Improvement of colonic healing by preoperative rectal irrigation with short-chain fatty acids in rats given radiotherapy

Enhancing intestinal anastomotic healing using butyrate: Systematic review and meta-analysis of experimental animal studies

BACKGROUND

Despite advancements in surgical technique and perioperative care, intestinal anastomoses still have a 10-15 per cent risk of leakage, which results in considerable morbidity and/or mortality. Recent animal studies have suggested that administration of butyrate to the anastomotic site results in enhanced anastomotic strength, which may prevent leakage. This systematic review and meta-analysis summarises current evidence concerning the effect of butyrate administration on anastomotic healing and will form a scientific basis for the development of new research into this subject.

METHODS

Animal studies on the effect of butyrate-based interventions in models of intestinal anastomotic healing were systematically retrieved from online databases. Bibliographical data, study characteristics and outcome data were extracted, and internal validity of the studies was assessed. Outcomes studied through meta-analysis concerned: anastomotic strength, anastomotic leakage, collagen metabolism and general histologic parameters of wound healing.

RESULTS

A comprehensive search and selection identified 19 relevant studies containing 41 individual comparisons. Design and conduct of most experiments were poorly reported resulting in an unclear risk of bias. Meta-analyses showed that butyrate administration significantly increases anastomotic strength (SMD 1.24, 0.88 to 1.61), collagen synthesis (SMD 1.44, 0.72 to 2.15) and collagen maturation, making anastomoses less prone to leakage in the early postoperative period (OR 0.37, 0.15 to 0.93).

CONCLUSION

This systematic review and meta-analysis shows that there is potential ground to investigate the use of butyrate in clinical trials to prevent anastomotic leakage in intestinal surgery. However, more research is necessary to define the best application form, dosage and administration route.

Gut homeostasis, injury, and healing: New therapeutic targets

The integrity of the gastrointestinal mucosa plays a crucial role in gut homeostasis, which depends upon the balance between mucosal injury by destructive factors and healing via protective factors. The persistence of noxious agents such as acid, pepsin, nonsteroidal anti-inflammatory drugs, or Helicobacter pylori breaks down the mucosal barrier and injury occurs. Depending upon the size and site of the wound, it is healed by complex and overlapping processes involving membrane resealing, cell spreading, purse-string contraction, restitution, differentiation, angiogenesis, and vasculogenesis, each modulated by extracellular regulators. Unfortunately, the gut does not always heal, leading to such pathology as peptic ulcers or inflammatory bowel disease. Currently available therapeutics such as proton pump inhibitors, histamine-2 receptor antagonists, sucralfate, 5-aminosalicylate, antibiotics, corticosteroids, and immunosuppressants all attempt to minimize or reduce injury to the gastrointestinal tract. More recent studies have focused on improving mucosal defense or directly promoting mucosal repair. Many investigations have sought to enhance mucosal defense by stimulating mucus secretion, mucosal blood flow, or tight junction function. Conversely, new attempts to directly promote mucosal repair target proteins that modulate cytoskeleton dynamics such as tubulin, talin, Ehm², filamin-a, gelsolin, and flightless I or that proteins regulate focal adhesions dynamics such as focal adhesion kinase. This article summarizes the pathobiology of gastrointestinal mucosal healing and reviews potential new therapeutic targets.

Review: Effect of Gut Microbiota and Its Metabolite SCFAs on Radiation-Induced Intestinal Injury

Gut microbiota is regarded as the second human genome and forgotten organ, which is symbiotic with the human host and cannot live and exist alone. The gut microbiota performs multiple physiological functions and plays a pivotal role in host health and intestinal homeostasis. However, the gut microbiota can always be affected by various factors and among them, it is radiotherapy that results in gut microbiota ¹²dysbiosis and it is often embodied in a decrease in the abundance and diversity of gut microbiota, an increase in harmful bacteria and a decrease in beneficial bacteria, thereby affecting many disease states, especially intestine diseases. Furthermore, gut microbiota can produce a variety of metabolites, among which short-chain fatty acids (SCFAs) are one of the most abundant and important metabolites. More importantly, SCFAs can be identified as second messengers to promote signal transduction and affect the occurrence and development of diseases. Radiotherapy can lead to the alterations of SCFAs-producing bacteria and cause changes in SCFAs, which is associated with a variety of diseases such as radiation-induced intestinal injury. However, the specific mechanism of its occurrence is not yet clear. Therefore, this review intends to emphasize the alterations of gut microbiota after radiotherapy and highlight the alterations of SCFAs-producing bacteria and SCFAs to explore the mechanisms of radiation-induced intestinal injury from the perspective of gut microbiota and its metabolite SCFAs.

Role of short-chain fatty acids in colonic inflammation, carcinogenesis, and mucosal protection and healing

Short-chain fatty acids (SCFAs), mainly acetate, propionate, and butyrate, produced by microbial fermentation of undigested food substances are believed to play a beneficial role in human gut health. Short-chain fatty acids influence colonic health through various mechanisms. In vitro and ex vivo studies show that SCFAs have anti-inflammatory and anticarcinogenic effects, play an important role in maintaining metabolic homeostasis in colonocytes, and protect colonocytes from external harm. Animal studies have found substantial positive effects of SCFAs or dietary fiber on colonic disease, but convincing evidence in humans is lacking. Most human intervention trials have been conducted in the context of inflammatory bowel disease. Only a limited number of those trials are of high quality, showing little or no favorable effect of SCFA treatment over placebo. Opportunities for future research include exploring the use of combination therapies with anti-inflammatory drugs, prebiotics, or probiotics; the use of prodrugs in the setting of carcinogenesis; or the direct application of SCFAs to improve mucosal healing after colonic surgery.

The effect of erythropoietin on anastomotic healing of irradiated rats

AIM

The aim of the present study is to evaluate the possible protective effects of erythropoietin (EPO) on anastomotic wound healing after preoperative radiotherapy according to its pleiotropic mechanism of action.

METHODS

Thirty-two male Wistar albino rats were randomized into four groups containing eight rats each: ANAS group, standard resection plus anastomosis; RT+ANAS group, radiation plus standard resection plus anastomosis; ANAS+EPO group, standard resection plus anastomosis plus EPO; RT+ANAS+EPO, radiation plus standard resection plus anastomosis plus EPO. All animals were sacrificed by cardiac puncture, and anastomotic healing was measured by bursting pressure, hydroxyproline (OHP) levels, myeloperoxidase (MPO) activity and histopathological evaluations. Malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), and matrix metalloproteinase-9 (MMP-9) were also measured in serum specimens.

RESULTS

OHP levels in the RT+ANAS + EPO group were significantly increased compared with other groups (p < .05). In contrast, MPO activity in the RT+ANAS+EPO group was significantly decreased compared with other groups (p < .05). Serum MDA levels were found to be decreased in the ANAS+EPO and RT+ANAS+EPO groups (p < .05). Group comparisons demonstrated that bursting pressure was significantly higher in EPO treated rats (p < .05). The histopathology results revealed that EPO treatment improves anastomotic wound healing though decreased necrosis and inflammatory cell infiltration and increased fibroblast activity.

CONCLUSION

The findings of the present study indicate that EPO contributes to wound healing and the strength of colon anastomosis following radiation due to its antioxidant and anti-inflammatory effects, but further studies are needed to explore the significance of these effects.

Enhancement of colonic anastomotic strength in rats by short-chain fatty acids

BACKGROUND

The present study is aiming at elucidating the effect of intraoperative lavage with short-chain fatty acids (SCFAs) on colonic anastomosis in rats.

METHODS

Forty male Wistar rats were randomized into four groups (10 rats each). After resection of a segment of transverse colon, an end-to-end anastomosis was performed. In the 1st group, no intraoperative large bowel lavage was performed; in the 2nd, a lavage with normal saline solution; in the 3rd, the animals received a diet rich in SCFAs pre- and postoperatively, and a lavage with normal saline was performed; and in the 4th group, an intraoperative lavage with SCFAs was carried out. On the 4th postoperative day, the animals were sacrificed. Septic complications, adhesions and anastomoses were graded macroscopically and histologically, and bursting pressure of the anastomoses, CRP, IL-6 and TNF-a was measured.

RESULTS

Fewer septic complications (abscesses and minimal ruptures) and adhesions were observed in the 4th group with the intraoperative lavage with SCFAs. The bursting pressure also, in the same group, was higher (73.3 mmHg), followed by the 1st group (67.1 mmHg).

CONCLUSION

Intraoperative lavage with SCFAs increases the bursting pressure of colonic anastomoses, while lavage with saline solution decreases it, in comparison to the group without lavage.

Butyrate enemas improve intestinal anastomotic strength in a rat model

INTRODUCTION

Anastomotic leakage is a common clinical complication with incidences up to 10% to 17% in colorectal surgery, leading to high morbidity and mortality. Butyrate is the product of colonic fermentation of indigestible carbohydrates and is considered beneficial to gastrointestinal healing. The aim of this study was to investigate the effect of intraluminal supplementation of butyrate on colonic anastomotic strength in a rat model.

METHODS

Wistar rats were randomly assigned to one of 3 groups (18 animals each). All rats underwent a 1-cm left colonic resection and end-to-end anastomosis with 4 interrupted sutures. Group I underwent no other treatment and served as the control, group II received daily 5 mL of 60 mM sodium butyrate enemas postoperatively, and group III received placebo enemas. On the third or seventh postoperative day, rats (n = 9 per time point) were anesthetized and anastomotic bursting strength was assessed.

RESULTS

As a consequence of anastomotic leakage, 3 rats (16.6%) in group I, 1 rat (5.6%) in group II, and 2 rats (11.2%) in group III died. Mean anastomotic bursting pressures at day 3 were not significantly different between groups (53, 64, and 68 mm Hg for group I, II, and III, respectively, P = .777). At day 7, bursting pressures were 118, 225, and 129 mm Hg for groups I, II, and III, respectively (P = .0006). Group II showed an increased mature-to-immature collagen ratio (P = .035).

CONCLUSION

Postoperative intestinal butyrate supplementation enhances anastomotic bursting strength in a left-sided partial colonic resection rat model, which can be explained by increased collagen synthesis and maturation.

Delayed anastomotic leakage following sphincter-preserving surgery for rectal cancer

PURPOSE

The aim of the present study was to investigate the characteristics of patients who developed delayed anastomotic leakage (DAL) following sphincter-preserving surgery for rectal cancer. We evaluated the following factors: (1) the incidence of DAL, (2) the clinical features of patients who developed DAL, (3) the risk factors for DAL, and (4) treatment outcomes.

METHODS

We reviewed the case histories of 1,838 rectal cancer patients who had undergone curative resection with sphincter preservation and without protective stoma formation between January 2000 and December 2006. DAL was defined as the development of a pelvic abscess or fistula around the anastomosis more than 3 weeks post-surgery in patients without tumor recurrence who had resumed a normal diet and defecation.

RESULTS

In 1.3% (24/1,838) of the patients, DAL developed on median postoperative day 99 (range 22-2,069). Pelvic abscess (50%) and anastomotic-vaginal fistula (41.7%) were the most common causes of DAL. Independent risk factors for the development of DAL were: (1) female gender (hazard ratio 3.03; 95% CI 1.06-8.8), (2) low-level anastomosis (< or = 4 cm from the anal verge) (hazard ratio 5.76; 95% CI 1.37-22.39), and (3) preoperative chemoradiation therapy (hazard ratio 4.56; 95% CI 1.4-14.92). Stoma formation was performed in all of the 24 patients. The 3-year stoma-retention rate in patients with DAL was significantly higher than in patients with early anastomotic leakage (72.2% vs 17.5%, P < 0.001).

CONCLUSIONS

DAL following sphincter-preserving surgery for rectal cancer occurred relatively frequently in our sample and was associated with female gender, a low level of anastomosis, and preoperative radiotherapy. DAL patients required long-term or permanent stomas.

Effect of 5-fluorouracil and mitomycin on the healing of intestinal anastomosis

OBJECTIVE

Antineoplastic agents affect the healing of intestinal anastomosis. The aim was to evaluate the effect of 5-fluorouracil (5-FU) and mitomycin on the healing of the intestinal anastomosis and their schedule of administration.

MATERIAL AND METHODS

Eighty-nine male albino Charles Foster rats with a mean weight of 256.57 g were divided into six groups. Group A represents the control, while in others varying schedules of chemotherapy (5-FU and mitomycin) were administered. The sacrifices were made on days 7, 14 and 21 postoperatively and bursting pressure and hydroxyproline content were measured.

RESULTS

Nine rats died before completion of the experiment and were excluded. Adhesions were noted in all rats on sacrifice. The mean bursting pressure of normal intestine (group A) was 252 mm Hg. The bursting pressure was lower on day 7 (208 mm Hg) and it subsequently increased by day 21 (230 mm Hg). The mean bursting pressure in groups B, C, D and E was 174, 194, 182 and 188 mm Hg and it subsequently increased to 232, 272, 244 and 286 mm Hg. There was no difference in the pattern of bursting pressure in colon and ileum. The mean hydroxyproline content of ileum (group A) on day 7 was 34.37 mg/g tissue. The hydroxyproline content of the ileum in groups B, C, D and E was 15.08, 27.03, 7.75 and 21.04 mg/g tissue. There was a significant decrease in hydroxyproline content following anastomosis and chemotherapy.

CONCLUSIONS

The effect of chemotherapy was pronounced when administered on the day of surgery or in the immediate pre- or postoperative period. Hence administration of chemotherapy during this period may be harmful.

Effects of Two Conventional Preoperative Radiation Schedules on Anastomotic Healing in the Rat Colon

BACKGROUND

Preoperative radiotherapy (RT) is an increasingly popular form of adjunct therapy for rectal cancer; however, little is known about its effects on matrix metalloproteinase (MMP) expression in colonic anastomotic healing.

METHODS

Wistar rats were irradiated to a total dose of 25 or 40 Gy. Four days after the end of RT, an end-to-end colorectal anastomosis was performed. Animals were sacrificed at 1, 3, and 7 days after the anastomosis. A control group was studied similarly, but was not irradiated.

RESULTS

No significant differences were found in peritonitis rate and anastomotic complications. The average bursting pressure and breaking strength were only reduced significantly in the rats irradiated with 40 Gy. However, the concentration and the content of hydroxyproline in anastomotic tissues were unchanged. In irradiated rats, MMP-2 and MMP-9 were significantly increased at 40 Gy, but not at 25 Gy. On the other hand, 25-Gy irradiation induced a smaller increase in the levels of the tissue inhibitors of metalloproteinase-1 compared with the controls.

CONCLUSION

Anastomotic strength is adversely affected by high-dose fractionated preoperative RT. In contrast, preoperative RT at 25 Gy in five fractions over 5 days is safe with regard to the maintenance of wound strength in colorectal anastomosis.

Effects of soluble fiber on matrix metalloproteinase-2 activity and healing of colon anastomosis in rats given radiotherapy

BACKGROUND AND AIMS

Soluble fiber is fermented by colonic microflora yielding short-chain fatty acids (SCFAs) in the colon. We aimed to investigate the effect of oral administration of soluble fiber on healing of anastomosis and matrix metalloproteinase-2 activity in radiotherapy received colonic anastomosis.

METHOD

Eighty-four Wistar rats were divided into six groups. All rats were performed a left colonic resection with end-to-end anastomosis. Group I received rat cow. Group II received soluble fiber orally for five consecutive days preoperatively as well as 3rd and 6th days postoperatively. Group III received SCFAs via rectum for five consecutive days preoperatively. Group IV received irradiation to the pelvis at a total dose of 24 Gy on the 10th and 5th days before the operation. Group V was exposed to irradiation like the rats in Group IV and oral treatment like the rats in Group II. Group VI received irradiation like the rats in Group IV and transrectal treatment like the rats in Group III. On the 3rd and 7th postoperative days, all the rats were anesthetized to evaluate the anastomosis healing clinically, histologically and biochemically.

RESULTS

Third and 7th day bursting pressures of the rats that were fed with a normal diet and exposed to radiotherapy were significantly decreased (P<0.001). Bursting pressures of Groups V and VI on the 7th day were significantly higher than the control group's bursting pressures (P<0.05). Hydroxyproline levels of Group IV were significantly decreased (P<0.001). Following oral soluble fiber and transrectal administration of SCFAs, these low levels reached to the levels of control radiotherapy group. Matrix metalloproteinase-2 activity of all the rats that were exposed to radiotherapy was higher than the control group (P<0.001). Matrix metalloproteinase-2 enzyme levels in the Groups V and VI were lower than the ones in the Group IV (P<0.001). The histologic parameters of anastomotic healing such as epithelial regeneration, exudate, necrosis, and fibroblast levels were significantly improved by the use of oral soluble fiber and transrectal SCFAs treatment.

CONCLUSION

Undesirable effects of preoperative radiotherapy on mechanical, histological and biochemical parameters can be overcome by oral soluble fiber. Oral soluble fiber administration has similar positive effects like the transrectal administration of the SCFA's.