Type 2 diabetes is characterized by impaired insulin secretion. Some but not all studies suggest that a decrease in ␤-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 ␤-cell volume, frequency of ␤-cell apoptosis and replication, and new islet formation from exocrine ducts (neogenesis). Relative ␤-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 ␤-cell volume compared with nondiabetic obese and lean cases, respectively. The frequency of ␤-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 ␤-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 ␤-cell mass is decreased in type 2 diabetes and that the mechanism underlying this is increased ␤-cell apoptosis. Since the major defect leading to a decrease in ␤-cell mass in type 2 diabetes is increased apoptosis, while new islet formation and ␤-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. Diabetes 52:102-110, 2003

Background: Amyloid-related degenerative diseases are associated with the accumulation of misfolded proteins as amyloid fibrils in tissue. In Alzheimer disease (AD), amyloid accumulates in several distinct types of insoluble plaque deposits, intracellular Aβ and as soluble oligomers and the relationships between these deposits and their pathological significance remains unclear. Conformation dependent antibodies have been reported that specifically recognize distinct assembly states of amyloids, including prefibrillar oligomers and fibrils.

OBJECTIVE-Little is known about the capacity, mechanisms, or timing of growth in ␤-cell mass in humans. We sought to establish if the predominant expansion of ␤-cell mass in humans occurs in early childhood and if, as in rodents, this coincides with relatively abundant ␤-cell replication. We also sought to establish if there is a secondary growth in ␤-cell mass coincident with the accelerated somatic growth in adolescence.RESEARCH DESIGN AND METHODS-To address these questions, pancreas volume was determined from abdominal computer tomographies in 135 children aged 4 weeks to 20 years, and morphometric analyses were performed in human pancreatic tissue obtained at autopsy from 46 children aged 2 weeks to 21 years.RESULTS-We report that 1) ␤-cell mass expands by severalfold from birth to adulthood, 2) islets grow in size rather than in number during this transition, 3) the relative rate of ␤-cell growth is highest in infancy and gradually declines thereafter to adulthood with no secondary accelerated growth phase during adolescence, 4) ␤-cell mass (and presumably growth) is highly variable between individuals, and 5) a high rate of ␤-cell replication is coincident with the major postnatal expansion of ␤-cell mass.CONCLUSIONS-These data imply that regulation of ␤-cell replication during infancy plays a major role in ␤-cell mass in adult humans. Diabetes 57:1584-1594, 2008

Aims/hypothesis: Type 1 diabetes is widely held to result from an irreversible loss of insulin-secreting beta cells. However, insulin secretion is detectable in some people with long-standing type 1 diabetes, indicating either a small population of surviving beta cells or continued renewal of beta cells subject to ongoing autoimmune destruction. The aim of the present study was to evaluate these possibilities. Materials and methods: Pancreatic sections from 42 individuals with type 1 diabetes and 14 non-diabetic individuals were evaluated for the presence of beta cells, beta cell apoptosis and replication, T lymphocytes and macrophages. The presence and extent of periductal fibrosis was also quantified. Results: Beta cells were identified in 88% of individuals with type 1 diabetes. The number of beta cells was unrelated to duration of disease (range 4-67 years) or age at death (range 14-77 years), but was higher (p<0.05) in individuals with lower mean blood glucose. Beta cell apoptosis was twice as frequent in type 1 diabetes as in control subjects (p<0.001), but beta cell replication was rare in both groups. The increased beta cell apoptosis in type 1 diabetes was accompanied by both increased macrophages and T lymphocytes and a marked increase in periductal fibrosis (p<0.001), implying chronic inflammation over many years, consistent with an ongoing supply of beta cells. Conclusions/interpretation: Most people with long-standing type 1 diabetes have beta cells that continue to be destroyed. The mechanisms underlying increased beta cell death may involve both ongoing autoimmunity and glucose toxicity. The presence of beta cells despite ongoing apoptosis implies, by definition, that concomitant new beta cell formation must be occurring, even after long-standing type 1 diabetes. We conclude that type 1 diabetes may be reversed by targeted inhibition of beta cell destruction.

Aims/hypothesisWe sought to establish the extent and basis for adaptive changes in beta cell numbers in human pregnancy.MethodsPancreas was obtained at autopsy from women who had died while pregnant (n = 18), post-partum (n = 6) or were not pregnant at or shortly before death (controls; n = 20). Pancreases were evaluated for fractional pancreatic beta cell area, islet size and islet fraction of beta cells, beta cell replication (Ki67) and apoptosis (TUNEL), and indirect markers of beta cell neogenesis (insulin-positive cells in ducts and scattered beta cells in pancreas).ResultsThe pancreatic fractional beta cell area was increased by ∼1.4-fold in human pregnancy, with no change in mean beta cell size. In pregnancy there were more small islets rather than an increase in islet size or beta cells per islet. No increase in beta cell replication or change in beta cell apoptosis was detected, but duct cells positive for insulin and scattered beta cells were increased with pregnancy.Conclusions/interpretationThe adaptive increase in beta cell numbers in human pregnancy is not as great as in most reports in rodents. This increase in humans is achieved by increased numbers of beta cells in apparently new small islets, rather than duplication of beta cells in existing islets, which is characteristic of pregnancy in rodents.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-010-1809-6) contains supplementary material, which is available to authorised users.

4Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MinnesotaOur aims were (1) by computed tomography (CT) to establish a population database for pancreas volume (parenchyma and fat) from birth to age 100 years, (2) in adults, to establish the impact of gender, obesity, and the presence or absence of type-2 diabetes on pancreatic volume (parenchyma and fat), and (3) to confirm the latter histologically from pancreatic tissue obtained at autopsy with a particular emphasis on whether pancreatic fat is increased in type-2 diabetes. We measured pancreas volume in 135 children and 1,886 adults (1,721 nondiabetic and 165 with type-2 diabetes) with no history of pancreas disease who had undergone abdominal CT scan between 2003 and 2006. Pancreas volume was computed from the contour of the pancreas on each CT image. In addition to total pancreas volume, parenchymal volume, fat volume, and fat/parenchyma ratio (F/P ratio) were determined by CT density. We also quantified pancreatic fat in autopsy tissue of 47 adults (24 nondiabetic and 23 with type-2 diabetes). During childhood and adolescence, the volumes of total pancreas, pancreatic parenchyma, and fat increase linearly with age. From age 20-60 years, pancreas volume reaches a plateau (72.4 6 25.8 cm 3 total; 44.5 6 16.5 cm 3 parenchyma) and then declines thereafter. In adults, total (*32%), parenchymal (*13%), and fat (*68%) volumes increase with obesity. Pancreatic fat content also increases with aging but is not further increased in type-2 diabetes. We provide lifelong population data for total pancreatic, parenchymal, and fat volumes in humans. Although pancreatic fat increases with aging and obesity, it is not increased in type-2 diabetes. Clin. Anat. 20:933-942, 2007. V V C 2007 Wiley-Liss, Inc.

Controversy exists regarding the potential regenerative influences of incretin therapy on pancreatic β-cells versus possible adverse pancreatic proliferative effects. Examination of pancreata from age-matched organ donors with type 2 diabetes mellitus (DM) treated by incretin therapy (n = 8) or other therapy (n = 12) and nondiabetic control subjects (n = 14) reveals an ∼40% increased pancreatic mass in DM treated with incretin therapy, with both increased exocrine cell proliferation (P < 0.0001) and dysplasia (increased pancreatic intraepithelial neoplasia, P < 0.01). Pancreata in DM treated with incretin therapy were notable for α-cell hyperplasia and glucagon-expressing microadenomas (3 of 8) and a neuroendocrine tumor. β-Cell mass was reduced by ∼60% in those with DM, yet a sixfold increase was observed in incretin-treated subjects, although DM persisted. Endocrine cells costaining for insulin and glucagon were increased in DM compared with non-DM control subjects (P < 0.05) and markedly further increased by incretin therapy (P < 0.05). In conclusion, incretin therapy in humans resulted in a marked expansion of the exocrine and endocrine pancreatic compartments, the former being accompanied by increased proliferation and dysplasia and the latter by α-cell hyperplasia with the potential for evolution into neuroendocrine tumors.

OBJECTIVE-Endoplasmic reticulum (ER) stress-induced apoptosis may be a common cause of cell attrition in diseases characterized by misfolding and oligomerisation of amyloidogenic proteins. The islet in type 2 diabetes is characterized by islet amyloid derived from islet amyloid polypeptide (IAPP) and increased ␤-cell apoptosis. We questioned the following: 1) whether IAPP-induced ␤-cell apoptosis is mediated by ER stress and 2) whether ␤-cells in type 2 diabetes are characterized by ER stress. RESEARCH DESIGN AND METHODS-The mechanism of IAPP-induced apoptosis was investigated in INS-1 cells and human IAPP (HIP) transgenic rats. ER stress in humans was investigated by ␤-cell C/EBP homologous protein (CHOP) expression in 7 lean nondiabetic, 12 obese nondiabetic, and 14 obese type 2 diabetic human pancreata obtained at autopsy. To assure specificity for type 2 diabetes, we also examined pancreata from eight cases of type 1 diabetes.RESULTS-IAPP induces ␤-cell apoptosis by ER stress in INS-1 cells and HIP rats. Perinuclear CHOP was rare in lean nondiabetic (2.6 Ϯ 2.0%) and more frequent in obese nondiabetic (14.6 Ϯ 3.0%) and obese diabetic (18.5 Ϯ 3.6%) pancreata. Nuclear CHOP was not detected in lean nondiabetic and rare in obese nondiabetic (0.08 Ϯ 0.04%) but six times higher (P Ͻ 0.01) in obese diabetic (0.49 Ϯ 0.17%) pancreata. In type 1 diabetic pancreata, perinuclear CHOP was rare (2.5 Ϯ 2.3%) and nuclear CHOP not detected. B oth type 1 and type 2 diabetes are characterized by deficits in ␤-cell mass and increased ␤-cell apoptosis (1-6). The mechanism that initiates ␤-cell apoptosis in type 1 diabetes is believed to be autoimmune-mediated cytokine production (5). Several mechanisms have been proposed for increased ␤-cell apoptosis in type 2 diabetes, including oxygen free radicals (7), free fatty acid toxicity (8), interleukin-1␤ (9), and formation of islet amyloid polypeptide (IAPP) toxic oligomers (10 -12). CONCLUSIONS-ERProgrammed cell death, or apoptosis, is important in multicellular organisms to permit organ development and remodeling (13). In disease states, apoptosis permits selective removal of cells that are damaged, particularly in relation to cell cycle, so that damage is not propagated (3,14). Apoptosis may be initiated by a wide variety of cellular insults, which are currently thought to act through at least three pathways that converge to accomplish irreversible destruction of the cell's chromosomes. These three major pathways have been designated as the extrinsic and intrinsic pathways and endoplasmic reticulum (ER) stress pathway (15,16). The extrinsic pathway is classically exemplified by cytokine-induced cell death, mediated through cell surface death receptors (17). The intrinsic pathway is most often described as a response to mitochondrial disruption, for example, secondary to oxygen free radicals (18). ER stress-induced apoptosis is classically ascribed to aggregates of misfolded protein that are believed to compromise the ER membrane (15).The human pancreatic ␤-cell is vulnerable to al...