Therapeutic Differentiation of Tumor-derived Insulin-producing Cells Selected for Resistance to Diabetogenic Drugs

Differentiation therapy has been proposed as a new approach to selectively engage the process of tumor cell differentiation during chemotherapy of cancer. Our recent in vitro study suggests that such an approach can be extended and utilized for the selection of tumor-derived insulin-producing cells for transplantation. Repeated treatment with streptozotocin selected toxin resistant subpopulation of insulin producing tumor RINmS cells, characterized increased level of insulin content and secretion. In the present study RINmS cells were found to have higher glucose sensitivity and insulin response compared with parental RINm cells. In addition, compounds known to induce elevated level of cAMP beta-cells, such as isobutyl methyl xanthine, and forskolin, potentiated glucose-induced insulin secretion of RINmS, but had no effect on the naive parental RINm cells. These experiments suggest that differentiation therapy can be utilized for engineering insulin producing cells with improved defense and secretory mechanisms

Streptozotocin and Alloxan-based Selection Improves Toxin Resistance of Insulin-Producing RINm Cells

The aim of our study was to develop a method for selection of subpopulations of insulin producing RINm cells with higher resistance to beta cell toxins. Cells, resistant to streptozotocin (RINmS) and alloxan (RINmA), were obtained by repeated exposure of parental RINm cells to these two toxins, while the defense capacity, was estimated by the MTT colorimetric method, and [3H]-thymidine incorporation assay. We found that RINmS and RINmA displayed higher resistance to both streptozotocin (STZ) and alloxan (AL) when compared to the parental RINm cells. In contrast, no differences in sensitivity to hydrogen peroxide were found between toxin selected and parental cells. Partial protection from the toxic effect of STZ and AL was obtained only in the parental RINm cells after preincubation of cells with the unmetabolizable 3- O-methyl-glucose. The possibility that GLUT-2 is involved in cell sensitivity to toxins was confirmed by Western blot analysis, which showed higher expression of GLUT-2 in parental RINm compared to RINmS and RINmA cells. In addition to the higher cell defense property evidenced in the selected cells, we also found higher insulin content and insulin secretion in both RINmS and RINmA cells when compared to the parental RINm cells. In conclusion, STZ and AL treatment can be used for selection of cell sub-populations with higher cell defense properties and hormone production. The different GLUT-2 expression in parental and re sistant cells suggest involvement of GLUT-2 in mechanisms of cell response to different toxins

Childhood Obesity

In March 2004 a group of 65 physicians and other health professionals representing nine countries on four continents convened in Israel to discuss the widespread public health crisis in childhood obesity. Their aim was to explore the available evidence and develop a consensus on the way forward. The process was rigorous, although time and resources did not permit the development of formal evidence-based guidelines. In the months before meeting, participants were allocated to seven groups covering prevalence, causes, risks, prevention, diagnosis, treatment, and psychology. Through electronic communication each group selected the key issues for their area, searched the literature, and developed a draft document. Over the 3-d meeting, these papers were debated and finalized by each group before presenting to the full group for further discussion and agreement. In developing a consensus statement, this international group has presented the evidence, developed recommendations, and provided a platform aimed toward future corrective action and ongoing debate in the international community

Long-term effects of intracranial islet grafting on cognitive functioning in a rat metabolic model of sporadic Alzheimer's disease-like dementia.

Accumulating evidence suggests that Alzheimer's disease is associated with brain insulin resistance, as are some other types of dementia. Intranasal insulin administration has been suggested as a potential approach to overcoming brain insulin resistance and improving cognitive functions. Islet transplantation into the cranial subarachnoid cavity was used as an alternative route for insulin delivery into the brain. Recently, the authors showed the short-term beneficial cognitive effect of a small number of intracranially grafted islets in rats with cognitive dysfunction induced by intracerebroventricular administration of streptozotocin (icv-STZ). This was associated with continuous and safe insulin delivery to the rat brain. The current study investigated the long-term effect of intracranial grafting of islets on cognitive functioning in icv-STZ rats. Severe dementia, associated with obesity and cerebral amyloid-β angiopathy, was induced in Lewis inbred rats by icv-STZ. Two months after icv-STZ, one hundred syngeneic islets were transplanted into the cranial subarachnoid space. Two and six months later, cognitive alterations were assessed by Morris water-maze tests. Islet graft survival was evaluated by immunohistochemical and biochemical assays. Improvement was found in spatial learning and memory of grafted rats as opposed to the sham-operated icv-STZ rats. The grafted islets showed intact morphology, intensive expression of insulin, glucagon and glucose transporter 2. Normoglycemic obesity and cerebral amyloid-β angiopathy were found in both grafted and sham-operated icv-STZ rats. In conclusion, islet grafting into cranial subarachnoid space provides an efficient and safe approach for insulin delivery to the brain, leading to a long-term attenuation of icv-STZ-induced cognitive dysfunction

Enhanced Oxygen Supply Improves Islet Viability in a New Bioartificial Pancreas

<p>The current epidemic of diabetes with its overwhelming burden on our healthcare system requires better therapeutic strategies. Here we present a promising novel approach for a curative strategy that may be accessible for all insulin-dependent diabetes patients. We designed a subcutaneous implantable bioartificial pancreas (BAP)-the "beta-Air" that is able to overcome critical challenges in current clinical islet transplantation protocols: adequate oxygen supply to the graft and protection of donor islets against the host immune system. The system consists of islets of Langerhans immobilized in an alginate hydrogel, a gas chamber, a gas permeable membrane, an external membrane, and a mechanical support. The minimally invasive implantable device, refueled with oxygen via subdermally implanted access ports, completely normalized diabetic indicators of glycemic control (blood glucose intravenous glucose tolerance test and HbA1c) in streptozotocin-induced diabetic rats for periods up to 6 months. The functionality of the device was dependent on oxygen supply to the device as the grafts failed when oxygen supply was ceased. In addition, we showed that the device is immuno-protective as it allowed for survival of not only isografts but also of allografts. Histological examination of the explanted devices demonstrated morphologically and functionally intact islets; the surrounding tissue was without signs of inflammation and showed visual evidence of vasculature at the site of implantation. Further increase in islets loading density will justify the translation of the system to clinical trials, opening up the potential for a novel approach in diabetes therapy.</p>

Oxygen partial pressure in the gas chamber.

<p>Levels of oxygen at the end of successive 24 h cycles were monitored in the central cavity and in the 2 side chambers. Solid black line, central cavity; solid grey line, side chambers. Data are presented as the 3^rd grade polynomial curves.</p