Increasing mode instability thresholds of fiber amplifiers by gain saturation

We show by numerical modeling that saturation of the population inversion reduces the stimulated thermal Rayleigh gain relative to the laser gain in large mode area fiber amplifiers. We show how to exploit this effect to raise mode instability thresholds by a substantial factor. We also demonstrate that when suppression of stimulated Brillouin scattering and the population saturation effect are both taken into account, counter-pumped amplifiers have higher mode instability thresholds than co-pumped amplifiers for fully Yb3+ doped cores, and confined doping can further raise the thresholds.

A comparative study of colorectal surgical outcome in a national audit separated by 15 years

AIM

The Wales-Trent Bowel Cancer Audit (WTBA) was carried out in 1993, and since 2001 Welsh Bowel Cancer Audits (WBCA) have taken place annually. Screening for bowel cancer in Wales was introduced in 2008. This study compared patient variables, the role of surgery and operative mortality rates over the 15-year interval between the WTBA and the last WBCA before the introduction of population screening.

METHOD

Data from the WTBA in 1993 were compared with those of the WBCA including patients diagnosed between April 2007 and March 2008.

RESULTS

In 1993, 1536 patients were diagnosed with colorectal cancer (CRC) compared with 1793 in 2007-2008. Patient demographics and American Society of Anesthesiology (ASA) score did not change during these periods. Surgical treatment for CRC decreased (93% in 1993 vs 80% in 2007-2008; P < 0.001) particularly in the use of resectional surgery (84% in 1993 vs 71% in 2007-2008; P < 0.001). The 30-day postoperative mortality rate fell from 7.4% in 1993 to 5.9% in 2007-2008 (P = 0.097). Advanced disease at operation was more prevalent in the WTBA (25% of all operated patients were Stage IV in 1993 vs 13% in 2007-2008; P < 0.001). The use of surgery in patients with metastatic disease also declined over this period.

CONCLUSION

Surgery is used less frequently in the management of CRC compared with 15 years previously, and is a factor in the reduction of the interpreted 30-day operative mortality.

Steady-periodic method for modeling mode instability in fiber amplifiers

We present a detailed description of the methods used in our model of mode instability in high-power, rare earth-doped, large-mode-area fiber amplifiers. Our model assumes steady-periodic behavior, so it is appropriate to operation after turn on transients have dissipated. It can be adapted to transient cases as well. We describe our algorithm, which includes propagation of the signal field by fast-Fourier transforms, steady-state solutions of the laser gain equations, and two methods of solving the time-dependent heat equation: alternating-direction-implicit integration, and the Green's function method for steady-periodic heating.

Utilization and optimization of a waste stream cellulose culture medium for pigment production by Penicillium spp

AIMS

This research sought to determine optimal corn waste stream-based fermentation medium C and N sources and incubation time to maximize pigment production by an indigenous Indonesian Penicillium spp., as well as to assess pigment pH stability.

METHODS AND RESULTS

A Penicillium spp. was isolated from Indonesian soil, identified as Penicillium resticulosum, and used to test the effects of carbon and nitrogen type and concentrations, medium pH, incubation period and furfural on biomass and pigment yield (PY) in a waste corncob hydrolysate basal medium. Maximum red PY (497.03 ± 55.13 mg l(-1)) was obtained with a 21 : 1 C : N ratio, pH 5.5-6.0; yeast extract-, NH(4) NO(3)-, NaNO(3)-, MgSO(4) ·7H(2) O-, xylose- or carboxymethylcellulose (CMC)-supplemented medium and 12 days (25 °C, 60-70% relative humidity, dark) incubation. C source, C, N and furfural concentration, medium pH and incubation period all influenced biomass and PY. Pigment was pH 2-9 stable.

CONCLUSIONS

Penicillium resticulosum demonstrated microbial pH-stable-pigment production potential using a xylose or CMC and N source, supplemented waste stream cellulose culture medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

Corn derived, waste stream cellulose can be used as a culture medium for fungal pigment production. Such application provides a process for agricultural waste stream resource reuse for production of compounds in increasing demand.

A selective inhibitor of EZH2 blocks H3K27 methylation and kills mutant lymphoma cells

EZH2 catalyzes trimethylation of histone H3 lysine 27 (H3K27). Point mutations of EZH2 at Tyr641 and Ala677 occur in subpopulations of non-Hodgkin's lymphoma, where they drive H3K27 hypertrimethylation. Here we report the discovery of EPZ005687, a potent inhibitor of EZH2 (K(i) of 24 nM). EPZ005687 has greater than 500-fold selectivity against 15 other protein methyltransferases and has 50-fold selectivity against the closely related enzyme EZH1. The compound reduces H3K27 methylation in various lymphoma cells; this translates into apoptotic cell killing in heterozygous Tyr641 or Ala677 mutant cells, with minimal effects on the proliferation of wild-type cells. These data suggest that genetic alteration of EZH2 (for example, mutations at Tyr641 or Ala677) results in a critical dependency on enzymatic activity for proliferation (that is, the equivalent of oncogene addiction), thus portending the clinical use of EZH2 inhibitors for cancers in which EZH2 is genetically altered.

A687V EZH2 is a gain-of-function mutation found in lymphoma patients

Heterozygous point mutations at Y641 and A677 in the EZH2 SET domain are prevalent in about 10-24% of Non-Hodgkin lymphomas (NHL). Previous studies indicate that these are gain-of-function mutations leading to the hypertrimethylation of H3K27. These EZH2 mutations may drive the proliferation of lymphoma and make EZH2 a molecular target for patients harboring these mutations. Here, another EZH2 SET domain point mutation, A687V, occurring in about 1-2% of lymphoma patients, is also shown to be a gain-of-function mutation that greatly enhances its ability to perform dimethylation relative to wild-type EZH2 and is equally proficient at catalyzing trimethylation. We propose that A687V EZH2 also leads to hypertrimethylation of H3K27 and may thus be a driver mutation in NHL.

Development of a social morbidity score in patients with chronic ulcerative colitis as a potential guide to treatment

AIM

Present quality of life instruments for inflammatory bowel disease do not evaluate many social aspects of patients' lives that are potentially important in clinical decision making. We have developed a new Social Impact of Chronic Conditions - Inflammatory Bowel Disease (SICC-IBD) questionnaire to assess these areas.

METHOD

A 34-item questionnaire was piloted to determine quality of life relating to education, personal relationships, employment, independence and finance. It was compared with the Short Form 36-Item version 2 (SF-36v2) and the Inflammatory Bowel Disease Questionnaire (IBDQ) in 150 patients with chronic ulcerative colitis on an endoscopic surveillance register who had never had surgery.

RESULTS

Reliability and validity testing enabled the questionnaire to be shortened to only eight items. There was a high level of reliability (Cronbach's α=0.72). The questionnaire correlated well with the social functioning domain of the SF-36 (rs=0.56) and was able to distinguish clinical severity of disease.

CONCLUSION

The SICC-IBD is a new tool for assessment of patients with ulcerative colitis, which has identified new aspects of social disability for further study and for potential use as an additional tool in therapy decisions.

Selective killing of mixed lineage leukemia cells by a potent small-molecule DOT1L inhibitor

Mislocated enzymatic activity of DOT1L has been proposed as a driver of leukemogenesis in mixed lineage leukemia (MLL). The characterization of EPZ004777, a potent, selective inhibitor of DOT1L is reported. Treatment of MLL cells with the compound selectively inhibits H3K79 methylation and blocks expression of leukemogenic genes. Exposure of leukemic cells to EPZ004777 results in selective killing of those cells bearing the MLL gene translocation, with little effect on non-MLL-translocated cells. Finally, in vivo administration of EPZ004777 leads to extension of survival in a mouse MLL xenograft model. These results provide compelling support for DOT1L inhibition as a basis for targeted therapeutics against MLL.

Mode competition in high power fiber amplifiers

Using a beam propagation model of Yb3+ doped, CW fiber amplifiers we show that gain saturation by a strong fundamental mode significantly suppresses the growth of higher order modes with parallel polarization, but enhances the growth of higher order modes with perpendicular polarization. We quantify this effect in straight and bent fibers, with full core or restricted area doping.

Mode instability in high power fiber amplifiers

For powers exceeding a sharp threshold in the vicinity of several hundred watts the beam quality from some narrow bandwidth fiber amplifiers is severely degraded. We show that this can be caused by transverse thermal gradients induced by the amplification process.

The National Bowel Cancer Audit: the risks and benefits of moving to open reporting of clinical outcomes

BACKGROUND

The government's proposals to openly report clinical outcomes poses challenges to the National Bowel Cancer Audit now funded by the UK department of health.

AIM

To identify the benefits and risks of open reporting and to propose ways the risks might be minimized.

METHODS

A review of the literature on clinical audit and the consequences of open reporting.

RESULTS

There are significant potential benefits of a national audit of bowel cancer including protecting patients from sub-standard care, providing clinicians with externally validated evidence of their performance, outcome data for clinical governance and evidence that increases in government expenditure are achieving improvements in survival from bowel cancer. These benefits will only be achieved if the audit captures most of the cases of bowel cancer in the UK, the data collected is complete and accurate, the results are risk adjusted and these are presented to the public in a way that is fair, clear and understandable. Involvement of clinicians who have confidence in the results of the audit and who actively compare their own results against a national standard is essential. It is suggested that a staged move to open reporting should minimise the risk of falsely identifying an outlying unit.

CONCLUSION

The fundamental aim of the National Bowel Cancer Audit is the pursuit of excellence by identification and adoption of best practice. This could achieve a continuous improvement in the care of all patients with bowel cancer in the UK. The ACPGBI suggests a safer way of transition to open reporting to avoid at least some of its pitfalls.

Conserved role of SIRT1 orthologs in fasting-dependent inhibition of the lipid/cholesterol regulator SREBP

The sterol regulatory element-binding protein (SREBP) transcription factor family is a critical regulator of lipid and sterol homeostasis in eukaryotes. In mammals, SREBPs are highly active in the fed state to promote the expression of lipogenic and cholesterogenic genes and facilitate fat storage. During fasting, SREBP-dependent lipid/cholesterol synthesis is rapidly diminished in the mouse liver; however, the mechanism has remained incompletely understood. Moreover, the evolutionary conservation of fasting regulation of SREBP-dependent programs of gene expression and control of lipid homeostasis has been unclear. We demonstrate here a conserved role for orthologs of the NAD(+)-dependent deacetylase SIRT1 in metazoans in down-regulation of SREBP orthologs during fasting, resulting in inhibition of lipid synthesis and fat storage. Our data reveal that SIRT1 can directly deacetylate SREBP, and modulation of SIRT1 activity results in changes in SREBP ubiquitination, protein stability, and target gene expression. In addition, chemical activators of SIRT1 inhibit SREBP target gene expression in vitro and in vivo, correlating with decreased hepatic lipid and cholesterol levels and attenuated liver steatosis in diet-induced and genetically obese mice. We conclude that SIRT1 orthologs play a critical role in controlling SREBP-dependent gene regulation governing lipid/cholesterol homeostasis in metazoans in response to fasting cues. These findings may have important biomedical implications for the treatment of metabolic disorders associated with aberrant lipid/cholesterol homeostasis, including metabolic syndrome and atherosclerosis.

Short interval time measurement by a parasitoid wasp

The number of eggs laid by the parasitoid wasp Trichogramma varies with host volume. The duration of the wasp's initial transit across the host surface during host examination is used to determine the number of eggs laid. A 2.5-second reduction in initial transit resulted in a 30% reduction in eggs oviposited, demonstrating that these wasps measure short time intervals. This measure is used for progeny allocation independent of host body size.

Genome biology of the cyclostomes and insights into the evolutionary biology of vertebrate genomes

The jawless vertebrates (lamprey and hagfish) are the closest extant outgroups to all jawed vertebrates (gnathostomes) and can therefore provide critical insight into the evolution and basic biology of vertebrate genomes. As such, it is notable that the genomes of lamprey and hagfish possess a capacity for rearrangement that is beyond anything known from the gnathostomes. Like the jawed vertebrates, lamprey and hagfish undergo rearrangement of adaptive immune receptors. However, the receptors and the mechanisms for rearrangement that are utilized by jawless vertebrates clearly evolved independently of the gnathostome system. Unlike the jawed vertebrates, lamprey and hagfish also undergo extensive programmed rearrangements of the genome during embryonic development. By considering these fascinating genome biologies in the context of proposed (albeit contentious) phylogenetic relationships among lamprey, hagfish, and gnathostomes, we can begin to understand the evolutionary history of the vertebrate genome. Specifically, the deep shared ancestry and rapid divergence of lampreys, hagfish and gnathostomes is considered evidence that the two versions of programmed rearrangement present in lamprey and hagfish (embryonic and immune receptor) were present in an ancestral lineage that existed more than 400 million years ago and perhaps included the ancestor of the jawed vertebrates. Validating this premise will require better characterization of the genome sequence and mechanisms of rearrangement in lamprey and hagfish.

Bacteriocin Typing of Burkholderia (Pseudomonas) solanacearum Race 1 of the French West Indies and Correlation with Genomic Variation of the Pathogen

Burkholderia solanacearum race 1 isolates indigenous to the French West Indies were characterized by bacteriocin typing and two genomic fingerprinting methods: pulsed-field gel electrophoresis of genomic DNA digested by rare-cutting restriction endonucleases (RC-PFGE) and PCR with primers corresponding to repetitive extragenic palindromic (REP), enterobacterial repetitive intergenic consensus (ERIC), and BOX elements (collectively known as rep-PCR). The survey comprised 24 reference strains and 65 isolates obtained from a field trial in Guadeloupe in 1993. Comparison of the data identified RC-PFGE as the most discriminatory method, delineating 17 pulsed-field gel profile types. rep-PCR and bacteriocin typing identified nine rep-PCR profile types and nine bacteriocin groups. Independent determination of similarity coefficients and clustering of RC-PFGE and rep-PCR data identified six groups common to both sets of data that correlated to biovar and bacteriocin groups. Further study of bacteriocin production in planta gave results consistent with in vitro bacteriocin typing. It was observed that spontaneous bacteriocin-resistant mutants exhibited a cross-resistance to other bacteriocins as identified by the typing scheme and that such mutants possessed a selective advantage for growth over isogenic nonmutants in the presence of a bacteriocin. The results are significant in the search for biological control of disease by nonpathogenic mutants of the wild-type organism.

Long-term failure and function after restorative proctocolectomy - a multi-centre study of patients from the UK National Ileal Pouch Registry

OBJECTIVE

There is little information on the long-term failure and function after restorative proctocolectomy (RPC). The results of data submitted to a national registry were analysed.

METHOD

The UK National Pouch Registry was established in 2004. By 2006, it comprised data collected from ten centres between 1976 and 2006. The long-term failure and functional outcome were determined. Trends over time were assessed using the gamma statistic or the Kruskal-Wallis statistic wherever appropriate.

RESULTS

In all, 2491 patients underwent primary RPC over a median of 54 months (range 1 month to 28.9 years). Of these, 127 (5.1%) underwent abdominal salvage surgery. The incidence of failure (excision or indefinite diversion) was 7.7% following primary and 27.5% following salvage RPC (P < 0.001). The median frequency of defaecation/24 h was five including one at night. Nocturnal seepage occurred in 8% at 1 year, rising to 15.4% at 20 years (P = 0.037). Urgency was experienced by 5.1% of patients at 1 year rising to 9.1% at 15 years (P = 0.022). Stool frequency and the need for antidiarrhoeal medication were greater following salvage RPC.

CONCLUSION

In patients retaining anal function after RPC, frequency of defaecation was stable over 20 years. Faecal urgency and minor incontinence worsened with time. Function after salvage RPC was significantly worse.

Abstract 3076: BVES, a novel adhesion molecule, acts as tumor modifier through modulation of tight-junction-associated signaling

BVES is novel adhesion protein that functions as a modulator of tight junction (TJ) formation with TJs level directly correlating with BVES expression. TJs, in addition to regulating paracellular passage of molecules, can also directly regulate Rho activity and transcriptional activation of cell cycle regulatory genes (ERBB2, PCNA, CDK4, and Cyclin-D1). Hence, alteration in BVES expression also modulates TJ associated signaling. Interestingly, overexpressing a dominant negative BVES induced human corneal epithelial cells to exhibit increased mesenchymal characteristics. Together, these observations led us to hypothesize that increasing BVES expression in carcinoma cells would induce an epithelial-like phenotype. To evaluate the function of BVES in carcinoma, a semi-adherent LIM2405 human colorectal cancer cell line was stably transfected with wild type BVES (WT-LIM2405) or empty vector (V-LIM2405) as control. Multiple stably transfected clonal isolates of LIM2405 overexpressing BVES exhibited increased epithelial features as evidenced by: i) uniform monolayer formation, ii) decreased vimentin and increased cytokeratin, Zo-1, and occludin expression, iii) decreased cellular motility (66% reduction, p&lt;0.001), and iv) decreased colony number in soft-agar assays (53.5%, p&lt;0.01). In addition, WT-LIM2405 cells progressively displayed reduced cellular proliferation, prolonged cell-doubling time (35%), and decreased S-phase and increased G1 fractions. This was more apparent with increasing confluence, suggesting that contact inhibition is restored with BVES expression. To evaluate the affect of BVES on tumor growth in vivo, V-LIM2405 and WT-LIM2405 cells were grown as orthotopic xenografts in athymic mice. WT-LIM2405 tumor growth was significantly attenuated (86%, p&lt;0.001). Intra-tumoral proliferation rates were equivalent, however apoptosis was increased in WT-LIM2405 tumors (TUNEL positive cells/HPF, p=0.04). We next surveyed BVES expression in colorectal carcinoma. 80% of human CRCs samples exhibited at least a 40% reduction in BVES protein by immunoblotting. In addition, immunolocalization studies showed disorganized or absent BVES and ZO-1 staining only in carcinomatous regions. BVES expression is decrease not only in colorectal cancer (p=0.004), but also in breast (p=0.018) and thyroid carcinoma (p=0.20). Global expression analysis of 250 staged CRC samples compared with normal and adenoma colon specimens showed a decrease in BVES expression as early as carcinoma in situ (p&lt;0.05). These findings indicate endogenous BVES expression is decrease in carcinoma and restoration of its’ expression induces an epithelial-like phenotype in colorectal cancer cells, thus implicating BVES as a tumor suppressor. Further investigation to determine the role of BVES in epithelial cancer biology is warranted and may lead to novel insight into targeted therapies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3076.

Recurrent nuclear DNA introgression accompanies chloroplast DNA exchange between two eucalypt species

Numerous studies within plant genera have found geographically structured sharing of chloroplast (cp) DNA among sympatric species, consistent with introgressive hybridization. Current research is aimed at understanding the extent, direction and significance of nuclear (nr) DNA exchange that accompanies putative cpDNA exchange. Eucalyptus is a complex tree genus for which cpDNA sharing has been established between multiple species. Prior phylogeographic analysis has indicated cpDNA introgression into the widespread forest species Eucalyptus globulus from its rare congener E. cordata. In this study, we use AFLP markers to characterize corresponding nrDNA introgression, on both a broad and fine spatial scale. Using 388 samples we examine (i) the fine-scale spatial structure of cp and nrDNA introgression from E. cordata into E. globulus at a site in natural forest and (ii) broad-scale patterns of AFLP marker introgression at six additional mixed populations. We show that while E. globulus and E. cordata retain strongly differentiated nuclear gene pools overall, leakage of nrDNA occurs at mixed populations, with some AFLP markers being transferred to E. globulus recurrently at different sites. On the fine scale, different AFLP fragments show varying distances of introgression into E. globulus, while introgression of cpDNA is extensive. The frequency of E. cordata markers in E. globulus is correlated with spatial proximity to E. cordata, but departs from expectations based on AFLP marker frequency in E. cordata, indicating that selection may be governing the persistence of introgressed fragments in E. globulus.

Some aspects of the gross and fine structure of the amphibian papilla in the labyrinth of the newt, Triturus cristatus

Each receptor cell in the sensory macula bears a number of stereocilia and one peripherally located kinocilium; in the two halves of the macula, the kinocilia lie on opposite sides of their associated stereocilia. The morphological axes of the receptor cells are approximately parallel to the long axis of the papilla. The gelatinous cupula overlying the macula extends almost to the opposite wall of the papilla. These structural features are discussed in connection with both the proposed function of the papilla as a vibration detector and the possible evolutionary relationships with other acousticolateralis receptors.

HDAC inhibitors regulate claudin-1 expression in colon cancer cells through modulation of mRNA stability

Expression and cellular distribution of claudin-1, a tight junction protein, is dysregulated in colon cancer and its overexpression in colon cancer cells induced dedifferentiation and increased invasion. However, the molecular mechanism(s) underlying dysregulated claudin-1 expression in colon cancer remains poorly understood. Histone deacetylase (HDAC)-dependent histone acetylation is an important mechanism of the regulation of cancer-related genes and inhibition of HDACs induces epithelial differentiation and decreased invasion. Therefore, in this study, we examined the role of HDAC-dependent epigenetic regulation of claudin-1 in colon cancer. In this study, we show that sodium butyrate and Trichostatin A (TSA), two structurally different and widely used HDAC inhibitors, inhibited claudin-1 expression in multiple colon cancer cell lines. Further studies revealed modulation of claudin-1 mRNA stability by its 3'-UTR as the major mechanism underlying HDAC-dependent claudin-1 expression. In addition, overexpression of claudin-1 abrogated the TSA-induced inhibition of invasion in colon cancer cells suggesting functional crosstalk. Analysis of mRNA expression in colon cancer patients, showed a similar pattern of increase in claudin-1 and HDAC-2 mRNA expression throughout all stages of colon cancer. Inhibition of claudin-1 expression by HDAC-2-specific small interfering RNA further supported the role of HDAC-2 in this regulation. Taken together, we report a novel post-transcriptional regulation of claudin-1 expression in colon cancer cells and further show a functional correlation between claudin-1 expression and TSA-mediated regulation of invasion. As HDAC inhibitors are considered to be promising anticancer drugs, these new findings will have implications in both laboratory and clinical settings.

Biochemical characterization, localization, and tissue distribution of the longer form of mouse SIRT3

SIRT3 is a key mitochondrial protein deacetylase proposed to play key roles in regulating mitochondrial metabolism but there has been considerable debate about its actual size, the sequences required for activity, and its subcellular localization. A previously cloned mouse SIRT3 has high sequence similarity with the C-terminus of human SIRT3 but lacks an N-terminal mitochondrial targeting sequence and has no detectable deacetylation activity in vitro. Using 5' rapid amplification of cDNA ends, we cloned the entire sequence of mouse SIRT3, as well as rat and rabbit SIRT3. Importantly, we find that full-length SIRT3 protein localizes exclusively to the mitochondria, in contrast to reports of SIRT3 localization to the nucleus. We demonstrate that SIRT3 has no deacetylation activity in vitro unless the protein is truncated, consistent with human SIRT3. In addition, we determined the inhibition constants and mechanism of action for nicotinamide and a small molecule SIRT3 inhibitor against active mouse SIRT3 and show that the mechanisms are different for the two compounds with respect to peptide substrate and NAD(+). Thus, identification and characterization of the actual SIRT3 sequence should help resolve the debate about the nature of mouse SIRT3 and identify new mechanisms to modulate enzymatic activity.

Amphibian sex determination: segregation and linkage analysis using members of the tiger salamander species complex (Ambystoma mexicanum and A. t. tigrinum)

Little is known about the genetic basis of sex determination in vertebrates though considerable progress has been made in recent years. In this study, segregation analysis and linkage mapping were performed to localize an amphibian sex-determining locus (ambysex) in the tiger salamander (Ambystoma) genome. Segregation of sex phenotypes (male and female) among the second generation individuals of interspecific crosses (Ambystoma mexicanum x Ambystoma tigrinum tigrinum) was consistent with Mendelian expectations, although a slight female bias was observed. Individuals from these same crosses were typed for single-nucleotide polymorphisms distributed throughout the genome to identify molecular markers for ambysex. A marker (E24C3) was identified approximately 5.9 cM from ambysex. Linkage of E24C3 to ambysex was independently validated in a second, intraspecific cross (A. mexicanum). Interestingly, ambysex locates to the tip of one of the larger linkage groups of the Ambystoma meiotic map. Considering that this location does not show reduced recombination, we speculate that the ambysex locus may have arisen quite recently, within the last few million years. Localization of ambysex sets the stage for gene identification and provides important tools for studying the effect of sex in laboratory and natural populations of this model amphibian system.

Small molecule activators of SIRT1 replicate signaling pathways triggered by calorie restriction in vivo

Background

Calorie restriction (CR) produces a number of health benefits and ameliorates diseases of aging such as type 2 diabetes. The components of the pathways downstream of CR may provide intervention points for developing therapeutics for treating diseases of aging. The NAD⁺-dependent protein deacetylase SIRT1 has been implicated as one of the key downstream regulators of CR in yeast, rodents, and humans. Small molecule activators of SIRT1 have been identified that exhibit efficacy in animal models of diseases typically associated with aging including type 2 diabetes. To identify molecular processes induced in the liver of mice treated with two structurally distinct SIRT1 activators, SIRT501 (formulated resveratrol) and SRT1720, for three days, we utilized a systems biology approach and applied Causal Network Modeling (CNM) on gene expression data to elucidate downstream effects of SIRT1 activation.

Results

Here we demonstrate that SIRT1 activators recapitulate many of the molecular events downstream of CR in vivo, such as enhancing mitochondrial biogenesis, improving metabolic signaling pathways, and blunting pro-inflammatory pathways in mice fed a high fat, high calorie diet.

Conclusion

CNM of gene expression data from mice treated with SRT501 or SRT1720 in combination with supporting in vitro and in vivo data demonstrates that SRT501 and SRT1720 produce a signaling profile that mirrors CR, improves glucose and insulin homeostasis, and acts via SIRT1 activation in vivo. Taken together these results are encouraging regarding the use of small molecule activators of SIRT1 for therapeutic intervention into type 2 diabetes, a strategy which is currently being investigated in multiple clinical trials.

Assessment of the mucosa of the indefinitely diverted ileo-anal pouch

OBJECTIVE

One surgical option to treat failure after restorative proctocolectomy (RPC) is indefinite diversion (ID) without excision of the pouch. The study aimed to assess the mucosal morphology of the pouch and ileoanal anastomosis (IAA) over time after ID with particular reference to inflammation, dysplasia and carcinoma.

METHOD

Patients with ID were identified from the hospital's Ileal Pouch Database. Individuals were invited by mail to attend for flexible pouchoscopy and biopsy from the ileal pouch and immediately distal to the IAA.

RESULTS

Of 1822 patients on the database, 28 had undergone ID. Of these, 20 patients (18 ulcerative colitis, one familial adenomatous polyposis, one pseudo-obstruction) of median age 42 (18-67) years took part. There were eight males. The median (range) intervals from diagnosis of primary disease, pouch surgery and ID to the time of study were 221 (63-410), 146 (31-314) and 44 (10-159) months respectively. One patient had dysplasia in the original resection specimen. Five patients developed type C changes in the pouch. Of these three were identified between RPC and ID, one developed between ID and the present assessment and one was identified for the first time at the present assessment. No case of dysplasia or cancer was found in any of the biopsies. Rectal mucosa was found in biopsies from the IAA in four patients (three stapled; one handsewn); this was inflamed in three patients.

CONCLUSION

At a median follow-up of 12 years after RPC and 3.6 years after indefinite diversion no instance of dysplasia or carcinoma in the ileal reservoir or distal to the IAA was found in any of the 20 patients having ID. Type C changes occurred at some time in five (25%) patients, indicating the importance of continued follow up.