Objective: The prevalence of type 2 diabetes mellitus escalates with aging although b-cell mass, a primary parameter of b-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 nZ20 non-diabetic organ donors with a mean age of 50.2G3.5 years (range 7-66 years) and mean body mass index of 25.7G0.9 kg/m 2 (17.2-33.1 kg/m 2 ) was morphometrically analyzed to determine b-cell volume, b-cell replication, b-cell apoptosis, islet neogenesis, and pancreatic duodenal homeobox-1 (PDX-1) expression. Results: Relative b-cell volume in human pancreata (mean 2.3G0.2%) remains constant with aging (rZ0.26, PZns). b-cell replication (rZ0.71, PZ0.0004) decreases age-dependently, while b-cell apoptosis does not change significantly (rZ0.42, PZ0.08). Concomitantly, PDX-1 expression is downregulated with age in human pancreatic tissue (rZ0.65, PZ0.002). The rate of islet neogenesis is not affected by aging (rZ0.13, PZns). Conclusions: In non-diabetic humans, aging is linked with impaired islet turnover possibly due to reduced PDX-1 expression. As b-cell replication is considered to be the main mechanism responsible for b-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.

Protein misfolding is a central mechanism for the development of neurodegenerative diseases and type 2 diabetes mellitus. The accumulation of misfolded α-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 β-cell hormone human islet amyloid polypeptide (h-IAPP) into toxic oligomers plays a central role in the induction of β-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 α-synuclein. We find that annexin A5 is coexpressed in human β-cells and that exogenous annexin A5 reduces the level of h-IAPP-induced apoptosis in human islets by ~50% and in rodent β-cells by ~90%. Experiments with transgenic expression of α-synuclein in Caenorhabditis elegans show that annexin A5 reduces α-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 α-synuclein misfolding and fibril formation. We conclude that annexin A5 might act as a molecular safeguard against the formation of toxic amyloid aggregates.

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 Ͻ 0.0001 for glargine, P ϭ 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 ϭ 0.4, threesample comparison).CONCLUSIONS -Regular human insulin and insulin glargine may be used to treat diabetes in patients with pancreatic cancer.

Type 2 diabetes (T2D) is characterized by islet dysfunction and beta-cell deficiency caused by apoptosis. One mechanism underlying induction of beta-cell apoptosis is stress in the endoplasmic reticulum (ER). Isolated human islets are a frequently used model to examine islet pathophysiology in T2D. Therefore it is important to establish how function and beta-cell turnover of human islets change in culture. Islets from four organ donors were cultured over four weeks. At 0, 1, 2, 3 and 4 weeks aliquots of islets were used for analysis of a) islet-cell turnover (replication by Ki-67 and apoptosis by TUNEL staining), b) the ER stress level (CHOP and phospho-eIF2alpha staining), c) fractional beta-cell content (insulin staining) and d) islet function (2 h static incubation). Culture duration positively correlated to replication (p=0.03) and negatively correlated to apoptosis (p=0.003). In comparison to islets in situ islet cell turnover is accelerated (>10-fold). The ER stress level was stable during the first three weeks, but showed a sharp increase (p<0.05) at four weeks. The fractional beta-cell content increased from 29+/-2% to 41+/-2% (p=0.0004). Islet function improved (p<0.0001). In conclusion, isolated human islets may be used for in vitro experiments for up to three weeks. During this time islet function and islet-cell turnover are stable. If islet culture is extended beyond three weeks ER stress may impair islet viability. Studies analyzing the pathophysiology of human T2D at the level of the endocrine pancreas need to confirm results obtained with isolated human islets by analysis of primary human pancreatic tissue.