In both type 1 and type 2 diabetes, pancreatic islet dysfunction results in part from cytokine-mediated inflammation. The ubiquitous eukaryotic translation initiation factor 5A (eIF5A), which is the only protein to contain the amino acid hypusine, contributes to the production of proinflammatory cytokines. We therefore investigated whether eIF5A participates in the inflammatory cascade leading to islet dysfunction during the development of diabetes. As described herein, we found that eIF5A regulates iNOS levels and that eIF5A depletion as well as the inhibition of hypusination protects against glucose intolerance in inflammatory mouse models of diabetes. We observed that following knockdown of eIF5A expression, mice were resistant to β cell loss and the development of hyperglycemia in the low-dose streptozotocin model of diabetes. The depletion of eIF5A led to impaired translation of iNOS-encoding mRNA within the islet. A role for the hypusine residue of eIF5A in islet inflammatory responses was suggested by the observation that inhibition of hypusine synthesis reduced translation of iNOS-encoding mRNA in rodent β cells and human islets and protected mice against the development of glucose intolerance the low-dose streptozotocin model of diabetes. Further analysis revealed that hypusine is required in part for nuclear export of iNOS-encoding mRNA, a process that involved the export protein exportin1. These observations identify the hypusine modification of eIF5A as a potential therapeutic target for preserving islet function under inflammatory conditions.

The nuclear receptor peroxisome proliferator-activated receptor ␥ (PPAR-␥) is an important target in diabetes therapy, but its direct role, if any, in the restoration of islet function has remained controversial. To identify potential molecular mechanisms of PPAR-␥ in the islet, we treated diabetic or glucose-intolerant mice with the PPAR-␥ agonist pioglitazone or with a control. Treated mice exhibited significantly improved glycemic control, corresponding to increased serum insulin and enhanced glucose-stimulated insulin release and Ca 2؉ responses from isolated islets in vitro. This improved islet function was at least partially attributed to significant upregulation of the islet genes Irs1, SERCA, Ins1/2, and Glut2 in treated animals. The restoration of the Ins1/2 and Glut2 genes corresponded to a two-to threefold increase in the euchromatin marker histone H3 dimethyl-Lys4 at their respective promoters and was coincident with increased nuclear occupancy of the islet methyltransferase Set7/9. Analysis of diabetic islets in vitro suggested that these effects resulting from the presence of the PPAR-␥ agonist may be secondary to improvements in endoplasmic reticulum stress. Consistent with this possibility, incubation of thapsigargin-treated INS-1 ␤ cells with the PPAR-␥ agonist resulted in the reduction of endoplasmic reticulum stress and restoration of Pdx1 protein levels and Set7/9 nuclear occupancy. We conclude that PPAR-␥ agonists exert a direct effect in diabetic islets to reduce endoplasmic reticulum stress and enhance Pdx1 levels, leading to favorable alterations of the islet gene chromatin architecture.Type 2 diabetes mellitus results from a combination of insulin resistance and progressive islet dysfunction (46). In many individuals, ␤-cell failure may precede the clinical diagnosis of diabetes, and landmark studies such as the United Kingdom Prospective Diabetes Study have shown a continued decrement in ␤-cell function despite treatment intervention with sulfonylureas, metformin, and insulin (52). Thiazolidinediones are orally active agents used in the treatment of type 2 diabetes that act as agonists for the nuclear transcription factor peroxisome proliferator-activated receptor ␥ (PPAR-␥) (60). Although thiazolidinediones are classically thought to act as peripheral insulin sensitizers, there is growing evidence from studies of human and animal models that these agents may also act to preserve and/or enhance ␤-cell function in the setting of progressive type 2 diabetes and insulin resistance (3, 12). PPAR-␥ is known to be expressed in the pancreatic islet (8, 48), and PPAR-responsive elements have been identified in the promoters of genes involved in glucose-stimulated insulin secretion, including Glut2, Gck, and Pdx1 (16,21,26,27,33). Reports from studies of ␤-cell lines, rodent models of progressive type 2 diabetes, and humans at risk for type 2 diabetes suggest that PPAR-␥ agonist administration leads to preservation of islet mass and function (10,13,18,22,25,33,57,58).Whereas the studies noted ab...

Islet ␤ cell dysfunction resulting from inflammation, ER stress, and oxidative stress is a key determinant in the progression from insulin resistance to type 2 diabetes mellitus. It was recently shown that the enzyme deoxyhypusine synthase (DHS) promotes early cytokine-induced inflammation in the ␤ cell. DHS catalyzes the conversion of lysine to hypusine, an amino acid that is unique to the translational elongation factor eIF5A. Here, we sought to determine whether DHS activity contributes to ␤ cell dysfunction in models of type 2 diabetes in mice and ␤ cell lines. A 2-week treatment of obese diabetic C57BLKS/J-db/db mice with the DHS inhibitor GC7 resulted in improved glucose tolerance, increased insulin release, and enhanced ␤ cell mass. Thapsigargin treatment of ␤ cells in vitro induces a picture of ER stress and apoptosis similar to that seen in db/db mice; in this setting, DHS inhibition led to a block in CHOP (CAAT/enhancer binding protein homologous protein) production despite >30-fold activation of Chop gene transcription. Blockage of CHOP translation resulted in reduction of downstream caspase-3 cleavage and near-complete protection of cells from apoptotic death. DHS inhibition appeared to prevent the cytoplasmic co-localization of eIF5A with the ER, possibly precluding the participation of eIF5A in translational elongation at ER-based ribosomes. We conclude that hypusination by DHS is required for the ongoing production of proteins, particularly CHOP, in response to ER stress in the ␤ cell.Obesity is increasing at a rapid rate worldwide, with estimates that place its prevalence at Ͼ300 million people. Obesity is perhaps the single greatest risk factor for the development of type 2 diabetes mellitus. The relationship between obesity and diabetes is complex, but it is apparent that a direct correlation exists between increasing visceral fat and insulin resistance (1-3). However, only ϳ30% of obese, insulinresistant individuals have diabetes, suggesting that other factors superimposing upon obesity must confer additional risks (4). It is now clear that defects in insulin secretion at the level of the islet ␤ cell are paramount in the transition from a normoglycemic, insulin-resistant state to frank diabetes (5), and it is postulated that underlying genetic defects at the level of the ␤ cell differentiates those who develop diabetes from those who do not (6). Prospective clinical (7) and autopsy (8) studies show significant reductions in ␤ cell function and mass, respectively, in the transition from obesity-induced insulin resistance to frank type 2 diabetes.The causes of islet dysfunction and death in the setting of insulin resistance include hyperglycemia, hyperlipidemia, cytokines, and deposition of islet amyloid polypeptide (9, 10). All of these causes stimulate intersecting pathways within the islet that lead to oxidative stress, inflammation, and endoplasmic reticulum (ER) 3 stress. These stress pathways are closely intertwined, such that activators of primarily one pathway acutely (e.g. cytokines ca...

Purpose of review Inducible pluripotent stem (iPS) cells derived from somatic cells represent a novel renewable source of tissue precursors. The potential of iPS cells is considered to be at least equivalent to that of human embryonic stem (hES) cells, facilitating the treatment or cure of diseases such as diabetes mellitus, spinal cord injuries, cardiovascular disease, and neurodegenerative diseases, but with the potential added benefit of evading the adaptive immune response that otherwise limits allogeneic cell-based therapies. This review discusses recent advances in pluripotency induction and the use of iPS cells to produce differentiated cells, while highlighting roadblocks to the widespread use of this technology in the clinical arena. Recent findings Whereas ethical and safety issues surrounding the use of human ES cells for the treatment of disease continue to be debated, use of iPS cells may be viewed as a more widely acceptable compromise. Since the first descriptions of inducible pluripotency from somatic cells, multiple laboratories have collectively made tremendous strides both in developing alternative, more clinically acceptable, induction strategies and in demonstrating the proof-of-principle that iPS cells can be differentiated into a variety of cell types to reverse mouse models of human disease. Summary Although the prospect of using patient-specific iPS cells has much appeal from an ethical and immunologic perspective, the limitations of the technology from the standpoint of reprogramming efficiency and therapeutic safety necessitate much more in-depth research before the initiation of human clinical trials.

Objective Obesity is a factor in the outcome and severity of pancreatic conditions. We examined the effect of hypercaloric diets on the pancreata of Ossabaw swine, a large animal model of metabolic syndrome and obesity. Methods Swine were fed with 1 of 4 diets: high-fructose (n = 9), atherogenic (n = 10), modified atherogenic (n = 6), or eucaloric standard diet (n = 12) for 24 weeks. Serum chemistries were measured, and pancreata were examined for histological abnormalities including steatosis, inflammation or fibrosis, insulin content, and oxidative stress. Results The fructose, atherogenic, and modified atherogenic diet groups exhibited obesity, metabolic syndrome, islet enlargement, and significantly increased pancreatic steatosis (22.9% ± 7.5%, 19.7% ± 7.7%, and 38.7% ± 15.3% fat in total tissue area, respectively) compared with controls (9.3% ± 1.9%; P < 0.05). The modified atherogenic diet group showed significantly increased oxidative stress levels as evidenced by elevated serum malondialdehyde (3.0 ± 3.3 vs 1.5 ± 0.3 μmol/L in controls; P = 0.006) and pancreatic malondialdehyde (0.1 ± 0.12 vs 0.04 ± 0.01 nmol/mg protein in controls; P = 0.01). None of the swine exhibited pancreatitis or cellular injury. Conclusions Ossabaw swine fed with a modified atherogenic diet developed significant pancreatic steatosis and increased oxidative stress, but no other histological abnormalities were observed.

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