Advancing type 2 diabetes therapy with iGlarLixi in older people: Pooled analysis of four randomized controlled trials.

AIM: To assess the efficacy and safety of iGlarLixi in older people (≥65 years) with type 2 diabetes (T2D) advancing or switching from oral agents, a glucagon-like peptide-1 receptor agonist (GLP-1RA), or basal insulin. MATERIALS AND METHODS: The data of participants aged <65 years and ≥65 years from four LixiLan trials (LixiLan-O, LixiLan-G, LixiLan-L, SoliMix) were evaluated over 26 or 30 weeks. RESULTS: Participants aged <65/≥65 years (n = 1039/n = 497) had a mean baseline body mass index of 31.4 and 30.7 kg/m2 and glycated haemoglobin (HbA1c) concentration of 66 mmol/mol (8.2%) and 65 mmol/mol (8.1%), respectively. Least squares mean HbA1c change from baseline to end of treatment (EOT) was -14.32 mmol/mol (-1.31%) (95% confidence interval [CI] -14.97, -13.77 [-1.37%, -1.26%]) for those aged <65 years and -13.66 mmol/mol (-1.25%) (95% CI -14.54, -12.79 [-1.33%, -1.17%]) for those aged ≥65 years. At EOT, achievement of HbA1c targets was similar between the group aged <65 years and the group aged ≥65 years: <53 mmol/mol (<7%) (59.0% and 56.5%, respectively), <59 mmol/mol (<7.5%) (75.5% and 73.0%, respectively) and <64 mmol/mol (<8%) (83.8% and 84.1%, respectively). The incidence and event rate of American Diabetes Association Level 1 hypoglycaemia during the studies were also comparable between the two groups: 26.7% and 28.2% and 1.7 and 2.1 events per patient-year for the group aged <65 years and the group aged ≥65 years, respectively. A clinically relevant reduction in HbA1c (>1% from baseline for HbA1c ≥64 mmol/mol [≥8%] or ≥0.5% from baseline for HbA1c <64 mmol/mol [<8%]) without hypoglycaemia was attained by 50.0% and 47.6% of participants aged <65 years and ≥65 years, respectively. Adverse events were similar between the two age groups. CONCLUSIONS: iGlarLixi is a simple, well-tolerated, once-daily alternative for treatment advancement in older people with T2D that provides significant improvements in glycaemic control without increasing hypoglycaemia risk, thus reducing the treatment burden.

Comparative efficacy and safety of Gla-300 versus IDegAsp in insulin-naïve people with type 2 diabetes mellitus uncontrolled on oral anti-diabetics.

AIM: To compare the efficacy and safety of insulin glargine-300 once daily (Gla-300) with insulin degludec/aspart (IDegAsp) once daily in patients with type 2 diabetes (T2D) inadequately controlled on oral anti-diabetic drugs (OADs). MATERIALS AND METHODS: A systematic literature review of randomized controlled trials was followed by an indirect treatment comparison of studies involving insulin naïve adults, inadequately controlled [glycated haemoglobin (HbA1c) ≥7.0%] on OADs, who received Gla-300 or IDegAsp once daily. Outcomes of interest were change in HbA1c, blood glucose, weight and insulin dose, as well as incidence and event rate of hypoglycaemia and other adverse events. RESULTS: Four trials with broadly similar baseline patient characteristics were included in the meta-analyses and indirect treatment comparison. At 24-28 weeks, the indirect comparison of Gla-300 to IDegAsp once daily estimated no statistically significant difference for change in HbA1c (%) from baseline [mean difference of 0.10% (95% CI: -0.20, 0.39; p = .52)]; a statistically significant mean difference of -1.31 kg (95% CI: -1.97, -0.65; p < .05) for change in body weight from baseline; statistically significant odds ratios of 0.62 (95% CI: 0.41, 0.93; p < .05) for incidence of any hypoglycaemia; and 0.47 (95% CI: 0.25, 0.87; p < .05) for incidence of anytime confirmed hypoglycaemia (plasma glucose <3.0-3.1 mmol/L). No significant differences were observed for insulin dose and adverse events. CONCLUSION: In insulin-naïve patients with T2D inadequately controlled on OADs, commencing Gla-300 shows a comparable HbA1c reduction, but with significantly less weight gain and a lower incidence of any and confirmed hypoglycaemia compared with commencing IDegAsp.

Similar glycaemic control and less hypoglycaemia during active titration after insulin initiation with glargine 300 units/mL and degludec 100 units/mL: A subanalysis of the BRIGHT study.

AIM: To further investigate glycaemic control and hypoglycaemia in BRIGHT, focusing on the titration period. MATERIALS AND METHODS: BRIGHT was a multicentre, open-label, randomized, active-controlled, two-arm, parallel-group, 24-week study in insulin-naïve patients with uncontrolled type 2 diabetes initiated on glargine 300 U/mL (Gla-300) (N = 466) or degludec (IDeg-100) (N = 463). Predefined efficacy and safety outcomes were investigated during the initial 12-week titration period. In addition, patients' characteristics and clinical outcomes were assessed descriptively, stratified by confirmed (≤3.9 mmol/L) hypoglycaemia incidence during the initial titration period. RESULTS: At week 12, HbA1c was comparable between Gla-300 (7.32%) and IDeg-100 (7.23%), with similar least squares (LS) mean reductions from baseline (-1.37% and - 1.39%, respectively; LS mean difference of 0.02; 95% confidence interval: -0.08 to 0.12). Patients who experienced hypoglycaemia during the initial titration period had numerically greater HbA1c reductions by week 12 than patients who did not (-1.46% vs. -1.28%), and higher incidence of anytime (24 hours; 73.3% vs. 35.7%) and nocturnal (00:00-06:00 hours; 30.0% vs. 11.9%) hypoglycaemia between weeks 13-24. CONCLUSIONS: The use of Gla-300 resulted in similar glycaemic control as IDeg-100 during the initial 12-week titration period of the BRIGHT study, when less anytime (24 hours) hypoglycaemia with Gla-300 versus IDeg-100 has been reported. Experiencing hypoglycaemia shortly after initiating Gla-300 or IDeg-100 may be associated with hypoglycaemia incidence in the longer term, potentially impacting glycaemic management.

Better glycaemic control and less hypoglycaemia with insulin glargine 300 U/mL vs glargine 100 U/mL: 1-year patient-level meta-analysis of the EDITION clinical studies in people with type 2 diabetes.

AIMS: To investigate the efficacy and safety of insulin glargine 300 U/mL (Gla-300) vs insulin glargine 100 U/mL (Gla-100) over 12 months in a patient-level meta-analysis, using data from the EDITION studies in people with type 2 diabetes (T2DM). METHODS: EDITION 1, 2 and 3 were multicentre, randomized, open-label, 2-arm, parallel-group, treat-to-target phase IIIa studies. Similar study designs and endpoints enabled a meta-analysis to be conducted. RESULTS: Reductions in glycated haemoglobin (HbA1c) were better sustained over 12 months with Gla-300 than with Gla-100 (least squares [LS] mean difference in change from baseline: -0.10 % [95% confidence interval {CI} -0.18 to -0.02] or -1.09 mmol/mol [95% CI -2.01 to -0.20]; P = .0174). Risk of confirmed (≤3.9 mmol/L) or severe hypoglycaemia was 15% lower with Gla-300 vs Gla-100 at night (relative risk 0.85 [95% CI 0.77-0.92]) and 6% lower at any time of day (relative risk 0.94 [95% CI 0.90-0.98]). Rates of hypoglycaemia were 18% lower with Gla-300 vs Gla-100 at night (rate ratio 0.82 [95% CI 0.67-0.99]), but comparable at any time of day. HbA1c <7.0 % without nocturnal hypoglycaemia was achieved by 24% more participants with Gla-300 than with Gla-100 (relative risk 1.24 [95% CI 1.03-1.50]). Severe hypoglycaemia was rare; in both treatment groups the incidence of events at any time of day was ≤3.6%, while rates were ≤0.08 events per participant-year. CONCLUSIONS: In a broad population of people with T2DM over 12 months, use of Gla-300 provided more sustained glycaemic control and significantly lower hypoglycaemia risk at night and at any time of day compared with Gla-100.

Glycaemic control and hypoglycaemia benefits with insulin glargine 300 U/mL extend to people with type 2 diabetes and mild-to-moderate renal impairment.

AIM: To investigate the impact of renal function on the safety and efficacy of insulin glargine 300 U/mL (Gla-300) and insulin glargine 100 U/mL (Gla-100). MATERIALS AND METHODS: A meta-analysis was performed using pooled 6-month data from the EDITION 1, 2 and 3 trials (N = 2496). Eligible participants, aged ≥18 years with a diagnosis of type 2 diabetes (T2DM), were randomized to receive once-daily evening injections of Gla-300 or Gla-100. Pooled results were assessed by two renal function subgroups: estimated glomerular filtration rate (eGFR) <60 and ≥60 mL/min/1.73 m2 . RESULTS: The decrease in glycated haemoglobin (HbA1c) after 6 months and the proportion of individuals with T2DM achieving HbA1c targets were similar in the Gla-300 and Gla-100 groups, for both renal function subgroups. There was a reduced risk of nocturnal (12:00-5:59 am) confirmed (≤3.9 mmol/L [≤70 mg/dL]) or severe hypoglycaemia with Gla-300 in both renal function subgroups (eGFR <60 mL/min/1.73 m2 : relative risk [RR] 0.76 [95% confidence interval {CI} 0.62-0.94] and eGFR ≥60 mL/min/1.73 m2 : RR 0.75 [95% CI 0.67-0.85]). For confirmed (≤70 mg/dL [≤3.9 mmol/L]) or severe hypoglycaemia at any time of day (24 hours) the hypoglycaemia risk was lower with Gla-300 vs Gla-100 in both the lower (RR 0.94 [95% CI 0.86-1.03]) and higher (RR 0.90 [95% CI 0.85-0.95]) eGFR subgroups. CONCLUSIONS: Gla-300 provided similar glycaemic control to Gla-100, while indicating a reduced overall risk of confirmed (≤3.9 and <3.0 mmol/L [≤70 and <54 mg/dL]) or severe hypoglycaemia, with no significant difference between renal function subgroups.

Activated protein C ameliorates diabetic nephropathy by epigenetically inhibiting the redox enzyme p66Shc.

The coagulation protease activated protein C (aPC) confers cytoprotective effects in various in vitro and in vivo disease models, including diabetic nephropathy. The nephroprotective effect may be related to antioxidant effects of aPC. However, the mechanism through which aPC may convey these antioxidant effects and the functional relevance of these properties remain unknown. Here, we show that endogenous and exogenous aPC prevents glomerular accumulation of oxidative stress markers and of the redox-regulating protein p66(Shc) in experimental diabetic nephropathy. These effects were predominately observed in podocytes. In vitro, aPC inhibited glucose-induced expression of p66(Shc) mRNA and protein in podocytes (via PAR-1 and PAR-3) and various endothelial cell lines, but not in glomerular endothelial cells. Treatment with aPC reversed glucose-induced hypomethylation and hyperacetylation of the p66(Shc) promoter in podocytes. The hyperacetylating agent sodium butyrate abolished the suppressive effect of aPC on p66(Shc) expression both in vitro and in vivo. Moreover, sodium butyrate abolished the beneficial effects of aPC in experimental diabetic nephropathy. Inhibition of p66(Shc) expression and mitochondrial translocation by aPC normalized mitochondrial ROS production and the mitochondrial membrane potential in glucose-treated podocytes. Genetic ablation of p66(Shc) compensated for the loss of protein C activation in vivo, normalizing markers of diabetic nephropathy and oxidative stress. These studies identify a unique mechanism underlying the cytoprotective effect of aPC. Activated PC epigenetically controls expression of the redox-regulating protein p66(Shc), thus linking the extracellular protease aPC to mitochondrial function in diabetic nephropathy.

Annexin A5 directly interacts with amyloidogenic proteins and reduces their toxicity.

Protein misfolding is a central mechanism for the development of neurodegenerative diseases and type 2 diabetes mellitus. The accumulation of misfolded alpha-synuclein protein inclusions in the Lewy bodies of Parkinson's disease is thought to play a key role in pathogenesis and disease progression. Similarly, the misfolding of the beta-cell hormone human islet amyloid polypeptide (h-IAPP) into toxic oligomers plays a central role in the induction of beta-cell apoptosis in the context of type 2 diabetes. In this study, we show that annexin A5 plays a role in interacting with and reducing the toxicity of the amyloidogenic proteins, h-IAPP and alpha-synuclein. We find that annexin A5 is coexpressed in human beta-cells and that exogenous annexin A5 reduces the level of h-IAPP-induced apoptosis in human islets by approximately 50% and in rodent beta-cells by approximately 90%. Experiments with transgenic expression of alpha-synuclein in Caenorhabditis elegans show that annexin A5 reduces alpha-synuclein inclusions in vivo. Using thioflavin T fluorescence, electron microscopy, and electron paramagnetic resonance, we provide evidence that substoichiometric amounts of annexin A5 inhibit h-IAPP and alpha-synuclein misfolding and fibril formation. We conclude that annexin A5 might act as a molecular safeguard against the formation of toxic amyloid aggregates.

Comparison of pancreas-transplanted type 1 diabetic patients with portal-venous versus systemic-venous graft drainage: impact on glucose regulatory hormones and the growth hormone/insulin-like growth factor-I axis.

CONTEXT: Pancreas grafts can be drained through the iliac vein (systemic drainage) or the portal vein. OBJECTIVE: We hypothesized that normalization of portal insulin in patients with portal pancreas graft drainage stimulates the GH/IGF-I axis and thereby contributes to glucose control. METHODS: We compared patients after combined kidney and pancreas transplantation with portal drainage (n = 7) to patients with systemic drainage of the pancreas graft (n = 8) and nondiabetic controls (n = 8). Overnight fasting sera were analyzed for free and total IGF-I and IGF-binding proteins. Glucose regulatory hormones were examined after an oral glucose tolerance test and GH after stimulation with GHRH. RESULTS: Systemic drainage led to higher basal and stimulated insulin levels than portal drainage (P < 0.05), but increments in response to oral glucose were reduced in both transplanted groups (P < 0.05 vs. controls). However, glucose tolerance was similar in all groups. Circulating free and total IGF-I and IGF-binding protein-3 were similar to control levels in the systemic drainage group but elevated in the portal drainage group (P < 0.05). Consistently, the GH response was reduced in the portal drainage group (P < 0.05 vs. controls) and correlated inversely with free IGF-I (r = -0.63, P < 0.05). CONCLUSION: Portal drainage of pancreatic endocrine secretion in pancreas graft recipients raises IGF-I and lowers GH secretion. These changes might explain that glucose regulation is maintained despite lower peripheral insulin levels, compared with patients with systemic graft drainage and nondiabetic control subjects.

Human islet amyloid polypeptide oligomers disrupt cell coupling, induce apoptosis, and impair insulin secretion in isolated human islets.

Insulin secretion from the 2,000-3,000 beta-cells in an islet is a highly synchronized activity with discharge of insulin in coordinate secretory bursts at approximately 4-min intervals. Insulin secretion progressively declines in type 2 diabetes and following islet transplantation. Both are characterized by the presence of islet amyloid derived from islet amyloid polypeptide (IAPP). In the present studies, we examined the action of extracellular human IAPP (h-IAPP) on morphology and function of human islets. Because oligomers of h-IAPP are known to cause membrane disruption, we questioned if application of h-IAPP oligomers to human islets would lead to disruption of islet architecture (specifically cell-to-cell adherence) and a decrease in coordinate function (e.g., increased entropy of insulin secretion and diminished coordinate secretory bursts). Both hypotheses are affirmed, leading to a novel hypothesis for impaired insulin secretion in type 2 diabetes and following islet transplantation, specifically disrupted cell-to-cell adherence in islets through the actions of membrane-disrupting IAPP oligomers.

Improved detectability of acute and subacute brainstem infarctions by combining standard axial and thin-sliced sagittal DWI.

BACKGROUND AND PURPOSE: Most false negative findings in DWI of ischemic stroke are in patients with minor deficits clinically localized to the brainstem. Our goal was to evaluate the benefit of a thin-sliced sagittal DWI in addition to conventional axial DWI at 1.5T for the detection of brainstem infarctions. METHODS: Data of patients with symptoms consistent with acute and subacute brainstem infarction and an MRI examination including standard axial DWI and thin-sliced sagittal DWI were retrospectively analyzed. Patients with the later diagnosis of a TIA, an inflammation or a tumor of the brainstem were excluded from analysis. Diffusion restrictions were identified by two independent raters blinded for the final clinical diagnosis in three separate reading steps: First, only axial DWI, secondly only sagittal DWI, and lastly both DWIs together. Presence and size of DWI-lesions were documented for each plane. Differences between the observers were settled in consensus in a separate joint reading. RESULTS: Of 73 included patients, 46 patients were clinically diagnosed with brainstem infarction. Inter-observer agreement was excellent for the detection of brainstem lesions in axial and sagittal DWI (kappa = 0.94 and 0.97). In 28/46 patients (60.9%) lesions were detected in the axial plane alone, whereas in 6 more patients (73.9%) lesions were detected in the review of both sequences together. All lesions undetectable in the axial plane were smaller than 5 mm in cranio-caudal direction. CONCLUSIONS: Thin-sliced sagittal DWI in addition to axial DWI improves the detection rate of brainstem infarction with little additional expenditure of time.

More Similarities Than Differences Testing Insulin Glargine 300 Units/mL Versus Insulin Degludec 100 Units/mL in Insulin-Naive Type 2 Diabetes: The Randomized Head-to-Head BRIGHT Trial.

OBJECTIVE: To compare insulin glargine 300 units/mL (Gla-300) versus insulin degludec 100 units/mL (IDeg-100) in this first head-to-head randomized controlled trial. RESEARCH DESIGN AND METHODS: BRIGHT (NCT02738151) was a multicenter, open-label, active-controlled, two-arm, parallel-group, 24-week, noninferiority study in insulin-naive patients with uncontrolled type 2 diabetes. Participants were randomized 1:1 to evening dosing with Gla-300 (N = 466) or IDeg-100 (N = 463), titrated to fasting self-monitored plasma glucose of 80-100 mg/dL. The primary end point was HbA1c change from baseline to week 24. Safety end points included incidence and event rates of hypoglycemia. RESULTS: At week 24, HbA1c improved similarly from baseline values of 8.7% (72 mmol/mol) in the Gla-300 group and 8.6% (70 mmol/mol) in the IDeg-100 group to 7.0% (53 mmol/mol)-least squares mean difference -0.05% (95% CI -0.15 to 0.05) (-0.6 mmol/mol [-1.7 to 0.6])-demonstrating noninferiority of Gla-300 versus IDeg-100 (P < 0.0001). Hypoglycemia incidence and event rates over 24 weeks were comparable with both insulins, whereas during the active titration period (0-12 weeks) the incidence and rate of anytime (24-h) confirmed hypoglycemia (≤70 and <54 mg/dL) were lower with Gla-300. Both insulins were properly titrated and exhibited no specific safety concerns. CONCLUSIONS: Gla-300 and IDeg-100 provided similar glycemic control improvements with relatively low hypoglycemia risk. Hypoglycemia incidence and rates were comparable with both insulins during the full study period but lower in favor of Gla-300 during the titration period. The choice between these longer-acting basal insulins may be determined by factors such as access and cost, alongside clinical considerations.

A Randomized Controlled Trial Comparing Efficacy and Safety of Insulin Glargine 300 Units/mL Versus 100 Units/mL in Older People With Type 2 Diabetes: Results From the SENIOR Study.

OBJECTIVE: SENIOR compared the efficacy and safety of insulin glargine 300 units/mL (Gla-300) with glargine 100 units/mL (Gla-100) in older people (≥65 years old) with type 2 diabetes. RESEARCH DESIGN AND METHODS: SENIOR was an open-label, two-arm, parallel-group, multicenter phase 3b trial designed to enroll ∼20% of participants aged ≥75 years. Participants were randomized 1:1 to Gla-300 or Gla-100, titrated to a fasting self-monitored plasma glucose of 5.0-7.2 mmol/L (90-130 mg/dL). RESULTS: In total, 1,014 participants were randomized (mean age: 71 years). Comparable reductions in HbA1c were observed from baseline to week 26 for Gla-300 (-0.89%) and Gla-100 (-0.91%) in the overall population (least squares mean difference: 0.02% [95% CI -0.092 to 0.129]) and for participants aged ≥75 years (-0.11% [-0.330 to 0.106]). Incidence and rates of confirmed (≤3.9 mmol/L [≤70 mg/dL]) or severe hypoglycemia events were low and similar between both treatment groups, with lower rates of documented symptomatic hypoglycemia with Gla-300. The lower risk of hypoglycemia with Gla-300 versus Gla-100 was more apparent in the subgroup aged ≥75 years versus the overall population. Significantly lower annualized rates of documented symptomatic (≤3.9 mmol/L [≤70 mg/dL]) hypoglycemia were observed (Gla-300: 1.12; Gla-100: 2.71; rate ratio: 0.45 [95% CI 0.25-0.83]). CONCLUSIONS: Efficacy and safety of Gla-300 was demonstrated in older people (≥65 years of age) with type 2 diabetes, with comparable reductions in HbA1c and similarly low or lower risk of documented symptomatic hypoglycemia versus Gla-100. A significant benefit in hypoglycemia reduction was seen in participants aged ≥75 years.

Pancreatic beta-cells secrete insulin in fast- and slow-release forms.

Insulin vesicles contain a chemically rich mixture of cargo that includes ions, small molecules, and proteins. At present, it is unclear if all components of this cargo escape from the vesicle at the same rate or to the same extent during exocytosis. Here, we demonstrate through real-time imaging that individual rat and human pancreatic beta-cells secrete insulin in heterogeneous forms that disperse either rapidly or slowly. In healthy pancreatic beta-cells maintained in culture, most vesicles discharge insulin in its fast-release form, a form that leaves individual vesicles in a few hundred milliseconds. The fast-release form of insulin leaves vesicles as rapidly as C-peptide leaves vesicles. Healthy beta-cells also secrete a slow-release form of insulin that leaves vesicles more slowly than C-peptide, over times ranging from seconds to minutes. Individual beta-cells make vesicles with both forms of insulin, though not all vesicles contain both forms of insulin. In addition, we confirm that insulin vesicles store their cargo in two functionally distinct compartments: an acidic solution, or halo, and a condensed core. Thus, our results suggest two important features of the condensed core: 1) It exists in different states among the vesicles undergoing exocytosis and 2) its dissolution determines the availability of insulin during exocytosis.

Replication increases beta-cell vulnerability to human islet amyloid polypeptide-induced apoptosis.

Type 2 diabetes is characterized by a relative beta-cell deficit as a result of increased beta-cell apoptosis and islet amyloid derived from the beta-cell peptide islet amyloid polypeptide (IAPP). Human IAPP (h-IAPP) but not mouse IAPP (m-IAPP) induces apoptosis when applied to cells in culture, a property that depends on the propensity of h-IAPP to oligomerize. Since beta-cell mass is regulated, the question arises as to why it is not adaptively increased in response to insulin resistance and hyperglycemia in type 2 diabetes. This adaptation might fail if dividing beta-cells preferentially underwent apoptosis. We tested the hypothesis that beta-cells are preferentially vulnerable to h-IAPP-induced apoptosis. We established a microculture environment to perform time-lapse video microscopy (TLVM) and studied beta-cells (RIN) and HeLa cells undergoing replication or apoptosis. Sequential images (every 10 min for 36 h in RIN or 24 h in HeLa cells) of cells in vivo were analyzed, and each mitotic and apoptotic event was documented. Freshly dissolved h-IAPP caused a dose-dependent increased rate of apoptosis (P < 0.0001) in both cell types. At low and medium levels of toxicity, cells that had previously undergone mitosis were more vulnerable to h-IAPP-induced apoptosis than nondividing cells (P < 0.05). In the first 3 h after mitosis (full cell cycle length 26 +/- 0.6 h), beta-cells were particularly susceptible to h-IAPP-induced apoptosis (P < 0.05). Neither m-IAPP nor mature amyloid aggregates of h-IAPP were cytotoxic (P = 0.49). To corroborate these cell culture studies, we examined sections of human pancreatic tissue (five cases of type 2 diabetes) and human islets incubated for 48 h +/- h-IAPP. Both were stained for apoptosis with the transferase-mediated dUTP nick-end labeling method and analyzed for the presence of paired apoptotic cells anticipated in the event of postmitotic apoptosis. In human pancreatic tissue 26 +/- 5% (single plane of examination) and in human islets incubated with h-IAPP 44 +/- 4% of apoptotic islet cells were paired. In conclusion, replicating beta-cells are preferentially vulnerable to h-IAPP-induced apoptosis in cell culture. Postmitotic apoptosis was also documented in humans with type 2 diabetes and in human islet tissue. We postulate that beta-cell deficiency in type 2 diabetes may result in part from failure to adaptively increase beta-cell mass due to increased vulnerability of replicating beta-cells to undergo apoptosis. If this postulate is correct, then inhibition of apoptosis should allow recovery of beta-cell mass in type 2 diabetes.

Beta-cell deficit and increased beta-cell apoptosis in humans with type 2 diabetes.

Type 2 diabetes is characterized by impaired insulin secretion. Some but not all studies suggest that a decrease in beta-cell mass contributes to this. We examined pancreatic tissue from 124 autopsies: 91 obese cases (BMI >27 kg/m(2); 41 with type 2 diabetes, 15 with impaired fasting glucose [IFG], and 35 nondiabetic subjects) and 33 lean cases (BMI <25 kg/m(2); 16 type 2 diabetic and 17 nondiabetic subjects). We measured relative beta-cell volume, frequency of beta-cell apoptosis and replication, and new islet formation from exocrine ducts (neogenesis). Relative beta-cell volume was increased in obese versus lean nondiabetic cases (P = 0.05) through the mechanism of increased neogenesis (P < 0.05). Obese humans with IFG and type 2 diabetes had a 40% (P < 0.05) and 63% (P < 0.01) deficit and lean cases of type 2 diabetes had a 41% deficit (P < 0.05) in relative beta-cell volume compared with nondiabetic obese and lean cases, respectively. The frequency of beta-cell replication was very low in all cases and no different among groups. Neogenesis, while increased with obesity, was comparable in obese type 2 diabetic, IFG, or nondiabetic subjects and in lean type 2 diabetic or nondiabetic subjects. However, the frequency of beta-cell apoptosis was increased 10-fold in lean and 3-fold in obese cases of type 2 diabetes compared with their respective nondiabetic control group (P < 0.05). We conclude that beta-cell mass is decreased in type 2 diabetes and that the mechanism underlying this is increased beta-cell apoptosis. Since the major defect leading to a decrease in beta-cell mass in type 2 diabetes is increased apoptosis, while new islet formation and beta-cell replication are normal, therapeutic approaches designed to arrest apoptosis could be a significant new development in the management of type 2 diabetes, because this approach might actually reverse the disease to a degree rather than just palliate glycemia.

Glucose stimulates pulsatile insulin secretion from human pancreatic islets by increasing secretory burst mass: dose-response relationships.

Insulin is secreted almost exclusively in discrete bursts, and physiological regulation is accomplished by modulation of the pulse mass. How the integrity of contiguous anatomic structures in the human pancreas (islets, splanchnic innervation, exocrine tissue, local hormones) directs the coordinated insulin secretion is not known. We posed the hypothesis that glucose stimulates insulin secretion from isolated human islets by an amplification of insulin pulse mass with no change in pulse frequency and that the glucose dose-response curve for the regulation of insulin pulse mass mirrors that recognized in vivo. Islets from five nondiabetic cadaveric donors were perifused in a recently validated perifusion system at 4 mM and subsequently at 8, 12, 16, or 24 mM glucose. The effluent was collected in 1-min intervals and used for the measurement of insulin (ELISA). Pulsatile insulin secretion was analyzed by deconvolution analysis. Total insulin secretion increased progressively (P < 0.0001). This augmentation was due to amplified pulse mass (3-fold, 24 mM vs. 4 mM glucose; P < 0.0001) with no change in pulse interval (approximately 4 min). Pulsatile insulin secretion was stimulated most effectively in a physiologic concentration range of 4-8 mM. The islet insulin content was significantly correlated to the magnitude of first and second phase insulin secretion (P < 0.0001). The quantifiable orderliness of pulsatile insulin secretion rose with escalating glucose concentration (P = 0.02). In conclusion, glucose stimulates pulsatile insulin secretion from isolated human islets by amplification of insulin pulse mass without altering pulse interval. The in vitro concentration-response relationship is comparable with that observed in vivo. These data imply that transplanted human islets should be able to reproduce glucose-regulated insulin secretion as observed in the intact human pancreas.