Superior beta cell proliferation, function and gene expression in a subpopulation of rat islets identified by high blood perfusion

AIMS/HYPOTHESIS

The blood perfusion of individual pancreatic islets is highly variable, with a subgroup of islets having high perfusion and blood vessels responsive to further blood flow increase induced by glucose. This study tested the hypothesis that there is heterogeneity between islets with regard to beta cell proliferation, function and gene expression based on differences in their blood perfusion.

METHODS

Fluorescent microspheres were injected into the ascending aorta, and then microsphere-containing and non-microsphere-containing pancreatic islets were isolated for investigation. By this procedure, the 5% of islets with the greatest blood perfusion were identified for study. Islet endothelial cells were isolated separately to investigate the role of improved vascular support in the observed differences.

RESULTS

The vascular network was found to be more dense and tortuous in microsphere-containing than other islets. The most highly blood-perfused islets also had a higher rate of beta cell proliferation, superior beta cell function and a markedly different gene expression from other islets. Cultured islets exposed to islet endothelial cell products had a similarly increased beta cell proliferation rate, yet significantly fewer changes in gene expression than observed in the most highly blood-perfused islets.

CONCLUSIONS/INTERPRETATION

A novel heterogeneity between islets was observed, with superior beta cell proliferation, function and gene expression in a subpopulation of islets identified by high blood perfusion. In contrast with a previously described population of low-oxygenated, sleeping islets, which are recruited into functionality when needed, the presently described heterogeneity is shown to remain in vitro after islet isolation.

Abstract 3862: The potential role of CD44 in liver regeneration

Background and Aim: Liver regeneration occurs after liver damage by ischaemia, hepatitis, or in hepatocellular carcinoma (HCC) patients receiving hepatic resection or liver transplantation. Understanding the molecular bases of this process will provide novel therapeutic approaches for patients with various liver diseases. Previous studies suggested the linkage between CD44, a multifunctional cell surface receptor, and liver regeneration. The detailed role of this receptor in liver regeneration, however, remained unclear. The present study aimed at elucidating the role of CD44 in liver regeneration. Materials and Methods: A mouse model of liver regeneration induced by partial hepatectomy (PH) was employed. Serum and liver tissues were collected at different time points after PH. ELISA was performed to measure hyaluronic acid (ligand for CD44) level in serum. Flow cytometry was done to characterize liver cell populations after PH. Liver regeneration was quantified by measurement of liver mass and by immunohistochemical staining for PCNA (a proliferation marker). Quantitative PCR was performed to compare gene expression pattern of 46 genes between CD45− CD44+ cells and their CD44− counterparts. Results: Firstly, serum hyaluronic acid level was elevated at the early stage of liver regeneration. Secondly, by flow cytometry, an increase in CD45− CD44+ cell population was found. Thirdly, immunohistochemical analysis revealed active hepatocyte proliferation during this period. Interestingly, the hepatectomy-induced cell proliferation was suppressed after treating mice with anti-CD44 antibody, suggesting a functional role of CD44 in liver regeneration. Lastly, dysregulation of genes involving in cell proliferation, angiogenesis, and metabolism of hyaluronic acid was disclosed in CD45− CD44+ cells. Conclusion: The present study indicated that CD44-mediated pathways are required for liver regeneration, which may have therapeutic implications in treating liver diseases, including HCC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3862. doi:1538-7445.AM2012-3862

Impact of internal mammary node inclusion in the radiation treatment volume on the outcomes of patients with breast cancer treated with locoregional radiation after six years of follow-up

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Background: There is ongoing controversy about radiotherapy (RT) to internal mammary nodes (IMNs). Proponents of IMN RT cite the survival benefit seen in postmastectomy RT trials that included IMNs. However, others point out that benefit cannot be definitively attributed to IMN inclusion, as other lymph node regions were included in the RT arms. The issue is important, as IMN RT potentially increases cardiac and respiratory morbidity.

Methods: 2,413 women referred to a provincial RT program with newly diagnosed node positive, or T3/4N0 non-M1 invasive breast cancer, treated with a complete course of locoregional RT from 2001 to 2006, were retrospectively identified in a provincial database. IMN RT inclusion versus exclusion was determined through review of patient charts and RT treatment plans. Breast cancer-specific survival (BCSS), relapse-free survival (RFS), and overall survival (OS) were compared between the two groups using univariate and multivariable analyses.

Results: Analyses were performed at a median follow-up of 6.2 years. 41.4% of the subjects received IMN RT. The 5-year BCSS for the IMN inclusion and exclusion group was 84.8% versus 82.9%, respectively (HR 0.93 [95% CI 0.76, 1.14]; p=.51); the 5-year RFS was 87.4% versus 86.9% (HR 0.993 [0.83, 1.19]; p=0.94); and the 5-year OS was 84.8% versus 82.9% (HR 0.84 [0.70, 1.01]; p=0.06). After controlling for potentially confounding variables, there was no significant difference in BCSS (HR 0.96 [0.78, 1.18], p=0.88), RFS (HR 1.02 [0.84, 1.22], p=0.87), or OS (HR 0.91 [0.76, 1.10]; p=0.35).

Conclusions: After a median follow-up of 6.2 years, this population-based study shows no benefit from including IMNs in the locoregional RT volume after adjusting for other prognostic and treatment variables.

Accuracy of symptoms and signs in predicting hypoxaemia among young children with acute respiratory infection: a meta-analysis

OBJECTIVE

To assess the accuracy of clinical symptoms and signs in predicting hypoxaemia among young children with acute respiratory infection (ARI).

METHODS

We conducted a systematic review and meta-analysis of prospective diagnostic studies that evaluated the accuracy of individual or combined clinical symptoms and signs in predicting hypoxaemia among children aged <5 years with ARI. MEDLINE® was searched for articles published between 1950 and March 2010. Measurement of arterial haemoglobin oxygen saturation by pulse oximetry was used as reference standard. The hierarchical summary receiver operating characteristic model for meta-analyses was applied.

RESULTS

Eleven diagnostic studies with 5787 patients were included in the review. There was substantial variation in sensitivity and specificity between different symptoms and signs as well as across studies. Cyanosis, inability to feed, head nodding, respiratory rate > 70/min and unresponsiveness/impaired rousability had high specificity but low sensitivity. In contrast, reported rapid breathing and crepitations in lung auscultation had relatively high sensitivity but low specificity. Five models of a combination of symptoms and signs presented moderate sensitivity (range 0.60-0.84) and specificity (range 0.63-0.82).

CONCLUSIONS

Neither single nor combined symptoms and signs have satisfactory performance in predicting hypoxaemia among young children with ARI. Improved access to pulse oximetry is needed in developing countries.

Prevalence and effectiveness of treatment of hypertension on cardiovascular morbidity and mortality in an elderly population aged 70 years and over

The prevalence of hypertension, effectiveness of blood pressure control and compliance, and the effectiveness of treatment on 18-month overall mortality and development of cardiovascular disease in an elderly Chinese population were studied. The study group examined were aged 70 years and over, and consisted of a random sample of subjects on the Old Age and Disability Allowance register. They were stratified by sex and 5-year age groups from 70-74 to 90+ years. Information obtained at baseline included medical history, use of drugs, and measurement of blood pressure. Subjects with a blood pressure > 160/90 were classified as hypertensive. The overall prevalence of hypertension was 48%, 19% being undiagnosed. Among subjects with a known history of hypertension and taking drugs, only approximately half had adequate control (BP < or = 160/90). One fifth of those with a known diagnosis of hypertension were not taking drugs. Subjects who developed stroke had a higher mean systolic and pulse pressure at baseline; no difference in mean pressures was observed for overall mortality or development of heart disease. No difference in mortality or development of cardiovascular disease was observed between the following groups: known history of hypertension and taking medication with controlled blood pressure, known history and taking medication and blood pressure poorly controlled or not taking drugs, and normal blood pressure with no history of hypertension.

Endothelial cell signalling supports pancreatic beta cell function in the rat

AIMS/HYPOTHESIS

The proximity of endothelial cells and beta cells in islets by necessity means that they are exposed to each other's products. Whereas islet endothelial cells require signals from beta cells to function properly, endothelin-1, thrombospondin-1 and laminins, among others, have been identified as endothelial-derived molecules, although their full effects on beta cells have not been explored. We tested the hypothesis that islet endothelial-derived products affect beta cell function.

METHODS

Endothelial cells from rat islets were proliferated and purified. Endothelium-conditioned culture medium (ECCM) was obtained by maintaining the endothelial cells in culture medium. Islet function was evaluated following exposure of cultured islets to standard culture medium or ECCM. Changes in mRNA levels for key beta cell metabolic enzymes were also measured in islets after ECCM exposure.

RESULTS

Glucose-stimulated insulin release and islet insulin content were markedly enhanced by exposure to ECCM. This was at least partly explained by improved mitochondrial function, as assessed by glucose oxidation and an upregulation of the mitochondrial gene for glycerol-3-phosphate dehydrogenase (mGpdh [also known as Gpd2]), combined with upregulation of the rate-limiting enzyme in the glycolysis, glucokinase, in the islets. The intracellular degradation of insulin was also decreased in the islets. Islet endothelial cells produced laminins, and the positive effects of islet endothelial cells were prevented by addition of a neutralising antibody to the beta1-chain of laminin. Addition of exogenous laminin stimulated islet function.

CONCLUSIONS/INTERPRETATION

This study provides proof of principle that endothelial cells can affect the function of beta cells in their vicinity and that this is at least partially mediated by laminins.

APOE gene polymorphisms and response to statin therapy

Published studies investigating the role of APOE gene on lipid response (total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides) to statin treatment have reported inconsistent results. A meta-analysis was conducted to estimate the lipid response to statin treatment among APOE genetic variants (e2 carriers, e3e3 homozygotes and e4 carriers). Twenty-four studies were included in the meta-analyses. The pooled mean reduction (Delta mu) in TC from baseline was significant for all variants (e2 carriers: Delta mu=-27.7% (-32.5 to -22.8%), e3e3: Delta mu=-25.3% (-28.0 to -22.6%) and e4 carriers: Delta mu=-25.1% (-29.3 to -21.0%)). Significant changes in LDL-C, HDL-C and triglyceride levels were also noted for all genotypes, although these changes did not differ significantly among genotypic groups. There was significant heterogeneity among the studies. Given these non-significant effects of APOE genotypes on lipid responses, there is little reason to consider the use of APOE genetic testing for guiding treatment with statins.

Organ-specific hemosiderosis and functional correlation in Chinese patients with thalassemia intermedia and hemoglobin H disease

We performed MRI assessment in 37 adult Chinese patients with thalassemia intermedia and hemoglobin H disease. Despite abnormal ferritin and liver T2*, only 5% of patients had cardiac hemosiderosis. The two patients with reduced ejection fraction had normal cardiac T2*. Half of the cases showed pituitary and pancreatic iron loading. Subclinical endocrine abnormalities (HOMA, insulin growth factor) showed correlation with pancreatic, pituitary, and cardiac MRI values. Prospective data with serial functional and imaging monitoring is needed to verify the utility for chelation to improve cardiac and endocrine function in this group of patients.

Intravenous esomeprazole for prevention of peptic ulcer re-bleeding: rationale/design of Peptic Ulcer Bleed study

BACKGROUND

A limited number of trials have investigated the efficacy of proton pump inhibitors for peptic ulcer bleeding, and some study design issues have been identified.

AIM

To present the design of a large trial evaluating the effects of intravenous esomeprazole on clinical outcomes in high-risk patients who have undergone endoscopic haemostasis for peptic ulcer bleeding.

METHODS

The Peptic Ulcer Bleed study is an international, randomized, double-blind, placebo-controlled trial comparing either esomeprazole 80 mg intravenous bolus infusion for 30 min followed by esomeprazole 8 mg/h intravenously for 71.5 h, or placebo infusion for 72 h, after successful endoscopic haemostasis in patients with peptic ulcer bleeding and associated high-risk stigmata. All patients will receive once daily oral esomeprazole 40 mg for 27 days after intravenous therapy. The primary end point is the rate of clinically significant re-bleeding during the first 72 h after endoscopy. Secondary end points include: rate of re-bleeding during the first 7 and 30 days after treatment; length of hospitalization; mortality; blood transfusion; endoscopic re-treatment and surgery.

RESULTS

Expected 2008.

CONCLUSIONS

The carefully designed protocol and quality control measures represent a pragmatic approach to contemporary challenges in peptic ulcer bleeding management and, it is hoped, qualify the Peptic Ulcer Bleed study as a new standard for future interventional studies.

Maternal obesity and risk of cesarean delivery: a meta-analysis

Despite numerous studies reporting an increased risk of cesarean delivery among overweight or obese compared with normal weight women, the magnitude of the association remains uncertain. Therefore, we conducted a meta-analysis of the current literature to provide a quantitative estimate of this association. We identified studies from three sources: (i) a PubMed search of relevant articles published between January 1980 and September 2005; (ii) reference lists of publications selected from the search; and (iii) reference lists of review articles published between 2000 and 2005. We included cohort designed studies that reported obesity measures reflecting pregnancy body mass, had a normal weight comparison group, and presented data allowing a quantitative measurement of risk. We used a Bayesian random effects model to perform the meta-analysis and meta-regression. Thirty-three studies were included. The unadjusted odd ratios of a cesarean delivery were 1.46 [95% confidence interval (CI): 1.34-1.60], 2.05 (95% CI: 1.86-2.27) and 2.89 (95% CI: 2.28-3.79) among overweight, obese and severely obese women, respectively, compared with normal weight pregnant women. The meta-regression found no evidence that these estimates were affected by selected study characteristics. Our findings provide a quantitative estimate of the risk of cesarean delivery associated with high maternal body mass.