Exploiting PI3K/mTOR signaling to accelerate epithelial wound healing

The molecular circuitries controlling the process of skin wound healing have gained new significant insights in recent years. This knowledge is built on landmark studies on skin embryogenesis, maturation, and differentiation. Furthermore, the identification, characterization, and elucidation of the biological roles of adult skin epithelial stem cells and their influence in tissue homeostasis have provided the foundation for the overall understanding of the process of skin wound healing and tissue repair. Among numerous signaling pathways associated with epithelial functions, the PI3K/Akt/mTOR signaling route has gained substantial attention with the generation of animal models capable of dissecting individual components of the pathway, thereby providing a novel insight into the molecular framework underlying skin homeostasis and tissue regeneration. In this review, we focus on recent findings regarding the mechanisms involved in wound healing associated with the upregulation of the activity of the PI3K/Akt/mTOR circuitry. This review highlights critical findings on the molecular mechanisms controlling the activation of mTOR, a downstream component of the PI3K–PTEN pathway, which is directly involved in epithelial migration and proliferation. We discuss how this emerging information can be exploited for the development of novel pharmacological intervention strategies to accelerate the healing of critical size wounds.     

Pancreatic Islet Vasculature Adapts to Insulin Resistance Through Dilation and Not Angiogenesis

Pancreatic islets adapt to insulin resistance through a complex set of changes, including β-cell hyperplasia and hypertrophy. To determine if islet vascularization changes in response to insulin resistance, we investigated three independent models of insulin resistance: ob/ob, GLUT4^+/−, and mice with high-fat diet–induced obesity. Intravital blood vessel labeling and immunocytochemistry revealed a vascular plasticity in which islet vessel area was significantly increased, but intraislet vessel density was decreased as the result of insulin resistance. These vascular changes were independent of islet size and were only observed within the β-cell core but not in the islet periphery. Intraislet endothelial cell fenestration, proliferation, and islet angiogenic factor/receptor expression were unchanged in insulin-resistant compared with control mice, indicating that islet capillary expansion is mediated by dilation of preexisting vessels and not by angiogenesis. We propose that the islet capillary dilation is modulated by endothelial nitric oxide synthase via complementary signals derived from β-cells, parasympathetic nerves, and increased islet blood flow. These compensatory changes in islet vascularization may influence whether β-cells can adequately respond to insulin resistance and prevent the development of diabetes.Pancreatic islets are highly vascularized, and this feature is critical for β-cells to rapidly sense the blood glucose and secrete insulin into the systemic circulation (1,2). Islet vascularization begins early in pancreas development and is maintained in adulthood as a consequence of islet cell production of angiogenic factors such as vascular endothelial growth factor-A (VEGF-A) and angiopoietin-1 (Ang-1) (3–6). These factors recruit endothelial cells (ECs), stimulate blood vessel growth and maturation, and in the case of VEGF-A, promote formation of EC fenestrations (5,6). In addition, ECs adjacent to pancreatic epithelium reciprocally influence islet cell differentiation and development (7,8).β-Cells have a remarkable ability to respond to changes in an organism’s metabolic state, such as changes in the blood glucose or increased insulin requirements. For example, when insulin resistance develops, β-cells of the pancreatic islet can dramatically increase insulin production and secretion with an increase of β-cell mass, thus maintaining normoglycemia (9,10). In this way, mouse models with marked insulin resistance and humans with obesity-related insulin resistance are hyperinsulinemic but not hyperglycemic. The mechanisms underlying this β-cell adaptation to insulin resistance and their subsequent failure in some individuals who develop type 2 diabetes are incompletely understood.Because of the highly vascularized state of pancreatic islets and the marked changes in β-cell size and number in the setting of insulin resistance, we hypothesized that the islet vasculature must adapt to these changes in β-cell mass and insulin requirements. We envisioned that a hyperplastic islet, like a growing tumor mass, would increase production of angiogenic factors to increase its vascular supply with expanding β-cell mass (11). To test this hypothesis, we examined islet vascularization in three mouse models of insulin resistance and found, unexpectedly, that islet vessel density was decreased, not increased, and that the intraislet vasculature became markedly dilated whereas vessels in the exocrine tissue were unchanged. The dilation of intraislet capillaries was independent of islet size, suggesting the vascular adaptation may primarily support increased β-cell insulin secretory demand rather than β-cell mass expansion. Moreover, these vascular changes were accompanied by an increase in islet parasympathetic innervation. Our results indicate that the metabolic state influences islet angioarchitecture and innervation, suggesting that islet neurovascular remodeling may influence whether β-cells can adequately respond to insulin resistance and maintain normoglycemia.     

Selective internal radiation therapy in patients with progressive neuroendocrine liver metastases

Purpose

To evaluate the safety and efficacy of selective internal radiation therapy (SIRT) in patients with unresectable liver metastases from neuroendocrine tumours (NETLMs).

Methods

This retrospective study included 40 patients with progressive NETLMs (22 women, 18 men, mean age 61.6 years) who underwent SIRT with ⁹⁰Y-labelled resin microspheres. Tumour response was evaluated according to the modified Response Evaluation Criteria in Solid Tumors (mRECIST) on CT or MR images. Medical records were reviewed.

Results

In the 40 patients, 54 evaluable SIRT procedures were performed, 33 to the right liver lobe (mean activity 1.31 GBq), 13 to the left lobe (mean activity 0.85 GBq), and 8 to both lobes (mean activity 1.61 GBq). Late follow-up imaging (mean 20 months) was performed after 44 of the treatments. Objective tumour response and disease control rates were 54 % (29 of 54 treatments) and 94 % (51 treatments), respectively, at the early follow-up examination (mean 3 months) and 34 % (15 treatments) and 57 % (25 treatments), respectively at the late follow-up examination. Mean overall survival from the first SIRT was 34,8 months and survival rates at 1, 2, 3 and 5 years were 76 %, 59 %, 52 % and 35 % respectively. Adverse effects were generally mild and easily manageable, except in one patient who died from radiation-induced liver failure. Of the 45 patients, 18 (45 %) had received peptide receptor radionuclide therapy (PRRT) prior to SIRT.

Conclusion

SIRT with ⁹⁰Y-labelled resin microspheres is a safe and effective treatment for patients with progressive NETLM, and also for those who have received prior PRRT.

     

Quality-of-life weights for the US population: self-reported health status and priority health conditions, by demographic characteristics

BACKGROUND: Many of the large ongoing national surveys of the US population contain a question that asks for the respondent's self-reported health status: "excellent," "very good," "good," "fair," or "poor." These surveys could be used to conduct cost-utility analyses of health care policies, treatments or other interventions if quality-of-life (QOL) weights for the self-reported health statuses were also available. OBJECTIVE: The objective of this study was to produce nationally representative QOL weights for self-reported health status and for 10 "priority" health conditions, by a series of demographic variables. RESEARCH DESIGN: The Medical Expenditure Panel Survey contains the questions from the EQ-5D health status measure. A recent study has calculated time-trade-off-derived QOL weights corresponding to the EQ-5D health states for a large sample of Americans. We use these data to construct QOL weights for the 5 self-reported health status categories and 10 priority health conditions, by a series of demographic variables. RESULTS: Mean and median QOL weights were produced for self-reported health status, the 10 priority health conditions, and the demographic variables. We also report mean QOL weights for the self-reported health state and priority health conditions, by the demographic variables. Finally, ordinary least squares and censored least absolute deviation regression equations were used to estimate adjusted QOL weights for these variables. CONCLUSIONS: By providing nationally representative QOL weights for self-reported health status and 10 priority health conditions, by demographic variable, we have facilitated the use of large national surveys for conducting cost-utility analysis and increased their value to researchers and policy makers.