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1.
Lactose digestion in humans: intestinal lactase appears to be constitutive whereas the colonic microbiome is adaptable.
Forsgård, RA
The American journal of clinical nutrition. 2019;(2):273-279
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Abstract
Globally, ∼70% of adults are deficient in intestinal lactase, the enzyme required for the digestion of lactose. In these individuals, the consumption of lactose-containing milk and dairy products can lead to the development of various gastrointestinal (GI) symptoms. The primary solution to lactose intolerance is withdrawing lactose from the diet either by eliminating dairy products altogether or substituting lactose-free alternatives. However, studies have shown that certain individuals erroneously attribute their GI symptoms to lactose and thus prefer to consume lactose-free products. This has raised the question whether consuming lactose-free products reduces an individual's ability to absorb dietary lactose and if lactose-absorbers should thus avoid these products. This review summarizes the current knowledge regarding the acclimatization of lactose processing in humans. Human studies that have attempted to induce intestinal lactase expression with different lactose feeding protocols have consistently shown lack of enzyme induction. Similarly, withdrawing lactose from the diet does not reduce intestinal lactase expression. Evidence from cross-sectional studies shows that milk or dairy consumption is a poor indicator of lactase status, corroborating the results of intervention studies. However, in lactase-deficient individuals, lactose feeding supports the growth of lactose-digesting bacteria in the colon, which enhances colonic lactose processing and possibly results in the reduction of intolerance symptoms. This process is referred to as colonic adaptation. In conclusion, endogenous lactase expression does not depend on the presence of dietary lactose, but in susceptible individuals, dietary lactose might improve intolerance symptoms via colonic adaptation. For these individuals, lactose withdrawal results in the loss of colonic adaptation, which might lower the threshold for intolerance symptoms if lactose is reintroduced into the diet.
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Goal-directed fluid therapy versus conventional fluid therapy in colorectal surgery: A meta analysis of randomized controlled trials.
Xu, C, Peng, J, Liu, S, Huang, Y, Guo, X, Xiao, H, Qi, D
International journal of surgery (London, England). 2018;:264-273
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Abstract
OBJECTIVES This meta-analysis was conducted to compare the effects of goal-directed fluid therapy (GDFT) versus conventional fluid therapy (CFT) in colorectal surgery on patients' postoperative outcome and to detect whether the results differ between studies with the Enhanced Recovery After Surgery (ERAS) protocol and those without, between studies using different devices for GDFT, or between different surgical approaches (laparoscopy or laparotomy). METHODS The Cochrane Library, PubMed, Embase, Wanfang Data and ClinicalTrials.com were searched for studies from January,1990 to February, 2018. Randomized controlled trials (RCTs) comparing both two abovementioned fluid therapy protocols in colorectal surgery were included. The primary outcome was 30-day mortality after surgery. Secondary outcomes were length of hospital stay (LOS), complication rate, ICU admission and gastrointestinal indicators. RESULTS Eleven studies were included, including a total of 1281 patients: the GDFT group included 624 patients and the control group included 657 patients. No significant differences were found between groups in 30-day mortality (relative risk, RR 0.86,0.28 to 2.63, P = 0.79), LOS (weighted mean difference, WMD 0.22,-0.1 to 0.55, P = 0.18), and ICU admission (RR 0.42, 0.17 to 1.04, P = 0.06). However, the GDFT group had a lower complication rate (RR 0.84,0.71 to 0.99, P = 0.04). In subgroup analyses, time to first flatus and time to tolerate an oral diet were shorter in GDFT group than the control group in studies who did not use the ERAS protocol. No publication bias was identified according to Begg's test. CONCLUSION Compared with conventional fluid therapy, GDFT may not improve patients' postoperative outcome in colorectal surgery. However, the improvement of gastrointestinal function associated with GDFT over conventional fluid therapy was significant in the surgeries that did not use the ERAS protocol.
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Effect of gum chewing on ameliorating ileus following colorectal surgery: A meta-analysis of 18 randomized controlled trials.
Liu, Q, Jiang, H, Xu, D, Jin, J
International journal of surgery (London, England). 2017;:107-115
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BACKGROUND AND OBJECTIVE Chewing gum, as an alternative to sham feeding, had been shown to hasten the recovery of gut function following abdominal surgery. However, conclusions remained contradictory. We sought to conduct an updated meta-analysis to evaluate the efficacy of gum chewing in alleviating ileus following colorectal surgery. METHODS We searched PubMed, EMBASE, and Cochrane Library Databases through February 2017 to identify randomized controlled trials (RCTs) evaluating the efficacy of the additional use of chewing gum following colorectal surgery. After screening for inclusion, data extraction, and quality assessment, meta-analysis was conducted by the Review Manager 5.3 software. The outcomes of interest were the time to first flatus, time to first bowel movement, length of hospital stay, and some clinically relevant parameters. We also performed subgroup analyses according to the type of surgical approaches or on trials that adopted enhanced recovery after surgery (ERAS) protocol or sugared gum. RESULTS A total of 18 RCTs, involving 1736 patients, were included. Compared with standardized postoperative care, Chewing gum resulted in a shorter passage to first flatus [WMD = -8.81, 95%CI: (-13.45, -4.17), P = 0.0002], earlier recovery of bowel movement [WMD = -16.43, 95%CI: (-22.68, -10.19), P < 0.00001], and a reduction in length of hospital stay [WMD = -0.89, 95%CI: (-1.72, -0.07), P = 0.03]. Chewing gum was also associated with a lower risk of postoperative ileus [OR = 0.41, 95%CI: (0.23, 0.73), P = 0.003]. No evidence of significant advantages in overall postoperative complication, nausea, vomiting, bloating, readmission and reoperation towards the addition of chewing gum was observed. Subgroup analyses all favored gum chewing. However, the findings are hampered by the significant heterogeneity between trials. CONCLUSIONS Based on current evidence, chewing gum offers an inexpensive, well-tolerated, safe and effective method to ameliorate ileus following colorectal surgery. However, tightly controlled, randomized and considerably larger multicenter trials are warranted to further validate our findings.
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Short-Chain Fatty Acid Transporters: Role in Colonic Homeostasis.
Sivaprakasam, S, Bhutia, YD, Yang, S, Ganapathy, V
Comprehensive Physiology. 2017;(1):299-314
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Abstract
Short-chain fatty acids (SCFA; acetate, propionate, and butyrate) are generated in colon by bacterial fermentation of dietary fiber. Though diffusion in protonated form is a significant route, carrier-mediated mechanisms constitute the major route for the entry of SCFA in their anionic form into colonic epithelium. Several transport systems operate in cellular uptake of SCFA. MCT1 (SLC16A1) and MCT4 (SLC16A3) are H+-coupled and mediate electroneutral transport of SCFA (H+: SCFA stoichiometry; 1:1). MCT1 is expressed both in the apical membrane and basolateral membrane of colonic epithelium whereas MCT4 specifically in the basolateral membrane. SMCT1 (SLC5A8) and SMCT2 (SLC5A12) are Na+-coupled; SMCT1-mediated transport is electrogenic (Na+: SCFA stoichiometry; 2:1) whereas SMCT2-mediated transport is electroneutral (Na+: SCFA stoichiometry; 1:1). SMCT1 and SMCT2 are expressed exclusively in the apical membrane. An anion-exchange mechanism also operates in the apical membrane in which SCFA entry in anionic form is coupled to bicarbonate efflux; the molecular identity of this exchanger however remains unknown. All these transporters are subject to regulation, notably by their substrates themselves; this process involves cell-surface receptors with SCFA as signaling molecules. There are significant alterations in the expression of these transporters in ulcerative colitis and colon cancer. The tumor-associated changes occur via transcriptional regulation by p53 and HIF1α and by promoter methylation. As SCFA are obligatory for optimal colonic health, the transporters responsible for the entry and transcellular transfer of these bacterial products in colonic epithelium are critical determinants of colonic function under physiological conditions and in disease states. © 2018 American Physiological Society. Compr Physiol 8:299-314, 2018.
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Review article: insights into colonic protein fermentation, its modulation and potential health implications.
Yao, CK, Muir, JG, Gibson, PR
Alimentary pharmacology & therapeutics. 2016;(2):181-96
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BACKGROUND Beneficial effects of carbohydrate fermentation on gastrointestinal health are well established. Conversely, protein fermentation generates harmful metabolites but their relevance to gastrointestinal health is poorly understood. AIM: To review the effects of increased protein fermentation on biomarkers of colonic health, factors influencing fermentative activity and potential for dietary modulation to minimise detrimental effects. METHODS A literature search was performed in PubMed, Medline, EMBASE and Google scholar for clinical and pre-clinical studies using search terms - 'dietary protein', 'fermentation', 'putrefaction', 'phenols', 'sulphide', 'branched-chain fatty acid', 'carbohydrate fermentation', 'gastrointestinal'. RESULTS High protein, reduced carbohydrate diets alter the colonic microbiome, favouring a potentially pathogenic and pro-inflammatory microbiota profile, decreased short-chain fatty acid production and increased ammonia, phenols and hydrogen sulphide concentrations. These metabolites largely compromise the colonic epithelium structure, causing mucosal inflammation but may also directly modulate the enteric nervous system and intestinal motility. Increased protein fermentation as a result of a high-protein intake can be attenuated by addition of oligosaccharides, resistant starch and nonstarch polysaccharides and a reduction in total protein or specifically, aromatic and sulphur-containing amino acids. These factors may have clinical importance as novel therapeutic approaches to problems, in which protein fermentation may be implicated, such as malodorous flatus, irritable bowel syndrome, ulcerative colitis and prevention of colorectal cancer. CONCLUSIONS The direct clinical relevance of excessive protein fermentation in the pathogenesis of irritable bowel syndrome, malodorous flatus and ulcerative colitis are underexplored. Manipulating dietary carbohydrate and protein intake have potential therapeutic applications in such settings and warrant further clinical studies.
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Achieving the best bowel preparation for colonoscopy.
Parra-Blanco, A, Ruiz, A, Alvarez-Lobos, M, Amorós, A, Gana, JC, Ibáñez, P, Ono, A, Fujii, T
World journal of gastroenterology. 2014;(47):17709-26
Abstract
Bowel preparation is a core issue in colonoscopy, as it is closely related to the quality of the procedure. Patients often find that bowel preparation is the most unpleasant part of the examination. It is widely accepted that the quality of cleansing must be excellent to facilitate detecting neoplastic lesions. In spite of its importance and potential implications, until recently, bowel preparation has not been the subject of much study. The most commonly used agents are high-volume polyethylene glycol (PEG) electrolyte solution and sodium phosphate. There has been some confusion, even in published meta-analyses, regarding which of the two agents provides better cleansing. It is clear now that both PEG and sodium phosphate are effective when administered with proper timing. Consequently, the timing of administration is recognized as one of the central factors to the quality of cleansing. The bowel preparation agent should be administered, at least in part, a few hours in advance of the colonoscopy. Several low volume agents are available, and either new or modified schedules with PEG that usually improve tolerance. Certain adjuvants can also be used to reduce the volume of PEG, or to improve the efficacy of other agents. Other factors apart from the choice of agent can improve the quality of bowel cleansing. For instance, the effect of diet before colonoscopy has not been completely clarified, but an exclusively liquid diet is probably not required, and a low-fiber diet may be preferable because it improves patient satisfaction and the quality of the procedure. Some patients, such as diabetics and persons with heart or kidney disease, require modified procedures and certain precautions. Bowel preparation for pediatric patients is also reviewed here. In such cases, PEG remains the most commonly used agent. As detecting neoplasia is not the main objective with these patients, less intensive preparation may suffice. Special considerations must be made for patients with inflammatory bowel disease, including safety and diagnostic issues, so that the most adequate agent is chosen. Identifying neoplasia is one of the main objectives of colonoscopy with these patients, and the target lesions are often almost invisible with white light endoscopy. Therefore excellent quality preparation is required to find these lesions and to apply advanced methods such as chromoendoscopy. Bowel preparation for patients with lower gastrointestinal bleeding represents a challenge, and the strategies available are also reviewed here.
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Colonic manifestations of PTEN hamartoma tumor syndrome: case series and systematic review.
Stanich, PP, Pilarski, R, Rock, J, Frankel, WL, El-Dika, S, Meyer, MM
World journal of gastroenterology. 2014;(7):1833-8
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AIM: To investigate our clinical experience with the colonic manifestations of phosphatase and tensin homolog on chromosome ten (PTEN) hamartoma tumor syndrome (PHTS) and to perform a systematic literature review regarding the same. METHODS This study was approved by the appropriate institutional review board prior to initiation. A clinical genetics database was searched for patients with PHTS or a component syndrome that received gastrointestinal endoscopy or pathology interpretation at our center. These patient's records were retrospectively reviewed for clinical characteristics (including family history and genetic testing), endoscopy results and pathology findings. We also performed a systematic review of the literature for case series of PHTS or component syndromes that reported gastrointestinal manifestations and investigations published after consensus diagnostic criteria were established in 1996. These results were compiled and reported. RESULTS Eight patients from our institution met initial inclusion criteria. Of these, 5 patients underwent 4.2 colonoscopies at mean age 45.8 ± 10.8 years. All were found to have colon polyps during their clinical course and polyp histology included adenoma, hyperplastic, ganglioneuroma and juvenile. No malignant lesions were identified. Two had multiple histologic types. One patient underwent colectomy due to innumerable polyps and concern for future malignant potential. Systematic literature review of PHTS patients undergoing endoscopy revealed 107 patients receiving colonoscopy at mean age 37.4 years. Colon polyps were noted in 92.5% and multiple colon polyp histologies were reported in 53.6%. Common polyp histologies included hyperplastic (43.6%), adenoma (40.4%), hamartoma (38.3%), ganglioneuroma (33%) and inflammatory (24.5%) polyps. Twelve (11.2%) patients had colorectal cancer at mean age 46.7 years (range 35-62). Clinical outcomes secondary to colon polyposis and malignancy were not commonly reported. CONCLUSION PHTS has a high prevalence of colon polyposis with multiple histologic types. It should be considered a mixed polyposis syndrome. Systematic review found an increased prevalence of colorectal cancer and we recommend initiating colonoscopy for colorectal cancer surveillance at age 35 years.
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Some are more equal than others: the role of "keystone" species in the degradation of recalcitrant substrates.
Ze, X, Le Mougen, F, Duncan, SH, Louis, P, Flint, HJ
Gut microbes. 2013;(3):236-40
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The microbial communities found in the mammalian large intestine and rumen efficiently degrade many recalcitrant substrates that are resistant to the host's digestive enzymes. These communities are known from molecular profiling to be highly diverse at the species and strain level, but it may be that only certain specialized organisms ("keystone species") have the ability to initiate degradation of such substrates, thus releasing energy on which the rest of the community depends. We have recently reported that Ruminococcus bromii has a superior ability to degrade certain forms of particulate resistant starch (RS) when compared with other highly abundant species of amylolytic bacteria found in the human colon and have presented evidence that this bacterium provides an example of a keystone species within the microbial community with respect to RS fermentation. The concept of keystone species can be equally relevant to other activities, e.g., those involved in stabilizing the community.
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Colonic necrosis in a young patient receiving oral kayexalate in sorbitol: case report and literature review.
Chou, YH, Wang, HY, Hsieh, MS
The Kaohsiung journal of medical sciences. 2011;(4):155-8
Abstract
Kayexalate (sodium polystyrene sulfonate) is a cation-exchange resin used to treat patients with hyperkalemia. Concomitant administration of kayexalate and sorbitol may induce gastrointestinal injury, which is potentially lethal. However, this well-documented complication is often underrecognized both clinically and pathologically. We propose a typical case along with colonoscopic photos and microscopic pictures. Additionally, we also present a review of the literature on this rare drug-induced side effect.
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Confocal laser endomicroscopy of the colon.
Gheonea, DI, Saftoiu, A, Ciurea, T, Popescu, C, Georgescu, CV, Malos, A
Journal of gastrointestinal and liver diseases : JGLD. 2010;(2):207-11
Abstract
Confocal laser endomicroscopy (CLE) has been recently proposed as a new technique that allows in vivo histologic assessment of mucosa during endoscopy. The most commonly used contrast agents are acriflavine hydrochloride and fluorescein sodium. For colon pathology assessment, the administration of fluorescein intravenously produces a strong staining of both surface epithelium and deeper layers of lamina propria. Confocal laser endomicroscopy is a feasible method to diagnose colon cancer in vivo. Furthermore, confirmation of neoplastic changes using CLE during colonoscopy may lead to major improvements in the clinical management of the patients with inflammatory bowel disease. Biopsies can be limited to targeted sampling of relevant lesions. Confocal laser endomicroscopy will certainly play an important diagnostic role during gastrointestinal endoscopy in the future, enabling the elimination of the diagnostic delay associated with conventional biopsy preparation and processing.