Ppy-KO islets but detect specific cells in the peripheral region of wild-type islets, were selected. Further studies demonstrated that the selected monoclonal antibody (23-2D3) specifically recognizes PP-producing cells, not only in mouse, but also in human and rat islets. The monoclonal antibodies with high binding specificity for PP developed in this study will be fundamental for future studies towards elucidating the expression profiles and the physiological roles of PP.

Association of accumulated advanced glycation end-products with a high prevalence of sarcopenia and dynapenia in patients with type 2 diabetes.

AIMS/INTRODUCTION: Advanced glycation end-products (AGEs), which are a major cause of diabetic vascular complications, accumulate in various tissues under chronic hyperglycemic conditions, as well as with aging in patients with diabetes. The loss of muscle mass and strength, so-called sarcopenia and dynapenia, has recently been recognized as a diabetic complication. However, the influence of accumulated AGEs on muscle mass and strength remains unclear. The present study aimed to evaluate the association of sarcopenia and dynapenia with accumulated AGEs in patients with type 2 diabetes. MATERIALS AND METHODS: We recruited 166 patients with type 2 diabetes aged ≥30 years (mean age 63.2 ± 12.3 years; body mass index 26.3 ± 4.9 kg/m2 ; glycated hemoglobin 7.1 ± 1.1%). Skin autofluorescence as a marker of AGEs, limb skeletal muscle mass index, grip strength, knee extension strength and gait speed were assessed. RESULTS: Sarcopenia and dynapenia were observed in 7.2 and 13.9% of participants, respectively. Skin autofluorescence was significantly higher in patients with sarcopenia and dynapenia. Skin autofluorescence was the independent determinant for skeletal muscle mass index, grip strength, knee extension strength, sarcopenia and dynapenia. CONCLUSIONS: Accumulated AGEs could contribute to reduced muscle mass and strength, leading to sarcopenia and dynapenia in patients with type 2 diabetes.

Up-Titration Strategy After DPP-4 Inhibitor-Based Oral Therapy for Type 2 Diabetes: A Randomized Controlled Trial Shifting to a Single-Dose GLP-1 Enhancer Versus Adding a Variable Basal Insulin Algorithm.

INTRODUCTION: It is unclear whether adding basal insulin or enhancing incretin signaling with a glucagon-like peptide-1 receptor agonist (GLP-1RA) is more effective as an up-titration strategy after dipeptidyl peptidase-4 inhibitor (DPP-4i)-based oral antidiabetic drug (OAD) therapy. GLP-1RAs can be injected without dose adjustment, unlike basal insulin. Our objective was to examine the efficacy of changing patients inadequately controlled with oral DPP-4i-based OAD therapy to injectable GLP-1RA and discontinuing the DPP4i versus adding basal insulin glargine (IGlar) with the continuation of the oral DPP4i. METHODS: Sixty patients with type 2 diabetes (T2DM) and glycated hemoglobin (HbA1c) between 7.0% and 10.0% on DPP-4i-based OAD therapy were randomized to either adding IGlar and remaining on the DPP-4i or liraglutide and discontinuing the DPP-4i for 24 weeks. Patients in the IGlar group started with 0.1 unit/kg and were titrated according to the algorithm. In the liraglutide group, the DPP-4i was replaced with liraglutide 0.9 mg/day, the maximum dose in Japan. We evaluated HbA1c, glycated albumin (GA), and anthropometrics. RESULTS: HbA1c was significantly lower at week 24 (- 1.0 ± 0.9% in the IGlar group and - 0.6 ± 0.8% in the liraglutide group), but the difference between groups was not significant. Changes in GA were similar (- 2.9 ± 3.2% vs. - 2.6 ± 3.2%) in both groups. Body weight (BW) was significantly lower only in the liraglutide group (+ 0.5 ± 2.6 kg vs. - 2.2 ± 2.0 kg). The rate of minor hypoglycemic episodes was similar for both groups. CONCLUSION: For poorly controlled T2DM on DPP-4i-based OAD therapy, switching to single-dose liraglutide to enhance incretin signaling is as effective as dose-titrated basal IGlar, but significant BW reduction was only seen in the liraglutide group. These results suggest that enhancing incretin signaling with a single-dose injectable GLP-1 RA might be an alternative to dose-titrated basal insulin therapy in patients with T2DM poorly controlled with DPP-4i-based OAD therapy. These findings should be confirmed in a longer and larger trial. TRIAL REGISTRATION: Trial Registry (UMIN-CTR) as UMIN000012224.

Accuracy and Time Delay of Glucose Measurements of Continuous Glucose Monitoring and Bedside Artificial Pancreas During Hyperglycemic and Euglycemic Hyperinsulinemic Glucose Clamp Study.

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.

Protein kinase C-δ signaling regulates glucagon secretion from pancreatic islets.

Accumulating evidence supports the "glucagonocentric hypothesis", in which antecedent α-cell failure and inhibition of glucagon secretion are responsible for diabetes progression. Protein kinase C (PKC) is involved in glucagon secretion from α-cells, although which PKC isozyme is involved and the mechanism underlying this PKC-regulated glucagon secretion remains unknown. Here, the involvement of PKCδ in the onset and progression of diabetes was elucidated. Immunofluorescence studies revealed that PKCδ was expressed and activated in α-cells of STZ-induced diabetic model mice. Phorbol 12-myristate 13-acetate (PMA) stimulation significantly augmented glucagon secretion from isolated islets. Pre-treatment with quercetin and rottlerin, PKCδ signaling inhibitors, significantly suppressed the PMA-induced elevation of glucagon secretion. While Go6976, a Ca2+-dependent PKC selective inhibitor did not suppress glucagon secretion. Quercetin suppressed PMA-induced phosphorylation of Tyr311 of PKCδ in isolated islets. However, quercetin itself had no effect on either glucagon secretion or glucagon mRNA expression. Our data suggest that PKCδ signaling inhibitors suppressed glucagon secretion. Elucidation of detailed signaling pathways causing PKCδ activation in the onset and progression of diabetes followed by the augmentation of glucagon secretion could lead to the identification of novel therapeutic target molecules and the development of novel therapeutic drugs for diabetes. J. Med. Invest. 64: 122-128, February, 2017.

A pilot study comparing the CGM-assessed glycemic profiles of patients with type 1 diabetes on insulin degludec and insulin glargine.

AIMS: To compare the diurnal glycemic profiles obtained with basal insulin degludec (InsDeg) and basal insulin glargine (InsGla) in patients with type 1 diabetes using continuous glucose monitoring (CGM) in an outpatient setting. METHODS: Twenty Japanese patients with type 1 diabetes who were using once-daily InsGla before supper as part of their multiple daily insulin injections were consecutively recruited. CGM was initiated before supper on day 1, and InsGla was switched to InsDeg at the same dose on day 3. The average CGM glucose profile obtained on days 1 and 2 was compared with the corresponding profile for days 5 and 6. The bolus insulin regimen was not changed during the study period. RESULTS: CGM glucose was significantly higher (p < 0.05) from 19:30 to 22:30 and significantly lower (p < 0.05) from 6:30 to 8:00 with basal InsDeg than with basal InsGla. The duration of hypoglycemia (<70 mg/dl) was the same regardless of whether basal InsDeg or basal InsGla was used. CONCLUSIONS: The peak in the action profile of InsDeg lasts longer and is possibly stronger than that of InsGla.

Advanced glycation end-products are a risk for muscle weakness in Japanese patients with type 1 diabetes.

Accumulation of advanced glycation end-products (AGEs) is thought to contribute to muscle weakness in a diabetic animal model. Skin autofluorescence is a proposed marker for accumulation of AGEs in the skin. We aimed to investigate the relationship between AGEs accumulation, sarcopenia and muscle function of Japanese patients with type 1 diabetes. A total of 36 patients with type 1 diabetes participated in the present cross-sectional study. Sarcopenia parameters (skeletal muscle mass index and knee extension strength) were compared with subcutaneous AGEs accumulation using skin autofluorescence. The prevalence of sarcopenia and impaired knee extension strength was 16.6% (men 0.0%, women 22.2%) and 47.2% (men 22.2%, women 55.6%), respectively. Knee extension strength was negatively correlated with skin autofluorescence (r² = 0.14, P < 0.05), but not with skeletal muscle mass index. In conclusion, the AGEs accumulation might be one of the reasons of impaired lower limb muscle function in Japanese patients with type 1 diabetes.

Non-invasive Measurement of Skin Autofluorescence as a Beneficial Surrogate Marker for Atherosclerosis in Patients with Type 2 Diabetes.

Advanced glycation end-products (AGEs) are thought to play a major role in the pathogenesis of diabetic vascular complications. Skin autofluorescence (AF) was recently reported to represent tissue AGEs accumulation with a non-invasive method. The aim of the present study was to evaluate association between AF value and diabetic vascular complications, such as retinopathy, nephropathy and cervical atherosclerosis using the carotid intima-media thickness (IMT), an established marker of cardiovascular disease in patients with type 2 diabetes. A total of 68 patients with type 2 diabetes were enrolled in a cross-sectional manner. AGEs accumulation was measured with AF reader. Clinical parameters were collected at the time of AF and IMT measurement. Max-IMT was correlated with age and AF (r=0.407, p=0.001), but not with HbA1c, GA, and pentosidine. Also, AF was not correlated with HbA1c, GA and pentosidine, but was correlated with age (r=0.560, p<0.001), duration of diabetes (r=0.256, p<0.05). Multivariate regression analysis revealed that AF, but not age, was an independent determinant of max-IMT. In conclusion, AF might be a beneficial surrogate marker for evaluating carotid atherosclerosis in patients with type 2 diabetes non-invasively. J. Med. Invest. 62: 126-129, August, 2015.

Expression mechanism of tryptophan hydroxylase 1 in mouse islets during pregnancy.

Serotonin signaling plays key roles in augmentation of pancreatic ß-cell function during pregnancy. Increased expression of tryptophan hydroxylase 1 (Tph1), a rate-limiting enzyme for serotonin synthesis by lactogenic hormones, is involved in this phenomenon. To investigate its mechanisms, we here performed 5'-RACE and identified ß-cell-specific transcription initiation sites for Tph1. Prolactin enhanced the expression of mRNA containing these exons; however, reporter gene plasmids containing the proximal 5'-flanking region of these exons did not show prolactin responsiveness in MIN6 cells. Prolactin-induced Tph1 expression was inhibited by a Jak2 inhibitor and was partially inhibited by an MEK1/2 or PI3K inhibitor. Therefore, we analyzed interferon γ-activated sequences (GAS) and found GAS-A about 9-kbp upstream of the transcription start site. The reporter gene plasmid containing the GAS-A region linked to a heterologous promoter showed increased promoter activity by prolactin, which was inhibited by the forced expression of a dominant-negative mutant form of Stat5A and a Jak2 inhibitor. Chromatin immunoprecipitation analysis showed that prolactin treatment augmented Stat5 binding to the GAS-A region in MIN6 cells, as well as in isolated mouse islets, and that Stat5 recognized the GAS-A region in pregnant mouse islets. In addition, the transactivation activity of Stat5 was enhanced by prolactin through the Erk and PI3K pathways in MIN6 cells. Finally, serotonin expression was attenuated in islets of ß-cell-specific Stat5-deficient mice compared with that of control littermates during pregnancy. Our findings suggest that prolactin-induced Tph1 expression is mediated by the activation of Jak2/Stat5, Erk, and PI3K pathways in ß cells.

Human IAPP-induced pancreatic ß cell toxicity and its regulation by autophagy.

Pancreatic islets in patients with type 2 diabetes mellitus (T2DM) are characterized by loss of ß cells and formation of amyloid deposits derived from islet amyloid polypeptide (IAPP). Here we demonstrated that treatment of INS-1 cells with human IAPP (hIAPP) enhances cell death, inhibits cytoproliferation, and increases autophagosome formation. Furthermore, inhibition of autophagy increased the vulnerability of ß cells to the cytotoxic effects of hIAPP. Based on these in vitro findings, we examined the pathogenic role of hIAPP and its relation to autophagy in hIAPP-knockin mice. In animals fed a standard diet, hIAPP had no toxic effects on ß cell function; however, hIAPP-knockin mice did not exhibit a high-fat-diet-induced compensatory increase in ß cell mass, which was due to limited ß cell proliferation and enhanced ß cell apoptosis. Importantly, expression of hIAPP in mice with a ß cell-specific autophagy defect resulted in substantial deterioration of glucose tolerance and dispersed cytoplasmic expression of p62-associated toxic oligomers, which were otherwise sequestrated within p62-positive inclusions. Together, our results indicate that increased insulin resistance in combination with reduced autophagy may enhance the toxic potential of hIAPP and enhance ß cell dysfunction and progression of T2DM.

[Role of zinc in type 2 diabetes].

Pancreatic ß cells contain the highest amount of zinc among cells within the human body, and hence, the relationship between zinc and diabetes has been of great interest. To date, many studies of zinc and diabetes have been reported, including studies demonstrating that diabetic patients and mice have a decreased amount of zinc in the pancreas. Zinc may counteract the deleterious effects of oxidative stress, which contributes to reduced insulin resistance, and may also protect pancreatic ß cells from glucolipotoxicity. Recently, we have shown that SLC30A8/zinc transporter 8, which is a transporter expressed on the surface of insulin granules, plays a key role in zinc transport into insulin granules and in the regulation of hepatic insulin clearance. Here, we review the role of zinc in whole-body maintenance and the latest information on the relationship between zinc and diabetes.

Beneficial effects of vildagliptin combined with miglitol on glucose tolerance and islet morphology in diet-controlled db/db mice.

Dipeptidyl peptidase-4 (DPP-4) inhibitors improve glycemic control in patients with type 2 diabetes primarily by increasing plasma active glucagon-like peptide-1 (GLP-1) levels. While various combination therapies based on DPP-4 inhibitors have been proposed for treatment of type 2 diabetes, the effects of combination therapy of DPP-4 inhibitors and alpha-glucosidase inhibitors on ß-cell function are less characterized. We evaluated the effects of long-term treatment with vildagliptin, a DPP-4 inhibitor, on metabolic parameters and ß-cell function, in combination with miglitol, an alpha-glucosidase inhibitor, in diet-controlled db/db mice. In this study, 6-week-old male db/db mice were provided with standard chow twice a day for 6 weeks. Meal tolerance tests and glucose tolerance tests showed that the combination therapy of vildagliptin with miglitol, but not each alone, suppressed postprandial glycemic excursion, enhanced postprandial active GLP-1 levels and prevented deterioration of glucose tolerance in the db/db mice. The combination treatment did not alter ß-cell mass, but resulted in preserved expression of glucose transporter 2, Zinc transporter 8 and MafA and reduced the number of α cells. These results suggest that the combination of vildagliptin and miglitol prevents the development of overt diabetes in diet-controlled pre-diabetic db/db mice by normalizing postprandial glucose and incretin response, and by preserving ß-cell structure and the expression of factors essential for ß-cell function.

The diabetes-susceptible gene SLC30A8/ZnT8 regulates hepatic insulin clearance.

Recent genome-wide association studies demonstrated that common variants of solute carrier family 30 member 8 gene (SLC30A8) increase susceptibility to type 2 diabetes. SLC30A8 encodes zinc transporter-8 (ZnT8), which delivers zinc ion from the cytoplasm into insulin granules. Although it is well known that insulin granules contain high amounts of zinc, the physiological role of secreted zinc remains elusive. In this study, we generated mice with ß cell-specific Slc30a8 deficiency (ZnT8KO mice) and demonstrated an unexpected functional linkage between Slc30a8 deletion and hepatic insulin clearance. The ZnT8KO mice had low peripheral blood insulin levels, despite insulin hypersecretion from pancreatic ß cells. We also demonstrated that a substantial amount of the hypersecreted insulin was degraded during its first passage through the liver. Consistent with these findings, ZnT8KO mice and human individuals carrying rs13266634, a major risk allele of SLC30A8, exhibited increased insulin clearance, as assessed by c-peptide/insulin ratio. Furthermore, we demonstrated that zinc secreted in concert with insulin suppressed hepatic insulin clearance by inhibiting clathrin-dependent insulin endocytosis. Our results indicate that SLC30A8 regulates hepatic insulin clearance and that genetic dysregulation of this system may play a role in the pathogenesis of type 2 diabetes.

Efficacy of pioglitazone on glycemic control and carotid intima-media thickness in type 2 diabetes patients with inadequate insulin therapy.

UNLABELLED: Aims/Introduction: The present study was designed to determine the effects of pioglitazone on glycemic control and atherosclerosis in patients with poorly controlled type 2 diabetes on insulin therapy. MATERIALS AND METHODS: The study was a prospective, randomized controlled trial involving 48 patients with inadequately controlled type 2 diabetes treated with insulin. We assigned patients to oral pioglitazone titrated from 15-30 mg (n = 22) or no pioglitazone (n = 26), to be taken in addition to their glucose-lowering drugs and other medications. Daily insulin doses and numbers were recorded during the study period. RESULTS: The adjusted mean glycosylated hemoglobin (HbA1c) values decreased significantly by 1.13 ± 1.50% and 0.55 ± 0.76% in the pioglitazone and control groups, respectively. Significant decrease of HbA1c level was observed in the pioglitazone group compared with the control group (P < 0.05). The insulin dose lowered by 0.04 ± 0.10 units/kg/day in the pioglitazone group and increased by 0.03 ± 0.10 units/kg/day in the control group (P < 0.05). The number of insulin injections decreased by 0.1 ± 0.6 times/day in the pioglitazone group and increased by 0.2 ± 0.4 times/day in the control group (P < 0.05). The carotid intima-media thickness estimated by B-mode echography was carried out in both groups and decreased significantly at the end-point only in the pioglitazone group, relative to the baseline. CONCLUSIONS: These findings show that pioglitazone is useful in improving glycemic control and preventing the progression of atherosclerosis in poorly-controlled type 2 diabetics on insulin therapy. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00064.x, 2010).

2-Methoxyestradiol ameliorates glucose tolerance with the increase in ß-cell mass in db/db mice.

UNLABELLED: Aims/Introduction: 2-Methoxyestradiol (2ME) is an estradiol metabolite with little estrogenic activity. Previous data identified its anti-carcinogenic properties and possible cardiovascular benefits. However, its effect on diabetes mellitus has not been fully elucidated. The aim of the present study was to determine the effects of 2ME on glucose metabolism in the diabetic state. MATERIALS AND METHODS: To evaluate the effects of 2ME, pellets of two different doses of the drug were implanted into female db/db mice at the age of 5 weeks. Intraperitoneal glucose tolerance test and insulin tolerance test were carried out at the age of 8 weeks. The pancreas was harvested for morphological analysis and ß-cell function at the age of 9 weeks. RESULTS: 2ME improved random blood glucose levels and glucose tolerance with increases in insulin levels during an intraperitoneal glucose tolerance test. Insulin sensitivity judged by an insulin tolerance test was comparable in the low- and high-dose 2ME groups and the control group. Although glucose-stimulated insulin secretion in isolated islets was comparable among the three groups, ß-cell mass in 2ME-treated groups was higher than the control group. In the 2ME-treated groups, the number of Ki67-positive cells in islets was higher, whereas the number of cleaved caspase-3-positive cells was comparable with the control. CONCLUSIONS: 2ME ameliorates glucose tolerance by promoting the proliferation of ß-cell mass in db/db mice. Our data suggests its potential clinical usefulness as a disease-modifying drug for type 2 diabetes mellitus. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00087.x, 2011).