Modern surgery for Crohn's disease: When to divert, impact of biologics on infectious complications, and surgical techniques to decrease post-operative recurrence of Crohn's disease.

Crohn's disease is a complex condition that confers a significant risk of requiring multiple surgeries. Questions that surgeons must frequently answer include: which patients benefit from diversion? Does monoclonal antibody therapy increase post-operative complications? And, are there surgical techniques that can prevent the recurrence of Crohn's disease? This review examines current data to answer these questions.

Survival outcomes of anal adenocarcinoma versus rectal adenocarcinoma: A retrospective cohort study.

BACKGROUND: Anal adenocarcinoma (AA) is a rare malignancy with decreased survival compared to rectal adenocarcinoma (RA). However, AA continues to be treated with similar algorithms compared to rectal cancer with minimal data regarding the efficacy of these treatment algorithms. METHODS: A retrospective chart review of patients with non-metastatic AA at a single tertiary-care institution from 1995 to 2020. This cohort was matched 2:1 to a group of RA patients for comparison. The primary outcome of interest was overall survival rates. RESULTS: Sixteen patients with stages I-III AA were matched to a cohort of RA. There were no significant differences between the cohorts with regard to patient demographics, comorbidities, disease stage or histologic features. There were also no significant differences in treatment modalities between the two cohorts with a majority undergoing multimodal therapy with chemoradiation and surgery. All patients with AA demonstrated significantly worse survival than all patients with rectal adenocarcinoma (five-year survival 47.7% vs. 82.3%, respectively. p < 0.05). When looking at a sub-group of patients who underwent combination chemoradiation and surgery from each cohort, anal adenocarcinoma continued to exhibit lower overall survival (five-year survival 41.6% and 86.4%, respectively. p < 0.05). In a multi-variable model that adjusted for location, American Joint Committee on Cancer (AJCC) stage and treatment pathway, tumor location in the anal canal was an independent predictor of overall survival (Hazard ratio [HR] 2.7, p < 0.05). CONCLUSION: AA has worse survival as compared to RA despite similar treatment. This study highlights the need to evaluate the current classification and treatment pathways to improve outcomes.

Changing disposition patterns in the era of COVID-19 after colon resections: A National Surgical Quality Improvement Program colectomy study.

BACKGROUND: The COVID-19 pandemic severely impacted post-hospitalization care facilities in the United States and hindered their ability to accept new patients for various reasons. This study aimed to assess the impact of the pandemic on discharge disposition after colon surgery and associated postoperative outcomes. METHODS: A retrospective cohort study was performed using the National Surgical Quality Improvement Participant Use File and targeted colectomy. Patients were divided into the following 2 cohorts: (1) pre-pandemic (2017-2019) and (2) pandemic (2020). The primary outcomes included discharge disposition-post-hospitalization facility versus home. The secondary outcomes were rates of 30-day readmissions and other postoperative outcomes. The multivariable analysis assessed for confounders and effect modification on discharge to home. RESULTS: Discharge to posthospitalization facilities decreased by 30% in 2020 compared to 2017 to 2019 (7% vs 10%, P < .001). This occurred despite an increase in emergency cases (15% vs 13%, P < .001) and open surgical approach (32% vs 31%, P < .001) in 2020. Multivariable analysis revealed that patients in 2020 had 38% lower odds of going to post-hospitalization facilities (odds ratio 0.62, P < .001) after adjusting for surgical indications and underlying comorbidities. This decrease in patients going to a post-hospitalization facility was not associated with an increased length of stay or an increase in 30-day readmissions or postoperative complications. CONCLUSION: During the pandemic, patients undergoing colonic resection were less likely to be discharged to a post-hospitalization facility. This shift was not associated with an increase in 30-day complications. This should prompt further research to assess the reproducibility of these associations, especially in a setting without a global pandemic.

Neoadjuvant chemotherapy does not increase risk for anastomotic leak for simultaneous resection of primary colon cancer with synchronous liver metastasis: A NSQIP-colectomy analysis.

BACKGROUND AND OBJECTIVES: In patients with colon cancer with synchronous liver metastasis, treatment algorithms are complex and often require multidisciplinary evaluation. Neoadjuvant therapy is frequently utilized, but there is an unclear relationship with postoperative outcomes in patients with simultaneous resection. METHODS: This is a retrospective cohort study from the National Surgical Quality Improvement Program and Targeted Colectomy databases. All patients with stage IV colon cancer undergoing simultaneous colectomy with synchronous liver metastasis resection or ablation between 2015 and 2019 were identified and categorized into subgroups based on receipt of neoadjuvant chemotherapy. Multivariable logistic regression was utilized to assess for risk factors of anastomotic leaks and serious postoperative complications. RESULTS: We identified 1006 patients who underwent simultaneous colectomy and liver operations. Of those, 418 (41.6%) received neoadjuvant chemotherapy within 90 days of surgery, while 588 (58.4%) had simultaneous upfront surgery. On multivariable logistic regression, neoadjuvant therapy was not associated with postoperative anastomotic leaks (odds ratio [OR]: 1.30; p = 0.39) or serious complications (OR: 1.04; p = 0.82). CONCLUSION: Neoadjuvant therapy does not increase postoperative complications in simultaneous colon and liver resections. These results may alleviate concerns regarding postoperative morbidity in the decision-making process of administering neoadjuvant therapy.

Characteristics and Outcomes of Right- Versus Left-Sided Early-Onset Colorectal Cancer.

BACKGROUND: Early-onset colorectal cancers are increasing in incidence. Studies reported more left-sided cancers in patients aged <50 years. Some advocate for screening via flexible sigmoidoscopy at age 40 years. OBJECTIVE: The purpose of this study was to investigate characteristics and outcomes in sporadic right- and left-sided early-onset colorectal cancers. DESIGN: This was a retrospective cohort study. SETTINGS: This study was conducted at a single, tertiary care institution. PATIENTS: This study included patients aged <50 years diagnosed with colorectal cancer between 2000 and 2018. MAIN OUTCOME MEASURES: We analyzed patient demographics, tumor characteristics, and survival. RESULTS: A total of 489 patients aged 20 to 49 years were identified from 2000 to 2018. The majority of patients were white (90%) and male (57%). The median age at diagnosis was 44 years, and 75% were diagnosed at age 40-49 years. There was a predominance of left-sided tumors (80%). The majority of patients presented with stage 3 (35%) and stage 4 (35%) disease. Right-sided tumors were more likely to have mucinous (24% vs 7.4%; p < 0.001) and signet-ring cell (4.4% vs 1.7%; p < 0.001) histology. There was no difference in age, sex, race, ethnicity, and stage at presentation. Right-sided tumors were associated with lower 5-year overall survival (44% vs 61%; p < 0.005) with the decrease in survival most prominent in right-sided stage 3 tumors (41% vs 72%; p < 0.0001) and in ages 40 to 49 years (43% vs 61%; p = 0.03). Sex, tumor location, increasing stage, and signet-ring cell histology were independent prognostic factors of overall survival. There was no difference in disease-free survival. LIMITATIONS: This study was a retrospective review at a single institution. CONCLUSIONS: The majority of early-onset colorectal cancers arise from age 40 to 49 years with a left-sided predominance but higher mortality in right-sided tumors. These findings provide further evidence in favor of recommending earlier initial screening colonoscopy for colorectal cancer. See Video Abstract at http://links.lww.com/DCR/B892 . CARACTERSTICAS Y RESULTADOS DEL CNCER COLORRECTAL DE INICIO TEMPRANO DEL LADO DERECHO FRENTE AL IZQUIERDO: ANTECEDENTES:Los cánceres colorrectales de aparición temprana están aumentando en incidencia. Los estudios han informado una preponderancia de cánceres en el lado izquierdo en pacientes <50 años, lo que ha llevado a algunos a abogar por la detección con sigmoidoscopia flexible a los 40 años.OBJETIVO:El propósito de nuestro estudio fue investigar las características del tumor y los resultados de los pacientes en cánceres colorrectales esporádicos del lado derecho e izquierdo de aparición temprana.DISEÑO:Este fue un estudio de cohorte retrospectivo.ENTORNO CLÍNICO:Este estudio se realizó en una única institución de atención terciaria.PACIENTES:Pacientes <50 años diagnosticados de cáncer colorrectal entre 2000 y 2018.RESULTADO PRINCIPAL:Analizamos los datos demográficos de los pacientes, las características del tumor, la supervivencia general y la supervivencia libre de enfermedad.RESULTADOS:Se identificaron un total de 489 pacientes de entre 20 y 49 años entre 2000 y 2018. La mayoría de los pacientes eran blancos (90%) y varones (57%). La mediana de edad en el momento del diagnóstico fue de 44 años y el 75% se diagnosticó entre los 40 y los 49 años. Predominó los tumores del lado izquierdo (80%). La mayoría de los pacientes presentaban enfermedad en estadio 3 (35%) y estadio 4 (35%). Los tumores del lado derecho tenían más probabilidades de tener histología mucinosa (24% frente a 7,4%, p < 0,001) y de células en anillo de sello (4,4% frente a 1,7%, p < 0,001). No hubo diferencia en edad, sexo, raza, etnia, estadio AJCC en la presentación. Los tumores del lado derecho se asociaron con una menor supervivencia general a 5 años (44% frente al 61%, p < 0,005) con la disminución de la supervivencia más prominente en los tumores del lado derecho en estadio 3 (41% frente al 72%, p < 0,0001) y en edades 40-49 (43% vs 61%, p = 0.03). El sexo, la ubicación del tumor, el estadio AJCC en aumento y la histología de las células en anillo de sello fueron factores pronósticos independientes de la supervivencia general. No hubo diferencias significativas en la supervivencia libre de enfermedad.LIMITACIONES:Este estudio fue una revisión retrospectiva en una sola institución.CONCLUSIONES:La mayoría de los cánceres colorrectales de aparición temprana surgen entre los 40 y los 49 años con un predominio en el lado izquierdo pero una mayor mortalidad en los tumores del lado derecho. Estos hallazgos proporcionan evidencia adicional a favor de recomendar una colonoscopia de detección inicial más temprana para el cáncer colorrectal. Consulte Video Resumen en http://links.lww.com/DCR/B892 . (Traducción-Dr. Ingrid Melo ).

Endoscopic management of colovesical and colovaginal fistulas with over-the-scope clips: A single-institution case series.

AIM: Conventional surgical management of colovesical and colovaginal fistulas can be morbid and is contraindicated in many patients. Our aim in this work is to evaluate our experience in the management of colovesical and colovaginal fistulas with endoscopic over-the-scope (OTS) clips. METHOD: A retrospective review of all patients who underwent attempted endoscopic OTS clip management of colovesical and colovaginal fistulas between 2013 and 2020 was performed. Preoperative risk factors, operative details and postoperative outcomes are reported. RESULTS: Ten patients were identified. Fistula types were: colovesical (five), rectovesical (two), colovaginal (two) and rectovaginal (one). The aetiology of the fistula was diverticular disease in seven (70%) cases and surgical complication of pelvic surgery in three (30%). The mean defect age was 157 ± 98 days, the mean defect diameter was 4.5 mm (range 2-10 mm) and the mean fistula length was 15 mm (range 2-25 mm). In nine (90%) cases, fistula identification and cannulation were performed through the nonenteric lumen of the fistula. Initial management with an OTS clip was technically successful in eight (80%) patients. Of the eight patients who underwent OTS clip placement, long-term success (mean follow-up 218 days, range 25-673 days) was achieved after initial intervention in four (50%) patients. One patient underwent serial OTS clip procedures and achieved long-term success after four interventions; three patients have not undergone a repeat procedure after initial failure. CONCLUSION: Endoscopic management of colovesical and colovaginal fistulas with OTS clips offers a promising therapeutic option for patients with contraindications to conventional surgical management. Immediate technical success and long-term success rates are similar to other gastrointestinal tract applications of OTS clips.

Better characterization of operation for ulcerative colitis through the National surgical quality improvement program: A 2-year audit of NSQIP-IBD.

INTRODUCTION: There is little consensus of quality measurements for restorative proctocolectomy with ileal pouch-anal anastomosis(RPC-IPAA) performed for ulcerative colitis(UC). The National Surgical Quality Improvement Program(NSQIP) cannot accurately classify RPC-IPAA staged approaches. We formed an IBD-surgery registry that added IBD-specific variables to NSQIP to study these staged approaches in greater detail. METHODS: We queried our validated database of IBD surgeries across 11 sites in the US from March 2017 to March 2019, containing general NSQIP and IBD-specific perioperative variables. We classified cases into delayed versus immediate pouch construction and looked for independent predictors of pouch delay and postoperative Clavien-Dindo complication severity. RESULTS: 430 patients received index surgery or completed pouches. Among completed pouches, 46(28%) and 118(72%) were immediate and delayed pouches, respectively. Significant predictors for delayed pouch surgery included higher UC surgery volume(p = 0.01) and absence of colonic dysplasia(p = 0.04). Delayed pouch formation did not significantly predict complication severity. CONCLUSIONS: Our data allows improved classification of complex operations. Curating disease-specific variables allows for better analysis of predictors of delayed versus immediate pouch construction and postoperative complication severity. SHORT SUMMARY: We applied our previously validated novel NSIP-IBD database for classifying complex, multi-stage surgical approaches for UC to a degree that was not possible prior to our collaborative effort. From this, we describe predictive factors for delayed pouch formation in UC RPC-IPAA with the largest multicenter effort to date.

Post-Discharge Opioid Prescribing Patterns and Risk Factors in Patients Undergoing Elective Colon and Rectal Surgery Without Complications.

BACKGROUND: Few studies have examined opioid usage in the post-discharge period. The primary aim of this study was to evaluate the need for post-discharge opioids in a unique set of patients: those undergoing colorectal operations and experiencing no surgical complications. The secondary aim was to examine the accuracy of the Opioid Risk Tool (ORT) to predict the need for additional opioid prescriptions. Our hypotheses were that few patients would require post-discharge opioids and that the ORT would predict patients requiring post-discharge opioids. METHODS: All patients undergoing elective colorectal surgery between January 2012 and December 2014 that did not experience NSQIP complications within 30 days or receive an opioid prescription in the 2 weeks prior to operation were reviewed. ORT score was calculated for all patients. Patients requiring post-discharge opioids within 1 year were compared to those not receiving additional opioids after discharge. RESULTS: There were 367 patients that met inclusion criteria and 56 (15%) received post-discharge opioids. Opioid use in the year prior to surgery was the only significant risk factor to receive post-discharge opioids. Opioids were prescribed for three distinct reasons by three groups of prescribers. The ORT did not accurately predict need for post-discharge opioids. CONCLUSIONS: Even among patients without complications, 15% received post-discharge opioid prescriptions. Previous opioid use within the year prior to surgery was a major risk factor for additional prescriptions. The timing and prescriber's specialty are impacted by the indication for post-discharge opioids. The ORT did not predict which patients would receive post-discharge opioids.

Randomized trial of drain antisepsis after mastectomy and immediate prosthetic breast reconstruction.

BACKGROUND: In this 2-site randomized trial, we investigated the effect of antiseptic drain care on bacterial colonization of surgical drains and infection after immediate prosthetic breast reconstruction. METHODS: With IRB approval, we randomized patients undergoing bilateral mastectomy and reconstruction to drain antisepsis (treatment) for one side, with standard drain care (control) for the other. Antisepsis care included both: chlorhexidine disc dressing at drain exit site(s) and irrigation of drain bulbs twice daily with dilute sodium hypochlorite solution. Cultures were obtained from bulb fluid at 1 week and at drain removal, and from the subcutaneous drain tubing at removal. Positive cultures were defined as ≥1+ growth for fluid and >50 CFU for tubing. RESULTS: Cultures of drain bulb fluid at 1 week (the primary endpoint) were positive in 9.9 % of treatment sides (10 of 101) versus 20.8 % (21 of 101) of control sides (p = 0.02). Drain tubing cultures were positive in 0 treated drains versus 6.2 % (6 of 97) of control drains (p = 0.03). Surgical site infection occurred within 30 days in 0 antisepsis sides versus 3.8 % (4 of 104) of control sides (p = 0.13), and within 1 year in three of 104 (2.9 %) of antisepsis sides versus 6 of 104 (5.8 %) of control sides (p = 0.45). Clinical infection occurred within 1 year in 9.7 % (6 of 62) of colonized sides (tubing or fluid) versus 1.5 % (2 of 136) of noncolonized sides (p = 0.03). CONCLUSIONS: Simple and inexpensive local antiseptic interventions with a chlorhexidine disc and hypochlorite solution reduce bacterial colonization of drains, and reduced drain colonization was associated with fewer infections.

Randomized controlled trial to reduce bacterial colonization of surgical drains after breast and axillary operations.

OBJECTIVE: To determine whether bacterial colonization of drains can be reduced by local antiseptic interventions. BACKGROUND: Drains are a potential source of bacterial entry into surgical wounds and may contribute to surgical site infection after breast surgery. METHODS: After institutional review board approval, patients undergoing total mastectomy and/or axillary lymph node dissection were randomized to standard drain care (control) or drain antisepsis (treated). Standard drain care comprised twice daily cleansing with alcohol swabs. Antisepsis drain care included (1) a chlorhexidine disc at the drain exit site and (2) irrigation of the drain bulb twice daily with dilute sodium hypochlorite (Dakin's) solution. Culture results of drain fluid and tubing were compared between control and antisepsis groups. RESULTS: Overall, 100 patients with 125 drains completed the study with 48 patients (58 drains) in the control group and 52 patients (67 drains) in the antisepsis group. Cultures of drain bulb fluid at 1 week were positive (1+ or greater growth) in 66% (38/58) of control drains compared with 21% (14/67) of antisepsis drains (P = 0.0001). Drain tubing cultures demonstrated more than 50 colony-forming units in 19% (8/43) of control drains versus 0% (0/53) of treated drains (P = 0.004). Surgical site infection was diagnosed in 6 patients (6%)--5 patients in the control group and 1 patient in the antisepsis group (P = 0.06). CONCLUSIONS: Simple and inexpensive local antiseptic interventions with a chlorhexidine disc and hypochlorite solution reduce bacterial colonization of drains. Based on these data, further study of drain antisepsis and its potential impact on surgical site infection rate is warranted (ClinicalTrials.gov Identifier: NCT01286168).

National practice patterns in preoperative and postoperative antibiotic prophylaxis in breast procedures requiring drains: survey of the American Society of Breast Surgeons.

BACKGROUND: To assess national practice patterns regarding use of perioperative antibiotics by surgeons performing breast operations requiring drainage tubes. METHODS: The members of the American Society of Breast Surgeons (ASBrS) were surveyed regarding use of perioperative antibiotics for breast operations requiring drains, with or without immediate tissue expander or implant reconstruction. RESULTS: Of 2,857 ASBrS members contacted, 917 (32 %) responded; all self-identified as surgeons. Of 905 evaluable respondents, most described themselves as general surgeons (46 %) or breast surgeons (46 %). For cases in which drains are anticipated, most respondents (86 %) reported routine use of preoperative prophylactic antibiotics, with 99 % selecting cephalosporins. Use of antibiotic >24 h postoperatively varied by whether or not reconstruction was performed. In nonreconstruction cases, the majority (76 %) reported "never/almost never" prescribing antibiotics beyond the 24-h postoperative period, but 16 % reported "always/almost always." In reconstruction cases, the majority (58 %) reported routine antibiotic use beyond 24 h, and the primary driver of the decision to use antibiotics was reported to be the plastic surgeon (83 %). Among those reporting use at >24 h, the duration recommended for nonreconstruction cases was "up to 1 week" in 38 % and "until drains removed" in 39 %; this was similar for reconstruction cases. CONCLUSIONS: Cephalosporins are utilized uniformly as preoperative antibiotic prophylaxis in breast operations requiring drains. However, use of postoperative antibiotic prophylaxis is strongly dependent on the presence of immediate breast reconstruction. Consensus is lacking on the role of postoperative antibiotic prophylaxis in breast operations utilizing drains.

Lessons learned from an unusual case of inflammatory breast cancer.

Inflammatory breast cancer (IBC) is a rare breast malignancy that is associated with poor long-term outcomes despite aggressive surgical and chemotherapeutic interventions. We recently treated a 56-year-old woman with right-sided IBC and biopsy-proven cutaneous metastases to her back and left breast. She underwent chemotherapy, bilateral modified radical mastectomy, and radiation therapy. One year after diagnosis, she is currently disease-free based on positron-emission tomography (PET) imaging and repeat skin biopsies. To provide insight into the management of IBC, we present this interesting case with a reflection on important lessons to be learned.

Mechanisms of glucose uptake in intestinal cell lines: role of GLUT2.

BACKGROUND: GLUT2 is translocated to the apical membrane of enterocytes exposed to glucose concentrations >∼50 mM. Mechanisms of GLUT2-mediated glucose uptake in cell culture models of enterocytes have not been studied. AIM: To explore mechanism(s) of glucose uptake in 3 enterocyte-like cell lines. METHODS: Glucose uptake was measured in Caco-2, RIE-1, and IEC-6 cell lines using varying concentrations of glucose (0.5-50 mM). Effects of phlorizin (SGLT1 inhibitor), phloretin (GLUT2 inhibitor), nocodazole and cytochalasin B (disrupters of cytoskeleton), calphostin C and chelerythrine (PKC inhibitors), and phorbol 12-myristate 13-acetate (PKC activator) were evaluated. RESULTS: Phlorizin inhibited glucose uptake in all 3 cell lines. Phloretin inhibited glucose uptake in Caco-2 and RIE-1 cells. Starving cells decreased glucose uptake in Caco-2 and RIE-1 cells. Glucose uptake was saturated at >10 mM glucose in all 3 cell lines when exposed briefly (<1 min) to glucose. After exposure for >5 min in Caco-2 and RIE-1 cells, glucose uptake did not saturate and K(m) and V(max) increased. This increase in glucose uptake was inhibited by phloretin, nocodazole, cytochalasin B, calphostin C, and chelerythrine. PMA enhanced glucose uptake by 20%. Inhibitors and PMA had little or no effect in the IEC-6 cells. CONCLUSION: Constitutive expression of GLUT2 in the apical membrane along with additional translocation of cytoplasmic GLUT2 to the apical membrane via an intact cytoskeleton and activated PKC appears responsible for enhanced carrier-mediated glucose uptake at greater glucose concentrations (>20 mM) in Caco-2 and RIE-1 cells. IEC-6 cells do not appear to express functional GLUT2.

Acute enterocyte adaptation to luminal glucose: a posttranslational mechanism for rapid apical recruitment of the transporter GLUT2.

BACKGROUND: Glucose absorption postprandially increases markedly to levels far greater than possible by the classic glucose transporter sodium-glucose cotransporter 1 (SGLT1). HYPOTHESIS: Luminal concentrations of glucose >50 mM lead to rapid, phenotypic, non-genomic adaptations by the enterocyte to recruit another transporter, glucose transporter 2 (GLUT2), to the apical membrane to increase glucose absorption. METHODS: Isolated segments of jejunum were perfused in vivo with glucose-containing solutions in anesthetized rats. Carrier-mediated glucose uptake was measured in 10 and 100 mM glucose solutions (n = 6 rats each) with and without selective inhibitors of SGLT1 and GLUT2. RESULTS: The mean rate of carrier-mediated glucose uptake increased in rats perfused with 100 mM versus 10 mM glucose to 13.9 ± 2.9 µmol from 2.1 ± 0.1 µmol, respectively (p < 0.0001). Using selective inhibitors, the relative contribution of GLUT2 to glucose absorption was 56% in the 100 mM concentration of glucose compared to the 10 mM concentration (27%; p < 0.01). Passive absorption accounted for 6% of total glucose absorption at 100 mM glucose. CONCLUSION: A small amount of GLUT2 is active at the lesser luminal concentrations of glucose, but when exposed to concentrations of 100 mM, the enterocyte presumably changes its phenotype by recruiting GLUT2 apically to markedly augment glucose absorption.

Differentiating passive from transporter-mediated uptake by PepT1: a comparison and evaluation of four methods.

BACKGROUND: To quantify transmembrane transport of dipeptides by PepT1, passive uptake (non-PepT1 mediated) must be subtracted from total (measured) uptake. Three methods have been described to estimate passive uptake: perform experiments at cold temperatures, inhibit target dipeptide uptake with a greater concentration of a second dipeptide, or use modified Michaelis-Menten kinetics. We hypothesized that performing uptake experiments at pH 8.0 would estimate passive uptake accurately, because PepT1 requires a proton gradient. Our aim was to determine the most accurate method to estimate passive uptake. METHODS: Caco-2 cells were incubated with various concentrations of glycyl-sarcosine (gly-sar) at pH 6.0 and at 37°C to measure total uptake. Passive uptake was estimated: (1) by incubating Caco-2 cells with varying concentrations of gly-sar at 4°C, (2) in the presence of 50 mM glycyl-leucine, (3) in solution at pH 8.0, or (4) using modified Michaelis-Menten kinetics. PepT1-mediated uptake was calculated by subtracting passive uptake from total uptake. K(m), V(max), and % gly-sar transported by PepT1 were calculated and compared. RESULTS: K(m), V(max), and % gly-sar transported by PepT1 varied from 0.7 to 2.4 mM, 8.4 to 21.0 nmol/mg protein/10 min, and 69% to 87%, respectively. Uptakes calculated with cold, 50 mM gly-leu and using modified Michaelis-Menten kinetics were similar but differed significantly from uptake at pH 8.0 (P < 0.001). CONCLUSIONS: Estimating passive uptake at pH 8.0 does not appear to be accurate. Measuring uptake at cold temperatures or in the presence of a greater concentration of a second dipeptide, and confirming results with modified Michaelis-Menten kinetics is recommended.

Absence of evidence of translocation of GLUT2 to the apical membrane of enterocytes in everted intestinal sleeves.

INTRODUCTION: Traditional models of intestinal glucose absorption confine GLUT2 to the basolateral membrane. Evidence suggests that GLUT2 is translocated to the apical membrane when the enterocyte is exposed to high luminal glucose concentrations. HYPOTHESIS: GLUT2 translocates to the apical membrane by a PKC signaling mechanism dependent on activity of SGLT1 and the cellular cytostructure. METHODS: Transporter-mediated glucose uptake was studied in rat jejunum using everted sleeves under seven conditions: Control, SGLT1 inhibition (phlorizin), GLUT2 inhibition (phloretin), both SGLT1 and GLUT2 inhibition, PKC inhibition (calphostin C or chelerythrine), and disruption of cellular cytostructure (nocodazole). Each condition was tested in iso-osmotic solutions of 1, 20, or 50 mM glucose for 1 or 5 min incubations (n = 6 rats each). RESULTS: Control rats exhibited a saturable pattern of uptake at both durations of incubation. Phlorizin (P ≤ 0.006 each) inhibited markedly and phloretin (P ≤ 0.01 each) inhibited partially glucose uptake in all concentrations and time. Phloretin and phlorizin together completely inhibited uptake (P = 0.004 each). Calphostin C, chelerythrine, and nocodazole had little effect on glucose uptake at either 1 or 5 min. Inhibition of SGLT1 led to near complete cessation of transporter-mediated glucose uptake, while GLUT2 inhibition led to partial inhibition, suggesting some constitutive expression of GLUT2 in the apical membrane. Disruption of PKC signaling or cytoskeletal integrity partially inhibited transporter-mediated glucose uptake only in 1 mM glucose, suggesting a non-specific effect. CONCLUSIONS: Under these conditions, it does not appear that GLUT2 is translocated to the apical membrane on the cellular cytostructure in response to PKC signaling.