Circumferential resection margin positivity due to direct or indirect tumour involvement in rectal cancer - a call for better stratification.

BACKGROUND: A positive circumferential resection margin (CRM) after rectal cancer surgery, which can be the result of direct or indirect tumour involvement, has consistently been associated with increased local recurrence and poorer survival. However, little is known of the differential impact of the mode of tumour involvement on outcomes. METHODS: 1460 consecutive patients undergoing rectal cancer resection between 2003 and 2018 were retrospectively assessed. Histopathology reports for patients with a positive CRM were reviewed to determine cases of direct (R1-tumour) or indirect tumour involvement (R1-other). Disease-free survival (DFS) and overall survival (OS) were assessed by Kaplan-Meier analysis. The role of the mode of CRM positivity was examined by univariate and multivariate Cox proportional hazards models. RESULTS: Eighty-five patients had an R1 resection due to CRM involvement (5.8%). Of those, 69 were due to direct tumour involvement, while 16 were from indirect causes. Kaplan-Meier analysis revealed that R1-other was associated with increased OS (hazard ratio 0.40, log-rank P = 0.006) and DFS (P = 0.043). Multivariate regression confirmed that the mode of CRM positivity was an independent predictor of OS. More interestingly, the patterns of recurrence were different between the two groups, with R1-tumour leading to significantly more local recurrence (P = 0.04). CONCLUSIONS: Our data strongly suggests that direct tumour involvement of the CRM confers worse prognosis after rectal cancer surgery. Importantly, differences in the site and frequency of recurrences make a case for better stratification of patients with a positive CRM to guide treatment decisions.

Postoperative decline in renal function after rectal resection and all-cause mortality: a retrospective cohort study.

AIM: Fluid loss, dehydration and resultant kidney injury are common when a diverting ileostomy is formed during rectal cancer surgery, the consequences of which are unknown. The aim of this retrospective single-site cohort study is to evaluate the impact of sustained postoperative renal dysfunction after rectal resection on long-term renal impairment and survival. METHOD: All patients with rectal adenocarcinoma undergoing resection between January 2003 and March 2017 were included, with follow-up to June 2020. The primary outcome was impact on long-term mortality attributed to a 25% or greater drop in estimated glomerular filtration rate (eGFR) following rectal resection. Secondary outcomes were the long-term effect on renal function resulting from the same drop in eGFR and the effect on long-term mortality and renal function of a 50% drop in eGFR. We also calculated the effect on mortality of a 1% drop in eGFR. RESULTS: A total of 1159 patients were identified. Postoperative reductions in eGFR of 25% and 50% were associated with long-term overall mortality with adjusted hazard ratios of 1.84 (1.22-2.77) (p = 0.004) and 2.88 (1.45-5.71) (p = 0.002). The median survival of these groups was 86.0 (64.0-108.0) months and 53.3 (7.8-98.8) months compared with 144.5 (128.1-160.9) months for controls. Long-term effects on renal function were demonstrated, with those who sustained a >25% drop in renal function having a 38.8% mean decline in eGFR at 10 years compared with 10.2% in controls. CONCLUSION: Persistent postoperative declines in renal function may be linked to long-term mortality. Further research is needed to assess causal relationships and prevention.

Technical assessment in minimally invasive complete mesocolic excision: Is the complete mesocolic excision competency assessment tool valid and reliable?

AIM: The complete mesocolic excision competency assessment tool (CMECAT) is a novel tool designed to assess technical skills in minimally invasive complete mesocolic excision (CME) surgery. The aim of this study was to assess construct validity and reliability of CMECAT in a clinical context. METHOD: Colorectal surgeons were asked to submit video recorded laparoscopic CME resections for independent assessment of their technical abilities. The videos were grouped by surgeons' training level, and four established CME experts were recruited as CMECAT assessors. Extended reliability analysis (G-theory) was applied to describe assessor agreement. RESULTS: A total of 19 videos and 72 assessments were included in the analysis. Overall, technical skills assessed by CMECAT improved with increased training level: the experts scored significantly better than the untrained surgeons (3.3 vs. 2.5 points; p < 0.01). On right-sided resections, significantly higher scores were reported with increased training level for all categories and sections, while for left-sided resections, the variance across groups was smaller and significantly higher scores were only reported for oncological safety describing items. Overall, assessor agreement was high (G-coefficient: 0.81). CONCLUSION: This study confirms that CMECAT can be applied to video recorded CME cases for technical skill assessment. Further, it can reliably assess technical performance in right sided CME surgery, where construct validity has now been established. More videos are required to evaluate its validity on left colonic CME. In the future, we hope CMECAT can improve feedback during CME training, serve as a tool in certification processes and contribute to distinguishing CME from conventional surgery in future research.

Development of a procedure-specific tool for skill assessment in left- and right-sided laparoscopic complete mesocolic excision.

AIM: To (1) develop an assessment tool for laparoscopic complete mesocolic excision (LCME) and (2) report evidence of its content validity. METHOD: Assessment statements were revealed through (1) semi-structured expert interviews and (2) consensus by the Delphi method, both involving an expert panel of five LCME surgeons. All experts were interviewed and then asked to rate LCME describing statements from 1 (strongly disagree) to 5 (strongly agree). Responses were returned anonymously to the panel until consensus was reached. Statements were directly included as content in the assessment tool if ≥60% of the experts responded "agree" or "strongly agree" (ratings 4 and 5), with the remaining responses being "neither agree nor disagree" (rating 3). Interclass correlation coefficient (ICC) was calculated for expert agreement evaluation. All included statements were subsequently reformulated as tool items and approved by the experts. RESULTS: Four Delphi rounds were performed to reach consensus. Disagreement was reported for statements describing instrument handling around pancreas; visualisation of landmarks before inferior mesenteric artery ligation; lymphadenectomy around the inferior mesenteric artery, and division of the terminal ileum and transverse colon. ICC in the last Delphi-round was 0.84. The final tool content included 73 statements, converted to 48 right- and 40 left-sided items for LCME assessment. CONCLUSION: A procedure-specific, video-based tool, named complete mesocolic excision competency assessment tool (CMECAT), has been developed for LCME skill assessment. In the future, we hope it can facilitate assessment of LCME surgeons, resulting in improved patient outcome after colon cancer surgery.

Anterior Resection Syndrome and Quality of Life With Long-term Follow-up After Rectal Cancer Resection.

BACKGROUND: Surgical and systemic therapies continue to advance, enabling restorative resections for distal rectal cancer. These operations are associated with low anterior resection syndrome. Recent studies with methodological and size limitations have investigated the incidence of low anterior resection syndrome after anterior resection. However, the long-term trajectory of low anterior resection syndrome and its effect on health-related quality of life remain unclear. OBJECTIVE: The purpose of this study was to assess the impact of anterior resection and reversal of ileostomy on long-term health-related quality of life and low anterior resection syndrome. DESIGN: Patient demographics were analyzed alongside low anterior resection syndrome and health-related quality-of-life qualitative scores (EORTC-QLQ-C30) obtained through cross-sectional postal questionnaires. SETTING: Patients who underwent anterior resection of the rectum for cancer with defunctioning ileostomy between 2003 and 2016 at 2 high-volume centers in the United Kingdom were identified, excluding those experiencing anastomotic leakage. PATIENTS: Among 478 eligible patients, 311 (65.1%) participated at a mean of 6.5 ± 0.2 years after anterior resection. Demographics and neoadjuvant chemoradiotherapy rates were similar ( p > 0.05) between participants and nonparticipants. RESULTS: The percentage of patients who experienced major low anterior resection syndrome was 53.4% (166/311). Health-related quality-of-life functional domain scores improved in the years after reversal of ileostomy, with significant changes in constipation ( p = 0.01), social function ( p = 0.03), and emotional scores ( p = 0.02), as well as a reduction in the prevalence of major low anterior resection syndrome ( p = 0.003). LIMITATIONS: The main limitation of this study was that the data collected were cross-sectional rather than longitudinal, and that nonresponders may have had worse cancer symptoms. CONCLUSIONS: In this first large-scale study assessing long-term function after anterior resection and reversal of ileostomy, there is a linear improvement in major low anterior resection syndrome beyond 6 years, alongside improvements in key quality-of-life measures. See Video Abstract at http://links.lww.com/DCR/B825 . SEGUIMIENTO A LARGO PLAZO DEL SNDROME DE RESECCIN ANTERIOR BAJA Y LA CALIDAD DE VIDA POR CNCER DE RECTO: ANTECEDENTES:Los tratamientos tanto quirúrgicos como sistémicos continúan evolucionando día a día, así éstos permiten resecciones restaurativas por cáncer de recto distal. Estas operaciones están asociadas con el síndrome de resección anterior baja. Estudios recientes con limitaciones tanto metodológicas como de talla han estudiado la incidencia del síndrome de resección anterior bajo post-quirúrgico. Sin embargo, la evolución a largo plazo del síndrome de resección anterior baja y su acción sobre la calidad de vida relacionadas con la salud siguen sin estar claros.OBJETIVO:Evaluar el impacto de la resección anterior baja y el cierre de la ileostomía en la calidad de vida relacionadas con la salud a largo plazo y el síndrome post-resección anterior.AJUSTE:Se incluyeron todos los pacientes sometidos a una reseccción anterior baja de recto por cáncer asociada a una ileostomía de protección entre 2003 y 2016 en dos centros de gran volumen en el Reino Unido, se excluyeron los pacientes que presentaron fuga anastomótica.DISEÑO:Se revisaron los datos demográficos de todos los pacientes que presentaban el síndrome de resección anterior baja, se revisaron las puntuaciones de la calidad de vida relacionadas con el estado general de salud (EORTC-QLQ-C30) obtenidas a través de cuestionarios transversales enviados por correo.PACIENTES:478 pacientes fueron escogidos, 311 (65,1%) participaron del estudio en una media de 6,5 ± 0,2 años después de la resección anterior. Las tasas demográficas y de radio-quimioterapia neoadyuvante fueron similares (p > 0,05) entre los participantes y los no participantes.RESULTADOS:El porcentaje de pacientes que experimentaron síndrome de resección anterior baja mayor fue del 53,4% (166/311).PRINCIPALES MEDIDAS DE RESULTADO:Las puntuaciones funcionales en la calidad de vida relacionadas con estado general de salud mejoraron en los años posteriores al cierre de la ileostomía de protección, los cambios fueron significativos con relación al estreñimiento (p = 0,01), con relación a la actividad social (p = 0,03) y con las puntuaciones emocionales (p = 0,02), así como con la reducción de la prevalencia del síndrome de resección anterior baja mayor (p = 0,003).LIMITACIONES:La principal limitación del presente estudio mostró que los datos recopilados fueron transversales y no longitudinales, y que los pacientes no respondedores pueden haber tenido peores síntomas relacionados con el cáncer.CONCLUSIONES:Este primer estudio a gran escala, evalúa la función a largo plazo después de la resección anterior baja y el cierre de la ileostomía, demuestra una mejoría lineal en el síndrome de resección anterior baja de grado importante, más allá de los 6 años, asociado con la mejoría en las medidas clave de calidad de vida. Consulte Video Resumen en http://links.lww.com/DCR/B825 . (Traducción-Dr. Xavier Delgadillo ).

Complete mesocolic excision versus conventional surgery for colon cancer: A systematic review and meta-analysis.

AIM: Complete mesocolic excision (CME) lacks consistent data advocating operative superiority compared to conventional surgery for colon cancer. We performed a systematic review and meta-analysis, analysing population characteristics and perioperative, pathological and oncological outcomes. METHODS: D3 extended lymphadenectomy dissection was considered comparable to CME, and D2 and D1 dissection to be comparable to conventional surgery. Outcomes reviewed included lymph node yield, R1 resection, overall complications, overall survival and disease-free survival. RESULTS: In all, 3039 citations were identified; 148 studies underwent full-text reviews and 31 matched inclusion criteria: total cohort 26 640 patients (13 830 CME/D3 vs. 12 810 conventional). Overall 3- and 5-year survival was higher in the CME/D3 group compared with conventional surgery: relative risk (RR) 0.69 (95% CI 0.51-0.93, P = 0.016) and RR 0.78 (95% CI 0.64-0.95, P = 0.011) respectively. Five-year disease-free survival also demonstrated CME/D3 superiority (RR 0.67, 95% CI 0.52-0.86, P < 0.001), with similar findings at 1 and 3 years. There were no statistically significant differences between the CME/D3 and conventional group in overall complications (RR 1.06, 95% CI 0.97-1.14, P = 0.483) or anastomotic leak (RR 1.02, 95% CI 0.81-1.29, P = 0.647). CONCLUSIONS: Meta-analysis suggests CME/D3 may have a better overall and disease-free survival compared to conventional surgery, with no difference in perioperative complications. Quality of evidence regarding survival is low, and randomized control trials are required to strengthen the evidence base.

Risk and consequences of dehydration following colorectal cancer resection with diverting ileostomy. A systematic review and meta-analysis.

AIM: This systematic review aims to assess dehydration prevalence and dehydration-related morbidity from diverting ileostomy compared to resections without ileostomy formation in adults undergoing colorectal resection for cancer. METHOD: MEDLINE, Embase, CENTRAL and ClinicalTrials.gov were searched for studies of any design that reported dehydration, renal function and dehydration-related morbidity in adult colorectal cancer patients with diverting ileostomy (last search 12 August 2020). Bias was assessed using the Cochrane Collaboration's tool for assessing risk of bias in randomized trials and the Risk of Bias in Non-randomized Studies of Interventions tool. RESULTS: Of 1927 screened papers, 22 studies were included (21 cohort studies and one randomized trial) with a total of 19 485 patients (12 209 with ileostomy). The prevalence of dehydration was 9.00% (95% CI 5.31-13.45, P < 0.001). The relative risk of dehydration following diverting ileostomy was 3.37 (95% CI 2.30-4.95, P < 0.001). Three studies assessing long-term trends in renal function demonstrated progressive renal impairment persisting beyond the initial insult. Consequences identified included unplanned readmission, delay or non-commencement of adjuvant chemotherapy, and development of chronic kidney disease. DISCUSSION: Significant dehydration is common following diverting ileostomy; it is linked to acute kidney injury and has a long-term impact on renal function. This study suggests that ileostomy confers significant morbidity particularly related to dehydration and renal impairment.

Method of pedicle division during laparoscopic right hemicolectomy affects lymph node yield and short-term outcomes.

BACKGROUND: Several ways of performing laparoscopic right hemicolectomy (RHC) have evolved. The vascular pedicle can be divided into extracorporeal (RHC-EC) or intracorporeal (RHC-IC). It is not known whether vessel ligation during RHC-EC is as central as during RHC-IC. We compare these approaches in terms of pathological and short-term clinical outcomes. METHODS: Patients undergoing elective laparoscopic RHC in a single centre (July 2013-September 2016) were identified. Data collection included operative details, length of stay, complications, specimen parameters including number and involvement of lymph nodes and recurrence. RESULTS: One hundred and sixty-nine patients were included (94 RHC-IC, 75 RHC-EC). For caecal and ascending colon cancers, mesocolic width was greater after RHC-IC than RHC-EC (7.9 cm versus 6.6 cm, P < 0.05), as was lymph node yield (19.5 versus 17.3, P < 0.05). There was no significant difference in length of colon resected, distal resection margin, number of positive nodes, proportion of node-positive tumours and R1 rate. Operative duration was higher for RHC-IC (163 min versus 91 min, P < 0.001), as was incidence of ileus (35% versus 15%, P < 0.05). Length of stay also tended to be higher (7.4 days versus 6.0 days, P = 0.19). There was no difference in disease recurrence (follow-up 12 months). Body mass index was positively correlated with lymph node yield for RHC-EC, but not for RHC-IC. CONCLUSION: Lymph node yield after laparoscopic RHC is adequate, whether the vascular pedicle is taken intracorporeal or extracorporeal, supporting the use of both approaches. RHC-IC yields more lymph nodes and greater mesocolic width, but involves a longer operation and higher incidence of ileus.

Long-term Quality of Life After Cytoreductive Surgery and Heated Intraperitoneal Chemotherapy for Pseudomyxoma Peritonei: A Prospective Longitudinal Study.

BACKGROUND: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are an established treatment for pseudomyxoma peritonei (PMP), but it is a major surgical procedure and may be associated with long-term morbidity. To date, health-related quality-of-life (HRQL) data among survivors are lacking. METHODS: A two-period qualitative study investigated patients undergoing CRS-HIPEC for PMP at a national peritoneal tumor center between 2003 and 2011. First, the European Organization for Research and Treatment (EORTC)-QLQ C30 HRQL questionnaire was used longitudinally preoperatively and at postoperative months 3, 6, 9, 12, 18, and 24, then yearly thereafter. Second, it was updated in 2016 as a cross-sectional study. Both studies were compared with age- and sex-matched reference populations (one-way t tests). RESULTS: A total of 553 longitudinal HRQL questionnaires were completed for 137 patients, truncated at 60 months. In the 2016 update, 85 responses were received from 103 survivors (mean follow-up period, 8.11 years). Patients' physical, role, and social function scores were impaired until 12 months postoperatively, after which the scores did not differ significantly from those of with reference populations. Similarly, fatigue, appetite loss, insomnia, and financial difficulties worsened significantly compared with reference populations in the first 12-months and then normalized. In contrast, impaired cognitive function (82.3 vs 88.5; P = 0.017), constipation (13.7 vs 7.3; P = 0.032), and diarrheal symptoms (15.1 vs 4.9; P = 0.0006) persisted through both periods. Global health scores did not differ significantly from those of the reference population. CONCLUSIONS: Beyond 12 months postoperatively, CRS-HIPEC for PMP is associated with a good quality of life except for some cognitive functional impairment and bowel disturbances.

PER1 modulates SGLT1 transcription in vitro independent of E-box status.

BACKGROUND AND AIMS: The intestine demonstrates profound circadian rhythmicity in glucose absorption in rodents, mediated entirely by rhythmicity in the transcription, translation, and function of the sodium glucose co-transporter SGLT1 (Slc5a1). Clock genes are rhythmic in the intestine and have been implicated in the regulation of rhythmicity of other intestinal genes; however, their role in the regulation of SGLT1 is unknown. We investigated the effects of one clock gene, PER1, on SGLT1 transcription in vitro. METHODS: Caco-2 cells were stably transfected with knockdown vectors for PER1 and mRNA expression of clock genes and SGLT1 determined using quantitative polymerase chain reaction (qPCR). Chinese hamster ovary (CHO) cells were transiently cotransfected with combinations of the PER1 expression vectors and the wild-type SGLT1-luciferase promoter construct or the promoter with mutated E-box sequences. RESULTS: Knockdown of PER1 increased native SGLT1 expression in Caco-2 enterocytes, while promoter studies confirmed that the inhibitory activity of PER1 on SGLT1 occurs via the proximal 1 kb of the SGLT1 promoter. E-box sites exerted a suppressive effect on the SGLT1 promoter; however, mutation of E-boxes had little effect on the inhibitory activity of PER1 on the SGLT1 promoter suggesting that the actions of PER1 on SGLT1 are independent of E-boxes. CONCLUSIONS: Our findings suggest that PER1 exerts an indirect suppressive effect on SGLT1, possibly acting via other clock-controlled genes binding to non-E-box sites on the SGLT1 promoter. Understanding the regulation of rhythmicity of SGLT1 may lead to new treatments for the modulation of SGLT1 expression in conditions such as malabsorption, diabetes, and obesity.

Upregulation of proapoptotic microRNA mir-125a after massive small bowel resection in rats.

OBJECTIVE: Short bowel syndrome remains a condition of high morbidity and mortality, and current therapeutic options carry significant side effects. To identify new treatments we focused on postresection changes in microRNAs--short noncoding RNAs, which suppress target genes--and suggest a previously undiscovered role for microRNA-125a (mir-125a) in intestinal adaptation. METHODS: Rats underwent either 80% massive small bowel resection or transection and were harvested after 48 hours. Jejunum was harvested for microRNA microarrays, laser capture microdissection, and RNA and protein analysis. Mir-125a was overexpressed in intestinal epithelium-6 (crypt-derived) cells (IEC-6) and effects on proliferation and apoptosis determined using MTS and flow cytometry. Expression of potential targets of mir-125a in rat jejunum and IEC-6 cells was determined using quantitative real-time polymerase chain reaction (RNA) and Western blotting (protein). RESULTS: Resection upregulated mir-125a and mir-214 by 2.4-folds and 3.2-folds, respectively. Highest levels of expression were noted in the crypt fraction. Mir-125a overexpression induced apoptosis and resultant growth arrest in IEC-6 cells. The expression of the prosurvival Bcl-2 family member Mcl-1 was downregulated in both mir-125a-overexpressing IEC-6 cells and in jejunum of resected rats, confirming Mcl-1 as a previously undiscovered target of mir-125a. CONCLUSIONS: Upregulation of mir-125a suppresses the prosurvival protein Mcl1, producing the increase in apoptosis known to accompany the proliferative changes characteristic of intestinal adaptation. Our data highlight a potential role for microRNAs as mediators of the adaptive process and may facilitate the development of new therapeutic options for short bowel syndrome.

Pharmacokinetics and tissue penetration of vancomycin continuous infusion as prophylaxis for vascular surgery.

OBJECTIVES: To determine the tissue penetration of vancomycin into perivascular fat and arterial wall during a continuous infusion of vancomycin, given as prophylaxis for vascular surgery. PATIENTS AND METHODS: Patients undergoing arterial reconstruction requiring antibiotic prophylaxis were included. Patients received a loading infusion of vancomycin the evening prior to surgery followed by a continuous 24 h infusion, calculated according to renal function. Three peri-operative serum samples and intra-operative perivascular fat and arterial wall samples were collected for vancomycin assay. RESULTS: Twenty-eight patients were included. Three serum samples were obtained from all patients, fat samples were available from 27 (96.4%) patients and vessel wall samples were available from 23 (82.1%) patients. Serum vancomycin concentrations were maintained within a relatively narrow range, while fat and arterial wall concentrations were highly variable. CONCLUSIONS: This study has shown that prophylactic administration of vancomycin with a loading infusion followed by a continuous infusion before and during vascular surgery achieves serum and vascular tissue concentrations that are above the MICs for most common organisms implicated in post-operative graft infection. However, penetration into perivascular fat tissues is poor.

MicroRNA mir-16 is anti-proliferative in enterocytes and exhibits diurnal rhythmicity in intestinal crypts.

BACKGROUND AND AIMS: The intestine exhibits profound diurnal rhythms in function and morphology, in part due to changes in enterocyte proliferation. The regulatory mechanisms behind these rhythms remain largely unknown. We hypothesized that microRNAs are involved in mediating these rhythms, and studied the role of microRNAs specifically in modulating intestinal proliferation. METHODS: Diurnal rhythmicity of microRNAs in rat jejunum was analyzed by microarrays and validated by qPCR. Temporal expression of diurnally rhythmic mir-16 was further quantified in intestinal crypts, villi, and smooth muscle using laser capture microdissection and qPCR. Morphological changes in rat jejunum were assessed by histology and proliferation by immunostaining for bromodeoxyuridine. In IEC-6 cells stably overexpressing mir-16, proliferation was assessed by cell counting and MTS assay, cell cycle progression and apoptosis by flow cytometry, and cell cycle gene expression by qPCR and immunoblotting. RESULTS: mir-16 peaked 6 hours after light onset (HALO 6) with diurnal changes restricted to crypts. Crypt depth and villus height peaked at HALO 13-14 in antiphase to mir-16. Overexpression of mir-16 in IEC-6 cells suppressed specific G1/S regulators (cyclins D1-3, cyclin E1 and cyclin-dependent kinase 6) and produced G1 arrest. Protein expression of these genes exhibited diurnal rhythmicity in rat jejunum, peaking between HALO 11 and 17 in antiphase to mir-16. CONCLUSIONS: This is the first report of circadian rhythmicity of specific microRNAs in rat jejunum. Our data provide a link between anti-proliferative mir-16 and the intestinal proliferation rhythm and point to mir-16 as an important regulator of proliferation in jejunal crypts. This function may be essential to match proliferation and absorptive capacity with nutrient availability.

Rapid upregulation of sodium-glucose transporter SGLT1 in response to intestinal sweet taste stimulation.

OBJECTIVE: We set out to examine the short-term regulation of the intestinal sodium/glucose cotransporter SGLT1 by its substrate glucose and sweet taste analogs. SUMMARY BACKGROUND DATA: Intestinal SGLT1 is a putative target for antidiabetic therapy; however, its physiological regulation is incompletely understood, limiting its application as a pharmacological target. While it is clearly regulated by dietary composition over a period of days, its short-term regulation by nutrients is unknown. METHODS: Sprague-Dawley rats were anesthetized, and the duodenum cannulated. D-glucose, D-fructose, saccharin, D-mannitol, and water were infused for 3 hours, before harvest of proximal jejunum for SGLT1 analysis with Western blotting and quantitative polymerase chain reaction. In further experiments, the receptor region was identified by D-glucose infusion of isolated regions. Lastly, the vagus was de-afferented with capsaicin, and 5HT3-receptor activation of vagal afferents inhibited using ondansetron, before repeating experiments using water or D-glucose infusion. RESULTS: Infusion of D-glucose led to 2.9-fold up-regulation in SGLT1 compared with water or iso-osmotic D-mannitol; this effect was replicated by D-fructose or saccharin. This response was strongest following isolated infusions of duodenum and proximal jejunum, with a blunted effect distally; topography matched the expression profile of sweet taste receptor T1R2/T1R3. The reflex was abolished by capsaicin pretreatment, and blunted by ondansetron. CONCLUSIONS: The agonist response implicates the luminal-based sweet-taste receptor T1R2/T1R3, with the reflex apparently involving vagal afferents. The proximal nature of the sensor coincides with the excluded biliopancreatic limb in Roux-en-Y gastric bypass, and this may provide a novel explanation for the antidiabetic effect of this procedure.

Restricted feeding phase shifts clock gene and sodium glucose cotransporter 1 (SGLT1) expression in rats.

The intestine exhibits striking diurnal rhythmicity in glucose uptake, mediated by the sodium glucose cotransporter (SGLT1); however, regulatory pathways for these rhythms remain incompletely characterized. We hypothesized that SGLT1 rhythmicity is linked to the circadian clock. To investigate this, we examined rhythmicity of Sglt1 and individual clock genes in rats that consumed food ad libitum (AL). We further compared phase shifts of Sglt1 and clock genes in a second group of rats following restricted feeding to either the dark (DF) or light (LF) phase. Rats fed during the DF were pair-fed to rats fed during the LF. Jejunal mucosa was harvested across the diurnal period to generate expression profiles of Sglt1 and clock genes Clock, Bmal1 (brain-muscle Arnt-like 1), ReverbA/B, Per(Period) 1/2, and Cry (Cryptochrome) 1/2. All clock genes were rhythmic in AL rats (P < 0.05). Sglt1 also exhibited diurnal rhythmicity, with peak expression preceding nutrient arrival (P < 0.05). Light-restricted feeding shifted the expression rhythms of Sglt1 and most clock genes (Bmal1, ReverbA and B, Per1, Per2, and Cry1) compared with dark-restricted feeding (P < 0.05). The Sglt1 rhythm shifted in parallel with rhythms of Per1 and ReverbB. These effects of restricted feeding highlight luminal nutrients as a key Zeitgeber in the intestine, capable of simultaneously shifting the phases of transporter and clock gene expression, and suggest a role for clock genes in regulating Sglt1 and therefore glucose uptake. Understanding the regulatory cues governing rhythms in intestinal function may allow new therapeutic options for conditions of dysregulated absorption such as diabetes and obesity.

Vancomycin continuous infusion as prophylaxis for vascular surgery.

Prosthetic graft infection is a devastating complication of vascular surgery that occurs in 3%-5% of clean prosthetic procedures. Staphylococci are the most frequently isolated pathogens, and thus surgical prophylaxis regimens often include vancomycin. However, the efficacy of these regimens in ensuring a required concentration of antibiotic is uncertain. This study aimed to determine if a continuous vancomycin infusion regimen administered perioperatively as surgical prophylaxis for vascular procedures maintained an adequate serum concentration. Thirty-four consecutive patients undergoing a vascular procedure requiring a prosthetic graft or patch were given vancomycin prophylaxis. Each patient received a loading dose calculated according to body weight 12 hours before surgery. A 24-hour continuous infusion was then started, based on calculated creatinine clearance. Serum vancomycin concentrations were checked on induction of anesthesia, 2 hours postoperatively, and at the end of the infusion. Perioperative fluid administration and blood loss were recorded. An estimated creatinine clearance was repeated on the second postoperative day. Of the 34 patients recruited, 7 did not have the anticipated procedure and 6 patients had incomplete sample collection. Twenty-one patients with complete sample collection were analyzed. The target concentration (10-25 mg/L) was achieved in 81% of all samples. All patients achieved the target concentration at 1 or more time points. The regimen employed provided appropriate concentrations at the time of intervention. No potentially toxic concentrations or adverse reactions to vancomycin were encountered. Vancomycin given as a continuous infusion delivers adequate serum concentration. Long-term graft infection rates are needed to show a clinical effect.

Circadian variation in intestinal dihydropyrimidine dehydrogenase (DPD) expression: a potential mechanism for benefits of 5FU chrono-chemotherapy.

BACKGROUND: 5-fluorouracil (5FU) is associated with significant GI side-effects. Randomized trials have shown a 50% reduction in severe diarrhea with chrono-chemotherapy versus conventional regimens at similar doses. Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme in 5FU breakdown. We hypothesized that DPD has a circadian expression pattern, accounting for the reduced GI side effects of chrono-modulated 5FU therapy. METHODS: Fifty-one rats were killed at 3-hourly intervals over 24 hours. DPD and thymidylate synthase (TS) mRNA in jejunal and colonic mucosa were measured using qRT-PCR. Cosinor analysis was used for statistical comparison. RESULTS: There was a significant circadian rhythm in the DPD mRNA expression in jejunum (1.7-fold, P < .001) and colon (1.5 fold, P < .01), with a peak expression in early sleep phase, and a trough at mid-wake cycle. TS also followed a circadian rhythm in jejunal mucosa with a peak at early rest phase. CONCLUSION: This rhythm in DPD expression may explain the benefit of chrono-chemotherapy. The peak of DPD expression in sleep phase in rats corresponds to time for lower GI adverse effects in chrono-chemotherapy in human trials. We believe better understanding of this process allows development of novel approaches to optimize the timing of chemotherapy without the administrative challenges of chronotherapy.

Diurnal expression of the rat intestinal sodium-glucose cotransporter 1 (SGLT1) is independent of local luminal factors.

BACKGROUND: The intestinal sodium-glucose cotransporter 1 (SGLT1) is responsible for all secondary active transport of dietary glucose, and it presents a potential therapeutic target for obesity and diabetes. SGLT1 expression varies with a profound diurnal rhythm, matching expression to nutrient intake. The mechanisms entraining this rhythm remain unknown. We investigated the role of local nutrient signals in diurnal SGLT1 entrainment. METHODS: Male Sprague-Dawley rats, which were acclimatized to a 12:12 light:dark cycle, underwent laparotomy with formation of isolated proximal jejunal loops (Thiry-Vella loops). Animals were recovered for 10 days before harvesting at 4 6-h intervals (Zeitgeber times ZT3, ZT9, ZT15, and ZT21, where ZT0 is lights on; n = 6-8). SGLT1 expression was assessed in protein, and mRNA extracts of mucosa were harvested from both isolated loops (LOOP) and remnant jejunum (JEJ). RESULTS: Isolated loops were healthy but atrophic with minimal changes to villus architecture. A normal anticipatory rhythm was observed in Sglt1 transcription in both LOOP and JEJ, with the peak signal at ZT9 (2.7-fold, P < .001). Normal diurnal rhythms were also observed in the protein signal, with peak expression in both LOOP and JEJ at ZT9 to 15 (2.1-fold, P < .05). However, an additional more mobile polypeptide band was also observed in all LOOP samples but not in JEJ samples (61 kDa vs 69 kDa). Enzymatic deglycosylation suggested this to be deglycosylated SGLT1. CONCLUSION: The persistence of SGLT1 rhythmicity in isolated loops indicates that diurnal induction is independent of local luminal nutrient delivery, and it suggests a reliance on systemic entrainment pathways. However, local luminal signals may regulate glycosylation and, therefore, the posttranslational handling of SGLT1.