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.

Beta-cell selective K(ATP)-channel activation protects beta-cells and human islets from human islet amyloid polypeptide induced toxicity.

BACKGROUND AND AIMS: In type 2 diabetes mellitus (T2DM) chronic beta-cell stimulation and oligomers of aggregating human islet amyloid polypeptide (h-IAPP) cause beta-cell dysfunction and induce beta-cell apoptosis. Therefore we asked whether beta-cell rest prevents h-IAPP induced beta-cell apoptosis. MATERIALS AND METHODS: We induced beta-cell rest with a beta-cell selective K(ATP)-channel opener (K(ATP)CO) in RIN cells and human islets exposed to h-IAPP versus r-IAPP. Apoptosis was quantified by time-lapse video microscopy (TLVM) in RIN cells and TUNEL staining in human islets. Whole islets were also studied with TLVM over 48h to examine islet architecture. RESULTS: In RIN cells and human islets h-IAPP induced apoptosis (p<0.001 h-IAPP versus r-IAPP). Concomitant incubation with K(ATP)CO inhibited apoptosis (p<0.001). K(ATP)CO also reduced h-IAPP induced expansion of whole islets (disintegration of islet architecture) by ~70% (p<0.05). Thioflavin-binding assays show that K(ATP)CO does not directly inhibit amyloid formation. CONCLUSIONS: Opening of K(ATP)-channels reduces beta-cell vulnerability to apoptosis induced by h-IAPP oligomers. This effect is not due to a direct interaction of K(ATP)CO with h-IAPP, but might be mediated through hyperpolarization of the beta-cell membrane induced by opening of K(ATP)-channels. Induction of beta-cell rest with beta-cell selective K(ATP)-channel openers may provide a strategy to protect beta-cells from h-IAPP induced apoptosis and to prevent beta-cell deficiency in T2DM.

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.

Therapeutic approaches based on beta-cell mass preservation and/or regeneration.

Beta-cell deficiency is a pathophysiologic component of diabetes mellitus and a primary cause of islet dysfunction. Islet dysfunction is a prerequisite for the development of diabetes mellitus since individuals with insulin resistance (e.g. obesity, pregnancy) do not develop hyperglycemia unless beta-cell compensation fails. Therefore, understanding of the biology and mechanisms involved in normal beta-cell adaptation may provide novel therapeutic targets for preservation and/or regeneration of beta-cell mass in diabetes mellitus. Normal adaptation of beta-cell mass occurs by beta-cell replication and/or neogenesis from precursor cells inside the pancreas. However, the relative importance of both processes for successful adaptation is unknown. In type-2 diabetes, the primary defect is increased beta-cell apoptosis. Since replicating beta-cells are more vulnerable to apoptosis, the proapoptotic diabetic milieu limits the regenerative capacity of the islet and directly causes accelerated islet loss. Therapeutic approaches need to address both processes of islet turnover (regeneration and cell loss) in order to be successful. It may be anticipated that such an intervention is also effective early in the course of diabetes or in prediabetic conditions.

Impaired islet turnover in human donor pancreata with aging.

OBJECTIVE: The prevalence of type 2 diabetes mellitus escalates with aging although beta-cell mass, a primary parameter of beta-cell function, is subject to compensatory regulation. So far it is unclear whether the proliferative capacity of pancreatic islets is restricted by senescence. MATERIALS AND METHODS: Human pancreatic tissue from n=20 non-diabetic organ donors with a mean age of 50.2+/-3.5 years (range 7-66 years) and mean body mass index of 25.7+/-0.9 kg/m(2) (17.2-33.1 kg/m(2)) was morphometrically analyzed to determine beta-cell volume, beta-cell replication, beta-cell apoptosis, islet neogenesis, and pancreatic duodenal homeobox-1 (PDX-1) expression. RESULTS: Relative beta-cell volume in human pancreata (mean 2.3+/-0.2%) remains constant with aging (r=0.26, P=ns). Beta-cell replication (r=0.71, P=0.0004) decreases age-dependently, while beta-cell apoptosis does not change significantly (r=0.42, P=0.08). Concomitantly, PDX-1 expression is downregulated with age in human pancreatic tissue (r=0.65, P=0.002). The rate of islet neogenesis is not affected by aging (r=0.13, P=ns). CONCLUSIONS: In non-diabetic humans, aging is linked with impaired islet turnover possibly due to reduced PDX-1 expression. As beta-cell replication is considered to be the main mechanism responsible for beta-cell regeneration, these changes restrict the flexibility of the aging human pancreas to adapt to changing demands for insulin secretion and increase the risk for the development of diabetes mellitus in older subjects.

Proliferation of colo-357 pancreatic carcinoma cells and survival of patients with pancreatic carcinoma are not altered by insulin glargine.

OBJECTIVE: It was reported that the long-acting insulin analogue glargine induces cell proliferation in a human osteosarcoma cell line and therefore might induce or accelerate tumor growth. Induction of cell proliferation would be particularly relevant for insulin treatment of subjects with diabetes and the potential of bearing tumor cells (e.g., a history of a malignant disease). RESEARCH DESIGN AND METHODS: Proliferation, apoptosis, and the expression levels of insulin receptor, IGF-I receptor, and insulin receptor substrate (IRS) 2 were analyzed in human pancreatic cancer cells (Colo-357) after incubation (72 h) with insulin glargine or regular human insulin at 0-100 nmol/l. A total of 125 subjects, after partial or total pancreatectomy due to pancreatic carcinoma, were analyzed over a median follow-up period of 22 months. RESULTS: There was no significant difference between glargine and regular human insulin with respect to regulation of proliferation and apoptosis of Colo-357 cells. The expression levels of insulin receptor, IGF-I receptor, and IRS2 as a downstream molecule of both receptor signaling pathways were not altered at any concentration tested. The insulin receptor was downregulated to a similar degree by glargine and regular human insulin at high insulin concentrations (P < 0.0001 for glargine, P = 0.002 for regular human insulin). The median survival time after pancreatic surgery was 15 months. Survival analysis showed that the time-dependent proportion of patients who survived was identical in patients receiving insulin glargine versus insulin treatment without glargine and control subjects without diabetes after surgery (P = 0.4, three-sample comparison). CONCLUSIONS: Regular human insulin and insulin glargine may be used to treat diabetes in patients with pancreatic cancer.

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.

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.

Induction of beta-cell rest by a Kir6.2/SUR1-selective K(ATP)-channel opener preserves beta-cell insulin stores and insulin secretion in human islets cultured at high (11 mM) glucose.

In health, most insulin is secreted in pulses. Type 2 diabetes mellitus (TTDM) is characterized by impaired pulsatile insulin secretion with a defect in insulin pulse mass. It has been suggested that this defect is partly due to chronic overstimulation of beta-cells imposed by insulin resistance and hyperglycemia, which results in depletion of pancreatic insulin stores. It has been reported that in TTDM overnight inhibition of insulin secretion (induction of beta-cell rest) leads to quantitative normalization of pulsatile insulin secretion upon subsequent stimulation. Recently, decreased orderliness of insulin secretion has been recognized as another attribute of impaired insulin secretion in TTDM. In the current studies we sought to address at the level of the isolated islet whether chronic elevated glucose concentrations induce both defects involved in impaired insulin secretion in TTDM: deficiency and decreased orderliness of insulin secretion. We use the concept of beta-cell rest, induced by a novel beta-cell selective K(ATP)-channel opener (KCO), NN414 (6-chloro-3-(1-methylcyclopropyl)amino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide), to test whether preservation of insulin stores leads to normalization of both processes in response to glucose stimulation. Human islets were isolated from three cadaveric organ donors and studied in perifusion experiments and static incubation. Acute activation of K(ATP)-channels suppressed insulin secretion from perifused human islets by approximately 90% (P < 0.0001). This KCO also inhibited glucagon secretion in a dose-dependent manner (P = 0.01). Static incubation at 11 and 16 vs. 4 mM glucose for 96 h decreased islet insulin stores by approximately 80% and 85% (P < 0.0001, respectively). In subsequent perifusion experiments, total insulin secretion ( approximately 30%; P < 0.01) from these islets and insulin pulse mass ( approximately 40%; P < 0.05) were both decreased (11 vs. 4 mM). The inhibition of insulin secretion during static incubation with KCO reduced the loss of islet insulin stores in a dose-dependent manner (P < 0.0001) and resulted in increased total insulin secretion (2.6-fold; P < 0.01) and insulin pulse mass (2.5-fold; P < 0.05) during subsequent perifusion. The orderliness of insulin secretion was significantly reduced after chronic incubation of human islets at 11 mM glucose (P = 0.04), but induction of beta-cell rest at 11 mM failed to normalize the regularity of insulin secretion during subsequent perifusion. We conclude that physiological increased glucose concentrations (11 mM), which are frequently observed in diabetes, lead to a loss of islet insulin stores and defective pulsatile insulin secretion as well as reduced orderliness of insulin secretion. Induction of beta-cell rest by selective activation of beta-cell K(ATP)-channels preserves insulin stores and pulsatile insulin secretion without restoring the orderliness of insulin secretion. Therefore, the concept of beta-cell rest may provide a strategy to protect beta-cells from chronic overstimulation and to improve islet function. Impaired glucose-regulated insulin secretion in TTDM may, however, partially involve mechanisms that are distinct from insulin stores and insulin secretion rates.

Diagnosis and localization of insulinoma after negative laparotomy by hyperinsulinemic, hypoglycemic clamp and intra-arterial calcium stimulation.

A 40-year-old woman with recurrent episodes of hypoglycemia was referred because of suspected insulinoma. Prolonged fasting was discontinued after 24 h due to symptomatic hypoglycemia (29 mg/dl, glucose/insulin-ratio 0.34). Magnetic resonance tomography showed a small 0.3 cm lesion in the body of the pancreas. During subsequent surgery a pancreatic tumor could not be detected, neither by manual palpation nor intraoperative ultrasonography. A hyperinsulinemic, sequentially eu- and hypoglycemic clamp confirmed the biochemical diagnosis of endogenous hyperinsulinemia and intra-arterial calcium stimulation localized calcium responsive tissue in the feeding distribution of the superior mesenteric artery. An octreotide scan was negative. During relaparotomy, six weeks after the initial surgery, the pancreatic body and tail were resected and a approximately 1 cm non-malignant insulinoma was found. Although the use of highly sensitive, and more sophisticated and expensive methods for the diagnosis and localization of insulinomas are not generally suggested, we recommend application of intra-arterial calcium stimulation if the tumor is not detected using conventional diagnostic procedures.

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.

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.